CA2099846A1 - Nonwoven web with low poisson ratio - Google Patents
Nonwoven web with low poisson ratioInfo
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- CA2099846A1 CA2099846A1 CA 2099846 CA2099846A CA2099846A1 CA 2099846 A1 CA2099846 A1 CA 2099846A1 CA 2099846 CA2099846 CA 2099846 CA 2099846 A CA2099846 A CA 2099846A CA 2099846 A1 CA2099846 A1 CA 2099846A1
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- Canada
- Prior art keywords
- web
- fibers
- polyethylene
- polyester
- surge
- Prior art date
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Abstract
Abstract of the Disclosure There is disclosed a method for dimensionally stabilizing a nonwoven web of thermoplastic bicomponent fibers to a low Poisson ratio. The process includes laying a web of the fibers on a carrier, subjecting the web of fibers to a source of heat, consolidating the web to a predetermined thickness by drawing the web through a caliper roll with a predetermined fixed gap, and cooling the web to set the web at the predetermined thickness. There is also disclosed a machine for dimensionally stabilizing a nonwoven web of thermoplastic bicomponent fibers to a low Poisson ratio. The machine includes a fiber forming head which first deposits thermoplastic bicomponent fibers onto a moving carrier to form a nonwoven web. The carrier moves the web downstream to a through-air bonder in which the web is subjected to heated air of sufficient temperature to soften the outer surface of the fibers. A caliper roll is located at the exit of the through-air bonder. The caliper roll has a predetermined fixed gap through which the heated web passes. A cooling zone is located downstream of the caliper roll in which cooling zone the nonwoven web is then subjected to cooling air in order to set the web at a predetermined thickness.
Description
NON~OVBN W~B ~IT~ L0~ POI880N RATI0 B~kground of th~ I~vo~tion This invention re:Lates generally to nonwoven webs of thermoplastic fibers and more particularly concerns a nonwoven web of thermoplastic fibers which has been stabilized to a low Poisson ratio.
Absorbent personal care products such as disposable diapers and incontinence garments are generally constructed with an impermeable outer cover, an absorbent system, and an inner liner. Such products sometimes leak at the leg, top front, or top back areas. Leakage can occur due to a variety of shortcomings in the products, one being an insufficient rate of fluid uptake by the absorbent system especially on the second or thixd liquid surge.
Such failure may not be due to the absorbent capacity of the product, but instead may be due to the inability of the absorbent system to uptake liquid rapidly enough to prevent puddling and leaking.
Therefore, there is a need for a nonwoven liner which can improve the handling of liquid surges and ef~ectively uptake and retain repeated loadings of liquid during use until the underlying absorbent system can accommodate the li~uid loading.
A survey of the prior art relating to such liners is laid out in detail in Application Ser. No.
757,760, filed Septe~ber 11, 1991, entitled Thin Absorbent Article Having Rapid Uptake Of Liquid, which is assigned to Rimberly-Clark Corporation, the y ~
assignee of the present invention. In addition, Application Ser. No. 757,760, discloses an improved nonwoven surge management fabric formed of bicomponent fibers, particularly for disposable diapers, that provides the necessary surge capabilities required to insure against leakage until the underlying absorbent system of the disposable diaper can accommodate the liquid loading. The disclosure of Application Ser.
No. 757,760 is therefore incorporated herein by reference as if fully set forth herein.
While the surge management fabric described in Application Ser. No. 757,7~0 is particularly effective for accomplishing the liquid handling -~
capabilities required to protect against puddling and leakage in a disposable diaper, the surge management fabric tends to stretch or neck when subjected to stress during the manufacturing process of the disposable diaper. Necking is a phenomena which results when a nonwoven web is subjected to stress in the machine direction causing it to narrow or neck in the cross machine direction thereby resulting in a web that is smaller in width than the untensioned web.
The tendency of a nonwoven fabric to neck is indicated by a dimensionless value called the Poisson ratio. The Poisson ratio is the ratio of horizontal strain to vertical strain for a material subjected to a uniform vertical stress. The stress is the unit loading on the material caused by an applied tension.
For nonwovens, the thickness of the web is generally not taken into account when calculating stress, and thus, the stress is typically reported a~ a force per unit width of the nonwoven web. The strain is the change in dimension caused by an applied stress, divided by the original dimension. Thus, the equation for Poisson ration (P) is: P = _ (-W/W?
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Absorbent personal care products such as disposable diapers and incontinence garments are generally constructed with an impermeable outer cover, an absorbent system, and an inner liner. Such products sometimes leak at the leg, top front, or top back areas. Leakage can occur due to a variety of shortcomings in the products, one being an insufficient rate of fluid uptake by the absorbent system especially on the second or thixd liquid surge.
Such failure may not be due to the absorbent capacity of the product, but instead may be due to the inability of the absorbent system to uptake liquid rapidly enough to prevent puddling and leaking.
Therefore, there is a need for a nonwoven liner which can improve the handling of liquid surges and ef~ectively uptake and retain repeated loadings of liquid during use until the underlying absorbent system can accommodate the li~uid loading.
A survey of the prior art relating to such liners is laid out in detail in Application Ser. No.
757,760, filed Septe~ber 11, 1991, entitled Thin Absorbent Article Having Rapid Uptake Of Liquid, which is assigned to Rimberly-Clark Corporation, the y ~
assignee of the present invention. In addition, Application Ser. No. 757,760, discloses an improved nonwoven surge management fabric formed of bicomponent fibers, particularly for disposable diapers, that provides the necessary surge capabilities required to insure against leakage until the underlying absorbent system of the disposable diaper can accommodate the liquid loading. The disclosure of Application Ser.
No. 757,760 is therefore incorporated herein by reference as if fully set forth herein.
While the surge management fabric described in Application Ser. No. 757,7~0 is particularly effective for accomplishing the liquid handling -~
capabilities required to protect against puddling and leakage in a disposable diaper, the surge management fabric tends to stretch or neck when subjected to stress during the manufacturing process of the disposable diaper. Necking is a phenomena which results when a nonwoven web is subjected to stress in the machine direction causing it to narrow or neck in the cross machine direction thereby resulting in a web that is smaller in width than the untensioned web.
The tendency of a nonwoven fabric to neck is indicated by a dimensionless value called the Poisson ratio. The Poisson ratio is the ratio of horizontal strain to vertical strain for a material subjected to a uniform vertical stress. The stress is the unit loading on the material caused by an applied tension.
For nonwovens, the thickness of the web is generally not taken into account when calculating stress, and thus, the stress is typically reported a~ a force per unit width of the nonwoven web. The strain is the change in dimension caused by an applied stress, divided by the original dimension. Thus, the equation for Poisson ration (P) is: P = _ (-W/W?
-- : .:
.. . . .
, j , .
2 ~
(-L/L) where, W= material width L= material length W = change in width L = change in length In order to accommodate such undesirable necking, it is often necessary to provide a web that is wider than required so that when the web is stretched, its necked width is still sufficient to extend the full width of the converting machine used to manufacture the disposable diaper. When the stress is released after the disposable diaper has been manufactured, the relaxed web returns to its original width producing unsightly gathers in the finished diaper. Consequently, there is a need in the art to provide a surge management fabric in accordance with the disclosure of Application Ser. No. 757,760 which is dimensionally stabilized in the cross machine direction so that when the surge management fabric is subjected to stress in the machine direction necking is minimized.
8u~ y o~ the Inv-~tion It is therefore an object of the present invention to provide a method fox dimensionally - stabilizing a nonwoven web of thermoplastic fibers so that necking is minimized.
It i9 also an object of the present invention to provide a machine for producing a di~ensionally stabilized nonwoven web of thermoplastic fibers.
It is an object of the present invention to provide a dimensionally stabilized nonwoven web of thermoplastic fibers which web is characterized by low necking and a low Poisson ratio.
It is particularly an object of the present , .: ~
~: : : , :
. . ~ -invention to provide a dimensionally stabilized nonwoven web of thermoplastic fibers in which some of the fibers are bicomponent fibers.
It is further an object of the present invention to provide a dimensionally stabilized nonwoven web of thermoplastic fibers having a predetermined thickness.
The foregoing objectives are achieved by a process for dimensionally stabilizing a nonwoven web of thermoplastic bicomponent fibers which process includes laying a web of the fibers on a carrier, -subjecting the web of fibers to a source of heat, consolidating the web to a predetermined thickness by passing the web through a predetermined fixed gap of a caliper roll, and cooling the web ~o set the web at the predetermined thickness. me foregoing objectives are also achieved by a machine in which a fiber forming head first deposits thermoplastic bicomponent fibers onto a moving carrier to form a nonwoven web.
The carrier moves the web downstream to a through-air bonder in which the web is subjected to heated air of sufficient temperature to soften the outer surface of the fibers. A caliper roll is located at the exit of the through-air bonder. The caliper roll has a predetermined fixed gap through which the heated web passes. A cooling zone is located downstream of the caliper roll in which cooling zone the nonwoven web is then subjected to cooling air (generally ambient temperature~ in order to set the web at a predetermined thickness. The predeter~ined thickness is established by the fixed gap of the caliper roll.
The foregoing objectives are also achieved by a nonwoven liner composed of bicomponent thermoplastic fibers and made in accordance with the above-identified process. The resulting web has a Poisson ratio of less than 2.0 and generally less than 1Ø Generally when calculating the Poisson ratio for 4 ~
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a material, the material is strained along its length.
To achieve a ratio as mentioned above, the material is placed under a strain of between about 1 and 10 percent with the target being about 5 percent strain.
As previously explained, the strain is the change in dimension, in this case the length, divided by the original dimension as a result of the applied stress.
Such a web therefore exhibits low necking when subjected to tension during winding and converting operations.
Other objects and advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings.
Brief Description of the Dr~wings Figure l is a schematic drawing showing a machine in accordance with the present invention for dimensionally stabilizing a nonwoven web containing thermoplastic bicomponent fibers.
Figure 2 is a graph of stress versus neckdown as determined for a preferred embodiment of the present invention and a comparative material.
Figure 3 is a graph of compression versus caliper for the same materials used to obtain the data shown in Figura 2.
Figure 4 is a graph of stress versus strain for the same materials used to obtain the data shown in Fi~ure 2.
D-tailed Desoription or th- Invention While the invention will be described in connection with a preferred embodiment and method, it will be understood that we do not intend to limit the invention to that embodiment or method. On the .. , . ~ ~, : ' : .
contrary, we ~ntend to cover all alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims.
As disclosed in Application Ser. No.
757,760, a surge management fabric is configured for placement either in contact with the skin of the wearer as a liner/surge fabric or as an underlying surge fabric between a top sheet and an underlying absorbent system. When the surge management fabric is used as an underlying surge fabric located between the top sheet and the absorbent system of a disposable diaper, the underlying surge fabric generally has a basis weight within the range of about 17-102 grams per square metèr (gsm) and includes at least about 25 percent by weight of bicomponent fibers to provide a desired bicomponent fiber bond matrix. Up to 100 percent by weight of the underlying surge fabric can be composed of bicomponent fibers, and accordingly, 0-75 percent by weight of the underlying surge fabric may comprise non-bicomponent fibers. In addition, the underlying surge fabric can comprise a blend of smaller diameter fibers and relatively larger diameter fibers. The smaller sized fibers have a denier of less than about 3 denier, and preferably have a denier within the range of about 0.9 - 3 denier. The larger sized fibers have a denier of greater than about 3 denier, and preferably have a denier within the range of about 3 - 18 denier. The lengths of the fibers employed in the underlying surge fabric are within the range of about 1-3 inches. The bond-matrix and the blend of fiber deniers can advantageously provide for and substantially maintain a desired pore size structure.
For example, the underlying surge fabric may comprise a nonwoven fibrous web which includes about 75 percent polyester fibers of at least 6 denier, such ::~ : -. : ~ ....... :
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8 4 Fi as PET (polyethylene terephthalate) fibers available from Hoechst Celanese of Charlotte, North Carolina.
The polyester fibers have a length ranging from about 1.5 - 2.0 inches in length. The remaining 25 percent of the fibrous web can be composed of bicomponent binder fibers of not more than 3 denier, and preferably about 1.5 denier. The bicomponent fiber length ranges from about 1.5 - 2 inches. Suitable bicomponent fibers are wettable or nonwettable, polyethylene/polypropylene bicomponent fibers, available from Chisso Corporation located in Osaka, Japan. The bicomponent fiber can be a composite, sheath-core type with the polypropylene forming the core and polyethylene forming the sheath of the composite fiber, or the bicomponent fiber can be a side by side type fiber with the polypropylene forming one side and the polyethylene forming the other side.
The polyester fibers and bicomponent fibers are generally homogeneously blended together and are not in a layered configuration. The fibers can be formed into a carded web which is thermally bonded, such as by through-air bonding or infrared bonding.
As another example, the underlying surge fabric may be composed of a bonded carded web which has a basis weight of about 50 gsD and includes a mixture of polyester (PET) single-component fibers and PET/polyethylene bicomponent fibers. The PET fibers comprise about 60 percent by weight of the nonwoven fabric, and are about 6 denier with an average fiber length of about 2 inches. The PET/polyethylene bicomponent fibers comprise about 40 percent by weight of the fabric, and are about 1.8 denier with an average fiber length of about 1.5 inches. The PET
forms the core and the polyethylene forms the sheath of the bicomponent fiber. In optional constructions, the larger-sized, PET single-component fibers may be replaced by bicomponent fibers. In further optional , - ;-.
arrangements, polypropylene/polyethylene bicomponent fibers may be employed to form the bicomponent fiber portion of any of the described underlying surge fabrics. In addition, the bicomponent fibers may be flat crimped or helically crimped.
The surge management fabric as previously stated can also be positioned in the diaper so that it is in contact with the skin of the wearer. Where the surge management fabric is in contact with the skin of the wearer, it may be configured as a two layer liner/surge fabric. The composite liner/surge fabric includes a bodyside liner layer adjacent the skin of the wearer and an inner surge layer positioned toward the underlying absorbent system. The layers can be separately laid and can have different structures and compositions. The fibers within each layer and the intermingling fibers between the layer portions are then suitably interconnected (such as by powder bonding, point bonding, adhesive bonding, latex bonding, or by through-air or infrared thermal bonding) to form a composite liner/surge fabric. The resultant composite liner/surge fabric has a total basis weight of not more than about 102 gsm.
Preferably the total basis weight is within the range of about 24 - 68 gsm, and more preferably is within the range of about 45 - 55 gsm. In addition, the - total average density of the composite liner/surge fabric is not more than about 0.10 g/cc, and preferably is not more than about 0.05 g/cc (as determined at .05 psi).
The inner surge layer has a basis weight within the range of about 17 - 85 gsm and includes at least about 25 percent by weight of bicomponent fibers to insure a bicomponent fiber bond-matrix. The inner surge layer also comprises a blend of smaller diameter fibers and relatively larger diameter fibers. The smaller sized fibers have a denier within the range of ... . . . .. .
,, ~. : ~ : :, ... : . - . .. .
about o.9 - 3 denier, and the larger sized fibers have a denier within the range of about 3 - 18 denier. The bond-matrix and the blend of fi~er deniers can advantageously provide for and substantially maintain a desired pore size structure within the inner surge layer. Conversely, in certain applications the surge layer may be used in conjunction with a conventional liner material in which case the basis weight of the surge layer will range between about 17 and about 102 lo gsm.
More particularly, the inner surge layer may be composed of a carded web which has a basis weight of about 34 gsm and includes a mixture of polyester (PET) single-component fibers, available from Hoechst-Celanese of Charlotte, North Carolina, and polyethylene/PET (PE/PET) sheath-core bicomponent fibers, available from BASF Corporation, Fibers Division, of Williamsburg, Virginia. The PET fibers can comprise about 60 percent by weight of the inner surge layer and have a denier of about 6 with an average fiber length of about 2 inches. The polyethylene/PET bicomponent fibers comprise about 40 percent by weight of the outerside layer, and have a denier of about 1.8 with an average fiber length of about 1.5 inchec. Optionally, the larger-sized, PET
single-component fibers may be replaced by bicomponant fib ers. As a fu rth er op tion, polyethylene/polypropylene (PE/PP), sheath-core bicomponent fibers may be employed to form the bicomponent fiber portion of any of the described fabrics. Suitable PE/PP bicomponent fibers are available from Chisso Corporation located in Osaka, Japan.
The bodyside liner layer of the liner/surge fabric includes at least some bicomponent fibers to provide desired levels of tactile softness and abrasion resistance. The bodyside liner layer has a ~ u ~
basis weight of at least about lo gsm, and the bicomponent fiber size is within the range of about 0.9 - 3 denier with a fiber length with the range of about 1 - 3 inches. Preferably, the fiber denier is within the range of about 1.5 - 3.0, and more preferably, is about 3.0 denier. A preferred fiber length is about 1.5 inches. For example, bodyside liner layer may comprise a carded web which has a basis weight of about 17 gsm and is composed of 100%
PET/polyethylene, sheath-core bicomponent fibers, obtained from BASF Corporation of Williamsburg, Virginia, with a fiber denier of about 1.8 and fiber lengths of about 1.5 inches.
In a particular embodiment of the composite liner/surge fabric, the inner surge layer forms approximately 65 weight percent of the composite liner/surge web and is composed of a blend of polyester fibers and bicomponent fibers. With respect to this blended inner surge layer, about 60 percent by weight of the blended inner surge layer is composed of polyester fibers of at least about 6 denier and with a fiber length within the range of about 1.5 - 2 inches. The remaining 40 percent of the blended inner surge layer is composed of bicomponent fibers of not more than about 3 denier, and preferably about 1.8 denier, with fiber lengths within the range of about 1.5 - 2 inches. The bodyside liner layer comprises the remaining 35 weight percent of the composite liner/surge fabric, and is composed of bicomponent fibers have a denier within the range of about 0.9 -3 to provide a soft liner type material appointed for placement against the wearer s skin. In a particular embodiment, the bodyside liner layer of the composite liner/surge fabric has a basis weight of about 15 gsm and is composed of bicomponent fibers of about 2 denier.
Another embodiment of the composite " , : ':: .~ , . , ' ::'' , ' ' .' :', . ~ '.. : , ' '. . : .
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liner/surge fabric can comprise a bodyside liner layer composed of about 100 percent polyethylene/polyester sheath-core bicomponent fibers of not more then about 3 denier. The bodyside liner layer has a basis weight of about 15 gsm. In addition, this embodiment of composite liner/surge web includes an inner surge layer composed of a 50/50 blend of polyester fibers of about 6 denier and polyester/polyethylene, sheath-core bicomponent fibers of not more than about 3 denier.
While the foregoing surge management fabrics including the underlying surge fabric and the liner/surge fabric provide excellent attributes for controlling and managing the distribution of liquids in a disposable diaper, the fabrics or webs described above when stretched in the machine direction exhibit significant necking during winding and converting operations. Particularly, such fabrics exhibit Poisson ratios above 2Ø We have found that surge management fabrics such as those described above can be produced with significant reduction in the necking and resultant reduction of Poisson ratio to near 1Ø
Such dimensional stabilization is achieved by subjecting the surge management fabrics to a source of heat and then passing the fabrics through a fixed gap of a caliper roll prior to cooling and setting the fibers.
- It also should be appreciated that while the foregoing description of materials has been in conjunction with the use of fibrous webs employing staple fibers, it al50 may be possible to utilize the present invention with other types of fibrous webs.
Examples of such other fibrous webs include spunbonded webs, melt blown webs, air laid webs, and solution spun webs to mention but a few.
Turning to Fig. 1, there is shown a surge management fabric forming machine 10. The fabric forming machine 10 comprises a web forming station 11, -~ ~0~84~
a foraminous carrier belt 18, a through-air bonder 28, and caliper roll 50.
The web forming station 11 includes a fiber forming head 12 which produces a curtain 14 of web forming fibers 16. The fibers 16 are the fibers described previously in connection with the surge managemen~- fabric and at least some of the fibers 16 are bicomponent fibers. The fibers 16 are deposited ~-~
on the moving foraminous carrier belt 18 above a vacuum box 20 in which reduced atmospheric pressure is attained by a vacuum pump 22. Under the influence of the reduced pressure in vacuum box 20, the fibers 16 are deposited on the foraminous carrier belt 18 to form a nonwoven web 24.
The foraminous belt 18 moves in the direction indicated by arrow 26 and carries the nonwoven web downstream from the web forming station 11 to the through-air bonder 28. The foraminous carrier belt 18 passes around drum 30 of the -through-air bonder 28 and around idlers 32, 34, 36, and 40 before returning to the web forming station.
The through-air bonder 28 is conventional in design such as the through-air bonders manufactured by Honeycomb Systems of Biddeford, Maine. The 2S through-air bonder 28 consists of the rotating drum 30 which has a porous outer surface 42 and a pipe 44 at the center of the drum through which a vacuum is drawn. A hood 46 is disposed around the majority of the circumference of the drum 30 and provides a source of heated air shown schematically by arrows 4~. The heated air 48 passes from the hood 46, through the web 24, the carrier belt 18, through the porous surface 42 of the drum 30, and out of pipe 44 to a source of vacuum (not shown). The heated air 48 serves to soften the external sheath of the bicomponent fibers thereby rendering them tacky. A caliper roll 50 is disposed at exit S2 of the through-air bonder 28. The . ::
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caliper roll 50 is mounted on a pivoting lever arm 54 which is moved toward and away from the surface 42 of the drum 30 by means of cylinder 56. Consequently, the caliper roll 50 can be set at a predetermined fixed gap 58 from the belt 18 which may or may not be backed by the surface 42 of the drum 30. In alternative arrangements, the gap 58 can be formed between the caliper roll 50 and the through-air bonder 28 surface or another roll. The size of the predetermined fixed gap 58 determines the Poisson ratio of the resulting web 24 because the compression of the web, while the fibers in the web are still tacky from the through-air bonder 28, affects the number and strength of the bonds between the fibers in the web. When`the web 24 passing through the gap 58, the caliper roll 50 compresses the web and the tacky fibers together to create more and stronger bonds between the fibers than if the web is uncompressed.
The enhanced bonding of the fibers in the compressed state produces a web with a lesser propensity to neck when strained.
The gap 58 is sized so that the desired web thickness is obtained and the Poisson ratio of the resulting web 24 is less than 2, and generally less than l. The particular size of the gap 58 required to obtain a particular web thickness and Poisson ratio varies depending on factors including the composition of the web 24 and the speed of the web through the gap. Typically, the thickness of the resulting web 24 will be equal to or greater than the thickness of the gap 58 and the faster the web moves through the gap, the thicker is the resulting web. In other words, to achieve a desired web thickness, a more narrow gap typically must be used at higher line speeds than at lower line speeds. The number and strength of the bonds created resist forces which would tend to reduce the wildth of the fabric and cause necking when the :,", . : :;: . . , ~
f) ~:
fabrlc is strained. In addition, the bonds created resist compressive forces so that the fabric better retains its loft.
On the downstream side of the caliper roll 50 there is located a vacuum seal 60 which allows ambient air to be drawn through the web 24 along a segment 62 of the surface 42 of the drum 30. The vacuum seal 60 assures that ambient air drawn into the drum 30 over the segment 62 passes through the nonwoven web 24 to cool and thereby set the bonds that have formed between the fibers.
Once the fabric has passed through cooling zone 62 adjacent the exit 52 of the through-air bonder 28, the web 24 has achieved sufficient integrity that it may be pulled from the carrier belt 18. The web 24 then passes around idle rolls 64 and 66 and then to a winding roll (not shown).
When the web 24 is formed on the machine 10 shown in Fig. 1, the resulting web exhibits low Poisson ratios of less than 2 and generally less than 1. The machine 10 shown in Fig. 1 was used to make webs in accordance with the following example.
~xam~le 1 A dimensionally stable, liner/surge, - nonwoven web having a basis weight of 1.5 osy was made according to the process described above and illustrated in Fig. 1. The liner layer had a basis weight of 0.5 osy and was positioned ad;acent the carrier belt. The liner layer comprised 100% M-1050, 3 denier, polyethylene/PET bicomponent fibers from 3ASF Corporation of Williamsburg, Virginia. The surge layer had a basis weight of 1.0 osy and was positioned to pass adjacent the caliper roll. The surge layer comprised 60% by weight T-295, 6 denier, PET
homofibers from Hoechst-Celanese of Charlotte, North :
~y~
Carolina, 35% by weight M-1051, 1.8 denier, polyethylene/PET bicomponent fibers from BASF
Corporation, and 5% by weight ES-HB, 2.0 denier, polyethylene/polypropylene bicomponent fibers from Chisso corporation of Osaka, Japan. Both the liner and surge layers were formed by blending and carding.
The line speed was 450 feet per minute, the temperature of the hot air in the through-alr bonder was 262 F, the hood pressure in the through-air bonder was 0.9" HzO, the size of the gap between the caliper roll and the carrier belt was 0.030 inches, and the cooling zone vacuum was less than 1" H2O. The resulting liner/surge material had a caliper of 0.080 inches, a density of 0.022 g/cc, strip tensile lS strengths (as measured on a 3 inch sample in accordance with ASTM D 1117-6) of 5400 g/3'' (MD) and 450 g/3" (CD), and a Poisson ratio of 0.99.
The low Poisson ratio of 0.99 for the sample fabric from Example 1 demonstrates the dimensional stability of that fabric. The dimensional stability of the sample fabric from Example 1 is also illustrated by the graphs shown in Figs. 2-4 which compare properties of that fabric to a comparative sample fabric made without using the caliper roll.
Figure 2 shows that as the stress exerted on the sa~ples is increased, the fabric sample from Example 1 bonded with the use of the caliper roll has a lower percentage of neckdown than the comparative sample. Figure 3 shows that, under lower pressure, the fabric sample from Example 1 is more resistant to compression than the comparative sample. Figure 4 shows that the sample of fabric from Example exhibits a much lower strain for a given stress. This indicates that nonwoven fabric is much more effectively bonded when a caliper roll is used in accordance with the present invention.
:
::, . ., ~ .
(-L/L) where, W= material width L= material length W = change in width L = change in length In order to accommodate such undesirable necking, it is often necessary to provide a web that is wider than required so that when the web is stretched, its necked width is still sufficient to extend the full width of the converting machine used to manufacture the disposable diaper. When the stress is released after the disposable diaper has been manufactured, the relaxed web returns to its original width producing unsightly gathers in the finished diaper. Consequently, there is a need in the art to provide a surge management fabric in accordance with the disclosure of Application Ser. No. 757,760 which is dimensionally stabilized in the cross machine direction so that when the surge management fabric is subjected to stress in the machine direction necking is minimized.
8u~ y o~ the Inv-~tion It is therefore an object of the present invention to provide a method fox dimensionally - stabilizing a nonwoven web of thermoplastic fibers so that necking is minimized.
It i9 also an object of the present invention to provide a machine for producing a di~ensionally stabilized nonwoven web of thermoplastic fibers.
It is an object of the present invention to provide a dimensionally stabilized nonwoven web of thermoplastic fibers which web is characterized by low necking and a low Poisson ratio.
It is particularly an object of the present , .: ~
~: : : , :
. . ~ -invention to provide a dimensionally stabilized nonwoven web of thermoplastic fibers in which some of the fibers are bicomponent fibers.
It is further an object of the present invention to provide a dimensionally stabilized nonwoven web of thermoplastic fibers having a predetermined thickness.
The foregoing objectives are achieved by a process for dimensionally stabilizing a nonwoven web of thermoplastic bicomponent fibers which process includes laying a web of the fibers on a carrier, -subjecting the web of fibers to a source of heat, consolidating the web to a predetermined thickness by passing the web through a predetermined fixed gap of a caliper roll, and cooling the web ~o set the web at the predetermined thickness. me foregoing objectives are also achieved by a machine in which a fiber forming head first deposits thermoplastic bicomponent fibers onto a moving carrier to form a nonwoven web.
The carrier moves the web downstream to a through-air bonder in which the web is subjected to heated air of sufficient temperature to soften the outer surface of the fibers. A caliper roll is located at the exit of the through-air bonder. The caliper roll has a predetermined fixed gap through which the heated web passes. A cooling zone is located downstream of the caliper roll in which cooling zone the nonwoven web is then subjected to cooling air (generally ambient temperature~ in order to set the web at a predetermined thickness. The predeter~ined thickness is established by the fixed gap of the caliper roll.
The foregoing objectives are also achieved by a nonwoven liner composed of bicomponent thermoplastic fibers and made in accordance with the above-identified process. The resulting web has a Poisson ratio of less than 2.0 and generally less than 1Ø Generally when calculating the Poisson ratio for 4 ~
' ~"'''' : . ,- . . ..
a material, the material is strained along its length.
To achieve a ratio as mentioned above, the material is placed under a strain of between about 1 and 10 percent with the target being about 5 percent strain.
As previously explained, the strain is the change in dimension, in this case the length, divided by the original dimension as a result of the applied stress.
Such a web therefore exhibits low necking when subjected to tension during winding and converting operations.
Other objects and advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings.
Brief Description of the Dr~wings Figure l is a schematic drawing showing a machine in accordance with the present invention for dimensionally stabilizing a nonwoven web containing thermoplastic bicomponent fibers.
Figure 2 is a graph of stress versus neckdown as determined for a preferred embodiment of the present invention and a comparative material.
Figure 3 is a graph of compression versus caliper for the same materials used to obtain the data shown in Figura 2.
Figure 4 is a graph of stress versus strain for the same materials used to obtain the data shown in Fi~ure 2.
D-tailed Desoription or th- Invention While the invention will be described in connection with a preferred embodiment and method, it will be understood that we do not intend to limit the invention to that embodiment or method. On the .. , . ~ ~, : ' : .
contrary, we ~ntend to cover all alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims.
As disclosed in Application Ser. No.
757,760, a surge management fabric is configured for placement either in contact with the skin of the wearer as a liner/surge fabric or as an underlying surge fabric between a top sheet and an underlying absorbent system. When the surge management fabric is used as an underlying surge fabric located between the top sheet and the absorbent system of a disposable diaper, the underlying surge fabric generally has a basis weight within the range of about 17-102 grams per square metèr (gsm) and includes at least about 25 percent by weight of bicomponent fibers to provide a desired bicomponent fiber bond matrix. Up to 100 percent by weight of the underlying surge fabric can be composed of bicomponent fibers, and accordingly, 0-75 percent by weight of the underlying surge fabric may comprise non-bicomponent fibers. In addition, the underlying surge fabric can comprise a blend of smaller diameter fibers and relatively larger diameter fibers. The smaller sized fibers have a denier of less than about 3 denier, and preferably have a denier within the range of about 0.9 - 3 denier. The larger sized fibers have a denier of greater than about 3 denier, and preferably have a denier within the range of about 3 - 18 denier. The lengths of the fibers employed in the underlying surge fabric are within the range of about 1-3 inches. The bond-matrix and the blend of fiber deniers can advantageously provide for and substantially maintain a desired pore size structure.
For example, the underlying surge fabric may comprise a nonwoven fibrous web which includes about 75 percent polyester fibers of at least 6 denier, such ::~ : -. : ~ ....... :
- ,: ~i : - .. . . .
8 4 Fi as PET (polyethylene terephthalate) fibers available from Hoechst Celanese of Charlotte, North Carolina.
The polyester fibers have a length ranging from about 1.5 - 2.0 inches in length. The remaining 25 percent of the fibrous web can be composed of bicomponent binder fibers of not more than 3 denier, and preferably about 1.5 denier. The bicomponent fiber length ranges from about 1.5 - 2 inches. Suitable bicomponent fibers are wettable or nonwettable, polyethylene/polypropylene bicomponent fibers, available from Chisso Corporation located in Osaka, Japan. The bicomponent fiber can be a composite, sheath-core type with the polypropylene forming the core and polyethylene forming the sheath of the composite fiber, or the bicomponent fiber can be a side by side type fiber with the polypropylene forming one side and the polyethylene forming the other side.
The polyester fibers and bicomponent fibers are generally homogeneously blended together and are not in a layered configuration. The fibers can be formed into a carded web which is thermally bonded, such as by through-air bonding or infrared bonding.
As another example, the underlying surge fabric may be composed of a bonded carded web which has a basis weight of about 50 gsD and includes a mixture of polyester (PET) single-component fibers and PET/polyethylene bicomponent fibers. The PET fibers comprise about 60 percent by weight of the nonwoven fabric, and are about 6 denier with an average fiber length of about 2 inches. The PET/polyethylene bicomponent fibers comprise about 40 percent by weight of the fabric, and are about 1.8 denier with an average fiber length of about 1.5 inches. The PET
forms the core and the polyethylene forms the sheath of the bicomponent fiber. In optional constructions, the larger-sized, PET single-component fibers may be replaced by bicomponent fibers. In further optional , - ;-.
arrangements, polypropylene/polyethylene bicomponent fibers may be employed to form the bicomponent fiber portion of any of the described underlying surge fabrics. In addition, the bicomponent fibers may be flat crimped or helically crimped.
The surge management fabric as previously stated can also be positioned in the diaper so that it is in contact with the skin of the wearer. Where the surge management fabric is in contact with the skin of the wearer, it may be configured as a two layer liner/surge fabric. The composite liner/surge fabric includes a bodyside liner layer adjacent the skin of the wearer and an inner surge layer positioned toward the underlying absorbent system. The layers can be separately laid and can have different structures and compositions. The fibers within each layer and the intermingling fibers between the layer portions are then suitably interconnected (such as by powder bonding, point bonding, adhesive bonding, latex bonding, or by through-air or infrared thermal bonding) to form a composite liner/surge fabric. The resultant composite liner/surge fabric has a total basis weight of not more than about 102 gsm.
Preferably the total basis weight is within the range of about 24 - 68 gsm, and more preferably is within the range of about 45 - 55 gsm. In addition, the - total average density of the composite liner/surge fabric is not more than about 0.10 g/cc, and preferably is not more than about 0.05 g/cc (as determined at .05 psi).
The inner surge layer has a basis weight within the range of about 17 - 85 gsm and includes at least about 25 percent by weight of bicomponent fibers to insure a bicomponent fiber bond-matrix. The inner surge layer also comprises a blend of smaller diameter fibers and relatively larger diameter fibers. The smaller sized fibers have a denier within the range of ... . . . .. .
,, ~. : ~ : :, ... : . - . .. .
about o.9 - 3 denier, and the larger sized fibers have a denier within the range of about 3 - 18 denier. The bond-matrix and the blend of fi~er deniers can advantageously provide for and substantially maintain a desired pore size structure within the inner surge layer. Conversely, in certain applications the surge layer may be used in conjunction with a conventional liner material in which case the basis weight of the surge layer will range between about 17 and about 102 lo gsm.
More particularly, the inner surge layer may be composed of a carded web which has a basis weight of about 34 gsm and includes a mixture of polyester (PET) single-component fibers, available from Hoechst-Celanese of Charlotte, North Carolina, and polyethylene/PET (PE/PET) sheath-core bicomponent fibers, available from BASF Corporation, Fibers Division, of Williamsburg, Virginia. The PET fibers can comprise about 60 percent by weight of the inner surge layer and have a denier of about 6 with an average fiber length of about 2 inches. The polyethylene/PET bicomponent fibers comprise about 40 percent by weight of the outerside layer, and have a denier of about 1.8 with an average fiber length of about 1.5 inchec. Optionally, the larger-sized, PET
single-component fibers may be replaced by bicomponant fib ers. As a fu rth er op tion, polyethylene/polypropylene (PE/PP), sheath-core bicomponent fibers may be employed to form the bicomponent fiber portion of any of the described fabrics. Suitable PE/PP bicomponent fibers are available from Chisso Corporation located in Osaka, Japan.
The bodyside liner layer of the liner/surge fabric includes at least some bicomponent fibers to provide desired levels of tactile softness and abrasion resistance. The bodyside liner layer has a ~ u ~
basis weight of at least about lo gsm, and the bicomponent fiber size is within the range of about 0.9 - 3 denier with a fiber length with the range of about 1 - 3 inches. Preferably, the fiber denier is within the range of about 1.5 - 3.0, and more preferably, is about 3.0 denier. A preferred fiber length is about 1.5 inches. For example, bodyside liner layer may comprise a carded web which has a basis weight of about 17 gsm and is composed of 100%
PET/polyethylene, sheath-core bicomponent fibers, obtained from BASF Corporation of Williamsburg, Virginia, with a fiber denier of about 1.8 and fiber lengths of about 1.5 inches.
In a particular embodiment of the composite liner/surge fabric, the inner surge layer forms approximately 65 weight percent of the composite liner/surge web and is composed of a blend of polyester fibers and bicomponent fibers. With respect to this blended inner surge layer, about 60 percent by weight of the blended inner surge layer is composed of polyester fibers of at least about 6 denier and with a fiber length within the range of about 1.5 - 2 inches. The remaining 40 percent of the blended inner surge layer is composed of bicomponent fibers of not more than about 3 denier, and preferably about 1.8 denier, with fiber lengths within the range of about 1.5 - 2 inches. The bodyside liner layer comprises the remaining 35 weight percent of the composite liner/surge fabric, and is composed of bicomponent fibers have a denier within the range of about 0.9 -3 to provide a soft liner type material appointed for placement against the wearer s skin. In a particular embodiment, the bodyside liner layer of the composite liner/surge fabric has a basis weight of about 15 gsm and is composed of bicomponent fibers of about 2 denier.
Another embodiment of the composite " , : ':: .~ , . , ' ::'' , ' ' .' :', . ~ '.. : , ' '. . : .
'~ 0 ~
liner/surge fabric can comprise a bodyside liner layer composed of about 100 percent polyethylene/polyester sheath-core bicomponent fibers of not more then about 3 denier. The bodyside liner layer has a basis weight of about 15 gsm. In addition, this embodiment of composite liner/surge web includes an inner surge layer composed of a 50/50 blend of polyester fibers of about 6 denier and polyester/polyethylene, sheath-core bicomponent fibers of not more than about 3 denier.
While the foregoing surge management fabrics including the underlying surge fabric and the liner/surge fabric provide excellent attributes for controlling and managing the distribution of liquids in a disposable diaper, the fabrics or webs described above when stretched in the machine direction exhibit significant necking during winding and converting operations. Particularly, such fabrics exhibit Poisson ratios above 2Ø We have found that surge management fabrics such as those described above can be produced with significant reduction in the necking and resultant reduction of Poisson ratio to near 1Ø
Such dimensional stabilization is achieved by subjecting the surge management fabrics to a source of heat and then passing the fabrics through a fixed gap of a caliper roll prior to cooling and setting the fibers.
- It also should be appreciated that while the foregoing description of materials has been in conjunction with the use of fibrous webs employing staple fibers, it al50 may be possible to utilize the present invention with other types of fibrous webs.
Examples of such other fibrous webs include spunbonded webs, melt blown webs, air laid webs, and solution spun webs to mention but a few.
Turning to Fig. 1, there is shown a surge management fabric forming machine 10. The fabric forming machine 10 comprises a web forming station 11, -~ ~0~84~
a foraminous carrier belt 18, a through-air bonder 28, and caliper roll 50.
The web forming station 11 includes a fiber forming head 12 which produces a curtain 14 of web forming fibers 16. The fibers 16 are the fibers described previously in connection with the surge managemen~- fabric and at least some of the fibers 16 are bicomponent fibers. The fibers 16 are deposited ~-~
on the moving foraminous carrier belt 18 above a vacuum box 20 in which reduced atmospheric pressure is attained by a vacuum pump 22. Under the influence of the reduced pressure in vacuum box 20, the fibers 16 are deposited on the foraminous carrier belt 18 to form a nonwoven web 24.
The foraminous belt 18 moves in the direction indicated by arrow 26 and carries the nonwoven web downstream from the web forming station 11 to the through-air bonder 28. The foraminous carrier belt 18 passes around drum 30 of the -through-air bonder 28 and around idlers 32, 34, 36, and 40 before returning to the web forming station.
The through-air bonder 28 is conventional in design such as the through-air bonders manufactured by Honeycomb Systems of Biddeford, Maine. The 2S through-air bonder 28 consists of the rotating drum 30 which has a porous outer surface 42 and a pipe 44 at the center of the drum through which a vacuum is drawn. A hood 46 is disposed around the majority of the circumference of the drum 30 and provides a source of heated air shown schematically by arrows 4~. The heated air 48 passes from the hood 46, through the web 24, the carrier belt 18, through the porous surface 42 of the drum 30, and out of pipe 44 to a source of vacuum (not shown). The heated air 48 serves to soften the external sheath of the bicomponent fibers thereby rendering them tacky. A caliper roll 50 is disposed at exit S2 of the through-air bonder 28. The . ::
.. .. .. .
': , : , ';
. ~
g 4 ~
caliper roll 50 is mounted on a pivoting lever arm 54 which is moved toward and away from the surface 42 of the drum 30 by means of cylinder 56. Consequently, the caliper roll 50 can be set at a predetermined fixed gap 58 from the belt 18 which may or may not be backed by the surface 42 of the drum 30. In alternative arrangements, the gap 58 can be formed between the caliper roll 50 and the through-air bonder 28 surface or another roll. The size of the predetermined fixed gap 58 determines the Poisson ratio of the resulting web 24 because the compression of the web, while the fibers in the web are still tacky from the through-air bonder 28, affects the number and strength of the bonds between the fibers in the web. When`the web 24 passing through the gap 58, the caliper roll 50 compresses the web and the tacky fibers together to create more and stronger bonds between the fibers than if the web is uncompressed.
The enhanced bonding of the fibers in the compressed state produces a web with a lesser propensity to neck when strained.
The gap 58 is sized so that the desired web thickness is obtained and the Poisson ratio of the resulting web 24 is less than 2, and generally less than l. The particular size of the gap 58 required to obtain a particular web thickness and Poisson ratio varies depending on factors including the composition of the web 24 and the speed of the web through the gap. Typically, the thickness of the resulting web 24 will be equal to or greater than the thickness of the gap 58 and the faster the web moves through the gap, the thicker is the resulting web. In other words, to achieve a desired web thickness, a more narrow gap typically must be used at higher line speeds than at lower line speeds. The number and strength of the bonds created resist forces which would tend to reduce the wildth of the fabric and cause necking when the :,", . : :;: . . , ~
f) ~:
fabrlc is strained. In addition, the bonds created resist compressive forces so that the fabric better retains its loft.
On the downstream side of the caliper roll 50 there is located a vacuum seal 60 which allows ambient air to be drawn through the web 24 along a segment 62 of the surface 42 of the drum 30. The vacuum seal 60 assures that ambient air drawn into the drum 30 over the segment 62 passes through the nonwoven web 24 to cool and thereby set the bonds that have formed between the fibers.
Once the fabric has passed through cooling zone 62 adjacent the exit 52 of the through-air bonder 28, the web 24 has achieved sufficient integrity that it may be pulled from the carrier belt 18. The web 24 then passes around idle rolls 64 and 66 and then to a winding roll (not shown).
When the web 24 is formed on the machine 10 shown in Fig. 1, the resulting web exhibits low Poisson ratios of less than 2 and generally less than 1. The machine 10 shown in Fig. 1 was used to make webs in accordance with the following example.
~xam~le 1 A dimensionally stable, liner/surge, - nonwoven web having a basis weight of 1.5 osy was made according to the process described above and illustrated in Fig. 1. The liner layer had a basis weight of 0.5 osy and was positioned ad;acent the carrier belt. The liner layer comprised 100% M-1050, 3 denier, polyethylene/PET bicomponent fibers from 3ASF Corporation of Williamsburg, Virginia. The surge layer had a basis weight of 1.0 osy and was positioned to pass adjacent the caliper roll. The surge layer comprised 60% by weight T-295, 6 denier, PET
homofibers from Hoechst-Celanese of Charlotte, North :
~y~
Carolina, 35% by weight M-1051, 1.8 denier, polyethylene/PET bicomponent fibers from BASF
Corporation, and 5% by weight ES-HB, 2.0 denier, polyethylene/polypropylene bicomponent fibers from Chisso corporation of Osaka, Japan. Both the liner and surge layers were formed by blending and carding.
The line speed was 450 feet per minute, the temperature of the hot air in the through-alr bonder was 262 F, the hood pressure in the through-air bonder was 0.9" HzO, the size of the gap between the caliper roll and the carrier belt was 0.030 inches, and the cooling zone vacuum was less than 1" H2O. The resulting liner/surge material had a caliper of 0.080 inches, a density of 0.022 g/cc, strip tensile lS strengths (as measured on a 3 inch sample in accordance with ASTM D 1117-6) of 5400 g/3'' (MD) and 450 g/3" (CD), and a Poisson ratio of 0.99.
The low Poisson ratio of 0.99 for the sample fabric from Example 1 demonstrates the dimensional stability of that fabric. The dimensional stability of the sample fabric from Example 1 is also illustrated by the graphs shown in Figs. 2-4 which compare properties of that fabric to a comparative sample fabric made without using the caliper roll.
Figure 2 shows that as the stress exerted on the sa~ples is increased, the fabric sample from Example 1 bonded with the use of the caliper roll has a lower percentage of neckdown than the comparative sample. Figure 3 shows that, under lower pressure, the fabric sample from Example 1 is more resistant to compression than the comparative sample. Figure 4 shows that the sample of fabric from Example exhibits a much lower strain for a given stress. This indicates that nonwoven fabric is much more effectively bonded when a caliper roll is used in accordance with the present invention.
:
::, . ., ~ .
Claims (12)
1. A method for dimensionally stabilizing a nonwoven web of thermoplastic fibers comprising the steps of:
a. laying a web of the fibers on a carrler;
b. subjecting the web of fibers to a source of heat;
c. consolidating the web to a predetermined thickness by passing the web through a predetermined fixed gap of a caliper roll; and d. cooling the web to set the predetermined thickness.
a. laying a web of the fibers on a carrler;
b. subjecting the web of fibers to a source of heat;
c. consolidating the web to a predetermined thickness by passing the web through a predetermined fixed gap of a caliper roll; and d. cooling the web to set the predetermined thickness.
2. The method of claim 1, wherein some of the fibers are thermoplastic bicomponent fibers.
3. The method of claim 2, wherein the bicomponent fibers are selected from the group consisting of: polyethylene/polypropylene, polyethylene/polyester, polypropylene/polypropylene, polyester/polyester, polyethylene/nylon, polyethylene/acrylic, polyethylene/polyvinyl acrylate, polyethylene/polyvinyl alcohol, polypropylene/nylon, polypropylene/acrylic, polypropylene/polyvinyl acrylate, polypropylene/polyvinyl alcohol, polyester/nylon, polyester/acrylic, polyester/polyvinyl acrylate and polyester/polyvinyl alcohol fibers.
4. The method of claim 1, wherein the fixed gap is set as a function of the predetermined thickness.
5. The method of claim 1, wherein the web is formed by laying more than one layer of fibers on the carrier prior to subjecting the web of fibers to the heat source.
6. The method of claim 1, wherein the fixed gap is set so that the resulting web has a Poisson ratio of less than 2Ø
7. In a machine for making a nonwoven web of thermoplastic fibers having a predetermined thickness, wherein the machine has a porous carrier, means for depositing the thermoplastic fibers on the carrier, a heat source located downstream from the means for depositing the thermoplastic fibers, and cooling means located downstream from the heat source, the improvement comprising a caliper roll with a predetermined fixed gap, the caliper roll being interposed between the heat source and the cooling means.
8. The machine of claim 7, wherein the fixed gap of the caliper roll is a function of the predetermined thickness required for the nonwoven web.
9. The machine of claim 7, wherein the heat source is a through air bonder having a porous carrier and the web is in contact with the carrier and subject to heated air for 90-300 degrees of rotation.
10. The machine of claim 7, wherein some of the fibers are thermoplastic bicomponent fibers.
11. A dimensionally stabilized nonwoven web resulting from the method of claim 1.
12. A dimensionally stabilized nonwoven web comprising a bonded matrix of thermoplastic bicomponent fibers, wherein the web has a Poisson ratio of less than 2Ø
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US99925992A | 1992-12-31 | 1992-12-31 | |
| US999,259 | 1992-12-31 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2099846A1 true CA2099846A1 (en) | 1994-07-01 |
Family
ID=25546100
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2099846 Abandoned CA2099846A1 (en) | 1992-12-31 | 1993-07-05 | Nonwoven web with low poisson ratio |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2099846A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1999032699A1 (en) * | 1997-12-19 | 1999-07-01 | Kimberly-Clark Worldwide, Inc. | Ultralight, converting friendly, nonwoven fabric |
-
1993
- 1993-07-05 CA CA 2099846 patent/CA2099846A1/en not_active Abandoned
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1999032699A1 (en) * | 1997-12-19 | 1999-07-01 | Kimberly-Clark Worldwide, Inc. | Ultralight, converting friendly, nonwoven fabric |
| AU743006B2 (en) * | 1997-12-19 | 2002-01-17 | Kimberly-Clark Worldwide, Inc. | Ultralight, converting friendly, nonwoven fabric |
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