Method for improving irregularity of bio-based polymer melt spinning fibers

Abstract

The invention discloses a method for improving the irregularity of bio-based polymer melt-spun fibers, which is characterized in that an antioxidant 1010 and a bio-based polymer such as polylactic acid (PLA) or bio-based polyamide 11 (PA11) are mixed according to a certain proportion and then are subjected to melt spinning to prepare the melt-spun fibers, so that the spun melt-spun fibers are more stable and uniform. The bio-based polymer can be degraded at a melting high temperature, so that the molecular weight and molecular weight distribution of the bio-based polymer are changed, and the uniformity of the bio-based polymer is influenced, and the melt-spun fiber prepared by mixing the bio-based polymer and the antioxidant 1010 is more uniform and stable.

Description

Technical Field

[0001] The invention belongs to the technical field of bio-based polymer fiber preparation and relates to a method for improving the unevenness of bio-based polymer melt-spun fibers. Background Art

[0002] Bio-based polymers such as polylactic acid (PLA) or polyamide 11 (PA11), as a bio-based polymer material derived from renewable resources, have shown great application potential in many fields such as medicine, packaging, and textiles due to their excellent biocompatibility, biodegradability, and recyclability. Taking PLA as an example, the preparation of this material is mainly based on the polymerization reaction of lactic acid monomers. By precisely controlling the reaction conditions, such as the type of catalyst, reaction temperature, pressure, and time, polylactic acid polymers with specific molecular weight and structural characteristics can be obtained. However, the molecular structure of polylactic acid is prone to thermal and water degradation, which brings considerable challenges to its melt spinning process.

[0003] In the process of preparing uniform polylactic acid melt fibers, it is crucial to ensure the uniformity, strength, thermal stability and other key properties of the fibers. These properties not only directly determine the service life and application range of the fibers, but also have a profound impact on their subsequent processing and the quality of the final products. Therefore, from raw material selection, optimization of polymerization reaction conditions to the design of spinning process, every link needs to be carefully planned and strictly controlled to maximize the advantages of polylactic acid materials while overcoming its inherent processing difficulties. At present, melt spinning is the mainstream technology for preparing bio-based polymer fibers such as polylactic acid. It heats polylactic acid particles to a molten state, extrudes the melt using a high-speed rotating screw, and forms continuous fiber filaments through the spinneret. However, the low crystallization rate and high viscosity of polylactic acid make its melt spinning process extremely sensitive to parameters such as temperature, pressure, and stretch ratio. If you are not careful, it may lead to problems such as uneven fiber structure, reduced strength or insufficient thermal stability. In order to overcome these technical difficulties, researchers have been constantly exploring and innovating, from improving polymerization reaction conditions, optimizing spinning process parameters, to introducing new additives or modification technologies, in order to improve the processing adaptability and fiber quality while maintaining the excellent performance of polylactic acid materials. For example, by selecting a suitable catalyst and adjusting the reaction conditions, the molecular weight distribution uniformity and crystallization rate of polylactic acid can be improved; by optimizing spinning process parameters, such as reducing the spinning speed and increasing the stretching ratio, the uniformity and strength of the fiber can be significantly improved; and by introducing a compatibilizer or other functional additives, the melt viscosity of polylactic acid can be adjusted to a certain extent, improving its processing performance.

[0004] As a thermoplastic aliphatic polyester, polylactic acid (PLA) is prone to hydrolysis under adverse conditions such as high temperature, high humidity or shear force due to its unique molecular structure, especially the ester bonds in the molecular chain. This chemical reaction will cause the polylactic acid molecular chain to break, thereby reducing its molecular weight and the overall performance of the polymer. In the melt spinning process, the polylactic acid raw material is heated to a molten state and conveyed and pressurized by a screw extruder. In this process, the shearing action of the screw and the flow of the melt in the extruder will generate a certain amount of shear force, which may lead to further breakage of the polylactic acid molecular chain. In addition, the selection and control of process parameters such as spinning temperature, humidity and stretching multiple also have an important influence on the degree of degradation of polylactic acid. Excessive temperature will accelerate the thermal degradation of polylactic acid, and excessive humidity will aggravate hydrolytic degradation. Due to the degradation of polylactic acid during the melt spinning process, the physical properties of the fiber, such as strength and toughness, will be significantly reduced. This decline is not only reflected in the overall performance, but may also show unevenness, that is, the fiber performance in different parts is quite different. Degradation will also cause changes in the cross-sectional morphology of the fiber. The fiber cross-section, which should be approximately circular, may have irregular shapes, cracks or gaps due to degradation. These morphological changes will further affect the physical properties and appearance quality of the fiber. In the longitudinal direction of the fiber, degradation may cause the appearance of irregular stripes and spots. These stripes and spots are usually formed by the rapid decomposition of the non-crystalline part of polylactic acid under the action of water, bacteria and oxygen. Their presence not only affects the uniformity of the fiber, but also reduces the aesthetics and use value of the fiber. Degradation will also have an uneven effect on the length and diameter of the fiber. Due to the breakage of the molecular chain and the decline in performance caused by degradation, the fiber may be more likely to break or form short fibers during the spinning process. At the same time, due to different degrees of degradation, the diameter of the fiber may also fluctuate. This unevenness in length and diameter will further affect the fineness and feel of the fiber, thereby affecting the quality of the final product.

[0005] Existing research focuses more on the modification of mechanical properties of bio-based polymer melt fibers such as polylactic acid, but less on uniformity. Summary of the invention

[0006] The purpose of the present invention is to provide a method for improving the unevenness of bio-based polymer melt-spun fibers in view of the deficiencies in the prior art. The method can effectively improve the uniformity of bio-based polymer melt fibers.

[0007] The technical solution adopted by the present invention is as follows:

[0008] A method for improving the unevenness of bio-based polymer melt-spun fibers, comprising mixing biomass polymer slices with an antioxidant 1010 in proportion and drying the mixture, and performing melt spinning to prepare melt-spun fibers, thereby improving the uniformity of the melt-spun fibers.

[0009] In the above technical solution, further, the bio-based polymer is one or more of PLA and PA11.

[0010] Furthermore, the particle size of the bio-based polymer slices is 3-4 mm, and the particle size of the antioxidant 1010 is 100-300 nm.

[0011] Furthermore, the mass ratio of the bio-based polymer to the antioxidant 1010 is 99.5-99.1:0.1-0.5.

[0012] Furthermore, the drying is vacuum drying, preferably at 60-90° C. for 12 hours.

[0013] Furthermore, the melt spinning is to put the dried mixture into a melt spinning machine for spinning, and obtain fibers after melt extrusion and drawing treatment; the spinning temperature during melt spinning is 190-205°C, the nozzle diameter is 1.0mm, the extrusion speed is 10-20mm / min, the first guide roller speed GR1 is 150mm / min, the second guide roller speed GR2 is 225mm / min, and the collection and winding speed is 300mm / min.

[0014] The polylactic acid melt fiber prepared by the method of the present invention has a strand unevenness of 3-5%, which is much more uniform than the polylactic acid fiber obtained by the conventional method (the strand unevenness is usually 7-10%).

[0015] The antioxidant 1010 of the present invention has good compatibility with polylactic acid / polyamide 11, has good uniformity after spinning and drawing, and the yarn unevenness and mechanical unevenness can stably reach 3-5%, and has certain mechanical properties.

[0016] The raw materials used in the present invention are bio-based polymers (such as polylactic acid Naturework 6201D) and antioxidant 1010, and the antioxidant is used to prevent the oxidation chain reaction. The antioxidant can react with the peroxide produced in materials such as polylactic acid, thereby terminating the oxidation chain reaction. This reaction process effectively prevents further oxidation degradation of materials such as polylactic acid and protects the integrity of the material. 2) Improve heat resistance. By adding antioxidants, the heat resistance of materials such as polylactic acid can be significantly improved. This helps to reduce the degradation rate of bio-based polymers such as polylactic acid in high temperature environments, thereby extending their service life. 3) Delay the aging process. Antioxidants can delay the aging process of materials such as polylactic acid and maintain their good physical properties and chemical stability. This is of great significance for improving the durability and service life of bio-based polymer products such as polylactic acid.

[0017] The bio-based polymer melt fiber modified with antioxidants is more uniform than before and has better fiber morphology and mechanical properties, allowing bio-based polymer products to be used in more fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The polylactic acid fiber prepared in Example 2;

[0019] Figure 2 This is an enlarged view of the polylactic acid fiber prepared in Example 2;

[0020] Figure 3 The melt spinning equipment used in the embodiment;

[0021] Figure 4 Schematic diagram of the breakage of the molecular chain of polylactic acid degradation;

[0022] Figure 5 Schematic diagram of the antioxidant's action in capturing free radicals;

[0023] Figure 6 This is the bio-based polyamide PA11 fiber prepared on a large scale in Example 5. DETAILED DESCRIPTION

[0024] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and specific embodiments. The bio-based polymer used in the embodiment has a particle size of 3-4 mm, and the particle size of the antioxidant 1010 is 100-300 nm.

[0025] Example 1

[0026] A method for improving the unevenness of bio-based polymer melt-spun fibers comprises the following steps: uniformly mixing 0.5% antioxidant 1010 and 99.5% polylactic acid, vacuum drying at 80°C for 12 hours, and then adding the mixture into a melt spinning machine for composite spinning, wherein the spinning temperature is 195°C, the nozzle diameter is 1.0 mm, the extrusion speed is 10 mm / min, the first guide roller speed GR1 is 150 mm / min, the second guide roller speed GR2 is 225 mm / min, and the collecting and winding speed is 300 mm / min, to obtain uniform polylactic acid melt fibers. It is found that after drawing, the fibers are uniform in thickness, the unevenness of the strands is 3.4%, and the unevenness of the strength is 3.1%.

[0027] Example 2

[0028] A method for improving the unevenness of bio-based polymer melt-spun fibers, comprising the following steps: uniformly mixing 0.3% antioxidant 1010 and 99.7% polylactic acid, vacuum drying at 80°C for 12 hours, and then adding the mixture into a melt spinning machine for composite spinning, wherein the spinning temperature is 195°C, the nozzle diameter is 1.0 mm, the extrusion speed is 10 mm / min, the first guide roller speed GR1 is 150 mm / min, the second guide roller speed GR2 is 225 mm / min, and the collection and winding speed is 300 mm / min to obtain uniform polylactic acid melt fibers, such as Figure 1 As shown, it was found that after stretching, the fiber thickness was uniform, the unevenness of the fiber was 2.9%, and the unevenness of the fiber strength was 3.2%.

[0029] Example 3

[0030] A method for improving the unevenness of bio-based polymer melt-spun fibers comprises the following steps: uniformly mixing 0.1% antioxidant 1010 and 99.9% polylactic acid, vacuum drying at 80°C for 12 hours, and then adding the mixture into a melt spinning machine for composite spinning, wherein the spinning temperature is 195°C, the nozzle diameter is 1.0 mm, the extrusion speed is 10 mm / min, the first guide roller speed GR1 is 150 mm / min, the second guide roller speed GR2 is 225 mm / min, and the collecting and winding speed is 300 mm / min, to obtain uniform polylactic acid melt fibers. It is found that after drawing, the fibers are uniform in thickness, the unevenness of the strands is 4.8%, and the unevenness of the strength is 4.1%.

[0031] Example 4

[0032] A method for improving the unevenness of bio-based polymer melt-spun fibers comprises the following steps: 0.1% antioxidant 1010 and 99.9% polylactic acid are mixed evenly, vacuum dried at 80°C for 6 hours, and then added into a melt spinning machine for composite spinning, the spinning temperature is 210°C, the nozzle diameter is 1.0mm, the extrusion speed is 20mm / min, the first guide roller speed GR1 is 150mm / min, the second guide roller speed GR2 is 225mm / min, the collection and winding speed is 300mm / min, and the obtained fibers have yarn defects in some places, broken ends occur during spinning, the unevenness is high, and the unevenness of the strips exceeds 9%. Analysis shows that the reason may be that the polylactic acid slices are not completely dried, and the high spinning temperature causes it to still be greatly degraded under the action of a small amount of antioxidants.

[0033] Example 5

[0034] A method for improving the unevenness of bio-based polymer melt-spun fibers comprises the following steps: uniformly mixing 0.2% antioxidant 1010 and 99.8% bio-based polyamide PA11, vacuum drying at 80°C for 12 hours, and then adding the mixture into a melt spinning machine for composite spinning, wherein the spinning temperature is 190°C, the nozzle diameter is 1.0 mm, the extrusion speed is 20 mm / min, the first guide roller speed GR1 is 150 mm / min, the second guide roller speed GR2 is 220 mm / min, the collecting and winding speed is 320 mm / min, and uniform PA11 melt fibers are obtained. It is found that after drawing, the fibers are uniform in thickness, the unevenness of the fibers is 5.0%, and the unevenness of the fibers is 3.1%.

[0035] Comparative Example 1

[0036] A method for preparing polylactic acid melt fiber comprises the following steps: vacuum drying polylactic acid slices at 80°C for 12 hours and then adding them into a melt spinning machine for spinning, wherein the spinning temperature is 195°C, the nozzle diameter is 1.0 mm, the extrusion speed is 10 mm / min, the first godet roller speed GR1 is 150 mm / min, the second godet roller speed GR2 is 225 mm / min, and the collection and winding speed is 300 mm / min, to obtain polylactic acid melt fiber, and it is found that after drafting, the fiber thickness is poor, the unevenness of the strands is 7.2%, and the unevenness of the strength is 6.2%. Polylactic acid is degraded during the melting process, and the random unevenness of the degradation leads to poor unevenness.

[0037] Comparative Example 2

[0038] A method for preparing polylactic acid melt fibers comprises the following steps: vacuum drying polylactic acid slices at 80°C for 12 hours and then adding them into a melt spinning machine for spinning, wherein the spinning temperature is 210°C, the nozzle diameter is 1.0 mm, the extrusion speed is 10 mm / min, the first guide roller speed GR1 is 150 mm / min, the second guide roller speed GR2 is 225 mm / min, and the collecting and winding speed is 300 mm / min. During spinning, the polylactic acid is carbonized due to its long residence time in the extruder, and thus has no spinnability.

[0039] Figure 4 The figure is a schematic diagram of the breakage of the polylactic acid degradation molecular chain. There are ester bonds in the polylactic acid molecules that are sensitive to water and heat. In a high-temperature aerobic and humid environment, the ester bonds will break, resulting in different degrees of degradation of the polylactic acid. During the degradation process, the long polylactic acid molecular chain will split into shorter parts and become lactic acid molecules. The present invention captures and stabilizes free radicals by adding antioxidants, thereby slowing down or inhibiting the oxidation reaction of polylactic acid under high-temperature moisture conditions. Figure 5This mechanism of action is similar to adding a "blocker" to a chemical reaction, which prolongs the stability and service life of polylactic acid by slowing down or blocking certain key steps. Antioxidants can also protect the polylactic acid molecular chain from high temperature damage, allowing it to maintain good stability and mechanical properties at high temperatures.

[0040] The above-described embodiments are only some of the preferred solutions of the present invention, but they are not intended to limit the present invention. A person skilled in the relevant technical field may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, any technical solution obtained by equivalent replacement or equivalent transformation falls within the protection scope of the present invention.

Claims

1. A method for improving the unevenness of bio-based polymer melt-spun fibers, characterized in that: The biomass polymer chips and the antioxidant 1010 are mixed in proportion and then dried, and melt-spun to prepare melt-spun fibers, thereby improving the uniformity of the melt-spun fibers.

2. The method for improving the unevenness of bio-based polymer melt-spun fibers according to claim 1, characterized in that: The bio-based polymer is one or more of PLA and PA11.

3. The method for improving the unevenness of bio-based polymer melt-spun fibers according to claim 1, characterized in that: The particle size of the bio-based polymer chips is 3-4 mm, and the particle size of the antioxidant 1010 is 100-300 nm.

4. The method for improving the unevenness of bio-based polymer melt-spun fibers according to claim 1, characterized in that: The mass ratio of the bio-based polymer to the antioxidant 1010 is 99.5-99.1:0.1-0.

5.

5. The method for improving the unevenness of bio-based polymer melt-spun fibers according to claim 1, characterized in that: The drying is vacuum drying at 60-90° C. for 12 h.

6. The method for improving the unevenness of bio-based polymer melt-spun fibers according to claim 1, characterized in that: During the melt spinning, the spinning temperature is 190-205° C., the nozzle diameter is 1.0 mm, the extrusion speed is 10-20 mm / min, the first guide roller speed GR1 is 150 mm / min, the second guide roller speed GR2 is 225 mm / min, and the collection and winding speed is 300 mm / min.

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