Dichloromethane-free process for producing cellulose triacetate fibers

Abstract

A dichloromethane-free wet spinning process for producing cellulose triacetate fibers having a silk factor greater than 8.0. A dichloromethane-free cellulose triacetate dope containing dimethylacetamide is controlled to a temperature in the range of 20 °C to 40 °C and wet spun in a coagulation bath containing dimethylacetamide and water. A jet drawing draw ratio in the range of 0.3 to 1.4 is applied to the wet spun CTA fibers, and the fibers can also be passed through a post-drawing step of jet drawing one or more times. During drying, the CTA fibers partially or completely shrink. By this process, CTA fiber(s) having a silk factor greater than 8.0 can be produced without using dichloromethane and without incurring the energy costs associated with other processes that require low or high coagulation bath temperatures.

Description

Technical Field

[0001] The present invention relates to a dichloromethane-free wet spinning process for producing cellulose triacetate fibers having a silk factor of at least 8.0.

Background Art

[0002] Cellulose triacetate (CTA) fibers have unique properties that make them highly desirable for textile applications. CTA has a crystallinity and low modulus that enable a silk-like feel with "washing and wearing" properties (i.e., good crease retention and low water absorption) better than other cellulose-based polymers such as cellulose diacetate or viscose. Unfortunately, due to the crystalline and polar nature of cellulose triacetate, cellulose triacetate is insoluble in all solvents except the most aggressive ones.

[0003] Historically, dichloromethane (DCM), also known as methylene chloride, and blends of DCM with alcohols such as methanol and / or ethanol have served as the primary solvent systems used to dissolve CTA in order to produce CTA having acceptable tensile strength and elongation. However, due to environmental, health, and regulatory issues, the use of DCM-based solvent systems has been significantly reduced. Although other solvents have been evaluated as alternatives to DCM, such evaluations have typically resulted in the production of CTA fibers with insufficient tensile strength, elongation at break, or silk factor. Many DCM-free processes for producing CTA fibers require low-temperature coagulation baths that need cooling and / or insulation, in addition to high-temperature washing steps to remove residual solvents. Due to the energy required to cool and / or heat such processing steps, these approaches are more expensive to operate and are difficult unless the existing processes can be improved.

[0004] The manufacturing process of making a fabric by knitting and weaving threads involves devices and processing steps that apply stress and strain to the knitting threads, which can result in weak fibers or knitting threads due to breakage of the knitting threads. Breakage leads to process downtime, loss of yield, and degradation of quality. Tensile strength and elongation at break (elongation rate) are two properties of knitting threads that are useful for measuring the suitability of knitting threads for use in a given fabric process or for use with a given apparatus.

[0005] Retention is a measure of the force required to break a fiber or knitting thread at a given denier or dtex and is typically expressed in units of g / den, g / dtex, or N / dtex. One technique for increasing the retention of CTA fibers and knitting threads is to utilize CTA polymers with a high degree of polymerization (DP). This is because high DP CTA polymers typically yield high retention CTA fibers. A common problem associated with this approach is that high DP CTA polymers tend to produce a more viscous CTA dope, which can make filtration and spinning difficult, especially at high speeds or in large volumes. The problem of high viscosity dope can be particularly problematic when working with dichloromethane-free solvent systems. Alternative means of increasing the retention of CTA fibers or knitting threads without using high DP CTA polymers involve stretching or elongating the coagulated fibers. By stretching / applying stress to the fibers, a certain degree of orientation can be imparted, which is translated into an increase in retention. The problem associated with increasing retention by stretching is that the resulting increase in orientation causes a decrease in the ductility of the fibers and a lower elongation rate.

[0006] The elongation rate, also known as elongation at break, is the ratio of the increase in the length of a knitting thread or fiber sample at the break point under a tensile load to the length of the sample before the load is applied. The elongation rate is expressed as a percentage and indicates how much the knitting thread or fiber elongates before breaking. As described above, the elongation rate also decreases when coagulated CTA fibers are stretched to improve retention.

[0007] Silk factor (SF) is an experimentally measured relationship between holding power and elongation used to predict the breaking envelope of a given fiber. The SF can be used to characterize the suitability of a fiber or yarn for use in a given process. The silk factor is herein,

Number

[0008] There is a market need to improve the silk factor of cellulose triacetate fibers produced by a dichloromethane-free process so that the resulting CTA fibers can be processed into filament yarns or converted into staple fibers for ring spinning and / or nonwoven applications.

[0009] It is beneficial to provide products having such properties from processes that do not utilize a dichloromethane solvent system, which can contribute to operator health issues and environmental pollution concerns. It is also beneficial to operate such a DCM-free process at or near ambient temperature in key processing steps such as coagulation.

Summary of the Invention

[0010] In one or more aspects, the present invention provides a) a dissolving step of dissolving cellulose triacetate in one or more dichloromethane-free dope solvents comprising at least dimethylacetamide to prepare a cellulose triacetate dope, b) The above cellulose triacetate dope is wet-spun in a dichloromethane-free coagulation bath to form one or more cellulose triacetate fibers with a jet drawing draw ratio in the range of 0.3 to 1.4. The above dichloromethane-free coagulation bath contains dimethylacetamide and water and is maintained in the temperature range of 20°C to 40°C, a wet spinning process; c) A drying process in which the one or more cellulose triacetate fibers are dried so as to shrink the one or more cellulose triacetate fibers, relating to a process for producing cellulose triacetate fibers having a silk factor of 8.0 or more.

[0011] In one or more embodiments, the present invention relates to wet-spun cellulose triacetate fibers. Generally, cellulose ester fibers exhibit a silk factor of at least 8.0. Further, the cellulose ester fibers include a cellulose ester having a DS of at least 2.6 アセチル and a number average degree of polymerization of 200 or less.

[0012] In one or more embodiments, the present science and technology relates to cellulose triacetate dope. Generally, CTA dope contains CTA in one or more solvents including dimethylacetamide, dimethylformamide, or a combination thereof. Further, CTA has a DS of at least 2.6 アセチル and a number average degree of polymerization of 200 or less. Further, the CTA dope exhibits a viscosity of 1,000 poises or less when measured at 90°C.

[0013] Embodiments of the present invention are described herein with reference to the following drawings.

Brief Description of the Drawings

[0014]

Figure 1

[0015]

Figure 2

[0016]

Figure 3

[0017]

Figure 4

[0018]

Figure 5

[0019]

Figure 6

[0020]

Figure 7

[0021]

Figure 8

[0022] This application generally relates to a DCM-free wet spinning process for preparing cellulose triacetate fibers. Such fibers can be utilized in downstream fiber conversion and fabric applications. Further, such DCM-free CTA fibers can be manufactured by a wet spinning process. In such a process, CTA is dissolved in a DCM-free solvent that may include dimethylacetamide and optionally one or more non-DCM solvents (e.g., dimethylformamide) to form a CTA dope. The resulting CTA dope is wet spun directly through a plurality of small holes at the immersion surface of a spinneret into a DCM-free coagulation bath containing dimethylacetamide and water. The solvent concentration and conditions of the DCM-free coagulation bath can be optimized to affect coagulation and fiber formation. The temperature of the coagulation bath is preferably maintained at or near ambient conditions. Further, one or more CTA fibers are drawn in a DCM-free coagulation bath under specific jet draw stretching conditions (e.g., with the ratio of the fiber take-up speed to the calculated speed of the CTA dope being the same as when exiting the spinneret and entering the first coagulation bath), to impart a desired polymer orientation within the one or more CTA fibers as the CTA fibers are formed. The jet draw stretch ratio (JDSR) is calculated according to the following formula: [Eq.] [wherein v 1 is the speed of the fiber (m / min) when exiting the spinneret surface, and v 2 is the speed of the fiber (m / min) at the take-up roll]. v 1 is calculated according to the following formula: [Eq.] [wherein F ドープ is the volumetric measured dope flow to the spinneret, the number of holes is the number of holes at the spinneret surface, and A ih is the area of an individual hole]. Additionally, one or more CTA fibers can also be further drawn after the first coagulation bath, thereby imparting additional polymer orientation in a post-jet draw stretching step(s).

[0023] More specifically, the wet spinning process described herein manufactures CTA fibers having a silk factor of 8.0 or greater by wet spinning without using a DCM-based solvent. By filtering the CTA dope, the fibers are formed by a spinneret, which enables the processability to be improved. The CTA available in the present invention can have a degree of polymerization ("DP") lower than that of conventional higher DP CTA used in a dichloromethane-free wet spinning process. The low DP CTA can enable the use of a high solid dope, which can increase the throughput of the wet spinning process and enable good morphological properties during fiber formation in the first coagulation bath.

[0024] FIG. 1 shows an exemplary wet spinning system for manufacturing CTA fibers. The description of FIG. 1 is a non-limiting example in which certain features can be omitted and / or rearranged. The additional features described herein and in FIG. 2 can also be added to the system shown in FIG. 1.

[0025] The wet spinning system described in FIG. 1 and herein can manufacture one or more CTA fibers exhibiting a silk factor of 8.0 or greater. Various features and properties of the wet spinning process and the resulting CTA fibers are described below. Although all of the following features and properties can be listed separately, it should be noted that each of the following features and / or properties of the wet spinning process, CTA dope, and CTA fibers are not mutually exclusive, can be combined, and can exist in any combination.

[0026] Returning to FIG. 1, in the dissolution step, at least one cellulose ester and at least one dissolution solvent can be introduced into the dope mixer 10 so as to form a CTA dope. The dope mixer 10 can comprise any conventional apparatus capable of mixing CTA and the dissolution solvent. An exemplary dope mixer 10 can include a continuous stirred tank reactor (“CSTR”). While in the dope mixer 10, the CTA and the dissolution solvent can be subjected to temperature and mixing conditions that facilitate dissolving the CTA in the dissolution solvent, thereby forming a CTA dope. For example, it is well known in the art that some cellulose ester dopes can be prepared by first cooling the dope to a low temperature to better mix the solvent with the polymer and then heating to a final mixing temperature. Alternatively, some prefer a faster “flash” type heating within the dope preparation process that minimizes degradation and rapidly dissolves the system into a solution.

[0027] In one embodiment, or in combination with any other recited embodiment, the CTA dope can have 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 35 wt% or less, 34 wt% or less, 33 wt% or less, 32 wt% or less, 31 wt% or less, 30 wt% or less, 29 wt% or less, 28 wt% or less, 27 wt% or less, 26 wt% or less, or 25 wt% or less, based on the total weight of the dope.

[0028] The CTA introduced into the dope mixer 10 can include any cellulose triacetate well known in the art. The cellulose triacetate usable in the present invention generally includes the following repeating units,

Chemical formula

[0029] Regarding cellulose ester polymers, the substitution level is usually expressed in terms of the degree of substitution ("DS"), which is the average number of non-OH substituents per anhydroglucose unit ("AGU"). Generally, conventional cellulose contains three hydroxyl groups in each AGU unit that can be substituted. Therefore, the DS can have a value between 0 and 3. However, low molecular weight CTA may have a total degree of substitution slightly above 3 due to the presence of end groups. Since the DS is a statistical average value, a value of 1 does not guarantee that each AGU has a single substituent. In some cases, unsubstituted AGUs may be present, some have two, and some have three substituents, and usually, the value is non-integer. "Total DS" is defined as the average number of all substituents per AGU. The degree of substitution of AGU can also mean a specific substituent such as hydroxyl, acetyl, propionyl, or butyryl, etc.

[0030] In one embodiment, or in combination with any other recited embodiment, the CTA has a DS of at least 2.60, at least 2.65, at least 2.70, at least 2.75, at least 2.80, at least 2.82, or at least 2.85, and / or 3.00 or less, 2.99 or less, 2.95 or less, 2.9 or less, or 2.88 or less アセチル and includes. In certain embodiments, the CTA has a DS in the range of 2.60 - 3.00, 2.65 - 2.99, 2.70 - 2.95, 2.75 - 2.90, 2.80 - 2.88, 2.82 - 2.88, or 2.85 - 2.88 アセチル and can include.

[0031] In addition, or alternatively, in one embodiment, or in combination with any other recited embodiment, the CTA has a DS of at least 0.0, at least 0.01, at least 0.05, at least 0.10, or at least 0.12, and / or 0.4 or less, 0.35 or less, 0.30 or less, 0.25 or less, 0.20 or less, 0.18 or less, or 0.15 or less OHIt includes. In certain embodiments, the cellulose ester includes a DSOH in the range of 0.0 to 0.4, 0.01 to 0.35, 0.05 to 0.30, 0.10 to 0.25, 0.12 to 0.18, or 0.12 to 0.15.

[0032] In one embodiment, or in combination with any other recited embodiment, the CTA can have a degree of acetylation of at least 56.2%, at least 56.9%, or at least 57.6%, and / or 61.5 wt% or less, 61.0 wt% or less, 60.3 wt% or less, 59.7 wt% or less, or 59 wt% or less. In certain embodiments, the CTA can have a degree of acetylation in the range of 56.2 to 61.5, 56.9 to 61, 57.6 to 60.3 wt%.

[0033] In addition, or alternatively, in one embodiment, or in combination with any other recited embodiment, the CTA can have a hydroxyl content of at least 0 wt%, at least 0.3 wt%, at least 0.6 wt%, or at least 1.2 wt%, and / or 2.4 wt% or less, 2.1 wt% or less, 1.8 wt% or less, or 1.5 wt% or less. In certain embodiments, the CTA can have a hydroxyl content in the range of 0.0 to 2.4, 0.3 to 2.1, 0.6 to 1.8, or 0.9 to 1.5 wt%.

[0034] In one embodiment, or in combination with any other recited embodiment, the CTA can have a number average degree of polymerization of at least 90, at least 100, at least 110, at least 120, at least 130, at least 140, at least 150, or greater than 150, or at least 151, or at least 153, or at least 155, or at least 160, at least 170, at least 180, at least 190, or at least 200. Additionally, or alternatively, in one embodiment, or in combination with any other recited embodiment, the CTA can have a number average degree of polymerization of 300 or less, or 290 or less, or 280 or less, or 270 or less, or 260 or less, or 250 or less, or 240 or less, or 230 or less, or 220 or less, or 210 or less, or 200 or less, or 190 or less, or 180 or less, or 170 or less, or 160 or less, or 150 or less, or 149 or less, or 148 or less, or 147 or less, or 146 or less, or 145 or less, or 144 or less, or 143 or less, or 142 or less, 141 or less, 140 or less, 139 or less, 138 or less, 137 or less, 136 or less, 135 or less, 134 or less, 133 or less, 132 or less, 131 or less, 130 or less, 129 or less, 128 or less, 127 or less, 126 or less, 125 or less, 124 or less, 123 or less, 122 or less, 121 or less, 120 or less, 119 or less, 118 or less, 117 or less, 116 or less, or 115 or less. In certain embodiments, the CTA can have a number average degree of polymerization in the range of 90 to 300, or 90 to 250, or 90 to 250, or 90 to 270, or 90 to 250, or 90 to 230, or 90 to 210, or 90 to 200, 90 to 190, 90 to 180, 90 to 170, 90 to 160, 90 to 150, 100 to 200, 100 to 190, 100 to 180, 100 to 170, 100 to 160, 100 to 150, or less than 90 to 150, or 90 to 149, or 90 to 147, or 90 to 145.

[0035] In one embodiment, or in combination with any other recited embodiment, the CTA can include a number average absolute molecular weight of at least 10,000, at least 15,000, at least 20,000, or at least 25,000, and / or 75,000 or less, 70,000 or less, 65,000 or less, 60,000 or less, 55,000 or less, 50,000 or less, 45,000 or less, 40,000 or less, 35,000 or less, or 30,000 or less, as measured by absolute molecular weight by gel permeation chromatography (“GPC”). In certain embodiments, the CTA can include a number average absolute molecular weight in the range of 10,000 - 75,000, 10,000 - 65,000, or 15,000 - 35,000, as measured by absolute number average by GPC.

[0036] In one embodiment, or in combination with any other recited embodiment, the CTA can include a weight average absolute molecular weight of at least 50,000, at least 55,000, at least 60,000, at least 65,000, at least 70,000, at least 75,000, at least 80,000, or at least 85,000, and / or 150,000 or less, 140,000 or less, 130,000 or less, 120,000 or less, 110,000 or less, 100,000 or less, or 95,000 or less, as measured by absolute molecular weight by GPC. In certain embodiments, the CTA can include a weight average absolute molecular weight in the range of 50,000 - 150,000, 70,000 - 120,000, or 80,000 - 95,000, as measured by absolute molecular weight by GPC.

[0037] In one embodiment, or in combination with any of the other recited embodiments, the CTA can have any of the above-described weight average absolute molecular weights as measured under ASTM D6474.

[0038] In one embodiment, or in combination with any other recited embodiment, the CTA can include a crystallinity of at least 1%, at least 2%, at least 5%, at least 10%, at least 15%, at least 20%, at least 25%, as measured according to ASTM F2625. Additionally, or alternatively, in one embodiment, or in combination with any other recited embodiment, the CTA can include a crystallinity of 25% or less, 20% or less, 15% or less, 10% or less, 9% or less, 8% or less, 7% or less, 6% or less, 5% or less, 4% or less, 3% or less, 2% or less, or 1% or less, as measured according to ASTM F2625. In certain embodiments, the CTA can include a crystallinity of 1 - 25% as measured according to ASTM F2625.

[0039] In one embodiment, or in combination with any other recited embodiment, the CTA can exhibit a glass transition temperature ( "T g ") 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, at least 175°C, at least 180°C, or at least 185°C, and / or 250°C or less, 245°C or less, 235°C or less, 230°C or less, 225°C or less, 220°C or less, 215°C or less, 210°C or less, 205°C or less, 200°C or less, 195°C or less, 190°C or less, or 185°C or less. To measure the T g of the CTA, the sample is dried until the moisture content is less than 10% by weight.

[0040] The CTA can be manufactured by any method well known in the art. Examples of cellulose ester manufacturing processes are taught in Kirk - Othmer, Encyclopedia of Chemical Technology, 5th Edition, Vol. 5, Wiley - Interscience, New York (2004), pp. 394 - 444.

[0041] One method of manufacturing cellulose triacetate involves the esterification of cellulose by mixing cellulose with a suitable organic acid, acid anhydride, and catalyst. Next, the cellulose is converted to cellulose triester, which can then be filtered to remove any gel particles or fibers. Next, water is added to the mixture to precipitate the CTA. The CTA can then be washed with water to remove reaction by-products and then dehydrated and dried.

[0042] Cellulose, the starting material for manufacturing CTA, can be obtained from various grades and sources, such as cotton linters, softwood pulp, hardwood pulp, corn fibers, and other agricultural sources, as well as bacterial cellulose. The starting material used to manufacture CTA can affect the resulting hemicellulose content in the obtained CTA.

[0043] In one embodiment, or in combination with any other recited embodiment, the CTA can contain a hemicellulose content of 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 recited embodiment, the CTA can contain a hemicellulose content of 10 wt% or less, 9 wt% or less, 8 wt% or less, 7 wt% or less, 6 wt% or less, 5 wt% or less, 4 wt% or less, 3 wt% or less, 2 wt% or less, or 1 wt% or less.

[0044] Examples of the dissolution solvent added to the dopant mixer 10 include one or more solvents capable of dissolving cellulose esters, particularly cellulose triacetate. The dissolution solvent must be added in a sufficient amount to efficiently dissolve CTA and thereby form a CTA dopant. In one embodiment, or in combination with any other recited embodiment, the CTA dopant can contain at least 25 wt%, 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%, or at least 99 wt% of one or more dissolution solvents based on the total weight of the dopant.

[0045] In one embodiment, or in combination with any other recited embodiment, the dissolution solvent can contain at least one alkylamide compound. An amide is a functional group in which a carbonyl carbon atom is bonded to a nitrogen atom and either a hydrogen or a carbon atom by a single bond. An amide is an organic compound having the general formula RC(=O)NR’R”. An alkylamide is substituted with a hydrogen or an alkyl group(s) in place of at least one of the R, R’, and R” groups.

[0046] In still other embodiments, the dissolution solvent includes dimethylacetamide, dimethylformamide, formamide, N-formylmorpholine, N-methyl-2-pyrrolidone, N-methylformamide, 2-pyrrolidone, tetramethylurea, N-vinylacetamide, or N-vinylpyrrolidone, or a combination thereof. In certain embodiments, the dissolution solvent can include dimethylacetamide, dimethylformamide, or a combination thereof.

[0047] In one embodiment, or in combination with any other recited embodiment, the CTA dope is DCM-free and can contain trace amounts of dichloromethane, acetone, ionic liquid, N-methylmorpholine N-oxide (NMMO), tertiary amine, metal oxide precursor, acetic acid, dihydric alcohol, or combinations thereof, or alternatively can be substantially free of these. In certain embodiments, the CTA dope contains less than 10 wt%, less than 9 wt%, less than 8 wt%, less than 7 wt%, less than 6 wt%, less than 5 wt%, less than 4 wt%, less than 3 wt%, less than 2 wt%, less than 1 wt%, less than 0.5 wt%, less than 0.1 wt%, less than 0.05 wt%, or less than 0.01 wt% of dichloromethane, acetone, ionic liquid, N-methylmorpholine N-oxide (NMMO), tertiary amine, metal oxide precursor, acetic acid, dihydric alcohol, or combinations thereof, based on the total weight of the CTA dope.

[0048] Depending on the type of cellulose ester and dissolution solvent used, the CTA dope may exhibit a desirable kinematic viscosity. In one embodiment, or in combination with any other recited embodiment, the CTA dope has 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 5,000 poise or less, 4,000 poise or less, 3,000 poise or less, 2,000 poise or less, 1,500 poise or less, 1,000 poise or less, 950 poise or less, 900 poise or less, 850 poise or less, 800 poise or less, 750 poise or less, 700 poise or less, 650 poise or less, 600 poise or less, 550 poise or less, or 500 poise or less at the spinning temperature utilized. Alternatively, the viscosity of the spinning dope can be any of these values when a sample of the dope composition used for spinning is taken and measured at 100 °C or 110 °C. It should be noted that in this "when measuring" standard, it is not necessary to use the CTA dope only at this specified temperature. Rather, this temperature standard merely provides a temperature threshold for measuring the viscosity of the CTA dope. Therefore, the "when measuring" standard does not reflect the actual use or practice of the CTA dope in any way. The viscosity defined herein is the "zero" shear viscosity obtained by extrapolating to a very low shear rate when plotting viscosity against shear rate, or alternatively, by using a Brookfield viscometer at a low spindle RPM. Desirably, the CTA dope has a viscosity of 1,000 poise or less, 950 poise or less, 900 poise or less, 850 poise or less, 800 poise or less, 750 poise or less, 700 poise or less, 650 poise or less, 600 poise or less, 550 poise or less, or 550 poise or less when measured at 100 °C or 110 °C.

[0049] In one embodiment, or in combination with any other recited embodiment, the CTA dope may contain some additives in addition to the CTA, or may contain no additives at all. Such additives may include, but are not limited to, plasticizers, antioxidants, heat stabilizers, pro-oxidants, acid scavengers, inorganic substances, pigments, colorants, matting agents, or combinations thereof.

[0050] Returning to FIG. 1, after forming the CTA dope in the dope mixer 10, the newly formed CTA dope can be passed through any dope holding tank 20 for temporary storage and / or degassing. The dope holding tank 20 can comprise any conventional storage tank well-known in the art capable of storing the CTA dope. While stored in the holding tank 20, the CTA dope can be passed through conditions that maintain the physical characteristics of the dope and / or facilitate the removal of air bubbles introduced during the mixing process. For example, storing the dope at a cooling temperature for too long a time can result in unacceptable gelation that adversely affects spinnability. This is especially true when the dope solid level increases to a higher level. Therefore, the temperature and pressure of the holding and / or degassing tank 20 can be optimized as needed to improve and maintain the quality of the CTA dope.

[0051] Next, as shown in FIG. 1, the CTA dope can be fed from the dope holding tank 20 through a pump 30 to a filter 40, whereby any large and undesirable particulates and gels can be removed from the CTA dope prior to spinning. The filter can comprise any conventional filter device and filter type well-known in the art.

[0052] After the dissolution step, in the wet spinning step, the filtered CTA dope can be fed into the spinneret 51, and at least the spinneret surface of the spinneret 51 is immersed in the DCM-free coagulation bath 50. In one embodiment, or in combination with any other recited embodiment, the temperature of the filtered CTA dope can be maintained at at least 20°C, at least 25°C, at least 30°C, at least 35°C, at least 40°C, at least 45°C, at least 50°C, at least 55°C, at least 60°C, at least 65°C, at least 70°C, at least 75°C, or at least 80°C, and / or at 120°C or below, 110°C or below, or 100°C or below. In certain embodiments, the surface of the spinneret 51 can be maintained at a temperature in the range of 20 to 120°C, 20 to 100°C, 20 to 80°C, 20 to 60°C, or 20 to 40°C.

[0053] As shown in FIG. 1, the filtered CTA dope is metered through the spinneret 51, thereby forming one or more CTA fibers 52 (measured by the number of holes in the surface of the spinneret) that coagulate in the DCM-free coagulation bath 50. Further, when coagulation occurs in the DCM-free coagulation bath 50, the one or more resulting CTA fibers 52 are passed through a jet drawing and stretching machine. As shown in FIG. 1, the process of forming the CTA fibers 52 is a wet spinning process. The wet spinning process is a process of spinning one or more CTA fibers 52 by metering a dope that passes through a spinneret 51 having one or more holes in the surface of the spinneret, and the surface of the spinneret is immersed in the DCM-free coagulation bath 50. The shape and size of the hole(s) of the spinneret 51 serve to measure the size and cross-sectional area of the one or more CTA fibers 52. The number of holes in the surface of the spinneret determines the number of fibers 52 that are simultaneously formed when the dope is metered through the spinneret 51. When the dope passes through the holes in the surface of the spinneret, the dope enters the liquid in the DCM-free coagulation bath 50 in the form of one or more individual fibers.

[0054] More specifically, in various embodiments, the filtered CTA dope can be spun through the holes of a spinneret having a hole area equal to a circular diameter of 20 to 200 micrometers at a speed of about 1 to 500 m / min. In one embodiment, or in combination with any of the other recited embodiments, the spinneret 51 can be maintained at a temperature of at least 20°C, at least 25°C, at least 30°C, at least 35°C, at least 40°C, at least 45°C, at least 50°C, at least 55°C, at least 60°C, at least 65°C, at least 70°C, at least 75°C, or at least 80°C, and / or 200°C or less, 180°C or less, 160°C or less, 140°C or less, 120°C or less, 110°C or less, or 100°C or less. In certain embodiments, the surface of the spinneret 51 can be maintained at a temperature in the range of 20 to 200°C, 20 to 120°C, 20 to 80°C, 20 to 60°C, or 20 to 40°C.

[0055] In one embodiment, or in combination with any other recited embodiment, based on the low DP and / or low molecular weight of the CTA forming the CTA dope, the CTA 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 5,000 poise or less, 4,000 poise or less, 3,000 poise or less, 2,000 poise or less, 1,500 poise or less, 1,000 poise or less, 950 poise or less, 900 poise or less, 850 poise or less, 800 poise or less, 750 poise or less, 700 poise or less, 650 poise or less, 600 poise or less, 550 poise or less, or 500 poise or less at the spinning temperature, before or during supply to the spinneret 51. This spinning temperature is typically the temperature of the dope as it passes through and enters the spinneret. As noted above, the viscosity as defined herein is the "zero" shear viscosity obtained by extrapolating to a very low shear rate when plotting viscosity against shear rate, or alternatively, by using a Brookfield viscometer at a low spindle RPM.

[0056] In spinneret 51, the filtered CTA dope can be extruded through one or more holes to form one or more CTA fibers 52. In spinneret 51 and within the DCM-free coagulation bath 50, the one or more CTA fibers 52 can combine with each other to form a bundle, or band, or braid of hundreds, or even thousands, of individual fibers 52 within the DCM-free coagulation bath 50. These bundles, or bands, or braids can contain at least 1, at least 10, at least 50, at least 100, at least 150, at least 200, at least 250, at least 300, at least 350, or at least 400, and / or 10,000 or fewer, 5,000 or fewer, 1,000 or fewer, 900 or fewer, 800 or fewer, 700 or fewer, or 600 or fewer fibers. The spinneret 51 can be operated at any suitable speed to produce one or more CTA fibers 52, which can then be assembled into a bundle, or band, or braid having a desired size and shape. As used herein, the term "individual filament fiber" means the continuous fiber first produced by the spinneret 51.

[0057] In one embodiment, or in combination with any other recited embodiment, one or more CTA fibers 52 are jet drawn and stretched in a DCM-free coagulation bath 50 at a jet draw stretch ratio (JDSR) of from 0.3 to 1.4 (inclusive). More specifically, in one embodiment, or in combination with any other recited embodiment, one or more CTA fibers can be stretched at a JDSR of at least 0.3 and / or 1.4 or less, or 1.3 or less, or 1.2 or less, or 1.1 or less, or 1.0 or less, or 0.9 or less, or 0.8 or less, or 0.7 or less, or 0.6 or less, or 0.5 or less, or 0.4 or less. Additionally, or alternatively, the JDSR can be at least 0.3, or at least 0.4, or at least 0.5, or at least 0.6, or at least 0.7, or at least 0.8. For example, one or more CTA fibers can be stretched at a JDSR in the range of 0.3 to 1.4, or 0.3 to 1.3, or 0.3 to 1.2, or 0.3 to 1.1, or 0.3 to 1.0, or 0.3 to 0.9, or 0.3 to 0.8, or 0.3 to 0.7, or 0.3 to 0.6, or 0.3 to 0.5, or 0.3 to 0.4.

[0058] The JDSR is the ratio of the speed (v2) at the surface of the first driven take-up roll 53 that pulls or stretches one or more CTA fibers through the DCM-free coagulation bath 50 to the speed (v 1 ) of the fiber 52 as it exits the orifice in the face of the spinneret 51. A JDSR of 0.3

Number

[0059] As described above, jet drawing elongation occurs in the DCM-free coagulation bath 50. Thus, in such an embodiment, any elongation of one or more CTA fibers after the initially driven take-up roll 53 is not jet drawing elongation. The elongation occurring after the initially driven take-up roll 53 is post-jet drawing elongation regardless of whether one or more CTA fibers are immersed in a liquid or drawn in air. The post-jet drawing ratio (PJDSR) for any post-jet drawing process step is the speed (v out ) of one or more fibers exiting the process step divided by the speed (v in) is calculated by dividing by. In such an embodiment, one or more CTA fibers may not experience a post-jet drawing stretching process, or may experience one post-jet drawing stretching process, or two or more post-jet drawing stretching processes. Any stretching of one or more CTA fibers after the initially driven take-up roll 53 is an operation separate from the jet drawing stretching, and this occurs in the DCM-free coagulation bath 50 before the crystal structure of the polymer fiber is fully grown.

[0060] The DCM-free coagulation bath 50 contains any of the following:

[0061] Water and a dope solvent, or water, a dope solvent, and a coagulation solvent other than the dope solvent.

[0062] When a coagulation solvent is used, the coagulation solvent can be an aqueous coagulation solvent containing water. Water is regarded as a poor solvent or a coagulant. The total amount of water from all sources contained in the coagulation bath 50 can be at least 1 wt%, at least 10 wt%, at least 15 wt%, at least 20 wt%, at least 25 wt%, at least 30 wt%, at least 35 wt%, at least 40 wt%, at least 45 wt%, 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%, or at least 99 wt% of water, based on the total weight of all the liquids in the coagulation bath 50. Additionally, or alternatively, in one embodiment, or in combination with any other recited embodiment, the amount of water in the coagulation bath 50 can be 99 wt% or less, 90 wt% or less, 80 wt% or less, 70 wt% or less, 60 wt% or less, 50 wt% or less, 40 wt% or less, 30 wt% or less, or 20 wt% or less of water, based on the total weight of the liquids in the coagulation bath. In certain embodiments, the coagulation bath 50 can contain 10 - 99, 20 - 80, 25 - 70, or 30 - 60 wt% of water, based on the total weight of the liquids in the coagulation bath 50. The total amount of the dope solvent in the coagulation bath 50 can be at least 0.1 wt%, at least 0.5 wt%, at least 1.0 wt%, at least 2.0 wt%, or at least 3.0 wt% based on the weight of all the liquids in the coagulation bath. Additionally, or alternatively, the total amount of the dope solvent in the coagulation bath 50 can be 80 wt% or less, 75 wt% or less, 70 wt% or less, 65 wt% or less, 60 wt% or less, 55 wt% or less, or 50 wt% or less based on the weight of all the liquids in the coagulation bath 50.Suitable ranges of the dope solvent in the coagulation bath 50 include 0.1 to 80, or 0.5 to 80, or 1 to 80, or 0.1 to 75, or 0.5 to 75, or 1 to 75, or 0.1 to 70, or 0.5 to 70, or 1 to 70, or 0.1 to 65, or 0.5 to 65, or 1 to 65, or 0.1 to 60, or 0.5 to 60, or 1 to 60, or 0.1 to 55, or 0.5 to 55, or 1 to 55, or 0.1 to 50, or 0.5 to 50, or 1 to 50% by weight, based on the total weight of all the liquids in the coagulation bath 50. The dope solvent in the coagulation bath 50 can be obtained as a fresh dope solvent added to the coagulation bath, or can be obtained by washing the residual dope solvent from the fibers or by leaching the residual dope solvent into the fibers when drawn through the coagulation bath 50, or can be both of these. The dope solvent can be at least one of the same solvents used to dissolve the dope composition in the CTA polymer prior to spinning. In one embodiment, or in combination with any of the other recited embodiments, the coagulation bath 50 contains only the dope solvent obtained from the residual dope solvent on or in the fibers. In one embodiment, or in combination with any of the other recited embodiments, the dope solvent in the coagulation bath 50 is obtained by adding a new constituent dope solvent to the coagulation bath 50 from both the residual dope solvent in and on the fibers.

[0063] In the DCM-free coagulation bath, the total amount of the coagulation solvent (regardless of its source and containing no water in any amount) can be at least 1 wt%, at least 5 wt%, at least 10 wt%, at least 15 wt%, or at least 20 wt% based on the total weight of the liquid in the coagulation bath 50. Additionally, or alternatively, in one embodiment, or in combination with any other recited embodiment, the coagulation solvent can contain up to 90 wt%, up to 80 wt%, up to 70 wt%, up to 65 wt%, up to 60 wt%, up to 50 wt%, up to 40 wt%, up to 30 wt%, up to 20 wt%, up to 10 wt%, up to 5 wt%, or up to 1 wt% of the additional solvent based on the total weight of the liquid in the DCM-free coagulation bath 50. The amount of the coagulation solvent in the DCM-free coagulation bath 50 can range from 1 to 90, 5 to 80, 10 to 70, 20 to 65, 5 to 65, or 10 to 60 wt% of at least one additional solvent based on the total weight of the liquid in the DCM coagulation bath 50.

[0064] Suitable coagulation solvents include at least one alkylamide compound. Examples of suitable alkylamide compound solvents include dimethylacetamide, dimethylformamide, formamide, N-formylmorpholine, N-methyl-2-pyrrolidone, N-methylformamide, 2-pyrrolidone, tetramethylurea, N-vinylacetamide, or N-vinylpyrrolidone, or combinations thereof. In one embodiment, or in combination with any other recited embodiment, the coagulation solvent includes dimethylacetamide, dimethylformamide, or combinations thereof.

[0065] In one embodiment, or in combination with any other recited embodiment, DCM is not added to the DCM-free coagulation bath 50, or the DCM-free coagulation bath 50 contains no DCM whatsoever, or the DCM-free coagulation bath 50 contains trace amounts (e.g., less than 1 wt%, or less than 5,000 ppm, or less than 1,000 ppm, or less than 500 ppm, or less than 100 ppm) of DCM. Trace amounts may, in some cases, be included in the DCM-free coagulation bath 50 due to inadequate cleaning and rinsing of the dope bath, or due to the DCM-free coagulation bath 50 having contained DCM prior to implementation, even when the added coagulation solvent contains no DCM whatsoever.

[0066] In one embodiment, or in combination with any other recited embodiment, DCM, and one or more additional solvents are not added to the DCM-free coagulation bath 50, or the DCM-free coagulation bath contains no DCM whatsoever and no one or more additional solvents whatsoever, or the DCM-free coagulation bath 50 contains trace amounts (e.g., less than 1 wt%, or less than 5,000 ppm, or less than 1,000 ppm, or less than 500 ppm, or less than 100 ppm) of DCM and one or more additional solvents. Such additional solvents include acetone, ionic liquids, N-methylmorpholine N-oxide (NMMO), tertiary amines, metal oxide precursors, acetic acid, dihydric alcohols, or combinations thereof.

[0067] In one embodiment, or in combination with any other recited embodiment, the DCM-free coagulation bath 50 can contain less than 10 wt%, less than 9 wt%, less than 8 wt%, less than 7 wt%, less than 6 wt%, less than 5 wt%, less than 4 wt%, less than 3 wt%, less than 2 wt%, less than 1 wt%, less than 0.5 wt%, less than 0.1 wt%, less than 0.05 wt%, or less than 0.01 wt% of any one of acetone, ionic liquid, N-methylmorpholine N-oxide (NMMO), tertiary amine, metal oxide precursor, acetic acid, and dihydric alcohol, or the coagulation bath 50 can contain an amount that is less than the combined amount of all of these solvents, based on the total weight of the liquid in the DCM-free coagulation bath 50.

[0068] In addition or alternatively, in one embodiment, or in combination with any other recited embodiment, the DCM-free coagulation bath 50 can be maintained at a temperature of at least 20 °C, or at least 25 °C, and / or 40 °C or lower, 35 °C or lower, including the coagulation solvent therein. In certain embodiments, the first coagulation bath 50 can be maintained at a temperature in the range of 20 to 40 °C, 20 to 35 °C, 20 to 30 °C, 25 to 40 °C, 30 to 40 °C, 35 to 40 °C, or 25 to 35 °C, including the coagulation solvent therein.

[0069] Although FIG. 1 shows a specific wet spinning technique, it is contemplated that the subsequent processing steps (after the take-up roll 53) can be arranged in various alternative orders. For example, the downstream steps of the process can include one or more additional coagulation steps, one or more washing steps, one or more post-jet drawing and stretching steps, one or more fiber finishing application steps, one or more drying steps, one or more heat treatment steps, a pressing step, a cutting step, a winding step, a packaging step, or combinations thereof, and can be arranged in various orders.

[0070] Desirably, one or more CTA fibers 52 formed within the DCM-free coagulation bath 50 are single-component fibers, which means having a single continuous phase. The single-component fibers can comprise only one type of material (e.g., CTA) or a composition blended uniformly. The single-component fibers are distinguishable from, and not considered as, "bicomponent" or "multicomponent fibers" that feature an internal phase or boundary defining regions of different compositions within the outer surface of the fiber. In one embodiment, or in combination with any other recited embodiment, the fibers within the first coagulation bath, or emerging from the first coagulation bath, or the final finished fibers are single-component and contain 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 wt%, or 100 wt% of a single type of polymer, such as CTA, based on the total weight of the fibers, excluding the weight of any finishing or cutting lubricant.

[0071] One or more CTA fibers 52 discharged from the spinneret 51 can have any suitable cross-sectional shape. Exemplary cross-sectional shapes include, but are not limited to, circular, kidney-shaped, ribbon-shaped, small blunt serrated, multi-lobed, or non-circular (other than circular). It is well known in the art that the shape of the cross-section is usually determined by the balance of the coagulating nucleic acid into the fiber relative to the rate at which the solvent diffuses from the fiber within the coagulation bath. When these balances are achieved, the fiber better retains a nearly circular shape. For example, by adjusting the temperature of the bath and / or the solvent level, fibers that are larger or smaller than circular, or alternatively, kidney-shaped or ribbon-shaped / lobe-shaped, can be produced.

[0072] In one embodiment, or in combination with any other recited embodiment, one or more fibers 52 emitted from spinneret 51 can have a substantially circular cross-sectional shape. As used herein, the term "cross-section" generally means the cross-section of a fiber measured in a direction perpendicular to the elongation direction of the fiber. The cross-sectional area and perimeter of a fiber can be determined and measured using quantitative image analysis ("QIA").

[0073] The cross-sectional shape of an individual fiber can also be characterized by a deviation from a circular cross-sectional shape. In some cases, this deviation can be characterized by the shape factor of the fiber, which is measured by the following formula:

Number

[0074] In some embodiments, the shape factor of one or more CTA fibers can be 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 having a completely circular cross-sectional shape is 1. The shape factor can be calculated from the cross-sectional area and perimeter of the fiber, both of which can be measured using QIA.

[0075] Furthermore, in certain embodiments, one or more CTA fibers 52 can be in the form of solid fibers (fibers having a solid cross-sectional shape without openings therein) and not in the form of hollow fibers.

[0076] As described above, the silk factor properties are useful for measuring the suitability of CTA fiber(s) produced by the present process in downstream applications. Retention is an important fiber property that measures the magnitude of the tension that can be applied to the fiber before breakage. Fibers with low retention can be pulled apart by applying a force smaller than that required to break fibers with high retention. For fabric production, a retention of less than 1.5 g / denier can be problematic because the fiber can break under normal operating conditions. In one embodiment, or in combination with any other recited embodiment, the CTA fiber(s) produced by the present process may exhibit at least 1.5 g / denier, or more than 1.5 g / denier, or at least 1.52 g / denier, or at least 1.55 g / denier, or at least 1.58 g / denier, or at least 1.6 g / denier, or at least 1.7 g / denier, or at least 1.8 g / denier, or at least 1.9 g / denier, or at least 2.0 g / denier, or at least 2.1 g / denier, or at least 2.2 g / denier, or at least 2.3 g / denier, or at least 2.4 g / denier, or at least 2.5 g / denier when measured in accordance with ASTM D22556.

[0077] The elongation rate, also known as the elongation at break point, is expressed as a percentage and indicates how much the yarn or fiber elongates before breakage. In one embodiment, or in combination with any other recited embodiment, the CTA fiber(s) produced by the present process may exhibit at least 15%, or at least 16%, or at least 17%, or at least 18%, or at least 19%, or at least 20%, or at least 21%, or at least 22%, or at least 23%, or at least 24%, or at least 25%, or at least 26%, or at least 27%, or at least 28%, or at least 29%, or at least 30% elongation at break when measured in accordance with ASTM D22556.

[0078] The silk factor ("SF") is an experimentally measured relationship between the holding force and the elongation rate, which is used to predict the breaking envelope of a given fiber. The silk factor can be used to characterize the suitability of the spun yarn or fiber for use in a given process, which is calculated based on the following formula:

Number

[0079] In one embodiment, or in combination with any other recited embodiment, the CTA fiber(s) produced by the present process may exhibit a silk factor of at least 5.0, or at least 6.0, or at least 7.0, or at least 7.5, or at least 8.0, or at least 8.5, or at least 9.0, where the elongation rate is expressed as a percentage (%) and the holding force is expressed as g / denier.

[0080] As described above, the CTA fiber(s) produced by the present process are formed as continuous fibers. In one embodiment, or in combination with any other recited embodiment, the fiber(s) produced by the present process can be continuous fiber(s), or can be cut to form staple fibers.

[0081] As shown in FIG. 1, one or more CTA fibers 52 can be wound around a take-up roll 53, thereby generating tension to pull the fiber from the DCM-free coagulation bath 50, and the fiber is guided to the downstream processes of the present process. The downstream processes can include, for example, one or more additional coagulation processes, one or more washing processes, one or more jet drawing and post-drawing processes, one or more fiber finishing application processes, one or more drying processes, one or more heat treatment processes, a calendering process, a cutting process, a winding process, a packaging process, or combinations thereof, which can be arranged in various orders.

[0082] Returning to FIG. 1, the CTA fibers 52 formed in the first coagulation bath 50 can be gathered into bands, bundles, or braids 54. The bands, bundles, or braids 54 can include a plurality of one or more CTA fibers 52. Each of these bands, bundles, braids can include at least 1, at least 10, at least 50, at least 100, at least 150, at least 200, at least 250, at least 300, at least 350, or at least 400, and / or 10,000 or less, 5,000 or less, 1,000 or less, 900 or less, 800 or less, 700 or less, or 600 or less individual fibers.

[0083] As shown in FIG. 1, after the wet spinning process, the bands, bundles, or braids 54 can be passed through one or more post-jet drawing and stretching (PJDS) processes 60 in order to be passed through post-jet drawing and stretching. This PJDS is different from JDS in that the stretching occurs after the driven take-up roll 53 (indicating the end of the wet spinning process), whereby the fibers have already undergone a certain degree of coagulation and crystallization. Since the post-jet drawing and stretching of the fibers is applied after the material has already partially solidified, if carried out excessively, it can cause micro-scale damage to the fiber(s). Thus, post-jet drawing and stretching can increase the holding force but usually also causes a significant decrease in the elongation rate.

[0084] During the post-jet drawing process 60, the band 54 can be further passed through additional stretching to change the length and width of the knitting yarn and to change the polymer orientation within the individual fibers. The PJDS process(es) can stretch the band 54 in air at ambient temperature, in heated air, in water at ambient temperature, in warm water, in an aqueous solvent at ambient temperature, in a heated aqueous solvent, in steam, or in any combination thereof. The post-jet drawing process(es) can involve passing the band 54 through a driven or speed-regulated draw roll, or a pair of draw rolls, which can add heat and improve the ductility of the fiber. The temperature increase of the band 54 can also be achieved by passing the band 54 through a warm water bath, or a steam box, or a stream of hot air to sufficiently soften the fiber for drawing. Generally, the speed (v out ) of each successive draw roll, or pair of draw rolls, is greater than the speed (v in ) of the previous draw roll or pair of draw rolls through which the band 54 is passed, such that additional crystallinity can be imparted and the denier per filament can be reduced when the band 54 is substantially stretched. The total post-jet drawing ratio is calculated by multiplying all the PJDS ratios of one or more post-jet drawing processes included in the process. For example, if the process consists of three post-jet drawing processes applied with PJDS ratios of 1.10, 1.25, and 1.33 respectively, the total post-jet drawing ratio is (1.10 × 1.25 × 1.33), i.e., 1.83. In one embodiment, or in combination with any other recited embodiment, the post-jet drawing and post-jet drawing processes can be combined with a washing process, a fiber finish application process, a drying process, and / or a heat treatment process.

[0085] Before or after the post-jet drawing stretching step 60, the band 54 can be introduced into one or more additional coagulation baths 70 and / or one or more washing steps 80. These additional coagulation baths typically contain the same solvent and operating conditions as the first coagulation bath 50, but usually with a lower solvent level than the first coagulation bath 50. Alternatively, in certain embodiments, the additional coagulation baths can be excluded or such additional baths can optionally be replaced by one or more washing steps.

[0086] The washing step 80 can include passing the band 54 through a bath containing water at various temperatures to facilitate removing residual solvent from the band 54. The washing step can also include the use of water sprayed onto the band 54. The washing temperature is typically in the range of approximately room temperature to a maximum of 99 °C, but it has been observed that the properties of the fiber(s) produced by this process tend to change as the washing temperature increases. Thus, it may be desirable to utilize a washing temperature of less than 90 °C, or less than 75 °C, or more desirably, less than 50 °C.

[0087] In one embodiment, or in combination with any of the other recited embodiments, after exiting the final washing step 80, the washed band 54 can be passed through a fiber finishing application step.

[0088] After any washing process and finishing application process, the band 54 can be passed through one or more drying processes 90. The one or more drying processes 90 can include any conventional drying device well-known in the art, including but not limited to hot air drying (unrestricted or partially restricted), infrared drying, heated godet roll drying, and ventilated perforated drum drying. Generally, when the band 54 dries, the fiber(s) constituting the above shrink in both the axial and longitudinal directions. In the one or more drying processes, the band 54 is not constrained in a way that prevents all shrinkage in the longitudinal direction. The fibers of the band 54 can dry without being constrained, and the band 54 can be placed on a moving dryer conveyor where no tension is applied to the shrinking fibers of the band, causing it to shrink completely in the longitudinal direction. Alternatively, the fibers of the band 54 can dry while being partially constrained, where the fibers shrink partially or completely depending on the tension applied to the band during drying. The amount of tension applied to the band 54 during drying can be controlled by varying the exit speed of the band 54 exiting the drying process relative to the entry speed of the band 54 entering the drying process. If the entry speed and the exit speed are equal, the band 54 is considered to be completely constrained, and in this case, no longitudinal shrinkage can occur when the fibers of the band 54 dry. If the exit speed of the band 54 is lower than the entry speed, the band 54 shrinks during drying. If the exit speed of the band 54 cannot be reduced without slackening to form the band 54 during drying, the band 54 is completely shrunk. Any exit speed that is lower than the entry speed but higher than the full shrinkage speed allows the band 54 to shrink partially.

[0089] In one embodiment, or in combination with any of the other recited embodiments, the band 54 can be passed through one or more heat treatment steps 100 before or after one or more drying steps 90. The one or more heat treatment steps 100 can include any conventional annealing apparatus, autoclaving apparatus, or combination well-known in the art. Generally, the heat treatment process steps can include (i) heating the fiber(s) or band to a temperature above half of its melting point, (ii) holding the fiber(s) or band at that temperature for a period of time, and (iii) then cooling the fiber(s) or band in a manner that reduces the internal stress in the fiber(s). In the one or more heat treatment steps, the band 54 cannot be constrained in a way that prevents all longitudinal shrinkage. The fiber(s) or band can be heat treated and unconstrained, and the band 54 can be freely longitudinally shrunk by placing it on a moving conveyor where no tension is applied to the band 54 during heat treatment. Alternatively, the fiber(s) of the band 54 can be heat treated and partially constrained, where it can shrink partially or fully depending on the tension applied to the band 54 during the heat treatment step. This tension can be controlled, like in the drying step, by varying the speed of the band 54 at the inlet and outlet of the heat treatment step. The one or more heat treatment steps 100 can be performed after or before any crimping step 110. In configurations where heat treatment follows crimping, the heat treatment step is thought to help set the crimp pattern in the fiber. The one or more heat treatment steps 100 can include hot air or steam and can be performed at atmospheric pressure, above atmospheric pressure, or under vacuum. In some configurations, one of the heat treatment steps can be performed in the finished package of CTA fiber.

[0090] In another embodiment of the present invention, the heat treatment step 100 can be performed at a temperature that is at least 20 °C below the Tg of the CTA fiber, at least 15 °C below the Tg of the CTA fiber, and at least 10 °C below the Tg of the CTA fiber.

[0091] In one embodiment, or in combination with any of the other recited embodiments, the continuous fiber(s) of the band 54 can be accumulated on a bobbin, core, or tube in the packaging step 130. The packaging step 130 can include any conventional winding and packaging apparatus known in the art.

[0092] In one embodiment, or in combination with any of the other recited embodiments, the band 54 can be passed through a crimping step that at least partially crimps the CTA fiber(s). In one embodiment, or in combination with any of the other recited embodiments, the CTA fiber and / or the band 54 can be crimped. Alternatively, in certain embodiments, the CTA fiber and / or the band 54 are not crimped.

[0093] The CTA fiber(s) and / or band 54 can pass through the crimping zone, where a shape such as a patterned wave can be imparted to at least a portion or substantially all of the individual fibers. In use, the crimping zone comprises at least one crimping device that mechanically crimps the CTA fiber(s). Generally, the CTA fiber(s) are preferably not crimped by thermal or chemical means (e.g., warm water bath, steam, air jet, or chemical coating), but rather are mechanically crimped using a suitable crimper. An example of a suitable type of mechanical crimper is a "stuffing box" or "stuffer box" crimper that utilizes multiple rollers to create friction, which buckles the CTA fiber(s) and causes the formation of crimps. Other types of crimpers may also be suitable. Examples of suitable devices for imparting crimped fibers are described, for example, in U.S. Patent Nos. 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.

[0094] Crimping can be performed such that the CTA fiber(s) has a crimp frequency of at least 5 CPI (crimps per inch), at least 7 CPI, at least 10 CPI, at least 12 CPI, at least 13 CPI, at least 15 CPI, or at least 17 CPI, and / or 30 CPI or less, 27 CPI or less, 25 CPI or less, 23 CPI or less, 20 CPI or less, or 19 CPI or less, as measured in accordance with ASTM D3937-12. In certain embodiments, the average CPI of the CTA fiber(s) that produce the band 54 and / or various downstream products can be in the range of 7 to 30 CPI, 10 to 30 CPI, 10 to 27 CPI, 10 to 25 CPI, 10 to 23 CPI, 10 to 20 CPI, 12 to 30 CPI, 12 to 27 CPI, 12 to 25 CPI, 12 to 23 CPI, 12 to 20 CPI, 15 to 30 CPI, 15 to 27 CPI, 15 to 23 CPI, 15 to 20 CPI, or 15 to 19 CPI.

[0095] In one embodiment, or in combination with any of the other recited embodiments, the crimp width of the CTA fiber(s) can vary during crimping, for example, it can be at least 0.85, at least 0.90, at least 0.93, at least 0.96, at least 0.98, at least 1.00, or at least 1.04 mm. Additionally, or alternatively, in one embodiment, or in combination with any of the other recited embodiments, the crimp width of the CTA fiber(s) can be at most 1.75 mm, at most 1.70 mm, at most 1.65 mm, at most 1.55 mm, at most 1.35 mm, at most 1.28 mm, at most 1.24 mm, at most 1.15 mm, at most 1.10 mm, at most 1.03 mm, or at most 0.98 mm.

[0096] Furthermore, in one embodiment, or in combination with any other recited embodiment, the CTA fiber(s) that make up band 54, and / or the staple fiber(s) produced therefrom, may have a crimp ratio of at least 1:1. As used herein, "crimp ratio" means the ratio of the non-crimped band or fiber length to the crimped band or fiber length. In certain embodiments, the CTA fiber(s), and / or the staple fiber(s) 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.

[0097] The crimp width and crimp ratio are measured according to the procedure outlined in U.S. Patent Application Publication No. 2020 / 0299822, which is hereby incorporated by reference herein to the extent that it does not conflict with the present disclosure.

[0098] Additionally, or alternatively, in one embodiment, or in combination with any other recited embodiment, one or more surface finishing agents can be applied to the CTA fiber(s) and / or the band 54 produced therefrom. The method of application is not limited and can include spraying, spray-on application, dipping, or squeezing, rubbing, or using a kiss roll. The location where the finishing agent is applied to the fiber or band 54 can vary depending on the function of the finishing agent. For example, a lubricant finishing agent can be applied after spinning and before calendering, or before combining the fibers into a band, bundle, or yarn. A cutting lubricant and / or an antistatic lubricant can be applied before or after calendering and before drying. A suitable amount of all the finishing agents on the CTA fiber (whether lubricant, cutting lubricant, antistatic electrical finishing agent, or others) can be at least 0.01 wt%, at least 0.02 wt%, at least 0.05 wt%, at least 0.10 wt%, at least 0.15 wt%, at least 0.20 wt%, at least 0.25 wt%, at least 0.30 wt%, at least 0.35 wt%, at least 0.40 wt%, at least 0.45 wt%, at least 0.50 wt%, at least 0.55 wt%, or at least 0.60 wt% of finish-on-yarn ("FOY") compared to the weight of the dry CTA fiber(s). Additionally, or alternatively, in one embodiment, or in combination with any other recited embodiment, the cumulative amount of the finishing agent can be present in an amount of FOY of 2.5 wt% or less, 2.0 wt% or less, 1.5 wt% or less, 1.2 wt% or less, 1.0 wt% or less, 0.9 wt% or less, 0.8 wt% or less, or 0.7 wt% or less based on the total weight of the dry fiber. The amount of the finishing agent on the fiber, expressed as wt%, can be measured by solvent extraction. As used herein, "FOY", or "finish on yarn", means the amount of the finishing agent on the fiber or yarn that is below any added water.

[0099] In one embodiment, or in combination with any of the other recited embodiments, the CTA fiber(s) can include at least one plasticizer or, alternatively, can be free of plasticizers. For example, the CTA fiber(s) can be at least partially coated with a dry plasticizer. The CTA fiber(s) can include less than 15 wt%, less than 12 wt%, less than 10 wt%, less than 9 wt%, less than 8 wt%, less than 7 wt%, less than 6 wt%, less than 5 wt%, less than 4 wt%, less than 3 wt%, less than 2 wt%, less than 1 wt%, less than 0.5 wt%, less than 0.1 wt%, less than 0.05 wt%, less than 0.01 wt%, less than 0.005 wt%, less than 0.001 wt%, or less than 0.0007 wt% of at least one plasticizer, based on the total weight of the CTA fiber. When present, the plasticizer can be a dopant and can be incorporated into the CTA fiber itself by spinning a dopant-containing dopant used to produce the flakes, and / or the plasticizer can be applied to the surface of the fiber by any of the methods used to apply a finishing agent. If desired, the plasticizer can be included in the finishing agent formulation.

[0100] The resulting CTA fibers can be used to produce a variety of end products such as tow bands, staple fibers, filament knitted yarns, spun knitted yarns, woven fabrics, nonwovens, and / or incorporated woven fabrics.

[0101] In one embodiment, or in combination with any other recited embodiment, the CTA fibers and / or bands 54 can be cut into staple fibers in the cutting step 120. Any suitable type of cutting device can be used that can cut the fibers to the desired length without unduly damaging the fibers. Examples of cutting devices include, but are not limited to, rotary cutters, guillotines, draw breakers, reciprocating blades, or combinations thereof. Once cut, the CTA staple fibers can be gathered, bagged, or packaged in another way for later transport, storage, and / or use in the packaging step 130. In various embodiments, the d50 length of the staple fibers can be at least 5 mm, at least 10 mm, at least 20 mm, at least 30 mm, at least 40 mm, or at least 50 mm, and / or 150 mm or less, 140 mm or less, 130 mm or less, 125 mm or less, 120 mm or less, 115 mm or less, 110 mm or less, 105 mm or less, 100 mm or less, or 95 mm or less.

[0102] Additionally, or alternatively, in one embodiment, or in combination with any other recited embodiment, the denier per filament (weight in grams of a 9000 m fiber length), i.e., the "DPF", of the CTA fiber(s) (whether CTA staple fiber or CTA continuous fiber) can be in the range of 0.5 to 20 or less, or 0.5 to 15 or less, or 0.5 to 10 or less, or 1 to 8 or less, or 1 to 5 or less, or 2 to 4 or less. The specific method for measurement is not limited, and when fibers are available from those where the staple fibers are cut, the ASTM 1577-07 method using the FAVIMAT vibrometer procedure, or microbalance weighing of a sample of known length or width analysis using any conventional optical microscope or analyzer, can be mentioned. The DPF also correlates with the maximum width of the fiber.

[0103] In addition, or alternatively, in one embodiment, or in combination with any other recited embodiment, the CTA fiber(s) and / or the CTA staple fiber(s) produced therefrom can include an average cross-sectional width of at least 1 micrometer, at least 2 micrometers, at least 3 micrometers, at least 4 micrometers, at least 5 micrometers, at least 6 micrometers, at least 7 micrometers, at least 8 micrometers, at least 9 micrometers, at least 10 micrometers, at least 11 micrometers, at least 12 micrometers, at least 13 micrometers, at least 14 micrometers, at least 15 micrometers, at least 16 micrometers, at least 17 micrometers, at least 18 micrometers, at least 19 micrometers, or at least 20 micrometers, and / or 300 micrometers or less, 200 micrometers or less, 150 micrometers or less, 100 micrometers or less, 90 micrometers or less, 80 micrometers or less, 70 micrometers or less, 60 micrometers or less, 50 micrometers or less, 40 micrometers or less, 30 micrometers or less, or 25 micrometers or less. In certain embodiments, the individual cellulose ester fibers and / or the staple fibers produced therefrom can include an average width in the range of 1 to 300 micrometers, 2 to 200 micrometers, 3 to 100 micrometers, 4 to 70 micrometers, 5 to 50 micrometers, or 8 to 30 micrometers.

[0104] In one embodiment, or in combination with any other recited embodiment, staple fibers can be used to form CTA spun yarns. The spun yarns are continuous twisted yarns containing short staple fibers that are mechanically wound together by a staple yarn spinning process. The staple yarn spinning process can be, but is not limited to, ring spinning, open-end spinning, air-jet spinning, compact spinning, siro spinning, vortex spinning, carding spinning, semi-carding spinning, wool spinning, and wet spinning using flax.

[0105] In one embodiment, or in combination with any other recited embodiment, CTA fibers can be used to form nonwoven articles such as nonwoven fabrics. Exemplary nonwoven articles can include wet-laid nonwoven fabrics, eolian nonwoven fabrics, flocked articles, and / or dry-laid nonwoven articles.

[0106] In one embodiment, or in combination with any other recited embodiment, CTA yarns can be used to form woven articles such as woven fabrics. The woven fabric can be formed on a loom by interweaving at least two yarns, one warp yarn, and one weft yarn, where the twist yarns of the warp yarns are oriented parallel and the weft yarn is interwoven at a certain angle with respect to the orientation of the warp yarns in an alternating pattern above and below the warp yarns.

[0107] In one embodiment, or in combination with any other recited embodiment, CTA yarns can be used to form knitted articles such as knitted fabrics. Such knitted fabrics can be formed by interlocking loops of the yarns.

[0108] In one embodiment, or in combination with any other recited embodiment, the final products described herein, including staple fibers, yarns, nonwovens, knitted articles, and woven articles, can include at least 0.25 wt%, at least 0.5 wt%, at least 0.75 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%, at least 7 wt%, at least 8 wt%, at least 9 wt%, at least 10 wt%, at least 12 wt%, at least 15 wt%, at least 18 wt%, at least 20 wt%, at least 25 wt%, at least 30 wt%, at least 35 wt%, at least 40 wt%, at least 45 wt%, 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 one or more CTA fibers, based on the total weight of the technology. Additionally, or alternatively, in one embodiment, or in combination with any other recited embodiment, the final products described herein, including staple fibers, yarns, nonwovens, knitted articles, and woven articles, can include 99 wt% or less, 95 wt% or less, 90 wt% or less, 85 wt% or less, 80 wt% or less, 75 wt% or less, 70 wt% or less, 65 wt% or less, 60 wt% or less, 55 wt% or less, 50 wt% or less, 45 wt% or less, 40 wt% or less, 35 wt% or less, 30 wt% or less, 25 wt% or less, 20 wt% or less, 15 wt% or less, 10 wt% or less, 9 wt% or less, 8 wt% or less, 7 wt% or less, 6 wt% or less, or 5 wt% or less of one or more CTA fibers, based on the total weight of the technology. In certain embodiments, the final product can be formed entirely from CTA fibers or can include 0.25 - 50 wt%, 1 - 99 wt%, 1 - 50 wt%, 50 - 99 wt%, 1 - 20 wt%, or 0.25 - 5 wt% of one or more CTA fibers, based on the total weight of the article.

[0109] Definition It should be understood that the following is not intended to be an exclusive list of defined terms. For example, other definitions may be provided in the foregoing description, such as when used in the context and in connection with the use of defined terms.

[0110] As used herein, the terms "a", "an", and "the" mean one or more.

[0111] As used herein, the term "and / or" when used in a list of two or more items means that any one of the listed items can be used by itself or any combination of two or more of the listed items can be used. For example, if a composition is described as containing components A, B, and / or C, the composition can contain A only, B only, C only, a combination of A and B, a combination of A and C, a combination of B and C, or a combination of A, B, and C.

[0112] As used herein, "comprising", "comprises", "comprise", "contain", "containing", and "contains" are open-ended transitional phrases used to indicate that the subject listed before this term passes to one or more of the elements listed after this term, and the element(s) listed after this transitional phrase are not necessarily the only elements constituting the subject.

[0113] As used herein, "having", "has", and "have" have the same open-ended meaning as the above "comprising", "comprises", and "comprise".

[0114] As used herein, the terms "including", "include", and "included" have the same open-ended meaning as the above terms "comprising", "comprises", and "comprise".

[0115] As used herein, the terms "containing", "contains", and "contained" have the same open-ended meaning as the above terms "comprising", "comprises", and "comprise".

[0116] Numerical ranges The description of the present invention uses numerical ranges to quantify certain specific parameters related to the present invention. When a numerical range is indicated, it should be understood that such a range is not to be construed as providing literal support only for claims that enumerate only the lower limit of the range, in addition to claims that enumerate only the upper limit of the range. For example, disclosure of a numerical range of 10 to 100 provides literal support for claims that enumerate "greater than 10" (no upper limit) and claims that enumerate "less than 100" (no lower limit).

[0117] Claims not limited to the disclosed embodiments The above preferred forms of the present invention are used merely for illustration and should not be used to limit the meaning for interpreting the scope of the present invention. Modifications to the above exemplary embodiments can be easily made by those skilled in the art without departing from the spirit of the present invention.

[0118] The inventors state herein that they intend to rely on the doctrine of equivalents to determine and investigate a reasonable and fair scope of the present invention in cases where the present invention relates to any device that departs from, but does not substantially deviate from, the literal scope of the present invention as recited in the following claims.

[0119] Example The following examples are intended to illustrate the present invention to teach those skilled in the art the implementation and use of the present invention and are not intended to limit the scope of the present invention in any way. As described below, several tests were carried out on the processes described by the present invention, in addition to samples manufactured under comparative process conditions.

[0120] Example 1 Using cellulose triacetate (CTA) manufactured by Eastman Chemical Co., Kingsport TN (Eastman CTA VM 149), a dope was prepared in a 500 mL three-necked flask. The CTA was dissolved in dimethylacetamide (DMAc) at a concentration of CTA in the range of 18-24% by weight based on the total weight of CTA and DMAc and maintained at 90 °C for 2 hours. A stirring speed of 400 RPM was used for the first 1.5 hours and then slowed to 150 RPM for the last 0.5 hours. The resulting spinning dope was cooled to 60 °C and degassed for 3 hours.

[0121] The spinning dope was transferred from a three-necked flask into a 50 mL stainless steel syringe equipped with a spinning pack that included a multi-filament spinneret and a single layer filter medium with a nominal pore size of 8 micrometers. The syringe and the spinning pack device were connected to a high-pressure syringe pump capable of accurately metering the spinning dope and controlling the dope flow rate to within ±1%. The face of the spinneret was composed of 19 circular holes, each having a diameter of 0.045 mm (45 micrometers) in measurement. The spinneret was immersed in a coagulation bath containing an aqueous solution of DMAc. The concentration of DMAc in the coagulation bath varied from 25 to 65 wt% based on the total weight of all the liquid in the bath. Wet spinning was carried out through the holes on the face of the immersed spinneret, so that the spinning dope formed CTA fibers. The CTA fibers were passed through the coagulation bath by guiding them with a non-driven guide roll and made into a driven take-up roll. The jet draw ratio was controlled by adjusting the surface speed of the driven take-up roll. When the calculated speed of the dope exiting the holes on the face of the spinneret was lower than the surface speed of the take-up roll, a jet draw ratio of less than 1.0 was obtained, but when the surface speed of the take-up roll was faster than the calculated exit speed of the dope, a jet draw ratio exceeding 1.0 was obtained. The fibers were fed from the driven take-up roll to a winder and wound onto a bobbin. The post-jet draw ratio was calculated by dividing the surface speed of the driven winder roll by the surface speed of the driven take-up roll. The post-jet draw ratio was carried out in air at room temperature.

[0122] At room temperature, the fibers on the bobbin were washed by immersing them in deionized water in an overflow water bath for 10 minutes. After washing, the fibers were cut from the bobbin. These obtained loose fibers were dried in a convection oven at 120 °C for 15 minutes.

[0123] The mechanical properties of the fibers were evaluated using a FAVIMAT in accordance with ASTM D1577-07(2018) for denier measurement and ASTM D3822 / D3822M-14(2020) (test conditions: 25 mm gauge length, 15 mm / min strain rate, 0.05 g / denier pretension) for retention and elongation measurements. The silk factor was calculated from the results of elongation and retention.

[0124] As can be seen in Table 1, for the mechanical properties of Comparative Samples 1 to 10, silk factors below 8.0 were obtained, while for Samples 11 and 12 manufactured according to the present invention, silk factors above 8.5 were obtained. By performing a wet spinning process in accordance with the limitations of the claims, a DCM-free process for manufacturing CTA fibers having a silk factor above 8.0 becomes possible.

Table 1

[0125] Example 2 CTA (Eastman CTA VM 149) manufactured by Eastman Chemical Co., Kingsport TN was dissolved in DMAc at a concentration of 20% by weight based on the total weight of CTA and DMAc and stirred at 100 °C until the dope became transparent and no visible swelling particles remained. The resulting dope was filtered through a 15 micrometer polyester nonwoven filter medium.

[0126] The filtered dope was wet-spun into CTA fibers by extrusion through a spinneret having 500 circular cross-sectional holes at 60 °C. CTA fibers were wet-spun using two spinnerets, one with holes having a measured diameter of 0.04 mm (40 micrometers) and the other with holes having a measured diameter of 0.060 mm (60 micrometers). The spinneret was immersed in a coagulation bath containing a coagulation solution of either 60 wt% DMAc and 40 wt% water or 40 wt% DMAc and 60 wt% water, based on the total weight of the solution controlled at a temperature of 25 °C. When exiting the spinneret, the fibers were passed through the coagulation bath by guiding them with a non-driven guide roll and then onto a driven take-up roll.

[0127] The extruded fibers were drawn through the coagulation bath by a driven take-up roll. The speed of the roll was varied to control the jet draw stretch ratio (JDSR) between 0.4 and 0.7 when using a 40-micrometer spinneret and between 0.7 and 1.1 when using a 60-micrometer spinneret. The jet draw stretch ratio was controlled by adjusting the surface speed of the take-up roll relative to the calculated speed of the dope exiting the spinneret.

[0128] After the driven take-up roll, the fibers were immersed and passed through a 25 °C drawing bath containing a solution of either 50 wt% DMAc / 50 wt% water or 30 wt% DMAc / 70 wt%, based on the total weight of the bath. A post-jet draw stretch ratio (PJDSR) of either 1.0 or 1.16 was applied to the drawing bath.

[0129] Next, the fibers were passed through one washing bath containing 100% water and two pairs of washing godet rolls to remove residual DMAc. After washing, the fibers were wound onto a bobbin. After winding the washed fibers onto the bobbin, the fibers were cut from the bobbin and dried in a convection oven at 120 °C without tension to allow for free shrinkage of the fibers.

[0130] In accordance with DIN 53816 standard (test conditions: 20 mm gauge length, 10 mm / min strain rate, 0.5 cN / tex pre-tension), the elongation and retention force were measured using Favimat M.

[0131] As can be confirmed in Table 2, the process of the present invention can produce a silk factor of 8.0 or more. In the set of this example, the higher the jet drawing ratio, the more it contributed to the high silk factor. Figure 3 shows that the optimal coagulation bath concentration may vary depending on the hole diameter of the spinneret. All the maximum silk factors produced with 60 micrometer holes were spun into a 60% DMAc coagulation bath, while 40% DMAc resulted in the maximum silk factor when using 40 micrometer holes. Furthermore, all these samples were produced by dry and unrestrained samples, which made them fully shrinkable during the drying process.

Table 2-1

Table 2-2

[0132] Example 3 The dope was prepared using Eastman CTA VM 149 flakes (Eastman Chemical Co., Kingsport TN). The CTA was dissolved in DMAc at a concentration of 18 wt%. The resulting dope was filtered through a BEKIPOR ST 15AL / 3 non-woven fabric type filter with a pore size of 15 micrometers. The filtered dope was supplied to a spinneret having 60 circular cross-section holes, each with a diameter of 0.063 mm (63 micrometers), at a temperature of 90 °C. The spinneret was immersed in a coagulation bath containing a solution of 60 wt% DMAc and 40 wt% water. When exiting the spinneret, the fibers were passed through the coagulation bath by guiding them with a non-driven guide roll and made into a driven take-up roll. The jet draw ratio was controlled by adjusting the surface speed of the driven take-up roll with respect to the calculated speed of the dope exiting the spinneret. Samples 0 to 3 were produced using a coagulation bath maintained at 25 °C, and samples 4 to 6 were produced using a coagulation bath maintained at 10 °C. The fibers were fed from the driven take-up roll to a winder and wound onto a bobbin. The bobbin was washed by immersion in an overflow water bath containing water at room temperature for 10 minutes. After washing, some samples of the fibers were cut from the bobbin and dried while unrestrained, while other samples were left on the bobbin for drying. These free fiber samples (cut from the bobbin) and the samples on the bobbin were dried in air at 120 °C for 15 minutes. By drying the fibers on the bobbin, the fibers were constrained and the shrinkage and relaxation capabilities during drying were limited. On the other hand, the fibers dried in a relaxed or free state were able to shrink and relax during the drying process.

[0133] The mechanical properties of the fibers were evaluated using a FAVIMAT according to ASTM D1577-07(2018) for denier measurement and ASTM D3822 / D3822M-14(2020) (test conditions: 25 mm gauge length, 15 mm / min strain rate, 0.05 g / denier pretension) for tenacity and elongation measurement. The silk factor was calculated from the results of elongation and tenacity.

[0134] As can be confirmed in Table 3 and FIGS. 2-5, the drying process of the present invention enables an unexpected increase in the tensile properties and silk factor of the produced CTA fibers. By drying the fibers in an unconstrained state, longitudinal shrinkage and relaxation of the fibers become possible, and an unexpectedly large elongation rate and silk factor are obtained compared to fibers constrained during drying by drying on a bobbin. The resulting silk factor is significantly greater than that of samples dried in a free state. [Table 3]

[0135] Example 4 In a glass jar, the solvent was first heated to the mixing temperature (nominal 90° C.) to prepare a cellulose triacetate dope. Next, CTA flakes were added to the heated solvent in an amount necessary to achieve the target % solids concentration for each experimental condition. Mechanical stirring was applied for 3 hours. The lid of the glass mixing jar had a hole sized to accommodate the shaft of the stir bar while minimizing solvent evaporation. After mixing, the dope was stored in an oven at the mixing temperature for 1 hour to dissipate air bubbles. Next, the dope was transferred to another oven and stored at 60° C. until testing.

[0136] Using the wet spinning line of the workbench, a single filament fiber sample was produced. The CTA dope was metered with a syringe pump and transferred to a syringe filter by either a 60 micrometer diameter or a 110 micrometer diameter needle immersed in a coagulation bath. The single filament was guided through the coagulation bath by an undriven guide roll and out from here. The temperature, DMAc concentration, and jet draw ratio were varied. The coagulation bath temperature varied from 11 °C to 20 °C, the DMAc concentration varied from 45 wt% to 60 wt% (based on the total weight of all the liquid in the coagulation bath), and the jet draw ratio varied from 0.7 to 5.7. The jet draw ratio was controlled by varying the surface speed of the driven winding spool after the coagulation bath relative to the calculated speed of the dope exiting the spinning needle. The post-jet draw ratio was not applied. The fiber sample was wound onto a spool using a winder set at the same speed as the take-up roll.

[0137] After winding, the spool was washed for 5 minutes in either a room temperature bath of 100 wt% water or 70 wt% water and 30 wt% DMAc. The samples were dried for 15 minutes at either 60 °C or 110 °C. Some of the samples were dried (constrained) on the bobbin, while others were cut from the bobbin (unconstrained) before drying.

[0138] The mechanical properties of the fiber samples were evaluated using a FAVIMAT according to ASTM D1577-07(2018) for denier measurement and ASTM D3822 / D3822M-14(2020) (test conditions: 25 mm gauge length, 15 mm / min strain rate, 0.05 g / denier pretension) for tenacity and elongation measurement. The silk factor was calculated from the results of elongation and tenacity. The results are shown in Table 4.

[0139] As can be seen in Figure 8, the positive effect of unconstrained drying on the silk factor characteristics of the fiber is not as significant when the jet draw ratio exceeds 1 (more specifically, exceeds 1.4).

Table 4-1

Table 4-2

Table 4-3

Table 4-4

Table 4-5

[0140] Example 5 Regarding dopant preparation, wet spinning, and washing, fiber samples were produced according to the method of Example 1. Next, the samples were dried in a convection oven at 120 °C for 10 minutes. Some samples were cut from the bobbins before drying, thereby allowing shrinkage (unconstrained), while other samples were dried on the bobbins to prevent shrinkage (constrained). The dried samples were cooled to ambient temperature, and the fiber properties of selected samples were tested. Regardless of whether they were dried constrained or unconstrained, the remaining samples were subjected to a further heat treatment step by placing them in a convection oven at 180 °C for 10 minutes. All samples were subjected to the heat treatment step in an unconstrained (removed from the bobbins) state.

[0141] Table 5 shows that the drying and annealing processes affect the tensile properties and silk factor of the CTA fibers of the present invention. Drying the fibers in an unconstrained state allows for relaxation and shrinkage of the fibers, resulting in a significantly greater elongation rate and a slightly lower holding force compared to fibers constrained during drying by drying on the bobbin. The resulting silk factor is also significantly greater than that of the unconstrained dried sample. Secondary heat treatment of the unconstrained dried fiber sample results in slight changes in the holding force, elongation rate, and silk factor. However, secondary heat treatment of the fiber sample dried while constrained (on the bobbin) shows a significant improvement in the elongation rate and silk factor, but little or no change in the holding force. Unexpectedly, the elongation rate and silk factor properties of the samples dried in a constrained state and subjected to an additional heat treatment step recovered to near the levels shown by the unconstrained dried fiber samples. By both unconstrained drying and unconstrained secondary heat treatment under appropriate temperature and time, the fibers can be effectively relaxed, resulting in a large silk factor.

Table 5

Claims

1. A manufacturing process for one or more cellulose triacetate ("CTA") fibers having a silk factor of 8.0 or more, comprising: a) a dissolution step of dissolving cellulose triacetate in a dichloromethane-free solvent containing dimethylacetamide to produce a cellulose triacetate dope; b) a wet spinning step in which the cellulose triacetate dope is wet spun through a dichloromethane-free coagulation bath maintained at a temperature in the range of 20°C to 40°C to form one or more CTA fibers at a jet draw ratio in the range of 0.3 to 1.4, the bath containing dimethylacetamide and water; c) a drying step in which the one or more CTA fibers are dried and shrunk during the drying step; The manufacturing process comprising the above steps.

2. The process according to claim 1, wherein the one or more CTA fibers have a silk factor of 8.5 or more.

3. The process according to claim 1 or 2, further comprising a heat treatment step, wherein the one or more fibers are heated to a temperature at least 10°C lower than the CTA fibers.

4. The process according to any one of claims 1 to 3, further comprising at least one post-jet draw stretching step, wherein the CTA fibers are further stretched to a total post-jet draw ratio in the range of 1.0 to 3.

0.

5. The process according to any one of claims 1 to 4, wherein the concentration of dimethylacetamide in the dichloromethane-free coagulation bath is at least 20% by weight and 65% by weight or less based on the total weight of the coagulation bath.

6. The process according to any one of claims 1 to 5, wherein the concentration of water in the coagulation bath is at least 35% by weight and 80% by weight or less based on the total weight of the coagulation bath.

7. The process according to any one of claims 1 to 6, wherein the one or more CTA fibers partially or completely shrink during the drying step.

8. The process according to any one of claims 3 to 7, wherein the heat treatment step further comprises steam and is carried out at a pressure greater than 1 atm.

9. The process according to any one of claims 1 to 8, further comprising a pressing step.

10. The process according to claim 9, wherein a heat treatment step follows the pressing step.

11. The process according to any one of claims 1 to 10, further comprising a cutting step, wherein the one or more CTA fibers are cut into CTA staple fibers.

12. The process according to any one of claims 1 to 11, further comprising a winding and packaging step for continuous fibers.

13. The process according to any one of claims 1 to 12, wherein the triacetate cellulose has a degree of substitution with respect to acetyl substituents of 2.6 or more.

14. The process according to any one of claims 1 to 13, wherein the one or more CTA fibers have a denier per filament of 0.5 to 20 or less.

15. The process according to any one of claims 1 to 14, wherein the triacetate cellulose dope contains a matting agent.

16. The process according to any one of claims 1 to 14, wherein the temperature of the triacetate cellulose dope is wet-spun at a temperature in the range of 20°C to 120°C or less.

17. The cellulose triacetate has a DS of at least 2.6 アセチル and a number average degree of polymerization of 200 or less, the cellulose triacetate dope according to claim 16.

18. The triacetate cellulose dope according to claim 17, which exhibits a viscosity of 1,000 poises or less when measured at 90°C.

19. Triacetate cellulose fibers produced according to the process according to any one of claims 1 to 18.

20. The cellulose triacetate has a DS of at least 2.6 アセチル The cellulose triacetate fiber according to claim 19, comprising a number average degree of polymerization of 200 or less.

Images