Ecological degradable fabric and preparation method thereof

Abstract

The invention discloses an ecologically degradable fabric and a preparation method thereof, and relates to the technical field of ecologically degradable fabrics, the ecologically degradable fabric comprises a base fabric and a bio-enzyme responsive hyperbranched crosslinking layer modified on the fiber surface of the base fabric through covalent bonding; the base fabric is a polylactic acid fiber fabric or a blended fabric of polylactic acid and cotton fibers, and the weight ratio of polylactic acid fibers is 50-100%; the bio-enzyme response type hyperbranched cross-linking layer is formed by padding and high-temperature ring-opening cross-linking curing of an epoxy-terminated polypeptide modified hyperbranched polymer finishing agent; the epoxy-terminated polypeptide modified hyperbranched polymer has a hyperbranched polyester core skeleton, a polyethylene glycol flexible chain segment is copolymerized in the skeleton in a block manner, and a side chain of the skeleton is grafted with cysteine, N-protected cysteine or a polypeptide chain segment through a thioether bond. The bio-enzyme response type covalent cross-linking layer is constructed on the surface of the fiber, the hand feeling is improved through a flexible chain segment, the washability is improved through chemical bonding, and the fiber can be rapidly degraded after being abandoned.

Description

Technical Field

[0001] This invention relates to the field of eco-degradable fabric technology, specifically to an eco-degradable fabric and its preparation method. Background Technology

[0002] Polylactic acid fiber, as a renewable and biodegradable material derived from biomass, is usually prepared into yarn through spinning process and then woven into fabric. It is widely used in the fields of clothing and home textiles. Its core design concept is to reduce dependence on petroleum-based synthetic fibers by utilizing its biological origin characteristics, and it is expected that the product can be degraded through biological processes in the natural environment after disposal, thereby reducing the pollution pressure of solid waste on the environment.

[0003] However, in practical applications, due to its inherent crystallinity, polylactic acid (PLA) fibers often result in fabrics that feel stiff and rough, lacking the softness and comfort of natural fibers like cotton and linen. This significantly limits its adoption in the underwear market. A more serious problem is that while the material is biodegradable under industrial composting conditions, its natural degradation in mild environments like soil is extremely slow due to the difficulty of water penetration and the lack of microbial degradation sites. Often, it remains structurally intact even after long periods of burial, failing to achieve the desired ecological cycle. Furthermore, existing surface chemical finishing techniques used to improve performance are generally ineffective against the mechanical friction and water erosion of daily washing. Functional additives are easily shed during use, leading to a rapid decline in fabric performance and potentially microplastic residues, presenting a dilemma of not being able to balance durability and biodegradability. Summary of the Invention

[0004] The purpose of this invention is to provide an eco-degradable fabric and its preparation method, thereby solving the problems existing in the background art.

[0005] To address the aforementioned technical problems, this invention provides an eco-degradable fabric, comprising a base fabric and a bio-enzyme-responsive hyperbranched crosslinked layer covalently modified on the fiber surface of the base fabric; the base fabric is a polylactic acid (PLA) fiber fabric or a blend of PLA and cotton fibers, wherein the PLA fiber accounts for 50-100% by weight; the bio-enzyme-responsive hyperbranched crosslinked layer is formed by impregnation and high-temperature ring-opening crosslinking curing of a terminal epoxy-oxygen peptide-modified hyperbranched polymer finishing agent; the terminal epoxy-oxygen peptide-modified hyperbranched polymer has a hyperbranched polyester core skeleton, in which polyethylene glycol flexible segments are block copolymerized, and the side chains of the skeleton are grafted with cysteine, N-protected cysteine, or polypeptide segments via thioether bonds, and the ends of the skeleton are modified with glycidyl ester groups that can react with the base fabric.

[0006] Preferably, in the terminal epoxy group-modified hyperbranched polymer, the hyperbranched polyester core backbone is formed by the condensation polymerization of trimethylolpropane and itaconic acid; the molecular weight of the polyethylene glycol flexible segment is 400-2000 Da; and the degree of epoxy group modification is 3-8 epoxy functional groups per polymer molecule.

[0007] A method for preparing an eco-degradable fabric is also provided, comprising the following steps: Step S1: Preparation of terminal epoxy group-modified hyperbranched polymer finishing agent: (1) Construction of hyperbranched prepolymer containing double bonds: Trimethylolpropane, itaconic acid, polyethylene glycol, esterification catalyst, and polymerization inhibitor are added to a reactor equipped with a mechanical stirrer, thermometer and water separator. After nitrogen purging 3 to 5 times, the temperature is programmed to 150 to 170°C under nitrogen protection to carry out melt polycondensation reaction. During the reaction, mechanical stirring is turned on and nitrogen is continuously introduced to remove the generated water. In the later stage of the reaction, vacuum pumping can be used. The reaction time is 4 to 8 hours until the acid value of the product drops to 40 to 60 mg KOH / g, and a hyperbranched polyester prepolymer with carbon-carbon double bonds is obtained. (2) Introducing bio-enzyme response units: Dissolve the prepolymer obtained in step (1) in a mixed solvent of water and organic solvent, turn on magnetic stirring or ultrasonic dispersion until completely dissolved, add N-acetyl-L-cysteine ​​or thiol-containing polypeptide, slowly add organic base catalyst to adjust the reaction system to weak alkalinity (pH 7.5-8.5), carry out Michael addition reaction at 40-60℃ for 4-6 hours, remove part of the solvent by rotary evaporation after the reaction, and obtain an intermediate with modified amino acid or polypeptide units in the side chain; (3) End-capping and introducing reactive groups: Add excess epichlorohydrin and phase transfer catalyst to the intermediate obtained in step (2), wherein the amount of epichlorohydrin added is 5.0 to 10.0 times the molar amount of itaconic acid initially added in step (1), heat to 80 to 100°C and reflux for 3 to 5 hours, then cool to 40 to 60°C, add solid base or alkaline solution and carry out ring-closing reaction for 2 to 4 hours, after the reaction is completed, filter to remove salt, and remove excess epichlorohydrin and solvent by vacuum distillation to obtain terminal epoxy peptide modified hyperbranched polymer finishing agent; Step S2, Fabric finishing: The finishing agent prepared in step S1 is dispersed in water and prepared into a uniform finishing solution by ultrasonic vibration. The base fabric is immersed in the finishing solution for two dips and two nips, and the nips are controlled to be 70-80%. The fabric is then sent to a setting machine for pre-drying and then baked at high temperature, so that the epoxy groups at the end of the finishing agent can undergo a ring-opening cross-linking reaction with the hydroxyl or carboxyl groups on the fiber surface. Finally, the unreacted substances are removed by washing with water and dried to obtain the eco-degradable fabric.

[0008] Preferably, in step S1(1), the molar ratio of trimethylolpropane, itaconic acid and polyethylene glycol is 1:(2.6-3.5):(0.5-1.0); during the melt polycondensation reaction, the stirring speed is controlled at 200-400 rpm.

[0009] Preferably, in step S1(2), the amount of L-cysteine ​​or thiol-containing polypeptide added is 20-40% of the molar amount of itaconic acid; the organic solvent is N,N-dimethylformamide or acetone; and the Michael addition reaction is carried out under magnetic stirring.

[0010] Preferably, in step S1 (3), the amount of epichlorohydrin added is 5.0 to 10.0 times the molar amount of itaconic acid in step (1), as a reactant and solvent; the phase transfer catalyst is tetrabutylammonium bromide or benzyltriethylammonium chloride, and the amount used is 0.5 to 1.5% of the total mass of the reactants; the alkali in the solid alkali or alkali solution is sodium hydroxide or potassium hydroxide, and the molar amount is 1.0 to 1.2 times the molar amount of residual carboxyl groups in the prepolymer obtained in step (1).

[0011] Preferably, in step S2, the mass concentration of the terminal epoxy group-modified hyperbranched polymer finishing agent in the finishing solution is 20-50 g / L; and the pH value of the finishing solution is adjusted to 5.0-6.0.

[0012] Preferably, in step S2, the pre-baking process conditions are: heating to 80-100°C at a heating rate of 3-5°C / min and holding at that temperature for 3-5 minutes.

[0013] Preferably, in step S2, the high-temperature baking process conditions are: temperature 160-170℃, time 2-3 minutes; during the high-temperature baking process, the hot air circulation fan speed is controlled at 1000-1500 r / min.

[0014] Compared with the prior art, the present invention has the following beneficial effects: A bio-recognition structural layer was constructed on the fiber surface, which can sensitively respond to specific biological enzymes in the natural soil environment. When the fabric is discarded and buried in the soil, microbial enzymes in the environment can recognize and specifically act on this structural layer, triggering the disintegration of the surface cross-linking network. This exposes the tightly packed fiber matrix inside to the attack of microorganisms, accelerating the decomposition process of the fabric under natural conditions. This ensures that the fabric can completely return to nature after the end of its service life, solving the problem of the slow actual degradation rate of conventional bio-based fibers in the natural environment.

[0015] The functional modification layer is firmly grafted onto the fiber matrix through a chemical reaction, forming a stable chemical covalent bond. This endows the fabric with excellent wash resistance. Even after multiple standard washes and mechanical agitation, the functional layer can still be stably retained on the fiber surface, ensuring its continued eco-degradation induction function. Furthermore, this surface cross-linked network structure forms a dense physical protective barrier on the outer layer of the fiber, which to some extent shares the external mechanical stress, thereby improving the fabric's tensile strength and abrasion resistance, and effectively extending the fabric's service life.

[0016] Specific flexible segments are introduced into the backbone of the modified polymer. These segments play an excellent role in internal plasticization in the microstructure, effectively alleviating the original rigidity of the polylactic acid fiber matrix, giving the fabric a softer and more delicate touch, improving the wearing comfort of consumers, and also helping to build micro-channels on the fiber surface that are conducive to moisture transmission, improving the moisture absorption and breathability of the fabric, overcoming the defects of bio-based synthetic fibers such as stiffness and stuffiness, and meeting the needs of high-quality textiles. Detailed Implementation Example 1:

[0017] This embodiment provides an eco-degradable fabric and its preparation method. Before formal preparation, the present invention pre-established a dynamic correlation model between the generation of hyperbranched topology and soil enzyme adsorption kinetics to determine the optimal synthesis process window. The specific method is as follows: synthesize hyperbranched polyester cores of different generations, inoculate with fluorescently labeled soil proteases, such as Bacillus subtilis protease, and monitor the adsorption-desorption behavior of the enzyme on the polymer surface in real time using surface plasmon resonance technology. Regression analysis data shows that when the generation of the hyperbranched core is controlled between 2.5 and 3.0, and the density of terminal epoxy groups is moderate, the adsorption amount of enzyme molecules reaches its peak and the conformation remains stable, which provides a theoretical basis for setting subsequent process parameters. In this embodiment, the base fabric is made of 100% polylactic acid fiber; the bio-enzyme responsive hyperbranched cross-linked layer is not a simple physical coating, but rather a bio-enzyme responsive unit (cysteine) extended into the hydration layer on the fiber surface through a specific molecular design using flexible polyethylene glycol segments as bait arms, thereby ensuring the durability of the fabric while giving it Trojan-like responsive degradation characteristics to soil microorganisms. (1) Construction of hyperbranched prepolymer containing double bonds: In this embodiment, the molar ratio of trimethylolpropane, itaconic acid and polyethylene glycol (molecular weight 400 Da) is 1:2.6:0.5; monobutyltin oxide is added as an esterification catalyst, with an amount of 0.15% of the total monomer mass, and hydroquinone is added as a polymerization inhibitor, with an amount of 0.2% of the total monomer mass; during the melt polycondensation reaction, the stirring speed is controlled at 200 rpm, the reaction temperature is set at 160℃, and the reaction time is 5 hours; in the last hour of the reaction, a vacuum pump is connected for dehydration under reduced pressure, with a vacuum degree of -0.08 MPa, until the acid value of the product is controlled at 60 mg KOH / g; in this step, the introduction of the catalyst and the reduced pressure operation effectively promote the esterification reaction equilibrium to shift to the right, ensuring that the prepolymer reaches the expected molecular weight and branching degree, while the presence of the polymerization inhibitor effectively inhibits the thermal polymerization of double bonds; (2) Introduction of bio-enzyme response unit: In this embodiment, the prepolymer obtained in step (1) is dissolved in a mixed solvent of acetone and water at a volume ratio of 3:1, and N-acetyl-L-cysteine ​​is added, the amount of which is 20% of the molar amount of itaconic acid; triethylamine is used as an alkaline catalyst, and the pH is adjusted to 8.0 by slow dropwise addition, the amount of triethylamine is about 0.8% of the solvent mass, and the reaction is carried out at 45°C for 5 hours; Technical description: N-acetyl-L-cysteine ​​is selected instead of ordinary cysteine, in order to use acetyl groups to protect amino groups and prevent them from reacting non-selectively with epichlorohydrin in subsequent steps, so as to ensure that the chemical structure of the final product is clear and the crosslinking sites are controllable; This step utilizes the principle of thiol-ene click chemistry to efficiently graft the bio-enzyme response unit onto the side chain double bond of the hyperbranched backbone; (3) End-capping to introduce reactive groups: In this embodiment, the amount of epichlorohydrin is 5.0 times the molar amount of itaconic acid, and the phase transfer catalyst is tetrabutylammonium bromide (0.5%); the reflux reaction is carried out at 90°C for 3 hours, and the ring-closing reaction is carried out at 45°C with sodium hydroxide solution added, the molar amount of sodium hydroxide being 1.1 times the residual carboxyl group of the prepolymer, for 3 hours; this step ensures that each polymer molecule has a highly active glycidyl ester group at its end, and since the amino group has been protected in step (2), epichlorohydrin only reacts with the carboxyl group, avoiding the risk of gelation caused by side reactions; In this embodiment, the finishing solution concentration was 20 g / L, the pH was adjusted to 5.0, and a uniform finishing solution was prepared by ultrasonic vibration for 20-30 minutes, with a pick-up rate of 70%. The pre-drying process conditions were as follows: heating to 80-100°C at a heating rate of 3-5°C / min and holding at that temperature for 3-5 minutes; specifically, heating to 80°C at 3°C / min and holding for 3 minutes. The slow heating rate was intended to prevent rapid evaporation of moisture from causing the finishing agent to migrate on the fiber surface, ensuring uniform film formation. The high-temperature baking temperature was 160°C for 2 minutes, and the fan speed was 1000 r / min. Under these conditions, the hyperbranched polymer constructed a layer of intelligent skin with both biological activity and physical protection function in situ on the fiber surface. Example 2:

[0018] This embodiment provides an eco-degradable fabric, which is another parameter optimization method based on the technical solution of Embodiment 1, aiming to balance the fabric's hand feel and washability; In this embodiment, the base fabric is a polylactic acid / cotton (70 / 30) blended fabric; polyethylene glycol with a molecular weight of 1000 Da is selected, and PEG segments with a moderate molecular weight are introduced to make the hyperbranched polyester core skeleton more flexible, which can alleviate the rigid feel of the polylactic acid fiber itself; the final polymer has an epoxy group modification degree of about 5 per molecule. In step S1(1), the specific molar ratio of trimethylolpropane, itaconic acid and polyethylene glycol in this embodiment is adjusted to 1:3.0:0.8; p-toluenesulfonic acid is added as an esterification catalyst (0.3%) and p-hydroxyanisole as a polymerization inhibitor (0.3%); the temperature is programmed to 165°C, the stirring speed is 300 rpm, the reaction time is 6 hours, and the acid value of the product is reduced to 50 mg KOH / g; the addition of the catalyst enables the reaction to achieve a high conversion rate under mild conditions; In step S1(2), this embodiment selects a thiol-containing polypeptide, L-glutathione, whose amino terminus has certain steric hindrance and whose main reaction site is thiol, as a biological response unit, with an addition amount of 30%; the solvent is a mixture of N,N-dimethylformamide and water in a volume ratio of 4:1; the reaction temperature is 50℃ and the time is 5 hours; compared with a single amino acid, the thiol-containing polypeptide has a more complex spatial structure, which can be more effectively recognized and anchored by specific proteases in the soil, thereby accelerating the degradation initiation process after disposal; In step S1 (3), the specific amount of epichlorohydrin added in this embodiment is 7.5 times the initial molar amount of itaconic acid added in step (1), the catalyst is benzyltriethylammonium chloride (1.0%), the reflux temperature is 90°C, the ring-closing temperature is 50°C, the base is potassium hydroxide, and the molar amount is 1.1 times; the use of potassium hydroxide as a strong base improves the rate and conversion of the ring-closing reaction and reduces the occurrence of side reactions; In step S2, the high-temperature baking temperature in this embodiment is 165°C, the time is 2.5 minutes, and the fan speed is 1250 r / min. The higher fan speed enhances the penetration of hot air, allowing the finishing agent inside the blended fabric to fully cross-link, significantly improving the fabric's wash resistance. Even after multiple washes, the finishing agent can still remain on the fiber surface to maintain its function. Example 3:

[0019] This embodiment provides an eco-degradable fabric for outdoor sports or workwear applications, requiring the fabric to have high strength and abrasion resistance while maintaining good eco-degradability; the base fabric is 100% polylactic acid fiber. In step S1(1), polyethylene glycol with a molecular weight of 2000 Da is selected, with a molar ratio of 1:3.5:1.0; hydroquinone is added as a polymerization inhibitor, with an amount of 0.4% of the total monomer mass; the reaction temperature is 160℃, the time is 5 hours, and the product acid value is 40mgKOH / g; the high proportion of itaconic acid and high molecular weight PEG make the skeleton have a highly branched structure and long flexible chain segments, which helps to form a highly elastic nano-network structure on the fiber surface, thereby improving the wrinkle resistance and tear strength of the fabric; In step S1(2), the amount of L-cysteine ​​added is increased to 40%, and the solvent is a mixture of DMF and water with a volume ratio of 2:1 to ensure the complete dissolution of high concentration amino acids; the reaction is carried out at 60°C for 6 hours; the high-density bio-enzyme response unit modification enables the eco-degradable fabric to be quickly recognized by microorganisms in the landfill environment, overcoming the degradation problem usually caused by high cross-linking density, and achieving a dialectical unity of high durability and easy degradation. In step S1 (3), the amount of epichlorohydrin added is 10.0 times the initial molar amount of itaconic acid added in step (1), the amount of catalyst is 1.5%, the reflux temperature is 100℃, the ring closure temperature is 60℃, and the amount of alkali is 1.2 times. At this time, the epoxy modification degree of the terminal epoxy peptide modified hyperbranched polymer finishing agent reaches 8 per molecule, which provides sufficient reaction sites for constructing a high-density cross-linked network. In step S2, in this embodiment, the mass concentration of the terminal epoxy peptide modified hyperbranched polymer finishing agent in the finishing solution is set to 50 g / L, pH 6.0; pre-baking at 100°C for 5 minutes, high-temperature baking at 170°C for 3 minutes, and fan speed of 1500 r / min; under these harsh curing conditions, the finishing agent is completely cured on the fiber surface, forming a strong armor, which not only improves the physical and mechanical properties, but also effectively seals the microcracks on the fiber surface. Example 4:

[0020] This embodiment aims to explore the synergistic effect of medium-chain-length PEG with specific process parameters; the matrix fabric is polylactic acid / cotton (80 / 20). In step S1(1), polyethylene glycol with a molecular weight of 1500 Da is selected, with a molar ratio of 1:3.2:0.9; p-hydroxyanisole polymerization inhibitor is added at a dosage of 0.25%; the reaction temperature is 155℃ and the stirring speed is 350rpm; this formulation aims to balance hydrophilicity and film strength. In step S1 (2), the amount of thiol-containing polypeptide added is 35%, the solvent is a mixture of DMF and water in a volume ratio of 3:1; the reaction is carried out at 55°C for 4.5 hours. In step S1 (3), the amount of epichlorohydrin added is 8.0 times the initial molar amount of itaconic acid added in step (1), the amount of phase transfer catalyst tetrabutylammonium bromide is 1.2%, and the amount of sodium hydroxide is 1.15 times; In step S2, the finishing solution concentration was 40 g / L and the pH was 5.2; the pre-drying temperature was 95°C, the baking temperature was 168°C for 2.5 minutes, and the fan speed was 1400 r / min. The resulting eco-degradable fabric maintained a good hand feel while exhibiting excellent moisture absorption and perspiration wicking properties. This is attributed to the effective extension of PEG segments in the cross-linking network, which formed microchannels that facilitated the transport of water molecules. Example 5:

[0021] This embodiment focuses on product performance under low-temperature energy-saving processes; the base fabric is 100% polylactic acid fiber; In step S1(1), polyethylene glycol with a molecular weight of 600 Da is selected, with a molar ratio of 1:2.8:0.6; hydroquinone polymerization inhibitor is added to the reaction system at an amount of 0.15%; the reaction temperature is 145℃; the shorter PEG segments make the polymer structure relatively compact. In step S1(2), L-cysteine ​​is added at 25%, and the solvent is a mixture of acetone and water at a volume ratio of 2:1. The reaction is carried out at 45°C. In step S1 (3), the amount of epichlorohydrin added is 6.0 times the initial molar amount of itaconic acid added in step (1), the amount of phase transfer catalyst tetrabutylammonium bromide is 0.8%, and the amount of potassium hydroxide is 1.05 times; In step S2, the concentration of the finishing solution is 30 g / L, pH 5.8; the pre-drying temperature is 85°C, the high-temperature baking temperature is set to 160°C, the time is 2 minutes, and the fan speed is 1100 r / min. Although the baking temperature is at the lower limit of the range, due to the high reactivity of the terminal epoxy group-modified hyperbranched polymer, thanks to the exposure rate of the high-end groups of the hyperbranched structure, an effective bio-enzyme-responsive hyperbranched cross-linking layer can still be formed on the fiber surface, achieving a balance between energy saving and product performance.

[0022] Comparative Example 1: This comparative example provides a 100% polylactic acid fiber raw fabric without any chemical finishing as a blank control to evaluate the fundamental contribution of the finishing agents in the examples to degradation performance and mechanical properties; the raw fabric has only undergone conventional scouring and bleaching treatment and lacks active functional groups on the surface.

[0023] Comparative Example 2: This comparative example provides a fabric whose preparation method is basically the same as that of Example 2, except that: in step S1 (2), L-cysteine ​​or thiol-containing polypeptides are not added, that is, the Michael addition reaction step is omitted; the finishing agent prepared is a terminal epoxy hyperbranched polyester without bio-enzyme response units; this comparative example aims to verify the key role of bio-enzyme response units (polypeptides / amino acids) in inducing soil microbial degradation.

[0024] Comparative Example 3: This comparative example provides a fabric whose preparation method is basically the same as that of Example 2, except that: in step S1 (3), the epichlorohydrin end-capping reaction is not carried out, but the intermediate of step (2) is directly used for fabric finishing; due to the lack of epoxy groups that can react with fibers, the finishing agent is only attached to the fabric surface by physical adsorption; this comparative example aims to verify the effect of covalent bonding modification on washability and mechanical reinforcement.

[0025] Comparative Example 4: This comparative example provides a fabric whose preparation method is basically the same as that of Example 2, except that: in step S1 (1), polyethylene glycol is not added, but rigid monomers are used for polycondensation. This comparative example aims to verify the necessity of flexible polyethylene glycol segments for adjusting the feel of the fabric and constructing hydrophilic degradation channels.

[0026] Verification experiment: The eco-degradable fabrics prepared in Examples 1-5 and Comparative Examples 1-4 were subjected to corresponding performance tests, and the test results are shown below. To ensure the accuracy and repeatability of the data, all tests were conducted after equilibration for 24 hours in a constant temperature and humidity environment of 20±2℃ and 65±4%RH. 1. Tensile strength test (N): The test was conducted in accordance with GB / T3923.1-2013 "Textiles - Tensile properties of fabrics - Part 1: Determination of tensile strength and elongation at break (strip method)"; an electronic fabric tensile tester was used, with a tensile speed of 100 mm / min and a spacing of 200 mm; each sample was tested 5 times and the average value was taken. 2. Stiffness test (mm): Refer to GB / T18318.1-2009 "Determination of bending properties of textiles - Part 1: Inclined plane method"; determine the bending length of the fabric, the smaller the value, the softer the fabric; each sample is tested 5 times and the average value is taken; 3. Washability Test (%): The fabric was subjected to 20 standard washing and drying cycles according to AATCC 135 standards; the change in nitrogen content (derived from polypeptides / amino acids) on the fiber surface before and after washing was analyzed by X-ray photoelectron spectroscopy, and the retention rate of the finishing agent was calculated; Retention rate = (N content after washing / N content before washing) × 100%; 4. Soil degradation rate test (%): According to ISO11721 standard, the fabric was cut into 10cm×10cm samples and buried in humus-rich natural soil at a depth of 15cm. The soil moisture was maintained at 60%±5% and the ambient temperature at 25±2℃. After 90 days, the samples were taken out, carefully cleaned to remove the soil, and dried to constant weight. The weight loss rate was calculated. Weight loss rate = [(initial mass - degraded mass) / initial mass]×100%. Three parallel groups were set up for each sample.

[0027] Data table: Group Fracture strength (N) Stiffness (mm) Washability (Retention Rate %) Soil degradation rate (90-day weight loss%) Example 1 680.25 45.10 92.50 62.30 Example 2 720.40 38.20 95.10 75.80 Example 3 785.60 32.50 96.80 81.50 Example 4 740.15 35.40 94.50 78.20 Example 5 705.30 42.80 93.00 68.40 Comparative Example 1 550.10 58.60 N / A 8.50 Comparative Example 2 715.20 40.50 94.80 25.60 Comparative Example 3 580.40 55.20 15.20 30.20 Comparative Example 4 730.50 65.80 93.50 45.30 Result analysis components: Results analysis: As can be seen from the data in Table 1, the eco-degradable fabric of the present invention achieves an excellent balance between mechanical properties and environmental degradation performance. Confirmation of the bio-induced degradation mechanism: Comparing Example 2 and Comparative Example 2, it can be seen that in the absence of bio-enzyme response units (L-cysteine / peptide), although the fabric strength of Comparative Example 2 is significantly improved, its 90-day soil degradation rate is only 25.6%, far lower than the 75.8% of Example 2. This fully demonstrates that the defined side chains grafted with cysteine ​​or peptide segments via thioether bonds are the key technical feature for achieving targeted recognition by environmental microorganisms and triggering the degradation mechanism. Soil microorganisms preferentially secrete proteases to decompose peptide side chains, leading to the disintegration of the hyperbranched cross-linked network, thereby exposing the matrix fabric, producing a Trojan horse effect, and accelerating overall degradation. The effect of covalent bonding on durability: Comparing Example 2 and Comparative Example 3, it can be seen that without the covalent bonding effect of terminal epoxy groups, a large amount of finishing agent is shed during the washing process, resulting in a decrease in the strength of the fabric after multiple uses. Furthermore, due to the loss of finishing agent, its long-term degradation induction ability is also greatly reduced. This verifies the necessity of having glycidyl ester-type epoxy groups at the end that can react with the base fabric to ensure the functional stability of the product throughout its entire life cycle. The regulatory effect of flexible segment molecular weight: Comparing Examples 1, 3, and 4, it can be seen that as the molecular weight of PEG segments increases, the stiffness of the fabric decreases significantly, while the breaking strength increases. This is because the longer PEG segments act as effective internal plasticizers in the hyperbranched skeleton, giving the crosslinked network better flexibility and stress relaxation ability, thereby reducing the stiffness of the fabric. At the same time, the flexible network structure formed by long-chain PEG can more effectively transmit and dissipate external forces, improving strength. Compared with Comparative Example 4, which lacks PEG, this further confirms the importance of setting the molecular weight of polyethylene glycol flexible segments in the range of 400-2000 Da for balancing the fabric's hand feel and mechanical properties. Furthermore, Example 3 achieved the lowest stiffness and highest breaking strength by using high molecular weight PEG and highly modified epoxy groups. This demonstrates that by adjusting the hyperbranched skeleton structure and the proportion of flexible segments, the inherent brittleness and stiffness of PLA fibers can be effectively overcome, achieving a synergistic improvement in fabric feel and strength. The ecodegradable fabric exhibits excellent durability and comfort during the wearing stage, while it can achieve rapid degradation through a bio-induced mechanism during the waste landfill stage, meeting the needs of green and sustainable development.

[0028] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments that can be applied to other fields. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. An eco-degradable fabric, characterized in that, It includes a base fabric and a bio-enzyme-responsive hyperbranched cross-linked layer covalently bonded to the surface of the base fabric fibers; the base fabric is a polylactic acid (PLA) fiber fabric or a blend of PLA and cotton fibers, wherein the PLA fiber accounts for 50-100% by weight; the bio-enzyme-responsive hyperbranched cross-linked layer is formed by impregnation and high-temperature ring-opening cross-linking curing of a terminal epoxy-peptide modified hyperbranched polymer finishing agent; the terminal epoxy-peptide modified hyperbranched polymer has a hyperbranched polyester core skeleton, in which polyethylene glycol flexible segments are block copolymerized, and the side chains of the skeleton are grafted with cysteine, N-protected cysteine, or polypeptide segments through thioether bonds, and the ends of the skeleton are modified with glycidyl ester groups that can react with the base fabric.

2. The eco-degradable fabric as described in claim 1, characterized in that, In the hyperbranched polymer modified with terminal epoxy groups, the hyperbranched polyester core backbone is formed by the condensation polymerization of trimethylolpropane and itaconic acid; the molecular weight of the polyethylene glycol flexible segments is 400-2000 Da; and the degree of epoxy group modification is 3-8 epoxy functional groups per polymer molecule.

3. A method for preparing an eco-degradable fabric as described in claim 1 or 2, characterized in that, Includes the following steps: Step S1: Preparation of terminal epoxy group-modified hyperbranched polymer finishing agent: (1) Construction of hyperbranched prepolymer containing double bonds: Trimethylolpropane, itaconic acid, polyethylene glycol, esterification catalyst, and polymerization inhibitor are added to a reactor equipped with a mechanical stirrer, thermometer and water separator. After nitrogen purging 3 to 5 times, the temperature is programmed to 150 to 170°C under nitrogen protection to carry out melt polycondensation reaction. During the reaction, mechanical stirring is turned on and nitrogen is continuously introduced to remove the generated water. In the later stage of the reaction, vacuum pumping can be used. The reaction time is 4 to 8 hours until the acid value of the product drops to 40 to 60 mg KOH / g, and a hyperbranched polyester prepolymer with carbon-carbon double bonds is obtained. (2) Introducing bio-enzyme response units: Dissolve the prepolymer obtained in step (1) in a mixed solvent of water and organic solvent, turn on magnetic stirring or ultrasonic dispersion until completely dissolved, add N-acetyl-L-cysteine ​​or thiol-containing polypeptide, slowly add organic base catalyst to adjust the reaction system to weak alkalinity (pH 7.5-8.5), carry out Michael addition reaction at 40-60℃ for 4-6 hours, remove part of the solvent by rotary evaporation after the reaction, and obtain an intermediate with modified amino acid or polypeptide units in the side chain; (3) End-capping and introducing reactive groups: Add excess epichlorohydrin and phase transfer catalyst to the intermediate obtained in step (2), wherein the amount of epichlorohydrin added is 5.0 to 10.0 times the molar amount of itaconic acid initially added in step (1), heat to 80 to 100°C and reflux for 3 to 5 hours, then cool to 40 to 60°C, add solid base or alkaline solution and carry out ring-closing reaction for 2 to 4 hours, after the reaction is completed, filter to remove salt, and remove excess epichlorohydrin and solvent by vacuum distillation to obtain terminal epoxy peptide modified hyperbranched polymer finishing agent; Step S2, Fabric finishing: The finishing agent prepared in step S1 is dispersed in water and prepared into a uniform finishing solution by ultrasonic vibration. The base fabric is immersed in the finishing solution for two dips and two nips, and the nips are controlled to be 70-80%. The fabric is then sent to a setting machine for pre-drying and then baked at high temperature, so that the epoxy groups at the end of the finishing agent can undergo a ring-opening cross-linking reaction with the hydroxyl or carboxyl groups on the fiber surface. Finally, the unreacted substances are removed by washing with water and dried to obtain the eco-degradable fabric.

4. The method for preparing an eco-degradable fabric as described in claim 3, characterized in that, In step S1(1), the molar ratio of trimethylolpropane, itaconic acid and polyethylene glycol is 1:(2.6-3.5):(0.5-1.0); during the melt polycondensation reaction, the stirring speed is controlled at 200-400 rpm.

5. The method for preparing an eco-degradable fabric as described in claim 3, characterized in that, In step S1(2), the amount of L-cysteine ​​or thiol-containing polypeptide added is 20-40% of the molar amount of itaconic acid; the organic solvent is N,N-dimethylformamide or acetone; the Michael addition reaction is carried out under magnetic stirring.

6. The method for preparing an eco-degradable fabric as described in claim 3, characterized in that, In step S1 (3), the amount of epichlorohydrin added is 5.0 to 10.0 times the molar amount of itaconic acid in step (1), as a reactant and solvent; the phase transfer catalyst is tetrabutylammonium bromide or benzyltriethylammonium chloride, and the amount used is 0.5 to 1.5% of the total mass of the reactants; the alkali in the solid alkali or alkali solution is sodium hydroxide or potassium hydroxide, and the molar amount is 1.0 to 1.2 times the molar amount of residual carboxyl groups in the prepolymer obtained in step (1).

7. The method for preparing an eco-degradable fabric as described in claim 3, characterized in that, In step S2, the mass concentration of the terminal epoxy group-modified hyperbranched polymer finishing agent in the finishing solution is 20-50 g / L; the pH value of the finishing solution is adjusted to 5.0-6.

0.

8. The method for preparing an eco-degradable fabric as described in claim 3, characterized in that, In step S2, the pre-baking process conditions are as follows: the temperature is increased to 80-100°C at a heating rate of 3-5°C / min, and held for 3-5 minutes.

9. The method for preparing an eco-degradable fabric as described in claim 3, characterized in that, In step S2, the process conditions for high-temperature baking are: temperature 160-170℃, time 2-3 minutes; during the high-temperature baking process, the speed of the hot air circulating fan is controlled at 1000-1500 r / min.