Bio-based polymer melt-blended functional fiber and preparation method thereof

Abstract

The present invention discloses a bio-based polymer melt-blended functional fiber and a preparation method thereof, wherein a liquid crystal elastomer is added to the melt spinning process of the bio-based polymer polylactic acid fiber for blending and melt spinning to improve the physical and mechanical properties of the fiber and form a functional fiber. Specifically, polylactic acid chips are mixed with a liquid crystal elastomer, and then the liquid crystal-polylactic acid blended fiber is prepared according to a melt spinning process. By regulating specific process parameters, liquid crystal-polylactic acid fibers can be successfully spun, and the prepared liquid crystal-polylactic acid blended fibers have excellent physical and mechanical properties, with an average fiber strength of up to 2.54 cN / dtex and an average elongation of 110.24%; at the same time, they also have the special properties of liquid crystal elastomers. The present invention can also directly produce liquid-dyed fibers with excellent performance, with an average fiber elongation of 196.02% and obvious temperature response characteristics. The method of the present invention is simple, can be mass-produced, and is a degradable and environmentally friendly fiber with extremely high application prospects.

Description

Technical Field

[0001] The present invention belongs to the technical field of chemical fiber preparation, and in particular relates to a bio-based polymer melt-blended functional fiber and a preparation method thereof. Background Art

[0002] In the field of fiber production, blended melt spinning technology has attracted considerable attention due to its unique advantages, particularly in the production of synthetic fibers. This technology involves mixing two or more different polymers and heating them to a molten state. Once the mixture reaches a desired uniformity and fluidity, it is spun into filaments through specialized equipment such as nozzles or rotary spinnerets.

[0003] The significant advantages of blended melt spinning technology lie in its high flexibility and cost control capabilities. By selecting polymers with different characteristics for blending, the final product's properties, such as strength and softness, can be effectively adjusted to meet diverse market demands. Furthermore, by blending inexpensive polymers with high-performance polymers, this technology can significantly reduce production costs while maintaining certain performance characteristics, achieving a balance between performance and cost.

[0004] In practical applications, blended melt spinning technology has demonstrated significant potential in fiber production. For example, polylactic acid (PLA) fiber, an environmentally friendly biodegradable material, is experiencing growing market demand. However, the limited softness of pure PLA fiber restricts its application in certain fields.

[0005] To address this problem, the present invention proposes a method for preparing melt-blended fibers by combining blended melt spinning technology with liquid crystal polymers. This method can effectively improve the softness and mechanical properties of PLA fibers, providing new possibilities for the widespread application of PLA fibers. The present invention develops a more efficient and economical method for preparing PLA toughened blends and further optimizes its spinning process to achieve large-scale production and widespread application of PLA blended fibers, which has important research significance and application value. Summary of the Invention

[0006] The purpose of the present invention is to solve the shortcomings of the current polylactic acid fiber in mechanical properties, such as poor toughness and easy breakage under stress, and to provide a bio-based polymer melt-blended functional fiber and a preparation method thereof. The liquid crystal-polylactic acid fiber produced by this method has excellent mechanical properties and has great application prospects as an environmentally friendly and sustainable material.

[0007] The present invention adopts the following technical solutions:

[0008] A bio-based polymer melt-blended functional fiber and a preparation method thereof, comprising:

[0009] The polylactic acid chips and liquid crystal elastomer (prepared by 2-methyl-1,4-phenylenebis(4-(3-(acryloyloxy)propoxy)benzoate)) are used as raw materials and are prepared by a melt spinning method. Specifically, in the spinning process, before adding the spinning raw materials, the polylactic acid chips are dried and mixed with a certain proportion of liquid crystal elastomer, and then the liquid crystal-polylactic acid fiber is prepared according to a series of spinning processes such as melt extrusion, spinning, stretching, and winding.

[0010] The liquid crystal elastomer is prepared from diacrylate reaction intermediate (RM82), 2,2'-(ethylenedioxy)dialkylthiol (EDDT), toluene, dipropylamine (DPA), dibutyltin dilaurate (DBTDL), butylated hydroxytoluene (BHT), and poly(cyclohexane diisocyanate) (Tris-Iso) as raw materials.

[0011] In the above technical solution, further, the amount of the liquid crystal elastomer added is 2% to 50% of the mass of the dry polylactic acid chips.

[0012] Furthermore, the melting temperature is 180° C. and the extrusion speed is 10 mm / min.

[0013] Furthermore, the stretching process is: double-roller stretching, the rotation speed of roller 1 is 150 rpm, the rotation speed of roller 2 is 225 rpm, and the spun fiber is first stretched by roller 1 and then by roller 2.

[0014] Furthermore, the winding process is as follows: reciprocating speed: 50 mm / min, take-up speed: 300 rpm.

[0015] The liquid crystal-polylactic acid fibers produced using this method possess excellent mechanical properties and properties unique to liquid crystal materials. The resulting fibers have a linear density of 25 to 40 dtex, an average strength of 2.54 cN / dtex, and an average elongation of 110.24%.

[0016] In addition, by adding coloring masterbatch to the raw materials, the above method can be used to conveniently produce liquid-colored fibers. Usually, the added mass of liquid crystal elastomer in the raw materials is 5.0% of the mass of dry polylactic acid chips, and the added amount of coloring masterbatch is 0.1% to 0.5% of the mass of dry polylactic acid chips; the obtained fiber linear density is 22 to 37 dtex, the average strength of the fiber is 1.44 cN / dtex, and the average elongation of the fiber can reach 196.02%.

[0017] The beneficial effects of the present invention are:

[0018] In response to the shortcomings of current polylactic acid fibers, such as poor toughness in mechanical properties and easy breakage under stress, the present invention provides a bio-based polymer melt-blended functional fiber and a preparation method thereof. The liquid crystal-polylactic acid fiber prepared by this method has excellent mechanical properties and color, and has obvious temperature response characteristics, and has great application prospects as an environmentally friendly and sustainable material.

[0019] The present invention adopts a blended melt spinning method to spin polylactic acid and liquid crystal elastomer to produce liquid crystal-polylactic acid fibers with excellent mechanical properties, which provides a new idea for the performance optimization of polylactic acid materials and a new reference for the application and promotion of polylactic acid materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a liquid crystal-polylactic acid fiber spun from liquid crystal elastomers with different proportions;

[0021] Figure 2 Liquid crystal-polylactic acid fibers are obtained by spinning liquid crystal elastomers with the same proportion and masterbatches with different proportions.

[0022] Figure 3 It is a liquid crystal elastomer particle;

[0023] Figure 4 is the stress-strain diagram of liquid crystal-polylactic acid fibers with different liquid crystal contents;

[0024] Figure 5 This is the stress-strain diagram of liquid crystal-polylactic acid fiber with the same liquid crystal content and different masterbatch content;

[0025] Figure 6 It is the spinning effect of liquid crystal elastomer and non-bio-based polymer polypropylene (PP) after compounding (no stable, uniform, continuous fibers, and no obvious temperature response characteristics)

[0026] Figure 7 This is a bar graph of the shrinkage state of the liquid crystal-fiber colored by the original solution at 70°C (the upper right corner is the heating time);

[0027] Figure 8 This is a bar graph of the liquid crystal-fiber shrinkage state at 90°C (the upper right corner is the heating time);

[0028] Figure 9 This is an optical microscope image of liquid crystal-fiber colored with the original solution at 100 times magnification. DETAILED DESCRIPTION

[0029] The present invention will be further described in detail below with reference to the accompanying drawings and specific examples.

[0030] Process route: PLA chip drying and raw material preparation → melt extrusion → spinning → stretching → winding spinning operation:

[0031] (1) Pour the material into the hopper (when the equipment is working, pay attention to add granular material in time);

[0032] (2) Set the temperature and install the appropriate extruder head;

[0033] (3) Wait for 5-10 minutes for the temperature to reach the set temperature and allow the machine temperature to balance;

[0034] (4) Adjust the appropriate extrusion speed, press the start button, and start the motor to extrude the fiber;

[0035] (5) After the material is extruded, start the drafting machine and the winding machine, and use tweezers to send the fiber to the drafting roller and the winding roller;

[0036] (6) The temperature and extrusion speed can be fine-tuned during the spinning process, and the corresponding drawing machine speed and winding speed also need to be fine-tuned accordingly.

[0037] Polylactic acid slice drying:

[0038] The polylactic acid slices were spread flat on a tray, placed in a vacuum oven, and dried at 80°C for 24 hours.

[0039] (1) Remove moisture

[0040] Polylactic acid is formed by the polymerization of lactic acid. There are ester bonds in the polylactic acid molecule, and ester bonds are easily hydrolyzed. Ester bond hydrolysis is the main way for polylactic acid to degrade. Moreover, the hydrolysis reaction can be automatically catalyzed by the groups (-COOH) produced by hydrolysis. The hydrolysis of the ester bond is slow at first, but then it will accelerate. The hydrolysis reaction occurs not only on the surface of the polylactic acid, but also penetrates into the entire polymer. For semi-crystalline polylactic acid, hydrolysis is divided into two stages: in the first stage, water molecules quickly diffuse into the amorphous region, followed by hydrolysis; the second stage is the hydrolysis of the crystalline region, which is relatively slow. For polylactic acid with an amorphous structure, the hydrolysis is only in the first stage.

[0041] Furthermore, water in the melt forms bubbles during spinning, which are trapped in the melt stream and can easily cause spinning drifting, lint, and broken yarns. This can even leave hidden dangers in the monofilaments, causing lint or breakage during subsequent stretching. Therefore, the chips must be dried before the high-temperature spinning process.

[0042] (2) Increase softening point

[0043] The raw material, polylactic acid chips, have an amorphous structure and a low softening point. When spinning these chips, they quickly soften and become sticky upon entering the screw extruder, causing "ringing" and blockages, interrupting production. However, dried chips partially crystallize, significantly raising their softening point. The higher the crystallinity, the higher the softening point, and the harder the chips. This prevents "ringing" when entering the screw extruder.

[0044] The dried PLA chips are thoroughly mixed with an appropriate proportion of compatibilizer and masterbatch. This mixture is then fed into a screw extruder for melting and extrusion. To ensure uniform and smooth filament discharge and prevent disruption to the subsequent spinning process, the feedstock must be kept uniform and stable at the feed port. Balanced and stable feed is a key factor influencing the quality of the final fiber. Furthermore, because the PLA extrusion speed during the spinning process is not fast, the PLA material remains in the screw for a relatively long time, increasing the likelihood of degradation. To minimize degradation of the PLA material and its impact on spinning quality, high-speed discharge is performed at regular intervals to produce a PLA melt with a relatively low degradation rate.

[0045] The melt extrusion of polylactic acid chips in an extruder involves a transition from a solid state to a high-temperature viscous fluid state. The extruder simultaneously performs the dual functions of extrusion, conveying, and heating and melting. As the chips travel along the screw groove toward the die, they undergo a physical transition from a glassy state to a highly elastic state and finally to a viscous fluid state.

[0046] This experiment uses Huizhi electrospinning desktop melt spinning equipment.

[0047] Spinning:

[0048] After the melt is ejected from the spinneret into a fine stream, it gradually cools and forms along the path of the filament. The temperature, diameter, speed, force, viscosity, and internal structure of each point on the filament are all changing. External conditions have a significant impact on the uniformity of the filament's fineness, strength and elongation unevenness, and post-drawing properties.

[0049] Along the spinning direction, the cooling process of the filament can be divided into three regions: flow deformation zone, solidification deformation zone and solid state movement zone.

[0050] 1. Flow deformation zone

[0051] After the melt leaves the spinneret micropores, it will expand within a distance of approximately 5-10 mm from the spinneret surface. This is due to the release of elastic deformation energy and static pressure energy generated by the sudden change in melt flow rate, resulting in an increase in diameter. This expansion is detrimental to spinning, not only causing uneven yarns but also causing spinneret adhesion, breakage, and fuzzy yarns. The degree of expansion can be reduced by appropriately reducing the melt viscosity, increasing the spinning temperature, and selecting spinnerets with a larger aspect ratio.

[0052] Although the temperature has dropped in the flow deformation zone, the flow properties are very good, so it is easy to become thinner after being subjected to tension. The resulting macromolecules have a low degree of axial arrangement and a very small degree of orientation.

[0053] 2. Solidification deformation zone

[0054] The solidification deformation zone is the most important area for cooling and solidification. Under the traction of the winding mechanism and certain cooling conditions, the melt flow changes the most in this area, and changes occur in temperature, viscosity, diameter and macromolecular structure, and gradually solidifies into filaments.

[0055] (1) Diameter change. Because the winding mechanism pulling speed V (called spinning speed or winding speed) greatly exceeds the spinneret speed V0 (that is, the speed at which the melt is ejected in the micropores), the filaments are stretched and thinned until the solidification point, and the diameter remains basically unchanged.

[0056] (2) Changes in melt temperature and viscosity. The melt stream is cooled by the surrounding air, causing its temperature to drop rapidly and its viscosity to rise rapidly. When the viscosity reaches a certain value, it loses its fluidity and becomes solid.

[0057] (3) Changes in the internal structure of the filaments. The internal structure of the filaments mainly includes orientation and crystallinity. Since the crystallization temperature needs to be below the melting point and above the glass transition temperature, and it takes a certain amount of time to proceed, the glass transition temperature of polylactic acid fibers is relatively high, and the temperature drops very quickly. Therefore, before crystallization has time, the temperature drops below the glass transition temperature, resulting in the internal structure of the filaments being in an amorphous (non-crystalline) state.

[0058] The degree to which macromolecular chains are regularly arranged along the axial direction of the filament under the action of external force is called the degree of orientation, which is measured by the size of the birefringence "Δn" (a larger Δn indicates a larger degree of orientation).

[0059] 3. Solid state mobile area

[0060] From the solidification point, the filaments move at the same pulling speed until the yarn is formed. A certain cooling distance is generally required to cool the filaments as they enter the filament reel or winding mechanism, so a tunnel is installed below the spinning chamber. However, as the spinning speed increases, the tunnel's role becomes less significant.

[0061] draft:

[0062] Drafting is a heat setting process for the spun fibers, with the goal of improving the quality of the fibers by changing their internal microstructure. The polylactic acid fibers are transferred from the spinneret to the drafting mechanism and passed through two drafting rollers to complete the drafting process.

[0063] Drawing machine: drawing roller: double roller, circumference 20 cm, speed: 0.1-300rpm, accuracy 0.1rpm, steering: one-button adjustment of roller steering.

[0064] Winding:

[0065] Winding is the final step in the production process, where the fibers or yarns are wound onto reels for storage, transport, and subsequent processing. This final step in the production chain is crucial for ensuring product quality and facilitating subsequent processing.

[0066] Fiber winder: Collecting roller: circumference 10cm, length 10cm, rotation speed: 0.1-300rpm, accuracy 0.1rpm, reciprocating distance: 0-15cm, adjustable, reciprocating speed: 1-1000mm / min, accuracy 1mm / min.

[0067] The liquid crystal elastomer used in the embodiments of the present invention is prepared using a diacrylate reaction intermediate (RM82), 2,2'-(ethylenedioxy)dialkylthiol (EDDT), toluene, dipropylamine (DPA), dibutyltin dilaurate (DBTDL), butylated hydroxytoluene (BHT), and poly(cyclohexane diisocyanate) (Tris-Iso) as raw materials.

[0068] Example 1

[0069] The above method was used to set the liquid crystal elastomer addition amount to 2%, 5%, 10%, 20%, 30%, and 50% of the mass of the dry polylactic acid chips, a total of six groups. Spinning temperature: 180℃, screw extrusion speed: 10mm / min, roller 1: 150rpm, roller 2: 225rpm, reciprocating speed: 50rpm, take-up speed: 300rpm, winding time: 12min, experiments were carried out; liquid crystal-polylactic acid fibers were successfully obtained in all cases. The obtained samples are as follows Figure 1 As shown in the figure, from left to right are 2%, 5%, 10%, 20%, 30%, and 50% liquid crystal-polylactic acid fiber samples.

[0070] Example 2

[0071] Using the above method, the liquid crystal elastomer addition rate was set at 5% of the mass of the dry polylactic acid chips, and the masterbatch addition rate was set at 0.1%, 0.3%, and 0.5% of the mass of the dry polylactic acid chips, for a total of three groups. The experiments were conducted at a spinning temperature of 180°C, a screw extrusion speed of 10 mm / min, roller 1 at 150 rpm, roller 2 at 225 rpm, a reciprocating speed of 50 mm / min, a take-up speed of 300 rpm, and a winding time of 12 minutes.

[0072] During the melt spinning process of polylactic acid, a certain proportion of liquid crystal elastomer is added. Figure 4 This method significantly improves the strength, elongation and modulus of polylactic acid fibers, providing a new way to prepare high-performance bio-based fibers.

[0073] In the preparation process of liquid crystal-polylactic acid fiber, the addition of masterbatch has a certain impact on the mechanical properties of the fiber. Figure 5 As the proportion of masterbatch increases, the mechanical properties of the fiber decrease to a certain extent. Therefore, it is necessary to optimize the combination ratio of masterbatch and liquid crystal elastomer during the preparation process to obtain the best fiber performance.

[0074] The experiment further found that the liquid crystal-polylactic acid fiber has thermal shrinkage characteristics within a specific temperature range. Figures 7 and 8 , when the temperature is 50℃, the fiber does not shrink. As shown in Table 1, it is the shrinkage deformation data of liquid crystal PLA fiber with different masterbatch addition ratios at 50℃. It can be seen that when the temperature is 50℃, the fiber has no dimensional change. When the temperature is between 50℃ and 70℃, the fiber begins to shrink and reaches the maximum shrinkage rate at 90℃. Figure 7 、 Figure 8 Furthermore, the experiment also found that within the selected temperature range, the lower the liquid crystal content, the greater the fiber shrinkage. This discovery is of great significance for understanding the thermal shrinkage mechanism of liquid crystal-polylactic acid fibers and optimizing their performance.

[0075] Table 1

[0076]

[0077] The present invention also tests and analyzes the color performance of liquid crystal-polylactic acid colored yarns with added color masterbatches. Figure 9 The solution coloring of liquid crystal-polylactic acid colored fibers also has good results, providing a new idea for the preparation of colored bio-based fibers.

[0078] It can be seen that the present invention successfully spun uniform continuous fibers by selecting bio-based fiber polylactic acid and liquid crystal elastomer, combined with regulating melt spinning parameters, and obtained functional fibers with excellent physical and mechanical properties while retaining the special properties of liquid crystal elastomer. It is worth noting that it is difficult to compound liquid crystal elastomer with polymer to maintain its spinnability. After a large number of experimental studies, liquid crystal elastomer cannot be successfully spun when mixed with most common polymers. When the liquid crystal elastomer is compounded with non-bio-based polymer polypropylene (PP) and melt-spun, uneven fibers can be spun, such as Figure 6 The spinning effect shown is that there are no stable, uniform, continuous fibers. More importantly, it has no obvious temperature response characteristics and cannot have the properties of liquid crystal elastomers.

[0079] The above-described embodiments provide a detailed description of the preparation scheme of the present invention. It should be understood that these embodiments are only used to illustrate the present invention and are not used to limit the present invention. Any modifications, supplements or similar substitutions made within the scope of the principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing bio-based polymer melt-blended functional fibers, characterized in that: include: The invention uses polylactic acid chips and liquid crystal elastomer as raw materials and adopts a melt spinning method to prepare the fiber. Specifically, the polylactic acid chips are dried and then mixed with the liquid crystal elastomer, and the liquid crystal-polylactic acid blend fiber is prepared according to a spinning process of melt extrusion, spinning, stretching, and winding. The liquid crystal elastomer is prepared using diacrylate reaction intermediate RM82, 2,2'-(ethylenedioxy)dialkyl mercaptan, toluene, dipropylamine, dibutyltin dilaurate, butylated hydroxytoluene, and poly(cyclohexane diisocyanate) as raw materials. The addition amount of the liquid crystal elastomer is 2% to 50% of the mass of the dry polylactic acid chips.

2. The method for preparing bio-based polymer melt-blended functional fibers according to claim 1, characterized in that: The polylactic acid slices are dried at 80° C. for 24 hours.

3. The method for preparing bio-based polymer melt-blended functional fibers according to claim 1, characterized in that: The melt extrusion temperature is 180° C. and the extrusion speed is 10 mm / min.

4. The method for preparing bio-based polymer melt-blended functional fibers according to claim 1, characterized in that: The stretching process is: double-roller stretching, with the rotation speed of roller 1 being 150 rpm and the rotation speed of roller 2 being 225 rpm.

5. The method for preparing bio-based polymer melt-blended functional fibers according to claim 1, characterized in that: The winding process is as follows: reciprocating speed: 50 mm / min, take-up speed: 300 rpm.

6. A bio-based polymer melt-blended functional fiber, characterized in that: The fiber is prepared by the method according to any one of claims 1 to 5, wherein the fiber linear density is 25 to 40 dtex, the average fiber strength is 2.54 cN / dtex, and the average fiber elongation is 110.24%.

7. A bio-based polymer melt-blended functional fiber, characterized in that: The product is prepared by the method according to any one of claims 1 to 5, and the raw materials also contain coloring masterbatch.

8. The bio-based polymer melt-blended functional fiber according to claim 7, characterized in that: The added amount of liquid crystal elastomer in the raw materials is 5.0% of the dry polylactic acid slice mass, and the added amount of coloring masterbatch is 0.1% to 0.5% of the dry polylactic acid slice mass.

9. The bio-based polymer melt-blended functional fiber according to claim 7, characterized in that: The fiber linear density is 22-37 dtex, the average fiber strength is 1.44 cN / dtex, and the average fiber elongation is 196.02%.

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