Airlaid nonwoven fabric

Abstract

A composite sheet material is provided comprising a first layer and an airlaid nonwoven layer overlying the first layer, wherein the airlaid nonwoven layer comprises a blend of bamboo-derived staple fibers and non-cellulosic staple fibers, the airlaid nonwoven layer having a first surface disposed against and thermally bonded to a surface of the first layer, and a second surface defining an outer surface of the composite sheet material.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Application No. 63 / 256,406, filed October 15, 2021, the contents of which are incorporated herein by reference.

[0002] The present invention relates generally to airlaid nonwoven fabrics for use in absorbent articles, and more particularly to airlaid nonwoven fabrics comprising a blend of bamboo-derived staple fibers and non-cellulosic staple fibers. [Background technology]

[0003] Nonwoven fabrics made from a variety of natural and synthetic fiber combinations are known to be used for the manufacture of absorbent articles, including disposable hygiene products such as diapers, femcare sanitary products, adult incontinent products, wet wipes, and the like. Summary of the Invention [Problem to be solved by the invention]

[0004] Despite significant advances in absorbent article manufacturing and design, there remains a need for absorbent articles with improved fluid management properties, reduced thickness, and increased softness. It is also important to utilize renewable / sustainable bio-based feedstocks to reduce the amount of synthetic plastic materials introduced into the environment. [Means for solving the problem]

[0005] One embodiment of the present invention is directed to an airlaid nonwoven fabric comprising a blend of non-cellulosic staple fibers and bamboo-derived staple fibers. Surprisingly, it has been discovered that the use of bamboo-derived staple fibers in place of conventional wood pulp fibers provides significant improvements in desirable fluid management properties, such as wicking speed and vertical wicking height, reduced caliper, and improved softness, as compared to the same airlaid nonwoven fabric comprising non-cellulosic staple fibers and conventional wood pulp fibers.

[0006] In one embodiment, a composite sheet material is provided comprising a first layer and an airlaid nonwoven layer overlying the first layer, where the airlaid nonwoven layer comprises a blend of bamboo-derived staple fibers and non-cellulosic staple fibers, the airlaid nonwoven layer having a first surface disposed toward and thermally bonded to a surface of the first layer and a second surface defining an outer surface of the composite sheet material.

[0007] In some embodiments, the first layer is selected from the group consisting of a spunbond nonwoven, a meltblown nonwoven, a spunlace nonwoven, a carded nonwoven, an airlaid nonwoven, a cellulosic tissue, a spunbond-meltblown-spunbond composite, a film, and combinations thereof. In a preferred embodiment, the first layer comprises a carded nonwoven fabric comprising a plurality of staple fibers air-through bonded to one another to form a coherent nonwoven fabric. In some embodiments, the first layer may comprise a composite structure, such as meltblown-spunbond (MS), spunbond-meltblown-spunbond composite (SMS), spunbond-meltblown-meltblown-spunbond composite (SMMS), etc. Such composites may be used alone or in combination with one or more of the materials described above.

[0008] In some embodiments, the airlaid nonwoven layer comprises multiple airlaid layers that are thermally bonded to adjacent airlaid layers. For example, the airlaid nonwoven layer can comprise 2 to 10 successive airlaid layers. In one embodiment, the airlaid nonwoven layer comprises 3 to 6 airlaid layers.

[0009] In some embodiments, the first layer comprises a carded nonwoven fabric comprising bicomponent staple fibers having a polyethylene sheath and a polypropylene or polyethylene terephthalate core or mixtures thereof. In some embodiments, the bicomponent staple fibers of the carded nonwoven fabric can have an average length of about 25 to about 60 millimeters (mm).

[0010] In some embodiments, the non-cellulosic fibers of the airlaid nonwoven fabric are bicomponent staple fibers having a polyethylene sheath and a polypropylene or polyethylene terephthalate core or mixtures thereof. In some embodiments, the non-cellulosic fibers can have an average length of about 0.8 to about 10 millimeters (mm).

[0011] In some embodiments, the first layer comprises a carded nonwoven fabric comprising polylactic acid (PLA) staple fibers, and the non-cellulosic fibers of the airlaid nonwoven comprise PLA having a sheath / core configuration, where the sheath comprises PLA.

[0012] In some embodiments, the first layer comprises a carded nonwoven fabric comprising a bio-based polymer.

[0013] In some embodiments, the non-cellulosic staple fibers of the airlaid nonwoven layer comprise a bio-based polymer.

[0014] In some embodiments, the bio-based polymer of the first layer or the airlaid layer comprises an aliphatic polyester, a bio-based polyethylene, a bio-based polypropylene, a bio-based polyester, such as bio-based polyethylene terephthalate (PET), or a combination thereof.

[0015] In some embodiments, the aliphatic polyester comprises polylactic acid (PLA), polybutylene succinate (PBS), or a combination or blend thereof.

[0016] In some embodiments, the basis weight of the composite sheet material is from about 25 to about 400 g / m 2 , for example, about 25 to 250 g / m 2 Or about 50 to about 100 g / m 2 , is.

[0017] In one embodiment, the bamboo-derived staple fibers have an average length of about 0.8 to about 3.0 mm and an average width of about 12 to about 22 microns.

[0018] In some embodiments, the bamboo-derived staple fibers have a length to width ratio that is from about 60 to about 120.

[0019] In one embodiment, a polymeric coating layer is deposited on the surface of the airlaid nonwoven layer, where the polymeric coating comprises ethylene vinyl acetate, ethylene acrylate, polyacrylate, phenylethylene butadiene, styrene butadiene acrylate, polyvinyl alcohol, bio-based latex, or mixtures thereof.

[0020] In some embodiments, the add-on dry weight of the polymeric coating is from about 1.5 to about 4 weight percent, based on the total weight of the composite sheet material.

[0021] In some embodiments, the composite sheet material comprises a carded nonwoven fabric made of staple fibers and at least one airlaid nonwoven layer overlying the carded nonwoven fabric, and wherein the composite sheet material has a weight of about 60 to about 100 g / m 2 and the composite sheet material exhibits a thickness in the range of about 0.5 to about 3.0 mm, a CD stiffness in the range of about 5 to about 15 mN / cm, and a MD stiffness in the range of about 20 to about 50 mN / cm.

[0022] In some embodiments, the composite sheet material exhibits a wicking rate of about 30 to about 50 mm / 15 sec, and a vertical fluid wicking height of about 30 to about 70 mm.

[0023] In some embodiments, the composite sheet material comprises a carded nonwoven fabric made of staple fibers and at least one airlaid nonwoven layer overlying the carded nonwoven fabric, and wherein the composite sheet material has a weight of about 60 to about 100 g / m 2 and the composite sheet material exhibits a thickness in the range of about 1.25 to about 1.40 mm, a CD stiffness in the range of about 6 to about 14 mN / cm, a MD stiffness in the range of about 25 to about 40 mN / cm, a wicking rate of about 32 to about 40 mm / 15 sec, and a vertical fluid wicking height of about 35 to about 65 mm.

[0024] In some embodiments, the composite sheets exhibit an increase in vertical wicking height in the range of 50-150% and an increase in wicking rate in the range of 40-120% when compared to the same composite sheet material in which the airlaid nonwoven layer comprises staple fibers that include conventional wood pulp fibers instead of bamboo-derived staple fibers.

[0025] In some embodiments, the composite sheets exhibit a reduction in MD stiffness in the range of 10-50% and a reduction in CD stiffness in the range of 10-60% when compared to the same composite sheet material in which the airlaid nonwoven comprises staple fibers that comprise conventional wood pulp fibers instead of bamboo-derived staple fibers.

[0026] In some embodiments, the airlaid nonwoven comprises one or more airlaid layers, and at least one of the airlaid layers comprises a superabsorbent polymer.

[0027] In some embodiments, the airlaid nonwoven layer is thermally bonded via an air-through bond, and the first layer is bonded to the overlying airlaid nonwoven layer via an air-through bond.

[0028] In some embodiments, the airlaid layer includes staple fibers that include conventional wood pulp fibers. In one such embodiment, the amount of conventional wood pulp fibers in the airlaid layer is from about 10 to about 90 weight percent, based on the combined weight of the conventional wood pulp fibers and the bamboo-derived staple fibers.

[0029] In some embodiments, the composite sheet material may comprise a component of an absorbent article.Embodiments of the present invention are also directed to the use of the composite sheet material in an absorbent article.

[0030] A further aspect of the present invention is also directed to a method of making a composite sheet comprising the steps of providing a first layer of sheet material; depositing a first airlaid layer on a surface of the first layer to form a composite sheet, wherein the first airlaid layer comprises a mixture of bamboo-derived staple fibers and non-cellulosic staple fibers; and air-through bonding the composite sheet with heated gas to melt the polymer of the non-cellulosic staple fibers and fuse adjacent fibers, the bamboo-derived staple fibers and the first layer, wherein the non-cellulosic staple fibers of the airlaid layer are adhered to one another.

[0031] In some embodiments, the method further comprises depositing a plurality of airlaid layers successively onto the first airlaid layer, hi some embodiments, the composite sheet comprises 2 to 10 airlaid layers successively deposited one on top of the other on the carded nonwoven substrate.

[0032] In some embodiments of the method, the first layer comprises a carded nonwoven fabric comprising bicomponent staple fibers having a polyethylene sheath and a polypropylene or polyethylene terephthalate core or mixtures thereof, and the non-cellulosic fibers of the airlaid nonwoven comprise bicomponent staple fibers having a polyethylene sheath and a polypropylene or polyethylene terephthalate core or mixtures thereof.

[0033] In some embodiments of the method, the bicomponent staple fibers of the carded nonwoven fabric have a length of about 25 to about 60 millimeters (mm), and the non-cellulosic fibers of the airlaid nonwoven fabric have a length of about 0.8 to about 10 millimeters (mm).

[0034] In one embodiment of the method, the carded nonwoven fabric comprises polylactic acid (PLA) staple fibers, and the non-cellulosic fibers comprise PLA bicomponent fibers having a sheath / core structure, where the sheath is comprised of PLA.

[0035] In some embodiments, the method includes the steps of depositing a coating layer of a polymer latex on a surface of an outermost airlaid layer, and then heating the composite sheet material to a temperature sufficient to cure and dry the polymer latex.

[0036] In some embodiments of the method, the method further comprises the step of adding a superabsorbent polymer to at least one of the airlaid nonwoven layers.

[0037] In one embodiment, providing a first layer of sheet material; depositing a first airlaid layer on a surface of the first layer to form a composite sheet, wherein the first airlaid layer comprises a mixture of bamboo-derived staple fibers and non-cellulosic staple fibers; and air-through bonding the composite sheet with heated gas to melt the polymer of the non-cellulosic staple fibers and fuse adjacent fibers, the bamboo-derived staple fibers and the first layer, wherein the non-cellulosic staple fibers of the airlaid layer are bonded to one another. A method of making a composite sheet is provided, comprising the steps of:

[0038] In one embodiment of the method, the method includes successively depositing a plurality of airlaid layers onto the first airlaid layer.

[0039] In some embodiments of the method, the composite sheet comprises 2 to 10 airlaid layers deposited in succession one on top of the other on the carded nonwoven substrate.

[0040] In some embodiments of the method, the first layer is selected from the group consisting of a spunbond nonwoven, a meltblown nonwoven, a spunlace nonwoven, a carded nonwoven, an airlaid nonwoven, a cellulosic tissue paper, a film, and combinations thereof.

[0041] In some embodiments of the method, the first layer comprises a carded nonwoven fabric comprising a plurality of staple fibers that are air-through bonded to one another to form an integral nonwoven fabric.

[0042] In some embodiments of the method, the airlaid nonwoven layer comprises a plurality of airlaid layers that are thermally bonded to adjacent airlaid layers.

[0043] In some embodiments of the method, the airlaid nonwoven layer comprises 2 to 10 airlaid layers, particularly 3 to 6 airlaid layers.

[0044] In some embodiments of the method, the first layer comprises a carded nonwoven fabric comprising bicomponent staple fibers having a polyethylene sheath and a polypropylene or polyethylene terephthalate core or mixtures thereof.

[0045] In some embodiments of the method, the non-cellulosic fibers are bicomponent staple fibers having a polyethylene sheath and a polypropylene or polyethylene terephthalate core or mixtures thereof.

[0046] In some embodiments of the method, the first layer comprises a carded nonwoven fabric comprising a bio-based polymer.

[0047] In some embodiments of the method, the non-cellulosic staple fibers of the airlaid nonwoven layer comprise a bio-based polymer.

[0048] In some embodiments of the method, the bio-based polymer comprises an aliphatic polyester, a bio-based polyethylene, a bio-based polypropylene, a bio-based polyester, such as bio-based polyethylene terephthalate (PET), or a combination thereof.

[0049] In some embodiments of the method, the aliphatic polyester comprises polylactic acid (PLA), polybutylene succinate (PBS), or a combination or blend thereof.

[0050] In some embodiments of the method, the composite sheet material has a basis weight of about 25 to 250 g / m 2 It is.

[0051] In some embodiments of the method, the bamboo-derived staple fibers have an average length of about 0.8 to about 3.0 mm and an average width of about 12 to about 22 microns.

[0052] In some embodiments of the method, the bamboo-derived staple fibers have a length to width ratio that is from about 60 to about 120.

[0053] In some embodiments of the method, the method further comprises the step of depositing a polymeric coating layer overlying the surface of the airlaid nonwoven layer, where the polymeric coating comprises ethylene vinyl acetate, ethylene acrylate, polyacrylate, phenylethylene butadiene, styrene butadiene acrylate, polyvinyl alcohol, a bio-based latex, or a mixture thereof.

[0054] In some embodiments of the method, the dry weight add-on of the polymeric coating is from about 1.5 to about 4 weight percent, based on the total weight of the composite sheet material.

[0055] In some embodiments of the method, the composite sheet material exhibits a thickness in the range of about 0.5 to about 3.0 mm, a CD stiffness in the range of about 5 to about 15 mN / cm, and a MD stiffness in the range of about 20 to about 50 mN / cm.

[0056] In some embodiments of the method, the composite sheet exhibits a wicking rate of about 30 to about 50 mm / 15 sec, and a vertical fluid wicking height of about 30 to about 70 mm.

[0057] In some embodiments of the method, the composite sheet exhibits a thickness in the range of about 1.25 to about 1.40 mm, a CD stiffness in the range of about 6 to about 14 mN / cm, a MD stiffness in the range of about 25 to about 40 mN / cm, a wicking rate of about 32 to about 40 mm / 15 sec, and a vertical fluid wicking height of about 35 to about 65 mm.

[0058] In some embodiments of the method, the composite sheet exhibits an increase in vertical wicking height in the range of 50-150% and an increase in wicking rate in the range of 40-120% compared to the same composite sheet material in which the airlaid nonwoven layer comprises staple fibers that include conventional wood pulp fibers instead of bamboo-derived staple fibers.

[0059] In some embodiments of the method, the composite sheet exhibits a reduction in MD stiffness in the range of 10-50%, and a reduction in CD stiffness in the range of 10-60%, as compared to the same composite sheet material in which the airlaid nonwoven layer comprises staple fibers that comprise conventional wood pulp fibers instead of bamboo-derived staple fibers.

[0060] In some embodiments of the method, the airlaid nonwoven comprises one or more airlaid layers, and at least one of the airlaid layers comprises a superabsorbent polymer.

[0061] In some embodiments of the method, the airlaid nonwoven layer is thermally bonded via an air-through bond, and the first layer is bonded to the overlying airlaid nonwoven layer via an air-through bond.

[0062] In a further aspect, an embodiment of the present invention is directed to an absorbent core for an absorbent article, the core comprising staple fibers derived from bamboo.

[0063] In one such aspect, the absorbent core comprises a first layer of fibers bonded together to form a coherent web; and an airlaid nonwoven layer overlying the first layer, where the airlaid nonwoven layer comprises a blend of bamboo-derived staple fibers and non-cellulosic staple fibers, the airlaid nonwoven layer having a first surface disposed against and thermally bonded to a surface of the first layer, and a second surface defining an outer surface of the composite sheet material.

[0064] In some aspects of the absorbent core, the first layer is selected from the group consisting of spunbond nonwovens, meltblown nonwovens, spunlace nonwovens, carded nonwovens, airlaid nonwovens, cellulosic tissue papers, and combinations thereof.

[0065] In some aspects of the absorbent core, the first layer comprises a carded nonwoven fabric including a plurality of staple fibers that are air-through bonded to one another to form an integral nonwoven fabric.

[0066] In some aspects of the absorbent core, the airlaid nonwoven layer comprises a plurality of airlaid layers that are thermally bonded to adjacent airlaid layers.

[0067] In some aspects of the absorbent core, the airlaid nonwoven fabric layer includes 2 to 10 airlaid layers, particularly 3 to 6 airlaid layers.

[0068] In some aspects of the absorbent core, the first layer comprises a carded nonwoven fabric comprising bicomponent staple fibers having a polyethylene sheath and a polypropylene or polyethylene terephthalate core, or mixtures thereof.

[0069] In some aspects of the absorbent core, the non-cellulosic fibers are bicomponent staple fibers having a polyethylene sheath and a polypropylene or polyethylene terephthalate core, or mixtures thereof.

[0070] In some aspects of the absorbent core, the first layer comprises a carded nonwoven fabric that includes a bio-based polymer.

[0071] In some aspects of the absorbent core, the non-cellulosic staple fibers of the airlaid nonwoven layer comprise a bio-based polymer.

[0072] In some aspects of the absorbent core, the bio-based polymer comprises an aliphatic polyester, a bio-based polyethylene, a bio-based polypropylene, a bio-based polyester such as bio-based polyethylene terephthalate (PET), or a combination thereof.

[0073] In some aspects of the absorbent core, the aliphatic polyester comprises polylactic acid (PLA), polybutylene succinate (PBS), or a combination or blend thereof.

[0074] In some aspects of the absorbent core, the basis weight of the composite sheet material is from about 25 to about 400 g / m 2 It is.

[0075] In some aspects of the absorbent core, the bamboo derived staple fibers have an average length of from about 0.8 to about 5.0 mm, for example, from about 1.0 to about 3.0 mm, and an average width of from about 12 to about 22 microns.

[0076] In some aspects of the absorbent core, the bamboo derived staple fibers have a length to width ratio that is from about 60 to about 120.

[0077] In some aspects of the absorbent core, the core exhibits a thickness in the range of about 0.5 to about 5.0 mm, e.g., about 0.5 to about 3.0 mm, a CD stiffness in the range of about 5 to about 15 mN / cm, and an MD stiffness in the range of about 20 to about 50 mN / cm.

[0078] In some aspects of the absorbent core, the core exhibits a wicking rate of about 30 to about 50 mm / 15 seconds and a vertical fluid wicking height of about 30 to about 70 mm.

[0079] In some aspects of the absorbent core, the core exhibits a thickness in the range of about 1.25 to about 1.40 mm, a CD stiffness in the range of about 6 to about 14 mN / cm, a MD stiffness in the range of about 25 to about 40 mN / cm, a wicking rate of about 32 to about 40 mm / 15 sec, and a vertical fluid wicking height of about 35 to about 65 mm.

[0080] In some aspects of the absorbent core, the core exhibits an increase in vertical wicking height in the range of 50-150% and an increase in wicking rate in the range of 40-120 compared to the same absorbent core material in which the airlaid nonwoven layer comprises staple fibers that include conventional wood pulp fibers instead of bamboo derived staple fibers.

[0081] In some aspects of the absorbent core, the core exhibits a reduction in MD stiffness in the range of 10-50% and a reduction in CD stiffness in the range of 10-60% when compared to the same absorbent core material in which the airlaid nonwoven layer comprises staple fibers that include conventional wood pulp fibers instead of bamboo-derived staple fibers.

[0082] In some aspects of the absorbent core, the airlaid nonwoven comprises one or more airlaid layers, and at least one of the airlaid layers comprises a superabsorbent polymer.

[0083] In some aspects of the absorbent core, the airlaid nonwoven layer is thermally bonded via an air-through bond, and the first layer is bonded to the overlying airlaid nonwoven layer via an air-through bond.

[0084] In some aspects of the absorbent core, the core comprises from about 10 to about 90 weight percent bamboo-derived staple fibers and from about 10 to about 90 weight percent staple fibers including conventional wood pulp fibers.

[0085] In some aspects of the absorbent core, the fibers of the core are adhered with a polymeric material including ethylene vinyl acetate, ethylene acrylate, polyacrylate, phenylethylene butadiene, styrene butadiene acrylate, polyvinyl alcohol, bio-based latex, or mixtures thereof.

[0086] In some aspects of the absorbent core, the add-on dry weight of the polymeric material is from about 1.5 to about 5 weight percent, based on the total weight of the absorbent core.

[0087] In some aspects of the absorbent core, the core further comprises a superabsorbent polymer.

[0088] In some aspects of the absorbent core, the basis weight of the composite sheet material is from about 25 to about 400 g / m 2 It is.

[0089] In some aspects of the absorbent core, the bamboo derived staple fibers have an average length of from about 0.8 to about 3.0 mm and an average width of from about 12 to about 22 microns.

[0090] In some aspects of the absorbent core, the bamboo derived staple fibers have a length to width ratio that is from about 60 to about 120.

[0091] In some aspects of the absorbent core, the absorbent core further comprises a tissue layer.

[0092] Having thus described the invention in general terms, reference is now made to the accompanying drawings, which are not necessarily drawn to scale, in which: [Brief description of the drawings]

[0093] [Figure 1] FIG. 1 is a cross-sectional side view of an airlaid nonwoven fabric in accordance with at least one embodiment of the present invention. [Diagram 2] FIG. 2 is a cross-sectional side view of an airlaid nonwoven fabric having multiple airlaid layers superimposed on one another. [Diagram 3] FIG. 3 is a composite sheet in accordance with at least one embodiment of the present invention. [Figure 4] FIG. 4 is a cross-sectional side view of a composite sheet in accordance with at least one embodiment of the present invention, where the composite sheet includes a plurality of airlaid layers. [Diagram 5] FIG. 5 is a cross-sectional side view of a composite sheet in accordance with at least one embodiment of the present invention, where the composite sheet includes a coating layer deposited on a surface of an outermost airlaid layer. [Figure 6A] FIG. 6A is a schematic diagram of a system for making a composite sheet in accordance with an embodiment of the present invention. [Figure 6B] FIG. 6B shows a schematic diagram of a forming head for preparing an airlaid layer in accordance with at least one embodiment of the present invention. [Figure 7] FIG. 7 is a cross-sectional side view of a composite sheet in accordance with at least one embodiment of the present invention, where the composite sheet includes a plurality of alternating ridges and channels formed on a surface of an outermost airlaid layer. [Figure 8] FIG. 8 illustrates the transport and distribution of fluid through a composite sheet material. [Figure 9] FIG. 9 is an illustration of an absorbent article in accordance with at least one embodiment of the present invention. [Figure 10] FIG. 10 is an illustration of an absorbent article in accordance with at least one embodiment of the present invention, where the absorbent article is in the form of a feminine sanitary pad. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0094] Detailed Description The present invention will now be more fully described hereinafter with reference to the accompanying drawings, in which some, but not all, embodiments of the present invention are shown. Indeed, these inventions may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein, but rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout. As used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural references unless the context clearly dictates otherwise.

[0095] definition

[0096] For purposes of this application, the following terms shall have the following meanings:

[0097] The term "fiber" refers to either a fiber having a finite length or a filament having an infinite length.

[0098] The term "staple fibers" refers to fibers having a finite length. Generally, staple fibers may have a length of about 2 to 200 millimeters (mm).

[0099] As used herein, the term "monocomponent" refers to fibers formed from one polymer or a single blend of polymers. Of course, this does not exclude fibers that have additives added for color, antistatic properties, lubricity, hydrophilicity, liquid repellency, etc.

[0100] As used herein, the term "multicomponent" refers to a fiber formed from at least two polymers (e.g., bicomponent fiber) extruded from separate extruders. The at least two polymers can each be the same or different from one another, or can be a blend of polymers. The polymers are arranged in substantially uniformly spaced individual zones across the cross section of the fiber. The components may be arranged in any desired configuration, such as sheath-core, side-by-side, segmented pie, island-in-the-sea, etc. Various methods for forming multicomponent fibers are described in U.S. Pat. No. 4,789,592 to Taniguchi et al., U.S. Pat. No. 5,336,552 to Strack et al., U.S. Pat. No. 5,108,820 to Kaneko et al., U.S. Pat. No. 4,795,668 to Kruege et al., U.S. Pat. No. 5,382,400 to Pike et al., U.S. Pat. No. 5,336,552 to Strack et al., and U.S. Pat. No. 6,200,669 to Marmon et al., which are incorporated by reference in their entireties herein. Multicomponent fibers having various irregular shapes are also described, for example, in U.S. Pat. No. 5,277,976 to Hogle et al., U.S. Pat. No. 5,162,074 to Hills, U.S. Pat. No. 5,466,410 to Hills, U.S. Pat. No. 5,069,970 to Largman et al., and U.S. Pat. No. 5,057,368 to Largman et al., which are incorporated by reference in their entireties herein.

[0101] As used herein, the terms "nonwoven," "nonwoven web," and "nonwoven fabric" refer to a structure or web of material formed without the use of a weaving or knitting process, which are intertwined but not in a discernible, repeating manner. Nonwoven webs have been formed in the past by a variety of conventional processes, such as the meltblown process, the spunbond process, and the staple fiber carding process.

[0102] As used herein, the term "carded fabric" refers to a nonwoven fabric that contains staple fibers that are aligned and oriented primarily in the machine direction using a carding process.

[0103] As used herein, the term "conventional pulp fibers" refers to cellulosic fibers typically derived from wood pulps, such as hardwood and softwood pulps, and does not include fibers derived from bamboo pulp.

[0104] As used herein, the term "meltblown" refers to a process in which fibers are formed by forcing a molten thermoplastic material through a plurality of thin, usually circular, die capillaries into a high velocity gas (e.g., air) stream that attenuates the molten thermoplastic material and forms fibers that can be made to microfiber diameters. The meltblown fibers are then carried by the gas stream and deposited on a collecting surface to form a web of random meltblown fibers. Such a process is disclosed, for example, in U.S. Patent No. 3,849,241 to Buntin et al.

[0105] As used herein, the term "machine direction" or "MD" refers to the direction of travel of a nonwoven web during manufacturing.

[0106] As used herein, the term "cross direction" or "CD" refers to the direction perpendicular to the machine direction and extending laterally across the width of the nonwoven web.

[0107] As used herein, the term "spunbond" refers to a process in which molten thermoplastic material is extruded as filaments from a plurality of thin, usually circular capillaries of a spinneret, which are then attenuated and stretched mechanically or pneumatically. The filaments are deposited on a collecting surface to form a web of randomly arranged, substantially continuous filaments that can then be bonded together to form an integral nonwoven fabric. The production of spunbond nonwoven webs is shown in patents such as U.S. Pat. Nos. 3,338,992; 3,692,613; 3,802,817; 4,405,297; and 5,665,300. Generally, these spunbonding processes include extruding filaments through a spinneret, quenching the filaments with an air stream to hasten the solidification of the molten filaments, applying draw tension to attenuate the filaments either by air pressure entraining them in the air stream or by winding them around mechanical draw rolls, depositing the drawn filaments on a foraminous collection surface to form a web, and bonding the web of loose filaments into a nonwoven fabric, which can be any thermal or chemical bonding process, typically thermal point bonding.

[0108] As used herein, the term "air through thermal bonding" includes passing the materials to be bonded, such as one or more fibrous webs, through a flow of heated gas, such as air, where the temperature of the heated gas is greater than the softening or melting temperature of at least one polymeric component of the materials to be bonded. Air through thermal bonding may also include passing the materials through a heated oven.

[0109] As used herein, the term "thermal point bonding" involves passing the material to be bonded, such as one or more fibrous webs, between a heated calender roll and an anvil roll, which is typically patterned so that the fabric is not bonded over its entire surface, but rather at discrete point bond sites.

[0110] As used herein, the term "polymer" generally includes, but is not limited to, homopolymers, copolymers (e.g., block copolymers, graft copolymers, random copolymers and alternating copolymers), terpolymers, and the like, as well as blends and modifications thereof. Moreover, unless otherwise limited, the term "polymer" is intended to include all possible geometric configurations of the material, such as those listed above, including isotactic, syndiotactic and random symmetries.

[0111] As used herein, the term "composite" can be a structure consisting of two or more layers bonded together, such as a film layer and a fiber layer or multiple fiber layers. The two layers of the composite structure may be bonded together such that a substantial portion of their common XY planar interface is bonded to one another.

[0112] Unless otherwise clear from the context, the term "about" encompasses values ​​within the standard measurement error range (e.g., SEM) of the stated value or a variation of ±0.5%, 1%, 5% or 10% from the specified value.

[0113] Embodiments of the present invention are directed to a sheet material comprising an airlaid nonwoven that is a blend of non-cellulosic staple fibers and bamboo-derived pulp fibers. Sheet materials according to one or more embodiments of the present invention are particularly useful in the manufacture of absorbent articles, particularly disposable feminine hygiene and incontinence products.

[0114] I. Airlaid nonwoven fabric

[0115] Referring to Figure 1, an airlaid nonwoven fabric is shown and generally designated by the reference numeral 2. The airlaid nonwoven fabric 2 includes a plurality of non-cellulosic staple fibers and bamboo-derived staple fibers blended in a monolayer 8. The monolayer 8 has an upper surface 4 and a lower surface 6. The non-cellulosic staple fibers and bamboo-derived staple fibers may be homogeneously blended or non-uniformly blended throughout the airlaid nonwoven fabric.

[0116] As described in more detail below, it has been discovered that airlaid nonwoven fabrics containing bamboo-derived staple fibers instead of conventional wood pulp fibers provide improvements in certain fluid handling properties as well as a reduction in the overall thickness of the airlaid nonwoven fabric compared to similarly prepared airlaid nonwoven fabrics containing conventional pulp fibers. In addition, airlaid nonwoven fabrics according to certain embodiments of the present invention exhibit improvements in softness compared to similarly prepared fabrics containing conventional pulp fibers. As such, airlaid nonwoven fabrics according to embodiments of the present invention are particularly useful in a variety of applications in the manufacture of absorbent articles. "Similarly prepared" or "similar airlaid nonwoven fabrics" means that the airlaid nonwoven fabrics have the same or substantially the same chemical properties and are processed under similar or identical processing conditions, except for the substitution of bamboo-derived staple fibers for conventional pulp fibers.

[0117] In some embodiments, airlaid nonwoven fabrics according to embodiments of the present invention exhibit a reduction in caliper in the range of 10-60%, particularly about 20-50%, and more particularly 25-45%, compared to a comparable airlaid nonwoven fabric, where the comparable airlaid nonwoven fabric comprises staple fibers that include conventional wood pulp fibers instead of bamboo-derived staple fibers.

[0118] In some embodiments, airlaid nonwoven fabrics according to embodiments of the invention exhibit a reduction in MD stiffness in the range of 10 to 50%, particularly about 15 to about 35%, and more particularly about 20 to about 30%, compared to a comparable airlaid nonwoven fabric, where the comparable airlaid nonwoven fabric comprises staple fibers that include conventional wood pulp fibers instead of bamboo-derived staple fibers.

[0119] In some embodiments, airlaid nonwoven fabrics according to embodiments of the invention exhibit a reduction in CD stiffness in the range of 10 to 60%, particularly about 20 to about 50%, and more particularly about 25 to about 45%, compared to a comparable airlaid nonwoven fabric, where the comparable airlaid nonwoven fabric comprises staple fibers that include conventional wood pulp fibers instead of bamboo-derived staple fibers.

[0120] Advantageously, a reduction in the stiffness of the airlaid nonwoven helps provide a reduction in overall stiffness in the absorbent article comprising the airlaid nonwoven, resulting in increased softness in the absorbent article. A reduction in thickness and an increase in softness are generally desirable because they help to improve the comfort and wearability of an absorbent article, as well as provide an article with improved discreetness.

[0121] Additionally, airlaid nonwoven fabrics according to certain embodiments of the present invention have been observed to exhibit improved softness (e.g., reduced stiffness) compared to similar airlaid nonwoven fabrics that include staple fibers that include conventional wood pulp fibers instead of bamboo-derived staple fibers.

[0122] Advantageously, these improvements associated with the use of bamboo-derived staple fibers are provided without significantly sacrificing other desirable fluid management properties of airlaid nonwovens, such as fluid acquisition time, fluid retention, and fluid absorption.

[0123] Additionally, airlaid nonwoven fabrics according to certain embodiments of the invention exhibit improved wicking properties (capillary action of fluid moving through the component) compared to similar airlaid nonwoven fabrics that contain staple fibers that include conventional wood pulp fibers instead of bamboo-derived staple fibers.

[0124] In some embodiments, airlaid nonwoven fabrics according to embodiments of the invention exhibit an increase in vertical wicking height in the range of 50 to 150%, particularly about 75 to about 140%, and more particularly about 90 to about 130%, compared to a comparable airlaid nonwoven fabric, where the comparable airlaid nonwoven fabric comprises staple fibers that include conventional wood pulp fibers instead of bamboo-derived staple fibers.

[0125] In certain embodiments, airlaid nonwoven fabrics according to the invention exhibit an increase in wicking rate in the range of 40-120%, particularly about 50-110%, and more particularly about 60-100%, compared to a comparable airlaid nonwoven fabric that includes staple fibers that include conventional wood pulp fibers instead of bamboo-derived staple fibers. In some embodiments, airlaid nonwoven fabrics according to embodiments of the invention exhibit an increase in wicking rate in the range of 75-95% compared to a comparable airlaid nonwoven fabric that includes staple fibers that include conventional wood pulp fibers instead of bamboo-derived staple fibers.

[0126] In some embodiments, the airlaid nonwoven may also include antimicrobial properties due to the naturally occurring antimicrobial agents present in bamboo.

[0127] The fibers of the airlaid nonwoven may be bonded to adjacent fibers using thermal, ultrasonic, mechanical, and adhesive bonds. In some embodiments, the airlaid layers may be bonded via hydrogen bonding. In some embodiments, the airlaid nonwoven fabric is thermally bonded by passing the airlaid nonwoven through a thermal bonding unit in which the airlaid nonwoven is subjected to a heated gas, e.g., air, at a temperature above the melting point of at least one polymeric material of the airlaid nonwoven. In a preferred embodiment, the airlaid nonwoven is passed through an air-through thermal bonding unit in which the flow of heated gas, e.g., air, is at a temperature above the softening or melting temperature of at least one polymeric component of the airlaid nonwoven.

[0128] In some embodiments, the fibers of the airlaid nonwoven may be bonded via thermal calendar bonding. In certain other embodiments, the fibers of the airlaid nonwoven are not subjected to thermal calendar bonding. In certain embodiments, the fibers of the airlaid nonwoven are not bonded via hydraulic entanglement, which is characterized by the absence of a hydraulic entanglement process in bonding the fibers.

[0129] In some embodiments, the airlaid nonwoven fabric 2 can include one or more airlaid layers. In this regard, FIG. 2 illustrates an embodiment of the invention in which the airlaid nonwoven fabric 2 includes multiple airlaid layers (layers 8a, 8b, and 8c) formed on top of one another. Preferably, each of the multiple airlaid layers is adjacent to and in direct contact with an immediately adjacent layer of the sheet material such that the adjacent layers are in fluid communication with one another. In embodiments including multiple airlaid nonwoven layers, adjacent layers can be bonded to one another using the bonding techniques previously discussed. Preferably, the multiple airlaid layers are thermally bonded to one another by passing the airlaid nonwoven fabric through an air-through bonding unit.

[0130] Typically, the airlaid nonwoven fabric has a density of about 25 to about 400 (g / m2), depending on the intended use. 2 In one embodiment, the airlaid nonwoven fabric has a basis weight in the range of about 40 to about 200 g / m 2 , more particularly about 50 to about 100 g / m 2 In a preferred embodiment, the airlaid nonwoven fabric has a basis weight ranging from about 35 to about 80 g / m 2 The sheet has a basis weight of 1.0 g.

[0131] The thickness of the airlaid nonwoven fabric may range from about 0.4 to about 4 mm, particularly from about 0.7 to about 3 mm, and more particularly from about 0.7 to about 2 mm. In a preferred embodiment, the airlaid nonwoven fabric has a thickness of about 0.8 to about 1.5 mm.

[0132] A. Staple fiber derived from bamboo

[0133] Bamboo-derived staple fibers can include treated and untreated bamboo pulp. Typical pulping methods for obtaining bamboo-derived staple fibers can include chemical pulping, chemi-mechanical pulping, thermo-mechanical pulping, and combinations thereof.

[0134] A wide variety of different bamboo species may be used. Both running bamboo and clumping bamboo may be utilized. In some embodiments, the bamboo-derived staple fibers may be derived from clumping bamboo.

[0135] Typically, bamboo-derived staple fibers for use in certain embodiments of the present invention exhibit an average length of 0.5 to 4.5 mm (e.g., 0.5 to 3 mm), particularly about 0.7 to about 2.5 mm, such as about 0.8 to about 2.2 mm, more particularly about 1.2 to about 2.0 mm. In a preferred embodiment, the bamboo-derived staple fibers exhibit an average length in the range of 1.6 to 1.8 mm.

[0136] In one embodiment, the bamboo-derived staple fibers exhibit a width (cross-sectional diameter) in the range of 10 to 30 microns, such as 10 to 26 microns, particularly from about 12 to about 22 microns, more particularly from about 14 to 20 microns. In a preferred embodiment, the bamboo-derived staple fibers exhibit a width in the range of 16 to 18 microns.

[0137] In some embodiments, the bamboo-derived staple fibers exhibit a length to width ratio that is about 130 to about 50, particularly about 120 to about 60 or about 110 to about 70, more particularly about 80 to about 100. In a preferred embodiment, the bamboo-derived staple fibers exhibit a length to width ratio that is about 92 to about 98.

[0138] The amount of bamboo-derived staple fibers in the airlaid nonwoven fabric is typically about 20 to about 95 weight percent, particularly about 30 to about 75 weight percent, based on the total weight of the airlaid nonwoven fabric. In a preferred embodiment, the amount of bamboo-derived staple fibers in the airlaid nonwoven fabric is about 40 to about 60 weight percent, based on the total weight of the airlaid nonwoven fabric.

[0139] In some embodiments, the cellulosic portion of the airlaid nonwoven fabric comprises 100% bamboo-derived staple fibers. In some embodiments, the cellulosic portion of the airlaid nonwoven fabric comprises at least 95% bamboo-derived staple fibers, such as 96%, at least 97%, at least 98%, or at least 99%.

[0140] B. Non-cellulosic Staple Fibers

[0141] The non-cellulosic staple fibers of the airlaid nonwoven typically have a length in the range of about 0.8 to about 15 mm, particularly about 3 to about 10 mm, and more particularly about 3 to about 6 mm.

[0142] Suitable materials for the non-cellulosic staple fibers for use in the airlaid nonwoven fabric can include monocomponent or multicomponent fibers, or a combination of monocomponent and multicomponent fibers. In a preferred embodiment, the non-cellulosic staple fibers of the airlaid nonwoven fabric comprise bicomponent fibers having a sheath / core configuration.

[0143] In one embodiment, the staple fiber comprises a bicomponent fiber having a sheath / core configuration. Examples of bicomponent fibers include side-by-side, islands-in-the-sea, and sheath / core configurations. Preferably, the fiber has a sheath / core structure, where the sheath comprises a first polymer component and the core comprises a second polymer component. In this configuration, the polymer of the first polymer component and the polymer of the second polymer component may be the same or different from each other. For example, in one embodiment, the sheath comprises a first polymer component and the core comprises a second polymer component, which may be different or the same as the first polymer component. In a preferred embodiment, the first polymer component and the second polymer component of the bicomponent fiber are different from each other.

[0144] In some embodiments, the staple fibers of the airlaid nonwoven may have a sheath / core configuration, where the core may be centrally located relative to the sheath. Alternatively, the core may be in an offset configuration relative to the sheath. As a result, when heat is applied, such as during bonding, the fibers may have a tendency to curl or crimp, which may help impart loft to the airlaid nonwoven.

[0145] In one embodiment, the first polymer component of the sheath comprises a polymer having a lower melting temperature than the melting temperature of the second polymer component comprising the core. The low melting point polymer of the sheath promotes adhesion, while the polymer component of the core having a higher melting temperature provides strength to the fibers and thus the final bonded nonwoven fabric.

[0146] In general, the weight percentage of the sheath to the weight percentage of the core in the fiber can vary widely depending on the desired properties of the nonwoven fabric. For example, the weight ratio of the sheath to the core can vary from about 10:90 to 90:10, particularly about 20:80 to 80:20. In a preferred embodiment, the weight ratio of the sheath to the core is about 60:40 to about 40:60, with a weight ratio of about 50:50 being preferred.

[0147] A wide variety of polymers can be used to make the non-cellulosic staple fibers for use in the airlaid nonwoven fabric. Examples of suitable fibers can include polyolefins, such as polypropylene and polyethylene and their copolymers, polyesters, such as polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT) and polybutylene terephthalate (PBT), nylon, polystyrene, copolymers, and blends thereof, as well as other synthetic polymers that can be used in the preparation of fibers. In one embodiment, the non-cellulosic staple fibers have a sheath / core configuration that includes a polyethylene sheath and a polypropylene core. In another embodiment, the staple fibers can have a sheath / core configuration that includes a polyethylene sheath and a polyester core, such as a core that includes polyethylene terephthalate.

[0148] In some embodiments, the non-cellulosic staple fibers may comprise a blend of fibers, such as a blend of bicomponent staple fibers having a polyethylene sheath and a polyethylene terephthalate core, where the bicomponent staple fibers have a polyethylene sheath and a polypropylene core. In one embodiment, the fibers of the airlaid nonwoven may comprise eccentric bicomponent staple fibers having a polyethylene sheath and a polyethylene terephthalate core, with a fineness of 4.3 dtex and an average length of 3 to 6 mm. An example of such a fiber is available from Indorama Polyester Industries Public Company Limited under the trade name TS47.

[0149] In one embodiment, the non-cellulosic staple fibers of the airlaid nonwoven fabric may include bicomponent staple fibers having a polyethylene sheath and a polyethylene terephthalate core. One such example is a bicomponent staple fiber having a fineness of 2.2 dtex and an average length of 3 mm, which is available from Toray Chemical Korea Inc. under the trade name EZBON A (UN-204). A further example is an eccentric bicomponent staple fiber having a polyethylene sheath and a polyethylene terephthalate core. Such fibers are available from Indorama Polyester Industries Public Company Limited under the trade name TS47 (fineness of 4.3 dtex and average length of 3 mm). Another example is a bicomponent staple fiber having a polyethylene sheath and a polyethylene terephthalate core, which is available from Trevira under the trade name T255 staple fiber. These staple fibers have a fineness of 4.3 dtex and an average length of 3 mm.

[0150] In another embodiment, the non-cellulosic staple fiber may comprise a bicomponent staple fiber having a polyethylene sheath and a polypropylene core. One such example is a staple fiber having a fineness of 4.0 dtex and an average length of 4 mm, which is available from Yangzhou Petrochemical Co. Ltd under the trade name Y116. Another example of a bicomponent staple fiber having a polyethylene sheath and a polypropylene core, a denier of 6.0 and an average length of 51 mm is available from JiangNan High Polymer Fiber under the trade name JNGX-PZ11-6*51L.

[0151] In some embodiments, the non-cellulosic fibers can include a blend of fibers, such as a blend including bicomponent PE / PET and PE / PP staple fibers.

[0152] The above-mentioned polymers are generally considered to be derived from synthetic sources, such as petroleum-derived polymers. In some embodiments, it may be desirable to provide an airlaid nonwoven fabric that includes one or more sustainable polymer components. In contrast to polymers derived from petroleum sources, sustainable polymers are generally derived from bio-based materials. In some embodiments, the sustainable polymer components are also considered to be biodegradable. A special class of biodegradable products made from bio-based materials are considered to be compostable if they are capable of being decomposed in a complex environment. The European standard EN 13432 "Proof of Compostability of Plastic Products" can be used to determine whether a fabric or film composed of sustainable content can be classified as compostable.

[0153] In one such embodiment, the airlaid nonwoven comprises non-cellulosic staple fibers that include a sustainable polymer. In some embodiments, the non-cellulosic staple fibers are substantially free of synthetic materials, such as petroleum-based materials and polymers. For example, the non-cellulosic staple fibers that comprise the airlaid nonwoven can have less than 25 weight percent non-biologically based materials, more preferably less than 20 weight percent, less than 15 weight percent, less than 10 weight percent, and even more preferably less than 5 weight percent non-biologically based materials, based on the total weight of the airlaid nonwoven.

[0154] In one embodiment, sustainable polymers for use can include aliphatic polyester-based polymers such as polylactic acid (PLA) and polybutylene succinate (PBS), and polyethylene of bio-based origin.

[0155] Aliphatic polyesters useful in the present invention may include homopolymers and copolymers of poly(hydroxyalkanoates) and those aliphatic polyesters derived from the reaction product of one or more polyols and one or more polycarboxylic acids, which are typically formed from the reaction product of one or more alkanediols and one or more alkanedicarboxylic acids (or acyl derivatives). Polyesters may also be derived from multifunctional polyols, such as glycerin, sorbitol, pentaerythritol, and combinations thereof, to form branched, star, and graft homopolymers and copolymers. Polyhydroxyalkanoates are generally formed from hydroxy acid monomer units or their derivatives. These include, for example, polylactic acid, polyhydroxybutyrate, polyhydroxyvalerate, polycaprolactone, and the like. Miscible and immiscible blends of aliphatic polyesters with one or more additional semicrystalline or amorphous polymers may also be used.

[0156] One useful class of aliphatic polyesters are the poly(hydroxyalkanoates) obtained by condensation or ring-opening polymerization of hydroxy acids, or derivatives thereof. Suitable poly(hydroxyalkanoates) may be represented by the formula: H(O--R--C(O)--). nOH, where R is an alkylene moiety having 1-20 carbon atoms, preferably 1-12 carbon atoms, which may be substituted by catenary oxygen atoms (attached to a carbon atom in the carbon chain), which may be linear or branched; n is a number such that the ester is polymerizable, preferably such that the molecular weight of the aliphatic polyester is at least 10,000 daltons, preferably at least 30,000 daltons, and most preferably at least 50,000 daltons. In some embodiments, the molecular weight of the aliphatic polyester is typically less than 1,000,000 daltons, preferably less than 500,000 daltons, and most preferably less than 300,000 daltons. R may further include one or more catenary (i.e. in-chain) ether oxygen atoms. In general, the R group of the hydroxy acid has pendant hydroxyl groups that are primary or secondary hydroxyl groups.

[0157] Useful poly(hydroxyalkanoates) include, for example, homopolymers and copolymers of poly(3-hydroxybutyrate), poly(4-hydroxybutyrate), poly(3-hydroxyvalerate), poly(lactic acid) (also known as polylactide), poly(3-hydroxypropanoate), poly(4-hydropentanoate), poly(3-hydroxypentanoate), poly(3-hydroxyhexanoate), poly(3-hydroxyheptanoate), poly(3-hydroxyoctanoate), polydioxanone, polycaprolactone, and polyglycolic acid (i.e., polyglycolide). Copolymers of two or more of the above hydroxy acids may also be used, such as poly(3-hydroxybutyrate-co-3-hydroxyvalerate), poly(lactate-co-3-hydroxypropanoate), poly(glycolide-co-p-dioxanone), and poly(lactic acid-co-glycolic acid). Blends of two or more of the poly(hydroxyalkanoates) may also be used, as well as blends with one or more semicrystalline or amorphous polymers and / or copolymers.

[0158] The aliphatic polyester may be a block copolymer of poly(lactic-co-glycolic acid). The aliphatic polyesters useful in the compositions of the present invention may include homopolymers, random copolymers, block copolymers, star-branched random copolymers, star-branched block copolymers, dendritic copolymers, hyperbranched copolymers, graft copolymers, and combinations thereof.

[0159] Another useful class of aliphatic polyesters includes those derived from the reaction product of one or more alkanediols with one or more alkanedicarboxylic acids (or acyl derivatives). Such polyesters have the general formula: [ka] wherein R' and R'' each represent an alkylene moiety which may be linear or branched having 1 to 20 carbon atoms, preferably 1 to 12 carbon atoms, and m is a number at which the ester is polymerizable, preferably such that the molecular weight of the aliphatic polyester is at least 10,000 daltons, preferably at least 30,000 daltons, and most preferably at least 50,000 daltons, but less than 1,000,000 daltons, preferably less than 500,000 daltons, and most preferably less than 300,000 daltons. Each n is independently 0 or 1. R' and R'' may further include one or more catenary (i.e., linear) ether oxygen atoms.

[0160] Examples of aliphatic polyesters include (a) one or more of the following diacids (or derivatives thereof): succinic acid; adipic acid; 1,12-dicarboxydodecane; fumaric acid; glutaric acid; diglycolic acid; and maleic acid; and (b) one or more of the following diols: ethylene glycol; polyethylene glycol; 1,2-propanediol; 1,3-propanediol; 1,2-propanediol; 1,2-butanediol; 1,3-butanediol; 1,4-butanediol; 2,3-butanediol; 1,6-hexanediol; 1,2-alkanediols having 5 to 12 carbon atoms; diethylene glycol; 300 polyethylene glycols having a molecular weight of from 400 to 8,000 daltons; propylene glycols having a molecular weight of from 300 to 4,000 daltons; block or random copolymers derived from ethylene oxide, propylene oxide or butylene oxide; dipropylene glycol; and polypropylene glycol, and (c) optionally, homopolymers and copolymers derived from minor amounts, i.e., 0.5 to 7.0 mole percent, of polyols having a functionality greater than 2, such as glycerol, neopentyl glycol and pentaerythritol.

[0161] Such polymers may include polybutylene succinate homopolymer, polybutylene adipate homopolymer, polybutylene adipate-succinate copolymer, polyethylene succinate-adipate copolymer, polyethylene glycol succinate homopolymer, and polyethylene adipate homopolymer.

[0162] Commercially available aliphatic polyesters include poly(lactide), poly(glycolide), poly(lactide-co-glycolide), poly(L-lactide-co-trimethylene carbonate), poly(dioxanone), poly(butylene succinate), and poly(butylene adipate).

[0163] The term "aliphatic polyester" includes, in addition to polyesters made exclusively from aliphatic and / or cycloaliphatic components, also polyesters which contain aromatic units in addition to aliphatic and / or cycloaliphatic units, so long as the polyesters have a substantially sustainable content.

[0164] In addition to PLA-based resins, nonwoven fabrics according to embodiments of the invention may include other polymers derived from aliphatic components having one carboxylic acid group and one hydroxyl group, alternatively referred to as polyhydroxyalkanoates (PHAs). Examples are polyhydroxybutyrate (PHB), poly-(hydroxybutyrate-co-hydroxyvaleterate) (PHBV), poly-(hydroxybutyrate-co-polyhydroxyhexanoate) (PHBH), polyglycolic acid (PGA), poly-(epsilon-caprolactone) (PCL), and preferably polylactic acid (PLA).

[0165] Examples of additional polymers that may be used in embodiments of the invention include polymers derived from a combination of an aliphatic component having two carboxylic acid groups and an aliphatic component having two hydroxyl groups, as well as polyesters derived from aliphatic diols and from aliphatic dicarboxylic acids, such as polybutylene succinate (PBSU), polyethylene succinate (PESU), polybutylene adipate (PBA), polyethylene adipate (PEA), and polytetramethylene adipate / terephthalate (PTMAT).

[0166] Useful aliphatic polyesters include aliphatic polyesters derived from semicrystalline polylactic acid. Poly(lactic acid) or polylactide (PLA) has lactic acid as its main degradation product, which is commonly found in nature, is non-toxic, and is widely used in the food, pharmaceutical, and medical industries. The polymer can be prepared by ring-opening polymerization of lactide, a dimer of lactic acid. Lactic acid is optically active, and the dimer appears in four different forms: L,L-lactide, D,D-lactide, D,L-lactide (mesolactide), and a racemic mixture of L,L- and D,D-. By polymerizing these lactides as pure compounds or blends, poly(lactide) polymers with different stereochemical properties and different physical properties, such as those mentioned above, including crystallinity, can be obtained. L,L- or D,D-lactide gives semicrystalline poly(lactide), while poly(lactide) obtained from D,L-lactide is amorphous.

[0167] Typically, polylactic acid-based polymers are prepared from dextrose, a sugar source obtained from field corn. In North America, corn is used because it is the most economical source of plant starch for ultimate conversion to sugar. However, it should be recognized that dextrose can be obtained from sources other than corn. Sugars are converted to lactic acid or lactic acid derivatives via fermentation through the use of microorganisms. The lactic acid can then be polymerized to form PLA. In addition to corn, other agriculturally derived sugar sources may be used, including rice, sugar beet, sugar cane, wheat, cellulosic materials such as xylose recovered from wood pulping, etc.

[0168] The polylactide preferably has a high enantiomeric ratio to maximize the inherent crystallinity of the polymer. The crystallinity of poly(lactic acid) is based on the regularity of the polymer backbone and its ability to crystallize with other polymer chains. When a relatively small amount of one enantiomer (e.g., D-) is copolymerized with the opposite enantiomer (e.g., L-), the polymer chain becomes irregularly shaped and the crystallinity decreases. For these reasons, when crystallinity is preferred, polylactic acid that is at least 85% of one isomer, at least 90% of one isomer, or at least 95% of one isomer is desirable to maximize the crystallinity.

[0169] In some embodiments, a near equimolar blend of D- and L-polylactide is also useful, which forms a unique crystalline structure that has a higher melting point (about 210° C.) than either D-poly(lactide) or L-poly(lactide) alone (about 190° C.), and has improved thermal stability.

[0170] Copolymers, including block and random copolymers, of poly(lactic acid) with other aliphatic polyesters may also be used. Useful comonomers include glycolide, beta-propiolactone, tetramethylglycolide, beta-butyrolactone, gamma-butyrolactone, pivalolactone, 2-hydroxybutyric acid, alpha-hydroxyisobutyric acid, alpha-hydroxyvaleric acid, alpha-hydroxyisovaleric acid, alpha-hydroxycaproic acid, alpha-hydroxyethylbutyric acid, alpha-hydroxyisocaproic acid, alpha-hydroxy-beta-methylvaleric acid, alpha-hydroxyoctanoic acid, alpha-hydroxydecanoic acid, alpha-hydroxymyristic acid, and alpha-hydroxystearic acid.

[0171] Blends of poly(lactic acid) with one or more other aliphatic polyesters or one or more other polymers may also be used. Examples of useful blends include poly(lactic acid) with polyvinyl alcohol, polyethylene glycol / polysuccinate, polyethylene oxide, polycaprolactone, and polyglycolide.

[0172] In some preferred embodiments, the aliphatic polyester component comprises a PLA-based resin. A wide variety of different PLA resins can be used to prepare nonwoven fabrics according to embodiments of the present invention. The PLA resin should have suitable molecular properties to be spun in a spunbond process. Suitable examples include PLA resins such as grades 6752D, 6100D and 6202D, supplied by NatureWorks LLC, Minnetonka, Minn. 55345, which are believed to be produced generally in accordance with the teachings of U.S. Patent No. 5,525,706 to Gruber et al. and U.S. Patent No. 6,807,973 to Gruber et al. Other examples of suitable PLA resins include L130, L175 and LX175, all of which are available from Corbion of Arkelsedijk 46, 4206 AC Gorinchem, the Netherlands.

[0173] In some embodiments, the non-cellulosic staple fibers have a sheath / core configuration, where both the sheath and the core comprise PLA resin. In these embodiments, an airlaid nonwoven fabric can be provided that is substantially free of synthetic polymeric components, such as petroleum-based materials and polymers. For example, the non-cellulosic staple fibers of the airlaid nonwoven fabric can have a bicomponent configuration in which both components are PLA-based, thereby producing a staple fiber that is 100% PLA. As used herein, "100% PLA" can also include up to 5% additives, including, by way of example only, additives and / or additive masterbatches to provide color, softness, slip, antistatic, lubricity, hydrophilicity, liquid repellency, antioxidant protection, and the like. In this regard, the non-cellulosic staple fibers may comprise 95-100% PLA, e.g., 96-100% PLA, 97-100% PLA, 98-100% PLA, 99-100% PLA, etc. When such additives are added as a masterbatch, the masterbatch carrier may comprise primarily PLA, e.g., to facilitate processing and maximize sustainable content in the fiber. For example, the non-cellulosic staple fibers of the airlaid nonwoven may include one or more additional additives. In such embodiments, for example, the additives may include at least one of a colorant, a softener, a slip agent, an antistatic agent, a lubricant, a hydrophilic agent, a liquid repellent agent, an antioxidant, and the like, or any combination thereof.

[0174] In one embodiment, the sheath PLA polymer may be the same PLA polymer as the core PLA polymer. In another embodiment, the sheath PLA polymer may be a different PLA polymer than the core PLA polymer. For example, the bicomponent staple fiber may include a PLA / PLA bicomponent fiber in which the sheath includes a first PLA grade, and the core includes a second PLA grade, the first PLA grade and the second PLA grade being different (e.g., the first PLA grade has a lower melting point than the second PLA grade). By way of example only, the first PLA grade may include up to about 5% crystallinity, and the second PLA grade may include about 40% to about 50% crystallinity.

[0175] In some embodiments, for example, the first PLA grade can include a melting point of about 125° C. to about 135° C., and the second PLA grade can include a melting point of about 155° C. to about 170° C. In further embodiments, for example, the first PLA grade can include a weight percent of the D isomer of about 4 to about 10 wt %, and the second PLA grade can include a weight percent of the D isomer of about 2 wt %.

[0176] For example, in one embodiment, the core can comprise PLA with a lower D% isomer of polylactic acid than the D% isomer of the PLA polymer used in the sheath.The PLA polymer with a lower D% isomer exhibits a higher degree of stress-induced crystallization during spinning, while the PLA polymer with a higher D% isomer remains more amorphous during spinning.The more amorphous sheath promotes adhesion, while the core with a higher degree of crystallization provides strength to the fiber and thus to the final bonded web.In one particular embodiment, Nature Works PLA Grade 6752 with 4% D isomer can be used as the sheath, while Nature Works Grade 6202 with 2% D isomer can be used as the core.

[0177] In some embodiments, the airlaid nonwoven fabrics of the present invention may comprise a biodegradable sustainable polymer component derived from an aliphatic component having one carboxylic acid group (or a polyester-forming derivative thereof, such as an ester group) and one hydroxyl group (or a polyester-forming derivative thereof, such as an ether group); or from a combination of an aliphatic component having two carboxylic acid groups (or a polyester-forming derivative thereof, such as an ester group) and an aliphatic component having two hydroxyl groups (or a polyester-forming derivative thereof, such as an ether group); or from a combination of an aliphatic component having two carboxylic acid groups (or a polyester-forming derivative thereof, such as an ester group) and an aliphatic component having two hydroxyl groups (or a polyester-forming derivative thereof, such as an ether group).

[0178] Additional non-limiting examples of biobased polymers include polymers produced directly from organisms, such as polyhydroxyalkanoates (e.g., poly(beta-hydroxyalkanoates), poly(3-hydroxybutyrate-co-3-hydroxyvalerate), NODAX 商標), and bacterial cellulose; polymers extracted from plants and biomass, such as polysaccharides and their derivatives (e.g., gums, cellulose, cellulose esters, chitin, chitosan, starch, chemically modified starches), proteins (e.g., zein, whey, gluten, collagen), lipids, lignin, and natural rubber; and modern polymers derived from naturally occurring monomers and their derivatives, such as bio-polyethylene, bio-polypropylene, polytrimethylene terephthalate, polylactic acid, nylon 11, alkyd resins, succinic acid-based polyesters, and bio-polyethylene terephthalate.

[0179] In some embodiments, the non-cellulosic staple fibers may comprise a bio-based polymer, including bio-based polyethylene derived from biological sources. For example, bio-based polyethylene can be prepared from sugars that are fermented to produce ethanol, which is then dehydrated to provide ethylene. An example of a suitable sugar cane-derived polyethylene is available from Braskem SA under the product name PE SHA7260.

[0180] In some embodiments of the non-cellulosic staple fibers, the sheath may include a bio-based polyethylene and the core may include a PLA polymer.

[0181] In some embodiments, the sheath may include a PLA or PBS polymer, and the core may include a synthetic polymer, such as polypropylene.

[0182] In some embodiments, the non-cellulosic staple fibers may include one or more additives that are blended with one or more polymers during the melt extrusion step. Examples of suitable additives include molecular filters and / or substrate filters, such as zeolites, ion exchange particles, activated carbon, and the like, colorants, such as pigments (e.g., TiO 2), UV stabilizers, hydrophobizing agents, hydrophilizing agents, antistatic agents, elastomers, compatibilizers, antioxidants, antiblocking agents, slip agents, optical brighteners, flame retardants, antimicrobial agents, such as copper oxide and zinc oxide.

[0183] In some embodiments, the bamboo-derived staple fibers may also be blended with staple fibers, including conventional pulp fibers, In such applications, the content of conventional wood pulp fibers may be 80% or less based on the total weight of pulp fibers in the airlaid layer (e.g., the combined content of bamboo-derived staple fibers and conventional pulp fibers).

[0184] Additional examples of conventional wood pulp fibers include pulps prepared from various pulping processes, such as kraft pulp, sulfite pulp, thermo-mechanical pulp, etc. Conventional wood pulp fibers include treated and untreated pulps. Examples of conventional wood pulp fibers can include softwood fibers having an average fiber length of greater than 1 millimeter (mm), particularly from about 2 mm to about 5 mm. Such softwood fibers can include, but are not limited to, northern softwood, southern softwood, redwood, red cedar, hemlock, pine (e.g., southern pines), spruce (e.g., black spruce), combinations thereof, and the like. Exemplary commercially available conventional wood pulp fibers suitable in the present invention include those available from Georgia Pacific under the trade name 4722. Hardwood fibers, such as eucalyptus, maple, birch, aspen, and the like, can also be used as conventional pulp fibers. In certain instances, secondary fibers obtained from recycled sources, such as fiber pulp, such as newsprint, recycled paperboard, and office waste, can be used.

[0185] In some embodiments, the airlaid nonwoven fabric may include a superabsorbent polymer or superabsorbent fiber mixed with bamboo-derived staple fibers and non-cellulosic fibers. When present, the superabsorbent polymer may be in the form of fibers, particles, gels, etc. Generally speaking, a superabsorbent material is a water-swellable material that can absorb at least about 10 times its weight, and in some cases at least about 30 times its weight, in an aqueous solution containing 0.9 weight percent sodium chloride. Superabsorbents may be formed from natural polymers, synthetic polymers, and modified natural polymers and materials. Examples of synthetic superabsorbent polymers include poly(acrylic acid) and poly(methacrylic acid), poly(acrylamide), poly(vinyl ether), copolymers of maleic anhydride with ethers and alpha-olefins, poly(vinylpyrrolidone), poly(vinylmorpholinone), poly(vinyl alcohol), and mixtures and copolymers thereof. Further superabsorbents include natural and modified natural polymers such as hydrolyzed acrylonitrile-grafted starch, acrylic acid grafted starch, methylcellulose, chitosan, carboxymethylcellulose, hydroxypropylcellulose, and natural gums such as alginates, xanthan gum, locust bean gum, and the like. Mixtures of natural and wholly or partially synthetic superabsorbent polymers may also be useful in the present invention. Particularly suitable superabsorbent polymers are HYSORB 8800AD available from BASF (Charlotte, NC) and FAVOR SXM 9300 available from Degrussa Superabsorber (Greensboro, NC). When a natural superabsorbent is present, it may comprise 100% of the superabsorbent or may be blended with a synthetic superabsorbent.

[0186] In embodiments in which the airlaid layer comprises multiple airlaid nonwoven layers, the superabsorbent polymer or fiber may be present in only one layer of the airlaid nonwoven, or may be present in multiple airlaid layers of the airlaid nonwoven. When present, the superabsorbent polymer or fiber may be present in an amount of about 5 to about 50 weight percent, particularly about 10 to about 10 weight percent, based on the total weight of the airlaid nonwoven layer in which the superabsorbent polymer or fiber is present.

[0187] Certain embodiments of the airlaid nonwoven fabrics according to the present invention are particularly useful in the manufacture of composite sheet materials and laminates. In particular, airlaid nonwoven fabrics according to one or more embodiments of the present invention may be combined with one or more additional layers to provide composite sheet materials that are particularly useful in the manufacture of absorbent articles. Examples of additional layers that may be combined with the airlaid nonwoven fabrics of the present invention include nonwoven fabrics, such as spunbond, meltblown, spunlace, airlaid, and carded fabrics; tissue layers, such as bamboo tissue layers and film layers; and combinations thereof.

[0188] In certain embodiments, the airlaid nonwoven fabrics of the present invention are particularly useful as components in acquisition / distribution layers or as absorbent cores in absorbent articles.

[0189] II. Fluid Transfer Layer of the Absorbent Article

[0190] In some embodiments, airlaid nonwoven fabrics according to embodiments of the present invention are particularly useful as fluid transfer layers in absorbent articles. Advantageously, the transfer layer serves to provide controlled transfer of fluid from a topsheet to the core. In particular, the transfer layer serves to provide temporary storage capacity for the fluid prior to transfer to the core.

[0191] In some embodiments, the transfer layer comprises an acquisition / distribution layer (AQDL) component in the manufacture of absorbent articles. The fluid AQDL component generally comprises a composite sheet material comprising an airlaid nonwoven of the present invention in combination with one or more additional layers, such as a carded nonwoven layer. In some embodiments, the additional layer may be selected from the group consisting of nonwovens, such as spunbond nonwovens, spunlace nonwovens, meltblown nonwovens, and carded nonwovens; films; and cellulosic tissue paper.

[0192] Referring to Figure 3, a composite sheet material in accordance with at least one embodiment of the present invention is shown and designated by the reference numeral 10. In the embodiment shown, the sheet material 10 comprises a fluid acquisition component 12 and an airlaid component 14 overlying the fluid acquisition component. The airlaid component 14 is in accordance with at least one embodiment of the present invention and comprises a blend of non-cellulosic staple fibers and bamboo-derived staple fibers. Examples of non-cellulosic staple fibers and bamboo-derived staple fibers are discussed above in connection with the airlaid nonwoven fabrics of the present invention.

[0193] In one embodiment, the fluid acquisition component includes at least one nonwoven layer having a first outer surface 16 and a second outer surface 18. Similarly, the airlaid component includes a first outer surface 20 and a second outer surface 22.

[0194] In one embodiment, the exterior surface 18 of the fluid acquisition component 12 is disposed adjacent to and opposite the exterior surface 20 of the airlaid component 14. In a preferred embodiment, the opposing exterior surfaces 18 and 20 of the fluid distribution component 12 and the airlaid nonwoven component 14 are disposed directly opposite one another such that the surfaces of each component contact one another.

[0195] In some embodiments, the airlaid nonwoven component 14 may comprise one or more airlaid layers. In this regard, Figure 4 illustrates an embodiment of the invention in which the airlaid component comprises multiple airlaid layers formed on a fluid acquisition component 12. Preferably, each of the multiple airlaid layers is adjacent to and in direct contact with an immediately adjacent layer of the airlaid component such that adjacent layers are in fluid communication with one another.

[0196] In some embodiments, both the non-cellulosic staple fibers of the airlaid component and at least a portion of the fibers of the fluid acquisition component include compatible polymers to help promote adhesion of the fibers in the two components to one another.

[0197] Typically, a fluid AQDL component must balance properties to quickly move fluid away from the wearer's skin and distribute it evenly within the absorbent core of an absorbent article. If the fluid is transported through the AQDL component too quickly, it may not distribute laterally (in the xy direction) through the layer. As a result, the fluid may become too localized in one area of ​​the absorbent core. Ideally, it is desirable for the fluid to move quickly through the fluid AQDL component while at the same time distributing the fluid laterally through the component. This allows the fluid to be absorbed over a large surface area of ​​the absorbent core.

[0198] To achieve this desired balance, it is important that the fluidic AQDL component has good fluid transport properties, good wicking properties (capillary action of fluid moving through the component), low fluid acquisition time (the length of time it takes for a material to absorb a given amount of fluid), and good fluid retention properties. The first three properties contribute to how quickly fluid moves from the wearer's skin into the absorbent core, and fluid retention properties help balance these properties to allow the fluid to be distributed laterally before transporting into the absorbent core.

[0199] Absorbent articles, such as femcare products, diapers and incontinence products, are typically intended to be worn by an individual, so the comfort of the material for the wearer is also important. If the material is not flexible, stiff or rigid, the wearer will most likely reject the absorbent article. It is therefore desirable for the absorbent article to provide a balance of the above-mentioned properties, as well as be elastic to provide the wearer with improved comfort and fit.

[0200] The inventors of the present invention have found that composite sheets according to the present invention provide a good balance of fluid absorbency, fluid wicking, fluid acquisition time, and fluid retention, as well as provide composite sheets with good flexibility, elasticity, and reduced thickness. As a result, composite sheet materials according to embodiments of the present invention are particularly useful as fluid AQDL components in the manufacture of absorbent articles.

[0201] In particular, composite sheet materials comprising the airlaid nonwoven fabric of the present invention exhibit a reduction in caliper, improved wicking capabilities, and increased softness compared to similar composite sheets comprising an airlaid nonwoven fabric having staple fibers that comprise conventional wood pulp fibers instead of bamboo-derived staple fibers.

[0202] Surprisingly, composite sheets according to embodiments of the present invention exhibit reduced caliper compared to similar composite sheets having fibers that include conventional wood pulp fibers, without significantly sacrificing the fluid retention properties of the composite sheet. Typically, for a given basis weight, one skilled in the art would expect that a reduction in caliper of the AQDL component would also result in a reduction in fluid retention because the voids between the fibers would be reduced. In contrast to this expectation, the inventors have discovered that the use of bamboo-derived staple fibers in place of fibers that include conventional wood pulp fibers provides a reduction in caliper in the range of 10-75%, without significantly sacrificing the fluid retention properties of the AQDL component.

[0203] In some embodiments, composite sheet materials according to embodiments of the present invention (i.e., comprising at least one airlaid nonwoven comprising bamboo-derived staple fibers) exhibit a reduction in caliper in the range of about 10 to about 60%, particularly about 20 to about 50%, and more particularly about 25 to about 45%, compared to a similar composite sheet in which the airlaid nonwoven component comprises staple fibers comprising conventional wood pulp fibers instead of the bamboo-derived staple fibers.

[0204] In some embodiments, the composite sheet material exhibits a thickness of any one of less than 2.0 mm, less than 1.95 mm, less than 1.90 mm, less than 1.85 mm, less than 1.80 mm, less than 1.75 mm, less than 1.70 mm, less than 1.65 mm, less than 1.60 mm, less than 1.55 mm, less than 1.50 mm, less than 1.45 mm, less than 1.40 mm, less than 1.35 mm, less than 1.30 mm, less than 1.25 mm, less than 1.20 mm, less than 1.15 mm, less than 1.10 mm, and less than 1.05 mm. In some embodiments, the composite sheet material has a thickness in the range of about 1.0 to about 2.0 mm, about 1.1 to about 1.9 mm, about 1.2 to about 1.3 mm, and about 1.25 to about 1.40 mm.

[0205] In some embodiments, composite sheet materials according to embodiments of the present invention exhibit a reduction in MD stiffness in the range of about 10 to about 50%, particularly about 15 to about 35%, and more particularly about 20 to about 30%, compared to a similar composite sheet comprising an airlaid nonwoven comprising staple fibers that comprise conventional wood pulp fibers instead of bamboo-derived staple fibers.

[0206] In one embodiment, a composite sheet material according to one or more embodiments of the present invention may exhibit a MD stiffness of less than 46 mN / cm, less than 44 mN / cm, less than 42 mN / cm, less than 40 mN / cm, less than 38 mN / cm, less than 36 mN / cm, less than 34 mN / cm, less than 32 mN / cm, less than 30 mN / cm, less than 28 mN / cm, less than 26 mN / cm, less than 24 mN / cm, less than 22 mN / cm, and less than 20 mN / cm. In some embodiments, the composite sheet material may exhibit a MD stiffness in the range of about 20 to about 50 mN / cm, such as about 25 to about 40 mN / cm, and about 28 to about 36 mN / cm. In one particular embodiment, the composite sheet material may exhibit a MD stiffness in the range of 25 to 40 mN / cm.

[0207] In some embodiments, composite sheet materials according to embodiments of the present invention exhibit a reduction in CD stiffness in the range of 10 to 60%, particularly about 20 to about 50%, and more particularly about 25 to about 45%, as compared to a similar composite sheet comprising an airlaid nonwoven comprising staple fibers that comprise conventional wood pulp fibers instead of bamboo-derived staple fibers.

[0208] In one embodiment, a composite sheet material according to one or more embodiments of the present invention may exhibit a CD stiffness of less than 15 mN / cm, less than 14 mN / cm, less than 13 mN / cm, less than 12 mN / cm, less than 11 mN / cm, less than 10 mN / cm, less than 9 mN / cm, less than 8 mN / cm, less than 7 mN / cm, less than 6 mN / cm, and less than 5 mN / cm. In some embodiments, the composite sheet material may exhibit a CD stiffness in the range of about 5 to about 15 mN / cm, such as about 6 to about 14 mN / cm, about 7 to 12 mN / cm, or 8 to 11 mN / cm.

[0209] Advantageously, a reduction in the stiffness of the composite sheet material helps provide a reduction in overall stiffness in an absorbent article including the composite sheet material, resulting in increased softness in the absorbent article. A reduction in thickness and an increase in softness are generally desirable because they help improve the comfort and wearability of the absorbent article, as well as provide an article with improved discreetness.

[0210] Additionally, composite sheet materials according to certain embodiments of the present invention have been observed to exhibit improved softness (e.g., reduced stiffness) as compared to similar composite sheet materials in which the airlaid nonwoven component includes staple fibers that include conventional wood pulp fibers instead of the bamboo-derived staple fibers.

[0211] Advantageously, these improvements associated with the use of bamboo-derived staple fibers are provided without significantly sacrificing other desirable fluid management properties of the composite sheet material, such as fluid acquisition time, fluid retention, fluid absorption, and fluid capacity.

[0212] Additionally, composite sheet materials according to certain embodiments of the present invention exhibit improved wicking properties (capillary action of fluid moving through the components) compared to similar composite sheet materials in which the airlaid nonwoven component includes conventional wood pulp staple fibers instead of bamboo-derived staple fibers.

[0213] In some embodiments, composite sheet materials according to embodiments of the present invention exhibit an increase in vertical wicking height in the range of about 50 to about 150%, particularly about 75 to about 140%, and more particularly about 90 to about 130%, as compared to a similar composite sheet material in which the airlaid nonwoven component comprises staple fibers that include conventional wood pulp fibers instead of the bamboo-derived staple fibers.

[0214] In certain embodiments, composite sheet materials according to embodiments of the invention exhibit an increase in wicking rate in the range of about 40 to about 120%, particularly about 50 to about 110%, and more particularly about 60 to about 100%, compared to a similar composite sheet material in which the airlaid nonwoven component comprises staple fibers that include conventional wood pulp fibers instead of bamboo-derived staple fibers. In some embodiments, composite sheet materials according to embodiments of the invention exhibit an increase in wicking rate in the range of 75 to 95% compared to a similar composite sheet material in which the airlaid nonwoven component comprises staple fibers that include conventional wood pulp fibers instead of bamboo-derived staple fibers.

[0215] In one embodiment, composite sheet materials according to embodiments of the invention exhibit wicking speeds of at least 30 mm / 15 sec, at least 32 mm / 15 sec, at least 34 mm / 15 sec, at least 36 mm / 15 sec, at least 38 mm / 15 sec, at least 40 mm / 15 sec, at least 42 mm / 15 sec, at least 44 mm / 15 sec, and at least 46 mm / 15 sec. In some embodiments, composite sheet materials according to embodiments of the invention exhibit wicking speeds of about 30 to about 50 mm / 15 sec, e.g., about 32 to about 40 mm / 15 sec, or about 34 to about 38 mm / 15 sec.

[0216] In one embodiment, a composite sheet material according to an embodiment of the invention exhibits a vertical wicking height of at least 30 mm, at least 32 mm, at least 34 mm, at least 36 mm, at least 38 mm, at least 40 mm, at least 42 mm, at least 44 mm, at least 46 mm, at least 48 mm, at least 50 mm, at least 52 mm, at least 54 mm, at least 56 mm, at least 58 mm, at least 60 mm, at least 62 mm, at least 64 mm, at least 66 mm, at least 68, or at least 70 mm. In some embodiments, a composite sheet material according to an embodiment of the invention exhibits a vertical wicking height of about 30 to about 70 mm, e.g., about 35 to about 65 mm, or about 40 to about 60 mm.

[0217] In one aspect, a composite sheet according to an embodiment of the present invention is characterized by a thickness in the range of about 1.0 to about 2.0 mm, a CD stiffness in the range of about 5 to 15 mN / cm, and a MD stiffness in the range of about 20 to about 50 mN / cm. In a further aspect, the composite sheet may also be characterized by a wicking rate of about 30 to about 50 mm / 15 sec, and a vertical wicking height of about 30 to about 70 mm.

[0218] In one aspect, a composite sheet according to an embodiment of the present invention is characterized by a thickness in the range of about 1.25 to about 1.40 mm, a CD stiffness in the range of about 6 to about 14 mN / cm, and a MD stiffness of about 25 to about 40 mN / cm. In a further aspect, the composite sheet may also be characterized by a wicking rate of about 32 to about 40 mm / 15 sec, and a vertical wicking height of about 35 to about 65 mm.

[0219] In one aspect, composite sheets according to certain embodiments of the present invention are characterized by a fluid acquisition time ranging from about 0.75 seconds to about 2 seconds, particularly from about 0.8 to about 1.5 seconds, and more particularly from about 0.84 to about 1.3 seconds.

[0220] In one aspect, composite sheets according to some embodiments of the present invention are characterized by a fluid absorption in the range of from about 15 to about 30 g / g, particularly from about 20 to about 26 g / g, and especially from about 20 to about 25 g / g.

[0221] In one aspect, composite sheets according to some embodiments of the present invention are characterized by a fluid retention in the range of about 8 to about 15 g / g, particularly about 9 to about 14 g / g, and more particularly about 10 to about 12 g / g.

[0222] In one aspect, composite sheets according to certain embodiments of the present invention are characterized by a vertical fluid wicking height in the range of about 10 to about 50 mm, particularly about 15 to about 45 mm, and more particularly about 15 to about 40 mm.

[0223] In one aspect, composite sheets according to certain embodiments of the present invention are characterized by a resiliency in the range of about 30 to about 60%, particularly about 35 to about 55%, and more particularly about 40 to about 50%.

[0224] In one embodiment, the composite sheet according to the present invention is characterized by a fluid acquisition time in the range of about 0.5 seconds to about 2 seconds, a fluid absorption in the range of about 15 to about 30 g / g, a fluid retention in the range of about 8 to about 15 g / g, a fluid wicking height in the range of about 10 to about 50 mm, and a recovery force in the range of about 30 to about 60%. For example, the composite sheet may have a fluid acquisition time in the range of about 0.65 to about 1.5 seconds, a fluid absorption in the range of about 20 to about 26 g / g, a fluid retention in the range of about 9 to about 14 g / g, a fluid wicking height in the range of about 15 to about 45 mm, and a recovery force in the range of about 35 to about 55%. In some embodiments, the composite sheet may have a fluid acquisition time in the range of about 0.84 to about 1.3 seconds; a fluid absorption in the range of about 20 to about 25 g / g; a fluid retention in the range of about 10 to about 12 g / g; a fluid wicking height in the range of about 15 to about 40 mm; and a recovery force in the range of about 40 to about 55%.

[0225] In a preferred embodiment, the composite sheet has a fluid acquisition of about 1.25 seconds; a fluid absorption of about 25 g / g; a fluid retention of about 10 g / g; a vertical fluid wicking height of about 40 mm; and a recovery force of about 40%.

[0226] The composite sheet has a basis weight of about 25 to about 400 grams per square meter (g / m 2 ), especially about 40 to about 225 g / m 2 , about 50~250g / m 2 , more particularly about 50 to about 180 g / m 2 In a preferred embodiment, the composite sheet has a weight of about 50 to 100 g / m 2 The sheet has a basis weight of

[0227] The thickness of the composite sheet may range from about 0.7 to about 6 mm, particularly from about 1.3 to about 4.5 mm, and more particularly from about 1.5 to about 3.0 mm. In a preferred embodiment, the composite sheet has a thickness that is about 1.6 to about 2.5 mm. In a preferred embodiment, the thickness of the composite sheet is about 1.0 to about 1.5 mm, particularly from about 1.2 to about 1.4 mm.

[0228] Typically, the mass of the fluid acquisition component comprises about 8 to about 85 weight percent of the composite sheet, based on the total weight of the composite sheet. In one embodiment, the mass of the fluid acquisition component comprises about 20 to about 75 weight percent, particularly about 30 to about 60 weight percent, of the composite sheet, based on the total weight of the composite sheet.

[0229] The mass of the airlaid component comprises about 15 to about 92 weight percent of the composite sheet, based on the total weight of the composite sheet. In one embodiment, the mass of the airlaid component comprises about 20 to about 80 weight percent, particularly about 30 to about 70 weight percent, of the composite sheet, based on the total weight of the composite sheet.

[0230] Fluid acquisition components

[0231] In one embodiment, the fluid acquisition component comprises a fluid acquisition layer comprising a nonwoven fabric that is relatively permeable and has a porous structure such that when fluid impinges on the surface of the fluid acquisition layer, the fluid is rapidly transported through the fluid acquisition layer and into the airlaid component 14. The permeability and porosity nature of the fluid acquisition layer may generally be characterized by the density of the layer. For example, the density of the fluid acquisition layer may be from about 0.02 to about 0.07 g / cm. 3 , particularly about 0.03 to about 0.06 g / cm 3 In a preferred embodiment, the density of the fluid acquisition layer is from about 0.04 to about 0.05 g / cm 3 It is.

[0232] A wide variety of different nonwoven fabrics can be used as the fluid acquisition layer. In one embodiment, the nonwoven fabric of the fluid acquisition layer comprises a carded nonwoven fabric containing staple fibers. The typical length of the staple fibers in the fluid acquisition layer can range from about 20 to about 100 mm, particularly from about 25 to about 60 mm, more particularly from about 35 to about 55 mm.

[0233] Other examples of nonwovens that may be used as the fluid acquisition layer include latex bonded carded fabrics and spunlaced nonwovens. The fibers of the fluid acquisition layer may be bonded in a variety of ways, such as thermal bonding, resin bonding, stitch bonding, mechanical bonding (e.g., needle punch or hydroentanglement), etc. In a preferred embodiment, the fibers of the fluid acquisition layer are bonded via air-through thermal bonding.

[0234] In some embodiments, the fibers of the fluid acquisition layer may be bonded via thermal calendar bonding. In certain other embodiments, the fibers of the fluid acquisition layer are not subjected to thermal calendar bonding. In certain embodiments, the fibers of the fluid acquisition layer are not bonded via hydraulic entanglement, characterized by the absence of a hydraulic entanglement process in bonding the fibers.

[0235] Suitable materials for the staple fibers for use in the fluid acquisition component may include monocomponent or multicomponent fibers, or a combination of monocomponent and multicomponent fibers. In a preferred embodiment, the staple fibers of the fluid acquisition component comprise bicomponent fibers having a sheath / core configuration.

[0236] In one embodiment, the staple fibers of the fluid acquisition component comprise bicomponent fibers having a sheath / core configuration. Examples of bicomponent fibers include side-by-side, islands-in-the-sea, and sheath / core configurations. Preferably, the fibers have a sheath / core structure, where the sheath comprises a first polymer component and the core comprises a second polymer component. In this configuration, the polymer of the first polymer component and the polymer of the second polymer component may be the same or different from each other. For example, in one embodiment, the sheath comprises a first polymer component and the core comprises a second polymer component, which may be different or the same as the first polymer component. In a preferred embodiment, the first polymer component and the second polymer component of the bicomponent fiber are different from each other.

[0237] In some embodiments, the staple fibers of the fluid acquisition component may have a sheath / core configuration, where the core may be centrally located relative to the sheath. Alternatively, the core may be in an offset configuration relative to the sheath. As a result, when heat is applied, such as during bonding, the fibers may have a tendency to curl or crimp, which may help provide loft to the fluid acquisition component.

[0238] In one embodiment, the first polymer component of the sheath comprises a polymer having a lower melting temperature than the melting temperature of the second polymer component comprising the core. The low melting point polymer of the sheath promotes adhesion, while the polymer component of the core having a higher melting temperature provides strength to the fibers and thus the final bonded nonwoven fabric.

[0239] In general, the weight percentage of the sheath to the weight percentage of the core in the fiber can vary widely depending on the desired properties of the nonwoven fabric. For example, the weight ratio of the sheath to the core can vary from about 10:90 to 90:10, particularly about 20:80 to 80:20. In a preferred embodiment, the weight ratio of the sheath to the core is about 60:40 to about 40:60, with a weight ratio of about 50:50 being preferred.

[0240] A wide variety of polymers can be used to prepare staple fibers for use in the fluid acquisition component. Examples of suitable fibers can include polyolefins, such as polypropylene and polyethylene and their copolymers, polyesters, such as polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT) and polybutylene terephthalate (PBT), nylon, polystyrene, copolymers, and blends thereof, as well as other synthetic polymers that can be used in the preparation of fibers. In one embodiment, the staple fibers have a sheath / core configuration that includes a polyethylene sheath and a polypropylene core. In another embodiment, the staple fibers can have a sheath / core configuration that includes a polyethylene sheath and a polyester core, such as a core that includes polyethylene terephthalate.

[0241] In some embodiments, the staple fibers of the fluid acquisition component may comprise a blend of fibers, such as a blend of bicomponent staple fibers having a polyethylene sheath and a polyethylene terephthalate core, where the bicomponent staple fibers have a polyethylene sheath and a polypropylene core. In one embodiment, the fibers of the fluid acquisition component may comprise eccentric bicomponent staple fibers having a polyethylene sheath and a polyethylene terephthalate core, having a fineness of 4.3 dtex and an average length of 38 to 51 mm. An example of such a fiber is available from Indorama Polyester Industries Public Company Limited under the trade name TS47.

[0242] In one embodiment, the staple fibers of the fluid acquisition component may comprise bicomponent staple fibers having a polyethylene sheath and a polyethylene terephthalate core. One such example is a bicomponent staple fiber having a fineness of 2.2 dtex and an average length of 3 mm, which is available from Toray Chemical Korea Inc. under the trade name EZBON A (UN-204). A further example is an eccentric bicomponent staple fiber having a polyethylene sheath and a polyethylene terephthalate core. Such fibers are available from Indorama Polyester Industries Public Company Limited under the trade name TS47 (fineness of 4.3 dtex and average length of 3 mm). Another example is a bicomponent staple fiber having a polyethylene sheath and a polyethylene terephthalate core, which is available from Trevira under the trade name T255 staple fiber. These staple fibers have a fineness of 4.3 dtex and an average length of 3 mm.

[0243] In another embodiment, the staple fiber of the fluid acquisition component may comprise bicomponent staple fiber having a polyethylene sheath and a polypropylene core. One such example is a staple fiber having a fineness of 4.0 dtex and an average length of 4 mm, which is available from Yangzhou Petrochemical Co. Ltd under the trade name Y116. Another example of a bicomponent staple fiber having a polyethylene sheath and a polypropylene core, a denier of 6.0 and an average length of 51 mm is available from JiangNan High Polymer Fiber under the trade name JNGX-PZ11-6*51L.

[0244] In some embodiments, the fluid acquisition component staple fibers may comprise a blend of fibers, such as a blend comprising bicomponent PE / PET and PE / PP staple fibers.

[0245] The above-mentioned polymers are generally considered to be derived from synthetic sources, such as petroleum-derived polymers. In some embodiments, it may be desirable to provide a fluid acquisition component that includes one or more sustainable polymer components. In contrast to polymers derived from petroleum sources, sustainable polymers are generally derived from bio-based materials. In some embodiments, the sustainable polymer components are also considered to be biodegradable. A special class of biodegradable products made from bio-based materials are considered to be compostable if they are capable of being decomposed in a complex environment. The European standard EN 13432 "Proof of Compostability of Plastic Products" can be used to determine whether a fabric or film composed of sustainable content can be classified as compostable.

[0246] In one such embodiment, the fluid acquisition component comprises staple fibers that include a sustainable polymer. In some embodiments, the fluid acquisition component staple fibers are substantially free of synthetic materials, such as petroleum-based materials and polymers. For example, the staple fibers that comprise the fluid acquisition component may have less than 25 weight percent non-bio-based materials, more preferably less than 20 weight percent mN / cm, less than 15 weight percent mN / cm, less than 10 weight percent, and even more preferably less than 5 weight percent non-bio-based materials, based on the total weight of the airlaid nonwoven.

[0247] In one embodiment, sustainable polymers for use can include aliphatic polyester-based polymers such as polylactic acid (PLA) and polybutylene succinate (PBS), bio-based polyethylene, bio-based polypropylene, bio-based polyesters such as bio-based polyethylene terephthalate (PET), and the like, and combinations thereof.

[0248] Aliphatic polyesters useful in the present invention may include homopolymers and copolymers of poly(hydroxyalkanoates) and those aliphatic polyesters derived from the reaction product of one or more polyols and one or more polycarboxylic acids, which are typically formed from the reaction product of one or more alkanediols and one or more alkanedicarboxylic acids (or acyl derivatives). Polyesters may also be derived from multifunctional polyols, such as glycerin, sorbitol, pentaerythritol, and combinations thereof, to form branched, star, and graft homopolymers and copolymers. Polyhydroxyalkanoates are generally formed from hydroxy acid monomer units or their derivatives. These include, for example, polylactic acid, polyhydroxybutyrate, polyhydroxyvalerate, polycaprolactone, and the like. Miscible and immiscible blends of aliphatic polyesters with one or more additional semicrystalline or amorphous polymers may also be used.

[0249] One useful class of aliphatic polyesters are the poly(hydroxyalkanoates) obtained by condensation or ring-opening polymerization of hydroxy acids, or derivatives thereof. Suitable poly(hydroxyalkanoates) may be represented by the formula: H(O--R--C(O)--). nOH, where R is an alkylene moiety having 1-20 carbon atoms, preferably 1-12 carbon atoms, which may be substituted by catenary oxygen atoms (attached to a carbon atom in the carbon chain), which may be linear or branched; n is a number such that the ester is polymerizable, preferably such that the molecular weight of the aliphatic polyester is at least 10,000 daltons, preferably at least 30,000 daltons, and most preferably at least 50,000 daltons. In some embodiments, the molecular weight of the aliphatic polyester is typically less than 1,000,000 daltons, preferably less than 500,000 daltons, and most preferably less than 300,000 daltons. R may further include one or more catenary (i.e. in-chain) ether oxygen atoms. In general, the R group of the hydroxy acid has pendant hydroxyl groups that are primary or secondary hydroxyl groups.

[0250] Useful poly(hydroxyalkanoates) include, for example, homopolymers and copolymers of poly(3-hydroxybutyrate), poly(4-hydroxybutyrate), poly(3-hydroxyvalerate), poly(lactic acid) (also known as polylactide), poly(3-hydroxypropanoate), poly(4-hydropentanoate), poly(3-hydroxypentanoate), poly(3-hydroxyhexanoate), poly(3-hydroxyheptanoate), poly(3-hydroxyoctanoate), polydioxanone, polycaprolactone, and polyglycolic acid (i.e., polyglycolide). Copolymers of two or more of the above hydroxy acids may also be used, such as poly(3-hydroxybutyrate-co-3-hydroxyvalerate), poly(lactate-co-3-hydroxypropanoate), poly(glycolide-co-p-dioxanone), and poly(lactic acid-co-glycolic acid). Blends of two or more of the poly(hydroxyalkanoates) may also be used, as well as blends with one or more semicrystalline or amorphous polymers and / or copolymers.

[0251] The aliphatic polyester may be a block copolymer of poly(lactic-co-glycolic acid). The aliphatic polyesters useful in the compositions of the present invention may include homopolymers, random copolymers, block copolymers, star-branched random copolymers, star-branched block copolymers, dendritic copolymers, hyperbranched copolymers, graft copolymers, and combinations thereof.

[0252] Another useful class of aliphatic polyesters includes those derived from the reaction product of one or more alkanediols with one or more alkanedicarboxylic acids (or acyl derivatives). Such polyesters have the general formula: [ka] wherein R' and R'' each represent an alkylene moiety which may be linear or branched having 1 to 20 carbon atoms, preferably 1 to 12 carbon atoms, and m is a number at which the ester is polymerizable, preferably such that the molecular weight of the aliphatic polyester is at least 10,000 daltons, preferably at least 30,000 daltons, and most preferably at least 50,000 daltons, but less than 1,000,000 daltons, preferably less than 500,000 daltons, and most preferably less than 300,000 daltons. Each n is independently 0 or 1. R' and R'' may further include one or more catenary (i.e., linear) ether oxygen atoms.

[0253] Examples of aliphatic polyesters include (a) one or more of the following diacids (or derivatives thereof): succinic acid; adipic acid; 1,12-dicarboxydodecane; fumaric acid; glutaric acid; diglycolic acid; and maleic acid; and (b) one or more of the following diols: ethylene glycol; polyethylene. glycol; 1,2-propanediol; 1,3-propanediol; 1,2-propanediol; 1,2-butanediol; 1,3-butanediol; 1,4-butanediol; 2,3-butanediol; 1,6-hexanediol; 1,2-alkanediols having 5 to 12 carbon atoms; diethylene glycol; polyethylene glycol having a molecular weight of 300 to 10,000 daltons, preferably 400 to 8,000 daltons; propylene glycol having a molecular weight of 300 to 4,000 daltons; block or random copolymers derived from ethylene oxide, propylene oxide or butylene oxide; dipropylene glycol; and polypropylene glycol, and (c) optionally, homopolymers and copolymers derived from small amounts, i.e., 0.5 to 7.0 mole percent, of polyols having a functionality greater than 2, such as glycerol, neopentyl glycol and pentaerythritol.

[0254] Such polymers may include polybutylene succinate homopolymer, polybutylene adipate homopolymer, polybutylene adipate-succinate copolymer, polyethylene succinate-adipate copolymer, polyethylene glycol succinate homopolymer, and polyethylene adipate homopolymer.

[0255] Commercially available aliphatic polyesters include poly(lactide), poly(glycolide), poly(lactide-co-glycolide), poly(L-lactide-co-trimethylene carbonate), poly(dioxanone), poly(butylene succinate), and poly(butylene adipate).

[0256] The term "aliphatic polyester" includes, in addition to polyesters made exclusively from aliphatic and / or cycloaliphatic components, also polyesters which contain aromatic units in addition to aliphatic and / or cycloaliphatic units, so long as the polyesters have a substantially sustainable content.

[0257] In addition to PLA-based resins, nonwoven fabrics according to embodiments of the invention may include other polymers derived from aliphatic components having one carboxylic acid group and one hydroxyl group, alternatively referred to as polyhydroxyalkanoates (PHAs). Examples are polyhydroxybutyrate (PHB), poly-(hydroxybutyrate-co-hydroxyvaleterate) (PHBV), poly-(hydroxybutyrate-co-polyhydroxyhexanoate) (PHBH), polyglycolic acid (PGA), poly-(epsilon-caprolactone) (PCL), and preferably polylactic acid (PLA).

[0258] Examples of additional polymers that may be used in embodiments of the invention include polymers derived from a combination of an aliphatic component having two carboxylic acid groups and an aliphatic component having two hydroxyl groups, as well as polyesters derived from aliphatic diols and from aliphatic dicarboxylic acids, such as polybutylene succinate (PBSU), polyethylene succinate (PESU), polybutylene adipate (PBA), polyethylene adipate (PEA), and polytetramethylene adipate / terephthalate (PTMAT).

[0259] Useful aliphatic polyesters include aliphatic polyesters derived from semicrystalline polylactic acid. Poly(lactic acid) or polylactide (PLA) has lactic acid as its main degradation product, which is commonly found in nature, is non-toxic, and is widely used in the food, pharmaceutical, and medical industries. The polymer can be prepared by ring-opening polymerization of lactide, a dimer of lactic acid. Lactic acid is optically active, and the dimer appears in four different forms: L,L-lactide, D,D-lactide, D,L-lactide (mesolactide), and a racemic mixture of L,L- and D,D-. By polymerizing these lactides as pure compounds or blends, poly(lactide) polymers with different stereochemical properties and different physical properties, such as those mentioned above, including crystallinity, can be obtained. L,L- or D,D-lactide gives semicrystalline poly(lactide), while poly(lactide) obtained from D,L-lactide is amorphous.

[0260] Typically, polylactic acid-based polymers are prepared from dextrose, a sugar source obtained from field corn. In North America, corn is used because it is the most economical source of plant starch for ultimate conversion to sugar. However, it should be recognized that dextrose can be obtained from sources other than corn. Sugars are converted to lactic acid or lactic acid derivatives via fermentation through the use of microorganisms. The lactic acid can then be polymerized to form PLA. In addition to corn, other agriculturally derived sugar sources may be used, including rice, sugar beet, sugar cane, wheat, cellulosic materials such as xylose recovered from wood pulping, etc.

[0261] The polylactide preferably has a high enantiomeric ratio to maximize the inherent crystallinity of the polymer. The crystallinity of poly(lactic acid) is based on the regularity of the polymer backbone and its ability to crystallize with other polymer chains. When a relatively small amount of one enantiomer (e.g., D-) is copolymerized with the opposite enantiomer (e.g., L-), the polymer chain becomes irregularly shaped and the crystallinity decreases. For these reasons, when crystallinity is preferred, polylactic acid that is at least 85% of one isomer, at least 90% of one isomer, or at least 95% of one isomer is desirable to maximize the crystallinity.

[0262] In some embodiments, a near equimolar blend of D- and L-polylactide is also useful, which forms a unique crystalline structure that has a higher melting point (about 210° C.) than either D-poly(lactide) or L-poly(lactide) alone (about 190° C.), and has improved thermal stability.

[0263] Copolymers, including block and random copolymers, of poly(lactic acid) with other aliphatic polyesters may also be used. Useful comonomers include glycolide, beta-propiolactone tetramethylglycolide, beta-butyrolactone, gamma-butyrolactone, pivalolactone, 2-hydroxybutyric acid, alpha-hydroxyisobutyric acid, alpha-hydroxyvaleric acid, alpha-hydroxyisovaleric acid, alpha-hydroxycaproic acid, alpha-hydroxyethylbutyric acid, alpha-hydroxyisocaproic acid, alpha-hydroxy-beta-methylvaleric acid, alpha-hydroxyoctanoic acid, alpha-hydroxydecanoic acid, alpha-hydroxymyristic acid, and alpha-hydroxystearic acid.

[0264] Blends of poly(lactic acid) with one or more other aliphatic polyesters or one or more other polymers may also be used. Examples of useful blends include poly(lactic acid) with polyvinyl alcohol, polyethylene glycol / polysuccinate, polyethylene oxide, polycaprolactone, and polyglycolide.

[0265] In some preferred embodiments, the aliphatic polyester component comprises a PLA-based resin. A wide variety of different PLA resins can be used to prepare nonwoven fabrics according to embodiments of the present invention. The PLA resin should have suitable molecular properties to be spun in a spunbond process. Suitable examples include PLA resins such as grades 6752D, 6100D and 6202D, supplied by NatureWorks LLC, Minnetonka, Minn. 55345, which are believed to be produced generally in accordance with the teachings of U.S. Patent No. 5,525,706 to Gruber et al. and U.S. Patent No. 6,807,973 to Gruber et al. Other examples of suitable PLA resins include L130, L175 and LX175, all of which are available from Corbion of Arkelsedijk 46, 4206 AC Gorinchem, the Netherlands.

[0266] In some embodiments, the staple fibers of the fluid acquisition component have a sheath / core configuration, where both the sheath and the core comprise PLA resin. In these embodiments, an airlaid nonwoven fabric can be provided that is substantially free of synthetic polymeric components, such as petroleum-based materials and polymers. For example, the staple fibers of the fluid acquisition component can have a bicomponent configuration in which both components are PLA-based, thereby producing a staple fiber that is 100% PLA. As used herein, "100% PLA" can also include up to 5% additives, including, by way of example only, additives and / or additive masterbatches to provide color, softness, slip, antistatic, lubricity, hydrophilicity, liquid repellency, antioxidant protection, and the like. In this regard, the staple fibers of the fluid acquisition component can include 95-100% PLA, e.g., 96-100% PLA, 97-100% PLA, 98-100% PLA, 99-100% PLA, and the like. When such additives are added as a masterbatch, for example, the masterbatch carrier may comprise primarily PLA to facilitate processing and maximize sustainable content in the fiber. For example, the staple fibers of the fluid acquisition component may comprise one or more additional additives. In such an embodiment, for example, the additives may comprise at least one of colorants, softeners, slip agents, antistatic agents, lubricants, hydrophilic agents, liquid repellents, antioxidants, and the like, or any combination thereof.

[0267] In one embodiment, the sheath PLA polymer may be the same PLA polymer as the core PLA polymer. In another embodiment, the sheath PLA polymer may be a different PLA polymer than the core PLA polymer. For example, the bicomponent staple fiber may include a PLA / PLA bicomponent fiber in which the sheath includes a first PLA grade, and the core includes a second PLA grade, the first PLA grade and the second PLA grade being different (e.g., the first PLA grade has a lower melting point than the second PLA grade). By way of example only, the first PLA grade may include up to about 5% crystallinity, and the second PLA grade may include about 40% to about 50% crystallinity.

[0268] In some embodiments, for example, the first PLA grade can include a melting point of about 125° C. to about 135° C., and the second PLA grade can include a melting point of about 155° C. to about 170° C. In further embodiments, for example, the first PLA grade can include a weight percent of the D isomer of about 4 to about 10 wt %, and the second PLA grade can include a weight percent of the D isomer of about 2 wt %.

[0269] For example, in one embodiment, the core can comprise PLA with a lower D% isomer of polylactic acid than the D% isomer of the PLA polymer used in the sheath.The PLA polymer with a lower D% isomer exhibits a higher degree of stress-induced crystallization during spinning, while the PLA polymer with a higher D% isomer remains more amorphous during spinning.The more amorphous sheath promotes adhesion, while the core with a higher degree of crystallization provides strength to the fiber and thus to the final bonded web.In one particular embodiment, Nature Works PLA Grade 6752 with 4% D isomer can be used as the sheath, while Nature Works Grade 6202 with 2% D isomer can be used as the core.

[0270] In some embodiments, the fluid acquisition component may comprise a sustainable polymer component of a biodegradable product derived from an aliphatic component having one carboxylic acid group (or a polyester-forming derivative thereof, such as an ester group) and one hydroxyl group (or a polyester-forming derivative thereof, such as an ether group); or from a combination of an aliphatic component having two carboxylic acid groups (or a polyester-forming derivative thereof, such as an ester group) and an aliphatic component having two hydroxyl groups (or a polyester-forming derivative thereof, such as an ether group); or from a combination of an aliphatic component having two carboxylic acid groups (or a polyester-forming derivative thereof, such as an ester group) and an aliphatic component having two hydroxyl groups (or a polyester-forming derivative thereof, such as an ether group).

[0271] Additional non-limiting examples of biobased polymers include polymers produced directly from organisms, such as polyhydroxyalkanoates (e.g., poly(beta-hydroxyalkanoates), poly(3-hydroxybutyrate-co-3-hydroxyvalerate), NODAX 商標), and bacterial cellulose; polymers extracted from plants and biomass, such as polysaccharides and their derivatives (e.g., gums, cellulose, cellulose esters, chitin, chitosan, starch, chemically modified starches), proteins (e.g., zein, whey, gluten, collagen), lipids, lignin, and natural rubber; and modern polymers derived from naturally occurring monomers and their derivatives, such as bio-polyethylene, bio-polypropylene, polytrimethylene terephthalate, polylactic acid, nylon 11, alkyd resins, succinic acid-based polyesters, and bio-polyethylene terephthalate.

[0272] In some embodiments, the fluid acquisition component staple fiber may comprise a bio-based polymer, including bio-based polyethylene derived from biological sources.For example, bio-based polyethylene can be prepared from sugars that are fermented to produce ethanol, which is then dehydrated to provide ethylene.An example of a suitable sugar cane-derived polyethylene is available from Braskem SA under the product name PE SHA7260.

[0273] In some embodiments of the fluid acquisition component staple fibers, the may include a bio-based polyethylene and the core may include a PLA polymer.

[0274] In some embodiments, the sheath may include a PLA or PBS polymer, and the core may include a synthetic polymer, such as polypropylene.

[0275] In some embodiments, the staple fibers of the fluid acquisition component may include one or more additives that are blended with one or more polymers during the melt extrusion step. Examples of suitable additives include molecular filters and / or substrate filters, such as zeolites, ion exchange particles, activated carbon, and the like, colorants, such as pigments (e.g., TiO 2), UV stabilizers, hydrophobizing agents, hydrophilizing agents, antistatic agents, elastomers, compatibilizers, antioxidants, antiblocking agents, slip agents, optical brighteners, flame retardants, antimicrobial agents, such as copper oxide and zinc oxide.

[0276] Airlaid nonwoven fabric components

[0277] As discussed above, the airlaid component comprises an airlaid nonwoven comprising a blend of non-cellulose staple fibers and bamboo-derived staple fibers. In one embodiment, the airlaid component comprises a plurality of airlaid nonwoven layers, one or more of which comprises a blend of non-cellulose staple fibers and bamboo-derived staple fibers. Preferably, when the airlaid nonwoven component comprises a plurality of airlaid nonwoven layers, each of the airlaid nonwoven layers comprises a blend of non-cellulose staple fibers and bamboo-derived staple fibers.

[0278] As previously discussed, the airlaid nonwoven component may be bonded to the fluid acquisition component using bonding techniques such as thermal bonding (e.g., calendar bonding or air through bonding), mechanical bonding (e.g., hydraulic entanglement or needle punching), chemical bonding (e.g., using adhesives or other adhesive resins), ultrasonic bonding, etc. In a preferred embodiment, the airlaid nonwoven component is thermally bonded to the fluid acquisition component by passing the composite sheet material through an air-through bonding unit where the composite sheet material is exposed to one or more streams of heated gas that is above the softening or melting temperature of at least one polymeric component of the composite sheet material.

[0279] Suitable polymers, materials, additives, and properties for the non-cellulosic staple fibers and the bamboo-derived staple fibers are discussed above in connection with the airlaid nonwoven fabrics.

[0280] Optional coating layer

[0281] In some embodiments, the composite sheet may further include a polymer-based coating layer deposited on the exterior surface 22 of the airlaid component. In this regard, FIG. 5 illustrates an embodiment of the invention in which a composite sheet material 10 includes a coating layer 24 disposed on the exterior surface of the airlaid component 14. In one embodiment, the coating layer may be applied with a composition including a carrier, such as water or an organic solvent, and a polymeric material dispersed in the carrier. For example, in one embodiment, the coating layer may include a latex formulation of an aqueous polymer dispersion of ethylene vinyl acetate, acrylate, polyacrylate, phenylethylene, butadiene, styrene butadiene-acrylic acid, polyvinyl alcohol, and mixtures thereof.

[0282] In one embodiment, the polymer-based layer comprises a bio-based latex of vegetable origin. Such a bio-based latex is available under the trade name OC-BIOBINDER. 商標 Available from OrganoClick under the name Lily 1450. Other bio-based materials include carboxymethylcellulose (CMC) and sodium carboxymethylcellulose (Na CMC).

[0283] In one embodiment, the latex formulation is available under the product name VINNAPAS 登録商標 Available from Wacker under 192192, these polymers are made from the monomers vinyl acetate and ethylene and have a solids content of about 45 to about 55%.

[0284] The coating layer may be applied to the composite sheet material in a variety of different ways, such as spray coating, foam coating, kiss coating, and the like.

[0285] In the case of an aqueous dispersion or emulsion, the coating layer is applied as a liquid, which is then dried and cured to form a solid coating adhered to the composite sheet. The amount of coating layer added to the composite sheet following any drying and curing steps is typically about 1 to about 5 weight percent, particularly about 1.5 to about 3 weight percent, and more particularly about 1.75 to about 2.25 weight percent, based on the total weight of the composite sheet.

[0286] In some embodiments, an optional coating layer, such as latex, may be added on the opposite side of the composite sheet material, in which case the additional dry weight of the optional coating layer may be from about 2 to about 10 weight percent, specifically from about 3 to about 6 weight percent, and more specifically from about 3.5 to about 4.5 weight percent, based on the total weight of the composite sheet.

[0287] Process for preparing the composite sheet

[0288] 6A, a system and associated process for preparing a composite sheet material is shown and designated by the reference character 26. The system 26 includes a source of fabric for use as the fluid acquisition layer 12. In the illustrated embodiment, the source is shown as a spool 28 on which a previously formed fluid acquisition layer is wound. However, it should be appreciated that the system may also include a fabric forming device, such as a card or spinning beam, for preparing the nonwoven fabric of the fluid acquisition layer in a continuous line to the remainder of the system 26.

[0289] As shown, the nonwoven fabric of the fluid acquisition layer 12 is removed from a spool 28 and deposited on a collecting surface 29, such as an endless belt. The fluid acquisition layer is then transported to a series of airlaid fabric forming heads (30a, 30b, 30c). At each forming head, a stream of cellulosic staple fibers and non-cellulosic staple fibers are uniformly mixed to form a stream of mixed staple fibers. A first forming head then deposits the mixed stream of staple fibers onto the surface of the fluid acquisition layer 12, and each of the other forming heads successively deposits additional airlaid layers. Vacuums 31a, 31b, and 31c are positioned below each of the forming heads to aid in depositing the mixed stream of fibers below the collecting surface and onto the fluid acquisition layer 12. The system may optionally include one or more pairs of compression rollers 32a and 32b positioned following each forming head. When present, the compression rollers 32a and 32b may be heated, for example to a temperature in the range of about 90 to about 110°C.

[0290] Although three airlaid forming heads are shown, it should be understood that the system may include any number of forming heads depending on the desired number of airlaid layers to be deposited on the fluid acquisition layer 12. For example, the number of airlaid forming heads may range from 1 to 10, such as 2 to 8, 3 to 6, and 4 to 5. It should also be recognized that during operation of the system, one or more forming heads may not be used.

[0291] Referring to Figure 6B, a forming head that may be used in certain embodiments of the present invention is illustrated. As can be seen, forming head 30a includes a plurality of agitators 35 that create turbulence within the forming head. The turbulence mixes the cellulosic staple fibers and non-cellulosic staple fibers to form a homogenous mixture. The forming head also includes a screen 33 that limits / controls the output of staple fibers from the forming head, thereby aiding in forming an evenly distributed airlaid layer.

[0292] Returning to FIG. 6A, the composite sheet material having the airlaid layer thus deposited is conveyed to a first heated oven 36a. The first heated oven is typically maintained at a temperature sufficient to soften and melt the non-cellulosic fibers of the airlaid layer. This melting causes the polymer to flow and fuse to adjacent fibers to provide a coherent composite sheet. For example, in an embodiment in which the non-cellulosic staple fibers comprise bicomponent fibers having a polyethylene sheath, the composite sheet material may be heated to a temperature above the melting point of the sheath but below the melting point of the core. For polyethylene, the oven temperature is typically from about 120 to about 165° C.

[0293] In some embodiments, the system may include one or more embossing rolls 34 that may be used to impart an embossed pattern onto the surface of the composite sheet. In some embodiments, the system may also include a pair of calibration rolls 38 to adjust the thickness / profile of the composite sheet and / or to aid in interlayer adhesion between adjacent layers. The calibration rolls 38 may define a nip or may be gapped. In some embodiments, the calibration rolls are heated, while in other embodiments, the calibration rolls are not heated.

[0294] Prior to thermal bonding in this first heated oven, the composite sheet is conveyed to application station 35, at which point a coating layer may be applied to the surface of the outermost airlaid layer. This coating layer may be applied using conventional techniques, such as conventional techniques known in the art, such as spray coating and kiss roll application. In a preferred embodiment, a coating of an aqueous latex dispersion is applied to the surface of the composite web. In some embodiments, a second applied coating layer may be applied to the opposite side of the coating via application station 37.

[0295] Following application of any second coating layer or any other material to the surface of the composite sheet, the composite sheet is conveyed to a second heated oven 36b which is maintained at a temperature to dry and cure the previously applied coating layer. Optionally, the composite sheet material can be further heated in a third oven 36c.

[0296] The bonded and dried composite sheet material may then be wound onto a roll 39. In some embodiments, the composite sheet may be cut successively in the machine direction to form a plurality of individual composite sheets, each wound onto a separate roll.

[0297] In some embodiments, it may be desirable to emboss a pattern onto the airlaid component of the composite sheet, for example using the embossing roll 34 shown in FIG. 6A. In this regard, FIG. 7 illustrates an embodiment of the invention in which surface 22 of composite sheet 10 has a plurality of alternating ridges R and channels / grooves C defined on the surface of the outermost airlaid layer. In absorbent article construction, the fluid acquisition layer is typically disposed toward the topsheet, while the airlaid component is disposed toward the absorbent core. Fluid entering the composite sheet material is distributed through the fluid acquisition layer and into one or more airlaid layers. As it is conveyed toward the absorbent core, the ridges and channels serve to further distribute the fluid, so that the fluid can be more evenly distributed throughout the airlaid layer and, therefore, throughout the absorbent core.

[0298] The pattern of alternating ridges and channels typically extends in the machine direction of the composite sheet material, although other directions, eg, diagonal or cross directions, or non-linear, eg, serpentine, and / or discontinuous configurations are possible.

[0299] The pattern may be produced by a roll having a pattern of alternating raised surfaces and grooves extending circumferentially around the roll. In some embodiments, the roll may be heated and pressure may be applied to the surface of the composite sheet material to help promote the formation of the pattern of alternating grooves and ridges. The width of each groove (e.g., the distance between adjacent ridges) may vary depending on the intended use of the absorbent article, but will typically range from about 0.2 to about 10 mm, particularly about 1 to about 6 mm, and more particularly about 2 to about 3 mm. The depth of each groove is typically about 0.1 to about 5 mm, particularly about 0.3 to about 3 mm.

[0300] As mentioned above, the composite sheet material of the present invention is particularly useful as a transfer layer in absorbent articles, such as an AQDL component. In particular, the composite sheet can rapidly transport fluid through the fluid acquisition layer and then distribute the fluid laterally through one or more airlaid layers. Fluid transport is illustrated in FIG. 8.

[0301] Absorbent core for absorbent article

[0302] In some embodiments of the invention, the airlaid nonwoven fabric of the invention may comprise a component of an absorbent core of an absorbent article. In such embodiments, the airlaid nonwoven fabric may comprise multiple airlaid nonwoven layers in accordance with embodiments of the invention. In particular, the absorbent core may comprise 1 to 10 airlaid nonwoven layers.

[0303] In addition, the airlaid nonwoven for use in absorbent cores may include one or more non-cellulosic staple fibers as previously described. For example, the non-cellulosic staple fibers may include polymers derived from synthetic polymers, such as polyolefins and polyesters; polyamides, such as nylon, and the like, or combinations or blends thereof. In some embodiments, the non-cellulosic staple fibers may include polymers derived from bio-based polymers, such as PLA, PBS, green polyolefins, such as green polyethylene, green polyesters, such as green polyethylene terephthalate, or combinations of one or more bio-based polymers, or blends of one or more bio-based polymers. Suitable examples of bio-based polymers have been discussed above.

[0304] In addition, the non-cellulosic staple fibers may include combinations and / or blends of polymers derived from synthetic and bio-based polymers.

[0305] As discussed above, the non-cellulosic staple fibers may include monocomponent or multicomponent fibers, or a combination of monocomponent and multicomponent fibers.

[0306] In absorbent core applications, the airlaid nonwoven fabric or, collectively, the airlaid nonwoven fabric layers typically have a basis weight ranging from about 25 to about 400 gsm, and a thickness ranging from about 0.4 to about 4 mm.

[0307] In addition to the airlaid nonwoven fabric of the present invention, the absorbent core may include a superabsorbent polymer. Suitable absorbent polymers are discussed above. When present, the SAP may be present in an amount of 10 to 90 weight percent, based on the total weight of the absorbent core.

[0308] In some embodiments, absorbent cores according to one or more embodiments of the present invention may include both non-cellulosic staple fibers and cellulosic fibers, including fibers derived from bamboo, hi some embodiments, the cellulosic fibers may include a mixture of bamboo-derived fibers and conventional wood pulp fibers.

[0309] Typically, the amount of bamboo-derived fiber in the absorbent core is from 5 to 100 weight percent, based on the total weight of the absorbent core. In a preferred embodiment, the amount of bamboo-derived fiber in the absorbent core is from about 75 to about 100 weight percent, based on the total weight of the absorbent core, with an amount of 85 to 100 weight percent being slightly more preferred.

[0310] In certain embodiments, the amount of bamboo-derived fiber in the absorbent core is about 5 weight percent or more, about 10 weight percent or more, about 15 weight percent or more, about 20 weight percent or more, about 25 weight percent or more, about 30 weight percent or more, about 35 weight percent or more, about 40 weight percent or more, about 45 weight percent or more, about 50 weight percent or more, about 55 weight percent or more, about 60 weight percent or more, about 65 weight percent or more, about 70 weight percent or more, about 75 weight percent or more, about 80 weight percent or more, about 85 weight percent or more, about 90 weight percent or more, about 95 weight percent or more, about 96 weight percent or more, about 97 weight percent or more, about 98 weight percent or more, or about 99 weight percent or more, based on the total weight of the absorbent core.

[0311] In certain embodiments, the amount of bamboo-derived fiber in the absorbent core is about 100 weight percent or less, about 99 weight percent or less, about 98 weight percent or less, about 97 weight percent or less, about 96 weight percent or less, about 95 weight percent or less, about 90 weight percent or less, about 85 weight percent or less, about 80 weight percent or less, about 75 weight percent or less, about 70 weight percent or less, about 65 weight percent or less, about 60 weight percent or less, about 55 weight percent or less, about 50 weight percent or less, about 45 weight percent or less, about 40 weight percent or less, about 35 weight percent or less, about 30 weight percent or less, about 25 weight percent or less, about 20 weight percent or less, about 15 weight percent or less, about 10 weight percent or less, or about 5 weight percent or less, based on the total weight of the absorbent core.

[0312] In some embodiments, absorbent cores comprising airlaid nonwoven fabrics according to embodiments of the present invention exhibit a reduction in caliper in the range of 10 to 60%, particularly about 20 to about 50%, and more particularly about 25 to about 45%, compared to a comparable airlaid nonwoven fabric, where the comparable airlaid nonwoven fabric comprises staple fibers that include conventional wood pulp fibers instead of bamboo-derived staple fibers.

[0313] In some embodiments, the absorbent core comprises at least one airlaid nonwoven layer comprising a blend of non-cellulosic staple fibers and bamboo-derived fibers. In this embodiment, the bamboo-derived fibers provide absorbency while the non-cellulosic fibers provide integrity and structural support for the absorbent core. Absorbent cores comprising a blend of non-cellulosic staple fibers and bamboo-derived staple fibers can be thermally bonded via one or more of calendar bonding, air-through thermal bonding, or a combination thereof.

[0314] In embodiments including non-cellulosic staple fibers, the absorbent core typically comprises from about 1 to about 30 weight percent based on the total weight of the core, and more particularly from about 2 to about 20 weight percent based on the total weight of the absorbent core. In preferred embodiments, the amount of non-cellulosic staple fibers in the absorbent core is typically from about 3 to about 10 weight percent based on the total weight of the absorbent core, and more preferably from about 4 to about 6 weight percent based on the total weight of the absorbent core.

[0315] In certain embodiments, the amount of non-cellulosic staple fibers in the absorbent core is about 1 weight percent or more, about 2 weight percent or more, about 3 weight percent or more, about 4 weight percent or more, about 5 weight percent or more, about 6 weight percent or more, about 7 weight percent or more, about 8 weight percent or more, about 9 weight percent or more, about 10 weight percent or more, about 11 weight percent or more, about 12 weight percent or more, about 13 weight percent or more, about 14 weight percent or more, about 15 weight percent or more, about 16 weight percent or more, about 17 weight percent or more, about 18 weight percent or more, about 19 weight percent or more, about 20 weight percent or more, about 21 weight percent or more, about 22 weight percent or more, about 23 weight percent or more, about 24 weight percent or more, about 25 weight percent or more, about 26 weight percent or more, about 27 weight percent or more, about 28 weight percent or more, about 29 weight percent or more, or about 30 weight percent or more, based on the total weight of the absorbent core.

[0316] In certain embodiments, the amount of non-cellulosic staple fibers in the absorbent core is about 30 weight percent or less, about 29 weight percent or less, about 28 weight percent or less, about 27 weight percent or less, about 26 weight percent or less, about 25 weight percent or less, about 24 weight percent or less, about 23 weight percent or less, about 22 weight percent or less, about 21 weight percent or less, about 20 weight percent or less, about 19 weight percent or less, about 18 weight percent or less, about 17 weight percent or less, about 16 weight percent or less, about 15 weight percent or less, about 14 weight percent or less, about 13 weight percent or less, about 12 weight percent or less, about 11 weight percent or less, about 10 weight percent or less, about 9 weight percent or less, about 8 weight percent or less, about 7 weight percent, about 6 weight percent or less, about 5 weight percent or less, about 4 weight percent or less, about 3 weight percent or less, about 2 weight percent or less, or about 1 weight percent or less, based on the total weight of the absorbent core.

[0317] In certain other embodiments, the absorbent core, including at least one airlaid nonwoven layer, may be free or substantially free of non-cellulosic staple fibers. For example, in some embodiments, the cellulosic fibers of the absorbent core may be bonded via a latex material or may be bonded via hydrogen bonds.

[0318] Suitable latex materials may be derived from synthetic or bio-based materials. Examples of suitable latex materials are discussed above. Typically, the amount of latex material used to bond the absorbent core is about 0.5 to about 15 weight percent, based on the total weight of the absorbent core. In some embodiments, the latex is present on an add-on dry weight basis from about 1.5 to about 20 weight percent, based on the total weight of the absorbent core. At weight percentages greater than 6 weight percent, the latex material is typically used in latex-bonded absorbent cores.

[0319] In some embodiments, the absorbent core may include non-cellulosic staple fibers and latex to adhere the cellulosic fibers.

[0320] In some embodiments, the one or more airlaid nonwoven layers may include a tissue layer. In one embodiment, the one or more airlaid nonwoven layers may be sandwiched between a pair of tissue layers. The tissue layer may include a tissue derived from bamboo fibers, conventional wood pulp fibers, or a combination thereof.

[0321] Absorbent articles

[0322] Composite sheets according to the present invention can be used in a wide variety of different articles, particularly a wide variety of absorbent articles.

[0323] 9, one embodiment of an absorbent article ("diaper") in accordance with an embodiment of the present invention is shown and is broadly designated by reference numeral 40. The diaper 40 includes a core region 42 in which an absorbent core 44 is disposed. A chassis region 46 surrounds the core region 42 and includes a front region 48, a rear region 50, and front and rear waist regions 52a and 52b. The chassis region, including the front, rear and core regions, generally has a composite structure including a liquid permeable topsheet and a liquid impermeable backsheet attached to one another along opposing surfaces to define a cavity therebetween in which the absorbent core is disposed.

[0324] The topsheet, the backsheet and the absorbent core may generally comprise any materials conventionally used in the manufacture of absorbent articles.

[0325] As shown in Figure 9, the diaper also includes a composite sheet material 10 (see Figure 3) in accordance with at least one embodiment of the present invention. The composite sheet 10 defines a fluid transport layer, such as the fluid acquisition and distribution system 90 (i.e., AQDL component) of the absorbent article. As discussed above, the composite sheet 10 defines a fluid distribution / acquisition component that serves to efficiently facilitate the transfer of fluid from the wearer to the absorbent core 44.

[0326] In some embodiments, the front and rear regions of the diaper each also include a pair of ears 54 disposed in the waist region of the diaper. (As used herein, the word "disposed" is used to mean that one or more elements of the diaper are formed (joined and disposed) in a particular place or location, either as a unitary structure with another element of the diaper or as a separate element joined to another element of the diaper.) The ears 54 provide an elastically extensible feature that provides a more comfortable and contoured fit by initially fitting the diaper closely to the wearer and maintaining this fit throughout wear, even after the diaper is loaded with exudates, because elastic side panels allow the sides of the diaper to stretch.

[0327] Additionally, the ears 54 develop and maintain a wearing force (tension) that enhances the tension developed and maintained by a fastening system, described in more detail below, to keep the diaper 40 on the wearer and enhance waist fit. As shown in Figure 9, the diaper includes a pair of rear ears 56a and 56b that are joined to the rear region 50 of the diaper chassis adjacent the rear waist region 52b, and a pair of front ears 58a and 58b that are joined to the front region 48 of the diaper chassis adjacent the front waist region 52a.

[0328] The front and back ears may be joined to the chassis region 46 by any bonding method known in the art, such as adhesive bonding, pressure bonding, heat bonding. In other embodiments, the front and / or back ears may be comprised of separate elements joined to the chassis region 46, where the chassis region 46 has a layer, element or substrate extending over the front and / or back ears. For example, each ear may comprise a portion of the diaper chassis region that extends from a side edge 60 of the chassis region and laterally outwardly along the side edge 60 to a longitudinal edge 62 of the diaper 40. In one embodiment, the ears generally extend longitudinally from a terminal edge 64 of the diaper 40 to the portion of the longitudinal edge 62 of the diaper 40 that forms the leg openings (this segment of the longitudinal edge 62 is designated as the leg edge 66). In some embodiments, the ears may comprise separate fabrics or webs that are joined to the topsheet or backsheet, hi other embodiments, each ear may be formed by portions of the topsheet and backsheet that extend beyond the side edges of absorbent core 44.

[0329] In one embodiment, the diaper 40 may also include elastic leg cuffs 70 to provide improved containment of liquids and other body exudates. Each elasticized leg cuff 70 may include a number of different embodiments to reduce leakage of bodily fluids in the leg regions. (The leg cuffs may also be referred to as leg bands, side flaps, barrier cuffs, or elastic cuffs.) U.S. Pat. No. 3,860,003, entitled "Contractable Side Portions for a Disposable Diaper," issued Jan. 14, 1975 to Buell, describes a disposable diaper which provides contractible leg openings having side flaps and one or more elastic members to provide elasticized leg cuffs (gasketing cuffs). U.S. Patent No. 4,909,803, issued March 20, 1990 to Aziz and Blaney, entitled "Disposable Absorbent Article Having Elasticized Flaps," describes a disposable diaper having "stand-up" elasticized flaps (barrier cuffs) for improved leg containment. U.S. Patent No. 4,695,278, issued to Lawson, entitled "Absorbent Article Having Dual Cuffs," describes a disposable diaper having dual cuffs that include gasket cuffs and barrier cuffs. U.S. Patent No. 4,704,115, issued November 3, 1987 to Buell, entitled "Disposable Waist Containment Garment," discloses a disposable diaper or incontinence garment having side edge leak-proof garters configured to contain free liquid within the garment. Each of these patents is incorporated herein by reference.US Pat. No. 6,476,289, entitled "Garment Having Elastomeric Laminate," describes various elastic leg cuff configurations that may also be used in embodiments of the present invention.

[0330] In a preferred embodiment, the leg cuffs may comprise a fabric layer having an SMS structure with a plurality of elastic strands integrated into the structure of the leg cuffs. Preferably, the leg cuffs comprise a material having liquid barrier properties.

[0331] One example of a fabric for use in forming leg cuffs comprises an SMS fabric having a spunbond nonwoven layer comprising bicomponent fibers having a sheath of a first polymer component and a core of a second polymer component. Examples of materials for the sheath and core include polyolefins such as polypropylene and polyethylene, polyesters, PLA-based polymers, and the like. In one embodiment, the bicomponent fibers comprise a polypropylene sheath and a PLA core. An example of a polypropylene material for use in this embodiment may have a melt flow rate (MFR) of 20 to 40 g / 10 min (measured according to ASTM D1238 (190° C. / 2.16 kg)), such as those offered by Total Petrochemicals and Refining USA, Inc. (La Port, TX, 77571 USA) as grade M 3766 (metallocene polypropylene) and grade M 3764 or grade M 3866 (Zeigler Natta polypropylene). A suitable material for use as the PLA core is available from Nature Works PLA as grade 6202 containing 2% D isomer. The meltblown layer may comprise polypropylene having a MFR of 1,300 g / 10 min (measured according to ASTM D1238 (190° C. / 2.16 kg)), such as that offered as grade 3962 by Total Petrochemicals and Refining USA, Inc. (La Port, TX, 77571 USA).

[0332] In a second example, the leg cuffs may include an SMS fabric having a spunbond nonwoven layer with bicomponent fibers having a PLA sheath and a PLA core, and a meltblown layer including PLA fibers. An example of a suitable PLA material for use as the sheath is PLA grade 6752 with 4% D isomer, and an example of a suitable PLA material for use as the core is PLA grade 6202 with 2% D isomer, both of which are available from NatureWorks. A suitable material for the PLA meltblown fibers is PLA grade 6252, which is also available from NatureWorks.

[0333] In a third embodiment, the leg cuffs may comprise a fabric having an SMS structure, where the spunbond nonwoven layer comprises a bicomponent fabric having a polypropylene sheath and a PLA core. Examples of suitable materials for the sheath and the core are described above. The meltblown layer may comprise meltblown fibers comprising a blend of PLA and polypropylene that have been regenerated from spunbond bicomponent fibers made of PP / PLA using the process taught in International Application No. PCT / US2015 / 012658.

[0334] In a fourth embodiment, the leg cuffs may comprise a fabric having an SMS structure, where the spunbond nonwoven layer comprises a bicomponent fabric having a PLA sheath and a PLA core. Examples of suitable materials for the sheath and the core are described above. As with the third embodiment described above, the meltblown layer may comprise meltblown fibers comprising a blend of PLA and polypropylene that have been regenerated from spunbond bicomponent fibers made of PP / PLA using the process taught in International Application No. CT / US2015 / 012658.

[0335] Preferably, the spunbond fabric for forming the leg cuffs has a sheath / core ratio of about 30 / 70 to about 70 / 30. In one embodiment, the basis weight of the SMS fabric is about 8 g / m 2 ~15g / m 2Preferably, the meltblown content comprises about 10 to about 30 weight percent based on the total weight of the SMS fabric. In some embodiments, the SMS fabric for use in forming the leg cuffs has a hydrohead value of greater than about 50 mm as measured according to INDA test method WSP80.6.

[0336] In some embodiments, the diaper 40 may also include elastic elements disposed around one or more of the waist region 52 and the elastic cuffs. For example, the diaper may also include at least one elastic waist feature (not shown) that helps provide improved fit and containment. The elastic waist feature is generally intended to elastically expand and contract to dynamically conform to the wearer's waist. The elastic waist feature preferably extends at least longitudinally outward from at least one waist end of the absorbent core, and generally forms at least a portion of the edge of the absorbent article. Disposable diapers may be constructed with two elastic waist features, one disposed in the front waist region and one disposed in the rear waist region. The elastic waist feature may be constructed in a number of different configurations, including those described in U.S. Pat. Nos. 4,515,595; 4,710,189; 5,151,092; and 5,221,274.

[0337] In some embodiments, the elastic features may be comprised of elastic elements comprising elastic strands or threads contractibly attached between the topsheet and backsheet of the diaper. Such strands or threads may be comprised of a bio-based material, such as natural rubber. As mentioned above, the natural rubber strands are covered by a nonwoven, such as the topsheet and / or the backsheet, so that the elastic members do not come into direct contact with the wearer's skin.

[0338] The absorbent article may include a fastening system that may be used to provide lateral tension to the periphery of the absorbent article to hold it on the wearer, as is typical for taped diapers. This fastening system is not necessary for pull-on style absorbent articles, such as training pants or adult incontinence absorbent articles, because the waist regions of these articles are already bonded.

[0339] The fastening system typically comprises fasteners, such as tape tabs, hook and loop fastening components, tabs & slots, buckles, buttons, snaps, and / or hermaphroditic fastening components, although any other known fastening means are generally acceptable. A landing zone is typically provided on the front waist region to which the fasteners can be releasably attached. When fastened, the fastening system interconnects the front waist region 52a and the rear waist region 52b. When fastened, the diaper 44 comprises a circumscribing waist opening and two circumscribing leg openings.

[0340] The fastening system may comprise an engaging member 80 and a receiving member 82 (also referred to as a landing zone). The engaging member 80 may comprise a hook, loop, adhesive, cohesive, tab, or other fastening mechanism. The receiving member 82 may comprise a hook, loop, slot, adhesive, cohesive, or other fastening mechanism into which the engaging member 80 may be received. Suitable engaging member 80 and receiving member 82 combinations are well known in the art and include, but are not limited to, hook / loop, hook / hook, adhesive / polymeric film, cohesive / cohesive, adhesive / adhesive, tab / slot, and button / buttonhole. Preferably, the fastening system may comprise a polymer derived from a bio-based material.

[0341] In this regard, Figure 9 further illustrates a fastening system in which the engagement members include a pair of tabs 80 joined to the back ears 56a and 56b and an associated landing zone 82 disposed on the front 84 of the diaper 40. In some embodiments, the tabs may include a pressure sensitive adhesive for adhesively attaching the tabs to the landing zone.

[0342] Some exemplary surface fastening systems are disclosed in U.S. Patent Nos. 3,848,594; 4,662,875; 4,846,815; 4,894,060; 4,946,527; 5,151,092; and 5,221,274 issued to Buell. An exemplary interlocking fastening system is disclosed in U.S. Patent No. 6,432,098. The fastening system may also provide a means for holding an article in a disposal configuration, as disclosed in U.S. Patent No. 4,963,140 issued to Robertson et al.

[0343] The fastening system may also include a primary fastening system and a secondary fastening system as disclosed in U.S. Pat. No. 4,699,622 to reduce overlap slippage or improve fit as disclosed in U.S. Pat. Nos. 5,242,436; 5,499,978; 5,507,736; and 5,591,152.

[0344] In a preferred embodiment, the fastening system may employ a hook and loop as described in U.S. Patent No. 9,084,701. In a preferred embodiment, the hook and loop fastening system includes a female fastening material made of a fibrous material and a male fastening material having hooks configured for the fibrous material.

[0345] In one embodiment, the female loop material comprises a bonded bicomponent fiber comprising a bio-based material, e.g., a spunbond bicomponent fiber having PLA, and a sheath comprising a polyethylene polymer derived from sugar cane. Examples of such materials are described above. One example of a suitable PLA polymer for the core is available from NatureWorks as PLA grade 6202.

[0346] A second fiber for use as a female loop component providing 50% bio-based material content comprises a petroleum-based polypropylene polymer sheath and a PLA core from NatureWorks under the product name PLA Grade 6202. Preferred polypropylenes for use in this embodiment typically have a melt flow rate (MFR) of 20-40 g / 10 min (measured according to ASTM D1238 (190° C. / 2.16 kg)), such as those offered by Total Petrochemicals and Refining USA, Inc. (La Port, TX, 77571 USA) as Grade M 3766 (metallocene polypropylene) and Grade M 3764 or Grade M 3866 (Zeigler Natta polypropylene).

[0347] Further examples of fibers for constructing a female loop material providing a 50% bio-based content include spunbond bicomponent fibers in which the core comprises a lignin-based polymer and the sheath comprises a petroleum-based polyethylene. Such fibers are disclosed as Examples 4, 5, 6, 7, 8 and 9 in EP 2,630,285 B1 and U.S. Patent Publication No. 2014 / 0087618.

[0348] Replacing the petroleum-based polyethylene sheath in these examples with a sheath made from sugarcane-derived polyethylene available from Braskem SA or corn-derived PLA available from NatureWorks, Inc. (both polymers disclosed above) provides fibers with up to 100% bio-based content.

[0349] A further example of a fiber that can be used to construct the female loop material is a bicomponent fiber having a core of (PLA) and a sheath that includes PLA. For example, in one embodiment, the core may include PLA with a lower %D isomer of polylactic acid than the %D isomer of the PLA polymer used in the sheath. PLA polymers with a lower %D isomer exhibit a higher degree of stress induced crystallization during spinning, while PLA polymers with a higher D isomer retain a more amorphous state during spinning. A more amorphous sheath promotes adhesion, and a core with a higher degree of crystallinity provides straightness to the fiber, which ultimately results in a bonded web.

[0350] In one particular embodiment, NatureWorks PLA grade PLA 6752, having 4% D isomer, can be used as the sheath, while NatureWorks grade 6202, having 2% D isomer, can be used as the core.

[0351] Further examples of fibers for use in female loop materials, providing at least 50% bio-based content, may include a 50 / 50 blend of cotton fibers and a petroleum-based polymer, such as polypropylene. An example of a polypropylene staple fiber useful for forming such a fabric is available from Fibervisions Corporation as grade T-198. An example of a cotton fiber for use in forming such a nonwoven fabric is available from the TJ Beall company under the product name TRUE COTTON. 登録商標 and fibers sold under the product name HIGH-Q ULTRA available from Barnhardt Manufacturing Company. 登録商標 This includes fibers sold under

[0352] The male hooks used in this fastening system for the preferred embodiment are also composed of significant sustainable content. The male fastening material with the hooks can be manufactured by casting, molding, profile extrusion, or microreplication, where the polymer used is corn-derived PLA, such as corn-derived PLA available from NatureWorks. NatureWorks offers a selection of grades for injection molding that can be used to manufacture the hooks, such as those mentioned above, including grades 3001D, 3052D, 3100HP, and 3251D.

[0353] Referring to FIG. 10, there is shown a further embodiment of an absorbent article in accordance with an embodiment of the present invention, where the absorbent article is in the form of a feminine sanitary pad, broadly designated by the reference numeral 100.

[0354] The pad 100 may comprise a topsheet 102, a backsheet 104, and an absorbent core 106 disposed therebetween. Preferably, the topsheet 102 and the backsheet 104 are joined to one another along opposing periphery edges to define a continuous seam 108 that extends to a periphery 110 of the pad 100. The continuous seam 108 may comprise a heat seal formed by thermally bonding the topsheet and the backsheet to one another. In other embodiments, the continuous seam 108 is formed by adhesively bonding the topsheet and the backsheet to one another.

[0355] Suitable materials for the topsheet, the backsheet and the absorbent core may comprise materials typically used in the construction of absorbent articles.

[0356] As shown, the pad 100 comprises a composite sheet 10 (see FIG. 3) that defines a fluid transport layer, e.g., a fluid AQDL component 112. The AQDL component is disposed between an absorbent core 106 and a topsheet 102. As previously discussed, the composite sheet that defines the fluid distribution / acquisition component comprises a fluid acquisition layer that includes a carded nonwoven and at least one airlaid layer that includes a blend of cellulosic staple and non-cellulosic fibers, where the fibers of the layers are thermally bonded to one another.

[0357] The various components of the absorbent article are typically joined via thermal or adhesive bonding. Examples of suitable adhesives include polyethylene, polypropylene, or ethylene vinyl acetate based melt adhesives. In some embodiments, the adhesive may include a bio-based adhesive. An example of a bio-based adhesive is a pressure sensitive adhesive available from Danimer Scientific under product code 92721.

[0358] In yet another aspect, certain embodiments of the present invention provide an absorbent article. According to certain embodiments, the absorbent article may include a composite sheet according to the present invention.

[0359] In this regard, composite sheets prepared according to embodiments of the present invention may be used in a wide variety of articles and applications. For example, embodiments of the present invention may be used for personal care applications such as baby care products (diapers, wipes), femin care products (pads and liners), adult care products (incontinence products), or cosmetic products (pads).

[0360] Working Example

[0361] The following examples are provided to illustrate one or more embodiments of the invention and are not to be construed as limiting the invention.

[0362] Unless otherwise defined, the technical terms used in the following embodiments have the same meaning as commonly understood by those skilled in the art to which the present invention belongs. The test reagents used in the following embodiments are conventional reagents unless otherwise specified, and the experimental methods are conventional methods unless otherwise specified.

[0363] Test Method

[0364] The thickness (caliper) was determined using a digital thickness gauge in accordance with EDANA 30.5-99. According to this test, a material sample is placed between two plates under pressure (0.5 kPa) and the distance between the two plates is reported in "mm".

[0365] By taking and cutting samples according to the requirements of different products, the size of the sample to be tested from the edge to the upper edge of the device should be less than 5mm. The sample should be conditioned under constant temperature and humidity conditions (23±2℃; relative humidity: 50%±5%) for at least 4 hours. If the sample is not conditioned, the temperature and humidity during the measurement should be recorded for comparison reference.

[0366] Basis weight

[0367] Basis weight was measured according to EDANA 40.3-90.

[0368] Mass determination: The mass of a unit area is the mass determination (gram weight) of the sample, with the unit g / m 2 It is.

[0369] Testing equipment: electronic balance (with a precision of 0.001 grams), a screen is installed around the balance to prevent air flow and other interference factors from affecting the balance.

[0370] The samples should be equilibrated for at least 4 hours under constant temperature and humidity conditions (23±2°C; relative humidity 50%±5%). If the balance is not implemented in an on-line real-time test, the temperature and humidity should be recorded while performing the measurements, for comparison reference only.

[0371] The sample to be tested is placed on the balance and after the balance reading has stabilized, the weight is recorded in grams.

[0372] Mass determination (GSM) = A / B Where: GSM: determined mass of sample; A: weight of sample; B: Area of ​​sample.

[0373] Tensile strength and elongation at break were measured according to EDANA 20.2-89.

[0374] Tensile strength: The tension required to break a sample of a specified size when pulled at a constant speed. The percentage of the original length of the sample when it is pulled to break is the breaking elongation (unit: "%)".

[0375] Test equipment: Zwick 2.5 strength tester

[0376] The sample is cut into a size of 200mm x 25.4mm, and the sample must be conditioned for at least 4 hours under constant temperature and humidity conditions (23±2℃; relative humidity 50%±5%). If conditioned is not performed in the online real-time test, the temperature and humidity at that time must be recorded and used as a basis for comparison.

[0377] Set up the test procedure according to the following test parameters: Maximum test limit: 100N; Test speed: 254mm / min; Clamping distance: 51mm; Clamping pressure: 5 bar.

[0378] Fluid retention was measured according to EDANA 10.4-02.

[0379] Liquid Absorption Capacity: After a sample is immersed in liquid for 10 minutes, the percentage of total weight increase is the absorption capacity of the sample.

[0380] Liquid Absorption Capacity: After a sample is immersed in liquid for 10 minutes, the total weight increase is the absorption capacity of the sample (g / g).

[0381] Retention: After the sample is immersed in the liquid for 10 minutes and the sample is kept in the container for 2 minutes, a 1976g weight is carefully placed on the sample and the increase in weight is the water retaining capacity of the sample (g / g).

[0382] Rewet (g)

[0383] The sample to be tested is placed on the absorbent core (applied to 150gsm SAP core (18% SAP) during the test). A φ60mm cylinder is placed at the center of the sample to be tested, 15ml of salt water is collected and put into the cylinder, and the time is started at the same time, after 5 minutes, several sheets of filter paper with known weight are placed on the surface of the sample (until the top filter paper does not absorb any liquid), and then a 1.2kg standard presser block is placed on the filter paper at the same time, and the time is started again, after 1 minute, the standard presser block is removed, and the mass of the filter paper on the surface of the sample is weighed by a balance, and the increased weight is taken as the reverse osmosis value. The smaller this value, the better rewetting performance will be expected.

[0384] Fluid acquisition was measured according to EDANA 150.5-02.

[0385] Acquisition: When 5 ml of 0.9% sodium chloride solution is permeated through the sample, the time of liquid passage is recorded in seconds by the circuit conductivity.

[0386] Testing equipment: Lister liquid penetration instrument

[0387] Wicking rate and vertical wicking height: Measured according to reference standard: EDANA 10.3-99

[0388] After one end of a vertically suspended sample is immersed in liquid for 5 minutes, the height to which the liquid rises along the sample is the suction range of the sample.

[0389] Sample size: The sample size is 30mm x 200mm.

[0390] The samples should be equilibrated for at least 4 hours under constant temperature and humidity conditions (23±2° C., relative humidity 50%±5%).

[0391] The test stand is placed in a plastic container, two rulers are fixed vertically, 0.9% NaCl solution or distilled water (according to the customer's request) is added, and the liquid level is adjusted so that the two rulers have a scale of 15 mm. A suitable amount of blue colorant is added into the solution for easy reading and mixed. The ruler is rotated out of the liquid surface, and the water on the surface is wiped clean, and the fully prepared sample is fixed to the ruler with a fishtail clip, and care is taken to adjust the bottom end of the ruler to the zero point. The ruler is rotated out of the liquid surface, and the time is started at the same time. The end of the ruler extended in the liquid is tilted slightly backwards to allow a certain gap between the ruler and the sample. After 5 minutes, the timer goes off and the two rulers are rotated out of the liquid surface and a reading is taken (observe how high the liquid surface rises along the sample, read the peak value, if any individual value is too high at the end of the sample, round it off and read the other peak value). The test result is the actual value minus 15mm to provide the wicking speed.

[0392] For vertical wicking rate, the above procedure is used except the liquid height is measured after 15 seconds.

[0393] The materials used in the composite sheets and comparative nonwoven fabrics are identified below. All percentages are by weight unless otherwise noted. All physical properties and compositional values ​​are approximate unless otherwise noted.

[0394] "Pulp-1" refers to treated pulp staple fiber derived from bamboo and is available from TAISON under the trade name "Bamboo Fluff". The bamboo staple fiber has an average length of 1.7 mm and an average width of approximately 18 microns. The bamboo staple fiber was prepared by pulping from chunk bamboo containing a blend of mainly Neosino calamus affinis, Linnania intermedia, Bambusa rigida Keng et Keng f., and Bambusa oldhamii. The properties of the bamboo fiber before pulping are as follows: average length 2.37mm; Average width 16.6 microns; length to width ratio 145; Wall thickness to cavity ratio of 1.7; and Cellulose content 48.08 weight percent and lignin content 26 weight percent.

[0395] "Pulp-2" refers to conventional treated pulp staple fiber available from Georgia Pacific under the product designation 4722.

[0396] "PE / PET-1" refers to a bicomponent staple fiber having a polyethylene sheath and a polyethylene terephthalate core, with a fineness of 2.2 dtex and an average length of 4 mm, which is available from Toray Chemical Korea Inc. under the product name FDL 17360.

[0397] "PE / PET-2" refers to a bicomponent staple fiber having a polyethylene sheath and a polyethylene terephthalate core, having a fineness of 2.2 dtex and an average length of 38 mm, which is available from Huvis under the product name N81S.

[0398] "Latex" refers to an aqueous polymer dispersion made from the monomers vinyl acetate and ethylene, which is available from Wacker under the product name VINNAPAS 登録商標 192. Latex formulations are diluted with water to have a solids content of 14-20%.

[0399] In the inventive examples described below, composite sheets according to embodiments of the invention were prepared by stacking two airlaid fabric layers on top of an air through bonded (ATB) carded fabric layer. The carded ATB fabrics used in inventive example 1 and comparative example 1 are as follows:

[0400] "ATB-1" refers to a carded fabric containing PE / PET-2 staple fibers. The carded fabric has a density of 20 g / m 2 The sheet had a basis weight of 1.0 g.

[0401] Preparation of Example 1 and Comparative Example 1

[0402] Unless otherwise indicated, the examples of the present invention were prepared according to the following procedure: In a first step, a pre-prepared fabric consisting of an air-through bonded, carded nonwoven fabric (ATB-1 fabric) was unwound from a spool and transferred onto a continuous mesh belt. The ATB fabric defines the fluid acquisition layer, and thus the fluid distribution component, of the composite sheet.

[0403] In Inventive Example 1, the ATB-1 fabric was conveyed to an airlaid forming head whereby a mixture of non-cellulosic (PET-1) and bamboo-derived staple fibers (Pulp-1) was deposited onto the ATB fabric to form the airlaid component of a composite sheet.

[0404] In Comparative Example 1, the ATB-1 fabric was transported to an airlaid forming head whereby a mixture of non-cellulosic (PET-1) and bamboo-derived staple fibers (Pulp-2) was deposited onto the ATB fabric to form the airlaid component of a composite sheet.

[0405] In Inventive Example 1 and Comparative Examples 1 and 2, an airlaid layer was deposited over the ATB fabric. The airlaid fabric layer was formed by a horizontal screen type molding technique using airlaid equipment obtained from M&J Company. The basis weight of the resulting composite sheet material was approximately 80 gsm for both Inventive Example 1 and Comparative Example 1.

[0406] In the airlaid process, the cellulosic staple and non-cellulosic fibers of one or more of the airlaid layers were mixed uniformly using airflow and multiple blades to create turbulence within each forming head. A vacuum was placed under the belt to assist in gathering the staple fibers onto the surface of the ATB fabric layer. After the first airlaid layer was deposited, a compression roller may optionally be placed between the first and second forming heads. The composite sheet is then transported to a second airlaid forming area where a second airlaid nonwoven layer is deposited over the previously deposited airlaid layer. This process is repeated until a desired amount of airlaid layers is deposited on the composite sheet. The resulting composite sheet may then be stabilized using heated rollers heated to a temperature of 80-180°C. The composite sheet was then transported to and passed through a first heated oven maintained at a temperature of about 120-165°C. At high speeds, it may be desirable to increase the temperature of the oven. The temperature of the first oven was selected to soften and melt the non-cellulosic fibers of both the airlaid layer and the fluid acquisition layer (e.g., the ATB layer) so that the fibers melt and flow together to form an integral composite sheet.

[0407] Prior to passing through the oven, the composite sheet was conveyed to a coating station where a coating layer of a latex formulation was deposited on the outermost airlaid surface to form a coating layer. The composite sheet was then heated in an oven to dry and cure the latex coating. The oven was maintained at a temperature of about 120 to about 150° C. Optionally, the composite sheet may be further dried in a third oven. The basis weight of the resulting composite sheet material was about 1000 g / m2.

[0408] Example 1 of the present invention

[0409] Inventive Example 1 was prepared by depositing two airlaid layers onto a previously prepared substrate of ATB-1. The airlaid layers contained a homogenous fiber mixture of Pulp-1 and PE / PET-1 fibers. After the two airlaid layers were deposited, a coating of a latex formulation was applied to the surface of the outermost airlaid layer. The composite sheet material was then passed sequentially through a series of ovens to bond the fibers together, and the latex formulation was dried and cured. The dry add-on weight of the latex layer was 3 weight percent based on the total dry weight of Inventive Example 1. The resulting composite sheet had a mass of 80 g / m 2 The sheet had a basis weight of 1.0 g.

[0410] Comparative Example 1

[0411] Comparative Example 1 was prepared by depositing two airlaid layers onto a previously prepared fabric of ATB-1. The airlaid layers contained a homogenous fiber mixture of Pulp-2 and PE / PET-1 fibers. A latex formulation of Latex was applied to Comparative Example 1 in a dry amount of 3 wt. % based on the total weight of the composite fabric. The fabric was dried in one or more ovens at a temperature of 150-160°C.

[0412] In Table 1 below, samples of Comparative Example 1 and Inventive Example 1 were obtained and evaluated for fluid management properties. As can be seen from the table, the fluid management properties were fairly comparable, despite a 34 percent reduction in thickness for the sample having bamboo-derived staple fibers instead of conventional wood pulp-containing fibers. For example, Inventive Example 1 had a 34% reduction in thickness compared to Comparative Example 1, while only showing a 9% reduction in fluid retention. This shows that the composite sheets of the present invention, despite being significantly thinner, still exhibit good fluid retention properties that are particularly favorable in absorbent articles.

[0413] [Table 1]

[0414] In Tables 2-4 below, the wicking properties and stiffness of the inventive composite sheet material were compared to similar composite sheet materials that did not include bamboo-derived staple fibers in the airlaid layer. The results in Tables 2 and 3 were obtained by taking six different samples of the inventive and comparative composite sheets and then measuring the listed properties. In Table 4, the average results from each measurement were compared to determine the increase / decrease and percent between the inventive and comparative composite sheets.

[0415] [Table 2]

[0416] [Table 3]

[0417] In Table 4 below, the average results for Comparative Example 1 and Inventive Example 1 are compared by determining the percent difference in the average values ​​for each measurement.

[0418] [Table 4]

[0419] As can be seen above, the wicking height and the wicking rate most significantly improved compared to the comparative composite sheet, indicating that the composite sheet of the present invention is expected to provide good liquid management properties in absorbent articles.

[0420] In addition, the composite sheet material of the present invention showed approximately a 40% decrease in CD stiffness and a 25% decrease in MD stiffness compared to the comparative composite sheet not containing bamboo-derived staple fibers, further indicating that absorbent articles comprising the composite sheet material of the present invention, and thus the airlaid nonwoven fabric of the present invention, are expected to provide a material with reduced stiffness while at the same time providing improvements in terms of liquid management properties, as evidenced by increases in wicking rate and wicking height.

[0421] Advantageously, the reduced stiffness and reduced thickness may provide an absorbent article that is more flexible, which in turn may help provide an increased level of comfort and discreetness to the wearer.

[0422] Many modifications and other embodiments of the inventions described herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. It is to be understood, therefore, that the invention is not limited to the specific embodiments disclosed, and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

1. 1. A composite sheet material comprising: a first layer; and an airlaid nonwoven layer overlying the first layer; Including, wherein the airlaid nonwoven layer comprises a blend of bamboo-derived staple fibers and non-cellulosic staple fibers, the airlaid nonwoven layer having a first surface disposed against and thermally bonded to a surface of the first layer, and a second surface defining an outer surface of the composite sheet material. The composite sheet material.

2. 10. The composite sheet material of claim 1, wherein the first layer is selected from the group consisting of spunbond nonwovens, meltblown nonwovens, spunlaced nonwovens, carded nonwovens, airlaid nonwovens, cellulosic tissue papers, films, and combinations thereof.

3. 3. The composite sheet material of claim 1 or 2, wherein the first layer comprises a carded nonwoven fabric comprising a plurality of staple fibers that are air-through bonded to one another to form a unitary nonwoven fabric.

4. 3. The composite sheet material of claim 1 or 2, wherein the airlaid nonwoven layer comprises a plurality of airlaid layers thermally bonded to adjacent airlaid layers.

5. 3. The composite sheet material of claim 1, wherein the airlaid nonwoven fabric layer comprises 2 to 10 airlaid layers.

6. An absorbent article comprising the composite sheet material of claim 1 or 2.

7. 1. A method of making a composite sheet, comprising: providing a first layer of sheet material; depositing a first airlaid layer on the surface of the first layer to form a composite sheet, wherein the first airlaid layer comprises a mixture of bamboo-derived staple fibers and non-cellulosic staple fibers; and air-through bonding the composite sheet with heated gas to melt the polymer of the non-cellulosic staple fibers and fuse adjacent fibers, the bamboo-derived staple fibers, and the first layer, wherein the non-cellulosic staple fibers of the airlaid layer are adhered to one another; The method comprising:

8. 8. The method of claim 7, further comprising sequentially depositing a plurality of airlaid layers onto the first airlaid layer.

9. An absorbent core for an absorbent article, the core comprising an airlaid layer comprising bamboo-derived staple fibers; The absorbent core is a first layer of fibers bonded together to form an integral web; and an airlaid nonwoven layer overlying the first layer; Including, wherein the airlaid nonwoven layer comprises a blend of bamboo-derived staple fibers and non-cellulosic staple fibers, the airlaid nonwoven layer having a first surface disposed toward and thermally bonded to a surface of the first layer, and a second surface defining an outer surface of the composite sheet material. The absorbent core.

10. 10. The absorbent core of claim 9, wherein the first layer is selected from the group consisting of spunbond nonwovens, meltblown nonwovens, spunlace nonwovens, carded nonwovens, airlaid nonwovens, spunbond-meltblown-spunbond composites (SMS), cellulosic tissue papers, films, and combinations thereof.

11. 11. The absorbent core of claim 9 or 10, wherein the first layer comprises a carded nonwoven fabric comprising a plurality of staple fibers that are air-through bonded to one another to form a unitary nonwoven fabric.

12. 11. The absorbent core according to claim 9, wherein the airlaid nonwoven fabric layer comprises 2 to 10 airlaid layers.

13. 11. The absorbent core of claim 9 or 10, wherein the first layer comprises a carded nonwoven fabric comprising a bio-based polymer.

14. 11. The absorbent core of claim 9 or 10, wherein the non-cellulosic staple fibers of the airlaid nonwoven layer comprise a bio-based polymer.

15. 15. The absorbent core of claim 13 or 14, wherein the bio-based polymer comprises an aliphatic polyester, a bio-based polyethylene, a bio-based polypropylene, a bio-based polyester, or a combination thereof.

16. 11. The absorbent core of claim 9 or 10, wherein said bamboo-derived staple fibers have an average length of from about 0.8 to about 3.0 mm and an average width of from about 12 to about 22 microns.

17. 11. The absorbent core of claim 9 or 10, wherein said bamboo-derived staple fibers have a length to width ratio of about 60 to about 120.

18. 11. The absorbent core of claim 9 or 10, wherein the airlaid nonwoven comprises one or more airlaid layers, and at least one of the airlaid layers comprises a superabsorbent polymer.

19. 10. The absorbent core of claim 9, further comprising a tissue layer.

Images