PROCESS FOR FORMING NONWOVEN WEBS

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to the benefit of U.S. Provisional Application No. 63/290,801, filed December 17, 2021 which is expressly incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

[0002] The present invention is generally directed to multicomponent filaments, nonwoven webs made from the multicomponent filaments, and processes for forming the nonwoven webs. In accordance with the present invention, the multicomponent filaments contain a crimp enhancement additive. More particularly, the present invention is directed to incorporating an additive into one of the polymers used to make multicomponent filaments. The additive produces an inherent crimp in the multicomponent filaments without the use of any post-crystallization/solidification crimping treatment. The process produces webs with improved fabric density and softness properties. The crimp enhancement additive incorporated into the filaments is a polyolefin homopolymer, in particular a polypropylene homopolymer.

BACKGROUND OF THE INVENTION

[0003] Nonwoven fabrics are used to make a variety of products which desirably have particular levels of softness, strength, uniformity, liquid handling properties such as absorbency, and other physical properties. Such products include towels, industrial wipers, incontinence products, filter products, infant care products such as baby diapers, absorbent feminine care products, and garments such as safety and other protective apparel. These products are often made with multiple layers of nonwoven fabrics to obtain the desired combination of properties. For example, disposable baby diapers made from polymeric nonwoven fabrics may include a soft and porous liner layer which fits next to the baby's skin, an impervious outer cover layer which is strong and soft, and one or more interior liquid handling layers which are soft, bulky and absorbent. [0004] Nonwoven fabrics such as the foregoing are commonly made by melt spinning thermoplastic materials, including through spunbond processes. Such fabrics made through a spunbond process are sometimes referred to as spunbond materials or spunbond nonwoven polymeric webs. Spunbond nonwoven polymeric webs are typically made from thermoplastic materials by extruding the thermoplastic material through a spinneret and drawing the extruded material into filaments with a stream of high velocity air to form a random web on a collecting surface.

[0005] Spunbond materials with desirable combinations of physical properties, especially combinations of softness, strength, and absorbency, have been produced, but limitations have been encountered. For example, for some applications, polymeric materials such as polypropylene may have a desirable level of strength but not a desirable level of softness. On the other hand, materials such as polyethylene may, in some cases, have a desirable level of softness but not a desirable level of strength. [0006] In an effort to produce nonwoven materials having desirable combinations of physical properties, spunbond nonwoven polymeric fabrics made from multicomponent or bicomponent filaments and fibers have been developed.

Multicomponent polymeric fibers or filaments include two or more polymeric components which remain distinct, and bicomponent polymeric fibers or filaments include two polymeric components which remain distinct. As used herein, the terms “filaments” and “fibers” mean strands of material and may be used interchangeably. In particular embodiments, the filaments of the present invention may be continuous or the filaments of the present invention may be discontinuous and thus have a definite length. The first and subsequent components of multicomponent filaments are arranged in substantially distinct zones across the cross-section of the filaments and extend continuously along the length of the filaments. Typically, one component exhibits different properties than the other so that the filaments exhibit properties of the two components. For example, one component may be polypropylene which is relatively strong and the other component may be polyethylene which is relatively soft. The end result is a strong yet soft nonwoven fabric. However, use of different polymers in the multicomponent filaments can make recycling the multicomponent filaments and webs made therefrom impractical or impossible if one of the polymers is not recyclable, as it would be difficult to separate the polymers to extract the recyclable one.

[0007] To increase the bulk or fullness of the multicomponent nonwoven webs for improved fluid management performance or for enhanced "cloth-like" feel of the webs, the bicomponent filaments or fibers are often crimped. Multicomponent filaments may be either mechanically crimped or, if the appropriate polymers are used, naturally crimped. As used herein, a naturally crimped filament is a filament that is crimped by activating a latent crimp contained in the filaments. For instance, in one embodiment, filaments can be naturally crimped by subjecting the filaments to a gas, such as a heated gas, after being drawn.

[0008] In general, it is far more preferable to construct filaments that can be naturally crimped as opposed to having to crimp the filaments in a separate mechanical process. Difficulties have been experienced in the past, however, in producing filaments that will crimp naturally to the extent required for the particular application. Also, it has been found to be very difficult to produce naturally crimped fine filaments, such as filaments having a linear density of less than two denier. Specifically, the draw force used to produce fine filaments usually prevents or removes any meaningful latent crimp attributes that may be contained in the filaments. As such, currently a need exists for a method of producing multicomponent filaments with enhanced inherent crimp properties without the need for the use of separate crimping treatments (e.g., mechanical crimping). Also, a need exists for nonwoven webs made from such filaments and processes for forming such webs.

SUMMARY OF THE INVENTION

[0009] The present invention recognizes and addresses the foregoing disadvantages, and others of prior art constructions and methods.

[0010] Accordingly, an object of the present invention is to provide a multicomponent filament with inherent crimp attributess.

[0011] Another object of the present invention is to provide improved nonwoven web, including spunbond webs, and processes for forming the same. [0012] Another object of the present invention is to provide nonwoven polymeric fabrics including highly crimped filaments and methods for economically making the same.

[0013] Another object of the present invention is to provide a process for inherently crimping multicomponent filaments.

[0014] It is another object of the present invention to provide a process for inherently crimping multicomponent filaments by adding to one of the components of the filaments a crimp enhancement additive.

[0015] Still another object of the present invention is to provide a inherently crimped filament that contains polypropylene in an about of about 90% or greater. [0016] Another object of the present invention is to provide multicomponent filaments with an average of at least about five crimps per inch and nonwoven webs made from such filaments.

[0017] These and other objects of the present invention are achieved by providing a process for forming a nonwoven web. The process includes the steps of melt spinning multicomponent filaments. The filaments including a first polymeric component and a second polymeric component. The second polymeric component has a faster solidification and/or crystallization rate than the first polymeric component. The second polymeric component contains a crimp enhancement additive. The crimp enhancement additive including a polyolefin homopolymer having a melt flow rate of less than about 20 g/10 min. The crimp enhancement additive causes the multicomponent filaments to inherently crimp as the filaments solidify and/or crystalize.

[0018] Once melt spun, the multicomponent filaments are drawn onto a forming surface for forming the nonwoven web. Thereafter, the multicomponent crimped filaments are formed into a nonwoven web for use in various applications.

[0019] In one embodiment, the multicomponent filaments have an average of at least about five crimps per inch. Preferably, the multicomponent filaments have an average of at least about five crimps per inch.

[0020] In one embodiment, the multicomponent filaments comprise greater than about 90% polypropylene by weight. Preferably, the multicomponent filaments comprise greater than about 95% polypropylene by weight. Preferably, the multicomponent filaments comprise greater than about 97% polypropylene by weight. [0021] In an embodiment, the crimp enhancement additive includes a polypropylene homopolymer. In one embodiment, the crimp enhancement additive is present in the second component in an amount of between about 5% and 50% by weight based on the weight of the second component. Preferably, the crimp enhancement additive is present in the second component in an amount between about 20% and 30% by weight based on the weight of the second component.

[0022] These and other objects of the present invention are also achieved by providing a nonwoven web including inherently crimped multicomponent filaments that have not been heat treated, wherein the multicomponent filaments have an average of at least about five crimps per inch.

[0023] In one embodiment, the multicomponent, inherently crimped filaments are made from at least a first polymeric component and a second polymeric component. In an embodiment, the second polymeric component includes a crimp enhancement additive and the second component exhibits a rate of solidification and/or crystallization faster than the rate of solidification and/or crystallization of the first component when solidifying and/or crystallizing from a molten state.

[0024] In one embodiment, the multicomponent filaments of the nonwoven web have an average of at least about five crimps per inch. Preferably, the multicomponent filaments have an average of at least about twenty crimps per inch.

[0025] In one embodiment, the nonwoven fabric has a TS7 softness of about 4 or less as measured by a TSA analyzer.

[0026] In one embodiment, the multicomponent filaments of the nonwoven web comprise greater than about 90% polypropylene by weight. Preferably, the multicomponent filaments of the nonwoven web comprise greater than about 95% polypropylene by weight. Preferably, the multicomponent filaments of the nonwoven web comprise greater than about 97% polypropylene by weight.

[0027] In an embodiment, the crimp enhancement additive is polypropylene homopolymer. In one embodiment, the crimp enhancement additive is present in the second component in an amount of between about 5% and 50% by weight based on the weight of the second component. Preferably, the crimp enhancement additive is present in the second component in an amount between about 20% and 30% by weight based on the weight of the second component.

[0028] In one embodiment, the nonwoven web contains multicomponent filaments with a denier between about 1 and about 2.5. In another embodiment, the nonwoven web has a fabric density of less than about 76 kg/m3.

[0029] These and other objects of the present invention are also achieved by providing multicomponent filaments with the composition described herein. The multicomponent filaments include a first polymeric component and a second polymeric component. The second polymeric component has a faster solidification and/or crystallization rate than the first polymeric component. The second polymeric component contains a crimp enhancement additive. The multicomponent filaments exhibit inherent crimps without heat treating. The multicomponent filaments have an average of at least about five crimps per inch. Preferably, the multicomponent filaments have an average of at least about twenty crimps per inch.

[0030] In one embodiment, the multicomponent filaments include greater than about 90% polypropylene by weight. Preferably, the multicomponent filaments include greater than about 95% polypropylene by weight. Preferably, the multicomponent filaments include greater than about 97% polypropylene by weight. [0031] In an embodiment, the crimp enhancement additive is polypropylene homopolymer. In one embodiment, the crimp enhancement additive is present in the second component in an amount between about 5% and 50% by weight based on the weight of the second component. Preferably, the crimp enhancement additive is present in the second component in an amount between about 20% and 30% by weight based on the weight of the second component.

[0032] In an embodiment, the multicomponent filaments are continuous. In one embodiment, the multicomponent filaments are discontinuous.

[0033] Other objects, features and aspects of the present invention are discussed in greater detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

[0034] A full and enabling disclosure of the present invention, including the best mode thereof, to one of ordinary skill in the art, is set forth more particularly in the remainder of the specification, including reference to the accompanying figures, in which:

[0035] FIG. 1 is a schematic drawing of a process line for making an embodiment of the present invention.

[0036] FIG. 2A is a schematic drawing illustrating the cross section of a filament made according to an embodiment of the present invention with the polymer components A and B in a side-by-side arrangement.

[0037] FIG. 2B is a schematic drawing illustrating the cross section of a filament made according to an embodiment of the present invention with the polymer components A and B in an eccentric sheath/core arrangement.

[0038] Repeat use of reference characters in the present specification and drawings is intended to represent same or analogous features or elements of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0039] It is to be understood by one of ordinary skill in the art that the present discussion is a description of exemplary embodiments only, and is not intended as limiting the broader aspects of the present invention, which broader aspects are embodied in the exemplary construction.

[0040] The present invention is generally directed to multicomponent filaments, to nonwoven webs, including spunbond webs, produced from the filaments, and to a process for forming nowoven webs from the filaments. In particular, the filaments are inherently crimped into, for instance, a helical arrangement. Crimping the filaments increases the bulk, the softness, and the drapability. The nonwoven webs also have improved fluid management properties and have an enhanced cloth-like appearance and feel.

[0041] Multicomponent filaments for use in the present invention contain at least two polymeric components. The polymeric components can be, for instance, in a side- by-side configuration or in an eccentric sheath-core configuration. The polymeric components are selected from semi-crystalline and crystalline thermoplastic polymers which have different crystallization and/or solidification rates with respect to each other in order for the filaments to undergo inherent crimping. More particularly, one of the polymeric components has a faster solidifying and/or crystallizing rate than the other polymeric component.

[0042] As used herein, the solidification and/or crystallization rate of a polymer refers to the rate at which a softened or melted polymer hardens and forms a fixed structure. It is believed that the solidification and/or crystallization rate of a polymer is influenced by different parameters including the melting temperature and the rate of crystallization of the polymer. For instance, a fast solidifying and/or crystallizing polymer typically has a melting point that is about 10 °F or higher, more desirably about 20 °F or higher, and most desirably about 30 °F or higher than a polymer that has a slower solidifying and/or crystallizing rate. It should be understood, however, that both polymeric components may have similar melting points if their crystallization rates are measurably different.

[0043] It is believed that the inherent crimping of multicomponent filaments is created in the filaments due to the differences in the shrinkage properties, i.e., differences in the rates of solidification and/or crystallization, between the polymeric components.

[0044] The present invention is directed to adding a crimp enhancement additive to one of the polymeric components to produce a faster solidification and/or crystallization rate in that component. In this manner, the differences between the solidification and/or crystallization rates of the two (or more) polymeric components creates multicomponent filaments exhibiting an inherent crimping. In particular, the crimp enhancement additive of the present invention is a polyolefin homopolymer, preferably a polypropylene homopolymer.

[0045] As used herein, “inherent crimping” means that the multicomponent filaments crimp upon solidifying and/or crystallizing without the use of any further crimping treatments, i.e., treatments to produce or activate crimp. Prior methods of producing crimp in multicomponent filaments have required that the filaments be subjected to additional steps to produce, enhance, or activate crimping in the filaments. Such steps include using heat to activate crimping during the drawing of the filaments or through air drying or the use of an air knife. In comparison, the multicomponent filaments of the present invention exhibit a high degree of crimp without the use of any of these additional or subsequent crimping treatments. Accordingly, the present invention allows for simplified and less energy intensive processes for the production of highly crimped multicomponent filaments and nonwoven webs formed therefrom.

[0046] In one embodiment, the multicomponent filaments have an average of at least about five crimps per inch. Preferably, the multicomponent filaments have an average of at least about 10 crimps per inch or at least about twenty crimps per inch or at least about 30 crimps per inch or at least about 40 crimps per inch or at least about 50 crimps per inch.

[0047] Besides creating multicomponent filaments that have an inherent crimp, it has also been discovered that the crimp enhancement additive of the present invention provides many other benefits and advantages. For instance, fabrics and webs made from the filaments have a higher bulk and a lower density. By being able to make lower density webs, less material is needed to make webs of a specified thickness and the webs are thus less expensive to produce. Besides having lower densities, the webs have also been found to be more cloth-like, to have a softer hand, and to have more stretch.

[0048] The webs and fabrics of the present invention are particularly useful for making various products including liquid and gas filters, personal care articles and garment materials. Personal care articles include infant care products such as disposable baby diapers, child care products such as training pants, and adult care products such as incontinence products and feminine care products. Suitable garments include safety apparel, work wear, and the like.

[0049] As described above, the fabric of the present invention can be made from continuous or discontinuous multicomponent polymeric filaments comprising at least first and second polymeric components. A preferred embodiment of the present invention is a polymeric fabric including continuous bicomponent filaments comprising a first polymeric component A and a second polymeric component B. The bicomponent filaments have a cross-section, a length, and a peripheral surface. The first and second components A and B are arranged in substantially distinct zones across the cross-section of the bicomponent filaments and extend continuously along the length of the bicomponent filaments. The second component B, in some embodiments, constitutes at least a portion of the peripheral surface of the bicomponent filaments continuously along the length of the bicomponent filaments. [0050] The first and second components A and B, for example, are arranged in either a side-by-side arrangement as shown in FIG. 2A or an eccentric sheath/core arrangement as shown in FIG. 2B so that the resulting filaments exhibit an inherent helical crimp. Polymer component A is the core of the filament and polymer component B is the sheath in the sheath/core arrangement. Methods for extruding multicomponent polymeric filaments into such arrangements are well-known to those of ordinary skill in the art.

[0051] Polymer component A and polymer component B must be selected so that the resulting bicomponent filament is capable of developing an inherent crimp. Preferably, polymer component B has a faster solidification rate than polymer component A. For instance, in one embodiment, polymer component B can have a higher melting temperature than polymer component A. In one embodiment, the rate of solidification and/or crystallization of the second component is at least about 5% faster than the rate of solidification and/or crystallization of the first component. Preferably, the rate of solidification and/or crystallization of the second component is at least about 10% faster, at least about 15%, at least about 20% faster, at least about 25% faster, at least about 30% faster, at least about 40% faster, at least about 50% faster, at least about 60% faster, at least about 70% faster, at least about 80% faster, at least about 90% faster, or at least about 100% faster than the rate of solidification and/or crystallization of the first component.

[0052] Preferably, polymer component A comprises polypropylene and component B also comprises polypropylene. When component A polypropylene and component B is also polypropylene, the bicomponent filaments may comprise greater than about 90% by weight polypropylene. More preferably, the bicomponent filaments may comprise greater than about 95% by weight polypropylene and greater than about 97% by weight polypropylene.

[0053] In one embodiment, the ratio of the first polymeric component (component A) to the second polymeric component (component B) is from about 50:50 to about 90:10 by weight. Preferably, the ratio of the first polymeric component (component A) to the second polymeric component (component B) is from about 50:50 to about 65:35 or from about 50:50 to about 75:25 by weight.

[0054] Suitable materials for preparing the multicomponent filaments of the present invention include fiber grade polypropylene with a melt flow rate of between about 20 g/10 min and about 55 g/10 min at 230 °C and a load of 2.16 kg as determined in accordance with ASTM D1238, such as PP3155E5, a polypropylene homopolymer, available from ExxonMobil of Houston, Tex.

[0055] In an embodiment, the crimp enhancement additive of the present invention is a polyolefin homopolymer. More preferably, the crimp enhancement additive is a polypropylene homopolymer. Preferably, the crimp enhancement additive is free of phthalates. For instance, one commercially available product that may be used as the crimp enhancement additive is a polypropylene homopolymer having an MFR (melt flow rate) of 14 g/10 min at 230 °C and a load of 2.16 kg as determined in accordance with ASTM D1238 and a density of 0.9 g/cm3.

[0056] In an embodiment, the crimp enhancement additive is present in the second component (component B) in an amount between about 5% and 50% by weight based on the weight of the second component. Preferably, the crimp enhancement additive is present in the second component (component B) in an amount between about 10% and 40% by weight based on the weight of the second component or between about 20% and 30% by weight based on the weight of the second component.

[0057] In an embodiment, the crimp enhancement additive has a melt flow rate (MFR) of less than about 20 g/ 10 min as measured at a temperature of 230 °C and a load of 2.16 kg as determined in accordance with ASTM D1238. Preferably, the crimp enhancement additive has a melt flow rate (MFR) between about 5 g/10 min and about 20 g/10 min or about 8 g/10 min to about 16 g/10 min or about 10 g/10 min to about 14 g/10 min as measured at a temperature of 230 °C and a load of 2.16 kg as determined in accordance with ASTM DI 238.

[0058] In an embodiment, the multicomponent filaments include two polymeric components A and B. Each of components A and B may also include additional ingredients in minor amounts. As used herein, the term “minor amount” means less than about 25% by weight of the component to which the ingredient is added. Suitable additional ingredients for use in the multicomponent filaments of the present invention include softness/loft enhancers, pigments, and slip aids.

[0059] Suitable pigments include white pigments such as titanium dioxide zinc dioxide. Preferably, the pigment is a white pigment such as SCC-4837, titanium dioxide, available from the Standridge Color Corporation, Social Circle, Ga. In an embodiment, the white pigment is present in the first component in an amount of about 1% by weight based on the weight of the first component. Preferably, the white pigment is present in the first component in an amount between about 0.5% and about 3% by weight or between about 1.0% and about 1.5% based on the weight of the first component. In an embodiment, the white pigment is present in the second component in an amount of about 1% by weight based on the weight of the second component. Preferably, the white pigment is present in the second component in an amount between about 0.5% and about 3% by weight or between about 1.0% and about 1.5% based on the weight of the second component. Preferably, the white pigment is present in both components in the amounts discussed above.

[0060] Suitable softness/loft enhancers include polypropylene/polyethylene copolymers, such as Vistamaxx 7050, a polypropylene/polyethylene copolymer containing 13% by weight of ethylene and having a mass flow rate of 45 g/10 min at 230 °C and a load of 2.16 kg as determined in accordance with ASTM D1238, available from ExxonMobil and Americhem 48137, a secondary fatty acid amide, available from Americhem of Cuyahoga Falls, OH. In an embodiment, the softness/loft enhancers are present in the first component in an amount between about 10% and about 20% by weight based on the weight of the first component. Preferably, the softness/loft enhancers are present in the first component in an amount between about 5% and about 25% by weight based on the weight of the first component. In an embodiment, softness/loft enhancers are present in the second component in an amount of about 1.5% by weight based on the weight of the second component. Preferably, the softness/loft enhancers are present in the second component in an amount between about 0.5% and about 3% by weight based on the weight of the second component. Preferably, the softness/loft enhancers are present in both components in the amounts discussed above. [0061] Suitable slip aids include primary and secondary amides. Primary amide slip aids include erucamide, available from the Sigma Aldrich, St. Louis, MO. In an embodiment, the slip aid is present in the first component in an amount of about 0.3% by weight based on the weight of the first component. Preferably, the slip aid is present in the first component in an amount between about 0.1% and about 1% by weight or between about 0.2% and about 0.5% based on the weight of the first component. In an embodiment, the slip aid is present in the second component in an amount of about 0.3% by weight based on the weight of the second component. Preferably, the slip aid is present in the second component in an amount between about 0.1% and about 1% by weight or between about 0.2% and about 0.5% based on the weight of the second component. Preferably, the slip aid is present in both components in the amounts discussed above.

[0062] In an embodiment, component A includes polypropylene, a propylene/ethylene copolymer, a secondary fatty acid amide, and a white pigment. In another embodiment, component B includes polypropylene, the crimp additive, a secondary fatty acid amide, and a white pigment. In one embodiment, component A includes polypropylene, a propylene/ethylene copolymer, a secondary fatty acid amide, and a white pigment and component B includes polypropylene, the crimp additive, a secondary fatty acid amide, and a white pigment.

[0063] In order to combine the crimp enhancement additive with polymer component B, in one embodiment, the polymers can be dry blended and extruded together during formation of the multicomponent filaments. In an alternative embodiment, the crimp enhancement additive and polymer component B can be melt blended prior to being formed into the filaments of the present invention.

[0064] One process for producing multicomponent filaments and nonwoven webs according to the present invention will now be discussed in detail with reference to FIG. 1. The following process is similar to the process described in U.S. Pat. No. 5,382,400 to Pike et al., which is incorporated herein by reference in its entirety. [0065] Turning to FIG 1, a process line 10 for preparing a preferred embodiment of the present invention is disclosed. In some embodiments, the filaments described herein, for example, can be made through either a “closed” or “open” spunbond system, as described below. The process line 10 is arranged to produce bicomponent continuous filaments, but it should be understood that the present invention comprehends nonwoven fabrics made with multicomponent filaments having more than two components. For example, the fabric of the present invention can be made with filaments having three or four or more components.

[0066] The process line 10 includes a pair of extruders 12a and 12b for separately extruding a polymer component A and a polymer component B. Polymer component A is fed into the respective extruder 12a from a first hopper 14a and polymer component B is fed into the respective extruder 12b from a second hopper 14b. Polymer components A and 3 are fed from the extruders 12a and 12b through respective polymer conduits 16a and 16b to a spinneret 18.

[0067] Spinnerets for extruding bicomponent filaments are well-known to those of ordinary skill in the art and thus are not described here in detail. Generally described, the spinneret 18 includes a housing containing a spin pack which includes a plurality of plates stacked one on top of the other with a pattern of openings arranged to create flow paths for directing polymer components A and B separately through the spinneret. The spinneret 18 has openings arranged in one or more rows. The spinneret openings form a downwardly extending curtain of filaments when the polymers are extruded through the spinneret. For the purposes of the present invention, spinneret 18 may be arranged to form side-by-side or eccentric sheath/core bicomponent filaments illustrated in FIGS. 2A and 2B.

[0068] The process line 10 also includes a quench blower 20 positioned adjacent the curtain of filaments extending from the spinneret 18. Air from the quench air blower 20 quenches the filaments extending from the spinneret 18. The quench air can be directed from one side of the filament curtain as shown FIG. 1, or both sides of the filament curtain.

[0069] A fiber draw unit or aspirator 22 is positioned below the spinneret 18 and receives the quenched filaments. Fiber draw units or aspirators for use in melt spinning polymers are well-known as discussed above. Suitable fiber draw units for use in the process of the present invention include a linear fiber aspirator of the type shown in U.S. Pat. No. 3,802,817 and educative guns of the type shown in U.S. Patent Nos. 3,692,618 and 3,423,266, the disclosures of which are incorporated herein by reference. [0070] Generally described, the fiber draw unit 22 includes an elongate vertical passage through which the filaments are drawn by aspirating air entering from the sides of the passage and flowing downwardly through the passage. A compressor (in an open system) or blower (in a closed system) 24 supplies aspirating air to the fiber draw unit 22. The aspirating air draws the filaments and ambient air through the fiber draw unit.

[0071] An endless foraminous forming surface 26 is positioned below the fiber draw unit 22 and receives the continuous filaments from the outlet opening of the fiber draw unit. The forming surface 26 travels around guide rollers 28. A vacuum 30 positioned below the forming surface 26 where the filaments are deposited draws the filaments against the forming surface.

[0072] The process line 10 further includes a bonding apparatus such as thermal point bonding rollers 34 (shown in phantom) or a through-air bonder 36. Thermal point bonders and through-air bonders are well-known to those skilled in the art and are not disclosed here in detail. Generally described, the through-air bonder 36 includes a perforated roller 38, which receives the web, and a hood 40 surrounding the perforated roller. Lastly, the process line 10 includes a winding roll 42 for taking up the finished fabric.

[0073] To operate the process line 10, the hoppers 14a and 14b are filled with the respective polymer components A and B. Polymer components A and B are melted and extruded by the respective extruders 12a and 12b through polymer conduits 16a and 16b and the spinneret 18. Although the temperatures of the molten polymers vary depending on the polymers used, when polypropylene is used for both components A and B, the preferred temperature of the polymers when extruded range from about 370 °F to about 530 °F and preferably range from 400 °F to about 470 °F.

[0074] As the extruded filaments extend below the spinneret 18, a stream of air from the quench blower 20 at least partially quenches the filaments to develop an inherent helical crimp in the filaments. The quench air preferably flows in a direction substantially perpendicular to the length of the filaments at a temperature of about 45 °F to about 90 °F and a velocity of from about 100 feet per minute to about 400 feet per minute. [0075] After quenching, the filaments are drawn into the vertical passage of the fiber draw unit 22 by a flow of a gas, such as air, from the compressor or blower 24 through the fiber draw unit. The fiber draw unit is preferably positioned 30 to 60 inches below the bottom a of the spinneret 18. The filaments inherently crimp during solidification/crystallization during and throughout the drawing process.

[0076] The crimped filaments are deposited through the outlet opening of the fiber draw unit 22 onto the traveling forming surface 26. The vacuum 20 draws the filaments against the forming surface 26 to form an unbonded, nonwoven web of continuous filaments. The pattern in which the filaments are deposited on the forming surface is not critical. However, preferably, the filaments may be deposited on the forming surface in a uniform manner to produce a web with consistent properties. In the past, the web was then typically lightly compressed by a compression roller and then thermal point bonded by rollers 34 or through-air bonded in the through-air bonder 36.

[0077] Lastly, the finished web is wound onto the winding roller 42 and is ready for further treatment or use. When used to make liquid absorbent articles, the fabric of the present invention may be treated with conventional surface treatments or contain conventional polymer additives to enhance the wettability of the fabric. For example, the fabric of the present invention may be treated with polyalkylene-oxide modified siloxanes and silanes such as polyalkylene-oxide modified polydimethyl-siloxane as disclosed in U.S. Pat. No. 5,057,361. Such a surface treatment enhances the wettability of the fabric.

[0078] The fabric of the present invention has a relatively high loft. The helical crimp of the filaments creates an open web structure with substantial void portions between filaments and the filaments are bonded at points of contact. In an embodiment, the nonwoven web of the present invention has a density of less than about 76 kg/m3. Preferably, the nonwoven web of the present invention typically has a density of less than about 75 kg/m3 or less than about 70 kg/m3 or less than about 60 kg/m3 or less than about 50 kg/m3 or less than about 40 kg/m3 or less than about 30 kg/m3 or less than about 25 kg/m3 or less than about 20 kg/m3 or less than about 10 kg/m3. [0079] In an embodiment, the nonwoven web of the present invention has a basis weight of about 19 GSM (g/m2). Preferably, the nonwoven web of the present invention typically has a basis weight of between about 10 GSM and about 60 GSM or between about 15 GSM and about 40 GSM or between about 20 GSM and about 30 GSM.

[0080] In an embodiment, the multicomponent filaments have denier between about 1.0 and about 3. Preferably, the multicomponent filaments have denier between about 1.0 and about 2.5 or between about 1.0 and 2.0.

[0081] In an embodiment, the nonwoven fabric has a TS7 softness of about 4 or less as measured by a TSA analyzer. Preferably, the nonwoven fabric has a TS7 softness of about 3 or less as measured by a TSA analyzer.

[0082] As discussed above, the crimp enhancement additive of the present invention allows for the production of highly crimped, fine filaments. In the past, naturally crimped fine filaments were difficult if not impossible to produce.

[0083] According to the present invention, filaments having an inherent crimp of at least about 10 crimps per inch can be produced at linear densities less than 2 denier, and particularly at less than about 1.2 denier. For most nonwoven webs, it is preferable for the filaments to have between about 10 crimps per inch and about 25 crimps per inch. Of particular advantage, filaments having an inherent crimp in the above range can be produced according to the present invention at a lower linear density than what has been possible in the past.

[0084] Thermal point bonding may be conducted in accordance with U.S. Pat. No. 3,855,046, the disclosure of which is incorporated herein by reference. When thermal point bonded, the fabric of the present invention exhibits a more cloth-like appearance and, for example, is useful as an outer cover for personal care articles or as a garment material.

[0085] Although the methods of bonding shown in FIG. 1 are thermal point bonding and through-air bonding, it should be understood that the fabric of the present invention may be bonded by other means such as oven bonding, ultrasonic bonding, hydroentangling or combinations thereof. Such bonding techniques are well-known to those of ordinary skill in the art and are not discussed here in detail. [0086] The bonding geometry used to form the nonwoven webs may enhance the loft, density, and softness of the nonwoven webs. In one embodiment, the bond geometry has a bond area of between about 5% and about 25%. Preferably, the bond geometry has a bond area of between about 8% and about 18% or the bond geometry has a bond area of about 10%. In one embodiment, the bond geometry has a patern discrete shapes in rows and columns or has an interlocking grid of repeating geometric shapes, such as diamonds or hexagons.

[0087] Spunbond meltblown spunbond (SMS) fabrics are tri laminate nonwoven fabrics. SMS is made up of a top layer of spunbond polypropylene, a middle layer of meltblown polypropylene, and a botom layer of spunbond polypropylene. The nonwoven webs of the present invention are well suited for use in SMS fabrics/laminates. In an embodiment of the present invention, an SMS fabric/laminate is formed from a top layer of a nonwoven web of the present invention, a middle layer of meltblown polypropylene, and a botom layer of a nonwoven web of the present invention.

[0088] Once produced, the nonwoven webs of the present invention can be used in many different and various applications. For instance, the webs can be used in filter products, in liquid absorbent products, in personal care articles, in garments, and in various other products.

EXAMPLES

[0089] The present invention may be beter understood with reference to the following Examples.

EXAMPLE NO. 1

[0090] Nonwoven webs were made according to the present invention having the following formulas:

A: Polypropylene homopolymer

B: Polypropylene/poly ethylene copolymer

C: Secondary fatty acid amide

D: Titanium dioxide

E: Crimp enhancement additive

[0091] All formulations demonstrated low density.

EXAMPLE NO. 2

[0092] Nonwoven webs were made according to the present invention having the following formula:

Component A: 87% wt Polypropylene homopolymer 10 % wt Polypropylene/polyethylene copolymer 1.5% wt Secondary fatty acid amide 1.5% wt Titanium dioxide

Component B: 67% wt Polypropylene homopolymer 30 % wt Crimp enhancement additive 1.5% wt Secondary fatty acid amide 1.5% wt Titanium dioxide

[0093] These webs each had a GSM of 20 and a low density.

[0094] These and other modifications and variations to the present invention may be practiced by those of ordinary skill in the art, without departing from the spirit and scope of the present invention, which is more particularly set forth in the appended claims. In addition, it should be understood that aspects of the various embodiments may be interchanged both in whole or in part. Furthermore, those of ordinary skill in the art will appreciate that the foregoing description is by way of example only and is not intended to limit the invention so further described in such appended claims.