Melt spinning of polylactic acid blend fibers.

Abstract

Methods for preparing monocomponent and multicomponent fibers comprising polylactic acid (PLA) are described. Exemplary fibers include coextruded bicomponent sheath-core fibers, in which the core comprises PLA and the sheath comprises a polyolefin. The fibers may include various colorants, such as naturally occurring colorants and / or flame retardants. Also described are fibers comprising PLA, such as fibers prepared by the methods of the disclosure, and related articles, such as textiles, apparel, synthetic fibers, and faux fur.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of and priority to U.S. Provisional Patent Application No. 63 / 323,924, filed March 25, 2023, the disclosure of which is incorporated herein by reference in its entirety.

[0002] The subject matter of the present disclosure, in some embodiments, relates to methods for preparing fibers comprising polylactic acid (PLA), for example by extrusion or melt spinning, as well as such fibers themselves and articles prepared from such fibers. In some embodiments, the subject matter of the present disclosure relates to bicomponent core-sheath fibers comprising a core comprising PLA and a sheath comprising a polyolefin. The core and / or sheath may further comprise one or more colorants and / or flame retardants. In some embodiments, the subject matter of the present disclosure relates to monocomponent PLA fibers comprising one or more colorants and / or flame retardants. [Background technology]

[0003] As concerns continue over the availability and environmental impact of products derived from petroleum-based chemicals, the use of renewable feedstocks is becoming increasingly attractive as an alternative in the production of a wide variety of products. Many products based on petroleum-based chemicals are insoluble in nature and release harmful substances when burned, creating serious waste problems. In contrast, polylactic acid (also known as polylactide or PLA) is a biodegradable thermoplastic polyester that can be produced from renewable resources such as corn (e.g., corn starch), tapioca, and sugar cane. When PLA decomposes, it produces lactic acid, which is non-toxic. As such, PLA is used in applications such as food packaging and medical implants.

[0004] However, there remains a need for methods of preparing fibers that include PLA. In particular, there is a continuing need for methods of preparing PLA-based fibers that have tunable properties, such as tunable color, strength, and texture, for use in a variety of different end uses. There is also a continuing need for methods of preparing PLA-based fibers that are flame retardant. Summary of the Invention

[0005] This summary lists several embodiments of the subject matter of the present disclosure, and often lists variations and modifications of these embodiments. This summary is merely illustrative of many different embodiments. Mention of one or more representative features of a given embodiment is also exemplary. Such embodiments can typically exist with or without one or more of the features mentioned, and similarly, those features can be applied to other embodiments of the subject matter of the present disclosure, whether or not they are listed in this summary. To avoid excessive repetition, this summary does not list or suggest all possible combinations of such features.

[0006] In some embodiments, the presently disclosed subject matter provides a method of preparing a fiber, the method comprising: (a) preparing a first solid mixture comprising polylactic acid (PLA); (b) preparing a second solid mixture comprising a polyolefin; and (c) co-extruding the first solid mixture and the second solid mixture to prepare a bicomponent core-sheath fiber comprising a core comprising the first solid mixture and a sheath comprising the second solid mixture.

[0007] In some embodiments, the first solid mixture and / or the second solid mixture further comprises one or more colorants, and optionally one or more of the one or more colorants is a flame retardant. In some embodiments, at least one of the one or more colorants is selected from the group consisting of minerals, animal products, and plant products. In some embodiments, at least one of the one or more colorants is selected from the group consisting of bone black, mica, and iron oxide.

[0008] In some embodiments, both the first solid mixture and the second solid mixture include bone black, optionally about 5 wt% bone black. In some embodiments, the first solid mixture and / or the second solid mixture further include a non-colorant flame retardant, optionally an "organic phosphate," and further optionally, the flame retardant is 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) or a polymeric polyphosphate. In some embodiments, the first solid mixture includes a PLA including about 1 weight percent (wt%) to about 20 wt% DOPO and about 5 wt% bone black, optionally a PLA including about 10 wt% DOPO and about 5 wt% bone black, and optionally, the bone black has a particle size of about 200 nm to about 5 μm.

[0009] In some embodiments, the second solid mixture comprises a bio-based polyolefin, optionally a bio-based polyethylene, In some embodiments, the second solid mixture comprises polyethylene, optionally a bio-based polyethylene, and one or more colorants, optionally about 5 wt% bone black.

[0010] In some embodiments, the bicomponent fibers are concentric or eccentric sheath-core fibers, and optionally, the bicomponent fibers are eccentric sheath-core fibers, and the method of the present invention further comprises (d) heating the fibers to a temperature of about 60° C. to about 80° C. In some embodiments, the weight ratio of core to sheath is about 80:20 to about 60:40.

[0011] In some embodiments, step (a) comprises melt compounding the first solid mixture to provide a compounded first solid mixture, optionally, the melt compounding is performed using a twin screw extruder and / or the melt compounding is performed at a temperature between about 150° C. and about 180° C. In some embodiments, step (b) comprises melt compounding the second solid mixture to provide a compounded second solid mixture, optionally, the melt compounding is performed using a twin screw extruder and / or at a temperature between about 140° C. and about 170° C. In some embodiments, the co-extrusion is performed at a temperature of about 150° C. to about 170° C. and / or a take-up speed of about 50 to about 200 meters per minute (m / min).

[0012] In some embodiments, the presently disclosed subject matter provides fibers prepared according to a method comprising: (a) preparing a first solid mixture comprising polylactic acid (PLA); (b) preparing a second solid mixture comprising a polyolefin; and (c) co-extruding the first solid mixture and the second solid mixture to prepare a bicomponent core-sheath fiber comprising a core comprising the first solid mixture and a sheath comprising the second solid mixture.

[0013] In some embodiments, the presently disclosed subject matter provides a bicomponent fiber comprising a core region comprising a first component comprising polylactic acid (PLA) and a sheath region comprising a second component comprising a polyolefin and at least partially surrounding the core region. In some embodiments, the PLA of the first component comprises APLA, CPLA, or a mixture of APLA and CPLA. In some embodiments, the PLA of the first component comprises a mixture of APLA and CPLA in a ratio of about 1:1 to about 1:4; optionally, about 1:1, about 1:2, about 1:3, or about 1:4.

[0014] In some embodiments, the first component and / or the second component further comprises one or more colorants, optionally one or more of the one or more colorants is a flame retardant. In some embodiments, at least one of the one or more colorants is selected from the group consisting of minerals, animal products, and plant products. In some embodiments, at least one of the one or more colorants is selected from the group consisting of bone black, mica, and iron oxide. In some embodiments, both the first component and the second component comprise bone black, optionally about 5 wt% bone black.

[0015] In some embodiments, the first component and / or the second component further comprises a non-colorant flame retardant, optionally an organic phosphate, and further optionally the flame retardant is 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) or a polymeric polyphosphate. In some embodiments, the first component comprises a PLA comprising about 1 weight percent (wt%) to about 20 wt% DOPO and about 5 wt% bone black, optionally a PLA comprising about 10 wt% DOPO and about 5 wt% bone black.

[0016] In some embodiments, the second component comprises a bio-based polyolefin, optionally a bio-based polyethylene, hi some embodiments, the second component comprises polyethylene, optionally a bio-based polyethylene, and one or more colorants, optionally about 5 wt% bone black.

[0017] In some embodiments, the bicomponent fibers are concentric or eccentric sheath-core fibers, and optionally, the bicomponent fibers are self-crimping eccentric sheath-core fibers. In some embodiments, the weight ratio of the core to the sheath is about 80:20 to about 60:40. In some embodiments, the bicomponent fibers have a linear density of about 35 grams per 9000 meters to about 70 grams per 9000 meters.

[0018] In some embodiments, the presently disclosed subject matter provides a method of preparing a fiber, the method comprising: (i) preparing a solid mixture comprising polylactic acid (PLA) and one or more colorants; and (ii) melt spinning the solid mixture, thereby preparing a PLA fiber, the PLA fiber having a substantially solid cross-section. In some embodiments, the PLA is a mixture of low crystalline melting temperature PLA (APLA) and high crystalline melting temperature PLA (CPLA), optionally with a ratio of APLA to CPLA of about 1:1 to about 1:4.

[0019] In some embodiments, one or more of the one or more colorants is a flame retardant. In some embodiments, at least one of the one or more colorants is selected from the group consisting of minerals, animal products, and plant products. In some embodiments, at least one of the one or more colorants is selected from the group including bone black, mica, and iron oxide.

[0020] In some embodiments, the solid mixture comprises about 0.5 weight (wt)% to about 10 wt% mica, optionally about 2 wt% to about 5 wt% mica. In some embodiments, the solid mixture further comprises up to about 20 wt% lignin, optionally about 10 wt% lignin. In some embodiments, the solid mixture further comprises a meltable solvent, optionally dimethylsulfone (DMSO-2), further optionally, the meltable solvent is present in about a 1:1 weight ratio with the lignin.

[0021] In some embodiments, the method of the present invention further comprises, after step (ii), optionally removing the meltable solvent using a water bath. In some embodiments, the method of the present invention further comprises contacting the fiber with a warm bath, thereby providing a crimped fiber. In some embodiments, the solids mixture further comprises a non-colorant flame retardant, optionally DOPO or polymeric polyphosphate. In some embodiments, melt spinning comprises melt spinning a monocomponent fiber.

[0022] In some embodiments, step (a) includes melt extruding the solid mixture at a temperature between about 150 degrees Celsius (° C.) and about 170° C. In some embodiments, the melt spinning is performed using a take-up speed of about 50 meters per minute (m / min) to about 100 m / min.

[0023] In some embodiments, the presently disclosed subject matter provides fibers prepared by a process comprising: (i) preparing a solid mixture comprising polylactic acid (PLA) and one or more colorants; and (ii) melt spinning the solid mixture, thereby preparing a PLA fiber, wherein the PLA fiber has a substantially solid cross-section.

[0024] In some embodiments, the presently disclosed subject matter provides a solid, monocomponent fiber comprising polylactic acid (PLA) and one or more colorants.

[0025] In some embodiments, the presently disclosed subject matter provides solid monocomponent fibers comprising polylactic acid (PLA), where the PLA comprises a mixture of low temperature crystallization melt PLA (APLA) and high temperature crystallization melt PLA (CPLA). In some embodiments, the ratio of APLA to CPLA is about 1:1 to about 1:4, about 1:2, about 1:2, about 1:3, or about 1:4. In some embodiments, the fibers of the present invention exhibit autogenous crimping at a temperature of about 60° C. to about 70° C. In some embodiments, the fibers of the present invention further comprise at least one or more colorants.

[0026] In some embodiments, the fibers of the present invention comprise at least one of one or more colorants, the colorants being selected from the group consisting of minerals, animal products, and plant products. In some embodiments, the fibers of the present invention comprise about 0.5 wt% to about 10 wt% mica, optionally about 2 wt% to about 5 wt% mica. In some embodiments, the fibers of the present invention comprise up to about 20 wt% lignin. In some embodiments, the fibers of the present invention further comprise a non-colorant flame retardant, optionally DOPO or polymeric polyphosphate.

[0027] In some embodiments, the presently disclosed subject matter provides a spun yarn prepared from the fibers (e.g., bicomponent or monocomponent fibers) as disclosed herein. In some embodiments, the presently disclosed subject matter provides a fabric prepared from the spun yarn, optionally, the fabric is a nonwoven fabric.

[0028] In some embodiments, the subject matter of the present disclosure provides an article of manufacture comprising a fiber (e.g., bicomponent or monocomponent fiber) as disclosed herein or a yarn or fabric prepared therefrom, optionally the article of manufacture is an article of clothing, a textile, artificial hair, or a faux fur. In some embodiments, the article of manufacture is biodegradable and / or sustainable. In some embodiments, the article of manufacture is self-extinguishing.

[0029] It is an object of the presently disclosed subject matter to provide methods for preparing fibers comprising polylactic acid (PLA), including both bicomponent and monocomponent fibers, as well as such fibers themselves and articles prepared from such fibers. This and other objects are achieved, in whole or in part, by the presently disclosed subject matter. Moreover, while the objects of the presently disclosed subject matter have been set forth above, other objects and advantages of the presently disclosed subject matter will become apparent to those skilled in the art after reviewing the following description and drawings. [Brief description of the drawings]

[0030] [Figure 1A]FIG. 1 is a schematic cutaway side view of a twin-screw extruder suitable for use in the methods of the presently disclosed subject matter, such as for use in melt compounding polylactic acid (PLA) resin and / or other polymer resins according to one embodiment of the presently disclosed subject matter. [Figure 1B] FIG. 1 is a schematic diagram of an apparatus for melt spinning bicomponent fibers according to one embodiment of the disclosed subject matter. [Figure 1C] 1C is a schematic cutaway side view of an exemplary spin pack configuration for use in the apparatus of FIG. 1B. The spin pack can be used for the preparation of a sheath-core bicomponent fiber comprising a core prepared from a first resin (e.g., a first compound resin such as a polylactic acid (PLA) compound resin) and a sheath prepared from a second resin (e.g., a second compound resin including, for example, polyethylene). [Figure 1D] FIG. 1 is a schematic perspective view illustrating an alternative apparatus for use in preparing fibers according to one embodiment of the presently disclosed subject matter. [Figure 1E] FIG. 1 is a schematic cut-away side view of a single screw extruder in accordance with the presently disclosed subject matter suitable for use in the methods of the presently disclosed subject matter, such as for use in melt compounding polylactic acid (PLA) resins and / or other polymer resins in accordance with one embodiment of the presently disclosed subject matter. [Figure 2A] 1 is a micrograph showing the cross section of an exemplary sheath / core bicomponent fiber of the presently disclosed subject matter. The scale bar at the bottom right represents 100 micrometers. [Figure 2B] 1 is a schematic diagram showing cross-sectional views of exemplary bicomponent fiber geometries, with one component shown shaded and the other component unshaded. From top to bottom, the exemplary geometries are side-by-side, sheath-core concentric, and sheath-core eccentric. [Diagram 3] Photographs of reels of an exemplary bicomponent fiber of the disclosed subject matter melt spun at different take-up speeds (50 meters per minute (m / min) or 100 m / min). [Figure 4] 1 is a photograph showing exemplary polylactic acid (PLA) monocomponent fibers of the presently disclosed subject matter containing different amounts of lignin as a colorant. [Figure 5A]1 is a 100x magnification photomicrograph of a cross section of a monocomponent polylactic acid (PLA) fiber of the presently disclosed subject matter containing 2 weight percent (wt%) mica. The scale bars on the bottom and right each represent 1000 micrometers. [Figure 5B] 1 is a 300x magnification photomicrograph of a cross section of a monocomponent polylactic acid (PLA) fiber of the presently disclosed subject matter containing 2 weight percent (wt%) mica. The scale bars on the bottom and right each represent 100 micrometers. [Figure 5C] 1 is a 200x magnification photomicrograph of a cross-section of a monocomponent polylactic acid (PLA) fiber of the presently disclosed subject matter containing 5 weight percent (wt%) mica. The scale bars on the bottom and right each represent 1000 micrometers. [Figure 5D] 1 is a 200x magnification photomicrograph of a longitudinal section of a monocomponent polylactic acid (PLA) fiber of the presently disclosed subject matter containing 2 weight percent (wt%) mica. The scale bar at the bottom right represents 1000 micrometers. [Figure 5E] 1 is a 100x magnification photomicrograph of a longitudinal section of a monocomponent polylactic acid (PLA) fiber of the presently disclosed subject matter containing 5 weight percent (wt%) mica. The scale bar at the bottom right represents 1000 micrometers. [Figure 5F] 1 is a 400x magnification photomicrograph of a longitudinal section of a neat monocomponent polylactic acid (PLA) fiber of the subject matter of the present disclosure. The scale bar at the bottom right represents 100 micrometers. [Figure 6A] 1 is a photographic image of a fiber containing both low temperature crystallizing melt polylactic acid (APLA) and high temperature crystallizing melt polylactic acid (CPLA) in a ratio of 1:2 APLA:CPLA. The APLA was provided as a resin concentrate compounded with brown iron oxide colorant (corresponding to "Trial 1" in the Examples). The fiber was processed at 200 degrees Celsius and a speed of 100 meters per minute. [Figure 6B]1 is a photographic image of a fiber containing both low temperature crystallizing melt polylactic acid (APLA) and high temperature crystallizing melt polylactic acid (CPLA) in a ratio of APLA:CPLA of 1:2. APLA was provided as a resin concentrate compounded with brown iron oxide colorant (corresponding to "Trial 1" in the Examples). The fiber was processed at 180°C to 190°C at a speed of 100 meters per minute. [Figure 6C] 1 is a photographic image of a fiber containing both low temperature crystallizing melt polylactic acid (APLA) and high temperature crystallizing melt polylactic acid (CPLA) in a ratio of APLA:CPLA of 1:4. APLA was provided as a resin concentrate compounded with brown iron oxide colorant (corresponding to "Trial 1" in the Examples). The fiber was processed at 200 degrees Celsius and a speed of 100 meters per minute. [Figure 7A] 1 is a photographic image of a fiber containing both low temperature crystallizing melt polylactic acid (APLA) and high temperature crystallizing melt polylactic acid (CPLA) in a ratio of APLA:CPLA of 1:4. APLA was provided as a resin concentrate compounded with brown iron oxide colorant (corresponding to "Trial 3" in the Examples). The fiber was processed at 170 degrees Celsius and a speed of 100 meters per minute. [Figure 7B] 1 is a photographic image of a fiber containing both low temperature crystallizing melt polylactic acid (APLA) and high temperature crystallizing melt polylactic acid (CPLA) in a ratio of APLA:CPLA of 1:4. APLA was provided as a resin concentrate compounded with brown iron oxide colorant (corresponding to "Trial 3" in the Examples). The fiber was processed at 200 degrees Celsius and a speed of 100 meters per minute. [Figure 8] 1 is a photographic image of a fiber containing both low temperature crystallizing melt polylactic acid (APLA) and high temperature crystallizing melt polylactic acid (CPLA) in a ratio of APLA:CPLA of 1:2. APLA was provided as a resin concentrate compounded with black iron oxide colorant (corresponding to "Trial 4" in the examples). The fiber was processed at 200 degrees Celsius and a speed of 100 meters per minute. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] The subject matter of the present disclosure will now be described in more detail. However, the subject matter of the present disclosure can be embodied in various forms and is not to be construed as being limited to the embodiments described below and in the accompanying examples. Rather, these embodiments are provided so that this disclosure will be complete and will fully convey the scope of the embodiments to those skilled in the art.

[0032] I. Definition The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the subject matter of the present disclosure.

[0033] Although the following terms are believed to be well understood by those of skill in the art, the following definitions are provided to facilitate description of the subject matter of the present disclosure.

[0034] All technical and scientific terms used herein are intended to have the same meaning as commonly understood by those skilled in the art, unless otherwise defined below. References to techniques employed herein are intended to refer to techniques commonly understood in the art, including variations of those techniques or equivalent substitutes for those techniques that would be apparent to those skilled in the art.

[0035] In describing the subject matter of the present disclosure, it will be understood that multiple techniques and steps are disclosed, each of which has separate advantages and each of which can be used in conjunction with one or more, and optionally all, of the other techniques disclosed.

[0036] Thus, for the sake of clarity, this specification refrains from unnecessarily repeating every possible combination of the individual steps, but the specification and claims should be read with the understanding that such combinations are fully within the scope of the present disclosure and claimed subject matter.

[0037] Following long-standing patent law convention, the terms "a," "an," and "the" refer to "one or more" when used in this application, including the claims. Thus, as used herein and in the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. For example, the phrase "a light source" refers to one or more light sources, including multiple light sources of the same type. Similarly, the phrase "at least one," when used herein to refer to an entity, refers to, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, 50, 75, 100 or more entities, including, but not limited to, integer values ​​between 1 and 100 and integer values ​​greater than 100. Thus, the terms "a," "an," "one or more," and "at least one" can be used interchangeably. Similarly, the terms "comprising," "including," and "having" can be used interchangeably. Moreover, it should be noted that the claims may be drafted to exclude optional elements. As such, this statement is intended to presuppose the use of exclusive terminology such as "solely," "only," and the like, or the use of a "negative" limitation in connection with the recitation of claim elements.

[0038] Unless otherwise indicated, all numerical values ​​expressing quantities such as temperature, time, concentration, length, width, height, and the like used in the specification and claims are understood to be modified in all instances by the term "about." The term "about" as used herein when referring to a measurable value, such as a quantity of mass, weight, time, volume, length, width, or temperature, is meant to encompass variations from the specified amount, in some embodiments ±20%, in some embodiments ±10%, in some embodiments ±5%, in some embodiments ±1%, in some embodiments ±0.5%, and in some embodiments ±0.1%, as appropriate for carrying out the disclosed method and / or using the disclosed subject matter. Thus, unless indicated to the contrary, the numerical parameters set forth in the specification and appended claims are approximations that may vary depending on the desired properties sought to be obtained by the disclosed subject matter.

[0039] As used herein, ranges can be expressed as from "about" one particular value and / or to "about" another particular value. When such a range is expressed, in some embodiments, it includes from one particular value and / or to the other particular value. Similarly, when values ​​are expressed as approximations, it is understood that by the use of "about" the antecedent, the particular value forms an embodiment. It will be further understood that the endpoints of each range are significant in relation to the other endpoint, and independently of the other endpoint. It is also understood that there are several values ​​disclosed herein, and that each value is also disclosed herein as "about" that particular value in addition to the value itself. For example, if a value of "10" is disclosed, then "about 10" is also disclosed. It is also understood that when a value is disclosed, values ​​"less than or equal to" the value, values ​​"greater than or equal to" the value, and possible ranges between the values ​​are also disclosed, as would be well understood by one of ordinary skill in the art. For example, if a value of "10" is disclosed, then "less than or equal to" the value is also disclosed, as well as "greater than or equal to 10." It is also understood that throughout the application, data are provided in a number of different formats, and that these data, in some embodiments, represent endpoints and starting points, and in some embodiments, represent ranges for any combination of the data points. For example, if a specific data point "10" and a specific data point "15" are disclosed, it is understood that values ​​between 10 and 15, as well as values ​​greater than 10 and 15, greater than or equal to 10 and 15, less than 10 and 15, less than or equal to 10 and 15, and equal to 10 and 15 are considered to be disclosed. It is also understood that each unit between two specific units is disclosed. For example, if 10 and 15 are disclosed, then 11, 12, 13, and 14 are also disclosed.

[0040] Numerical ranges recited herein by endpoints include all numbers and fractions subsumed within that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.90, 4, 4.24, and 5). Similarly, numerical ranges recited herein by endpoints include all sub-ranges subsumed within that range (e.g., 1 to 5 includes 1-1.5, 1.5-2, 2-2.75, 2.75-3, 3-3.90, 3.90-4, 4-4.24, 4.24-5, 2-5, 3-5, 1-4, and 2-4).

[0041] As used herein, the term "and / or" when used in the context of a list of entities refers to the entities present either alone or in combination. Thus, for example, the phrase "A, B, C, and / or D" includes not only A, B, C, and D individually, but also all combinations and subcombinations of A, B, C, and D.

[0042] The term "comprising" is synonymous with "including," "containing," or "characterized by" and is inclusive or open-ended and does not exclude additional unrecited elements and / or method steps. "Comprising" is a term of art that means that the specified elements and / or steps are present, but that other elements and / or steps can be added and still fall within the scope of the relevant subject matter.

[0043] As used herein, the phrase "consisting essentially of" limits the scope of the associated disclosure or claim to certain materials and / or steps that do not materially affect the basic and novel characteristics of the subject matter of the disclosure and / or claims.

[0044] As used herein, the phrase "consisting of" excludes any element, step, or ingredient not specifically recited. Note that when the phrase "consisting of" appears in a clause in the body of a claim rather than immediately following a preamble, it limits only the elements recited in that clause and does not exclude other elements from the claim as a whole.

[0045] With respect to the terms "comprising," "consisting of," and "consisting essentially of," when one of these three terms is used in this specification, the subject matter of this disclosure and claims may include use of either of the other two terms.

[0046] As used herein, the terms "optional" and "optionally" indicate that the subsequently described event, circumstance, element, and / or method step may or may not occur and / or may or may not be present, including cases where the event, circumstance, element, or method step does not occur, as well as cases where it does occur and / or is present.

[0047] As used herein, "monomer" refers to a non-polymerizable molecule that can be polymerized, thereby providing a building block, ie, an atom or group of atoms, to the essential structure of a macromolecule.

[0048] As used herein, the term "macromolecule" refers to a molecule of high relative molecular weight, the structure of which is composed of multiple repeating units derived from molecules of lower relative molecular weight, such as monomers and / or oligomers.

[0049] "Oligomer" refers to a molecule of intermediate relative molecular weight, whose structure is composed of multiple (e.g., 2, 3, 4, 5, 6, 7, 8, 9 or 10) small repeating units derived from a molecule of lower relative molecular weight.

[0050] As used herein, the terms "polymer," "polymeric," and "polymeric matrix" refer to a material that includes macromolecules. In some embodiments, the term "polymer" can include both oligomeric molecules and molecules with a larger number of repeating units (e.g., >10, >20, >50, >100). In some embodiments, "polymer" refers to a macromolecule having at least 10 repeating units. "Copolymer" refers to a polymer derived from two or more types of monomers.

[0051] The term "thermoplastic" can refer to a polymer that can be softened and / or molded above a certain temperature, but is solid below that temperature.

[0052] The term "bioplastic" refers to thermoplastic polymers that can be prepared from renewable resources (e.g., plant-derived monomers) and are also called "bio-based."

[0053] The term "polyester" refers to a polymer or copolymer that contains a backbone or main chain with bonds of the formula --O--C(.dbd.O)--.

[0054] The term "bioplastic polyester" as used herein refers to thermoplastic polyesters (also called "biobased polyesters") that can be prepared from renewable resources (e.g., monomers derived from plants) and / or biodegradable polyesters, which can be biobased or synthetic (e.g., prepared from monomers derived from petroleum-based materials). Bioplastic polyesters are typically aliphatic esters. Exemplary biobased polyesters include, but are not limited to, polylactic acid (PLA), which can be isotactic (i.e., poly(L-lactic acid) or poly(D-lactic acid)) or syndiotactic (i.e., poly(D,L-lactic acid)).

[0055] "Biodegradable" refers to a material that breaks down or decays by natural biological processes. Biodegradable materials can be broken down, for example, by cellular machinery, proteins, enzymes, hydrolytic chemicals or reducing agents present in biological fluids or soils, intracellular components, etc., into components that can be reused or disposed of without significant toxic effects on the environment. Thus, as used herein, the term "biodegradable" refers to both enzymatic and non-enzymatic breakdown or degradation of polymer structures. In some embodiments, degradation time is a function of polymer composition and morphology. Suitable degradation times can range from hours or days to weeks or years.

[0056] The term "lignocellulosic" refers to compositions that contain both lignin and cellulose. In some embodiments, lignocellulosic materials can contain hemicellulose, a polysaccharide that can contain saccharide monomers other than glucose. Typically, lignocellulosic materials contain about 30-45% by weight cellulose, about 20-35% by weight hemicellulose, and about 3-35% by weight lignin.

[0057] Lignocellulosic biomass includes various plants and plant materials, such as paper sludge; wood and wood-related materials, such as sawdust or cotton particle board, leaves, or trees, such as poplar trees; fiber from wood or non-wood plants; grasses, such as switchgrass and sudangrass; grass clippings; rice husks; bagasse (e.g., bagasse (e.g., sugarcane bagasse), jute, hemp, flax, kapok, coir, bamboo, sisal, abaca, hay, straw, miscanthus, corn cob, corn stover, whole porant corn, bamboo, and palm hair. In some embodiments, the lignocellulosic biomass is selected from the group including, but not limited to, herbaceous materials, agricultural residues, forestry residues, municipal solid waste, waste paper, pulp and paper mill residues, or combinations thereof.

[0058] "Lignin" is a polyphenolic substance composed of phenylpropane units linked by ether and carbon-carbon bonds. Lignin may be highly branched and cross-linked. Lignin may have significant structural variations that depend, at least in part, on the plant source involved.

[0059] As used herein, the term "fiber" refers to an elongated strand of material having a length to width ratio of greater than about 10, greater than about 25, greater than about 50, or greater than about 100. Fibers typically have a round or substantially round cross-section. Other cross-sectional shapes of the fibers of the invention include, but are not limited to, oval, square, triangular, rectangular, star, trilobal, pentapelal, octolobal, and flat (i.e., "ribbon"-like) shapes. The fibers of the invention can also have any desired diameter, for example, thicker fibers (or "rods") can be chopped or pelletized, and thinner fibers can be used to prepare spun yarns or fabrics. In some embodiments, the fibers of the invention have a diameter of less than about 250 microns, less than about 200 microns, less than about 150 microns, less than about 100 microns, less than about 75 microns, less than about 50 microns, less than about 25 microns, or less than about 10 microns. In some embodiments, the fibers of the invention have a thickness of about 1 micron to about 250 microns. In some embodiments, the fibers of the present invention have a thickness of more than about 250 microns. For example, thick fibers or rods that can be chopped to provide pellets can have a thickness of several hundred microns (e.g., about 300 microns, about 400 microns, about 500 microns, or about 750 microns) to several millimeters (mm) (e.g., about 5 mm, about 10 mm, or about 25 mm). In some embodiments, the thick fibers or rods can have a diameter of about 1 mm to about 5 mm (e.g., 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm, or about 5 mm). In some embodiments, the thick fibers or rods can be chopped into pellets having a length of about 1 mm to about 5 mm (e.g., 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm, or about 5 mm).

[0060] The terms "monofilament fiber" and "monofiber" refer to continuous strands of material of indefinite (i.e., not predetermined) length, while the term "staple fiber" refers to discontinuous strands of material of definite length (i.e., strands that have been cut or otherwise divided into segments of predetermined length).

[0061] As used herein, "melt spun fibers" are fibers produced by the melt spinning process. Melt spinning is a process in which a melt is extruded through one or more dies, such as one or more die capillaries (e.g., spinnerets), as molten filaments while simultaneously applying an elongational force to attenuate the molten filaments. The molten filaments solidify upon cooling below their melting temperature to form fibers. The term "melt spun" encompasses stable fiber spun (including staple and continuous fiber spun) and bulk continuous filament fibers. In some embodiments, the melt spun fibers can be cold-drawn.

[0062] The term "melt compounding" or "compounding" as used herein refers to the process of melt blending materials, such as polymers, with other additives. Melt compounding typically involves both heating and mixing of materials. In some embodiments, the terms "melt compounding" and "compounding" as used herein refer to a method of blending a mixture (e.g., a solid mixture) including PLA resin and one or more other components (e.g., a meltable solvent, a flame retardant, and / or a colorant) to provide a homogenous blended composition or a more homogenous blended composition. In some embodiments, compounding further includes extruding the blended composition (i.e., the compounded resin concentrate). Thus, the term "melt compounding" as used herein may encompass processes such as melt extrusion and melt spinning. In some embodiments, the term "melt compounding" or "compounding" is not limited to additive manufacturing techniques such as 3D printing, but further includes any technique involving an apparatus, such as an extruder, that can melt and mix the mixture.

[0063] The term "masterbatch" as used herein refers to a compounded polymer resin (e.g., compounded PLA resin) containing one or more additives (e.g., color additives). Typically, a masterbatch contains a more concentrated amount of one or more additives than the end-use polymer prepared from the masterbatch. For example, a masterbatch can contain a concentrated mixture of pigments and / or other additives (e.g., flame retardants) and can be prepared using a heating process or extrusion (e.g., twin-screw extrusion) to encapsulate the pigments and / or other additives in a matrix of a carrier polymer. The masterbatch can be cooled and cut (e.g., pelletized) and used to add the pigments and / or other additives to additional polymers (e.g., by extrusion of a mixture of the masterbatch and polymer). In some embodiments, the use of a masterbatch can provide more consistent color and / or other additive properties in the end-use polymer than if the pigments and / or other additives were compounded as raw materials during the preparation of the end-use polymer. In some embodiments, the terms "masterbatch," "resin concentrate," and "compounded resin concentrate" can be used interchangeably.

[0064] In some embodiments, a compounded resin concentrate or masterbatch may also be referred to herein as a "solids mix." However, in some embodiments, the term "solids mix" may refer to a compounded resin mix that includes a lower concentration of pigments and / or other additives (e.g., the concentration of pigments and / or other additives in the final end-use product). Thus, in some embodiments, a "solids mix" may be a spin dope that is used to melt spin the final fiber for use in the end use (e.g., as a spun yarn or fabric). In some embodiments, a "solids mix" may also refer to a mixture of resins and additives (e.g., a mixture of resins, colorants, flame retardants, and / or meltable solvents) that are compounded (e.g., by extrusion).

[0065] II. General Considerations The subject matter of the present disclosure relates, in some embodiments, to melt extrusion of mono- and multi-component polylactic acid (PLA) fibers with a wide range of colors, and the fibers themselves. In some embodiments, the fibers can be melt spun from a mixture of PLA resins with low and high crystallization melt temperatures (e.g., in the range of 125°C to 135°C for low crystallization melt PLA (also referred to herein as "APLA") and 160°C to 180°C for high crystallization melt PLA (also referred to herein as "CPLA"). PLA with a low crystallization melt temperature can provide softness as well as thermally induced texture at high temperatures. PLA with a high crystallization melt temperature can provide improved mechanical strength and / or heat resistance, as well as the ability to melt spin at higher extrusion temperatures.

[0066] The fibers of the present disclosure have a substantially solid body and can be provided in a variety of neutral or earth colors, such as, for example, black, white, brown, red, yellow, gray, and combinations thereof. In some embodiments, the PLA fibers are melt spun from a resin concentrate (e.g., comprising a compound mixture of low temperature crystallizing melt PLA resin and high temperature crystallizing melt PLA resin) that includes a biologically derived colorant, such as a mineral, animal product, or plant product. For example, the fiber resin concentrate can include mica or bone charcoal (also referred to herein as bone black (BB)) to provide a black fiber, iron oxide to provide a black or brown fiber that may have a reddish hue, or lignin to provide a yellow to brown fiber. The iron oxides can be referred to, for example, as black oxide, brown oxide (e.g., amber brown oxide), yellow oxide, or red oxide, depending on the color they provide. For example, "black oxide" has the formula Fe 3 O 4 "Red oxide" has the formula Fe 2 O3, "yellow oxide" may have the formula FeOOH. Iron oxides of various colors are known in the art and are commercially available from a variety of companies that supply pigments as described elsewhere herein.

[0067] In some embodiments, a meltable solvent (e.g., dimethylsulfone (i.e., DMSO-2, also known as methylsulfonylmethane (MSM)) can be added as a compatibilizer to polymer-containing mixtures, such as PLA resins and mixtures thereof, that are compounded to prepare the fibers described herein. For example, in some embodiments, the meltable solvent can be used to alter the melting behavior of the resulting compounded resin concentrate or solid mixtures prepared therefrom, to impart a soft hand (e.g., a soft feel or softness to the touch) to the fibers, to provide the ability to easily parcel the fibers, to aid in compatibilizing the lignin with the PLA and / or to reduce agglomeration of the lignin, to uniformly disperse inorganic pigments throughout the PLA, and / or to deepen the color of the fibers.

[0068] In some embodiments, the resin concentrate (or solid mixture) for use herein may include flame retardants such as, but not limited to, other flame retardant organic phosphates, including polymeric flame retardant polyphosphates. Thus, in some embodiments, the fibers of the present invention may be flame retardant or self-extinguishing. Other suitable flame retardants are disclosed elsewhere herein. Indeed, any suitable flame retardant may be provided in accordance with the subject matter of the present disclosure, as would be apparent to one of ordinary skill in the art upon review of this disclosure.

[0069] In some embodiments, the fibers of the present invention are bicomponent fibers, such as sheath-core fibers, with a core comprising PLA and a sheath comprising a polyolefin. The sheath-core fibers can provide improved softness and / or feel. Additionally, the layering effect provided by the sheath-core geometry can enhance the ability to tune the color of the fiber. In some embodiments, the polyolefin sheath is a bio-based polyolefin, such as bio-based polyethylene, to enhance the sustainability of the fiber.

[0070] The fibers of the present disclosure can be used to prepare sustainable / biodegradable and / or recyclable clothing or textiles, nonwoven mats, artificial hair and fake fur. Melt compounded PLA mixtures can also be used in other applications, such as 3D printing applications.

[0071] III. Representative Methods, Compositions, and Systems Generally, melt spinning involves melting a polymer into a viscous liquid that is extruded through a spinneret to produce fibers. Melt spinning can also be considered a form of melt extrusion. Thus, the terms "melt spinning" and "melt extrusion" can be used interchangeably herein.

[0072] If melt spinning is not possible for a particular polymer, solution spinning or dry spinning can be performed. Solution spinning involves preparing a dilute solution of the polymer (e.g., less than about 30 wt% dissolved polymer), which is extruded, solidified, and the solvent removed into filaments. Dry spinning involves dissolving the polymer in a volatile solvent, extruding it through a spinneret, and then using hot air to slowly evaporate the volatile solvent leaving a solid filament. However, these processes can have slow production rates and / or poor fiber properties. Therefore, the ability to melt spin the fibers can be advantageous. As described herein, in some embodiments, methods are provided for melt spinning PLA fibers with a variety of colors, thermally induced textures, good mechanical properties (e.g., moderate strain to break), and soft to the touch.

[0073] The fibers of the present disclosure may be monocomponent or multicomponent. The term "component" as used herein with respect to fibers is defined as an independent element of the fiber that has a spatial relationship to another element of the fiber. Thus, the term "multicomponent" as used herein is defined as a fiber having two or more separate elements in a spatial relationship to each other. The term multicomponent includes "bicomponent," which is a fiber having two separate elements in a spatial relationship to each other. See FIG. 2B. The different components of a multicomponent fiber can be located in substantially different regions across the cross section of the fiber and extend continuously along the length of the fiber. The bicomponent and multicomponent fibers of the present disclosure subject matter can be side-by-side, sheath-core, segmented pie, ribbon, islands-in-the-sea, or any combination thereof. The sheath may be continuous or discontinuous around the core. The fibers of the present disclosure subject matter can have different cross-sectional shapes, including, but not limited to, circular, elliptical, star, square, triangular, rectangular, and irregular shapes.

[0074] In some embodiments, the subject matter of the present disclosure provides a method for preparing a bicomponent PLA fiber. In some embodiments, the method includes: (a) preparing a first solid mixture comprising PLA; (b) preparing a second solid mixture comprising a polyolefin; and (c) co-extruding the first solid mixture and the second solid mixture. In some embodiments, co-extruding the first solid mixture and the second solid mixture prepares a bicomponent core-sheath fiber comprising a core comprising the first solid mixture and a sheath comprising the second solid mixture. Thus, in some embodiments, the subject matter of the present disclosure provides a bicomponent PLA fiber.

[0075] In some embodiments, other additives known in the art of spin-melting fibers can be optionally included in the first and / or second solid mixtures, such as, but not limited to, plasticizers, fillers, elongation agents, slip agents, flame retardants, antioxidants, and colorants. In some embodiments, one or both of the first and second solid mixtures further include one or more colorants. Any suitable colorant can be used, such as dyes, pigments, or any other material capable of imparting color to the solid mixture and the resulting fiber. In some embodiments, the colorant can also impart flame retardant properties. Thus, in some embodiments, one or more of the one or more colorants are flame retardants. For example, both lignin and iron oxide can impart color as well as fire extinguishing properties. More specifically, lignin can impart fire extinguishing / flame retardant properties to products containing lignin due to the high char yield of the lignin aromatic backbone after decomposition. In some embodiments, for example to enhance the sustainability of the fibers of the present disclosure, one or more (or all) of the colorants are natural colorants, i.e., naturally occurring minerals, animal products (e.g., dyes derived from insects or chars derived from animal bones), or plant products (e.g., lignin). In some embodiments, the colorants are selected from the group including, but not limited to, bone black, mica, and iron oxide.

[0076] In some embodiments, the first and / or second solid mixture comprises iron oxide. In some embodiments, when iron oxide is used as a colorant, it may be present in the first or second solid mixture (or the resin concentrate used to prepare the solid mixture) at about 10 wt% or less (e.g., about 5 wt% or about 7 wt%). Suitable iron oxide particle sizes are about 5 μm or less or about 200 nm or less. In some embodiments, the iron oxide has a particle size of about 200 nm. Suitable iron oxide colorants are available, for example, from Just Pigments (Tucson, AZ, USA) and TKB Trading (Oakland, CA, USA). In some embodiments, lignin may be incorporated into one or both of the solid mixtures (i.e., the first and / or second solid mixtures) to impart color.

[0077] In some embodiments, both the first solid mixture and the second solid mixture contain bone black. A bone black suitable for use herein is bone black sold under the trade name EBONEX® 3D, which has a particle size of about 500 nm to about 12 μm (Ebonex, Melvindale, Michigan, USA). In some embodiments, one or both of the solid mixtures contains about 0.1 wt% to about 10 wt% bone black (e.g., about 0.1 wt%, about 0.5 wt%, about 1 wt%, about 2 wt%, about 3 wt%, about 4 wt%, about 5 wt%, about 6 wt%, about 7 wt%, about 8 wt%, about 9 wt%, or about 10 wt% bone black). In some embodiments, the bone black has an average particle size of about 500 nanometers to about 12 microns. In some embodiments, bone black has a particle size of about 200 nanometers (nm) to about 12 microns (μm) (e.g., about 200 nm, about 300 nm, about 400 nm, about 500 nm, about 600 nm, about 700 nm, about 800 nm, about 900 nm, about 1.0 μm, about 1.5 μm, about 2.0 μm, about 2.5 μm, about 3.0 μm, about 3.5 μm, about 4.0 μm, about 4.5 μm, or about 5.0 μm). In some embodiments, both solid mixtures contain about 5 wt% bone black. In some embodiments, both solid mixtures contain less than about 5 wt% bone black.

[0078] In some embodiments, the first and / or second solid mixture is formed from a compound resin that contains other additives (e.g., other additives known in the art of spin melt fibers, such as, but not limited to, plasticizers, fillers, spreaders, slip agents, flame retardants, antioxidants, colorants, etc.), one or more additional compound resins (e.g., second and third compound resins), and resins having either a high or low melting temperature. In some embodiments, the first solid mixture includes APLA, CPLA, or both APLA and CPLA. In some embodiments, the ratio of APLA to CPLA is about 1:1 to about 1:4 (e.g., about 1:1, 1:2, 1:3, or about 1:4).

[0079] In some embodiments, the first and / or second solid mixture includes a non-colorant flame retardant (i.e., a flame retardant that does not impart color). For example, in some embodiments, the non-colorant flame retardant is an organic phosphate, such as, but not limited to, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO). In some embodiments, the flame retardant is ammonium polyphosphate (APP), APP, and calcium carbonate (CaCO 3 ), or polymeric polyphosphate flame retardants. For example, suitable polymeric polyphosphate flame retardants include polyphosphate oligomers, homopolymers and copolymers (e.g., polyphosphate polymers containing phosphonate esters), such as those described in U.S. Patent Nos. 6,861,499; 7,666,932; 7,816,486; 8,093,320; 8,975,367; and 9,290,653, the disclosures of each of which are incorporated herein by reference in their entirety. In some embodiments, the polymeric polyphosphate flame retardant is a polymeric polyphosphate sold under the trade name NOFIA® (available from FRX Polymers, Inc., Chelmsford, Massachusetts, USA, e.g., NOFIA® HM 1100, also referred to herein as "FRX" or "FRX 1100", which is a clear, high flow polymer with a glass transition temperature (Tg) of about 105° C.).

[0080] In some embodiments, the first solid mixture can include PLA with up to about 20 wt% DOPO (e.g., about 1 wt% to about 20 wt% DOPO). Thus, in some embodiments, the first solid mixture can include PLA and about 1 wt% DOPO, about 2 wt% DOPO, about 3 wt% DOPO, about 4 wt% DOPO, about 5 wt% DOPO, about 6 wt% DOPO, about 7 wt% DOPO, about 8 wt% DOPO, about 9 wt% DOPO, about 10 wt% DOPO, about 11 wt% DOPO, about 12 wt% DOPO, about 13 wt% DOPO, about 14 wt% DOPO, about 15 wt% DOPO, about 16 wt% DOPO, about 17 wt% DOPO, about 18 wt% DOPO, about 19 wt% DOPO, or about 20 wt% DOPO. In some embodiments, the first solid mixture further comprises one or more colorants (e.g., one or more natural colorants). For example, in some embodiments, the first solid mixture comprises PLA that includes both DOPO and bone black. In some embodiments, the first solid mixture comprises PLA, about 1 wt% to about 20 wt% DOPO, and about 5 wt% bone black. In some embodiments, the first solid mixture comprises PLA that includes about 10 wt% DOPO and about 5 wt% bone black. In some embodiments, the bone black has a particle size of about 200 nm to about 5 μm.

[0081] The use of polyolefins in the second mixture may be desirable due to the transparency of polyolefins, which may help tune the color of the fiber (e.g., because colorants from both the core and the sheath may contribute to the color of the final fiber). Suitable polyolefins for the second solid mixture include, but are not limited to, thermoplastic polyolefins, such as polyethylene, polypropylene, polyalphaolefins, and copolymers thereof. In some embodiments, the polyolefin is polyethylene. In some embodiments, the polyolefin of the second mixture is a bio-based polyolefin, i.e., a polyolefin prepared from a renewable feedstock instead of fossil fuels. In some embodiments, the bio-based polyolefin is derived from sugar. In some embodiments, the bio-based polyolefin is a bio-based polyethylene. Suitable bio-based PEs are available, for example, from Braskem, São Paulo, Brazil. For example, the bio-based PE may be a low density bio-based PE with a melt flow index (MFI) of 22, manufactured by Braskem.

[0082] In some embodiments, the second solid mixture includes one or more colorants. In some embodiments, the one or more colorants include natural colorants. In some embodiments, the second solid mixture includes the same colorants as the first solid mixture. In some embodiments, the second solid mixture includes a different colorant or a different concentration of colorant than the first solid mixture. In some embodiments, the second solid mixture includes bone black (e.g., about 5 wt% bone black). In some embodiments, the second solid mixture includes iron oxide (e.g., about 5 wt% or about 7 wt% iron oxide).

[0083] The bicomponent sheath-core fiber may be a concentric sheath-core bicomponent fiber or a concentric sheath-core bicomponent fiber. See FIG. 2B. In some embodiments, the eccentric shape helps impart self-crimping behavior to the fiber after processing under tension (with or without additional heating). The sheath-core bicomponent fiber may be prepared by co-extruding a solid mixture using a spinneret pack as shown in FIG. 1B and FIG. 1C. The sheath-core ratio and shape of the sheath-core fiber may vary depending on the spinneret pack used. In some embodiments, the weight ratio of the core to the sheath is about 80:20 to about 60:40 (e.g., about 80:20, about 78:22; about 76:24; about 74:26; about 72:28; about 70:30; about 68:32; about 66:34; about 64:36; about 62:38; or about 60:40).

[0084] In some embodiments, providing the first and / or second solid mixture may involve melt compounding, for example, using a single screw extruder, a twin screw extruder, or any other device capable of melting and mixing solids. In some embodiments, the melt compounded mixture may be extruded into chopped or pelletized rods (see FIG. 1A) prior to melt spinning. Alternatively, melt compounding may be performed as part of melt spinning, with the compounded melt being fed directly into a spinneret or other extrusion head suitable for extruding fibers of the desired thickness. Alternatively or additionally, feeding the first and / or second solid mixture may include grinding, for example, using a high speed mixer (e.g., at 500 rpm or higher), during drying. In some embodiments, melt spinning may be performed by melting the first and / or second solid mixture (e.g., pellets of a previously melt compounded mixture) in separate multi-zone extruders fed into the same spinneret pack, and co-extruding the melt to provide filaments of fibers having a sheath-core configuration. See FIG. 1B.

[0085] In some embodiments, step (a) includes melt compounding the first solid mixture to provide a compounded first solid mixture (e.g., using a twin screw extruder as shown in FIG. 1A). In some embodiments, the melt compounding is performed at a temperature between about 150° C. and about 180° C. (e.g., about 150° C., about 155° C., about 160° C., about 165° C., about 170° C., about 175° C., or about 180° C.). In some embodiments, step (b) includes melt compounding the second solid mixture to provide a compounded second solid mixture. In some embodiments, the melt compounding is performed using a twin screw extruder and / or at a temperature between about 140° C. and about 170° C. (e.g., about 140° C., about 145° C., about 150° C., about 155° C., about 160° C., about 165° C., or about 170° C.).

[0086] In some embodiments, the coextrusion in step (c) is carried out at a temperature of about 150° C. to about 170° C. (e.g., about 150° C., about 155° C., about 160° C., about 165° C., or about 170° C.). In some embodiments, the coextrusion is carried out at a take-up speed of about 50 to about 200 meters per minute (m / min) (e.g., about 50 m / min, about 60 m / min, about 70 m / min, about 80 m / min, about 90 m / min, about 100 m / min, about 120 m / min, about 140 m / min, about 160 m / min, about 180 m / min, or about 200 m / min). In some embodiments, the bicomponent fibers of the present invention have a linear density of about 35 to about 70 denier (g / 9000 meters).

[0087] In some embodiments, the method of the present invention may further include drawing the fibers of the present invention. In some embodiments, the method of the present invention may further include a heat treatment step (e.g., step (d)) to change the texture of the fibers of the present invention. For example, in some embodiments, the bicomponent fibers (e.g., eccentric bicomponent fibers) can be annealed at a temperature of about 60°C to about 80°C (e.g., about 60°C, about 65°C, about 70°C, about 75°C, or about 80°C) to induce self-crimping behavior of the fibers. Thus, in some embodiments, the fibers of the present invention are self-crimping. In some embodiments, the self-crimping fibers are eccentric bicomponent fibers.

[0088] In some embodiments, the presently disclosed subject matter provides a method of making PLA fibers, the method comprising (i) preparing a solid mixture comprising PLA (e.g., including APLA, CPLA, or a mixture of APLA and CPLA) and (ii) melt spinning the solid mixture, thereby preparing a PLA fiber comprising a substantially solid body / cross-section. In some embodiments, the solid mixture comprising PLA includes one or more meltable solvents (e.g., to improve fiber softness), flame retardants (to provide self-extinguishing properties), and colorants (to provide tunable colors).

[0089] In some embodiments, the method includes (i) preparing a solid mixture comprising PLA and one or more colorants, and (ii) melt spinning the solid mixture, thereby preparing a PLA fiber comprising a substantially solid body / cross-section. In some embodiments, the PLA fibers of the present invention are white, gray, red, gold / yellow, brown, black, or combinations thereof (e.g., reddish brown). Thus, in some embodiments, the subject matter of the present disclosure provides bicomponent PLA fibers. In some embodiments, the PLA fibers of the present invention are monocomponent PLA fibers. In some embodiments, the PLA fibers of the present invention can be melt spun using an apparatus such as that shown in FIG. ID.

[0090] In some embodiments, the PLA in the solid mixture containing PLA comprises or consists of APLA. In some embodiments, the PLA in the solid mixture comprises or consists of CPLA. In some embodiments, the PLA in the solid mixture comprises both APLA and CPLA. In some embodiments, the ratio of APLA to CPLA is about 1:1 to about 1:4 (e.g., about 1:1, 1:2, 1:3, or about 1:4).

[0091] As described herein above, the colorant(s) of the solid mixture containing PLA can be any suitable colorant. In some embodiments, one of the colorants may also have flame retardant properties, thus imparting flame retardant properties to the fiber. In some embodiments, at least one or all of the colorant(s) can be natural colorants, such as minerals, animal products, or plant products, for example, to enhance the sustainability of the fiber of the present invention. In some embodiments, at least one of the colorant(s) is selected from bone black, iron oxide, and mica, which can be used to provide a black or tan fiber.

[0092] For example, in some embodiments, the solid mixture includes about 0.5 weight (wt)% mica to about 10 wt% mica (e.g., about 0.5 wt%, about 1.0 wt%, about 2 wt%, about 3 wt%, about 4 wt%, about 5 wt%, about 6 wt%, about 7 wt%, about 8 wt%, about 9 wt%, or about 10 wt% mica). In some embodiments, the solid mixture includes about 2 wt% mica to about 5 wt% mica. In some embodiments, the one or more colorants include lignin. In some embodiments, the solid mixture includes up to about 20 wt% lignin (e.g., about 1 wt% to about 20 wt% lignin), for example, to impart a brown color. In some embodiments, the solid mixture includes about 10 wt% lignin.

[0093] In some embodiments, the solid mixture comprises about 10 wt% or less of iron oxide, for example to impart a black or brown color, optionally a reddish brown or golden color. In some embodiments, the solid mixture comprises about 1 wt)% to about 10 wt% of iron oxide (e.g., about 1 wt%, about 2 wt%, about 3 wt%, about 4 wt%, about 5 wt%, about 6 wt%, about 7 wt%, about 8 wt%, about 9 wt%, or about 10 wt% of iron oxide). In some embodiments, the solid mixture comprises about 5 wt% or about 7 wt% of iron oxide. In some embodiments, the solid mixture comprises a mixture of different iron oxides (e.g., two or more or more iron oxides) in a total amount of 10 wt% or less. As mentioned above, in some embodiments, the iron oxide can have a particle size of about 5 μm or less or about 200 nm or less. In some embodiments, the iron oxide has a particle size of about 200 nm.

[0094] In some embodiments, for example to improve melt and / or spinning behavior and / or improve color blending, a solids mixture can be prepared by mixing a pre-prepared resin concentrate (i.e., a compounded resin mixture or masterbatch) including PLA (CPLA, APLA, or both CPLA and APLA) and a colorant with additional pristine PLA (CPLA, APLA, or both CPLA and APLA). In some embodiments, the additional PLA is CPLA. In some embodiments, the PLA in the pre-prepared resin concentrate is APLA. In some embodiments, the colorant is iron oxide (e.g., about 5 wt % or about 7 wt % iron oxide). In some embodiments, the ratio of pre-prepared resin concentrate to pristing PLA is about 1:1 to about 1:4 (e.g., about 1:1, about 1:2, about 1:3, or about 1:4). Using additional or a majority of the CPLA allows the spinning temperature (eg, 170° C., 180° C., 190° C., 200° C. or 210° C.) or speed (eg, m / min) to be increased.

[0095] Additionally or alternatively, in some embodiments, the solid mixture can include a meltable solvent to improve melting behavior. Any suitable compound can be used as the meltable solvent, provided that the compound is solid at room temperature but melts at temperatures below those employed in melt spinning (e.g., from less than about 100°C to about 230°C). Thus, in some embodiments, the meltable solvent has a melting temperature of about 40°C to about 230°C. In some embodiments, the meltable solvent has a melting temperature of about 60°C to about 180°C or about 60°C to about 120°C. Also, suitable meltable solvents are those that can be mixed with the PLA and colorant during compounding to provide a homogenous solid mixture. In some embodiments, the meltable solvent is selected from the group including, but not limited to, dimethylsulfone (DMSO-2) with a melting temperature (Tm) of about 109°C; DMSO-2 with lithium chloride or zinc chloride (e.g., using about 5% to about 12% chloride salt); choline salts, such as choline acetate (Tm=81°C), choline isobutyrate (Tm=68°C), choline isovalerate (Tm=61°C) and choline 2-methylbutyrate (Tm=90°C); and 1-ethyl-3-methylimidazolium acetate salts with or without DMSO-2. See Elhi et al., Molecules, 2020, 25(7), 1691. In some embodiments, the meltable solvent comprises or consists of DMSO-2. In some embodiments, the solid mixture may include a 1:1 weight ratio of DMSO-2 and lignin.

[0096] Although the inclusion of a meltable solvent can improve compounding and melt spinning, it may be desirable to remove the meltable solvent after the fiber is formed. Thus, in some embodiments, the method of the present disclosure further comprises removing the meltable solvent after step (ii). For example, the meltable solvent can be removed by washing, e.g., by pulling the fiber out of the water bath under tension. In some embodiments, the water bath can be a room temperature water bath (e.g., about 18°C ​​to about 25°C). In some embodiments, the water bath can have a temperature of room temperature or above and less than 100°C. In some embodiments, the water bath is at a temperature of about 60°C to about 80°C (e.g., about 60°C, about 70°C, or about 80°C). In some embodiments, the fibers of the present invention have a residence time in the water bath of at least about 45 seconds.

[0097] In some embodiments, the method of the present invention may further comprise a heat treatment step (iii) to change the texture of the fibers of the present invention (e.g., monocomponent fibers). For example, treating the fibers of the present invention with hot water causes the fibers to shrink and increases the bulk of the fibers. In some embodiments, this effect or property may be referred to herein as "self-crimping". In some embodiments, the heat treatment step (iii) further comprises contacting the fibers with a hot bath, thereby providing a crimped fiber. In some embodiments, the hot bath has a temperature greater than about 40°C. In some embodiments, the hot bath has a temperature of about 40°C to about 85°C (e.g., about 40°C, about 45°C, about 50°C, about 55°C, about 60°C, about 65°C, about 70°C, about 75°C, about 80°C, or about 85°C). In some embodiments, the hot bath has a temperature between about 60°C and about 70°C. In some embodiments, the fibers may be in contact with or immersed in the hot bath for a time ranging from about 1 minute to about 10 minutes. In some embodiments, the time is about 5 minutes. In some embodiments, the contacting may include immersing the fiber or bundle of fibers in a hot bath. In some embodiments, the contacting may include, for example, withdrawing the fiber from the hot bath such that the total residence time of any portion of the fiber in the hot bath is about 1 to about 10 minutes. For example, the fiber can be withdrawn from the hot bath and collected on a take-up spool as part of a continuous process together with fiber spinning or as part of a separate process after spinning and pre-collecting the fiber. In some embodiments, the hot bath used in the heat treatment step (iii) may be the same water bath used to remove the meltable solvent. In some embodiments, the meltable solvent is removed in a first water bath (e.g., a water bath at room temperature) and then contacted with a hot bath (e.g., at a temperature of about 60°C to about 70°C) to induce self-crimping of the fiber.

[0098] Other additives known in the art of spin melt fiber, such as plasticizers, fillers, elongation agents, slip agents, flame retardants, antioxidants, and colorants, can be optionally included in the solid mixture. In some embodiments, the solid mixture further comprises a plasticizer. Suitable plasticizers include, but are not limited to, phthalates (e.g., dioctyl phthalate (DOP)); biodegradable citrates (e.g., acetyl triethyl citrate or tributyl citrate); glycerol; organic acids (e.g., tartaric acid or mucic acid); and mixtures thereof. In some embodiments, lignin can be added as both a plasticizer and a colorant.

[0099] In some embodiments, the solids mixture comprises a non-colorant flame retardant, optionally DOPO, ammonium polyphosphate (APP), APP, and CaCO 3 or a polymeric polyphosphate flame retardant (such as those sold under the trade name NOFIA® (FRX Polymers, Chelmsford, Massachusetts, USA; also referred to herein as "FRX"). In some embodiments, the non-colorant flame retardant is DOPO. In some embodiments, the non-colorant flame retardant is a polymeric polyphosphate flame retardant. In some embodiments, the polymeric polyphosphate flame retardant can improve the processability of the fiber. When used, the polymeric polyphosphate flame retardant can be present at 10 wt% or more of the fiber, such as about 20 wt% to about 30 wt% (i.e., about 20, 22, 24, 26, 28, or about 30 wt%) to provide the best self-extinguishing properties to the fiber.

[0100] As mentioned above, in some embodiments, the fibers of the present invention comprise or consist of low temperature crystallized melt PLA (i.e., APLA), high temperature crystallized melt PLA (i.e., CPLA), or a mixture of APLA and CPLA. In some embodiments, the fibers of the present invention comprise or consist of APLA (or an APLA resin concentrate further comprising one or more of a colorant, a meltable solvent, and a flame retardant) and CPLA (or a CPLA resin concentrate further comprising one or more of a colorant, a meltable solvent, and a flame retardant) in a weight ratio of about 1:1 to about 1:4 (e.g., about 1:1, about 1:2, about 1:3, or about 1:4). In some embodiments, the APLA resin concentrate comprises about 87 wt% APLA, about 5 wt% iron oxide, about 3 wt% DOPO, and about 5 wt% DMSO-2.

[0101] The solid mixture can be melt compounded as described herein above. In some embodiments, step (a) comprises melt extruding the solid mixture at a temperature between about 150 degrees Celsius and about 220° C. (e.g., about 150° C., about 160° C., about 170° C., about 180° C., about 190° C., about 200° C., or about 220° C.). In some embodiments, step (a) comprises melt extruding the solid mixture at a temperature between about 160° C. and about 200° C. (e.g., about 160° C., about 165° C., about 170° C., about 175° C., about 180° C., about 185° C., about 190° C., about 195° C., or about 200° C.) or between about 150° C. and about 170° C. (e.g., about 150° C., about 155° C., about 160° C., about 165° C., or about 170° C.). In some embodiments, melt spinning is performed at a take-up speed of about 50 meters per minute (m / min) to about 100 m / min (e.g., about 50 m / min, about 60 m / min, about 70 m / min, about 80 m / min, about 90 m / min, or about 100 m / min). In some embodiments, the methods of the invention can include one or more post-melt spinning steps. For example, in some embodiments, the methods of the invention further include drawing the bioplastic fibers at an elevated temperature after melt spinning.

[0102] In addition to providing methods for preparing the fibers of the present disclosure, the subject matter of the present disclosure also relates to the fibers themselves and products prepared from the fibers. For example, in some embodiments, the fibers of the present disclosure can be converted into spun yarns, used to manufacture woven or nonwoven materials, or used to prepare artificial hair or fur. In some embodiments, the fibers or materials prepared therefrom are biodegradable. In some embodiments, they are self-extinguishing. In some embodiments, the fibers are essentially instantaneous self-extinguishing (i.e., self-extinguishing in a flame test of a few seconds or less).

[0103] In some embodiments, the presently disclosed subject matter provides a bicomponent fiber comprising a core region (or "core") comprising a first component comprising PLA, and a sheath region (or "sheath") comprising a second component comprising a polyolefin (e.g., polyethylene) and at least partially surrounding the core region. In some embodiments, the first and / or second components further comprise one or more colorants. In some embodiments, the one or more colorants are selected from the group comprising minerals, animal products, and plant products. In some embodiments, the one or more colorants are selected from bone black, iron oxide, and mica. In some embodiments, one or more of the one or more colorants are also flame retardants.

[0104] In some embodiments, the first component and the second component each comprise bone black. In some embodiments, the first component and the second component each comprise about 5 wt% bone black.

[0105] In some embodiments, the first and / or second component includes a non-colorant flame retardant (i.e., a material that provides flame retardant properties but does not impart color). In some embodiments, the first and / or second component further includes an organophosphate flame retardant. In some embodiments, the flame retardant is DOPO. In some embodiments, the flame retardant is APP, APP and CaCO 3or polymeric polyphosphate (i.e., FRX). In some embodiments, the flame retardant is a polymeric polyphosphate.

[0106] In some embodiments, the fibers of the present invention include a core that includes or consists of PLA with DOPO (e.g., about 1 wt% to about 20 wt% DOPO) and bone black (e.g., about 5 wt% bone black). In some embodiments, the core includes about 10 wt% DOPO and about 5 wt% bone black. In some embodiments, the sheath includes or consists of a bio-derived polyolefin, such as bio-PE. Thus, in some embodiments, the second component includes polyethylene. In some embodiments, the polyethylene is bio-PE. In some embodiments, the second component further includes one or more colorants. In some embodiments, the second component includes bone black (e.g., about 5 wt% bone black).

[0107] In some embodiments, the biocomponent fibers are concentric sheath-core fibers. In some embodiments, the biocomponent fibers are eccentric sheath-core fibers. In some embodiments, the eccentric sheath-core fibers are self-crimping. In some embodiments, the weight ratio of the core to the sheath is about 80:20 to about 60:40 (e.g., about 80:20, 75:25, 70:30, 65:35, or about 60:40). In some embodiments, the weight ratio of the core to the sheath is about 80:20 to about 70:30. In some embodiments, the core comprises about 80 wt% of the fiber and the sheath comprises about 20 wt% of the fiber.

[0108] In some embodiments, the biocomponent fibers of the present invention have a linear density of about 35 grams per 9000 meters to about 70 grams per 9000 meters. In some embodiments, the biocomponent fibers of the present invention have a linear density of about 35 to about 70 denier.

[0109] In some embodiments, the presently disclosed subject matter provides monocomponent fibers comprising or consisting of PLA and one or more colorants (e.g., one or more colorants selected from minerals, animal products, or plant products). In some embodiments, the one or more colorants are selected from bone black, iron oxide, and mica. In some embodiments, the one or more colorants comprise or consist of lignin. In some embodiments, the PLA fibers comprise a substantially solid body / cross-section. In some embodiments, the PLA fibers are white, gray, red, gold, brown, or black. In some embodiments, the fibers of the present invention comprise or consist of low temperature crystallized melt PLA (i.e., APLA), high temperature crystallized melt PLA (i.e., CPLA), or a mixture of APLA and CPLA.

[0110] In some embodiments, the presently disclosed subject matter provides a fiber (eg, a solid monocomponent fiber) that includes PLA (eg, APLA, CPLA, or a mixture of APLA and CPLA) and a flame retardant.

[0111] In some embodiments, the presently disclosed subject matter provides fibers (e.g., solid monocomponent fibers) comprising a mixture of APLA and CPLA. In some embodiments, the APLA and CPLA are in a ratio of about 1:1 to about 1:4 (e.g., about 1:1, 1:about 1:2, about 1:3, or about 1:4). In some embodiments, the fibers of the present invention exhibit self-shrink behavior at elevated temperatures (e.g., when heated in a water bath). In some embodiments, the fibers of the present invention exhibit self-shrink behavior at temperatures of about 60°C to about 70°C (e.g., about 60°C, about 65°C, or about 70°C). In some embodiments, the fibers of the present invention exhibit self-shrink behavior when heated in a water bath to temperatures of about 60°C to about 70°C (e.g., about 60°C, about 65°C, or about 70°C). In some embodiments, the presently disclosed subject matter further comprises one or more colorants (e.g., one or more colorants selected from minerals, animal products, or plant products). In some embodiments, the one or more colorants are selected from bone black, iron oxide, and mica. In some embodiments, the one or more colorants comprise or consist of lignin. In some embodiments, the PLA fibers comprise a substantially solid body / cross-section. In some embodiments, the PLA fibers are white, gray, red, gold, brown, or black.

[0112] In some embodiments, the fibers of the present invention comprise or consist of APLA (or an APLA resin concentrate further comprising one or more of a colorant, a meltable solvent, and a flame retardant) and CPLA (or a CPLA resin concentrate further comprising one or more of a colorant, a meltable solvent, and a flame retardant) in a weight ratio of about 1:1 to about 1:4 (e.g., about 1:1, about 1:2, about 1:3, or about 1:4). In some embodiments, the APLA resin concentrate comprises about 87 wt% APLA, about 5 wt% iron oxide, about 3 wt% DOPO, and about 5 wt% DMSO-2.

[0113] In some embodiments, the presently disclosed subject matter provides monocomponent fibers comprising or consisting of PLA and lignin (e.g., about 0.4 wt% lignin to about 10 wt% lignin) and / or bone black (e.g., about 5 wt% bone black). In some embodiments, the fibers of the present invention comprise about 0.4 wt% lignin, about 3.5 wt% lignin, or about 10 wt% lignin. In some embodiments, the fibers of the present invention comprise up to about 20 wt% lignin. In some embodiments, the presently disclosed subject matter provides monocomponent fibers comprising or consisting of PLA and iron oxide (e.g., about 5 wt% to about 7 wt% of one or more iron oxides).

[0114] In some embodiments, the presently disclosed subject matter provides monocomponent fibers that include or consist of PLA and a non-colorant flame retardant (e.g., DOPO, APP, or FRX). In some embodiments, the flame retardant is DOPO or FRX. In some embodiments, the presently disclosed subject matter provides monocomponent fibers that include or consist of PLA and DOPO (e.g., about 3 wt%, about 5 wt%, about 10 wt%, about 15 wt%, or about 20 wt% DOPO). In some embodiments, the presently disclosed subject matter provides monocomponent fibers that include or consist of PLA and mica (e.g., about 2 wt% to about 5 wt% mica). In some embodiments, the presently disclosed subject matter provides monocomponent fibers that include or consist of PLA and mica (e.g., about 2 wt% to about 5 wt% mica). In some embodiments, the presently disclosed subject matter provides monocomponent fibers that include PLA (e.g., a mixture of APLA and CPLA), iron oxide, and DOPO or FRX. In some embodiments, the presently disclosed subject matter provides monocomponent fibers that further include a meltable solvent (e.g., DMSO-2). In some embodiments, the fibers (e.g., monocomponent fibers) of the present invention are self-crimping, hi some embodiments, the fibers of the present invention are self-extinguishing.

[0115] The claimed fibers (e.g., monocomponent and bicomponent fibers) of the present disclosure can be used to prepare various articles. For example, the fibers of the present disclosure can be used to prepare yarns. In some embodiments, the yarns can be used to prepare fabrics. The fabrics can be woven or nonwoven. In some embodiments, the fabrics are nonwoven. In some embodiments, the subject matter of the present disclosure provides an article of manufacture selected from the group including apparel, textiles, artificial hair, and faux fur prepared from the fibers, yarns, or fabrics as disclosed herein. In some embodiments, the article of manufacture is biodegradable and / or sustainable. In some embodiments, the article of manufacture (e.g., biodegradable or sustainable articles) of the present invention is self-extinguishing.

[0116] 1A-1E, there are systems according to the subject matter of the present disclosure that are suitable for carrying out the methods of the subject matter of the present disclosure. For example, FIG. 1A shows a twin screw extruder 104 suitable for use in melt extrusion or melt compounding of a mixture including PLA or other polymers (e.g., polyolefins). The mixture M (including a polymer, e.g., PLA, and one or more other components, such as colorants, meltable solvents, and flame retardants) can be inserted into a hopper opening 109 in a direction A1 and driven by a screw 122 through an interior space 126 of the extruder 104 to produce a filament F from an outlet 107. As shown in FIG. 1A, the twin screw extruder 104 includes a motor 121 capable of rotating and driving the twin screw 122 of the extruder 104. The extruder 104 can be configured to provide zones operable to melt, mix, and homogenize the mixture M so that the filament F can be extruded in the direction of arrow A3. In some embodiments, the melt zone MZ, mixing zone MX, and homogenization zone HG occur in sequence starting from the motor 121 toward the exit 107 of the extruder 104. After exiting the twin screw extruder 104 in the direction A3 from the exit 107, the filaments F can be collected, cut to desired lengths, or chopped into pellets for further compounding or z-melt spinning, for example on a spool.

[0117] For example, FIG. 1E shows a single screw extruder 102 suitable for use in melt extrusion or melt compounding of a mixture including PLA or other polymers (e.g., polyolefins). The mixture M (including a polymer, e.g., PLA, and one or more other components, such as colorants, meltable solvents, and flame retardants) can be inserted into a hopper opening 108 in a direction A1 and driven by a screw 120 through an interior space 124 of the extruder 102 to produce a filament F from an outlet 107. As shown in FIG. 1E, the single screw extruder 102 includes a motor 121 capable of rotating the screw 120 of the extruder 102 in a direction A4. The extruder 104 of FIG. 1A can be configured to provide zones operable to melt, mix, and homogenize the mixture M so that the filament F can be extruded in the direction of arrow A3. In some embodiments, the melting zone MZ, the mixing zone MX, and the homogenization zone HG occur in sequence starting from the motor 121 toward the outlet 107 of the extruder 102. After exiting the extruder 102 in direction A3 from outlet 107, for example on a spool, the filaments F can be collected, cut to a desired length, or chopped into pellets for further compounding or melt spinning.

[0118] Homogenization can be improved by the number of zones or passes through the extruder (e.g., the single screw extruder of FIG. 1E or the twin screw extruder of FIG. 1A). Homogenization is indicated by a smooth rod-like extrudate emerging from the extruder. For example, two to three passes through the extruder can be made for homogenization. However, in some embodiments, the pellets can be sufficiently homogenized after one pass through an extruder in the form of a Barbender compounder having four zones, although additional passes can be considered. The temperature can be gradually increased from zone to zone. For example, in some embodiments, zone 1 of an extruder in the form of a Barbender compounder can be at a temperature of 140° C., zone 2 at 160° C., and zones 3 and 4 at 180° C. (±15° C. for each zone). Similar zone temperatures can be used for melt spinning, but the zone temperatures are around +10° C. for each other. Non-limiting representative temperature ranges, mixing speeds, and other parameters are disclosed elsewhere herein.

[0119] In some embodiments, fibers (e.g., monocomponent fibers) of the disclosed subject matter can be melt spun using a system such as system 100 of FIG. 1D. System 100 includes an extruder 102, which can be, by way of non-limiting example, a single screw extruder as depicted in FIG. 1E or a twin screw extruder as depicted in FIG. 1A. Extruder 102 can further include a hopper 108 (which can optionally be a double hopper (i.e., a hopper with two openings) as depicted in FIG. 1A), and a mixture M (e.g., a mixture of PLA, meltable solvent, colorant, and flame retardant) according to the disclosed subject matter can be fed to hopper 108 in the direction of arrow A1. An airpass device 110 follows extruder 102 in line, and filaments F extruded from an outlet 107 of extruder 102 move across airpass device 110 in the direction of arrow A2. Airpass device 110 can be used to aid in solidification of the filaments, for example, in embodiments where removal of meltable solvent is not desired. An example of an extruder and air path is commercially available under the trade name Filabot® (Triex Corporation, Barrie, Vermont). The filament F is wound on a take-up roller 112. A representative example of the take-up roller 112 is also commercially available under the trade name Filabot Spooler: Precision Filament Winder. In some embodiments, the filament F is drawn across the air path 110, wound by motorized reels 114 and 116, and collected on a spool 118 on the take-up roller 112. The speed of the take-up roller is adjusted to tune the diameter of the collected filament. As the winding speed of a continuous filament increases, the filament diameter decreases.

[0120] FIG. 1B illustrates an apparatus 130 suitable for preparing the bicomponent fibers of the subject matter of the present disclosure. The apparatus 130 includes two extruders 132 and 134, which are used to extrude two different mixtures, one for the first component / compound resin concentrate corresponding to the core of the bicomponent fiber, and one for the second component / compound resin concentrate corresponding to the sheath of the bicomponent fiber. The extruders 132 and 134 can be independently single-screw or twin-screw extruders, such as those shown in FIG. 1A or 1E. Thus, in some embodiments, as shown in FIG. 1B, each of the extruders 132 and 134 can include three zones, MZ, MX, and HG, arranged in sequence such that the zone HG is located adjacent to the exit pipe 135 of the extruders 132 and 134. The flow of the molten compound resin concentrate in the exit pipe 135 can be controlled by a gear pump 136 and fed to a die pack 140 via a pipe 137.

[0121] FIG. 1C is a cross-sectional view of the die pack 140 of the apparatus 130 of FIG. 1B. As shown in FIG. 1C, the die pack 140 can include multiple openings for the entry of the molten compound resin concentrate from the pipe 137. For example, the die pack 140 can include a central opening 141 for the molten compound resin concentrate M1 corresponding to the core of the bicomponent fiber fed from one of the extruders 132 or 134 of the apparatus 130. The die pack 140 can further include two or more side / peripheral openings 142 for the entry of the molten compound resin concentrate M2 corresponding to the sheath of the bicomponent fiber fed from the other of the extruders 132 or 134. The molten compound resin concentrate M2 can then be packed around the central sheath of the molten compound resin concentrate M1 at or near the exit 143 of the die pack 140 to form the bicomponent fiber F' upon exiting the die pack 140. Continuing with FIG. 1B, the bicomponent fiber F' can be collected on a take-up device 150 (eg, a take-up spool) that rotates in a direction A4.

[0122] As discussed above, the FIG. 1D air pass can serve to aid in solidifying the fiber. Thus, in some embodiments, an air pass can be used, for example, when it is not necessarily desired to remove the meltable solvent. Alternatively, a solvent bath can be used to solidify the fiber. In some embodiments, the solvent bath can be used to remove the meltable solvent. In some embodiments, an air pass can be used to solidify the fiber, for example, to remove the meltable solvent, prior to exposing the fiber to a solvent bath.

[0123] In some embodiments, the spun or extruded fibers can be pulled through a wash bath (e.g., using rollers) for desired processing, such as removing molten solvent. These rollers can keep the fiber under tension while the molten solvent is removed, so that even if the non-solvent components (e.g., PLA or PE) soften in the bath, the fiber can retain its shape during removal. Baths and other related components for bath processing of fibers are known in the art and are commercially available.

[0124] In some embodiments, the fibers can be directed to a pelletizer to form pellets from the fibers and collect the pellets in a collector. Pelletizers suitable for preparing pellets of the fibers of the present disclosure are known in the art and are commercially available. These pellets can be used, for example, as engineering plastics. It is further noted that the pelletizer and collector can be implemented with an extruder and an air gap as yet another embodiment, as shown in FIG. 1D. Indeed, any configuration of system components is provided herein and falls within the scope of the subject matter of the present disclosure, as would be apparent to one of ordinary skill in the art upon review of this disclosure.

[0125] Additional examples of commercially available equipment that can be employed in accordance with the subject matter of the present disclosure include a Brabender compounder (CW Brabender Instruments, South Hackensack, NJ, USA) or a LIST kneading reactor (LIST Technology, Arisdorf, Switzerland) (which can be employed to pelletize hemp / meltable solvent / polyester mixtures), a Hills melt extrusion screw extruder (Hills, West Melbourne, FL, USA) (which can process pellets into fibers), and an Engel Injection Molding Machinery (Engel Machinery, York, PA, USA). In some embodiments, additive manufacturing techniques and equipment, such as those of 3D Systems, Inc. (Rock Hill, SC, USA) for 3D printers for additive manufacturing, can be employed in the methods of the subject matter of the present disclosure. EXAMPLES

[0126] The following examples are included to provide guidance to those skilled in the art for practicing representative embodiments of the subject matter of the present disclosure. Those skilled in the art will appreciate that, in light of this disclosure and the general state of the art, the following examples are intended to be illustrative only, and that numerous changes, modifications and alterations can be made without departing from the scope of the subject matter of the present disclosure.

[0127] Common methods The linear density of the fibers can be measured using ASTM D8171-18 (Standard Test Method for Determining the Density of Flax Fibers). The mechanical properties can be measured using ASTM D2256 / D2256M-21 (Standard Test Method for Tensile Properties of Yarns by the Single Strand Method), ASTM D3217 / D3217M-15 (Standard Test Method for Breaking Strength of Fibers Manufactured in a Loop or Knot Configuration) or ASTM D3822 / D3822M (Standard Test Method for Tensile Properties of Single Fibers). The pyrolysis characteristics and char yield can be determined as described in Subasinghe et al. (International Journal of Smart and Nano Materials, 7:3, 202-220 (2016)).

[0128] PLA was purchased from Natureworks, Inc. (Plymouth, MN, USA). APLA is a low crystallization melt PLA, available for example under the trade name INGEO® 6060 from Natureworks, Inc. (Plymouth, MN, USA). CPLA (high crystallization melt PLA) includes PLA such as those sold under the trade names INGEO® 6100 and INGEO® 6400 (Natureworks, Inc., Plymouth, MN, USA). The bone black (BB) used is a product sold under the trade name EBONEX® 3D (Ebonex, Inc., Melvindale, MI) with particle sizes ranging from 500 nm to 12 μm. BioPE is a low density bioPE, MFI22, from Braskem, São Paulo, Brazil. Lignin is BIOPIVA TMThe product is sold under the trade name NOFIA® HM100 (UPM Biochemicals, Leuna, Germany). FRX (i.e., polymeric polyphosphate flame retardant) is sold under the trade name NOFIA® HM100 (also called FRX1100) by FRX Polymers, Inc., Chelmsford, Massachusetts, USA, and is a transparent phosphorus-based homopolymer with a phosphorus content of 10.8 wt% and a Tg of 105°C. DOPO is product D18742S from TCI America, Inc., Portland, Oregon, USA. DMSO-2 (or MSM) was obtained from Bulk Supplements, Inc., Henderson, Nev., USA, or Ingredient Depot, Inc., Brossard, Canada.

[0129] Example 1 Biocomponent Fibers An exemplary bicomponent fiber comprising a PLA (i.e., APLA, Naturework, Plymouth, Minnesota, USA, such as sold under the trade name INGEO® 6060) / 10 wt% DOPO / 5 wt% bone black (BB) core and a bio-PE / 5 wt% BB sheath was prepared with a core / sheath ratio of 80 / 20 using a 72 filament spinneret packet. Melt compounding and melt spinning parameters were used as described in Table 1 below. An exemplary melt compounding and melt spinning apparatus is shown in Figures 1A-1C.

[0130] TIFF2025510088000002.tif72170

[0131] Mechanical testing was performed using ASTM D2256. The resulting fiber properties are shown in Table 2 below. The fiber diameters ranged from 39 microns (at a take-up speed of 200 m / min) to 84 microns. Figure 2A is a micrograph of the cross section of the bicomponent fiber melt spun at a take-up speed of 50 m / min. The fiber had a concentric core-shell morphology. See Figure 2B. Photographic images of reels of bicomponent fiber melt spun at take-up speeds of 50 m / min and 100 m / min are shown in Figure 3.

[0132] TIFF2025510088000003.tif55170

[0133] Example 2 Monocomponent Fiber Exemplary colored monocomponent PLA fibers were prepared using lignin (e.g., 10 wt%), BB (e.g., 5 wt%), and a mixture of lignin (10 wt%) and BB (5 wt%) as colorants. The PLA is the APLA described in Example 1. PLA / lignin fibers containing up to 20% lignin were prepared. To overcome lignin clumping and fiber transparency, lignin was mixed with DMSO-2 in a 1:1 ratio. This changed the melting behavior of the blend and improved the mixing of PLA and lignin. It also provided an opaque fiber with no visible clumps. An exemplary PLA / lignin / DMSO-2 solids blend is as follows: 20 g PLA, 4 g DMSO-2, and 4 g lignin.

[0134] Figure 4 shows photographic images of PLA / lignin fibers prepared with different amounts of lignin. The more lignin, the darker the fiber.

[0135] Monocomponent PLA fibers containing 5 wt%, 10 wt%, 15 wt%, or 20 wt% DOPO were prepared by melt spinning at 190°C–195°C.

[0136] Monocomponent PLA fibers using mica as a colorant were prepared with 2 wt% mica or 5 wt% mica. Photomicrographs of the cross-section of the PLA fiber prepared with 2 wt% mica are shown in Figures 5A and 5B at 100x and 300x magnification, respectively. Figure 5C is a photomicrograph of the cross-section of the PLA fiber prepared with 5 wt% mica at 200x magnification. The red scale bar in Figures 5A and 5C represents 1000 microns. The red scale bar in Figure 5B represents 100 microns. Figures 5D and 5E are photomicrographs of the outer surface of PLA fibers containing 2 wt% and 5 wt% mica, respectively. Figure 5D is at 200x magnification, and Figure 5E is at 100x magnification. For comparison, Figure 5F shows the raw PLA fiber at 400x magnification. The red scale bars in Figures 5D and 5E represent 1000 microns, and the red scale bar in Figure 5F represents 100 microns.

[0137] Example 3 Fibers containing iron oxide colorants "Masterbatches" (referred to as "trials 1-4") of melt compounded PLA with different iron oxide pigments were prepared. The batch ingredients and processing parameters are shown in Table 3 below. Each masterbatch had a ratio of APLA:iron oxide pigment:DOPO:DMSO-2 of 0.87:0.05:0.03:0.05. APLA is a low temperature crystallizing melt PLA, available, for example, under the trade name INGEO® 6060 from Natureworks, Inc. (Plymouth, Minnesota, USA). Brown iron oxide (D) was product CP-88003-1 from Just Pigments, Inc. (Tucson, Arizona, USA). The other iron oxides listed in Table 3 were obtained from TKB Trading, Inc. (Oakland, California, USA).

[0138] APLA was fed into the extruder through one feed hopper after drying at 40°C for 8 hours. The other ingredients were added to the second feed hopper. The processing temperature was 160°C. The feed ratio was 6.69. The extruded fibers were dried in an air bath.

[0139] TIFF2025510088000004.tif108170

[0140] Melt spinning of fibers was carried out using pure Trial 1, Pure Trial 4, and various blends of Trial 1, 3, 4 with CPLA (high temperature crystallizing melt PLA, such as those sold under the trade names INGEO® 6100 and INGEO® 6400 (Natureworks, Inc., Plymouth, Minnesota, USA)) as described below. The ratios given below for the various Trials and CPLA are by weight.

[0141] Trial 1 Pure: Trial 1, melt spun at 200°C, showed a very high resin melt flow rate. With an extruder speed of 1 or less and a fillerbot take-up speed of 40 m / min, ultra-fine fibers were spun. Fibers spun at 190°C also yielded high flow rates, but not as high as at 200°C. Fibers were spun with ultra-fine fibers at a fillerbot take-up speed of 100 m / min. At 180°C, the melt flow rate drops. A fillerbot take-up speed of 100 m / min resulted in ultra-fine fibers that were continuously spun without breakage. At 170°C, there was also a drop in flow rate, and a fillerbot take-up speed of 100 m / min resulted in continuously spun fibers without breakage. At 160°C or 150°C, a drop in flow rate was observed. The extruder speed was reduced to 1 and fine fibers were spun at a take-up speed of 100 m / min.

[0142] Trial 1 + CPLA 1:4 (weight ratio): At 170°C and a take-up speed of 100 m / min on the Fillabot, some separation was observed, which was believed, without being bound by any theory, to be due to the high concentration of CPLA causing a low flow rate. At 180°C or 190°C, ultrafine fibers were produced continuously without breakage during spinning. At 200°C, the flow rate was high, so the extruder speed was less than one revolution, but ultrafine fibers were produced continuously without breakage.

[0143] Additional trial 1 + CPLA fiber: Trial 1 + CPLA at a weight ratio of 1:1 gave very good dark fine fibers at 200°C and a take-up speed of 100 m / min on the fillerbot. Fibers were also produced at melt spinning temperatures of 180°C-190°C and the same take-up speeds. Trial 1 + CPLA at a weight ratio of 1:2 processed at 190°C and 100 m / min gave very good fine fibers with brighter colors compared to the master batch (Trial 1) alone. Trial 1 + CPLA at a weight ratio of 1:4 processed at 200°C and 100 m / min gave very good fine fibers with brighter colors compared to the fibers with a weight ratio of 1:2. See Figures 6A-6C. All trials with natural CPLA processed at 160°C did not produce fibers because the CPLA could not melt at that temperature. At 170°C, natural CPLA showed a decrease in flow rate.

[0144] Trial 3+CPLA 1:4: Trial 3+CPLA in a weight ratio of 1:4 was processed at 200°C with a take-up speed of 100 m / min on the fillerbot, providing continuous fiber delivery without breakage. The extruder speed was 1 and ultra-fine fibers were obtained, see Figure 7B. At 190°C or 180°C, ultra-fine fibers were produced using the same parameters as at 200°C. At 170°C, the results were similar to 180°C, but with thicker fibers, see Figure 7A.

[0145] Trial 4 Pure: At 200°C, Trial 4 could be spun into fiber. The flow rate was not as high as Trial 1 (Brown). At an extruder speed of 1 and a take-up speed of 40 m / min, fine fibers were obtained. At 190°C, the flow rate decreased, but the fiber strength was improved and the fiber was less brittle than at 200°C. Spinning was possible at about 100 m / min, but fiber take-up speeds of 50 m / min to 70 m / min were optimal. At 180°C, a take-up speed of 45 m / min and an extruder speed of 1 spun fine fibers. At 170°C, fine complete fibers were obtained at take-up speeds up to 100 m / min. At 160°C, the flow rate decreased compared to 170°C to 200°C, but fibers were completely spun at a take-up speed of 100 m / min. At 150°C, Trial 4 flowed fast but was not spinnable.

[0146] Trial 4+CPLA: Trial 4+CPLA at a weight ratio of 1:2 at temperatures of 150°C or 160°C failed to provide good fibers because CPLA did not melt at those lower temperatures. At 170°C, this mixture provided fine fibers continuously at a take-up speed of 100 m / min. At 180°C, fine fibers were spun at a take-up speed of 100 m / min and an extruder speed of 1. At 190°C, the flow rate was increased. Fine fibers were spun at a take-up speed of 100 m / min and an extruder speed of 1. At 200°C, the flow rate was increased. Fine fibers were still spun at a take-up speed of 100 m / min. Ultra-fine fibers were provided continuously without breakage and the extruder speed was less than 1. See Figure 8.

[0147] Trial 4+CPLA at 200°C and 1:1 weight ratio had a high flow rate. Spinning was performed at a take-up speed of 100 m / min and an extruder RPM of 1, providing ultra-fine fibers continuously without breakage. At 190°C and 180°C, spinning was similar to that at 200°C, only with a reduced flow rate. At 170°C, the flow rate was reduced, but fine fibers with good strength were spun at a take-up speed of 100 m / min.

[0148] At 200°C, Trial 4+CPLA in a weight ratio of 1:4 was continuously spun at a take-up speed of 100 m / min and an extruder RPM of less than 1. At 190°C and 180°C, the same spinning was achieved as at 200°C with a take-up speed of 100 m / min and an extruder RPM of 1. At 170°C, an increase in viscosity was observed, but spinning was successful and provided strong fibers.

[0149] Example 4 Polymer-based flame retardant fiber Table 4 lists an APLA compounded resin concentrate (INGEO® 6060) and a CPLA compounded resin concentrate containing about 20 wt% to about 30 wt% of a polymeric polyphosphate flame retardant, referred to herein as "FRX" (or FRX 1100, sold by FRX Polymers, Inc., Chelmsford, Massachusetts, USA under the trade name NOFIA® HM100). Fibers melt spun from each of these concentrates exhibited flame retardant properties.

[0150] TIFF2025510088000005.tif71170

[0151] One of the CPLA / FRX samples was tested for self-crimping by exposure to a hot bath. No self-crimping was observed up to a temperature of 85° C., indicating that the FRX increased the melting temperature of the sample compared to the APLA sample, and also that the use of CPLA in place of APLA increased the melting temperature.

[0152] Fiber preparation using Filabot for samples containing 10 wt% FRX FR: Two blends were prepared using 2g FRX, 1.4g black oxide, and 1g DMSO-2 with 15.6g APLA or 15.6g CPLA. The APLA sample did not spin well. There appeared to be issues with stretching the material due to its brittle nature. The material showed inconsistent flame retardancy. Similarly, the CPLA sample did not spin well and showed inconsistent flame retardancy. However, the use of FRX appears to have made the fiber stronger and less brittle when it contained a higher amount of pigment (e.g., 7% colorant). Thus, the use of FRX is useful in providing fibers with a richer color (e.g., in both concentrates) and when blending concentrates with natural polymers. This effect increases with increasing amounts of FRX.

[0153] Example 5 Filabot spinning using PE Spinning trials were carried out at 190 °C and fillerbot speeds of 40, 50, and 60 m / min using the following ratios of polyethylene masterbatch (i.e., PE-black; PE melt-compounded with 5 wt % black oxide and 2.5% DOPO) and natural polyethylene (natural PE). 1. PE-Black:Natural PE 1:0 2. PE-Black:Natural PE (1:1)

[0154] Good fibers were spun at 180°C and a filabot speed of 50 m / min for both 1 and 2, indicating that the color of the PE resin concentrates could be adjusted as needed to provide color variations.

[0155] Example 6 1B color PLA fiber Trials were conducted to obtain 1B color from various PLA masterbatches (pre-melt compounded PLA / iron oxide resin concentrate containing 5 wt% DMSO-2, 3 wt% DOPO, and 5 wt% iron oxide) and natural CPLA using a Filabot machine for melt spinning.

[0156] In the first trial, the following mixture was melt spun: Natural CPLA=60g CPLA black masterbatch (i.e., CPLA 5wt% black oxide) = 35g Brown oxide APLA master batch (APLA containing 5wt% brown oxide) = 5g

[0157] This mixture was successfully spun at 190°C. The fibres appeared darker at a speed of 40-50 m / min and browner at 80 m / min. The highest amount of 1B was obtained at the same temperature at a speed of 60-70 m / min.

[0158] In the second trial, brown fibers were obtained using the following mixture: Natural CPLA=50g Black oxide APLA masterbatch (APLA containing 5 wt% black oxide) = 25g Brown oxide (D) master batch (APLA containing 5 wt% of brown oxide (D)) = 25 g The fibers were spun at 190°C at a Filabot speed of 60-70 m / min, with 70 m / min giving the best color.

[0159] These trials suggest that the spinning speed can be adjusted to further tune the final fiber color.

[0160] Example 7 High Temperature Treatment The self-crimping behavior of APLA monofilament fibers was tested by exposing the fiber bundles to a hot bath at 30°C to 40°C. Increasing the temperature of the water bath from 45°C to 47°C resulted in a new texture when the fiber bundles were exposed to the water bath for 5 minutes. To accommodate the use of a hotter bath, mixed PLA fibers were prepared.

[0161] Filabot spinning with mixed PLA at extruder speed 1, filabot speed 60 m / min and temperature 190° C. After spinning, the fibers were exposed to a hot bath at the indicated temperature for 5 minutes to evaluate the self-crimp behavior. 1. APLA+CPLA 1:1: No crimp at 40°C (similar to fibers containing only APLA), crimp appears at 50°C to 60°C. 2. APLA+CPLA 2:1: Same as the APLA:CPLA 1:1 sample, but the 1:1 sample had greater crimp. 3.APLA+CPLA 1:2: No shrinkage was observed at 40℃~50℃, but very good shrinkage was observed at 60℃.

[0162] Individual PLA and FRX (APLA or CPLA containing 20 wt% FRX) were filler-bot spun at an extruder speed of 0.5 m / min to 1 m / min, a filler-bot speed of 60 m / min, and a temperature of 210° C. After spinning, the fibers were contacted with a hot bath at the indicated temperatures to evaluate their self-crimp behavior. 1.APLA+FRX: Due to high flow rate, extruder RPM is 0.5. No shrinkage at 40~50℃, slight shrinkage at 60℃, very good shrinkage at 70℃. 2.CPLA+FRX: Compared to the APLA+FRX sample, the flow rate is lower, so the extruder speed is 1. No crimp at 40℃ to 50℃, some crimp at 60℃ (not as much as APLA+FRX), and very good crimp at 70℃.

[0163] Effect of high temperature treatment on particle separation: The extruder speed was 1-2, the fillerbot speed was 60m / min, and the temperature was 190℃-200℃. Two kinds of PLA containing black oxide were fillerbot-spun. 1.APLA + black oxide (7wt%): did not work at either 190℃ or 200℃. 2. CPLA + Black Oxide (7 wt%): Did not work at 190°C, but worked at 200°C at filabot speed 2 with some unevenness indicating blending issues.

[0164] This was to observe the blend properties of the polymer and BO, and there was a problem with the blending: none of the samples were miscible.

[0165] The two types of PLA, black oxide (BO; 7 wt%), and DMSO-2 (2 wt%) were spun into fillerbot fibers at an extruder speed of 0.5-1, a fillerbot speed of 60 m / min, and a temperature of 210 °C. 1.APLA+BO(7wt%)+DMSO-2(2wt%). Due to low flow rate, extruder speed was 2, fillerbot speed was 30m / min, and temperature was 190℃. The blend was good. There was no crimp at 4℃, and crimp appeared at 50℃. 2.CPLA+BO(7wt%)+DMSO-2(2wt%): Extruder speed 1, fillerbot speed 60m / min, temperature 190~200℃, it works perfectly, good blending. As the temperature increases, the fibers become finer. No crimp at 40℃, crimp appears at 50℃, best crimp appears at 60℃.

[0166] The addition of DMSO-2 improved the blends of PLA and BO, with the CPLA sample exhibiting better properties compared to the APLA sample. Overall, no particle segregation was observed in any of the samples.

[0167] FRX Effects: The extruder speed was 1, the fillerbot speed was 60m / min, and the temperature was 210℃. Two kinds of PLA including black oxide and FRX were spun by fillerbot. 1.APLA+Black Oxide(7wt%)+FRX(20wt%): Does not work at 190℃ due to low flow rate, but works well at 200℃ to 210℃. Some unevenness is observed. No crimp at 50℃ to 60℃, very good crimp at 70℃. 2. CPLA + Black Oxide (7wt%) + FRX (20wt%): Did not work at 190℃ due to low flow rate, but works well at 205℃~210℃. No shrinkage at 50℃~60℃, good shrinkage at 70℃~75℃.

[0168] The inclusion of FRX increases the Tm of PLA, allowing it to be spun at temperatures closer to the typical commercial PLA spinning temperatures, for example, from about 200° C. to about 240° C. The fibers were self-extinguishing without melt dripping. The inclusion of FRX in this way allows for temperature tuning, including tuning the temperature for texture, providing additional flexibility in product end use and manufacturing.

[0169] Example 8 Multifilament yarns from melt-spun monocomponent filaments. Exemplary monocomponent filaments were prepared by melt spinning APLA-black masterbatch (ALPA-blk), CPLA, and FRX in a 2:2:1 ratio. The APLA-black masterbatch contained APLA, 5 wt% black oxide, 3 wt% DOPO, and 5 wt% DMSO-2, and was compounded in a twin screw extruder. The melt compounding and melt spinning parameters were as described in Table 5 below. Exemplary melt compounding and melt spinning equipment are shown in Figures 1A-1C.

[0170] TIFF2025510088000006.tif95170

[0171] Tensile mechanical testing of the resulting 144 filament yarn was performed using ASTM D2256 / D2256M-21 (i.e., 70°F (21.1°C), 65% relative humidity (RH), 12 inches per minute crosshead speed, 10 inch gauge length). Mechanical properties of the spun yarn are shown in Table 6.

[0172] TIFF2025510088000007.tif65170

[0173] Therefore, melt spinning of pigmented PLA can be carried out on a pilot scale to obtain yarns of desired colors.

[0174] All references cited in this disclosure, including, but not limited to, all patents, patent applications and their publications, scientific journal articles, and database entries (e.g., the GENBANK database entry and all annotations available therein), to the extent that they supplement, explain, provide background to, or teach the methodology, techniques, and / or compositions employed herein, are incorporated herein by reference in their entirety.

[0175] Although the systems and methods of the present invention have been described herein with reference to certain aspects, features, and exemplary embodiments, it will be understood that the utility of the subject matter is not so limited, but rather extends to and encompasses numerous other variations, modifications, and alternative embodiments as would be suggested to one of ordinary skill in the art of the subject matter based on the disclosure herein. Various combinations and subcombinations of the structures and features described herein are contemplated and will be apparent to those of ordinary skill in the art having knowledge of this disclosure. Any of the various features and elements as disclosed herein may be combined with one or more of the other disclosed features and elements, unless otherwise indicated herein to the contrary. Accordingly, it is intended that the subject matter claimed hereinafter be broadly construed, as including within its scope all such variations, modifications, and alternative embodiments, and as including equivalents of the claims.

Claims

1. 1. A method for preparing a fiber, comprising the steps of: (a) preparing a first solid mixture comprising polylactic acid (PLA); (b) preparing a second solid mixture comprising a polyolefin; and (c) co-extruding the first solid mixture and the second solid mixture to prepare a bicomponent sheath-core fiber comprising a core comprising the first solid mixture and a sheath comprising the second solid mixture. The method includes:

2. 10. The method of claim 1, wherein the first solid mixture and / or the second solid mixture further comprises one or more colorants, optionally one or more of the one or more colorants being a flame retardant.

3. 3. The method of claim 2, wherein at least one of the one or more colorants is selected from the group consisting of minerals, animal products, and plant products.

4. 4. The method of claim 3, wherein at least one of the one or more colorants is selected from the group consisting of bone black, mica, and iron oxide.

5. 5. The method of claim 4, wherein both the first solids mixture and the second solids mixture include bone black, optionally at about 5 wt.% bone black.

6. 6. The method of any one of claims 1 to 5, wherein the first solid mixture and / or the second solid mixture further comprises a non-colorant flame retardant, optionally an organic phosphate, and further optionally, the flame retardant is 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) or a polymeric polyphosphate.

7. 7. The method of claim 6, wherein the first solid mixture comprises PLA comprising about 1 weight percent (wt%) to about 20 wt% DOPO and about 5 wt% bone black, optionally about 10 wt% DOPO and about 5 wt% bone black, optionally wherein the bone black has a particle size of about 200 nm to about 5 μm.

8. 8. The method of any one of claims 1 to 7, wherein the second solid mixture comprises a bio-based polyolefin, optionally a bio-based polyethylene.

9. 8. The method of any one of claims 1 to 7, wherein the second solids mixture comprises polyethylene, optionally bio-based polyethylene, and one or more colorants, optionally about 5 wt% bone black.

10. 10. The method of any one of claims 1 to 9, wherein the bicomponent fibers are concentric or eccentric sheath-core fibers, optionally the bicomponent fibers are eccentric sheath-core fibers, further comprising heating the bicomponent fibers to a temperature of about 60°C to about 80°C.

11. 11. The method of any one of claims 1 to 10, wherein the weight ratio of core to sheath is from about 80:20 to about 60:

40.

12. 12. The method of any one of claims 1 to 11, wherein step (a) comprises melt compounding the first solid mixture to provide a compounded first solid mixture, optionally wherein the melt compounding is performed using a twin screw extruder and / or wherein the melt compounding is performed at a temperature between about 150°C and about 180°C.

13. 13. The method of any one of claims 1 to 12, wherein step (b) comprises melt compounding the second solid mixture to provide a compounded second solid mixture, optionally wherein the melt compounding is carried out using a twin screw extruder and / or at a temperature of about 140°C and about 170°C.

14. 14. The method of any one of claims 1 to 13, wherein the coextrusion is carried out at a temperature of about 150°C to about 170°C and / or a take-up speed of about 50 to about 200 meters per minute (m / min).

15. A fiber prepared according to the method of any one of claims 1 to 14.

16. A bicomponent fiber, a core region comprising a first component comprising polylactic acid (PLA); a sheath region at least partially surrounding the core region, the sheath region comprising a second component comprising a polyolefin.

17. 17. The bicomponent fiber of claim 16, wherein the PLA of the first component comprises APLA, CPLA, or a mixture of APLA and CPLA.

18. 20. The bicomponent fiber of claim 17, wherein the first component PLA comprises a mixture of APLA and CPLA in a ratio of about 1:1 to about 1:4; optionally, about 1:1, about 1:2, about 1:3, or about 1:

4.

19. 19. The bicomponent fiber of any one of claims 16 to 18, wherein the first component and / or the second component further comprise one or more colorants, optionally one or more of the one or more colorants are flame retardants.

20. 20. The bicomponent fiber of claim 19, wherein at least one of the one or more colorants is selected from the group consisting of minerals, animal products, and plant products.

21. 21. The bicomponent fiber of claim 20, wherein at least one of the one or more colorants is selected from the group consisting of bone black, mica, and iron oxide.

22. 22. The bicomponent fiber of claim 21, wherein both the first component and the second component contain bone black, optionally at about 5 wt.% bone black.

23. 23. The bicomponent fiber of any one of claims 16 to 22, wherein the first component and / or the second component further comprises a non-colorant flame retardant, optionally an organic phosphate, and further optionally, the flame retardant is 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) or a polymeric polyphosphate.

24. 24. The bicomponent fiber of claim 23, wherein the first component comprises PLA comprising about 1 weight percent (wt%) to about 20 wt% DOPO and about 5 wt% bone black, optionally about 10 wt% DOPO and about 5 wt% bone black.

25. 25. The bicomponent fiber of any one of claims 16 to 24, wherein the second component comprises a bio-based polyolefin, optionally a bio-based polyethylene.

26. 25. The bicomponent fiber of any one of claims 16 to 24, wherein the second component comprises polyethylene, optionally bio-based polyethylene, and one or more colorants, optionally about 5 wt% bone black.

27. 27. The bicomponent fiber of any one of claims 16 to 26, wherein the bicomponent fiber is a concentric or eccentric sheath-core fiber, optionally wherein the bicomponent fiber is a self-crimping eccentric sheath-core fiber.

28. 28. The bicomponent fiber of any one of claims 16 to 27, wherein the weight ratio of core to sheath is from about 80:20 to about 60:

40.

29. 29. The bicomponent fiber of any one of claims 16 to 28, wherein the bicomponent fiber has a linear density of from about 35 grams per 9000 meters to about 70 grams per 9000 meters.

30. 1. A method for preparing a fiber, comprising the steps of: (i) preparing a solid mixture comprising polylactic acid (PLA) and one or more colorants; and (ii) melt-spinning said solid mixture, thereby preparing PLA fibers. wherein the PLA fibers have a substantially solid cross-section.

31. 31. The method of claim 30, wherein the PLA is a mixture of low temperature crystallized melt PLA (APLA) and high temperature crystallized melt PLA (CPLA), optionally with a ratio of APLA to CPLA of about 1:1 to about 1:

4.

32. 32. The method of claim 30 or 31, wherein one or more of the one or more colorants is a flame retardant.

33. 32. The method of claim 30 or 31, wherein at least one of the one or more colorants is selected from the group consisting of minerals, animal products, and plant products.

34. 34. The method of claim 33, wherein at least one of the one or more colorants is selected from the group consisting of bone black, mica, and iron oxide.

35. 35. The method of claim 34, wherein the solids mixture comprises from about 0.5 weight (wt) % mica to about 10 wt % mica, optionally from about 2 wt % mica to about 5 wt % mica.

36. 36. The method of any one of claims 30 to 35, wherein the solid mixture further comprises up to about 20 wt.% lignin, optionally wherein the solid mixture comprises about 10 wt.% lignin.

37. 37. The method of any one of claims 30 to 36, wherein the solid mixture further comprises a meltable solvent, optionally dimethylsulfone (DMSO-2), and further optionally, the meltable solvent is present in about a 1:1 weight ratio with the lignin.

38. 38. The method of claim 37, further comprising removing the meltable solvent after step (ii), optionally with a water bath.

39. 39. The method of any one of claims 30 to 38, further comprising contacting the fiber with a warm bath, thereby providing a crimped fiber.

40. 40. The method of any one of claims 30 to 39, wherein the solids mixture further comprises a non-colorant flame retardant, optionally DOPO or polymeric polyphosphate.

41. 41. The method of any one of claims 30 to 40, wherein melt spinning comprises melt spinning a monocomponent fiber.

42. 42. The method of any one of claims 30 to 41, wherein step (a) comprises melt extruding the solid mixture at a temperature between about 150 degrees Celsius (°C) and about 170°C.

43. 43. The method of any one of claims 30 to 42, wherein the melt spinning is carried out using a take-up speed of about 50 meters per minute (m / min) to about 100 m / min.

44. 44. A fiber prepared according to the method of any one of claims 30 to 43.

45. A solid, monocomponent fiber comprising polylactic acid (PLA) and one or more colorants.

46. A solid, monocomponent fiber comprising polylactic acid (PLA), the PLA comprising a mixture of low temperature crystallized melt PLA (APLA) and high temperature crystallized melt PLA (CPLA).

47. 47. The solid, monocomponent fiber of claim 46, wherein the ratio of APLA to CPLA is from about 1:1 to about 1:4, about 1:2, about 1:2, about 1:3, or about 1:

4.

48. 48. The solid, monocomponent fiber of claim 46 or 47, which exhibits autogenous crimping at a temperature of about 60°C to about 70°C.

49. 49. The solid, monocomponent fiber of any one of claims 46 to 48, further comprising a colorant.

50. 50. The fiber of claim 45 or 49, wherein at least one of the one or more coloring agents is selected from the group consisting of minerals, animal products, and plant products.

51. 51. The fiber of claim 50, wherein the fiber comprises from about 0.5 wt% mica to about 10 wt% mica, optionally from about 2 wt% to about 5 wt% mica.

52. 51. The fiber of claim 50, wherein the fiber comprises up to about 20 wt% lignin.

53. 53. The fiber of any one of claims 45 to 52, wherein the fiber further comprises a non-colorant flame retardant, optionally DOPO or polymeric polyphosphate.

54. 54. A spun yarn prepared from the bicomponent fiber of any one of claims 15 to 29 or the fiber of any one of claims 45 to 53.

55. 55. A fabric prepared from the spun yarn of claim 54, optionally a nonwoven fabric.

56. 54. An article of manufacture comprising the bicomponent fiber of any one of claims 15 to 29, the fiber of any one of claims 45 to 53, the spun yarn of claim 54, or the fabric of claim 55, optionally being an article of clothing, a textile, artificial hair or fake fur.

57. 57. The article of manufacture of claim 56, which is biodegradable and / or sustainable.

58. 58. The article of manufacture of claim 56 or 57, which is self-extinguishing.

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