Light-absorbing heat-generating polylactic acid fiber and preparation method and application thereof

Abstract

The application discloses an optical heating polylactic acid fiber and a preparation method and application thereof, relates to the technical field of functional fibers, and discloses the optical heating polylactic acid fiber, which comprises a skin layer component and a core layer component; the raw material of the core layer component comprises modified optical heating material; the modified optical heating material is modified nano cesium tungsten bronze particles; and the surface of the modified nano cesium tungsten bronze particles is grafted with methoxyl polyethylene glycol mercapto. The optical heating polylactic acid fiber solves the problem that nano powder is prone to agglomeration in the preparation process of the optical heating polylactic acid fiber in the prior art. The polylactic acid fiber has good fluidity and excellent tensile strength, can be made into short fibers and filaments, and the fabric thereof is suitable for the field of agricultural heat preservation covering materials and has a wide application prospect.

Description

Technical Field

[0001] This invention belongs to the field of functional fiber materials technology, and relates to a light-absorbing and heat-generating polylactic acid fiber, its preparation method and application. Background Technology

[0002] Polylactic acid (PLA) is derived from renewable biomass resources and is completely biodegradable. It has advantages such as being lightweight and breathable, making it an ideal base material for agricultural covering products. However, crops have rigid requirements for temperature during growth. Under natural environmental conditions, especially in the low temperatures of early spring, agricultural insulation covering materials made from traditional PLA materials rely only on passive heat insulation and do not have the ability to actively generate heat. This results in limited warming effect in the low-temperature early spring environment and significant performance shortcomings under extreme weather conditions.

[0003] To achieve active heat generation and enhance insulation in traditional polylactic acid (PLA) materials, common methods include blending carbon-based and inorganic photothermal powders into the PLA melt. However, this method has the following drawbacks: Since carbon-based and inorganic photothermal powders are typically nanoparticles, they are prone to agglomeration in PLA melt, leading to fiber breakage during spinning and a significant decrease in fiber strength. Furthermore, these nanoparticles tend to be distributed on the fiber surface and are easily detached due to friction during practical applications, resulting in rapid degradation of heating performance. Additionally, carbon-based photothermal powders are often dark black, resulting in a limited color range for the obtained PLA-based agricultural covering products.

[0004] These problems directly lead to premature damage to agricultural mulch products in the field, resulting in the loss of core functions such as heat preservation and pest control. Furthermore, the heat-generating performance rapidly diminishes due to rain erosion and wind friction, and the detached nanoparticles may pollute the soil and water sources. In addition, dark-colored mulch may exacerbate soil overheating during hot seasons, which is detrimental to crop roots; while light-colored or transparent mulch is more advantageous under specific climates and crop conditions.

[0005] Therefore, there is an urgent need for a PLA functional fiber that combines biodegradability, long-lasting photothermal heating, light color, and large-scale melt spinning for use in agricultural insulation covering materials, which has significant practical application value. Summary of the Invention

[0006] The purpose of this invention is to solve the problems of easy agglomeration, easy distribution on the fiber surface, and single color of conventional photothermal powders in the preparation process of light-absorbing and heat-generating polylactic acid fibers in the prior art. The invention provides a polylactic acid fiber with excellent dispersibility and efficient light-absorbing and heat-generating properties, as well as its preparation method and application.

[0007] The technical problem to be solved by this invention can be achieved through the following technical solution: In a first aspect, the present invention provides a light-absorbing and heat-generating polylactic acid fiber, which includes a sheath component and a core component; the raw material of the core component includes 3-5 parts of modified light-absorbing and heat-generating material; The modified light-absorbing and heat-generating material includes modified nano-cesium tungsten bronze particles; the surface of the modified nano-cesium tungsten bronze particles is grafted with monothiol polyethylene glycol segments.

[0008] By employing the above technical solution, polylactic acid fibers are prepared into a core-sheath structure. The modified light-absorbing and heat-generating material is located in the core layer and is tightly wrapped by the sheath, preventing it from falling off or being damaged due to friction, thus ensuring the durability of the light-absorbing and heat-generating effect. Furthermore, the sheath isolates air and moisture, preventing oxidation or failure of the core material and extending the fiber's lifespan. This design maximizes photothermal conversion efficiency, resulting in a better heating experience.

[0009] Furthermore, modified light-absorbing and heat-generating materials include modified nano-cesium tungsten bronze particles. Since traditional light-absorbing and heat-generating materials are mostly black or dark gray, they severely limit the color and fashion design of textiles. However, products made from nano-cesium tungsten bronze particles can be light-colored or transparent. When applied to agricultural films, they can provide the most natural growth light and avoid the unknown impact on crop growth and quality that may be caused by changes in light quality.

[0010] However, due to their high surface energy, nano-cesium tungsten bronze particles still exhibit a tendency to agglomerate within a polylactic acid matrix. Therefore, this invention modifies the nano-cesium tungsten bronze particles by grafting methoxy polyethylene glycol (PEG) mercaptoyl groups onto their surface. The thiol groups in the methoxy polyethylene glycol mercaptoyl groups have a strong affinity for the metal atoms on the surface of the nano-cesium tungsten bronze particles, forming stable chemical bonds that firmly "anchor" and anchor the methoxy polyethylene glycol mercaptoyl groups to the particle surface, creating a uniform, ordered, and relatively thin interfacial layer. The strong steric hindrance effect of this interfacial layer effectively prevents the nano-cesium tungsten bronze particles from re-agglomerating.

[0011] Furthermore, the polyethylene glycol chains in the methoxy polyethylene glycol mercapto segments exhibit good compatibility with polylactic acid. Therefore, the grafted modified cesium tungsten bronze nanoparticles can be better dispersed in the polylactic acid matrix, and the interfacial bonding between the two can be enhanced, avoiding phase separation and performance degradation caused by poor compatibility. At the same time, it can also improve the problem of easy migration of cesium tungsten bronze nanoparticles.

[0012] Preferably, the raw materials for the modified nano-cesium tungsten bronze particles include nano-cesium tungsten bronze particles and methoxy polyethylene glycol mercapto in a mass ratio of (90-100):(30-40).

[0013] Preferably, the preparation of modified nano-cesium tungsten bronze particles includes the following process steps: Solution preparation: Dissolve the methoxy polyethylene glycol mercapto group in an organic solvent to prepare a 4.5-5 mM solution; Immersion assembly: Immerse the cleaned and dried nano-cesium tungsten bronze particles into the above solution and react at room temperature for 1-5 hours. After the reaction is completed, filter, wash and dry to obtain the final product.

[0014] Preferably, the organic solvent includes any one of methanol, ethanol, dichloromethane, and N,N-dimethylformamide.

[0015] Preferably, the particle size of the nano-cesium tungsten bronze particles is 30nm-50nm.

[0016] More preferably, the particle size of the nano-cesium tungsten bronze particles is 30 nm.

[0017] By adopting the above technical solution, the strong affinity of the thiol group in the methoxy polyethylene glycol mercapto compound for the copper metal surface is utilized to stably "anchor" the polyethylene glycol segments with good biocompatibility to the surface of nano-cesium tungsten bronze particles. The grafted modified nano-cesium tungsten bronze particles can be better dispersed in the polylactic acid matrix, enhancing the interfacial bonding force between the two and avoiding phase separation and performance degradation caused by poor compatibility.

[0018] Preferably, the core layer component includes the following raw materials in parts by weight: 35-55 parts of polylactic acid.

[0019] Preferably, the skin layer component comprises the following raw materials in parts by weight: 35-65 parts polylactic acid, 1-10 parts nano silica, and 0.5-5 parts nucleating agent.

[0020] Preferably, the nucleating agent is one or a combination of two of sebacic acid dibenzoylhydrazine and adipic acid di(2-benzoylhydrazine).

[0021] Preferably, the weight ratio of the cortex component to the core component is (22-42):(62-82).

[0022] More preferably, the weight ratio of the cortex component to the core component is 32:70.

[0023] By employing the above technical solution, polylactic acid fibers are prepared into a core-sheath structure. The light-absorbing and heat-generating material is placed in the core layer, and the heat-generating material is tightly wrapped by the sheath, preventing it from falling off or being damaged due to friction, thus ensuring the durability of the light-absorbing and heat-generating effect. Furthermore, the sheath isolates the material from air and moisture, preventing oxidation or failure of the core material and extending the fiber's lifespan. This design maximizes photothermal conversion efficiency, resulting in a better heating experience.

[0024] Secondly, the present invention also provides a method for preparing light-absorbing and heat-generating polylactic acid fibers, which includes the following process steps: S1: Melt-blend the raw materials of the core layer components and extrude and granulate to obtain the core layer masterbatch; S2: Melt-blend the raw materials of the cortex component, and then extrude and granulate to obtain cortex masterbatch; S3: After mixing the core layer masterbatch and the sheath masterbatch, the fibers are spun together, cooled, drawn, and wound to obtain light-absorbing and heat-generating polylactic acid fiber.

[0025] Preferably, the melt blending temperature of steps S1 and S2 is 170-210°C.

[0026] Preferably, the temperature for core-sheath composite spinning is 185-220℃.

[0027] Thirdly, the present invention also provides the application of polylactic acid fiber in the field of agricultural thermal insulation covering materials. The light-absorbing and heat-generating polylactic acid fiber obtained above can be used to prepare finished thermal insulation cloth.

[0028] The beneficial effects of this invention are: 1. This invention uses modified nano-cesium tungsten bronze particles as the main light-absorbing and heat-generating modifier. These particles can efficiently absorb near-infrared light and convert it into heat energy, giving polylactic acid fibers excellent light-absorbing and heat-generating capabilities. Furthermore, products made from nano-cesium tungsten bronze particles maintain high transparency, and their color can be controlled within a certain range. Modified nano-cesium tungsten bronze particles can achieve excellent heat insulation while also allowing functional fabrics to have a rich variety of colors.

[0029] 2. The modified nano-cesium tungsten bronze particles of this invention are further grafted with monothiol polyethylene glycol segments. The chemical structure and polarity of the polyethylene glycol chains enable the modified light-absorbing and heat-generating material to have good compatibility with the polylactic acid matrix. Therefore, the modified nano-cesium tungsten bronze particles can better integrate into the polymer matrix, effectively solving the problem of easy agglomeration of nanoparticles in the preparation process of light-absorbing and heat-generating polylactic acid fibers in the prior art.

[0030] 3. This invention prepares polylactic acid fibers into a core-sheath structure, placing the light-absorbing and heat-generating material in the core layer. The heat-generating material is tightly wrapped by the sheath, preventing it from falling off or being damaged due to friction or washing, thus ensuring the durability of the light-absorbing and heat-generating effect. Sunlight penetrates the fiber sheath and shines on the light-absorbing material in the core layer, thereby converting light energy into heat energy and achieving the light-absorbing and heat-generating effect. In addition, the sheath can isolate air and moisture, preventing the core material from oxidizing or failing, and extending the fiber life. This design maximizes the photothermal conversion efficiency, bringing a better heating experience. Detailed Implementation

[0031] The specific embodiments of the present invention will be described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0032] Preparation Example Preparation Example 1: A modified light-absorbing and heat-generating material is prepared by the following process steps: S1: Dissolve 0.4g of methoxy polyethylene glycol mercapto with a molecular weight of 2000 in 44.4ml of methanol to prepare a 4.5mM solution; S2: After cleaning and drying 1g of 30nm nano-cesium tungsten bronze particles, immerse them in the above solution and react at room temperature for 3 hours. After the reaction is complete, wash with methanol 3 times and deionized water 2 times. Dry in a vacuum oven at 50℃ for 12 hours to obtain the modified light-absorbing and heat-generating material.

[0033] Preparation Example 2, a modified light-absorbing and heat-generating material, differs from Preparation Example 1 only in that an equal amount of methoxy polyethylene glycol mercapto groups with a molecular weight of 1000 are used to replace methoxy polyethylene glycol mercapto groups with a molecular weight of 2000.

[0034] Preparation Example 3 is a modified light-absorbing and heat-generating material, which differs from Preparation Example 1 only in that an equal amount of methoxy polyethylene glycol mercapto groups with a molecular weight of 5000 are used to replace methoxy polyethylene glycol mercapto groups with a molecular weight of 2000.

[0035] Preparation Example 4 is a modified light-absorbing and heat-generating material, which differs from Preparation Example 1 only in that 0.4g of methoxy polyethylene glycol mercapto is replaced with 0.5g of methoxy polyethylene glycol mercapto.

[0036] Preparation Example 5, a modified light-absorbing and heat-generating material, differs from Preparation Example 1 only in that 0.4g of methoxy polyethylene glycol mercapto is replaced with 0.2g of methoxy polyethylene glycol mercapto.

[0037] Example Example 1: A light-absorbing and heat-generating polylactic acid fiber was prepared according to the following process steps: S1, the core layer component is obtained by mixing 45 parts of polylactic acid with an intrinsic viscosity of 0.68-0.70 dL / g and 4 parts of the modified light-absorbing and heat-generating material prepared in Preparation Example 1 in a high-speed mixer, then adding it to a twin-screw extruder and performing melt extrusion granulation at a temperature of 170-210℃. S2, the skin layer component is obtained by mixing 50 parts of polylactic acid with an intrinsic viscosity of 0.68-0.70 dL / g, 5 parts of nano silica and 3 parts of sebacic acid dibenzoyl hydrazine in a high-speed mixer, then adding it to a twin-screw extruder and melt extruding and granulating at a temperature of 170-210℃. S3. After the core layer component and the sheath component are melt-extruded separately, the temperature is set to 185-220℃. After core-sheath composite spinning, cooling, stretching and winding, light-absorbing and heat-generating polylactic acid fiber is obtained.

[0038] Example 2 is a light-absorbing and heat-generating polylactic acid fiber, which differs from Example 1 only in that the modified light-absorbing and heat-generating material prepared in Example 1 is replaced with an equal amount of the modified light-absorbing and heat-generating material prepared in Example 2.

[0039] Example 3 is a light-absorbing and heat-generating polylactic acid fiber, which differs from Example 1 only in that the modified light-absorbing and heat-generating material prepared in Example 1 is replaced with an equal amount of the modified light-absorbing and heat-generating material prepared in Example 3.

[0040] Example 4: A light-absorbing and heat-generating polylactic acid fiber, which differs from Example 1 only in that an equal amount of the modified light-absorbing and heat-generating material prepared in Example 4 is used to replace the modified light-absorbing and heat-generating material prepared in Example 1.

[0041] Example 5 is a light-absorbing and heat-generating polylactic acid fiber, which differs from Example 1 only in that the modified light-absorbing and heat-generating material prepared in Example 1 is replaced with an equal amount of the modified light-absorbing and heat-generating material prepared in Example 5.

[0042] Example 6, a light-absorbing and heat-generating polylactic acid fiber, differs from Example 1 only in that the raw materials of the core layer component include 45 parts of polylactic acid and 3 parts of the modified light-absorbing and heat-generating material prepared in Example 1.

[0043] Example 7, a light-absorbing and heat-generating polylactic acid fiber, differs from Example 1 only in that the raw materials of the core layer component include 45 parts of polylactic acid and 5 parts of the modified light-absorbing and heat-generating material prepared in Example 1.

[0044] Example 8, a light-absorbing and heat-generating polylactic acid fiber, differs from Example 1 only in that 3 parts of sebacic acid dibenzoylhydrazine are replaced with 3 parts of adipic acid di(2-benzoylhydrazine).

[0045] Comparative Example Comparative Example 1 is a light-absorbing and heat-generating polylactic acid fiber, which differs from Example 1 only in that the amount of modified light-absorbing and heat-generating material prepared in Example 1 is 8 parts.

[0046] Comparative Example 2 is a light-absorbing and heat-generating polylactic acid fiber, which differs from Example 1 only in that the amount of the modified light-absorbing and heat-generating material prepared in Example 1 is 1 part.

[0047] Comparative Example 3 is a light-absorbing and heat-generating polylactic acid fiber, which differs from Example 1 only in that an equal amount of unmodified nano-cesium tungsten bronze particles are used to replace the modified light-absorbing and heat-generating material prepared in Example 1.

[0048] Performance testing The fibers obtained in Examples 1-8 and Comparative Examples 1-6 were subjected to performance tests, and the test procedures are as follows: Tensile properties: in accordance with GB / T1040.2-2022 standard; Melt flow rate: According to GB / T3682-2000 standard, the test conditions are 2.16 kg and 190℃.

[0049] The results of the above experiments are shown in Table 1: Table 1 Performance test results

[0050] As can be seen from Examples 1, 2, and 3, the modification effects of using methoxy polyethylene glycol thiol groups with different molecular weights on nano-cesium tungsten bronze particles are not significantly different. Compared to Example 1, Example 2 shows a slightly better flowability and a slightly worse tensile strength. This may be because the methoxy polyethylene glycol thiol groups with smaller molecular weights have shorter molecular chains, less steric hindrance, a higher number of thiol moles per unit mass, and higher reactivity. Compared to Example 1, Example 3 shows a slightly worse flowability, but no significant change in tensile strength.

[0051] Compared with Example 1, it can be seen from Examples 1 and 2 that adding large or small amounts of modified light-absorbing and heat-generating material leads to poor flowability, while the tensile strength remains relatively unchanged. This may be because with small amounts, the particles can be dispersed more uniformly and independently. PLA molecular chains, which could originally slide freely, are strongly hindered by adsorption on the particle surface, increasing flow resistance. When the amount added is high, the distance between particles decreases sharply, resulting in excessively close particle spacing. The "bonding layers" on different particle surfaces overlap and entangle, forming a loose three-dimensional physical network in the entire system. During flow, additional shear force is required to disrupt this network, manifested as yield stress. Once the network is disrupted, severe frictional resistance still exists between the deagglomerated particles and between the particles and the PLA chains, leading to a sharp increase in shear viscosity.

[0052] As can be seen from Example 1 and Comparative Example 3, compared with the addition of unmodified light-absorbing and heat-generating material, the light-absorbing and heat-generating material modified with methoxy polyethylene glycol mercapto can significantly improve the flowability of light-absorbing and heat-generating polylactic acid fiber. This is because the chemical structure and polarity of the polyethylene glycol chain give it good compatibility with polylactic acid.

[0053] The above-disclosed embodiments are merely a few specific examples of the present invention. However, the embodiments of the present invention are not limited thereto, and any variations that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A light-absorbing and heat-generating polylactic acid fiber, characterized in that, The light-absorbing and heat-generating polylactic acid fiber comprises a sheath component and a core component; the raw material of the core component includes 3-5 parts of modified light-absorbing and heat-generating material; The modified light-absorbing and heat-generating material includes modified nano-cesium tungsten bronze particles; the surface of the modified nano-cesium tungsten bronze particles is grafted with monothiol polyethylene glycol segments.

2. The light-absorbing and heat-generating polylactic acid fiber according to claim 1, characterized in that, The raw materials for the modified nano-cesium tungsten bronze particles include nano-cesium tungsten bronze particles and methoxy polyethylene glycol mercapto in a mass ratio of (90-100):(30-40).

3. The light-absorbing and heat-generating polylactic acid fiber according to claim 2, characterized in that, The particle size of the nano-cesium tungsten bronze particles is 30nm-50nm.

4. The light-absorbing and heat-generating polylactic acid fiber according to claim 2, characterized in that, The preparation of the modified nano-cesium tungsten bronze particles includes the following process steps: Solution preparation: Dissolve the methoxy polyethylene glycol mercapto group in an organic solvent to prepare a 4.5-5 mM solution; Immersion assembly: Immerse the cleaned and dried nano-cesium tungsten bronze particles into the above solution and react at room temperature for 1-5 hours. After the reaction is completed, filter, wash and dry to obtain the final product.

5. The light-absorbing and heat-generating polylactic acid fiber according to claim 1, characterized in that, The core layer component also includes 35-55 parts by weight of polylactic acid.

6. The light-absorbing and heat-generating polylactic acid fiber according to claim 1, characterized in that, The weight ratio of the cortex component to the core component is (22-42):(62-82).

7. The light-absorbing and heat-generating polylactic acid fiber according to claim 1, characterized in that, The skin layer component comprises the following raw materials in parts by weight: 35-65 parts polylactic acid, 1-10 parts nano silica, and 0.5-5 parts nucleating agent.

8. The light-absorbing and heat-generating polylactic acid fiber according to claim 7, characterized in that, The nucleating agent includes one or a combination of two of sebacic acid dibenzoylhydrazine and adipic acid di(2-benzoylhydrazine).

9. A method for preparing light-absorbing and heat-generating polylactic acid fiber, used to prepare the light-absorbing and heat-generating polylactic acid fiber according to any one of claims 1-8, characterized in that, The process includes the following steps: S1: Melt-blend the raw materials of the core layer components and extrude and granulate to obtain the core layer masterbatch; S2: Melt-blend the raw materials of the cortex component, and then extrude and granulate to obtain cortex masterbatch; S3: After mixing the core layer masterbatch and the sheath masterbatch, the fibers are spun together, cooled, drawn, and wound to obtain light-absorbing and heat-generating polylactic acid fiber.

10. An application of a light-absorbing and heat-generating polylactic acid fiber, characterized in that, The light-absorbing and heat-generating polylactic acid fiber described in any one of claims 1-8 can be used to prepare finished thermal insulation fabric.

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