Polyethylene fiber non-woven fabric as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of preparation of non-woven fabrics, and discloses a polyethylene fiber non-woven fabric as well as a preparation method and application thereof. The polyethylene fiber non-woven fabric is prepared from a gel spinning solution through differential electrostatic spinning; the gel spinning solution contains polyethylene, white oil and gallic acid and is prepared under the action of supercritical carbon dioxide. The preparation method comprises the following steps: 1) mixing polyethylene, white oil and gallic acid, introducing supercritical carbon dioxide to form a gel spinning solution, and cooling to obtain a colloid; 2) processing the obtained colloid on a screw type differential electrostatic spinning device to obtain a non-woven fabric; (3) carrying out cold pressing and stretching on the obtained non-woven fabric, then shaping, carrying out ultrasonic extraction, drying and removing an extracting agent; and 4) stretching and hot-pressing the non-woven fabric obtained in the step 3) again to obtain the polyethylene fiber non-woven fabric. The prepared non-woven fabric is smooth in surface, free of defects such as obvious holes and adjustable in fiber morphology.

Description

Technical Field

[0001] This invention belongs to the field of nonwoven fabric preparation technology, specifically relating to a polyethylene fiber nonwoven fabric, a method for preparing the polyethylene fiber nonwoven fabric, and the application of the polyethylene fiber nonwoven fabric in the field of medical protection. Background Technology

[0002] In recent years, gel spinning and solution electrospinning have become the main preparation processes for polyethylene fibers and nonwoven fabrics. According to the different solvent volatility, gel spinning is divided into wet spinning and dry spinning. Due to solvent evaporation, dry gel spinning and solution electrospinning produce surface defects in the fibers. Nayak et al. prepared fibers by electrospinning polyethylene dissolved in decahydronaphthalene and cyclohexanone with many pores and grooves on the surface (Nayak P, Ghosh AK, Bhatnagar N. Preparation and Characterization of Electrospun Mat of Ultra-high Molecular Weight Polyethylene / High-Density Polyethylene Blends[J]. Fibers and Polymers, 2023, 24(10): 3421-3433). Wet gel spinning detangles molecular chains at high temperatures, which causes a decrease in molecular weight. Wu Bochao tested the molecular weight of nascent ultra-high molecular weight polyethylene fibers prepared at different temperatures (Preparation and characterization of high-performance ultra-high molecular weight polyethylene fibers [D]. Shenzhen University, 2017). At a processing temperature of 290℃, the molecular weight was degraded by 71%.

[0003] Supercritical carbon dioxide fluid, under conditions above critical (temperature 304.1 K, pressure 7.38 MPa), possesses both the dissolving power of a liquid and the flowability of a gas, and is commonly used as a foaming agent for polymers.

[0004] Gallic acid, a natural polyphenol, has hydroxyl and catechol groups. By adsorbing onto the cell wall of bacteria, it disrupts the cell wall structure and cell membrane permeability, thus playing an antibacterial, antiviral, and anticancer role. Kim et al. added gallic acid to PCL, and the viscosity of the composite system decreased and the conductivity increased significantly (Kim JW, Park S, Park K, et al. Non-Toxic Natural Additives to Improve the Electrical Conductivity and Viscosity of Polycaprolactone for Melt Electrospinning[J]. Applied Sciences, 2023, 13(3): 1844).

[0005] Single-needle electrospinning suffers from problems such as difficulty in cleaning blockages and low spinning efficiency. Yang Weimin et al. invented an open-type micro-spinning nozzle (CN201210371918.8 airflow-assisted inner cone-shaped flow-dividing electrospinning nozzle), which uses the coupling shearing of the inner cone surface and the central airflow to uniformly divide the liquid film, thus solving the problem of low efficiency of single-needle nozzles.

[0006] Currently, while ensuring the breathability of medical breathable membranes, higher requirements are placed on the strength, breathability, and comfort of high-strength medical breathable membranes. Patent document CN108000997B discloses a high-strength polyester spunbond nonwoven fabric quicklime desiccant packaging film and its production method. This packaging film consists of spunbond nonwoven fabric and a breathable membrane, but the two materials are connected by an adhesive, reducing the film's breathability. Patent document CN105966016A discloses a high-strength water-resistant and breathable nonwoven fabric, which consists of two nonwoven fabric layers, a reinforced waterproof and breathable layer, breathable pores, and a reinforcing fiber web. However, the breathability of this high-strength water-resistant and breathable membrane relies solely on the reinforced waterproof and breathable layer and the breathable pores, resulting in poor breathability and requiring the reinforcing fiber web for strength. Summary of the Invention

[0007] In view of the above-mentioned problems in the prior art, the inventors of this invention have discovered that when using supercritical carbon dioxide fluid to process polyethylene melt, due to the large molecular weight and high crystallinity of polyethylene, the elastic collapse of pure polyethylene melt leads to carbon dioxide leakage. Therefore, it is necessary to introduce a good solvent to assist in the unwinding of polyethylene molecular chains with supercritical carbon dioxide. Although supercritical carbon dioxide cannot directly dissolve polyethylene, the swelling of its small molecules on polyethylene allows the small molecules of the good solvent to better enter the gaps between polyethylene molecular chains, reducing the processing temperature of polyethylene and slowing down the decrease in molecular weight. Based on this, the purpose of this invention is to provide a polyethylene fiber nonwoven fabric, its preparation method, and its application. This invention uses supercritical carbon dioxide fluid to assist in the unwinding of polyethylene molecular chains, reducing the processing temperature and solving the problem of severe molecular weight degradation of polyethylene at high temperatures. The resulting fiber-formed nonwoven fabric has high strength, and this nonwoven fabric also has application value in antibacterial barrier properties.

[0008] A first aspect of the present invention provides a polyethylene fiber nonwoven fabric, which is prepared by differential electrospinning of a gel spinning solution; the gel spinning solution contains polyethylene, white oil and gallic acid, and is prepared under the action of supercritical carbon dioxide.

[0009] A second aspect of the present invention provides a method for preparing the above-mentioned polyethylene fiber nonwoven fabric, the method comprising the following steps:

[0010] 1) Mix polyethylene, white oil and gallic acid, and pass supercritical carbon dioxide through to form a gel spinning solution. After cooling, a colloid is obtained.

[0011] 2) The obtained colloid is processed on a screw-type differential electrospinning equipment to obtain nonwoven fabric;

[0012] 3) The obtained nonwoven fabric is cold-pressed, stretched, then shaped and ultrasonically extracted, dried and the extractant is removed;

[0013] 4) Stretch and hot-press the nonwoven fabric obtained in step 3) again to obtain the polyethylene fiber nonwoven fabric.

[0014] A third aspect of the present invention provides the application of the above-described polyethylene fiber nonwoven fabric in the field of medical protection.

[0015] Compared with the prior art, the technical solution of the present invention has the following advantages:

[0016] 1) This invention establishes a supercritical carbon dioxide fluid, white oil, and gallic acid gel system suitable for electrospinning. Supercritical carbon dioxide causes polyethylene to swell, reducing the processing temperature of polyethylene and decreasing the degradation of polyethylene molecular weight. At the same time, gallic acid increases the conductivity of the spinning system, making the non-polar polyethylene fibers easier to stretch and refine by electrostatic force. In addition, the antibacterial properties of gallic acid make the prepared polyethylene nonwoven fabric valuable for medical protection.

[0017] 2) In this invention, the polyethylene concentration is higher than that of traditional gel spinning and solution electrospinning, which is beneficial to improve industrial production capacity. Moreover, the polyethylene nonwoven fabric prepared by the above technical solution has a fiber diameter of less than 5μm, a relatively smooth surface, no obvious defects such as pores, and adjustable fiber morphology. The tensile strength of the nonwoven fabric can reach 80MPa.

[0018] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0019] Figure 1 A schematic diagram of the equipment for preparing gel spinning solution;

[0020] Figure 2 This is a schematic diagram of a screw-type differential electrospinning device.

[0021] Figure 3 This is a scanning electron microscope (SEM) image of the polyethylene fiber nonwoven fabric from Example 1.

[0022] Figure 4 This is a scanning electron microscope (SEM) image of the polyethylene fiber nonwoven fabric from Example 1.

[0023] Figure 5 This is a photograph of the polyethylene fiber nonwoven fabric from Example 1.

[0024] Explanation of reference numerals in the attached diagram: 1. Carbon dioxide cylinder; 2. Autoclave; 3. Agitator; 4. Pressure relief port; 5. Feed inlet; 6. Central airflow inlet; 7. Extrusion screw; 8. Feed hopper; 9. Motor; 10. High-voltage electrostatic generator; 11. Collecting roller; 12. Differential electrostatic spinning nozzle; 13. Corner head. Detailed Implementation

[0025] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0026] According to a first aspect of the present invention, a polyethylene fiber nonwoven fabric is provided, which is prepared by differential electrospinning of a gel spinning solution; wherein the gel spinning solution contains polyethylene, white oil and gallic acid, and is prepared under the action of supercritical carbon dioxide.

[0027] The polyethylene used in this invention can be any type of polyethylene conventionally used in the art. For example, the polyethylene can be selected from one or more of low-density polyethylene, high-density polyethylene, linear low-density polyethylene, and ultra-high molecular weight polyethylene.

[0028] According to the present invention, based on the total mass of polyethylene, white oil and gallic acid, the mass percentage of polyethylene can be 5-50%, preferably 5-35%; the mass ratio of polyethylene to gallic acid can be 90-100:0-10, and the mass of gallic acid is not 0, preferably 90-99:1-10.

[0029] Preferably, the polyethylene fiber diameter of the polyethylene fiber nonwoven fabric is less than 8 μm, and more preferably less than 5 μm.

[0030] The tensile strength of the polyethylene fiber nonwoven fabric of the present invention can be 40-80 MPa.

[0031] According to a second aspect of the present invention, a method for preparing a polyethylene fiber nonwoven fabric is provided, the method comprising the following steps:

[0032] 1) Mix polyethylene, white oil and gallic acid, and pass supercritical carbon dioxide through to form a gel spinning solution. After cooling, a colloid is obtained.

[0033] 2) The obtained colloid is processed on a screw-type differential electrospinning equipment to obtain nonwoven fabric;

[0034] 3) The obtained nonwoven fabric is cold-pressed, stretched, then shaped and ultrasonically extracted, dried and the extractant is removed;

[0035] 4) Stretch and hot-press the nonwoven fabric obtained in step 3) again to obtain the polyethylene fiber nonwoven fabric.

[0036] The preparation of the gel spinning solution of the present invention can be completed in an autoclave. Polyethylene, white oil and gallic acid are added to the autoclave, and supercritical carbon dioxide is introduced under stirring. After stabilization, a gel spinning solution is formed. After depressurization, the gel spinning solution is taken out and cooled to form a colloid.

[0037] In the preferred case, the temperature during the preparation of the gel spinning solution is 120-250℃, the heating and stirring time is 1-2 hours, and the addition of supercritical carbon dioxide makes the pressure reach 8-20MPa.

[0038] In step 2) of this invention, the colloid is placed in the screw extrusion assembly of the equipment and heated. After passing through the splitter plate, it reaches the differential electrospinning head and generates a Taylor cone under the action of high voltage electrostatic field force to form a jet. The jet is then collected by the equipment to obtain nonwoven fabric.

[0039] Preferably, the temperature of the differential electrospinning head is 180-230℃; the high-voltage electrostatic field is 25-45KV; and the distance between the differential electrospinning head and the electrode plate is 6-10cm. The high-voltage electrostatic field of this invention can be generated by a high-voltage electrostatic generator, and the electrode plate is the electrode plate that generates the high-voltage electrostatic field. This is common knowledge and will not be elaborated upon here.

[0040] According to the present invention, the cold pressing pressure can be 5-10 MPa, and the cold pressing time can be 8-30 s.

[0041] In this invention, tensile force is applied to the nonwoven fabric for shaping during ultrasonic extraction, the extraction time can be 3-15 min, and the extraction temperature can be 30-65℃.

[0042] Preferably, the extractant is one or more of xylene, p-xylene, dichloromethane, and dichloroethane.

[0043] The nonwoven fabric extracted by ultrasonic extraction according to the present invention can be dried in an air-drying box to remove the extractant.

[0044] According to the present invention, the porosity and fiber morphology of the nonwoven fabric are adjusted by re-stretching and hot pressing. Preferably, the re-stretching ratio is 1-4 times; the hot pressing temperature is 25-65℃, the hot pressing pressure is 2-10MPa, and the hot pressing time is 3-12s.

[0045] According to a third aspect of the present invention, the present invention provides the application of the above-described polyethylene fiber nonwoven fabric in the field of medical protection.

[0046] The substances and parameters not limited in this invention can be selected according to existing technology, which is a conventional technical means in this field.

[0047] The present invention will be further described below with reference to embodiments. However, the invention is not limited to these embodiments.

[0048] In the following examples and comparative examples, the raw materials used were sourced from the following sources:

[0049] Linear low-density polyethylene: Zhenhai Refining & Chemical R546u, Sinopec Shanghai Petrochemical Co., Ltd.;

[0050] High-density polyethylene: 5000S, Sinopec Yangzi Petrochemical;

[0051] Ultra-high molecular weight polyethylene: L0504F, Sinopec Yanshan Petrochemical;

[0052] White oil: Lanhua Lubrication Technology Co., Ltd.;

[0053] Gallic acid: Shanghai Aladdin Biochemical Technology Co., Ltd.

[0054] Example 1

[0055] use Figure 1 and Figure 2 The equipment shown is used to prepare polyethylene fiber nonwoven fabric. The specific steps are as follows:

[0056] (1) Linear low-density polyethylene, white oil and gallic acid are prepared into a 30wt% polyethylene mixture, wherein the mass ratio of polyethylene to gallic acid is 99:1. The prepared mixture is introduced into a high-pressure reactor 2 at 190℃ through the feed port 5. After turning on the agitator 3, carbon dioxide from the carbon dioxide cylinder 1 is introduced into the high-pressure reactor 2 to reach a pressure of 15MPa. After stirring for 1.5h, the pressure is released through the pressure relief port 4 and cooled to obtain a colloid.

[0057] (2) The colloid is placed into the feed hopper 8 of the extrusion screw 7. Under the action of the motor 9 and heating, the colloid forms a liquid film at the differential electrostatic spinning nozzle 12 at 220°C. The liquid film generates a jet under the high voltage electrostatic action of the 40KV electrode plate (connected to the high voltage electrostatic generator 10) at a distance of 6.5cm from the nozzle. At the same time, the hot airflow at 220°C at the central airflow inlet 6 of the nozzle, connected to the corner die head 13, further shears, stretches and refines the liquid film and jet, and finally forms a nonwoven fabric on the collecting roller 11.

[0058] (3) The nonwoven fabric from step (2) is cold-pressed and stretched to fix it. The cold-pressing pressure is 8 MPa and the cold-pressing time is 20 s. It is then ultrasonically extracted with xylene solvent at 50℃ for 15 min. After drying in a fume hood for 6 h, it is stretched twice and hot-pressed. The hot-pressing temperature is 60℃ and the hot-pressing pressure is 6 MPa. The hot-pressing time is 8 s. The result is as follows: Figure 4 The polyethylene fiber nonwoven fabric shown is... Figure 3 The image shows a scanning electron microscope (SEM) image of the polyethylene fiber. The average diameter of the polyethylene fiber is about 5 μm, and there are no obvious pores or defects on the fiber surface. The tensile strength of the polyethylene fiber nonwoven fabric is 45 MPa.

[0059] Example 2

[0060] use Figure 1 and Figure 2 The equipment shown is used to prepare polyethylene fiber nonwoven fabric. The specific steps are as follows:

[0061] (1) High-density polyethylene, white oil and gallic acid are prepared into a 30wt% polyethylene mixture, wherein the mass ratio of polyethylene to gallic acid is 99:1. The prepared mixture is introduced into a high-pressure reactor 2 at 190℃ through the feed port 5. After turning on the agitator 3, carbon dioxide from the carbon dioxide cylinder 1 is introduced into the high-pressure reactor 2 to reach a pressure of 16.5MPa. After stirring for 2 hours, the pressure is released through the pressure relief port 4 and cooled to obtain a colloid.

[0062] (2) The colloid is placed into the feed hopper 8 of the extrusion screw 7. Under the action of the motor 9 and heating, the colloid forms a liquid film at the differential electrospinning nozzle 12 at 220°C. The liquid film generates a jet under the high voltage electrostatic action of the 40KV electrode plate (connected to the high voltage electrostatic generator 10) at a distance of 6.5cm from the nozzle. At the same time, the hot airflow at 220°C at the central airflow inlet 6 of the nozzle, connected to the corner die head 13, further shears, stretches and refines the liquid film and jet, and finally forms a nonwoven fabric on the collecting roller 11.

[0063] (3) The nonwoven fabric in step (2) is cold-pressed and stretched to fix it. The cold pressing pressure is 8 MPa and the cold pressing time is 20 s. It is ultrasonically extracted with xylene solvent at 50℃ for 15 min. After drying in a fume hood for 6 h, it is stretched twice and hot-pressed. The hot pressing temperature is 60℃, the hot pressing pressure is 6 MPa, and the hot pressing time is 8 s. The average fiber diameter of the obtained polyethylene fiber nonwoven fabric is about 3 μm. There are no obvious pore defects on the fiber surface and the morphology is controllable. The tensile strength of the polyethylene fiber nonwoven fabric is 60 MPa.

[0064] Example 3

[0065] use Figure 1 and Figure 2 The equipment shown is used to prepare polyethylene fiber nonwoven fabric. The specific steps are as follows:

[0066] (1) Prepare a 15wt% polyethylene mixture by mixing ultra-high molecular weight polyethylene, white oil and gallic acid, wherein the mass ratio of polyethylene to gallic acid is 99:1. The prepared mixture is introduced into a high-pressure reactor 2 at 190℃ through the feed port 5. After turning on the agitator 3, carbon dioxide from the carbon dioxide cylinder 1 is introduced into the high-pressure reactor 2 to reach a pressure of 18MPa. After stirring for 2 hours, the pressure is released through the pressure relief port 4 and cooled to obtain a colloid.

[0067] (2) The colloid is placed into the feed hopper 8 of the extrusion screw 7. Under the action of the motor 9 and heating, the colloid forms a liquid film at the differential electrostatic spinning nozzle 12 at 220°C. The liquid film generates a jet under the high voltage electrostatic action of the 40KV electrode plate (connected to the high voltage electrostatic generator 10) at a distance of 6.5cm from the nozzle. At the same time, the hot airflow at 220°C at the central airflow inlet 6 of the nozzle, connected to the corner die head 13, further shears, stretches and refines the liquid film and jet, and finally forms a nonwoven fabric on the collecting roller 11.

[0068] (3) The nonwoven fabric in step (2) is cold-pressed and stretched to fix it. The cold pressing pressure is 8 MPa and the cold pressing time is 20 s. It is ultrasonically extracted with xylene solvent at 50℃ for 15 min. After drying in a fume hood for 6 h, it is stretched twice and hot-pressed. The hot pressing temperature is 60℃, the hot pressing pressure is 6 MPa, and the hot pressing time is 8 s. The fiber diameter of the obtained polyethylene fiber nonwoven fabric is about 0.8 μm. There are no obvious pore defects on the fiber surface. The morphology is controllable. The tensile strength of the polyethylene fiber nonwoven fabric is 80 MPa.

[0069] Comparative Example 1

[0070] Same as Example 1, except that supercritical carbon dioxide was not introduced into the autoclave. A small amount of continuous and discontinuous jets appeared, making it impossible to form a fabric.

[0071] Comparative Example 2

[0072] Same as Example 1, except that gallic acid was not added. A continuous jet could not be formed, and the fabric could not be formed.

[0073] Compared with Comparative Examples 1-2, the addition of supercritical carbon dioxide and gallic acid in Examples 1-3 allows non-polar polyethylene materials to be formed by electrospinning. The gel spinning solution simultaneously satisfies processability and molding properties, resulting in polyethylene fibers and their non-woven fabrics. The diameter of the polyethylene non-woven fibers is less than 5 μm, the surface is relatively smooth, and there are no obvious defects such as pores. The fiber morphology is adjustable, and the tensile strength of the non-woven fabric can reach 80 MPa.

[0074] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A polyethylene fiber nonwoven fabric, characterized in that, The polyethylene fiber nonwoven fabric is prepared by differential electrospinning of a gel spinning solution; the gel spinning solution contains polyethylene, white oil and gallic acid, and is prepared under the action of supercritical carbon dioxide.

2. The polyethylene fiber nonwoven fabric according to claim 1, wherein, The polyethylene is selected from one or more of low-density polyethylene, high-density polyethylene, linear low-density polyethylene, and ultra-high molecular weight polyethylene. Based on the total mass of polyethylene, white oil and gallic acid, the mass percentage of polyethylene is 5-50%, preferably 5-35%; the mass ratio of polyethylene to gallic acid is 90-100:0-10, and the mass of gallic acid is not 0, preferably 90-99:1-10.

3. The polyethylene fiber nonwoven fabric according to claim 1, wherein, The polyethylene fiber nonwoven fabric has a polyethylene fiber diameter of less than 81 μm, preferably less than 5 μm, and a tensile strength of 40-80 MPa.

4. The method for preparing polyethylene fiber nonwoven fabric according to any one of claims 1-3, characterized in that, The preparation method includes the following steps: 1) Mix polyethylene, white oil and gallic acid, and pass supercritical carbon dioxide through to form a gel spinning solution. After cooling, a colloid is obtained. 2) The obtained colloid is processed on a screw-type differential electrospinning equipment to obtain nonwoven fabric; 3) The obtained nonwoven fabric is cold-pressed, stretched, then shaped and ultrasonically extracted, dried and the extractant is removed; 4) Stretch and hot-press the nonwoven fabric obtained in step 3) again to obtain the polyethylene fiber nonwoven fabric.

5. The method for preparing polyethylene fiber nonwoven fabric according to claim 4, wherein, The temperature during the preparation of the gel spinning solution is 120-250℃, the heating and stirring time is 1-2 hours, and the addition of supercritical carbon dioxide makes the pressure reach 8-20MPa.

6. The method for preparing polyethylene fiber nonwoven fabric according to claim 4, wherein, In step 2), the colloid is placed in the screw extrusion assembly of the equipment and heated. After passing through the splitter plate, it reaches the differential electrospinning head. Under the action of the high voltage electrostatic field, a Taylor cone is generated and a jet is formed. The nonwoven fabric is obtained through the collection assembly of the equipment.

7. The method for preparing polyethylene fiber nonwoven fabric according to claim 6, wherein, The temperature of the differential electrospinning head is 180-230℃; the high voltage electrostatic field is 25-45KV; and the distance between the differential electrospinning head and the electrode plate is 6-10cm.

8. The method for preparing polyethylene fiber nonwoven fabric according to claim 4, wherein, The cold pressing pressure is 5-10MPa, and the cold pressing time is 8-30s; During ultrasonic extraction, tension is applied to the nonwoven fabric to set its shape. The extraction time is 3-15 minutes, and the extraction temperature is 30-65℃. The extractant is one or more of xylene, p-xylene, dichloromethane, and dichloroethane.

9. The method for preparing polyethylene fiber nonwoven fabric according to claim 4, wherein, The re-stretch ratio is 1-4 times; the hot-pressing temperature is 25-65℃, the hot-pressing pressure is 2-10MPa, and the hot-pressing time is 3-12s.

10. The application of the polyethylene fiber nonwoven fabric according to any one of claims 1-3 in the field of medical protection.

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