Composite non-woven fabric medical protective clothing material and preparation method thereof

Abstract

The application discloses a kind of composite non-woven medical protective clothing materials and preparation method thereof, it is related to medical protective clothing material technical field.The method is first modified nanoparticle, thermoplastic polymer is blended into film with polyethylene, is extracted and is expanded hole by acid solution and enzymatic hydrolysis, and hydrophobic treatment is made to obtain hydrophobic microporous polyethylene film;Modified phyllosilicates, reinforcing fiber, hollow glass microsphere, sepiolite and crosslinking agent are added to water-based polyurethane to form coating liquid, which is coated on the film and solidified to obtain a reinforced modified film;Finally, it is compounded with polypropylene non-woven fabric.The material has high air permeability, strong liquid repellency and high tear resistance, and the coating does not block the hole.

Description

Technical Field

[0001] This invention relates to the field of medical protective clothing materials technology, specifically to a composite nonwoven medical protective clothing material and its preparation method. Background Technology

[0002] Medical protective clothing is essential protective equipment worn by healthcare workers when in contact with patients with infectious diseases. Its core function is to block the transmission of pathogens, bodily fluids, and blood. Currently, the mainstream materials for medical protective clothing include: polypropylene spunbond-meltblown-spunbond (SMS) nonwoven fabric, flash-evaporated high-density polyethylene nonwoven fabric, and polypropylene nonwoven fabric / polyethylene film composites. Among these, the structure of polypropylene nonwoven fabric and polyethylene film bonded together with an adhesive is the most widely used due to its abundant raw material sources, low cost, and mature processing technology, dominating the domestic low-to-mid-range medical protective clothing market. However, traditional polypropylene nonwoven fabric / polyethylene film composites inherently present a contradiction between breathability and protective properties. Although ordinary polyethylene film has excellent liquid barrier properties, its dense, non-porous film structure results in extremely low water vapor permeability. After prolonged use, sweat vapor cannot be effectively expelled, causing discomfort such as stuffiness and skin maceration, severely impacting the work efficiency of healthcare workers. In existing technologies, the method of filling polyethylene with inorganic particles and then stretching to create pores (fill-stretch method) can improve air permeability to a certain extent. However, relying solely on stretching to debond the micropores results in uneven pore size distribution and poor pore connectivity, limiting the improvement in air permeability. Furthermore, residual filler particles reduce the film's flexibility. In addition, thin-film polyethylene materials inherently have poor tear resistance, and microporous treatment, while improving air permeability, further weakens mechanical properties. The microporous structure introduces numerous defects into the film, becoming a preferred path for crack initiation and propagation, leading to a significant decrease in tear strength. Frequent limb movements by medical personnel wearing the film can easily cause it to tear and break, resulting in loss of protective function. Therefore, there is a trade-off between improving air permeability and maintaining mechanical properties. In summary, how to significantly improve the air permeability of polyethylene films while maintaining their liquid barrier properties, and effectively solve the problem of decreased mechanical properties caused by microporous treatment, achieving synergistic optimization of air permeability, liquid barrier properties, and tear resistance, is a key technical problem that urgently needs to be solved in this field. Summary of the Invention

[0003] The purpose of this invention is to provide a composite nonwoven medical protective clothing material and its preparation method to solve the technical problems mentioned in the background.

[0004] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing a composite nonwoven medical protective clothing material includes the following steps: (1) After surface-modified inorganic nanoparticles and enzymatically hydrolyzable thermoplastic natural polymer components are melt-blended with polyethylene resin to form a film, the resulting filled film is subjected to biaxial stretching to create pores. Then, the inorganic nanoparticles are dissolved by organic acid solution treatment and the thermoplastic natural polymer components are hydrolyzed by enzyme solution treatment to remove them. The film is then subjected to selective extraction to expand the pores. Finally, the film is subjected to organosilane hydrophobic treatment to obtain a hydrophobic microporous polyethylene film. (2) Organic modified layered silicate, surface-treated reinforcing short fibers, hollow glass microspheres, activated sepiolite and crosslinking agent are dispersed in an aqueous polyurethane emulsion to prepare a composite reinforcing coating liquid. The hydrophobic microporous polyethylene film is surface-activated on one side and then coated with the composite reinforcing coating liquid and cured to obtain a reinforced modified polyethylene film. (3) The reinforced modified polyethylene film is combined with polypropylene nonwoven fabric by an adhesive to obtain composite nonwoven medical protective clothing material.

[0005] This invention significantly improves the air permeability of polyethylene films by constructing a multi-level microporous structure. Specifically, modified nano-calcium carbonate and thermoplastic starch are introduced as functional pore-forming components into a linear low-density polyethylene matrix. During subsequent biaxial stretching, a significant difference in elastic modulus exists between the rigid calcium carbonate particles and the flexible polyethylene matrix. Tensile stress concentrates at the interface between the two, leading to interfacial debonding and the formation of initial micropores around the calcium carbonate particles. Simultaneously, the thermoplastic starch phase is elongated and oriented under tensile force, forming interconnected channel precursors. Subsequently, the calcium carbonate particles are dissolved in citric acid solution, further expanding and interconnecting the micropores at the locations of the nano-sized calcium carbonate particles. Finally, the thermoplastic starch component is hydrolyzed and removed by α-amylase treatment, transforming its occupied micron-sized phase region space into additional pore channels. This results in a hierarchical microporous structure where two scales coexist: nano- to submicron-sized calcium carbonate debonding and dissolution pores and micron-sized starch hydrolysis pores. These two levels of channels are interconnected, forming a pore network that extends throughout the film's thickness. This network allows water vapor molecules to diffuse and transport rapidly, while the tortuous paths and multi-level pore size distribution effectively prevent direct penetration by liquid water, thus improving air permeability while maintaining liquid barrier function. Finally, a hydrophobic polysiloxane thin layer is generated in situ on the micropore walls using a sol-gel reaction with methyltrimethoxysilane, imparting low surface energy properties to the pore walls. This allows the film to maintain stable air permeability and reliable liquid repellency even under high humidity or bodily fluid contact conditions.

[0006] On the other hand, a significant improvement in tear resistance is achieved by constructing a multi-component synergistic reinforcing coating on the surface of a microporous polyethylene film. Specifically, organically modified montmorillonite is ultrasonically dispersed in an aqueous polyurethane matrix and then fully exfoliated to form a high aspect ratio nanosheet structure uniformly distributed within the coating. When the film is subjected to tearing loads, these montmorillonite nanosheets force the crack tip to repeatedly deflect and circumvent, significantly extending the actual crack propagation path and thus greatly increasing the energy required for tearing failure. The surface roughness of the aramid short fibers after alkaline etching treatment increases, exposing the -NH- and -C=O polar groups in the amide groups. These groups can form intermolecular hydrogen bonds with the -NH- and -C=O groups contained in the urethane bonds in the aqueous polyurethane molecular chain, thereby establishing a good interfacial bond. The aramid fibers themselves have extremely high tensile strength and modulus, playing a bridging role in the crack propagation direction. The fibers transfer the load across both sides of the crack and continuously consume external energy input through frictional slippage at the interface between the fiber and the matrix, effectively inhibiting rapid crack penetration. The waterborne polyurethane matrix itself possesses excellent flexibility and adhesion to polyethylene substrates. After cross-linking and curing with polycarbodiimide, the cohesive strength and resistance to damp heat aging of the coating are significantly improved, ensuring that the reinforced coating will not lose its protective function due to cohesive failure of the matrix during long-term use. The crack deflection mechanism of montmorillonite sheets, the bridging toughening mechanism of aramid fibers, and the toughness support of the cross-linked polyurethane matrix form a multiple synergistic toughening effect, enabling the overall tear resistance of the microporous polyethylene film to meet the stringent requirements for material mechanical reliability in medical protective clothing.

[0007] Preferably, the surface-modified inorganic nanoparticles in step (1) are surface-modified nano-calcium carbonate, the thermoplastic natural polymer component is thermoplastic starch, and the polyethylene resin is linear low-density polyethylene.

[0008] Preferably, the surface-modified inorganic nanoparticles are nano-calcium carbonate that has undergone stearic acid surface modification treatment; the thermoplastic starch is prepared by mixing corn starch and glycerol at a mass ratio of 85:(35-40) and then plasticizing and granulating by twin-screw extrusion. The mass ratio of the polyethylene resin, surface-modified nano-calcium carbonate, and thermoplastic starch is 50:(38-45):(10-15).

[0009] Preferably, the selective extraction and pore-expansion in step (1) includes: first immersing the stretched microporous membrane in a 10-15% citric acid aqueous solution at 50-70°C for 2-6 hours to dissolve the inorganic nanoparticles; then immersing it in an α-amylase solution with pH=5.5-7.0 at 40-60°C for 3-5 hours to hydrolyze and remove the thermoplastic natural polymer components.

[0010] Preferably, the organosilane hydrophobication treatment in step (1) is as follows: the microporous polyethylene film is immersed in an alcohol / water solution of methyltrimethoxysilane for dip coating and pulling, and then cured at 80-100°C for 30-60 min after drying.

[0011] Preferably, the organic modified layered silicate in step (2) is montmorillonite modified by long-chain alkylamine intercalation, the reinforcing short fiber is aramid short fiber treated with alkaline surface etching, the activated sepiolite is calcined activated sepiolite, and the crosslinking agent is polycarbodiimide crosslinking agent.

[0012] Preferably, the composite reinforced coating liquid is composed of: 100 parts by weight of waterborne polyurethane emulsion, 3-8 parts by weight of organic modified layered silicate, 6-12 parts by weight of surface-treated reinforcing short fibers, 5-8 parts by weight of hollow glass microspheres, 3-6 parts by weight of activated sepiolite, and 1-3 parts by weight of crosslinking agent; the particle size of the hollow glass microspheres is 15-30 μm.

[0013] This invention discovered in experiments that the process of coating a composite reinforcing coating liquid onto a hydrophobic microporous polyethylene film negatively impacts the construction of a multi-level microporous permeable structure on the polyethylene film. Although the micropore walls have been hydrophobized, the corona treatment applied to the film surface during the coating process increases the surface energy of the coated surface. Furthermore, the mechanical pressure applied during microgravure coating causes the waterborne polyurethane emulsion to still penetrate into the micropores of the corona-activated film surface. After the coating cures, the penetrated micropores are immediately blocked, resulting in a significant decrease in the water vapor permeability of the film and affecting the air permeability of the polyethylene film. To address this technical problem, this invention introduces hollow glass microspheres and sepiolite into the reinforcing coating formulation, utilizing their synergistic effect to solve the problem of coating penetration and pore blockage. Hollow glass microspheres, with a particle size ranging from 15 to 30 μm, are much larger than the pore size of microporous polyethylene films. During coating, these microspheres preferentially accumulate at the micropore openings, forming a physical shield that effectively prevents polyurethane emulsion from seeping deeper into the micropores, limiting the coating's penetration depth to a very shallow area on the film surface. Simultaneously, the hollow structure of the microspheres retains a certain degree of gas permeability. Sepiolite, a natural fibrous hydrous magnesium silicate mineral, has a crystal structure with continuous nanoscale channels arranged along the fiber axis. Water vapor molecules can be transported along these channels, thus constructing additional gas-phase diffusion paths within the coating matrix. After calcination and activation, the zeolite water in the sepiolite crystals is removed, the channel volume increases, and the transport efficiency is further improved. The surface shielding effect of hollow glass microspheres and the channel transport effect of sepiolite work synergistically, enabling the reinforced coating to impart good tear resistance to the film without significantly sacrificing air permeability, achieving a good balance between tear resistance and air permeability.

[0014] Preferably, the surface activation treatment in step (2) is corona treatment or plasma treatment.

[0015] Preferably, the polypropylene nonwoven fabric in step (3) is a polypropylene spunbond nonwoven fabric; the adhesive is a hot melt adhesive; the composite temperature is 105-110℃; and the pressure is 0.2-0.4MPa.

[0016] A composite nonwoven medical protective clothing material includes a polypropylene nonwoven base layer, an adhesive layer, a microporous polyethylene film layer, and a composite reinforcing coating layer stacked sequentially; the microporous polyethylene film layer contains a hierarchically distributed microporous structure and the microporous walls are hydrophobically treated; the composite reinforcing coating contains organically modified layered silicates, surface-treated reinforcing short fibers, hollow glass microspheres, and activated sepiolite.

[0017] Compared with the prior art, the beneficial effects of the present invention are: 1. By constructing a nano- to micro-level microporous structure and combining it with hydrophobic treatment of the pore walls, the membrane can quickly allow water vapor to pass through (perspiration and breathability), while effectively blocking liquid water from penetrating, and remains stable in high humidity or contact with body fluids.

[0018] 2. A multi-component synergistic reinforcing coating was constructed on the surface of the film. The synergistic effect of the three mechanisms—montmorillonite nanosheets deflecting cracks, aramid fiber bridging and bearing, and polyurethane matrix toughness support—significantly improved the tear resistance of the film and met the stringent mechanical requirements.

[0019] 2. The introduction of hollow glass microspheres (physical shielding against penetration) and sepiolite (providing additional gas channels) effectively solves the industry problem of coating liquid seeping into and blocking micropores during the coating process. While significantly improving tear resistance, it ensures that the high air permeability of the film is not sacrificed. Attached Figure Description

[0020] Figure 1 This is a SEM image of the surface of the composite nonwoven medical protective clothing material prepared in Example 4 of the present invention. Detailed Implementation

[0021] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0022] Example 1 A method for preparing a composite nonwoven medical protective clothing material includes the following steps: Step (1): Take 500g of nano-calcium carbonate with a particle size of about 60nm and disperse it in 3000mL of anhydrous ethanol. Stir and heat to 78℃ under the condition of reflux condenser. Add 16g of stearic acid and continue stirring for 2.5h. Filter, wash 3 times with anhydrous ethanol, dry at 80℃ for 4h, grind and pass through a 200-mesh sieve to obtain surface-modified nano-calcium carbonate.

[0023] Mix 170g of corn starch with 78g of glycerol evenly, seal and equilibrate at room temperature for 24 hours, then feed the mixture into a twin-screw extruder (temperature 120 / 130 / 140 / 145 / 140℃, speed 120rpm) for extrusion granulation to obtain thermoplastic starch granules.

[0024] Weigh 500g of linear low-density polyethylene resin, 420g of surface-modified nano-calcium carbonate, 130g of thermoplastic starch, 3g of antioxidant 1010 and 8g of calcium stearate, mix at high speed for 6 minutes and then feed into a twin-screw extruder (L / D=40:1, temperature 150 / 160 / 170 / 178 / 185 / 180℃, speed 220rpm), extrude, water-cool and pelletize, dry at 60℃ for 2 hours to obtain filler masterbatch.

[0025] The filler masterbatch was cast into a film at 185°C using a single-screw casting machine with a cooling roller at 30°C and a traction speed of 8 m / min to obtain a filled polyethylene film with a thickness of approximately 100 μm. The filled film was preheated to 95°C, stretched longitudinally by 3.0 times, and then transversely by 2.0 times at a stretching rate of 80 mm / min. It was then heat-set at 102°C for 5 min to obtain a stretched microporous film. The stretched microporous film was immersed in a 12% citric acid aqueous solution and gently stirred and soaked at 60°C for 4 h. It was then removed and washed with deionized water until neutral. It was then transferred to an α-amylase solution (800 U / mL, pH adjusted to 6.0 with phosphate buffer) and gently stirred and soaked at 50°C for 4 h. It was then removed, washed, and dried under reduced pressure at 45°C to constant weight to obtain a multi-level microporous polyethylene film.

[0026] 4g of methyltrimethoxysilane was dissolved in a mixed solvent of 90mL anhydrous ethanol and 10mL deionized water. The pH was adjusted to 3.5 with hydrochloric acid, and the mixture was stirred at room temperature for 1h for pre-hydrolysis. The microporous membrane was then immersed in the solution and pulled at a rate of 1.5mm / s. After drying at room temperature for 30min, the membrane was cured at 90℃ for 40min to obtain a hydrophobic microporous polyethylene film.

[0027] Step (2): Disperse 50g of sodium-based montmorillonite in 2000mL of deionized water and stir at 80℃ for 2h to swell; dissolve 20g of octadecylamine in 600mL of ethanol / water (1:1) and add 8mL of 1mol / L hydrochloric acid to protonate it, slowly add it to the montmorillonite dispersion, stir at 80℃ for 6h, filter, wash 3 times each with hot water and ethanol, vacuum dry at 60℃ for 12h, grind through a 300-mesh sieve to obtain organically modified montmorillonite.

[0028] Aramid short fibers (approximately 1 mm in length and 12 μm in diameter) were immersed in a 5% sodium hydroxide aqueous solution, etched at 50°C for 30 min, removed and washed until neutral, and dried at 80°C for 4 h to obtain surface-treated aramid short fibers.

[0029] Take 7g of organically modified montmorillonite and add it to 20g of deionized water for ultrasonic dispersion (200W, 30min); take 100g of aqueous polyurethane emulsion (solid content 38%) and add the above dispersion, 10g of surface-treated aramid short fibers, and 7g of hollow glass microspheres (particle size 15-30μm, density 0.3g / cm³) sequentially under low-speed stirring (300rpm). 3 5g of calcined sepiolite (calcined at 400℃ for 2h to activate, fiber length 2μm) and 2.5g of polycarbodiimide crosslinking agent were mixed and stirred for 30min to obtain a composite reinforced coating liquid. One side of the hydrophobic microporous film was then subjected to corona treatment (40W·min / m). 2 The film is coated with a wet film of 65 μm using a microgravure coating at a speed of 20 m / min. It is then pre-baked at 50°C for 20 min, cured at 80°C for 45 min, and finally cured at 105°C for 20 min to obtain a reinforced modified polyethylene film.

[0030] Step (3): Take 40g / m 2 Polypropylene spunbond nonwoven fabric is produced by melting polyolefin hot melt adhesive at 150℃ and then rolling it onto the surface of the nonwoven fabric (adhesive application rate: 12g / m²). 2 The uncoated side of the reinforced modified polyethylene film is bonded to the adhesive side, and then hot-pressed at 108℃ and 0.3MPa with a roller speed of 15m / min. After cooling and winding, the composite nonwoven medical protective clothing material is obtained.

[0031] Example 2 A method for preparing a composite nonwoven medical protective clothing material includes the following steps: Step (1): Take 500g of nano-calcium carbonate with a particle size of about 60nm and disperse it in 3000mL of anhydrous ethanol. Stir and heat to 78℃ under the condition of reflux condenser. Add 16g of stearic acid and continue stirring for 2.5h. Filter, wash 3 times with anhydrous ethanol, dry at 80℃ for 4h, grind and pass through a 200-mesh sieve to obtain surface-modified nano-calcium carbonate.

[0032] Mix 170g of corn starch with 73g of glycerol evenly, seal and equilibrate at room temperature for 24 hours, then feed the mixture into a twin-screw extruder (temperature 120 / 130 / 140 / 145 / 140℃, speed 120rpm) for extrusion granulation to obtain thermoplastic starch granules.

[0033] Weigh 500g of linear low-density polyethylene resin, 390g of surface-modified nano-calcium carbonate, 110g of thermoplastic starch, 3g of antioxidant 1010 and 8g of calcium stearate, mix them at high speed for 6 minutes and then put them into a twin-screw extruder (L / D=40:1, temperature 150 / 160 / 170 / 178 / 185 / 180℃, speed 220rpm), extrude, water-cool and pelletize, and dry at 60℃ for 2 hours to obtain filler masterbatch.

[0034] The filler masterbatch was cast into a film at 185°C using a single-screw casting machine with a cooling roller at 30°C and a traction speed of 8 m / min to obtain a filled polyethylene film with a thickness of approximately 100 μm. The filled film was preheated to 95°C, stretched longitudinally by 3.0 times, and then transversely by 2.0 times at a stretching rate of 80 mm / min. It was then heat-set at 102°C for 5 min to obtain a stretched microporous film. The stretched microporous film was immersed in a 12% citric acid aqueous solution and gently stirred and soaked at 60°C for 4 h. It was then removed and washed with deionized water until neutral. It was then transferred to an α-amylase solution (800 U / mL, pH adjusted to 6.0 with phosphate buffer) and gently stirred and soaked at 50°C for 4 h. It was then removed, washed, and dried under reduced pressure at 45°C to constant weight to obtain a multi-level microporous polyethylene film.

[0035] 4g of methyltrimethoxysilane was dissolved in a mixed solvent of 90mL anhydrous ethanol and 10mL deionized water. The pH was adjusted to 3.5 with hydrochloric acid, and the mixture was stirred at room temperature for 1h for pre-hydrolysis. The microporous membrane was then immersed in the solution and pulled at a rate of 1.5mm / s. After drying at room temperature for 30min, the membrane was cured at 90℃ for 40min to obtain a hydrophobic microporous polyethylene film.

[0036] Step (2): Disperse 50g of sodium-based montmorillonite in 2000mL of deionized water and stir at 80℃ for 2h to swell; dissolve 20g of octadecylamine in 600mL of ethanol / water (1:1) and add 8mL of 1mol / L hydrochloric acid to protonate it, slowly add it to the montmorillonite dispersion, stir at 80℃ for 6h, filter, wash 3 times each with hot water and ethanol, vacuum dry at 60℃ for 12h, grind through a 300-mesh sieve to obtain organically modified montmorillonite.

[0037] Aramid short fibers (approximately 1 mm in length and 12 μm in diameter) were immersed in a 5% sodium hydroxide aqueous solution, etched at 50°C for 30 min, removed and washed until neutral, and dried at 80°C for 4 h to obtain surface-treated aramid short fibers.

[0038] Take 4g of organically modified montmorillonite and add it to 20g of deionized water for ultrasonic dispersion (200W, 30min); take 100g of aqueous polyurethane emulsion (solid content 38%) and add the above dispersion, 8g of surface-treated aramid short fibers, and 6g of hollow glass microspheres (particle size 15-30μm, density 0.3g / cm³) sequentially under low-speed stirring (300rpm). 34g of calcined sepiolite (calcined at 400℃ for 2h to activate, fiber length 2μm) and 1.5g of polycarbodiimide crosslinking agent were mixed and stirred for 30min to obtain a composite reinforced coating liquid. One side of the hydrophobic microporous film was then subjected to corona treatment (40W·min / m). 2 The film is coated with a wet film of 65 μm using a microgravure coating at a speed of 20 m / min. It is then pre-baked at 50°C for 20 min, cured at 80°C for 45 min, and finally cured at 105°C for 20 min to obtain a reinforced modified polyethylene film.

[0039] Step (3): Take 40g / m 2 Polypropylene spunbond nonwoven fabric is produced by melting polyolefin hot melt adhesive at 150℃ and then rolling it onto the surface of the nonwoven fabric (adhesive application rate: 12g / m²). 2 The uncoated side of the reinforced modified polyethylene film is bonded to the adhesive side, and then hot-pressed at 108℃ and 0.3MPa with a roller speed of 15m / min. After cooling and winding, the composite nonwoven medical protective clothing material is obtained.

[0040] Example 3 A method for preparing a composite nonwoven medical protective clothing material includes the following steps: Step (1): Take 500g of nano-calcium carbonate with a particle size of about 60nm and disperse it in 3000mL of anhydrous ethanol. Stir and heat to 78℃ under the condition of reflux condenser. Add 16g of stearic acid and continue stirring for 2.5h. Filter, wash 3 times with anhydrous ethanol, dry at 80℃ for 4h, grind and pass through a 200-mesh sieve to obtain surface-modified nano-calcium carbonate.

[0041] Mix 170g of corn starch with 75g of glycerin evenly, seal and equilibrate at room temperature for 24 hours, then feed the mixture into a twin-screw extruder (temperature 120 / 130 / 140 / 145 / 140℃, speed 120rpm) for extrusion granulation to obtain thermoplastic starch granules.

[0042] Weigh 500g of linear low-density polyethylene resin, 400g of surface-modified nano-calcium carbonate, 120g of thermoplastic starch, 3g of antioxidant 1010 and 8g of calcium stearate, mix them at high speed for 6 minutes and then put them into a twin-screw extruder (L / D=40:1, temperature 150 / 160 / 170 / 178 / 185 / 180℃, speed 220rpm), extrude, water-cool and pelletize, and dry at 60℃ for 2 hours to obtain filler masterbatch.

[0043] The filler masterbatch was cast into a film at 185°C using a single-screw casting machine with a cooling roller at 30°C and a traction speed of 8 m / min to obtain a filled polyethylene film with a thickness of approximately 100 μm. The filled film was preheated to 95°C, stretched longitudinally by 3.0 times, and then transversely by 2.0 times at a stretching rate of 80 mm / min. It was then heat-set at 102°C for 5 min to obtain a stretched microporous film. The stretched microporous film was immersed in a 12% citric acid aqueous solution and gently stirred and soaked at 60°C for 4 h. It was then removed and washed with deionized water until neutral. It was then transferred to an α-amylase solution (800 U / mL, pH adjusted to 6.0 with phosphate buffer) and gently stirred and soaked at 50°C for 4 h. It was then removed, washed, and dried under reduced pressure at 45°C to constant weight to obtain a multi-level microporous polyethylene film.

[0044] 4g of methyltrimethoxysilane was dissolved in a mixed solvent of 90mL anhydrous ethanol and 10mL deionized water. The pH was adjusted to 3.5 with hydrochloric acid, and the mixture was stirred at room temperature for 1h for pre-hydrolysis. The microporous membrane was then immersed in the solution and pulled at a rate of 1.5mm / s. After drying at room temperature for 30min, the membrane was cured at 90℃ for 40min to obtain a hydrophobic microporous polyethylene film.

[0045] Step (2): Disperse 50g of sodium-based montmorillonite in 2000mL of deionized water and stir at 80℃ for 2h to swell; dissolve 20g of octadecylamine in 600mL of ethanol / water (1:1) and add 8mL of 1mol / L hydrochloric acid to protonate it, slowly add it to the montmorillonite dispersion, stir at 80℃ for 6h, filter, wash 3 times each with hot water and ethanol, vacuum dry at 60℃ for 12h, grind through a 300-mesh sieve to obtain organically modified montmorillonite.

[0046] Aramid short fibers (approximately 1 mm in length and 12 μm in diameter) were immersed in a 5% sodium hydroxide aqueous solution, etched at 50°C for 30 min, removed and washed until neutral, and dried at 80°C for 4 h to obtain surface-treated aramid short fibers.

[0047] Take 5g of organically modified montmorillonite and add it to 20g of deionized water for ultrasonic dispersion (200W, 30min); take 100g of aqueous polyurethane emulsion (solid content 38%) and add the above dispersion, 9g of surface-treated aramid short fibers, and 6.5g of hollow glass microspheres (particle size 15-30μm, density 0.3g / cm³) sequentially under low-speed stirring (300rpm). 3 4.5g of calcined sepiolite (calcined at 400℃ for 2h to activate, fiber length 2μm) and 2g of polycarbodiimide crosslinking agent were mixed and stirred for 30min to obtain a composite reinforced coating liquid. One side of the hydrophobic microporous film was then subjected to corona treatment (40W·min / m). 2 The film is coated with a wet film of 65 μm using a microgravure coating at a speed of 20 m / min. It is then pre-baked at 50°C for 20 min, cured at 80°C for 45 min, and finally cured at 105°C for 20 min to obtain a reinforced modified polyethylene film.

[0048] Step (3): Take 40g / m 2 Polypropylene spunbond nonwoven fabric is produced by melting polyolefin hot melt adhesive at 150℃ and then rolling it onto the surface of the nonwoven fabric (adhesive application rate: 12g / m²). 2 The uncoated side of the reinforced modified polyethylene film is bonded to the adhesive side, and then hot-pressed at 108℃ and 0.3MPa with a roller speed of 15m / min. After cooling and winding, the composite nonwoven medical protective clothing material is obtained.

[0049] Example 4 A method for preparing a composite nonwoven medical protective clothing material includes the following steps: Step (1): Take 500g of nano-calcium carbonate with a particle size of about 60nm and disperse it in 3000mL of anhydrous ethanol. Stir and heat to 78℃ under the condition of reflux condenser. Add 16g of stearic acid and continue stirring for 2.5h. Filter, wash 3 times with anhydrous ethanol, dry at 80℃ for 4h, grind and pass through a 200-mesh sieve to obtain surface-modified nano-calcium carbonate.

[0050] Mix 170g of corn starch with 80g of glycerin evenly, seal and equilibrate at room temperature for 24 hours, then feed the mixture into a twin-screw extruder (temperature 120 / 130 / 140 / 145 / 140℃, speed 120rpm) for extrusion granulation to obtain thermoplastic starch granules.

[0051] Weigh 500g of linear low-density polyethylene resin, 450g of surface-modified nano-calcium carbonate, 150g of thermoplastic starch, 3g of antioxidant 1010 and 8g of calcium stearate, mix them at high speed for 6 minutes and then put them into a twin-screw extruder (L / D=40:1, temperature 150 / 160 / 170 / 178 / 185 / 180℃, speed 220rpm), extrude, water-cool and pelletize, and dry at 60℃ for 2 hours to obtain filler masterbatch.

[0052] The filler masterbatch was cast into a film at 185°C using a single-screw casting machine with a cooling roller at 30°C and a traction speed of 8 m / min to obtain a filled polyethylene film with a thickness of approximately 100 μm. The filled film was preheated to 95°C, stretched longitudinally by 3.0 times, and then transversely by 2.0 times at a stretching rate of 80 mm / min. It was then heat-set at 102°C for 5 min to obtain a stretched microporous film. The stretched microporous film was immersed in a 15% citric acid aqueous solution and gently stirred and soaked at 70°C for 6 h. It was then removed and washed with deionized water until neutral. It was then transferred to an α-amylase solution (800 U / mL, pH adjusted to 7.0 with phosphate buffer) and gently stirred and soaked at 60°C for 5 h. It was then removed, washed, and dried under reduced pressure at 45°C to constant weight to obtain a multi-level microporous polyethylene film.

[0053] 4g of methyltrimethoxysilane was dissolved in a mixed solvent of 90mL anhydrous ethanol and 10mL deionized water. The pH was adjusted to 3.5 with hydrochloric acid, and the mixture was stirred at room temperature for 1h for pre-hydrolysis. The microporous membrane was then immersed in the solution and pulled at a rate of 1.5mm / s. After drying at room temperature for 30min, the membrane was cured at 100℃ for 60min to obtain a hydrophobic microporous polyethylene film.

[0054] Step (2): Disperse 50g of sodium-based montmorillonite in 2000mL of deionized water and stir at 80℃ for 2h to swell; dissolve 20g of octadecylamine in 600mL of ethanol / water (1:1) and add 8mL of 1mol / L hydrochloric acid to protonate it, slowly add it to the montmorillonite dispersion, stir at 80℃ for 6h, filter, wash 3 times each with hot water and ethanol, vacuum dry at 60℃ for 12h, grind through a 300-mesh sieve to obtain organically modified montmorillonite.

[0055] Aramid short fibers (approximately 1 mm in length and 12 μm in diameter) were immersed in a 5% sodium hydroxide aqueous solution, etched at 50°C for 30 min, removed and washed until neutral, and dried at 80°C for 4 h to obtain surface-treated aramid short fibers.

[0056] Take 8g of organically modified montmorillonite and add it to 20g of deionized water for ultrasonic dispersion (200W, 30min); take 100g of aqueous polyurethane emulsion (solid content 38%), and add the above dispersion, 12g of surface-treated aramid short fibers, and 8g of hollow glass microspheres (particle size 15-30μm, density 0.3g / cm³) sequentially under low-speed stirring (300rpm). 3 6g of calcined sepiolite (calcined at 400℃ for 2h to activate, fiber length 2μm) and 3g of polycarbodiimide crosslinking agent were mixed and stirred for 30min to obtain a composite reinforced coating liquid. One side of the hydrophobic microporous film was then subjected to corona treatment (40W·min / m). 2 The film is coated with a wet film of 65 μm using a microgravure coating at a speed of 20 m / min. It is then pre-baked at 50°C for 20 min, cured at 80°C for 45 min, and finally cured at 105°C for 20 min to obtain a reinforced modified polyethylene film.

[0057] Step (3): Take 40g / m 2 Polypropylene spunbond nonwoven fabric is produced by melting polyolefin hot melt adhesive at 150℃ and then rolling it onto the surface of the nonwoven fabric (adhesive application rate: 12g / m²). 2 The uncoated side of the reinforced modified polyethylene film is bonded to the adhesive side, and then hot-pressed at 110℃ and 0.4MPa with a roller speed of 15m / min. After cooling and winding, the composite nonwoven medical protective clothing material is obtained.

[0058] Example 5 A method for preparing a composite nonwoven medical protective clothing material includes the following steps: Step (1): Take 500g of nano-calcium carbonate with a particle size of about 60nm and disperse it in 3000mL of anhydrous ethanol. Stir and heat to 78℃ under the condition of reflux condenser. Add 16g of stearic acid and continue stirring for 2.5h. Filter, wash 3 times with anhydrous ethanol, dry at 80℃ for 4h, grind and pass through a 200-mesh sieve to obtain surface-modified nano-calcium carbonate.

[0059] Mix 170g of corn starch with 70g of glycerin evenly, seal and equilibrate at room temperature for 24 hours, then feed the mixture into a twin-screw extruder (temperature 120 / 130 / 140 / 145 / 140℃, speed 120rpm) for extrusion granulation to obtain thermoplastic starch granules.

[0060] Weigh 500g of linear low-density polyethylene resin, 380g of surface-modified nano-calcium carbonate, 100g of thermoplastic starch, 3g of antioxidant 1010 and 8g of calcium stearate, mix at high speed for 6 minutes and then feed into a twin-screw extruder (L / D=40:1, temperature 150 / 160 / 170 / 178 / 185 / 180℃, speed 220rpm), extrude, water-cool and pelletize, and dry at 60℃ for 2 hours to obtain filler masterbatch.

[0061] The filler masterbatch was cast into a film at 185°C using a single-screw casting machine with a cooling roller at 30°C and a traction speed of 8 m / min to obtain a filled polyethylene film with a thickness of approximately 100 μm. The filled film was preheated to 95°C, stretched longitudinally by 3.0 times, and then transversely by 2.0 times at a stretching rate of 80 mm / min. It was then heat-set at 102°C for 5 min to obtain a stretched microporous film. The stretched microporous film was immersed in a 10% citric acid aqueous solution and gently stirred and soaked at 50°C for 2 h. It was then removed and washed with deionized water until neutral. It was then transferred to an α-amylase solution (800 U / mL, pH adjusted to 5.5 with phosphate buffer) and gently stirred and soaked at 40°C for 3 h. It was then removed, washed, and dried under reduced pressure at 45°C to constant weight to obtain a multi-level microporous polyethylene film.

[0062] 4g of methyltrimethoxysilane was dissolved in a mixed solvent of 90mL anhydrous ethanol and 10mL deionized water. The pH was adjusted to 3.5 with hydrochloric acid, and the mixture was stirred at room temperature for 1h for pre-hydrolysis. The microporous membrane was then immersed in the solution and pulled at a rate of 1.5mm / s. After drying at room temperature for 30min, the membrane was cured at 80℃ for 30min to obtain a hydrophobic microporous polyethylene film.

[0063] Step (2): Disperse 50g of sodium-based montmorillonite in 2000mL of deionized water and stir at 80℃ for 2h to swell; dissolve 20g of octadecylamine in 600mL of ethanol / water (1:1) and add 8mL of 1mol / L hydrochloric acid to protonate it, slowly add it to the montmorillonite dispersion, stir at 80℃ for 6h, filter, wash 3 times each with hot water and ethanol, vacuum dry at 60℃ for 12h, grind through a 300-mesh sieve to obtain organically modified montmorillonite.

[0064] Aramid short fibers (approximately 1 mm in length and 12 μm in diameter) were immersed in a 5% sodium hydroxide aqueous solution, etched at 50°C for 30 min, removed and washed until neutral, and dried at 80°C for 4 h to obtain surface-treated aramid short fibers.

[0065] Take 3g of organically modified montmorillonite and add it to 20g of deionized water for ultrasonic dispersion (200W, 30min); take 100g of aqueous polyurethane emulsion (solid content 38%) and add the above dispersion, 6g of surface-treated aramid short fibers, and 5g of hollow glass microspheres (particle size 15-30μm, density 0.3g / cm³) sequentially under low-speed stirring (300rpm). 3 3g of calcined sepiolite (calcined at 400℃ for 2h to activate, fiber length 2μm) and 1g of polycarbodiimide crosslinking agent were mixed and stirred for 30min to obtain a composite reinforced coating liquid. One side of the hydrophobic microporous film was then subjected to corona treatment (40W·min / m). 2 The film is coated with a wet film of 65 μm using a microgravure coating at a speed of 20 m / min. It is then pre-baked at 50°C for 20 min, cured at 80°C for 45 min, and finally cured at 105°C for 20 min to obtain a reinforced modified polyethylene film.

[0066] Step (3): Take 40g / m 2 Polypropylene spunbond nonwoven fabric is produced by melting polyolefin hot melt adhesive at 150℃ and then rolling it onto the surface of the nonwoven fabric (adhesive application rate: 12g / m²). 2 The uncoated side of the reinforced modified polyethylene film is bonded to the adhesive side, and then hot-pressed at 105℃ and 0.2MPa with a roller speed of 15m / min. After cooling and winding, the composite nonwoven medical protective clothing material is obtained.

[0067] Comparative Example 1: A common LLDPE film with the same thickness (100 μm) as in Example 4 (without the filling granulation, stretching pore formation, selective extraction pore expansion and hydrophobic treatment in step (1)) was used to directly construct a composite reinforcing coating on the film surface according to the method of step (2) in Example 4, and then composited with polypropylene nonwoven fabric according to step (3) in Example 4.

[0068] Comparative Example 2: After completing the preparation of the hydrophobic microporous polyethylene film according to step (1) of Example 4, step (2) was not performed (without coating the composite reinforcing coating), and the hydrophobic microporous polyethylene film was directly composited with polypropylene nonwoven fabric according to step (3) of Example 4.

[0069] Comparative Example 3: The method of Example 4 was followed, except that hollow glass microspheres and calcined sepiolite were not added in step (2) of the coating liquid preparation. All other conditions and operations were the same as in Example 4.

[0070] Comparative Example 4: The method of Example 4 was followed, except that 8g of hollow glass microspheres were added to the coating liquid in step (2) but calcined sepiolite was not added. All other conditions and operations were the same as in Example 4.

[0071] Comparative Example 5: The method of Example 4 was followed, except that 6g of calcined sepiolite was added in step (2) of the coating liquid preparation but hollow glass microspheres were not added. All other conditions and operations were the same as in Example 4.

[0072] Comparative Example 6: The method of Example 4 was followed, except that the hydrophobic treatment step was omitted in step (1) (the methyltrimethoxysilane dip-coating and curing treatment was not performed), and the multi-level microporous polyethylene film was directly used in step (2). The other conditions and operations were the same as in Example 4.

[0073] Comparative Example 7: The method of Example 4 was followed, except that the selective extraction and pore-expansion step was omitted in step (1) (citric acid dissolution treatment and α-amylase hydrolysis treatment were not performed), and the stretched microporous membrane was directly hydrophobized. The other conditions and operations were the same as in Example 4.

[0074] Performance testing 1. Water vapor transmission rate (WVTR) test: Cut the sample into a circle with a diameter of 70 mm, seal it on a permeation cup containing desiccant (anhydrous calcium chloride), and place it in a constant temperature and humidity chamber at a temperature of (38±2)℃ and a relative humidity of (90±2)%. Weigh the sample every 1 hour for 24 hours. Calculate the water vapor transmission rate based on the increase in mass of the permeation cup. Perform parallel tests on 5 samples per group and take the average value. The unit is g / (m²). 2 •24h).

[0075] 2. Hydrostatic pressure resistance test: Cut the sample into pieces with an area of ​​not less than 100 cm². 2 The circular sample is clamped between the upper and lower rings of the hydrostatic pressure tester, with the test surface facing down. Distilled water is uniformly pressurized from below the sample at a rate of 60 cmH2O / min. The water pressure value at the third point of seepage on the sample surface is recorded as the hydrostatic pressure resistance. Five samples are tested in parallel in each group, and the average value is taken. The unit is kPa.

[0076] 3. Tear strength test: Cut the sample into a rectangle of 200mm×50mm, and make a 100mm long cut along the center line of the length direction from one end to form two tongues. Clamp them in the upper and lower clamps of the universal testing machine and tear them at a tensile speed of 100mm / min. Record the maximum force value during the tearing process. Test the warp (MD) and weft (CD) directions separately. Test 5 samples in parallel in each direction and take the average value. The unit is N.

[0077] 4. Fracture strength test: Cut the specimen into strips of 300mm×50mm, clamp them in the upper and lower clamps of the universal testing machine with a clamping distance of 200mm, and stretch them at a tensile speed of 100mm / min until fracture. Record the maximum force value at fracture (fracture strength) and the elongation at fracture (fracture elongation). Perform parallel tests on 5 specimens in each direction and take the average value. The unit of fracture strength is N and the unit of fracture elongation is N.

[0078] 5. Synthetic blood penetration resistance test: Place the sample horizontally on the test device, and apply 2 mL of synthetic blood (prepared with red dye, surfactant and thickener, with a surface tension of 0.042±0.002 N / m) to the outer surface of the sample at a pressure of 1.75 kPa. After maintaining contact for 5 minutes, observe whether there are traces of synthetic blood penetration on the inner surface of the sample, and judge as "pass (qualified) / fail (unqualified)".

[0079] Table 1: Performance Test Results of Examples and Comparative Samples Comparative Example 1 uses a regular dense PE film without microporous treatment, and its WVTR is only 182 g / (m²). 2 •24h), while the WVTR of Example 4 was as high as 4317g / (m 2 (24h) This fully demonstrates the decisive role of the hierarchical microporous structure in improving air permeability. Comparative Example 7, which only underwent stretching pore-forming without selective extraction pore-expanding treatment, had a WVTR of only 1453 g / (m³). 2 The tear strength of Comparative Example 2 (without the reinforcing coating) was significantly lower than that of Example 4 (24h), indicating that selective extraction and pore-expansion are key steps in achieving a hierarchical microporous structure and high air permeability. Comparative Example 2, without the reinforcing coating, had a tear strength of only 8.6 / 7.3N and a breaking strength of only 27.5N, significantly lower than the 28.3 / 26.5N and 61.8N of Example 4, respectively. This demonstrates that the microporous PE film exhibits extremely poor mechanical properties without the reinforcement coating, failing to meet the requirements for use in medical protective clothing. Comparative Example 3, without hollow glass microspheres and sepiolite, had a WVTR of only 1823 g / (m³). 2 • 24h); Comparative Example 4, containing only microbeads, had a WVTR of 3185 g / (m 2 • 24h); Comparative Example 5, containing only sepiolite, had a WVTR of 2527 g / (m²·24h); while Example 4, containing both, achieved a WVTR of 4317 g / (m²·24h). 2The effect of 24h was significantly higher than the simple sum of the effects of using either material alone, demonstrating a synergistic effect between the physical shielding effect of hollow glass microspheres and the channel transport effect of sepiolite. Comparative Example 6, after omitting the MTMS hydrophobication treatment, showed a sharp drop in hydrostatic pressure resistance to 5.6 kPa and failed the synthetic blood penetration test, indicating that hydrophobication treatment is a necessary condition for maintaining the liquid barrier performance of the microporous membrane.

[0080] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the essence and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a composite nonwoven medical protective clothing material, characterized in that, Includes the following steps: (1) After surface-modified inorganic nanoparticles and enzymatically hydrolyzable thermoplastic natural polymer components are melt-blended with polyethylene resin to form a film, the resulting filled film is subjected to biaxial stretching to create pores. Then, the inorganic nanoparticles are dissolved by organic acid solution treatment and the thermoplastic natural polymer components are hydrolyzed by enzyme solution treatment to remove them. The film is then subjected to selective extraction to expand the pores. Finally, the film is subjected to organosilane hydrophobic treatment to obtain a hydrophobic microporous polyethylene film. The surface-modified inorganic nanoparticles are surface-modified nano-calcium carbonate, the thermoplastic natural polymer component is thermoplastic starch, and the polyethylene resin is linear low-density polyethylene. The surface-modified inorganic nanoparticles are nano-calcium carbonate that has undergone stearic acid surface modification treatment. The thermoplastic starch is prepared by mixing corn starch and glycerin at a mass ratio of 85:(35-40) and then plasticizing and granulating it by twin-screw extrusion. The mass ratio of the linear low-density polyethylene, surface-modified nano-calcium carbonate, and thermoplastic starch is 50:(38-45):(10-15). The selective extraction and pore-expansion method includes: first, immersing the stretched microporous membrane in a 10-15% (w / w) citric acid aqueous solution at 50-70°C for 2-6 hours to dissolve inorganic nanoparticles; then immersing it in an α-amylase solution with pH 5.5-7.0 at 40-60°C for 3-5 hours to hydrolyze and remove thermoplastic natural polymer components. The organosilane hydrophobication treatment is as follows: the microporous polyethylene film is immersed in an alcohol / water solution of methyltrimethoxysilane for dip coating and pulling, and then cured at 80-100℃ for 30-60 min after drying; (2) Organic modified layered silicate, surface-treated reinforcing short fibers, hollow glass microspheres, activated sepiolite and crosslinking agent are dispersed in an aqueous polyurethane emulsion to prepare a composite reinforcing coating liquid. The hydrophobic microporous polyethylene film is surface-activated on one side and then coated with the composite reinforcing coating liquid and cured to obtain a reinforced modified polyethylene film. The organically modified layered silicate is montmorillonite modified by long-chain alkylamine intercalation; the reinforcing short fiber is aramid short fiber treated with alkaline etching; the activated sepiolite is sepiolite that has undergone calcination activation treatment; and the crosslinking agent is polycarbodiimide crosslinking agent. The composite reinforced coating liquid is composed of: 100 parts by weight of waterborne polyurethane emulsion, 3-8 parts by weight of organic modified layered silicate, 6-12 parts by weight of surface-treated reinforcing short fibers, 5-8 parts by weight of hollow glass microspheres, 3-6 parts by weight of activated sepiolite, and 1-3 parts by weight of crosslinking agent; the particle size of the hollow glass microspheres is 15-30 μm. The surface activation treatment is either corona treatment or plasma treatment; (3) The reinforced modified polyethylene film is combined with polypropylene nonwoven fabric using an adhesive to obtain composite nonwoven medical protective clothing material; The polypropylene nonwoven fabric is a polypropylene spunbond nonwoven fabric; the adhesive is a hot melt adhesive, the composite temperature is 105-110℃, and the pressure is 0.2-0.4MPa.

2. A composite nonwoven medical protective clothing material prepared by the preparation method described in claim 1, characterized in that, The material comprises a polypropylene nonwoven fabric base layer, an adhesive layer, a microporous polyethylene film layer, and a composite reinforcing coating, which are stacked sequentially. The microporous polyethylene film layer contains a hierarchically distributed microporous structure and the microporous walls are hydrophobically treated. The composite reinforced coating contains organically modified layered silicates, surface-treated reinforcing short fibers, hollow glass microspheres, and activated sepiolite.

Images