Preparation process of anti-static polylactic acid superfine fiber fabric

Abstract

The invention relates to the technical field of polylactic acid fibers, and discloses a preparation process of an anti-static polylactic acid superfine fiber fabric, star-shaped polylactic acid grafted carbon nanotubes are prepared from tetra (hydroxymethyl) phosphorus chloride, 2-amino-4, 6-dimethoxy-1, 3, 5-triazine and the like as raw materials, and the star-shaped polylactic acid grafted carbon nanotubes and polylactic acid slices are subjected to melt spinning to obtain the polylactic acid superfine fiber fabric; the star-shaped polylactic acid grafted carbon nanotubes have a structure similar to that of a polylactic acid matrix, so that the carbon nanotubes are uniformly dispersed in a polymer matrix and form relatively strong interface bonding, migration and precipitation are avoided, and the star-shaped polylactic acid grafted carbon nanotubes have anti-static durability; the structure of the superfine fiber fabric contains nitrogen and phosphorus synergistic flame-retardant elements, so that the exchange between a fiber matrix and oxygen and heat in the air can be blocked, and the flame-retardant property of the superfine fiber fabric is improved; the density of the fiber fabric can be increased by the formed cross-linked network structure, so that the mechanical property of the superfine fiber fabric is remarkably improved.

Description

Technical Field

[0001] The invention relates to the technical field of polylactic acid fibers, in particular to a preparation process of an antistatic polylactic acid ultrafine fiber fabric. Background Art

[0002] Polylactic acid microfiber fabric is a new type of fabric based on sustainable biomass raw materials, with biodegradability and excellent physical properties. With people's increasing attention to environmental protection and health, its application prospects will be broader; due to the extremely small fiber diameter of polylactic acid microfiber fabric, it has an extremely high specific surface area and excellent softness, breathability, moisture absorption and other properties, which makes it have broad application prospects in clothing, bedding, sanitary products and other fields; however, in relatively dry seasons with a lack of air circulation, polylactic acid fiber fabrics are prone to static electricity, which will affect the comfort of wearing and cause the fabric to easily absorb dust or hair. In addition, static electricity may also cause spark discharge, causing fire and other dangers. Therefore, improving the anti-static and flame retardant properties of polylactic acid fiber fabrics has become a hot topic of current research.

[0003] In the prior art, in order to avoid static electricity problems on fiber fabrics, some antistatic detergents or antistatic sprays are generally used. Most of them are outer coatings with poor heat resistance and durability, which are harmful to the skin. In addition, they suffer large losses and fail quickly under application conditions such as friction and washing, and are not suitable for use on polylactic acid fiber fabrics. Patent No. CN115058789B discloses a method for preparing flexible antistatic polylactic acid fibers, in which an antistatic agent is added to polylactic acid in a prepolymerization stage with low molecular weight and low viscosity, thereby giving the polylactic acid fibers better antistatic properties. Compared with the process of adding antistatic agents to polylactic acid slices, the method greatly reduces energy consumption and reduces production costs. However, the added antistatic agent still has poor compatibility with the polylactic acid matrix, and the added antistatic agent is a small molecule antistatic agent, which is easy to migrate and precipitate, and the antistatic durability needs to be further enhanced.

[0004] Carbon nanotubes have a hollow tubular structure, a large specific surface area, strong adsorption capacity and excellent electrical conductivity, but they have poor interfacial bonding with the polylactic acid matrix and are unevenly dispersed, which often leads to a decline in mechanical properties and processing performance. At the same time, polylactic acid itself has poor toughness, low impact resistance and poor filling fluidity, which limits its application in fiber fabrics. The present invention aims to modify the surface of carbon nanotubes by synthesizing a star-shaped polylactic acid with flame retardant properties, improve the easy agglomeration of carbon nanotubes in the polylactic acid matrix, make them uniformly dispersed in the polymer matrix and form a strong interfacial bond, give full play to the toughening and strengthening effects, avoid migration and precipitation, and have anti-static durability and good flame retardant properties. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a preparation process of antistatic polylactic acid microfiber fabric, to prepare a polylactic acid fiber fabric with good antistatic performance and excellent flame retardant performance, and to broaden its application range.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions: A preparation process of an antistatic polylactic acid microfiber fabric is carried out according to the following steps: Step (1): under a nitrogen atmosphere, add six-arm star-shaped phosphorus nitrogen-based polylactic acid and N,N-dimethylacetamide to a reaction flask, stir evenly, add acyl chloride carbon nanotubes and pyridine, react at 115-130° C. for 24-48 hours, cool to room temperature, filter with a microporous filter membrane, wash with methanol, and dry to obtain star-shaped polylactic acid grafted carbon nanotubes.

[0007] Step (2): placing the polylactic acid dry slices and the star-shaped polylactic acid grafted carbon nanotubes in a Haake torque rheometer, melt-blending them at a temperature of 175-190° C. and a rotation speed of 40-60 r / min for 5-10 minutes, adding them to a spinning machine, extruding them through a spinning assembly and a spinneret, and then cooling, oiling, stretching, and winding them to obtain an antistatic polylactic acid ultrafine fiber fabric.

[0008] Preferably, in step (1), the ratio of six-arm star-shaped phosphorus nitrogen-based polylactic acid, acyl chloride carbon nanotubes, and pyridine is 100 g: (25-40) g: (18-25) g.

[0009] Preferably, in step (2), the ratio of the polylactic acid dry chips to the star-shaped polylactic acid grafted carbon nanotubes is 100 g:(2-10) g.

[0010] Preferably, in step (2), the temperature of each zone of the spinning machine is 180-200°C, the spinning speed is 750-1000 m / min, and the stretching temperature is 80-90°C.

[0011] Preferably, the preparation process of the six-arm star-shaped phosphorus-nitrogen-based polylactic acid in step (1) is carried out according to the following steps: Step S1: under a nitrogen atmosphere, tetrakis(hydroxymethyl)phosphonium chloride and ethanol were added to a reaction flask, stirred evenly, and then 2-amino-4,6-dimethoxy-1,3,5-triazine was added and stirred for reaction. After the reaction was completed, the mixture was allowed to stand for precipitation, filtered, washed with ethanol, and dried to obtain a tetrakis(triazinebismethoxy)phosphonium intermediate.

[0012] Step S2: Under a nitrogen atmosphere, add tetrakis(triazinebismethoxy)phosphorus intermediate and dichloromethane to a reaction flask, stir evenly, add boron tribromide, react at 0-20°C for 16-32 hours, add methanol to quench, extract with ethyl acetate and deionized water, concentrate the organic phase, and dry to obtain a hexahydroxyphosphorus nitrogen intermediate.

[0013] Step S3: Add lactide, hexahydroxyphosphorus nitrogen intermediate and stannous octoate to the reactor under nitrogen atmosphere, evacuate to vacuum, react at 140-160° C. for 12-24 hours, cool after the reaction, add chloroform to dissolve, then add methanol to precipitate, filter, wash with ethanol, and dry to obtain a six-arm star-shaped phosphorus nitrogen-based polylactic acid.

[0014] Preferably, in step S1, the ratio of tetrakis(hydroxymethyl)phosphonium chloride to 2-amino-4,6-dimethoxy-1,3,5-triazine is 1 mol:(4.1-4.5) mol.

[0015] Preferably, the reaction temperature in step S1 is 20-35° C., and the reaction time is 2-5 h.

[0016] Preferably, in step S2, the ratio of the tetrakis(triazinebismethoxy)phosphorus intermediate to boron tribromide is 1 mol:(6.5-8) mol.

[0017] Preferably, the lactide in step S3 is any one of D-lactide, L-lactide or D,L-lactide.

[0018] Preferably, in step S3, the ratio of lactide, hexahydroxyphosphorus nitrogen intermediate, and stannous octoate is 1 mol: (0.15-0.25) mol: (0.02-0.05) mol.

[0019] Compared with the prior art, the present invention has the following beneficial effects: (1) Carbon nanotubes have a large aspect ratio and a large number of π bonds. Electrons can move through the π bonds to form current, and a partial conductive path can be formed inside the fiber. As the content of carbon nanotubes increases, a complete conductive network structure is gradually formed. At the same time, carbon nanotubes are also lubricants, which have a certain lubricity on the fiber surface and can reduce the friction coefficient, thereby inhibiting and reducing the generation of static charge. Star-shaped polylactic acid grafted carbon nanotubes have a structure similar to that of the polylactic acid matrix and have good interfacial compatibility, so that the carbon nanotubes are evenly dispersed in the polymer matrix and form a strong interfacial bond, avoiding migration and precipitation, and having anti-static and long-lasting properties.

[0020] (2) Star-shaped polylactic acid grafted carbon nanotubes contain triazine rings, which decompose to produce inert gases when heated, diluting the concentration of oxygen and combustible gases in the air. At the same time, they have excellent carbonization ability. When the material is burned by a fire source, a foam-like protective layer will be formed to isolate the fire source and the material, thereby slowing down or preventing the spread of the flame. In addition, phosphorus-containing substances decompose to produce phosphoric acid or polyphosphoric acid during combustion, and then form a dense carbon layer, isolating the matrix from heat and oxygen in a solid form. Phosphorus and nitrogen elements synergistically act as flame retardants, and further cross-link into a denser carbon layer during the combustion process, blocking the exchange of oxygen and heat between the fiber matrix and the air, significantly improving the flame retardant properties of the microfiber fabric.

[0021] (3) Carbon nanotubes can be chemically grafted with multi-arm polylactic acid, making them uniformly dispersed in the polylactic acid matrix, improving the interaction between composite materials, forming a cross-linked network structure, and increasing the density of the fiber fabric; at the same time, the carbon nanotubes have a large specific surface area, which increases the contact area with the matrix and provides a guarantee for physical entanglement, thereby significantly improving the mechanical properties of the ultrafine fiber fabric and broadening its application range. DETAILED DESCRIPTION

[0022] The technical solutions of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0023] Unless otherwise stated, the raw materials and reagents used in this application are commercially available or can be prepared by known methods.

[0024] Preparation of chlorinated carbon nanotubes: 1g of carbon nanotubes was placed in a mixture of 120mL of sulfuric acid and concentrated nitric acid (volume ratio of 3:1), ultrasonically oscillated at room temperature for 30min, stirred and reacted in an 80°C oil bath for 4h, then diluted with 2L of deionized water, filtered with a microporous filter membrane, washed until neutral, and vacuum dried at 70°C for 24h to obtain carboxylated carbon nanotubes; 1g of carbon nanotubes was added to 100mL of thionyl chloride, ultrasonically oscillated for 15min, and then 2-3mL of N,N-dimethylformamide was added as a catalyst, and reacted in an oil bath at 70°C for 48h. The remaining thionyl chloride was removed by reduced pressure distillation, the product was washed with tetrahydrofuran, and dried to obtain chlorinated carbon nanotubes.

[0025] Tetrakis(hydroxymethyl)phosphonium chloride, CAS number is 124-64-1.

[0026] 2-Amino-4,6-dimethoxy-1,3,5-triazine, CAS number 3140-73-6. Example

[0027] (1) Under nitrogen atmosphere, 45 mmol of tetrakis(hydroxymethyl)phosphonium chloride and 270 mL of ethanol were added to a reaction flask. After stirring evenly, 190 mmol of 2-amino-4,6-dimethoxy-1,3,5-triazine was added and reacted at 25 °C for 4 h. The mixture was allowed to stand for precipitation, filtered, washed with ethanol, and dried to obtain the tetrakis(triazine dimethoxy)phosphonium intermediate.

[0028] (2) Under nitrogen atmosphere, 42 mmol of tetrakis(triazinebismethoxy)phosphorus intermediate and 605 mL of dichloromethane were added to the reaction flask. After stirring evenly, 315 mmol of boron tribromide was added. The mixture was reacted at 5 °C for 24 h. Methanol was added to quench the mixture. The mixture was extracted with ethyl acetate and deionized water. The organic phase was concentrated and dried to obtain the hexahydroxyphosphorus nitrogen intermediate.

[0029] (3) Under nitrogen atmosphere, 35 mmol of D-lactide, 7 mmol of hexahydroxyphosphorus nitrogen intermediate, and 1.4 mmol of stannous octoate were added to the reactor, the nitrogen was evacuated to vacuum, and the reaction was carried out at 150°C for 18 hours. After the reaction, the reaction was cooled, chloroform was added to dissolve, and then methanol was added to precipitate. The reaction was filtered, washed with ethanol, and dried to obtain a six-arm star-shaped phosphorus nitrogen-based polylactic acid. The preparation reaction formula is as follows:

[0030] (4) Under nitrogen atmosphere, 10 g of six-arm star-shaped phosphorus nitrogen-based polylactic acid and 45 mL of N,N-dimethylacetamide were added to the reaction flask, stirred evenly, and then 2.5 g of acyl chloride carbon nanotubes and 2.2 g of pyridine were added. The mixture was reacted at 120 °C for 32 h, cooled to room temperature, filtered with a microporous filter membrane, washed with methanol, and dried to obtain star-shaped polylactic acid grafted carbon nanotubes.

[0031] (5) 100 g of PLA dry chips and 2 g of star-shaped PLA grafted carbon nanotubes were placed in a Haake torque rheometer, melt-blended at a temperature of 185 °C and a rotation speed of 50 r / min for 8 min, added to a spinning machine, and extruded through a spinning assembly and a spinneret. The temperature of each zone of the spinning machine was 190 °C, the spinning speed was 900 m / min, and the stretching temperature was 85 °C. The fabric was then cooled, oiled, stretched, and wound to obtain an antistatic PLA microfiber fabric. Example

[0032] (1) Under nitrogen atmosphere, add 120 mmol of tetrakis(hydroxymethyl)phosphonium chloride and 600 mL of ethanol to a reaction flask. After stirring evenly, add 492 mmol of 2-amino-4,6-dimethoxy-1,3,5-triazine. React at 35°C for 2 h. Let stand to precipitate, filter, wash with ethanol, and dry to obtain tetrakis(triazine dimethoxy)phosphonium intermediate.

[0033] (2) Under nitrogen atmosphere, 105 mmol of tetrakis(triazinebismethoxy)phosphorus intermediate and 1050 mL of dichloromethane were added to the reaction flask. After stirring evenly, 682.5 mmol of boron tribromide was added. The mixture was reacted at 20 °C for 16 h. Methanol was added to quench the mixture. The mixture was extracted with ethyl acetate and deionized water. The organic phase was concentrated and dried to obtain the hexahydroxyphosphorus nitrogen intermediate.

[0034] (3) Under nitrogen atmosphere, 90 mmol of L-lactide, 13.5 mmol of hexahydroxyphosphorus nitrogen intermediate and 1.8 mmol of stannous octoate were added to the reactor, and nitrogen was evacuated to vacuum. The reaction was carried out at 160 °C for 12 h. After the reaction, the reaction was cooled, chloroform was added to dissolve, and then methanol was added to precipitate. The mixture was filtered, washed with ethanol, and dried to obtain a six-arm star-shaped phosphorus nitrogen-based polylactic acid.

[0035] (4) Under nitrogen atmosphere, 10 g of six-arm star-shaped phosphorus nitrogen-based polylactic acid and 40 mL of N,N-dimethylacetamide were added to the reaction flask, stirred evenly, and then 2.9 g of acyl chloride carbon nanotubes and 1.8 g of pyridine were added. The mixture was reacted at 130 °C for 24 h, cooled to room temperature, filtered with a microporous filter membrane, washed with methanol, and dried to obtain star-shaped polylactic acid grafted carbon nanotubes.

[0036] (5) 100 g of PLA dry chips and 4 g of star-shaped PLA grafted carbon nanotubes were placed in a Haake torque rheometer, melt-blended at a temperature of 190 °C and a rotation speed of 60 r / min for 5 min, added to a spinning machine, and extruded through a spinning assembly and a spinneret. The temperature of each zone of the spinning machine was 200 °C, the spinning speed was 1000 m / min, and the stretching temperature was 90 °C. The fabric was then cooled, oiled, stretched, and wound to obtain an antistatic PLA microfiber fabric. Example

[0037] (1) Under nitrogen atmosphere, add 65 mmol of tetrakis(hydroxymethyl)phosphonium chloride and 520 mL of ethanol to a reaction flask. After stirring evenly, add 292.5 mmol of 2-amino-4,6-dimethoxy-1,3,5-triazine. React at 20°C for 5 h, let it stand for precipitation, filter, wash with ethanol, and dry to obtain tetrakis(triazine dimethoxy)phosphonium intermediate.

[0038] (2) Under nitrogen atmosphere, add 60 mmol of tetrakis(triazinebismethoxy)phosphorus intermediate and 900 mL of dichloromethane to the reaction flask. After stirring evenly, add 480 mmol of boron tribromide and react at 0°C for 32 h. Add methanol to quench, extract with ethyl acetate and deionized water, concentrate the organic phase, and dry to obtain the hexahydroxyphosphorus nitrogen intermediate.

[0039] (3) Under nitrogen atmosphere, 50 mmol of D,L-lactide, 12.5 mmol of hexahydroxyphosphorus nitrogen intermediate and 2.5 mmol of stannous octoate were added to the reactor, and nitrogen was evacuated to vacuum. The reaction was carried out at 140 °C for 24 h. After the reaction, the reaction was cooled, chloroform was added to dissolve, and then methanol was added to precipitate. The mixture was filtered, washed with ethanol, and dried to obtain a six-arm star-shaped phosphorus nitrogen-based polylactic acid.

[0040] (4) Under nitrogen atmosphere, 10 g of six-arm star-shaped phosphorus nitrogen-based polylactic acid and 55 mL of N,N-dimethylacetamide were added to the reaction flask, stirred evenly, and then 3.3 g of acyl chloride carbon nanotubes and 2.5 g of pyridine were added. The mixture was reacted at 115 °C for 48 h, cooled to room temperature, filtered through a microporous filter membrane, washed with methanol, and dried to obtain star-shaped polylactic acid grafted carbon nanotubes.

[0041] (5) 100 g of PLA dry chips and 6 g of star-shaped PLA grafted carbon nanotubes were placed in a Haake torque rheometer, melt-blended at a temperature of 175 °C and a rotation speed of 40 r / min for 10 min, added to a spinning machine, and extruded through a spinning assembly and a spinneret. The temperature of each zone of the spinning machine was 180 °C, the spinning speed was 750 m / min, and the stretching temperature was 80 °C. The fabric was then cooled, oiled, stretched, and wound to obtain an antistatic PLA microfiber fabric. Example

[0042] (1) Under nitrogen atmosphere, add 80 mmol of tetrakis(hydroxymethyl)phosphonium chloride and 550 mL of ethanol to a reaction flask. After stirring evenly, add 340 mmol of 2-amino-4,6-dimethoxy-1,3,5-triazine. React at 30°C for 4 h, let it stand for precipitation, filter, wash with ethanol, and dry to obtain tetrakis(triazine dimethoxy)phosphonium intermediate.

[0043] (2) Under nitrogen atmosphere, add 72 mmol of tetrakis(triazinebismethoxy)phosphorus intermediate and 900 mL of dichloromethane to the reaction flask. After stirring evenly, add 540 mmol of boron tribromide and react at 15 °C for 20 h. Add methanol to quench, extract with ethyl acetate and deionized water, concentrate the organic phase, and dry to obtain the hexahydroxyphosphorus nitrogen intermediate.

[0044] (3) Under nitrogen atmosphere, 65 mmol of D-lactide, 15.6 mmol of hexahydroxyphosphorus nitrogen intermediate and 2.48 mmol of stannous octoate were added to the reactor, and nitrogen was evacuated to vacuum. The reaction was carried out at 155 °C for 22 h. After the reaction, the reaction was cooled, chloroform was added to dissolve, and then methanol was added to precipitate. The reaction was filtered, washed with ethanol, and dried to obtain a six-arm star-shaped phosphorus nitrogen-based polylactic acid.

[0045] (4) Under nitrogen atmosphere, 10 g of six-arm star-shaped phosphorus nitrogen-based polylactic acid and 45 mL of N,N-dimethylacetamide were added to the reaction flask, stirred evenly, and then 3.7 g of acyl chloride carbon nanotubes and 2 g of pyridine were added. The mixture was reacted at 120 °C for 36 h, cooled to room temperature, filtered through a microporous filter membrane, washed with methanol, and dried to obtain star-shaped polylactic acid grafted carbon nanotubes.

[0046] (5) 100 g of PLA dry chips and 8 g of star-shaped PLA grafted carbon nanotubes were placed in a Haake torque rheometer, melt-blended at a temperature of 180 °C and a rotation speed of 55 r / min for 8 min, added to a spinning machine, and extruded through a spinning assembly and a spinneret. The temperature of each zone of the spinning machine was 185 °C, the spinning speed was 800 m / min, and the stretching temperature was 90 °C. The fabric was then cooled, oiled, stretched, and wound to obtain an antistatic PLA microfiber fabric. Example

[0047] (1) Under nitrogen atmosphere, 30 mmol of tetrakis(hydroxymethyl)phosphonium chloride and 220 mL of ethanol were added to a reaction flask. After stirring evenly, 130.5 mmol of 2-amino-4,6-dimethoxy-1,3,5-triazine was added and reacted at 35 °C for 5 h. The mixture was allowed to stand for precipitation, filtered, washed with ethanol, and dried to obtain the tetrakis(triazine dimethoxy)phosphonium intermediate.

[0048] (2) Under nitrogen atmosphere, add 25 mmol of tetrakis(triazinebismethoxy)phosphorus intermediate and 350 mL of dichloromethane to the reaction flask, stir evenly, add 180 mmol of boron tribromide, react at 5 °C for 24 h, add methanol to quench, extract with ethyl acetate and deionized water, concentrate the organic phase, and dry to obtain the hexahydroxyphosphorus nitrogen intermediate.

[0049] (3) Under nitrogen atmosphere, 20 mmol of L-lactide, 3.6 mmol of hexahydroxyphosphorus nitrogen intermediate and 0.7 mmol of stannous octoate were added to the reactor, and nitrogen was evacuated to vacuum. The reaction was carried out at 160 °C for 24 h. After the reaction, the reaction was cooled, chloroform was added to dissolve, and then methanol was added to precipitate. The reaction was filtered, washed with ethanol, and dried to obtain a six-arm star-shaped phosphorus nitrogen-based polylactic acid.

[0050] (4) Under nitrogen atmosphere, 10 g of six-arm star-shaped phosphorus nitrogen-based polylactic acid and 48 mL of N,N-dimethylacetamide were added to the reaction flask, stirred evenly, and then 4 g of acyl chloride carbon nanotubes and 2.4 g of pyridine were added. The mixture was reacted at 130 °C for 48 h, cooled to room temperature, filtered through a microporous filter membrane, washed with methanol, and dried to obtain star-shaped polylactic acid grafted carbon nanotubes.

[0051] (5) 100 g of PLA dry chips and 10 g of star-shaped PLA grafted carbon nanotubes were placed in a Haake torque rheometer, melt-blended at a temperature of 190 °C and a rotation speed of 50 r / min for 10 min, added to a spinning machine, and extruded through a spinning assembly and a spinneret. The temperature of each zone of the spinning machine was 195 °C, the spinning speed was 950 m / min, and the stretching temperature was 85 °C. The fabric was then cooled, oiled, stretched, and wound to obtain an antistatic PLA microfiber fabric.

[0052] Comparative Example 1 (1) Under nitrogen atmosphere, 35 mmol of D-lactide and 7 mmol of dipentaerythritol (structural formula: , CAS No. 126-58-9) and 1.4 mmol of stannous octoate, evacuate to vacuum with nitrogen, react at 150°C for 18 hours, cool after the reaction, add chloroform to dissolve, then add methanol to precipitate, filter, wash with ethanol, and dry to obtain six-arm star-shaped polylactic acid.

[0053] (2) Under nitrogen atmosphere, 10 g of six-arm star-shaped polylactic acid and 45 mL of N,N-dimethylacetamide were added to the reaction flask, stirred evenly, and then 2.5 g of acyl chloride carbon nanotubes and 2.2 g of pyridine were added. The mixture was reacted at 120 °C for 32 h, cooled to room temperature, filtered with a microporous filter membrane, washed with methanol, and dried to obtain star-shaped polylactic acid grafted carbon nanotubes.

[0054] (3) 100 g of PLA dry chips and 2 g of star-shaped PLA grafted carbon nanotubes were placed in a Haake torque rheometer, melt-blended at a temperature of 185 °C and a rotation speed of 50 r / min for 8 min, added to a spinning machine, and extruded through a spinning assembly and a spinneret. The temperature of each zone of the spinning machine was 190 °C, the spinning speed was 900 m / min, and the stretching temperature was 85 °C. The fabric was then cooled, oiled, stretched, and wound to obtain a PLA microfiber fabric.

[0055] Comparative Example 2 100 g of polylactic acid dry chips and 2 g of six-arm star-shaped phosphorus-nitrogen-based polylactic acid (prepared in Example 1) were placed in a Haake torque rheometer, melt-blended at a temperature of 185°C and a rotation speed of 50 r / min for 8 minutes, added to a spinning machine, and extruded through a spinning assembly and a spinneret, wherein the temperature of each zone of the spinning machine was 190°C, the spinning speed was 900 m / min, and the stretching temperature was 85°C. The fabric was then cooled, oiled, stretched, and wound to obtain a polylactic acid microfiber fabric.

[0056] Comparative Example 3 100g of polylactic acid dry chips and 2g of carbon nanotubes were placed in a Haake torque rheometer, melt-blended at a temperature of 185°C and a rotation speed of 50r / min for 8min, added to a spinning machine, and extruded through a spinning assembly and a spinneret. The temperature of each zone of the spinning machine was 190°C, the spinning speed was 900m / min, and the stretching temperature was 85°C. The fabric was then cooled, oiled, stretched, and wound to obtain a polylactic acid microfiber fabric.

[0057] Resistivity test: The prepared polylactic acid microfiber fabric sample was cut into 30mm short fibers, rubbed into a fluffy shape, and balanced under standard conditions for 48 hours. Then, the fiber resistivity meter was used for testing. Each sample was tested 10 times and the average value was taken.

[0058] Friction electrostatic voltage test: The prepared polylactic acid microfiber fabric sample was woven into a 5cm×20cm knitted fabric using a hand-cranked knitting machine, and the induced electrostatic voltage of the fabric was tested using a friction-type fabric static tester. Each sample was tested 10 times and the average value was taken.

[0059] Table 1 Antistatic performance test <![CDATA[比电阻×10 -8 (Ω·cm)]]> Tribo-triboelectric voltage (V) Example 1 8.96 988 Example 2 7.52 905 Example 3 5.84 824 Example 4 4.10 708 Example 5 3.88 670 Comparative Example 1 9.02 995 Comparative Example 2 18.35 1680 Comparative Example 3 14.21 1325 The antistatic performance of fiber fabrics is characterized by specific resistivity. As specific resistivity decreases, the insulation of the fiber fabric decreases, the conductivity increases, and the antistatic performance improves. The antistatic performance of fiber fabrics is characterized by the induced static voltage after friction. The smaller the induced static voltage after friction, the better the antistatic performance of the fiber fabric. The test results in the table above show that with the increase of the content of star-shaped polylactic acid grafted carbon nanotubes, the antistatic performance of polylactic acid microfiber fabrics gradually increases. The specific resistivity of Example 4 is 4.10×10 -8 Ω·cm, and a tribostatic voltage of 708V, indicating excellent antistatic performance. This is because, on the one hand, carbon nanotubes have a large aspect ratio and a large number of π bonds. Electrons can move through the π bonds to form current, forming a partial conductive path within the fiber. As the carbon nanotube content increases, a complete conductive network structure gradually forms. At the same time, carbon nanotubes are also lubricants, with a certain lubricity on the fiber surface, which can reduce the friction coefficient and thus inhibit and reduce the generation of static charge. On the other hand, the star-shaped polylactic acid grafted carbon nanotubes have a structure similar to that of the polylactic acid matrix and have good interfacial compatibility. The carbon nanotubes are evenly dispersed in the polymer matrix and form a strong interfacial bond, avoiding migration and precipitation, and have long-lasting antistatic performance.

[0060] Comparative Example 1 does not contain carbon nanotubes and has no antistatic properties; the carbon nanotubes added in Comparative Example 3 are not modified, have poor compatibility with the polylactic acid matrix, are easily agglomerated, are difficult to form a good conductive path, and have poor antistatic properties.

[0061] Flame retardant performance test: The test is carried out in accordance with GB / T 5455-2014 standard, and the flame retardant performance of microfiber fabrics is evaluated by afterflaming time and damage length.

[0062] Table 2 Flame retardant performance test Afterglow time (s) Damage length (mm) Example 1 10.3 19.6 Example 2 8.2 17.2 Example 3 5.5 14.9 Example 4 3.1 11.5 Example 5 2.4 8.8 Comparative Example 1 38.5 52.7 Comparative Example 2 11.0 19.2 Comparative Example 3 42.8 55.4 The test results in the table above show that the flame retardancy of the polylactic acid microfiber fabric gradually improves with increasing content of star-shaped polylactic acid grafted carbon nanotubes. In Example 5, the afterflame time was only 2.4 seconds, and the damaged length was 8.8 mm, indicating good flame retardancy. This is because the star-shaped polylactic acid grafted carbon nanotubes contain triazine rings, which decompose upon heating to produce inert gases, diluting the oxygen and combustible gas concentrations in the air. They also have excellent charring ability. When the material is exposed to a fire source, a foam-like protective layer is formed, isolating the fire source from the material, thereby slowing or preventing the spread of flames. Furthermore, phosphorus-containing substances decompose upon combustion to produce phosphoric acid or polyphosphoric acid, which in turn forms a dense char layer that insulates the matrix from heat and oxygen in a solid form. The phosphorus and nitrogen elements synergistically act as flame retardants, further cross-linking during combustion to form a denser char layer, blocking the exchange of oxygen and heat between the fiber matrix and the air, significantly improving the flame retardancy of the microfiber fabric. Comparative Examples 1 and 3 do not contain phosphorus and nitrogen flame retardants and therefore lack flame retardancy.

[0063] Mechanical properties test: The test was carried out using an electronic strength tester for chemical fiber filaments with a clamping distance of 200 mm. Each sample was tested 10 times and the average value was taken.

[0064] Table 3 Mechanical properties test Breaking strength (cN / dtex) Example 1 1.76 Example 2 1.81 Example 3 1.95 Example 4 2.06 Example 5 2.15 Comparative Example 1 1.72 Comparative Example 2 1.63 Comparative Example 3 1.48 It can be seen from the test results in the above table that with the increase of the content of star-shaped polylactic acid grafted carbon nanotubes, the mechanical properties of the polylactic acid microfiber fabric gradually increase, and Example 5 reaches 2.15 cN / dtex. The main reason is that the carbon nanotubes and the multi-arm polylactic acid are chemically grafted, so that they are evenly dispersed in the polylactic acid matrix, which improves the interaction between the composite materials, forms a cross-linked network structure, and increases the density of the fiber fabric; at the same time, the carbon nanotubes have a large specific surface area, which increases the contact area with the matrix, provides a guarantee for physical entanglement, and thus significantly improves the mechanical properties of the microfiber fabric.

[0065] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment as above, it is not intended to limit the present invention. Any technician familiar with the present profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A preparation process for antistatic polylactic acid microfiber fabric, characterized in that: The preparation process is carried out according to the following steps: Step (1), under a nitrogen atmosphere, add six-arm star-shaped phosphorus nitrogen-based polylactic acid and N,N-dimethylacetamide to a reaction flask, stir evenly, add acyl chloride carbon nanotubes and pyridine, react at 115-130°C for 24-48h, cool to room temperature, filter with a microporous filter membrane, wash with methanol, and dry to obtain star-shaped polylactic acid grafted carbon nanotubes; Step (2): placing the polylactic acid dry slices and the star-shaped polylactic acid grafted carbon nanotubes in a Haake torque rheometer, melt-blending them at a temperature of 175-190° C. and a rotation speed of 40-60 r / min for 5-10 minutes, adding them to a spinning machine, extruding them through a spinning assembly and a spinneret, and then cooling, oiling, stretching, and winding them to obtain an antistatic polylactic acid ultrafine fiber fabric.

2. The preparation process of the antistatic polylactic acid microfiber fabric according to claim 1, characterized in that: In the step (1), the ratio of six-arm star-shaped phosphorus nitrogen-based polylactic acid, chlorinated carbon nanotubes, and pyridine is 100 g: (25-40) g: (18-25) g.

3. The preparation process of the antistatic polylactic acid microfiber fabric according to claim 1, characterized in that: In the step (2), the ratio of the polylactic acid dry chips to the star-shaped polylactic acid grafted carbon nanotubes is 100 g: (2-10) g.

4. The preparation process of the antistatic polylactic acid microfiber fabric according to claim 1, characterized in that: In the step (2), the temperature of each zone of the spinning machine is 180-200°C, the spinning speed is 750-1000m / min, and the stretching temperature is 80-90°C.

5. The preparation process of the antistatic polylactic acid microfiber fabric according to claim 1, characterized in that: The preparation process of the six-arm star-shaped phosphorus-nitrogen-based polylactic acid in step (1) is carried out according to the following steps: Step S1: under a nitrogen atmosphere, add tetrakis(hydroxymethyl)phosphonium chloride and ethanol to a reaction flask, stir evenly, then add 2-amino-4,6-dimethoxy-1,3,5-triazine, stir and react. After the reaction is completed, allow to stand and precipitate, filter, wash with ethanol, and dry to obtain a tetrakis(triazinebismethoxy)phosphonium intermediate; Step S2: under a nitrogen atmosphere, add tetrakis(triazinebismethoxy)phosphorus intermediate and dichloromethane to a reaction flask, stir evenly, add boron tribromide, react at 0-20°C for 16-32 hours, add methanol to quench, extract with ethyl acetate and deionized water, concentrate the organic phase, and dry to obtain a hexahydroxyphosphorus nitrogen intermediate; Step S3: Add lactide, hexahydroxyphosphorus nitrogen intermediate and stannous octoate to the reactor under nitrogen atmosphere, evacuate to vacuum, react at 140-160° C. for 12-24 hours, cool after the reaction, add chloroform to dissolve, then add methanol to precipitate, filter, wash with ethanol, and dry to obtain a six-arm star-shaped phosphorus nitrogen-based polylactic acid.

6. The preparation process of the antistatic polylactic acid microfiber fabric according to claim 5, characterized in that: In the step S1, the ratio of tetrakis(hydroxymethyl)phosphonium chloride to 2-amino-4,6-dimethoxy-1,3,5-triazine is 1 mol: (4.1-4.5) mol.

7. The process for preparing the antistatic polylactic acid microfiber fabric according to claim 5, characterized in that: In step S1, the reaction temperature is 20-35° C., and the reaction time is 2-5 h.

8. The process for preparing the antistatic polylactic acid microfiber fabric according to claim 5, characterized in that: In the step S2, the ratio of the tetrakis(triazinebismethoxy)phosphorus intermediate to boron tribromide is 1 mol:(6.5-8) mol.

9. The process for preparing the antistatic polylactic acid microfiber fabric according to claim 5, characterized in that: In step S3, the lactide is any one of D-lactide, L-lactide or D,L-lactide.

10. The process for preparing the antistatic polylactic acid microfiber fabric according to claim 5, characterized in that: In step S3, the ratio of lactide, hexahydroxyphosphorus nitrogen intermediate, and stannous octoate is 1 mol: (0.15-0.25) mol: (0.02-0.05) mol.

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