Preparation method of high-strength degradable bicomponent spunbond nonwoven fabric

Abstract

The application discloses a preparation method of high-strength degradable bicomponent spun-bonded non-woven fabric, and relates to the technical field of non-woven fabric preparation. Polylactic acid and polybutylene adipate terephthalate are used as main raw materials, chain extenders, nucleating agents and bio-based toughening agents are introduced, and the non-woven fabric is prepared through a double-screw melting blending, skin-core composite spinning, airflow drafting and hot rolling reinforcing process. The obtained non-woven fabric has high strength, high flexibility and excellent biodegradability, and is suitable for one-time packaging, medical and health products and agricultural covering materials.

Description

Technical Field

[0001] This invention relates to the field of nonwoven fabric preparation technology, and in particular to a method for preparing a high-strength biodegradable bicomponent spunbond nonwoven fabric. Background Technology

[0002] Nonwoven fabrics are nonwoven materials formed directly from short fibers or continuous filaments through mechanical, thermal, or chemical bonding processes, without the spinning and weaving processes of traditional textiles. Due to their advantages such as high production efficiency, short process flow, high material utilization, low cost, and the ability to achieve functional designs, nonwoven fabrics have been widely used in medical and health fields, personal care, packaging materials, agricultural coverings, building waterproofing, filtration materials, and automotive interiors. With the increasing prominence of global plastic pollution, traditional polypropylene spunbond nonwoven fabrics are difficult to degrade naturally after use, resulting in the long-term accumulation of large amounts of waste in the environment, which has become a significant challenge for the industry. Therefore, developing biodegradable nonwoven materials that combine excellent performance and environmental friendliness has become an important research direction in the field of nonwoven materials in recent years.

[0003] Polylactic acid (PLA) is an aliphatic polyester material obtained by polymerizing lactic acid produced from renewable biomass resources such as corn, cassava, and sugarcane through fermentation. It boasts advantages such as renewable sources, good biocompatibility, excellent processing performance, and biodegradability under industrial composting conditions, making it considered one of the most promising bio-based biodegradable polymers for industrialization. However, PLA molecules have relatively high rigidity and a slow crystallization rate, resulting in fibers and nonwoven fabrics that typically exhibit high brittleness, low elongation at break, and insufficient tear resistance, limiting their application in high-strength packaging materials, sanitary materials, and agricultural covering materials.

[0004] Poly(butylene adipate) terephthalate (PBAT) is a typical aliphatic-aromatic copolyester material with excellent flexibility, elongation, and biodegradability. Its elongation at break is significantly higher than that of PLA, effectively compensating for PLA's high brittleness. Currently, PLA / PBAT blending modification has become one of the most mature technical routes in the field of fully biodegradable materials. Related patent CN103254597A discloses a PLA / PBAT biodegradable composite material and its preparation method, which improves the material's toughness through PLA / PBAT blending. However, it also points out the poor compatibility between PLA and PBAT, which easily leads to phase separation, thus affecting the material's overall mechanical properties.

[0005] To further promote the development of biodegradable nonwoven fabrics, researchers have begun to explore the application of the PLA / PBAT system in meltblown nonwoven fabrics, spunbond nonwoven fabrics, and composite nonwoven materials. For example, Chinese patent CN105586712A discloses a PBAT meltblown biodegradable nonwoven fabric and its preparation method, which obtains a nonwoven material with high softness through the PBAT meltblown process, but its material strength and dimensional stability are still insufficient. In recent years, CN115819931B has further proposed a biodegradable meltblown nonwoven fabric material and its preparation method, which improves the performance of filter materials by regulating the PLA-based system, but it still mainly focuses on the meltblown structure and is difficult to simultaneously meet the comprehensive requirements of high strength and high toughness.

[0006] In addition, the existing PLA / PBAT system faces the following technical challenges in the production of spunbond nonwoven fabrics: (1) PLA and PBAT have a large difference in polarity and insufficient interfacial bonding. During the melt blending process, they are prone to forming obvious phase separation structures, which leads to fiber breakage, fuzzing and unstable spinning during fiber stretching. (2) PLA has high melt strength while PBAT has low melt viscosity. The rheological properties of the two materials are significantly different. In the bicomponent spinning process, uneven component distribution and fiber structure defects are easily generated, which affects the uniformity of the web. (3) In the traditional PLA / PBAT random blending system, the toughening effect of PBAT is limited. When the PBAT content increases, although the elongation at break increases, the material strength decreases significantly, making it difficult to obtain both high strength and high toughness at the same time. (4) Existing biodegradable nonwoven fabrics generally adopt a single-component structure design, with a single internal functional distribution of fibers, making it difficult to fully utilize the synergistic advantages of PLA's high strength and PBAT's high toughness. (5) Ordinary hot rolling reinforcement process can easily lead to insufficient PLA crystallization, which affects the dimensional stability and heat resistance of nonwoven fabric.

[0007] On the other hand, international patent WO2014124563A1 discloses a PLA / PBAT biodegradable film and laminate material, which achieves a balance between material flexibility and degradability by optimizing the ratio of PLA to PBAT. However, it is mainly used in the fields of film and laminated products, and does not provide an effective solution for the spinning stability, fiber refinement ability and thermal bonding performance required for continuous filament spunbond nonwoven fabrics.

[0008] Therefore, how to develop a method for preparing PLA / PBAT bicomponent spunbond nonwoven fabric with high strength, high toughness, excellent processing performance and good biodegradability, which addresses the problems of insufficient compatibility between PLA and PBAT systems, poor spinning stability, difficulty in balancing strength and toughness, and insufficient structural stability after hot rolling, has become an urgent technical problem to be solved in this field. Summary of the Invention

[0009] Based on the problems raised in the background art, the present invention proposes a method for preparing high-strength biodegradable bicomponent spunbond nonwoven fabric.

[0010] The technical solution is as follows: A method for preparing a high-strength biodegradable bicomponent spunbond nonwoven fabric includes the following steps: S1. Raw material pretreatment: Weigh out 65-75 parts of polylactic acid, 25-35 parts of poly(butylene adipate / terephthalate), 0.5-1.2 parts of epoxy chain extender, 0.3-0.8 parts of nucleating agent, 2-6 parts of toughening agent, and 0.2-0.6 parts of antioxidant, according to the weight percentage. Place the polylactic acid and poly(butylene adipate / terephthalate) separately in a vacuum drying oven and dry at 75-85°C for 4-8 hours to control the moisture content to below 300 ppm. S2, melt blending granulation: The raw material processed in step S1 is added to a twin-screw extruder for melt blending. The temperatures of each temperature zone are controlled sequentially as follows: 165-175℃, 170-180℃, 175-185℃, 180-190℃, 185-195℃, and 190-200℃. The screw speed is 250-400 rpm, and the melt residence time is 1.5-4 min. The blended masterbatch is obtained by extrusion, cooling, and pelletizing. S3, Preparation of two-component melts: The blended masterbatch obtained in step S2 is fed into the skin extruder and the core extruder, respectively. PLA accounts for 85-92% of the total mass of the skin melt, and PBAT accounts for 75-90% of the total mass of the core melt. The mass ratio of skin to core is controlled at 70:30-80:20. S4, Composite spinning: Melt spinning is performed using a core-spinning composite spinneret. The spinning temperature is controlled at 205–225℃, the melt pressure is controlled at 8–15MPa, the spinneret diameter is 0.25–0.40mm, and the spinneret density is 2500–5000 holes / m. S5, airflow stretches into a net: The spun nascent fibers are cooled by cooling air and then enter the drafting device. They are drafted by airflow at 20-35°C with a drafting ratio of 1800-3200 times, resulting in continuous filaments with an average fiber diameter of 12-25 μm, which are then evenly laid to form a fiber web. S6, Hot-rolled reinforcement: The fiber web is conveyed to a hot rolling mill for hot bonding. The hot rolling temperature is 110-130℃, the hot rolling pressure is 30-60kN, the hot rolling line speed is 30-120m / min, and the embossing area ratio is 15-25%. S7. Cooling and winding: After being hot-rolled, the nonwoven fabric is cooled to below 35°C by cooling rollers and then wound up to obtain a high-strength biodegradable PLA / PBAT bicomponent spunbond nonwoven fabric.

[0011] In some embodiments, the polylactic acid is spinning-grade polylactic acid with a melt flow rate of 25–40 g / 10 min and a weight-average molecular weight of 8 × 10⁻⁶. 4 ~15×10 4 .

[0012] In some embodiments, the melt flow rate of the poly(butylene adipate) / terephthalate is 5–20 g / 10 min, and the number-average molecular weight is 6 × 10⁻⁶. 4 ~12×10 4 .

[0013] In some embodiments, the epoxy chain extender is one or two of ADR-4368, ADR-4468, and epoxy-functionalized styrene-acrylate copolymer.

[0014] In some embodiments, the nucleating agent is one or two of talc, sodium phosphate nucleating agents, and dibenzyl sorbitol nucleating agents.

[0015] In some embodiments, the toughening agent is a block copolymer type heat-resistant acetylated tributyl citrate toughening agent, and its preparation method is as follows: By weight proportions: 100 parts citric acid, 80-90 parts 2,4-dihydroxydiphenyl sulfone, 70-80 parts 1,8-dihydroxynaphthalene, SO4 2-0.2–0.3 parts of TiO2 solid superacid catalyst were added, along with 300–350 parts of anhydrous xylene as an azeotropic solvent. All raw materials were added to a reactor and stirred until completely homogeneous and dissolved. The system was prepolymerized at a constant temperature of 118–126°C and a vacuum of -0.088–-0.092 MPa for 5–7 hours, using the xylene azeotropic system to continuously remove the water generated in the reaction. After the reaction was completed, the temperature was raised to 130–140°C and held at a high vacuum of -0.093–-0.098 MPa for 1.5–2.5 hours to remove unreacted monomers, oligomers, and most of the solvent, thus obtaining a block copolymer type heat-resistant acetylated tributyl citrate toughening agent.

[0016] In some embodiments, the antioxidant is one or two of antioxidant 1010, antioxidant 168, and antioxidant 1076.

[0017] In some embodiments, the cooling air temperature in step S5 is 16–22°C; the cooling air velocity is 0.4–1.2 m / s; and the stretching air pressure is 0.12–0.28 MPa.

[0018] In some embodiments, the hot rolling roll in step S6 is a dotted diamond embossing roll; the embossing density is 120-260 dots / cm²; and the embossing depth is 0.15-0.40 mm.

[0019] Reaction mechanism: This invention addresses the shortcomings of traditional single-phase PLA nonwoven fabrics, such as high brittleness, insufficient toughness, high heat shrinkage, and weak interlayer bonding. It also addresses the poor two-phase compatibility, easy phase separation, weak mechanical matching, easy breakage during high-speed spinning, and degradation performance degradation inherent in conventional PLA / PBAT blends. The invention constructs a two-component spunbond reinforcement and toughening integrated system, incorporating precise moisture-controlled pretreatment of raw materials, synergistic modification and compatibilization with multiple additives, controllable melt chain extension using a twin-screw extruder, differentiated melt ratios between the core and sheath, gradient airflow stretching, and precise hot rolling consolidation. Through multiple mechanisms including polymer chain extension and reconstruction, interfacial compatibility modification, crystallization behavior regulation, functional division of the core and sheath structure, and synergistic modification with block toughening, this process achieves a simultaneous balance of high strength, high toughness, high dimensional stability, and excellent degradation performance in biodegradable nonwoven fabrics. The process first involves deep vacuum drying of the PLA and PBAT biodegradable polyester raw materials to prevent trace amounts of moisture from causing polymer chain hydrolysis and breakage during high-temperature melting, thus avoiding degradation of the matrix's mechanical properties and ensuring the stability of the subsequent melt spinning system.

[0020] In this system, the epoxy chain extender can covalently react with the terminal hydroxyl and carboxyl groups of PLA and PBAT molecular chains, effectively extending the molecular chain segments, increasing melt viscosity and elasticity, eliminating interfacial gaps between the two phases, suppressing phase separation defects, and significantly improving the interfacial bonding strength of the blend system. The nucleating agent can effectively induce PLA to crystallize in a regular manner, increase the crystallization rate and crystallinity, refine the grain structure, reduce thermal shrinkage and dimensional deformation after fiber forming, and improve the heat resistance and structural stability of the material. The antioxidant can inhibit the thermo-oxidative aging and degradation of polymers during high-temperature melting, spinning, and hot rolling, ensuring the integrity of the matrix molecular structure. The core of this invention utilizes a self-synthesized block copolymerized, heat-resistant acetylated tributyl citrate toughening agent. A multi-component raw material synergistically constructs a highly efficient heat-resistant toughening system: citric acid serves as the main chain-forming monomer, constructing a flexible aliphatic polyester backbone, providing the system with basic toughness and molecular slip capability; 2,4-dihydroxydiphenyl sulfone contains a rigid sulfone benzene ring structure, which can be embedded in flexible segments, improving the toughening agent's heat resistance and high-temperature stability, and preventing decomposition and failure of the toughening agent under high-temperature spinning conditions; 1,8-dihydroxynaphthalene provides polycyclic aromatic rigid sites, assisting in regulating the regularity of the block structure, improving the compatibility of the toughening agent with the polyester matrix, and achieving uniform dispersion; SO4²⁻ / TiO2 solid superacid catalyst efficiently catalyzes the esterification prepolymerization and condensation reaction of multiple monomers, precisely constructing a rigid-flexible alternating block structure, ultimately obtaining a functional additive with heat resistance, compatibility, and toughening effect.

[0021] By employing a twin-screw gradient temperature-controlled melt blending process, uniform dispersion of various additives is achieved, completing the integrated modification of molecular chain extension, compatibilization, and toughening, resulting in a blended masterbatch with uniform performance. Subsequently, a differentiated sheath-core bicomponent melt ratio design is adopted. The high PLA ratio in the sheath layer imparts high rigidity, high strength, and abrasion resistance to the fiber surface, while the high PBAT ratio in the core layer imparts high toughness, high elongation, and deformation resistance to the fiber inner layer, achieving optimized functional zoning of individual fiber structures. Precise airflow cooling and stretching control the fiber orientation, followed by targeted hot rolling to solidify the structure and establish uniform bonding points, reducing stress concentration and improving the overall interlayer bonding strength and mechanical balance of the nonwoven fabric. This entire process significantly optimizes the material's mechanical and molding properties without damaging the biodegradable polyester molecular skeleton, ultimately yielding a high-strength, high-toughness, high-dimensional stability, and fully biodegradable bicomponent spunbond nonwoven fabric.

[0022] Compared with the prior art, the present invention has the following advantages: (1) The present invention adopts a PLA / PBAT two-component composite system, with high-strength PLA as the main load-bearing phase and high-toughness PBAT as the toughening phase. By reasonably controlling the ratio of the two, the material can simultaneously possess the high modulus properties of PLA and the high elongation properties of PBAT. (2) This invention introduces an epoxy chain extender to construct an interfacial compatible system. The epoxy groups in the chain extender can react with the active groups at the ends of PLA and PBAT molecular chains, thereby increasing the interfacial bonding strength between the two phases, reducing phase separation, thus improving the uniformity of the internal structure of the fiber, reducing stress concentration, and improving the overall mechanical properties and processing stability of the material.

[0023] (3) The invention adopts a technical route that combines chain extension and viscosity enhancement with two-component melt spinning, which improves melt elasticity and melt strength, reduces fiber breakage, dripping and fiber thickness fluctuations during spinning, makes the continuous spinning process more stable, meets the continuous production needs of high-speed spunbond production lines, and improves product consistency and production efficiency.

[0024] (4) The present invention adopts a dual-component structure design consisting of PLA enriched skin layer and PBAT enriched core layer, so that the outer layer of the fiber maintains high rigidity and wear resistance, while the inner layer maintains good flexibility and impact resistance, thereby achieving performance division and synergistic optimization from the structural level.

[0025] (5) The present invention promotes PLA crystallization through nucleating agents, improves fiber crystallization rate and crystallinity, reduces heat shrinkage, and enables the obtained nonwoven fabric to maintain good dimensional stability during storage, transportation and use, while improving the material's heat resistance and mechanical retention rate.

[0026] (6) The PLA and PBAT used in this invention are both biodegradable polyester materials. The amount of chain extender, toughening agent and auxiliaries added is low and will not significantly affect the degradation behavior of the materials. The resulting nonwoven fabric can be gradually degraded into carbon dioxide, water and biomass under industrial composting conditions, realizing green recycling. Detailed Implementation

[0027] The features of the present invention are further illustrated below through embodiments, but the scope of protection of this patent is not limited to the embodiments. Example 1

[0028] S1. Raw material pretreatment: Weigh 65 kg of polylactic acid (PLA), 25 kg of poly(butylene adipate / terephthalate), 0.5 kg of epoxy chain extender, 0.3 kg of nucleating agent, 2 kg of toughening agent, and 0.2 kg of antioxidant; place PLA and poly(butylene adipate / terephthalate) separately in a vacuum drying oven and dry at 75°C for 4 hours to control the moisture content below 300 ppm; the PLA used is spinning-grade PLA with a melt flow rate of 25 g / 10 min and a weight-average molecular weight of 8 × 10⁻⁶. 4 The melt flow rate of the poly(butylene adipate) / terephthalate used was 5 g / 10 min, and the number average molecular weight was 6 × 10⁻⁶. 4The epoxy chain extender selected is ADR-4368; the nucleating agent selected is talc; and the antioxidant selected is antioxidant 1010.

[0029] S2. Melt blending and granulation: The raw material processed in step S1 is added to a twin-screw extruder for melt blending. The temperatures of each zone are controlled sequentially as 165℃, 170℃, 175℃, 180℃, 185℃, and 190℃. The screw speed is 250 rpm, and the melt residence time is 1.5 min. After extrusion, cooling, and pelletizing, blended masterbatch is obtained.

[0030] S3. Preparation of two-component melt: The blended masterbatch obtained in step S2 is fed into the skin extruder and the core extruder respectively. PLA accounts for 85% of the total mass of the skin melt, and PBAT accounts for 75% of the total mass of the core melt. The mass ratio of skin to core is controlled at 70:30.

[0031] S4. Composite spinning: Melt spinning is performed using a core-sheath type composite spinneret. The spinning temperature is controlled at 205℃, the melt pressure is controlled at 8MPa, the spinneret diameter is 0.25mm, and the spinneret density is 2500 holes / m.

[0032] S5. Airflow drawing and web formation: The spun nascent fibers are cooled by cooling air and then enter the drawing device. The cooling air temperature is 16℃ and the cooling air speed is 0.4m / s. Airflow drawing is carried out under the conditions of 20℃ drawing air and 0.12MPa drawing air pressure, with a drawing ratio of 1800 times, to obtain continuous filaments with an average fiber diameter of 12μm, which are then evenly laid to form a fiber web.

[0033] S6. Hot rolling reinforcement: The fiber web is conveyed to the hot rolling mill for hot bonding. The hot rolling roll adopts a dot-shaped diamond embossing roll, the hot rolling temperature is 110℃, the hot rolling pressure is 30kN, the hot rolling line speed is 30m / min, the embossing area ratio is 15%, the embossing density is 120 dots / cm², and the embossing depth is 0.15mm.

[0034] S7. Cooling and winding: The hot-rolled nonwoven fabric is cooled to below 35°C by cooling rollers and then wound up to obtain a high-strength biodegradable PLA / PBAT bicomponent spunbond nonwoven fabric.

[0035] The toughening agent used in this embodiment is a block copolymer type heat-resistant acetylated tributyl citrate toughening agent. Its preparation method is as follows: Citric acid 100 kg, 2,4-dihydroxydiphenyl sulfone 80 kg, 1,8-dihydroxynaphthalene 70 kg, SO4²- / TiO2 solid superacid catalyst 0.2 kg, and 300 kg of anhydrous xylene as an azeotropic solvent are added. All raw materials are added to a reaction vessel and stirred until completely homogeneous and dissolved. The system is prepolymerized at a constant temperature of -0.088 MPa and 118°C for 5 hours under constant temperature esterification, utilizing the xylene azeotropic system to continuously remove the water generated in the reaction. After the reaction is completed, the temperature is raised to 130°C and held at a high vacuum of -0.093 MPa for 1.5 hours to remove unreacted monomers, oligomers, and most of the solvent, obtaining the block copolymer type heat-resistant acetylated tributyl citrate toughening agent. Example 2

[0036] S1. Raw material pretreatment: Weigh 70 kg of polylactic acid (PLA), 30 kg of poly(butylene adipate / terephthalate), 0.8 kg of epoxy chain extender, 0.55 kg of nucleating agent, 4 kg of toughening agent, and 0.4 kg of antioxidant; place PLA and poly(butylene adipate / terephthalate) separately in a vacuum drying oven and dry at 80°C for 6 hours to control the moisture content below 300 ppm; the PLA used is spinning-grade PLA with a melt flow rate of 32 g / 10 min and a weight-average molecular weight of 11 × 10⁻⁶. 4 The melt flow rate of the poly(adipate) / butylene terephthalate used was 12 g / 10 min, and the number average molecular weight was 9 × 10⁻⁶. 4 The epoxy chain extender selected is ADR-4468; the nucleating agent selected is sodium phosphate nucleating agent; and the antioxidant selected is antioxidant 168.

[0037] S2. Melt blending and granulation: The raw material processed in step S1 is added to a twin-screw extruder for melt blending. The temperatures of each zone are controlled sequentially as 170℃, 175℃, 180℃, 185℃, 190℃, and 195℃. The screw speed is 320 rpm, and the melt residence time is 2.5 min. After extrusion, cooling, and pelletizing, blended masterbatch is obtained.

[0038] S3. Preparation of two-component melt: The blended masterbatch obtained in step S2 is fed into the skin extruder and the core extruder respectively. PLA accounts for 88% of the total mass of the skin melt, and PBAT accounts for 82% of the total mass of the core melt. The mass ratio of skin to core is controlled at 75:25.

[0039] S4. Composite spinning: Melt spinning is performed using a core-sheath type composite spinneret. The spinning temperature is controlled at 215℃, the melt pressure is controlled at 11MPa, the spinneret diameter is 0.32mm, and the spinneret density is 3750 holes / m.

[0040] S5. Airflow drawing and web formation: The spun nascent fibers are cooled by cooling air and then enter the drawing device. The cooling air temperature is 19℃ and the cooling air speed is 0.8m / s. Airflow drawing is carried out under the conditions of 28℃ drawing air and 0.20MPa drawing air pressure, with a drawing ratio of 2500 times, to obtain continuous filaments with an average fiber diameter of 18μm, which are then evenly laid to form a fiber web.

[0041] S6. Hot Rolling Reinforcement: The fiber web is conveyed to the hot rolling mill for hot bonding. The hot rolling roll adopts a dotted diamond embossing roll, the hot rolling temperature is 120℃, the hot rolling pressure is 45kN, the hot rolling line speed is 75m / min, the embossing area ratio is 20%, the embossing density is 190 dots / cm², and the embossing depth is 0.27mm.

[0042] S7. Cooling and winding: The hot-rolled nonwoven fabric is cooled to below 35°C by cooling rollers and then wound up to obtain a high-strength biodegradable PLA / PBAT bicomponent spunbond nonwoven fabric.

[0043] The toughening agent used in this embodiment is a block copolymer type heat-resistant acetylated tributyl citrate toughening agent. Its preparation method is as follows: Citric acid 100 kg, 2,4-dihydroxydiphenyl sulfone 85 kg, 1,8-dihydroxynaphthalene 75 kg, SO4²- / TiO2 solid superacid catalyst 0.25 kg, and anhydrous xylene as an azeotropic solvent are added. All raw materials are added to a reaction vessel and stirred until completely homogeneously dissolved. The system is kept at a vacuum of -0.090 MPa and a temperature of 122°C for 6 hours for constant-temperature esterification prepolymerization, utilizing the xylene azeotropic system to continuously remove the water generated in the reaction. After the reaction is completed, the temperature is raised to 135°C and held at a high vacuum of -0.095 MPa for 2.0 hours to remove unreacted monomers, oligomers, and most of the solvent, obtaining the block copolymer type heat-resistant acetylated tributyl citrate toughening agent. Example 3

[0044] S1. Raw material pretreatment: Weigh 73 kg of polylactic acid (PLA), 33 kg of poly(butylene adipate / terephthalate), 1.0 kg of epoxy chain extender, 0.7 kg of nucleating agent, 5 kg of toughening agent, and 0.5 kg of antioxidant; place PLA and poly(butylene adipate / terephthalate) separately in a vacuum drying oven and dry at 83°C for 7 hours to control the moisture content below 300 ppm; the PLA used is spinning-grade PLA with a melt flow rate of 36 g / 10 min and a weight-average molecular weight of 13 × 10⁻⁶. 4 The melt flow rate of the poly(adipate) / butylene terephthalate used was 16 g / 10 min, and the number average molecular weight was 10 × 10⁻⁶. 4 The epoxy chain extender is a combination of ADR-4368 and ADR-4468; the nucleating agent is a combination of talc and dibenzyl sorbitol nucleating agent; the antioxidant is a combination of antioxidant 1010 and 1076.

[0045] S2. Melt blending and granulation: The raw material processed in step S1 is added to a twin-screw extruder for melt blending. The temperatures of each zone are controlled sequentially as 172℃, 178℃, 182℃, 188℃, 192℃, and 198℃. The screw speed is 360 rpm, and the melt residence time is 3.2 min. After extrusion, cooling, and pelletizing, blended masterbatch is obtained.

[0046] S3. Preparation of two-component melt: The blended masterbatch obtained in step S2 is fed into the skin extruder and the core extruder respectively. PLA accounts for 90% of the total mass of the skin melt, and PBAT accounts for 86% of the total mass of the core melt. The mass ratio of skin to core is controlled at 78:22.

[0047] S4. Composite spinning: Melt spinning is performed using a core-sheath type composite spinneret. The spinning temperature is controlled at 220℃, the melt pressure is controlled at 13MPa, the spinneret diameter is 0.36mm, and the spinneret density is 4300 holes / m.

[0048] S5. Airflow drawing and web formation: The spun nascent fibers are cooled by cooling air and then enter the drawing device. The cooling air temperature is 21℃ and the cooling air speed is 1.0m / s. Airflow drawing is carried out under the conditions of 32℃ drawing air and 0.24MPa drawing air pressure, with a drawing ratio of 2900 times, to obtain continuous filaments with an average fiber diameter of 22μm, which are then evenly laid to form a fiber web.

[0049] S6. Hot Rolling Reinforcement: The fiber web is conveyed to the hot rolling mill for hot bonding. The hot rolling roll adopts a dotted diamond embossing roll, the hot rolling temperature is 126℃, the hot rolling pressure is 52kN, the hot rolling line speed is 95m / min, the embossing area ratio is 22%, the embossing density is 230 dots / cm², and the embossing depth is 0.33mm.

[0050] S7. Cooling and winding: The hot-rolled nonwoven fabric is cooled to below 35°C by cooling rollers and then wound up to obtain a high-strength biodegradable PLA / PBAT bicomponent spunbond nonwoven fabric.

[0051] The toughening agent used in this embodiment is a block copolymer type heat-resistant acetylated tributyl citrate toughening agent. Its preparation method is as follows: Citric acid 100 kg, 2,4-dihydroxydiphenyl sulfone 88 kg, 1,8-dihydroxynaphthalene 78 kg, SO4²- / TiO2 solid superacid catalyst 0.28 kg, and 340 kg of anhydrous xylene as an azeotropic solvent are added. All raw materials are added to a reaction vessel and stirred until completely homogeneous and dissolved. The system is kept under vacuum of -0.091 MPa and temperature of 124°C for 6.5 h for constant-temperature esterification prepolymerization, utilizing the xylene azeotropic system to continuously remove the water generated in the reaction. After the reaction is completed, the temperature is raised to 138°C and held under high vacuum of -0.096 MPa for 2.2 h to remove unreacted monomers, oligomers, and most of the solvent, obtaining the block copolymer type heat-resistant acetylated tributyl citrate toughening agent. Example 4

[0052] S1. Raw material pretreatment: Weigh 75 kg of polylactic acid (PLA), 35 kg of poly(butylene adipate / terephthalate), 1.2 kg of epoxy chain extender, 0.8 kg of nucleating agent, 6 kg of toughening agent, and 0.6 kg of antioxidant; place PLA and poly(butylene adipate / terephthalate) separately in a vacuum drying oven and dry at 85°C for 8 hours to control the moisture content below 300 ppm; the PLA used is spinning-grade PLA with a melt flow rate of 40 g / 10 min and a weight-average molecular weight of 15 × 10⁻⁶. 4 The melt flow rate of the poly(adipate) / butylene terephthalate used was 20 g / 10 min, and the number average molecular weight was 12 × 10⁻⁶. 4 The epoxy chain extender is selected from epoxy-functionalized styrene-acrylate copolymer; the nucleating agent is selected from dibenzyl sorbitol nucleating agents; and the antioxidant is selected from antioxidant 1076.

[0053] S2. Melt blending and granulation: The raw material processed in step S1 is added to a twin-screw extruder for melt blending. The temperature of each temperature zone is controlled sequentially as 175℃, 180℃, 185℃, 190℃, 195℃, and 200℃. The screw speed is 400 rpm and the melt residence time is 4 min. After extrusion, cooling, and pelletizing, blended masterbatch is obtained.

[0054] S3. Preparation of two-component melt: The blended masterbatch obtained in step S2 is fed into the skin extruder and the core extruder respectively. PLA accounts for 92% of the total mass of the skin melt, and PBAT accounts for 90% of the total mass of the core melt. The mass ratio of skin to core is controlled at 80:20.

[0055] S4. Composite spinning: Melt spinning is performed using a core-sheath type composite spinneret. The spinning temperature is controlled at 225℃, the melt pressure is controlled at 15MPa, the spinneret diameter is 0.40mm, and the spinneret density is 5000 holes / m.

[0056] S5. Airflow drawing and web formation: The spun nascent fibers are cooled by cooling air and then enter the drawing device. The cooling air temperature is 22℃ and the cooling air speed is 1.2m / s. Airflow drawing is carried out under the conditions of 35℃ drawing air and 0.28MPa drawing air pressure, with a drawing ratio of 3200 times, to obtain continuous filaments with an average fiber diameter of 25μm, which are then evenly laid to form a fiber web.

[0057] S6. Hot rolling reinforcement: The fiber web is conveyed to the hot rolling mill for hot bonding. The hot rolling roll adopts a dot-shaped diamond embossing roll, the hot rolling temperature is 130℃, the hot rolling pressure is 60kN, the hot rolling line speed is 120m / min, the embossing area ratio is 25%, the embossing density is 260 dots / cm², and the embossing depth is 0.40mm.

[0058] S7. Cooling and winding: The hot-rolled nonwoven fabric is cooled to below 35°C by cooling rollers and then wound up to obtain a high-strength biodegradable PLA / PBAT bicomponent spunbond nonwoven fabric.

[0059] The toughening agent used in this embodiment is a block copolymer type heat-resistant acetylated tributyl citrate toughening agent. Its preparation method is as follows: Citric acid 100 kg, 2,4-dihydroxydiphenyl sulfone 90 kg, 1,8-dihydroxynaphthalene 80 kg, SO4²- / TiO2 solid superacid catalyst 0.3 kg, and 350 kg of anhydrous xylene as an azeotropic solvent are added. All raw materials are added to a reaction vessel and stirred until completely homogeneous and dissolved. The system is prepolymerized at a constant temperature of -0.092 MPa and 126°C for 7 hours under constant temperature esterification, utilizing the xylene azeotropic system to continuously remove the water generated in the reaction. After the reaction is completed, the temperature is raised to 140°C and held at a high vacuum of -0.098 MPa for 2.5 hours to remove unreacted monomers, oligomers, and most of the solvent, obtaining the block copolymer type heat-resistant acetylated tributyl citrate toughening agent.

[0060] Comparative Example 1 S1. Raw material pretreatment: Weigh 65 kg of polylactic acid (PLA), 25 kg of poly(butylene adipate / terephthalate), 0.5 kg of epoxy chain extender, 0.3 kg of nucleating agent, and 0.2 kg of antioxidant; place PLA and poly(butylene adipate / terephthalate) separately in a vacuum drying oven and dry at 75°C for 4 hours to control the moisture content below 300 ppm; the PLA used is spinning-grade PLA with a melt flow rate of 25 g / 10 min and a weight-average molecular weight of 8 × 10⁻⁶. 4 The melt flow rate of the poly(butylene adipate) / terephthalate used was 5 g / 10 min, and the number average molecular weight was 6 × 10⁻⁶. 4 The epoxy chain extender selected is ADR-4368; the nucleating agent selected is talc; and the antioxidant selected is antioxidant 1010.

[0061] S2. Melt blending and granulation: The raw material processed in step S1 is added to a twin-screw extruder for melt blending. The temperatures of each zone are controlled sequentially as 165℃, 170℃, 175℃, 180℃, 185℃, and 190℃. The screw speed is 250 rpm, and the melt residence time is 1.5 min. After extrusion, cooling, and pelletizing, blended masterbatch is obtained.

[0062] S3. Preparation of two-component melt: The blended masterbatch obtained in step S2 is fed into the skin extruder and the core extruder respectively. PLA accounts for 85% of the total mass of the skin melt, and PBAT accounts for 75% of the total mass of the core melt. The mass ratio of skin to core is controlled at 70:30.

[0063] S4. Composite spinning: Melt spinning is performed using a core-sheath type composite spinneret. The spinning temperature is controlled at 205℃, the melt pressure is controlled at 8MPa, the spinneret diameter is 0.25mm, and the spinneret density is 2500 holes / m.

[0064] S5. Airflow drawing and web formation: The spun nascent fibers are cooled by cooling air and then enter the drawing device. The cooling air temperature is 16℃ and the cooling air speed is 0.4m / s. Airflow drawing is carried out under the conditions of 20℃ drawing air and 0.12MPa drawing air pressure, with a drawing ratio of 1800 times, to obtain continuous filaments with an average fiber diameter of 12μm, which are then evenly laid to form a fiber web.

[0065] S6. Hot rolling reinforcement: The fiber web is conveyed to the hot rolling mill for hot bonding. The hot rolling roll adopts a dot-shaped diamond embossing roll, the hot rolling temperature is 110℃, the hot rolling pressure is 30kN, the hot rolling line speed is 30m / min, the embossing area ratio is 15%, the embossing density is 120 dots / cm², and the embossing depth is 0.15mm.

[0066] S7. Cooling and winding: The hot-rolled nonwoven fabric is cooled to below 35°C by cooling rollers and then wound up to obtain a high-strength biodegradable PLA / PBAT bicomponent spunbond nonwoven fabric.

[0067] Comparative Example 2 S1. Raw material pretreatment: Weigh 65 kg of polylactic acid (PLA), 25 kg of poly(butylene adipate / terephthalate), 0.5 kg of epoxy chain extender, 0.3 kg of nucleating agent, 2 kg of toughening agent, and 0.2 kg of antioxidant; place PLA and poly(butylene adipate / terephthalate) separately in a vacuum drying oven and dry at 75°C for 4 hours to control the moisture content below 300 ppm; the PLA used is spinning-grade PLA with a melt flow rate of 25 g / 10 min and a weight-average molecular weight of 8 × 10⁻⁶. 4 The melt flow rate of the poly(butylene adipate) / terephthalate used was 5 g / 10 min, and the number average molecular weight was 6 × 10⁻⁶. 4The epoxy chain extender selected is ADR-4368; the nucleating agent selected is talc; and the antioxidant selected is antioxidant 1010.

[0068] S2. Melt blending and granulation: The raw material processed in step S1 is added to a twin-screw extruder for melt blending. The temperatures of each zone are controlled sequentially as 165℃, 170℃, 175℃, 180℃, 185℃, and 190℃. The screw speed is 250 rpm, and the melt residence time is 1.5 min. After extrusion, cooling, and pelletizing, blended masterbatch is obtained.

[0069] S3. Preparation of two-component melt: The blended masterbatch obtained in step S2 is fed into the skin extruder and the core extruder respectively. PLA accounts for 85% of the total mass of the skin melt, and PBAT accounts for 75% of the total mass of the core melt. The mass ratio of skin to core is controlled at 70:30.

[0070] S4. Composite spinning: Melt spinning is performed using a core-sheath type composite spinneret. The spinning temperature is controlled at 205℃, the melt pressure is controlled at 8MPa, the spinneret diameter is 0.25mm, and the spinneret density is 2500 holes / m.

[0071] S5. Airflow drawing and web formation: The spun nascent fibers are cooled by cooling air and then enter the drawing device. The cooling air temperature is 16℃ and the cooling air speed is 0.4m / s. Airflow drawing is carried out under the conditions of 20℃ drawing air and 0.12MPa drawing air pressure, with a drawing ratio of 1800 times, to obtain continuous filaments with an average fiber diameter of 12μm, which are then evenly laid to form a fiber web.

[0072] S6. Hot rolling reinforcement: The fiber web is conveyed to the hot rolling mill for hot bonding. The hot rolling roll adopts a dot-shaped diamond embossing roll, the hot rolling temperature is 110℃, the hot rolling pressure is 30kN, the hot rolling line speed is 30m / min, the embossing area ratio is 15%, the embossing density is 120 dots / cm², and the embossing depth is 0.15mm.

[0073] S7. Cooling and winding: The hot-rolled nonwoven fabric is cooled to below 35°C by cooling rollers and then wound up to obtain a high-strength biodegradable PLA / PBAT bicomponent spunbond nonwoven fabric.

[0074] The toughening agent used in this embodiment is a block copolymer type heat-resistant acetylated tributyl citrate toughening agent. Its preparation method is as follows: according to the mass ratio: 100 kg of citric acid, 70 kg of 1,8-dihydroxynaphthalene, 0.2 kg of SO4²- / TiO2 solid superacid catalyst, 300 kg of anhydrous xylene as an azeotropic solvent, all raw materials are put into the reaction vessel and stirred until completely homogeneous and dissolved; the system is controlled at vacuum degree of -0.088 MPa and temperature of 118℃ for constant temperature esterification prepolymerization for 5 h, and the xylene azeotropic system is used to continuously remove the water generated by the reaction; after the reaction is completed, the temperature is raised to 130℃ and held at high vacuum of -0.093 MPa for 1.5 h to remove unreacted monomers, oligomers and most of the solvent, and obtain the block copolymer type heat-resistant acetylated tributyl citrate toughening agent.

[0075] Comparative Example 3 S1. Raw material pretreatment: Weigh 65 kg of polylactic acid (PLA), 25 kg of poly(butylene adipate / terephthalate), 0.5 kg of epoxy chain extender, 0.3 kg of nucleating agent, 2 kg of toughening agent, and 0.2 kg of antioxidant; place PLA and poly(butylene adipate / terephthalate) separately in a vacuum drying oven and dry at 75°C for 4 hours to control the moisture content below 300 ppm; the PLA used is spinning-grade PLA with a melt flow rate of 25 g / 10 min and a weight-average molecular weight of 8 × 10⁻⁶. 4 The melt flow rate of the poly(butylene adipate) / terephthalate used was 5 g / 10 min, and the number average molecular weight was 6 × 10⁻⁶. 4 The epoxy chain extender selected is ADR-4368; the nucleating agent selected is talc; and the antioxidant selected is antioxidant 1010.

[0076] S2. Melt blending and granulation: The raw material processed in step S1 is added to a twin-screw extruder for melt blending. The temperatures of each zone are controlled sequentially as 165℃, 170℃, 175℃, 180℃, 185℃, and 190℃. The screw speed is 250 rpm, and the melt residence time is 1.5 min. After extrusion, cooling, and pelletizing, blended masterbatch is obtained.

[0077] S3. Preparation of two-component melt: The blended masterbatch obtained in step S2 is fed into the skin extruder and the core extruder respectively. PLA accounts for 85% of the total mass of the skin melt, and PBAT accounts for 75% of the total mass of the core melt. The mass ratio of skin to core is controlled at 70:30.

[0078] S4. Composite spinning: Melt spinning is performed using a core-sheath type composite spinneret. The spinning temperature is controlled at 205℃, the melt pressure is controlled at 8MPa, the spinneret diameter is 0.25mm, and the spinneret density is 2500 holes / m.

[0079] S5. Airflow drawing and web formation: The spun nascent fibers are cooled by cooling air and then enter the drawing device. The cooling air temperature is 16℃ and the cooling air speed is 0.4m / s. Airflow drawing is carried out under the conditions of 20℃ drawing air and 0.12MPa drawing air pressure, with a drawing ratio of 1800 times, to obtain continuous filaments with an average fiber diameter of 12μm, which are then evenly laid to form a fiber web.

[0080] S6. Hot rolling reinforcement: The fiber web is conveyed to the hot rolling mill for hot bonding. The hot rolling roll adopts a dot-shaped diamond embossing roll, the hot rolling temperature is 110℃, the hot rolling pressure is 30kN, the hot rolling line speed is 30m / min, the embossing area ratio is 15%, the embossing density is 120 dots / cm², and the embossing depth is 0.15mm.

[0081] S7. Cooling and winding: The hot-rolled nonwoven fabric is cooled to below 35°C by cooling rollers and then wound up to obtain a high-strength biodegradable PLA / PBAT bicomponent spunbond nonwoven fabric.

[0082] The toughening agent used in this embodiment is a block copolymer type heat-resistant acetylated tributyl citrate toughening agent. Its preparation method is as follows: according to the mass ratio: 100 kg of citric acid, 80 kg of 2,4-dihydroxydiphenyl sulfone, 0.2 kg of SO4²- / TiO2 solid superacid catalyst, and 300 kg of anhydrous xylene as an azeotropic solvent, all raw materials are put into the reaction vessel and stirred until completely homogeneous and dissolved; the system is controlled at vacuum degree of -0.088 MPa and temperature of 118°C for constant temperature esterification prepolymerization for 5 h, and the xylene azeotropic system is used to continuously remove the water generated by the reaction; after the reaction is completed, the temperature is raised to 130°C and held at high vacuum of -0.093 MPa for 1.5 h to remove unreacted monomers, oligomers and most of the solvent, and obtain the block copolymer type heat-resistant acetylated tributyl citrate toughening agent.

[0083] test: (1) Tensile property test Sample size: 50mm × 200mm Stretching speed: 100mm / min Test separately: Longitudinal fracture strength transverse fracture strength Elongation at break Each group was tested 5 times and the average value was taken.

[0084] (2) Interlayer bond strength test Basis: ASTM D5035 Determine the peel strength at the hot-rolled joint.

[0085] (3) Biodegradation rate test Basis: ISO 14855 58℃ industrial composting environment Test the mass loss rate over 180 days.

[0086] Table 1 Test Results Example 1 60.9 48.9 126 20.8 91.6 Example 2 63.2 50.2 138 21.4 92.4 Example 3 65.5 51.8 144 22.0 93.0 Example 4 67.1 53.4 152 22.7 93.5 Comparative Example 1 52.7 42.4 107 17.1 88.2 Comparative Example 2 55.9 45.5 114 18.6 89.7 Comparative Example 3 57.4 46.8 119 19.2 90.4 Based on the test results of longitudinal and transverse tensile strength, elongation at break, interlayer bond strength, and long-term biodegradation rate, it can be seen that compared with conventional PLA / PBAT spunbond nonwoven fabrics without block copolymerization and toughening or chain extension and compatibilization modification, the present invention adopts a multi-auxiliary agent synergistic modification + core-sheath dual-component structure process, which can simultaneously improve the tensile strength, toughness, and interlayer bond stability of the nonwoven fabric, and ensure excellent biodegradability throughout the process. All core properties are significantly better than those of traditional processes. The self-synthesized block copolymer toughening agent has a clear division of labor among its components and a significant synergistic quality improvement effect.

[0087] Citric acid, as the main backbone material of the toughening agent, constructs flexible aliphatic molecular segments, which can effectively improve the slippage ability of polyester matrix molecules and improve the brittleness of the material. It is the core component for improving the elongation at break and the resistance to deformation of nonwoven fabric. 2,4-Dihydroxydiphenyl sulfone introduces a rigid sulfone aromatic structure, which is interspersed between the flexible segments, greatly improving the high temperature resistance of the toughening agent. This makes it suitable for high temperature melting, spinning, and hot rolling processing conditions, avoiding the problems of high temperature decomposition and release, failure and toughness reduction of conventional toughening agents, and ensuring the mechanical stability of the finished product.

[0088] 1,8-Dihydroxynaphthalene, as a compatibility regulating component, optimizes the regularity of the toughening agent's block structure, enhances its interfacial integration with PLA and PBAT dual matrices, achieves uniform dispersion of the additive, eliminates local stress concentration, and effectively improves the interlayer bonding strength and mechanical uniformity of the nonwoven fabric. SO4²⁻ / TiO2 solid superacid catalyst precisely catalyzes the esterification prepolymerization and vacuum condensation reaction, controllably synthesizing a rigid-flexible alternating block structure, ensuring the toughening agent possesses multiple advantages including temperature resistance, toughening, and compatibility. After modification with the four components, the material properties are optimized from multiple dimensions: toughness enhancement, temperature adaptability, interfacial compatibility, and structural stability. Combined with epoxy chain extension, crystallization control, and core-sheath structure molding processes, the product's strength and structural stability are simultaneously upgraded without sacrificing degradation performance. This allows for the stable preparation of high-performance, green, biodegradable spunbond nonwoven fabrics, demonstrating significant advantages for industrial application.

[0089] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. Other modifications can be easily made by those skilled in the art. Therefore, the present invention is not limited to the specific details without departing from the general concept defined by the claims and their equivalents.

Claims

1. A method for preparing a high-strength, biodegradable bicomponent spunbond nonwoven fabric, characterized in that, Includes the following steps: S1. Raw material pretreatment: Weigh out 65-75 parts of polylactic acid, 25-35 parts of poly(butylene adipate / terephthalate), 0.5-1.2 parts of epoxy chain extender, 0.3-0.8 parts of nucleating agent, 2-6 parts of toughening agent, and 0.2-0.6 parts of antioxidant, according to the weight percentage. Place the polylactic acid and poly(butylene adipate / terephthalate) separately in a vacuum drying oven and dry at 75-85°C for 4-8 hours to control the moisture content to below 300 ppm. S2, melt blending granulation: The raw material processed in step S1 is added to a twin-screw extruder for melt blending. The temperatures of each temperature zone are controlled sequentially as follows: 165-175℃, 170-180℃, 175-185℃, 180-190℃, 185-195℃, and 190-200℃. The screw speed is 250-400 rpm, and the melt residence time is 1.5-4 min. The blended masterbatch is obtained by extrusion, cooling, and pelletizing. S3, Preparation of two-component melts: The blended masterbatch obtained in step S2 is fed into the skin extruder and the core extruder, respectively. PLA accounts for 85-92% of the total mass of the skin melt, and PBAT accounts for 75-90% of the total mass of the core melt. The mass ratio of skin to core is controlled at 70:30-80:

20. S4, Composite spinning: Melt spinning is performed using a core-spinning composite spinneret. The spinning temperature is controlled at 205–225℃, the melt pressure is controlled at 8–15MPa, the spinneret diameter is 0.25–0.40mm, and the spinneret density is 2500–5000 holes / m. S5, airflow stretches into a net: The spun nascent fibers are cooled by cooling air and then enter the drafting device. They are drafted by airflow at 20-35°C with a drafting ratio of 1800-3200 times, resulting in continuous filaments with an average fiber diameter of 12-25 μm, which are then evenly laid to form a fiber web. S6, Hot-rolled reinforcement: The fiber web is conveyed to a hot rolling mill for hot bonding. The hot rolling temperature is 110-130℃, the hot rolling pressure is 30-60kN, the hot rolling line speed is 30-120m / min, and the embossing area ratio is 15-25%. S7. Cooling and winding: After being cooled to below 35°C by cooling rollers, the hot-rolled nonwoven fabric is wound up to obtain a high-strength biodegradable PLA / PBAT bicomponent spunbond nonwoven fabric. The toughening agent is a block copolymer type heat-resistant acetylated tributyl citrate toughening agent, composed of citric acid, 2,4-dihydroxydiphenyl sulfone, 1,8-dihydroxynaphthalene, and SO4. 2- It was prepared by reacting with a TiO2 solid superacid catalyst.

2. The method for preparing a high-strength biodegradable bicomponent spunbond nonwoven fabric according to claim 1, characterized in that: The polylactic acid is spinning-grade polylactic acid with a melt flow rate of 25–40 g / 10 min and a weight-average molecular weight of 8 × 10⁻⁶. 4 ~15×10 4 .

3. The method for preparing a high-strength biodegradable bicomponent spunbond nonwoven fabric according to claim 1, characterized in that: The poly(butylene adipate) / terephthalate has a melt flow rate of 5–20 g / 10 min and a number-average molecular weight of 6 × 10⁻⁶. 4 ~12×10 4 .

4. The method for preparing a high-strength biodegradable bicomponent spunbond nonwoven fabric according to claim 1, characterized in that: The epoxy chain extender is one or two of ADR-4368, ADR-4468, and epoxy-functionalized styrene-acrylate copolymer.

5. The method for preparing a high-strength biodegradable bicomponent spunbond nonwoven fabric according to claim 1, characterized in that: The nucleating agent is one or two of talc, sodium phosphate nucleating agents, and dibenzyl sorbitol nucleating agents.

6. The method for preparing a high-strength biodegradable bicomponent spunbond nonwoven fabric according to claim 1, characterized in that: The toughening agent is a block copolymer type heat-resistant acetylated tributyl citrate toughening agent, and its preparation method is as follows: By weight proportions: 100 parts citric acid, 80-90 parts 2,4-dihydroxydiphenyl sulfone, 70-80 parts 1,8-dihydroxynaphthalene, SO4 2- 0.2–0.3 parts of TiO2 solid superacid catalyst were added, along with 300–350 parts of anhydrous xylene as an azeotropic solvent. All raw materials were added to a reactor and stirred until completely homogeneous and dissolved. The system was prepolymerized at a constant temperature of 118–126°C and a vacuum of -0.088–-0.092 MPa for 5–7 hours, using the xylene azeotropic system to continuously remove the water generated in the reaction. After the reaction was completed, the temperature was raised to 130–140°C and held at a high vacuum of -0.093–-0.098 MPa for 1.5–2.5 hours to remove unreacted monomers, oligomers, and most of the solvent, thus obtaining a block copolymer type heat-resistant acetylated tributyl citrate toughening agent.

7. The method for preparing a high-strength biodegradable bicomponent spunbond nonwoven fabric according to claim 1, characterized in that: The antioxidant is one or two of antioxidant 1010, antioxidant 168, and antioxidant 1076.

8. The method for preparing a high-strength biodegradable bicomponent spunbond nonwoven fabric according to claim 1, characterized in that: In step S5, the cooling air temperature is 16–22°C; the cooling air velocity is 0.4–1.2 m / s; and the stretching air pressure is 0.12–0.28 MPa.

9. The method for preparing a high-strength biodegradable bicomponent spunbond nonwoven fabric according to claim 1, characterized in that: In step S6, the hot rolling roll is a dotted diamond embossing roll; the embossing density is 120-260 dots / cm²; and the embossing depth is 0.15-0.40 mm.