High-power drafting melt spinning liquid crystal filament fiber and preparation method thereof

Abstract

The preparation method comprises the following steps: drying a liquid crystal elastomer (LCE) polymer in a vacuum oven, carrying out melt extrusion through double screws, and drafting by using continuous drafting and winding equipment capable of accurately controlling the rotating speed, so as to obtain the LCE melt-spun liquid crystal filament fiber through a one-step continuous process. The whole melt extrusion is carried out in a fuming cupboard, so that the residual solvent in the melt extrusion process can be quickly volatilized, the residual chemical solvent is not loaded on the filament fiber, and the LCE melt spinning liquid crystal filament fiber under the condition of different draft multiples is obtained. Under the condition of high-power drafting, the network structure of the LCE polymer is fully oriented and arranged, and is fully drafted, the diameter is obviously thinned, the mechanical property is obviously improved, the LCE polymer is not easy to break, and the elastic elongation and the elastic resilience are obviously changed. The method has remarkable performance advantages and application potential in the fields of intelligent wearing textiles, flexible fiber textile materials and environmental response textile fabrics.

Description

Technical Field

[0001] The present invention belongs to the field of chemical fibers of liquid crystal polymer melt-spun fibers, and relates to highly drawn melt-spun liquid crystal filament fibers and a preparation method thereof. Background Art

[0002] Liquid crystals are the general term for orientation-ordered fluids. Such fluids are between anisotropic crystalline states and isotropic liquid states, and are a kind of intelligent soft material, with the characteristics of the fluidity of a liquid and the orderliness of a crystal. The unique properties of liquid crystal materials have application values that cannot be replaced by other materials, and can be applied in display technology, high-strength materials, optical fields, medical fields, and electronic fields. Liquid crystal polymers (LCPs) refer to polymers that can exist in a liquid crystal state under certain conditions, and have both the advantages of the orientation orderliness of low-molecular liquid crystals and the advantages of high-molecular polymers. LCPs have the characteristics of high strength and high modulus, and can be used as structural materials in military, mechanical, and aerospace fields; the excellent properties of LCPs in aspects such as light, electricity, and magnetism can be used as functional materials in information storage and image display fields. Due to the superior properties of LCPs, the application scope of LCPs is continuously diversified, the product types are increasing, and the application fields are also increasing.

[0003] Liquid crystal elastomers (LCEs) are an emerging branch in the research field of liquid crystal polymers in the past decade or so. LCEs have the dual characteristics of liquid crystals and elastomers, and have both orderliness, fluidity, and elasticity. The most prominent feature of LCEs is their stress orientation characteristics, elastic deformation and recovery, temperature responsiveness, and environmental responsiveness. LCEs contract along the orientation direction when heated and stretch along the orientation direction when cooled, and have reversible shape change performance. The unique properties of LCEs determine that it has broad application prospects in many other fields, can convert a mechanical force field into an optoelectronic signal under certain conditions, and is applied in the fields of optical switches or waveguides. In terms of artificial intelligence, by changing the reversible curling and stretching performance of LCEs in different directions, it can be applied in high-speed controllers. Currently, LCEs are developing towards the direction of multi-functionality, life-orientation, and intelligence, and are applied in many fields such as smart wearables, smart-responsive textiles, artificial muscles, soft robots, aerospace, biomedical engineering, electronics, and optics.

[0004] Due to the excellent orientation, piezoelectricity, ferroelectricity, soft elasticity, optics and other properties of LCEs, it has become a very popular field in the research of intelligent materials in various countries in the world, and has also become the forefront field of soft intelligent textiles. Through extensive technical research at home and abroad, it is found that there is currently no relevant report on the large-scale preparation technology of highly oriented and high-mechanical-property LCE melt-spun fibers.

[0005] The present invention provides a method for preparing highly drawn melt-spun liquid crystal long filament fibers. Using LCE as a raw material, melt-spun liquid crystal long filament fibers are prepared under different draw ratio conditions, and the fiber morphology, thermal responsiveness, and mechanical properties are studied. By optimizing the preparation technology of LCE melt-spun filaments and regulating the properties, the fibers have good morphology, elastic deformation and recovery, response and deformation recovery at different temperatures, and are expected to be widely used in the fields of soft textile materials, smart wearables, and environment-responsive textiles. Summary of the Invention

[0006] In view of the deficiencies of the prior art, the present invention provides highly drawn melt-spun liquid crystal long filament fibers and a method for preparing the same. Using a liquid crystal elastomer polymer, melt spinning is carried out to obtain liquid crystal elastomer melt-spun long filament fibers under different draw ratios. The technical solution adopted by the present invention is as follows:

[0007] A method for preparing highly drawn melt-spun liquid crystal long filament fibers, comprising the following steps:

[0008] 1) The LCE polymer is melt-extruded through a twin-screw extruder, and a suitable melt-extrusion temperature is controlled so that the LCE polymer is completely melted and can be smoothly extruded;

[0009] 2) The LCE as-spun fibers are successively passed through a drawing and winding device to obtain long filament fibers under different draw ratios;

[0010] 3) Under the condition that the extrusion speed V1 is constant, by increasing the winding speed V2, LCE long filament fibers with a high draw ratio can be obtained.

[0011] Furthermore, before melt-extrusion, the LCE polymer needs to be dried in a vacuum oven at 85 °C for 24 - 48 h to obtain a completely dry polymer, preventing moisture from affecting the fiber morphology and fiber quality during the melt spinning process.

[0012] Furthermore, the LCE polymer is melt-extruded through a twin-screw extruder, the extrusion temperature is 170 - 180 °C, and the melt-extrusion speed is 70 rpm.

[0013] Furthermore, the as-spun fibers of the LCE polymer need to be drawn by a drawing and winding device with continuously and precisely controllable rotation speed, and the winding speed is 70 - 840 rpm.

[0014] Furthermore, the LCE polymer melt-spun long filament fibers are obtained through a one-step continuous process of twin-screw melt extrusion and continuous drawing and winding equipment.

[0015] Furthermore, the melt-extrusion of the LCE polymer is carried out in a fume hood, which can ensure the rapid volatilization of residual solvents during the melt-extrusion process and prevent the long filament fibers from being loaded with residual chemical solvents.

[0016] Furthermore, the LCE melt-spun filament fibers are directly subjected to temperature response, mechanical property, and tensile resilience tests.

[0017] The high-draft melt-spun liquid crystal filament fibers are prepared by the above method.

[0018] The calculation formula for the draft ratio of the liquid crystal elastomer melt-spun fiber is: draft ratio = winding speed V2 / extrusion speed V1. Under the condition of controlling the extrusion speed V1, different draft ratios of the liquid crystal elastomer melt-spun fiber can be obtained by controlling different winding speeds. The draft ratio of conventional melt-spun fibers ≤ 3 is ordinary drafting, which is feasible for spinning general chemical fibers such as polyester and nylon, and fibers with a certain degree of orientation, certain mechanical properties, uniformity, and stability can be obtained. However, for liquid crystal elastomer polymers, ordinary drafting at low draft ratios (≤ 3) cannot achieve the anisotropic arrangement of the network structure of the liquid crystal elastomer polymer, cannot achieve effective orientation arrangement, the mechanical properties of the prepared melt-spun fibers are poor, and they are easy to break, which does not meet the usage requirements, and it is even more impossible to carry out fabric processing. Due to the poor mechanical properties of the fibers, the processing of woven fabrics and knitted fabrics cannot be carried out, which limits the application of LCE filament fibers. Therefore, after many previous experiments, by controlling different winding speeds and under the condition of increasing the winding speed, high-draft LCE melt-spun filament fibers can be obtained, the orientation can be improved, the mechanical properties can be improved, the fibers meet the processing requirements of textiles (woven fabrics, knitted fabrics), and then subsequent fabric applications can be carried out.

[0019] The beneficial effects of the present invention are as follows:

[0020] 1) In the present invention, the LCE polymer melt-spun filament fibers undergo a process of drying in a vacuum oven, twin-screw melt extrusion, exhaust in a fume hood, continuous drafting and winding, and performance testing of filament fibers.

[0021] 2) The performance change rules of the LCE melt-spun filament fibers under different draft ratios are provided, providing a technical solution for the optimized preparation of the LCE melt-spun filament fibers.

[0022] 3) Under the condition of low draft ratio (≤ 3), the diameter of the LCE melt-spun filament fibers is relatively thick and the mechanical properties are poor because the network structure of the LCE polymer has not been fully oriented and stretched, which does not meet the performance requirements for use.

[0023] 4) During the process of changing the draw ratio from low ( > 3) to high ( < 10), the mechanical properties of the LCE melt - spun long - filament fibers are gradually improved and continuously enhanced. Since the network structure of the LCE polymer is not fully oriented and not fully drawn at this time, although the mechanical properties are increasing, they still do not meet the usage requirements. During the manual drawing process, there are still cases where fibers break, and the influence law of the draw ratio on the mechanical properties of the LCE melt - spun long - filament fibers is continuously optimized.

[0024] 5) Under high - draw ratio (≥10), continuous and uniform LCE melt - spun long - filament fibers can be obtained. The maximum mechanical properties of its single filament are 2.94 cN / tex, and the maximum elongation at break is 750%. It has high - strength and high - elasticity mechanical properties. At room temperature, the high elasticity of this LCE melt - spun long - filament fiber is close to that of spandex fibers, and it has the recoverability of elastic deformation. It is a flexible fiber with certain mechanical properties.

[0025] 6) The LCE melt - spun long - filament fibers can quickly undergo temperature - responsive deformation at 85°C. The temperature - response time is 1 - 2 s, and the entire duration of the temperature response is 5 - 10 s. It has the performance characteristics of rapid temperature response and long - lasting deformation.

[0026] 7) The deformation rate at a fixed temperature (85°C) is 10 - 20%, showing the characteristic of small deformation at a certain temperature. This small deformation meets the wearing requirements of environmentally responsive textiles. If there is large deformation at a fixed temperature, it cannot meet the wearing requirements of textiles and cannot be used.

[0027] 8) At a fixed temperature (85°C), the deformation of the LCE melt - spun long - filament fibers is irregular, showing two - way changes in the axial and transverse directions of the fibers. It is not a two - dimensional planar deformation but a three - dimensional up - and - down undulating deformation. That is, at a fixed temperature, the LCE melt - spun long - filament fibers show the characteristics of three - dimensional random response deformation. Description of the Drawings

[0028] Figure 1 is the high - draw - ratio process of the melt - spun fiber of the liquid - crystal elastomer polymer in Example 1 of the present invention

[0029] Figure 2 is the liquid - crystal elastomer polymer in Example 1 of the present invention

[0030] Figure 3 is the high - draw - ratio melt - spinning equipment of the liquid - crystal elastomer polymer in Example 1 of the present invention

[0031] Figure 4 is the 1 - fold - drawn long - filament fiber of the liquid - crystal elastomer polymer in Example 1 of the present invention

[0032] Figure 5 The filament fiber is a 3-fold drawn one of the liquid crystal elastomer polymer in Example 2 of the present invention

[0033] Figure 6 The filament fiber is a 5-fold drawn one of the liquid crystal elastomer polymer in Example 3 of the present invention

[0034] Figure 7 The filament fiber is a 7-fold drawn one of the liquid crystal elastomer polymer in Example 4 of the present invention

[0035] Figure 8 The filament fiber is a 9-fold drawn one of the liquid crystal elastomer polymer in Example 5 of the present invention

[0036] Figure 9 The single filament fiber is a 10-fold drawn one of the liquid crystal elastomer polymer in Example 6 of the present invention

[0037] Figure 10 The wound filament fiber is a 10-fold drawn one of the liquid crystal elastomer polymer in Example 6 of the present invention

[0038] Figure 11 The wound filament fiber is a 10-fold drawn one of the liquid crystal elastomer polymer in Example 6 of the present invention

[0039] Figure 12 The wound filament fiber is a 12-fold drawn one of the liquid crystal elastomer polymer in Example 7 of the present invention Detailed implementation manners

[0040] The technical method of the present invention will be further described below in conjunction with the accompanying drawings and specific embodiments

[0041] Example 1

[0042] As shown in Figures 1-4 The preparation method of the highly drawn melt-spun liquid crystal filament fiber includes the following steps: drying the LCE polymer in a vacuum oven at 85°C for 24 hours; performing melt extrusion through a twin-screw extruder, with the extrusion temperature being 170 - 180°C and the melt extrusion speed being 70 rpm; performing drawing using a continuous drawing and winding device, with the winding speed being 70 rpm; the LCE melt-spun liquid crystal filament fiber is obtained through a one-step continuous process of twin-screw melt extrusion and continuous drawing and winding device; the melt extrusion is carried out in a fume hood, which can ensure the rapid volatilization of residual solvents during the melt extrusion process and prevent the long filament fiber from being loaded with residual chemical solvents, obtaining an LCE melt-spun liquid crystal filament fiber with a draw ratio of 1 fold. At a low draw ratio, the network structure of the LCE polymer is not fully oriented and arranged, nor is it fully drawn, with a relatively thick diameter and poor mechanical properties, because it does not meet the performance requirements for use

[0043] Example 2

[0044] As shown in Figures 1-3 , Figures 5, the preparation method of the high-draft melt-spun liquid crystal filament fiber comprises the following steps: drying the LCE polymer in a vacuum oven at 85 °C for 48 h; performing melt extrusion through a twin-screw extruder, with the extrusion temperature being 170-180 °C and the melt extrusion speed being 70 rpm; performing drafting using a continuous drafting and winding device, with the winding speed being 210 rpm; the LCE melt-spun liquid crystal filament fiber is obtained through a one-step continuous process of twin-screw melt extrusion and a continuous drafting and winding device; the melt extrusion is carried out in a fume hood, which can ensure the rapid volatilization of the residual solvent during the melt extrusion process, and there will be no residual chemical solvent loaded on the filament fiber, obtaining an LCE melt-spun liquid crystal filament fiber with a draft ratio of 3 times. At a low draft ratio, the network structure of the LCE polymer is not fully oriented and arranged, nor is it fully drafted, with a relatively thick diameter and poor mechanical properties, because it does not meet the performance requirements for use.

[0045] Example 3

[0046] As shown in Figures 1-3 , Figures 6, the preparation method of the high-draft melt-spun liquid crystal filament fiber comprises the following steps: drying the LCE polymer in a vacuum oven at 85 °C for 48 h; performing melt extrusion through a twin-screw extruder, with the extrusion temperature being 170-180 °C and the melt extrusion speed being 70 rpm; performing drafting using a continuous drafting and winding device, with the winding speed being 350 rpm; the LCE melt-spun liquid crystal filament fiber is obtained through a one-step continuous process of twin-screw melt extrusion and a continuous drafting and winding device; the melt extrusion is carried out in a fume hood, which can ensure the rapid volatilization of the residual solvent during the melt extrusion process, and there will be no residual chemical solvent loaded on the filament fiber, obtaining an LCE melt-spun liquid crystal filament fiber with a draft ratio of 5 times. At a low draft ratio, the network structure of the LCE polymer is not fully oriented and arranged, nor is it fully drafted, with a relatively thick diameter and poor mechanical properties, not meeting the performance requirements for use.

[0047] Example 4

[0048] As shown in Figures 1-3, as shown in Figures 7, the preparation method of high-draft melt-spun liquid crystal filament fiber includes the following steps: drying the LCE polymer in a vacuum oven at 85 °C for 48 h; performing melt extrusion through a twin-screw extruder, with the extrusion temperature being 170 - 180 °C and the melt extrusion speed being 70 rpm; performing drafting using a continuous drafting and winding device, with the winding speed being 490 rpm; the LCE melt-spun liquid crystal filament fiber is obtained through a one-step continuous process of twin-screw melt extrusion and continuous drafting and winding device; the melt extrusion is carried out in a fume hood, which can ensure the rapid volatilization of residual solvents during the melt extrusion process, and there will be no residual chemical solvents loaded on the filament fiber, obtaining an LCE melt-spun liquid crystal filament fiber with a drafting multiple of 7 times. The network structure of the LCE polymer is not fully oriented and aligned, nor is it fully drafted, the diameter gradually becomes thinner, the mechanical properties are poor, it is easy to break, and the elastic elongation and elastic recovery are not significant.

[0049] Example 5

[0050] As Figures 1-3 , as shown in Figures 8, the preparation method of high-draft melt-spun liquid crystal filament fiber includes the following steps: drying the LCE polymer in a vacuum oven at 85 °C for 24 h; performing melt extrusion through a twin-screw extruder, with the extrusion temperature being 170 - 180 °C and the melt extrusion speed being 70 rpm; performing drafting using a continuous drafting and winding device, with the winding speed being 630 rpm; the LCE melt-spun liquid crystal filament fiber is obtained through a one-step continuous process of twin-screw melt extrusion and continuous drafting and winding device; the melt extrusion is carried out in a fume hood, which can ensure the rapid volatilization of residual solvents during the melt extrusion process, and there will be no residual chemical solvents loaded on the filament fiber, obtaining an LCE melt-spun liquid crystal filament fiber with a drafting multiple of 9 times. The network structure of the LCE polymer is not fully oriented and aligned, nor is it fully drafted, the diameter gradually becomes thinner, although the mechanical properties are improved to a certain extent, it is still easy to break, and the elastic elongation and elastic recovery are not significant.

[0051] Example 6

[0052] As Figures 1-3, as shown in FIGS. 9-11, a method for preparing highly drawn melt-spun liquid crystal filament fibers includes the following steps: drying the LCE polymer in a vacuum oven at 85 °C for 24 h; performing melt extrusion through a twin-screw extruder, with the extrusion temperature being 170-180 °C and the melt extrusion speed being 70 rpm; performing drawing using a continuous drawing and winding device, with the winding speed being 700 rpm; the LCE melt-spun liquid crystal filament fibers are obtained through a one-step continuous process of twin-screw melt extrusion and a continuous drawing and winding device; the melt extrusion is carried out in a fume hood, which can ensure the rapid volatilization of residual solvents during the melt extrusion process and prevent the long filament fibers from being loaded with residual chemical solvents, obtaining LCE melt-spun liquid crystal filament fibers with a draw ratio of 10 times. Under the condition of high draw ratio, the network structure of the LCE polymer is fully oriented and arranged, achieving sufficient drawing, with a significantly reduced diameter, obvious improvement in mechanical properties, not easily broken, and significant changes in elastic elongation and elastic recovery. Under the condition of high draw ratio, continuous and uniform LCE melt-spun filament fibers can be obtained, with the maximum mechanical property of a single filament being 2.94 cN / tex and the maximum elongation at break being 750%, having high-strength and high-elastic mechanical properties. At room temperature, the high elasticity of the LCE melt-spun filament fibers is close to that of spandex fibers, and it has the recovery of elastic deformation, being a flexible fiber with certain mechanical properties. The LCE melt-spun filament fibers can quickly undergo temperature-responsive deformation at 85 °C, with the temperature-responsive time being 1-2 s and the entire temperature-responsive duration being 5-10 s, having the performance characteristics of rapid temperature response and long deformation duration. The deformation rate at a fixed temperature (85 °C) is 10-20%, having the characteristics of small deformation at a certain temperature, and this small deformation meets the wearing requirements of environment-responsive textiles. At a fixed temperature (85 °C), the deformation of the LCE melt-spun filament fibers is irregular, showing two-way changes in the axial and transverse directions of the fiber, not a two-dimensional planar deformation, but an up-and-down undulating deformation in three-dimensional space. That is, the LCE melt-spun filament fibers exhibit the characteristics of three-dimensional random response deformation at a fixed temperature.

[0053] Example 7

[0054] As Figures 1-3As shown in 12, the preparation method of high-drawing melt-spun liquid crystal filament fiber comprises the following steps: drying the LCE polymer in a vacuum oven at 85°C for 24 hours; melt-extruding through a twin screw, the extrusion temperature is 170-180°C, and the melt extrusion speed is 70rpm; drawing by a continuous drawing and winding device, the winding speed is 840rpm; the LCE melt-spun liquid crystal filament fiber is obtained by a one-step continuous process of twin screw melt extrusion and continuous drawing and winding equipment; the melt extrusion is carried out in a fume hood, which can ensure that the residual solvent in the melt extrusion process evaporates quickly, and the filament fiber will not be loaded with residual chemical solvents, and the LCE melt-spun liquid crystal filament fiber with a drawing multiple of 12 times is obtained. Under high-drawing conditions, the network structure of the LCE polymer is fully oriented and arranged, fully drawn, the diameter is significantly thinned, the mechanical properties are significantly improved, it is not easy to break, and the elastic elongation and elastic recovery change significantly. Under high-multiple drafting conditions, continuous and uniform LCE melt-spun filament fibers can be obtained, and the maximum mechanical properties of the single fiber are 2.94cN / tex, and the maximum elongation at break is 750%, with high strength and high elasticity. Under normal temperature, the high elasticity of the LCE melt-spun filament fiber is close to that of spandex fiber, and it has the recovery of elastic deformation, and is a flexible fiber with certain mechanical properties. LCE melt-spun filament fibers can quickly respond to temperature deformation at 85℃, and the temperature response time is 1-2s, and the duration of the entire temperature response is 5-10s. It has the performance characteristics of rapid temperature response and long deformation duration. The deformation rate at a fixed temperature (85℃) is 10-20%, and it has a small deformation characteristic at a certain temperature. This small deformation meets the wearing requirements of environmentally responsive textiles. At a fixed temperature (85℃), the deformation of LCE melt-spun filament fibers is irregular, showing the characteristics of bidirectional changes in the axial and lateral directions of the fiber. It is not a two-dimensional deformation of the plane, but an up-and-down deformation in three-dimensional space. That is, LCE melt-spun filament fibers exhibit the characteristics of three-dimensional random response deformation at a fixed temperature.

Claims

1. A method for preparing high-drawn melt-spun liquid crystal filament fibers, characterized in that: It is prepared by a one-step continuous process of twin-screw melt extrusion and continuous drawing and winding, comprising the following steps: 1) After the LCE polymer is completely dried, it is melt-extruded through a twin-screw extruder, and the melt-extrusion temperature is controlled so that the LCE polymer is completely melted and can be extruded smoothly; 2) passing the extruded LCE primary fibers through a drawing and winding device capable of accurately controlling the rotation speed to obtain liquid crystal filament fibers at different drawing multiples; 3) When the extrusion speed V1 is constant, the winding speed V2 is increased to obtain LCE liquid crystal filament fibers with a high drawing multiple.

2. The method for preparing high-drawn melt-spun liquid crystal filament fibers according to claim 1, characterized in that: The LCE polymer needs to be dried in a vacuum oven at 85° C. for 24-48 hours before melt extrusion to obtain a completely dry polymer to prevent moisture from affecting the fiber morphology and fiber quality during the melt spinning process.

3. The method for preparing high-drawn melt-spun liquid crystal filament fibers according to claim 1, characterized in that: The LCE polymer is melt-extruded by a twin-screw extruder at a temperature of 170-180° C. and a melt-extrusion speed of 70 rpm.

4. The method for preparing high-drawn melt-spun liquid crystal filament fibers according to claim 1, characterized in that: The nascent fibers of the LCE polymer need to be drawn through a continuous, precisely controllable speed drawing and winding device, and the receiving and winding speed is controlled to be 70-840 rpm.

5. The method for preparing high-drawn melt-spun liquid crystal filament fibers according to claim 1, characterized in that: The melt extrusion and drawing of the LCE polymer are carried out in a fume hood to ensure that the residual solvent in the melt extrusion process evaporates quickly and no residual chemical solvent is loaded on the filament fiber.

6. The method for preparing high-drawn melt-spun liquid crystal filament fibers according to claim 1, characterized in that: The ratio of the winding speed V2 to the extrusion speed V1 should be greater than 3.

7. The method for preparing high-drawn melt-spun liquid crystal filament fibers according to claim 1, characterized in that: The ratio of the winding speed V2 to the extrusion speed V1 should be no less than 10.

8. High-drawn melt-spun liquid crystal filament fiber, characterized in that: Prepared by the method according to any one of claims 1 to 7.

9. The high-drawn melt-spun liquid crystal filament fiber according to claim 8, characterized in that: The fiber produced under the condition that the ratio of the winding speed V2 to the extrusion speed V1 is not less than 10 has a maximum single-filament mechanical property of 2.94 cN / tex, a maximum elongation at break of 750%, and exhibits three-dimensional spatial random response deformation at a fixed temperature.

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