A method for mass production of continuous and uniform liquid crystal elastomer melt-spun fibers

Abstract

The application discloses a method for preparing continuous and uniform liquid crystal elastomer melt-spun fibers on a large scale. The liquid crystal elastomer is prepared from a diacrylate reaction intermediate (RM82), 2,2'-(ethylenedioxy) dialkyl mercaptan (EDDT), toluene, dipropylamine (DPA), dibutyl tin dilaurate (DBTDL), butylated hydroxytoluene (BHT) and poly(cyclohexane diisocyanate) (Tris-Iso) as raw materials, and then melt spinning is performed. The method can prepare continuous and uniform liquid crystal elastomer melt-spun fibers on a large scale. The liquid crystal elastomer melt-spun fibers obtained by the method have good resilience, and the maximum elongation deformation under the action of external force can reach 3 times. After being placed in an oven at 85 DEG C for a certain period of time, it is found that the liquid crystal elastomer melt-spun fibers have certain flexibility, better resilience, good retraction performance and the maximum retraction speed is 1.33 cm / s.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of intelligent macromolecule and self-driven high-performance high-deformation intelligent fiber, and particularly relates to a method for large-scale preparation of continuous and uniform liquid crystal elastomer melt-spun fibers. BACKGROUND

[0002] Liquid crystal polymer is a polymer existing in a liquid crystal state under certain conditions, which has both the orientation order characteristic of liquid crystal and the performance of polymer. The polymer in a liquid crystal state has orientation and flowability, and this unique property makes it have important application potential and value.

[0003] Liquid crystal elastomer is developed on the basis of liquid crystal polymer, and has the properties of liquid crystal and elastomer, and has order and flowability. It is a new type of intelligent material, and has attracted widespread attention due to its soft elasticity and reversible shape change. And this unique material property makes it have irreplaceable application value.

[0004] Liquid crystal elastomer (LCEs) fiber has great and reversible deformation capacity, and can produce shape changes such as contraction, bending and wrinkling under external stimuli such as light and heat, and can be applied in the fields of mechanical actuators, optical devices, artificial organs, intelligent textiles, soft robots, sensors, drivers, artificial muscles and the like. However, limited by stimulation delay source and structure design, the current LCEs fiber has not achieved a large contraction ratio, and there is no technical approach to scale production and application of liquid crystal elastomer fiber.

[0005] Liquid crystal elastomer fibers can be pulled out from the polymer melt with tweezers. The average diameter of these fibers is usually between several to several hundred microns, and the shape change can be significantly observed between 20%-35%. The fiber range of several hundred nanometers to several nanometers can be prepared by electrospinning. Liquid crystal elastomer films can be prepared by using the electrospinning method. The film shows unusual mechanical properties, which depends on the length change and nonlinear stress-strain relationship. At present, the electrospinning method is mainly used to prepare liquid crystal elastomer films, rather than single fibers or multifilaments.

[0006] Using a microfluidic device, liquid crystal elastomer fibers with a fiber diameter of 20-50 μm can also be prepared. This wet spinning process can form single fibers, and the fibers have reversible contraction properties. However, the wet spinning speed is low, the number of holes of the spinneret is more than that of melt spinning, the process flow is complex, and the production cost is high.

[0007] Melt spinning is a chemical fiber spinning method in which a polymer is heated and melted, extruded through a spinneret, and cooled and solidified in air to form fibers. Melt spinning is characterized by high spinning speeds (1000-7000 m / min), the absence of solvents and precipitants, and their recovery and recycling systems, simple equipment, and a short process flow. It is an economical, convenient, and efficient fiber forming method, ideal for large-scale production of fiber materials.

[0008] In view of this, the present invention successfully obtains a method for preparing continuous and uniform liquid crystal elastomer melt-spun fibers on a large scale. Summary of the Invention

[0009] The object of the present invention is to provide a method for preparing continuous and uniform liquid crystal elastomer melt-spun fibers on a large scale, so as to prepare liquid crystal elastomer melt-spun fibers.

[0010] The technical solution adopted in the present invention is as follows:

[0011] A method for large-scale preparation of continuous and uniform liquid crystal elastomer melt-spun fibers comprises the following steps: 1) mixing a diacrylate reaction intermediate RM82, 2,2'-(ethylenedioxy)dialkylthiol EDDT, butylated hydroxytoluene BHT, dipropylamine DPA, and toluene, and stirring to form a uniform solution;

[0012] 2) adding dibutyltin dilaurate DBTDL to the homogeneous solution obtained in 1) and stirring uniformly;

[0013] 3) After the solution obtained in 2) is allowed to stand for a certain period of time, poly(cyclohexane diisocyanate) Tris-Iso and toluene are added and stirred evenly;

[0014] 4) pouring the solution obtained in 3) into a mold by solution injection molding and leaving it for a certain time to solidify;

[0015] 5) moving the mold prepared in 4) into an oven for heating and drying to completely evaporate the solvent;

[0016] 6) The liquid crystal elastomer is taken out from the mold and melt-spun to obtain liquid crystal elastomer melt-spun fibers.

[0017] In the above technical solution, further, the ratio of the amount of each raw material added in steps 1), 2), and 3) is: RM82: EDDT: BHT: DPA: toluene in step 1): DBTDL: Tris-Iso: toluene in step 3) is in the range of (140-150): (45-50): (2-3): 1: (85-90): (5-10): (27-40): (86-90).

[0018] Further, the time for placing in step 3) is at least 24 hours.

[0019] Further, the time for placing after injection molding in step 4) is 24-48 hours.

[0020] Further, the temperature for heating drying in step 5) is 70-85℃, and the time is 24-48 hours.

[0021] Further, the melting spinning in step 6) is performed by using a double screw extruder.

[0022] Further, the temperature for screw extrusion is 180-230℃.

[0023] Further, the speed for screw extrusion is 40-80r / min.

[0024] Further, the temperature for screw extrusion is preferably 220℃, and the speed for screw extrusion is preferably 40r / min; and a continuous and uniform large-scale liquid crystal elastomer melt-spun fiber can be prepared.

[0025] The liquid crystal elastomer is a polymer material which can exhibit elasticity in a liquid crystal state or an isotropic state after being moderately chemically or physically cross-linked from a liquid crystal polymer. The microstructure and order of liquid crystal molecules can be changed under external stimuli (force, heat, light, electricity, magnetism, etc.), resulting in different properties. The liquid crystal elastomer has shape memory function, can realize stable and repeated transformation of two shapes under the action of different temperatures of heating and cooling, and has large shape change range. Therefore, the temperature has a great influence on the performance of the liquid crystal elastomer, and the control of the spinning temperature is particularly important in the preparation of liquid crystal elastomer fibers. Because the fiber properties are different under different spinning temperatures, too high spinning temperature cannot obtain fibers, and the fiber will be in the form of liquid water. Too low spinning temperature will cause the liquid crystal elastomer to be unable to melt and be extruded. Unlike the melt spinning method of other thermoplastic polymers, the melt spinning of liquid crystal elastomer not only considers the influence of spinning temperature on fiber formation, but also considers the influence of temperature response on fiber properties. Because the liquid crystal elastomer has different response behaviors under the action of temperature, the fiber properties are affected. Therefore, when preparing melt-spun fibers of liquid crystal elastomer by using melt spinning technology, not only the spinning temperature, but also the response behavior of liquid crystal elastomer fibers under different temperatures should be considered. However, the melt spinning of other polymers such as polyester and nylon only needs to control the spinning temperature and range, and does not need to consider the response behavior of the fiber to temperature, because these polymers do not have temperature response effect. However, the liquid crystal elastomer polymer is sensitive to temperature and will have different response behaviors according to the temperature, so it is difficult to realize the melt spinning of liquid crystal elastomer to obtain continuous and uniform fibers with excellent properties.

[0026] The synthesis of the common liquid crystal elastomer is by using "one-bath one-step method", liquid crystal monomer, chain extender, crosslinking agent, solvent and the like are placed together to stir and react and polymerize to obtain the liquid crystal elastomer polymer, the liquid crystal elastomer obtained by the "one-bath one-step method" has small elastic deformation and poor mechanical property when melt spinning. Therefore, on the basis of repeated tests, the application proposes a "one-bath two-step method" of liquid crystal elastomer synthesis method, namely, the reaction raw materials are added in steps, the first step is to mix RM82, EDDT, BHT, DPA and toluene, stir uniformly to form a uniform solution, the second step is to add DBTDL, stir to form a uniform solution, so that the crosslinking agent is crosslinked to a better extent, the liquid crystal elastomer molecule forms a network topology structure inside through the crosslinking effect of the chain, realizes the effective combination of the entropy elasticity of the polymer network and the liquid crystal orientation, and has good elastic deformation, shape memory and external stimulus response effect.

[0027] The application has the following beneficial effects:

[0028] The application successfully obtains a method for large-scale preparation of continuous and uniform liquid crystal elastomer melt-spun fibers. The prepared fibers have good resilience, and for the fibers with an original length of 5 cm, the maximum elongation under external force can reach 15 cm, and the elongation deformation can reach 3 times. After being placed in an oven at 85 DEG C for 5 min, the fibers are found to have certain flexibility and better resilience, and have good elastic elongation and retraction performance. After being placed in an oven at 85 DEG C, the liquid crystal elastomer melt-spun fibers have good retraction performance after being elongated by external force, and the maximum retraction speed is 1.33 cm / s. BRIEF DESCRIPTION OF DRAWINGS

[0029] The application will be further described below in combination with the drawings:

[0030] Figure 1 The liquid crystal elastomer melt-spun fiber prepared in Example 1;

[0031] Figure 2 The liquid crystal elastomer melt-spun fiber prepared in Example 2;

[0032] Figure 3 The liquid crystal elastomer melt-spun fiber prepared in Example 3;

[0033] Figure 4 The liquid crystal elastomer melt-spun fiber prepared in Example 4;

[0034] Figure 5 The liquid crystal elastomer melt-spun fiber prepared in Example 5;

[0035] Figure 6The liquid crystal elastomer melt-spun fiber prepared in Example 6;

[0036] Figure 7 The liquid crystal elastomer melt-spun fiber prepared in Example 7;

[0037] Figure 8 The liquid crystal elastomer melt-spun fiber prepared in Example 8;

[0038] Figure 9 The liquid crystal elastomer melt-spun fiber prepared in Example 9;

[0039] Figure 10 The liquid crystal elastomer melt-spun fiber prepared in Example 10;

[0040] Figure 11 The liquid crystal elastomer melt-spun fiber prepared in Example 11;

[0041] Figure 12 The uniform and continuous liquid crystal elastomer melt-spun fibers prepared on a large scale in Example 9;

[0042] Figure 13 Comparison of the liquid crystal elastomer melt-spun fibers prepared in Example 9 after being placed at room temperature and after being taken out of an oven at 85°C for 5 minutes;

[0043] Figure 14 The liquid crystal elastomer melt-spun fiber prepared in Example 9 is placed in an oven at 85° C. for 3 seconds and then taken out;

[0044] Figure 15 The liquid crystal elastomer melt-spun fiber prepared in Example 9 was placed in an oven at 85° C. for 3 seconds and then taken out and spontaneously shrunk along the fiber axis. DETAILED DESCRIPTION

[0045] The technical solution of the present invention is further described below with reference to the accompanying drawings and specific embodiments:

[0046] In the following examples, the diacrylate reaction intermediate (RM82), 2,2'-(ethylenedioxy)dialkylthiol (2,2'-(Ethylenedioxy)diethanethiol, EDDT), toluene as solvent, dipropylamine (DPA), dibutyltin dilaurate (DBTDL), butylated hydroxytoluene (BHT) as catalyst, and poly(cyclohexane diisocyanate) ((2,4,6-Trioxotriazine-1,3,5(2H,4H,6H)-triyl)tris(chexamethylene)isocyanate, Tris-Iso) as crosslinker are all commercially available. The twin-screw extruder used is also commercially available.

[0047] The liquid crystal elastomer is synthesized by "one bath two-step method", the first step is to mix RM82, EDDT, BHT, DPA, toluene, stir evenly, form a uniform solution. The second step is to add DBTDL, stir, form a uniform solution, after 24h. Add crosslinking agent Tris-Iso and toluene again, stir evenly, form a uniform solution, solution injection molding, 24h curing, heating in 85℃ oven for 24h, remove residual solvent, form a liquid crystal elastomer. The mass ratio of RM82:EDDT:BHT:DPA:toluene added first:DBTDL:Tris-Iso:toluene added later can be (140-150):(45-50):(2-3):1:(85-90):(5-10):(27-40):(86-90).

[0048] Example 1: The above synthesized liquid crystal elastomer is spun by double screw extrusion, the screw extrusion temperature used is 230℃, the extrusion speed is 50r / min.

[0049] Example 2: The above synthesized liquid crystal elastomer is spun by double screw extrusion, the screw extrusion temperature used is 220℃, the extrusion speed is 50r / min.

[0050] Example 3: The above synthesized liquid crystal elastomer is spun by double screw extrusion, the screw extrusion temperature used is 210℃, the extrusion speed is 50r / min.

[0051] Example 4: The above synthesized liquid crystal elastomer is spun by double screw extrusion, the screw extrusion temperature used is 200℃, the extrusion speed is 50r / min.

[0052] Example 5: The above synthesized liquid crystal elastomer is spun by double screw extrusion, the screw extrusion temperature used is 190℃, the extrusion speed is 50r / min.

[0053] Example 6: The above synthesized liquid crystal elastomer is spun by double screw extrusion, the screw extrusion temperature used is 180℃, the extrusion speed is 50r / min.

[0054] Example 7: The above synthesized liquid crystal elastomer is spun by double screw extrusion, the screw extrusion temperature used is 220℃, the extrusion speed is 80r / min.

[0055] Example 8: The above synthesized liquid crystal elastomer is spun by double screw extrusion, the screw extrusion temperature used is 220℃, the extrusion speed is 60r / min.

[0056] Example 9: The liquid crystal elastomer synthesized above is spun by double screw extrusion, the screw extrusion temperature used is 220°C, and the extrusion speed is 40r / min.

[0057] Example 10: The liquid crystal elastomer synthesized above is spun by double screw extrusion, the screw extrusion temperature used is 220°C, and the extrusion speed is 20r / min.

[0058] Example 11: The liquid crystal elastomer synthesized above is spun by double screw extrusion, the screw extrusion temperature used is 220°C, and the extrusion speed is 40r / min, and during the extrusion process, the ultra-fine melt-spun fiber is formed by manual drawing.

[0059] The fiber forming effects of the above examples are shown in Table 1 and Table 2, Table 1 is the fiber forming effect of different extrusion temperatures, and Table 2 is the fiber forming effect of different extrusion speeds; the fibers prepared in each example are specifically shown in Figures 1-15 It can be seen from the hand-pulling verification and response test evaluation that the continuous and uniform liquid crystal elastomer melt-spun fiber can be successfully prepared on a large scale by using the optimized preparation method of the application, and the obtained fiber has excellent elongation and rebound performance.

[0060] Table 1 Fiber forming effect of different extrusion temperatures

[0061]

[0062] Table 2 Fiber forming effect of different extrusion speeds

[0063]

Claims

1. A method for mass production of continuous and uniform liquid crystal elastomer melt-spun fibers, characterized by: Comprising the following steps: 1) mixing diacrylate reaction intermediate RM82, 2,2'-(ethylenedioxy)diethanol thiol EDDT, butylated hydroxytoluene BHT, dipropylamine DPA and toluene, stirring uniformly to form a uniform solution; 2) adding dibutyltin dilaurate DBTDL to the uniform solution obtained in 1), stirring uniformly; 3) placing the solution obtained in 2) for a certain period of time and then adding poly(cyclohexane diisocyanate) Tris-Iso and toluene, stirring uniformly; 4) pouring the solution obtained in 3) into a mold by solution casting, placing for a certain period of time for curing; 5) moving the mold of 4) to an oven for heating and drying, so that the solvent is completely volatilized; 6) taking the liquid crystal elastomer out of the mold, and melt spinning to obtain a liquid crystal elastomer melt spun fiber; wherein the melt spinning is performed by a double screw melt extrusion method, the temperature range of the screw extrusion is 190-220°C, and the screw extrusion speed is 40-50 r / min.

2. The method of large-scale production of continuous and uniform liquid crystalline elastomer melt-spun fibers according to claim 1, characterized in that: The proportions of the amounts of each raw material added in steps 1), 2) and 3) are as follows: The mass ratio of RM82:EDDT:BHT:DPA:toluene in step 1):DBTDL:Tris-Iso:toluene in step 3) is (140-150):(45-50):(2-3):1:(85-90):(5-10):(27-40):(86-90).

3. The method of large-scale production of continuous and uniform liquid crystalline elastomer melt-spun fibers according to claim 1, characterized in that: The certain period of time in step 3) is at least 24 h.

4. The method of large-scale production of continuous and uniform liquid crystalline elastomer melt-spun fibers according to claim 1, characterized in that: The curing after casting in step 4) is performed for 24-48 h.

5. The method of large-scale production of continuous and uniform liquid crystalline elastomer melt-spun fibers according to claim 1, characterized in that: The temperature for heating and drying in step 5) is 70-85°C, and the time is 24-48 h.

6. The method of large-scale production of continuous and uniform liquid crystalline elastomer melt-spun fibers according to claim 1, characterized in that: The screw extrusion temperature is 220°C, and the extrusion speed is 40 r / min.

7. A liquid crystal elastomer melt-spun fiber, characterized by, The method is prepared by using any one of claims 1-6.

Images