Classifications

• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
  • D01F2/00—Monocomponent artificial filaments or the like of cellulose or cellulose derivatives; Manufacture thereof
  • D01F2/24—Monocomponent artificial filaments or the like of cellulose or cellulose derivatives; Manufacture thereof from cellulose derivatives
  • D01F2/28—Monocomponent artificial filaments or the like of cellulose or cellulose derivatives; Manufacture thereof from cellulose derivatives from organic cellulose esters or ethers, e.g. cellulose acetate
  • D01F2/30—Monocomponent artificial filaments or the like of cellulose or cellulose derivatives; Manufacture thereof from cellulose derivatives from organic cellulose esters or ethers, e.g. cellulose acetate by the dry spinning process
• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
  • D01D1/00—Treatment of filament-forming or like material
  • D01D1/02—Preparation of spinning solutions
• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
  • D01D5/00—Formation of filaments, threads, or the like
  • D01D5/04—Dry spinning methods

Definitions

• the disclosure also provides a cellulose ester fiber formed according to one or both of the above processes.
• the present application generally relates to a dry spinning process for preparing a cellulose diacetate (“CDA”) fiber and/or a cellulose triacetate (“CTA”) fiber that exhibits low color formation.
• CDA cellulose diacetate
• CTA cellulose triacetate
• Such fibers can be utilized in expanded application opportunities in downstream fiber converting and end use apparel applications.
• cellulose ester fibers may be produced by using a dry spinning process.
• the cellulose ester is at least partially dissolved in a solvent (e.g., N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, and mixtures thereof), and the resulting dope is extruded through a small spinneret orifice into a spinning cabinet where the solvent is flashed off.
• a solvent e.g., N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, and mixtures thereof
• At least one cellulose ester and at least one dissolution solvent may be introduced into a dope mixer so as to form the cellulose ester dope.
• the dope mixer can comprise any conventional device capable of mixing the cellulose ester and the dissolution solvent.
• Exemplary dope mixers can include a continuous stirred tank reactor (“CSTR”). While in the dope mixer, the cellulose ester and solvent can be subjected to temperature and mixing conditions that facilitate the dissolution of the cellulose ester into the dissolution solvent, thereby forming the cellulose ester dope.
• the cellulose ester dope can comprise a solids content of at least 15%, at least 16%, at least 17%, at least 18%, at least 19%, at least 20%, at least 21%, at least 22%, or at least 23% by weight and/or not more than 35%, not more than 34%, not more than 33%, not more than 32%, not more than 31%, not more than 30%, not more than 29%, or not more than 28% by weight, based on the total weight of the dope.
• the cellulose ester dope can comprise a solids content in the range of 15% to 35%, 16% to 34%, 17% to 33%, 17% to 22%, 18% to 32%, 19% to 31 %, 20% to 31 %, 21 % to 30%, 22% to 29%, or 23% to 28% by weight, based on the total weight of the dope.
• the cellulose ester can include any cellulose ester known in the art, and particularly those that contain an acetyl group.
• Cellulose esters that can be used for the present invention generally comprise repeating units of the structure: wherein R 1 , R 2 , and R 3 are selected independently from the group consisting of hydrogen or straight chain alkanoyls having from 2 to 10 carbon atoms.
• Exemplary alkanoyls include acetyl, propionyl, and/or butyryl.
• the substitution level is usually expressed in terms of degree of substitution (“DS”), which is the average number of non-OH substituents per anhydroglucose unit (“AGU”).
• DS degree of substitution
• AGU anhydroglucose unit
• conventional cellulose contains three hydroxyl groups in each AGU unit that can be substituted; therefore, DS can have a value between zero and three.
• low molecular weight cellulose esters can have a total degree of substitution slightly above 3 due to end group contributions. Because DS is a statistical mean value, a value of 1 does not assure that every AGU has a single substituent. In some cases, there can be unsubstituted AGU’s, some with two and some with three substituents.
• the “Total DS” is defined as the average number of all of substituents per AGU and typically the value will be a non-integer.
• the degree of substitution per AGU can also refer to a particular substituent, such as, for example, hydroxyl, acetyl, butyryl, or propionyl.
• the cellulose ester comprises a DSacetyi of at least 1 .5, at least 1 .55, at least 1 .6, at least 1 .65, at least 1 .7, at least 1 .75, at least 1 .8, at least 1 .85, at least 1 .9, at least 1 .95, at least 2.0, at least 2.05, at least
• the cellulose ester may comprise a DSacetyi in the range of 2.6 to 2.95, 2.7 to 2.95, 1 .5 to 2.6, 1 .6 to 2.6, 1 .7 to 2.6, 1 .8 to 2.6, 1 .9 to 2.6, 2.0 to 2.6, 2.05 to 2.6, 2.1 to 2.6, 2.15 to 2.6, 2.2 to 2.6, 2.25 to 2.55, 2.3 to 2.5, or 2.38 to 2.45.
• the cellulose ester comprises a DSOH of at least 0.05, at least 0.1 , at least 0.2, at least 0.3, at least 0.4, or at least 0.5 and/or not more than 1 .5, not more than 1 .4, not more than 1 .3. not more than 1 .2, not more than 1 .1 , or not more than 1 .0.
• the cellulose ester comprises a DSOH in the range of 0.05 to 1 .5, 0.1 to 1 .5, 0.2 to 1 .4, 0.3 to 1 .2, 0.4 to 1 .1 , or 0.5 to 1.0.
• the cellulose ester comprises a DSpropionyi of at least 0.1 , at least 0.2, or at least 0.3 and/or not more than 1 .5, not more than 1 .4, not more than 1 .3, not more than 1 .2, not more than 1 .1 , not more than 1 .0, not more than 0.9, not more than 0.8, not more than 0.7, not more than 0.6, not more than 0.5, or not more than 0.4.
• the cellulose ester comprises a DSpropionyi in the range of 0.1 to 1 .5, 0.1 to 1 .2, 0.1 to 0.8, 0.1 to 0.4, 0.2 to 1 .5, 0.2 to 1 .2, 0.2 to 0.8, 0.2 to 0.4, 0.3 to 1 .5, 0.3 to 1 .2, 0.3 to 0.8, or 0.3 to 0.6.
• the cellulose ester may comprise a Total DS in the range of 1 .5 to 2.95, 1 .6 to 2.85, 1 .7 to 2.8, 1 .8 to 2.75, 1 .9 to 2.7, 2.0 to 2.65, 2.05 to 2.6, 2.1 to 2.6, 2.15 to 2.6, 2.2 to 2.6, 2.25 to 2.55, 2.3 to 2.5, or 2.38 to 2.45.
• the cellulose ester can be a cellulose diacetate and/or cellulose triacetate.
• the cellulose ester can comprise a mixed cellulose ester, such as cellulose acetate butyrate or cellulose acetate propionate.
• the cellulose ester can have an acetyl content of at least 30%, at least 35%, or at least 40% by weight and/or not more than 62.5%, not more than 60%, not more than 55%, not more than 50%, or not more than 45% by weight on a combined acetic acid weight percent basis.
• the cellulose ester may have a degree of acetylation in the range of 30% to 62.5%, 35% to 55%, 35% to 50%, 35% to 45%, 40% to 62.5%, 40% to 60%, 40% to 55%, 40% to 50%, or 40% to 45% by weight.
• the cellulose ester can have a hydroxyl content of at least 0.3%, at least 0.5%, at least 1%, at least 2%, at least 3%, or at least 4% by weight and/or not more than 20%, not more than 15%, not more than 10%, or not more than 5% by weight.
• the cellulose ester may have a hydroxyl content in the range of 0.3% to 20%, 0.5% to 20%, 2% to 15%, 3% to 10%, or 4% to 5% by weight.
• the cellulose ester can have a number average degree of polymerization of at least 100, at least 110, at least 120, at least 130, at least 140, at least 150, at least 160, at least 170, at least 180, at least 190, at least 200, at least 210, at least 220, at least 230, at least 240, at least 250, at least 260, or at least 265.
• the cellulose ester can have a number average degree of polymerization of not more than 1 ,000, not more than 900, not more than 800, not more than 700, not more than 600, not more than 500, not more than 400, not more than 350, not more than 325, not more than 300, not more than 290, not more than 280, not more than 270, not more than 260, not more than 250, not more than 240, not more than 230, not more than 220, not more than 210, not more than 200, not more than 190, not more than 180, not more than 170, not more than 160, not more than 150, not more than 149, not more than 148, not more than 147, not more than 146, not more than 145, not more than 144, not more than 143, not more than 142, not more than 141 , not more than 140, not more than 139, not more than 138, not more than 137, not more
• the cellulose ester can have a number average degree of polymerization in the range of 100 to 1 ,000, 100 to 500, 100 to 400, 100 to 300, 100 to 250, 100 to 200, 100 to 150, 100 to 135, 100 to 200, 100 to 150, 100 to 135, 100 to 180, 100 to 150, 100 to 145, 100 to 140, 100 to 135, or 100 to 130.
• the cellulose ester can comprise a number average absolute molecular weight in Daltons, of at least 5,000 Daltons, at least 10,000 Daltons, at least 15,000 Daltons, at least 20,000 Daltons, or at least 25,000 Daltons and/or not more than 75,000 Daltons, not more than 70,000 Daltons, not more than 65,000 Daltons, not more than 60,000 Daltons, not more than 55,000 Daltons, not more than 50,000 Daltons, not more than 45,000 Daltons, not more than 40,000 Daltons, not more than 35,000 Daltons, or not more than 30,000 Daltons as measured by gel permeation chromatography (“GPC”) according to ASTM D6474.
• GPC gel permeation chromatography
• the cellulose ester can comprise a number average absolute molecular weight in the range of 5,000 Daltons to 75,000 Daltons, 10,000 Daltons to 65,000 Daltons, or 15,000 Daltons to 35,000 Daltons as measured by GPC according to ASTM D6474.
• the cellulose ester can comprise a weight-average absolute molecular weight of at least 50,000 Daltons, at least 55,000 Daltons, at least 60,000 Daltons, at least 65,000 Daltons, at least 70,000 Daltons, at least 75,000 Daltons, at least 80,000 Daltons, or at least 85,000 Daltons and/or not more than 150,000 Daltons, not more than 140,000 Daltons, not more than 130,000 Daltons, not more than 120,000 Daltons, not more than 110,000 Daltons, not more than 100,000 Daltons, or not more than 95,000 Daltons as measured by GPC according to ASTM D6474.
• the cellulose ester can comprise a weight-average absolute molecular weight in the range of 50,000 Daltons to 150,000 Daltons, 70,000 Daltons to 120,000 Daltons, or 80,000 Daltons to 95,000 Daltons as measured by GPC according to ASTM D6474.
• the cellulose ester can comprise a crystallinity of at least 1 %, at least 2%, at least 5%, at least 10%, at least 15%, or at least 20% as measured according to ASTM F2625. Additionally or alternatively, in one embodiment or in combination with any other mentioned embodiments, the cellulose ester can comprise a crystallinity of not more than 25%, not more than 20%, not more than 15%, not more than 10%, not more than 9%, not more than 8%, not more than 7%, not more than 6%, not more than 5%, not more than 4%, not more than 3%, not more than 2%, or not more than 1% as measured according to ASTM F2625. In certain embodiments, the cellulose ester can comprise a crystallinity of 1% to 99%, 1% to 50%, 1% to 30%, 1% to 20%, or 1% to 15% as measured according to ASTM F2625.
• the cellulose ester can exhibit a glass transition temperature of at least 120°C, at least 125°C, at least 130°C, at least 135°C, at least 140°C, at least 145°C, at least 150°C, at least 155°C, at least 160°C, at least 165°C, at least 170°C, or at least 175°C and/or not more than 250°C, not more than 245°C, not more than 240°C, not more than 235°C, not more than 230°C, not more than 225°C, not more than 220°C, not more than 215°C, not more than 210°C, not more than 205°C, not more than 200°C, not more than 195°C, not more than 190°C, or not more than 185°C.
• the cellulose esters can be produced by any method known in the art. Examples of processes for producing cellulose esters are taught in Kirk-Othmer, Encyclopedia of Chemical Technology, 5th Edition, Vol. 5, Wiley-lnterscience, New York (2004), pp. 394-444.
• One method of producing cellulose esters involves esterification of the cellulose by mixing cellulose with the appropriate organic acids, acid anhydrides, and catalysts. Cellulose is then converted to a cellulose triester. Ester hydrolysis is then performed by adding a water-acid mixture to the cellulose triester, which can then be filtered to remove any gel particles or fibers. Water is then added to the mixture to precipitate the cellulose ester. The cellulose ester can then be washed with water to remove reaction by-products followed by dewatering and drying.
• Cellulose the starting material for producing cellulose esters
• the starting material used to produce the cellulose esters may affect the resulting hemicellulose content in the resulting cellulose esters.
• the cellulose ester can comprise a hemicellulose content of at least 0.25%, at least 0.5%, at least 1%, at least 2%, at least 3%, at least 4%, at least 5%, at least 6%, or at least 7% by weight. Additionally or alternatively, in one embodiment or in combination with any other mentioned embodiments, the cellulose ester can comprise a hemicellulose content of not more than 10%, not more than 9%, not more than 8%, not more than 7%, not more than 6%, not more than 5%, not more than 4%, not more than 3%, not more than 2%, or not more than 1% by weight.
• the dissolution solvent added to the dope mixer can include one or more solvents capable of dissolving a cellulose ester, particularly cellulose diacetate and/or cellulose triacetate.
• the dissolution solvent comprises a solvent chosen from N,N-dimethylformamide, N,N- dimethylacetamide, or dimethyl sulfoxide, or mixtures thereof.
• acetone is minimized or avoided as a dissolution solvent.
• the dope comprises not more than 50%, not more than 45%, not more than 40%, not more than 35%, not more than 30%, not more than 25%, not more than 20%, not more than 15%, not more than 10%, not more than 5%, not more than 4%, not more than 3%, not more than 2%, not more than 1%, or 0% by weight acetone, based on the total weight of the cellulose ester dope.
• the cellulose ester may be added to the dope so that the dope comprises at least 5%, at least 8%, at least 10%, at least 12%, at least 15%, at least 18%, at least 20%, or at least 22% by weight cellulose ester, and/or not more than 35%, not more than 33%, not more than 30%, not more than 29%, not more than 25%, not more than 22%, or not more than 20% by weight cellulose ester, based on the total weight of the dope.
• the cellulose ester dope comprises 5% to 35%, 10% to 33%, 12% to 30%, 15% to 29%, or 25% to 29% by weight of cellulose ester, based on the total weight of the dope.
• the cellulose ester is present in the dope at a level of at least 35%, at least 40%, at least 55%, at least 65%, at least 75%, at least 85%, at least 95%, at least 98%, or 100% by weight, based on total solids in the dope.
• the cellulose ester is present in the dope from 35% to 100%, from 45% to 100%, from 55% to 100%, from 55% to 98%, from 65% to 98%, or from 75% to 98%, based on total solids in the dope.
• the dope when the cellulose ester comprises CTA, the dope comprises at least 10%, at least 10%, at least 12%, at least 15%, at least 17%, at least 19%, or at least 21 % by weight CTA, and/or not more than 27%, not more than 25%, not more than 24%, or not more than 22% by weight CTA, based on the total weight of the dope. In certain embodiments, the cellulose ester dope comprises 10% to 27%, 12% to 24%, or 15% to 22% by weight CTA, based on the total weight of the dope.
• the dissolution solvent should be added in sufficient quantities so as to effectively dissolve the cellulose ester, thereby forming the cellulose ester dope.
• the cellulose ester dope can comprise at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, or at least 95%, or 99% and/or not more than 99%, not more than 95%, not more than 90%, or not more than 85% by weight of one or more dissolution solvents, based on the total weight of the dope.
• the cellulose ester dope comprises 65% to 99%, 70% to 95%, 75% to 95%, 80% to 95%, or 90% to 99% by weight of one or more dissolution solvents, based on the total weight of the dope.
• the cellulose ester dope may comprise some or no additives in addition to the cellulose ester.
• additives can include, but are not limited to, plasticizers, antioxidants, thermal stabilizers, prooxidants, inorganics, pigments, colorants, antistatic agents, optical brighteners, lubricants, fillers, or combinations thereof.
• the dope is prepared by mixing the cellulose ester, solvent, and any other components at lower temperatures. In certain embodiments, this mixing is performed by mixing at a temperature of at least 45°C, at least 46°C, at least 47°C, at least 48°C, at least 49°C, at least 50°C, at least 51 °C, at least 52°C, at least 53°C, at least 54°C, at least 55°C, at least 56°C, at least 57°C, at least 58°C, at least 59°C, or at least 60°C and/or not more than 140°C, not more than 130°C, not more than 120°C, not more than 110°C, not more than 105°C, not more than 104°C, not more than 103°C, not more than 102°C, not more than 101 °C, not more than 100°C, not more than 99°C, not more than 98°C, not more than 97°
• the spinneret may be operated at any speed suitable to produce individual filament fibers, which are then assembled into bundles having desired size and shape.
• individual filament fiber refers to the continuous filament that is initially produced by each hole in the face of the spinneret.
• the individual cellulose ester fibers discharged from the spinneret may have any suitable transverse cross-sectional shape.
• Exemplary cross-sectional shapes include, but are not limited to, round or other than round (non-round).
• the individual fibers discharged from the spinneret may have a substantially round cross-sectional shape.
• cross-section generally refers to the transverse cross-section of the fiber measured in a direction perpendicular to the direction of elongation of the fiber.
• the cross-section of the fiber may be determined and measured using Quantitative Image Analysis (“QIA”).
• QIA Quantitative Image Analysis
• the cellulose ester fibers and/or the yarn produced therefrom may exhibit a tenacity of at least 0.2 g/denier, at least 0.3 g/denier, at least 0.4 g/denier, at least 0.5 g/denier, at least 0.6 g/denier, at least 0.7 g/denier, at least 0.8 g/denier, at least 0.9 g/denier, at least 1 g/denier, at least 1 .1 g/denier, at least 1 .2 g/denier, at least 1 .3 g/denier, at least 1 .4 g/denier, at least 1 .5 g/denier, at least 1 .6 g/denier, at least 1 .7 g/denier, at least 1 .8 g/denier, at least 1 .9 g/denier, or at least 2 g/denier, and/or not more than 3.
• Elongation also known as elongation at break, is expressed as a percentage and it is indicative of how much a yarn or filament will stretch before it breaks.
• the cellulose ester fibers and/or the yarn produced therefrom may exhibit an elongation at break of at least 10%, at leastl 5%, at least 16%, at least 17%, at least 18%, at least 19%, at least 20%, at least 21%, at least 22%, at least 23%, at least 24%, at least 25%, at least 26%, at least 27%, at least 28%, at least 29%, or at least 30% as measured according to ASTM D22556.
• Silk factor is an empirically determined relationship between tenacity and elongation that is used to predict the failure envelope of a given fiber.
• Silk Factor can be used to characterize a yarn or fiber’s suitability for use in a given process and is calculated based on the following formula:
• the cellulose ester fibers and/or the yarn produced therefrom may exhibit a silk factor of at least 5.0, at least 6.0, at least 7.0, or at least 7.6, where elongation is defined as a percentage and tenacity is in grams/denier.
• spandex yarn bobbins are wound with significant amount of winder draw wherein the winder speed is typically 5% faster than the speed of the previous roll; for cellulose ester continuous filament fibers, it is desirable to have less than 3% winder draw, less than 2% winder draw, less than 1% winder draw, less than 0.8% winder draw, less than 0.5% winder draw.
• the cellulose ester fibers, the cellulose ester bundle, band, or yarn, and/or staple fibers produced therefrom may have a crimp ratio of at least 1 :1.
• “crimp ratio” refers to the ratio of the non-crimped tow length to the crimped tow length.
• the cellulose ester fibers, the cellulose ester yarns, and/or staple fibers produced therefrom may have a crimp ratio of at least 1 :1 , at least 1.1 :1 , at least 1 .125:1 , at least 1 .15:1 , or at least 1.2:1 .
• the cellulose ester fibers can include at least one plasticizer or, in the alternative, no plasticizer.
• the cellulose ester fibers may comprise less than 30, less than 12, less than 10, less than 9, less than 8, less than 7, less than 6, less than 5, less than 4, less than 3, less than 2, less than 1 , less than 0.5 weight percent of at least one plasticizer, based on the total weight of the cellulose ester fiber.
• the plasticizer may be incorporated into the fiber itself by spinning a dope containing a plasticizer, contained in a flake used to make the dope, and/or the plasticizer may be applied to the surface of the fiber or filament by any of the methods used to apply a finish. If desired, the plasticizer can be contained in the finish formulation.
• the cellulose ester fibers and/or the yarns formed therefrom can exhibit a weight loss of at least 5%, at least 10%, at least 15%, or at least 20% after burial in soil for 60 days and/or a weight loss of at least 15%, at least 20%, at least 25%, at least 30%, or at least 35% after 15 days of exposure in a composter.
• the rate of degradation may vary depending on the particular end use of the fibers. Exemplary test conditions are provided in U.S. Pat. Nos. 5,870,988 and 6,571 ,802, incorporated herein by reference. [0078]
• the cellulose ester fibers and/or the yarns formed therefrom can be compostable.
• a material must meet the following four criteria: (1 ) the material must be biodegradable; (2) the material must be disintegrable; (3) the material must not contain more than a maximum amount of heavy metals; and (4) the material must not be ecotoxic.
• the term “disintegrable” refers to the tendency of a material to physically decompose into smaller fragments when exposed to certain conditions. Disintegration depends both on the material itself, as well as the physical size and configuration of the article being tested. Ecotoxicity measures the impact of the material on plant life, and the heavy metal content of the material is determined according to the procedures laid out in the standard test method.
• the cellulose ester fibers and/or the yarns formed therefrom can be industrially compostable, home compostable, or both.
• the cellulose ester fibers can satisfy four criteria: (1 ) biodegrade in that at least 90% carbon content is converted within 180 days; (2) disintegrable in that least 90% the material disintegrates within 12 weeks; (3) does not contain heavy metals beyond the thresholds established under the EN12423 standard; and (4) the disintegrated content supports future plant growth as humus; where each of these four conditions are tested per the ASTM D6400, ISO 17088, or EN 13432 method.
• the cellulose ester fibers and/or the yarns formed therefrom can exhibit a biodegradation of at least 70 percent in a period of not more than 50 days, when tested under aerobic composting conditions at ambient temperature (28°C ⁇ 2°C) according to ISO 14855-1 (2012).
• the cellulose ester fibers and/or the yarns formed therefrom can exhibit a biodegradation of at least 60 percent in a period of not more than 45 days, when tested under aerobic composting conditions at a temperature of 58°C ( ⁇ 2°C) according to ISO 14855-1 (2012). In some cases, they can exhibit a biodegradation of at least 60 percent in a period of not more than 44 days when tested under these conditions, also called “industrial composting conditions.” These may not be aqueous or anaerobic conditions.
• the resulting cellulose ester fibers may be used to produce a vast array of end products, such as tow band, staple fibers, filament yarns, spun yarns, woven articles, nonwoven articles, and/or knitted textiles.
• the cellulose ester fibers and/or the cellulose ester yarns described above may be cut into staple fibers.
• Any suitable type of cutting device may be used that is capable of cutting the fibers to a desired length without excessively damaging the fibers. Examples of cutting devices can include, but are not limited to, rotary cutters, guillotines, stretch breaking devices, reciprocating blades, or combinations thereof. Once cut, the cellulose ester staple fibers may be baled or otherwise bagged or packaged for subsequent transportation, storage, and/or use.
• the cellulose ester fibers may be formed into a nonwoven article, such as a nonwoven textile.
• exemplary nonwoven articles can include wet-laid nonwoven articles, air-laid non-woven articles, carded articles, and/or dry-laid non-woven articles.
• Sample #5 was mixed at 50°C instead of 90°C to determine a practical lower temperature limit for hot mixing. This sample took about twice as long to go into solution relative to 90°C. Another sample (#6) was mixed at room temperature but did not go into solution even after 3 hours.
• dopes were prepared using the cold mixing process similar to Example 1 above, except an additional amount of a stabilizing additive (either 0.5 or 1 wt%) was also included. Starting moisture was 1.3 wt% for all of the CDA samples.
• Additives represented a range of possible stabilizing agents representing acids, buffers, antioxidants, etc.
• the mixtures of citric acid and potassium citrate were next best having intermediate levels of color formation. Samples #13, #14, and #15 still had some undissolved solids as the additives did not go completely in solution.
• Sample #31 also included a comparison with a highly dried sample at 0.5% citric acid to see if moisture made a difference.
• samples of film were cast and annealed for various times.
• the films were cast from the same dope (#10).
• the film was cast and annealed at 180C for 20 minutes in a hot air oven to dry the film (see Table IV).
• the citric acid film was very yellow after 20 minutes as this is above its melting and degradation is likely occurring due to oxygen exposure. In a typical dry spinning cabinet, the temperature exposure will only occur for just a few seconds (and likely with a nitrogen blanket). So to better reflect spinning conditions, a second film (#41) was cast and dried for 4 minutes at 180C, which was the minimum time needed to dry the film. As observed, the color dropped significantly and resulted in much better color than the other samples. Samples were also completely dry and free of any DMF odor. Lastly, sample #47 was cast from the same dope but
• SUBSTITUTE SHEET (RULE 26) annealed at 150C for 20minutes. This sample also had excellent color similar to that at 180C for 4 minutes. In the remaining examples, samples of other acids were also cast into film and annealed using the 4min protocol at 180C. Dopes containing citric acid had lower yellowness than the control at all levels of citric acid addition. In contrast, malic and tartaric at 0.5% were slightly more yellow than the control.

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