A method for preparing high-performance regenerated cellulose fibers suitable for industrial filaments and the fibers themselves.

Abstract

This invention discloses a method for preparing high-performance regenerated cellulose fibers suitable for industrial applications, and the resulting fibers. The preparation steps include: mixing one or more cellulose pulps, with an average degree of polymerization greater than 800 and a molecular weight distribution index of 1.3-2.2; mixing and dissolving the mixed pulps with an NMMO aqueous solution to form a cellulose solution; extruding the cellulose solution through a spinneret, passing it through a temperature buffer zone, entering a multi-stage air bath, and undergoing high-ratio stretching; then coagulating, washing, and micro-stretching to obtain pre-heat-treated fibers; and finally, drying and heat-stabilizing the pre-heat-treated fibers, followed by winding to obtain the final product. This invention exhibits excellent flow and stretching properties of the cellulose solution, significantly improving the stretching orientation of the fiber formation. Furthermore, by controlling the stretching tension and micro-stretching, the fiber structure is stabilized, resulting in high-strength, high-modulus regenerated cellulose fibers that meet the requirements for industrial applications.

Description

Technical Field

[0001] This invention belongs to the field of industrial filament production, and specifically relates to a method for preparing high-performance regenerated cellulose fiber that can be used in industrial filament production, as well as the fiber itself. Background Technology

[0002] In the field of industrial fibers, traditional synthetic fibers are widely used due to their superior physical and mechanical properties, such as high strength, high modulus, and impact resistance, to meet the demands of complex industrial environments. With the acceleration of industrial modernization, the application scope of industrial fibers is constantly expanding, and the performance requirements are gradually increasing. However, traditional synthetic fibers suffer from creep damage during use, which has become a major challenge for the application of industrial fibers.

[0003] The application of regenerated cellulose fibers in the industrial field is relatively limited, mainly because their strength and modulus cannot meet the requirements of practical applications. Traditional regenerated cellulose fibers, especially those prepared by the viscose method, are constrained by production process limitations, resulting in reduced polymerization degree and insufficient stretching during wet spinning, which leads to fiber mechanical properties that cannot meet the demands of high-performance industrial applications.

[0004] New solvent-based methods for preparing regenerated cellulose fibers, such as lyocell fibers, have achieved significant breakthroughs through improved crystallinity and specialized spinning processes. These advancements have resulted in significantly enhanced breaking strength and initial modulus, creating immense potential for industrial applications. Lyocell fibers exhibit excellent thermal dimensional stability, virtually no creep, and superior heat resistance, making them superior to traditional synthetic industrial fibers.

[0005] However, for lyocell fibers, the mechanical properties of fibers produced by conventional production processes still fall short of the requirements for industrial applications. While the use of ultra-high degree polymerized pulp raw materials and the composite application of lyocell fibers have made some progress in improving lyocell fiber performance, challenges remain in continuous production, energy reduction, and achieving industrial-scale production. Most improvement methods involve complex processes and high costs, limiting their widespread application in actual production.

[0006] Against this backdrop, although lyocell fiber possesses excellent heat resistance, fatigue resistance, dimensional stability, and good bonding with rubber, its mechanical properties remain insufficient, and the issue of continuous production has not yet been resolved. Therefore, the application of regenerated cellulose fibers in the industrial field still faces a series of challenges.

[0007] In view of the above, the present invention is hereby proposed. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a method for preparing high-performance regenerated cellulose fiber that can be used in industrial yarns and the fiber itself. The regenerated cellulose fiber prepared has a breaking strength greater than 5.5 cN / dtex and an initial modulus greater than 100 cN / dtex, that is, the regenerated cellulose fiber has excellent mechanical properties.

[0009] To solve the above-mentioned technical problems, the basic concept of the technical solution adopted by the present invention is as follows:

[0010] A method for preparing high-performance regenerated cellulose fibers suitable for industrial applications, comprising the following steps:

[0011] (1) Mix one or more cellulose pulps, and the average degree of polymerization after mixing is greater than 800 and the molecular weight distribution index is 1.3-2.2; mix the mixed pulp with NMMO aqueous solution to swell and dissolve to prepare a cellulose solution;

[0012] (2) The cellulose solution is extruded through the spinneret assembly, passes through the temperature buffer zone, enters the multi-stage air bath, and is subjected to high stretching. Then, it is coagulated, washed, and micro-stretched to obtain the pre-heat-treated fiber.

[0013] (3) The fiber is obtained by drying and heat stabilization treatment and winding.

[0014] Furthermore, in step (1), the shear viscosity of the cellulose solution is in the range of 80-1200 Pa·s, and the intersection modulus Gc of the dynamic rheological storage modulus and loss modulus of the cellulose solution is 400-1000 Pa.

[0015] The cellulose solution of this invention has good fluidity and stretchability, wherein the cellulose mass fraction is 5-14 wt%. However, excessively high system viscosity is not conducive to spinning. Therefore, the viscosity of the cellulose solution should not be too high.

[0016] Furthermore, in step (2), after the cellulose solution is extruded by the spinneret assembly, it first enters a temperature buffer zone of 0.2-15 mm for buffering, and then enters a multi-stage air bath with variable temperature for stretching.

[0017] Furthermore, the stretch ratio of the cellulose solution after extrusion is greater than or equal to 8, and the aspect ratio of the spinneret in the spinneret assembly is greater than 4.

[0018] Preferably, the residence time of the cellulose solution in the spinneret is not less than 1 second;

[0019] Preferably, the spinneret assembly has independent temperature control, with the temperature controlled between 100-145℃.

[0020] According to the above preparation method, the spinneret assembly is provided with a temperature buffer zone on the lower side of the spinneret plate. After the high-viscosity cellulose solution is extruded in fine streams, the orifice expansion section will not cool down immediately, thereby improving the tensile strength of the fiber.

[0021] Furthermore, in step (2), the multi-stage air bath is achieved by using a blower to blow air from the outer periphery of the fiber bundle towards the center, with the air temperature decreasing step by step;

[0022] Preferably, the multi-stage air bath includes at least a first-stage air bath and a second-stage air bath, with the first-stage air bath having a wind temperature of 30-70℃ and the second-stage air bath having a wind temperature of 5-15℃.

[0023] Preferably, the blowing air forms a semi-circular air curtain.

[0024] Cellulose solution streams undergo initial cooling and solidification in an air bath. Excessive solidification limits the fiber stretching ratio. This invention stages the air bath, which to some extent alleviates the problem of excessive tension during stretching caused by excessively rapid solidification of the fiber skin. On the other hand, it can also optimize the stretching stability of the spinning solution during extrusion by controlling the secondary blowing conditions, so that the stretching ratio meets the preparation requirements.

[0025] Furthermore, in step (2), the fiber bundle tension F1 (cN) during the fiber bundle coagulation and washing stages satisfies the formula: (0.75 × total fiber bundle fineness / 1.08). 1.1 ≤F1(cN)≤(1.55×total fineness of tow / 1.08) 1.1 .

[0026] The above preparation method uses a composite washing method of high-pressure spraying device and contact plate washing in the water washing stage to ensure high fiber washing efficiency.

[0027] Furthermore, in step (2), when the fiber bundle tension F2 (cN) is slightly stretched after washing, it satisfies the formula: (0.25 × total fineness of the fiber bundle). 1.25 ≤F2(cN)≤(0.42×total fineness of the tow) 1.25 .

[0028] The micro-stretching after washing ensures the further orientation of the uncrystallized fiber macromolecules.

[0029] Furthermore, in step (2), the moisture content of the fiber bundle during micro-stretching is 120% ≤ moisture content ≤ 160%;

[0030] Preferably, the temperature during micro-stretching is 120-150℃.

[0031] Furthermore, in step (3), the fiber bundle tension F3 (cN) during drying heat stabilization is ≤1.2 × total fiber bundle fineness;

[0032] Preferably, the drying thermal stability temperature is 100-170℃;

[0033] Preferably, the drying thermal stability is achieved through a graded drying method, with the drying temperature set in a gradient from high to low.

[0034] When the fiber bundle tension is F3 during drying and heat stability, the highly stretched and oriented supramolecular structure of the fiber gradually becomes more perfect, and the fiber structure becomes more stable under continuous stretching with lower tension.

[0035] The present invention also provides a high-performance regenerated cellulose fiber that can be used in industrial yarns, prepared by any of the preparation methods described above, having a breaking strength greater than 5.5 cN / dtex and an initial modulus greater than 100 cN / dtex.

[0036] Preferably, the regenerated cellulose fiber is further processed into the final industrial yarn product by twisting. The fiber twist is less than 100. Twisting can be carried out in a two-in-one or three-in-one manner according to the application to ensure that the fiber performance meets the specific application requirements of industrial yarn.

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

[0038] 1. The method for preparing regenerated cellulose fiber provided by the present invention starts from raw materials and does not use pure ultra-high degree polymerized pulp. It achieves high-efficiency preparation of cellulose solution through combined raw materials. The prepared cellulose solution reduces dissolution energy consumption and improves preparation efficiency while maintaining a high cellulose concentration, and ensures excellent tensile properties of the solution.

[0039] 2. The method for preparing regenerated cellulose fibers provided by this invention increases the residence time within the orifice using a spinneret with a large aspect ratio, thereby minimizing internal stress and elastic deformation during the extrusion process of the spinning solution. A temperature buffer zone and a multi-stage variable-temperature air bath are employed to gradually mitigate the stretching conditions of the cellulose solution in the air bath, optimizing the stretching stability and tensile strength of the cellulose solution during extrusion, and delaying the fiber solidification point to achieve ultra-high fiber stretching and improve fiber stretching orientation in the air gap section.

[0040] 3. The method for preparing regenerated cellulose fibers provided by the present invention improves the uniformity of fibers by controlling the forming tension of fibers during the coagulation, washing and initial drying stages, breaks through the stretching bottleneck under the existing process, stabilizes the effective orientation of fibers after high stretching, and ensures high mechanical strength and uniformity of nascent fibers.

[0041] 4. The method for preparing regenerated cellulose industrial fibers provided by this invention involves steam heat treatment and micro-stretching of nascent fibers with high water content and incompletely formed aggregated structures, which further arranges the cellulose macromolecules in an orderly manner and improves crystallization, thereby further improving the strength and modulus of the fibers; and through secondary thermal stabilization under low tension, the internal stress of the fibers is gradually eliminated, further ensuring the stability and durability of the fiber properties.

[0042] 5. This invention prepares cellulose dope with high tensile properties through a novel solvent method, controls the molecular weight distribution, average molecular weight and flow tensile properties of the raw materials, optimizes the orifice extrusion stretching process, significantly improves the stretching orientation of fiber forming, and achieves the goal of stably preparing high-strength and high-modulus regenerated cellulose fibers by controlling the stretching tension and secondary stabilizing the orientation.

[0043] 6. During the fiber preparation process, by setting up a multi-stage temperature-varying large gap air bath gradient, the pore expansion section of the cellulose solution will not cool down immediately after the fine stream is extruded, thereby improving the tensile strength; by controlling the tension of stretching and heat treatment, the fiber achieves stable stretching orientation during the formation of a three-dimensional ordered structure, improving the final orientation degree of the fiber, greatly enhancing the strength and modulus of the fiber, and enabling regenerated cellulose fibers to meet the requirements for industrial use.

[0044] By effectively combining the aforementioned beneficial effects, the fiber birefringence can reach above 0.052, the fiber breaking strength can reach above 5.5 cN / dtex, and the initial modulus can reach above 100 cN / dtex, thus realizing the preparation of high-performance regenerated cellulose fibers. Furthermore, appropriate twisting can further enhance the performance of the regenerated cellulose fibers.

[0045] The specific embodiments of the present invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0046] The accompanying drawings, as part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention, but do not constitute an undue limitation of the invention. Obviously, the drawings described below are merely some embodiments, and those skilled in the art can obtain other drawings based on these drawings without creative effort. In the drawings:

[0047] Figure 1 This is a schematic diagram of the assembly structure of the production equipment for regenerated cellulose fibers according to the present invention;

[0048] Figure 2 This is a schematic diagram of a multi-stage air bath device.

[0049] In the diagram: 1. Spinneret assembly; 2. Primary air blowing device; 3. Temperature buffer zone; 4. Secondary air blowing device; 5. Solidification zone; 6. Washing zone; 7. Washing zone stretching device; 8. Micro-stretching zone; 9. Drying and thermal stabilization zone. Detailed Implementation

[0050] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments are described clearly and completely below. The following embodiments are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0051] In the description of this invention, it should be noted that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0052] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0053] Example 1

[0054] like Figure 1 and Figure 2 As shown, this embodiment adopts the following... Figure 1 and Figure 2 The equipment shown is used to prepare high-performance regenerated cellulose fibers suitable for industrial filament production; the preparation steps are as follows:

[0055] (1) First, the two types of pulp were mixed. After mixing, the molecular weight distribution was measured to be 2.0 and the average degree of polymerization was 850.

[0056] After mixing, cellulose pulp and NMMO aqueous solution were mixed to prepare a cellulose solution with a cellulose mass concentration of 9%; the shear viscosity of the cellulose solution was 600 Pa·s (measured at 105℃ and a shear rate of 0.8 (1 / s)); the dynamic modulus intersection point G of the solution was... c The Pa is 784.5.

[0057] (2) The cellulose solution was extruded through the spinneret 1, and the length-to-diameter ratio of the spinneret plate of the spinneret 1 was 5. The spinneret was independently temperature controlled at 115℃. After extrusion, it was naturally cooled through a 5mm temperature buffer zone 3. Then it was subjected to high-ratio stretching in a 50mm multi-stage air bath, with a maximum stretching ratio of 10.3 times. The multi-stage air bath used a first-stage blowing device 2 for first-stage blowing at a temperature of 55℃ and a second-stage blowing device 4 for second-stage blowing at a temperature of 14℃. A nascent fiber sample with a specification of 1000dtex was prepared.

[0058] The nascent fiber sample enters the coagulation zone 5 for coagulation, enters the washing zone 6 for washing, and is then micro-stretched in the micro-stretching zone 8 to obtain preliminarily heat-treated fibers. During the coagulation and washing stages, the fiber bundle tension F1 is 2320 cN. After washing, during micro-stretching, the fiber bundle tension F2 is 1880 cN. During micro-stretching, the fiber bundle moisture content is 150% and the temperature is 128℃.

[0059] (3) The fiber underwent preliminary heat treatment and was dried and heat stabilized in the drying and heat stabilization zone 9. Then it was wound to obtain the fiber sample (1). The drying and heat stabilization temperature was 110℃, and the fiber bundle tension F3 was 1169cN during drying and heat stabilization.

[0060] Example 2

[0061] like Figure 1 and Figure 2 As shown, this embodiment adopts the following... Figure 1 and Figure 2 The equipment shown is used to prepare high-performance regenerated cellulose fibers suitable for industrial filament production; the preparation steps are as follows:

[0062] (1) First, the two types of pulp were mixed. After mixing, the molecular weight distribution was measured to be 1.3 and the average degree of polymerization was 810.

[0063] After mixing, cellulose pulp and NMMO aqueous solution were mixed to prepare a cellulose solution with a cellulose mass concentration of 3%; the shear viscosity of the cellulose solution was 100 Pa·s (measured at 105℃ and a shear rate of 0.8 (1 / s)); the dynamic modulus intersection point G of the solution was... c The Pa is 410.

[0064] (2) The cellulose solution was extruded through the spinneret 1, and the length-to-diameter ratio of the spinneret plate of the spinneret 1 was 5. The spinneret was independently temperature controlled and the temperature was controlled at 100℃. After extrusion, it was naturally cooled through the 5mm temperature buffer 3. Then it entered the 50mm multi-stage air bath for high-ratio stretching, with a maximum stretching ratio of 15 times. The multi-stage air bath used the first-stage blowing device 2 for the first-stage blowing at a temperature of 30℃ and the second-stage blowing device 4 for the second-stage blowing at a temperature of 5℃. A nascent fiber sample with a specification of 600dtex was prepared.

[0065] The nascent fiber sample was coagulated in coagulation zone 5, washed in washing zone 6, and then micro-stretched in micro-stretching zone 8 to obtain preliminarily heat-treated fibers. During the coagulation and washing stages, the fiber bundle tension F1 was 818 cN. After washing and micro-stretching, the fiber bundle tension F2 was 551 cN. The moisture content of the fiber bundle during micro-stretching was 120%.

[0066] (3) The fiber undergoes preliminary heat treatment and is dried and heat stabilized in the drying and heat stabilization zone 9, and then wound to obtain the fiber. The drying and heat stabilization temperature is 100℃, and the fiber bundle tension F3 is 420cN during drying and heat stabilization.

[0067] Example 3

[0068] like Figure 1 and Figure 2 As shown, this embodiment adopts the following... Figure 1 and Figure 2 The equipment shown is used to prepare high-performance regenerated cellulose fibers suitable for industrial filament production; the preparation steps are as follows:

[0069] (1) First, the two types of pulp were mixed. After mixing, the molecular weight distribution was measured to be 2.2 and the average degree of polymerization was 900.

[0070] After mixing, cellulose pulp and NMMO aqueous solution were mixed to prepare a cellulose solution with a cellulose mass concentration of 11%; the shear viscosity of the cellulose solution was 1200 Pa·s (measured at 105℃ and a shear rate of 0.8 (1 / s)); the dynamic modulus intersection point G of the solution was... c The Pa is 518.

[0071] (2) The cellulose solution was extruded through the spinneret 1, and the length-to-diameter ratio of the spinneret plate of the spinneret 1 was 6. The spinneret was independently temperature controlled at 145℃. After extrusion, it was naturally cooled through a 5mm temperature buffer zone 3. Then it was subjected to high-ratio stretching in a 50mm multi-stage air bath, with a maximum stretching ratio of 9 times. The multi-stage air bath used a first-stage blowing device 2 for first-stage blowing at a temperature of 70℃ and a second-stage blowing device 4 for second-stage blowing at a temperature of 15℃. A nascent fiber sample with a specification of 1150dtex was prepared.

[0072] The nascent fiber sample was coagulated in coagulation zone 5, washed in washing zone 6, and then micro-stretched in micro-stretching zone 8 to obtain preliminarily heat-treated fibers. The fiber bundle tension F1 during the coagulation and washing stages was 3590 cN; the fiber bundle tension F2 during micro-stretching after washing was 2130 cN; and the fiber bundle moisture content during micro-stretching was 160%.

[0073] (3) The fiber undergoes preliminary heat treatment and is dried and heat stabilized in the drying and heat stabilization zone 9, and then wound to obtain the fiber. The drying and heat stabilization temperature is 170℃, and the fiber bundle tension F3 is 1360cN during drying and heat stabilization.

[0074] Example 4

[0075] like Figure 1 and Figure 2 As shown, this embodiment adopts the following... Figure 1 and Figure 2 The equipment shown is used to prepare high-performance regenerated cellulose fibers suitable for industrial filament production; the preparation steps are as follows:

[0076] (1) First, the two types of pulp were mixed. After mixing, the molecular weight distribution was measured to be 1.4 and the average degree of polymerization was 830.

[0077] After mixing, cellulose pulp and NMMO aqueous solution were mixed to prepare a cellulose solution with a cellulose mass concentration of 10%; the shear viscosity of the cellulose solution was 960 Pa·s (measured at 105℃ and a shear rate of 0.8 (1 / s)); the dynamic modulus intersection point G of the solution was... c The Pa is 978.

[0078] (2) The cellulose solution was extruded through the spinneret 1, and the length-to-diameter ratio of the spinneret plate of the spinneret 1 was 5. The spinneret was independently temperature controlled and the temperature was controlled at 120℃. After extrusion, it was naturally cooled through the 5mm temperature buffer 3. Then it entered the 50mm multi-stage air bath for high-ratio stretching, with a maximum stretching ratio of 12 times. The multi-stage air bath used the first-stage blowing device 2 for the first-stage blowing at a temperature of 60℃ and the second-stage blowing device 4 for the second-stage blowing at a temperature of 8℃. A nascent fiber sample with a specification of 860dtex was prepared.

[0079] The nascent fiber sample was coagulated in coagulation zone 5, washed in washing zone 6, and then micro-stretched in micro-stretching zone 8 to obtain preliminarily heat-treated fibers. The fiber bundle tension F1 during the coagulation and washing stages was 1660 cN; the fiber bundle tension F2 during micro-stretching after washing was 1034 cN; and the fiber bundle moisture content during micro-stretching was 150%.

[0080] (3) The fiber undergoes preliminary heat treatment and is dried and heat stabilized in the drying and heat stabilization zone 9, and then wound to obtain the fiber. The drying and heat stabilization temperature is 100℃, and the fiber bundle tension F3 is 940cN during drying and heat stabilization.

[0081] Example 5:

[0082] The fiber sample (1) in Example 1 was twisted using a two-in-one twisting method. Twisted yarns with twists of 20, 50, 80, and 150 corresponded to twisted fiber samples No. 1.1-1.4. The mechanical properties of the fiber samples were tested according to GB / T 14344-2008 Test Method for Tensile Properties of Chemical Fiber Filaments. The mechanical properties of the twisted fibers are shown in the table below.

[0083]

[0084] As shown in the table above, Example 4 obtained an industrial yarn product by twisting the fiber prepared in Example 1. In particular, the twist should not be too high, as excessive twist will cause a sharp decline in the mechanical properties of the fiber.

[0085] Comparative Example 1

[0086] The only difference between this comparative example and Example 1 is that the maximum stretching ratio is controlled at 4.7 times, the fiber bundle tension F1 during the fiber bundle coagulation and washing stage is 1120cN; the fiber bundle tension F2 during the micro-stretching after washing is 950cN; and the fiber bundle tension F3 during the drying and heat stabilization is 689cN, thus obtaining fiber sample (2).

[0087] Comparative Example 2

[0088] The only difference between this comparative example and Example 1 is that the maximum stretching ratio is controlled at 8.5 times, the fiber bundle tension F1 during the fiber bundle coagulation and washing stage is 1840cN; the fiber bundle tension F2 during the micro-stretching after washing is 1525cN; and the fiber bundle tension F3 during the drying and heat stabilization is 954cN, thus obtaining fiber sample (3).

[0089] The mechanical properties of the fiber samples prepared in Example 1, Comparative Example 1, and Comparative Example 2 were tested according to the test method in "GB / T 14344-2008 Test Method for Tensile Properties of Chemical Fiber Filaments". The results are shown in Table 1 below:

[0090] Table 1:

[0091]

[0092] As can be seen from the table above, the fiber prepared by the method of the present invention in Example 1 has good physical properties, with a breaking strength of 5.88 cN / dtex and an initial modulus of 135.33 cN / dtex. The fiber properties of samples (1)-(3) are positively correlated with the stretch ratio. Under the condition of meeting the tension requirements, the mechanical properties of the fiber prepared by the lower stretch ratio are relatively low.

[0093] Comparative Example 3

[0094] The only difference between this comparative example and Example 1 is that:

[0095] (1) A pulp with a molecular weight distribution of 1.2 and an average degree of polymerization of 860 was used; after mixing, the cellulose pulp was mixed with NMMO aqueous solution to prepare a cellulose solution with a cellulose mass concentration of 9%; the shear viscosity of the cellulose solution was 812 Pa·s (measured at 105℃ and a shear rate of 0.8 (1 / s)), and the dynamic modulus intersection point G of the solution was... c The Pa is 856.

[0096] (2) The maximum stretching ratio of the air bath high-stretch is 7.6 times. Fiber samples were obtained (4).

[0097] The mechanical properties of the fiber samples prepared in Example 1 and Comparative Example 3 were tested according to the test method in GB / T 14344-2008 "Test Method for Tensile Properties of Chemical Fiber Filaments". The results are shown in Table 2 below:

[0098] Table 2:

[0099]

[0100] Compared to Example 1, this comparative example did not meet the parameter requirements for high-stretch dope, with a reduced maximum stretch ratio, high fiber tension, poor spinning stability, and relatively low mechanical properties. The fiber properties of Comparative Example 3 compared to Example 1 are shown in Table 2. Using pulp with a smaller molecular weight distribution, the dope's stretchability was limited, making it difficult to improve fiber stretching and resulting in lower fiber mechanical properties.

[0101] Comparative Example 4

[0102] (1) Two types of pulp were mixed and the molecular weight distribution was measured to be 1.8 and the average degree of polymerization was 900 after mixing.

[0103] After mixing, cellulose pulp and NMMO aqueous solution were mixed to prepare a cellulose solution with a cellulose mass concentration of 7.5%; the shear viscosity of the cellulose solution was 538 Pa·s (measured at 105℃ and a shear rate of 0.8 (1 / s)); the dynamic modulus intersection point G of the solution was... c The Pa is 605.12.

[0104] (2) The cellulose solution was extruded through the spinneret 1, and the length-to-diameter ratio of the spinneret plate of the spinneret 1 was 5. The spinneret was independently temperature controlled at 120℃. After extrusion, it was naturally cooled through a 3mm temperature buffer 3. Then it entered a 40mm multi-stage air bath for high-ratio stretching, with a maximum stretching ratio of 13.7 times. The multi-stage air bath used a first-stage blowing device 2 for first-stage blowing at a temperature of 55℃ and a second-stage blowing device 4 for second-stage blowing at a temperature of 12℃. A nascent fiber sample with a specification of 1000dtex was prepared.

[0105] The nascent fiber sample enters the coagulation zone 5 for coagulation, enters the washing zone 6 for washing, and is then micro-stretched in the micro-stretching zone 8 to obtain preliminarily heat-treated fibers. During the coagulation and washing stages, the fiber bundle tension F1 is 2504 cN. After washing, during micro-stretching, the fiber bundle tension F2 is 1730 cN. During micro-stretching, the fiber bundle moisture content is 140% and the temperature is 125℃.

[0106] (3) The fiber underwent preliminary heat treatment and was dried and heat stabilized in the drying and heat stabilization zone 9. Then it was wound to obtain the fiber sample (1). The drying and heat stabilization temperature was 120℃, and the fiber bundle tension F3 was 1120cN during drying and heat stabilization.

[0107] In this comparative example, the fiber obtained by solidifying the fiber bundle, washing it, and treating it with a fiber bundle tension of 2504 cN is recorded as fiber sample (1); the fiber obtained by washing it and then slightly stretching it with a fiber bundle tension of 1730 cN is recorded as fiber sample (2); and the fiber obtained by drying and heat stabilizing it with a fiber bundle tension of 1120 cN is recorded as fiber sample (3).

[0108] The fiber orientation of samples (1)-(3) was tested by birefringence method and their mechanical strength was determined. The test method was in accordance with GB / T 14344-2008 Test Method for Tensile Properties of Chemical Fiber Filaments. The results are shown in Table 3 below.

[0109] Table 3:

[0110]

[0111] As can be seen from the table above, the fiber properties differ at different stages. As the process of gradual stretching and stabilization of orientation proceeds, the mechanical properties of the fiber increase.

[0112] Comparative Example 5:

[0113] The only difference between this comparative example and comparative example 4 is that the moisture content of the fiber bundle during micro-stretching is 110% and the temperature is 145℃; fiber sample (4) was obtained.

[0114] Comparative Example 6

[0115] The only difference between this comparative example and comparative example 4 is that: no temperature buffer zone is set, and only a single-stage air bath is used for high-ratio stretching, with a maximum stretching ratio of 7.2 times; fiber sample (5) is obtained.

[0116] Comparative Example 7

[0117] The only difference between this comparative example and comparative example 4 is that the aspect ratio of the spinneret of spinneret assembly 1 is 2.5; and fiber sample (6) is obtained.

[0118] The mechanical properties of the fiber samples prepared in Comparative Examples 4-7 were tested according to the test method in GB / T14344-2008 "Test Method for Tensile Properties of Chemical Fiber Filaments". The results are shown in Table 4 below:

[0119] Table 4:

[0120]

[0121] Compared with Comparative Example 4, Comparative Example 5 showed that the fiber with lower moisture content performed poorly in the secondary thermal stabilization orientation process, and the improvement in fiber performance was limited.

[0122] Comparative Example 6 uses a blowing method without a temperature buffer zone, and the blowing method is singular rather than multi-stage. The maximum stretch ratio is only 7.2 times, which is not enough to effectively increase the stretch ratio of the fiber and thus the mechanical properties of the fiber are difficult to improve.

[0123] Comparative Example 7 uses a spinneret with a smaller aspect ratio. Compared with Comparative Example 4, the fiber spun using a spinneret with a larger aspect ratio shows a significant improvement in performance.

[0124] Comparative Example 8:

[0125] (1) Using a pulp with an average degree of polymerization of 580, the molecular weight distribution was determined to be 1.4;

[0126] A cellulose solution with a cellulose mass concentration of 10% was prepared by mixing cellulose pulp with an NMMO aqueous solution; the shear viscosity of the cellulose solution was 560 Pa·s (measured at 105℃ and a shear rate of 0.8 (1 / s)); the dynamic modulus intersection point G of the solution was... c The Pa is 685.3.

[0127] (2) The cellulose solution was extruded through the spinneret 1, and the length-to-diameter ratio of the spinneret plate of the spinneret 1 was 5. The spinneret was independently temperature controlled and the temperature was controlled at 115℃. After extrusion, it was naturally cooled through the 5mm temperature buffer 3. Then it entered the 50mm multi-stage air bath for high-ratio stretching, with a maximum stretching ratio of 12.5 times. The multi-stage air bath used the first-stage blowing device 2 for the first-stage blowing at a temperature of 50℃ and the second-stage blowing device 4 for the second-stage blowing at a temperature of 14℃. A nascent fiber sample with a specification of 1000dtex was prepared.

[0128] The nascent fiber sample enters the coagulation zone 5 for coagulation, enters the washing zone 6 for washing, and is then micro-stretched in the micro-stretching zone 8 to obtain preliminarily heat-treated fibers. During the coagulation and washing stages, the fiber bundle tension F1 is 2300 cN. After washing, during micro-stretching, the fiber bundle tension F2 is 1790 cN. During micro-stretching, the fiber bundle moisture content is 150% and the temperature is 132℃.

[0129] (3) The fiber underwent preliminary heat treatment and was dried and heat stabilized in the drying and heat stabilization zone 9. Then it was wound to obtain the fiber sample (1). The drying and heat stabilization temperature was 100℃, and the fiber bundle tension F3 was 1100cN during drying and heat stabilization.

[0130] The mechanical properties of the fiber samples prepared in Comparative Example 8 were tested according to the test method in GB / T14344-2008 "Test Method for Tensile Properties of Chemical Fiber Filaments". The results are shown in Table 5 below:

[0131] Table 5:

[0132]

[0133] This comparative example uses pulp raw material with a lower degree of polymerization to prepare fibers using this preparation method. Although the obtained fiber samples have a high degree of orientation, the mechanical properties of the fibers are difficult to meet higher requirements. It can be seen that selecting pulp raw material with a high degree of polymerization is beneficial to improving the mechanical properties of regenerated cellulose.

Claims

1. A method for the production of high performance regenerated cellulose fibers useful for industrial threads, characterized by, The preparation steps comprise: (1) mixing one or more cellulose pulps, the average polymerization degree of the mixed pulps being greater than 800 and the molecular weight distribution index being 1.3-2.2; mixing and swelling the mixed pulps with an aqueous NMMO solution to prepare a cellulose solution; (2) extruding the cellulose solution through a spinning pack, passing through a temperature buffer zone, entering a multi-stage air bath, and performing high-drawing, and then performing coagulation, washing, and micro-drawing to obtain a preliminarily heat-treated fiber; (3) drying and heat-stabilizing the preliminarily heat-treated fiber, and winding the fiber to obtain the fiber product; In the step (2), the multi-stage air bath is formed by blowing air from the periphery to the center of the fiber bundle by using a blowing device, and the air temperature gradually decreases; the multi-stage air bath at least comprises a first-stage air bath and a second-stage air bath, the air temperature of the first-stage air bath is 30-70℃, and the air temperature of the second-stage air bath is 5-15℃; the blowing forms a semi-annular blowing air curtain. In the step (2), the fiber tow is condensed and washed, and the fiber tow tension F1 satisfies the formula: (0.75 x total fineness of the fiber tow / 1.08) 1.1 ≤ F1 ≤ (1.55 x total fineness of the fiber tow / 1.08) 1.1 wherein the unit of F1 is cN, and the unit of the total fineness of the fiber tow is dtex; In the step (2), when the fiber tows are micro-stretched after water washing, the fiber tow tension F2 satisfies the formula: (0.25 x total fineness of the tows) 1.25 ≤ F2 ≤ (0.42 x total fineness of the tows) 1.25 wherein the unit of F2 is cN and the unit of the total fineness of the tows is dtex. In the step (3), the fiber bundle tension F3 during the drying and heat-stabilizing is ≤1.2×total fineness of the fiber bundle, wherein the unit of F3 is cN, and the unit of the total fineness of the fiber bundle is dtex; the drying and heat-stabilizing temperature is 100-170℃; the drying and heat-stabilizing is performed in a stepwise drying manner, and the drying temperature is set in a gradient from high to low.

2. A process for the production of high performance regenerated cellulose fibers useful in industrial threads according to claim 1, characterized by, In the step (1), the shear viscosity of the cellulose solution is 80-1200 Pa.s, and the intersection modulus Gc of the dynamic rheological storage modulus and loss modulus of the cellulose solution is 400-1000 Pa.

3. The method for preparing high-performance regenerated cellulose fiber suitable for industrial filaments according to claim 1, characterized in that, In the step (2), after the cellulose solution is extruded through the spinning pack, the cellulose solution first enters a temperature buffer zone with a length of 0.2-15 mm for buffering, and then enters a multi-stage air bath with variable temperature for drawing.

4. The method for preparing high-performance regenerated cellulose fiber suitable for industrial filaments according to claim 3, characterized in that, The drawing multiple of the cellulose solution after extrusion is greater than or equal to 8, and the length-diameter ratio of the spinning plate of the spinning pack is greater than 4.

5. The method for preparing high-performance regenerated cellulose fiber suitable for industrial filaments according to claim 3, characterized in that, The residence time of the cellulose solution in the spinning pack is not less than 1 s.

6. The method for preparing high-performance regenerated cellulose fiber suitable for industrial filaments according to claim 3, characterized in that, The spinning pack is independently temperature-controlled, and the temperature is controlled to be 100-145℃.

7. A process for the production of high performance regenerated cellulose fibres useful in technical yarns according to any one of claims 1 to 6, characterised in that, In the step (2), the moisture content of the fiber bundle during the micro-drawing is 120%-160%.

8. The method for preparing high-performance regenerated cellulose fiber suitable for industrial filaments according to claim 7, characterized in that, The temperature during the micro-drawing is 120-150℃.

9. A high performance regenerated cellulose fibre useful in technical yarns, characterised in that, The fiber prepared by the preparation method of the above claim 1 has a fiber breaking strength greater than 5.5 cN / dtex and an initial modulus greater than 100 cN / dtex.

10. A high performance regenerated cellulose fibre useful for industrial threads according to claim 9, characterized by the fact that, The fiber can be processed into industrial yarns by twisting, and the twist of the fiber is ≤100.

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