Environment-friendly geotextile based on waste fiber regeneration and preparation method thereof

Abstract

The invention relates to the field of geosynthetic materials, and discloses an environment-friendly geotextile based on waste fiber regeneration and a preparation method thereof, and the geotextile comprises a regenerated cellulose non-woven base material and a microporous composite network attached to the base material. The microporous composite network is formed by reacting and curing a working solution A and a working solution B and then washing; the working solution A comprises polyvinyl alcohol, a polycarboxylic acid cross-linking agent, a sacrificial pore-forming agent and a zirconium catalyst; and the working solution B contains potassium methyl silicate. The preparation method comprises the following steps: sequentially padding a base material in a working solution A and a working solution B, and carrying out intermediate drying between the two times of padding; then carrying out high-temperature curing; and finally, carrying out post-washing to dissolve out the sacrificial pore-forming agent. The problems that the regenerated cellulose base material is low in wet strength and high in water absorption rate are solved, and the prepared geotextile has high wet strength, low water absorption rate and good water permeability.

Description

Technical Field

[0001] This invention relates to the field of geosynthetics, specifically to an environmentally friendly geotextile based on the recycling of waste fibers and its preparation method. Background Technology

[0002] Geotextiles are permeable textiles used in civil engineering, widely employed for functions such as filtration, drainage, isolation, and reinforcement. Currently, commercially available geotextiles are primarily made from petroleum-based synthetic fibers such as polypropylene (PP) or polyester (PET) through processes like needle punching or thermal bonding. While these materials offer stable performance, their raw materials rely on non-renewable petroleum resources, and they are difficult to degrade in the environment after disposal, thus creating an environmental burden.

[0003] With increasing emphasis on environmental protection and resource recycling, the preparation of regenerated cellulose nonwoven fabrics from biomass resources such as waste textiles and their use as geotextile substrates has become a research direction.

[0004] However, regenerated cellulose nonwoven fabric substrates possess inherent hydrophilicity due to the large number of hydroxyl groups on the cellulose macromolecules. This strong hydrophilicity leads to high water absorption and significant swelling upon contact with water, and its wet mechanical strength decreases substantially compared to its dry state. This low wet strength and high water absorption limit the application of regenerated cellulose substrates in the field of geotextiles, as geotextiles must maintain structural stability and sufficient mechanical properties in their application environments (such as hydraulic and geotechnical engineering) to achieve effective filtration and reinforcement functions.

[0005] Therefore, this invention proposes an environmentally friendly geotextile based on the recycling of waste fibers and its preparation method to overcome the shortcomings of the prior art. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides an environmentally friendly geotextile based on recycled waste fibers and its preparation method. This solves the problems of low wet strength and high water absorption of existing recycled cellulose nonwoven fabric substrates, which lead to defects in water resistance and water permeability filtration when used as geotextiles.

[0007] To address the above problems, the present invention provides the following technical solution: In a first aspect, the present invention provides an environmentally friendly geotextile based on the recycling of waste fibers, employing the following technical solution: An environmentally friendly geotextile based on recycled waste fibers includes: a regenerated cellulose nonwoven fabric substrate; a microporous composite network attached to the regenerated cellulose nonwoven fabric substrate, wherein the microporous composite network is formed by reacting and curing working solution A and working solution B and then washing; working solution A is an acidic solution containing polyvinyl alcohol, a polycarboxylic acid crosslinking agent, a sacrificial pore-forming agent and a zirconium catalyst; working solution B is an alkaline solution containing potassium methylsilicate.

[0008] By adopting the above technical solution, this invention employs a technical path of sequential processing with two liquids (working liquid A and working liquid B). The working mechanism of this technical solution is reflected in: 1. First, polyvinyl alcohol (PVA), polycarboxylic acid crosslinking agent, zirconium catalyst and sacrificial pore-forming agent are infiltrated into the substrate through working solution A (acidic); 2. Subsequently, the substrate carrying acidic working solution A is immersed in working solution B (alkaline). Potassium methylsilicate (PMS) in working solution B is stable under alkaline conditions, but when it comes into contact with acidic working solution A on the surface of the substrate, the sudden pH change triggers in-situ hydrolysis and polycondensation of potassium methylsilicate; 3. The hydrolysis products of potassium methylsilicate (Si-OH) condense on the fiber surface to form a cross-linked, water-insoluble polysiloxane (Si-O-Si) hydrophobic network. This network coats the fiber, giving the material low water absorption. 4. Simultaneously, in the subsequent high-temperature curing step, the zirconium-based catalyst catalyzes the esterification reaction between the hydroxyl groups of polyvinyl alcohol (PVA) and the carboxyl groups of polycarboxylic acids to form a PVA-polycarboxylic acid crosslinking network. This network is interwoven between the fibers, improving the wet strength of the substrate. 5. In the final post-washing step, the sacrificial pore-forming agent is dissolved, leaving microporous channels in the composite network (polysiloxane network and PVA crosslinked network) formed in (3) and (4) above.

[0009] The composite network formed by (3) and (4) above imparts wet strength and hydrophobicity to the substrate, and the microporous channels formed by (5) retain the water permeability of the material, thereby solving the problems of low wet strength and high hydrophilicity of regenerated cellulose substrate.

[0010] Preferably, the microporous composite network is formed by reacting and curing working solution A and working solution B, which contain the following raw materials in parts by weight: Working solution A, based on 100 parts by weight, is made from the following raw materials in parts by weight: 10-15 parts polyvinyl alcohol; 5-10 parts polycarboxylic acid crosslinking agent; 5-15 parts sacrificial pore-forming agent; 0.5-2.0 parts zirconium-based catalyst; balance water; Working solution B, based on 100 parts by weight, is made from the following raw materials in parts by weight: 3-8 parts potassium methylsilicate aqueous solution; balance water. By adopting the above technical solution, the dosage range of each component is limited, ensuring a balance between wet strength, hydrophobicity, and water permeability.

[0011] Further preferably, working solution A, based on 100 parts by weight, is made from raw materials comprising the following parts by weight: 12.5 parts of polyvinyl alcohol; 7.5 parts of polycarboxylic acid crosslinking agent; 10 parts of sacrificial pore-forming agent; 1.2 parts of zirconium catalyst; and the balance being water; working solution B, based on 100 parts by weight, is made from raw materials comprising the following parts by weight: 5.5 parts of potassium methylsilicate aqueous solution; and the balance being water.

[0012] Preferably, the polyvinyl alcohol is PVA-1788; the polycarboxylic acid crosslinking agent is citric acid. By adopting the above technical solution, PVA-1788 has good film-forming properties and reactivity, and citric acid, as a polycarboxylic acid crosslinking agent, can undergo esterification crosslinking with PVA.

[0013] Preferably, the sacrificial pore-forming agent is polyethylene glycol; the zirconium-based catalyst is an aqueous solution of zirconium acetylacetonate or zirconium acetate. By adopting the above technical solution, polyethylene glycol is readily soluble in water and can be easily removed in the subsequent washing step as a pore-forming agent; the aqueous solution of zirconium acetylacetonate or zirconium acetate can be used as a catalyst for the esterification reaction of PVA with citrate.

[0014] Secondly, the present invention provides a method for preparing an environmentally friendly geotextile based on recycled waste fibers, employing the following technical solution: A method for preparing an environmentally friendly geotextile based on recycled waste fibers includes the following steps: immersing a regenerated cellulose nonwoven fabric substrate in a working solution A containing polyvinyl alcohol, a polycarboxylic acid crosslinking agent, a sacrificial pore-forming agent, and a zirconium-based catalyst for a first padding; subjecting the regenerated cellulose nonwoven fabric substrate after the first padding to intermediate drying; immersing the intermediate-dried regenerated cellulose nonwoven fabric substrate in a working solution B containing potassium methylsilicate for a second padding; subjecting the regenerated cellulose nonwoven fabric substrate after the second padding to high-temperature curing to form a composite network; and post-washing the high-temperature cured regenerated cellulose nonwoven fabric substrate to dissolve the sacrificial pore-forming agent and form micropores.

[0015] By adopting the above technical solution, this preparation method employs a combined process of sequential impregnation with two liquids (working solution A and working solution B), pH triggering, high-temperature curing, and post-washing to form pores. The functions of each step are: First impregnation (step S1): An acidic working solution A (containing PVA, citric acid, sacrificial pore-forming agent and zirconium catalyst) is introduced into the regenerated cellulose nonwoven fabric substrate.

[0016] Intermediate drying (step S2): Remove moisture, allowing the components of working solution A to adhere to the fiber surface, providing a uniform reaction substrate for subsequent padding with working solution B, and preventing working solution B from being diluted.

[0017] Second padding (step S3): The substrate carrying the acidic component is immersed in the alkaline working solution B. Potassium methylsilicate (PMS) in the working solution B is triggered to hydrolyze upon contact with the acidic substance, providing reactants for the subsequent polycondensation reaction.

[0018] High-temperature curing (step S4): Under high-temperature conditions, two key reactions occur simultaneously in the system: (1) Zirconium catalyst catalyzes the esterification and crosslinking reaction between the hydroxyl groups of polyvinyl alcohol (PVA) and the carboxyl groups of polycarboxylic acid (citric acid) to form a PVA-polycarboxylic acid crosslinking network, which imparts high wet strength to the substrate; (2) The hydrolysis product (Si-OH) of potassium methylsilicate undergoes a dehydration condensation reaction to form a polysiloxane (Si-O-Si) network, which provides hydrophobic properties.

[0019] Post-washing (step S5): After the composite network is formed by high-temperature curing, the sacrificial pore-forming agent (such as polyethylene glycol) acting as a temporary site-occupying agent is dissolved from the composite network by hot water washing, thereby forming through-hole micropores on the dense composite network and restoring the material's water permeability.

[0020] Preferably, the liquid carryover rate is controlled to be 80% to 110% during the first and second impregnation processes. By adopting the above technical solution, this liquid carryover rate range ensures sufficient adhesion of working fluid A and working fluid B to form a composite network, while avoiding increased drying energy consumption due to excessive liquid carryover.

[0021] Preferably, the intermediate drying temperature is 80–100°C, and the time is 2–5 minutes. By adopting the above technical solution, this process condition can effectively remove moisture and concentrate the working solution component A, preventing PVA and other components from degrading or undergoing unintended reactions before high-temperature curing.

[0022] Preferably, the high-temperature curing temperature is 140–170°C, and the time is 3–5 minutes. By adopting the above technical solution, this temperature and time range can ensure that the esterification and crosslinking reaction of PVA and the polycondensation reaction of potassium methylsilicate can both proceed fully, forming a structurally stable composite network.

[0023] Preferably, the temperature of the subsequent washing is 60–80°C. By adopting the above technical solution, hot water in this temperature range can dissolve polyethylene glycol as a sacrificial pore-forming agent without damaging the composite network that has already been cured at high temperature.

[0024] This invention provides an environmentally friendly geotextile based on recycled waste fibers and its preparation method. It has the following beneficial effects: 1. This invention uses polyvinyl alcohol (PVA) and polycarboxylic acid (citric acid) as a crosslinking system and cures it at high temperature under the action of a zirconium catalyst to form a PVA-polycarboxylic acid esterification crosslinking network between the fibers of the regenerated cellulose nonwoven fabric substrate. This network effectively enhances the bonding force between the fibers, significantly improves the wet mechanical strength of the geotextile, and solves the problem of low wet strength of the original regenerated cellulose substrate. 2. This invention employs a process of sequential impregnation with working solution A (acidic) and working solution B (alkaline, containing potassium methylsilicate). When the substrate carrying working solution A is immersed in working solution B, the sudden pH change triggers in-situ hydrolysis and condensation reaction of potassium methylsilicate, forming a layer of polysiloxane hydrophobic network (Si-O-Si) on the fiber surface. This hydrophobic network effectively coats the hydrophilic cellulose fibers, significantly reducing the water absorption rate of the geotextile and improving its water resistance. 3. This invention introduces a sacrificial pore-forming agent (polyethylene glycol) into the working solution A. This pore-forming agent is fixed within the formed composite network during the high-temperature curing step and dissolved in the final post-washing step, thereby forming microporous channels within the composite network. This design achieves high wet strength and low water absorption while retaining the vertical permeability required of geotextile as a filtration material. Attached Figure Description

[0025] Figure 1 This is a schematic diagram illustrating the mechanical properties of the present invention; Figure 2 This is a schematic diagram illustrating the water resistance performance of the present invention; Figure 3 This is a schematic diagram illustrating the water permeability of the present invention. Detailed Implementation

[0026] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] The main raw materials and reagents used in the following examples and comparative examples have the following sources and specifications. Reagents not specifically mentioned are all commercially available analytical grade or higher grade products.

[0028] Waste cotton textiles: These are derived from post-consumer waste clothing or textile production scraps, which are sorted, cleaned, and crushed, resulting in a cellulose content (mass fraction) greater than 95.0%. This raw material is used in the preparation example to prepare regenerated cellulose nonwoven fabric substrate.

[0029] N-Methylmorpholine-N-oxide: CAS No.: 7529-22-8; In the preparation example of this invention, an aqueous solution of NMMO with a mass fraction of 50.0% was used as a solvent for cellulose.

[0030] Polyvinyl alcohol: CAS No.: 9002-89-5; In this embodiment of the invention, PVA-1788 is specifically used, which is a partially alcoholyzed polyvinyl alcohol homopolymer with an average degree of polymerization of 1700±100 and a degree of alcoholysis of 87.0% to 89.0 mol.

[0031] Citric acid: CAS No.: 77-92-9; Anhydrous citric acid, a ternary organic carboxylic acid, is specifically used in this embodiment of the invention as the main crosslinking agent.

[0032] Zirconium acetylacetonate: CAS No.: 17501-44-9; used as a coupling catalyst in the embodiments of the present invention, which exhibits Lewis acid catalytic activity under acidic conditions and serves as a coupling center to anchor organic / inorganic components.

[0033] Zirconium acetate: CAS No.: 7585-20-8; used as a coupling catalyst in this embodiment of the invention, specifically using its aqueous solution, with an effective ZrO2 content (mass fraction) of 18.0%.

[0034] Polyethylene glycol: CAS No.: 25322-68-3; In the embodiments of this invention, PEG-4000 (number average molecular weight of 3500-4500 g / mol) and PEG-6000 (number average molecular weight of 5000-7000 g / mol) are specifically used, which act as water-soluble sacrificial template agents in the crosslinking network.

[0035] Potassium methylsilicate (PMS): CAS No.: 31795-24-1; In this embodiment of the invention, its aqueous solution is used, with an effective solid content (mass fraction) of 32.5%. It is an alkaline siloxane precursor and is used as a building material for hydrophobic networks.

[0036] Sodium hypophosphite monohydrate: CAS No.: 10039-56-2; used as a conventional comparative catalyst in the comparative example of this invention.

[0037] Preparation example: Preparation Example 1: Regenerated cellulose nonwoven fabric substrate (180 g / m²) 2 Preparation of ) This preparation example provides a mass per unit area of ​​180 g / m². 2 The regenerated cellulose nonwoven fabric substrate includes the following steps: (1) Dissolution: The waste cotton textile dry pulp described in the raw material section is mixed with a 50.0% NMMO aqueous solution (the mass ratio of NMMO to cellulose dry weight is 10:1) and propyl gallate (0.8% of the mass of NMMO); under a vacuum of -0.09MPa, the mixture is stirred and heated to 105℃ and kept warm for 2 hours to fully dissolve the cellulose, resulting in a spinning solution with a cellulose content (mass fraction) of 10.0%. (2) Spinning: After filtering the spinning solution from step (1), it is extruded through a spinneret with an aperture of 80 μm, passes through an air gap of 10 cm, and enters a deionized water coagulation bath at 10 °C to regenerate cellulose filaments. (3) Post-treatment: The regenerated fiber filaments are washed multiple times (to remove NMMO), oiled, dried at 110°C, and cut into regenerated cellulose short fibers with a length of 60 mm and a fineness of 2.5 dtex. (4) Substrate forming: The regenerated cellulose short fibers obtained in step (3) are opened, carded, and cross-laid (controlling the uniformity of the web laying), and then subjected to pre-needling and main needle-punching processes (needling density 450 needles / cm). 2 Prepared to a unit area mass of 180 g / m² 2 Nonwoven fabric substrate.

[0038] Preparation Example 2: Regenerated cellulose nonwoven fabric substrate (250 g / m²) 2 Preparation of ) This preparation example provides a unit area mass of 250 g / m². 2 The regenerated cellulose nonwoven fabric substrate includes the following steps: (1) Dissolving: Same as step (1) in preparation example 1; (2) Spinning: Same as step (2) in preparation example 1; (3) Post-processing: Same as step (3) of preparation example 1, to obtain regenerated cellulose short fibers; (4) Substrate forming: The regenerated cellulose short fibers obtained in step (3) are opened, carded, and cross-laid, and the lamination parameters are adjusted to increase the fiber content per unit area. Then, they are pre-needle-punched and main needle-punched (needle-punching density 550 needles / cm). 2 Prepared to a unit area mass of 250 g / m² 2 Nonwoven fabric substrate.

[0039] Example 1: This example provides a method for preparing an environmentally friendly geotextile, including the following steps: (1) Preparation of working solution A: Weigh 12.5 parts of PVA-1788 by mass, add 60 parts of deionized water at 85℃ and stir to dissolve, then cool to room temperature (20-30℃); add 7.5 parts of citric acid and 10 parts of PEG-6000 in sequence and stir to dissolve; finally add 1.2 parts of zirconium acetylacetonate and add deionized water to 100 parts, stir evenly and set aside. (2) Preparation of working solution B: Weigh 5.5 parts by weight of potassium methylsilicate (PMS) aqueous solution (solid content 32.5%), add it to deionized water, make up to 100 parts, stir well and set aside. (3) Preparation process: First impregnation: Take the nonwoven fabric substrate prepared in Example 1 (180 g / m²) 2 The sample is immersed in working fluid A at room temperature (20-30℃) and rolled using a rolling mill to control the liquid carry-over rate to 90%. Intermediate drying: Dry the damp cloth in a 90℃ hot air oven for 3 minutes; Second padding: The dried substrate is immersed in working solution B and rolled by a rolling mill, with the liquid content controlled at 90%. High-temperature curing: Cur the damp cloth in a high-temperature oven at 155℃ for 4 minutes; Post-washing: Wash the cured geotextile in hot deionized water at 70℃ for 8 minutes; Final drying: Dry the washed geotextile at 100℃ for 3 minutes to obtain the finished product.

[0040] Example 2: This example provides a method for preparing an environmentally friendly geotextile, including the following steps: (1) Preparation of working solution A: Weigh 10 parts of PVA-1788 by mass, add 60 parts of deionized water at 85℃ and stir to dissolve, cool to room temperature (20-30℃); add 5 parts of citric acid and 5 parts of PEG-6000 in sequence and stir to dissolve; finally add 0.5 parts of zirconium acetylacetonate and add deionized water to 100 parts, stir evenly and set aside. (2) Preparation of working solution B: Weigh 3 parts by weight of potassium methylsilicate (PMS) aqueous solution (solid content 32.5%), add it to deionized water, make up to 100 parts, stir well and set aside. (3) Preparation process: First impregnation: Take the nonwoven fabric substrate prepared in Example 1 (180 g / m²) 2 Immerse it in working fluid A at room temperature (20-30℃), and roll it with a rolling mill to control the liquid carry-over rate to 80%; Intermediate drying: Dry the damp cloth in an 80℃ hot air oven for 5 minutes; Second padding: The dried substrate is immersed in working solution B and rolled by a rolling mill, with the liquid content controlled at 80%. High-temperature curing: Cur the damp cloth in a high-temperature oven at 140℃ for 5 minutes; Post-washing: Wash the cured geotextile in hot deionized water at 60℃ for 10 minutes; Final drying: Dry the washed geotextile at 90℃ for 3 minutes to obtain the finished product.

[0041] Example 3: This example provides a method for preparing an environmentally friendly geotextile, including the following steps: (1) Preparation of working solution A: Weigh 15 parts of PVA-1788 by mass, add 60 parts of deionized water at 85℃ and stir to dissolve, cool to room temperature (20-30℃); add 10 parts of citric acid and 15 parts of PEG-6000 in sequence and stir to dissolve; finally add 2.0 parts of zirconium acetylacetonate and add deionized water to 100 parts, stir evenly and set aside. (2) Preparation of working solution B: Weigh 8 parts by weight of potassium methylsilicate (PMS) aqueous solution (solid content 32.5%), add it to deionized water, make up to 100 parts, stir well and set aside. (3) Preparation process: First impregnation: Take the nonwoven fabric substrate prepared in Example 2 (250 g / m²) 2 The sample is immersed in working fluid A at room temperature (20-30℃) and rolled using a rolling mill to control the liquid carry-over rate to 110%. Intermediate drying: Dry the damp cloth in a 100℃ hot air oven for 2 minutes; Second impregnation: The dried substrate is immersed in working solution B and rolled by a rolling mill, with the liquid content controlled at 110%. High-temperature curing: Cur the damp cloth in a 170℃ oven for 3 minutes. Post-washing: Wash the cured geotextile in hot deionized water at 80℃ for 5 minutes; Final drying: Dry the washed geotextile at 110℃ for 2 minutes to obtain the finished product.

[0042] Example 4: This example provides a method for preparing an environmentally friendly geotextile, including the following steps: (1) Preparation of working solution A: Weigh 12.5 parts of PVA-1788 by mass, add 60 parts of 85℃ deionized water and stir to dissolve, cool to room temperature (20-30℃); add 7.5 parts of citric acid and 10 parts of PEG-4000 in sequence and stir to dissolve; finally add 1.2 parts of zirconium acetate aqueous solution (effective ZrO2 content 18.0%), and add deionized water to 100 parts, stir evenly and set aside. (2) Preparation of working solution B: Weigh 5.5 parts by weight of potassium methylsilicate (PMS) aqueous solution (solid content 32.5%), add it to deionized water, make up to 100 parts, stir well and set aside. (3) Preparation process: First impregnation: Take the nonwoven fabric substrate prepared in Example 2 (250 g / m²) 2 Immerse it in working fluid A at room temperature (20-30℃), and roll it with a rolling mill to control the liquid carry-over rate to 100%; Intermediate drying: Dry the damp cloth in a 90℃ hot air oven for 3 minutes. Second padding: The dried substrate is immersed in working solution B and rolled by a rolling mill to control the liquid content to 100%; High-temperature curing: Cur the damp cloth in a 160℃ oven for 3 minutes. Post-washing: Wash the cured geotextile in hot deionized water at 70℃ for 8 minutes; Final drying: Dry the washed geotextile at 100℃ for 3 minutes to obtain the finished product.

[0043] Comparative example: Comparative Example 1: Compared with Example 1, the difference is that in the preparation of working solution A in step (1), 1.2 parts of zirconium acetylacetonate are replaced with an equimolar amount of sodium hypophosphite monohydrate (1.27 parts), while the other components and preparation process are the same.

[0044] Comparative Example 2: Compared with Example 1, the difference is that the second immersion (i.e., without using working liquid B, potassium methylsilicate) and the second rolling step in step (3) are omitted, while the remaining steps (including high-temperature curing and post-washing) are the same.

[0045] Comparative Example 3: Compared with Example 1, the difference is that: in the preparation of working solution A in step (1), 10 parts of PEG-6000 (sacrificial pore-forming agent) are not added, and the post-washing step is omitted in step (3). The remaining components and preparation process are the same.

[0046] Comparative Example 4: The difference from Example 1 is that all the chemical components (PVA, citric acid, zirconium acetylacetonate, PEG6000, potassium methylsilicate) of working solution A and working solution B in Example 1 were mixed and formulated into a single working solution according to the proportions in Example 1, for use in the subsequent padding step.

[0047] Comparative Example 5: The difference from Example 1 is that the nonwoven fabric substrate prepared in Example 1 was used directly as the comparison sample, and no chemical treatment steps were performed as in Example 1.

[0048] Test example: Test Example 1: Working Fluid Stability Test Experimental objective: This test case aims to verify the necessity of the pH-isolated dual-bath process (i.e., using acidic working solution A and alkaline working solution B separately) adopted in this invention, and to evaluate the chemical compatibility and stability of mixing all active components in a single working solution (such as Comparative Example 4).

[0049] The experimental steps are as follows: (1) Solution preparation

[0050] Solution A (Example 1): Prepare working solution A (containing PVA, citric acid, zirconium acetylacetonate, and PEG-6000) according to step (1) of Example 1.

[0051] Solution B (Example 1): Prepare working solution B (containing potassium methylsilicate) according to step (2) of Example 1.

[0052] Solution C (Comparative Example 4): Following the description of Comparative Example 4, all chemical components (PVA, citric acid, zirconium acetylacetonate, PEG-6000, potassium methylsilicate) contained in working solution A and working solution B in Example 1 were mixed in the same proportion and deionized water was added to bring the total to 100 parts.

[0053] (2) Observation methods

[0054] Place freshly prepared solutions A, B, and C into clean 100mL beakers and seal them to stand at room temperature (25±2℃). Visually observe and record the macroscopic state of the solutions at time points of 0 min, 15 min, 30 min, 60 min, and 120 min, focusing on whether turbidity, flocculent matter, gel, or precipitation occurs.

[0055] The experimental data are shown in Table 1: Table 1: Observation results of working fluid stability

[0056] Conclusion: The data from Test Example 1 (Table 1) demonstrate the necessity of using a separate two-bath process; Solution A (acidic bath) remained clear and stable for 120 minutes, indicating that citric acid, as a chelating agent, inhibited the hydrolysis and precipitation of zirconium acetylacetonate in the aqueous phase, forming a stable solution; the stability of solution B (alkaline bath) is consistent with the characteristic of potassium methylsilicate to maintain hydrolysis equilibrium under strongly alkaline conditions.

[0057] Solution C (the mixed bath of Comparative Example 4) underwent a chemical reaction upon mixing (0 min), resulting in turbidity and precipitation. The mechanism is as follows: the acidic substance (citric acid) in solution A neutralizes the alkaline substance (potassium methylsilicate) in solution B. Under conditions of decreased pH and instability, the hydrolysis-condensation reaction equilibrium of potassium methylsilicate (PMS) is disrupted, and the reaction proceeds towards condensation. The zirconium catalyst in the system acts as a catalytic center, accelerating this condensation reaction, which leads to the gelation and precipitation of the siloxane network in the solution (rather than on the surface of the fiber substrate).

[0058] The results indicate that a process route that mixes all active components (acidic crosslinking system, zirconium catalyst, and basic hydrophobic precursor) in a single working solution is not feasible and cannot yield a stable working solution suitable for industrial padding. The technical solution of this invention (as in Examples 1-4) employs a pH-isolated two-bath process to separate two chemically incompatible systems in the process sequence. This solution utilizes the fiber substrate as a reaction carrier, bringing the two systems into contact during the second padding. In-situ polymerization is achieved through a pH mutation occurring on the fiber surface, thus resolving the chemical incompatibility of the working solution and making the solution technologically feasible.

[0059] Test Example 2: Mechanical Performance Test Experimental Objective: This test aims to evaluate the mechanical properties of the examples and comparative samples under dry and wet conditions, particularly the breaking strength and wet strength retention rate. This test verifies the improvement effect of the present invention's technical solution on the wet strength of the substrate.

[0060] The experimental steps are as follows: (1) Samples from Examples 1-4, Comparative Examples 1-3 and Comparative Example 5 were selected; (2) In accordance with GB / T-15788-2017 Geotextiles and Related Products - Wide Strip Tensile Test, all test samples were conditioned for 24 hours under standard atmospheric conditions (temperature 20±2℃, relative humidity 65±5%). (3) Take the conditioned sample and test it on a tensile testing machine, and record its dry breaking strength (kN / m). (4) Take another conditioned sample and immerse it in deionized water at (25±2℃) for 24 hours. After taking out the sample, immediately test it on a tensile testing machine and record its wet breaking strength (kN / m); (5) Calculate the wet strength retention rate according to the formula: Wet strength retention rate (%) = (wet fracture strength / dry fracture strength) × 100%.

[0061] The experimental data are shown in Table 2: Table 2: Mechanical Performance Test Data

[0062] Note: The dry strength baseline values ​​of Examples 3 and 4 are higher than those of other samples because they adopted the 250 g / m² value of Preparation Example 2. 2 The substrate was used, while the other samples used the 180 g / m² substrate from Preparation Example 1. 2 Substrate.

[0063] Conclusion: Refer to Appendix Figure 1 and Table 2;

[0064] The wet strength retention rate of Comparative Example 5 (untreated substrate) (32.3%) indicates that the regenerated cellulose substrate has low wet strength due to the disruption of the hydrogen bond network in water.

[0065] Comparative Example 2 (PVA / citric acid / zirconium treatment only, lacking PMS) showed a higher wet strength retention rate (74.9%) than Comparative Example 5; this demonstrates that the cross-linked network formed by PVA, citric acid, and zirconium catalyst bonds cellulose and PVA, improving the wet strength of the substrate.

[0066] The wet strength retention rates (87.0%-94.5%) of Examples 1-4 were improved compared to Comparative Example 2. The comparison between Example 1 (92.7%) and Comparative Example 2 (74.9%) showed the effect of the hydrophobic network formed by potassium methylsilicate (PMS). This hydrophobic network coats the outside of the cross-linked fiber structure, reduces the penetration of water into the fiber interior, protects the esterification bond network of PVA / cellulose, and improves the wet strength retention rate.

[0067] The wet strength retention rate of Comparative Example 1 (using SHP catalyst) (58.6%) was lower than that of Example 1 (92.7%) and Comparative Example 2 (74.9%); this indicates that in this multi-component system of PVA and citric acid, the efficiency of the SHP catalyst is lower than that of the zirconium coupling catalyst selected in this invention; in addition to catalyzing esterification reactions, zirconium catalysts (such as zirconium acetylacetonate) can also serve as coupling centers to anchor the PVA / cellulose network and the PMS network.

[0068] Comparative Example 3 (lacking PEG pore formation) had the highest wet strength retention rate (96.8%), because the intact composite film layer (without pores) provided stronger mechanical bonding and hydrophobic barrier. Example 1 (92.7%) had a wet strength retention rate close to that of Comparative Example 3, indicating that the microporous structure formed by the dissolution of the sacrificial pore-forming agent (PEG) did not significantly damage the integrity and hydrophobic protection of the composite network, thus retaining high wet strength performance.

[0069] The present invention solves the problem of low wet strength of regenerated cellulose substrate by using composite crosslinking of PVA / citric acid / zirconium catalyst, combined with the construction of hydrophobic network of potassium methylsilicate, and the application of sacrificial pore-forming agent, while retaining the permeability of geotextile.

[0070] Test Example 3: Water Resistance Test Experimental objective: This test case aims to evaluate the water absorption rate of the example and comparative samples, in order to quantify and verify the effectiveness of the hydrophobic network (i.e., potassium methylsilicate system) constructed by the technical solution of the present invention, and the degree of improvement on the hydrophilicity of the substrate.

[0071] The experimental steps are as follows: (1) Take samples from Examples 1-4, Comparative Examples 1-3 and Comparative Example 5; (2) The test method for water absorption rate is in GB / T-21655.1-2008 "Textiles - Evaluation of moisture absorption and quick-drying properties - Part 1: Single combination test method"; (3) Dry all samples to be tested in a 60℃ oven to constant weight, weigh them, and record their dry weight. ); (4) Completely immerse the constant-weight sample in deionized water at (25±2℃) for 24 hours. (5) Remove the sample, hang it for 1 minute to drip off excess surface moisture, and immediately weigh its wet mass. ); (6) Calculate the water absorption rate: .

[0072] The experimental data are shown in Table 3: Table 3: Water Absorption Rate Test Data

[0073] Note: Examples 3 and 4 and Comparative Examples 3 and 5 The baseline values ​​differ because they are based on substrates with different basis weights; the water absorption rate data in Table 3 can be used to create a bar chart to visually show the differences in water resistance between the samples.

[0074] Conclusion: Refer to Appendix Figure 2 The water absorption rate data in Table 3 reflects the sample's resistance to moisture and verifies the technical mechanism of the present invention.

[0075] Comparative Example 5 (untreated substrate) had a water absorption rate as high as 412.9%, demonstrating the hydrophilicity of the regenerated cellulose material itself due to the presence of a large number of exposed hydroxyl groups.

[0076] Comparative Example 2 (lacking PMS hydrophobic treatment) still had a high water absorption rate (237.9%); this indicates that although the cross-linked network formed by PVA / citric acid / zirconium improved the wet strength (as shown in Test Example 2), the network itself was still hydrophilic (PVA and citric acid are both rich in polar groups) and could not prevent water intrusion.

[0077] The water absorption rates of Examples 1-4 (21.4%-38.2%) were all reduced by an order of magnitude compared to Comparative Example 2 (237.9%). This demonstrates the mechanism of the invention: potassium methylsilicate (PMS) introduced during the second padding process hydrolyzes and condenses under the in-situ pH abrupt change on the acidic substrate surface, forming a hydrophobic polysiloxane network covering the fiber surface. This network prevents water molecules from contacting the internal hydrophilic cellulose / PVA matrix, thus making the material as a whole hydrophobic.

[0078] The data for Example 2 (38.2%) and Example 3 (21.4%) correspond to the lower and upper limits of chemical dosage, respectively; the results show that the high concentration of PMS (Example 3) formed a denser hydrophobic network, resulting in a further reduction in water absorption.

[0079] Comparative Example 3 (non-porous) had the lowest water absorption rate (14.6%) among all samples; this is consistent with its physical structure, in which a non-porous, dense composite membrane layer provides a hydrophobic barrier.

[0080] Compared with Comparative Example 1 (25.8%) and Comparative Example 3 (14.6%), the water absorption rate of Example 1 was slightly higher. This phenomenon demonstrates the role of the sacrificial pore-forming agent (PEG): PEG is dissolved in the post-washing step, forming a microporous structure on the hydrophobic network (which leads to a slight increase in water absorption rate), thereby providing a physical channel for subsequent water permeability (Test Example 4).

[0081] The data from Test Example 3 confirms that the present invention constructs a hydrophobic network using a potassium methylsilicate (PMS) system, thus solving the hydrophilicity problem of the substrate. Furthermore, by combining it with a sacrificial pore-forming agent (PEG), hydrophobicity is achieved while retaining the pore structure required for water permeability.

[0082] Test Example 4: Permeability Test Experimental Objective: This test case aims to evaluate the vertical permeability of the example and comparative samples, which is a core functional indicator of geotextile as a filtration and drainage material. This test is used to verify whether the sacrificial pore-forming agent (PEG) in the technical solution of this invention has successfully formed effective permeable channels after constructing cross-linked and hydrophobic networks.

[0083] The experimental steps are as follows: (1) Test samples: Examples 1-4, Comparative Examples 1-3 and Comparative Example 5; (2) Test standard: According to GB / T-15789-2016 Geotextiles and related products - Determination of vertical permeability, the constant head method is adopted; (3) Sample preparation: Immerse all samples to be tested in deionized water at (25±2℃) for 24 hours to ensure that the samples (especially those treated with hydrophobicity) are fully wetted before testing to eliminate interference from air bubbles during the testing process. (4) Test method: The wetted sample is installed in the sample tube of the vertical permeameter and a constant water head pressure of 50 mm is applied; after the water flow reaches a stable state through the sample, the timing is started and the amount of water (V) that permeates through the sample in 180 seconds (s) is collected. (5) Data calculation: Based on the collected water volume (V), sample thickness (L, see Table 4), and sample area (A, fixed at 50 cm²), 2 The vertical permeability coefficient was calculated using the test time (t=180s) and head difference (H=5cm).

[0084] The experimental data are shown in Table 4: Table 4: Vertical penetration performance test data

[0085] Conclusion: Refer to Appendix Figure 3 Table 4 shows the effects of different chemical treatments on the vertical permeability coefficient of geotextiles.

[0086] The permeability coefficient of Comparative Example 5 (untreated substrate) was 0.094 cm / s; the permeability coefficient of Comparative Example 2 (PVA / Zr treatment only, no PMS) was 0.081 cm / s, indicating that the PVA crosslinking network slightly filled the pores, but the substrate still maintained high water permeability.

[0087] The permeability coefficient (0.00014 cm / s) of Comparative Example 3 (lacking PEG pore-forming agent) is close to 0. After PVA / Zr crosslinking and PMS hydrophobic treatment, the composite network (PVA / Zr crosslinked network and PMS hydrophobic network) formed on the surface of this sample, due to the absence of a sacrificial pore-forming agent, resulted in the blockage of pores between fibers. Without the pore-forming step, the remaining components would cause the material to form a hydrophobic membrane (refer to Test Example 3), losing the permeability function of the geotextile.

[0088] The permeability coefficients of Examples 1-4 (0.039-0.068 cm / s) were all higher than those of Comparative Example 3 (0.00014 cm / s); this comparison demonstrates the role of sacrificial pore-forming agent (PEG); PEG was blended with the PVA / Zr system as a site-filling agent before high-temperature curing, and was dissolved in the post-washing step after curing, forming interconnected microporous channels in the composite network, thus enabling the material to achieve water permeability.

[0089] The permeability coefficient of Example 2 (low concentration component) (0.068 cm / s) is higher than that of Example 3 (high concentration component, 0.039 cm / s); the high concentration of chemicals (Example 3) forms a thicker composite network, resulting in increased resistance to water flow; the low concentration of chemicals (Example 2) forms a thinner composite network, with correspondingly lower pore resistance.

[0090] Combining the data from Test Example 2 (wet strength) and Test Example 3 (water absorption), the present invention improves the problems of low wet strength and high water absorption of regenerated cellulose substrates by combining the crosslinking of PVA / Zr, the hydrophobic construction of PMS, and the sacrificial pore formation of PEG, while retaining the vertical permeability required for the material as a geotextile.

[0091] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An environmentally friendly geotextile based on recycled waste fibers, characterized in that, include: Regenerated cellulose nonwoven fabric substrate; A microporous composite network attached to the regenerated cellulose nonwoven fabric substrate, wherein the microporous composite network is formed by the reaction and curing of working solution A and working solution B and subsequent washing; The working solution A is an acidic solution containing polyvinyl alcohol, a polycarboxylic acid crosslinking agent, a sacrificial pore-forming agent, and a zirconium-based catalyst. The working solution B is an alkaline solution containing potassium methylsilicate.

2. The environmentally friendly geotextile based on recycled waste fibers according to claim 1, characterized in that, The microporous composite network is formed by the reaction and curing of working solution A and working solution B, which contain the following raw materials in parts by weight: The working fluid A, based on 100 parts by weight, is made from raw materials comprising the following parts by weight: 10-15 parts of polyvinyl alcohol; 5-10 parts of polycarboxylic acid crosslinking agent; 5-15 parts of sacrificial pore-forming agent; Zirconium-based catalyst, 0.5–2.0 parts; Remaining water; The working fluid B, on a 100-part basis, is made from raw materials comprising the following parts by weight: 3-8 parts of potassium methylsilicate aqueous solution; Remaining water.

3. The environmentally friendly geotextile based on recycled waste fibers according to claim 2, characterized in that, The working solution A, based on 100 parts by weight, is made from the following raw materials comprising: 12.5 parts polyvinyl alcohol; 7.5 parts polycarboxylic acid crosslinking agent; 10 parts sacrificial pore-forming agent; 1.2 parts zirconium catalyst; and the balance being water; the working solution B, based on 100 parts by weight, is made from the following raw materials comprising: 5.5 parts potassium methylsilicate aqueous solution; and the balance being water.

4. The environmentally friendly geotextile based on recycled waste fibers according to claim 1, characterized in that, The polyvinyl alcohol is PVA-1788; the polycarboxylic acid crosslinking agent is citric acid.

5. The environmentally friendly geotextile based on recycled waste fibers according to claim 1, characterized in that, The sacrificial pore-forming agent is polyethylene glycol; the zirconium-based catalyst is zirconium acetylacetonate or zirconium acetate aqueous solution.

6. A method for preparing the environmentally friendly geotextile based on waste fiber recycling according to any one of claims 1-5, characterized in that, Includes the following steps: The regenerated cellulose nonwoven fabric substrate is immersed in working solution A, which contains polyvinyl alcohol, polycarboxylic acid crosslinking agent, sacrificial pore-forming agent and zirconium catalyst, for the first impregnation. The regenerated cellulose nonwoven fabric substrate after the first impregnation treatment is subjected to intermediate drying; The intermediate-dried regenerated cellulose nonwoven fabric substrate is immersed in working solution B containing potassium methylsilicate for a second impregnation. The regenerated cellulose nonwoven fabric substrate after the second impregnation treatment is cured at high temperature to form a composite network; The regenerated cellulose nonwoven fabric substrate after high-temperature curing is then washed to dissolve the sacrificial pore-forming agent and form micropores.

7. The method for preparing an environmentally friendly geotextile based on recycled waste fibers according to claim 6, characterized in that, The first and second impregnation processes control the liquid carryover rate to be 80%–110%.

8. The method for preparing an environmentally friendly geotextile based on recycled waste fibers according to claim 6, characterized in that, The intermediate drying temperature is 80-100℃, and the time is 2-5 minutes.

9. The method for preparing an environmentally friendly geotextile based on recycled waste fibers according to claim 6, characterized in that, The high-temperature curing temperature is 140-170℃, and the time is 3-5 minutes.

10. The method for preparing an environmentally friendly geotextile based on recycled waste fibers according to claim 6, characterized in that, The temperature of the subsequent washing is 60–80°C.

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