CN117916413A

CN117916413A - Dry spinning of cellulose acetate fibers

Info

Publication number: CN117916413A
Application number: CN202280058133.7A
Authority: CN
Inventors: M·D·谢尔比; M·E·斯图尔特; J·C·梅因; T·S·多顿; J·M·艾伦; 李湧
Original assignee: Eastman Chemical Co
Current assignee: Eastman Chemical Co
Priority date: 2021-08-26
Filing date: 2022-08-16
Publication date: 2024-04-19
Also published as: EP4392601A1; KR20240044539A; WO2023027910A1; JP2024531481A

Abstract

Cellulose ester fibers are produced using a dry spinning system and method. The process uses one or more of N, N-dimethylformamide, N-dimethylacetamide, dimethylsulfoxide, or a mixture thereof as a dissolution solvent. The method minimizes or avoids fiber discoloration.

Description

Dry spinning of cellulose acetate fibers

Technical Field

The present application relates generally to spinning of fibers. More particularly, the present application relates generally to dry spinning cellulose esters into fibers.

Background

Cellulose acetate fibers are traditionally dry spun using acetone as the spin solvent. With the growth of the filament market, there is a need to increase spinning capacity, but adding new production lines is quite expensive in view of the need to recover solvents, capital expenditure, etc. One cost effective alternative is to use the idle dry spinning capacity available in the acrylic and polyurethane fiber markets. But these techniques involve the use of DMF (N, N-dimethylformamide) or DMAc (N, N-dimethylacetamide) as solvents. Although DMF is a very effective solvent, DMF requires a much higher operating temperature than acetone due to its higher boiling point. These higher operating temperatures in turn cause degradation of cellulose acetate and/or DMF, which can lead to unacceptable yellowness in the fiber. Thus, there is a need for a dry spinning process using DMF that results in less color formation.

Summary of The Invention

The present disclosure provides a method of producing cellulose ester fibers, wherein the method comprises dry spinning a cellulose ester dope via a spinneret to produce one or more of the fibers. The cellulose ester dope comprises at least 35 wt% cellulose ester on a solids basis dissolved or dispersed in a solvent selected from the group consisting of N, N-dimethylformamide, N-dimethylacetamide, dimethylsulfoxide, or a mixture thereof. If the solvent comprises N, N-dimethylacetamide:

(i) The cellulose ester dope comprises not greater than 50 wt% acetone based on the total weight of the cellulose ester dope; or (b)

(Ii) The cellulose ester dope comprises 0 wt% cellulose nanocrystals; or (b)

(Iii) (i) and (ii).

The total weight of any polyurethane, polyolefin, nylon, polyester, and/or polyurethaneurea that may be present in the cellulose ester dope is not greater than 60 weight percent based on the total solids in the cellulose ester dope.

The present disclosure also provides a method of producing cellulose ester fibers, wherein the method comprises dry spinning a cellulose ester dope via a spinneret to produce one or more of the fibers. The cellulose ester dope comprises a cellulose ester dissolved or dispersed in a solvent selected from the group consisting of N, N-dimethylformamide, N-dimethylacetamide, dimethylsulfoxide, or a mixture thereof. If the solvent comprises N, N-dimethylacetamide:

(Ii) The cellulose ester dope comprises 0 wt% cellulose nanocrystals; or (b)

(Iii) (i) and (ii);

the cellulose ester dope comprises not greater than 10 wt.% polyurethane and not greater than 50 wt.% acrylonitrile-vinyl acetate copolymer, both based on total solids in the cellulose ester dope. The total weight of any polyurethane, polyolefin, nylon, polyester, and/or polyurethaneurea that may be present in the cellulose ester dope is not greater than 60 weight percent based on the total solids in the cellulose ester dope.

The present disclosure also provides cellulose ester fibers formed according to one or both of the above methods.

The present disclosure further provides a yarn, article, woven article, nonwoven article, staple fiber, and/or knit fabric comprising cellulose ester fibers formed according to one or both of the above methods.

Detailed description of the preferred embodiments

The present application relates generally to a dry spinning process for preparing cellulose diacetate ("CDA") fibers and/or cellulose triacetate ("CTA") fibers that exhibit low color formation. Such fibers may be used with expanded application opportunities in downstream fiber conversion and end use apparel applications. In addition, such cellulose ester fibers can be produced using a dry spinning process. In this process, the cellulose ester is at least partially dissolved in a solvent (e.g., N-dimethylformamide, N-dimethylacetamide, dimethylsulfoxide, and mixtures thereof), and the resulting dope is extruded through small orifices into a spin basket, where the solvent is flashed off.

At least one cellulose ester and at least one dissolution solvent may be introduced into the dope mixer to form a cellulose ester dope. The dope mixer may comprise any conventional device capable of mixing the cellulose ester and the dissolution solvent. An exemplary dope mixer may include a continuous stirred tank reactor ("CSTR"). While in the dope mixer, the cellulose ester and solvent may be subjected to temperature and mixing conditions that promote dissolution of the cellulose ester into the dissolution solvent, thereby forming a cellulose ester dope.

In one embodiment, or in combination with any other mentioned embodiment, the cellulose ester dope may comprise a solids content of at least 15 wt%, at least 16 wt%, at least 17 wt%, at least 18 wt%, at least 19 wt%, at least 20 wt%, at least 21 wt%, at least 22 wt%, or at least 23 wt% and/or no greater than 35 wt%, no greater than 34 wt%, no greater than 33 wt%, no greater than 32 wt%, no greater than 31 wt%, no greater than 30 wt%, no greater than 29 wt%, or no greater than 28 wt%, based on the total weight of the dope. For example, the cellulose ester dope may comprise a solids content of 15 wt.% to 35 wt.%, 16 wt.% to 34 wt.%, 17 wt.% to 33 wt.%, 17 wt.% to 22 wt.%, 18 wt.% to 32 wt.%, 19 wt.% to 31 wt.%, 20 wt.% to 31 wt.%, 21 wt.% to 30 wt.%, 22 wt.% to 29 wt.%, or 23 wt.% to 28 wt.%, based on the total weight of the dope.

Cellulose esters may include any cellulose esters known in the art, particularly those containing acetyl groups. Cellulose esters useful in the present invention generally comprise repeating units of the structure:

Wherein R ¹、R² and R ³ are independently selected from hydrogen or a linear alkanoyl group having 2 to 10 carbon atoms. Exemplary alkanoyl groups include acetyl, propionyl and/or butyryl.

For cellulose esters, the substitution level is typically expressed in terms of the degree of substitution ("DS"), which is the average number of non-OH substituents per anhydroglucose unit ("AGU"). Typically, conventional cellulose contains three hydroxyl groups in each AGU unit that may be substituted; thus, DS may have a value of 0 to 3. However, low molecular weight cellulose esters may have a total degree of substitution slightly above 3 due to the end group contribution. Since DS is a statistical average, a value of 1 cannot ensure that each AGU has a single substituent. In some cases, unsubstituted AGUs may be present, some with two substituents and some with three substituents. "Total DS" is defined as the average of all substituents per AGU, and this value is typically a non-integer. The degree of substitution per AGU may also relate to specific substituents, such as hydroxy, acetyl, butyryl or propionyl.

In one embodiment, or in combination with any other mentioned embodiment, the cellulose ester has a DS _{Acetyl group} 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 2.1, at least 2.15, at least 2.2, at least 2.25, at least 2.3, at least 2.35, or at least 2.38, and/or not greater than 2.95, not greater than 2.9, not greater than 2.8, not greater than 2.7, not greater than 2.6, not greater than 2.55, not greater than 2.5, or not greater than 2.45. In certain embodiments, the cellulose ester may have a DS _{Acetyl group} 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.

Additionally or alternatively, in one embodiment or in combination with any other mentioned embodiment, the cellulose ester has a DS _OH 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 greater than 1.5, not greater than 1.4, not greater than 1.3, not greater than 1.2, not greater than 1.1, or not greater than 1.0. In certain embodiments, the cellulose ester has a DS _OH 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.

Additionally or alternatively, in one embodiment or in combination with any other mentioned embodiment, the cellulose ester has a DS _{Butyryl group} of at least 0.1, at least 0.2, or at least 0.3 and/or not greater than 1.5, not greater than 1.4, not greater than 1.3, not greater than 1.2, not greater than 1.1, not greater than 1.0, not greater than 0.9, not greater than 0.8, not greater than 0.7, not greater than 0.6, not greater than 0.5, or not greater than 0.4. In certain embodiments, the cellulose ester has a DS _{Butyryl group} 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.

Additionally or alternatively, in one embodiment or in combination with any other mentioned embodiment, the cellulose ester has a DS _{Propionyl radical} of at least 0.1, at least 0.2, or at least 0.3 and/or not greater than 1.5, not greater than 1.4, not greater than 1.3, not greater than 1.2, not greater than 1.1, not greater than 1.0, not greater than 0.9, not greater than 0.8, not greater than 0.7, not greater than 0.6, not greater than 0.5, or not greater than 0.4. In certain embodiments, the cellulose ester has a DS _{Propionyl radical} 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.

Additionally or alternatively, in one embodiment or in combination with any other mentioned embodiment, the cellulose ester has a total DS 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 2.1, at least 2.15, at least 2.2, at least 2.25, at least 2.3, at least 2.35, or at least 2.38, and/or not greater than 2.95, not greater than 2.9, not greater than 2.85, not greater than 2.8, not greater than 2.75, not greater than 2.7, not greater than 2.65, not greater than 2.6, not greater than 2.55, not greater than 2.5, or not greater than 2.45. In certain embodiments, the cellulose ester may have a total DS 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.

In one embodiment or in combination with any other mentioned embodiment, the cellulose ester may be cellulose diacetate and/or cellulose triacetate. Or in certain embodiments, the cellulose ester may comprise a mixed cellulose ester, such as cellulose acetate butyrate or cellulose acetate propionate.

In one embodiment, or in combination with any other mentioned embodiment, the cellulose ester may have an acetyl content of at least 30 wt.%, at least 35 wt.%, or at least 40 wt.%, and/or no greater than 62.5 wt.%, no greater than 60 wt.%, no greater than 55 wt.%, no greater than 50 wt.%, or no greater than 45 wt.%, based on the total acetic acid weight percent. In certain embodiments, the cellulose ester may have a degree of acetylation of 30 wt.% to 62.5 wt.%, 35 wt.% to 55 wt.%, 35 wt.% to 50 wt.%, 35 wt.% to 45 wt.%, 40 wt.% to 62.5 wt.%, 40 wt.% to 60 wt.%, 40 wt.% to 55 wt.%, 40 wt.% to 50 wt.%, or 40 wt.% to 45 wt.%.

Additionally or alternatively, in one embodiment or in combination with any other mentioned embodiment, the cellulose ester may have a hydroxyl content of at least 0.3 wt%, at least 0.5wt%, at least 1wt%, at least 2 wt%, at least 3 wt%, or at least 4 wt% and/or no greater than 20 wt%, no greater than 15 wt%, no greater than 10 wt%, or no greater than 5 wt%. In certain embodiments, the cellulose ester may have a hydroxyl content of 0.3 wt.% to 20 wt.%, 0.5 wt.% to 20 wt.%, 2 wt.% to 15 wt.%, 3 wt.% to 10 wt.%, or 4wt.% to 5 wt.%.

In one embodiment, or in combination with any other mentioned embodiment, the cellulose ester may 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. Additionally or alternatively, in one embodiment or in combination with any other mentioned embodiment, the cellulose ester may have no greater than 1,000, no greater than 900, no greater than 800, no greater than 700, no greater than 600, no greater than 500, no greater than 400, no greater than 350, no greater than 325, no greater than 300, no greater than 290, no greater than 280, no greater than 270, no greater than 260, no greater than 250, no greater than 240, no greater than 230, no greater than 220, no greater than 210, no greater than 200, no greater than 190, no greater than 180, no greater than 170, no greater than 160, no greater than 150, no greater than 149, no greater than 148, no greater than 147, no greater than 146, no greater than 145, no greater than 144, no greater than 143, no greater than 142, no greater than 141, no greater than 140, no greater than 139, no greater than 138, no greater than 137, no greater than 136, no greater than 135, no greater than 134, no greater than 132, no greater than 180, no greater than 130, no greater than 122, no greater than 116, no greater than 121, no greater than 125, no greater than 122, no greater than 125, no greater than 121, no greater than 125, no greater than 130, no greater than 15. In certain embodiments, the cellulose ester may have a number average degree of polymerization 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.

In one embodiment, or in combination with any other mentioned embodiment, the cellulose ester may have a number average absolute molecular weight in daltons as measured by gel permeation chromatography ("GPC") according to ASTM D6474 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 greater than 75,000 daltons, not greater than 70,000 daltons, not greater than 65,000 daltons, not greater than 60,000 daltons, not greater than 55,000 daltons, not greater than 50,000 daltons, not greater than 45,000 daltons, not greater than 40,000 daltons, not greater than 35,000 daltons, or not greater than 30,000 daltons. In certain embodiments, the cellulose ester may have a number average absolute molecular weight 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.

In one embodiment, or in combination with any other mentioned embodiment, the cellulose ester may have 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 no greater than 150, 000 daltons, no greater than 140, 000 daltons, no greater than 130, 000 daltons, no greater than 120,000 daltons, no greater than 110, 000 daltons, no greater than 100, 000 daltons, or no greater than 95,000 daltons as measured by GPC according to ASTM D6474. In certain embodiments, the cellulose ester may have a weight average absolute molecular weight 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.

In one embodiment, or in combination with any other mentioned embodiment, the cellulose ester may have 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 embodiment, the cellulose ester may have a crystallinity of no greater than 25%, no greater than 20%, no greater than 15%, no greater than 10%, no greater than 9%, no greater than 8%, no greater than 7%, no greater than 6%, no greater than 5%, no greater than 4%, no greater than 3%, no greater than 2%, or no greater than 1% as measured according to ASTM F2625. In certain embodiments, the cellulose ester may have 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.

In one embodiment or in combination with any other mentioned embodiment, the cellulose ester may exhibit a glass transition temperature of at least 120 ℃, at least 125 ℃, at least 130 ℃, at least 135 ℃, at least 140 ℃, at least 145 ℃, at least 150 ℃, at least 155 ℃, at least 160 ℃, at least 165 ℃, at least 170 ℃, or at least 175 ℃ and/or no greater than 250 ℃, no greater than 245 ℃, no greater than 240 ℃, no greater than 235 ℃, no greater than 230 ℃, no greater than 225 ℃, no greater than 220 ℃, no greater than 215 ℃, no greater than 210 ℃, no greater than 205 ℃, no greater than 200 ℃, no greater than 195 ℃, no greater than 190 ℃, or no greater than 185 ℃.

Cellulose esters may be produced by any method known in the art. Examples of methods for producing cellulose esters are taught in Kirk-Othmer, encyclopedia of Chemical Technology, 5 th edition, volume 5, wiley-Interscience, new York (2004), pages 394-444.

One method of producing cellulose esters involves the esterification of cellulose by mixing the cellulose with a suitable organic acid, anhydride and catalyst. The cellulose is then converted to cellulose triester. Ester hydrolysis is then performed by adding the 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 may then be washed with water to remove reaction byproducts, followed by dehydration and drying.

Cellulose, the starting material for producing cellulose esters, is available in various grades and sources, such as from cotton linters, softwood pulp, hardwood pulp, corn fiber and other agricultural sources, and bacterial cellulose, among others. The starting materials used to produce cellulose esters can affect the resulting hemicellulose content in the resulting cellulose ester.

In one embodiment, or in combination with any other mentioned embodiment, the cellulose ester may have a hemicellulose content of at least 0.25 wt.%, at least 0.5 wt.%, at least 1 wt.%, at least 2 wt.%, at least 3 wt.%, at least 4 wt.%, at least 5 wt.%, at least 6 wt.%, or at least 7 wt.%. Additionally or alternatively, in one embodiment or in combination with any other mentioned embodiment, the cellulose ester may have a hemicellulose content of no greater than 10 wt%, no greater than 9 wt%, no greater than 8 wt%, no greater than 7 wt%, no greater than 6 wt%, no greater than 5 wt%, no greater than 4 wt%, no greater than 3 wt%, no greater than 2 wt%, or no greater than 1 wt%.

The dissolution solvent added to the dope mixer may comprise one or more solvents capable of dissolving cellulose esters, particularly cellulose diacetate and/or cellulose triacetate. In one embodiment or in combination with any other mentioned embodiment, the dissolution solvent comprises a solvent selected from N, N-dimethylformamide, N-dimethylacetamide or dimethylsulfoxide or a mixture thereof.

In one embodiment, or in combination with any of the other mentioned embodiments, the use of acetone as a dissolution solvent is minimized or avoided. In certain embodiments (e.g., when N, N-dimethylacetamide is present in the dope), the dope comprises no greater than 50 wt%, no greater than 45 wt%, no greater than 40 wt%, no greater than 35 wt%, no greater than 30 wt%, no greater than 25 wt%, no greater than 20 wt%, no greater than 15 wt%, no greater than 10 wt%, no greater than 5 wt%, no greater than 4 wt%, no greater than 3 wt%, no greater than 2 wt%, no greater than 1 wt% or 0 wt% acetone based on the total weight of the cellulose ester dope.

The cellulose ester may be added to the dope such that the dope comprises at least 5 wt%, at least 8 wt%, at least 10 wt%, at least 12 wt%, at least 15 wt%, at least 18 wt%, at least 20 wt%, or at least 22 wt% of the cellulose ester, and/or no greater than 35 wt%, no greater than 33 wt%, no greater than 30 wt%, no greater than 29 wt%, no greater than 25 wt%, no greater than 22 wt%, or no greater than 20 wt% of the cellulose ester, based on the total weight of the dope. In certain embodiments, the cellulose ester dope comprises 5 wt.% to 35 wt.%, 10 wt.% to 33 wt.%, 12 wt.% to 30 wt.%, 15 wt.% to 29 wt.%, or 25 wt.% to 29 wt.% of the cellulose ester, based on the total weight of the dope.

In one embodiment, or in combination with any other mentioned embodiment, the cellulose ester is present in the dope in an amount of at least 35 wt%, at least 40 wt%, at least 55 wt%, at least 65 wt%, at least 75 wt%, at least 85 wt%, at least 95 wt%, at least 98 wt%, or 100 wt%, based on the total solids in the dope. In certain embodiments, the cellulose ester is present in the dope at 35% to 100%, 45% to 100%, 55% to 98%, 65% to 98%, or 75% to 98% based on total solids in the dope.

In one embodiment, or in combination with any other mentioned embodiment, when the cellulose ester comprises CDA, the dope comprises at least 10 wt%, at least 13 wt%, at least 15 wt%, at least 18 wt%, at least 20 wt%, at least 22 wt%, or at least 24 wt% CDA, and/or no greater than 35 wt%, no greater than 33 wt%, no greater than 30 wt%, or no greater than 29 wt% CDA, based on the total weight of the dope. In certain embodiments, the cellulose ester dope comprises 10 wt.% to 35 wt.%, 15 wt.% to 33 wt.%, 18 wt.% to 33 wt.%, 20 wt.% to 30 wt.%, or 24 wt.% to 29 wt.% CDA based on the total weight of the dope.

In one embodiment, or in combination with any other mentioned embodiment, when the cellulose ester comprises CTA, the dope comprises at least 10 wt%, at least 12 wt%, at least 15 wt%, at least 17 wt%, at least 19 wt%, or at least 21 wt% of CTA, and/or no greater than 27 wt%, no greater than 25 wt%, no greater than 24 wt%, or no greater than 22 wt% of CTA, based on the total weight of the dope. In certain embodiments, the cellulose ester dope comprises from 10 wt.% to 27 wt.%, from 12 wt.% to 24 wt.%, or from 15 wt.% to 22 wt.% of CTA, based on the total weight of the dope.

The dissolution solvent should be added in an amount sufficient to effectively dissolve the cellulose ester, thereby forming a cellulose ester dope. In one embodiment, or in combination with any other mentioned embodiment, the cellulose ester dope may comprise at least 65 wt%, at least 70 wt%, at least 75 wt%, at least 80 wt%, at least 85 wt%, at least 90 wt%, or at least 95 wt% or 99 wt% and/or no greater than 99 wt%, no greater than 95 wt%, no greater than 90 wt%, or no greater than 85 wt% of one or more dissolution solvents, based on the total weight of the dope. In certain embodiments, the cellulose ester dope comprises from 65 wt.% to 99 wt.%, from 70 wt.% to 95 wt.%, from 75 wt.% to 95 wt.%, from 80 wt.% to 95 wt.%, or from 90 wt.% to 99 wt.% of one or more dissolution solvents, based on the total weight of the dope.

The water or moisture content of the dope can be kept relatively low. In one embodiment, or in combination with any other of the mentioned embodiments, the cellulose ester dope has a moisture content of not greater than 4 wt%, not greater than 3.5 wt%, not greater than 3 wt%, not greater than 2.5 wt%, not greater than 1.5 wt%, not greater than 1.4 wt%, not greater than 1.3 wt%, not greater than 1.2 wt%, not greater than 1.1 wt%, not greater than 1 wt%, not greater than 0.9 wt%, not greater than 0.8 wt%, not greater than 0.7 wt%, or not greater than 0.6 wt%, based on the total weight of the cellulose ester dope.

Due to the type of cellulose ester and dissolution solvent used, the cellulose dope may exhibit a desirable operating viscosity. In one embodiment, or in combination with any other of the mentioned embodiments, the cellulose ester dope may exhibit a viscosity of at least 10 poise, at least 20 poise, at least 30 poise, at least 40 poise, at least 50 poise, at least 60 poise, at least 70 poise, at least 80 poise, at least 90 poise, or at least 100 poise, and/or no greater than 3,000 poise, no greater than 2,000 poise, no greater than 1,500 poise, no greater than 1,000 poise, no greater than 950 poise, no greater than 900 poise, no greater than 850 poise, no greater than 800 poise, no greater than 750 poise, no greater than 700 poise, no greater than 650 poise, no greater than 600 poise, no greater than 550 poise, or no greater than 500 poise, as measured at the spinning temperature used to make the fibers. This spinning temperature is nominally the temperature at which the dope passes through and into the spinneret. Viscosity as defined herein is the "zero" shear viscosity obtained by extrapolation to very low shear rates, or by use of a brookfield viscometer at low rotor RPM, when the viscosity is plotted against shear rate. Thus, the threshold value of "as measured" does not reflect the use or practice of the actual cellulose ester dope in any way.

In one embodiment or in combination with any other mentioned embodiment, the cellulose ester dope may exhibit a viscosity of at least 10 poise, at least 20 poise, at least 30 poise, at least 40 poise, at least 50 poise, at least 60 poise, at least 70 poise, at least 80 poise, at least 90 poise, or at least 100 poise, and/or no more than 5,000 poise, no more than 4,000 poise, no more than 3,000 poise, no more than 2,000 poise, no more than 1,500 poise, no more than 1,000 poise, no more than 950 poise, no more than 900 poise, no more than 850 poise, no more than 800 poise, no more than 750 poise, no more than 700 poise, no more than 650 poise, no more than 600 poise, no more than 550 poise, or no more than 500 poise, measured at 25 ℃,50 poise, 60, 70 poise, 60 poise, or 100 poise. It should be noted that this "as measured" standard does not require that the cellulose ester dope be used only at this specified temperature; instead, this temperature criterion simply provides a temperature threshold for measuring the viscosity of the cellulose ester dope. Thus, the threshold value of "as measured" does not reflect the use or practice of the actual cellulose ester dope in any way. Viscosity can be measured using a brookfield viscometer at low rotor RPM.

In one embodiment, or in combination with any of the other mentioned embodiments, the cellulose ester dope may contain some or no additives other than cellulose esters. Such additives may include, but are not limited to, plasticizers, antioxidants, heat stabilizers, pro-oxidants, inorganics, pigments, colorants, antistatic agents, optical brighteners, lubricants, fillers, or combinations thereof.

In one embodiment or in combination with any other mentioned embodiment, an organic acid (mono-and/or multi-functional) may be included to prevent color formation in the final fiber, especially when the spin dope is heated to a higher temperature. Exemplary such acids include those selected from citric acid, malic acid, maleic acid, succinic acid, lactic acid, acetic acid, tartaric acid, or propane-1, 2, 3-tricarboxylic acid, or mixtures thereof.

In one embodiment, or in combination with any other mentioned embodiment, the cellulose ester dope comprises at least 0.01 wt%, at least 0.05 wt%, at least 0.06 wt%, at least 0.07 wt%, at least 0.08 wt%, at least 0.09 wt%, at least 0.1 wt%, at least 0.2 wt%, or at least 0.3 wt% and/or no more than 2 wt%, no more than 1.5 wt%, no more than 1.4 wt%, no more than 1.3 wt%, no more than 1.2 wt%, no more than 1.1 wt%, no more than 1 wt%, no more than 0.9 wt%, or no more than 0.8 wt% of a multifunctional acid based on the weight of the dope. In certain embodiments, the cellulose ester dope comprises 0.01 wt.% to 2 wt.%, 0.01 wt.% to 1.5 wt.%, 0.05 wt.% to 1.5 wt.%, 0.08 wt.% to 1.3 wt.%, or 0.1 wt.% to 1 wt.% of a polyfunctional acid, based on the total weight of the dope.

In one embodiment or in combination with any other mentioned embodiment (e.g., when N, N-dimethylacetamide is present in the spin dope), the spin dope comprises 0 wt% cellulose nanocrystals. Cellulose nanocrystals include rod-like nanoparticles (e.g., less than 20nm in diameter and less than 500nm in length) produced by controlled acid hydrolysis of cellulose-based materials such as plants and trees.

In one embodiment, or in combination with any other mentioned embodiment, the spin dope comprises no greater than 20 wt%, no greater than 15 wt%, no greater than 10 wt%, no greater than 5 wt%, no greater than 3 wt%, no greater than 2 wt%, no greater than 1 wt%, or 0 wt% of a non-cellulose ester polymer based on total solids in the spin dope.

In one embodiment, or in combination with any other mentioned embodiment, the total weight of any polyurethane, polyolefin, nylon, polyester, and/or polyurethaneurea that may be present in the cellulose ester dope is not greater than 65 wt.%, not greater than 60 wt.%, not greater than 55 wt.%, not greater than 50 wt.%, not greater than 45 wt.%, not greater than 40 wt.%, not greater than 35 wt.%, not greater than 30 wt.%, not greater than 25 wt.%, not greater than 20 wt.%, not greater than 15 wt.%, not greater than 10 wt.%, not greater than 5 wt.%, not greater than 4 wt.%, not greater than 3 wt.%, not greater than 2 wt.%, not greater than 1 wt.%, or 0 wt.%, based on the total solids in the cellulose ester dope.

In one embodiment, or in combination with any other mentioned embodiment, any polyurethane that may be present in the cellulose ester dope is present in an amount of no greater than 10 wt.%, no greater than 9 wt.%, no greater than 8 wt.%, no greater than 7 wt.%, no greater than 6 wt.%, no greater than 5 wt.%, no greater than 4 wt.%, no greater than 3 wt.%, no greater than 2 wt.%, no greater than 1 wt.%, or 0 wt.%, based on the total solids in the cellulose ester dope.

In one embodiment, or in combination with any other mentioned embodiment, any polyurethaneurea that may be present in the cellulose ester dope is present in an amount of no greater than 10 wt.%, no greater than 9 wt.%, no greater than 8 wt.%, no greater than 7 wt.%, no greater than 6 wt.%, no greater than 5 wt.%, no greater than 4 wt.%, no greater than 3 wt.%, no greater than 2 wt.%, no greater than 1 wt.%, or 0 wt.%, based on the total solids in the cellulose ester dope.

In one embodiment, or in combination with any other mentioned embodiment, any acrylonitrile-vinyl acetate copolymer that may be present in the cellulose ester dope is present in an amount of no greater than 50 wt.%, no greater than 45 wt.%, no greater than 40 wt.%, no greater than 35 wt.%, no greater than 30 wt.%, no greater than 25 wt.%, no greater than 20 wt.%, no greater than 15 wt.%, no greater than 10 wt.%, no greater than 5 wt.%, no greater than 4 wt.%, no greater than 3 wt.%, no greater than 2 wt.%, no greater than 1 wt.%, or 0 wt.%, based on the total solids in the cellulose ester dope.

In one embodiment, or in combination with any of the other mentioned embodiments, the dope is prepared by mixing the cellulose ester, solvent, and any other components at a lower temperature. In certain embodiments, such mixing is performed by mixing at a temperature of at least 45 ℃, at least 46 ℃, at least 47 ℃, at least 48 ℃, at least 49 ℃, at least 50 ℃, at least 51 ℃, at least 52 ℃, at least 53 ℃, at least 54 ℃, at least 55 ℃, at least 56 ℃, at least 57 ℃, at least 58 ℃, at least 59 ℃, or at least 60 ℃, and/or no greater than 140 ℃, no greater than 130 ℃, no greater than 120 ℃, no greater than 110 ℃, no greater than 105 ℃, no greater than 104 ℃, no greater than 103 ℃, no greater than 102 ℃, no greater than 101 ℃, no greater than 100 ℃, no greater than 99 ℃, no greater than 98 ℃, no greater than 97 ℃, no greater than 96 ℃, or no greater than 95 ℃. In certain embodiments, such temperatures are 45 ℃ to 140 ℃, 45 ℃ to 105 ℃, 47 ℃ to 103 ℃, or 50 ℃ to 100 ℃.

In one embodiment, or in combination with any other mentioned embodiment, such mixing is performed for at least 5 minutes, at least 6 minutes, at least 8 minutes, at least 10 minutes, at least 12 minutes, at least 14 minutes, or at least 15 minutes and/or no more than 48 hours, no more than 36 hours, no more than 24 hours, no more than 20 hours, no more than 16 hours, no more than 12 hours, or no more than 8 hours. In certain embodiments, such time is from 5 minutes to 48 hours, from 5 minutes to 36 hours, from 5 minutes to 24 hours, or from 5 minutes to 8 hours.

In one embodiment, or in combination with any other mentioned embodiment, the dope is prepared by first slurrying the cellulose ester, solvent, and any other components, and then cooling to a very low temperature. In certain embodiments, such a temperature is at least-100 ℃, at least-75 ℃, at least-70 ℃, at least-65 ℃, at least-60 ℃, at least-55 ℃, or at least-50 ℃ and/or not more than 5 ℃, not more than 4 ℃, not more than 3 ℃, not more than 2 ℃, not more than 1 ℃, not more than 0 ℃, not more than-5 ℃, or not more than-10 ℃, and is stored at one of the above temperatures for at least 1 hour, at least 2 hours, at least 3 hours, at least 4 hours, at least 5 hours, at least 6 hours, at least 7 hours, at least 8 hours, at least 9 hours, or at least 10 hours, and/or not more than 48 hours, not more than 36 hours, not more than 30 hours, not more than 24 hours, or not more than 15 hours. In certain embodiments, such temperatures are-100 ℃ to 5 ℃, -75 ℃ to 0 ℃, -65 ℃ to 0 ℃, or-50 ℃ to-5 ℃, and/or the storage time is 1 hour to 48 hours, 3 hours to 36 hours, 5 hours to 24 hours, or 7 hours to 10 hours. In certain embodiments, the spin dope is warmed to room temperature and mixed at room temperature prior to dry spinning (SPIN DRYING).

After the cellulose ester dope is formed, it may be transported to an optional dope reservoir for temporary storage and/or degassing. The dope reservoir may comprise any conventional reservoir known in the art capable of storing cellulose ester dope. While stored in the tank, the cellulose ester dope may be subjected to conditions that are favorable to maintaining the physical properties of the dope and/or to removing air bubbles introduced during the mixing step. The temperature and pressure of the storage and/or degassing tanks can be optimized as needed to enhance and maintain the quality of the cellulose ester dope.

The cellulose ester dope may then be pumped from the dope reservoir to a filter, which may remove any large and undesirable particulates and gels from the cellulose ester dope prior to spinning. The filter may comprise any conventional filtration device and filter type known in the art. After filtration, the filtered cellulose ester dope may be pumped to a spinneret located near or in an evaporation chamber or cabinet.

The cellulose ester dope may be metered through a spinneret, thereby forming one or more fibers. The shape and size of the one or more holes in the spinneret help determine the cross-section of the one or more fibers. The number of holes in the spinneret surface determines the number of fibers that are simultaneously formed when the dope is metered into the spinneret. As the dope passes through the holes in the spinneret surface, filaments are formed.

More particularly, in one embodiment or in combination with any other mentioned embodiment, the cellulose ester dope may be spun through a spinneret orifice having a design known in the art (e.g., having an orifice area equivalent to a circular diameter of 20 to 200 microns) at a rate of 10 to 1,000 m/min. In one embodiment or in combination with any other mentioned embodiment, the spinneret can be maintained at a temperature of at least 75 ℃, at least 80 ℃, at least 85 ℃, at least 90 ℃, at least 95 ℃, or at least 100 ℃ and/or no greater than 175 ℃, no greater than 170 ℃, no greater than 165 ℃, no greater than 160 ℃, no greater than 155 ℃, or no greater than 150 ℃. In certain embodiments, the head of the spinneret can be maintained at a temperature of 75 ℃ to 175 ℃, 85 ℃ to 165 ℃, 95 ℃ to 160 ℃, or 100 ℃ to 150 ℃.

At the spinneret, the cellulose ester dope may be extruded through a plurality of holes to form continuous cellulose ester fibers. At the spinneret, the fibers can be drawn to form bundles of multiple filaments, or hundreds of filaments, or even thousands of filaments. Each of the bundles may include at least 10, at least 20, at least 30, at least 40, at least 50, at least 60, at least 70, at least 80, at least 90, at least 100, at least 150, at least 200, at least 250, at least 300, at least 350, or at least 400 and/or no greater than 1, 000, no greater than 900, no greater than 800, no greater than 700, or no greater than 600 fibers. The spinneret can be run at any speed suitable for producing the monofilament fibers and then assembling the monofilament fibers into bundles of the desired size and shape. The term "monofilament fiber" as used herein refers to continuous filaments that were initially produced by each hole in the spinneret surface.

The fibers are extruded through a spinneret into a vertical spin pack, which may have walls nominally between 150 ℃ and 240 ℃, and may contain a nominal 200-500 ℃ gas within the pack, where the solvent is flashed or evaporated. In certain embodiments, the evaporating comprises exposing the spun fiber to a temperature of at least 100 ℃, at least 110 ℃, at least 120 ℃, at least 130 ℃, at least 140 ℃, at least 145 ℃, at least 150 ℃, at least 153 ℃, at least 155 ℃, at least 160 ℃, at least 165 ℃, at least 170 ℃, at least 175 ℃, at least 180 ℃, at least 185 ℃, or at least 189 ℃, and/or no greater than 500 ℃, no greater than 400 ℃, no greater than 375 ℃, no greater than 350 ℃, no greater than 325 ℃, no greater than 300 ℃, no greater than 275 ℃, no greater than 250 ℃, no greater than 240 ℃, no greater than 230 ℃, or no greater than 220 ℃. In certain embodiments, such temperatures are 100 ℃ to 500 ℃, 110 ℃ to 400 ℃,1 ℃ to 375 ℃, 130 ℃ to 350 ℃, 140 ℃ to 300 ℃, or 150 ℃ to 250 ℃.

It should be noted that the cellulose ester fibers formed may be in the form of monocomponent fibers formed from only one material (e.g., cellulose ester) or a uniformly blended composition, and thus are not considered "bicomponent" or "multicomponent fibers" characterized by internal phases or boundaries defining different compositions within the outer surface of the fibers. In one embodiment, or in combination with any other mentioned embodiment, the resulting cellulose ester fibers may comprise at least 50 wt%, at least 55 wt%, at least 60 wt%, at least 65 wt%, at least 70 wt%, at least 75 wt%, at least 80 wt%, at least 85 wt%, at least 90 wt%, at least 95 wt%, at least 99 wt%, or at least 99.9 wt% of the cellulose ester, based on the total weight of the fibers. In certain embodiments, the cellulose ester fibers may be formed entirely from cellulose esters.

The individual cellulose ester fibers exiting the spinneret can have any suitable cross-sectional shape. Exemplary cross-sectional shapes include, but are not limited to, circular or other than circular (non-circular). In one embodiment, or in combination with any of the other mentioned embodiments, the filaments discharged from the spinneret can have a substantially circular cross-sectional shape. As used herein, the term "cross-section" generally refers to a transverse cross-section of a fiber measured in a direction perpendicular to the direction of elongation of the fiber. The cross-section of the fiber can be determined and measured using quantitative image analysis ("QIA").

The cross-sectional shape of a single fiber can also be characterized in terms of its deviation from a circular cross-sectional shape. In some cases, this deviation can be characterized by the shape factor of the fiber, which is determined by the following formula: form factor = perimeter/(4pi x cross-sectional area) 1/2. In some embodiments, the individual cellulose ester fibers may have a form factor of 1 to 2,1 to 1.8, 1 to 1.7, 1 to 1.5, 1 to 1.4, 1 to 1.25, 1 to 1.15, or 1 to 1.1. The shape factor of a fiber with a perfectly circular cross-sectional shape is 1. The shape factor can be calculated from the cross-sectional area of the fiber that can be measured using QIA.

Furthermore, in certain embodiments, the cellulose ester fibers may be in the form of solid fibers (fibers having a solid cross-sectional shape without holes) rather than hollow fibers.

In one embodiment, or in combination with any other mentioned embodiment, while a typical spin basket for spandex fibers may have more than 30 ends (or yarns), it is desirable for cellulose esters to have no more than 30 ends/basket (ends per cabinet), no more than 25, no more than 20, no more than 15, no more than 10, no more than 8, no more than 6, no more than 4 ends/basket. The reduction in the number of warp yarns in the vertical spin basket enables adequate solvent evaporation at lower temperatures, which is beneficial in preventing fiber discoloration.

In one embodiment, or in combination with any other mentioned embodiment, it is desirable to stretch the cellulose ester fibers no more than 2x, no more than 1.8x, no more than 1.6x, no more than 1.4x, no more than 1.2x, where the stretch ratio is defined as the ratio of the fiber velocity at the outlet of the vertical spin basket to the fiber velocity at the outlet of the spinneret orifice.

In one embodiment, or in combination with any other mentioned embodiment, the cellulose ester fibers and/or yarns made therefrom may exhibit 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 no greater than 3.0, or no greater than 2.5 g/denier, no greater than 2.3 g/denier, no greater than 2.1 g/denier, no greater than 2.9 g/denier, or no greater than 1.9 g/denier, as measured according to ASTM D22556.

Elongation, also known as elongation at break, is expressed as a percentage and indicates how much the yarn or filament will stretch before breaking. In one embodiment, or in combination with any other mentioned embodiment, the cellulose ester fibers and/or yarns made therefrom may exhibit an elongation at break of at least 10%, at least 15%, 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 ("SF") is an empirically determined relationship between tenacity and elongation that is used to predict the failure envelope (failure envelope) of a given fiber. The silk factor can be used to characterize the suitability of a yarn or fiber for a given process and is calculated based on the following formula:

In one embodiment, or in combination with any other mentioned embodiment, the cellulose ester fibers and/or yarns made therefrom may exhibit a silk factor of at least 5.0, at least 6.0, at least 7.0, or at least 7.6, wherein elongation is defined as a percentage, tenacity in grams per denier.

As described above, the cellulose ester fibers are formed into continuous filament fibers. Thus, in one embodiment or in combination with any other mentioned embodiment, the cellulose ester fibers may have an aspect ratio (L/D) of at least 10:1, at least 20:1, at least 30:1, at least 40:1, at least 50:1, at least 100:1, at least 500:1, at least 1,000:1, or at least 10,000:1.

After evaporation or solvent flashing, the continuous filament fibers may accumulate on the core or tube at a winder and may be sent to an optional downstream process. Notably, as the present disclosure relates to dry spinning processes, the fibers are not passed or pulled through a coagulation bath after evaporation or solvent flash. The fibers may be wound around a take-up roll that provides tension and pulls the fibers into a downstream step of the process, which may include, for example, one or more annealing sections, a winder, a crimper, a cutter, or a combination thereof.

In one embodiment, or in combination with any other mentioned embodiment, although the spandex yarn bobbin is wound by a significant amount of winder stretch (WINDER DRAW), where the winder speed is typically 5% faster than the speed of the previous roll; however, for cellulose ester continuous filament fibers, it is desirable to have less than 3% winder tension (WINDER DRAW), less than 2% winder tension, less than 1% winder tension, less than 0.8% winder tension, less than 0.5% winder tension.

The continuous filament cellulose ester fibers may be gathered into bundles, bands, or yarns. The bundle, belt or yarn may comprise a plurality of cellulose ester fibers. Each of these bundles, tapes or yarns may comprise at least 20, at least 30, at least 40, at least 50, at least 60, at least 70, at least 80, at least 90, at least 100, at least 150, at least 200, at least 250, at least 300, at least 350 or at least 400 and/or no more than 1,000, no more than 900, no more than 800, no more than 700 or no more than 600 filaments.

In one embodiment, or in combination with any other mentioned embodiment, the cellulose ester fibers and/or bundles of cellulose esters, bands, or yarns may pass through a crimping zone where a patterned wavy shape may be imparted to at least a portion or substantially all of the individual fibers. When used, the crimping zone includes at least one crimping device for mechanically crimping the fibers. In general, cellulose ester fibers are desirably not crimped by thermal or chemical means (e.g., hot water bath, steam, air jet, or chemical coating), but rather are mechanically crimped using a suitable crimper. One example of a suitable type of mechanical crimping machine is a "stuffing box" or "stuffer box (stuffer box)" crimping machine that uses multiple rollers to create friction, which causes the fibers to bend and form crimps. Other types of crimping machines may also be suitable. Examples of devices suitable for providing crimped fibers are described, for example, in U.S. patent 9,179,709;2,346,258;3,353,239;3,571,870;3,813,740;4,004,330;4,095,318;5,025,538;7,152,288; and 7,585,442, each of which is incorporated herein by reference to the extent not inconsistent with the present disclosure.

In one embodiment, or in combination with any other mentioned embodiment, crimping may be performed such that the cellulose ester fibers have a crimp frequency of at least 5, at least 7, at least 10, at least 12, at least 13, at least 15, or at least 17 and/or at most 30, at most 27, at most 25, at most 23, at most 20, or at most 19 crimps per inch ("CPI") as measured according to ASTM D3937-12. In certain embodiments, the average CPI of the fibers used to make the cellulose ester bundles, tapes or yarns and/or various downstream products may be 7 to 30CPI, 10 to 27CPI, 10 to 25CPI, 10 to 23CPI, 10 to 20CPI, 12 to 30CPI, 12 to 27CPI, 12 to 25CPI, 12 to 23CPI, 12 to CPI, 15 to 30CPI, 15 to 27CPI, 15 to 23CPI, 15 to 20CPI, or 15 to 19CPI.

In one embodiment or in combination with any other mentioned embodiment, the crimp amplitude of the fibers when crimped may be different and may be, for example, at least 0.85, 0.90, 0.93, 0.96, 0.98, 1.00, or 1.04mm. Additionally or alternatively, in one embodiment or in combination with any other mentioned embodiment, the crimp amplitude of the fibers may be at most 1.75, at most 1.70, at most 1.65, at most 1.55, at most 1.35, at most 1.28, at most 1.24, at most 1.15, at most 1.10, at most 1.03, or at most 0.98mm.

In addition, in one embodiment or in combination with any other mentioned embodiment, the cellulose ester fibers, cellulose ester bundles, tapes or yarns, and/or staple fibers made therefrom may have a crimp ratio of at least 1:1. As used herein, "crimp ratio" refers to the ratio of the uncrimped strand length to the crimped strand length. In certain embodiments, the cellulose ester fibers, cellulose ester yarns, and/or staple fibers made 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.

Curl amplitude and curl ratio are measured according to the procedure outlined in U.S. patent application publication No. 2020/0299822, which is incorporated herein by reference to the extent not inconsistent with the present disclosure.

Additionally or alternatively, in one embodiment or in combination with any other mentioned embodiment, one or more types of surface finishes may be applied to the cellulose ester fibers and/or bundles, tapes, or yarns made therefrom. The method of application is not limited and may include the use of spray coating, wicking application, dipping, or the use of squeeze rolls, lick (1 ick) rolls, or feed (kiss) rolls. The location at which the finish is applied to the fibers may vary with the function of the finish. For example, the lubricant finish may be applied after spinning and before crimping or before gathering the fibers into bundles. The cutting lubricant and/or antistatic lubricant may be applied before or after crimping and before drying. Suitable amounts of all finishes (whether lubricant, cutting lubricant, antistatic finish, or otherwise) on cellulose ester fibers may be at least 0.01%, at least 0.02%, at least 0.05%, at least 0.10%, at least 0.15%, at least 0.20%, at least 0.25%, at least 0.30%, at least 0.35%, at least 0.40%, at least 0.45%, at least 0.50%, at least 0.55%, or at least 0.60% of a finish-on-yarn ("FOY") relative to the weight of dry cellulose ester fibers. Additionally or alternatively, in one embodiment or in combination with any other mentioned embodiment, the cumulative amount of finish may be present in an amount of no greater than 2.5%, no greater than 2.0%, no greater than 1.5%, no greater than 1.2%, no greater than 1.0%, no greater than 0.9%, no greater than 0.8%, or no greater than 0.7% foy, based on the total weight of the dry fiber. The amount of finish on the fibers, expressed as weight percent, can be determined by solvent extraction. As used herein, "FOY" or "yarn-borne finish" refers to the amount of finish on the fiber or yarn minus any added water.

In one embodiment, or in combination with any of the other mentioned embodiments, the cellulose ester fibers may comprise at least one plasticizer, or alternatively, 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 fibers. When present, the plasticizer may be incorporated into the fiber itself by spinning a dope containing the plasticizer contained in a pulp (flake) used to make the dope, and/or the plasticizer may be applied to the surface of the fiber or filament by any method used to apply a finish. If desired, plasticizers may be included in the finish formulation.

In one embodiment, or in combination with any other mentioned embodiment, the cellulose ester fibers and/or yarns formed therefrom may be biodegradable. As used herein, the term "biodegradable" generally refers to the tendency of a material to chemically decompose under certain environmental conditions. The extent of degradation can be characterized by the loss of sample weight over a given period of exposure to certain environmental conditions. In some cases, cellulose ester fibers and/or yarns formed therefrom may exhibit a weight loss of at least 5%, at least 1O%, at least 15%, or at least 20% after 60 days of burial in soil, 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 degradation rate may vary depending on the particular end use of the fiber. Exemplary test conditions are provided in U.S. patent 5,870,988 and 6,571,802, which are incorporated herein by reference.

In one embodiment, or in combination with any other mentioned embodiment, the cellulose ester fibers and/or yarns formed therefrom may be compostable. The material must meet the following four criteria to be considered "compostable": (1) the material must be biodegradable; (2) the material must be disintegrable; (3) the heavy metal content of the material must not exceed a maximum amount; and (4) the material must not be eco-toxic. The term "disintegrable" refers to the tendency of a material to physically break down into smaller pieces when exposed to certain conditions. The disintegration depends on the material itself, as well as the physical size and structure of the article being tested. The effect of the material on plant longevity was measured for ecotoxicity and the heavy metal content of the material was determined according to the procedure outlined in the standard test methods.

In one embodiment, or in combination with any other mentioned embodiment, the cellulose ester fibers and/or yarns formed therefrom may be industrially compostable, home compostable, or both. In such embodiments, the cellulose ester fibers may meet four criteria: (1) Biodegradation to convert at least 90% of the carbon content within 180 days; (2) Disintegrable such that at least 90% of the material disintegrates within 12 weeks; (3) Does not contain heavy metals exceeding the threshold established under the EN12423 standard; and (4) the disintegrated content as humus supporting future plant growth; wherein each of these four conditions is tested according to ASTM D6400, ISO 17088 or EN 13432 methods.

In one embodiment, or in combination with any other mentioned embodiment, the cellulose ester fibers and/or yarns formed therefrom may exhibit at least 70% biodegradation for a period of no more than 50 days when tested under aerobic composting conditions at ambient temperature (28 ℃ ± 2 ℃) according to ISO 14855-1 (2012). In some cases, cellulose ester fibers and/or yarns formed therefrom may exhibit at least 70% biodegradation over a period of no more than 49, no more than 48, no more than 47, no more than 46, no more than 45, no more than 44, no more than 43, no more than 42, no more than 41, no more than 40, no more than 39, no more than 38, or no more than 37 days when tested under these conditions, also referred to as "home composting conditions. These conditions may not be aqueous or anaerobic.

In one embodiment, or in combination with any other mentioned embodiment, the cellulose ester fibers and/or yarns formed therefrom may exhibit at least 60% biodegradation for a period of no more than 45 days when tested under aerobic composting conditions at 58 ℃ (±2 ℃) according to ISO 14855-1 (2012). In some cases, cellulose ester fibers and/or yarns formed therefrom may exhibit at least 60% biodegradation for a period of no more than 44 days when tested under these conditions, also referred to as "industrial composting conditions". These may not be aqueous or anaerobic conditions.

The resulting cellulose ester fibers can be used to produce a wide variety of end products, such as tow bands, staple fibers, filament yarns, spun yarns (spun yarns), woven articles, nonwoven articles, and/or knitted fabrics.

In one embodiment, or in combination with any of the other mentioned embodiments, the cellulose ester fibers and/or cellulose ester yarns described above may be cut into staple fibers. Any suitable type of cutting device capable of cutting the fibers to the desired length without unduly damaging the fibers may be used. Examples of cutting devices may include, but are not limited to, rotary cutters, choppers (guillotines), stretch breaking devices, reciprocating blades, or combinations thereof. Once cut, the cellulose ester staple fibers may be packaged or otherwise bagging or packaging for subsequent transport, storage, and/or use. In one embodiment or in combination with any other mentioned embodiment, the d50 length of the staple fibers may be at least 5, at least 10, at least 20, at least 30, at least 40, or at least 50mm and/or not greater than 150, not greater than 140, not greater than 130, not greater than 125, not greater than 120, not greater than 115, not greater than 110, not greater than 105, not greater than 100, or not greater than 95mm.

Additionally or alternatively, in one embodiment or in combination with any other mentioned embodiment, the denier per filament (weight in grams of 9000 meters of fiber length) or "DPF" of the cellulose ester fibers (whether cellulose ester staple fibers or cellulose ester continuous fibers) may be from 0.5 to less than 20. The particular method used for measurement is not limited and includes ASTM 1577-07 method using FAVIMAT vibrometer procedures (if filaments for cutting short fibers are available), microbalance weight measurement of samples of known length, or width analysis using any convenient optical microscope or analyzer. The DPF may also be associated with a maximum width of the fibers.

In one embodiment, or in combination with any of the other mentioned embodiments, the staple fibers may be formed into cellulose ester staple yarns. The spun yarn is a continuous strand (continuous strands) comprising chopped staple fibers (short staple fibers) mechanically entangled by a spun yarn spinning process. The spun yarn spinning process may be, but is not limited to, ring spinning, open-end spinning, air jet spinning, compact spinning, siro spinning, vortex spinning, combed spinning, semi-combed spinning, carded spinning (woolen spinning), and wet spinning with flax.

In one embodiment, or in combination with any of the other mentioned embodiments, the cellulose ester fibers may be formed into a nonwoven article, such as a nonwoven. Exemplary nonwoven articles may include wet laid nonwoven articles, air laid nonwoven articles, carded articles, and/or dry laid nonwoven articles.

In one embodiment, or in combination with any of the other mentioned embodiments, the cellulose ester yarns may be formed into a woven article, such as a woven fabric. The woven fabric may be formed on a loom by interlacing at least two yarns (warp and weft) with the warp strands oriented in parallel and the weft yarns interlaced in alternating patterns above and below the warp at an angle to the orientation of the warp.

In one embodiment, or in combination with any of the other mentioned embodiments, the cellulose ester yarns may be formed into a knitted article, such as a knitted fabric. Such a knitted fabric may be formed by interlocking of yarn loops.

In one embodiment, or in combination with any other mentioned embodiment, the end products described herein, including staple fibers, yarns, nonwoven articles, knitted articles, and woven articles, may comprise, consist essentially of, or consist of cellulose ester fibers. The end products, including staple fibers, yarns, nonwoven articles, knitted articles, and woven articles, described herein may comprise at least 0.25, at least 0.5, at least 0.75, at least 1, at least 2, at least 3, at least 4, at least 5, at least 6, at least 7, at least 8, at least 9, at least 10, at least 12, at least 15, at least 18, at least 20, at least 25, at least 30, at least 35, at least 40, at least 45, at least 50, at least 55, at least 60, at least 65, at least 70, at least 75, at least 80, at least 85, at least 90, at least 95, at least 99, or at least 99.9 weight percent of one or more cellulose ester fibers based on the total weight of the article. Additionally or alternatively, in one embodiment, or in combination with any other mentioned embodiment, the end products described herein, including staple fibers, yarns, nonwoven articles, knitted articles, and woven articles, may comprise not greater than 99, not greater than 95, not greater than 90, not greater than 85, not greater than 80, not greater than 75, not greater than 70, not greater than 65, not greater than 60, not greater than 55, not greater than 50, not greater than 45, not greater than 40, not greater than 35, not greater than 30, not greater than 25, not greater than 20, not greater than 15, not greater than 10, not greater than 9, not greater than 8, not greater than 7, not greater than 6, or not greater than 5 weight percent of one or more cellulose ester fibers based on the total weight of the article. In certain embodiments, the final product may be formed entirely of cellulose ester fibers, or comprise from 0.25 to 50, from 1 to 99, from 1 to 50, from 50 to 99, from 1 to 20, or from 0.25 to 5 weight percent of one or more cellulose ester fibers, based on the total weight of the article.

Additional advantages of the various embodiments will be apparent to those skilled in the art upon review of the disclosure herein and the following examples of operation. It is to be appreciated that the various embodiments described herein are not necessarily mutually exclusive unless otherwise indicated herein. For example, features described or illustrated in one embodiment may be included in other embodiments as well, but are not necessarily included. Accordingly, the present disclosure encompasses various combinations and/or integrations of the specific embodiments described herein.

Definition of the definition

It should be understood that the following is not intended to constitute an exclusive list of defined terms. Other definitions may be provided in the foregoing description, such as when used herein along with the defined terms.

The terms "a," "an," and "the" as used herein mean one or more.

The term "and/or" as used herein when used in a list of two or more items means that any one of the listed items may be used alone or any combination of two or more of the listed items may be used. For example, if a composition is described as containing components A, B, and/or C, the composition may contain a alone; only B; only C; a combination comprising a and B; a combination comprising a and C; a combination comprising B and C; or a combination containing A, B and C.

The terms "comprising," "including," and "containing" as used herein are open-ended transition terms used to transition from a subject recited before the term to one or more elements recited after the term, where the one or more elements recited after the transition term are not necessarily the only elements that make up the subject.

The term "having" as used herein has the same open-ended meaning as "comprising" provided above.

The term "comprising" as used herein has the same open-ended meaning as "comprising" provided above.

Numerical range

The present specification uses a range of values to quantify certain parameters relating to the invention. It should be understood that when numerical ranges are provided, these ranges should be construed as literally supporting claim limitations that list only the lower limit of the range and claim limitations that list only the upper limit of the range. For example, a numerical range of 10 to 100 is literally supported by the claims reciting "greater than 10" (without an upper limit) and by the claims reciting "less than 100" (without a lower limit).

In addition, it should be understood that the list of values following a descriptor, such as "at least" and "no greater than," provides literal support for a range based on all values following the descriptor. For example, a statement that "at least 2, 5, or 10 and/or not greater than 100, 50, or 25" will provide literal support for a range of "at least 25", "not greater than 50", and "at least 10 and not greater than 25".

Examples

The following examples illustrate methods according to the present disclosure. It is to be understood that these embodiments are provided by way of illustration only and nothing therein should be taken as a limitation upon the overall scope.

Materials and methods

The dope was prepared by using fresh bottles of reagent grade DMF to minimize any contamination or residual water. Each dope contained 25 grams EASTMAN CA 394-60 cellulose acetate (CDA) and 75 grams DMF solvent. For the "hot mix" case, the DMF is first heated in a jar to the desired mixing temperature (typically 90 ℃) for 15 minutes before adding the CDA powder. The jar has a lid that minimizes the ingress of atmospheric air. Mixing was started using a mechanical stirrer for 1 hour after which time the sample was removed, cooled to room temperature, and tested for color and haze.

For the "cold mix" sample, CDA was slurried with DMF at room temperature, then the jar was sealed and inserted into a cooler filled with dry ice where it was stored for 4 hours, then allowed to warm to room temperature, then rolled overnight at room temperature to complete homogenization of the mix. Several additional samples were run, with the samples inserted into a standard laboratory freezer instead of dry ice, but the procedure was otherwise identical.

The moisture content of the starting CDA was measured using a Sartorius Mark 3 analyzer (Goettinggen, germany). The As-received sample (As-RECEIVED SAMPLES) had a moisture content of 1.3% by weight. Wet CDA samples with a moisture content of 3.5 wt% were obtained from open bags already in the laboratory for several months. A dried sample having a moisture content of 0.1 wt% was obtained by drying the wet sample in a vacuum oven at 60 ℃.

The color and haze of the dope samples were determined by pouring the dope into 20mm cuvettes using Hunter Labs Ultrascan Pro (reston, VA) system. The cuvette was then inserted into the chamber for optical testing. The values are typically measured after initial dope mixing and then measured again after storage at 120 c (to simulate the temperature of dry spinning) for 2 hours. Colors are reported as L (gray scale), a (red to green scale) and b (blue to yellow). High b values represent more yellow samples. Some samples showed very low L, which means they were very dark.

Film casting of the samples was performed to simulate fiber spinning in order to more easily obtain color measurements. After storage at 120 ℃, the dope was cooled to 90 ℃ and then cast on a glass plate (also heated to 90 ℃) using a doctor blade. The nominal thickness of the final film is 40um to 70um. The film was annealed at 180 ℃ for 20 minutes to remove solvent (some samples were annealed for less time to better simulate the bin (cabinet) conditions). The same instrument was also used to measure color and haze (without correction for thickness differences) on film samples in transmission mode.

The absolute molecular weight was measured on the cast film using GPC by dispersing the sample into NMP solvent. The GPC column was calibrated using absolute Mw standards.

Examples 1 to 7

Effects of moisture and temperature on dope formation

Wet and dry samples made using the "hot mix" and "cold mix" methods were compared. The color and haze of the dope were measured after mixing and after 2 hours at 120 c (see table I). Sample #1 had minimal yellowing (lowest b) and was made using a more wet cellulose sample and with a cold mix process. Suboptimal is #4, which is made by hot mixing with a dry sample. Interestingly, "cold and wet" or "hot and dry" produced the lowest yellowness. All other combinations are inferior and are approximately the same relative to each other.

TABLE I influence of moisture and mixing temperature

Film haze values, all with low color relative to the spin dope, were also shown. Slight differences in values between film samples are mainly due to differences in film thickness.

Sample #5 was mixed at 50 ℃ instead of 90 ℃ to determine the actual lower temperature limit of the hot mix. The sample took about twice as long to dissolve relative to 90 ℃. The other sample (# 6) was mixed at room temperature, but did not dissolve even after 3 hours. However, a sample (# 7) of the dope stored at-10℃in the freezer produced a good quality dope.

Examples 10 to 16

Additive effects by cold mixing

In this example, a cold mix process similar to example 1 above was used to prepare a dope, except that additional amounts of stabilizing additives (0.5 or 1 wt%) were also included. The starting moisture was 1.3 wt% for all CDA samples. Additives represent a range of possible stabilizers, acids, buffers, antioxidants, etc. As observed and shown in table II, the addition of citric acid had the most pronounced effect on b and significantly reduced color formation. The mixture of citric acid and potassium citrate (# 12 and # 13) is suboptimal with moderate levels of color formation. Samples #13, #14, and #15 still had some undissolved solids because the additives were not completely dissolved. Acetate added as buffer performed the worst as these had the highest color formation (worse than no additive at all). Note that #15 had low b, but as shown by very low L, the sample darkened during heating.

TABLE II Cold mix dope Using Dry ice

Examples 20 to 37

Additive effect by thermal mixing at 90 DEG C

These examples are similar to #10 described above, except that the samples are mixed at 90 ℃. Furthermore, for all additives (except #30 to #32, which used 0.5 wt%) the additive content was reduced to 0.15 wt% to help minimize undissolved particles. All samples had 1.3 wt% starting moisture except #31, which had 0.1% moisture. As with cold mixing, various salts and buffers tend to make the color worse. Monofunctional acetic acid also has the same effect. The only sample with the lower color contained multifunctional citric acid. Succinic acid (# 32) does not produce good color in the film, even though it is multifunctional like citric acid.

Note that the content of 0.15 wt% is a lower limit effective to reduce color. A more desirable target is about 0.3 to 0.7 wt% based on the data. At higher levels of 1% according to the previous examples, the color was not significantly improved compared to 0.5% loading.

Sample #31 also included a comparison to a highly dried sample at 0.5% citric acid to see if moisture had an effect. Comparison with #10, #11 and #20 shows that moisture is less critical for citric acid, as the amount appears to be a more important variable.

Samples #32-37 compare other multifunctional acids under these ideas, which may also contribute to color stabilization. Citric acid was observed to control color much better than succinic acid, malic acid, or tartaric acid.

Table III hot mix spinning dope at 90 DEG C

Examples 40 to 48

Influence of acid on film casting color

In this example, film samples were cast and annealed for different times. In samples #40 and #41, films were cast from the same spin dope (# 10). In #40, the films were cast and annealed in a hot air oven at 180 ℃ for 20 minutes to dry the films (see table IV). Note that the citric acid film is very yellow after 20 minutes, as this is above its melting point and degradation may occur due to oxygen exposure. In a typical dry spinning cabinet, temperature exposure occurs for only a few seconds (and possibly with a nitrogen blanket). Therefore, in order to better reflect the spinning conditions, the second film (# 41) is cast and dried at 180 ℃ for 4 minutes, which is the shortest time required to dry the film. As observed, the color drops significantly and gives a much better color than the other samples. The sample was also completely dry and free of any DMF odor. Finally, sample #47 was cast from the same dope, but annealed at 150 ℃ for 20 minutes. The sample also had an excellent color similar to that at 180 ℃ for 4 minutes. In the remaining examples, samples of other acids were also cast into films and annealed using a protocol of 4 minutes at 180 ℃. At all citric acid addition levels, the citric acid containing spin dope had a lower yellowness than the control. In contrast, 0.5% malic acid and tartaric acid were slightly more yellow than the control.

TABLE IV film haze and annealing time

The claims are not limited by the disclosed embodiments

The preferred forms of the invention described above are to be used as illustration only and should not be used in a limiting sense to interpret the scope of the present invention. Modifications to the above-described exemplary embodiments may be readily made by those skilled in the art without departing from the spirit of the invention.

The inventors hereby state their intent to rely on the doctrine of equivalents to determine and assess the reasonably fair scope of the present invention as pertains to any matter not materially departing from but outside the literal scope of the invention as set forth in the following claims.

Claims

1. A method of producing cellulose ester fibers, the method comprising dry spinning a cellulose ester dope via a spinneret to produce one or more of the fibers, wherein the cellulose ester dope comprises dissolved and/or dispersed solids (hereinafter "solids") and a solvent, at least 35% by weight of the solids comprising cellulose ester, and the solvent comprises N, N-dimethylformamide, N-dimethylacetamide, or dimethylsulfoxide, or a mixture thereof, provided that if the solvent comprises N, N-dimethylacetamide:

(Ii) The cellulose ester dope comprises 0wt% cellulose nanocrystals based on the total weight of the cellulose ester dope; or (b)

(Iii) (i) and (ii),

Wherein the total weight of polyurethane, polyolefin, nylon, polyester, and/or polyurethaneurea, if present in the cellulose ester dope, is not greater than 60 weight percent based on the total solids in the cellulose ester dope.

2. The process according to claim 1, wherein the cellulose ester dope comprises no more than 10 wt.% polyurethane or polyurethaneurea, based on total solids in the cellulose ester dope.

3. The process according to claim 1 or 2, wherein the cellulose ester dope comprises not more than 50 wt% acrylonitrile-vinyl acetate copolymer based on total solids in the cellulose ester dope.

4. The process according to any of the preceding claims, wherein the cellulose ester fibers comprise at least 50 weight percent of the cellulose ester obtained from the cellulose ester dope.

5. The process according to any of the preceding claims, wherein the cellulose ester has a DS _{Acetyl group} of at least 1.5 and/or not greater than 2.95.

6. The process according to any of the preceding claims, wherein the cellulose ester has a glass transition temperature of at least 120 ℃ and/or not greater than 250 ℃.

7. The method according to any of the preceding claims, wherein the dry spinning comprises:

spinning the cellulose ester dope to produce spun fibers containing the solvent; and

Evaporating the solvent from the spun fibers.

8. The process according to any of the preceding claims, wherein the cellulose ester dope comprises a multifunctional acid.

9. The process according to any of the preceding claims, wherein the cellulose ester dope has a moisture content of not greater than 4wt%, based on the total weight of the cellulose ester dope.

10. The process according to any one of the preceding claims, further comprising preparing the cellulose ester dope as follows: pulping said cellulose ester and said solvent, then cooling said dope to a temperature of at least-100 ℃ and/or not greater than 5 ℃, and storing at one of said temperatures for at least 1 hour.

11. The process according to any of the preceding claims, wherein the cellulose ester dope of any of claims 1-8, wherein b is not greater than 0.75.

12. Cellulose ester fibers formed according to any of the preceding claims.

13. A yarn comprising the cellulose ester fibers formed according to claim 12.

14. An article comprising the cellulose ester fibers formed according to claim 12.

15. A woven article comprising the cellulose ester fibers formed according to claim 12.

16. A nonwoven article comprising the cellulose ester fibers formed according to claim 12.

17. A staple fiber comprising the cellulose ester fiber formed according to claim 12.

18. A knitted fabric comprising the cellulose ester fibers formed according to claim 12.

19. The method according to claim 7, wherein evaporating said solvent from said spun fibers is performed in a spin basket.

20. The process according to claim 16, wherein the spun fibers are drawn in the spin basket to a draw ratio of no more than 2 x.