Preparation method of lyocell filament fiber

Abstract

The invention belongs to the technical field of fiber production and manufacturing, and relates to a preparation method of lyocell filament fibers, which comprises the following steps: crushing pulp, putting the crushed pulp into a purified solution, stirring to ensure that the pulp is in full contact with the purified solution, treating at 70-90 DEG C for 1-1.5 hours, filtering out the residual pulp, and drying to obtain the lyocell filament fibers. And the pulp is washed by using the same amount of desalted water, and is rolled to remove moisture in the pulp, so that the problem that the existing lyocell filament fiber is relatively poor in fiber strength after being produced is solved.

Description

Technical Field

[0001] The invention belongs to the technical field of fiber production and manufacturing, and relates to a method for preparing lyocell filament fibers. Background Art

[0002] Lyocell fiber is known as the green fiber of the 21st century. Lyocell fiber is made of natural cellulose, such as wood pulp, bamboo pulp, etc. It is directly dissolved in NMMO (N-methylmorpholine-N-oxide) solvent and made into a cellulose fiber through wet spinning. The production process is simple, green and environmentally friendly, and the fiber performance is excellent. Therefore, the research, production and application of Lyocell fiber have developed rapidly in recent years.

[0003] Currently, large-scale production research on the market is still concentrated on lyocell staple fibers. Although the process flow of lyocell filament fibers has many similarities with that of staple fibers, there are great differences in actual production, including material handling methods, production equipment, process conditions, spinning molding, and performance.

[0004] Due to the limitation of production scale, the pulp for making lyocell filament fibers is usually the dissolving pulp for making viscose fibers. Although the dissolving pulp has a relatively high cellulose content, the lyocell fibers produced still have the following disadvantages: the lyocell filament fibers produced have the problem of poor fiber strength. Summary of the invention

[0005] In order to solve the above technical problems, the purpose of the present invention is to provide a method for preparing lyocell filament fibers, which solves the problem that the existing lyocell filament fibers have poor fiber strength after production.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is: a method for preparing lyocell filament fiber. The method comprises the following steps:

[0007] S1: crushing the pulp, placing the crushed pulp in a purified liquid, stirring it to ensure that the pulp is fully in contact with the purified liquid, treating it at 70-90°C for 1-1.5h, filtering out the remaining pulp, washing it with an equal amount of desalted water, and rolling it to remove moisture from the pulp;

[0008] S2: adding the rolled dried pulp and NMMO solvent with a mass concentration of 74-76% into a swelling kettle in a certain proportion, stirring and adding thickener and stabilizer, and conveying to a dissolver after swelling is completed, and drawing the vacuum to within -95kpa to -98kpa at a temperature of 90-120°C, and slowly stirring until the pulp is completely dissolved to obtain a spinning solution;

[0009] S3: The spinning solution is filtered through a filter, then pressurized by a metering pump and extruded from a spinneret, cooled by side blowing and quickly enters a coagulation bath to coagulate into a tow. The tow is then drawn, washed, oiled, dried and rolled to obtain Lyocell filament fibers.

[0010] Furthermore, the purified solution includes sodium hydroxide at a concentration of 3-5 wt %.

[0011] By adopting the above technical solution, the concentration setting avoids the loss of purification effect due to too low a concentration, and also avoids the problem of excessive decomposition of cellulose due to the concentration exceeding 5wt%.

[0012] Furthermore, the bath ratio of pulp to purifying agent is 1:10 to 1:20.

[0013] By adopting the above technical solution, the bath ratio will affect the actual production efficiency. If there is too much purified liquid, there will be more water and less material, and the efficiency will be reduced. If there is too little purified liquid, there will be more water and less material, and the equipment cannot operate normally, and the actual purification effect will also be reduced. The bath ratio is set to maintain the best ratio parameters between the purified liquid and the material, and optimize and improve the production efficiency under the premise of ensuring the normal operation of the equipment.

[0014] Furthermore, the thickener includes one or a mixture of carboxymethyl cellulose (CMC), methyl cellulose (MC) and hydroxyethyl cellulose (HEC), and the addition ratio is within 2-3% of the pulp cellulose.

[0015] By adopting the above technical solution and appropriately adding thickener, the viscosity of the lyocell fiber can be increased, ensuring that high-strength and high-modulus lyocell filament fibers can be obtained in combination with a special fine-hole spinneret during the spinning process.

[0016] Furthermore, the stabilizer includes one of propyl gallate or hydroxylamine, and the added amount is within 0.2% to 0.3% of the weight of the NMMO solvent.

[0017] By adopting the above technical scheme, the addition of stabilizer can improve the stability of solvent and the dissolution quality of cellulose through various mechanisms, thereby ultimately improving the overall quality and production efficiency of fiber products. It also has the effect of reducing the decomposition of cellulose and NMMO solvent in the production process and improving safety. The dissolution weight ratio is appropriate to avoid the problem of increased costs due to excessive use of materials.

[0018] Furthermore, the coagulation bath is an aqueous solution containing low-concentration NMMO, wherein the mass percentage content of NMMO in the coagulation bath is within 8 to 12%, and the temperature of the coagulation bath is within 18 to 24°C.

[0019] By adopting the above technical solution, the temperature of the coagulation bath is within the range of 18 to 24°C, and this temperature setting is suitable for the high-temperature spinning stock solution to quickly cool down and coagulate into a spinning bundle after entering the low-temperature coagulation bath.

[0020] Furthermore, the spinneret hole diameter is within 0.5 mm to 0.8 mm.

[0021] By adopting the above technical solution, the selection of the aperture can avoid the problem that the aperture is too large, resulting in no pressure on the spinning and the stock liquid cannot form a bundle of fibers, and also avoid the problem that the aperture is too small, resulting in the stock liquid cannot be sprayed out into fibers.

[0022] Furthermore, the pulp includes one or a mixture of bamboo pulp, cotton pulp and wood pulp.

[0023] By adopting the above technical scheme, bamboo pulp has the soft feel of normal fibers, and cotton pulp has a high cellulose content and few impurities after processing, which is conducive to the subsequent dissolution and spinning processes. High-quality wood pulp has a high cellulose content and is suitable for large-scale industrial production, and has good wear resistance and durability. The above-mentioned centralized mixing can achieve different effects according to their respective characteristics, which not only improves the overall performance of the fiber, but also provides more possibilities for product development. By making full use of the advantages of various pulps, environmentally friendly and high-performance lyocell fibers can be produced to meet diverse market needs.

[0024] Compared with the prior art, the advantages of the present invention are:

[0025] 1. The present application has studied and found that the problem of uneven molecular structure of lyocell filament fibers during the spinning process of the filament fibers, which leads to the problem of too low fiber strength, is that the presence of lignin and hemicellulose in the pulp will affect the strength and modulus of the filament fibers. The presence of hemicellulose and lignin will interfere with the dissolution, regeneration and molecular structure formation of cellulose from multiple aspects, resulting in unevenness inside and on the surface of the fibers. Specifically, they will affect the consistency of the dissolution and regeneration process of cellulose, change the crystallinity and orientation of cellulose, increase the defects and stress concentration inside the fibers, and affect the characteristics of the fiber surface. In the present invention, a purified liquid is added to the pulp to reduce the influence of lignin and hemicellulose on it, so that the molecular structure is more uniform during the spinning process of the filament fibers, so that the strength and modulus of the manufactured filament fibers can be improved.

[0026] 2. In the present invention, the viscosity of the lyocell fiber can be increased by adding a thickener, ensuring that a high-strength and high-modulus lyocell filament fiber can be obtained by cooperating with a spinneret during the spinning process. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the production process of the present invention. DETAILED DESCRIPTION

[0028] The present invention is further described in detail below with reference to the accompanying drawings.

[0029] Reference Figure 1 , a method for preparing lyocell filament fiber. The method comprises the following steps:

[0030] S1: crushing the pulp, placing the crushed pulp in a purified liquid, stirring it to ensure that the pulp is fully in contact with the purified liquid, treating it at 70-90°C for 1-1.5h, filtering out the remaining pulp, washing it with an equal amount of desalted water, and rolling it to remove moisture from the pulp;

[0031] S2: adding the rolled dried pulp and NMMO solvent with a mass concentration of 74-76% into a swelling kettle in a certain proportion, stirring and adding thickener and stabilizer, and conveying to a dissolver after swelling is completed, and drawing the vacuum to 95-98 kPa at a temperature of 90-120°C, and slowly stirring until the pulp is completely dissolved to obtain a spinning solution;

[0032] S3: The spinning solution is filtered through a filter, then pressurized by a metering pump and extruded from a spinneret, cooled by side blowing and quickly enters a coagulation bath to coagulate into a tow. The tow is then drawn, washed, oiled, dried and rolled to obtain Lyocell filament fibers.

[0033] In this embodiment, the spinning solution is filtered through a filter, wherein the filter may be a candle wick fine filter system.

[0034] In this embodiment, the purified liquid is sodium hydroxide with a concentration of 3-5wt%. Adding the purified sodium hydroxide liquid to the pulp raw material has the following advantages:

[0035] 1. It can effectively dissolve and remove the lignin component in pulp. Lignin is part of the plant cell wall and is an obstacle to the extraction of non-wood fiber. After alkaline treatment with sodium hydroxide, lignin can be separated from cellulose to improve the purity of cellulose;

[0036] Degradation of hemicellulose: In addition to lignin, sodium hydroxide can also help degrade hemicellulose, which is also present in plant cell walls and will affect the solubility and spinning properties of cellulose to a certain extent. By selecting 3-5wt% of sodium hydroxide for appropriate alkaline treatment, these impurities can be reduced, thereby improving the quality of the final fiber and increasing the strength and modulus of Lyocell fiber.

[0037] 2. Improve the reactivity of cellulose

[0038] Alkaline conditions help to destroy part of the crystalline structure of cellulose, making it easier to be dissolved by the NMMO solvent, thereby ensuring that the cellulose can be evenly dispersed in the solvent to form a stable solution, which is beneficial to the subsequent spinning operation.

[0039] 3. Prevent microbial growth

[0040] A high concentration of alkaline environment is not conducive to the survival of microorganisms, so adding an appropriate amount of sodium hydroxide can also inhibit the reproduction of bacteria and other microorganisms and ensure the sanitary conditions of the production process.

[0041] In this embodiment, the pulp includes one or a mixture of bamboo pulp, cotton pulp and wood pulp. The bamboo pulp has a generally soft feel. After processing, the cotton pulp has a high cellulose content and few impurities, which is beneficial to the subsequent dissolution and spinning processes. The high-quality wood pulp has a high cellulose content, is suitable for large-scale industrial production, and has good wear resistance and durability. The above-mentioned concentrated mixing can achieve different effects according to their respective characteristics, which not only improves the overall performance of the fiber, but also provides more possibilities for product development. By making full use of the advantages of various pulps, lyocell fibers that are both environmentally friendly and high-performance can be produced to meet diverse market demands.

[0042] In this embodiment, the bath ratio of pulp to purifying agent is 1:10-1:20. The bath ratio will affect the actual production efficiency. If there is too much purified liquid, there will be more water and less material, and the efficiency will be reduced. If there is too little purified liquid, there will be more water and less material, and the equipment cannot operate normally, and the actual purification effect will also be reduced. The bath ratio is set to maintain the optimal ratio parameters between the purified liquid and the material, and optimize and improve the production efficiency under the premise of ensuring the normal operation of the equipment.

[0043] In this embodiment, the thickener includes one or a mixture of carboxymethyl cellulose (CMC), methyl cellulose (MC) and hydroxyethyl cellulose (HEC), and the addition ratio is within 2-3% of the pulp cellulose. By adding the thickener, the following benefits are achieved:

[0044] One benefit is that it can increase the viscosity of the spinning solution, making it more stable when passing through the spinneret, reducing the phenomenon of broken wires, and appropriate high viscosity helps to form uniform and elongated filament fibers;

[0045] The second benefit is that these thickeners can make the spinning solution show good shear thinning properties, that is, the viscosity decreases when subjected to shear force (such as when extruded through a spinneret), while maintaining a higher viscosity in a static state. This property is crucial to ensure a stable spinning process;

[0046] The three benefits are: enhancing the fiber's formability and promoting molecular arrangement. The presence of thickeners can help cellulose molecules to better align during the dissolution process, thereby forming a more ordered structure when regenerated into fibers. This not only improves the fiber's mechanical strength, but also improves its surface smoothness and flatness.

[0047] The four benefits are: by optimizing the rheological properties of the spinning solution, the thickener helps reduce the defects inside the fiber, making the fiber more uniform and reducing the risk of breakage;

[0048] The fifth advantage is that after subsequent spinneret extrusion and then in the coagulation bath, the thickener can be used to adjust the diffusion rate of the NMMO solvent from the inside to the outside of the fiber, thereby controlling the speed and quality of fiber forming. The appropriate diffusion rate helps to obtain the ideal fiber diameter and structure.

[0049] In this embodiment, the stabilizer includes one of propyl gallate or hydroxylamine, and the added amount is within 0.2% to 0.3% by weight of the NMMO solvent. The addition of the stabilizer can improve the stability of the solvent and the dissolution quality of cellulose through various mechanisms, thereby ultimately improving the overall quality and production efficiency of the fiber product. It also has the effect of reducing the decomposition of cellulose and NMMO solvent during the production process and improving safety. The dissolution weight ratio is appropriate to avoid the problem of increased costs due to excessive use of materials.

[0050] In this embodiment, the coagulation bath is an aqueous solution containing low concentration NMMO, wherein the mass percentage of NMMO in the coagulation bath is within 8-12%, and the temperature of the coagulation bath is within 18-24°C. The temperature setting is suitable for the high-temperature spinning solution to enter the low-temperature coagulation bath and then quickly cool down and coagulate to form a spinning bundle.

[0051] In this embodiment, the spinneret aperture is 0.5 mm to 0.8 mm. The selection of the aperture avoids the problem that the aperture is too large, resulting in no pressure on the spinneret and the stock solution cannot form a bundle, and also avoids the problem that the aperture is too small, resulting in the stock solution cannot be sprayed out.

[0052] Embodiment 1:

[0053] The pulp was broken into flocs and immersed in a purified solution prepared with 3wt% NaOH at a bath ratio of 1:20. The solution was treated at 60°C with stirring. The pulp was filtered out after 30 minutes. Desalted water of the same mass as the purified solution was added and mixed evenly. The reaction was continued for 30 minutes. The pulp was dried and set aside.

[0054] The NMMO solvent with a mass concentration of 50% is concentrated to 76% by vacuum distillation, and then the purified cellulose pulp and 76% NMMO are added to the swelling kettle at a ratio of 1:10, stirred and 3% carboxymethyl cellulose (CMC) by weight of cellulose and 1 / 10,000th of the weight of the solvent are added, and after 40 minutes, it is transported into the dissolving machine, vacuumed to -97kpa at 105°C, and stirred until the cellulose pulp is completely dissolved to obtain the spinning solution;

[0055] The spinning solution is filtered through a filter to remove impurities, then measured by a metering pump and extruded from the micropores of the spinneret, passes through a side-blowing section and enters a coagulation bath at a temperature of 20°C, and is stretched, washed, oiled and dried to obtain high-strength and high-modulus Lyocell filament fibers.

[0056] After testing, the breaking strength of the prepared fiber was 5.5 cN / dtex, the breaking elongation was 3.2%, and the fiber modulus was 154 Gpa.

[0057] Embodiment 2:

[0058] The pulp was broken into flocs and immersed in a purified solution prepared with 4wt% NaOH at a bath ratio of 1:15. The solution was treated at 60°C with stirring. The pulp was filtered out after 30 minutes. Desalted water at a bath ratio of 1:25 was added and mixed evenly. The reaction was continued for 30 minutes. The pulp was dried and set aside.

[0059] The NMMO solvent with a mass concentration of 50% is concentrated to 75% by vacuum distillation, and then the purified cellulose pulp and 75% NMMO are added to the swelling kettle at a ratio of 1:11, stirred and 5% hydroxyethyl cellulose (HEC) by weight of cellulose and 1 / 10,000th of the weight of the solvent are added, and after 40 minutes, it is transported into a dissolver, vacuumed to -97.5kpa at 100°C, and stirred until the cellulose pulp is completely dissolved to obtain a spinning solution;

[0060] The spinning solution is filtered through a filter to remove impurities, then measured by a metering pump and extruded from the micropores of the spinneret, passes through a side-blowing section and enters a coagulation bath at a temperature of 20°C, and is stretched, washed, oiled and dried to obtain high-strength and high-modulus Lyocell filament fibers.

[0061] After testing, the breaking strength of the prepared fiber was 5.6 cN / dtex, the breaking elongation was 3.0%, and the fiber modulus (anti-deformation ability) was 134 Gpa.

[0062] Embodiment 3:

[0063] The pulp is broken into flocs and set aside without any other treatment.

[0064] The NMMO solvent with a mass concentration of 50% is concentrated to 75% by vacuum distillation, and then the cellulose pulp and 75% NMMO are added to the swelling kettle at a ratio of 1:11.5, stirred and 20,000th of the weight of the solvent propyl gallate is added, and after 40 minutes, it is transported to the dissolver, vacuumed to -97.5kpa at 100°C, and stirred until the cellulose pulp is completely dissolved to obtain the spinning solution;

[0065] The spinning solution is filtered through a filter to remove impurities, then measured by a metering pump and extruded from the micropores of the spinneret, passes through a side-blowing section and enters a coagulation bath at a temperature of 20°C, and is stretched, washed, oiled and dried to obtain high-strength and high-modulus Lyocell filament fibers.

[0066] After testing, the breaking strength of the prepared fiber was 3.3 cN / dtex, the breaking elongation was 4.0%, and the fiber modulus (anti-deformation ability) was 60 Gpa.

[0067] Although the preferred embodiments of the present invention are described in detail above, it should be clearly understood that various modifications and variations are possible for those skilled in the art. Any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing lyocell filament fiber, characterized in that: The steps include: S1: crushing the pulp, placing the crushed pulp in a purified solution, stirring it to ensure that the pulp is fully in contact with the purified solution, treating it at 70-90° C. for 1-1.5 hours, filtering out the remaining pulp, washing it with an equal amount of desalted water, and rolling it to remove moisture from the pulp; S2: adding the rolled dried pulp and NMMO solvent with a mass concentration of 74-76% into a swelling kettle in a certain proportion, stirring and adding a thickener and a stabilizer, and conveying the pulp into a dissolver after the swelling is completed, and drawing the vacuum to 95-98 kPa at a temperature of 90-120° C., and slowly stirring until the pulp is completely dissolved to obtain a spinning solution; S3: The spinning solution is filtered through a filter, then pressurized by a metering pump and extruded from a spinneret, then cooled by side blowing and quickly enters a coagulation bath to coagulate into a filament bundle, and the filament bundle is then drawn, washed, oiled, dried and rolled to obtain Lyocell filament fibers.

2. The method for preparing a lyocell filament fiber according to claim 1, characterized in that: The purified solution includes sodium hydroxide with a concentration of 3-5wt%.

3. The method for preparing a lyocell filament fiber according to claim 1, characterized in that: The bath ratio of the pulp to the purifying agent is 1:10 to 1:

20.

4. The method for preparing a lyocell filament fiber according to claim 1, characterized in that: The thickener includes one or a mixture of carboxymethyl cellulose (CMC), methyl cellulose (MC) and hydroxyethyl cellulose (HEC), and the added ratio is within 2-3% of the pulp cellulose.

5. The method for preparing a lyocell filament fiber according to claim 1, characterized in that: The stabilizer includes one of propyl gallate or hydroxylamine, and the added amount is within 0.2% to 0.3% of the weight of the NMMO solvent.

6. The method for preparing lyocell filament fiber according to claim 1, characterized in that: The coagulation bath comprises an aqueous solution containing low-concentration NMMO, wherein the mass percentage content of NMMO in the coagulation bath is within 8-12%, and the temperature of the coagulation bath is within 18-24°C.

7. The method for preparing lyocell filament fiber according to claim 1, characterized in that: The spinneret aperture is within the range of 0.5 mm to 0.8 mm.

8. The method for preparing lyocell filament fiber according to claim 1, characterized in that: The pulp includes one or a mixture of bamboo pulp, cotton pulp and wood pulp.

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