Melt spinning of blended polylactic acid fibers

Abstract

Methods of preparing mono- and multi-component fibers comprising polylactic acid (PLA) are described. Exemplary fibers include co-extruded bicomponent core-sheath fibers where the core includes PLA and the sheath includes polyolefin. The fibers can include various colorants, such as colorants derived from natural materials and/or flame retardants. Also described are fibers comprising PLA, e.g., the fibers prepared by the disclosed methods, and related articles, such as textiles, clothing, synthetic fibers, and faux fur.

1 . A method of preparing a fiber, wherein the method comprises:
 (a) preparing a first mixture of solids comprising polylactic acid (PLA);   (b) preparing a second mixture of solids comprising a polyolefin; and   (c) co-extruding said first mixture of solids and said second mixture of solids to prepare a bicomponent core-sheath fiber comprising a core comprising said first mixture of solids and a sheath comprising said second mixture of solids.   
     
     
         2 . The method of  claim 1 , wherein the first mixture of solids and/or the second mixture of solids further comprises one or more coloring agents, optionally wherein one or more of the one or more coloring agents is a flame retardant. 
     
     
         3 . The method of  claim 2 , wherein at least one of the one or more coloring agents is selected from the group consisting of a mineral, an animal product, and a plant product. 
     
     
         4 . The method of  claim 3 , wherein at least one of the one or more coloring agents is selected from the group consisting of bone black, mica, and an iron oxide. 
     
     
         5 . The method of  claim 4 , wherein the first mixture of solids and the second mixture of solids both comprise bone black, optionally about 5 wt % bone black. 
     
     
         6 . The method of  claim 1 , wherein the first mixture of solids and/or the second mixture of solids further comprises a non-coloring agent flame retardant, optionally an organophosphate, further optionally wherein the flame retardant is 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) or a polymeric polyphosphate. 
     
     
         7 . The method of  claim 6 , wherein the first mixture of solids comprises PLA with about 1 weight % (wt %) to about 20 wt % DOPO and about 5 wt % bone black, optionally PLA with 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 . The method of  claim 1 , wherein the second mixture of solids comprises a bio-derived polyolefin, optionally a bio-derived polyethylene. 
     
     
         9 . The method of  claim 1 , wherein the second mixture of solids comprises polyethylene, optionally a bio-derived polyethylene, and one or more coloring agents, optionally about 5 wt % bone black. 
     
     
         10 . The method of  claim 1 , wherein the bicomponent fiber is a concentric or eccentric core-sheath fiber, optionally wherein the bicomponent fiber is an eccentric core-sheath fiber and the method further comprises heating the fiber to a temperature of about 60° C. to about 80° C. 
     
     
         11 . The method of  claim 1 , wherein the weight ratio of core to sheath is about 80:20 to about 60:40. 
     
     
         12 . The method of  claim 1 , wherein step (a) comprises melt compounding the first mixture of solids to provide a compounded first mixture of solids, optionally wherein the melt compounding is performed using a twin-screw extruder and/or wherein the melt compounding is performed at a temperature of about 150° C. and about 180° C. 
     
     
         13 . The method of  claim 1 , wherein step (b) comprises melt compounding the second mixture of solids to provide a compounded second mixture of solids, optionally wherein the melt compounding is performed using a twin-screw extruder and/or at a temperature of about 140° C. and about 170° C. 
     
     
         14 . The method of  claim 1 , wherein the co-extruding is performed at a temperature of about 150° C. to about 170° C. and/or at a take-up speed of about 50 to about 200 meters per minute (m/min). 
     
     
         15 . A fiber prepared according to the method of  claim 1 . 
     
     
         16 . A bicomponent fiber comprising:
 a core region comprising a first component comprising polylactic acid (PLA); and   a sheath region at least partially surrounding the core region comprising a second component comprising a polyolefin.   
     
     
         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 . The bicomponent fiber of  claim 17 , wherein 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. 
     
     
         19 . The bicomponent fiber of  claim 16 , wherein the first component and/or the second component further comprises one or more coloring agents, optionally wherein one or more of the one or more coloring agents is a flame retardant. 
     
     
         20 . The bicomponent fiber of  claim 19 , wherein at least one of the one or more coloring agents is selected from the group consisting of a mineral, an animal product, and a plant product. 
     
     
         21 . The bicomponent fiber of  claim 20 , wherein at least one of the one or more coloring agents is selected from the group consisting of bone black, mica, and an iron oxide. 
     
     
         22 . The bicomponent fiber of  claim 21 , wherein the first component and the second component both comprise bone black, optionally about 5 wt % bone black. 
     
     
         23 . The bicomponent fiber of  claim 16 , wherein the first component and/or the second component further comprise a non-coloring agent flame retardant, optionally an organophosphate, further optionally wherein the flame retardant is 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) or a polymeric polyphosphate. 
     
     
         24 . The bicomponent fiber of  claim 23 , wherein the first component comprises PLA with about 1 weight % (wt %) to about 20 wt % DOPO and about 5 wt % bone black, optionally PLA with about 10 wt % DOPO and about 5 wt % bone black. 
     
     
         25 . The bicomponent fiber of  claim 16 , wherein the second component comprises a bio-derived polyolefin, optionally a bio-derived polyethylene. 
     
     
         26 . The bicomponent fiber of  claim 16 , wherein the second component comprises polyethylene, optionally a bio-derived polyethylene, and one or more coloring agents, optionally about 5 wt % bone black. 
     
     
         27 . The bicomponent fiber of  claim 16 , wherein the bicomponent fiber is a concentric or eccentric core-sheath fiber, optionally wherein the bicomponent fiber is an eccentric core-sheath fiber that is self-crimping. 
     
     
         28 . The bicomponent fiber of  claim 16 , wherein the weight ratio of core to sheath is about 80:20 to about 60:40. 
     
     
         29 . The bicomponent fiber of  claim 16 , wherein the bicomponent fiber has a linear density of about 35 grams per 9000 meters to about 70 grams per 9000 meters. 
     
     
         30 . A method of preparing a fiber, wherein the method comprises:
 (i) preparing a mixture of solids comprising polylactic acid (PLA) and one or more coloring agents; and   (ii) melt-spinning said mixture of solids, thereby preparing a PLA fiber, wherein said PLA fiber has a substantially solid cross-section.   
     
     
         31 . The method of  claim 30 , wherein the PLA is a mixture of low crystalline melting temperature PLA (APLA) and high crystalline melting temperature PLA (CPLA), optionally wherein the ratio of APLA to CPLA is about 1:1 to about 1:4. 
     
     
         32 . The method of  claim 30 , wherein one or more of the one or more coloring agents is a flame retardant. 
     
     
         33 . The method of  claim 30 , wherein at least one of the one or more coloring agents is selected from the group consisting of a mineral, an animal product, and a plant product. 
     
     
         34 . The method of  claim 33 , wherein at least one of the one or more coloring agents is selected from the group consisting of bone black, mica, and an iron oxide. 
     
     
         35 . The method of  claim 34 , wherein the mixture of solids comprises about 0.5 weight (wt) % mica to about 10 wt % mica, optionally about 2 wt % mica to about 5 wt % mica. 
     
     
         36 . The method of  claim 30 , wherein the mixture of solids further comprises up to about 20 wt % lignin, optionally wherein the mixture of solids comprises about 10 wt % lignin. 
     
     
         37 . The method of  claim 30 , wherein the mixture of solids further comprises a meltable solvent, optionally dimethyl sulfone (DMSO-2), further optionally wherein said meltable solvent is present in about a 1:1 weight ratio with lignin. 
     
     
         38 . The method of  claim 37 , wherein the method further comprises removing the meltable solvent after step (ii), optionally using a water bath. 
     
     
         39 . The method of  claim 30 , wherein the method further comprises contacting the fiber with a hot water bath, thereby providing a crimped fiber. 
     
     
         40 . The method of  claim 30 , wherein the mixture of solids further comprises a non-coloring agent flame retardant, optionally DOPO or a polymeric polyphosphate. 
     
     
         41 . The method of  claim 30 , wherein the melt-spinning comprises melt-spinning a monocomponent fiber. 
     
     
         42 . The method of  claim 30 , wherein step (a) comprises melt-extruding the mixture of solids at a temperature between about 150 degrees Celsius (° C.) and about 170° C. 
     
     
         43 . The method of  claim 30 , wherein the melt-spinning is performed using a take-up speed of about 50 meters per minute (m/min) to about 100 m/min. 
     
     
         44 . A fiber prepared according to the method of  claim 30 . 
     
     
         45 . A solid, monocomponent fiber comprising a polylactic acid (PLA) and one or more coloring agents. 
     
     
         46 . A solid, monocomponent fiber comprising a polylactic acid (PLA), wherein the PLA comprises a mixture of low crystalline melting temperature PLA (APLA) and high crystalline melting temperature PLA (CPLA). 
     
     
         47 . The solid, monocomponent fiber of  claim 46 , wherein 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. 
     
     
         48 . The solid, monocomponent fiber of  claim 46 , wherein the fiber exhibits self-crimping at a temperature of about 60° C. to about 70° C. 
     
     
         49 . The solid, monocomponent fiber of  claim 46 , further comprising a coloring agent. 
     
     
         50 . The fiber of  claim 45 , wherein at least one of the one or more coloring agents is selected from the group consisting of a mineral, an animal product, and a plant product. 
     
     
         51 . The fiber of  claim 50 , wherein fiber comprises about 0.5 wt % mica to about 10 wt % mica, optionally about 2 wt % to about 5 wt % mica. 
     
     
         52 . The fiber of  claim 50 , wherein the fiber comprises up to about 20 wt % lignin. 
     
     
         53 . The fiber of  claim 45 , wherein the fiber further comprises a non-coloring agent flame retardant, optionally DOPO or a polymeric polyphosphate. 
     
     
         54 . A yarn prepared from the bicomponent fiber of  claim 15 . 
     
     
         55 . A fabric prepared from the yarn of  claim 54 , optionally wherein the fabric is a non-woven fabric. 
     
     
         56 . An article of manufacture comprising the bicomponent fiber of  claim 15 , optionally wherein the article of manufacture is an article of clothing, a textile, synthetic hair, or faux fur. 
     
     
         57 . The article of manufacture of  claim 56 , wherein the article of manufacture is biodegradable and/or sustainable. 
     
     
         58 . The article of manufacture of  claim 56 , wherein the article of manufacture is self-extinguishing. 
     
     
         59 . A yarn prepared from the fiber of  claim 45 . 
     
     
         60 . A fabric prepared from the yarn of  claim 59 , optionally wherein the fabric is a non-woven fabric. 
     
     
         61 . An article of manufacture comprising the fiber of  claim 45 , optionally wherein the article of manufacture is an article of clothing, a textile, synthetic hair, or faux fur. 
     
     
         62 . An article of manufacture comprising the yarn of  claim 54 , optionally wherein the article of manufacture is an article of clothing, a textile, synthetic hair, or faux fur. 
     
     
         63 . An article of manufacture comprising the fabric of  claim 55 , optionally wherein the article of manufacture is an article of clothing, a textile, synthetic hair, or faux fur. 
     
     
         64 . An article of manufacture comprising the yarn of  claim 59 , optionally wherein the article of manufacture is an article of clothing, a textile, synthetic hair, or faux fur. 
     
     
         65 . An article of manufacture comprising the fabric of  claim 60 , optionally wherein the article of manufacture is an article of clothing, a textile, synthetic hair, or faux fur.