BR112019003303B1 - SCREEN SPINNING NONWOVEN FABRIC, ABSORBENT ARTICLE, PROCESS FOR PREPARING A POLYLACTIC ACID SPUNNING NONWOVEN FABRIC (PLA) AND SYSTEM FOR PREPARING A POLYLACTIC ACID SCREENING NONWOVEN FABRIC (PLA) - Google Patents

Abstract

The present invention relates to nonwoven fabrics having a plurality of fibers that are consolidated together to form a cohesive batt, the fibers comprising a mixture of a polylactic acid (PLA) and at least one secondary alkanesulfonate. Non-woven fabrics exhibit increased tensile strengths, elongation and toughness.

Description

TECHNICAL FIELD OF THE INVENTION

[0001] The presently described invention relates in general to non-woven fabrics and, more specifically, to non-woven fabrics comprising polylactic acid (PLA).

BACKGROUND OF THE INVENTION

[0002] Nonwoven fabrics are used in a variety of applications such as clothing, disposable medical products, diapers, personal care products, among others. New products under development for these applications demand high performance, including comfort, conformability to the body, freedom of body movement, good softness and drape, adequate tensile strength and durability, and resistance to surface abrasion and the formation of pilling (curling) or fuzzing (clumps of fibers without formation) on the surface. Thus, the non-woven fabrics that are used in these types of products must be developed to meet these performance requirements.

[0003] Traditionally, such nonwoven fabrics are prepared from thermoplastic polymers such as polyester, polystyrene, polyethylene and polypropylene. These polymers are generally very stable and can remain in the environment for a long time. Recently, however, there has been a trend towards articles and products being considered environmentally friendly and sustainable. As part of this trend, there has been a desire to create eco-friendly products made with more sustainable content in order to reduce the content of petroleum-based materials.

[0004] Polylactic acid or polylactide (PLA)-based polymers provide a cost-effective way to nonwoven fabrics, obtained by continuous spinning, with sustainable content that can be quickly converted into products for consumers. To fully realize the cost-effective benefits of PLA-based consumer products, PLA must be convertible into nonwovens and then into the final consumer product at very high speeds with minimal waste. However, due to the propensity for static electricity generation and build-up on fibers with surface PLA polymer, it is difficult to combine the spinning, matting, and consolidation steps at the very high speeds required to produce economically attractive spunbond (continuously spun) PLA with ideal fabric properties.

[0005] To address this need, nonwovens have been developed with a bicomponent sheath/core structure in which PLA is present in the core and a synthetic polymer, such as polypropylene, in the sheath. An example of such a nonwoven fabric is described in U.S. Pat. No. 6,506,873. The presence of the synthetic polymer in the sheath provides the necessary properties for commercial production of nonwovens comprising PLA at high speeds. While commercial production of nonwovens comprising PLA with synthetic polymers in the hem is possible, the industry (and its consumers) are looking for nonwovens with PLA on the fabric surface, either having PLA in the hem or being 100% PLA.

[0006] Thus, there is still a need for fabrics with PLA that exhibit improved mechanical properties.

Summary of the invention

[0007] One or more embodiments of the invention can address one or more of the problems mentioned above. Certain embodiments according to the invention provide spunbond (continuously spun) polylactic acid (PLA) nonwoven fabrics, sustainable composites including said fabrics, and sustainable articles including said fabrics and/or composites. Specifically, embodiments of the invention are directed to fabrics, composites and articles comprising PLA.

[0008] Certain embodiments according to the invention are directed to a spunbond (continuously spun) nonwoven fabric comprising a plurality of fibers that are consolidated together to form a cohesive batt, wherein the fibers comprise a mixture of a polylactic acid (PLA) and at least one secondary alkane sulphonate. In some embodiments, the mixture is present on a surface of the plurality of fibers.

[0009] In one embodiment, at least one secondary alkanesulfonate comprises an alkane chain having C10-C18, and wherein at least one of the secondary carbons of the alkane chain includes a sulfonate moiety. For example, at least one secondary alkanesulfonate has at least one of the following structures: where m + n is a number between 7 and 16, and X is independently a C1-C4 alkyl or absent. In some embodiments, at least one secondary alkanesulfonate has the following structure: where m + n is a number between 8 and 15 and, in particular, where m + n is a number between 11 and 14. In some embodiments, the at least one secondary alkanesulfonate comprises a sodium or potassium salt.

[0010] In certain embodiments, at least one secondary alkanesulfonate is present in an amount ranging from approximately 0.0125 to 2.5 weight percent based on the total weight of the fiber. For example, the fiber can have a bicomponent sheath/core arrangement in which the blend is present in the sheath, and in which the secondary alkanesulfonate is present in the sheath in an amount ranging from approximately 0.1 to 0.75 weight percent based on the total weight of the sheath. In another embodiment, the fiber can have a bicomponent sheath/core arrangement in which the blend is present in the sheath, and in which the secondary alkane sulfonate is present in the sheath in an amount ranging from approximately 0.2 to 0.6 weight percent based on the total weight of the sheath. In yet another embodiment, the fiber has a bicomponent sheath/core arrangement in which the blend is present in the sheath, and in which the secondary alkane sulfonate is present in the sheath in an amount ranging from approximately 0.3 to 0.4 percent by weight, based on the total weight of the sheath.

[0011] In one embodiment, the plurality of fibers comprise bicomponent fibers. In some embodiments, the plurality of fibers comprise bicomponent fibers, and at least one secondary alkanesulfonate is present in one of the fiber components. In one embodiment, the bicomponent fibers have a sheath/core configuration and the sheath comprises a blend of PLA and at least one secondary alkanesulfonate. In some embodiments, the core comprises PLA and does not include a secondary alkanesulfonate. In still other embodiments, the bicomponent fibers comprise a side-by-side arrangement.

[0012] In one embodiment, the core comprises at least one polyolefin, one polyester, one PLA or any combination thereof. In a preferred embodiment, the sheath and core comprise PLA. In certain embodiments, the sheath comprises a first grade PLA, the core comprises a second grade PLA, and the first grade PLA and the second grade PLA are different.

[0013] Surprisingly, the inventors found that adding the secondary alkanesulfonate to the PLA resin improves the mechanical properties of the fabric. Specifically, the fabric may exhibit an increase in tensile strength, elongation, and toughness in at least one of the machine directions or in the transverse direction compared to an identical fabric that does not include a secondary alkanesulfonate. For example, the fabric can exhibit an increase in tensile strength in at least one of the machine directions or in the cross direction of at least 50% compared to an identical fabric that does not include a secondary alkanesulfonate.

[0014] In yet another aspect, embodiments of the invention are directed to a spunbond nonwoven fabric comprising a plurality of fibers that are consolidated together to form a cohesive batt, wherein the fibers comprise between 95 and 100% polylactic acid (PLA), and wherein the fibers exhibit a Root Mean Square Tenacity Index per grammage value of at least 55 N/m2. In one embodiment, the fabric has a Root Mean Square Tenacity Index per gram weight greater than 65 N%/g/m 2 , such as greater than 85 N%/g/m 2 . In a preferred embodiment, the fabric has a Root Mean Square Toughness Index per weight value between approximately 65 and 150 N%/g/m 2 . Preferably, the fabric comprises fibers with less than 5% by weight of additives, and most preferably less than 4% by weight, based on the total weight of the fabric.

[0015] Additional aspects of the invention are directed to articles comprising the nonwoven fabric and to a process and system for preparing the fabric.

Brief description of the various views of the drawing(s)

[0016] Having thus described the invention in general terms, reference will now be made to the accompanying drawings, which are not necessarily to scale, and in which:

[0017] Figures 1A and 1B are SEM (scanning electron microscope) images of individual consolidation spots on a surface of a non-woven fabric that does not include a secondary alkanesulfonate;

[0018] Figures 2A and 2B are SEM images of individual consolidation points on a surface of a nonwoven fabric that includes a secondary alkanesulfonate;

[0019] Figure 3 is a schematic diagram of the PLA spunbond nonwoven fabric preparation system according to certain embodiments of the invention;

[0020] Figures 4A-4C are schematic diagrams illustrating the positioning of the first ionization source in accordance with certain embodiments of the invention;

[0021] Figures 5A-5D are cross-sectional views of composites according to certain embodiments of the invention;

[0022] Figure 6A is an illustration of an absorbent article according to at least one embodiment of the invention;

[0023] Figure 6B is a cross-sectional view of the absorbent article of Figure 6A, taken along line 7272 of Figure 6A; It is

[0024] Figure 7 is an illustration of an absorbent article according to at least one embodiment of the invention in which the absorbent article is in the form of a feminine sanitary pad.

Detailed description of the invention

[0025] The invention will now be described in more detail below with reference to the accompanying drawings, in which some, but not all, embodiments of the invention are shown. In fact, this invention can be embodied in many different forms, and it should not be construed as limited to the embodiments presented herein; rather, these modalities are provided so that this description will satisfy applicable legal requirements. Like numbers refer to similar elements throughout the text. In this specification, and in the appended claims, the singular forms "a", "an", "the" "the" include plural referents unless the context clearly indicates otherwise.

[0026] In accordance with certain embodiments, the invention includes polylactic acid (PLA) spunbond nonwoven fabrics, sustainable composites including said fabrics, and absorbent articles including said fabrics and/or composites. Specifically, embodiments of the invention are directed to fabrics, composites and articles in which PLA is present on the surface of the fabric.

[0027] PLA spunbond non-woven fabrics and sustainable composites including said fabrics can be used in a wide variety of applications, including diapers, feminine care products, cleansers, incontinence products, agricultural products (e.g., root wraps, seed bags, crop covers and/or the like), industrial products (e.g., work overalls, airplane pillows, car trunk lining and soundproofing materials) and products for domestic use (eg pad for removing scratches from furniture, mattress pads and/or the like).

I.Definitions

[0028] For the purposes of this patent application, the following terms shall have the meanings below:

[0029] The term "fiber" can refer to a fiber of finite length or a filament of infinite length.

[0030] In this specification, the term "monocomponent" refers to fibers formed from a polymer or formed from a single blend of polymers. Of course, this does not exclude fibers to which additives have been added for color, antistatic properties, lubrication, hydrophilicity, liquid repellency, etc.

[0031] In this specification, the term "multicomponent" refers to fibers formed from at least two polymers (eg, bicomponent fibers) that are extruded from separate extruders. The two polymers at least can be, each independently, the same or different from each other, or they can be a mixture of polymers. The polymers are arranged in distinct zones, substantially in constant position, in the cross-section of the fibres. Components can be arranged in any desired configuration, such as sheath-core, side-by-side, pie, islands in the sea, and so on. Various methods for forming multicomponent fibers are described in U.S. Pat. No. 4,789,592, issued to Taniguchi et al., and U.S. Patents Nos 5,336,552 issued to Strack et al., 5,108,820 issued to Kaneko et al., 4,795,668 issued to Kruege et al., 5,382,400 issued to Pike et al., 5,336,552 issued to Strack et al., and 6,200,669 issued to Marmon et al., the contents of which are hereby incorporated, in their entirety, by reference in this patent application. It is also possible to form multicomponent fibers of various irregular shapes, as described in U.S. Pat. Nos. 5,277,976 Issued Hogle et al., 5,162,074 Issued Hills, 5,466,410 Issued Hills, 5,069,970 Issued Largman et al., and 5,057,368 Issued Largman et al., the contents of which are incorporated herein, in their entirety, by reference in this patent application.

[0032] In this specification, the term “nonwoven”, “nonwoven batt” and “nonwoven fabric” refer to a structure or a blanket of material that has been formed without the use of weaving or knitting processes to produce a structure of individual fibers or yarns that intersect or intersperse, but not in an identifiable, repeated manner. In the past, nonwoven webs have been formed by a variety of conventional processes, such as meltblown, spunbond, and staple fiber carding processes.

[0033] In this specification, the term "blow spinning" refers to a process in which fibers are formed by extruding a molten thermoplastic material through a plurality of fine, normally circular capillary matrices in high-velocity gas streams (e.g., air), which attenuates the molten thermoplastic material and forms fibers, which can be reduced to microfiber diameters. Thereafter, the molten and blown fibers are carried by the gas flow and deposited on a collecting surface to form a mat of randomly dispersed fibers, such a process is described, for example, in U.S. Patent No. 3,849,241 issued to Buntin et al.

[0034] In this descriptive report, the term “machine direction” or “MD” refers to the direction of travel of the non-woven mat during manufacturing.

[0035] In this descriptive report, the term “transverse direction” or “CD” refers to a direction that is perpendicular to the direction of the machine and extends laterally across the width of the nonwoven mat.

[0036] In this specification, the term "spunbond" refers to a process involving the extrusion of a molten thermoplastic material, in the form of filaments, through a plurality of thin, usually circular capillaries of a spinneret, the filaments then attenuated and stretched by mechanical or pneumatic means. The filaments are deposited onto a collecting surface to form a mat of substantially continuous, randomly arranged filaments, which thereafter may be consolidated to form a cohesive non-woven fabric. The production of continuous spinning nonwoven webs is illustrated in patents such as, for example, U.S. Pat. Nos. 3,338,992; 3,692,613, 3,802,817; 4,405,297 and 5,665,300. In general, these continuous spinning processes include extruding the filaments through a spinneret, quenching the filaments with an air stream to accelerate solidification of the molten filaments, attenuating the filaments by applying a drawing stress, either pneumatically dragging the filaments in an air stream or mechanically winding them around mechanical drawing cylinders, depositing of the filaments stretched over a porous collecting surface to form a mat and collection and consolidation of the loose filament mat into a non-woven fabric. Consolidation can be by any thermal or chemical consolidation treatment, thermal consolidation in spots being typical.

[0037] In this specification, the term "spot thermal consolidation" involves passing a material, such as one or more fiber mats to be consolidated, between a heated calender cylinder and an anvil roller. The calender roll is typically patterned so that fabric consolidation occurs at distinct stitch locations rather than across the entire surface of the web.

[0038] In this specification, the term "polymer" generally includes, among others, homopolymers, copolymers, such as, for example, block, graft, random and alternating copolymers, terpolymers, etc. and mixtures and modifications thereof. Furthermore, unless specifically limited, the term "polymer" shall include all possible geometric configurations of the material, including isostatic, syndiotactic and random symmetries.

[0039] The term "composite" in this specification may be a structure comprising two or more layers, such as a film layer and a fiber layer, or a plurality of fiber layers fused together. The two layers of a composite structure can be joined in such a way that a substantial part of the common X-Y plane of the layers interfaces, in accordance with certain embodiments of the invention.

[0040] Embodiments of the invention are directed to nonwoven fabrics comprising polylactic acid that exhibit improvements in strengths and toughness. In one embodiment, the present invention provides a spunbond nonwoven fabric comprising a plurality of fibers which are joined together to form a cohesive batt, and wherein the fibers of the plurality comprise a blend of a PLA resin and at least one secondary alkanesulfonate. As explained in more detail below, the inclusion of a secondary alkanesulfonate in the PLA resin improves the strength and toughness of the fabric compared to an identical fabric that does not include the secondary alkanesulfonate.

[0041] At least one secondary alkanesulfonate typically comprises an alkane chain having C10-C18, with at least one of the secondary carbons of the alkane chain including a sulfonate moiety. Specifically, the at least one secondary alkanesulfonate may comprise a secondary C13-C17 alkanesulfonic acid, sodium salt.

[0042] The alkane chain is generally linear, although some chains may include some minimal branching (eg, C1-C4 side chain branching). Typically, the alkane chain will have from 10 to 18 carbon atoms, with an alkane chain length between 14 and 17 carbon atoms being slightly more preferred. Secondary alkanesulfonate can include mono and disulfonic acids. However, the amount of monosulfonic acids in the secondary alkanesulfonate can generally be greater than 90%.

[0043] In one embodiment, at least one secondary alkanesulfonate has one of the following structures: where m+n is a number between 7 and 16 and X is independently a C1-C4 alkyl or absent. In a preferred embodiment, the secondary alkanesulfonate has the following structure: where m+n is a number between 8 and 15, and more preferably, m+n is a number between 11 and 14. The secondary alkanesulfonate typically comprises a sodium or potassium salt, but other cations could be used, such as a calcium or magnesium salt. Alternatively, a quaternary ammonium compound composed of modified fatty alkyl substrates, such as those based on coconut or stearyl, could be used. Such quaternary amines are available from Air Products and Chemicals, Inc. of Allentown, PA 18195-1501, USA.

[0044] In one embodiment, the secondary alkanesulfonate can be provided in a masterbatch vehicle resin. For example, in one embodiment, the secondary alkanesulfonate is provided in a PLA carrier polymeric resin which is blended with PLA prior to spinning the fibers. Typically, the amount of secondary alkane sulfonate in the PLA masterbatch is between approximately 5 and 25 weight percent based on the total weight of the masterbatch, with an amount of 10 to 20 weight percent being slightly more typical. The masterbatch can also include additional additives, such as one or more compatibilizers. A commercial example of a secondary alkanesulfonate that can be used in embodiments of the claimed invention includes SUKANO® under the product name S546-Q1, which is a sodium salt of C14-C17 secondary alkanesulfonate in a PLA masterbatch. One skilled in the art would recognize that creating a masterbatch for a secondary alkane sulfonate constitutes a compromise between maximizing the use of PLA resins with fluidity very similar to that observed for the base resin of the fiber, such as, for example, NatureWorks 6202D or 6252 D (Flow index g/10 minutes (210°C) 15 -30 or 15, respectively), and the ease of suspending the secondary alkane sulphonate in a polymer of PLA. Thus, a suitable masterbatch might be between a grade of PLA such as Nature Works 6362D with a higher melt index (melt index g/10 minutes (210°C)) of 70 - 85.

[0045] A wide variety of PLA resins can be used to prepare nonwoven fabrics in accordance with embodiments of the invention. In general, polylactic acid-based polymers are prepared from dextrose, a sugar source derived from field corn. In North America, corn is used as it is the most economical source of vegetable starch for final conversion to sugar. However, it must be recognized that dextrose can be derived from sources other than corn. Sugar is converted into lactic acid or a derivative of lactic acid via fermentation using microorganisms. The lactic acid can then be polymerized to form PLA. In addition to corn, other agriculturally based sugar sources can be used including rice, sugar beet, sugar cane, wheat, cellulosic materials such as xylose recovered from wood pulp, and the like.

[0046] The PLA resin must have the appropriate molecular properties to be spun in continuous spinning processes (spunbond). Examples of suitable ones include PLA resins supplied by NatureWorks LLC, of Minnetonka, such as MN 55345, grade 6752D, 6100D, and 6202D, which are believed to be generally produced following the teachings of U.S. Patents 5,525,706 and 6,807,973, both issued to Gruber et al. Other examples of suitable PLA resins may include L130, L175 and LX175, all from Corbion of Arkelsedijk 46, 4206 A C Gorpolegadaem, The Netherlands.

[0047] In some embodiments, nonwoven fabrics may be biodegradable. “Biodegradable” refers to a material or product that degrades or decomposes under environmental conditions that include the action of microorganisms. Thus, a material is considered biodegradable if a specified reduction in the material's tensile strength and/or maximum elongation or other critical physical or mechanical property is observed after exposure to a defined biological environment for a defined time. Depending on the defined biological conditions, a fabric composed of PLA could or could not be considered biodegradable.

[0048] A special class of biodegradable products made with bio-based material could be considered compostable if it could be degraded in a composting environment. The European standard EN 13432, "Proof of Compostability of Plastic Products" can be used to determine whether a fabric or film made of sustainable content could be classified as compostable.

[0049] In some embodiments, PLA nonwoven fabrics may comprise sustainable polymeric components of biodegradable products that are derived from an aliphatic component having a carboxylic acid group (or a polyester forming a derivative thereof, such as an ester group) and a hydroxyl group (or a polyester forming a derivative thereof, such as an ether group) or may be derived from a combination of an aliphatic component with two carboxylic acid groups (or a polyester forming a derivative thereof, such as an ester group) with an aliphatic component an atic having two hydroxyl groups (or a polyester forming a derivative thereof, such as an ether group).

[0050] The term "aliphatic polyester" includes - in addition to polyesters formed exclusively by aliphatic and/or cycloaliphatic components - also polyesters that contain, in addition to aliphatic and/or cycloaliphatic units, aromatic units, provided that the polyester has a substantial sustainable content.

[0051] In addition to PLA-based resins, nonwoven fabrics according to embodiments of the invention may include other polymers derived from an aliphatic component having a carboxylic acid group and a hydroxyl group, which are alternatively called polyhydroxyalkanoates (PHA). Examples are polyhydroxybutyrate (PHB), poly-(hydroxybutyrate-co-hydroxyvalerate) (PHBV), poly-(hydroxybutyrate-co-polyhydroxyhexanoate) (PHBH), polyglycolic acid (PGA), poly-(epsilon-caprolactone) (PCL) and, preferably, polylactic acid (PLA).

[0052] Examples of additional polymers that can be used in embodiments of the invention include polymers derived from a combination of an aliphatic component having two carboxylic acid groups with an aliphatic component having two hydroxyl groups are polyesters derived from aliphatic diols and aliphatic dicarboxylic acids such as polybutylene succinate (PBSU), polyethylene succinate (PESU), polybutylene adipate (PBA), polyethylene adipate ( PEA), polytetramethylene adipate/terephthalate (PTMAT).

[0053] The nonwoven fabrics according to the invention may comprise monocomponent, bicomponent or multicomponent fibers. Examples of bicomponent fibers include side-by-side arrays, offshore islands, and sheath/core. Preferably, the fibers have a sheath/core structure in which the sheath comprises a first polymeric component and the core comprises a second polymeric component. In this arrangement, the polymers of the first and second polymeric component can be the same or different from each other.

[0054] In a preferred embodiment, the fibers of the nonwoven fabric have a bicomponent configuration, in which the PLA blend comprising the secondary alkanesulfonate comprises a first polymeric component defining a sheath, and a second polymeric component comprises the core. Advantageously, the inventors have found that blending the secondary alkanesulfonate into the polymeric component defining the sheath provides nonwoven fabrics with improved strength and toughness. Furthermore, such improvements in physical properties can be achieved in the absence of mixing the secondary alkanesulfonate into the core-defining polymeric component, which can help to reduce the overall costs of preparing the nonwoven fabric.

[0055] In preferred embodiments, the sheath and core comprise a PLA resin. In these embodiments, a PLA spunbond nonwoven fabric substantially free of synthetic polymeric components such as petroleum-based materials and polymers can be provided. For example, the PLA spunbond nonwoven fabric fibers can have a bicomponent arrangement where the two components are PLA-based to thereby produce a fiber that is 100% PLA.

[0056] In this specification, "PLA 100%" may also include up to 5% of additives including additives and/or masterbatches of additives to provide, by way of example only, color, softness, slip, antistatic protection, lubricity, hydrophilicity, liquid repellency, antioxidant protection and the like. In this regard, the nonwoven fabric may comprise PLA 95-100%, such as PLA 96-100%, PLA 97-100%, PLA 98-100%, PLA 99100%, etc. When such additives are added as a masterbatch, for example, the masterbatch vehicle can primarily comprise PLA, in order to facilitate processing and maximize sustainable content within the fibers.

[0057] For example, the PLA spunbond nonwoven fabric layer may comprise one or more additional additives. In such embodiments, for example, the additive may comprise at least a colorant, a softening agent, a glidant, an antistatic agent, a lubricant, a hydrophilic agent, a liquid repellent, an antioxidant and the like or any combination thereof.

[0058] In one embodiment, the PLA polymer of the sheath may be the same PLA polymer as that of the core. In other embodiments, the PLA polymer of the sheath may be a different PLA polymer than that of the core. For example, the bicomponent fibers may comprise reverse PLA/PLA bicomponent fibers, such that the sheath comprises a first grade PLA, the core comprises a second grade PLA, and the first grade PLA and the second grade PLA are different (e.g., the first grade PLA has a higher melting point than the second grade PLA). By way of example only, the first grade PLA can comprise up to approximately 5% crystallinity, and the second grade PLA can comprise between about 40% and 50% crystallinity.

[0059] In other embodiments, for example, the first grade PLA may comprise a melting point between approximately 125°C and 135°C, and the second grade PLA may comprise a melting point between approximately 155°C and 170°C. In further embodiments, for example, the first grade PLA can comprise a weight percent D-isomer of between approximately 4% by weight and 10% by weight, and the second grade PLA can comprise a weight percent D-isomer of approximately 2% by weight.

[0060] For example, in one embodiment, the core may comprise a PLA having a lower % of the D-isomer of polylactic acid than that % of the D-isomer of the PLA polymer used in the sheath. PLA polymer with lower % D-isomer will exhibit a higher degree of stress-induced crystallization during spinning, while PLA polymer with higher % D-isomer will retain a more amorphous state during spinning. The more amorphous sheath will promote consolidation while the core exhibiting a higher degree of crystallization will provide fiber strength and thus the final consolidated network. In one particular embodiment, NatureWorks PLA Grade PLA 6752 with 4% D-isomer can be used as the sheath, while NatureWorks Grade 6202 with 2% D-isomer can be used as the core.

[0061] In general, the weight percentage of the hem to that of the core in the fibers can vary greatly depending on the desired properties of the nonwoven fabric. For example, the sheath to core weight ratio can vary between about 10:90 and 90:10, and in particular between about 20:80 and 80:20. In a preferred embodiment, the sheath to core weight ratio is approximately 25:75 to 35:65, with a weight ratio of approximately 30:70 being preferred.

[0062] In other embodiments, a nonwoven fabric comprising bicomponent fibers is provided in which one of the polymeric components comprises a mixture of a PLA polymer and the secondary alkanesulfonate, and the other polymeric component comprises a synthetic polymer, such as a petroleum-derived polymer. Examples of synthetic polymers that can be used in embodiments of the invention may include polyolefins, such as polypropylene and polyethylene, polyesters, such as polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT) and polybutylene terephthalate (PBT), nylons, polystyrenes, copolymers and mixtures thereof, in addition to other synthetic polymers that can be used in the preparation of fibers.

[0063] The amount of the secondary alkanesulfonate in the fibers will generally depend on where the secondary alkanesulfonate is present in the fiber structure, and the desired ultimate properties of the nonwoven fabric. In general, the amount of the secondary alkanesulfonate can range from approximately 0.0125 weight percent to 2.5 weight percent based on the total weight of the polymer component of the fiber in which the secondary alkanesulfonate is present. For example, in monocomponent fibers, the weight percent of the secondary alkane sulfonate in the fibers will be based on the total weight of the fiber. In such a case, the amount of secondary alkanesulfonate can range from approximately 0.0125 weight percent to 2.5 weight percent based on the total weight of the fiber. However, in the case of a bicomponent fiber, the weight percent secondary alkanesulfonate will be based on the total weight of the component in which the secondary alkanesulfonate is present. For example, in the case of a bicomponent fiber with a sheath-to-core weight ratio of 30:70 and in which the secondary alkanesulfonate is present only in the sheath, the weight percent secondary alkanesulfonate in the fiber can range from approximately 0.0125 weight percent to 2.5 weight percent based on the total weight of the sheath, resulting in a secondary alkanesulfonate weight percent of 0.00375 to 0.750, based on the total fiber weight.

[0064] In one embodiment, the amount of the secondary alkanesulfonate can be at least any one of the following: at least 0.0125, at least 0.0250, at least 0.0375, at least 0.050, at least 0.0625, at least 0.075, at least 0.100, at least 0.125, at least 0.150, at least 0.187 5, at least 0.2, at least 0.2475, at least 0.25, at least 0.3 at least 0.375, at least 0.40, at least 0.495, at least 0.50, at least 0.60, at least 0.80, at least 0.9904, at least 1.0, at least 1.25, at least 1.2375, at least 1, 5, at least 1.875, at least 2.0 and at least 2.50, based on the total weight of the polymeric component of the fiber in which the secondary alkanesulfonate is present. In other embodiments, the amount of the secondary alkanesulfonate can be less than any of the following: 0.0250; 0.0375; 0.050; 0.0625; 0.075; 0.100; 0.125; 0.150; 0.1875; 0.2; 0.2475; 0.25; 0.3; 0.375; 0.40; 0.495; 0.50; 0.60; 0.80; 0.9904; 1.0; 1.25; 1.2375; 1.5; 1.875; 2.0 and 2.50 weight percent. It should also be recognized that the amount of the secondary alkanesulfonate present in a polymeric component of the fiber also ranges between the amounts mentioned above.

[0065] In a preferred embodiment, the fibers have a bicomponent structure in which both the core and sheath comprise a PLA polymer, and the sheath includes the secondary alkanesulfonate, present in an amount of between approximately 0.1 and 1 percent by weight, based on the total weight of the component of the sheath, and in particular between approximately 0.1 and 0.75, more particularly between approximately 0.2 and 0.6 percent by weight, and even more particularly between approximately 0.3 and 0.4 weight percent based on the total weight of the sheath component. Although the secondary alkanesulfonate has generally been described as present in a monocomponent fiber or in the sheath of a bicomponent fiber, it should be recognized that other arrangements are encompassed by embodiments of the present invention. For example, the secondary alkanesulfonate can be present only in the core and not the sheath of a bicomponent fiber, or the secondary alkanesulfonate can be present in both the sheath and the core.

[0066] Since the amount of secondary alkanesulfonate in the fibers may vary depending on the amount of secondary alkanesulfonate in the masterbatch polymer, the structure of the fiber (e.g., monocomponent or bicomponent) and, in the case of bicomponent, the ratio of a first component to a second polymeric component in the fiber, the following tables provide exemplary ranges of secondary alkanesulfonate in various fiber structures, and at various loadings of secondary alkanesulfonate in the masterb polymer catch and several masterbatch loadings on the PLA polymer. Table 1A: Amounts of secondary alkanesulfonate (SAS) in the sheath of a bicomponent fiber having a sheath-to-core weight ratio of 50:50 in various SAS and MasterBatch (MB) shipments Table 1B: Amounts of secondary alkanesulfonate (SAS) in fabric composed of bicomponent fibers with sheath/core weight ratio of 50:50 in various SAS and Master Batch (MB) shipments Table 2A: Amounts of secondary alkanesulfonate (SAS) in the sheath of a bicomponent fiber with a sheath-to-core weight ratio of 30:70 in various SAS and MasterBatch (MB) shipments Table 2B: Amounts of secondary alkanesulfonate (SAS) in a fabric comprising bicomponent fibers with a sheath-to-core weight ratio of 30:70 at various SAS and MasterBatch (MB) shipments Table 3: Amounts of secondary alkanesulfonate (SAS) in a fabric comprising monocomponent PLA fibers at various SAS and MasterBatch (MB) loadings

[0067] According to certain embodiments, for example, the non-woven fabric can have a grammage between approximately 7 grams per square meter (gsm) and 150 gsm. In other embodiments, for example, the fabric may have a basis weight between approximately 8 gsm and 70 gsm. In certain embodiments, for example, the fabric may comprise a weight between approximately 10 gsm and 50 gsm. In further embodiments, for example, the fabric can have a weight between approximately 11 gsm and 30 gsm. Accordingly, in certain embodiments, the fabric may have a weight of at least approximately any of the following: 7, 8, 9, 10, and 11 gsm and/or at most approximately 150, 100, 70, 60, 50, 40, and 30 gsm (e.g., approximately 9-60 gsm, approximately 11-40 gsm, etc.).

[0068] Furthermore, fabrics prepared according to embodiments of the invention can be characterized by an area shrinkage of less than 5%. In further embodiments, for example, the fabrics can be characterized by an area shrinkage of less than 2%.

[0069] According to certain embodiments, for example, the fibers may have a linear bulk density of between approximately 1 dtex and 5 dtex. In other embodiments, for example, the fibers can have a dtex between approximately 1.5 dtex and 3 dtex. In further embodiments, for example, the fibers can have a linear bulk density of between approximately 1.6 dtex and 2.5 dtex. Thus, in certain embodiments, the linear bulk density of the fibers is at least approximately any one of the following: 1; 1.1; 1.2; 1.3; 1.4; 1.5 and 1.6 dtex and/or at most approximately 5; 4.5; 4; 3.5; 3 and 2.5 dtex (e.g. approximately 1.4-4.5 dtex, approximately 1.6-3 dtex, etc.).

[0070] Advantageously, the inventors of the present invention have found that the addition of the secondary alkanesulfonate to the PLA resin provides significant increases in mechanical properties compared to an identical or similarly prepared nonwoven fabric that does not include the secondary alkanesulfonate. In this regard, nonwoven fabrics according to embodiments of the present invention can exhibit tensile strengths that are 50% greater compared to a similarly prepared nonwoven fabric that does not include the secondary alkanesulfonate. In some embodiments, the nonwoven fabric can exhibit a tensile strength that is 50% to 200% greater than the tensile strength of a similarly prepared nonwoven fabric that does not include the secondary alkanesulfonate.

[0071] Specifically, nonwoven fabrics according to the present invention can exhibit increases in machine direction (MD) tensile strengths that are between approximately 55 and 125% compared to a nonwoven fabric prepared in the same way that does not include the secondary alkanesulfonate. In some embodiments, the nonwoven fabric of the invention can exhibit an increase in MD tensile strength ranging between approximately 50 and 150%, such as between approximately 55 and 125%, between approximately 65 and 110%, between approximately 85 and 110%, or between approximately 90 and 110%, as compared to a similarly prepared nonwoven fabric that does not include the secondary alkanesulfonate.

[0072] In some embodiments, nonwoven fabrics according to the present invention can exhibit increases in tensile strengths in the transverse direction (CD) that are between approximately 50 and 200% compared to a nonwoven fabric prepared in the same way that does not include the secondary alkanesulfonate. In some embodiments, the nonwoven fabric of the invention can exhibit an increase in CD tensile strength ranging from approximately 50 to 170%, such as between approximately 55 and 165%, between approximately 65 and 160%, between approximately 85 and 150%, or between approximately 90 and 125%, as compared to a similarly prepared nonwoven fabric that does not include the secondary alkanesulfonate.

[0073] Nonwoven fabrics according to embodiments of the present invention also exhibit increased tenacity compared to a similarly prepared nonwoven fabric that does not include the secondary alkanesulfonate. The tenacity of nonwoven fabrics can be compared by examining the product resulting from multiplying the observed percent elongation and the observed tensile strength of the fabric. The product of this multiplication is called the Tenacity Index, which is approximately proportional to the area under the stress-strain curve. As discussed below in the Test Methods section, all stress and elongation values are obtained according to the German Method 10 DIN 53857, in which a sample 5 cm wide and 100 mm distance between marks at a crosshead speed of 200 mm/min were recorded at peak. As the Toughness Index is the product of multiplying Stress X % Elongation, the units of the Toughness Index are (N/5 cm) -%. As all mechanical properties result from testing a 5 cm wide specimen, the Toughness Index units in this document will be simplified to N - %.

[0074] Nonwoven fabrics according to the present invention can exhibit an MD Tenacity Index that is between approximately 2000 and 7500 N%, and in particular between approximately 2300 and 6500 and more particularly between approximately 2300 and 6000 N%, and a CD Tenacity Index that is between approximately 1000 and 5000 N% and in particular between approximately 1. 250 and 5,000 and more particularly between approximately 1,250 and 3,500 N%.

[0075] In one embodiment, the nonwoven fabric of the invention can exhibit an increase in MD Tenacity Index that is from 20 to 1250% compared to a similarly prepared nonwoven fabric that does not include the secondary alkanesulfonate. For example, the nonwoven fabric of the invention can exhibit an increase in MD Tenacity Index equal to any one or more than one of at least 25%, at least 100%, at least 200%, at least 300%, at least 400%, at least 500%, at least 600%, at least 700%, at least 800%, at least 900%, at least 1,000%, at least 1 .050%, at least 1100%, at least 1150%, at least 1200%, at least 1250%, at least 1300% or at least 1500%, as compared to a similarly prepared nonwoven fabric that does not include the secondary alkanesulfonate.

[0076] In some embodiments, the nonwoven fabric of the invention can exhibit an increase in the CD Tenacity Index that is between approximately 50 and 1000% compared to a similarly prepared nonwoven fabric that does not include the secondary alkanesulfonate. For example, the nonwoven fabric of the invention can exhibit an increase in the CD Tenacity Index equal to any one or more than one of at least 60%, at least 75%, at least 80%, at least 85%, at least 90%, at least 100%, at least 150%, at least 200%, at least 250%, at least 300%, at least 350%, at least 400%, at least 500%, at least 550%, at least 600%, at least 700%, at least 800%, at least 900%, at least 1000% or at least 1025%, as compared to a similarly prepared nonwoven fabric that does not include the secondary alkanesulfonate.

[0077] To account for variations in weights, it may also be useful to consider the Relative Tenacity Index of the nonwoven fabric of the invention compared to a similarly prepared nonwoven fabric that does not include the secondary alkanesulfonate. The nonwoven fabric of the invention also exhibited significant increases in tenacity compared to the nonwoven fabric of Comparative Examples. The Relative Toughness Index is calculated from the Toughness Index, which is then normalized to grammage. The Tenacity Index can be divided by basis weight to provide a Toughness Index normalized with units of N %/g/m2.

[0078] Nonwoven fabrics according to the present invention can exhibit an MD Relative Tenacity Index which is between approximately 50 and 150 N %/g/m2, in particular between approximately 75 and 125, and more particularly between approximately 85 and 115 N %/g/m2, and a CD Relative Tenacity Index which is between approximately 40 and 100 N %/g/m2, in particular between approximately 4 5 and 85, and more particularly between approximately 45 and 75 N%/g/m2.

[0079] In one embodiment, the nonwoven fabric of the invention can exhibit an increase in MD Relative Tenacity Index that is between 100 and 1000% compared to a similarly prepared nonwoven fabric that does not include the secondary alkanesulfonate. In a preferred embodiment, the nonwoven fabric of the invention can exhibit an increase in MD Relative Tenacity Index that is between approximately 80 and 500%, and more preferably between approximately 140 and 480%, compared to a similarly prepared nonwoven fabric that does not include the secondary alkanesulfonate. For example, the nonwoven fabric of the invention can exhibit an increase in MD Relative Tenacity Index equal to any or more of at least 100%, at least 125%, at least 150%, at least 175%, at least 200%, at least 225%, at least 250%, at least 275%, at least 300%, at least 325%, at least 350%, at least 37 5%, at least 400%, at least 425%, at least 450%, at least 475%, at least 500%, at least 525%, at least 550%, at least 575%, at least 600%, at least 625%, at least 650%, at least 675%, at least 700%, at least 725%, at least 750%, at least 775%, at least 800%, at least 825%, at least 850%, at least 875%, at least 900%, at least 925%, at least 950, at least 975% or at least 1000%, as compared to a similarly prepared nonwoven fabric that does not include the secondary alkanesulfonate.

[0080] In one embodiment, the nonwoven fabric of the invention can exhibit an increase in the Relative Tenacity Index CD that is between 100 and 1000% compared to a similarly prepared nonwoven fabric that does not include the secondary alkanesulfonate. In a preferred embodiment, the nonwoven fabric of the invention can exhibit an increase in the Relative Tenacity Index CD that is between approximately 140 and 500%, and more preferably between approximately 140 and 410%, compared to a similarly prepared nonwoven fabric that does not include the secondary alkanesulfonate. For example, the nonwoven fabric of the invention may exhibit an increase in MD [sic] Relative Tenacity Index equal to any one or more of at least 100%, at least 125%, at least 150%, at least 175%, at least 200%, at least 225%, at least 250%, at least 275%, at least 300%, at least 325%, at least 350%, at least 375%, at least 400%, at least 425%, at least 450%, at least 475%, at least 500%, at least 525%, at least 550%, at least 575%, at least 600%, at least 625%, at least 650%, at least 675%, at least 700%, at least 725%, at least 750%, at least 775%, at least 800%, at least 825%, at least 850%, at least 875%, at least 900%, at least 925%, at least 950, at least 975% or at least 1,000%, as compared to a similarly prepared nonwoven fabric that does not include the secondary alkanesulfonate.

[0081] When comparing properties of different nonwovens, it is often useful to compare the root mean square of the combined MD and CD values of the property of interest. This method allows the comparison of isolated values. The root mean square provides a single number that combines the input MD and CD values by taking the square root of the sum of the square of the MD value plus the square of the CD value. Using the root mean square method to combine MD and CD results is particularly useful if the samples to be compared were taken on different machines or under some different condition that might influence the MD/CD ratio. The root mean square of the Tenacity Index by grammage is calculated with the following formula: where MDTI is the Toughness Index in the machine direction and CDTI is the Toughness Index in the transverse direction.

[0082] Nonwoven fabrics according to the invention may have a Root Mean Square Tenacity Index by grammage that is at least 55 N %/g/m 2 , more preferably at least 65 N %/g/m 2 , and even more preferably at least 70 N %/g/m 2 . In one embodiment, the fabric has a Root Mean Square Tenacity Index per grammage value between approximately 55 and 250 N%/g/m2, in particular between approximately 65 and 150 N%/g/m2, and more particularly between approximately 65 and 100 N%/g/m2. In one embodiment, the fabric has a Root Mean Square Tenacity Index by Weight of at least 75, at least 80, at least 85, at least 90, at least 95, at least 100, at least 105, at least 110, at least 115, at least 120, at least 125, at least 130, at least 135, at least 140, at least 1 45, at least 150, at least 155, at least 160, at least 165, at least 170, at least 175, at least 180, at least 185, at least 190, at least 195 and at least 200 N %/g/m2.

[0083] With “similarly prepared nonwoven fabric”, it should be understood that the polymeric composition of the comparison nonwoven fabric is identical with the exception of the secondary alkanesulfonate, and that slight variations in processing conditions such as temperature (e.g., extruder, calendering, and die temperatures), pulling speeds, and pressures may exist.

[0084] Without intending to be bound by theory, it is believed that the presence of the secondary alkanesulfonate in the fibers may help to improve the consolidation of the fibers to each other, resulting in improvements in the mechanical properties of the nonwoven fabric. In this regard, Figures 1A and 1B are Scanning Electron Microscope (SEM) images of a non-woven fabric, obtained at 250x and 100x magnification, respectively, and Figures 2A and 2B are SEM images of a non-woven fabric according to the present invention, obtained at 250x and 100x magnification, respectively. The fabric of Figures 1A and 1B are identical to the fabric of Figures 2A and 2B with the exception that the fabric of Figures 1A and 1B does not include a secondary alkanesulfonate. In both fabrics, the fabric was consolidated by stitches with a calender cylinder.

[0085] The SEM images of the fabric of Figures 1A and 1B show that the individual fibers of the consolidated stitches were loosely consolidated to each other. More specifically, the fibers are observed to exhibit relatively poor melting and polymer flow during consolidation. In contrast, the SEM images of the tissue in Figures 2A and 2B exhibited good polymer melting and flow within each consolidated spot. As can be seen in Figure 2B, this results in each consolidated spot exhibiting a film-like appearance due to melting and polymer flow. Fabric of the invention exhibited significant improvements in healing compared to fabric that did not include the secondary alkanesulfonate.

[0086] According to certain embodiments, for example, the fabric may comprise a machine direction (MD) tensile strength at peak between approximately 25 N/5 cm and 150 N/5 cm. In other embodiments, for example, the fabric may comprise a peak MD tensile strength of between approximately 50 N/5 cm and 150 N/5 cm. In further embodiments, for example, the fabric may comprise a peak MD tensile strength of between approximately 65 N/5 cm and 90 N/5 cm. Thus, in certain embodiments, the fabric may comprise an MD tensile strength at peak of at least approximately any of the following: 25, 26, 27, 28, 29, 30, 50, 60, 70, 80, 100, 110, 120, 130 N/5 cm and 140 N/5 cm, and/or at most approximately 175, 150, 145, 140, 130, 120 N/5 cm, and 110, 100, and 90 N/5 cm (eg approx. 25-175 N/5 cm, approx 80-140 N/5 cm, etc.).

[0087] In certain embodiments, for example, the fabric may comprise a tensile strength in the cross machine direction (CD) at peak between approximately 20 N/5 cm and 85 N/5 cm. In other embodiments, for example, the fabric may comprise a peak CD tensile strength of between approximately 25 N/5 cm and 75 N/5 cm. In some embodiments, for example, the fabric may comprise a peak CD tensile strength of between approximately 29 N/5 cm and 74 N/5 cm. Thus, in certain embodiments, the fabric may comprise a peak CD tensile strength of at least approximately any one of the following: 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, and 30 N/5 cm and/or, at most, approximately 85, 80, 75, 70, 65, 60, and 50 N/5 cm (e.g., approximately 2 0-85 N/5 cm, approximately 25-75 N/5 cm, etc.).

[0088] According to certain embodiments, for example, the fabric may comprise an MD elongation percentage at peak between approximately 20% and 50%. In other embodiments, for example, the fabric may comprise a peak MD elongation percentage of between approximately 25% and 45%. In further embodiments, for example, the tissue can comprise a peak MD elongation percentage between approximately 28% and 41%. Thus, in certain embodiments, the fabric may comprise an MD elongation percentage at peak of at least approximately any one of the following: 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39 and 40% and/or at most approximately 50 , 45, 44, 43, 42, 41, 40, 39, 38, 37, 36, 35, 34, 33, 32, 31 and 30% (e.g. approximately 20-50%, approximately 21-45%, etc.).

[0089] In certain embodiments, for example, the fabric may comprise a peak CD elongation percentage between approximately 30% and 75%. In other embodiments, for example, the tissue can comprise a percentage of CD elongation at peak between approximately 35% and 60%. In some embodiments, for example, the tissue may comprise a peak CD elongation percentage of between approximately 40% and 50%. Thus, in certain embodiments, the fabric may comprise a percentage CD elongation at peak of at least approximately any one of the following: 10, 15, 20, 25, 30, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, and 49% and/or at most approximately 55, 50 , 49, 48 and 47% (e.g. approximately 10-55%, approximately 15-50%, etc.).

[0090] According to certain embodiments, specific processes can be used to prepare the PLA spunbond nonwoven fabric. In such embodiments, the process can include providing a molten or semi-molten PLA resin stream that includes at least one secondary alkanesulfonate, forming a plurality of drawn PLA continuous filaments, depositing the plurality of PLA continuous filaments onto a collecting surface, exposing the plurality of PLA continuous filaments to ions, and consolidating the plurality of PLA continuous filaments to form the PLA spunbond nonwoven fabric. According to certain embodiments, for example, forming the plurality of continuous PLA filaments may comprise spinning the plurality of continuous PLA filaments, drawing the plurality of continuous PLA filaments, and randomly dispersing the plurality of continuous PLA filaments.

[0091] In this regard, the spunbond nonwoven mat can be produced, for example, by the conventional continuous spinning process, in which the molten polymer is extruded into continuous filaments that are subsequently cooled rapidly (quenched), attenuated or stretched mechanically by drawing cylinders or pneumatically by a liquid at high speed and collected in random arrangement on a collecting surface. After collecting the filaments, any thermal, chemical or mechanical consolidation treatment can be used to form a consolidated mat in such a way that a cohesive structure for the mat results.

[0092] According to certain embodiments, for example, the process can occur at a fiber drawing speed greater than about 2500 m/min. In other embodiments, for example, the process can occur at a fiber drawing speed of between about 3000 m/min and 4000 m/min. In further embodiments, for example, the process can occur at a fiber drawing speed of between about 3000 m/min and 5500 m/min. Thus, in certain embodiments, the process may occur at a fiber stretching speed at least equal to approximately any one of the following: 2501, 2550, 2600, 2650, 2700, 2750, 2800, 2850, 2900, 2950 and 3000 m/min and/or at most approximately 5500, 4000, 395 0, 3900, 3850, 3800, 3750, 3700, 3650, 3600, 3550 and 3500 m/min (e.g. approximately 2700-3800 m/min, approximately 3000-3700 m/min, etc.).

[0093] According to certain embodiments, for example, consolidating the web to form the PLA spunbond nonwoven fabric may comprise spot thermal consolidation of the web with heat and pressure by means of a calender with a pair of cooperating rollers including a patterned roller. In such embodiments, for example, dot thermal setting of the batt may comprise imparting a three-dimensional geometric pattern for consolidation onto the PLA spunbond nonwoven fabric. The patterned roll may comprise a three-dimensional geometric pattern for consolidation. In some embodiments, for example, the consolidation pattern can include at least a diamond pattern, a hexagonal dotted pattern, an elliptical oval pattern, a cylindrical pattern, or any combination thereof. In some embodiments, the calender can include a release liner to minimize the deposit of molten or semi-molten polymer on the surfaces of one or more of the rolls. As an example, such a release coating is described in European Patent Application No. 1 432 860, the contents of which are hereby incorporated, in their entirety, by reference in this patent application.

[0094] According to certain embodiments, for example, the process may further comprise dissipating the static charge of the PLA spunbond nonwoven fabric next to the calender by means of the static control unit. In some embodiments, for example, the static control unit may comprise an ionization source. In further embodiments, for example, the ionization source can comprise an ionization bar. However, in other embodiments, for example, dissipating the static charge from the PLA spunbond nonwoven fabric may comprise placing the PLA spunbond nonwoven fabric in contact with a bar for static discharge.

[0095] According to certain embodiments, for example, the process may further comprise cutting the PLA spunbond nonwoven fabric to obtain cut PLA spunbond nonwoven fabric, exposing a cut PLA spunbond nonwoven fabric to ions via a third ionization source, and rewinding the cut PLA spunbond nonwoven fabric into cylinders. In such embodiments, for example, the third ionization source may comprise an ionization bar.

[0096] According to certain embodiments, for example, the process may further comprise increasing the humidity while forming the plurality of continuous PLA filaments. In such embodiments, for example, increasing the humidity may comprise applying at least steam, evaporative cooling, fog or any combination thereof to the plurality of continuous PLA filaments.

[0097] Certain embodiments according to the invention provide systems for preparing a PLA spunbond nonwoven fabric. In accordance with certain embodiments, the system includes a first source of PLA configured to deliver a stream of molten or semi-molten PLA resin, a source of at least one secondary alkanesulfonate configured to introduce at least one secondary alkanesulfonate into the PLA source, a rotating rod in fluid communication with the first source of PLA, a collection surface disposed below an outlet of the rotating rod on which continuous PLA filaments are disposed to form the PLA spunbond nonwoven fabric, a first source of ionization positioned from and arranged to expose the continuous PLA filaments to ions and a calender positioned downstream of the first ionization source. The rotating rod, according to certain embodiments, is configured for extruding and drawing a plurality of continuous PLA filaments.

[0098] In this regard, the spunbond nonwoven batt can be produced, for example, by the conventional continuous spinning process on a continuous spinning machine such as, for example, Reifenhauser's Reicofil-3 line or Reicofil-4 line, as described in the U.S. Patent No 5,814,349, issued to Geus et al, the contents of which are hereby incorporated, in their entirety, by reference in this patent application, in which molten polymer is extruded into continuous filaments, which are subsequently rapidly cooled, pneumatically attenuated by a high-velocity liquid, and collected in random array on a collecting surface. In some embodiments, continuous filaments are collected with the aid of a vacuum source positioned below the collection surface. After collecting the filaments, any thermal, chemical or mechanical consolidation treatment can be used to form a consolidated blanket in such a way that a cohesive structure for the blanket results. As will be understood by one skilled in the art, examples of thermal consolidation can include airflow consolidation, in which hot air is forced through the web to soften the polymer on the outside of certain fibers in the web, followed by at least limited compression of the web, or calender consolidation where the web is compressed between two rollers, at least one of which is heated, and typically one is an embossing roll.

[0099] In some embodiments, for example, the collection surface may comprise conductive fibers. The conductive fibers can include monofilament yarns made of polyethersulfone conditioned with polyamide (eg Huycon - LX 135). In machine direction, the fibers comprise polyamide conditioned polyethersulfone. In the cross-machine direction, the fibers comprise polyamide conditioned polyethersulfone in combination with additional polyethersulfone.

[0100] With reference to Figure 3, for example, a schematic diagram of the continuous spinning PLA nonwoven fabric preparation system according to certain embodiments of the invention is illustrated.

[0101] As shown in Figure 3, a source of PLA (ie funnel) 2 is in fluid communication with the rotating rod 4 via the extruder 6. At least one secondary alkanesulfonate is then mixed with the PLA resin in the extruder 6 to provide a molten or semi-molten stream of PLA that is introduced into the rotating rod 4. It should be noted that the secondary alkanesulfonate can be introduced directly into the extruder or can be introduced into a source of PLA (e.g. the hopper) before the PLA resin is introduced into the extruder.

[0102] Although Figure 3 illustrates an embodiment with two PLA sources 2 and two extruders 6, the system may include any number of polymer sources (e.g., PLA, synthetic polymer such as polypropylene, polyethylene, etc.) and extruders, as indicated by a particular application and understood by any person skilled in the art. After extrusion, the extruded polymer can then enter a plurality of spinnerets (not shown) for spinning into filaments. After spinning, the spun filaments can then be drawn (ie, attenuated) via a drawing unit (not shown) and randomly dispersed in a diffuser (28 in Figures 4A-4C). The rotating rod 4 produces a curtain of filaments (30 in Figures 4A-4C) which is deposited onto the collection surface 10 at point 8.

[0103] In one embodiment, the filaments so deposited can then be consolidated to form a cohesive mat. In some embodiments, a pair of cooperating rollers 12 (also referred to herein as a "press roller") stabilize the web of continuous PLA filaments by compressing the web prior to delivery to the calender 14 for consolidation. In some embodiments, for example, the press roll can include a ceramic coating deposited on the surface of the roll. In certain embodiments, for example, one roll of the pair of cooperating rolls 12 can be positioned above the collection surface 10, and a second roll of the pair of cooperating rolls 12 can be positioned below the collection surface 10. Finally, the consolidated PLA nonwoven fabric, obtained by continuous spinning, moves to a rewinder 16, where the fabric is rewound into rolls.

[0104] In the course of their investigation, the inventors discovered that the generation of static discharges during fiber spinning and processing of the web when PLA is exposed on the fiber surface promotes winding of the web on the press rolls and the calender of the continuous spinning machine. Such mat curling is undesirable and has generally prevented the high speed production of fabrics including 100% PLA, or fabrics in which PLA is exposed on the surface of the fibers. One method of addressing mat winding is to increase the humidity of the continuous spinning process, for example by injecting steam into the air stream used to rapidly cool the newly spun fibers or provide a mist or fine cloud of moisture around the press rolls where the spun fibers are initially formed into an unconsolidated mat. While excess moisture provides some protection against mat winding, the addition of high humidity over a period of time can promote continuous spinning machine corrosion and the growth of mold or microorganisms harmful to the use of nonwovens in hygienic and medical operations.

[0105] Another method to reduce the static charge accumulated in the nonwoven fabric is to place the blanket where the PLA is exposed on the fiber surface in contact with a static charge conducting bar, which helps to ground the blanket, thus dissipating the charge buildup. However, this approach requires direct contact between the nonwoven mat and the conductive substrate, and at such points of contact there is still the possibility of direct discharge of static electricity through the space with possible resultant injury to the operator, equipment damage, and fire hazard.

[0106] Advantageously, the inventors have discovered that it is possible to prepare fabrics including 100% PLA at commercially viable processing speeds by positioning one or more ionization sources in close proximity to the nonwoven fabric. For example, in one embodiment, an ionization source 18 can be positioned near the rotating rod 4 and rewinder 16 to actively dissipate/neutralize static charge without coming into contact with tissue. As explained below, the ionization source exposes the non-woven fabric to a current of ions, which act to neutralize static charges on the non-woven fabric. The ion stream can include positive ions, negative ions, and combinations thereof.

[0107] In some embodiments, it may be desirable to also position a static control unit 20 close to the calender 14. The static control unit 20 can be a passive bar for static charges that requires contact with the fabric or an active ionization bar, which does not require contact with the fabric. Finally, an optional moisture unit 26 can be used in conjunction with the rotating rod 4 and/or press roll 12 to reduce static discharge from added moisture.

[0108] According to certain embodiments, for example, the first ionization source can be positioned above the collection surface and downstream of a point where continuous PLA filaments are deposited on the collection surface. However, in other embodiments, for example, the first source of ionization may be positioned between the outlet of the rotating rod and the collection surface.

[0109] As previously discussed, the system may further comprise a press roller positioned downstream of the rotary rod outlet. In this regard, the press roll can be configured to stabilize the PLA continuous filament mat by compressing said mat prior to delivering the PLA continuous fibers from the outlet of the rotating rod towards the calender. In those embodiments including the press roll, for example, the first source of ionization may be positioned downstream of the press roll. In other embodiments, for example, the first ionization source can be positioned between the rotating rod and the press roll.

[0110] In some embodiments and as shown in Figure 3, the system may comprise a vacuum source 24 arranged below the collection surface to draw the plurality of continuous PLA filaments from the exit of the rotating rod over the collection surface before delivery to the calender.

[0111] Figures 4A-4C, for example, are schematic diagrams illustrating the positioning of the first ionization source in accordance with certain embodiments of the invention. As shown in Figure 4A, the first ionization source 18 is positioned downstream of the outlet (i.e. diffuser) 28 of the rotating rod 4, but upstream of the press roll 12. In Figure 4B, however, the first ionization source 26 is positioned downstream of the press roll 12. In Figure 2C, the first ionization source is positioned downstream of the point 8 at which the curtain of filaments 30 are deposited on the collection surface, but also inside the outlet 46.

[0112] Preferably, the ionization source comprises a device that is capable of actively discharging ions using electrodes, ionizing air nozzles, ionizing air blowers and the like. In one embodiment, the ionization source comprises an active discharge ionizer bar that actively discharges ions towards the non-woven tissue. Examples of suitable ionization bars might include the Elektrostatik E3412 electrostatic discharge electrode.

[0113] In one embodiment, the ionization bar can extend over the blanket in the transverse direction. Preferably, the ionizer bar extends in the transverse direction across the full width of the nonwoven fabric. In additional embodiments, the ionizer bar can extend below the mat and collection surface in the transverse direction. However, positioning the ionizer bar under the collection surface may be less effective than positioning the ionizer bar over the mat in the transverse direction.

[0114] According to certain embodiments, for example, the first ionization source and the collection surface can be separated by a distance between approximately 1 inch and approximately 24 inches. In other embodiments, for example, the first ionization source and the collection surface can be separated by a distance of between approximately 1 inch and 12 inches. In further embodiments, for example, the first ionization source and the collection surface can be separated by a distance of between approximately 1 inch and 5 inches. Thus, in certain embodiments, the first ionization source and the collection surface may be separated by a distance of at least approximately any one of the following: 1; 1.25; 1.5; 1.75 and 2 inches and/or maximum approximately 24, 20, 16, 12, 10, 9, 8, 7, 6, and 5 inches (e.g., approximately 1.5-10 inches, approximately 2-8 inches, etc.).

[0115] According to certain embodiments, for example, the system may further comprise a static control unit positioned and arranged to dissipate static charges from the PLA spunbond nonwoven fabric next to the calender. In some embodiments, for example, the static control unit may be positioned upstream and adjacent to the calender. In other embodiments, however, the static control unit may be positioned downstream and adjacent to the calender.

[0116] In some embodiments, for example, the static control unit may comprise a passive bar for static charges. In such embodiments, the static control unit may be in contact with the PLA spunbond nonwoven fabric in order to dissipate static charges. In other embodiments, however, the static control unit may comprise a second ionization source. Therefore, the second ionization source can actively dissipate the static charges of the PLA spunbond nonwoven fabric such that contact by the second ionization source with the PLA spunbond nonwoven fabric is not required to dissipate the static charge.

[0117] According to certain embodiments, for example, the system may further comprise a rewinder that is positioned downstream of the calender. In such embodiments, for example, the system may also include a third ionization source positioned and arranged to expose the continuous spinning PLA nonwoven fabric to ions near the rewinder. In some embodiments, for example, the at least one first ionization source, the static charge control source (e.g., the second ionization source) or the third ionization source may comprise an ionization bar. In this regard, for example, the first ionization source, the static charge control source and the third ionization source can be configured to actively dissipate the static charge created during the preparation of the PLA spunbond nonwoven fabric.

[0118] According to certain embodiments, for example, the system may further comprise a humidification unit positioned within or downstream of the rotating rod. In such embodiments, for example, the humidification unit may comprise at least a misting unit, a misting unit, an evaporative cooling unit or any combination thereof. In this regard, for example, one can increase the humidity on the rotating rod during forming the plurality of continuous PLA filaments and/or close to the press roll(s) (in those embodiments that use at least one press roll) in order to further control the static charge that develops during the production of the PLA nonwoven fabric by continuous spinning.

[0119] Nonwoven fabrics according to embodiments of the invention can be used to prepare a variety of different structures. For example, in some embodiments, the nonwoven fabric of the invention can be combined with one or more additional layers to prepare a composite or laminate material. Examples of such composites/laminates may include a spunbond composite, a spunbond-meltblown composite (SM), spunbond-meltblown-spunbond composite (SMS) or a spunbond-meltblown-meltblown-spunbond composite (SMMS). In some embodiments, composites including a layer of the nonwoven fabric of the invention and one or more layers of film can be prepared.

[0120] For example, Figures 5A-5D are cross-sectional views of composites according to certain embodiments of the invention. For example, Figure 5A illustrates a spunbond-meltblown (SM) composite 50 having a spunbond-meltblown-spunbond (SMS) layer 52 in accordance with embodiments of the present invention and a blow-spun layer 54. the blown 54 inserted between the spunbond PLA nonwoven fabric layers 52. Figure 5C illustrates an SMS composite 58 having a continuous spinning PLA nonwoven fabric layer 52, a different continuous spinning layer 60, and a blown spinning layer 54 inserted between the two continuous spinning layers 52, 6. Finally, Figure 4D illustrates a spunbond-meltblown-meltblown-sp composite unbond (SMMS) 62 having a continuous spinning PLA nonwoven fabric layer 52, a different continuous spinning layer 60 and two blown spinning layers 54 inserted between the two continuous spinning layers 52, 60. Although composite SMMS 62 has been shown with two different continuous spinning layers 52 and 60, the two continuous spinning layers may be the continuous spinning PLA nonwoven fabric layer 52.

[0121] In these multilayer structures, the grammage of the PLA spunbond nonwoven fabric layer can vary from 7 g/m2 to 150 g/m2. In such multilayer laminates, meltblown and spunbond fibers could have PLA on the surface to ensure optimal consolidation. In some embodiments in which the spunbond layer forms part of a multilayer structure (e.g. SM, SMS and SMMS), the amount of blow-spun fibers in the structure can vary between approximately 5 and 30%, and in particular between approximately 5 and 15% of the structure as a percentage of the structure as a whole.

[0122] The multilayer structures according to embodiments can be prepared in a variety of ways including continuous in-line processes, where each layer is prepared in successive order on the same line, or by depositing a blow-spinning layer over a previously formed continuous-spinning layer. The layers of the multilayer structure can be consolidated together to form a multilayer composite sheet material using thermal consolidation, mechanical consolidation, adhesive consolidation, hydroentanglement or combinations thereof. In certain embodiments, the plies are spot consolidated together with heat by passing the multiply structure through a pair of calender rolls.

[0123] In yet another aspect, certain embodiments of the invention provide absorbent articles. In accordance with certain embodiments, the absorbent article may include a nonwoven fabric in accordance with the present invention. In one embodiment, a sustainable composite can be provided that includes at least two nonwoven fabric layers, wherein the at least one nonwoven fabric layer can include a PLA spunbond nonwoven fabric layer in which a secondary alkanesulfonate is incorporated. The PLA spunbond nonwoven fabric layer may include a plurality of fibers, such that PLA may be present on a surface of the plurality of fibers. In some embodiments, the absorbent article may be sustainable, however the sustainability of the absorbent article depends on other materials incorporated in the absorbent article in addition to the sustainable composite.

[0124] In this regard, fabrics prepared according to embodiments of the invention can be used in a wide variety of articles and applications. For example, embodiments of the invention can be used in personal care applications, e.g., baby care products (diapers, wet wipes), feminine care products (pads, sanitary towels, tampons), adult care products (incontinence products) or cosmetic applications (pads), agricultural applications, e.g. root wraps, seed bags, crop covers, industrial applications e.g. car trunks and soundproofing materials, and household products, eg mattress and cushion linings to remove scratches from furniture.

[0125] Figure 6A, for example, is an illustration of an absorbent article (here, shown as a diaper) in accordance with at least one embodiment of the invention and generally designated by the reference numeral 70. The diaper 70 may include an absorbent core 74. Figure 6B is a cross-sectional view of the diaper 70 of Figure 5A, taken along line 7272 of Figure 5A. As shown in Figure 6B, the absorbent core 74 may be inserted between a topsheet 80 and a backsheet 82. As discussed further herein, one or both of the topsheet 80 and the backsheet 82 may include a PLA spunbond nonwoven fabric and/or a sustainable composite including a PLA spunbond nonwoven fabric layer as discussed in more detail above.

[0126] The topsheet 30 is positioned adjacent an outermost surface of the absorbent core 74 and is preferably joined to the core and backsheet 82 by fastening means (not shown) such as those well known in the art. For example, the topsheet 80 may be secured to the absorbent core 74 by a continuous uniform layer of a patterned, adhesive layer of adhesive or an arrangement of separate lines, spirals or dots of adhesive.

[0127] In this descriptive report, the term "joined" covers configurations in which an element is attached directly to the other element, by attaching the element directly to the other element, and configurations in which the element is attached to the other element indirectly by attaching the element to intermediate element(s), which, in turn, are affixed to the other element. In a preferred embodiment of the present invention, the top sheet 80 and the back sheet 82 are joined directly to each other at the periphery of the diaper 86 and indirectly by joining the sheets to the absorbent core 74 by fastening means (not shown).

[0128] Preferably, the top sheet 80 conforms, feels smooth and is not irritating to the user's skin. Furthermore, the topsheet 80 is permeable allowing liquids (e.g., urine) to readily penetrate through its thickness. A suitable top sheet can be produced from a wide variety of materials, such as porous foams; reticulated foams; plastic films with openings; woven or non-woven blankets of natural fibers (eg wood or cotton fibers) or a combination of natural and synthetic fibers.

[0129] In some embodiments, the topsheet may be treated with a surfactant to help ensure proper transport of liquids through the topsheet and into the absorbent core. An example of a suitable surfactant is available from Momentive Performance Materials under the trade name NUWETTM 237.

[0130] In one embodiment, at least the top sheet or the back sheet includes a nonwoven fabric comprising continuous filaments of PLA containing a secondary alkaline sulfonate as previously discussed.

[0131] In a preferred embodiment, the topsheet comprises at least 75 weight percent of biobased materials, such as at least 75 weight percent of the PLA spunbond nonwoven fabric of the invention. Additional examples of bio-based polymers that can be used in embodiments of the invention include polymers produced directly by organisms, such as polyhydroxyalkanoates (e.g., poly(beta-hydroxyalkanoate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate, NODAXTM), 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 starch), proteins (e.g., zein, whey protein, gluten, collagen), lipids, lignins, and natural rubber; and current polymers derived from natural source monomers and derivatives such as biopolyethylene, biopolypropylene, polytrimethylene terephthalate, polylactic acid, NYLON 11, alkyd resins, succinic acid-based polyesters, and biopolyethylene terephthalate.

[0132] There are a number of manufacturing techniques that can be used to produce the topsheet 80. For example, the topsheet 80 can be a nonwoven batt of fibers. When the topsheet comprises a nonwoven batt, the batt can be obtained by continuous spinning, carding, wet spinning, blow spinning, hydroentangling, combinations of the foregoing or the like. A preferred topsheet comprises a continuous spun nonwoven fabric in which the fibers are thermoset together to form a cohesive batt.

[0133] The backsheet 82 is positioned adjacent an opposing surface of the absorbent core 74 and preferably joined to the core by fastening mechanisms (not shown) such as those well known in the art. Suitable attachment mechanisms are described in connection with joining the topsheet 80 to the absorbent core 74. Alternatively, the attachment means may comprise heat-activated adhesives, pressure-activated adhesives, ultrasonic adhesives, dynamic mechanical adhesives, or any other suitable attachment means or combinations of such attachment mechanisms as are known in the art.

[0134] The backsheet 82 is impervious to liquids (e.g., urine) and is preferably made from a thin plastic film, although other flexible liquid impervious materials may also be used. In this specification, the term "flexible" refers to materials that adapt and will readily conform to the general shape and contours of the human body. The backsheet 82 prevents exudates absorbed and contained in the absorbent core 74 from wetting articles in contact with the diaper 70 such as sheets and undergarments. The backsheet 82 may thus comprise a woven or nonwoven material, polymeric films such as thermoplastic films, or composite materials such as a film-covered nonwoven material.

[0135] In some embodiments, the material for the backsheet may include the previously discussed biobased polymers and, in particular, the PLA spunbond fabric of the invention described above. In some embodiments, the backsheet can include additional bio-based polymers. For example, biobased polymers for use in the backsheet may include polymers directly produced by organisms, such as polyhydroxyalkanoates (e.g., poly(betahydroxyalkanoate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate, NODAXTM), 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 starch), proteins (e.g., zein, whey protein, gluten, collagen), lipids, lignins, and natural rubber; and current polymers derived from natural source monomers and derivatives such as biopolyethylene, biopolypropylene, polytrimethylene terephthalate, polylactic acid, NYLON 11, alkyd resins, succinic acid-based polyesters, and biopolyethylene terephthalate.

[0136] In one embodiment, the backsheet may comprise a laminated structure having a layer with a liquid-impermeable film that is joined to a non-woven mat. Suitable films can be prepared from the biobased polymers discussed above. In one example, the film may comprise a polyethylene polymer derived from sugar cane, such as a polyethylene film grade SEB853/72 or SPB681/59 grade recommended by Braskem S.A. for lamination. Suitable films may also include additives such as CaCO3 to improve film breathability while still maintaining liquid barrier properties. In some embodiments, the backsheet layer may comprise a laminated structure having a biobased film layer, such as those previously discussed, i.e., laminated to a fabric layer with a spunbond-meltblown-spunbond (SMS) structure.

[0137] The absorbent core 74 may comprise any material that is capable of absorbing liquids and exudates. Preferably, the absorbent core comprises at least 75% by weight of biobased materials. In one embodiment, the core wrapping materials can comprise a fabric layer including a spunbond fabric, a spunbond-meltblown (SM) fabric, or an SMS fabric. An example of a core wrap including an SMS fabric comprises a spunbond nonwoven layer, containing bicomponent fibers with a PLA sheath (e.g., NatureWorks, PLA Grade 6752 with 4% D-isomer), and a PLA core (e.g., NatureWorks Grade 6202 with 2% D-isomer). In one embodiment, the blow-spun layer of the SMS fabric can be composed of PLA blow-spun fibers (e.g., NatureWorks PLA grade 6252).

[0138] Figure 7 is an illustration of an absorbent article according to at least one embodiment of the invention, wherein the absorbent article is in the form of a feminine sanitary pad, generally designated by the reference numeral 100. The pad 100 may include a top sheet 102, a back sheet 104, and an absorbent core 106 disposed therebetween. Preferably, the top sheet 102 and the back sheet 104 are joined together along opposite outer edges, defining a continuous seam 108 that extends at the periphery 110 of the pad 100. The continuous seam 108 may comprise a heat seal that is formed by thermally bonding the top sheet to the back sheet. In other embodiments, the continuous seam 108 is formed by adhesively bonding the top sheet to the back sheet.

[0139] As in the embodiments discussed above, the pad 100 preferably comprises a non-woven fabric in accordance with the present invention. That is, a spunbond nonwoven fabric comprising fibers that are a blend of a PLA resin and a secondary alkaline sulfonate.

[0140] In some embodiments, the pad 100 can comprise sustainable articles with a biobased material content of at least 75 percent by weight, based on the total weight of the pad, such as a biobased material content of at least 80%, 85%, 90%, or 95% by weight of the pad. Suitable materials for the topsheet, backsheet, and absorbent core are discussed previously.

[0141] In some embodiments, the pad 100 may also include a liquid acquisition layer 112 that is disposed between the absorbent core 106 and the topsheet 102. In one embodiment, a liquid acquisition layer could be made by carding a batt composed of a blend of 7 denier 2 inch long Type 820 PLA Type 820 hollow chopped fibers plus 2 inch long Type 821 PLA Type 821 solid chopped fibers in length (both available from Fiber Innovations Technology - Johnson City, TN); treating the resulting carded mat, by means of an applicator cylinder (kiss roll), with a cooked starch suspension (for example, type STABITEX 65401 from Cargill); exposing a resulting batt of fiber and starch to elevated temperature through a combination of hot air and contact with heated dryer cylinders to cure and dry the batt and rewinding and cutting the resulting roll into daughter rolls for use in the absorbent article.

[0142] Various components of the absorbent article are typically joined together via thermal or adhesive bonding. When an adhesive is employed, the adhesive preferably comprises a biobased adhesive. An example of a bio-based adhesive is a pressure sensitive adhesive available from Danimer Scientific under part number 92721.

[0143] According to certain embodiments, for example, at least the PLA spunbond nonwoven fabric layer may include bicomponent fibers. In some embodiments, for example, the bicomponent fibers may comprise a side-by-side arrangement. However, in other embodiments, for example, the bicomponent fibers may comprise a sheath and a core. In further embodiments, for example, the bicomponent fibers can comprise reversed bicomponent fibers. In certain embodiments, for example, the sheath may comprise PLA. In further embodiments, for example, the core can comprise at least one polyolefin, a polyester or any combination thereof. In some embodiments, for example, the core can comprise at least polypropylene, polyethylene, polyethylene terephthalate, PLA, or any combination thereof. In certain embodiments, for example, the sheath and core can comprise PLA.

[0144] According to certain embodiments, for example, the sheath may comprise a first grade PLA, the core may comprise a second grade PLA, and the first grade PLA and the second grade PLA may be different. In some embodiments, for example, the first grade PLA can comprise up to approximately 5% crystallinity, and the second grade PLA can comprise between approximately 40% and 50% crystallinity. In other embodiments, for example, the first grade PLA can comprise a melting point between approximately 125°C and 135°C, and the second grade PLA can comprise a melting point between approximately 155°C and 170°C. In further embodiments, for example, the first grade PLA can comprise a weight percent D-isomer of between approximately 4% by weight and 10% by weight, and the second grade PLA can comprise a weight percent D-isomer of approximately 2% by weight. In some embodiments, for example, the bicomponent fibers may comprise about 70% by weight of the core and about 30% by weight of the sheath.

However, in other embodiments, for example, at least the PLA spunbond nonwoven fabric layer may comprise a plurality of monocomponent PLA fibers including a blend of a PLA resin and a secondary alkanesulfone.

[0146] In a preferred embodiment, the PLA nonwoven fabrics according to the present invention can be used to produce sustainable absorbent articles. Examples of sustainable absorbent articles can be found in U.S. Patent Application No. 14/839,026 to Chester et al., incorporated in full by reference in this patent application.

[0147] According to certain embodiments, for example, at least the PLA spunbond nonwoven fabric layer may comprise a three-dimensional geometric pattern for consolidation. In such embodiments, for example, the pattern for consolidation may comprise at least a diamond pattern, a hexagonal dotted pattern, an elliptical oval pattern, a cylindrical pattern or any combination thereof.

Examples

[0148] The following examples are provided to illustrate one or more embodiments of the present invention and are not to be construed as a limitation of the invention.

[0149] The non-woven fabrics according to the invention were prepared using Reicofil-3 line or Reicofil-4 line from Reifenhaeuser. Each example was prepared using the setup described in Example 1 unless otherwise noted. Furthermore, unless otherwise noted, all percentages are percentages by weight. Materials used in the examples are identified below.

test methods

[0150] The title was calculated from the microscopic measurement of the fiber diameter and the density of a known polymer according to the German method C-1570 for textiles.

[0151] The grammage was generally determined following the German CM-130 method for textiles, based on the weight of 10 layers of fabric cut into squares of 10 X 10 cm.

[0152] Traction was determined according to method 10 DIN 53857 using a sample 5 cm wide, 100 mm distance between markings and crosshead speed of 200 mm/min. Tensile strengths were measured at peak.

[0153] The elongation was determined according to method 10 DIN 53857 using a 5 cm wide sample, 100 mm distance between markings and crosshead speed of 200 mm/min. Elongations were measured at peak.

[0154] The fabric shrinkage was determined by cutting three samples taken in the width of the blanket with the nominal dimensions of MD of 29.7 cm and CD of 21.0 cm; measuring actual MD and CD width at three locations on the sheet; placing the sample in water heated to 60 °C for 1 minute; and remeasuring the MD and CD dimensions at the above three locations. The average width measured after exposure divided by the original measurement X 100% provided the % shrinkage. A low % shrinkage value suggests that the continuous fibers comprising PLA were spun and drawn at sufficient speed to produce, upon consolidation, a stable high strength fabric.

Comparative Examples 1, 2 and 3

[0155] In Comparative Examples 1, 2 and 3, a 100% PLA bicomponent fabric was prepared on a Reicofil-4 rod. A press roller (press roller, R-4) was positioned on the collection surface downstream from where the filaments are deposited on the collection surface. An Ionis Elektrostatik E3412 ESD electrode (i.e. ionization bar) was positioned above and extending over the collection surface in the transverse direction and placed approximately 1 to 3 inches above the collection surface and 2 to 3 inches downstream of the R-4 press roll.

[0156] The fabrics were bicomponent, sheath/core Grade 6752 30/70 NatureWorks / Grade 6202 NatureWorks NatureWorks 30/70, made with ionization bars positioned as discussed above to simulate static electricity. The fabrics of Comparative Examples 1, 2 and 3 were produced at rotating rod temperatures of 235°C in the extruder and 240°C in the die. The fabric of Comparative Example 1 was produced with fiber drawing speed of 3600 m/min and line speed of 145 m/min. The calender for Comparative Example 1 exhibited calender temperatures of 160°C for the pattern roll and 147°C for the anvil roll and calender pressure of 40 N/mm.

[0157] The fabric of Comparative Example 2 was produced with fiber drawing speed of 3800 m/min and line speed of 90 m/min. The calender for Comparative Example 2 exhibited calender temperatures of 160°C for the pattern roll and 147°C for the anvil roll and calender pressure of 40 N/mm.

[0158] The fabric of Comparative Example 3 was produced with fiber drawing speed of 3200 m/min and line speed of 145 m/min. The calender for Comparative Example 3 exhibited calender temperatures of 160°C for the pattern roll and 147°C for the anvil roll and calender pressure of 40 N/mm. The mechanical properties of Comparative Examples 1, 2 and 3 are summarized in Tables 4 and 5 below.

Inventive example 1

[0159] In Inventive Example 1, a 100% PLA bicomponent fabric with a sheath/core structure was prepared in which 2 percent by weight of a masterbatch comprising a PLA resin and a secondary alkanesulfonate was added to the polymeric component that defined the sheath. The system configuration is the same as described above for Comparative Examples 1, 2 and 3.

[0160] The fabric was a bicomponent sheath/core Grade 6752 NatureWorks /Grade 6202 NatureWorks 30/70, made with ionizing rods as discussed above to minimize static electricity generation. In the sheath extruder, 2% by weight of a masterbatch of Sukano Antistatic Product S 546 was combined with NatureWorks Grade 6752 to provide the bicomponent fiber sheath. NOZZLE. The fabric of Inventive Example 1 was produced at spindle temperatures of 235°C in the extruder and 240°C in the die. The fabric of Inventive Example 1 was produced with fiber drawing speed of 3800 m/min and line speed of 145 m/min. The calender for Inventive Example 1 exhibited calender temperatures of 160°C for the pattern roll and 147°C for the anvil roll and calender pressure of 40 N/mm. The properties of Inventive Example 1 are summarized in Tables 4 and 5 below.

Inventive Example 2

[0161] In Inventive Example 2, a 100% PLA bicomponent fabric having a sheath/core arrangement was prepared, in which 3 percent by weight of a masterbatch comprising a PLA resin and a secondary alkanesulfonate was added to the polymeric component that defined the sheath. The system configuration is the same as described above for Comparative Examples 1, 2 and 3.

[0162] The fabric was a bicomponent sheath/core Grade 6752 NatureWorks / Grade 6202 NatureWorks 30/70, made with ionization rods as discussed above to minimize static electricity generation. In the sheath extruder, 3% by weight of a masterbatch of Sukano Antistatic Product S 546 was combined with NatureWorks Grade 6752 to provide the Example 12 BICO sheath. The fabric of Inventive Example 2 was produced at spindle temperatures of 235°C in the extruder and 240°C in the die. The fabric of Inventive Example 2 was produced with fiber drawing speed of 3550 m/min and line speed of 145 m/min. The calender for Inventive Example 2 exhibited calender temperatures of 160°C for the pattern roll and 147°C for the anvil roll and calender pressure of 40 N/mm. The properties of Inventive Example 2 are summarized in Tables 4 and 5 below.

Inventive Example 3

[0163] In Inventive Example 3, a 100% PLA bicomponent fabric with sheath/core arrangement was prepared, in which 2 percent by weight of a masterbatch comprising a PLA resin and a secondary alkanesulfonate was added to the polymeric component that defined the sheath. The system configuration is the same as described above for Comparative Examples 1, 2 and 3.

[0164] The fabric was bicomponent, sheath/core NatureWorks Grade 6752 / NatureWorks Grade 6202 30/70, made with ionization rods as discussed above to minimize static electricity generation. In the hem extruder, 2% by weight of a masterbatch of Sukano Antistatic Product S 546 was combined with NatureWorks Grade 6752 to provide the fabric hem. The fabric was produced at rotating rod temperatures of 235 °C in the extruder and 240 °C in the die. The fabric was produced with a fiber stretching speed of 3400 m/min and a line speed of 90 m/min. The calender for Inventive Example 3 exhibited calender temperatures of 160°C for the pattern roll and 147°C for the anvil roll and calender pressure of 40 N/mm. The properties of Inventive Example 3 are summarized in Tables 4 and 5 below.

Inventive Example 4

[0165] In Inventive Example 4, a 100% PLA bicomponent fabric with a sheath/core arrangement was prepared, in which 2 percent by weight of a masterbatch comprising a PLA resin and a secondary alkanesulfonate was added to the polymeric component defining the sheath. The system configuration is the same as described above for Comparative Examples 1, 2 and 3.

[0166] The fabric was a bicomponent sheath/core Grade 6752 NatureWorks / Grade 6202 NatureWorks 30/70, made with ionization rods as discussed above to minimize static electricity generation. In the hem extruder, 2% by weight of a masterbatch of Sukano Antistatic Product S 546 was combined with NatureWorks Grade 6752 to provide the bicomponent fabric hem. The fabric of Inventive Example 4 was produced at spindle temperatures of 235°C in the extruder and 240°C in the die. The fabric of Inventive Example 4 was produced with a fiber drawing speed of approximately 3400 m/min and a line speed of 241 m/min, producing a calculated weight of 15 grams/square meter. The calender for Inventive Example 4 exhibited calender temperatures of 160°C for the pattern roll and 147°C for the anvil roll and calender pressure of 40 N/mm. The mechanical properties of Inventive Example 14 were not evaluated. Table 4: Mechanical properties of nonwovens *Calculated weight for sample produced. Table 5: Normalized properties for weights Table 6: Percentage increase in MD and CD relative index in toughness Percent increase: (final value - initial value) / initial value x 100 Table 7: Shrinkage resistance of PLA spunbond fabric

[0167] From Tables 4 and 5 above, it can be seen that the nonwoven fabrics of the invention exhibit significant improvements in mechanical properties compared to nonwoven fabrics prepared in the same way that do not include the secondary alkanesulfonate. In this regard, the results provided in Table 5 are especially revealing. In Table 5, the results have been normalized to account for differences in weights. Based on these data, it can be seen that the nonwoven fabrics of the invention exhibited an increase in tensile strengths greater than 50% compared to the Comparative Examples. For example, the nonwoven fabrics of the invention exhibited an increase in MD tensile strength ranging from 55.6% (comparison of Inventive Example 3 with Comparative Example 2) to 110.2% (comparison of Inventive Example 2 with Comparative Example 1). With respect to CD tensile strength, the nonwoven fabrics of the invention exhibited an increase in CD tensile strength ranging from 57.3% (comparison of Inventive Example 1 with Comparative Example 2) to 162.8% (comparison of Inventive Example 3 with Comparative Example 1).

[0168] The nonwoven fabrics of the invention also exhibited significant increases in tenacity compared to the nonwoven fabrics of Comparative Examples. Table 5 below shows the relative toughness index MD and CD (normalized for grammage) of Comparative Examples 1-3 and Examples 1-3 of the Invention. For example, the nonwoven fabrics of the invention exhibited an increase in MD relative tenacity index ranging from 80.5% (comparison of Inventive Example 1 with Comparative Example 2) to 476% (comparison of Inventive Example 3 with Comparative Example 1). With respect to the relative tenacity index CD, the nonwoven fabrics of the invention exhibited an increase in the relative tenacity index CD ranging from 143% (comparison of Inventive Example 1 with Comparative Example 2) to 411% (comparison of Inventive Example 3 with Comparative Example 1).

[0169] When comparing the properties of different nonwovens, it is often useful to compare the root mean square of the combined MD and CD property values of interest. This method allows the comparison of isolated values. The root mean square gives a single number that combines the entered MD and CD values, taking the square root of the sum of the MD value plus the square of the CD value. Using the root mean square method to combine MD and CD results is especially useful if the samples to be compared were taken on different machines or under some different condition that could influence the MD/CD ratio. Table 5 below shows the Root Mean Square Toughness Index by Grammage for Comparative Samples 1 - 3 as well as Samples 1 -3 of the invention. The Root Mean Square values of the Toughness Index normalized to grammage show comparative samples grouped between 10 and 40 N %/g/m2. On the other hand, the nonwoven fabrics of the invention exhibited values of the root mean square of the tenacity index above 65 N %/g/m2 and, in particular, within a range of 55 to 100 N %/g/m2. Thus, a very clear root-mean-square separation of the normalized toughness index values can be seen for the fabrics of the invention and the comparative samples.

[0170] To further assess the basis for increases in tensile strength, elongation, and toughness of the nonwoven fabrics of the invention, SEM images of the fabric surfaces of Comparative Example 1 and Inventive Example 1 were obtained. Figures 1A and 1B are SEM images of Comparative Example 1 taken at 250x and 100x magnification, respectively. Figures 2A and 2B are SEM images of Inventive Example 1 taken at 250x and 100x magnification, respectively. Images were obtained with a PERSONAL SEM 75, from RJ Lee Instruments Ltd., and a DESK V Sputterer, from Denton Vacuum. As the SEM images were taken at low magnification, 100X and 250X, gold sputtering was not necessary. 5 mm x 5 mm samples were obtained from each tissue, and placed in the SEM instrument. A small vacuum was obtained and then images were captured.

[0171] Surprisingly, a significant difference in sizing between fibers was observed. Specifically, the fabric sticking points of Comparative Example 1 showed that the individual fibers were loosely bonded and that there was minimal flow of polymer gluing adjacent fibers together. In comparison, the glue points of the fabric of Inventive Example 1 showed significant melting and flow of the polymer from the individual fibers. Thus, the fabric of the invention exhibited significant improvements in sizing compared to the comparative fabric that did not include the secondary alkanesulfonate.

[0172] In the examples below, the effect of the carrier resin for the secondary alkanesulfonate on the physical properties was explored. As explained below, the improvements in mechanical properties in the fabrics were shown to be due primarily to the presence of the secondary alkanesulfonate and not to the presence of a lower molecular weight carrier resin in the masterbatch.

Comparative Example 4

[0173] In Comparative Example 4, a 100% PLA bicomponent fabric with a hem/core arrangement was prepared in which 0.5% weight percent NatureWorks Grade 6302 was added to the polymeric component defining the hem. NatureWorks Grade 6302 is typically used as the carrier polymer for masterbatches added to PLA polymer formulations. It is believed, therefore, that this PLA resin provides a good approximation of the PLA resin in the secondary alkanesulfonate. The system configuration is the same as described above for Comparative Examples 1, 2 and 3.

[0174] The fabric was a bicomponent sheath/core Grade 6752 NatureWorks / Grade 6202 NatureWorks 30/70, made with ionization rods as discussed above to minimize static electricity generation. In the hem extruder, 0.5% weight percent of NatureWorks Grade 6302, 2% by weight, was combined with NatureWorks Grade 6752 to provide the bicomponent fabric hem. The fabric of Comparative Example 4 was made under processing conditions similar to those used for Inventive Examples 1-4, with the exceptions shown in Table 8 below, and the thread speed was adjusted to give a final weight of 25 GSM. The properties of Comparative Example 4 are summarized below in Table 9, below.

Comparative Example 5

[0175] In Comparative Example 5, a 100% PLA bicomponent fabric with a hem/core arrangement was prepared in which 1.0% by weight of NatureWorks Grade 6302 was added to the polymeric component defining the hem. The system configuration is the same as described above for Comparative Examples 1, 2 and 3.

[0176] The fabric was a bicomponent sheath/core Grade 6752 NatureWorks / Grade 6202 NatureWorks 30/70, made with ionizing rods as discussed above to minimize static electricity generation. In the hem extruder, 1.0% weight percent of NatureWorks Grade 6302, 2% by weight, was combined with NatureWorks Grade 6752 to provide the bicomponent fabric hem. The fabric of Comparative Sample 4 was made under processing conditions similar to those used for Inventive Examples 1-4, except as shown in Table 8 below, and the thread speed was adjusted to give a final weight of 25 GSM. The properties of Comparative Example 5 are summarized below in Table 9.

Comparative Example 6

[0177] In Comparative Example 6, a bicomponent 100% PLA fabric with a hem/core arrangement was prepared in which 2.0% weight percent NatureWorks Grade 6302 was added to the polymeric component defining the hem. The system configuration is the same as described above for Comparative Examples 1, 2 and 3.

[0178] The fabric was a bicomponent sheath/core Grade 6752 NatureWorks / Grade 6202 NatureWorks 30/70, made with ionization rods as discussed above to minimize static electricity generation. In the hem extruder, 2.0% weight percent of NatureWorks Grade 6302, 2% by weight, was combined with NatureWorks Grade 6752 to provide the bicomponent fabric hem. The fabric of Comparative Example 6 was made under processing conditions similar to those used for Inventive Examples 1-4, except as shown in Table 8 below, and the thread speed was adjusted to give a final weight of 25 GSM. The properties of Comparative Example 6 are summarized below in Table 9 below.

Comparative Example 7

[0179] In Comparative Example 7, a 100% PLA bicomponent fabric with hem/core arrangement was prepared, in which 3.5% weight percent NatureWorks Grade 6302 was added to the polymeric component that defined the hem. The system configuration is the same as described above for Comparative Examples 1, 2 and 3.

[0180] The fabric was a bicomponent sheath/core Grade 6752 NatureWorks / Grade 6202 NatureWorks 30/70, made with ionization rods as discussed above to minimize static electricity generation. In the hem extruder, 3.5% weight percent of NatureWorks Grade 6302, 2% by weight, was combined with NatureWorks Grade 6752 to provide the bicomponent fabric hem. The fabric of Comparative Sample 7 was made under processing conditions similar to those used for Examples 1-4 of this invention, except as shown in Table 8 below, and the thread speed was adjusted to give a final weight of 25 GSM. The properties of Comparative Sample 7 are summarized below in Table 9 below.

Inventive Example 5

[0181] In Inventive Example 5, a 100% PLA bicomponent fabric with sheath/core arrangement was prepared, in which 0.3 weight percent of a masterbatch comprising a PLA resin and a secondary alkanesulfonate was added to the polymeric component defining the sheath. The system configuration is the same as described above for Comparative Examples 1, 2 and 3.

[0182] The fabric was a bicomponent sheath/core Grade 6752 NatureWorks / Grade 6202 NatureWorks 50/50, made with ionization rods as discussed above to minimize static electricity generation. In the hem extruder, 0.3% by weight of a Sukano Product S 546 masterbatch was combined with NatureWorks Grade 6752 to provide the bicomponent fabric hem. The fabric of Inventive Example 5 was produced under processing conditions similar to those used for Inventive Examples 1-4, except as shown in Table 8 below, and the thread speed was adjusted to give a final weight of 28 GSM. The properties of Inventive Example 5 are summarized below in Table 9 below.

Inventive Example 6

[0183] In Inventive Example 5, a 100% PLA bicomponent fabric with sheath/core arrangement was prepared, in which 0.3 weight percent of a masterbatch comprising a PLA resin and a secondary alkanesulfonate was added to the polymeric component defining the sheath. The system configuration is the same as described above for Inventive Examples 1, 2 and 3.

[0184] The fabric was a bicomponent sheath/core Grade 6752 NatureWorks / Grade 6202 NatureWorks 50/50, made with ionizing rods as discussed above to minimize static electricity generation. In the hem extruder, 0.3% by weight of a Sukano Product S 546 masterbatch was blended with NatureWorks Grade 6752 to provide the bicomponent fabric hem. The fabric of Inventive Example 6 was produced under processing conditions similar to those used for Inventive Examples 1-4, except as shown in Table 8 below, and the thread speed was adjusted to give a final weight of 23 GSM. The properties of Inventive Example 6 are summarized below in Table 9 below. Table 8: Process Conditions for Comparative Examples 4-7 and Inventive Examples 5-6 Table 9. Mechanical properties

[0185] There was no visible difference in consolidation sites for the above nonwovens (Comparative Examples 4-7) produced with PLA 6302 used as an additive compared to the above nonwovens made using the addition of the masterbatch of Sukano Product 546 (Examples 5 and 6 of the invention). However, considering the mechanical data summarized in Table 9, a significant difference was observed between Comparative Examples and Inventive Examples 5 and 6. Specifically, the Examples including secondary alkanesulfonate exhibited improvements in MD and CD tensile strength, MD and CD elongation, and MD and CD toughness index compared to Comparative Examples that only include the PLA resin from the masterbatch but not the secondary alkanesulfonate. Thus, it can be seen that the improvement in properties is attributed to the presence of the secondary alkanesulfonate and not the lower molecular weight PLA resin in the masterbatch.

[0186] It was also observed that, during fabric production, the fabrics of Inventive Examples 5 and 6 were more stable during calendering consolidation as compared to the fabrics of Comparative Examples 4-7.

[0187] In the following examples, the hydrophilic nature of PLA fabrics, and the effects of secondary alkanesulfonate on the hydrophilicity of fabrics were investigated. Inventive Examples 7-12 were prepared according to the fabric of Fabrics 6 and 7 of the invention. In each example, the amount of Sukano additive added to the sheath was varied, and the effects on Liquid Run-Off and Liquid Strike-through were evaluated at different time periods. The results are summarized in Tables 10 and 11 below.

[0188] Run-Off data were measured according to the procedures stipulated in test method WSP 80.9, and Strikethrough data as measured by test method WSP 70.3.

[0189] The Run-Off data measures the percentage of a specified volume of liquid that runs from a fabric/absorbent combination that is supported at a specified angle from the vertical. The tissue under evaluation is positioned covering an absorbent material. During the test procedure, liquid oozes from the fabric and may, or may not, be absorbed into the absorbent material placed beneath the fabric being tested. If the fabric is hydrophobic, a very high % of the liquid seeps down and out of the fabric/pad combination into a collection container. If the fabric is very hydrophilic, practically all the liquid is absorbed by the fabric/absorbent combination and the % run-off (Run-off) is almost equal to zero. The Runoff test is normally repeated on the same piece of fabric three times. This procedure simulates multiple urinations by the baby or adult in the diaper. Most typical commercial topsheets show a very low % sag at first damage. However, Run-off values normally increase in the second and third damages, as the surfactant is removed and transported to the absorbent material below the fabric under test. Thus, all hydrophilic surfactant can be lost after a first urination. As a result, repeated urination by a user, such as an infant, can result in a loss of fabric hydrophilicity, which can undesirably lead to diaper leakage.

[0190] The Strike Through data measures the time for a specified volume of liquid applied downwards at a 90 degree angle to the surface of the fabric under test with an absorbent layer on the back. Penetration values after single or multiple damages can be measured. A low strike through value suggests that the liquid will quickly penetrate the treated hydrophilic fabric and that it can be absorbed by the absorbent material simulating the diaper core. Results after multiple strike through tests provide an indication of the permanence of the surfactant treatment. Increasing strikethrough values with multiple damage suggests that the surfactant is being drawn into the underlying absorbent material, such as an absorbent core, with the risk that the diaper topsheet will become hydrophobic and the diaper will leak. An optimized topsheet will provide strikethrough values of 4 seconds or even less after up to three damages. Table 10: Run-Off test results Table 11: Strike-through test results

[0191] The % Run-Off and Strike-Through data in Tables 10 and 11 surprisingly demonstrated that not only does the secondary alkanesulfonate improve the mechanical properties of the PLA fabric, but it also modifies the fabrics' properties regarding liquid transport.

[0192] In addition, the results demonstrate that the flow (Run-Off) and penetration (Strike-through) are dependent, at least in part, on the level of secondary alkanesulfonate as well as the age of the tissue. For example, within two weeks, 100% PLA fabrics containing 0.25% and 0.5% of the additive exhibited hydrophobic properties, as measured by sag and penetration. One month after production, fabrics containing 0.25% and 0.5% of the additive still exhibited hydrophobic properties. However, at higher additive levels, a response suggestive of decreasing hydrophobicity is observed. Surprisingly and unexpectedly, the response is opposite to that seen with typical surfactant-treated topsheets. Initial oozing and penetration suggest a hydrophobic fabric. However, after the second and third damage, the fabric exhibits hydrophilic properties.

[0193] This effect suggests that it is possible to prepare tissues according to the invention that provide hydrophilic properties after multiple urination. Specifically, fabrics for use as a topsheet can be prepared, where the fabric is treated with a low surfactant added to provide initial hydrophilicity, but which then takes advantage of the additive to provide wash-resistant hydrophilicity after multiple damages. Such a topsheet may be of particular interest for use in night diapers and incontinence products.

Non-limiting exemplary modalities

[0194] Having described various aspects and embodiments of the invention herein, additional specific embodiments of the invention include those set forth in the following paragraphs.

[0195] Certain embodiments according to the invention are directed to a spunbond nonwoven fabric comprising a plurality of fibers that are consolidated together to form a cohesive batt, wherein the fibers comprise a mixture of a polylactic acid (PLA) and at least one secondary alkane sulfonate. In some embodiments, the mixture is present on a surface of the plurality of fibers. In one embodiment, the at least one secondary alkanesulfonate comprises an alkane chain having C10-C18 and wherein at least one of the secondary carbons of the alkane chain includes a sulfonate moiety. For example, at least one secondary alkanesulfonate has one of the following structures: where m + n is a number between 7 and 16 and X is independently a C1-C4 alkyl or absent. In some embodiments, at least one secondary alkanesulfonate has the following structure: where m + n is a number between 8 and 15, and especially where m + n is a number between 11 and 14. In some embodiments, the at least one secondary alkanesulfonate comprises a sodium or potassium salt.

[0196] In certain embodiments, at least one secondary alkanesulfonate is present in an amount ranging from approximately 0.0125 to 2.5 percent by weight, based on the total weight of the fiber. For example, the fiber can have a bicomponent sheath/core arrangement in which the blend is present in the sheath and the secondary alkanesulfonate is present in the sheath in an amount ranging from approximately 0.1 to 0.75 weight percent based on the total weight of the sheath. In another embodiment, the fiber can have a bicomponent sheath/core arrangement in which the blend is present in the sheath and the secondary alkane sulfonate is present in the sheath in an amount ranging from approximately 0.2 to 0.6 percent by weight based on the total weight of the sheath. In yet another embodiment, the fiber has a bicomponent sheath/core arrangement in which the blend is present in the sheath and in which the secondary alkane sulfonate is present in the sheath in an amount ranging from approximately 0.3 to 0.4 weight percent based on the total weight of the sheath.

[0197] In one embodiment, the plurality of fibers comprise bicomponent fibers. In some embodiments, the plurality of fibers comprise bicomponent fibers and at least one secondary alkanesulfonate is present in only one of the fiber components. In one embodiment, the bicomponent fibers have a sheath/core configuration and the sheath comprises a blend of the PLA and at least one secondary alkanesulfonate. In some embodiments, the core comprises PLA and does not include a secondary alkanesulfonate. In still other embodiments, the bicomponent fibers comprise a side-by-side arrangement.

[0198] In one embodiment, the core comprises at least one polyolefin, a polyester, a PLA or any combination thereof. In a preferred embodiment, the sheath and core comprise PLA. In certain embodiments, the sheath comprises a first grade PLA, the core comprises a second grade PLA, and the first grade PLA and the second grade PLA are different.

[0199] In some embodiments, the fabric exhibits an increase in tensile strength in at least one of the machine directions or in the transverse direction compared to an identical fabric that does not include a secondary alkanesulfonate. For example, the fabric can exhibit an increase in tensile strength in at least one of the machine directions or in the cross direction of at least 50% compared to an identical fabric that does not include a secondary alkanesulfonate.

[0200] In one embodiment, the fabric exhibits an increase in tensile strength in at least one of the machine directions or in the transverse direction that is between 50% and 200% compared to an identical fabric that does not include a secondary alkanesulfonate.

[0201] In one embodiment, the fabric exhibits an increase in tensile strength in the machine direction that is between approximately 50 and 150% compared to an identical fabric that does not include a secondary alkanesulfonate.

[0202] In one embodiment, the fabric exhibits an increase in tensile strength in the machine direction that is between approximately 55 and 125% compared to an identical fabric that does not include a secondary alkanesulfonate.

[0203] In one embodiment, the fabric exhibits an increase in tensile strength in the machine direction that is between approximately 65 and 110% compared to an identical fabric that does not include a secondary alkanesulfonate.

[0204] In one embodiment, the fabric exhibits an increase in tensile strength in the machine direction that is between approximately 65 and 110% compared to an identical fabric that does not include a secondary alkanesulfonate.

[0205] In one embodiment, the fabric exhibits an increase in tensile strength in the machine direction that is between approximately 85 and 110% compared to an identical fabric that does not include a secondary alkanesulfonate.

[0206] In one embodiment, the fabric exhibits an increase in tensile strength in the machine direction that is between approximately 90 and 110% compared to an identical fabric that does not include a secondary alkanesulfonate.

[0207] In one embodiment, the fabric exhibits an increase in tensile strength in the transverse direction that is between approximately 50 and 200% compared to an identical fabric that does not include a secondary alkanesulfonate.

[0208] In one embodiment, the fabric exhibits an increase in tensile strength in the transverse direction that is between approximately 50 and 170% compared to an identical fabric that does not include a secondary alkanesulfonate.

[0209] In one embodiment, the fabric exhibits an increase in tensile strength in the transverse direction that is between approximately 55 and 165% compared to an identical fabric that does not include a secondary alkanesulfonate.

[0210] In one embodiment, the fabric exhibits an increase in tensile strength in the transverse direction that is between approximately 65 and 160% compared to an identical fabric that does not include a secondary alkanesulfonate.

[0211] In one embodiment, the fabric exhibits an increase in tensile strength in the transverse direction that is between approximately 85 and 150% compared to an identical fabric that does not include a secondary alkanesulfonate.

[0212] In one embodiment, the fabric exhibits an increase in tensile strength in the transverse direction that is between approximately 90 and 125% compared to an identical fabric that does not include a secondary alkanesulfonate.

[0213] In one embodiment, the fabric exhibits an increase in elongation in at least one of the machine directions or in the transverse direction compared to an identical fabric that does not include a secondary alkanesulfonate.

[0214] In one embodiment, the fabric exhibits a machine direction tenacity index that is between approximately 2,000 and 7,500 N%.

[0215] In one embodiment, the fabric exhibits a machine direction tenacity index that is between approximately 2,300 and 6,500 N%.

[0216] In one embodiment, the fabric exhibits a machine direction tenacity index that is between approximately 2,300 and 6,000 N%.

[0217] In one embodiment, the fabric exhibits a tenacity index in the transverse direction that is between approximately 1,000 and 5,000 N%.

[0218] In one embodiment, the fabric exhibits a tenacity index in the transverse direction that is between approximately 1250 and 5000 N%.

[0219] In one embodiment, the fabric exhibits a tenacity index in the transverse direction that is between approximately 1250 and 3500 N%.

[0220] In one embodiment, the fabric exhibits an increase in machine direction toughness index that is between approximately 20 and 1250% compared to an identical fabric that does not include a secondary alkanesulfonate.

[0221] In one embodiment, the fabric exhibits an increase in machine direction toughness index that is at least 100% compared to an identical fabric that does not include a secondary alkanesulfonate.

[0222] In one embodiment, the fabric exhibits an increase in toughness index in the transverse direction that is between approximately 50 and 1000% compared to an identical fabric that does not include a secondary alkanesulfonate.

[0223] In one embodiment, the fabric exhibits an increase in toughness index in the transverse direction that is at least 85% compared to an identical fabric that does not include a secondary alkanesulfonate.

[0224] In some embodiments, the fabric exhibits a relative tenacity index in the machine direction that is between approximately 50 and 150 N %/g/m2, such as a relative tenacity index in the machine direction that is between approximately 75 and 125 N %/g/m2 and, in particular, a relative tenacity index in the machine direction that is between approximately 85 and 115 N %/g/m2. In one embodiment, the fabric exhibits a Relative Tenacity Index in the transverse direction that is between approximately 40 and 100 N%/g/m2, and a Relative Tenacity Index in the transverse direction that is between approximately 45 and 85 N%/g/m2.

[0225] In certain embodiments, the fabric exhibits an increase in relative toughness index in the machine direction that is between approximately 100 and 1,000% compared to an identical fabric that does not include a secondary alkanesulfonate, such as an increase in relative toughness index in the machine direction that is from 80 to 500% compared to an identical fabric that does not include a secondary alkanesulfonate.

[0226] In one embodiment, the fabric exhibits an increase in relative tenacity index in the transverse direction that is at least 100% compared to an identical fabric that does not include a secondary alkanesulfonate, such as an increase in relative tenacity index in the transverse direction that is between approximately 140 and 410% compared to an identical fabric that does not include a secondary alkanesulfonate.

[0227] Additional aspects of the invention are directed to a spunbond nonwoven fabric comprising a plurality of fibers that are consolidated together to form a cohesive batt, wherein the fibers comprise from 95 to 100% polylactic acid (PLA), and wherein the fibers exhibit a Root Mean Square Tenacity Index per grammage value that is at least 55 N%/g/m2. In one such embodiment, the root-mean-square Toughness Index per grammage is a value greater than 65 N%/g/m2, such as a value between approximately between approximately 65 and 150 N%/g/m2. In one embodiment, the fibers of the fabric comprise less than 5% by weight of additives.

[0228] Aspects of the invention are also directed to absorbent articles comprising a nonwoven fabric with fibers including a blend of a PLA resin and at least one secondary alkanesulfonate. Examples of absorbent articles include diapers and feminine sanitary pads.

[0229] Additional aspects of the invention are directed to a process for preparing polylactic acid (PLA) spunbond nonwoven fabrics, the process comprising: mixing a PLA resin and at least one secondary alkanesulfonate under heat and pressure to form a molten or semi-molten PLA resin stream; forming a plurality of continuous PLA filaments from said stream; depositing the plurality of continuous PLA filaments onto a collection surface; exposing the plurality of continuous PLA filaments to ions; and consolidating the plurality of PLA continuous filaments to form the PLA spunbond nonwoven fabric, wherein the continuous filaments comprise a mixture of PLA and at least one secondary alkane sulphonate.

[0230] In one embodiment, the filaments comprise a mixture of PLA and at least one secondary alkanesulfonate. The filaments can be single component or bicomponent. In a preferred embodiment, the filaments have a bicomponent sheath/core configuration, in which the sheath comprises a mixture of PLA and at least one secondary alkanesulfonate. In some embodiments, the core can comprise PLA or a synthetic polymer, such as a polyolefin or a polyester. Preferably, the core comprises PLA.

[0231] Advantageously, the process can be carried out at relatively high drawing speeds. For example, continuous filaments can be drawn at a fiber drawing speed of greater than about 2500 m/min., such as a fiber drawing speed of between about 3000 m/min and 5500 m/min., or a fiber drawing speed of between about 3000 m/min and 4000 m/min.

[0232] In one embodiment, the step of exposing a plurality of continuous PLA filaments to ions comprises passing the filaments into close proximity to an ionization source, such as an ionization bar. In one embodiment, the ionization source comprises an ionization bar that is positioned above the collection surface and in the transverse direction of the tissue.

[0233] In one embodiment, the step of consolidating the continuous filaments to form the PLA spunbond nonwoven fabric comprises spot thermal consolidation of the mat with heat and pressure through a calender with a pair of cooperating rollers including a patterned roller. In some embodiments, dot thermal consolidation of continuous filaments comprises imparting a three-dimensional geometric pattern for consolidation onto the PLA spunbond nonwoven fabric.

[0234] In one embodiment, consolidating the pattern on the PLA spunbond nonwoven fabric comprises transmitting at least a diamond pattern, a hexagonal dotted pattern, an elliptical oval pattern, a cylindrical pattern or any combination thereof on the PLA spunbond nonwoven fabric. In some embodiments, the consolidation pattern covers between approximately 5% and 30% of the surface area of the patterned roll. For example, the consolidation pattern can cover between about 10% and 25% of the surface area of the patterned roll.

[0235] In one embodiment, the process further comprises dissipating the static charge of the PLA spunbond nonwoven fabric next to the calender via a first static control unit. In one embodiment, the static control unit comprises a second source of ionization, such as an ionization bar. For example, the second ionization source may comprise an ionization bar extending over at least a plurality of continuous PLA filaments or the PLA spunbond nonwoven fabric in transverse direction.

[0236] In one embodiment, dissipating the static charge from the PLA spunbond nonwoven fabric comprises placing the PLA spunbond nonwoven fabric in contact with a static bar.

[0237] In some embodiments, the process may further comprise cutting PLA spunbond nonwoven fabric to obtain cut PLA spunbond nonwoven fabric; exposing a cut PLA spunbond nonwoven fabric to ions via a third ionization source; and rewinding the cut PLA spunbond nonwoven fabric into rolls. In one embodiment, the third ionization source comprises an ionization bar extending over at least a plurality of continuous PLA filaments or the PLA spunbond nonwoven fabric in a transverse direction.

[0238] Additional aspects of the invention are directed to a system for preparing polylactic acid (PLA) spunbond nonwoven fabrics, the system comprising: a first source of PLA and a source of secondary alkanesulfonate, configured to supply a stream comprising molten or semi-molten PLA resin and the secondary alkanesulfonate; a rotating rod in fluid communication with the first source of PLA, the rotating rod configured to extrude and draw a plurality of continuous filaments of PLA, the continuous filaments of PLA comprising a mixture of the PLA and the secondary alkanesulfonate; a collecting surface disposed below an outlet of the rotating rod onto which the continuous PLA filaments are deposited to form the PLA spunbond nonwoven fabric; a first ionization source positioned and arranged to expose the continuous PLA filaments to ions; and a calender positioned downstream of the first ionization source.

[0239] In one embodiment, the first ionization source is positioned above the collection surface and downstream of a point where continuous PLA filaments are deposited on the collection surface. In another embodiment, the first ionization source is positioned between the rotating rod outlet and the collection surface. Preferably, the first ionization source and the collection surface are separated by a distance between approximately 1 inch and 24 inches, such as a distance between approximately 1 inch and 12 inches, and in particular, a distance between approximately 1 inch and 5 inches.

[0240] In some embodiments, the system may further comprise a static control unit positioned and arranged to dissipate static discharges from the PLA spunbond nonwoven fabric near the calender. In one embodiment, the static control unit comprises a passive bar for static charges, a second ionization source, or a combination thereof.

[0241] In one embodiment, the system includes a press roller positioned downstream of the rotary rod outlet. In some embodiments, the system may comprise a vacuum source disposed below the collection surface.

[0242] In certain embodiments, the system may include a rewinding machine that is positioned downstream of the calender; and a third ionization source positioned and arranged to expose the PLA spunbond nonwoven fabric to ions, next to the rewinder.

[0243] In one embodiment, at least the first ionization source, the static discharge control source or the third ionization source comprises an ionization bar extending over at least a plurality of continuous PLA filaments or the PLA spunbond nonwoven fabric in transverse direction. In one embodiment, the first ionization source, the static control source, and the third ionization source are configured to actively dissipate the static charge created during preparation of the PLA spunbond nonwoven fabric.

[0244] In one embodiment, the first source of ionization is positioned downstream of the press roll. In some embodiments, the first ionization source is positioned between the rotating rod and the press roll. When present, the static control unit can be positioned upstream and adjacent to the calender. In other embodiments, the static control unit is positioned downstream and adjacent to the calender.

[0245] In one embodiment, the calender comprises a pair of cooperating rollers including a patterned roller, wherein the patterned roller comprises a three-dimensional geometric pattern for consolidation. In some embodiments, the consolidation pattern comprises at least a diamond pattern, a hexagonal dotted pattern, an elliptical oval pattern, a cylindrical pattern, or any combination thereof. In one embodiment, the consolidation pattern comprises between about 5% and 30% of the surface area of the patterned roll, such as between about 10% and 25% of the surface area of the patterned roll.

[0246] In one embodiment, the system is configured to produce a nonwoven fabric of continuous filaments with bicomponent arrangement. In one embodiment, the continuous filaments have a sheath/core arrangement. In a preferred embodiment, the system is configured to produce filaments in which the mixture of PLA and the secondary alkanesulfonate defines the sheath. In some embodiments, the core comprises a PLA resin. the PLA resin can be the same or different from that of the sheath. In one embodiment, the core is free of the secondary alkanesulfonate.

[0247] In some embodiments, the secondary alkanesulfonate is present in an amount ranging from approximately 0.0125 to 2.5 percent by weight, based on the total weight of the fiber. In one embodiment, the continuous filaments have a bicomponent sheath/core arrangement in which the blend is present in the sheath, and in which the secondary alkanesulfonate is present in the sheath in an amount ranging from approximately 0.1 to 0.75 weight percent based on the total weight of the sheath.

[0248] In a particular embodiment, the system is configured to prepare continuous filaments with a bicomponent sheath/core arrangement, in which the mixture is present in the sheath and in which the secondary alkanesulfonate is present in the sheath in an amount ranging from approximately 0.2 to 0.6 percent by weight, based on the total weight of the sheath. In other embodiments, the system is configured to produce continuous filaments with a bicomponent sheath/core arrangement, in which the mixture is present in the sheath and in which the secondary alkane sulfonate is present in the sheath in an amount ranging from approximately 0.3 to 0.4 percent by weight, based on the total weight of the sheath.

[0249] Modifications of the invention set forth herein will come to the mind of the person skilled in the art in the subject to which the invention pertains, with the benefit of the teachings presented in the preceding descriptions and in the associated drawings. Therefore, it is to be understood 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 used herein, these terms are used in a genetic and descriptive sense only and are not intended to be limiting.

Claims (13)

1. Continuously spun nonwoven fabric comprising a plurality of filaments that are consolidated together to form a cohesive batt, wherein the filaments comprise a mixture of a polylactic acid (PLA) and at least one secondary alkanesulfonate, and wherein the fabric exhibits at least one of the following: an increase in tensile strength in at least one of the machine directions or in the cross direction compared to an identical fabric that does not include the at least one secondary alkanesulfonate; and an increase in elongation in at least one of the machine directions or in the transverse direction compared to an identical fabric that does not include the at least one secondary alkanesulfonate, wherein the at least one secondary alkanesulfonate has one of the following structures: wherein n or m + n is a number between 7 and 16, and wherein the at least one secondary alkanesulfonate is present in an amount ranging from about 0.0125 to 2.5 weight percent, based on the total weight of the filaments. Fabric according to claim 1, characterized in that the mixture is present on a surface of the plurality of filaments. Fabric according to any one of claims 1 or 2, characterized in that the at least one secondary alkanesulfonate comprises an alkane chain having C10-C18 and in which at least one of the secondary carbons of the alkane chain includes a sulfonate moiety. Fabric according to any one of Claims 1 to 3, characterized in that the at least one secondary alkanesulfonate has the following structure: where m + n is a number between 8 and 15. A fabric according to any one of claims 1 to 4, characterized in that the filament has a bicomponent sheath/core arrangement in which the blend is present in the sheath and in which the secondary alkanesulfonate is present in the sheath in an amount ranging from about 0.1 to 0.75 percent by weight, based on the total weight of the sheath. 6. Absorbent article, characterized in that it comprises the fabric as defined in any one of claims 1 to 5. Absorbent article according to claim 6, characterized in that the article comprises a diaper or a sanitary pad. A process for preparing a polylactic acid (PLA) continuous spinning nonwoven fabric as defined in claim 1, characterized in that the process comprises: mixing a PLA resin and at least one secondary alkanesulfonate under heat and pressure to form a stream of molten or semi-molten PLA resin; forming a plurality of continuous PLA filaments from said stream; depositing the plurality of continuous PLA filaments onto a collection surface; exposing the plurality of continuous PLA filaments to ions; and consolidating the plurality of PLA continuous filaments to form the PLA continuous spinning nonwoven fabric, wherein the continuous filaments comprise a mixture of PLA and the at least one secondary alkanesulfonate. Process according to Claim 8, characterized in that the at least one secondary alkanesulfonate has the following structure: where m + n is a number between 8 and 15. Process according to any one of claims 8 or 9, characterized in that forming the plurality of continuous PLA filaments comprises forming bicomponent fibers with a side-by-side or sheath/core orientation. Process according to claim 10, characterized in that the sheath comprises a mixture of PLA and the at least one secondary alkanesulfonate. 12. System for preparing a continuous spinning polylactic acid (PLA) nonwoven fabric as defined in any one of claims 1 to 5, characterized in that the system comprises: a first source of PLA (2) and a source of a secondary alkanesulfonate, configured to supply a stream comprising molten or semi-molten PLA resin and the secondary alkanesulfonate; a rotating rod (4) in fluid communication with the first source of PLA, the rotating rod configured to extrude and draw a plurality of continuous PLA filaments (30), wherein the continuous PLA filaments comprise a mixture of the PLA and the secondary alkanesulfonate; a collecting surface (10) disposed below an outlet of the rotating rod onto which the PLA continuous filaments are deposited to form the PLA continuous spinning nonwoven fabric; a first ionization source (18) positioned and arranged to expose the continuous PLA filaments to ions; and a calender (14) positioned downstream of the first ionization source. 13. System according to claim 12, characterized in that the secondary alkanesulfonate has the following structure: where m + n is a number between 8 and 15.