Preparation method of lyocell bamboo fiber and lyocell bamboo fiber

Abstract

The invention discloses a lyocell bamboo fiber preparation method and lyocell bamboo fibers.The preparation method comprises the steps that 1, pulp at least containing one kind of bamboo pulp is directly mixed with an NMMO aqueous solution containing a modifier to obtain pulp congee, and the modifier at least contains two active groups; and (2) dehydrating and dissolving the slurry porridge to obtain a spinning solution, enabling a relaxation time spectrum of the spinning solution to have bimodal distribution, spinning the spinning solution through spinning equipment, washing with water, oiling and drying to obtain the lyocell bamboo fiber. The pulp is directly mixed with the NMMO aqueous solution containing the modifier to form pulp porridge, the pulp is not subjected to other treatment, and antibacterial components in the pulp are fully reserved; the pulp porridge can be dehydrated and dissolved at low temperature to obtain the spinning solution, the process avoids degradation of the spinning solution caused by too high temperature, and the relaxation time spectrum of the spinning solution has bimodal distribution, that is, stress with different distributions exists in fibers in the cellulose forming process, which is beneficial for retaining active antibacterial micromolecules in the bamboo pulp.

Description

Technical Field

[0001] The present invention belongs to the field of fiber production. Specifically, it relates to a preparation method of Lyocell bamboo fiber and Lyocell bamboo fiber. Background Art

[0002] Cellulose is the main component of plant cell walls and can be sourced from trees, cotton, hemp, and other plants. It is widely distributed in nature and is inexhaustible. Generally, most organic compounds containing hydroxyl groups are soluble in water, such as alcohols, glucose, etc., but cellulose is insoluble in water and most organic solvents. This is because the molecular weight of cellulose is generally large, ranging from several hundred to tens of thousands, and it easily forms intramolecular and intermolecular hydrogen bonds. This force will cover a part of the affinity of hydroxyl groups for water, making cellulose insoluble or hardly soluble in general organic solvents.

[0003] Due to the decreasing petroleum resources and the influence of factors such as the advocacy of nature, health, and environmental protection awareness, people's attention has gradually shifted to regenerated cellulose fibers. Lyocell fiber, commonly known as "Tencel", uses natural plant fibers as raw materials and emerged in the mid-1990s. It is regarded as the most valuable product in the history of man-made fibers in the past half century and has a variety of excellent properties of both natural fibers 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 disadvantages of natural cellulose materials, such as single product, single performance, and being greatly affected by the environment. At the same time, it can reduce the large amount of acidic and alkaline substances required in the production process of traditional cellulose materials, get rid of the pollution problems generated in the production process of traditional cellulose materials, and expand the application fields of cellulose materials. It has the two major advantages of "sustainable development" and "environmental protection" and is a "green material" in the true sense, with very broad application prospects.

[0005] However, in the current production process of Lyocell fiber, using enzyme treatment or acid-base treatment of pulp will damage the activity of internal chemical substances in the pulp, resulting in the loss of fiber functionality. And the active molecules in the pulp will dissolve in the NMMO solution and precipitate during the spinning process, further leading to worse fiber functionality.

[0006] In view of this, the present invention is specifically 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 to achieve the purpose of enhancing the binding force between cellulose and active substances in the pulp and improving the antibacterial performance of the fiber.

[0008] To solve the above technical problems, the basic concept of the technical solution adopted in the present invention is as follows:

[0009] A preparation method of lyocell bamboo fiber, the preparation steps include:

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

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

[0012] The production of cellulose materials by the NMMO solvent method is a new process for producing cellulose materials without chemical reactions. This process mainly dissolves cellulose pulp in an NMMO aqueous solution to obtain a viscous spinning solution, and then produces cellulose materials by a dry-jet wet spinning process. At the same time, the NMMO precipitated in the coagulation bath is recovered and reused, and the recovery rate is as high as 99.8%. The entire production system is closed-loop, without waste discharge and no pollution to the environment. The spinning solution prepared by dissolving cellulose in an NMMO aqueous solution is extruded from a spinneret, passes through an air bath for a period of time, so that the filaments are quickly cooled and preliminarily formed, and then enter the coagulation bath tank. The filaments enter the coagulation bath for two-way diffusion to form primary fibers.

[0013] However, there are still many problems in the current preparation of lyocell bamboo fiber by the dry-jet wet spinning process. First of all, in the dry-jet wet spinning process, the fiber forming process is too fast, which will cause the rapid precipitation of antibacterial small molecule substances (such as: bamboo quinone), and it is difficult for small molecule substances to remain in the fiber; furthermore, the internal solubility parameter of lyocell fiber is usually 40 kJ / m 3 , while the solubility parameter of small molecule substances such as bamboo quinone is between 15 - 25 kJ / m 3 . The large difference in solubility parameters between the two will lead to the difficulty of long-term retention of small molecule substances inside the prepared fiber; in addition, in the dry-jet wet spinning process, the fiber crystal units are highly oriented and arranged to form a crystal structure in the air gap stage. The time for the fiber to form this highly oriented structure is usually 0.01 - 0.03 s; under the spinning process conditions, after the spinning solution forms fibers, there is still stress inside and it continuously decreases with time, showing a stress relaxation phenomenon. Usually, its stress relaxation time is 0.04 - 0.1 s; while the active substances inside the fiber (such as: bamboo quinone) do not show a stress relaxation phenomenon. The stress relaxation time difference of different substances inside the fiber will cause the active substances to migrate out of the fiber, resulting in a decrease in the content of small molecule substances inside the fiber; generally speaking, when preparing lyocell bamboo fiber by the dry-jet wet spinning process, the content of small molecules in the lyocell bamboo fiber is less, and the antibacterial performance of the fiber decreases.

[0014] In addition, some methods for preparing Lyocell bamboo fiber require the use of enzymes or acid-base treatment of pulp, which can also cause the destruction of small molecule substances inside the pulp; alternatively, in some preparation methods, a relatively high temperature is required to prepare a spinning solution containing bamboo pulp. The excessively high temperature will destroy the small molecule structure, causing the small molecule substances to fundamentally lose their functionality.

[0015] In order to improve the retention rate of active small molecule substances inside the Lyocell fiber, the present invention uses the dry-jet wet spinning method to prepare Lyocell bamboo fiber. Among them, the pulp is directly mixed with an NMMO aqueous solution containing a modifier to form a pulp porridge. The pulp is not subjected to other treatments, fully retaining the antibacterial components in the pulp; the pulp porridge can be dehydrated and dissolved at a low temperature to obtain a spinning solution. This process avoids the degradation of the spinning solution caused by too high a temperature, and the relaxation time spectrum of the spinning solution has a bimodal distribution, that is, there are different distributions of stress 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 the active groups can chemically react with the active small molecules (such as bamboo quinone) inside 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 increasing the retention rate of the active substances (such as antibacterial molecules) in the spinning solution inside the Lyocell fiber.

[0017] Furthermore, in the step (1), the active groups in the modifier include one or more of epoxy groups, alkenyl groups, siloxane 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 step (2), the relaxation times in the relaxation time spectrum of the spinning solution are 0.001 - 0.1 s and 0.1 - 0.5 s in sequence.

[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. 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 cellulose in the pulp is 0.05-2%.

[0023] Furthermore, in the step (1), the pulp includes a bamboo pulp and a wood pulp, and the degrees of polymerization of the bamboo pulp and the wood pulp are different; alternatively, the pulp includes two bamboo pulps with different degrees of polymerization;

[0024] Preferably, the mass fraction of the 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, during the spinning process in the step (2), an NMMO aqueous solution with a mass fraction of 20-40% is used as the coagulation bath;

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

[0029] In the present invention, an aqueous solution of NMMO is used as the coagulation bath, and the mass fraction of NMMO is 20-50%; once the concentration is too low, it will cause violent diffusion of NMMO inside the fiber during the spinning process, which is not conducive to the retention of small molecules inside the fiber; once the concentration is too high, it will lead to too slow diffusion of NMMO and it is difficult to spin and form efficiently.

[0030] The spinning gas temperature is 2-18°C; too low a temperature will cause the fiber temperature to drop rapidly, the relaxation time to extend, and the rapid increase in the internal stress of the fiber will make it difficult to retain small molecules; too high a temperature will make it difficult to spin and form efficiently.

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

[0032] Furthermore, polyethylene glycol or ammonium chloride may be added to the coagulation bath in the 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 increase the retention rate of antibacterial small molecule substances inside the fiber.

[0034] Further, in the step (2), the pulp porridge is subjected to evaporation dehydration, and the partial pressure of 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 the thermal decomposition of active molecules inside the bamboo pulp, it is necessary to further reduce the temperature of the spinning solution. In actual production, it is difficult to control this temperature. The present invention achieves the purpose of reducing the temperature of the spinning solution by controlling the pressure of water vapor.

[0036] The present invention also provides a Lyocell bamboo fiber prepared by using the preparation method described in any one of 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 increase the retention rate of active small molecule substances inside the Lyocell fiber, the present invention prepares Lyocell bamboo fiber by using the dry-jet wet spinning method. Among them, 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, fully retaining the antibacterial components in the pulp; the pulp porridge can be dehydrated and dissolved at a low temperature to obtain a spinning solution. This process avoids the degradation of the spinning solution caused by too high temperature, and the relaxation time spectrum of the spinning solution has a bimodal distribution, that is, there are different distributions of stress inside the fiber during the cellulose forming process, which is beneficial 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 the active groups can chemically react with the active small molecules (such as bamboo quinone) inside 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 increasing the retention rate of active substances (such as antibacterial molecules) in the spinning solution inside the Lyocell fiber. Description of the Drawings

[0040] Figure 1 The relaxation time spectrum diagram of the spinning solution in Example 1 and Experimental Example 1 of the present invention; where τ1 is 0.001 - 0.1 s and τ2 is 0.1 - 0.5 s Detailed Embodiments

[0041] To make the objectives, 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 antibacterial properties of the obtained Lyocell fibers were tested by the method of GB / T 20944.1-2007 in this invention.

[0043] The determination method of the relaxation time spectrum in this invention is as follows: the frequency sweep test of the spinning solution at 90 °C was carried out by a rheometer, and the relaxation time spectrum was calculated by the Maxwell model.

[0044] Example 1

[0045] (1) The wood pulp (degree of polymerization is 770) and bamboo pulp (degree of polymerization is 350) were mixed to make pulp, in which the mass fraction of bamboo pulp in the pulp was 70%, and the mass fraction of wood pulp was 30%.

[0046] (2) 1 part of the pulp was directly mixed with 9 parts of NMMO aqueous solution containing a modifier to obtain a pulp porridge. Among them, the mass fraction of NMMO in the NMMO aqueous solution was 75%, the modifier was sodium borate, and the mass ratio of sodium borate to cellulose in the pulp was 0.01%. Zinc oxide bactericide was also added to the NMMO aqueous solution, and the mass ratio of zinc oxide bactericide to cellulose in the pulp was 1%.

[0047] (3) The above-mentioned pulp porridge was first dehydrated preliminarily, the dehydration temperature was 90 °C, and the vacuum degree was 9 KPa; then it was evaporated and dehydrated by a thin film evaporator, and the water vapor partial pressure during the evaporation and dehydration process was 4.5 kPa; after dehydration and dissolution, the spinning solution was obtained. The relaxation time spectrum of the spinning solution had a bimodal distribution, specifically as Figure 1 shown. In this example, the relaxation times in the relaxation time spectrum of the spinning solution were τ1: 0.001-0.1 s and τ2: 0.1-0.5 s in turn.

[0048] (4) The spinning solution was extruded from the spinneret, passed through an air bath, the gas temperature was 16 °C, and the time passing through the air bath was 0.08 s to quickly cool and preliminarily form the filaments, and then entered the coagulation bath. An aqueous solution of NMMO was used as the coagulation bath, the mass fraction of NMMO was 26%, and ammonium chloride was added to the coagulation bath, and the mass fraction of ammonium chloride in the coagulation bath was 0.1%. The filaments entered the coagulation bath for two-way diffusion, and the as-spun fibers were obtained after washing, oiling, and drying.

[0049] Example 2

[0050] (1) One kind of bamboo pulp (degree of polymerization is 1000) and another kind of bamboo pulp (degree of polymerization is 200) were mixed to make pulp;

[0051] (2) Mix 1 part of pulp directly with 9 parts of an NMMO aqueous solution containing a modifier to obtain a pulp porridge. Among them, the mass fraction of NMMO in the NMMO aqueous solution is 50%, the modifier is γ-methacryloyloxypropyltrimethoxysilane, and the mass ratio of γ-methacryloyloxypropyltrimethoxysilane to the cellulose in the pulp is 0.005%. Zinc oxide bactericide is also added to the NMMO aqueous solution, and the mass ratio of the zinc oxide bactericide to the cellulose in the pulp is 1%;

[0052] (3) The above-mentioned pulp 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 through a thin-film evaporator, and the water vapor partial pressure during the evaporation 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 a spinneret, passes through an air bath with a gas temperature of 18 °C and a residence time of 0.05 s in the air bath to quickly cool and preliminarily form the filaments, and then enters a coagulation bath. An aqueous solution of NMMO is used as the coagulation bath, and the mass fraction of NMMO is 20%. Polyethylene glycol is added to the coagulation bath, and the mass fraction of polyethylene glycol in the coagulation bath is 0.05%. The filaments enter the coagulation bath for two-way diffusion, and the nascent fibers are obtained through washing, oiling, and drying, which are the Lyocell bamboo fibers.

[0054] Example 3

[0055] (1) Mix wood pulp (degree of polymerization: 770) and bamboo pulp (degree of polymerization: 350) to make pulp, among which the mass fraction of bamboo pulp in the pulp is 30%, and the mass fraction of wood pulp is 70%;

[0056] (2) Mix 1 part of pulp directly with 9 parts of an NMMO aqueous solution containing a modifier to obtain a pulp porridge. Among them, the mass fraction of NMMO in the NMMO aqueous solution is 85%, the modifier is 1,3,5-triacryloyl-hexahydro-1,3,5-triazine, and the mass ratio of 1,3,5-triacryloyl-hexahydro-1,3,5-triazine to the cellulose in the pulp is 0.1%. Chitin bactericide is also added to the NMMO aqueous solution, and the mass ratio of the chitin bactericide to the cellulose in the pulp is 2%;

[0057] (3) The above-mentioned pulp 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 through a thin-film evaporator, and the water vapor partial pressure during the evaporation 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, passes through an air bath with a gas temperature of 15 °C for 0.04 s, rapidly cools and is preliminarily formed, then enters the coagulation bath. An aqueous solution of NMMO is used as the coagulation bath, with the mass fraction of NMMO being 40%. Ammonium chloride is added to the coagulation bath, and the mass fraction of ammonium chloride in the coagulation bath is 0.1%. The filament enters the coagulation bath for two-way diffusion, and the primary fiber is formed, followed by washing, oiling, and drying to obtain Lyocell bamboo fiber.

[0059] Example 4

[0060] (1) Wood pulp (degree of polymerization is 770) and bamboo pulp (degree of polymerization is 350) are mixed to make pulp, where the mass fraction of bamboo pulp in the pulp is 10%, and the mass fraction of wood pulp is 90%.

[0061] (2) 1 part of the pulp is directly mixed with 9 parts of an aqueous NMMO solution containing a modifier to obtain a pulp porridge. Among them, the mass fraction of NMMO in the aqueous NMMO solution is 78%, the modifier is sodium borate, and the mass ratio of sodium borate to the cellulose in the pulp is 0.05%. A copper oxide bactericide is also added to the aqueous NMMO solution, and the mass ratio of the copper oxide bactericide to the cellulose in the pulp is 0.05%.

[0062] (3) The above-mentioned pulp porridge is first preliminarily dehydrated at a temperature of 90 °C and a vacuum degree of 9 KPa; then it is evaporated and dehydrated through a thin-film evaporator, and the water vapor partial pressure during the evaporation and dehydration process is 4 kPa; after dehydration and dissolution, the 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, passes through an air bath with a gas temperature of 16 °C for 0.06 s, rapidly cools and is preliminarily formed, then enters the coagulation bath. An aqueous solution of NMMO is used as the coagulation bath, with the mass fraction of NMMO being 30%. Ammonium chloride is added to the coagulation bath, and the mass fraction of ammonium chloride in the coagulation bath is 0.1%. The filament enters the coagulation bath for two-way diffusion, and the primary fiber is formed, followed by washing, oiling, and drying to obtain Lyocell bamboo fiber.

[0064] Experimental Example 1

[0065] This experimental example examines the influence of different pulps on fiber properties:

[0066] The difference between Experimental Group 1 and Example 1 is only that: only wood pulp with a degree of polymerization of 770 is used to prepare the spinning solution, and the relaxation time spectrum of the spinning solution has a unimodal distribution (as Figure 1 shown).

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

[0068] In this experimental example, the relaxation time spectrum of the spinning solution and the antibacterial properties of Lyocell bamboo fiber were tested respectively, and the results are shown in Table 1 below:

[0069] Table 1:

[0070]

[0071] 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 antibacterial zone of the initial Lyocell bamboo fiber obtained is relatively narrow. When the relaxation time spectrum of the spinning solution has a double-peak distribution but the content of bamboo pulp is relatively low, the width of the antibacterial zone is also relatively narrow. Therefore, selecting the spinning solution corresponding to the relaxation time spectrum with a double-peak distribution and controlling the mass fraction of bamboo pulp in the pulp to be higher than 10% helps to improve the antibacterial properties of Lyocell bamboo fiber.

[0072] Experimental Example 2

[0073] This experimental example investigated the influence of the addition or non-addition of a modifier and the amount of the modifier added on the fiber properties;

[0074] The difference between Experimental Group 1 and Example 1 is only that: no modifier is added to the NMMO aqueous solution in step (2).

[0075] The difference between Experimental Group 2 and Example 1 is only that: the mass ratio of sodium borate to cellulose in the pulp in step (2) is 0.001%.

[0076] The difference between Experimental Group 3 and Example 1 is only that: the mass ratio of sodium borate to cellulose in the pulp in step (2) is 0.2%.

[0077] In this experimental example, the relaxation time spectrum of the spinning solution and the antibacterial properties of Lyocell bamboo fiber were tested respectively, and the results are shown in Table 2 below:

[0078] Table 2:

[0079]

[0080] As can be seen from the above table, when no modifier is added or the amount of the modifier added is too small, the width of the antibacterial zone will decrease significantly after the fiber is washed 12 times, that is, the durability of the antibacterial properties of Lyocell bamboo fiber is relatively poor. However, the amount of the modifier added should not be too much, otherwise the cellulose cannot be dissolved, and thus the spinning solution cannot be prepared. Therefore, it is best to select the mass ratio of the modifier to cellulose in the pulp to be in the range of 0.005 - 0.1%.

[0081] Experimental Example 3

[0082] This experimental example investigated the influence of the type of coagulation bath on the fiber properties;

[0083] The difference between Experimental Group 1 and Example 1 is only that ammonium chloride is not added to the coagulation bath.

[0084] The difference between Experimental Group 2 and Example 1 is only that the coagulation bath is pure water.

[0085] The difference between Experimental Group 3 and Example 1 is only that the mass fraction of NMMO in the NMMO aqueous solution of the coagulation bath is 15%.

[0086] The difference between Experimental Group 4 and Example 1 is only that the mass fraction of NMMO in the NMMO aqueous solution of the coagulation bath is 45%.

[0087] In this experimental example, the antibacterial properties of Lyocell bamboo fiber were tested, and the results are shown in Table 3 below:

[0088] Table 3:

[0089]

[0090] 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 Lyocell bamboo fiber is smaller and the antibacterial effect is poor. That is, adding ammonium chloride to the coagulation bath helps to improve the retention rate of antibacterial small molecule substances inside the fiber, thereby enhancing the antibacterial effect of Lyocell bamboo fiber.

[0091] Comparing Experimental Group 2 with Example 1, it can be seen that using an aqueous solution of NMMO as the coagulation bath is beneficial to improving the retention rate of antibacterial substances inside the fiber, thereby enhancing the antibacterial effect and antibacterial persistence of the fiber.

[0092] Comparing Experimental Group 3 and Experimental Group 4 with Example 1, it can be seen that a relatively low mass fraction of NMMO in the NMMO aqueous solution of the coagulation bath will cause intense diffusion of NMMO inside the fiber during the spinning process, which is not conducive to the retention of small molecule substances inside the fiber; once the mass fraction of NMMO is too high, it will lead to too slow diffusion of NMMO and it is difficult to form a spun fiber. Therefore, controlling the mass fraction of NMMO in the NMMO aqueous solution of the coagulation bath to be 20 - 40% helps to improve the antibacterial properties of the fiber while ensuring a relatively high spinning efficiency.

[0093] Experimental Example 4

[0094] This experimental example examines the influence of the mixing method of pulp and NMMO aqueous solution on the fiber properties;

[0095] The difference between Experimental Example 4 and Example 1 is only that in step (2), the pulp is first treated with enzymes and then mixed with the NMMO aqueous solution containing the modifier to obtain a pulp porridge.

[0096] Experimental Example 5

[0097] This experimental example examines the influence of the partial pressure of water vapor during the evaporation dehydration process on the fiber properties;

[0098] The difference between Experimental Example 5 and Example 1 is only that: the partial pressure of water vapor during the evaporation dehydration process is 7.5 kPa.

[0099] The antibacterial properties of the Lyocell bamboo fibers of Experimental Example 4 and Experimental Example 5 were tested, and the results are shown in Table 4 below:

[0100] Table 4:

[0101]

[0102] Comparing Experimental Example 4 with Example 1, it can be seen that after the pulp is treated with enzymes, the content of antibacterial components in the pulp will be significantly reduced, thereby reducing the antibacterial properties of the fiber. In the present invention, 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, fully retaining the antibacterial components in the pulp, which helps to improve the antibacterial properties of the fiber.

[0103] Comparing Experimental Example 5 with Example 1, it can be seen that if the partial pressure of water vapor during the evaporation dehydration process is too high, then the temperature during the evaporation 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. In the present invention, controlling the partial pressure of water vapor below 7.5 kPa helps to reduce the temperature of the spinning solution, fully retaining the active antibacterial molecules in the bamboo pulp, thereby improving the antibacterial properties of the fiber.

[0104] The above are only the preferred embodiments of the present invention, and do not impose any form of limitation on the present invention. Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art of this patent, without departing from the scope of the technical solution of the present invention, may make some changes or modifications using the technical content prompted above as equivalent embodiments of equivalent changes. However, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

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

2. The preparation method of a kind of lyocell bamboo fiber according to claim 1, characterized in that: 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-methacryloyloxypropyltrimethoxysilane, and the cellulose crosslinking agent includes 1,3,5-triacryloyl-hexahydro-1,3,5-triazine.

3. The preparation method of a lyocell bamboo fiber according to claim 1 or 2, characterized in that: In the relaxation time spectrum of the spinning solution in the step (2), the relaxation times are 0.001 - 0.1 s and 0.1 - 0.5 s in sequence.

4. A method for preparing lyocell bamboo fiber according to any one of claims 1-3, characterized in that: 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. A method for preparing lyocell bamboo fiber according to any one of claims 1-4, characterized in that: In the step (1), the pulp includes one bamboo pulp and one wood pulp, and the polymerization degrees of the bamboo pulp and the wood pulp are different; or, the pulp includes two bamboo pulps with different polymerization degrees; Preferably, the mass fraction of bamboo pulp in the pulp is 10 - 100%; preferably 30 - 100%; Preferably, the polymerization degree of the bamboo pulp is 200 - 1000.

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

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

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

9. A preparation method of lyocell bamboo fiber according to any one of claims 1-8, characterized in that: In the step (2), the pulp porridge is dehydrated by evaporation, and the 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 in that: Prepared by using the preparation method according to any one of claims 1 - 9 above.

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