Non-fibrillated lyocell fibers, methods of making and using the same

Abstract

The application discloses a non-fibrillated Lyocell fiber and a preparation method and application thereof, and belongs to the technical field of functional fiber preparation. The application realizes that the prepared non-fibrillated Lyocell fiber has good anti-fibrillation performance and good mechanical performance by the following steps: high-voltage rotating electrostatic field is applied in a dry air section spinning process, the application direction of the high-voltage rotating electrostatic field is perpendicular to the spinning direction, the electric field strength is 1-10 kV / cm, and the electric field rotating speed is 70-90 r / min; high-voltage rotating electrostatic field is applied in a first coagulation bath process, the application direction of the high-voltage rotating electrostatic field is perpendicular to the spinning direction, the electric field strength is 3-15 kV / cm, and the electric field rotating speed is 90-120 r / min. In addition, the operation is simple, and the application is more suitable for industrial use.

Description

Technical Field

[0001] This invention relates to a non-fibrillated Lyocell fiber, its preparation method, and its application, belonging to the field of functional fiber preparation technology. Background Technology

[0002] Lyocell fiber is a novel regenerated cellulose fiber produced using N-methylmorpholine-N-oxide (NMMO) as a solvent via dry-jet wet spinning technology. Compared to other regenerated cellulose fibers, it boasts environmentally friendly and pollution-free production, superior mechanical properties, and excellent wearability, earning it the reputation as one of the most promising "green fibers" of the 21st century. However, under wet conditions and repeated mechanical friction, Lyocell fibers exhibit a large number of fine fibers that peel off from their surface, a process known as fibrillation. This fibrillation makes Lyocell fabrics more prone to pilling, thus affecting their comfort and aesthetics. Therefore, developing Lyocell fibers with fibrillation capabilities has become a key direction for the high-quality development of Lyocell fibers.

[0003] As is well known, the fibrillation mechanism of Lyocell fibers is mainly attributed to the weak bonding force between their fibrils. This is due to the unique dissolution and spinning process of Lyocell fibers, which results in a high degree of orientation and crystallinity in their structure. While this structure gives them high strength in the axial direction, their radial strength is relatively weak, leading to weak bonding force between their fibrils.

[0004] Currently, the main focus of domestic and international research on the preparation methods of antigen-fibrillated Lyocell fibers is on improving the radial strength of the fibers, i.e., increasing the bonding force between the fibrils. Generally, the preparation methods can be divided into two types: chemical crosslinking modification and physical process optimization.

[0005] Among them, chemical crosslinking modification refers to loading crosslinking agents into the interior or surface of Lyocell fibers through blending spinning or finishing, thereby enhancing the lateral bonding force between fibrils. For example, CN 114232120A discloses a method for preparing antigen-fibrillated cellulose fibers, which uses tannic acid as a crosslinking agent and adds it to the cellulose spinning solution in a certain ratio, and prepares antigen-fibrillated cellulose fibers by wet spinning or dry-spray wet spinning technology. The shortcomings of this method are: (1) Tannic acid is an organic acid, while NMMO solution is weakly alkaline. When tannic acid is added to the cellulose spinning solution, it will cause the pH value of the spinning solution to decrease, which will lead to the decomposition of some NMMO and affect the spinning quality. (2) As we all know, Lyocell fiber is called green fiber, mainly because the recovery rate of its spinning solvent (NMMO) is greater than 98%. The introduction of tannic acid will inevitably make the spinning and solvent recovery process more complicated, thereby affecting the quality and cost of Lyocell fiber. Other methods improve antigen-fibrillated Lyocell fibers by increasing the amount and dispersion uniformity of graphene in the cellulose system, such as CN 116219565 A. This method requires the use of monolayer graphene oxide and control of its lateral dimensions and the number and type of polar groups, which has high process requirements and is complex to operate.

[0006] Physical-based process optimization refers to improving the antigen-fibrillating properties of Lyocell fibers by adjusting parameters such as draw ratio and spinning speed during the spinning process, thereby reducing the crystallinity and orientation of the fibers. While these physical optimizations can enhance the antigen-fibrillating properties of Lyocell fibers, they often also lead to a decrease in the mechanical properties of the fibers.

[0007] Therefore, it is urgent to propose a method for preparing Lyocells with non-fibrillation functions without damaging the properties of Lyocell fibrils.

[0008] An electric field is a common method used to assist spinning. For example, electrospinning (Yin Jing, Gao Lulu, Xu Lan. Research progress on electrospinning device and its mechanical mechanism 1). Mechanics and Practice, 2021, 43(4):489-505 DOI:10.6052 / 1000-0879-20-444) uses the electric field force generated by a high voltage electric field to excite the Taylor cone of the nozzle to form a jet flow and finally obtain nanofibers; there are also some methods that use an additional electric field or magnetic field to control the trajectory of the jet flow to obtain ordered nanofibers, etc. However, the role of the electric field in these methods is to focus on the jet flow area and assist the fiber stretching and uniform spinning along the spinning direction. Summary of the Invention

[0009] [Technical Issues]

[0010] Conventional preparation of Lyocells with non-fibrillation function can damage their performance and is complex, making it unsuitable for large-scale industrial use.

[0011] [Technical Solution]

[0012] To address the aforementioned issues, this invention employs a high-voltage electrostatic field-assisted preparation of non-fibrillated Lyocell fibers. This results in non-fibrillated Lyocell fibers exhibiting excellent antigen fibrillation properties and good mechanical properties. Furthermore, the process is simple and more suitable for industrial application.

[0013] This invention is based on the fact that the electrostatic force generated by the high-voltage rotating electrostatic field is perpendicular to the stretching direction of Lyocell fibers. This electrostatic force creates a weak rotational stretching force along the warp direction of the nascent Lyocell fibers, thereby enhancing the bonding force between the Lyocell fiber fibrils. Subsequently, after the first stage coagulation bath, the high-voltage rotating electrostatic field is further assisted to impart a weak rotational stretching force along the warp direction to the fibers inside the fibers, thus endowing Lyocell fibers with the ability to undergo fibrillation.

[0014] The first objective of this invention is to provide a method for preparing non-fibrillated Lyocell fibers, comprising the following steps:

[0015] The cellulose spinning solution is spun through a dry-jet air section, followed by a first coagulation bath, a second coagulation bath, washing, drying, and winding to obtain non-fibrillated Lyocell fibers.

[0016] In the dry-jet air section spinning process, a high-voltage rotating electrostatic field is applied. The direction of application of the high-voltage rotating electrostatic field is perpendicular to the spinning direction. The electric field strength is 1 to 10 kV / cm and the electric field rotation speed is 70 to 90 rpm.

[0017] A high-voltage rotating electrostatic field is applied during the first coagulation bath process. The direction of the high-voltage rotating electrostatic field is perpendicular to the spinning direction, the electric field strength is 3-15 kV / cm, and the electric field rotation speed is 90-120 rpm.

[0018] In one embodiment of the present invention, the method for preparing the cellulose spinning solution is as follows:

[0019] The dried cellulose pulp was mixed with an NMMO aqueous solution with a mass fraction of 70-85%. Under mechanical stirring, the temperature was raised to 90-105℃, and then the solution was distilled under reduced pressure to -0.09--0.12 MPa. After the cellulose was completely dissolved and formed a viscous liquid similar to amber, a cellulose spinning solution with a concentration of 8-12 wt% was obtained.

[0020] The mass ratio of cellulose pulp to NMMO aqueous solution is 1:9.

[0021] Cellulose pulp refers to various commercially available regenerated cellulose fiber pulps such as wood pulp, cotton pulp, bamboo pulp, and hemp pulp. Specification requirements: meet the first-class or higher standards as specified in industry standards (FZ / T 51001-2002, FZ / T 51002-2023, FZ / T 51009-2023).

[0022] In one embodiment of the present invention, the length of the dry-jet air section spinning is 2-30 mm, preferably 10-20 mm; the side air blowing rate is 1-20 m / s, the spinning speed is 80-200 m / min; and the air gap is 8-12 mm.

[0023] In one embodiment of the present invention, the high-voltage rotating electrostatic field applied during the dry-jet air section spinning process and the high-voltage rotating electrostatic field applied during the first coagulation bath process have the same direction of rotation.

[0024] In one embodiment of the present invention, the first coagulation bath is an NMMO aqueous solution with a mass fraction of 5-40%, the temperature of the coagulation bath is 20-60°C, the length of the coagulation bath is 1.5-2.5m, and the stretching ratio is 0.5-5.

[0025] In one embodiment of the present invention, the second coagulation bath is pure water, and the coagulation bath temperature is 30-50°C, the coagulation bath length is 1.5-3.5m, and the draw ratio is 0.1-2.5.

[0026] In one embodiment of the present invention, the number of times the water is washed is 1 to 3.

[0027] In one embodiment of the present invention, the drying is carried out in a tunnel dryer, with a drying temperature of 45-105°C and a drying time of 5-60 minutes.

[0028] The second objective of this invention is to obtain non-fibrillated Lyocell fibers prepared by the method described herein.

[0029] The third objective of this invention is the application of the non-fibrillated Lyocell fiber described herein in the preparation of functional yarns and functional materials.

[0030] In one embodiment of the present invention, the functional materials include medical and hygiene products, clothing products, furniture products, etc.

[0031] The fourth objective of this invention is to provide a method for improving the fibrillation properties of Lyocell fibers based on an electrostatic field, comprising the following steps:

[0032] The cellulose spinning solution is spun through a dry-jet air section, followed by a first coagulation bath, a second coagulation bath, washing, drying, and winding to obtain non-fibrillated Lyocell fibers.

[0033] In the dry-jet air section spinning process, a high-voltage rotating electrostatic field is applied. The direction of application of the high-voltage rotating electrostatic field is perpendicular to the spinning direction, the electric field strength is 1 to 10 kV / cm, and the electric field rotation speed is 70 to 90 rpm.

[0034] A high-voltage rotating electrostatic field is applied during the first coagulation bath process. The direction of the high-voltage rotating electrostatic field is perpendicular to the spinning direction, the electric field strength is 3-15 kV / cm, and the electric field rotation speed is 90-120 rpm.

[0035] [Beneficial Effects]

[0036] (1) In this invention, a high-voltage rotating electrostatic field is used as an auxiliary method for preparing non-fibrillated Lyocell fibers. The principle is mainly based on the fact that, within the high-voltage rotating electrostatic field, the electrostatic force generated is perpendicular to the stretching direction of the Lyocell fibers. Therefore, this electrostatic force will form a weak rotational stretching force along the warp direction of the Lyocell fibers, thereby enhancing the bonding force between the Lyocell fiber fibrils. Subsequently, after the first stage coagulation bath, the high-voltage rotating electrostatic field is continued to further impart a weak rotational stretching force along the warp direction to the fibers inside the fibers, thereby endowing the Lyocell fibers with the ability to undergo fibrillation. Moreover, the introduction of the high-voltage rotating electrostatic field will not have a negative impact on the dissolution, spinning, and solvent recovery of Lyocell fibers, and is a green, environmentally friendly, and sustainable physical modification method.

[0037] (2) Compared with Lyocell fibers prepared by conventional Lyocell fiber spinning technology, non-fibrillated Lyocell fibers prepared by the method of the present invention can improve their fibrillation ability without damaging the fiber strength.

[0038] (3) Compared with non-fibrillated Lyocell fibers prepared based on chemical cross-linking modification technology, the method of the present invention can prepare Lyocell fibers with higher antifibrillation performance, and the wet abrasion cycles can be greater than 350 times.

[0039] (4) The method of the present invention has no adverse effects on the preparation of spinning mother liquor, the optimization of spinning process and the recovery of solvent, and the process flow is simpler, safer, more efficient and greener. Attached Figure Description

[0040] Figure 1 The flowchart shows the method for preparing non-fibrillated Lyocell fibers in Example 1.

[0041] Figure 2 SEM image of the non-fibrillated Lyocell fibers prepared in Example 1.

[0042] Figure 3 Microscopic image of the non-fibrillated Lyocell fibers prepared in Example 1 after ultrasonic vibration for 20 min.

[0043] Figure 4 SEM image of conventional Lyocell fibers prepared for Comparative Example 1.

[0044] Figure 5 Microscopic image of conventional Lyocell fibers prepared for Comparative Example 1 after ultrasonic vibration for 20 min. Detailed Implementation

[0045] The preferred embodiments of the present invention are described below. It should be understood that the embodiments are for better explanation of the present invention and are not intended to limit the present invention.

[0046] Test method:

[0047] 1. Mechanical property testing:

[0048] Test and evaluate according to the methods specified in the industry standard (FZ / T 52019-2018).

[0049] 2. Wet friction test:

[0050] Test and evaluate according to the methods specified in the industry standard (FZ / T 52019-2018).

[0051] Raw materials used in the examples:

[0052] Cellulose pulp: Commercially available regenerated cellulose fiber cotton pulp: Pulp that meets or exceeds the first-class standard specified in the industry standard (FZ / T 51001-2002).

[0053] Pure water: Deionized water.

[0054] Example 1

[0055] A method for preparing non-fibrillated Lyocell fibers, such as Figure 1 It includes the following steps:

[0056] (1) Add the dried dissolved wood pulp into a stainless steel stirring tank, add an 80wt% NMMO aqueous solution at a mass ratio of 1:9, then heat to 90℃, and then continue stirring under a negative pressure of -0.1MPa. After the cellulose is completely dissolved and forms a viscous liquid similar to amber, a 10% cellulose spinning solution is obtained.

[0057] (2) The cellulose spinning solution is spun through a dry-jet air section, a first coagulation bath, a second coagulation bath, washed with water, dried, and wound to obtain non-fibrillated Lyocell fibers.

[0058] In the dry-jet air section spinning process, a high-voltage rotating electrostatic field is applied. The direction of the high-voltage rotating electrostatic field is perpendicular to the spinning direction, the electric field strength is 5kV / cm, and the electric field rotation speed is 80 rpm. The spinning length is 20mm, the side air blowing rate is 20m / s, the spinning speed is 120m / min, and the air gap is 10mm.

[0059] The first coagulation bath is a 40% NMMO aqueous solution with a temperature of 40℃, a length of 2m, and a draw ratio of 2.2. Simultaneously, a high-voltage rotating electrostatic field is applied during the first coagulation bath process. The direction of the high-voltage rotating electrostatic field is perpendicular to the spinning direction, the electric field strength is 8kV / cm, and the electric field rotation speed is 100 rpm.

[0060] The high-voltage rotating electrostatic field applied during the dry-jet air section spinning process and the high-voltage rotating electrostatic field applied during the first coagulation bath process have the same direction of rotation.

[0061] The second coagulation bath is made of pure water, the coagulation bath temperature is 40℃, the coagulation bath length is 3m, and the stretching ratio is 1.5.

[0062] The fibers were washed three times and dried at 95°C for 40 minutes in a tunnel dryer to obtain non-fibrillated Lyocell fibers (1.3 dtex fineness).

[0063] Example 2

[0064] In Example 1, the electric field strength of the high-voltage rotating electrostatic field during the dry-jet air section spinning process was adjusted to 4 kV / cm, and the electric field strength of the high-voltage rotating electrostatic field during the first coagulation bath process was adjusted to 5 kV / cm; all other aspects remained the same as in Example 1, resulting in non-fibrillated Lyocell fibers.

[0065] Example 3

[0066] In Example 1, the electric field strength of the high-voltage rotating electrostatic field during the dry-jet air section spinning process was adjusted to 7 kV / cm, and the electric field strength of the high-voltage rotating electrostatic field during the first coagulation bath process was adjusted to 4 kV / cm; all other aspects remained the same as in Example 1, resulting in non-fibrillated Lyocell fibers.

[0067] Example 4

[0068] In Example 1, the electric field strength of the high-voltage rotating electrostatic field during the dry-jet air section spinning process was adjusted to 6 kV / cm, and the electric field strength of the high-voltage rotating electrostatic field during the first coagulation bath process was adjusted to 10 kV / cm; all other aspects remained the same as in Example 1, resulting in non-fibrillated Lyocell fibers.

[0069] Example 5

[0070] In Example 1, the electric field strength of the high-voltage rotating electrostatic field during the dry-jet air section spinning process was adjusted to 8 kV / cm, and the electric field strength of the high-voltage rotating electrostatic field during the first coagulation bath process was adjusted to 7 kV / cm; all other aspects remained the same as in Example 1, resulting in non-fibrillated Lyocell fibers.

[0071] Comparative Example 1

[0072] The dry-jet air-spinning process and the application of the high-voltage rotating electrostatic field in the first coagulation bath in Example 1 are omitted, while other aspects remain the same as in Example 1, resulting in non-fibrillated Lyocell fibers.

[0073] Comparative Example 2

[0074] The application of the high-voltage rotating electrostatic field in the dry-jet air section spinning process in Example 1 is omitted, while everything else remains the same as in Example 1, resulting in non-fibrillated Lyocell fibers.

[0075] Comparative Example 3

[0076] The application of the high-pressure rotating electrostatic field in the first coagulation bath in Example 1 is omitted, while everything else remains the same as in Example 1, resulting in non-fibrillated Lyocell fibers.

[0077] Comparative Example 4

[0078] In Example 1, the rotation speed of the high-voltage rotating electrostatic field in the dry-jet air section spinning and the first coagulation bath was adjusted to 0, while other aspects remained the same as in Example 1, resulting in non-fibrillated Lyocell fibers.

[0079] Comparative Example 5

[0080] The second coagulation bath in Example 1 was omitted, while everything else remained the same as in Example 1, resulting in non-fibrillated Lyocell fibers.

[0081] The obtained non-fibrillated Lyocell fibers were subjected to performance testing, and the test results are as follows:

[0082] Table 1 Key spinning parameters and Lyocell fiber properties for each example and comparative example.

[0083]

[0084] As can be seen from Table 1:

[0085] Comparing the test results of Example 1 with those of Comparative Examples 1-3, and evaluating the antigen-fibrillating performance of Lyocell fibers by the number of wet friction cycles, the Lyocell fibers prepared in Example 1 achieved a wet friction cycle of 382, ​​which is much higher than that of the Lyocell fibers prepared in Comparative Examples 1-3, and met the superior grade requirements specified in the industry standard FZ / T 52019-2018 "Lyocell Short Fiber". This indicates that applying a high-voltage electrostatic field in the air section and the first coagulation bath helps to improve the antigen-fibrillating performance of Lyocell fibers.

[0086] Comparing the mechanical properties of Lyocell fibers prepared in Example 1 with those in Comparative Examples 1-3, it can be seen that the mechanical properties of the prepared Lyocell fibers are basically the same, and all meet the requirements of the superior grade of FZ / T 52019-2018 "Lyocell Short Fiber". This shows that applying a high voltage electrostatic field in the air section and the first coagulation bath will not affect the mechanical properties of Lyocell fibers.

[0087] The Lyocell fibers prepared in Example 1 and Comparative Example 4 have basically the same mechanical properties, but there is a large difference in the number of wet friction cycles. This indicates that the rotation speed of the high-voltage rotating electrostatic field has a significant impact on improving the antigen fibrillation performance of Lyocell fibers, but has little impact on their mechanical properties.

[0088] The Lyocell fibers prepared in Comparative Example 5 had poor mechanical and wet friction properties, indicating that the second coagulation bath had a good effect on further solidifying the Lyocell fibers, thus helping to improve their mechanical and wet friction properties.

[0089] Figures 2-5 SEM images of Lyocell fibers prepared for Example 1 and Comparative Example 1 after ultrasonic vibration for 20 min. Figures 2-5 It can be seen that the non-fibrillated Lyocell fiber prepared in Example 1 had a very smooth surface after ultrasonic vibration for 20 minutes, and no fibrillation occurred; while the conventional Lyocell fiber prepared in Comparative Example 1 showed fibrillation on its surface after ultrasonic vibration for 20 minutes.

[0090] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make various modifications and alterations without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the claims.

Claims

1. A method for preparing non-fibrillated Lyocell fibers, characterized in that, Includes the following steps: The cellulose spinning solution is spun through a dry-jet air section, followed by a first coagulation bath, a second coagulation bath, washing, drying, and winding to obtain non-fibrillated Lyocell fibers. In the dry-jet air section spinning process, a high-voltage rotating electrostatic field is applied. The direction of application of the high-voltage rotating electrostatic field is perpendicular to the spinning direction, the electric field strength is 1~10kV / cm, and the electric field rotation speed is 70~90 revolutions / min. A high-voltage rotating electrostatic field is applied during the first coagulation bath process. The direction of the high-voltage rotating electrostatic field is perpendicular to the spinning direction, the electric field strength is 3~15kV / cm, and the electric field rotation speed is 90~120 rpm.

2. The method according to claim 1, characterized in that, The length of the dry-jet air section spinning is 2~30mm; the side-blowing speed is 1~20m / s, the spinning speed is 80~200m / min; and the air gap is 8~12mm.

3. The method according to claim 1, characterized in that, The length of the dry-jet air section spinning is 10~20mm.

4. The method according to claim 1, characterized in that, The high-voltage rotating electrostatic field applied during the dry-jet air section spinning process and the high-voltage rotating electrostatic field applied during the first coagulation bath process have the same direction of rotation.

5. The method according to claim 1, characterized in that, The first coagulation bath is a 5%~40% NMMO aqueous solution. The temperature of the coagulation bath is 20~60℃, the length of the coagulation bath is 1.5~2.5m, and the stretching ratio is 0.5~5.

6. The method according to claim 1, characterized in that, The second coagulation bath is made of pure water, with a temperature of 30-50℃, a length of 1.5-3.5m, and a draw ratio of 0.1-2.

5.

7. The method according to claim 1, characterized in that, Wash 1 to 3 times.

8. The method according to claim 1, characterized in that, The drying process is carried out in a tunnel dryer at a temperature of 45-105℃ for 5-60 minutes.

9. The non-fibrillated Lyocell fiber prepared by the method according to any one of claims 1 to 8.

10. The application of the non-fibrillated Lyocell fiber according to claim 9 in the preparation of functional yarns or functional materials.

11. A method for improving the fibrillation properties of Lyocell fibers based on an electrostatic field, characterized in that, Includes the following steps: The cellulose spinning solution is spun through a dry-jet air section, followed by a first coagulation bath, a second coagulation bath, washing, drying, and winding to obtain non-fibrillated Lyocell fibers. In the dry-jet air section spinning process, a high-voltage rotating electrostatic field is applied. The direction of application of the high-voltage rotating electrostatic field is perpendicular to the spinning direction, the electric field strength is 1~10kV / cm, and the electric field rotation speed is 70~90 revolutions / min. A high-voltage rotating electrostatic field is applied during the first coagulation bath process. The direction of the high-voltage rotating electrostatic field is perpendicular to the spinning direction, the electric field strength is 3~15kV / cm, and the electric field rotation speed is 90~120 rpm.

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