Preparation method for lyocell bamboo fiber, and lyocell bamboo fiber

Abstract

Disclosed in the present invention are a preparation method for a lyocell bamboo fiber, and a lyocell bamboo fiber. The preparation method comprises the preparation steps of: (1) directly mixing a pulp containing at least one type of bamboo pulp with an NMMO aqueous solution containing a modifier so as to obtain a pulp paste, wherein the modifier at least contains two active groups; and (2) dehydrating and dissolving the pulp paste to obtain a spinning solution, wherein the relaxation time spectrum of the spinning solution has a bimodal distribution, and spinning the spinning solution by means of a spinning device, followed by washing with water, oiling and drying, so as to obtain a lyocell bamboo fiber. The pulp of the present invention is directly mixed with the NMMO aqueous solution containing the modifier so as to form the pulp paste, without subjecting the pulp paste to other treatments, thereby fully retaining antimicrobial components in the pulp; the pulp paste can be dehydrated and dissolved at a low temperature to obtain the spinning solution, thus avoiding the degradation of the spinning solution caused by an overly high temperature; moreover, the relaxation time spectrum of the spinning solution has a bimodal distribution, that is, different stress distributions are present within the fiber during cellulose molding, thereby being conducive to the retention of active antimicrobial small molecules within the bamboo pulp.

Description

Preparation method of lyocell bamboo fiber and lyocell bamboo fiber Technical Field

[0001] The invention belongs to the field of fiber production, and in particular relates to a preparation method of lyocell bamboo fiber and the lyocell bamboo fiber. Background Art

[0002] Cellulose is the primary component of plant cell walls and can be derived from trees, cotton, hemp, and other plants. It is widely distributed in nature and is inexhaustible. Generally speaking, most organic substances containing hydroxyl groups, such as alcohol and glucose, are readily soluble in water, but cellulose is insoluble in water and most organic solvents. This is because cellulose generally has a large molecular weight, ranging from a few hundred to tens of thousands, and readily forms intramolecular and intermolecular hydrogen bonds. These forces can partially override the hydroxyl group's affinity for water, rendering cellulose insoluble in water or poorly soluble in common organic solvents.

[0003] Due to the dwindling availability of petroleum resources and the growing awareness of nature, health, and environmental protection, people are gradually turning their attention to regenerated cellulose fibers. Lyocell, commonly known as "Tencel," is made from natural plant fibers. It debuted in the mid-1990s and is hailed as the most valuable product in the history of man-made fibers over the past half century, combining the excellent properties of both natural and synthetic fibers.

[0004] Lyocell fiber is a green fiber. Its raw material is cellulose, which is inexhaustible in nature. There is no chemical reaction in the production process. The cellulose material prepared by the NMMO solvent method avoids the shortcomings of natural cellulose materials such as single product, single performance, and great environmental impact. At the same time, it can reduce the large amount of acidic and alkaline substances required in the production process of traditional cellulose materials, and get rid of the pollution problems caused by the production process of traditional cellulose materials. It can also expand the application field of cellulose materials, and has the two major advantages of "sustainable development" and "environmental protection". It is a truly "green material" with very broad application prospects.

[0005] However, in the current lyocell fiber production process, the use of enzyme treatment or acid-base treatment of pulp will destroy the activity of chemical substances inside the pulp, resulting in loss of fiber functionality; and the active molecules in the pulp will dissolve in the NMMO solution and precipitate during the spinning process, further causing the fiber functionality to deteriorate.

[0006] In view of this, the present invention is proposed. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a preparation method of lyocell bamboo fiber and lyocell bamboo fiber, so as to achieve the purpose of enhancing the binding force between cellulose and active substances in pulp and improving the antibacterial properties of the fiber.

[0008] In order to solve the above technical problems, the basic concept of the technical solution adopted by the present invention is:

[0009] A method for preparing lyocell bamboo fiber, comprising the following steps:

[0010] (1) mixing pulp comprising at least one bamboo pulp and an NMMO aqueous solution containing a modifier to obtain pulp porridge, wherein the modifier contains at least two active groups;

[0011] (2) The porridge is dehydrated and dissolved to obtain a spinning solution, and the relaxation time spectrum of the spinning solution has a bimodal distribution. The spinning solution is spun by a spinning device, washed with water, oiled, and dried to obtain lyocell bamboo fiber.

[0012] The NMMO solvent method is a novel process for producing cellulose materials without chemical reactions. This process primarily involves dissolving cellulose pulp in an NMMO aqueous solution to produce a viscous spinning solution, which is then produced using a dry-jet wet spinning process. Simultaneously, the NMMO precipitated in the coagulation bath is recovered and reused, with a recovery rate of up to 99.8%. The entire production system is a closed-loop, waste-free, and environmentally friendly process. The spinning solution, prepared by dissolving cellulose in the NMMO aqueous solution, is extruded from a spinneret and passed through an air bath to rapidly cool and initially shape the filaments. The filaments then enter a coagulation bath, where they diffuse bidirectionally to form nascent fibers.

[0013] However, there are still many problems in the preparation of lyocell bamboo fiber using the dry-jet wet spinning process. First, the fiber forming process is too fast during the dry-jet wet spinning process, which will cause the antibacterial small molecules (such as bamboo quinone) to precipitate quickly, making it difficult for small molecules to remain in the fiber; secondly, the internal solubility parameter of lyocell fiber is usually 40kJ / m 3 , while the solubility parameters of small molecules such as bamboo quinone are between 15-25kJ / m 3The solubility parameters of the two are quite different, which will make it difficult for the small molecular substances in the prepared fiber to be retained for a long time; in addition, in the process of dry-jet wet spinning, the fiber crystal units are highly oriented in the air gap stage to form a crystalline structure, and the time for the fiber to form this highly oriented structure is usually 0.01-0.03s; under the spinning process conditions, after the spinning solution forms the fiber, there is still stress inside and it continues to decrease with time, and stress relaxation occurs, and its stress relaxation time is usually 0.04-0.1s; while the active substances in the fiber (such as bamboo quinone) do not undergo stress relaxation. The difference in stress relaxation time of different substances in the fiber will cause the active substances to migrate out of the fiber, resulting in a decrease in the content of small molecular substances in the fiber; on the whole, when lyocell bamboo fiber is prepared by dry-jet wet spinning, the content of small molecules in lyocell bamboo fiber is relatively low, and the antibacterial properties of the fiber are reduced.

[0014] In addition, some methods for preparing lyocell bamboo fiber require the use of enzymes or acids and alkalis to treat the pulp, which will also cause the small molecules inside the pulp to be destroyed; or, some preparation methods require the use of higher temperatures to prepare the spinning solution containing bamboo pulp. Excessively high temperatures will destroy the small molecule structure, causing the small molecules to fundamentally lose their functionality.

[0015] In order to improve the retention rate of active small molecules inside lyocell fiber, the present invention adopts a dry-jet wet spinning method to prepare lyocell bamboo fiber, wherein the pulp is directly mixed with an NMMO aqueous solution containing a modifier to form a pulp porridge, and the pulp is not subjected to other treatments, thereby fully retaining the antibacterial components in the pulp; the pulp porridge can be dehydrated and dissolved at low temperature to obtain a spinning solution, and this process avoids the degradation of the spinning solution due to excessively high temperature, and the relaxation time spectrum of the spinning solution has a bimodal distribution, that is, there are stresses with different distributions inside the fiber during the cellulose forming process, which is conducive to retaining the active antibacterial small molecules in the bamboo pulp.

[0016] In the NMMO system, cellulose is in an ionized state. The modifier of the present invention contains at least two active groups, one of which can chemically react with active small molecules (such as bambooquinone) in the pulp, and the other group can react with cellulose, thereby reducing the solubility parameter difference between the active small molecules and cellulose, and further improving the retention rate of active substances (such as antibacterial molecules) in the spinning solution within the lyocell fiber.

[0017] Furthermore, in step (1), the active groups in the modifier include one or more of epoxy groups, alkenyl groups, silicon-oxygen bonds, and hydroxyl groups;

[0018] Preferably, the modifier is selected from one or more of borates, silane coupling agents, and cellulose crosslinking agents;

[0019] Preferably, the borate includes sodium borate, the silane coupling agent includes γ-methacryloxypropyltrimethoxysilane, and the cellulose crosslinking agent includes 1,3,5-triacryloyl-hexahydro-1,3,5-triazine.

[0020] Furthermore, in the relaxation time spectrum of the spinning solution in step (2), the relaxation times are 0.001-0.1s and 0.1-0.5s respectively.

[0021] Furthermore, in the step (1), the mass concentration of cellulose in the pulp is 8-16%, preferably 10-13%, and the mass ratio of the modifier to the cellulose in the pulp is 0.005-0.1%, preferably 0.01-0.05%.

[0022] Furthermore, a bactericide may be added to the NMMO aqueous solution containing the modifier, and the bactericide is selected from one or more of zinc oxide, copper oxide, chitin, organosilicon quaternary ammonium salt, and polyhexamethylene biguanide; the mass ratio of the bactericide to the mass ratio of cellulose in the pulp is 0.05-2%.

[0023] Furthermore, in step (1), the pulp comprises a bamboo pulp and a wood pulp, wherein the bamboo pulp and the wood pulp have different degrees of polymerization; or, the pulp comprises two bamboo pulps with different degrees of polymerization;

[0024] Preferably, the mass fraction of bamboo pulp in the pulp is 10-100%, preferably 30-100%;

[0025] Preferably, the degree of polymerization of the bamboo pulp is 200-1000.

[0026] Furthermore, in the step (1), the mass fraction of NMMO in the NMMO aqueous solution is 50-85%; preferably, 68-78%.

[0027] Furthermore, in the spinning process of step (2), an NMMO aqueous solution with a mass fraction of 20-40% is used as a coagulation bath;

[0028] Preferably, the mass fraction of NMMO in the NMMO aqueous solution is 24-30%.

[0029] The present invention uses an aqueous solution of NMMO as a coagulation bath, with a mass fraction of NMMO of 20-50%. If the concentration is too low, the NMMO will diffuse violently inside the fiber during the spinning process, which is not conducive to the retention of small molecular substances inside the fiber. If the concentration is too high, the NMMO diffusion process will be too slow, making it difficult to spin efficiently.

[0030] The spinning gas temperature is 2-18℃; too low a temperature will cause the fiber temperature to drop rapidly, the relaxation time to be prolonged, and the rapid increase of stress in the fiber will make it difficult to retain small molecular substances; too high a temperature will make it difficult to spin efficiently.

[0031] The time for passing through the air gap during spinning is 0.01-0.08s; specifically, the time for passing through the air gap during spinning is 0.01-0.08s by controlling the air gap length and the yarn output speed; under the conditions of specified production line capacity and fiber specifications, the yarn output speed is adjusted by adjusting the spinneret aperture.

[0032] Furthermore, polyethylene glycol or ammonium chloride may be added to the coagulation bath in step (2); preferably, the mass fraction of polyethylene glycol or ammonium chloride in the coagulation bath is 0-0.1%.

[0033] Adding polyethylene glycol or ammonium chloride to the coagulation bath can effectively improve the retention rate of antibacterial small molecules inside the fiber.

[0034] Furthermore, in the step (2), the porridge is dehydrated by evaporation, and the gas partial pressure of the water vapor generated during the evaporation process is 2-7.5 kPa, preferably 4-6 kPa.

[0035] In the present invention, the temperature of the spinning solution should be controlled below 110°C to ensure sufficient production safety. In order to avoid high-temperature decomposition of active molecules inside the bamboo pulp, the temperature of the spinning solution needs to be further lowered. However, this temperature control is difficult in the actual production process. The present invention achieves the purpose of lowering the spinning solution temperature by controlling the pressure of water vapor.

[0036] The present invention also provides a lyocell bamboo fiber, which is prepared by any preparation method described in the above technical solutions.

[0037] After adopting the above technical solution, the present invention has the following beneficial effects compared with the prior art.

[0038] In order to improve the retention rate of active small molecules in lyocell fibers, the present invention adopts a dry-jet wet spinning method to prepare lyocell bamboo fibers, wherein pulp is directly mixed with an NMMO aqueous solution containing a modifier to form a pulp porridge, and the pulp is not subjected to other treatments, thereby fully retaining the antibacterial components in the pulp; the pulp porridge can be dehydrated and dissolved at low temperature to obtain a spinning solution, and this process avoids degradation of the spinning solution due to excessively high temperature; and the relaxation time spectrum of the spinning solution has a bimodal distribution, that is, different distributions of stress exist inside the fiber during the cellulose molding process, which is conducive to retaining the active antibacterial small molecules in the bamboo pulp.

[0039] In the NMMO system, cellulose is in an ionized state. The modifier of the present invention contains at least two active groups, one of which can chemically react with active small molecules (such as bambooquinone) in the pulp, and the other group can react with cellulose, thereby reducing the solubility parameter difference between the active small molecules and cellulose, and further improving the retention rate of active substances (such as antibacterial molecules) in the spinning solution within the lyocell fiber. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1, relaxation time spectrum of spinning solution of Example 1 and Experimental Example 1 of the present invention; wherein τ1 is 0.001-0.1s, τ2 is 0.1-0.5s DETAILED DESCRIPTION

[0041] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments are clearly and completely described below. The following embodiments are used to illustrate the present invention but are not used to limit the scope of the present invention.

[0042] The present invention adopts the method of GB / T 20944.1-2007 to test the antibacterial performance of the obtained lyocell fiber.

[0043] The relaxation time spectrum of the present invention is determined by performing a frequency sweep test on the spinning solution at 90° C. using a rheometer, and calculating the relaxation time spectrum using a Maxwell model.

[0044] Example 1

[0045] (1) Wood pulp (degree of polymerization: 770) and bamboo pulp (degree of polymerization: 350) are mixed to prepare pulp, wherein the mass fraction of bamboo pulp in the pulp is 70% and the mass fraction of wood pulp is 30%;

[0046] (2) directly mixing one part of pulp with nine parts of an aqueous solution of NMMO containing a modifier to obtain a porridge, wherein the mass fraction of NMMO in the aqueous solution is 75%, the modifier is sodium borate, the mass ratio of sodium borate to the mass ratio of cellulose in the pulp is 0.01%, and a zinc oxide sterilizer is also added to the aqueous solution of NMMO, and the mass ratio of the zinc oxide sterilizer to the mass ratio of cellulose in the pulp is 1%;

[0047] (3) The porridge is first subjected to preliminary dehydration at a dehydration temperature of 90° C. and a vacuum degree of 9 kPa; then, it is subjected to evaporation dehydration by a thin film evaporator, and the water vapor partial pressure during the evaporation dehydration process is 4.5 kPa; after dehydration and dissolution, a spinning solution is obtained, and the relaxation time spectrum of the spinning solution has a bimodal distribution, as specifically shown in FIG1 . In the relaxation time spectrum of the spinning solution in this embodiment, the relaxation times are τ1: 0.001-0.1 s and τ2: 0.1-0.5 s, respectively;

[0048] (4) The spinning solution is extruded from the spinneret and passed through an air bath with an air temperature of 16°C for 0.08 seconds, allowing the filaments to cool rapidly and initially form. The filaments then enter a coagulation bath using an aqueous solution of NMMO (26% by mass) and ammonium chloride (0.1% by mass). The filaments diffuse bidirectionally in the coagulation bath to form nascent fibers, which are then washed, oiled, and dried to obtain lyocell bamboo fibers.

[0049] Example 2

[0050] (1) mixing a bamboo pulp (with a degree of polymerization of 1000) and another bamboo pulp (with a degree of polymerization of 200) to prepare pulp;

[0051] (2) directly mixing one part of pulp with nine parts of an aqueous solution of NMMO containing a modifier to obtain a porridge, wherein the mass fraction of NMMO in the aqueous solution is 50%, the modifier is γ-methacryloxypropyltrimethoxysilane, the mass ratio of γ-methacryloxypropyltrimethoxysilane to the mass ratio of cellulose in the pulp is 0.005%, and a zinc oxide sterilizer is also added to the aqueous solution of NMMO, and the mass ratio of the zinc oxide sterilizer to the mass ratio of cellulose in the pulp is 1%;

[0052] (3) The porridge is first subjected to preliminary dehydration at a dehydration temperature of 90° C. and a vacuum degree of 9 kPa; then, it is evaporated and dehydrated by a thin film evaporator, and the water vapor partial pressure during the evaporation and dehydration process is 2 kPa; after dehydration and dissolution, a spinning solution is obtained, and the relaxation time spectrum of the spinning solution has a bimodal distribution;

[0053] (4) The spinning solution is extruded from the spinneret and passed through an air bath at an air temperature of 18°C ​​for 0.05 seconds, allowing the filaments to rapidly cool and initially form. The filaments then enter a coagulation bath using an aqueous solution of NMMO (20% by mass) and polyethylene glycol (0.05% by mass). The filaments diffuse bidirectionally in the coagulation bath to form nascent fibers, which are then washed, oiled, and dried to obtain lyocell bamboo fibers.

[0054] Example 3

[0055] (1) Wood pulp (degree of polymerization: 770) and bamboo pulp (degree of polymerization: 350) are mixed to prepare pulp, wherein the mass fraction of bamboo pulp in the pulp is 30% and the mass fraction of wood pulp is 70%;

[0056] (2) directly mixing one part of pulp with nine parts of an NMMO aqueous solution containing a modifier to obtain a porridge, wherein the mass fraction of NMMO in the NMMO aqueous solution is 85%, the modifier is 1,3,5-triacryloyl-hexahydro-1,3,5-triazine, the mass ratio of 1,3,5-triacryloyl-hexahydro-1,3,5-triazine to the mass ratio of cellulose in the pulp is 0.1%, and a chitin bactericide is also added to the NMMO aqueous solution, and the mass ratio of the chitin bactericide to the mass ratio of cellulose in the pulp is 2%;

[0057] (3) The porridge is first subjected to preliminary dehydration at a dehydration temperature of 90° C. and a vacuum degree of 9 kPa; then, it is evaporated and dehydrated by a thin film evaporator, and the water vapor partial pressure during the evaporation and dehydration process is 6 kPa; after dehydration and dissolution, a spinning solution is obtained, and the relaxation time spectrum of the spinning solution has a bimodal distribution;

[0058] (4) The spinning solution is extruded from the spinneret and passed through an air bath with an air temperature of 15°C for 0.04 seconds, allowing the filaments to cool rapidly and initially form. The filaments then enter a coagulation bath using an aqueous solution of NMMO (40% by mass) and ammonium chloride (0.1% by mass). The filaments diffuse bidirectionally in the coagulation bath to form nascent fibers, which are then washed, oiled, and dried to obtain lyocell bamboo fibers.

[0059] Example 4

[0060] (1) Wood pulp (with a degree of polymerization of 770) and bamboo pulp (with a degree of polymerization of 350) are mixed to prepare pulp, wherein the mass fraction of bamboo pulp in the pulp is 10% and the mass fraction of wood pulp is 90%;

[0061] (2) directly mixing one part of pulp with nine parts of an aqueous solution of NMMO containing a modifier to obtain a porridge, wherein the mass fraction of NMMO in the aqueous solution is 78%, the modifier is sodium borate, the mass ratio of sodium borate to cellulose in the pulp is 0.05%, and a copper oxide sterilizing agent is added to the aqueous solution of NMMO, the mass ratio of the copper oxide sterilizing agent to cellulose in the pulp is 0.05%;

[0062] (3) The porridge is first subjected to preliminary dehydration at a dehydration temperature of 90° C. and a vacuum degree of 9 kPa; then, it is evaporated and dehydrated by a thin film evaporator, and the water vapor partial pressure during the evaporation and dehydration process is 4 kPa; after dehydration and dissolution, a spinning solution is obtained, and the relaxation time spectrum of the spinning solution has a bimodal distribution;

[0063] (4) The spinning solution is extruded from the spinneret and passed through an air bath with an air temperature of 16°C for 0.06 seconds, allowing the filaments to cool rapidly and initially form. The filaments then enter a coagulation bath using an aqueous solution of NMMO (30% by mass) and ammonium chloride (0.1% by mass). The filaments diffuse bidirectionally in the coagulation bath to form nascent fibers, which are then washed, oiled, and dried to obtain lyocell bamboo fibers.

[0064] Experimental Example 1

[0065] This experiment investigates the effects of different pulps on fiber properties:

[0066] The only difference between Experimental Group 1 and Example 1 is that only wood pulp with a degree of polymerization of 770 was used to prepare the spinning solution, and the relaxation time spectrum of the spinning solution had a single peak distribution (as shown in FIG1 ).

[0067] The only difference between Experimental Group 2 and Example 1 is that the mass fraction of bamboo pulp in the pulp is 5%, and the mass fraction of wood pulp is 95%.

[0068] This experimental example tested the relaxation time spectrum of the spinning solution and the antibacterial properties of lyocell bamboo fiber. The results are shown in Table 1 below:

[0069] Table 1:

[0070] As can be seen from the above table, when the relaxation time spectrum of the spinning solution has only a single-peak distribution, the width of the initial fiber antibacterial zone of the obtained lyocell bamboo fiber is narrow. When the relaxation time spectrum of the spinning solution has a bimodal distribution but the bamboo pulp content is low, the width of the antibacterial zone is also relatively narrow. Therefore, selecting a spinning solution corresponding to a relaxation time spectrum with a bimodal distribution and controlling the mass fraction of bamboo pulp in the pulp to be higher than 10% will help improve the antibacterial properties of lyocell bamboo fiber.

[0071] Experimental Example 2

[0072] This experimental example investigates the effects of not adding a modifier and the amount of modifier added on fiber properties;

[0073] The only difference between Experimental Group 1 and Example 1 is that no modifier is added to the NMMO aqueous solution in step (2).

[0074] The only difference between Experimental Group 2 and Example 1 is that the mass ratio of sodium borate to cellulose in the pulp in step (2) is 0.001%.

[0075] The only difference between Experimental Group 3 and Example 1 is that the mass ratio of sodium borate to cellulose in the pulp in step (2) is 0.2%.

[0076] This experimental example tested the relaxation time spectrum of the spinning solution and the antibacterial properties of lyocell bamboo fiber. The results are shown in Table 2 below:

[0077] Table 2:

[0078] As can be seen from the above table, when no modifier is added or the amount of modifier added is too small, the width of the inhibition zone will be significantly reduced after the fiber is washed 12 times, that is, the antibacterial performance of Lyocell bamboo fiber is not durable. However, the amount of modifier added should not be too much, otherwise it will cause the cellulose to be insoluble and the spinning solution cannot be prepared. Therefore, the best effect is selected when the mass ratio of the modifier to the mass of cellulose in the pulp is within the range of 0.005-0.1%.

[0079] Experimental Example 3

[0080] This experimental example investigated the effect of coagulation bath type on fiber properties;

[0081] The only difference between Experimental Group 1 and Example 1 is that no ammonium chloride is added to the coagulation bath.

[0082] The only difference between Experimental Group 2 and Example 1 is that the coagulation bath is pure water.

[0083] The only difference between Experimental Group 3 and Example 1 is that the mass fraction of NMMO in the NMMO aqueous solution in the coagulation bath is 15%.

[0084] The only difference between Experimental Group 4 and Example 1 is that the mass fraction of NMMO in the NMMO aqueous solution in the coagulation bath is 45%.

[0085] This experimental example tested the antibacterial properties of lyocell bamboo fiber, and the results are shown in Table 3 below:

[0086] Table 3:

[0087] Comparing Experimental Group 1 with Experimental Example 1, it can be seen that when ammonium chloride is not added to the coagulation bath, the width of the antibacterial zone of the Lyocell bamboo fiber is smaller and the antibacterial effect is biased. That is, adding ammonium chloride to the coagulation bath helps to increase the retention rate of antibacterial small molecules inside the fiber, thereby improving the antibacterial effect of Lyocell bamboo fiber.

[0088] Comparing Experimental Group 2 with Example 1, it can be seen that using an aqueous solution of NMMO as a coagulation bath is beneficial to improving the retention rate of antibacterial substances inside the fiber, thereby improving the antibacterial effect and antibacterial durability of the fiber.

[0089] Comparing Experimental Group 3 and Experimental Group 4 with Example 1, it can be seen that a low mass fraction of NMMO in the NMMO aqueous solution in the coagulation bath will cause a violent diffusion of NMMO inside the fiber during the spinning process, which is not conducive to the retention of small molecular substances inside the fiber; once the mass fraction of NMMO is too high, the NMMO diffusion process will be too slow, making it difficult to spin into shape. Therefore, controlling the mass fraction of NMMO in the NMMO aqueous solution in the coagulation bath to 20-40% is helpful to improve the antibacterial properties of the fiber while ensuring high spinning efficiency.

[0090] Experimental Example 4

[0091] This experimental example investigates the effect of the mixing method of pulp and NMMO aqueous solution on fiber properties;

[0092] The only difference between Experimental Example 4 and Example 1 is that in step (2), the pulp is first treated with an enzyme and then mixed with an NMMO aqueous solution containing a modifier to obtain a pulp porridge.

[0093] Experimental Example 5

[0094] This experimental example investigates the effect of water vapor partial pressure on fiber properties during evaporative dehydration.

[0095] The only difference between Experimental Example 5 and Example 1 is that the water vapor partial pressure during the evaporative dehydration process is 7.5 kPa.

[0096] The antibacterial properties of the lyocell bamboo fibers of Experimental Examples 4 and 5 were tested, and the results are shown in Table 4 below:

[0097] Table 4:

[0098] Comparing Experimental Example 4 with Example 1, it can be seen that enzyme treatment of the pulp significantly reduces the content of antibacterial components in the pulp, thereby reducing the antibacterial properties of the fiber. The pulp of the present invention is directly mixed with the NMMO aqueous solution containing the modifier to form a pulp porridge. The pulp is not subjected to other treatments, which fully retains the antibacterial components in the pulp and helps to improve the antibacterial properties of the fiber.

[0099] Comparing Experimental Example 5 with Example 1, it can be seen that if the water vapor partial pressure during the evaporation and dehydration process is too high, then the temperature during the evaporation and dehydration process will also be too high, which will cause the antibacterial molecules inside the pulp to be decomposed by high temperature, thereby reducing the antibacterial properties of the fiber. The present invention controls the water vapor partial pressure to be lower than 7.5 kPa, which helps to reduce the spinning solution temperature and fully retain the active antibacterial molecules in the bamboo pulp, thereby improving the antibacterial properties of the fiber.

[0100] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as above in terms of a preferred embodiment, it is not intended to limit the present invention. Any technician familiar with this patent can make slight changes or modifications to equivalent embodiments using the above technical content without departing from the scope of the technical solution of the present invention. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the solution of the present invention.

Claims

1. A method for preparing lyocell bamboo fiber, characterized in that: The preparation steps include: (1) directly mixing pulp comprising at least one bamboo pulp with an NMMO aqueous solution containing a modifier to obtain pulp porridge, wherein the modifier contains at least two active groups; (2) The porridge is dehydrated and dissolved to obtain a spinning solution, and the relaxation time spectrum of the spinning solution has a bimodal distribution. The spinning solution is spun by a spinning device, washed with water, oiled, and dried to obtain lyocell bamboo fiber.

2. The method for preparing lyocell bamboo fiber according to claim 1, wherein: In the step (1), the active groups in the modifier include one or more of epoxy groups, alkenyl groups, silicon-oxygen bonds, and hydroxyl groups; Preferably, the modifier is selected from one or more of borates, silane coupling agents, and cellulose crosslinking agents; Preferably, the borate includes sodium borate, the silane coupling agent includes γ-methacryloxypropyltrimethoxysilane, and the cellulose crosslinking agent includes 1,3,5-triacryloyl-hexahydro-1,3,5-triazine.

3. The method for preparing lyocell bamboo fiber according to claim 1 or 2, wherein: The relaxation times in the relaxation time spectrum of the spinning solution in step (2) are 0.001-0.1s and 0.1-0.5s respectively.

4. The method for preparing lyocell bamboo fiber according to any one of claims 1 to 3, wherein: In the step (1), the mass concentration of cellulose in the pulp is 8-16%, preferably 10-13%, and the mass ratio of the modifier to the cellulose in the pulp is 0.005-0.1%, preferably 0.01-0.05%.

5. The method for preparing lyocell bamboo fiber according to any one of claims 1 to 4, wherein: In the step (1), the pulp comprises a bamboo pulp and a wood pulp, wherein the bamboo pulp and the wood pulp have different degrees of polymerization; or the pulp comprises two bamboo pulps with different degrees of polymerization; Preferably, the mass fraction of bamboo pulp in the pulp is 10-100%, preferably 30-100%; Preferably, the degree of polymerization of the bamboo pulp is 200-1000.

6. A method for preparing lyocell bamboo fiber according to any one of claims 1 to 5, characterized in that: In the step (1), the mass fraction of NMMO in the NMMO aqueous solution is 50-85%; preferably, 68-78%.

7. The method for preparing lyocell bamboo fiber according to any one of claims 1 to 6, wherein: In the spinning process of step (2), a NMMO aqueous solution with a mass fraction of 20-40% is used as a coagulation bath; Preferably, the mass fraction of NMMO in the NMMO aqueous solution is 24-30%.

8. The method for preparing lyocell bamboo fiber according to claim 7, wherein: In the coagulation bath of step (2), one or both of polyethylene glycol and ammonium chloride are added; preferably, the mass fraction of polyethylene glycol or ammonium chloride in the coagulation bath is 0-0.1%.

9. The method for preparing lyocell bamboo fiber according to any one of claims 1 to 8, wherein: In the step (2), the porridge is dehydrated by evaporation, and the gas partial pressure of the water vapor generated during the evaporation process is 2-7.5 kPa, preferably 4-6 kPa.

10. A lyocell bamboo fiber, characterized by: The preparation is prepared by the preparation method described in any one of claims 1 to 9.

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