Degradable nonwoven fabric and preparation process thereof

Abstract

The application discloses a degradable non-woven fabric and a preparation process thereof, and relates to the technical field of degradable polymer materials. The degradable non-woven fabric comprises the following raw materials in parts by weight: 45-60 parts of modified polylactic acid, 15-25 parts of modified bamboo fiber, 8-15 parts of polycaprolactone, 5-10 parts of polybutylene succinate, 2-5 parts of tributyl citrate, 1-3 parts of nano-hydroxyapatite, 0.5-1.2 parts of vitamin E, and 0.3-0.8 parts of polyaspartic acid. The raw material ratio of the degradable non-woven fabric is scientific, and the modified polylactic acid and the modified bamboo fiber serve as the core, and the degradable non-woven fabric has good degradability and mechanical properties. The preparation process is precisely controllable, the compatibility of the raw materials is improved through multi-stage modification, the degradable non-woven fabric is formed through processes such as melt spinning and hot rolling, internal stress can be eliminated, the finished product is environment-friendly and stable in quality, and the practicality and ecological friendliness can be effectively balanced.

Description

Technical Field

[0001] This invention relates to the field of biodegradable polymer materials technology, specifically to a biodegradable nonwoven fabric and its preparation process. Background Technology

[0002] Nonwoven fabrics are a core material in medical and health products, packaging materials, agricultural coverings and other fields. Their annual consumption continues to rise, and the environmental pressure caused by their disposal has become a pain point that the industry urgently needs to address.

[0003] Currently, while some biodegradable nonwoven fabrics are available on the market, their core raw material is mostly polylactic acid (PLA), which suffers from defects such as insufficient toughness, poor heat resistance, and low compatibility with natural fibers. PLA-based nonwoven fabrics are prone to brittleness at low temperatures and exhibit significant mechanical property degradation in high-humidity environments, making them unsuitable for applications requiring stringent strength and stability, such as medical surgical gowns and food packaging. Meanwhile, while natural bamboo fiber possesses renewable and biodegradable properties, its strong surface polarity and high crystallinity make it prone to agglomeration when directly added to a polymer matrix, resulting in weak interfacial bonding in the composite material and failing to fully exert its reinforcing effect.

[0004] In addition, existing biodegradable nonwoven fabric preparation processes have many limitations: some processes rely on highly toxic solvents, which do not conform to the concept of green production; some modification methods are simple and can only achieve single-level performance optimization, making it difficult to take into account biodegradability, mechanical strength and processing adaptability; and the degradation cycle of most products does not match the use cycle, either degrading too early and losing its use value, or degrading incompletely and leaving residues in the environment.

[0005] Faced with this industry predicament, developing a new type of biodegradable nonwoven fabric that combines excellent mechanical properties, stable performance, and high biodegradability, with a green and controllable manufacturing process, has become a key direction for breaking through industry bottlenecks and realizing the green transformation of the nonwoven fabric industry. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a biodegradable nonwoven fabric and its preparation process, solving the problems of insufficient mechanical properties, poor fiber compatibility, environmentally unfriendly processes, and low degradation adaptability of biodegradable nonwoven fabrics prepared by existing technologies.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A biodegradable nonwoven fabric comprising the following raw materials in parts by weight: 45-60 parts modified polylactic acid, 15-25 parts modified bamboo fiber, 8-15 parts polycaprolactone, 5-10 parts polybutylene succinate, 2-5 parts tributyl citrate, 1-3 parts nano hydroxyapatite, 0.5-1.2 parts vitamin E, and 0.3-0.8 parts polyaspartic acid.

[0008] Furthermore, the modified polylactic acid is prepared using the following specific steps: A1. Add polylactic acid to xylene and stir at 200-250 r / min in a water bath at 75-80℃ until it swells. Add maleic anhydride and dicumyl peroxide to the system, heat to 110-120℃, and react at a constant temperature for 3-4 h under a nitrogen atmosphere. Then add ethylene glycol diglycidyl ether and continue to react at a constant temperature for 1.5-2 h. After the reaction is completed, cool to room temperature, precipitate the product with anhydrous ethanol, filter, and dry in a vacuum drying oven at 60-70℃ for 8-10 h to obtain the first modified polylactic acid. Maleic anhydride was grafted onto the polylactic acid (PLA) molecular chain under the initiation of dicumyl peroxide, introducing polar groups and enhancing the subsequent reaction activity; ethylene glycol diglycidyl ether was used for epoxy chain extension to improve the brittleness of PLA and initially enhance the flexibility and cross-linking degree of the molecular chain, laying the foundation for subsequent modification.

[0009] A2. The first-modified polylactic acid was dispersed in ethyl acetate and ultrasonically dispersed at 300W for 30-40 min to form a uniform suspension. The caprolactam-terminated polyurethane prepolymer and dibutyltin dilaurate were added, and the mixture was stirred at 250-300 r / min for 2.5-3 h under nitrogen protection at 85-90℃. The total amount of polyethylene glycol was added in three portions, with an interval of 20 min between each addition. After all additions were completed, the reaction was continued for 1-1.5 h. After the reaction was completed, the ethyl acetate was removed by vacuum distillation at -0.09 MPa and 45℃. The product was then vacuum dried at 80℃ for 10 h to obtain the second-modified polylactic acid. Caprolactam-terminated polyurethane prepolymers are grafted onto polylactic acid chains to further enhance toughness; polyethylene glycol (2000-4000 g / mol) added in batches is uniformly block-into the molecular chain, which greatly improves the flexibility and resistance to low-temperature brittleness of polylactic acid, while also enhancing its compatibility with other components.

[0010] A3. Dissolve chitosan in a 1% (w / w) dilute acetic acid solution and sodium alginate in deionized water, stirring until completely dissolved. Add the second-modified polylactic acid to the chitosan solution, sonicate at 300W for 20-30 min, then slowly add sodium alginate solution to adjust the pH of the system to 5.5-6.0. Add 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and glycerol, and stir at 200-250 r / min at 50-55℃ for 2 h. After filtration, wash with deionized water until neutral, and dry in a vacuum drying oven at 65℃ for 12 h to obtain modified polylactic acid.

[0011] Chitosan and sodium alginate form a polyelectrolyte complex under acidic conditions, which encapsulates polylactic acid (PLA). This enhances PLA's biocompatibility and biodegradability, strengthens its interfacial bonding with natural bamboo fiber, and improves the material's moisture resistance. The modified PLA possesses excellent flexibility, compatibility, and biodegradability, solving the problems of high brittleness, poor compatibility with natural fibers, and mechanical property degradation in high-humidity environments associated with pure PLA. It can serve as a core substrate for nonwoven fabrics, providing stable mechanical support and environmentally friendly properties for the finished product.

[0012] Furthermore, the modified bamboo fiber is prepared using the following specific steps: B1. Add bamboo fiber to a 5% (w / w) dilute sulfuric acid solution and etch at a constant temperature of 60-65℃ with stirring at 150-200 r / min for 1-1.5 h. Wash with deionized water until neutral, then add a 3% (w / w) sodium hydroxide solution and treat with alkali at 70℃ with stirring at 200-250 r / min for 2 h. Then add 30% (w / w) hydrogen peroxide and react at 50℃ for 30 min. Finally, add silane coupling agent KH-550 and react at 80℃ for 1 h. After filtration and drying, the first modified bamboo fiber is obtained. Dilute sulfuric acid etching and sodium hydroxide alkaline treatment remove impurities from the surface of bamboo fiber, reduce crystallinity, and increase specific surface area; hydrogen peroxide oxidation enhances surface activity; silane coupling agent KH-550 is used to graft active groups, improve the interfacial compatibility between bamboo fiber and polymer matrix, and avoid agglomeration problems when added directly.

[0013] B2. The first modified bamboo fiber was added to anhydrous toluene and ultrasonically dispersed at 350W for 40 min. The temperature was raised to 90℃ under a nitrogen atmosphere. Octadecyl isocyanate and pyridine were added and stirred at a constant temperature of 250-300 r / min for 3-3.5 h. Stearic acid was then added and the reaction was continued for 1-1.5 h. After the reaction was completed, the mixture was cooled and washed 3-4 times with petroleum ether to remove unreacted reagents. The mixture was then vacuum dried at 70℃ for 8 h to obtain the second modified bamboo fiber. Octadecyl isocyanate and stearic acid are grafted onto the surface of bamboo fiber to reduce its surface polarity, improve hydrophobicity and dispersibility, and enhance the interfacial bonding force of bamboo fiber in the polymer matrix, thereby reducing stress concentration.

[0014] B3. The modified bamboo fiber was dispersed in anhydrous ethanol and ultrasonically dispersed for 30 min. Sodium hexametaphosphate was added to adjust the dispersibility of the system. Using the co-precipitation method, 0.5 mol / L calcium nitrate solution and 0.3 mol / L diammonium hydrogen phosphate solution were added dropwise under stirring at 300 r / min. The pH of the system was adjusted to 9-10 with 25% ammonia water. The temperature was raised to 60℃ and the reaction was kept at a constant temperature for 2 h. After the reaction was completed, the mixture was filtered, washed with deionized water until neutral, and vacuum dried at 80℃ for 10 h to obtain the modified bamboo fiber.

[0015] Hydroxyapatite was loaded onto the surface of bamboo fiber using a co-precipitation method. The rigidity of hydroxyapatite enhances the mechanical strength and heat resistance of the bamboo fiber. Simultaneously, hydroxyapatite synergistically promotes material degradation and strengthens the rigidity of the nonwoven fabric. The modified bamboo fiber exhibits good dispersibility, rigidity, and compatibility, retaining the biodegradable and renewable properties of natural fibers while acting as a reinforcing filler to form a stable interfacial bond with the modified polylactic acid matrix. This significantly improves the tensile strength, tear resistance, and other mechanical properties of the nonwoven fabric, while ensuring overall biodegradability.

[0016] Furthermore, the polyethylene glycol in A2 has a molecular weight of 2000-4000 g / mol and a suitable chain length, which can effectively improve the flexibility of polylactic acid. When A2 is added in three batches, the amount added each time is 40%, 30%, and 30% of the total amount, respectively. Adding it in batches in proportion can avoid excessive or insufficient local grafting, ensure uniform molecular linking, and thus ensure the overall stability of the modified polylactic acid and enhance its compatibility with other components.

[0017] Furthermore, during the co-precipitation reaction of B3, the dropping rate of calcium nitrate solution and diammonium hydrogen phosphate solution is 2-3 ml / min. The low-speed dropping can prevent excessive local concentration from causing hydroxyapatite agglomeration. In addition, the pH of the system is kept stable in the range of 9-10 during the dropping process, providing a suitable alkaline environment for the formation and loading of hydroxyapatite, ensuring that hydroxyapatite is uniformly deposited on the surface of bamboo fiber, and improving the rigidity and dispersibility of bamboo fiber.

[0018] Furthermore, the ratio of polylactic acid, maleic anhydride, dicumyl peroxide, and ethylene glycol diglycidyl ether in A1 is 500g: 40-50g: 1-1.5g: 7-10ml.

[0019] Furthermore, the ratio of the first modified polylactic acid, ethyl acetate, caprolactam-terminated polyurethane prepolymer, dibutyltin dilaurate, and polyethylene glycol in A2 is 500g: 200-250ml: 60-75g: 0.5-1g: 15-20g.

[0020] Furthermore, the ratio of chitosan, dilute acetic acid solution, sodium alginate, deionized water, second-modified polylactic acid, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, and glycerol in A3 is 25-30g: 300-350ml: 10-12g: 500-600ml: 500g: 4-5g: 5-8ml.

[0021] Furthermore, the ratio of bamboo fiber, dilute sulfuric acid solution, sodium hydroxide solution, hydrogen peroxide, and silane coupling agent KH-550 in B1 is 500g: 300-350ml: 250-300ml: 20-25ml: 7-10ml.

[0022] Furthermore, the ratio of the first modified bamboo fiber, anhydrous toluene, octadecyl isocyanate, pyridine, and stearic acid in B2 is 500g: 180-200ml: 30-35g: 3-4ml: 12-15g.

[0023] Furthermore, the ratio of the amount of the second modified bamboo fiber, anhydrous ethanol, sodium hexametaphosphate, calcium nitrate solution, and diammonium hydrogen phosphate solution in B3 is 500g: 150-180ml: 2-4g: 100-125ml: 60-75ml.

[0024] A process for preparing a biodegradable nonwoven fabric specifically includes the following steps: S1. The modified polylactic acid, polycaprolactone, and polybutylene succinate are dried in a vacuum drying oven at 80℃ for 6-8 hours to remove moisture from the raw materials; the modified bamboo fiber is dried in an oven at 105℃ for 2 hours; 1-3 parts of nano hydroxyapatite, 0.5-1.2 parts of vitamin E, and 0.3-0.8 parts of polyaspartic acid are premixed evenly to prepare a premixed additive; the drying step can remove moisture from the raw materials and avoid bubble defects during processing; the premixed additive ensures uniform dispersion of the additive. S2. Add 45-60 parts of dried modified polylactic acid, 8-15 parts of polycaprolactone, and 5-10 parts of polybutylene succinate to the main feed port of the twin-screw extruder. Add 15-25 parts of modified bamboo fiber through the side feed port. Add the above premixed additives and 2-5 parts of tributyl citrate through the additive feed port. Set the temperatures of each section of the twin-screw extruder as follows: Zone 1 140-145℃, Zone 2 150-155℃, Zone 3 160-165℃, Zone 4 155-160℃, Die head temperature 150-155℃, and screw speed 200-250 r / min. The extruded melt is water-cooled and pelletized at 25℃ to obtain biodegradable nonwoven fabric masterbatch. The masterbatch particle size is controlled at 2-3 mm. Vacuum dry at 70℃ for 4 hours. The segmented temperature control and multi-feed port design ensure that the raw materials are fully mixed and do not undergo thermal degradation, resulting in masterbatch with uniform particle size. S3. Add the dried masterbatch to a melt spinning machine, set the spinning temperature to 155-160℃, the melt pressure to 2.5-3.0MPa, the spinneret orifice diameter to 0.3mm, and the spinning speed to 800-1000m / min; the spun nascent fibers are cooled by side blowing at a temperature of 25-30℃ and a wind speed of 0.5-0.8m / s, and then hot-drawn by a drawing machine at a drawing temperature of 70-75℃ and a drawing ratio of 3-3.5 times to obtain biodegradable fiber filaments; the melt spinning and hot drawing parameters ensure stable fiber filament formation and excellent mechanical properties; S4. The drawn fiber filaments are fed into a carding machine, with a carding speed of 15-20 m / min. The fiber web is then fed into a hot rolling mill for thermal bonding and forming, with a hot rolling temperature of 110-115℃, a hot rolling pressure of 2.0-2.5 MPa, and a hot rolling speed of 10-15 m / min. The formed nonwoven fabric undergoes finishing processes, including edge trimming and winding. The wound nonwoven fabric is then placed in an environment with room temperature and a relative humidity of 50-60% for 24 hours for conditioning to eliminate internal stress, resulting in the finished biodegradable nonwoven fabric. Carding and hot rolling make the fiber web dense and formed, while conditioning eliminates internal stress and improves the dimensional stability of the finished product. The overall process ensures the stable quality of the nonwoven fabric.

[0025] Furthermore, in the S1 premixed additive, the nano-hydroxyapatite has a particle size of 50-80 nm. Nano-hydroxyapatite within this particle size range exhibits excellent synergistic effects in reinforcement and degradation. During premixing, vitamin E and polyaspartic acid should be pre-stirred at 40-45°C for 15 min, and then nano-hydroxyapatite should be added and ultrasonically dispersed for 20 min. Pre-stirring vitamin E and polyaspartic acid first can improve their compatibility, and subsequent ultrasonic dispersion can prevent the nano-hydroxyapatite from agglomerating, ensuring that the additives are evenly distributed in the substrate and fully exerting the functions of each additive.

[0026] Furthermore, in S2, the feeding rate of the twin-screw extruder is as follows: the main feed port feed rate is 15-20 kg / h, the side feed port feed rate is 5-8 kg / h, and the auxiliary feed port feed rate is 1-2 kg / h. The precise matching of the feed port rates can achieve orderly mixing of raw materials in proportion, which avoids uneven dispersion of modified bamboo fiber caused by excessively fast feeding of the main raw material, and also prevents abnormal local concentration caused by excessively slow feeding of the auxiliary material. At the same time, it eliminates the problem of material blockage and ensures the continuity of production and the stability of masterbatch quality.

[0027] This invention provides a biodegradable nonwoven fabric and its preparation process, which has the following beneficial effects: 1. This biodegradable nonwoven fabric possesses excellent comprehensive mechanical properties, solving the problems of brittleness and insufficient toughness in traditional polylactic acid-based biodegradable nonwoven fabrics. Its core raw material, modified polylactic acid, undergoes a three-step modification process to achieve molecular chain grafting and coating, improving the flexibility and compatibility of the polymer chains. The modified bamboo fiber surface is loaded with hydroxyapatite, possessing both rigidity and dispersibility, forming a stable interfacial bond with the polylactic acid matrix. Simultaneously, the compounding of polycaprolactone and polybutylene succinate further optimizes the material's ductility. After hot stretching and hot rolling, the finished nonwoven fabric possesses sufficient tensile strength to meet the needs of medical and packaging applications, while also exhibiting good tear resistance, preventing failure due to external force during use.

[0028] 2. This product combines high efficiency and biodegradability with environmental friendliness, adhering to green principles throughout the entire supply chain from raw materials to finished products. At the raw material level, both modified polylactic acid and modified bamboo fiber are biodegradable components, and the added additives such as polyaspartic acid and vitamin E promote the degradation process of the material in the natural environment, avoiding secondary pollution caused by traditional additive residues. At the preparation level, solvents used in the modification and molding processes can be effectively removed through vacuum distillation and washing, leaving no toxic or harmful residues. After disposal, the product can gradually degrade into small molecules in the natural environment, preventing white pollution. Furthermore, natural components such as bamboo fiber enable biomass recycling, aligning with the industrial environmental protection requirements under the "dual carbon" target.

[0029] 3. This nonwoven fabric possesses excellent processing adaptability and finished product stability, meeting the needs of large-scale production and multi-scenario applications. Its manufacturing process employs segmented temperature-controlled twin-screw extrusion and melt spinning, with precise matching of feed rates at each port to ensure uniform raw material mixing and prevent material blockage. The masterbatch particle size can be controlled within 2-3mm, ensuring the continuity of subsequent spinning. The parameter settings for hot drawing and hot rolling allow the fibers to form a dense and uniform fiber web. After moisture conditioning to eliminate internal stress, the finished product exhibits strong dimensional stability. Under different environments such as high and low temperatures and high humidity, its mechanical properties and morphology do not easily degrade significantly, making it widely applicable in medical supplies, food packaging, agricultural mulch films, and many other fields.

[0030] 4. This product achieves high-value utilization and synergistic performance improvement of biomass resources, combining economic value and ecological benefits. Using bamboo fiber as the core natural raw material, a multi-step process involving etching, silane coupling, grafting modification, and hydroxyapatite loading transforms the originally highly crystalline and difficult-to-disperse bamboo fiber into a high-performance reinforcing filler. This not only improves the rigidity and heat resistance of the nonwoven fabric but also expands the application pathways of agricultural and forestry waste such as bamboo, reducing dependence on petroleum-based raw materials. Simultaneously, the synergistic effect of modified polylactic acid and modified bamboo fiber allows the product to maintain biodegradability while reducing costs compared to pure high-end biodegradable resin-based nonwoven fabrics, thus balancing the economic benefits for enterprise production with the industry's green transformation needs. Detailed Implementation

[0031] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] Example 1: Preparation of biodegradable nonwoven fabric. The specific preparation steps are as follows: S1. Modified polylactic acid, polycaprolactone, and polybutylene succinate were dried in a vacuum drying oven at 80℃ for 6 hours to remove moisture from the raw materials; modified bamboo fiber was dried in an oven at 105℃ for 2 hours; 0.5 parts of vitamin E and 0.3 parts of polyaspartic acid were pre-stirred at 40℃ for 15 minutes, and then 1 part of nano-hydroxyapatite was added and ultrasonically dispersed for 20 minutes to prepare a premixed additive. S2. Add 45 parts of dried modified polylactic acid, 8 parts of polycaprolactone, and 5 parts of polybutylene succinate to the main feed port of the twin-screw extruder at a feed rate of 15 kg / h. Add 15 parts of modified bamboo fiber through the side feed port at a feed rate of 5 kg / h. Add the above premixed additives and 2 parts of tributyl citrate through the additive feed port at a feed rate of 1 kg / h. Set the temperatures of each section of the twin-screw extruder as follows: Zone 1 140℃, Zone 2 150℃, Zone 3 160℃, Zone 4 155℃, and the die head temperature 150℃. Set the screw speed to 200 r / min. The extruded melt is water-cooled and pelletized at 25℃ to obtain biodegradable nonwoven fabric masterbatch. The masterbatch particle size is controlled at 2 mm. Vacuum dry at 70℃ for 4 hours. S3. The dried masterbatch is added to a melt spinning machine. The spinning temperature is set to 155℃, the melt pressure is controlled at 2.5MPa, the spinneret orifice diameter is 0.3mm, and the spinning speed is 800m / min. The spun nascent fibers are cooled by side blowing at 25℃ and 0.5m / s, and then hot-drawn by a drawing machine at 70℃ and a draw ratio of 3 times to obtain biodegradable fiber filaments. S4. The drawn fiber filaments are fed into a carding machine, and the carding speed is set to 15m / min. The fiber web blank is fed into a hot rolling mill for hot bonding and forming, and the hot rolling temperature is set to 110℃, the hot rolling pressure is 2.0MPa, and the hot rolling speed is 10m / min. The formed nonwoven fabric is then finished, including edge trimming and winding. The wound nonwoven fabric is placed in an environment with room temperature and 50% relative humidity for 24 hours for moisture conditioning to eliminate internal stress and obtain the finished biodegradable nonwoven fabric.

[0033] Example 2: Preparation of biodegradable nonwoven fabric. The specific preparation steps are as follows: S1. Modified polylactic acid, polycaprolactone, and polybutylene succinate were dried in a vacuum drying oven at 80℃ for 8 hours to remove moisture from the raw materials; modified bamboo fiber was dried in an oven at 105℃ for 2 hours; 1.2 parts of vitamin E and 0.8 parts of polyaspartic acid were pre-stirred at 45℃ for 15 minutes, and then 3 parts of nano-hydroxyapatite were added and ultrasonically dispersed for 20 minutes to prepare a premixed additive. S2. Add 60 parts of dried modified polylactic acid, 15 parts of polycaprolactone, and 10 parts of polybutylene succinate to the main feed port of the twin-screw extruder at a feed rate of 20 kg / h. Add 25 parts of modified bamboo fiber through the side feed port at a feed rate of 8 kg / h. Add the above premixed additives and 5 parts of tributyl citrate through the additive feed port at a feed rate of 2 kg / h. Set the temperatures of each section of the twin-screw extruder as follows: Zone 1 145℃, Zone 2 155℃, Zone 3 165℃, Zone 4 160℃, and the die head temperature 155℃. Set the screw speed to 250 r / min. The extruded melt is water-cooled and pelletized at 25℃ to obtain biodegradable nonwoven fabric masterbatch. The masterbatch particle size is controlled at 3 mm. Vacuum dry at 70℃ for 4 hours. S3. The dried masterbatch is added to a melt spinning machine. The spinning temperature is set to 160℃, the melt pressure is controlled at 3.0MPa, the spinneret orifice diameter is 0.3mm, and the spinning speed is 1000m / min. The spun nascent fibers are cooled by side blowing at 30℃ and 0.8m / s, and then hot-drawn by a drawing machine at 75℃ and a draw ratio of 3.5 times to obtain biodegradable fiber filaments. S4. The drawn fiber filaments are fed into a carding machine, and the carding speed is set to 20m / min. The fiber web is fed into a hot rolling mill for hot bonding and forming, and the hot rolling temperature is set to 115℃, the hot rolling pressure is 2.5MPa, and the hot rolling speed is 15m / min. The formed nonwoven fabric is then finished, including edge trimming and winding. The wound nonwoven fabric is placed in an environment with room temperature and relative humidity of 60% for 24 hours for moisture conditioning to eliminate internal stress and obtain the finished biodegradable nonwoven fabric.

[0034] Example 3: Preparation of biodegradable nonwoven fabric. The specific preparation steps are as follows: S1. The modified polylactic acid, polycaprolactone, and polybutylene succinate were dried in a vacuum drying oven at 80℃ for 7 hours to remove moisture from the raw materials; the modified bamboo fiber was dried in an oven at 105℃ for 2 hours; 1 part vitamin E and 0.5 part polyaspartic acid were pre-stirred at 42℃ for 15 minutes, and then 2 parts nano hydroxyapatite were added and ultrasonically dispersed for 20 minutes to prepare a premixed additive. S2. Add 52 parts of dried modified polylactic acid, 11 parts of polycaprolactone, and 7 parts of polybutylene succinate to the main feed port of the twin-screw extruder at a feed rate of 17 kg / h. Add 20 parts of modified bamboo fiber through the side feed port at a feed rate of 6 kg / h. Add the above premixed additives and 3 parts of tributyl citrate through the additive feed port at a feed rate of 1.5 kg / h. Set the temperatures of each section of the twin-screw extruder as follows: Zone 1 142℃, Zone 2 152℃, Zone 3 162℃, Zone 4 157℃, and the die head temperature 152℃. Set the screw speed to 225 r / min. The extruded melt is water-cooled and pelletized at 25℃ to obtain biodegradable nonwoven fabric masterbatch. The masterbatch particle size is controlled at 2.5 mm. Vacuum dry at 70℃ for 4 hours. S3. The dried masterbatch is added to a melt spinning machine. The spinning temperature is set to 157℃, the melt pressure is controlled at 2.7MPa, the spinneret orifice diameter is 0.3mm, and the spinning speed is 900m / min. The spun nascent fibers are cooled by side blowing at a temperature of 27℃ and a wind speed of 0.6m / s. Then, they are hot-drawn by a drawing machine at a drawing temperature of 72℃ and a drawing ratio of 3.2 times to obtain biodegradable fiber filaments. S4. The drawn fiber filaments are fed into a carding machine, and the carding speed is set to 17 m / min. The fiber web blank is fed into a hot rolling mill for hot bonding and forming, and the hot rolling temperature is set to 112℃, the hot rolling pressure is 2.2 MPa, and the hot rolling speed is 12 m / min. The formed nonwoven fabric is then finished, including edge trimming and winding. The wound nonwoven fabric is placed in an environment with room temperature and relative humidity of 55% for 24 hours for moisture conditioning to eliminate internal stress and obtain the finished biodegradable nonwoven fabric.

[0035] Example 4: Preparation of modified polylactic acid. The specific preparation steps are as follows: A1. Add 500g of polylactic acid to xylene and stir at 200r / min in a 75℃ water bath until swollen; add 40g of maleic anhydride and 1g of dicumyl peroxide to the system, heat to 110℃, and react at a constant temperature for 3h under a nitrogen atmosphere; then add 7ml of ethylene glycol diglycidyl ether and continue to react at a constant temperature for 1.5h; after the reaction is completed, cool to room temperature, precipitate the product with anhydrous ethanol, filter, and dry in a vacuum drying oven at 60℃ for 8h to obtain the first modified polylactic acid; A2. 500g of the first-modified polylactic acid was dispersed in 200ml of ethyl acetate and ultrasonically dispersed at 300W for 30min to form a uniform suspension. 60g of caprolactam-terminated polyurethane prepolymer and 0.5g of dibutyltin dilaurate were added, and the mixture was stirred at 250r / min for 2.5h at 85℃ under nitrogen protection. 15g of polyethylene glycol was added in three portions, with each addition being 40%, 30%, and 30% of the total amount, 20min apart. After all additions were completed, the reaction continued for 1h. After the reaction was completed, ethyl acetate was removed by vacuum distillation at -0.09MPa and 45℃. The product was then vacuum dried at 80℃ for 10h to obtain the second-modified polylactic acid. A3. Dissolve 25g of chitosan in 300ml of 1% (w / w) dilute acetic acid solution, and dissolve 10g of sodium alginate in 500ml of deionized water, stirring until completely dissolved. Add 500g of the second-modified polylactic acid to the chitosan solution, sonicate at 300W for 20min, and then slowly add sodium alginate solution to adjust the pH of the system to 5.5. Add 4g of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and 5ml of glycerol, and stir at 200r / min at 50℃ for 2h. After filtration, wash with deionized water until neutral, and dry in a vacuum drying oven at 65℃ for 12h to obtain modified polylactic acid.

[0036] Example 5: Preparation of modified polylactic acid. The specific preparation steps are as follows: A1. Add 500g of polylactic acid to xylene and stir at 250r / min in an 80℃ water bath until swollen; add 50g of maleic anhydride and 1.5g of dicumyl peroxide to the system, heat to 120℃, and react at a constant temperature for 4h under a nitrogen atmosphere; then add 10ml of ethylene glycol diglycidyl ether and continue to react at a constant temperature for 2h; after the reaction is completed, cool to room temperature, precipitate the product with anhydrous ethanol, filter, and dry in a vacuum drying oven at 70℃ for 10h to obtain the first modified polylactic acid; A2. 500g of the first-modified polylactic acid was dispersed in 250ml of ethyl acetate and ultrasonically dispersed at 300W for 40min to form a uniform suspension. 75g of caprolactam-terminated polyurethane prepolymer and 1g of dibutyltin dilaurate were added, and the mixture was stirred at 300r / min for 3h at 90℃ under nitrogen protection. 20g of polyethylene glycol was added in three portions, with each addition being 40%, 30%, and 30% of the total amount, 20min apart. After all additions were completed, the reaction continued for 1.5h. After the reaction was completed, ethyl acetate was removed by vacuum distillation at -0.09MPa and 45℃. The product was then vacuum dried at 80℃ for 10h to obtain the second-modified polylactic acid. A3. Dissolve 30g of chitosan in 350ml of 1% (w / w) dilute acetic acid solution, and dissolve 12g of sodium alginate in 600ml of deionized water, stirring until completely dissolved. Add 500g of the second-modified polylactic acid to the chitosan solution, sonicate at 300W for 30min, and then slowly add sodium alginate solution to adjust the pH of the system to 6.0. Add 5g of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and 8ml of glycerol, and stir at 250r / min at 55℃ for 2h. After filtration, wash with deionized water until neutral, and dry in a vacuum drying oven at 65℃ for 12h to obtain modified polylactic acid.

[0037] Example 6: Preparation of modified bamboo fiber. The specific preparation steps are as follows: B1. Add 500g of bamboo fiber to 300ml of 5% sulfuric acid solution and etch at 60℃ with stirring at 150r / min for 1h. Wash with deionized water until neutral, then add 250ml of 3% sodium hydroxide solution and alkali treat at 70℃ with stirring at 200r / min for 2h. Then add 20ml of 30% hydrogen peroxide and react at 50℃ for 30min. Finally, add 7ml of silane coupling agent KH-550 and keep the reaction at 80℃ for 1h. After filtration and drying, the first modified bamboo fiber is obtained. B2. Add 500g of the first-modified bamboo fiber to 180ml of anhydrous toluene, ultrasonically disperse at 350W for 40min, and heat to 90℃ under a nitrogen atmosphere; add 30g of octadecyl isocyanate and 3ml of pyridine, and stir at 250r / min for 3h; then add 12g of stearic acid and continue the reaction for 1h; after the reaction is completed, cool, wash three times with petroleum ether to remove unreacted reagents, and vacuum dry at 70℃ for 8h to obtain the second-modified bamboo fiber; B3. Disperse 500g of the second-modified bamboo fiber in 150ml of anhydrous ethanol and ultrasonically disperse for 30min. Add 2g of sodium hexametaphosphate to adjust the dispersibility of the system. Using the co-precipitation method, simultaneously add 100ml of 0.5mol / L calcium nitrate solution and 60ml of 0.3mol / L diammonium hydrogen phosphate solution at a stirring rate of 2ml / min under a stirring rate of 300r / min. Adjust the pH of the system to 9 with 25% ammonia water. Heat to 60℃ and react at a constant temperature for 2h. After the reaction is completed, filter, wash with deionized water until neutral, and vacuum dry at 80℃ for 10h to obtain the modified bamboo fiber.

[0038] Example 7: Preparation of modified bamboo fiber. The specific preparation steps are as follows: B1. Add 500g of bamboo fiber to 350ml of 5% sulfuric acid solution and etch at 65℃ with stirring at 200r / min for 1.5h. Wash with deionized water until neutral, then add 300ml of 3% sodium hydroxide solution and alkali treat at 70℃ with stirring at 250r / min for 2h. Then add 25ml of 30% hydrogen peroxide and react at 50℃ for 30min. Finally, add 10ml of silane coupling agent KH-550 and keep the reaction at 80℃ for 1h. After filtration and drying, the first modified bamboo fiber is obtained. B2. Add 500g of the first-modified bamboo fiber to 200ml of anhydrous toluene, ultrasonically disperse at 350W for 40min, and heat to 90℃ under a nitrogen atmosphere; add 35g of octadecyl isocyanate and 4ml of pyridine, and stir at 300r / min for 3.5h; then add 15g of stearic acid and continue the reaction for 1.5h; after the reaction is completed, cool, wash 4 times with petroleum ether to remove unreacted reagents, and vacuum dry at 70℃ for 8h to obtain the second-modified bamboo fiber; B3. Disperse 500g of the second-modified bamboo fiber in 180ml of anhydrous ethanol and sonicate for 30min. Add 4g of sodium hexametaphosphate to adjust the dispersibility of the system. Using the co-precipitation method, simultaneously add 125ml of 0.5mol / L calcium nitrate solution and 75ml of 0.3mol / L diammonium hydrogen phosphate solution at a stirring rate of 3ml / min under a stirring rate of 300r / min. Adjust the pH of the system to 10 with 25% ammonia water. Heat to 60℃ and react at a constant temperature for 2h. After the reaction is completed, filter, wash with deionized water until neutral, and vacuum dry at 80℃ for 10h to obtain the modified bamboo fiber.

[0039] Comparative Example 1: A biodegradable nonwoven fabric was prepared. The specific preparation steps are as follows: The remaining steps remain the same, except that the modified polylactic acid prepared in Example 4 used in Example 3 is replaced with unmodified polylactic acid to prepare a biodegradable nonwoven fabric.

[0040] Comparative Example 2: Biodegradable nonwoven fabric was prepared. The specific preparation steps are as follows: The remaining steps remain the same, except that the modified bamboo fiber prepared in Example 7 used in Example 3 is replaced with unmodified bamboo fiber to prepare a biodegradable nonwoven fabric.

[0041] Comparative Example 3: Biodegradable nonwoven fabric was prepared. The specific preparation steps are as follows: The remaining steps remain unchanged, except that the modified polylactic acid prepared in Example 4 used in Example 3 is replaced with unmodified polylactic acid, and the modified bamboo fiber prepared in Example 7 is replaced with unmodified bamboo fiber, to prepare a biodegradable nonwoven fabric.

[0042]

[0043] Based on the performance test results, compared with Comparative Examples 1-3 which used unmodified polylactic acid and unmodified bamboo fiber, the biodegradable nonwoven fabrics prepared in Examples 1-3 of this invention have significant advantages in comprehensive performance: In terms of mechanical properties, the breaking strength (142.5-164.0 N / 50mm) and breaking elongation (35.2%-42.5%) of the products in the examples are much higher than those in the comparative examples (breaking strength 78.5-113.0 N / 50mm, breaking elongation 9.8%-20.3%), and Example 3 has the best mechanical performance; in terms of biodegradability, the soil degradation rate of the products in the examples reaches 68.5%-76.8% after 180 days, far exceeding the 38.7%-52.6% of the comparative examples; in terms of water vapor transmission rate, which is related to air permeability, the examples are 8500-9200 g / (m³). 2 (24h), which is also significantly better than the comparative ratio of 5500-7000g / (m 2 (24h), fully demonstrating the synergistic effect of modified polylactic acid and modified bamboo fiber on the significant improvement of nonwoven fabric performance.

[0044] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

Claims

1. A biodegradable nonwoven fabric, characterized in that: It contains the following raw materials in parts by weight: 45-60 parts modified polylactic acid, 15-25 parts modified bamboo fiber, 8-15 parts polycaprolactone, 5-10 parts polybutylene succinate, 2-5 parts tributyl citrate, 1-3 parts nano hydroxyapatite, 0.5-1.2 parts vitamin E, and 0.3-0.8 parts polyaspartic acid; The modified polylactic acid is prepared using the following specific steps: A1. Add polylactic acid to xylene and stir at 200-250 r / min in a water bath at 75-80℃ until it swells. Add maleic anhydride and dicumyl peroxide to the system, heat to 110-120℃, and react at a constant temperature for 3-4 h under a nitrogen atmosphere. Then add ethylene glycol diglycidyl ether and continue to react at a constant temperature for 1.5-2 h. After the reaction is completed, cool to room temperature, precipitate the product with anhydrous ethanol, filter, and dry in a vacuum drying oven at 60-70℃ for 8-10 h to obtain the first modified polylactic acid. A2. The first-modified polylactic acid was dispersed in ethyl acetate and ultrasonically dispersed at 300W for 30-40 min to form a uniform suspension. The caprolactam-terminated polyurethane prepolymer and dibutyltin dilaurate were added, and the mixture was stirred at 250-300 r / min for 2.5-3 h under nitrogen protection at 85-90℃. The total amount of polyethylene glycol was added in three portions, with an interval of 20 min between each addition. After all additions were completed, the reaction was continued for 1-1.5 h. After the reaction was completed, the ethyl acetate was removed by vacuum distillation at -0.09 MPa and 45℃. The product was then vacuum dried at 80℃ for 10 h to obtain the second-modified polylactic acid. A3. Dissolve chitosan in a 1% (w / w) dilute acetic acid solution and sodium alginate in deionized water, stirring until completely dissolved. Add the second-modified polylactic acid to the chitosan solution, sonicate at 300W for 20-30 min, then slowly add sodium alginate solution to adjust the pH of the system to 5.5-6.

0. Add 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and glycerol, and stir at 200-250 r / min at 50-55℃ for 2 h. After filtration, wash with deionized water until neutral, and dry in a vacuum drying oven at 65℃ for 12 h to obtain modified polylactic acid.

2. The biodegradable nonwoven fabric according to claim 1, characterized in that: The modified bamboo fiber is prepared using the following specific steps: B1. Add bamboo fiber to a 5% (w / w) dilute sulfuric acid solution and etch at a constant temperature of 60-65℃ with stirring at 150-200 r / min for 1-1.5 h. Wash with deionized water until neutral, then add a 3% (w / w) sodium hydroxide solution and treat with alkali at 70℃ with stirring at 200-250 r / min for 2 h. Then add 30% (w / w) hydrogen peroxide and react at 50℃ for 30 min. Finally, add silane coupling agent KH-550 and react at 80℃ for 1 h. After filtration and drying, the first modified bamboo fiber is obtained. B2. The first modified bamboo fiber was added to anhydrous toluene and ultrasonically dispersed at 350W for 40 min. The temperature was raised to 90℃ under a nitrogen atmosphere. Octadecyl isocyanate and pyridine were added and stirred at a constant temperature of 250-300 r / min for 3-3.5 h. Stearic acid was then added and the reaction was continued for 1-1.5 h. After the reaction was completed, the mixture was cooled and washed 3-4 times with petroleum ether to remove unreacted reagents. The mixture was then vacuum dried at 70℃ for 8 h to obtain the second modified bamboo fiber. B3. Disperse the second modified bamboo fiber in anhydrous ethanol, ultrasonically disperse for 30 min, and add sodium hexametaphosphate to adjust the dispersibility of the system. The co-precipitation method was used, with 0.5 mol / L calcium nitrate solution and 0.3 mol / L diammonium hydrogen phosphate solution added dropwise simultaneously under stirring at 300 r / min. The pH of the system was adjusted to 9-10 with 25% ammonia solution. The temperature was raised to 60℃ and the reaction was kept at a constant temperature for 2 hours. After the reaction was completed, the mixture was filtered, washed with deionized water until neutral, and then vacuum dried at 80℃ for 10 hours to obtain modified bamboo fiber.

3. The biodegradable nonwoven fabric according to claim 1, characterized in that: The polyethylene glycol in A2 has a molecular weight of 2000-4000 g / mol, and when it is added to A2 in three portions, the amount added each time is 40%, 30%, and 30% of the total amount, respectively, to ensure the uniformity of the modified polylactic acid molecular linkages.

4. The biodegradable nonwoven fabric according to claim 2, characterized in that: During the co-precipitation reaction of B3, the dropping rate of calcium nitrate solution and diammonium hydrogen phosphate solution is 2-3 ml / min, and the pH of the system is kept stable in the range of 9-10 during the dropping process to ensure the loading effect of hydroxyapatite on the bamboo fiber surface.

5. The biodegradable nonwoven fabric according to claim 1, characterized in that: The ratio of polylactic acid, maleic anhydride, dicumyl peroxide, and ethylene glycol diglycidyl ether in A1 is 500g: 40-50g: 1-1.5g: 7-10ml; The ratio of the first modified polylactic acid, ethyl acetate, caprolactam-terminated polyurethane prepolymer, dibutyltin dilaurate, and polyethylene glycol in A2 is 500g: 200-250ml: 60-75g: 0.5-1g: 15-20g. The ratio of chitosan, dilute acetic acid solution, sodium alginate, deionized water, second-modified polylactic acid, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, and glycerol in A3 is 25-30g: 300-350ml: 10-12g: 500-600ml: 500g: 4-5g: 5-8ml.

6. The biodegradable nonwoven fabric according to claim 2, characterized in that: The ratio of bamboo fiber, dilute sulfuric acid solution, sodium hydroxide solution, hydrogen peroxide, and silane coupling agent KH-550 in B1 is 500g: 300-350ml: 250-300ml: 20-25ml: 7-10ml; The ratio of the first modified bamboo fiber, anhydrous toluene, octadecyl isocyanate, pyridine, and stearic acid in B2 is 500g: 180-200ml: 30-35g: 3-4ml: 12-15g; The ratio of the amount of the second modified bamboo fiber, anhydrous ethanol, sodium hexametaphosphate, calcium nitrate solution, and diammonium hydrogen phosphate solution in B3 is 500g: 150-180ml: 2-4g: 100-125ml: 60-75ml.

7. A process for preparing a biodegradable nonwoven fabric, characterized in that: Specifically, it includes the following steps: S1. Dry the modified polylactic acid, polycaprolactone, and polybutylene succinate in a vacuum drying oven at 80℃ for 6-8 hours to remove moisture from the raw materials; dry the modified bamboo fiber in an oven at 105℃ for 2 hours; premix 1-3 parts of nano hydroxyapatite, 0.5-1.2 parts of vitamin E, and 0.3-0.8 parts of polyaspartic acid evenly to prepare a premixed additive. S2. Add 45-60 parts of dried modified polylactic acid, 8-15 parts of polycaprolactone, and 5-10 parts of polybutylene succinate to the main feed port of the twin-screw extruder. Add 15-25 parts of modified bamboo fiber through the side feed port. Add the above premixed additives and 2-5 parts of tributyl citrate through the additive feed port. Set the temperatures of each section of the twin-screw extruder as follows: Zone 1 140-145℃, Zone 2 150-155℃, Zone 3 160-165℃, Zone 4 155-160℃, Die head temperature 150-155℃, and screw speed 200-250 r / min. The extruded melt is water-cooled and pelletized at 25℃ to obtain biodegradable nonwoven fabric masterbatch. The masterbatch particle size is controlled at 2-3 mm. Vacuum dry at 70℃ for 4 hours. S3. Add the dried masterbatch to a melt spinning machine, set the spinning temperature to 155-160℃, the melt pressure to 2.5-3.0MPa, the spinneret orifice diameter to 0.3mm, and the spinning speed to 800-1000m / min; the spun nascent fibers are cooled by side blowing at a temperature of 25-30℃ and a wind speed of 0.5-0.8m / s, and then hot-drawn by a drawing machine at a drawing temperature of 70-75℃ and a drawing ratio of 3-3.5 times to obtain biodegradable fiber filaments; S4. Feed the drawn fiber filaments into a carding machine and set the carding speed to 15-20 m / min. Feed the fiber web blank into a hot rolling mill for hot bonding and forming. Set the hot rolling temperature to 110-115℃, the hot rolling pressure to 2.0-2.5 MPa, and the hot rolling speed to 10-15 m / min. Perform finishing on the formed nonwoven fabric, including edge trimming and winding. Place the wound nonwoven fabric in an environment with room temperature and relative humidity of 50-60% for 24 hours for moisture conditioning to eliminate internal stress and obtain the finished biodegradable nonwoven fabric.

8. The preparation process of a biodegradable nonwoven fabric according to claim 7, characterized in that: In the S1 premixed additive, the particle size of nano-hydroxyapatite is 50-80nm. During premixing, vitamin E and polyaspartic acid should be pre-stirred at 40-45℃ for 15min, and then nano-hydroxyapatite should be added and ultrasonically dispersed for 20min to ensure uniform dispersion of the additive system.

9. The preparation process of a biodegradable nonwoven fabric according to claim 7, characterized in that: In S2, the feeding rate of the twin-screw extruder is as follows: the main feed port feed rate is 15-20 kg / h, the side feed port feed rate is 5-8 kg / h, and the auxiliary feed port feed rate is 1-2 kg / h. The feed rates of each feed port are matched to ensure that the raw materials are fully mixed and that no material blockage occurs.

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