Patent Publication Number: US-2021189601-A1

Title: Fibers including an alkylene oxide-containing non ionic surfactant, articles, and methods

Description:
BACKGROUND 
     Thermal comfort depends upon the heat release from the human body. Moisture release is one mechanism of heat loss. An average human can lose 1200 milliliters (mL) perspiration per hour in heavy activity from the Apocrine and Eccrine sweat glands during vigorous physical activity. Cotton can absorb such perspiration (e.g., moisture regain is 7.0-8.5% moisture at 65% Relative Humidity (RH)), whereas polyester and nylon, which are more hydrophobic in nature, cannot. For example, polyester fabrics can only retain 0.4% moisture at 65% RH. 
     The rate at which water vapor moves through a fabric plays an important role in determining a person&#39;s comfort, as it influences the cool/warmth sensation and aids in regulating body temperature. This process is called moisture vapor transmission or wicking. 
     A vast majority of active wear apparel is made of polyester or nylon, which do not allow moisture on its surface, because of their hydrophobic natures, and do not pass vapor easily through the pores of the fabrics, resulting in limited wicking capability across fabrics made of polyester or nylon fibers. This can lead to either accumulation of moisture at the surface of the fabric or outright repulsion of moisture back to the surface of the skin, thereby impeding the flow of moisture through and across the fabric. Therefore, a person may experience or perceive discomfort when wearing polyester garments. Cotton absorbs better, but it does not wick efficiently either, leading to discomfort. 
     Attempts to improve water absorbency/wicking of a polyester fabric involve the following approaches: (1) use of a different spinning nozzle to make a differently shaped fiber; (2) use of hollow microporous fibers; (3) incorporation of two or three layers of hydrophilic fabric (e.g., cotton) with hydrophobic polyester fabric in a construction; and (4) applying a hydrophilic agent to the surface of hydrophobic fiber. 
     Other methods are still needed to impart hydrophilicity to aromatic polyester-containing fibers and nylon-6-containing fibers. 
     SUMMARY OF THE DISCLOSURE 
     The present disclosure provides fibers, articles including such fibers, and methods of making and using such fibers. The fibers include an alkylene oxide-containing nonionic surfactant. 
     In one embodiment, the present disclosure provides a fiber including: a base polymer that includes an aromatic polyester or nylon-6; and an alkylene oxide-containing nonionic surfactant mixed within the base polymer; wherein the alkylene oxide-containing nonionic surfactant has a melting point of greater than 25° C. and an HLB of greater than 10. 
     In one embodiment, the present disclosure provides a plurality of fibers as described herein, which may be in the form of a yarn or a web, for example. In one embodiment, an article is provided that includes a plurality of fibers as described herein, wherein a first portion of the plurality of fibers include: a base polymer including an aromatic polyester or nylon-6; an alkylene oxide-containing nonionic surfactant mixed within the base polymer, wherein the alkylene oxide-containing nonionic surfactant has a melting point of greater than 25° C. and an HLB of greater than 10; and a dye; wherein the dye is present in a greater amount in the first portion of the fibers than in other portions of the fibers of the article. 
     The present disclosure provides a method of making fibers as described herein, the method including: providing a base polymer comprising an aromatic polyester or nylon-6; providing an alkylene oxide-containing nonionic surfactant, wherein the alkylene oxide-containing nonionic surfactant has a melting point of greater than 25° C. and an HLB of greater than 10; melt mixing the alkylene oxide-containing nonionic surfactant with the base polymer; and forming a plurality of fibers, each of which includes the alkylene oxide-containing nonionic surfactant mixed within the base polymer. 
     The present disclosure also provides a method of differentially dyeing a fibrous substrate, the method including: providing a fibrous substrate including a first portion of fibers and a second portion of fibers; applying the same type and amount of dye under the same conditions to the first and second portions of the fibrous substrate; wherein the first and second portions of the fibrous substrate differentially absorb the dye. The fibrous substrate includes: a first portion of fibers including: a base polymer including an aromatic polyester or nylon-6; and an alkylene oxide-containing nonionic surfactant mixed within the base polymer, wherein the alkylene oxide-containing nonionic surfactant has a melting point of greater than 25° C. and an HLB of greater than 10; and a second portion of fibers including: a base polymer that is the same as in the first portion; and optionally an alkylene oxide-containing nonionic surfactant mixed within the base polymer, wherein the amount (including no such surfactant) and/or type of the alkylene oxide-containing nonionic surfactant is different than that in the first portion. 
     As used herein, “alkylene oxide” refers to a divalent group that is an oxy group bonded directly to an alkylene group, wherein the term “alkylene” refers to a divalent group that is a radical of an alkane and includes groups that are linear, branched, cyclic, bicyclic, or a combination thereof. Unless otherwise indicated, the alkylene group typically has 1 to 30 carbon atoms. In some embodiments, the alkylene group has 1 to 20 carbon atoms, 1 to 10 carbon atoms, 1 to 6 carbon atoms, or 1 to 4 carbon atoms. Examples of “alkylene” groups include methylene, ethylene, propylene, 1,4-butylene, 1,4-cyclohexylene, and 1,4-cyclohexyldimethylene. 
     As used herein, “alkyl” refers to a monovalent group that is a radical of an alkane and includes straight-chain, branched, cyclic, and bicyclic alkyl groups, and combinations thereof, including both unsubstituted and substituted alkyl groups. Unless otherwise indicated, the alkyl groups typically contain from 1 to 72 carbon atoms. In some embodiments, the alkyl groups contain 1 to 45 carbon atoms, 1 to 30 carbon atoms, 1 to 10 carbon atoms. Examples of alkyl groups include, but are not limited to, methyl, ethyl, n-propyl, n-butyl, n-pentyl, isobutyl, t-butyl, isopropyl, n-octyl, n-heptyl, ethylhexyl, cyclopentyl, cyclohexyl, cycloheptyl, and the like. 
     The terms “polymer” and “polymeric material” include, but are not limited to, organic homopolymers, copolymers, such as for example, block, graft, random and alternating copolymers, terpolymers, etc., and blends and modifications thereof. Furthermore, unless otherwise specifically limited, the term “polymer” shall include all possible geometrical configurations of the material. These configurations include, but are not limited to, isotactic, syndiotactic, and atactic symmetries. 
     Herein, the term “comprises” and variations thereof do not have a limiting meaning where these terms appear in the description and claims. Such terms will be understood to imply the inclusion of a stated step or element or group of steps or elements but not the exclusion of any other step or element or group of steps or elements. By “consisting of” is meant including, and limited to, whatever follows the phrase “consisting of.” Thus, the phrase “consisting of” indicates that the listed elements are required or mandatory, and that no other elements may be present. By “consisting essentially of” is meant including any elements listed after the phrase, and limited to other elements that do not interfere with or contribute to the activity or action specified in the disclosure for the listed elements. Thus, the phrase “consisting essentially of” indicates that the listed elements are required or mandatory, but that other elements are optional and may or may not be present depending upon whether or not they materially affect the activity or action of the listed elements. Any of the elements or combinations of elements that are recited in this specification in open-ended language (e.g., comprise and derivatives thereof), are considered to additionally be recited in closed-ended language (e.g., consist and derivatives thereof) and in partially closed-ended language (e.g., consist essentially, and derivatives thereof). 
     The words “preferred” and “preferably” refer to embodiments of the disclosure that may afford certain benefits, under certain circumstances. However, other claims may also be preferred, under the same or other circumstances. Furthermore, the recitation of one or more preferred claims does not imply that other claims are not useful, and is not intended to exclude other claims from the scope of the disclosure. 
     In this application, terms such as “a,” “an,” and “the” are not intended to refer to only a singular entity, but include the general class of which a specific example may be used for illustration. The terms “a,” “an,” and “the” are used interchangeably with the term “at least one.” The phrases “at least one of” and “comprises at least one of” followed by a list refers to any one of the items in the list and any combination of two or more items in the list. 
     As used herein, the term “or” is generally employed in its usual sense including “and/or” unless the content clearly dictates otherwise. 
     The term “and/or” means one or all of the listed elements or a combination of any two or more of the listed elements. 
     Also herein, all numbers are assumed to be modified by the term “about” and in certain embodiments, preferably, by the term “exactly.” As used herein in connection with a measured quantity, the term “about” refers to that variation in the measured quantity as would be expected by the skilled artisan making the measurement and exercising a level of care commensurate with the objective of the measurement and the precision of the measuring equipment used. Herein, “up to” a number (e.g., up to 50) includes the number (e.g., 50). 
     Also herein, the recitations of numerical ranges by endpoints include all numbers subsumed within that range as well as the endpoints (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, 5, etc.). 
     As used herein, the term “room temperature” refers to a temperature of 20° C. to 25° C. or 22° C. to 25° C. 
     The term “in the range” or “within a range” (and similar statements) includes the endpoints of the stated range. 
     When a group is present more than once in a formula described herein, each group is “independently” selected, whether specifically stated or not. For example, when more than one R group is present in a formula, each R group is independently selected. Furthermore, subgroups contained within these groups are also independently selected. 
     Reference throughout this specification to “one embodiment,” “an embodiment,” “certain embodiments,” or “some embodiments,” etc., means that a particular feature, configuration, composition, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. Thus, the appearances of such phrases in various places throughout this specification are not necessarily referring to the same embodiment of the invention. Furthermore, the particular features, configurations, compositions, or characteristics may be combined in any suitable manner in one or more embodiments. 
     The above summary of the present disclosure is not intended to describe each disclosed embodiment or every implementation of the present invention. The description that follows more particularly exemplifies illustrative embodiments. In several places throughout the application, guidance is provided through lists of examples, which examples may be used in various combinations. In each instance, the recited list serves only as a representative group and should not be interpreted as an exclusive list. Thus, the scope of the present disclosure should not be limited to the specific illustrative structures described herein, but rather extends at least to the structures described by the language of the claims, and the equivalents of those structures. Any of the elements that are positively recited in this specification as alternatives may be explicitly included in the claims or excluded from the claims, in any combination as desired. Although various theories and possible mechanisms may have been discussed herein, in no event should such discussions serve to limit the claimable subject matter. 
    
    
     DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS 
     The present disclosure provides fibers, articles including such fibers, and methods of making and using such fibers. The fibers include an alkylene oxide-containing nonionic surfactant mixed within (i.e., incorporated within) a base polymer that includes an aromatic polyester or nylon-6. Due to the incorporation of the surfactant, the fibers are capable of absorbing liquid (e.g., water). In certain embodiments, the fibers are capable of wicking liquid as exemplified by water or an 80/20 (by weight) water/isopropanol mixture. This makes the fibers, as well as yarns, threads, webs, and other articles that include such fibers capable of absorbing moisture, and, preferably, wicking perspiration away from a body (e.g., a perspiring human body). 
     For example, in certain embodiments, a meltblown web of a plurality of the fibers demonstrates absorption of a water drop within 5 minutes, within 1 minute, within 30 seconds, within 10 seconds, or instantaneously, according to the Water Drop Test of the Examples Section. 
     In certain embodiments, a meltblown web of a plurality of the fibers wicks an 80/20 water/isopropanol mixture according to the Vertical Wicking Test of the Examples Section. In certain embodiments, a meltblown web of a plurality of the fibers wicks an 80/20 water/isopropanol mixture according to the Vertical Wicking Test to a distance of at least 5 cm, at least 6 cm, at least 7 cm, at least 8 cm, at least 9 cm, or at least 10 cm after 5 minutes. 
     Specifically, the present disclosure provides a fiber including: an aromatic polyester (e.g., polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT), polybutylene terephthalate (PBT), or mixtures thereof), or nylon-6 (as the base polymer); and an alkylene oxide-containing nonionic surfactant mixed within (e.g., as a result of melt blending) the aromatic polyester or nylon-6. In this context, “mixed within” or “mixed with” or “mixture” refers to the nonionic surfactant being incorporated in the bulk of a fiber, not merely as a coating on a fiber. 
     Base Polymer 
     The base polymer for making the fibers include aromatic polyesters and nylon-6. 
     The Federal Trade Commission definition of a polyester fiber is “a manufactured fiber in which the fiber forming substance is any long-chain synthetic polymer composed of at least 85% by weight of an ester of a substituted aromatic carboxylic acid,” including but not restricted to substituted terephthalic units, p(—R—O—CO—C 6 H 4 —CO—O—) x , and parasubstituted hydroxy-benzoate units, p(—R—O—CO—C 6 H 4 —O—) x . 
     In certain embodiments, the aromatic polyester is selected from polyethylene terephthalate (PET), polyethylene terephthalate glycol (PETG), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polypropylene terephthalate, and combinations thereof (including mixtures or copolymers thereof). In certain embodiments, the aromatic polyester is selected from polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT), polybutylene terephthalate (PBT), and combinations thereof. In certain embodiments, the aromatic polyester is selected from polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT), and combinations thereof. Commercially available sources of aromatic polyesters include Nan Ya Plastics Corp. (Wharton, Tex.), Eastman Chemical Co. (Kingsport, Tenn.), Unifi (Greensboro, N.C.). 
     Nylon-6, also known as polycaprolactam, polyamide-6, and poly(hexano-6-lactam), has the formula [—N(H)—(CH 2 ) 5 —C(O)—] n , wherein n=the number of repeating units. Commercially available sources of nylon-6 include BASF (Ludwigshafen, Germany). 
     A mixture of polymers can be used as the base polymer if desired. The base polymer (including a polymer mixture) is present in each fiber (or a plurality of fibers) in a major amount (i.e., in an amount of greater than 50 wt-%). In certain embodiments, each fiber (or a plurality of fibers) includes at least 90 percent by weight (wt-%), at least 95 wt-%, at least 97 wt-%, or at least 98 wt-%, of the base polymer, based on the total weight of the fiber (or plurality of fibers). In certain embodiments, each fiber (or a plurality of fibers) includes up to 99.9 wt-%, up to 99.5 wt-%, up to 99.0 wt-%, or up to 98.5 wt-% of the base polymer, based on the total weight of the fiber (or plurality of fibers). 
     Surfactant 
     Mixed within the bulk of each fiber is an alkylene oxide-containing nonionic surfactant that has a hydrophile lipophile balance (HLB) of at least 10. In certain embodiments, the alkylene oxide-containing nonionic surfactant has an HLB of at least 11, at least 12, at least 13, at least 14, or at least 15. In certain embodiments, the alkylene oxide-containing nonionic surfactant has an HLB of up to 20. 
     The HLB (Hydrophilic-Lipophilic Balance) is calculated as a number between 0 and 20 by Griffin&#39;s Method: 
     
       
         
           
             
               H 
                
               
                   
               
                
               L 
                
               
                   
               
                
               B 
             
             = 
             
               20 
               × 
               
                 
                   M 
                   Hydrophilic 
                 
                 M 
               
             
           
         
       
     
     where: 
     M Hydrophilic  is the molecular mass of the hydrophilic portion of the molecule
         M is the molecular mass of the entire molecule.       

     Furthermore, the alkylene oxide-containing nonionic surfactant has a melting point of greater than 25° C. In certain embodiments, the alkylene oxide-containing nonionic surfactant has a melting point of at least 30° C., or at least 40° C., or at least 50° C. In certain embodiments, the alkylene oxide-containing nonionic surfactant has a decomposition temperature of at least 250° C., which is the temperature at which 5% of the weight of the surfactant is lost. There is no upper limit for the decomposition temperature. 
     In certain embodiments, the alkylene oxide-containing nonionic surfactant has an average molecular weight of at least 900 grams/mole, at least 1000 grams/mole, or at least 4000 grams/mole. In certain embodiments, the alkylene oxide-containing nonionic surfactant has an average molecular weight of up to 5000 grams/mole. 
     In certain embodiments, the alkylene oxide-containing nonionic surfactant includes an ethylene oxide-containing nonionic surfactant, an ethylene oxide/propylene oxide-containing nonionic surfactant, or a combination thereof. In certain embodiments, the alkylene oxide-containing nonionic surfactant does not include propylene oxide moieties. 
     In certain embodiments, the alkylene oxide-containing nonionic surfactant includes an ethylene oxide-containing nonionic surfactant. In certain embodiments, the ethylene oxide-containing nonionic surfactant has the following Formula (I): 
       R 1 —[C(O)] r -(EO) n1 —[C(O)] r —R 2   (I)
 
     wherein:
         R 1 =(C12-C72)alkyl (preferably, a linear or branched alkyl);   EO=Ethylene Oxide;   n1=3-100;   each r is independently 0 or 1 (preferably, 0); and   R 2 =H or a (C1-C10)alkyl.       

     In certain embodiments, the alkylene oxide-containing nonionic surfactant includes an ethylene oxide/propylene oxide-containing nonionic surfactant. In certain embodiments, the ethylene oxide/propylene oxide-containing nonionic surfactant has the following Formula (II) or (III): 
       R 3 —[C(O)] r -(EO) n2 —(PO) m -(EO) n2 —[C(O)] r —R 3   (II)
 
       (PO) m -(EO) n2 —[C(O)] r —R 3   (III)
 
     wherein:
         each R 3  is independently H or a (C1-C72)alkyl (preferably, a linear or branched alkyl);   EO=Ethylene Oxide;   PO=Propylene Oxide;   each r is independently 0 or 1 (preferably, 0);   each n2 is independently 10-100; and   each m is independently 5-65.       

     In certain embodiments, the alkylene oxide-containing nonionic surfactant includes an ethylene oxide-containing amine nonionic surfactant having the following Formula (IV): 
       R 4 —N-{(EO) n1 —R 5 } 2   (IV)
 
     wherein:
         R 4 =(C8-C22)alkyl (preferably, a linear or branched alkyl);   EO=Ethylene Oxide;   n1=3-100; and   R 5 =H or a (C1-72)alkyl.
 
A mixture of alkylene oxide-containing nonionic surfactants can be used if desired.
       

     In certain embodiments, each fiber (or plurality of fibers) includes at least 0.1 wt-%, at least 0.5 wt-%, at least 1.0 wt-%, or at least 1.5 wt-%, of the alkylene oxide-containing nonionic surfactant, based on the total weight of the fiber (or plurality of fibers). In certain embodiments, each fiber (or plurality of fibers) includes up to 5.0 wt-% (or up to 2.0 wt-%) of the alkylene oxide-containing nonionic surfactant, based on the total weight of the fiber (or plurality of fibers). 
     Optional Additives 
     In certain embodiments, the fibers further include talc mixed within the bulk of each fiber. In certain embodiments, each fiber (or plurality of fibers) includes at least 0.5 wt-% talc, based on the total weight of the fiber (or plurality of fibers). In certain embodiments, each fiber (or plurality of fibers) includes up to 3.0 wt-% talc, based on the total weight of the fiber (or plurality of fibers). 
     In certain embodiments, the fibers further include one or more additives such as antioxidants (e.g., hindered light amine stabilizers, etc.), flame retardants, UV stabilizers, colorants (e.g., pigments or dyes), softeners, antimicrobial agents, antistatic agents, optical brighteners, and combinations thereof. 
     Typically, such optional additives are mixed within the bulk of each fiber. These optional additives could also be applied to the surface of the fibers and/or fabric. 
     One of skill in the art can readily determine the amounts of such additives. 
     In any fiber, or plurality of fibers, the sum of all components equals 100% by weight. 
     Methods of Making and Using 
     The fibers of the present disclosure can be made using a variety of techniques. A plurality of such fibers may be used to make yarns or threads. Such fibers, yarns, and/or threads may be incorporated into a fabric (e.g., textile or cloth), which may be formed by knitting, 
     weaving, crocheting, knotting, or pressing (e.g., felt). A plurality of the fibers may be bonded together in at least point locations. Typical fabrics are knitted, woven, or nonwoven webs. 
     Fiber forming methods typically include melt extrusion. In accordance with known technology, such as continuous filament spinning for yarn or fibers, and nonwoven processes such as spunbond production and meltblown production, the fibers are formed by extrusion of the molten polymer through small orifices. In general, the fibers thus formed are then drawn or elongated to induce molecular orientation and affect crystallinity, resulting in a reduction in diameter and an improvement in physical properties. In nonwoven processes such as spunbonding and meltblowing, the fibers are directly deposited onto a foraminous surface, such as a moving flat conveyor and are at least partially consolidated by any of a variety of bonding means. 
     Preferred fiber forming methods include melt spinning. Exemplary melt spinning techniques are described in the Handbook of Fiber Chemistry, Second Edition, M. Lewin and 
     E. Pearce, ed., Chapter 1, pages 1-30 (1998). 
     It is known to those skilled in the art to combine processes or the fabrics from different processes to produce composite fabrics which possess certain desirable characteristics. Examples of this are combining spunbond and meltblown fabrics to produce a laminate fabric. Additionally, either or both of these processes may be combined in any arrangement with a staple fiber carding process or bonded fabrics resulting from a nonwoven staple fiber carding process. In such described laminate fabrics, the layers are generally at least partially consolidated. 
     Nonwoven fabrics of the present disclosure may have a carded fiber structure or comprise a mat in which the fibers are distributed in a random array. The fabric may be formed and bonded by any one of numerous known processes including hydroentanglement or spun-lace techniques, or by air-laying or melt-blowing fibers, batt drawing, stitchbonding, etc., depending upon the end use of the article to be made from the fabric. 
     Typically, such methods involve melt mixing (i.e., melt blending) with extrusion temperatures for preparation of the fibers in a range of 285° C. to 300° C. 
     In one embodiment, the method involves: providing a base polymer that includes an aromatic polyester or nylon-6; providing an alkylene oxide-containing nonionic surfactant, wherein the alkylene oxide-containing nonionic surfactant has a melting point of greater than 25° C. and an HLB of greater than 10; melt mixing the alkylene oxide-containing nonionic surfactant with the base polymer; and forming a plurality of fibers, each of which includes the alkylene oxide-containing nonionic surfactant mixed within the base polymer. 
     The fibers of the present disclosure may be continuous or staple fibers. A plurality of fibers of the present disclosure may be formed into a web (nonwoven or woven), a yarn, or other articles that include a plurality of fibers. Such articles may be in the form of fabrics suitable for use in making active wear apparel with desirable absorption and moisture wicking performance, as described herein. 
     In addition to absorbing and wicking moisture, fibers of the present disclosure can be used in methods of differential dyeing, and articles that result therefrom. That is, while differential dyeing techniques of fibers (e.g., as used to dye carpets) conventionally use different polymers in the fibers of the various regions of a fibrous substrate, fibers of the present disclosure allow for the use of the same base polymer in the fibers of the various regions of a fibrous substrate mixed with different amounts (including no alkylene oxide-containing nonionic surfactant) and/or different types of alkylene oxide-containing nonionic surfactants. 
     For example, in one embodiment, a method of differentially dyeing a fibrous substrate is provided that includes: providing a fibrous substrate including: a first portion of fibers including: a base polymer including an aromatic polyester or nylon-6; and an alkylene oxide-containing nonionic surfactant mixed within the base polymer, wherein the alkylene oxide-containing nonionic surfactant has a melting point of greater than 25° C. and an HLB of greater than 10; and a second portion of fibers including: a base polymer that is the same as in the first portion; and optionally an alkylene oxide-containing nonionic surfactant mixed within the base polymer, wherein the amount and/or type of the alkylene oxide-containing nonionic surfactant is different than that in the first portion. In this second portion, there may be no alkylene oxide-containing nonionic surfactant. 
     The method of differential dyeing further includes applying the same type and amount of dye under the same conditions to the first and second portions of the fibrous substrate, wherein the first and second portions of the fibrous substrate differentially absorb the dye. It will be understood that, while this embodiment describes only two portions, a fibrous substrate can include numerous portions of fibers with differing types and/or amounts of alkylene oxide-containing nonionic surfactants (including no such surfactant). 
     Thus, the present disclosure also provides an article that includes a plurality of fibers as described herein, wherein a first portion (of any desired number of portions, e.g., two, three, four, etc.) of the plurality of fibers includes: an aromatic polyester or nylon-6; and an alkylene oxide-containing nonionic surfactant mixed within the aromatic polyester or nylon-6; wherein the alkylene oxide-containing nonionic surfactant has a melting point of greater than 25° C. and an HLB of greater than 10; and a dye; wherein the dye is present in a greater amount in the first portion of the fibers than in other portions of the fibers of the article. 
     Fiber Sizes 
     The fibers can be formed in a variety of lengths and widths. They may also be referred to as filaments. They typically have a circular cross-section, but may also have a non-circular cross-section, such as multilobal (e.g., trilobal or pentalobal), hexagonal, or irregular shape. Such fibers may be continuous or staple fibers. 
     In certain embodiments, an individual fiber has a fiber size of at least 1 Denier (D), or at least 5 D. In certain embodiments, an individual fiber has a fiber size of up to 100 D, up to 65 D, up to 50 D, or up to 30 D. 
     In certain embodiments, an individual fiber has a median fiber diameter or an effective fiber diameter of at least 5 microns (i.e., micrometers), at least 10 microns, or at least 20 microns. In certain embodiments, an individual fiber has a median fiber diameter of up to 125 microns, up to 100 microns, up to 80 microns, or up to 70 microns. The values of the median and effective fiber diameters are often within ±25%. 
     The term “median fiber diameter” means fiber diameter determined by producing one or more images of the fiber structure, such as by using a scanning electron microscope; measuring the fiber diameter of clearly visible fibers in the one or more images resulting in a total number of fiber diameters, x; and calculating the median fiber diameter of the x fiber diameters. Typically, x is greater than 20, more preferably greater than 50, and desirably ranges from 50 to 200. 
     The term “effective fiber diameter” or “EFD” is the apparent diameter of the fibers in a fiber web based on an air permeation test in which air at 1 atmosphere and room temperature is passed through a web sample at a specified thickness and face velocity (typically 5.3 cm/sec), and the corresponding pressure drop is measured. Based on the measured pressure drop, the Effective Fiber Diameter is calculated as set forth in C. N. Davies,  The Separation of Airborne Dust and Particulates, Institution of Mechanical Engineers , London Proceedings, D3 (1952). 
     EXEMPLARY EMBODIMENTS 
     Embodiment 1 is a fiber comprising: a base polymer comprising an aromatic polyester or nylon-6; and an alkylene oxide-containing nonionic surfactant mixed within the base polymer; wherein the alkylene oxide-containing nonionic surfactant has a melting point of greater than 25° C. and an HLB of greater than 10. 
     Embodiment 2 is the fiber of embodiment 1 wherein the alkylene oxide-containing nonionic surfactant has a melting point of at least 30° C. (or at least 40° C., or at least 50° C.). 
     Embodiment 3 is the fiber of embodiment 1 or 2 wherein the alkylene oxide-containing nonionic surfactant has an average molecular weight of at least 900 grams/mole (or at least 1000 grams/mole, or at least 4000 grams/mole). 
     Embodiment 4 is the fiber of any one of the previous embodiments wherein the alkylene oxide-containing nonionic surfactant has an average molecular weight of up to 5000 grams/mole. 
     Embodiment 5 is the fiber of any one of the previous embodiments wherein the alkylene oxide-containing nonionic surfactant has a decomposition temperature of at least 250° C. (temperature at which 5% weight loss occurs). 
     Embodiment 6 is the fiber of any one of the previous embodiments wherein the alkylene oxide-containing nonionic surfactant has an HLB of at least 11 (at least 12, at least 13, at least 14, or at least 15). 
     Embodiment 7 is the fiber of any one of the previous embodiments wherein the alkylene oxide-containing nonionic surfactant has an HLB of up to 20. 
     Embodiment 8 is the fiber of any one of the previous embodiments wherein the alkylene oxide-containing nonionic surfactant comprises an ethylene oxide-containing nonionic surfactant, an ethylene oxide/propylene oxide-containing nonionic surfactant, or a combination thereof. Embodiment 9 is the fiber of embodiment 8 wherein the alkylene oxide-containing nonionic surfactant comprises an ethylene oxide-containing nonionic surfactant. 
     Embodiment 10 is the fiber of any one of the previous embodiments wherein the alkylene oxide-containing nonionic surfactant does not include propylene oxide moieties. 
     Embodiment 11 is the fiber of any one of embodiments 8 through 10 wherein the alkylene oxide-containing nonionic surfactant is an ethylene oxide-containing nonionic surfactant having the following Formula (I): 
       R 1 —[C(O)] r -(EO) n1 —[C(O)] r —R 2   (I)
 
     wherein:
         R 1 =(C12-C72)alkyl (preferably, a linear or branched alkyl);   EO=Ethylene Oxide;   n1=3-100;   each r is independently 0 or 1 (preferably, 0); and   R 2 =H or a (C1-C10)alkyl.       

     Embodiment 12 is the fiber of embodiment 8 wherein the alkylene oxide-containing nonionic surfactant is an ethylene oxide/propylene oxide-containing nonionic surfactant having the following Formula (II) or (III): 
       R 3 —[C(O)] r -(EO) n2 —(PO) m -(EO) n2 —[C(O)] r —R 3   (II)
 
       (PO) m -(EO) n2 —[C(O)] r —R 3   (III)
 
     wherein:
         each R 3  is independently H or a (C1-C72)alkyl (preferably, a linear or branched alkyl);   EO=Ethylene Oxide;   PO=Propylene Oxide;   each r is independently 0 or 1 (preferably, 0);   each n2 is independently 10-100; and   each m is independently 5-65.       

     Embodiment 13 is the fiber of embodiment 8 wherein the alkylene oxide-containing nonionic surfactant includes an ethylene oxide-containing amine nonionic surfactant having the following Formula (IV): 
       R 4 —N-{(EO) n1 —R 5 } 2   (IV)
 
     wherein:
         R 4 =(C8-C22)alkyl (preferably, a linear or branched alkyl);   EO=Ethylene Oxide;   n1=3-100; and   R 5 =H or a (C1-C72)alkyl.       

     Embodiment 14 is the fiber of any one of the previous embodiments comprising at least 0.1 wt-% (or at least 0.5 wt-%, or at least 1.0 wt-%, or at least 1.5 wt-%) of the alkylene oxide-containing nonionic surfactant, based on the total weight of the fiber. 
     Embodiment 15 is the fiber of any one of the previous embodiments comprising up to 5.0 wt-% (or up to 2.0 wt-%) of the alkylene oxide-containing nonionic surfactant, based on the total weight of the fiber. 
     Embodiment 16 is the fiber of any one of the previous embodiments further comprising talc. 
     Embodiment 17 is the fiber of embodiment 16 comprising at least 0.5 wt-% talc, based on the total weight of the fiber. 
     Embodiment 18 is the fiber of embodiment 16 or 17 comprising up to 3.0 wt-% talc, based on the total weight of the fiber. 
     Embodiment 19 is the fiber of any of the previous embodiments further comprising one or more antioxidants, flame retardants, UV stabilizers, colorants, softeners, antimicrobial agents, antistatic agents, optical brighteners, or combinations thereof. 
     Embodiment 20 is the fiber of any one of the previous embodiments wherein a meltblown web of a plurality of the fibers wicks an 80/20 water/isopropanol mixture according to the Vertical Wicking Test of the Examples Section. 
     Embodiment 21 is the fiber embodiment 20 wherein a meltblown web of a plurality of the fibers wicks an 80/20 water/isopropanol mixture according to the Vertical Wicking Test to a distance of at least 5 cm (or at least 6 cm, or at least 7 cm, or at least 8 cm, or at least 9 cm, or at least 10 cm). 
     Embodiment 22 is the fiber of any one of the previous embodiments wherein a meltblown web of a plurality of the fibers demonstrates absorption of a water drop within 5 minutes (or within 1 minute, or within 30 seconds, or within 10 seconds, or instantaneously) according to the Water Drop Test of the Examples Section. 
     Embodiment 23 is the fiber of any one of the previous embodiments having a median fiber diameter or an effective fiber diameter of at least 5 microns (or at least 10 microns, or at least 20 microns). 
     Embodiment 24 is the fiber of any one of the previous embodiments having a median fiber diameter or an effective fiber diameter of up to 125 microns (up to 100 microns, up to 80 microns, or up to 70 microns). 
     Embodiment 25 is the fiber of any one of the previous embodiments having a fiber size of at least 1 Denier (or at least 5 D). 
     Embodiment 26 is the fiber of any one of the previous embodiments having a fiber size of up to 100 Denier (up to 65 D, up to 50 D, or up to 30 D). 
     Embodiment 27 is the fiber of any one of the previous embodiments which is a continuous or staple fiber. 
     Embodiment 28 is the fiber of any of the previous embodiments wherein the base polymer comprises an aromatic polyester selected from polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT), and mixtures thereof. 
     Embodiment 29 is a plurality of fibers of any one of the previous embodiments. 
     Embodiment 30 is the plurality of fibers of embodiment 29 which is in the form of a yarn. 
     Embodiment 31 is the plurality of fibers of embodiment 29 which is in the form of a web. 
     Embodiment 32 is an article comprising a plurality of fibers of any one of embodiments 1 through 28, wherein a first portion of the plurality of fibers comprises: a base polymer comprising an aromatic polyester or nylon-6; an alkylene oxide-containing nonionic surfactant mixed within the base polymer, wherein the alkylene oxide-containing nonionic surfactant has a melting point of greater than 25° C. and an HLB of greater than 10; and a dye; wherein the dye is present in a greater amount in the first portion of the fibers than in other portions of the fibers of the article. 
     Embodiment 33 is a method of making fibers of any one of embodiments 1 through 28, the method comprising: providing a base polymer comprising an aromatic polyester or nylon-6; providing an alkylene oxide-containing nonionic surfactant, wherein the alkylene oxide-containing nonionic surfactant has a melting point of greater than 25° C. and an HLB of greater than 10; melt mixing the alkylene oxide-containing nonionic surfactant with the base polymer; and forming a plurality of fibers, each of which comprises the alkylene oxide-containing nonionic surfactant mixed within the base polymer. 
     Embodiment 34 is the method of embodiment 33 wherein a meltblown web of a plurality of the fibers demonstrates absorption of a water drop within 5 minutes (or within 1 minute, or within 30 seconds, or within 10 seconds, or instantaneously) according to the Water Drop Test of the Examples Section. 
     Embodiment 35 is the method of embodiment 33 or 34 wherein a meltblown web of a plurality of the fibers wicks an 80/20 water/isopropanol mixture according to the Vertical Wicking Test of the Examples Section. 
     Embodiment 36 is the method of embodiment 35 wherein a meltblown web of a plurality of the fibers wicks an 80/20 water/isopropanol mixture according to the Vertical Wicking Test to a distance of at least 5 cm (or at least 6 cm, or at least 7 cm, or at least 8 cm, or at least 9 cm, or at least 10 cm). 
     Embodiment 37 is a method of differentially dyeing a fibrous substrate, the method comprising: providing a fibrous substrate comprising: a first portion of fibers comprising: a base polymer comprising an aromatic polyester or nylon-6; and an alkylene oxide-containing nonionic surfactant mixed within the base polymer, wherein the alkylene oxide-containing nonionic surfactant has a melting point of greater than 25° C. and an HLB of greater than 10; and a second portion of fibers comprising: a base polymer comprising an aromatic polyester or nylon-6 that is the same as in the first portion; and optionally an alkylene oxide-containing nonionic surfactant mixed within the base polymer, wherein the amount (including no alkylene oxide-containing nonionic surfactant) and/or type of the alkylene oxide-containing nonionic surfactant is different than that in the first portion. The method further includes applying the same type and amount of dye under the same conditions to the first and second portions of the fibrous substrate; wherein the first and second portions of the fibrous substrate differentially absorb the dye. 
     Embodiment 38 is the method of embodiment 37 wherein the alkylene oxide-containing nonionic surfactant has a melting point of at least 30° C. (or at least 40° C., or at least 50° C.). 
     Embodiment 39 is the method of embodiment 37 or 38 wherein the alkylene oxide-containing nonionic surfactant has an average molecular weight of at least 900 grams/mole (or at least 1000 grams/mole, or at least 4000 grams/mole). 
     Embodiment 40 is the method of any one of embodiments 37 through 39 wherein the alkylene oxide-containing nonionic surfactant has an average molecular weight of up to 5000 grams/mole. 
     Embodiment 41 is the method of any one of embodiments 37 through 40 wherein the alkylene oxide-containing nonionic surfactant has a decomposition temperature of at least 250° C. (temperature at which 5% weight loss occurs). 
     Embodiment 42 is the method of any one of embodiments 37 through 41 wherein the alkylene oxide-containing nonionic surfactant has an HLB of at least 11 (at least 12, at least 13, at least 14, or at least 15). 
     Embodiment 43 is the method of any one of embodiments 37 through 42 wherein the alkylene oxide-containing nonionic surfactant has an HLB of up to 20. 
     Embodiment 44 is the method of any one of embodiments 37 through 43 wherein the alkylene oxide-containing nonionic surfactant comprises an ethylene oxide-containing nonionic surfactant, an ethylene oxide/propylene oxide-containing nonionic surfactant, or a combination thereof. 
     Embodiment 45 is the method of embodiment 44 wherein the alkylene oxide-containing nonionic surfactant comprises an ethylene oxide-containing nonionic surfactant. 
     Embodiment 46 is the method of any one of embodiments 37 through 45 wherein the alkylene oxide-containing nonionic surfactant does not include propylene oxide moieties. 
     Embodiment 47 is the method of any one of embodiments 44 through 46 wherein the alkylene oxide-containing nonionic surfactant has the following Formula (I): 
       R 1 —[C(O)] r -(EO) n1 —[C(O)] r —R 2   (I)
 
     wherein:
         R 1 =(C12-C72)alkyl (preferably, a linear or branched alkyl);   EO=Ethylene Oxide;   n1=3-100;   each r is independently 0 or 1 (preferably, 0); and   R 2 =H or a (C1-C10)alkyl.       

     Embodiment 48 is the method of embodiment 44 wherein the alkylene oxide-containing nonionic surfactant is an ethylene oxide/propylene oxide-containing nonionic surfactant having the following Formula (II) or (III): 
       R 3 —[C(O)] r -(EO) n2 —(PO) m -(EO) n2 —[C(O)] r —R 3   (II)
 
       (PO) m -(EO) n2 —[C(O)] r —R 3   (III)
 
     wherein:
         each R 3  is independently H or a (C1-C72)alkyl (preferably, a linear or branched alkyl);   EO=Ethylene Oxide;   PO=Propylene Oxide;   each n2 is independently 10-100;   each r is independently 0 or 1 (preferably, 0); and   each m is independently 5-65.       

     Embodiment 49 is the method of embodiment 44 wherein the alkylene oxide-containing nonionic surfactant includes an ethylene oxide-containing amine nonionic surfactant having the following Formula (IV): 
       R 4 —N-{(EO) n1 —R 5 } 2   (IV)
 
     wherein:
         R 4 =(C8-C22)alkyl (preferably, a linear or branched alkyl);   EO=Ethylene Oxide;   n1=3-100; and   R 5 =H or a (C1-C72)alkyl.       

     Embodiment 50 is the method of any one of embodiments 37 through 49 wherein the fibers comprise at least 0.1 wt-% (or at least 0.5 wt-%, or at least 1.0 wt-%, or at least 1.5 wt-%) of the alkylene oxide-containing nonionic surfactant, based on the total weight of the fiber. 
     Embodiment 51 is the method of any one of embodiments 37 through 50 wherein the fibers comprise up to 5.0 wt-% (or up to 2.0 wt-%) of the alkylene oxide-containing nonionic surfactant, based on the total weight of the fiber. 
     Embodiment 52 is the method of any one of embodiments 37 through 51 wherein the fibers further comprise talc. 
     Embodiment 53 is the method of embodiment 52 wherein the fibers comprise at least 0.5 wt-% talc, based on the total weight of the fiber. 
     Embodiment 54 is the method of embodiment 52 or 53 wherein the fibers comprise up to 3.0 wt-% talc, based on the total weight of the fiber. 
     Embodiment 55 is the method of any one of embodiments 37 through 54 wherein the fibers have a median fiber diameter or an effective fiber diameter of at least 5 microns (or at least 10 microns, or at least 20 microns). 
     Embodiment 56 is the method of any one of embodiments 37 through 55 wherein the fibers have a median fiber diameter or an effective fiber diameter of up to 125 microns (up to 100 microns, up to 80 microns, or up to 70 microns). 
     Embodiment 57 is the method of any one of embodiments 37 through 56 wherein the fibers have a fiber size of at least 1 Denier (or at least 5 D). 
     Embodiment 58 is the method of any one of embodiments 37 through 57 wherein the fibers have a fiber size of up to 100 Denier (up to 65 D, up to 50 D, or up to 30 D). 
     Embodiment 59 is the method of any one of embodiments 37 through 58 wherein the fibers are continuous or staple fibers. 
     Embodiment 60 is the method of any one of embodiments 37 through 59 wherein the base polymer of the fibers comprise an aromatic polyester selected from polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT), and mixtures thereof. 
     Embodiment 61 is the method of any one of embodiments 37 through 60 wherein the base polymer of the fibers comprise nylon-6. 
     EXAMPLES 
     These Examples are merely for illustrative purposes and are not meant to be overly limiting on the scope of the appended claims. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the present disclosure are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. 
     Unless otherwise noted, all parts, percentages, ratios, etc. in the examples are by weight. Unless otherwise specified, all reagents used in the examples were obtained, or are available, from general chemical suppliers such as, for example, Sigma Aldrich Company, Saint Louis, Mo., or may be synthesized by conventional methods. 
     Materials 
       
     
       
         
           
               
             
               
                   
               
             
            
               
                 NANYA N211 Polyethylene terephthalate (PET) resin, available  
               
               
                 from Nan Ya Plastics Corporation, Livingston, NJ 
               
               
                 SORONA 3301, Polytrimethylene terephthalate (PTT) resin,  
               
               
                 available from E.I. du Pont de Nemours and Company,  
               
               
                 Wilmington, DE 
               
               
                 ULTRAMID B24 Nylon-6 resin, available from BASF  
               
               
                 Corporation, Florham Park, NJ 
               
               
                 METOCENE MF650W, Polypropylene homopolymer (PP) resin,  
               
               
                 available from LyondellBasell, Houston, TX 
               
               
                 TERGITOL 15-S-30, a secondary alcohol ethoxylate, nonionic  
               
               
                 surfactant (HLB value = 17.4, MW~1500 1 , melting point =  
               
               
                 41° C.), available from Dow Chemical Company, Midland, MI 
               
               
                 UNITHOX 480, a primary alcohol ethoxylate, nonionic  
               
               
                 surfactant (HLB value = 16, MW = 2300, melting point = 86° C.),  
               
               
                 available from Baker Hughes Incorporated, Houston, TX 
               
               
                 UNITHOX 490, a primary alcohol ethoxylate, nonionic  
               
               
                 surfactant (HLB 2  value = 18, MW = 4600, melting point =  
               
               
                 71° C.), available from Baker Hughes Incorporated, Houston, TX 
               
               
                 UNITHOX 550, a primary alcohol ethoxylate, nonionic surfactant  
               
               
                 (HLB value = 10, MW = 1100, melting point = 99° C.),  
               
               
                 available from Baker Hughes Incorporated, Houston, TX 
               
               
                 PLURONIC F108, a difunctional ethylene oxide-propylene  
               
               
                 oxide block copolymer, nonionic surfactant (HLB value = 16,  
               
               
                 MW = 14600, melting point = 57° C.), available from BASF SE,  
               
               
                 Ludwigshafen, Germany 
               
               
                 GENAPOL PF 80 FP, an ethylene oxide-propylene oxide block  
               
               
                 copolymer (80% w/w ethylene oxide), nonionic surfactant  
               
               
                 (HLB value = 16, MW = 8000, melting point = 57° C.), 
               
               
                 available from Clariant, Muttenz, Switzerland 
               
               
                 ETHOMEEN 18/60, an ethoxylated octadecylamine, nonionic  
               
               
                 surfactant (HLB value = 18, MW = 2500, melting point = 46° C.),  
               
               
                 purchased from Akso Nobel N.V., Amsterdam, Netherlands 
               
               
                 Talc, available from Sigma-Aldrich, St. Louis, MO  
               
               
                 Sodium Carbonate, available from Sigma-Aldrich, St. Louis, MO 
               
               
                 HOSTAPAL DTC, surfactant, available from Archroma,  
               
               
                 Muttenz, Switzerland 
               
               
                 AMECRON BLUE AC-E, a blue disperse dye, available from  
               
               
                 American Dyestuff Corporation, Clifton, NJ 
               
               
                 GLUCOPON 425N, an alkyl polyglycoside surfactant, available  
               
               
                 from BASF, Florham Park, NJ 
               
               
                   
               
               
                   1 proximate MW calculated using HLB value and moles of ethylene oxide 
               
               
                   2 All HLB values in Materials Table were calculated by Griffin&#39;s Method described above 
               
            
           
         
       
     
     Test Methods 
     Water Absorbency 
     Water absorbency was tested using AATCC Test Method 79-2014, “Absorbency of Textiles.” 
     This test measures the ability of a fabric to take up water. Prior to testing, the fabric samples were conditioned for 24 hours in a standard atmosphere having a relative humidity of 65%±2% at 21° C.±1° C. (70° F.±2° F.). Testing was performed under the same conditions. The fabric sample was placed in an embroidery hoop or similar device to suspend the fabric. Care was taken to make sure that the fabric was free of wrinkles or creases but without stretching or distorting the fabric. A burette or a medicine dropper was used to dispense one drop of distilled or deionized water (41±3° C. (105±5° F.)) onto the surface of the fabric from a distance of 10 millimeters (mm) below the tip of the burette or medicine dropper. A stopwatch was used to measure the time that it takes for the water drop to completely disappear (i.e., until the water drop absorbs completely). This was indicated by a loss of light reflectivity of the water drop (i.e., when it changes to a dull wet spot due the absorbent propensity of the fabric). Absorption time was monitored for 30 minutes (rather than 60 seconds as in AATCC Test Method 79-2014). The time was recorded to the nearest second if the absorption time was less than 60 seconds, and to the nearest minute if the absorption time was greater than 60 seconds. The reported values are an average of three tests. Shorter times indicate better absorbency. A value of “zero” in this test indicates that the water drop disappears immediately. 
     Vertical Wicking 
     This test evaluates the ability of a fabric to transport liquid and is applicable to woven, knitted, or nonwoven fabrics. The rate (distance per unit of time) liquid travels along and/or through a vertical fabric sample was visually observed, manually timed and recorded at specified intervals. Vertical wicking was tested using AATCC Test Method 197-2013, “Vertical Wicking of Textiles,” Option B, with the following modifications. Fabric samples were heat treated at 160° C. for 2 minutes. Fabric samples were cut such that the long dimension of the fabric sample was parallel to the down-web (machine) direction of the fabric. The liquid used for testing was 80/20 deionized water/isopropyl alcohol having a surface tension of 32 dyne/cm. A small binder clip was attached to the end of the fabric sample that was submerged in the test liquid to prevent the sample from floating in the liquid. The distance that the liquid wicked after 5.0±0.1 minutes and 30.0±0.1 minutes was recorded. The reported values are an average of three tests. 
     Dye Differential 
     Dyeing Procedure: Fabric samples with and without the hydrophilic additive (i.e.—treated and untreated) were competitively dyed to see if one fabric sample took up more dye than the other. Prior to dyeing, all fabric samples were heat set for 2 minutes at 160° C. Dyeing was carried out using an AHIBA IR PRO dyeing machine (available from Datacolor, Lawrenceville, N.J.) under the following conditions: 100:1 liquor ratio (mass of dye bath to mass nonwoven); 2 weight percent (wt-%) AMECRON BLUE AC-E dye based on the weight of the nonwoven fabric; 1 gram of GLUCOPON surfactant per liter of water. The dye bath was heated to 130° C. using the dye machine&#39;s maximum rate. The dye bath temperature was then maintained at 130° C. for 30 minutes, and then cooled back down to room temperature as quickly as possible. During this cycle, the dye machine spun at 25 rotations per minute and switched direction every 1 minute. The nonwoven was rinsed under running DI water to remove residual surfactant (indicated by observing no lathering). After rinsing the samples were dried at 65° C. for 1 hour. 
     Color comparison procedure: A CHROMA METER CR-410 colorimeter (available from Konica Minolta, Ramsey, N.J.) was set up with a D65 light source as described in the instruction manual. The meter was calibrated with a white calibration plate (provided with the equipment) according to the instruction manual, and was set to read color differences and the color space L*a*b*. L*a*b* values were recorded for fabric samples with and without surfactant additive. 
     A color difference value, ΔE, was calculated using the following equation: 
       Δ E =[(Δ L *) 2 +(Δ a *) 2 +(Δ b *) 2 ] 1/2  
 
       where: Δ L*=L*   experimental   −L*   control  
 
       Δ a*=a*   experimental   −a*   control  
 
       Δ b*=b*   experimental   −b*   control  
 
     A larger ΔE value indicates that there is greater dye differential 
     Effective Fiber Diameter or “EFD” 
     EFD is the apparent diameter of the fibers in a fiber web based on an air permeation test in which air at 1 atmosphere and room temperature is passed through a web sample at a specified thickness and face velocity (typically 5.3 cm/sec), and the corresponding pressure drop is measured. Based on the measured pressure drop, the Effective Fiber Diameter is calculated as set forth in C. N. Davies,  The Separation of Airborne Dust and Particulates, Institution of Mechanical Engineers , London Proceedings, IB (1952). 
     Examples 1-13 and Comparative Examples 1-5 
     Melt blown nonwoven fabrics were prepared from polyester or nylon-6 base polymer resins extruded with different types and concentrations of surfactant additives. For comparison, melt blown nonwoven fabrics were prepared from polypropylene polymer resin extruded with different types and concentrations of surfactant additives. Melt blown nonwoven fabrics were prepared without any surfactant additives as control samples. 
     The melt blown nonwoven fabric examples were extruded on an experimental melt blown line, as taught, for example, in van Wente, “Superfine Thermoplastic Fibers,” Industrial Engineering Chemistry, Vol. 48, pages 1342 et sec (1956), or in Report No. 4364 of the Naval Research Laboratories, published May 25, 1954 entitled “Manufacture of Superfine Organic Fibers” by van Wente, A., Boone, C. D., and Fluharty, E. L. The extruder used was a Davis-Standard 20 mm twin screw extruder (Davis-Standard, Pawcatuck, Conn.). For surfactant additives UNITHOX 490, UNITHOX 480, UNITHOX 550, and PLURONIC F108, and GENAPOL PF 80 FP, the twin screw extruder was starve fed from two feeders—one for the base polymer and one for the surfactant additive. For TERGITOL 15-S-30, the surfactant additive and base polymer were weighed individually and mixed in a 5-gallon pail for one minute using a mixer head affixed to a basic hand drill until a visually homogeneous mixture was obtained (when the base polymer used was PET, the polymer resin was dried overnight in an oven at 255° (124° C.) and mixed with the surfactant additive while the polymer resin was still hot). This mixture was then added to the extruder hopper. For ETHOMEEN 18/60, the surfactant additive was added as a side stream partway up the extruder using a heated syringe pump. This produced unsatisfactory nonwoven webs with very uneven fiber densities across the web because the liquid surfactant and the molten polymer never fully mixed in the extruder. With sufficient mixing between the surfactant input and the die, it is expected that ETHOMEEN 18/60 could fully mix with the PET resin and form a uniform web that would exhibit good absorbency and wicking properties; however, we were unable to do this on our equipment. For this reason, webs made from these three additives were not measured for absorbency or wicking. The melt blown nonwoven fabric compositions are provided in Table 1 and the process conditions used to prepare the melt blown nonwoven fabrics (by base polymer) are summarized in Table 2. 
     
       
         
           
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                 Example 
                 Base Polymer 
                 Additive 
               
               
                   
               
             
            
               
                 Control 1 
                 NANYA N211 PET 
                 none 
               
               
                 Example 1 
                 NANYA N211 PET 
                 5.0 wt-% UNITHOX 490 
               
               
                 Example 2 
                 NANYA N211 PET 
                 2.0 wt-% UNITHOX 490 
               
               
                 Example 3 
                 NANYA N211 PET 
                 1.0 wt-% UNITHOX 490 
               
               
                 Example 4 
                 NANYA N211 PET 
                 0.5 wt-% UNITHOX 490 
               
               
                 Example 5 
                 NANYA N211 PET 
                 2.0 wt-% UNITHOX 480 
               
               
                 Example 6 
                 NANYA N211 PET 
                 2.0 wt-% TERGITOL 15-S-30 
               
               
                 Example 7 
                 NANYA N211 PET 
                 2.0 wt-% 1:1 blend  
               
               
                   
                   
                 UNITHOX 490/Talc 
               
               
                 Example 8 
                 NANYA N211 PET 
                 2.0 wt-% PLURONIC F108 
               
               
                 Example 9 
                 NANYA N211 PET 
                 2.0 wt-% GENAPOL PF 80 FP 
               
               
                 Comparative 
                 NANYA N211 PET 
                 2.0 wt-% UNITHOX 550 
               
               
                 Example 1 
                   
                   
               
               
                 Control 2 
                 ULTRAMID B24  
                 None 
               
               
                   
                 Nylon-6 
                   
               
               
                 Example 10 
                 ULTRAMID B24  
                 2.0 wt-% UNITHOX 490 
               
               
                   
                 Nylon-6 
                   
               
               
                 Example 11 
                 ULTRAMID B24  
                 2.0 wt-% UNITHOX 480 
               
               
                   
                 Nylon-6 
                   
               
               
                 Example 12 
                 ULTRAMID B24  
                 2.0 wt-% 1:1 blend  
               
               
                   
                 Nylon-6 
                 UNITHOX 490/480 
               
               
                 Example 13 
                 ULTRAMID B24  
                 2.0 wt-% 1:1 blend  
               
               
                   
                 Nylon-6 
                 UNITHOX 490/Talc 
               
               
                 Control 3 
                 METOCENE  
                 none 
               
               
                   
                 MF650W PP 
                   
               
               
                 Comparative 
                 METOCENE  
                 2.0 wt-% UNITHOX 490 
               
               
                 Example 2 
                 MF650W PP 
                   
               
               
                 Comparative 
                 METOCENE  
                 1.0 wt-% UNITHOX 490 
               
               
                 Example 3 
                 MF650W PP 
                   
               
               
                 Comparative 
                 METOCENE  
                 2.0 wt-% UNITHOX 480 
               
               
                 Example 4 
                 MF650W PP 
                   
               
               
                 Comparative 
                 METOCENE  
                 2.0 wt-% 1:1 blend  
               
               
                 Example 5 
                 MF650W PP 
                 UNITHOX 490/480 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
               
             
               
                 TABLE 2 
               
               
                   
               
               
                 Process 
                 NANYA  
                 ULTRAMID  
                 METOCENE 
               
               
                 Condition 
                 N211 PET 
                 B24 Nylon-6 
                 MF650W 
               
               
                   
               
             
            
               
                 Extrusion 
                 260° C. 
                 240° C. 
                 260° C. 
               
               
                 Temperature 
                   
                   
                   
               
               
                 Primary Air 
                 360° C. 
                 310° C. 
                 355° C. 
               
               
                 Temperature 
                   
                   
                   
               
               
                 Air Pressure 
                 4 psi (27.6 kPa) 
                 7 psi (48.3 kPa) 
                 4 psi (27.6 kPa) 
               
               
                 Air Gap Width 
                 0.03 inches  
                 0.03 inches  
                 0.03 inches  
               
               
                   
                 (0.76 mm) 
                 (0.76 mm) 
                 (0.76 mm) 
               
               
                 Polymer 
                 10 lbs/hr  
                 10 lbs/hr  
                 10 lbs/hr  
               
               
                 Throughput Rate 
                 (4.5 kg/hr) 
                 (4.5 kg/hr) 
                 (4.5 kg/hr) 
               
               
                 Die to Collector 
                 2.875 inches 
                 4.25 inches 
                 12.5 inches 
               
               
                 Distance 
                   
                   
                   
               
               
                 Basis Weight 
                 100 grams/meter 2   
                 100 grams/meter 2   
                 50 grams/meter 2   
               
               
                 Effective Fiber 
                 20 ± 2 μm 
                 20 ± 2 μm 
                 12 ± 2 μm 
               
               
                 Diameter 
               
               
                   
               
            
           
         
       
     
     Examples 14-18 
     Knit fabric was prepared from drawn texturized yarn (DTY) made from fiber grade polyethylene terephthalate (PET) or polytrimethylene terephthalate (PTT) base resin with different concentrations of surfactant additives. The surfactant additive was compounded into a masterbatch prior to being used to make DTY. Knit fabric was also prepared without any surfactant additives as control samples. 
     Preparation of Surfactant/Polyester Masterbatch 
     In a typical procedure, the surfactant additive was compounded into a 20% weight surfactant, 80% weight polyester masterbatch. This was carried out using a fully intermeshing co-rotating twin screw extruder having conveying and kneading sections with three temperature zones that was fitted with a standard pelletizing die. Fiber grade PET or PTT resin flakes were added at the neck of the extruder and solid surfactant was added as a side-stream in temperature zone 1. The strands were run through a water bath and into a pelletizing puller, drained and dried as is known in the art. 
     Preparation of Drawn Texturized Yarn 
     Neat fiber grade PET or PTT resin was combined with the additive masterbatch at letdown ratios resulting in 1.0%, 1.5%, and 2.0% surfactant additive in the final fiber. The mixed resins were fed into a single screw extruder containing a feed zone, compression (plasticizing) zone; and a metering (pumping) zone leading to a multi-orifice spinneret. The fibers were drawn and texturized in line resulting in DTY (1200 denier yarn strand with 120 fibers per yarn strand). The yarn made using PTT resin and 2.0% surfactant additive broke too frequently too effectively draw fiber, so it was not collected. 
     Preparation of Knit Fabric 
     Each sample of DTY was knit into a sleeve. The gauge of the knitted fabric was 7 stitches per inch and the basis weight of the fabric was 180-190 grams/meter 2 . Prior to heat-setting, the knit fabric was scoured in a solution of 1.5 g/L sodium carbonate and 1.0 g/L HOSTAPAL DTC surfactant for 30 minutes at 70° C. followed by a rinse in room temperature water. The knitted fabric compositions are provided in Table 3. 
     
       
         
           
               
               
               
               
             
               
                   
                 TABLE 3 
               
               
                   
                   
               
               
                   
                 Example 
                 Base Polymer 
                 Additive 
               
               
                   
                   
               
             
            
               
                   
                 Control 4 
                 PET 
                 None 
               
               
                   
                 Example 14 
                 PET 
                 1.0 wt-% UNITHOX 490 
               
               
                   
                 Example 15 
                 PET 
                 1.5 wt-% UNITHOX 490 
               
               
                   
                 Example 16 
                 PET 
                 2.0 wt-% UNITHOX 490 
               
               
                   
                 Control 5 
                 PTT 
                 None 
               
               
                   
                 Example 17 
                 PTT 
                 1.0 wt-% UNITHOX 490 
               
               
                   
                 Example 18 
                 PTT 
                 1.5 wt-% UNITHOX 490 
               
               
                   
                   
               
            
           
         
       
     
     The absorbency of the melt blown nonwoven and knit fabric examples was tested according to the Water Absorbency test method described above. Heat setting (for example, at 110° C. to 200° C. for 1 to 20 minutes) fabric samples may in some cases improve the effectiveness of the surfactant additive in imparting hydrophilicity, particularly for PET and PTT. Absorption times before and after heat setting are provided in Table 4. 
     
       
         
           
               
               
               
               
             
               
                   
                 TABLE 4 
               
               
                   
                   
               
               
                   
                   
                   
                 Absorption Time  
               
               
                   
                   
                 Absorption Time  
                 (after heat setting at  
               
               
                   
                 Example 
                 (before heat set) 
                 160° C. for 2 minutes) 
               
               
                   
                   
               
             
            
               
                   
                 Control 1 
                 no absorption observed 
                 no absorption observed 
               
               
                   
                 Example 1 
                 zero 
                 zero 
               
               
                   
                 Example 2 
                 1.7 minutes 
                 zero 
               
               
                   
                 Example 3 
                 no absorption observed 
                 zero 
               
               
                   
                 Example 4 
                 no absorption observed 
                 Zero 
               
               
                   
                 Example 5 
                  16 minutes 
                 10 seconds 
               
               
                   
                 Example 6 
                 zero 
                 zero 
               
               
                   
                 Example 7 
                 1.0 minutes 
                 zero 
               
               
                   
                 Example 8 
                 no absorption observed 
                 zero 
               
               
                   
                 Example 9 
                 no absorption observed 
                 zero 
               
               
                   
                 Comparative 
                 no absorption observed 
                 no absorption observed 
               
               
                   
                 Example 1 
                   
                   
               
               
                   
                 Control 2 
                 no absorption observed 
                  3.3 minutes 
               
               
                   
                 Example 10 
                 1.8 minutes 
                  2.3 minutes 
               
               
                   
                 Example 11 
                 2.8 minutes 
                  7.7 minutes 
               
               
                   
                 Example12 
                 2.5 minutes 
                 15.7 minutes 
               
               
                   
                 Example 13 
                  21 minutes 
                 20.7 minutes 
               
               
                   
                 Control 3 
                 no absorption observed 
                 no absorption observed 
               
               
                   
                 Comparative 
                 no absorption observed 
                 no absorption observed 
               
               
                   
                 Example 2 
                   
                   
               
               
                   
                 Comparative 
                 no absorption observed 
                 no absorption observed 
               
               
                   
                 Example 3 
                   
                   
               
               
                   
                 Comparative 
                 no absorption observed 
                 no absorption observed 
               
               
                   
                 Example 4 
                   
                   
               
               
                   
                 Comparative 
                 no absorption observed 
                 no absorption observed 
               
               
                   
                 Example 5 
                   
                   
               
               
                   
                 Control 4 
                 no absorption observed 
                 no absorption observed 
               
               
                   
                 Example 14 
                 no absorption observed 
                 zero 
               
               
                   
                 Example 15 
                 no absorption observed 
                 zero 
               
               
                   
                 Example 16 
                 22 seconds 
                  6 seconds 
               
               
                   
                 Control 5 
                 no absorption observed 
                 no absorption observed 
               
               
                   
                 Example 17 
                 20 seconds 
                 zero 
               
               
                   
                 Example 18 
                  3 seconds 
                 zero 
               
               
                   
                   
               
            
           
         
       
     
     The wicking ability of the PET and nylon melt blown nonwoven fabric examples was tested according to the Vertical Wicking test method described above. Vertical wicking results are provided in Table 5. 
     
       
         
           
               
               
               
               
             
               
                   
                 TABLE 5 
               
               
                   
                   
               
               
                   
                   
                 Height (cm) after  
                 Height (cm) after  
               
               
                   
                 Example 
                 5 minutes 
                 30 minutes 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                   
                 Control 1 
                 3.7 
                 6.3 
               
               
                   
                 Example 1 
                 9.7 
                 11.1 
               
               
                   
                 Example 2 
                 7.9 
                 10.9 
               
               
                   
                 Example 3 
                 5.9 
                 9.2 
               
               
                   
                 Example 4 
                 5.9 
                 8.8 
               
               
                   
                 Example 5 
                 5.7 
                 9.4 
               
               
                   
                 Example 6 
                 9.2 
                 14.7 
               
               
                   
                 Example 7 
                 8.2 
                 12.0 
               
               
                   
                 Example 8 
                 4.2 
                 6.4 
               
               
                   
                 Example 9 
                 7.7 
                 8.4 
               
               
                   
                 Control 2 
                 6.9 
                 11.7 
               
               
                   
                 Example 10 
                 8.2 
                 12.9 
               
               
                   
                 Example 11 
                 7.9 
                 13.1 
               
               
                   
                 Example 12 
                 8.6 
                 13.8 
               
               
                   
                 Example 13 
                 7.1 
                 10.9 
               
               
                   
                   
               
            
           
         
       
     
     The test data shows that the melt blown nonwoven fabric samples that were prepared from PET and Nylon-6 fibers having a polyethylene alkylene-oxide type nonionic surfactant additive gave improved water absorbency and vertical wicking compared to the fabric samples prepared from PET and Nylon-6 fibers without any surfactant additive. No improvement in water absorbency was observed for the melt blown nonwoven fabric samples that were prepared from polypropylene fibers having a polyethylene alkylene-oxide type nonionic surfactant additive compared to the polypropylene fabric samples that were prepared without any surfactant additive. Since no absorption was observed, the polypropylene melt blown nonwoven fabric samples were not tested for vertical wicking. 
     It should be noted that fibers of a nonwoven fabric prepared using a melt blown procedure will not have as much directionality (alignment of the fibers in the downweb direction versus the crossweb direction) compared to fabrics prepared by other methods such as, for example, knitted or woven fabrics. Fabrics having more fiber directionality would be expected to have higher vertical wicking values. 
     The PET melt blown fabric samples were also dyed and tested for dye differential properties according to the Dye Differential test method described above. The dyed melt blown fabric samples having the surfactant additive visually appeared darker than the control melt blown fabric samples without any surfactant additive. Color difference values, ΔE, are provided in Table 6. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 6 
               
               
                   
                   
               
               
                   
                 Example 
                 ΔE 
               
               
                   
                   
               
             
            
               
                   
                 Example 1 
                 3.70 
               
               
                   
                 Example 2 
                 3.80 
               
               
                   
                 Example 3 
                 5.10 
               
               
                   
                 Example 4 
                 6.41 
               
               
                   
                 Example 5 
                 1.87 
               
               
                   
                   
               
            
           
         
       
     
     The complete disclosures of the patents, patent documents, and publications cited herein are incorporated by reference in their entirety as if each were individually incorporated. To the extent that there is any conflict or discrepancy between this specification as written and the disclosure in any document that is incorporated by reference herein, this specification as written will control. Various modifications and alterations to this disclosure will become apparent to those skilled in the art without departing from the scope and spirit of this disclosure. It should be understood that this disclosure is not intended to be unduly limited by the illustrative embodiments and examples set forth herein and that such examples and embodiments are presented by way of example only with the scope of the disclosure intended to be limited only by the claims set forth herein as follows.