High-toughness regenerated cellulose fiber

Abstract

A high tenacity regenerated cellulosic fiber is disclosed. The high tenacity regenerated cellulosic fiber is prepared from a cellulosic feedstock comprising 5-100% by weight of pretreated bacterial cellulose having a degree of polymerization in the range of 450-2000; and 0-95% by weight of an additional cellulosic material selected from the group consisting of dissolving grade pulp, recycled cotton pulp, reclaimed cellulosic materials, and mixtures thereof. The fiber has a tenacity of at least 4.5 grams / denier and an elongation of at least 10% as measured according to ASTM D 3822.

Description

Technical Field

[0001] The present disclosure relates to highly tough regenerated cellulose-based fibers obtained from bacterial cellulose and a method for manufacturing the fibers.

Background Art

[0002] It is known to manufacture fibers from cellulose derived from wood pulp and other plants. Although there are various possibilities for cellulose raw materials, the most commonly used ones are all plant-derived, and plant materials are subjected to an extraction process that consumes time and energy to produce cellulose pulp. For example, to produce cellulose pulp from wood, it is necessary to peel the bark and chip it, and then treat the wood chips with hot sodium hydroxide / sodium sulfide. Intensive forestry and its related infrastructure consume a large amount of resources, which has become an issue in meeting the increasing demand for cellulose raw materials in the industry.

[0003] Bacterial cellulose (also known as microbial cellulose) provides a more sustainable potential cellulose source as an alternative to conventional plant-derived cellulose sources. Furthermore, bacterial cellulose is much easier to obtain with a much higher purity than plant-derived cellulose that is usually contaminated with lignin and hemicellulose.

[0004] Bacterial cellulose is prepared using a fermentation process by various bacteria, particularly bacteria of the genera Acetobacter, Gluconobacter, Gluconoacetobacter, and Komagataeibacter, and acts on various carbon sources such as carbohydrates and alcohols. Bacterial cellulose is composed of a superfine network of highly uniaxially oriented cellulose nanofibers (3 - 8 nm). Due to this type of 3D structure, bacterial cellulose achieves a high crystallinity of about 60 - 80% and excellent physicochemical and mechanical properties.

[0005] The production of bacterial cellulose is described in detail in the literature such as "Hestrin and Schramm, Biochemical Journal 1954, 58(2), 345~352", "Iguchi et al., Journal of Materials Science 2000, 35, 261~270", "Wu and Li, Journal of Bioscience and Bioengineering 2015, 120(4), 444~449", "Basu et al., Carbohydrate Polymers 2019, 207, 684~693", etc.

[0006] Bacterial cellulose has been applied in various fields such as biomedicine, the food industry, papermaking, cosmetics, and pharmaceuticals. Currently, the fashion industry is becoming increasingly "eco-led" and promoting "sustainable clothing". Although textile fibers based on natural and renewable resources are more environmentally friendly compared to conventional petroleum-derived alternatives, they are more expensive and not completely without environmental impact. Regulations and market forces are constantly seeking environmentally friendly and cost-effective solutions. Bacterial cellulose is a promising alternative that is environmentally friendly and sustainable, replacing plant-derived cellulose-based fibers.

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, reports on the use of bacterial cellulose in fiber production are very limited. An efficient production process for lyocell fibers using bacterial cellulose has not yet been developed.

[0008] "Makarov et al, Fiber Chemistry, Vol. 51, No. 3, September, 2019" discloses the production of cellulose-based films by the solid-phase dissolution method. To promote the dissolution of bacterial cellulose in NMMO and achieve an 8% solution, solid-phase activation was necessary. Even after using the solid-phase dissolution method in N-methylmorpholine-N-oxide (NMMO) monohydrate, complete dissolution of bacterial cellulose could not be achieved. The solution preparation time was also as long as about 12 hours. Due to the high degree of polymerization, the viscosity of the obtained bacterial cellulose-NMMO solution was very high, about 10 5 Pa·s, making it difficult to spin fibers. Due to the high viscosity, the concentration of bacterial cellulose in NMMO was limited to 6%, and the toughness of the cellulose fibers thus formed was only 3.8 g / d and the elongation was 6.6%, which was significantly lower than that of standard lyocell fibers.

[0009] "Shanshan et al., Carbohydrate Polymers Vol. 87 (2012) pages 1020~1025" discloses achieving the dissolution of the as-formed bacterial cellulose pellicle formed by making a film from bacterial cellulose in NMMO by the phase inversion technique. The bacterial cellulose solution was prepared with a low bacterial cellulose content of 3%.

[0010] "Gao et al., Carbohydrate Polymers 2011, 83(3), 1253~1256" reports on the use of bacterial cellulose with a degree of polymerization of 2,700. To prepare a dope with a cellulose concentration of 7%, long-time dissolution was carried out at 80°C for 12 hours while performing high-speed energy-concentrated stirring, so the solubility in NMMO seemed to be difficult. Furthermore, the fibers obtained by spinning from this dope had a low toughness of only 0.5~1.69 g / d compared to the toughness of typical lyocell fibers of about 4.0~4.4 g / d.

[0011] The specification of Chinese Patent No. 101492837 describes a method for preparing regenerated bacterial cellulose fibers by using bacterial cellulose having a high degree of polymerization of 1500 to 16000, dissolving it in a suitable solvent such as an ionic liquid to prepare a solution in the range of 1 to 30%, and then filtering and spinning.

[0012] International Publication No. 00 / 23516 describes using bacterial cellulose together with plant-derived cellulose in a composition in the range of 0.01 to 5% in dissolved or undissolved form.

[0013] The specification of Chinese Patent Application Publication No. 101230494 describes using a complex mixture of various high and low degree of polymerization celluloses including "natural" cellulose, bacterial cellulose, kenaf, hemp, jute, flax, etc. in combination with polyacrylonitrile. The cellulose mixture and polyacrylonitrile dissolve in ionic liquid but not in NMMO. When using low and high degree of polymerization bacterial cellulose in combination with flax and polyacrylonitrile in 1-allyl-3-methylimidazolium chloride, fibers with a toughness of 2.6 g / d were produced.

[0014] The conventionally known techniques using bacterial cellulose are limited in application or not applied at all in the production of environmentally friendly regenerated cellulose-based fibers. Also, such methods face drawbacks such as low concentration of the cellulose solution, long dissolution time, high viscosity of the cellulose solution, etc. Furthermore, the conventionally known fibers obtained using bacterial cellulose exhibit lower toughness compared to standard lyocell fibers.

[0015] High-tenacity regenerated cellulose fibers are disclosed. The high-tenacity regenerated cellulose fibers are prepared from a cellulose-based raw material, and the cellulose-based raw material comprises 5 to 100% by weight of pretreated bacterial cellulose having a degree of polymerization in the range of 450 to 2000; and 0 to 95% by weight of an additional cellulose-based material selected from the group consisting of dissolving grade pulp, recycled cotton pulp, recycled cellulose-based materials, and mixtures thereof. The fibers have a tenacity of at least 4.5 grams / denier and an elongation of at least 10% as measured according to ASTM D 3822.

[0016] Also disclosed is a method for preparing the regenerated cellulose fibers having a tenacity of at least 4.5 grams / denier and an elongation of at least 10% as measured according to ASTM D 3822. The method includes the step of subjecting bacterial cellulose to a pretreatment step to obtain pretreated bacterial cellulose having a degree of polymerization in the range of 450 to 2000, the pretreatment step including treating the bacterial cellulose with a pretreatment agent selected from the group consisting of oxidizing agents, acids, alkalis, and mixtures thereof; preparing a premix by mixing a cellulose-based raw material comprising, based on the total weight of the cellulose-based raw material, 5 to 100% by weight of the pretreated bacterial cellulose and 0 to 95% by weight of an additional cellulose-based material selected from the group consisting of dissolving grade pulp, recycled cotton pulp, recycled cellulose-based materials, and mixtures thereof, with a solvent, and subsequently dissolving the cellulose in a dissolving apparatus to obtain a dope solution; and extruding the dope solution prepared through a fine orifice, followed by air-gap spinning and regeneration in a spinning bath to obtain the regenerated cellulose fibers.

Mode for Carrying Out the Invention

[0017] To facilitate understanding of the principles of the present disclosure, embodiments are referred to herein and described using specific language. Nevertheless, no limitation of the scope of the present disclosure is thereby intended, and such changes and further modifications in the disclosed compositions and methods, as well as such further applications of the principles of the present disclosure, are intended to be those that would ordinarily occur to one of ordinary skill in the art to which the present disclosure pertains.

[0018] It will be understood by those skilled in the art that the foregoing general description and the following detailed description are exemplary and explanatory of the present disclosure and are not intended to limit the present disclosure.

[0019] References throughout this specification to "one embodiment", "an embodiment", or similar terms mean that a particular feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment of the present disclosure. Thus, appearances of the phrases "in one embodiment", "in an embodiment", and similar language throughout this specification may, but do not necessarily, refer to the same embodiment.

[0020] As used herein, the term "bacterial cellulose" is intended to mean that cellulose is prepared using a fermentation process by various microorganisms, particularly bacteria of the genera Acetobacter, Gluconobacter, Gluconoacetobacter, and Komagataeibacter, and acts on various carbon sources such as carbohydrates and alcohols. The bacterial cellulose used in the present disclosure was obtained from various commercial sources outside India.

[0021] As used herein, the term "toughness" is intended to mean the breaking strength (in gram-force units) of a fiber divided by the denier.

[0022] As used herein, the term "elongation" is intended to mean elongation at the break point.

[0023] In the broadest sense, the present disclosure relates to high-tenacity regenerated cellulose-based fibers obtained from bacterial cellulose and methods for manufacturing said fibers. In particular, the present invention relates to high-tenacity regenerated cellulose-based fibers prepared from a cellulose-based raw material, wherein the cellulose-based raw material comprises 5 to 100% by weight of pretreated bacterial cellulose having a degree of polymerization in the range of 450 to 2000; and 0 to 95% by weight of an additional cellulose-based material selected from the group consisting of dissolving pulp, bamboo pulp, hemp, recycled cotton pulp, recycled cellulose-based materials and mixtures thereof; and the fibers have a tenacity of at least 4.5 grams / denier and an elongation of at least 10% as measured according to ASTM D 3822.

[0024] The present disclosure also provides a method for preparing the aforementioned high-tenacity regenerated cellulose-based fibers. The method comprises: (a) subjecting bacterial cellulose to a pretreatment step to obtain pretreated bacterial cellulose having a degree of polymerization in the range of 450 to 2000, said pretreatment step comprising treating the bacterial cellulose with a pretreatment agent selected from the group consisting of oxidizing agents, acids, alkalis and mixtures thereof; (b) preparing a premix by mixing a cellulose-based raw material comprising 5 to 100% by weight of said pretreated bacterial cellulose and 0 to 95% by weight of an additional cellulose-based material selected from the group consisting of dissolving pulp, bamboo pulp, hemp, recycled cotton pulp, recycled cellulose-based materials and mixtures thereof, based on the total weight of the cellulose-based raw material, with a solvent, and subsequently dissolving the cellulose in a dissolving apparatus to obtain a dope solution; and (c) extruding the dope solution prepared through a fine orifice, subsequently air-gap spinning, and regenerating in a spinning bath to obtain the regenerated cellulose-based fibers. comprises.

[0025] The inventors have found that by reducing the degree of polymerization of bacterial cellulose from its natural level (about 2500 to 10000) to an optimal degree of polymerization in the range of 450 to 2000, particularly in the range of 500 to 1500, it becomes possible to produce regenerated cellulose-based fibers having high toughness and elongation. In particular, by using bacterial cellulose having an optimized degree of polymerization, it has been found that the solubility in a solvent is improved, and a high-concentration bacterial cellulose solution having a low viscosity and a cellulose concentration of about 9 to 15% can be obtained. This enables the formation of regenerated cellulose-based molded articles such as fibers having high toughness and elongation.

[0026] According to one embodiment, the pretreated bacterial cellulose has a degree of polymerization in the range of 450 to 2000. In some embodiments, the pretreated bacterial cellulose has a degree of polymerization in the range of 500 to 1500.

[0027] According to one embodiment, to obtain the pretreated bacterial cellulose, the pretreatment of the bacterial cellulose is performed using an acid selected from the group consisting of mineral acids, organic acids, and combinations thereof. Examples of mineral acids include sulfuric acid (H2SO4), hydrochloric acid (HCl), nitric acid (HNO3), phosphoric acid (H3PO4), etc., and examples of organic acids include oxalic acid, formic acid, acetic acid, etc., but are not limited thereto. According to one embodiment, the pretreatment is carried out using an oxidizing agent such as sodium hypochlorite. According to one embodiment, the pretreatment is performed using an alkali including but not limited to sodium hydroxide, potassium hydroxide, ammonium hydroxide. According to one embodiment, the pretreatment is carried out using a combination of one or more acids, alkalis, and oxidizing agents to further reduce the degree of polymerization of the bacterial cellulose.

[0028] According to one embodiment, the pretreatment agent is used at a concentration in the range of 0.1 to 10%. In some embodiments, the concentration of the pretreatment agent varies between 0.5 and 5%. The ratio of the material to the liquid (MLR) is maintained in the range of 8 to 40.

[0029] According to one embodiment, the pretreatment step includes additional treatment to reduce the amount of metal impurities such as iron (Fe) from bacterial cellulose. This treatment is performed to reduce the Fe content to less than 20 ppm. In some embodiments, this treatment is carried out to reduce the Fe content to less than 10 ppm. The additional treatment includes treating the bacterial cellulose with a chelating agent. Any known chelating agent can be used. According to one embodiment, the chelating agent is selected from the group consisting of ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), and diethylenetriaminepentamethyphosphonic acid (DTMPA). The chelating agent is used at a concentration in the range of 0.1 to 0.8% by weight based on the weight of the bacterial cellulose. The chelating agent is added before, during, or after the addition of the pretreatment agent. Reducing the iron content of the bacterial cellulose reduces the decomposition of the NMMO solvent and enables the dissolution of the bacterial cellulose at high temperatures.

[0030] According to one embodiment, the pretreatment step is carried out at a temperature in the range of 30 to 100 °C. In some embodiments, the pretreatment step is carried out at a temperature in the range of 50 to 90 °C. According to one embodiment, the pretreatment step is carried out for a period in the range of 15 minutes to 20 hours. In some embodiments, the pretreatment is carried out for a period of 2.5 to 4.5 hours. The pretreatment is carried out in one, two, or multiple steps. By performing the pretreatment in multiple stages, the decrease in the degree of polymerization and the efficient removal of iron can be controlled.

[0031] According to one embodiment, after the pretreatment step, the pretreated bacterial cellulose is subjected to a washing step. The washing step consists of multiple washes with cold or hot pure water. In some embodiments, hot pure water is used.

[0032] According to one embodiment, the pretreated bacterial cellulose is further subjected to a size reduction step. The size reduction step can be carried out using a high-speed mixer, ball mill, shredder, etc. The size reduction step promotes the dissolution of the bacterial cellulose in the solvent in step (b) of the method.

[0033] According to one embodiment, the additional cellulose material is selected from the group consisting of dissolving pulp, recycled cellulose-based materials, recycled cotton, and other plant-derived cellulose pulps including bamboo and hemp. The additional cellulose-based material is added in an amount in the range of 0 to 95% by weight. According to one embodiment, the additional cellulose-based material has a degree of polymerization in the range of 500 to 2000. Specifically, dissolving pulp with a degree of polymerization of 500 to 700 and recycled cotton with a degree of polymerization of 500 to 2000 prepared from the purification of textile cotton waste are used.

[0034] According to one embodiment, in step (b), a premix is prepared by mixing the cellulose-based raw material with a solvent. Here, the premix is prepared by mixing the cellulose-based raw material with an aqueous solvent of 65 to 80% (w / w) in a required ratio under temperature and pressure conditions where cellulose dissolution does not occur and the cellulose uniformly absorbs the solvent. According to one embodiment, the premix is carried out for 0 to 6 hours. In some embodiments, the premix time is maintained at 0 to 60 minutes, particularly 10 to 40 minutes. During the premix, the obtained mixture of the pretreated bacterial cellulose, the additional cellulose-based material, and the solvent is left as it is at a temperature of 25 to 90 °C with or without shear. This promotes the dissolution of cellulose in the solvent. Then, the premix is subjected to high-shear mixing at a temperature in the range of 90 to 110 °C, followed by evaporating water at a high temperature in the range of 90 to 115 °C and low pressure to remove excess water from the mixture, obtaining a cellulose solution with a cellulose content of about 9 to 15 wt%.

[0035] According to one embodiment, the premix further contains additives such as TiO2, surfactants, pigments, carbon black, etc.

[0036] In the next step, the pre-mixed dissolution is carried out according to a standard lyocell process known in the art. According to one embodiment, the dissolution is performed by subjecting the pre-mix in the dissolving apparatus to a high temperature in the range of 70 - 115 °C, particularly 90 - 110 °C, under a vacuum of about 500 - 750 mmHg. According to one embodiment, the dissolving apparatus is selected from the group consisting of a sigma mixer, a reactor kneader, a wiped film evaporator, etc. The solvent is selected from the group consisting of N-methylmorpholine-N-oxide (NMMO), ionic liquids, dimethyl sulfoxide / calcium chloride, and dimethylacetamide / lithium chloride. In some embodiments, the solvent is NMMO.

[0037] According to one embodiment, the dope solution obtained in step (b), when measured using a typical oscillatory rheometer, has a viscosity in the range of 10 2 ~10 4 Pa·s.

[0038] In the next step, depending on the viscosity of the solution, the dope solution is extruded through a suitable nozzle at a temperature in the range of 105 °C ± 20 °C. The extruded solution is subjected to air-gap spinning and regenerated in a spinning bath. The spinning bath contains a solvent at a concentration in the range of 5 - 30 wt% in water. The fibers are drawn out, optionally cut into staple fibers, washed, bleached, finished, and dried.

[0039] According to one embodiment, the resulting high-tenacity regenerated cellulose-based fibers have an average linear density in the range of 0.6 - 2.0 denier, depending on the flow and spinning speed.

[0040] It will be apparent to those skilled in the art that various modifications and variations can be made to the methods / processes of the present disclosure without departing from the scope of the present disclosure. Other embodiments will be apparent to those skilled in the art upon consideration of the specification and examples of the methods / processes disclosed herein. The specification and examples are to be considered as illustrative only, and it is intended that the true scope of the present disclosure be indicated by the following claims and their equivalents.

Examples

[0041] Estimation of Degree of Polymerization (DP) For pretreated bacterial cellulose: The degree of polymerization of pretreated bacterial cellulose is estimated by measuring the limiting viscosity of cellulose dissolved in a cuprammonium ethylene diamine (CED) solution according to ISO standard number ISO5351:2010. In this method, a known amount of cellulose is dissolved in the CED solution, and the viscosities of the sample solution and the solvent are measured using a viscometer. The limiting viscosity is calculated according to the ISO method. The degree of polymerization is estimated by an empirical formula given by Equation [1]. DP = 1.7806[η] - 94.799 Equation [1] Here, [η] is the limiting viscosity and DP is the degree of polymerization.

[0042] Example 1: Separation of Bacterial Cellulose The pellicle of bacterial cellulose was collected from nata de coco production, physically scraped off the thin film from the surface, and cleaned by washing the pellicle with water. The pellicle was about 36 cm × 24 cm, and the average weight in the wet state was 685 g. After drying, the average weight of the obtained bacterial cellulose sheet was 7 g. The sheet (1 kg) was shredded into small flakes (about 3 mm × 8 mm) using a cross-cut paper shredder, and this was added to hot water (40 L at 90 °C) containing Tween 80 (0.4 L) and NaOH (0.9 kg), and stirred occasionally for 15 minutes. The flakes were collected by filtration through a nylon mesh and pressed to remove the excess liquid. Then, the flakes were washed in hot water (40 L at 90 °C) for 15 minutes while stirring occasionally. The flakes were collected again by filtration through a nylon mesh and pressed to remove the excess liquid. This washing cycle in hot water was repeated, and the obtained flakes were added to water (40 L at room temperature). Then, the pH was adjusted to 6 by adding a 50% w / w sulfuric acid solution, and stirred occasionally for 15 minutes. The flakes were filtered and collected with a nylon mesh, pressed to remove the excess liquid, and dried with warm air to obtain "bacterial cellulose flakes" with a DP of about 1500 (limiting viscosity of about 873).

[0043] Example 1a: Separation of Bacterial Cellulose The pellicles of bacterial cellulose obtained from nata de coco production were cleaned by physically scraping a thin film from the surface and washing the pellicles with water. The pellicles were approximately 36 cm × 24 cm and on average contained 7 grams of bacterial cellulose. One hundred (100) wet pellicles were soaked in a blender for 3 minutes, and the resulting pulp was placed into a nylon mesh bag in a washer / spin dryer. Hot water (40 L at 90 °C) containing Tween 80 (0.4 L) and NaOH (0.6 kg) was added, and the contents were stirred occasionally over 15 minutes. Excess liquid was then removed by spin drying. Hot water (40 L at 90 °C) was added to the machine, and the contents were immersed for 15 minutes with occasional stirring and then spin dried again. This washing / spin cycle was repeated, and water (40 L at room temperature) was added. The pH was then adjusted to 6 by adding 50% (w / w) sulfuric acid solution, and the mixture was stirred occasionally over 15 minutes. The mixture was spin dried again to remove as much excess liquid as possible. The resulting pulp was removed from the nylon bag, formed into a disk approximately 22 cm in diameter using a hydraulic press, and the remaining excess liquid was removed. The disk was dried with warm air and then shredded with a cross-cut paper shredder to obtain "bacterial cellulose chips" with a DP of approximately 2200 (limiting viscosity of approximately 1300).

[0044] Example 2: Pretreatment of Bacterial Cellulose Using NaOH A mixture of 2% (w / w) bacterial cellulose flakes (obtained in Example 1) was prepared in water and treated with 50% (w / w) NaOH solution to produce a final NaOH concentration of 10% (w / w) and a cellulose loading of 1.6% (w / w). The reaction mixture was stirred at 60 °C for 16.2 hours, and the solids were collected by vacuum filtration. The wet flakes were added to water at a w / v ratio of approximately 1:50 to obtain a basic mixture, which was then neutralized with glacial acetic acid. The solids were then collected by vacuum filtration and dried in an oven at 70 °C overnight. The DP of this material was 706 (limiting viscosity 450 mL / g).

[0045] Example 3: Pretreatment of Bacterial Cellulose Using NaOH The bacterial cellulose flakes were pulped in water to provide a 2.0% (w / w) cellulose suspension. A 50% (w / w) NaOH solution was added to the pulp to obtain a final NaOH concentration of 18% (w / w) and a cellulose loading of 1.3% (w / w). The reaction mixture was then stirred at 60 °C for 1 hour, after which the solid was collected by vacuum filtration and placed in a round-bottom flask fitted with a rubber septum (approximately 25 mL per 1 g of bacterial cellulose used). By this process, the DP decreased from 1500 to 973. The reaction using this pretreated mixture was carried out by immersing the flask in a water bath at 50 °C with magnetic stirring at the time intervals described in Table 1. At each time interval shown in Table 1, water was added to the solid, the resulting basic mixture was neutralized with glacial acetic acid, vacuum filtered to isolate the solid, washed with water, and then dried in an oven at 70 °C overnight. The resulting DP after each time interval is listed in Table 1.

[0046] [Table 1] Table 1: Intrinsic viscosity results of Example 3

[0047] Example 4: H 2 SO 4 Pretreatment of Bacterial Cellulose Using Water was added to the bacterial cellulose flakes, followed by the addition of sulfuric acid to produce a final concentration of 1% (w / w) sulfuric acid and a cellulose loading of 4% (w / w). The reaction mixture was then heated at 75 °C at the time intervals specified in Table 2. The solid was collected by vacuum filtration, then added to water at a w / v ratio of approximately 1:40, and the mixture was neutralized with a 10% (w / w) aqueous NaOH solution. The solid was then collected by vacuum filtration, washed with water, and dried in an oven at 50 °C overnight.

[0048] [Table 2] Table 2: Intrinsic viscosity results of Example 4

[0049] Example 5: H 2 SO 4 Pretreatment of Bacterial Cellulose Using The weighed amount of bacterial cellulose with an initial DP of approximately 1500 (limiting viscosity of approximately 873) and a high Fe level (38 ppm) was added to water at a material-to-liquid ratio of 1:30 specified in Table 3, and then sulfuric acid was added to produce sulfuric acid with a final concentration of 0.5% (v / v). Subsequently, the reaction mixture was heated at a temperature of 75 °C for 4 hours (Table 3). The solid was collected by vacuum filtration, subsequently added to water at a w / v ratio of approximately 1:40, and the mixture was neutralized with a 10% w / w NaOH solution. The solid was then collected by vacuum filtration, washed with water, and dried overnight in an oven at 50 °C. The resulting DP and Fe content are listed in Table 3.

[0050] Example 6: H 2 SO 4 Pretreatment of Bacterial Cellulose Using The process of Example 5 was used, but the sulfuric acid concentration was set to 1% v / v and applied to bacterial cellulose with an initial DP of approximately 1500. The resulting cellulose had a DP of 830 and an Fe content of 20 ppm, respectively, and is listed in Table 3.

[0051] Example 7: H 2 SO 4 Pretreatment of Bacterial Cellulose Using The process of Example 6 was used, but the treatment temperature was increased to 85 °C and the MLR was decreased to 1:25. The resulting cellulose had a DP of 650 and an Fe content of 18 ppm, respectively, and is listed in Table 3.

[0052] Examples 8 and 9: Pretreatment of Bacterial Cellulose Using Hydrochloric Acid Bacterial cellulose with a DP of approximately 1600 to 2500 and an average iron content of approximately 76 ppm was treated with HCL at a concentration in the range of 0.5 - 1.5% (w / w) and an MLR in the range of 1:10 to 1:13. The treatment temperature was maintained at 75 °C and the treatment time was varied between 3 - 4 hours. After treatment, the mixture was neutralized with 10% NaOH, followed by washing, drying, and comminution. The resulting DP and Fe content of the cellulose are listed in Table 3.

[0053]

Table 3

[0054] Examples 10 - 12: Pretreatment of Bacterial Cellulose Using Sodium Hypochlorite Bacterial cellulose with a DP of approximately 1500 and an Fe content of approximately 56 ppm was treated at 60 °C for various times at a 1:15 MLR using 1% w / w sodium hypochlorite as specified in Table 4. After treatment, the bacterial cellulose was washed 2 - 3 times with boiling water and then dried in an air oven at 60 °C. The resulting bacterial cellulose had a reduced DP and Fe as shown in Table 4.

[0055] Example 13: Pretreatment of Bacterial Cellulose Using Sodium Hypochlorite and EDTA Bacterial cellulose with a DP of approximately 1500 and an Fe content of approximately 56 ppm was treated for 50 minutes at a 1:15 MLR using 1% w / w sodium hypochlorite, followed by treatment with a 0.4 wt% (based on the weight of the dry pulp) EDTA solution at 60 °C for 30 minutes. After treatment, the bacterial cellulose was washed 2 - 3 times with boiling water and then dried in an air oven at 60 °C. The resulting bacterial cellulose had a reduced DP and Fe as shown in Table 4.

[0056]

Table 4

[0057] Example 14: Preparation of Fibers Using Dissolving - Grade Pulp (DGP) (Control) The cellulose solution is prepared from standard DGP with a DP of approximately 600 according to the standard lyocell preparation process without pre - mixing. The prepared dope is spun into fibers with a denier and tenacity of 1.18 and 4.3 g / d, respectively.

[0058] Example 15: Preparation of Cellulose Solution Using Treated Bacterial Cellulose The cellulose solution was prepared by pre-mixing the treated bacterial cellulose from Example 10, which had a DP of 900 (limiting viscosity 560 mL / g) and an Fe content of 40 ppm, with the dissolving grade pulp at 50% by weight in NMMO for 40 minutes. A solution with a cellulose concentration of 12% was prepared in 76% by weight of NMMO. The pre-mixing containing cellulose and NMMO was mixed for 40 minutes without stirring. After mixing, high shear was applied to prepare the cellulose-NMMO slurry at about 100 °C. According to the cellulose-NMMO state diagram known in the art, the slurry was subjected to a temperature of about 110 °C and a vacuum of 600 mmHg to remove water. The zero-shear viscosity of the resulting dope was found to be in the range of about 10 3 Pa·s.

[0059] Example 16: Preparation of Cellulose Solution Using Treated Bacterial Cellulose A cellulose solution was prepared by pre-mixing sulfuric acid-treated bacterial cellulose with a DP of 688 (limiting viscosity 440 mL / g) and an Fe content of about 20 ppm at a cellulose percentage of 12% for 40 minutes and then dissolving it according to the standard Lyocell process. The resulting viscosity was found to be in the range of about 10 3 Pa·s.

[0060] Examples 17 - 21: Preparation of Cellulose Solution Using Treated Bacterial Cellulose A cellulose solution containing 12.5% cellulose from sulfuric acid-treated bacterial cellulose with a DP of 635 (limiting viscosity 410 mL / g) and an Fe content of <10 ppm was prepared in NMMO with a dissolving grade pulp having a DP of 600 (limiting viscosity about 390 mL / g) at different blend ratios in the range of 10 - 100 wt% with a short pre-mixing time of 30 minutes.

[0061] In Example 20, by increasing the draw during spinning of the dope, low fiber fine diners of 0.6 were prepared.

[0062] Example 22: Preparation of Cellulose Solution Using Bacterial Cellulose Subjected to High - Shear Mixing A 12.5 wt% cellulose solution in NMMO was prepared from bacterial cellulose pretreated with a high-shear mixer and having a DP of 1500 (in the range of an intrinsic viscosity of 873). The bacterial cellulose was mixed with excess water, and then the excess water was squeezed out so that the wet bacterial cellulose contained 4 to 5 times the moisture content of the dry weight of the bacterial cellulose. The wet pulp was blended with dissolving-grade pulp (DP about 600) so that the ratio of wet bacterial cellulose in the mixture was about 10 wt%. Then, the mixture was used to prepare a cellulose solution according to the standard Lyocell process.

[0063] Example 23: Preparation of Cellulose Solution Using Treated Bacterial Cellulose A 12.5 wt% cellulose solution was prepared by premixing sulfuric acid-treated bacterial cellulose having a DP of 653 (intrinsic viscosity 420 mL / g) and an Fe content of about 10 ppm in an amount of 40 wt% with 60 wt% recycled cotton pulp (DP about 650) for 30 minutes, and then dissolving it according to the standard Lyocell process described above.

[0064] Example 24: Preparation of Cellulose Solution from 100% Treated Bacterial Cellulose A 12 wt% cellulose solution in NMMO was prepared from 100% bacterial cellulose treated with HCl and having a DP of about 830 (intrinsic viscosity 520 mL / g) according to the standard Lyocell process described above.

[0065] Example 25: Preparation of Cellulose Solution Using Treated Bacterial Cellulose A 12.5 wt% cellulose solution was prepared by premixing hydrochloric acid-treated bacterial cellulose having a DP of 520 (intrinsic viscosity 340 mL / g) and an Fe content of about 17 ppm in a weight ratio of 40% with 60 wt% recycled cotton pulp (DP about 650) for 40 minutes, and then dissolving it according to the standard Lyocell process described above.

[0066] The bacterial cellulose solutions formed in Examples 14 to 25 were extruded through an appropriate nozzle in a temperature range of 105°C ± 15°C according to the viscosity of the solution. The cellulose fibers were regenerated after passing through a spinneret and an air gap and then through a spinning bath with an NMMO concentration of 20 - 22% in water. The details and characteristics of the processes of the fibers produced in Examples 14 to 25 are summarized in Table 5 below.

[0067]

Table 5

[0068] Observation: It was observed that the fibers produced using the treated bacterial cellulose of the present disclosure exhibited toughness and elongation equal to or greater than those of conventional cellulose-based fibers produced from dissolving-grade cellulose pulp.

Industrial Applicability

[0069] The disclosed highly tough regenerated cellulose-based fibers are obtained from bacterial cellulose and have similar or improved mechanical properties compared to lyocell fibers prepared from dissolving-grade pulp. These fibers are environmentally friendly and reduce the burden on plant-derived cellulose sources.

[0070] The disclosed process addresses the issue of using bacterial cellulose in the production of regenerated cellulose-based fibers, particularly lyocell fibers. The disclosed process can reduce the degree of polymerization of bacterial cellulose and thus the viscosity of the cellulose solution for fiber production. The disclosed process enables a reduction in the degree of polymerization of bacterial cellulose along with a reduction in the level of metal impurities. The reduction in the degree of polymerization and metal impurities promotes the dissolution of bacterial cellulose in NMMO, making the resulting solution suitable for the commercial production of lyocell fibers.

[0071] Also, the disclosed process requires a shorter premixing time compared to the processes disclosed in the prior art.

[0072] The disclosed process enables the preparation of a cellulose solution containing a high percentage of bacterial cellulose, from about 9 to 15%, having a viscosity in the spinnable range measured using a typical rheometer. The disclosed process minimizes the degradation of cellulose at high temperatures. Also, ultrafine denier lyocell fibers up to 0.6 denier could be obtained.

Claims

1. A highly tough regenerated cellulose-based fiber prepared from a cellulose-based raw material, wherein the cellulose-based raw material is - Pretreated bacterial cellulose having a degree of polymerization in the range of 450 to 2000, the pretreated bacterial cellulose containing bacterial cellulose treated with a pretreatment agent selected from the group consisting of oxidizing agents, acids, alkalis, and mixtures thereof, 5 to 100% by weight; and - 0 to 95% by weight of additional cellulose-based materials selected from the group consisting of dissolving pulp, bamboo pulp, hemp, recycled cotton pulp, recycled cellulose-based materials, and mixtures thereof; comprising The fiber is a highly tough regenerated cellulose-based fiber having a toughness of at least 4.5 grams / denier and an elongation of at least 10% as measured according to ASTM D 3822.

2. The fiber according to claim 1, wherein the degree of polymerization of the pretreated bacterial cellulose is in the range of 500 to 1500.

3. The fiber according to claim 1, wherein the highly tough regenerated cellulose-based fiber has an average linear density in the range of 0.6 to 2.0 denier.

4. A method for preparing a highly tough regenerated cellulose-based fiber having a toughness of at least 4.5 grams / denier and an elongation of at least 10% as measured according to ASTM D 3822, comprising (a) subjecting bacterial cellulose to a pretreatment step to obtain pretreated bacterial cellulose having a degree of polymerization in the range of 450 to 2000, the pretreatment step comprising treating the bacterial cellulose with a pretreatment agent selected from the group consisting of oxidizing agents, acids, alkalis, and mixtures thereof; (b) preparing a preliminary mixture by mixing a cellulose-based raw material comprising 5 to 100% by weight of the pretreated bacterial cellulose and 0 to 95% by weight of additional cellulose-based materials selected from the group consisting of dissolving pulp, recycled cotton pulp, recycled cellulose-based materials, and mixtures thereof, based on the total weight of the cellulose-based raw material, with a solvent, and subsequently dissolving the cellulose in a dissolving apparatus to obtain a dope solution; (c) extruding the dope solution through a fine orifice, followed by air-gap spinning and regeneration in a spinning bath to obtain the regenerated cellulose-based fiber. A method comprising

5. The method according to claim 4, wherein the degree of polymerization of the pretreated bacterial cellulose obtained in step (a) is in the range of 500 to 1500.

6. The method according to claim 4, wherein the pretreatment step includes an additional treatment for reducing the amount of metal impurities in the bacterial cellulose, and the treatment includes treating the bacterial cellulose with a chelating agent.

7. The method according to claim 4, wherein the pretreatment agent is an oxidizing agent selected from the group consisting of sodium hypochlorite, potassium hypochlorite, hydrogen peroxide, ozone, and combinations thereof.

8. The pretreatment agent is an acid selected from the group consisting of sulfuric acid (H 2 SO 4 ), hydrochloric acid (HCl), nitric acid (HNO 3 ), and phosphoric acid (H 3 PO 4 ), oxalic acid, formic acid, acetic acid, and combinations thereof. The method according to claim 4.

9. The method according to claim 4, wherein the pretreatment agent is an alkali selected from the group consisting of sodium hydroxide, potassium hydroxide, ammonium hydroxide, and combinations thereof.

10. The method according to claim 6, wherein the chelating agent is selected from the group consisting of ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), and diethylenetriaminepentakis (DTMPA).

11. The method according to claim 4 or 6, wherein the pretreatment step is carried out at a temperature in the range of 30 to 100 °C for a time in the range of 1 to 20 hours.

12. The method according to claim 4 or 6, wherein after the pretreatment step, the pretreated bacterial cellulose is subjected to a washing step.

13. The method according to claim 4, 6 or 12, wherein the pretreated bacterial cellulose is subjected to a size reduction step.

14. The method according to claim 4, wherein the premixing is prepared by mixing the cellulosic raw material and the solvent in step (b) with or without applying shear at a temperature between 25 °C and 90 °C for a period between 0 and 6 hours.

15. The method according to claim 4 or 14, wherein the solvent is selected from the group consisting of N-methylmorpholine-N-oxide (NMMO), ionic liquids, dimethyl sulfoxide / calcium chloride, and dimethylacetamide / lithium chloride.

16. The preliminary mixture further contains an additive selected from the group consisting of TiO 2 , a surfactant, a pigment, and carbon black. The method according to claim 4 or 14.

Images