A method and apparatus for producing lyocell filaments

Abstract

The application discloses a method for producing lyocell filaments, and belongs to the technical field of novel cellulose fiber production, and comprises the following steps: pulp raw material pretreatment, squeezing and crushing, premixing, spinning solution preparation and spinning, wherein, the cellulase is added in the pulp raw material pretreatment, the wet spinning is adopted in the spinning, and the segmented countercurrent washing is adopted in the washing; the spinning equipment used in the method is also disclosed; the pretreatment enzyme hydrolysis process is adopted, the uniformity of the pulp raw material is effectively improved, and the quality of the spinning solution is improved; the wet spinning process control is simpler and easier, and the product quality stability is better; the water consumption of the washing section can be reduced, the washing efficiency is greatly improved, the problem of large steam consumption in the NMMO solvent evaporation and concentration process and high solvent recovery cost can be effectively solved.

Description

Technical Field

[0001] This invention relates to the field of novel cellulose fiber production technology, and in particular to a method and equipment for producing lyocell filaments. Background Technology

[0002] Currently, renewable cellulose filaments are mainly viscose fiber filaments. However, the production process of viscose filaments causes serious environmental pollution problems. Therefore, many viscose filament manufacturers are gradually closing their viscose filament production plants and transforming to develop new cellulose filament production technologies.

[0003] As is well known, lyocell fiber is a new type of green regenerated cellulose fiber. No chemical reactions occur during the dissolution of the cellulose raw material, making the entire production process green and environmentally friendly. The production of lyocell staple filament has been industrialized, and the technology is relatively mature. However, there are relatively few reports on the production of lyocell filament, because there are still many technical shortcomings. The following points stand out: (1) Since the production speed of filament is much higher than that of short filament, it means that the uniformity of the filament and the continuity of the production process are very important. In particular, the requirements for the spinning solution are higher than those for the lyocell short filament. Otherwise, the quality of the product will fluctuate greatly. The most obvious manifestation is that there is a significant difference in the uniformity of dyeing at the end. (2) Since the regeneration of lyocell fiber is usually carried out by dry-jet wet spinning, such as Chinese patent applications CN111164243A and CN113454273A, the fluctuation of process air parameters during dry-jet spinning will have a serious impact on the filament. Furthermore, if the air gap distance is not set properly, it will also lead to the occurrence of yarn bundling, making it difficult to control the process. (3) Since the washing of filament is often done by continuously rinsing with fresh water, the water consumption is large. Moreover, the NMMO concentration in the washing solution is low, and the amount of steam consumed during subsequent solvent evaporation and recovery is even greater, resulting in higher energy consumption. Summary of the Invention

[0004] One of the objectives of this invention is to provide a continuous spinning apparatus for producing lyocell filaments to solve the aforementioned problems.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A spinning apparatus for producing lyocell filaments includes, in sequence, a forming device, a drawing device, a washing device, a steam drying device, and a bobbin forming device; wherein,

[0007] The forming apparatus includes a spinneret, a coagulation bath, and a regeneration bath.

[0008] The traction device includes a guide wheel, a traction roller, and a stretching roller;

[0009] The washing device comprises a water washing device and an oiling device; at least two water washing zones are arranged in the water washing device, a water washing nozzle is arranged above each water washing zone, a water storage tank is arranged below each water washing zone, and the water inlet pipe of the water washing nozzle is communicated with the water storage tank; an oiling nozzle is arranged above each oiling zone in the oiling device, an oil storage tank is arranged below each oiling zone, and the oil inlet pipe of the oiling nozzle is communicated with the oil storage tank; the yarn in the forming device passes through the traction device, the washing device and the steam drying device in sequence and then reaches the bobbin forming device.

[0010] As a preferred technical scheme, the number of water washing zones in the water washing device is 5-10, and the number of oiling zones in the oiling device is 1-2.

[0011] The second object of the present application is to provide a method for producing lyocell filaments by using the above-mentioned device, and the technical scheme comprises the following steps:

[0012] (1) pulp raw material pretreatment

[0013] Wood pulp raw material with a polymerization degree of 700-800 is put into a pulp stirring tank containing dissolved water, and cellulase corresponding to 0.1-1% of the mass of the wood pulp raw material is added for activation pretreatment; after the activation treatment, the pH of the pulp is adjusted to inactivate the enzyme;

[0014] (2) pulp raw material squeezing and crushing

[0015] The activated pulp is squeezed and crushed to obtain pulp raw material containing 50-60 wt% of water, and the polymerization degree of the pulp raw material is 400-500;

[0016] (3) pulp premixing

[0017] The squeezed pulp raw material is premixed with NMMO solution with a concentration of 80-84 wt% in a premixing device to prepare cellulose suspension;

[0018] (4) preparation of spinning solution

[0019] The cellulose suspension obtained by premixing is transported to a dissolving device for vacuum dehydration and dissolution to obtain cellulose solution with a concentration of 8-10 wt%;

[0020] (5) spinning

[0021] Lyocell filaments are prepared by wet spinning using a spinning device, the spinning speed is 60-120 m / min, and the yarn draft ratio is 10-30%; the yarn regenerated from the coagulation bath passes through the traction device, the washing device, the steam drying device and then reaches the bobbin forming device to obtain lyocell filaments.

[0022] As a preferred technical scheme:

[0023] In step (1), the dissolving water is deionized water, and the water temperature is 50-60 DEG C;

[0024] The stirring speed of the slurry mixing tank is 50-80 rpm, and the stirring time is 30-40 min, so that the pulp raw material is fully activated.

[0025] As a preferred technical solution:

[0026] In step (2), the pressing equipment during pressing is a double-net press containing S pressing area and double roller pressing area, the pulp feeding concentration is 4-5 wt%, the temperature is 20-40 DEG C, and the pulp concentration is 40-50 wt%;

[0027] The crushing equipment during crushing is the same as the crusher used after the viscose fiber press.

[0028] As a preferred technical solution:

[0029] The premixing device is a horizontal paddle stirring premixing machine, the rotating speed is 80-90 rpm, and the material residence time is 60-180 seconds.

[0030] As a preferred technical solution:

[0031] In step (5), the coagulation bath is a 10-20 wt% NMMO aqueous solution, the coagulation bath immersion length is 500-900 mm, the coagulation bath depth is 100-300 mm, and the coagulation bath temperature is 10-30 DEG C.

[0032] As a preferred technical solution:

[0033] In step (5), the number of water washing zones in the water washing equipment is 5-10, each water washing zone is provided with a water washing nozzle above, each water washing nozzle is correspondingly provided with a water storage tank below, and the water temperature of the water washing zone is 40-60 DEG C.

[0034] As a preferred technical solution:

[0035] The number of oiling zones in the oiling equipment is 1-2, each oiling zone is provided with an oiling nozzle above, each oiling nozzle is correspondingly provided with an oil storage tank below, and the oil temperature of the oiling zone is 50-60 DEG C.

[0036] The present application proposes a new method for continuously spinning lyocell filaments, which can not only effectively solve the process fluctuation problem in the production process of lyocell filaments, but also greatly improve the washing efficiency, effectively solve the problems of large steam consumption and high solvent recovery cost in the solvent recovery process of NMMO solvent evaporation concentration.

[0037] Compared with the prior art, the present application has the following advantages:

[0038] 1. Since the production speed of filaments is much higher than that of staple filaments, the requirements for the uniformity of the filaments and the continuity of the production process are very high, especially the requirements for the spinning solution are higher than those for lyocell staple filaments; the present invention adopts a pretreatment enzymatic hydrolysis process, which effectively improves the uniformity of pulp raw materials and improves the quality of spinning solution.

[0039] 2. Traditional methods for regenerating lyocell fibers typically involve dry-jet wet spinning. During dry-jet spinning, fluctuations in process air parameters can severely impact the filament, and improper air gap settings can lead to yarn bundling, making process control difficult. This invention uses a wet spinning process to produce lyocell filaments. Compared to dry-jet wet spinning, this avoids fluctuations in process air parameters and the impact of air gaps on filament performance, making process control simpler and easier, and resulting in better product quality stability.

[0040] It should be noted that traditional viscose fibers, due to their low cellulose content and low degree of polymerization, have low viscosity spinning solutions, thus typically employing wet spinning processes. The NaOH solvent system used for viscose fibers is not as effective at dissolving cellulose as NMMO solvents. Therefore, even with the degree of polymerization reduced to around 400, the maximum solubility of the viscose fiber spinning solution can only reach 9 wt%. At a cellulose concentration of 9 wt%, the viscosity of the viscose fiber spinning solution is also much lower than that of the Lyocell fiber spinning solution. Low-viscosity solutions are not suitable for dry-jet wet spinning. Therefore, viscose fibers cannot be spun using dry-jet wet spinning and must be spun using wet spinning processes.

[0041] While the degree of polymerization of pulp raw materials used for lyocell fiber is generally 700-800, this invention uses cellulase to activate and pretreat the pulp raw materials, reducing the polymerization to 400-500. After premixing and swelling, the resulting cellulose solution has a concentration of 8-10 wt%. Since the spinning solution concentration used for producing lyocell filaments is around 8-10 wt%, and experimental results show that cellulose dissolved in NMMO at an 8% concentration has a certain degree of fluidity, this invention addresses the issue of high viscosity in the lyocell cellulose solution. Since a gear pump is used for conveying the solution, the high viscosity allows for increased pump speed to achieve better delivery. Compared to the lyocell staple filament process, this invention uses pulp raw materials with a lower degree of polymerization and a lower cellulose concentration in the spinning solution. Under these conditions, the spinning solution has a certain degree of fluidity, although the viscosity is still higher than that of viscose fiber spinning solution, but it meets the requirements for wet spinning.

[0042] 3. Since the current continuous filament washing often uses fresh water to flush all the time, the water consumption is large, and the NMMO concentration in the washing liquid is low, which consumes more steam in the subsequent solvent evaporation and recovery, and the energy consumption is high; the present application adopts a segmented countercurrent washing, which not only can reduce the water consumption of the washing section, but also can effectively solve the problems of large steam consumption and high solvent recovery cost in the solvent evaporation and concentration process. Specifically, because the segmented countercurrent washing of the present application reuses the used water, the water consumption during washing will be lower. The final washing liquid will have a higher NMMO solution concentration due to repeated use, so that the steam consumption will naturally be reduced during subsequent evaporation and concentration, and the energy consumption will also be reduced. BRIEF DESCRIPTION OF DRAWINGS

[0043] Figure 1 Figure 1 is a structure schematic diagram of a continuous spinning device in Example 1 of the present application;

[0044] Figure 2 Figure 4 is a photo of lyocell filaments prepared in Example 1.

[0045] In the figure: 1, spinneret; 2, coagulation bath; 3, guide wheel; 4, traction roller; 5, drafting roller; 6, washing nozzle; 7, water storage tank; 8, washing device; 9, oiling nozzle; 10, oil storage tank; 11, oiling device; 12, steam dryer; 13, winding device. DETAILED DESCRIPTION

[0046] The present application will be further described below with reference to the accompanying drawings.

[0047] Example 1:

[0048] A method for producing lyocell filaments, comprising the following steps:

[0049] (1) Pretreatment of pulp raw material

[0050] The wood pulp with a degree of polymerization of 700 is put into a pulp stirring tank containing the prepared dissolving water, and 0.65% of the mass of the pulp raw material of commercially available cellulase (Hunan Liker Kang Biological Co., Ltd., cellulase L50) is added for activation pretreatment. After activation treatment, the pH of the pulp is adjusted to 9 to inactivate the enzyme, wherein

[0051] The dissolving water is deionized water, and the water temperature is 55°C;

[0052] The stirring speed of the pulp stirring tank is 60 rpm, and the stirring time is 30 min, so that the pulp raw material is fully activated;

[0053] (2) Pulp raw material pressing and crushing

[0054] The activated pulp in step (1) is crushed by pressing to obtain a pulp stock containing 55 wt% of water, and the polymerization degree of the stock is 450;

[0055] The pressing equipment is a double-net press containing S-pressing zone and counter-roller pressing zone, the feeding pulp concentration is 4.5 wt%, the temperature is 25℃, and the discharging pulp concentration is 45 wt%;

[0056] The crushing equipment is the same as the crusher used after the existing viscose fiber press;

[0057] (3) Pulp stock premixing

[0058] The pulp stock crushed by pressing in step (2) is premixed with NMMO solution with a concentration of 84 wt% to prepare a cellulose suspension,

[0059] The premixing device is a horizontal paddle stirring premixer, the rotating speed is 85 rpm, the material residence time is about 120 seconds, and the cellulose suspension is obtained;

[0060] (4) Spinning solution preparation

[0061] The cellulose suspension obtained by premixing is transported to a dissolving device for vacuum dehydration and dissolution to obtain a cellulose solution with a concentration of 9.0 wt%, and the solution is filtered after defoaming and used for subsequent spinning solution,

[0062] The defoaming method adopts vacuum defoaming, and the filter screen size is 15 μm;

[0063] (5) Spinning

[0064] A continuous spinning equipment as shown in Figure 1 is used to prepare lyocell filaments by wet spinning, the cellulose stock solution is extruded from the spinneret 1 (the nozzle aperture is 0.078 mm, 30 holes) by compressed air, and the formed yarn is obtained by regeneration in the coagulation bath 2; the formed yarn passes through the guide wheel 3, the traction roller 4 and the drawing roller 5 to enter the washing equipment 8, and then reaches the oiling equipment 11; after washing and oiling, the yarn enters the steam drying device 12 for drying, and the dried yarn is wound into a bobbin in the winding equipment 13, i.e. lyocell filaments are obtained, and the photo is shown in Figure 2 ,

[0065] The specific structure of the continuous spinning equipment used in this embodiment is shown in Figure 1 ,

[0066] It comprises a forming device, a traction device, a washing device, a steam dryer 12 and a winding equipment 13 connected in sequence; wherein the forming device comprises a spinneret 1, a coagulation bath 2 and a regeneration bath;

[0067] The traction device comprises a guide wheel 3, a traction roller 4 and a drafting roller 5; the washing device comprises a water washing equipment 8 and an oiling equipment 11;

[0068] In this embodiment, the water washing equipment comprises 5 water washing zones, the water temperature is 50℃, and above each water washing zone is provided with a water washing nozzle 6, a total of five water washing nozzles 6, i.e. Figure 1 6a, 6b, 6c, 6d, 6e in the above, below which are correspondingly provided with five water storage tanks 7, i.e. Figure 1 7a, 7b, 7c, 7d, 7e in the above, the water inlet pipe of the water washing nozzle 6 and the water storage tank 7 are communicated for circulation; in the water washing section, the washing water of the water washing zone of the latter section will enter the water washing zone of the former section, i.e. the washing water of 7a will enter the nozzle of 6b, and so on, the washing water of the most front end 7e has the highest NMMO solvent concentration, and the washing water of 7e will enter the solvent circulation and recovery system;

[0069] In this embodiment, the oiling equipment comprises an oiling zone, the oil temperature is 50℃, and above each oiling zone is provided with an oiling nozzle 9, and below which is provided with an oil storage tank 10, the oil inlet pipe of the oiling nozzle 9 is communicated with the oil storage tank 10 for circulation, and the oil agent used in the oiling zone is a conventional filament oil agent;

[0070] The yarn in the forming device (bath) passes through the traction device, the washing device and the steam drying device in turn and then reaches the bobbin forming equipment;

[0071] In this embodiment, the coagulation bath 2 is a 15 wt% NMMO aqueous solution, the bath temperature is 20℃, the bath depth is 200 mm, and the immersion length is 800 mm;

[0072] The speed of the traction roller 4 V1 = 50 m / min, the speed of the drafting roller 5 V2 = 60 m / min, and the yarn drafting ratio is 20%.

[0073] Example 2

[0074] On the basis of Example 1, this embodiment is different from Example 1 in that the coagulation bath in the wet spinning process is a 10 wt% NMMO aqueous solution; other process conditions and the used equipment are consistent with those of Example 1, and will not be repeated here.

[0075] Example 3

[0076] On the basis of Example 1, this embodiment is different from Example 1 in that the speed of the traction roller 4 V1 = 80 m / min, the speed of the drafting roller 5 V2 = 96 m / min, and the yarn drafting ratio is 20%. Other process conditions and the used equipment are consistent with those of Example 1, and will not be repeated here.

[0077] Comparative Example 1

[0078] On the basis of Example 1, the comparative example is the same as Example 1, the difference is that the spinning process uses the existing dry-jet wet spinning process, the prepared spinning solution is extruded from the spinneret, then side blowing is used for cooling, after cooling, it is introduced into NMMO aqueous solution for coagulation bath solidification, to obtain cellulose filament fiber; the air gap of the spinneret is 10 mm, the coagulation bath temperature is 20℃, the NMMO concentration in the coagulation bath is 15 wt%. The side blowing speed is 3 m / s, the humidity is 5 g / kg (water / air), and the temperature is 20℃. Other process conditions and used equipment are consistent with Example 1, and will not be repeated here.

[0079] Comparative Example 2

[0080] On the basis of Example 1, the comparative example is the same as Example 1, the difference is that the pulp raw material does not use cellulase for enzymolysis in the pretreatment process. Other process conditions and used equipment are consistent with Example 1, and will not be repeated here.

[0081] The above-mentioned lyocell fibers prepared by different methods are respectively taken 10 batches of samples for testing, and the average value and standard deviation of 10 test data are calculated, and the specific results are as follows:

[0082]

[0083] From the above results, the following conclusions can be drawn:

[0084] (1) Comparing Example 1 and Comparative Example 1, compared with the dry-jet wet spinning process, the lyocell filament prepared by the wet spinning process is more stable in performance index, and the test data fluctuation is smaller. However, the filament prepared by the wet spinning process will be lower in fiber strength than the filament prepared by the dry-jet wet spinning process, and the elongation will be higher.

[0085] (2) Comparing Example 1 and Comparative Example 2, using pretreatment enzymolysis process can improve the quality of the spinning solution, thereby improving the stability of the filament product.

[0086] (3) Comparing Example 1 and Example 2, reducing the concentration of NMMO in the coagulation bath is beneficial to improve the stability of the filament product.

[0087] (4) Comparing Example 1 and Example 3, increasing the spinning speed will reduce the stability of the filament product to some extent.

[0088] The above only describes the preferred embodiments of the present application, and is not intended to limit the present application, any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for producing lyocell filaments, characterized in that, Includes the following steps: (1) Pretreatment of pulp raw materials Wood pulp raw material with a degree of polymerization of 700-800 is put into a pulp mixing tank containing pre-mixed dissolving water, and then 0.1-1% of cellulase equivalent to the mass of the wood pulp raw material is added for activation pretreatment; after activation treatment, the pH of the pulp is adjusted to inactivate the enzyme. (2) Pressing and crushing of pulp raw materials The activated pulp is pressed and pulverized to obtain pulp raw material with a water content of 50-60 wt% and a degree of polymerization of 400-500. (3) Pulp premixing A cellulose suspension was prepared by premixing the pressed pulp raw material with an NMMO solution of 80-84 wt% in a premixing device. (4) Preparation of spinning solution The premixed cellulose suspension is transported to a dissolving device for vacuum dehydration and dissolution to obtain a cellulose solution with a concentration of 8-10 wt%. (5) Spinning Lyocell filaments are prepared by wet spinning using spinning equipment. The spinning equipment includes a forming device, a traction device, a washing device, a steam drying device, and a coiling device arranged sequentially. The forming device includes a spinneret, a coagulation bath, and a regeneration bath. The traction device includes guide rollers, traction rollers, and draft rollers. The washing device includes a water washing device and an oiling device. The water washing device has at least two washing zones, each with a water washing nozzle above and a water storage tank below, with the water inlet pipe of the water washing nozzle connected to the water storage tank. The oiling device has an oiling nozzle above and an oil storage tank below each oiling zone, with the oil inlet pipe of the oiling nozzle connected to the oil storage tank. The filaments from the forming device pass sequentially through the traction device, washing device, and steam drying device before reaching the coiling device. The spinning speed is 60-120 m / min, and the filament draw ratio is 10-30%. The filaments regenerated from the coagulation bath are then fed into the winding equipment via a traction device, a washing device, and a steam drying device to obtain Lyocell filaments.

2. The method according to claim 1, characterized in that: The washing equipment has 5 to 10 washing zones; the oiling equipment has 1 to 2 oiling zones.

3. The method according to claim 1, characterized in that: In step (1), the dissolved water is deionized water, and the water temperature is 50-60℃; The stirring speed of the pulp mixing tank is 50-80 rpm, and the stirring time is 30-40 min, so as to fully activate the pulp raw materials.

4. The method according to claim 1, characterized in that: In step (2), the pressing equipment used during pressing is a double-net press containing an S-press zone and a double-roller pressing zone, with a pulp concentration of 4-5 wt%, a temperature of 20-40℃, and an output pulp concentration of 40-50 wt%.

5. The method according to claim 1, characterized in that: The premixing device is a horizontal paddle mixer with a rotation speed of 80-90 rpm and a material residence time of 60-180 seconds.

6. The method according to claim 1, characterized in that: In step (5), the coagulation bath is a 10-20 wt% NMMO aqueous solution, the coagulation bath length is 500-900 mm, the coagulation bath depth is 100-300 mm, and the coagulation bath temperature is 10-30℃.

7. The method according to claim 1, characterized in that: In step (5), the number of water washing zones in the water washing equipment is 5 to 10. Each water washing zone is equipped with a water washing nozzle above it and a water storage tank is provided below each water washing nozzle. The water temperature in the water washing zone is 40 to 60°C.

8. The method according to claim 1, characterized in that: The oiling equipment has 1 to 2 oiling zones, each with an oiling nozzle above it and an oil storage tank below it. The oil temperature in the oiling zone is 50 to 60°C.

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