Patent Application
20050153615
This invention relates to fibrous material, including fibrous structures containing particle, which are useful in the manufacture of disposable diapers, adult incontinence pads, sanitary napkins and the like. More particularly, the invention is directed to fibrous articles having very high loads of particles, particularly particles of superabsorbent polymer.
Absorbent articles such as disposable diapers, adult incontinence pads, sanitary napkins, panty liners and the like, are generally provided with an absorbent core to receive and retain body liquids. The absorbent core is usually sandwiched between a liquid pervious top sheet, whose function is to allow the passage of fluid to the core, and a liquid impervious backsheet, whose function is to contain the fluid and to prevent it from passing through the absorbent article to the garment of the wearer of the absorbent article.
An absorbent core for diapers and adult incontinence pads frequently includes fibrous batts or webs constructed of defiberized, loose, fluffed, hydrophilic, cellulosic fibers. The core may also include a layer or stratum containing superabsorbent polymer (SAP) particles, granules, flakes or fibers, often referred to as the storage layer or stratum.
In recent years, market demand for an increasingly thinner and more comfortable absorbent article has increased. Such an article may be obtained by decreasing the thickness of the diaper core, by reducing the amount of fibrous material used in the core while increasing the amount of SAP particles, and by calendering or pressing the core to reduce caliper and hence, increase density.
Such higher density cores do not absorb liquid as rapidly as lower density cores because the compacting of the core (densification) results in smaller effective pore size. Accordingly, to maintain suitable liquid absorption, it is necessary to provide a lower density layer having a larger pore size above the high-density absorbent core to increase the rate of uptake of liquid discharged onto the absorbent article. The low-density layer is typically referred to as an acquisition layer. Multiple layer absorbent core designs involve a more complicated manufacturing process.
The storage layer portion of a disposable diaper for example, is generally formed in place, during the converting process, from loose, fluffed cellulose. Such cellulose material is generally not available in preformed roll form because it exhibits insufficient web strength, owing to its lack of interfiber bonding or entanglement, to be unwound directly onto and handled in absorbent pad-making equipment.
Ultra-thin feminine napkins are generally produced from roll-goods based nonwoven material. Such a roll of preformed absorbent core material is unwound directly onto the absorbent article converting equipment without the defiberization step required for fluff-based products, such as diapers and incontinence pads. The nonwoven web is typically bonded or consolidated in a fashion that gives it sufficient strength to be handled in the converting process. These webs may also contain SAP particles.
The web consolidation mechanisms used in the roll-goods approach to making preformed cores provide strength and dimensional stability to the web. Such mechanisms include latex bonding, bonding with thermoplastic or bicomponent fibers or thermoplastic powders, hydroentanglement, needle punching, carding or the like. At high particle loading, however, the core structures exhibit poor particle containment. In other words, some of the particles tend to escape from the structure during manufacture, handling, shipping and converting and in use. This can result in the fouling of manufacturing and converting equipment as well as negative consumer perception of the product.
There is a need for an absorbent core material which facilitates fluid transport from an acquisition zone to a storage zone, exhibits good particle containment at high particle loading, provides high pliability even at high particle loading, is thin but has a high absorbent capacity in use, and can be delivered in roll-goods form to simplify the manufacturing and converting processes.
Published PCT application WO 00/71790 discloses an absorbent article including a layer of functional particles, optionally provided in lanes, wherein the lateral edges of the article are free of functional particles and may be sealed to contain loose particles within the structure.
It is an object of the invention to provide a fibrous web comprising functional particles present at high loading, which can be formed into absorbent articles.
It is another object of the invention to provide a method of making a fibrous web including functional particles present at high loading, which can be formed into absorbent articles.
It is another object of the invention to provide an improved fibrous material including a high load of functional particles and exhibits high pliability.
In one embodiment this invention is a material including
In one embodiment the material comprises from about 0.1 weight percent to about 10 weight percent total binder which comprises a first binder, a second binder, and, optionally, a third binder, where each binder can be the same as or different from any other binder. The material may further comprise (H) a carrier, which may be a cellulosic tissue carrier or a synthetic material. The material may further comprise
In one embodiment the material has
In another embodiment this invention is a nonwoven material with a pliability of about 400 1/N or greater comprising from about 75 to about 95 weight percent SAP.
In another embodiment this invention is a process for the production of a material comprising depositing on a removable support, a carrier or on a carrier on a support a mixture of SAP, fibers and binder, where the material comprises from about 60 weight percent to about 95 weight percent SAP and has a pliability of about 400 I/N or greater.
Preferred aspects are those wherein:
In another embodiment this invention includes an absorbent core having:
The material of the invention as well as a core of this type can be produced in a continuous process which is a series of unit operations, preferably including unit operations involving airlaying of fibrous mixtures through individual airlaying heads. The absorbent core may also be produced with adhesives in a conventional converting operation.
The materials of this invention and cores containing them are useful in various fields including us in absorbent products in the form of a diaper, training pant, incontinent device, feminine hygiene device, surgical drape, wound dressing, or cable wrap.
Here the lanes are offset from the lanes of the stratum of
All patent and patent applications cited in this specification are hereby incorporated by reference into this specification. In case of conflict in terminology, the present disclosure controls.
The present invention is directed to a stratified fibrous web which comprises a plurality of functional particle strata. Each functional particle stratum includes lanes or zones of functional particles, and each lane or zone is separated from an adjacent lane or zone.
Adjacent functional particle strata are oriented such that when viewing the web in the Z-direction, the functional particle lane or zone of one functional particle stratum does not directly overlay, or superimpose, a functional particle lane or zone from the next adjacent functional particle stratum. In other words, the lanes or zones for a first functional particle strata are offset from the lanes or zones of the next adjacent functional particle strata.
With reference to
Stratum 2 of
The spaces 14 between lanes in strata 2 and 4, preferably are substantially free of functional particles, fibers or any other material. Optionally, non-functional material such as fibers may be provided between the lanes. During the manufacturing process, some minor portion of the particles may migrate from the lanes to the spaces before the fibers are fixed in place by curing of fibers, without adverse effect.
With reference to
The resultant multistrata structure includes alternating strata of fibers and functional particles, such that the lanes of functional particles are substantially surrounded by fibers.
The lateral edges of the multistrata structure of
The multistrata structure of
The multistrata structure of
Lanes
The lanes of the functional particle strata are shown in
The preferred amount of coverage of a given functional particle stratum by the functional particles depends upon the application and the thickness, density and other parameters of the particles. Generally, it is preferred that the lanes of the stratum cover at least 30% and preferably 40% and most preferably 50% of the X-Y area of the stratum.
Functional Particles
The functional particle lane is intended to receive particles, flakes, powder, granules, or the like.
The particles may include any functional powder or other particles having a particle diameter of up to 3,000 microns (μ). The particle area may include a particle loading of from 2 to 2,000 gsm (grams per square meter), more preferably from 2 to 1,000 gsm, even more preferably from 10 to 600 gsm, and most preferably from 100 to 250 gsm.
The particles may be superabsorbent polymers (“SAP”) or other functional material. Other suitable particles include odor control agents, e.g., zeolites or calcium carbonate, fragrances, detergents and the like.
A superabsorbent polymer is a water soluble compound that has been cross-linked to render it water insoluble but still swellable to at least about 15 times its own weight in physiological saline solution. These superabsorbent materials generally fall into three classes, namely starch graft copolymers, cross-linked carboxymethylcellulose derivatives, and modified hydrophilic polyacrylates. Examples of absorbent polymers include hydrolyzed starch-acrylontrile graft co-polymer, saponified acrylic acid ester-vinyl co-polymer, modified cross-linked polyvinyl alcohol, neutralized cross-linked polyacrylic acid, cross-linked polyacrylate salt, and carboxylated cellulose. The preferred superabsorbent materials, upon absorbing fluids, form hydrogels.
The superabsorbent polymer materials have relatively high gel volume and relatively high gel strength as measured by the shear modulus of the hydrogel. Such preferred materials also contain relatively low levels of polymeric materials which can be extracted by contact with synthetic urine. Superabsorbent polymers are well-known and are commercially available. One example is a starch graft polyacrylate hydrogel marketed under the name IM 1000 (Hoechst-Celanese, Portsmouth, Va.). Other commercially available superabsorbent polymers are marketed under the trademark Sanwet (Sanyo Kasei Kogyo Kabushiki, Japan), Sumika Gel and SA60S (Sumitomo Kagaku Kabushiki Haishi, Japan), Favor (Stockhausen, Garyville, La.), Kolon GS3500 superabsorbent polymer granules, Kolon, Korea; and the ASAP series (Chemdal, Aberdeen, Miss.). Superabsorbent particulate polymers are also described in detail in U.S. Pat. Nos. 4,102,340 and Re. 32, 649. An example of a suitable SAP is surface cross-linked acrylic acid based powder such as Stockhausen 9350 or SX FAM 70 (Greensboro, N.C.).
Fibers
The fibers suitable for use in the structures of the present invention may include cellulosic or synthetic fibers or blends thereof. Most preferred is wood cellulose. Also preferred is cotton linter pulp, chemically modified cellulose such as crosslinked cellulose fibers and highly purified cellulose fibers, such as Buckeye HPF (each available from Buckeye Technologies Inc., Memphis, Tenn.). The fluff fibers may be blended with synthetic fibers, for example polyester such as PET, nylon, polyethylene or polypropylene.
The fiber-containing strata may also include thermoplastic binding material, which may be blended with the cellulosic or synthetic fibers. Suitable thermoplastic binding material includes thermoplastic fibers, such as bicomponent thermoplastic fibers (“bico”). Preferred thermoplastic binding fibers provide enhanced adhesion for a wide range of materials, including synthetic and natural fibers, particles, and synthetic and natural carrier sheets. An exemplary thermoplastic bico fiber is Celbond Type 255 Bico fiber from Hoechst Celanese.
Other suitable thermoplastic fibers include polypropylenes, polyesters, nylons and other olefins, or modifications thereof. A preferred thermoplastic fiber is FiberVisions type AL-Adhesion-C Bicomponent Fiber, which contains a polypropylene core and an activated copolyolefin sheath.
When the matrix fibers are cellulosic or synthetic fibers (or blends thereof), each stratum positioned between the functional particle strata may preferably contain from about 1 to 20 gsm of cellulosic of synthetic fibers. A thermoplastic bonding material may be present in the stratum in the amount of 2 to 50% by weight, more preferably 3 to 20%, most preferably about 10% of the total weight of the stratum. Most preferably, the stratum between the functional particle strata includes 3.0 gsm fluff pulp and 1.0 gsm of bico.
Binders
Aside from the thermoplastic fibers discussed above, other suitable binders for use in the structures of the invention include binders in liquid form or having a liquid carrier, including latex binders. Useful latex binders include vinyl acetate and acrylic ester copolymers, ethylene vinyl acetate copolymers, styrene butadiene carboxylate copolymers, and polyacrylonitriles, and sold, for example, under the trade names of Airbond, Airflex and Vinac of Air Products, Inc., Hycar and Geon of Goodrich Chemical Co., and Fulatex of H. B. Fuller Company. Alternatively, the binder may be a non-latex binder, such as epichlorohydrin and the like.
The invention contemplates two separate binder applications. In the first application, the binder is applied to the structure so as to contact only the particle free area or lane, which is adjacent the areas or lanes containing the particles disposed between the first and second layers. The binder may be applied in the form of a spray, foam, or mist. In preferred embodiments, the binders are diluted to contain 3 to 25% solids, more preferably 6 to 12% solids, most preferably 10%.
A binder which is diluted to have a relatively high solids content (such as 10%) is ideal for acting in the highly compacted, small pore environment of the particle free area, wherein the seals are formed. The environment results in fast wicking, and the high solids content reduces migration of the binder to the other areas of the web.
The second binder application involves application of a binder, in the form of a foam, spray or mist, to substantially the entire surface of the structure (as an “overall binder”), in order to reduce dust-off on the exterior and interior of the structure. In preferred embodiments, the overall binders are diluted to contain 1 to 20% solids, more preferably 2 to 10% solids, even more preferably 2 to 4% solids, and most preferably about 3.5% solids. While the binder will penetrate to reduce dust-off and to immobilize the functional particles, it will not provide a significant contribution to the structural integrity of the web.
The use of two binder applications allows independent control of the seal area stiffness and the non-seal area stiffness. The stiffness of either region can be controlled by the selection of binder type, solids content and amount of binder applied to the respective regions. This addresses the need to deliver requisite seal strength and maintain sufficient flexibility for the comfort of the user.
Seals
The fibers of the structures of the present invention may be fixed in place to provide integrity to the structure using heat-activated fibers or other binding agents. In certain embodiments a thermoplastic binding material is used and seals are formed when the structure is compacted or densified by pressure or pressure and heat. The seals may be further strengthened by subsequent curing in a curing oven. It is preferred to use thermoplastic fibers as the binder fiber, and heat as the curing agent. Heat can be applied to cure the fibers at the end of the airlaying process, or alternatively, periodically at various stages of the process.
In an alternative embodiment, the sealing may be provided by the application of a liquid binder (or binder in a liquid carrier), after compacting or densification of the web. In such embodiments, the binder is targeted to contact the particle-free areas, and to avoid the particle areas. The binder wicks into the densified region, and forms seals upon drying and curing. Further, in these embodiments, the upper and lower strata optionally contain a thermoplastic binding material.
In another embodiment, seals are formed by application of a liquid binder (or a binder in a liquid carrier) in the particle free zone only, wherein the binder wicks into the densified region and forms strong seals upon drying and curing, without densification of the particle free zone.
In preferred embodiments, seals are formed by compacting or densification of the particle-free areas, followed by application of a binder which is targeted to contact the particle-free areas, and to avoid the particle areas. The binder wicks into the densified region, and forms seals upon drying and curing. In these preferred embodiments, the upper and lower strata each contain a thermoplastic binding material, which strengthens the seals upon densification and curing.
The heat seals are substantially free of functional particles, and the resultant seal is stronger than a seal having particles at the seal interface. When the structure of the invention is subjected to a liquid insult, there are substantially no particles (such as SAP particles) within the sealed area which can swell and disrupt the integrity of the seal.
In certain embodiments of the invention, the article is an absorbent article.
The fibrous structure having improved particle containment may be delivered in roll-goods form, or in other packaging formats such as festooning, and is particularly useful as an absorbent core for disposable absorbent articles such as diapers, adult incontinence pads and briefs, and feminine sanitary napkins.
Airlaid Manufacture of a Structure of the Invention
Preferably, the structure of the present invention is prepared as an airlaid web. The airlaid web is typically prepared by disintegrating or defiberizing a cellulose pulp sheet or sheets, typically by hammermill, to provide individualized fibers. The individualized fibers are then air conveyed to forming heads on the airlaid web forming machine. Several manufacturers make airlaid web forming machines, including M&J Fibretech of Denmark and Dan-Web, also of Denmark. The forming heads include rotating or agitated drums, generally in a race track configuration, which serves to maintain fiber separation until the fibers are pulled by vacuum onto a foraminous condensing drum or foraminous forming conveyor (or forming wire). Other fibers, such as a synthetic thermoplastic fiber, may also be introduced to the forming head through a fiber dosing system which includes a fiber opener, a dosing unit and an air conveyor. Where multiple layers are desired, such as a distribution layer and an acquisition layer, separate forming heads may be provided for each type of layer.
In preferred embodiments, the material and structures of the invention contain a carrier tissue. Optionally the use of a compaction roll prior to the introduction of the particle areas can be used to eliminate the need for the tissue.
As contemplated by the present invention, one or more forming heads of the airlaid web forming machine distributes the desired fiber for the lower layer of the absorbent structure.
SAP granules or other particles are then applied to the upper surface of this web. The particles are applied in lanes in the machine direction with particle-free zones or lanes therebetween. Other particles include odor control agents, e.g., zeolites or calcium carbonate, fragrances, detergents and the like.
A second layer is then formed over the top of the lower layer having the particles applied thereto. Another stratum of SAP granules or other particles are then applied to the upper surface in lanes. The lanes are applied such that the granules do not superimpose over the granules in the particle-containing stratum below. Subsequent alternating layers of fibers and granules may be added as desired.
Optionally, a carrier tissue 20a may be unwound from the supply roll 21. The tissue 20a is rolled on to screen 18. The tissue may alternatively be used as a carrier or as the lower stratum 16 of the absorbent article. As contemplated for the present invention, a forming head 24 of the airlaid web-forming machine distributes the desired fiber to form the lower stratum 16 of the absorbent structure. Cellulosic fibers may be obtained by disintegrating or defiberizing a cellulose pulp sheet or sheets, typically by hammermill, to provide individualized fibers. The individualized fibers are then air conveyed to forming heads on the airlaid web-forming machine. Cellulosic fiber and optionally thermoplastic fibers are added to the cellulose tissue 20a by forming head 24.
Several manufacturers make airlaid web forming machines, including M&J Fibretech of Denmark and Dan-Web, also of Denmark. The forming heads include rotating drums, or agitators generally in a racetrack configuration, which serve to maintain fiber separation until the fibers are pulled by vacuum onto a foraminous condensing drum or foraminous forming conveyor (or forming wire). For example, in machines manufactured by M&J Fibretech, the forming head includes a rotary agitator above a screen. Other fibers, such as a synthetic thermoplastic fiber, may also be introduced to the forming head through a fiber dosing system, which includes a fiber opener, a dosing unit and an air conveyor. Where multiple strata are desired, such as a fluff pulp distribution stratum and a synthetic fiber acquisition stratum, multiple forming heads are provided, one for each type of stratum.
In a nip formed by a pair of calender rolls 26, the fibers are optionally compressed to the desired thickness and density. The lower stratum 16 may be compacted at this point in the manufacturing process to close the pores of the web if the particles are fine and to prevent spillage on to the forming wire.
Particles are applied to the lower stratum 16 by particle applicator 28. SAP granules or other particles are thus applied to the upper surface of the lower stratum 16. Referring now to
A second strata of fibers 18 is applied by forming head 34, which applies cellulosic fibers, and optionally can also apply a thermoplastic fiber such as a bicomponent fiber. Subsequent layers can be added on top of the second layer.
After the second stratum is applied the web may pass under another particle applicator 28 (not shown) to apply another stratum of particles, followed by another stratum of fibers applied by another forming head 34 (not shown). In this way, the web may be built up by a desired number of alternating strata of fibers and particles.
A series of ovens is used in processes of the invention, for drying, curing or thermal bonding.
The airlaid web 23 is heated to a temperature in the range of from 125 to 180° C. at oven 50. When thermoplastic fibers are used, including preferably bico fibers, the curing temperature and dwell time must be sufficient to melt the fibers and cause binding. An overall binder is applied to the airlaid web 23 at 52. This binder can be applied by spray, foam or mist, and is applied to reduce dust-off on the surface of the structure.
The air laid web 23 is heated in a second oven 54 at a temperature in the range of from 125 to 180° C. The airlaid web 23 can be treated at pressure in the range of from 0.1 to 10 psi, preferably 1.5 psi. As a result of this process, heat seals between the thermoplastic material and the fibers of the upper and lower layers are formed. The heat seals are substantially free of particles (especially SAPs), which could disrupt the heat seal upon exposure to moisture. The finished web is then rolled for future use. This continuous band of fibrous web can be slit or cut to form individual absorbent articles in a cutting unit, which has not been depicted in this figure.
Optionally, the finished web may be slit or perforated at the heat seal to yield narrow slit core material having a heat seal along both edges. The heat seals to be slit must be of sufficient width to provide two effective seals after slitting.
In other embodiments, various other layers containing other types and amounts of fibers may be applied above or below the upper and lower layers of the structure of the present invention. For example, the absorbent article may also contain a fluid previous top sheet and a fluid impervious backsheet. Exemplary absorbent articles which can be formed from absorbent cores of the invention include diapers, feminine sanitary napkins, and adult incontinence products.
Exemplary Embodiments of the Invention
Examples 1, 2, 4 and 5 were manufactured on a airlaid pilot machine made by Danweb which has three forming heads, and to which has been added a between-the-head SAP dosing system. In order to obtain more than three layers, the structures were made by passing the web through the forming process more than once. On each pass the material was slightly pressed at the end of the line. The final thickness was adjusted on the last pass. The SAP powder was placed in discrete lanes with the aid of divider boxes as depicted schematically in
The raw materials used in the Examples are Foley Fluff (FF), a southern softwood bleached kraft fluff pulp, Buckeye Technologies Inc.; T-255 polyolefin bicomponent fiber, 2.8 dpf, KoSa; 3024 cellulosic carrier tissue, 18 gsm, Cellu Tissue Co; T-224 polyester fiber, 15 dpf×6 mm, KoSa; Sumitomo SA60S superabsorbent polymer granules, Sumitomo, Japan, Favor 880 superabsorbent polymer granules, Degussa, USA, Kolon GS3500 superabsorbent polymer granules, Kolon, Korea and Airflex 124 latex emulsion, Air Products Chemicals.
The materials of Examples 1, 2, 4 and 5 have a plurality of layers produced in two passes through the three head airlaying machine, with layer 1 made first on the cellulosic carrier, followed by the first SAP feed in lanes, followed by layer 2, followed by a second SAP feed in lanes, where the lanes of SAP from the second SAP feeder are offset in the cross machine direction from the location of the lanes of SAP from the first SAP feeder, so that, looking at the material from the top down the Z dimension perpendicular to the machine direction and the cross machine direction, the lanes of SAP from successive feeds do not superimpose.
Below is given in reverse order the composition used to produce Examples 1, 2, 4 and 5. SAP amounts in grams per square meter (gsm) for a particular SAP feed are an overall basis weight for that feed. Since the SAP is laid down in lanes, the amount of SAP at successive locations in the cross machine direction varies from zero or about zero between the lanes of SAP to about 100 percent in the lanes.
The first pass through the three head airlaid forming system laid the materials in the amounts indicated below in reverse order, starting with Head 1 laying a FF and bico mixture on the cellulosic carrier tissue. In the second pass, layer 4 was laid by Head 3.
The first pass through the three head airlaid forming system laid the materials in the amounts indicated below in reverse order, starting with Head 1 laying a FF and bico mixture on the cellulosic carrier tissue. The second pass started with between head SAP feeder 1, followed by airlaying Layer 4 by Head 2.
A web was manufactured on the three-head Danweb airlaid machine with the SAP fed through the forming heads. The raw materials used were ND416 compressible pulp, Weyerhaeuser, Tacoma Wash.; T-255 bicomponent fiber, 2.8 dpf, KoSa; 3024 cellulosic carrier tissue, 18 gsm, Cellu Tissue Co; T-224 polyester fiber, 15 dpf×6 mm, KoSa; Kolon GS3500 superabsorbent polymer granules, Kolon, Korea; and Airflex 124 latex emulsion, Air Products Chemicals. The basis weight was 318 gsm, and the caliper was 0.9 mm.
As used herein, “pliability” is the inverse of the amount of force necessary to bend a sheet of material of the invention. As the force necessary to bend the sheet increases, the pliability of the sheet decreases.
Pliability can be measured by the following procedure, using a Gurley tester (Model 4171, Gurley Precision Instruments, Troy, NY).
Adjust height so that a gap of 1.0 inch exists between the point where the sample exits the custom clamp and the point where the sample will contact the lever arm.
Ensure that lever arm is not moving. Press motor button to move sample towards lever arm.
Continue pressing motor button until sample clears lever arm. While doing this, observe and note the highest number reached on the scale. Repeat this in the opposite direction.
7. Multiply the average reading on the scale by the appropriate conversion factor found on the chart.
The result is Stiffness, which is expressed in milligrams force, mg. Pliability, P, is defined here according to the following formula:
P=106/9.81 *Stiffness.
The result, P, is expressed here in 1 per Newton, 1/N.
Table 1 below has data for Examples 1, 2, 4 and 5 of this invention, Comparative Example 3 and for several prior art materials which are used in commercial products.
Examples 1, 2, 4 and 5: New bonded structures
Example 3: Prior-art bonded structure
Competitive airlaid core: Nova Thin, no binder
Commercial diaper core Huggies, no binder
This structure was produced in three individual passes through the three head airlaid line. During the first pass, the first forming head deposited a mixture of 21.5 gsm Foley fluff and 2.3 gsm T-255 KoSa 2.8 dpf bicomponent fibers onto an 18 gsm forming tissue from Cellutissue. Next 45.0 gsm of Kolon MG2600 from Kolon Chemical company was deposited in lanes onto the web. The second forming head added a mixture of 21.5 gsm Foley fluff and 2.3 gsm T-255 KoSa 2.8 dpf bicomponent fibers. After the structure was cured in an oven, 2.0 gsm AF-124 latex foam was added to the tissue side of the absorbent. Basis weight at this point was 113 gsm.
The second pass started by using the structure made in the first pass as the carrier material. The first head added 3.0 gsm Foley fluff and 1.0 gsm T-255 KoSa 2.8 dpf bicomponent fibers. Next 45.0 gsm of Kolon MG2600 from Kolon Chemical company was deposited in lanes onto the web. This addition of SAP to the web was aligned so the SAP lanes in the first structure were not directly below. The second forming head added a mixture of 21.5 gsm Foley fluff and 2.3 gsm T-255 KoSa 2.8 dpf bicomponent fibers. Again, 45.0 gsm of Kolon MG2600 from Kolon Chemical company was deposited in lanes onto the web.
This addition of sap to the web was aligned so the first sap lanes were not directly below the second. The third head deposited a mixture of 21.5 gsm Foley fluff and 2.3 gsm T-255 KoSa 2.8 dpf bicomponent fibers.
The third pass started by using the structure made in the second pass as the carrier material. Only the third head was used in this pass. The third head added a mixture of 27.0 gsm Wellman 213×1 6 dpf polyester fibers and 53.0 gsm AL-Delta 6.7 dtx fibers from ES Fiber Visions. The final thickness was reached by compaction of the web to 2.5 mm. The basis weight was 332 gsm.
This structure was produced in two individual passes through the three head airlaid line.
During the first pass, the first forming head deposited a mixture of 20.0 gsm Foley fluff and 2.0 gsm T-255 KoSa 2.8 dpf bicomponent fibers onto an 18 gsm forming tissue from Cellutissue. Next 30.0 gsm of Kolon MG2600 from Kolon Chemical company was deposited in lanes onto the web. The second forming head added a mixture of 21.0 gsm Foley fluff and 2.0 gsm T-255 KoSa 2.8 dpf bicomponent fibers. Basis weight was 93 gsm at this point.
The second pass started by using the structure made in the first pass as the carrier material. Only the third head was used in this pass. The third head added a mixture of 17.0 gsm Wellman 213×1 6 dpf polyester fibers and 33.0 gsm AL-Delta 6.7 dtx fibers from ES Fiber Visions. The final thickness was reached by compaction of the web to 2.2 mm. The basis weight was 140 gsm.
An absorbent core was made by joining the material of Example 7 as an upper layer ASP (acquisition and storage ply) with the material of Example 5 as a lower layer DSP (distribution and storage ply) in a DUOCORE absorbent core structure. The materials were joined by means of a polymer spray adhesive, Super 77 available from 3 M, St. Paul, Minn. The area of the ASP was less than that of the DSP. An alternative version of this core with no adhesive was made as part of the acquisition time test procedure which follows.
Acquisition Time/Rewet/Wicking Distance Test Method
The result for this core was a 1st insult acquisition time of 49.2 seconds, 2nd of 104 seconds and third of 129 seconds.
This core was made by the procedure used in Example 8, except that the ASP was the material of Example 6 and the SAP was the material of Example 5. The result for this core was a 1st insult acquisition time of 42.9 seconds, 2nd of 80 seconds and third of 102 seconds.
Various materials, structures and manufacturing processes useful in the practice of this invention are disclosed in U.S. Patent No.'s 6,241,713; 6,353,148; 6,353,148;6,171,441; 6,159,335; 5,695,486; 6,344,109; 5,068,079; 5,269,049; 5,693,162; 5,922,163; 6,007,643; and 6,355,079; and in U.S. Patent applications with serial numbers and filing dates, 09/211,935 filed 12/15/98; 09/232,783 filed 1/19/99; 09/719,338 filed 1/17/01; 09/475,850 filed 12/30/99; 09/469,930 filed 12/21/99; 09/578,603 filed 5/25/00; 05/25/00; 05/593,409 filed 6/14/00; 09/325,764 filed 6/8/99 allowed; 09/774,248 filed 1/30/01; and 09/854,179 filed 5/11/01, all of which are hereby incorporated by reference in their entirety.
It was discovered that folding of structures described in the invention results in significant improvement in their acquisition properties. This improvement is illustrated with but not limited to the examples summarized in Table 3. Based on these results we can see improvements of the performance of the folded structures over the unfolded samples having the same overall basis weight as the folded ones in the folded configuration (see
*)C-folding: A 21.7 cm wide by 66 cm long material, each edge was folded over approximately 4.3 cm dividing the layer into thirds (4.3 cm folded, 4.3 cm unfolded open, 4.3 cm folded) for a total width of about 13 cm (see cross-sections folded and unfolded sheets,
The results in Table 4 illustrate the effect of the Treated FOLEY FLUFF®on the performance of the Absorbent System I composed of the topsheet, curly-fiber layer, airlaid insert, fluff and poly backsheet. As seen from the data, the acquisition of Example 15 with Treated FOLEY FLUFF® was significantly faster than the acquisition of Example 11 with FOLEY FLUFF®. The sample with SW-16 fibers had also improved capacity over the sample with FF.
MoliCare Super AI diapers from Hartmann (as above) were used as control products. In this case the airlaid cores were first C-folded as shown in
Effect of Bonded Acquisition Ply and Treated FOLEY FLUFF® on Fluid Intake of Folded High-SAP Airlaid in Whole Absorbent System
To make a bonded acquisition pad, several MoliCare Super diapers were taken apart and the acquisition pads removed. The removed curly fibers were then used to make an airlaid handsheet using a lab pad blowing apparatus, with an addition of 8% KoSa T-255, 2.8 dpf fibers. The pad was cured at 160 C for 10 minutes. These acquisition pads had basis weight of about 159 gsm and their thickness was about 3.8 mm. The basis weight of the unbonded acquisition layers of curly fibers in the original diapers was about 154 gsm and their thickness was about 2.0 mm. They were added to the Molicare Super diaper shell along with Example 15. Example 15 was in a C-fold configuration as shown in
All examples were manufactured on a 3-head airlaid pilot Danweb machine with 2 between-head SAP dosing systems. The SAP powder was placed in discrete lanes along the machine direction (MD). The lanes were formed with the aid of divider boxes depicted in
The structures of Examples 17 and 18 comprise a thicker layer of bonded cellulose fibers for enhanced wicking performance.
Any conventional means of dosing SAP onto an airlaid forming wire may be used with the divider box shown in
Raw materials:
*Overall basis weight
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US03/01252 | 1/15/2003 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 60350324 | Jan 2002 | US | |
| 60373410 | Apr 2002 | US |
