Preparation method and application of microgel nucleating agent modified polylactic acid composite fiber

Abstract

This invention discloses a method for preparing and applying polylactic acid (PLA) composite fibers modified with a microgel nucleating agent, relating to the technical field of PLA modification. The method comprises the following raw materials in parts by weight: 90-95 parts PLA resin; 1-5 parts multi-component epoxy monomers; 1-4 parts ring-opening agent; and 0-5 parts functional additives. This invention introduces a microgel nucleating agent into PLA through an in-situ melt reaction. This agent acts as both a nucleating agent to improve crystallinity and a physical crosslinking agent. The introduction of the microgel nucleating agent generates a three-dimensional network structure within the PLA, restricting the free movement of PLA chain segments and improving the system's elastic modulus and shear deformation resistance. Simultaneously, the physical interpenetrating crosslinking network allows the PLA chains a certain degree of sliding freedom in the molten state, ensuring fluidity during melt spinning. The preparation of the microgel nucleating agent in this method does not require a separate synthesis step; it can be added together with the additives during melt blending without adding extra processing steps.

Description

Technical Field

[0001] This invention relates to the field of polylactic acid modification technology, and in particular to a method for preparing polylactic acid composite fibers modified with microgel nucleating agents and their application. Background Technology

[0002] Polylactic acid (PLA) is a biodegradable polymer made from renewable resources such as corn or sugarcane, exhibiting good biocompatibility and environmental friendliness. However, traditional PLA materials suffer from drawbacks such as poor toughness, low glass transition temperature, and inadequate thermal stability and wear resistance, severely limiting their commercial application.

[0003] Due to the irregularity of PLA molecular chains, carbonyl groups on the chains form intermolecular or intramolecular hydrogen bonds with hydrogen atoms on adjacent chains. This results in poor molecular chain mobility, affecting the diffusion rate of the molecular chains into the crystal lattice. Consequently, the regular arrangement of molecular chains is severely affected during melt cooling, resulting in a heat distortion temperature (HDT) of only 55-65℃. Furthermore, PLA suffers from difficulties in homogeneous nucleation, large spherulite size, and slow crystallization rate during melt spinning. This leads to low mechanical strength and poor heat resistance in PLA fibers, severely limiting their application in apparel, home textiles, and automotive interiors. With increasing attention from academia and industry to heat-resistant PLA materials, research on heat-resistant PLA materials both domestically and internationally is becoming increasingly in-depth. Currently, the main methods for improving the heat resistance of PLA materials include blending modification, chain structure modification, and crystallization modification. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention discloses a method for preparing and applying polylactic acid (PLA) composite fibers modified with microgel nucleating agents. This method introduces a microgel nucleating agent into PLA via an in-situ melt reaction. This agent acts as both a nucleating agent to improve crystallinity and a physical crosslinking agent. The introduction of the microgel nucleating agent generates a three-dimensional network structure within the PLA, restricting the free movement of PLA chain segments and improving the system's elastic modulus and shear resistance. Simultaneously, the physically interpenetrating crosslinked network allows the PLA chains a certain degree of sliding freedom in the molten state, ensuring fluidity during melt spinning.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A microgel nucleating agent modified polylactic acid composite fiber, characterized in that it comprises the following raw materials in parts by weight:

[0007] 90-95 parts of PLA resin;

[0008] 1-5 parts of multi-component epoxy monomers;

[0009] Ring-opening agent 1-4 parts;

[0010] Functional additives: 0-5 parts.

[0011] Furthermore, the multi-element epoxy monomer is selected from one of epoxidized soybean oil, epoxidized castor oil, epoxidized palm oil, epoxidized rapeseed oil, and catechin multi-element epoxy.

[0012] Furthermore, the ring-opening agent is selected from one of tannic acid, cashew nut phenol, dopamine oligomer, and gallic acid modified product.

[0013] Furthermore, the molar ratio of the multi-component epoxy monomer to the ring-opening agent is 0.5:9.5-9.5:0.5.

[0014] Furthermore, the functional additives include antioxidants, antibacterial agents, plasticizers, and whitening agents.

[0015] This invention also discloses a method for preparing polylactic acid composite fibers modified with microgel nucleating agents, the specific process of which is as follows:

[0016] a. Mix PLA resin, multi-component epoxy monomers, ring-opening agents and additives in a certain proportion evenly, add them to a mixer for melt blending, control the melt temperature at 170-230℃, the blending time at 3-10 min, and the rotor speed at 20-120 r / min to obtain masterbatch; after pulverizing the masterbatch, send it to a micro spinning machine for melt spinning, and cool it in air to obtain microgel nucleating agent modified polylactic acid composite fiber nascent filament;

[0017] Alternatively, mix PLA resin, multi-component epoxy monomers, ring-opening agents, and additives in a certain proportion evenly, and add them to a twin-screw extruder at a uniform speed. Set the extruder temperature to 140-230℃ and the screw speed to 15-100 r / min to obtain masterbatch. After granulation, the masterbatch is fed into a micro-spinning machine for melt spinning and cooled in air to obtain microgel nucleating agent modified polylactic acid composite fiber spun chips.

[0018] Furthermore, in a and b, the melt blending equipment selected is a mixer, a single-screw extruder, a twin-screw extruder, a three-screw extruder, or a four-screw extruder.

[0019] Furthermore, in a and b, the melt spinning conditions are: spinning temperature of 160-240°C, hot drawing temperature of 80-120°C, heat setting temperature of 60-120°C, and drawing ratio of 1.5, 2.0, 2.5, and 3.0.

[0020] Furthermore, the polylactic acid composite fiber modified with microgel nucleating agent has a strength greater than 2.5 cN / dtex, a crystallinity of 50%, and a glass transition temperature of 85℃; it exhibits no obvious thermal curling in boiling water or 100℃ hot air, and a thermal shrinkage rate of 3-10%.

[0021] This invention also discloses the application of the above-mentioned microgel nucleating agent modified polylactic acid composite fiber in clothing, home textiles, and automotive interiors.

[0022] The beneficial effects of this invention, compared with the prior art, are as follows:

[0023] This method introduces a microgel nucleating agent into PLA via in-situ melt reaction. This microgel nucleating agent acts as both a nucleating agent to improve crystallinity and a physical crosslinking agent. The introduction of the microgel nucleating agent generates a three-dimensional network structure within the PLA, restricting the free movement of PLA chain segments and improving the system's elastic modulus and shear deformation resistance. Simultaneously, the physically interpenetrating crosslinked network allows the PLA chains a certain degree of sliding freedom in the molten state, ensuring fluidity during melt spinning.

[0024] In this method, the preparation of the microgel nucleating agent does not require a separate synthesis step. It can be added together with the auxiliary agents (such as antibacterial agents, antioxidants, and flame retardants) during the melt blending process without adding any additional process steps.

[0025] Alternatively, a one-step spinning method can be used, in which the PLA melt containing microgels can be directly used for melt spinning by controlling the screw length, reaction temperature, and residence time.

[0026] The microgel nucleating agent system generated by this in-situ melt reaction is applicable not only to PLA fibers but also to the preparation of PLA-based composite materials. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the DSC curve structure of pure PLA (6201D) and polylactic acid composite fiber modified with the prepared microgel nucleating agent in Example 2 of the present invention.

[0028] Figure 2 The loss factor of PLA characterized by DMA and the polylactic acid composite fiber modified with the microgel nucleating agent prepared in Example 2 of this invention.

[0029] Figure 3 This is a photograph of the heat shrinkage of pure PLA (LX175) and polylactic acid composite fibers modified with the prepared microgel nucleating agent in Example 4 of the present invention at 100°C. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] This invention introduces a microgel nucleating agent into PLA via in-situ melt reaction. This microgel nucleating agent can improve the crystallinity of PLA fibers and increase their glass transition temperature. Simultaneously, branched PLA or free radical cross-linked PLA can also improve its crystallinity, glass transition temperature, and strength, but its processing performance will decrease. This invention aims to provide a method for preparing a microgel nucleating agent that both acts as a nucleating agent and constructs a physical cross-linked network within PLA, resulting in a convenient and efficient modification of PLA and improved PLA fiber properties.

[0032] Example 1

[0033] A method for preparing polylactic acid composite fibers modified with microgel nucleating agents, the specific process is as follows:

[0034] (1) Mix 50g of spinning grade PLA (6201D, Natureworks), 3.5g of epoxidized soybean oil and 1.5g of tannic acid evenly, add them to a mixer for melt blending, control the melting temperature at 200℃, the blending time at 6min, and the rotor speed at 80r / min to obtain the masterbatch.

[0035] (2) After the masterbatch is crushed, it is fed into a micro spinning machine for melt spinning and cooled in the air to obtain microgel nucleating agent modified polylactic acid composite fiber nascent filament (PLA composite fiber 1).

[0036] The melt spinning conditions were as follows: spinning temperature 205℃, hot drawing temperature 110℃, heat setting temperature 90℃, drawing ratio 2.5, and drawing rate 100m / min.

[0037] Example 2

[0038] A method for preparing polylactic acid composite fibers modified with microgel nucleating agents, the specific process is as follows:

[0039] (1) Mix 50g of spinning grade PLA (6201D, Natureworks), 3.0g of epoxidized soybean oil and 2.0g of tannic acid evenly, and add them into a twin-screw extruder at a uniform speed. The temperatures of each section are 140℃, 160℃, 175℃, 185℃ and 200℃ respectively, and the screw speed is set to 60r / min to obtain the masterbatch.

[0040] (2) After the masterbatch is granulated, it is fed into a micro spinning machine for melt spinning and cooled in the air to obtain microgel nucleating agent modified polylactic acid composite fiber spinning chips (PLA composite fiber 2).

[0041] The melt spinning conditions were as follows: spinning temperature 210℃, hot drawing temperature 115℃, heat setting temperature 95℃, drawing ratio 2.5, and drawing rate 150m / min.

[0042] The thermal properties of pure PLA and PLA composite fiber 2 when the draw ratio is 2 are shown in Table 1. Neither the drawn pure PLA fiber nor the PLA composite fiber 2 exhibits a significant glass transition temperature or cold crystallization temperature. The melting temperature T of the PLA composite fiber 2 is [not specified]. m1 and T m2 Compared to pure PLA fibers, the temperature increases are 3.5℃ and 5.7℃ respectively, and the crystallinity reaches over 45%.

[0043] Table 1

[0044] sample <![CDATA[T g (℃)]]> <![CDATA[T c (℃)]]> <![CDATA[T m1 (℃)]]> <![CDATA[T m2 (℃)]]> <![CDATA[ΔH c (J / g)]]> <![CDATA[ΔH m (J / g)]]> <![CDATA[χ m (%)]]> Pure PLA (6201D) - - 152.8 141.7 - 38.3 40.0 PLA composite fiber 2 - - 156.3 147.4 - 37.8 46.2

[0045] The loss factor (Tanδ) results from DMA testing showed that the Tg (86.9℃) of PLA composite fiber 2 was 8.5℃ higher than that of pure PLA fiber (78.4℃). Figure 2 ).

[0046] Example 3

[0047] A method for preparing polylactic acid composite fibers modified with microgel nucleating agents, the specific process is as follows:

[0048] (1) Mix 50g of spinning grade PLA (6201D, Natureworks), 3.5g of epoxidized soybean oil, 1.5g of tannic acid, 0.25g of antioxidant, 0.50g of plasticizer and 0.1g of whitening agent evenly, add them to the internal mixer for melt blending, control the melting temperature at 200℃, and obtain the masterbatch.

[0049] (2) After the masterbatch is crushed, it is fed into a micro spinning machine for melt spinning and cooled in the air to obtain microgel nucleating agent modified polylactic acid composite fiber nascent filament (PLA composite fiber 3).

[0050] The melt spinning conditions were as follows: spinning temperature 210℃, hot drawing temperature 110℃, heat setting temperature 95℃, drawing ratio 2.0, and drawing rate 100m / min.

[0051] Example 4

[0052] A method for preparing polylactic acid composite fibers modified with microgel nucleating agents, the specific process is as follows:

[0053] (1) Mix 50g of spinning grade PLA (LX175, Total), 3.0g of epoxidized soybean oil, 2.0g of tannic acid, 0.25g of antioxidant, 0.50g of plasticizer and 0.1g of antibacterial agent evenly, and add them into a twin-screw extruder at a uniform speed. The temperatures of each section are 150℃, 170℃, 190℃, 200℃ and 210℃ respectively, and the screw speed is set to 60r / min to obtain the masterbatch.

[0054] (2) After the masterbatch is granulated, it is fed into a micro spinning machine for melt spinning and cooled in the air to obtain microgel nucleating agent modified polylactic acid composite fiber spinning chips (PLA composite fiber 4).

[0055] The melt spinning conditions were as follows: spinning temperature 210℃, hot drawing temperature 115℃, heat setting temperature 95℃, drawing ratio 2.5, and drawing rate 150m / min.

[0056] The results of the air thermal stability experiment at 100℃ are as follows: Figure 3 As shown in Table 2, both pure PLA (6201D) and the nascent PLA (LX175) filaments from Example 4 crimped in hot air at 100°C, with a heat shrinkage rate exceeding 50%. After hot stretching, the pure PLA fiber still crimped, with a heat shrinkage rate of 12.6%. In contrast, the composite fiber from Example 4 did not crimp, with a heat shrinkage rate of 7.5%, indicating that microgel nucleation can significantly improve the thermal stability of the PLA composite fiber.

[0057] Table 2

[0058] sample curly Shrinkage rate / % PLA (6201D Navel Silk) yes 54.0 Pure PLA yes 12.6 PLA (LX175) Naked Silk yes 53.0 PLA composite fiber 4 no 7.5

[0059] Example 5

[0060] A method for preparing polylactic acid composite fibers modified with microgel nucleating agents, the specific process is as follows:

[0061] (1) Mix 50g of spinning grade PLA (6201D, Natureworks), 0.5g of tetracyclic epoxy monomer, 0.5g of tannic acid, 0.25g of antioxidant, 0.1g of antibacterial agent and 0.1g of whitening agent evenly, and add them into a twin-screw extruder at a uniform speed. The temperatures of each section are 150℃, 170℃, 190℃, 200℃ and 210℃ respectively, and the screw speed is set to 60r / min to obtain the masterbatch.

[0062] (2) After the masterbatch is granulated, it is fed into a micro spinning machine for melt spinning and cooled in the air to obtain microgel nucleating agent modified polylactic acid composite fiber spinning chips (PLA composite fiber 5).

[0063] The melt spinning conditions were as follows: spinning temperature 210℃, hot drawing temperature 115℃, heat setting temperature 100℃, drawing ratio 2.5, and drawing rate 130m / min.

[0064] The mechanical properties of the polylactic acid composite fibers modified with microgel nucleating agents prepared in the above embodiments were tested, and the results are shown in Table 3 below. The strength of the composite fibers after thermal stretching was significantly improved compared with the nascent fibers.

[0065] Table 3

[0066] sample Nascent fiber strength (cN / dtex) Strength after hot stretching (cN / dtex) Pure PLA (6201D) 0.80±0.10 2.75±0.20 PLA composite fiber 1 0.82±0.07 2.63±0.12 PLA composite fiber 2 1.00±0.09 2.43±0.18 PLA composite fiber 3 1.03±0.03 2.31±0.08 PLA composite fiber 4 1.01±0.06 2.45±0.11 PLA composite fiber 5 1.54±0.06 3.10±0.22

[0067] Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A polylactic acid composite fiber modified with a microgel nucleating agent, characterized in that, The ingredients include the following parts by weight: 90-95 parts of PLA resin; 1-5 parts of multi-component epoxy monomers; Ring-opening agent 1-4 parts; Functional additives: 0-5 parts; The multi-electrode epoxy monomer is selected from one of epoxidized soybean oil, epoxidized castor oil, epoxidized palm oil, epoxidized rapeseed oil, and catechin multi-electrode epoxy. The ring-opening agent is selected from one of tannic acid, cashew nut phenol, and dopamine oligomers; The molar ratio of the multi-component epoxy monomer to the ring-opening agent is 0.5:9.5-9.5:0.5; The functional additives include antioxidants, antibacterial agents, plasticizers, and whitening agents.

2. The method for preparing polylactic acid composite fibers modified with microgel nucleating agents as described in claim 1, characterized in that, The specific process is as follows: a. Mix PLA resin, multi-component epoxy monomer, ring-opening agent and additives in a certain proportion evenly, add them to the internal mixer for melt blending, control the melt temperature to 170-230°C, the blending time to 3-10 min, and the rotor speed to 20-120 r / min to obtain the masterbatch; After the masterbatch is crushed, it is fed into a micro spinning machine for melt spinning and cooled in air to obtain the nascent polylactic acid composite fiber modified with microgel nucleating agent. Alternatively, mix PLA resin, multi-component epoxy monomers, ring-opening agents, and additives in a certain proportion evenly, and add them to a twin-screw extruder at a uniform speed. Set the extruder temperature to 140-240°C and the screw speed to 20-200 r / min to obtain masterbatch. After granulation, the masterbatch is fed into a micro-spinning machine for melt spinning and cooled in air to obtain microgel nucleating agent modified polylactic acid composite fiber spun chips.

3. The method for preparing polylactic acid composite fibers modified with microgel nucleating agents as described in claim 2, characterized in that, In both a and b, the melt spinning conditions are: spinning temperature of 160-240°C, hot drawing temperature of 80-120°C, heat setting temperature of 60-120°C, drawing ratio of 1.5, 2.0, 2.5, and 3.0, and drawing rate of 100-2000 cm / min.

4. The method for preparing polylactic acid composite fibers modified with microgel nucleating agents as described in claim 3, characterized in that, The polylactic acid composite fiber modified with microgel nucleating agent has a strength greater than 2.5 cN / dtex, a crystallinity of over 45%, and a glass transition temperature of 86.9°C. It exhibits no obvious thermal curling in boiling water or 100°C hot air and has a thermal shrinkage rate of 3-10%.

5. The application of polylactic acid composite fibers modified with microgel nucleating agents as described in claim 1 in clothing, home textiles, and automotive interiors.

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