Method for manufacturing a herbicidal and moisturizing nonwoven fabric and use thereof

Abstract

The application discloses a kind of herbicide moisture-retention nonwoven fabric manufacturing method and its application, belong to soil covering material technical field.The nonwoven fabric includes upper covering layer, intermediate support layer and lower contact layer, the upper surface of upper covering layer is loaded with reflective filler particles and hydrophobic wax layer, the lower surface of lower contact layer is loaded with sodium carboxymethyl cellulose, sodium alginate and bacteriostatic anti-degradation agent water-absorbing coating, the asymmetric wetting gradient with static water contact angle difference ≥80 ° is formed between upper covering layer and lower contact layer, realize liquid water one-way downward transmission and inhibit reverse evaporation;The reflectivity of upper covering layer is ≥0.80, infrared emissivity is ≥0.85, with daytime radiation cooling function;Total gram weight 230~290g / m 2 , photosynthetic active radiation transmittance <5%, weed control by physical shading;Lower contact layer is crosslinked by citric acid, and the degradation half-life period is adjustable for 6~12 months.The application has the properties of weeding, moisture-retention and cooling, and the degradation period is controllable, suitable for forest seedling raising.

Description

Technical Field

[0001] This invention relates to the field of soil cover materials technology, and in particular to a method for manufacturing a weed-controlling and moisture-retaining nonwoven fabric and its application. Background Technology

[0002] In the process of forest tree seedling cultivation and seedling production, weed control and soil moisture management are key factors affecting seedling survival rates. Traditional methods include manual weeding, chemical herbicides, and plastic film mulching. Manual weeding is time-consuming, labor-intensive, and costly. While chemical herbicides are highly efficient, they pose problems such as environmental pollution, soil residues, and herbicide resistance, and are more likely to cause phytotoxicity to sensitive seedlings.

[0003] Plastic mulching is a commonly used physical method for weed control and soil water retention. However, the amount of traditional polyethylene mulch film remaining in the soil is increasing year by year. This can block soil capillaries, disrupt water and air transport channels, damage soil structure, and gradually break down into microplastics, which can enter the human body through the food chain, posing potential health hazards. my country's agricultural film recycling rate has long been low, with large amounts of film remaining in the fields. To address this problem, biodegradable mulch films have been promoted in recent years, but existing biodegradable mulch films still face challenges in practical applications, including a degradation rate that heavily depends on environmental conditions, a difficulty in matching the degradation period with the crop growth cycle, and relatively high overall costs.

[0004] As an alternative, weed-control fabrics are mainly made of polypropylene or polyester spunbond nonwoven fabrics, which suppress weed growth through physical shading. However, these products mostly use non-degradable synthetic fibers, and after long-term use, fragments accumulate in the soil, leading to soil degradation. Existing weed-control and moisture-retaining composite fabrics, while combining weed control and moisture retention functions, use polyester nonwoven fabric as the base material, load with chemical herbicides, and use superabsorbent resin as the moisture-retaining layer. This poses both environmental risks from chemical herbicides and plastic pollution due to the non-degradability of polyester. Furthermore, existing products generally lack heat protection for shallow-rooted seedlings in the high temperatures of summer.

[0005] Therefore, there is an urgent need for the forestry seedling industry to develop an agricultural covering material that can physically shade and control weeds, provide long-lasting moisture retention, actively reduce root zone temperature during the hot summer season, and has a controllable degradation cycle. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing technologies by proposing a method for manufacturing weed-removing and moisture-retaining nonwoven fabric and its application.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A method for manufacturing a weed-controlling and moisture-retaining nonwoven fabric includes the following steps: (1) Wet web forming and crosslinking pretreatment: The upper cover layer fiber, the middle support layer fiber and the lower contact layer fiber are wet web formed to obtain the upper cover layer base fabric, the middle support layer base fabric and the lower contact layer base fabric; wherein, after the lower contact layer base fabric is web formed, it is subjected to crosslinking pretreatment to obtain the crosslinked pretreated lower contact layer base fabric.

[0008] (2) Top Cover Coating: A coating liquid containing reflective filler particles and oxidized starch is coated on the upper surface of the top cover base fabric and dried to obtain the top cover functional base fabric; in the coating liquid, the mass ratio of reflective filler particles to oxidized starch dry base is (2-5):1, the mass ratio of water to the total mass of reflective filler particles and oxidized starch dry base is (4-10):1, and the coating amount is 10-25 g / m² (dry weight). 2 The reflective filler particles are BaSO4 with a particle size of 200 nm to 2 μm.

[0009] (3) Hot pressing composite: The upper cover layer functional base fabric, the middle support layer base fabric and the cross-linked pretreated lower contact layer base fabric are stacked, and polylactic acid hot melt mesh film is placed between the layers. The composite nonwoven fabric is obtained by hot pressing at 155-165℃.

[0010] (4) Wax layer application and water-absorbing coating crosslinking: Wax powder and hydrophobic fumed silica are applied to the upper surface of the upper cover layer of the composite nonwoven fabric. The mass ratio of wax powder to hydrophobic fumed silica is (19-99):1. After being melted by infrared heating, the wax layer is naturally cooled to form a hydrophobic wax layer. A coating liquid containing sodium carboxymethyl cellulose, sodium alginate and antibacterial and anti-degradation agent is applied to the lower surface of the lower contact layer of the composite nonwoven fabric. Then, CaCl2 solution is used for ion crosslinking and curing to obtain the weed-removing and moisture-retaining nonwoven fabric.

[0011] Preferably, in step (1), the upper covering layer fiber comprises jute fiber and wood pulp fiber in a mass ratio of 70:30; the middle support layer fiber comprises jute fiber and core-sheath type polylactic acid bicomponent short fiber in a mass ratio of 90:10; and the lower contact layer fiber comprises cotton linter fiber.

[0012] Preferably, in step (1), the concentration of the wet web forming is 0.02-0.05%; the crosslinking pretreatment involves immersing the lower contact layer base fabric after wet web forming in an aqueous solution containing citric acid and sodium hypophosphite, curing it at 140-160°C for 3-5 minutes, and then washing and drying it; the amount of citric acid used is 5-17% of the dry weight of the lower contact layer fiber, and the amount of sodium hypophosphite used is 50% of the amount of citric acid used; the bath ratio of the impregnation is 1:20.

[0013] Preferably, in step (3), the polylactic acid hot melt web film has a basis weight of 6 g / m². 2 .

[0014] Preferably, in step (4), the wax powder is either carnauba wax or plant-derived fatty acid wax, the particle size D50 of the wax powder is 10-30 μm, and the spreading amount is 2-6 g / m³. 2 The hydrophobic fumed silica has a particle size of 50–200 nm.

[0015] Preferably, in step (4), the infrared heating is to control the fabric surface temperature at 90-110°C, and the wax powder melts and then naturally cools and crystallizes at room temperature.

[0016] Preferably, in step (4), the coating liquid is composed of sodium carboxymethyl cellulose, sodium alginate, antibacterial and antidegradation agent and water in a mass ratio of 6:3:2:2000; the antibacterial and antidegradation agent is any one of tannic acid, chitosan or chitosan quaternary ammonium salt.

[0017] Preferably, in step (4), the specification of the weed-controlling and moisture-retaining nonwoven fabric is 230-290 g / m². 2 The photosynthetically active radiation transmittance is <5%.

[0018] Preferably, in step (4), the weighted average reflectance of the upper cover layer of the weed-removing and moisture-retaining nonwoven fabric under the AM1.5 standard solar spectrum is ≥0.80, and the infrared emissivity in the atmospheric window 8-13μm band is ≥0.85; the static water contact angle of the upper cover layer of the weed-removing and moisture-retaining nonwoven fabric is ≥130°, and the roll-off angle is <20°; the difference in static water contact angle between the upper surface of the upper cover layer and the lower surface of the lower contact layer of the weed-removing and moisture-retaining nonwoven fabric is ≥80°, forming an asymmetric wettability gradient.

[0019] The application of the weed-controlling and moisture-retaining nonwoven fabric in forest tree seedling cultivation and / or seedling cultivation involves laying the weed-controlling and moisture-retaining nonwoven fabric in the seedbed or between planting rows with the upper covering layer facing upwards and the lower contact layer in contact with the soil. The asymmetric wettability gradient enables irrigation water to penetrate downwards and inhibits soil moisture from evaporating upwards.

[0020] The preparation principle and mechanism of action of the weed-killing and moisture-retaining nonwoven fabric of this invention are explained as follows: I. Preparation Principle: 1. Fiber selection and wet web forming: The upper cover layer is made of jute fiber and wood pulp fiber, such as bleached sulfate wood pulp, in a mass ratio of 70:30. Jute fiber has high crystallinity, and the natural micropores and rough morphology of the fiber surface provide a structured substrate for subsequent anchoring of reflective filler particles and wax layers. The addition of wood pulp short fibers improves the uniformity of wet web formation, ensuring that the fiber pore network retains necessary gas permeation channels after receiving the coating liquid. The intermediate support layer is mainly jute, supplemented with core-sheath type polylactic acid bicomponent short fibers (90:10). The melting point of the sheath of these short fibers is about 130-140℃, significantly lower than the melting point of the core layer (about 165-175℃). In the subsequent hot pressing process, the sheath preferentially melts to form bonding points, giving the intermediate layer mechanical coherence without the need for external chemical adhesives. The lower contact layer uses cotton linter fibers with a cellulose content of over 95% and abundant surface hydroxyl groups, providing reaction sites for subsequent cross-linking treatment and anchoring of the water-absorbing coating.

[0021] 2. Crosslinking pretreatment: The lower contact layer substrate is cured at 140–160 °C in a citric acid and sodium hypophosphite system. At high temperature, the two adjacent carboxyl groups in the citric acid molecule first dehydrate to form a five-membered cyclic anhydride intermediate, which then undergoes esterification with the hydroxyl groups of cellulose to generate ester crosslinks. Sodium hypophosphite catalyzes the formation of the anhydride and inhibits the degradation of the cellulose backbone under acidic conditions during this process. The crosslinking treatment introduces residual carboxyl groups into the lower contact layer fibers, improving the interfacial adhesion between the subsequent hydrophilic absorbent coating and the substrate, while also significantly enhancing the dimensional stability of the lower contact layer under water-saturated conditions.

[0022] 3. Construction of coating liquid and wax layer: The top coating uses oxidized starch as a biodegradable binder, blended with BaSO4 reflective filler particles with a particle size of 200 nm to 2 μm. The oxidized starch firmly anchors the filler particles to the surface of the top coating fiber, forming a radiation-cooling functional layer after drying. The wax layer uses carnauba wax or plant-derived fatty acid wax micropowder (particle size D50 of 10–30 μm), which is sprinkled on the surface of the top coating in solid powder form and then heated to 90–110 °C by infrared heating to melt and spread, followed by natural slow cooling and crystallization. Carnauba wax has a melting point of approximately 82–86 °C, and 90–110 °C is sufficient for it to completely melt and spread without thermal decomposition. Slow cooling is key to controlling the formation of a hierarchical micro-nano rough structure of wax crystals—wax esters and fatty alcohol molecules have sufficient time to assemble into lamellar crystals and needle-like protrusions during slow cooling, creating the surface roughness required for hydrophobicity; rapid cooling will result in an overly smooth wax film, making it difficult to achieve the Cassie-Baxter cushion state required for strong hydrophobicity. Furthermore, the introduction of nano-hydrophobic silica into the wax layer serves two purposes. First, it co-crystallizes with the wax crystals during slow cooling, constructing a micro-nano composite rough structure that significantly enhances the hardness and wear resistance of the wax layer. Second, nano-silica exhibits strong ultraviolet scattering, effectively inhibiting the photocatalytic degradation and aging of natural wax. Simultaneously, the molten wax penetrates into the fiber micro-gap and solidifies, forming a "deeply rooted" mechanical interlock. Even with slight surface wear, the anchored wax layer remaining on the shallow surface can still maintain the necessary hydrophobicity.

[0023] 4. Water-absorbing coating and ion crosslinking: A mixed coating solution of sodium carboxymethyl cellulose and sodium alginate was applied to the lower surface of the contact layer and then treated with calcium chloride solution. Calcium ions formed an egg-box coordination structure with the guluronic acid blocks in sodium alginate, and simultaneously formed ion bridges with the carboxymethyl groups of sodium carboxymethyl cellulose. The two networks interpenetrated to construct a three-dimensional network hydrogel layer with both high water absorption and water insolubility. To further slow down the biodegradation rate of the coating in moist soil rich in microorganisms, antibacterial and anti-degradation agents were introduced into the coating solution. When tannic acid was selected, its abundant ortho-phenolic hydroxyl groups formed a dense multi-hydrogen bond network with polysaccharide molecules, endowing the coating with broad-spectrum antibacterial properties and preventing microorganisms from colonizing the coating surface. When chitosan quaternary ammonium salt was selected, it dissolved under neutral conditions and formed polyelectrolyte complex microdomains with polysaccharides, enhancing network strength while providing antibacterial function. This design ensures that the coating maintains its moisture retention function during the 6-12 month seedling cycle. When using ordinary chitosan, it can be pre-dissolved in dilute acetic acid and then mixed with the polysaccharide solution. The electrostatic interaction between amino and carboxyl groups forms a polyelectrolyte complex, which also imparts antibacterial properties to the coating and enhances the network structure.

[0024] 5. Hot-pressing composite: A layer of polylactic acid (PLA) hot-melt web is placed between each of the three base fabric layers, and the layers are hot-pressed together at 155–165°C. This temperature window is higher than the melting point of the PLA sheath and the hot-melt web (approximately 130–150°C), but lower than the thermal degradation initiation temperature of jute and cotton fibers (the hemicellulose component decomposes at approximately 200°C), ensuring that the fiber body is not damaged by heat. The molten PLA penetrates into the pores of adjacent fiber layers under pressure, and after cooling, forms a mechanical interlock that runs through the interfaces of each layer.

[0025] II. Mechanism of Action: 1. Unidirectional water transport driven by asymmetric wettability gradient: After being treated with carnauba wax, the upper surface of the upper cover layer has a static water contact angle of ≥130°. The lower surface of the lower contact layer has a contact angle of ≤50° due to the intrinsic hydrophilicity of cotton fibers and the composite water-absorbing coating of sodium carboxymethyl cellulose and sodium alginate. The difference in contact angle between the two sides is ≥80°, forming an asymmetric wettability gradient from the hydrophobic surface to the hydrophilic surface.

[0026] When the upper surface of the cover layer comes into contact with irrigation water, the droplets are forced into the fabric pores under gravity. Once the tip of the droplet reaches the interface between the hydrophilic intermediate support layer and the lower contact layer fibers, capillary action is generated within the pores of the hydrophilic layer, continuously pumping water downwards to the lower contact layer and ultimately infiltrating the soil. Asymmetric wettability results in a significant difference in the critical breakthrough pressure between the hydrophobic and hydrophilic sides—low forward breakthrough pressure and high reverse breakthrough pressure—thus giving the fabric "fluid diode" behavior: water flows freely downwards, while evaporation is hindered in the reverse direction.

[0027] In the reverse path, the bound water in the lower contact layer water-absorbing coating must first overcome the strong hydrogen bonding with carboxyl and hydroxyl groups before it can escape through phase transition; the vaporized water vapor encounters the hydrophobic channels of the upper cover layer during its upward diffusion. The hydrophobic pore walls have no affinity for gaseous water molecules, and the water vapor migrates only through molecular diffusion driven by the concentration gradient, and its transport flux is much lower than that of the liquid flow driven by forward capillary.

[0028] 2. The daytime radiative cooling effect of reflective filler particles: The weighted average reflectance of the BaSO4 filler particles on the upper surface of the overlay layer is ≥0.80 in the AM1.5 standard solar spectrum (0.3–2.5 μm band), and the infrared emissivity in the atmospheric window (8–13 μm band) is ≥0.85. The passive radiative cooling principle is based on two parallel processes: the atmosphere is nearly transparent in the 8–13 μm band, allowing objects to directly emit infrared thermal radiation into outer space (approximately a 3K cold trap) through this window; simultaneously, it maximizes the reflection of solar radiation at wavelengths of 0.3–2.5 μm, reducing radiative heat gain. These two processes work together to achieve passive cooling of the object significantly lower than the surface temperature of bare soil and heat-absorbing overlays under similar conditions, without consuming external energy.

[0029] The selection of the reflective filler particle size between 200 nm and 2 μm has a clear optical basis: according to Mie scattering theory, the scattering efficiency reaches its maximum when the particle size matches the target light wavelength. The particle size distribution of 200 nm to 2 μm effectively covers the main energy band of the solar spectrum (visible light 400–700 nm and near-infrared 0.7–2.5 μm), achieving efficient broadband reflection. This particle size is much smaller than the atmospheric window wavelength of 8–13 μm, making the particles nearly transparent to the mid-infrared band. The mid-infrared emission of the upper covering layer mainly relies on the molecular vibration absorption of COC, C-OH, and ester carbonyl groups in jute and cotton fibers, as well as the ester carbonyl groups in the wax layer. This constructs a dual-mechanism synergistic system of "strong scattering of solar-band particles and mid-infrared fiber matrix emission," maintaining a lower temperature on the fabric surface under direct sunlight and further weakening the thermodynamic driving force of liquid water evaporating into gas.

[0030] 3. Physical shading for weed control: Total weight of nonwoven fabric: 230-290 g / m 2 By combining the scattering and extinction of reflective filler particles with the high-density coverage of the fiber network, the transmittance in the photosynthetically active radiation band (PAR, 400–700 nm) is reduced to <5%. The light compensation point of a plant is the minimum light threshold required to maintain a positive carbon balance. When the light intensity is below the light compensation point, respiration consumption exceeds photosynthetic carbon assimilation, and the plant cannot accumulate dry matter. A transmittance of <5% means that the actual light intensity after application is far lower than the light compensation point of most germinating weeds (especially common C3 and some C4 weed seedlings). Seedlings yellow and die due to continuous light starvation, failing to establish themselves as mature plants. This weeding mechanism is purely physical and does not chemically interfere with the soil microbial community.

[0031] 4. Synergistic moisture retention function of chemical cross-linking and ionic cross-linking: After the lower contact layer cotton linters are cross-linked with citric acid / sodium hypophosphite, ester cross-linking points are introduced between the cellulose molecular chains, reducing the molecular accessibility of cellulase to β-1,4-glycosidic bonds and slowing down the microbial degradation rate of the fiber in the soil environment. The degradation cycle can be controlled within a certain range by adjusting the amount of citric acid and the curing temperature. The sodium carboxymethyl cellulose-sodium alginate composite absorbent coating on the lower surface of the lower contact layer is treated with Ca... 2+ After ionic cross-linking, Ca 2+ The egg-box coordination structure with sodium alginate and guluronic acid blocks anchors the coating to the surface of the lower contact layer fibers in an insoluble but swellable form, allowing for rapid water absorption and storage after irrigation or rainfall, and maintaining the integrity of the three-dimensional network during repeated wet-dry cycles without easy loss. Combined with the Janus structure, which is hydrophobic on top and hydrophilic on the bottom, which inhibits evaporation, the effective retention time of a single irrigation water in the rhizosphere soil can be significantly extended.

[0032] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention utilizes the hydrophobic wax layer of the upper cover layer and the lower contact layer Ca 2+ The cross-linked hydrophilic and absorbent coating creates an asymmetric wettability gradient. During irrigation, water is rapidly pumped downwards and infiltrates under the combined force of gravity and capillary action of the hydrophilic layer; during evaporation, water vapor migrates only through low-flux molecular diffusion in the hydrophobic channels. This fluid diode behavior, characterized by "unimpeded downward water flow and impeded reverse evaporation," achieves the dual functions of rapid water permeability and efficient evaporation suppression.

[0033] 2. This invention involves coating the upper surface of the base fabric with a coating liquid containing BaSO4 reflective filler (particle size 200nm~2μm) and oxidized starch to form a radiative cooling functional layer. The BaSO4 particles provide efficient broadband reflection of the main energy bands of the solar spectrum while remaining nearly transparent to the mid-infrared band. Mid-infrared emission primarily relies on the molecular vibrational absorption of COC, C-OH groups in jute and cotton fibers, as well as the ester carbonyl groups in the wax layer, constructing a dual-mechanism synergistic system of "solar band particle scattering and mid-infrared band fiber emission." Combined with the self-cleaning properties of the hydrophobic wax layer with a roll-off angle <20° on the upper surface, the attenuation of reflectivity due to dust accumulation is reduced, achieving passive cooling during the day.

[0034] 3. This invention achieves a total weight of 230–290 g / m² through hot-pressing composite of three layers of fiber base fabric. 2 The high-density fiber network, combined with reflective filler for light scattering and extinction, results in a photosynthetically active radiation transmittance of less than 5%, lower than the light compensation point of most weeds. Germinating seedlings, due to continuous light starvation, cannot maintain a positive carbon balance, achieving purely physical shading weed control without disturbing soil microorganisms.

[0035] 4. In this invention, the cotton linter fibers in the lower contact layer are pretreated with citric acid and sodium hypophosphite for cross-linking. This introduces ester cross-linking points between the cellulose molecular chains, reducing the accessibility of cellulase to β-1,4-glycosidic bonds and slowing down the degradation rate by soil microorganisms. By adjusting the amount of citric acid and the curing temperature, the degradation half-life can be adjusted within 6 to 12 months to match different seedling cycles of forest trees, and mechanical and functional stability can be maintained within the corresponding cycle. Detailed Implementation

[0036] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with existing known technologies. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0037] Example 1: A method for using a weed-controlling and moisture-retaining nonwoven fabric, comprising the following steps: (1) Wet web forming and crosslinking pretreatment: The upper cover layer fiber (35g jute fiber and 15g bleached sulfate wood pulp, mass ratio 70:30), the middle support layer fiber (99g jute fiber and 11g core-shell type polylactic acid bicomponent short fiber treated with 0.5% sodium carbonate solution soaked for 30min and saponified, mass ratio 90:10) and the lower contact layer fiber (50g cotton linter fiber) were dispersed in deionized water, and 0.05g of a composite dispersant of polyethylene oxide and sodium lignosulfonate (mass ratio 2:1) was added to each to prepare a suspension slurry with a web forming concentration of 0.02wt%.

[0038] The upper cover layer base fabric (50 g / m²) is obtained by forming and drying the fabric using a wet-laid wire mesh forming machine. 2 ), intermediate support layer base fabric (weight 110g / m²) 2 ) and the lower contact layer base fabric (50 g / m²) 2 ).

[0039] The lower contact layer base fabric was impregnated in 1000 mL of an aqueous solution containing 2.5 g of citric acid (5% of the dry weight of the lower contact layer fiber) and 1.25 g of sodium hypophosphite (50% of the amount of citric acid), with a bath ratio of 1:20 (fiber mass: solution mass), and soaked at room temperature for 30 min. After removal, it was rolled to a roll yield of 80%, pre-dried at 85℃ for 10 min, then cured at 140℃ for 3 min, washed with deionized water for 10 min, and dried at 50℃ until the moisture content was <8%.

[0040] The on-grid concentration of the wet-laid network is 0.02%.

[0041] (2) Top coating: Disperse 3.33g of oxidized starch in 40g of deionized water, heat to 85℃ and gelatinize for 30min, cool and add 6.67g of barium sulfate powder (D50=0.8μm), stir and disperse evenly to obtain coating liquid.

[0042] The above coating liquid was applied to the upper surface of the upper cover layer base fabric using a metering rod, with a coating amount of 10 g / m² (dry weight). 2 The upper cover layer functional base fabric is obtained by drying at 105℃ for 15 minutes.

[0043] The mass ratio of barium sulfate to oxidized starch dry base is 2:1; the mass ratio of water to the total amount of reflective filler particles and oxidized starch dry base in the coating liquid is 4:1.

[0044] (3) Hot-pressing composite: The upper cover layer functional base fabric, the middle support layer base fabric, and the lower contact layer base fabric that has undergone cross-linking pretreatment are stacked, and polylactic acid hot melt mesh film (6 g / m² per layer) is placed between the layers. 2The composite nonwoven fabric is obtained by hot pressing at 155℃, linear pressure of 35N / mm and linear speed of 5m / min.

[0045] (4) Wax layer application and water-absorbing coating crosslinking: Carnauba wax micropowder (D50 of 10-30 μm) and hydrophobic fumed silica (particle size of 100 nm) are applied to the upper surface of the composite nonwoven fabric cover layer. The mass ratio of the wax powder to the hydrophobic fumed silica is 19:1, and the amount of carnauba wax micropowder applied is 2 g / m². 2 The wax powder is heated to 90°C on the surface of the upper cover layer by mid-wave infrared heating, which melts the wax powder. Then it is naturally cooled to form a hydrophobic wax layer.

[0046] A coating solution containing 0.3g sodium carboxymethyl cellulose, 0.15g sodium alginate, 0.1g tannic acid, and 100g water (mass ratio of sodium carboxymethyl cellulose, sodium alginate, tannic acid, and water is 6:3:2:2000) was sprayed onto the lower surface of the lower contact layer of the composite nonwoven fabric. The wet weight of the sprayed solution was 25g / m². 2 After drying to semi-dryness at 70℃, spray with a 1.0wt% calcium chloride solution at a rate of 5g / m³. 2 Let it stand for 5 minutes, rinse with deionized water, and then dry at 80℃ to obtain weed-removing and moisture-retaining non-woven fabric.

[0047] Example 2: A method for using a weed-controlling and moisture-retaining nonwoven fabric, comprising the following steps: (1) Wet web forming and crosslinking pretreatment: The upper cover layer fiber (42g jute fiber and 18g bleached sulfate wood pulp, mass ratio 70:30), the middle support layer fiber (99g jute fiber and 11g core-shell type polylactic acid bicomponent short fiber treated with 0.5% sodium carbonate solution soaked for 30min and saponified, mass ratio 90:10) and the lower contact layer fiber (60g cotton linter fiber) were dispersed in deionized water, and 0.05g of a composite dispersant of polyethylene oxide and sodium lignosulfonate (mass ratio 2:1) was added to each to prepare a suspension slurry with a web forming concentration of 0.035wt%.

[0048] The upper cover layer base fabric (60 g / m²) is obtained by forming and drying the fabric using a wet wire mesh forming machine. 2 ), intermediate support layer base fabric (weight 110g / m²) 2 ) and the lower contact layer base fabric (60 g / m²) 2 ).

[0049] The lower contact layer base fabric was impregnated in 1200 mL of an aqueous solution containing 6.6 g of citric acid (11% of the dry weight of the lower contact layer fiber) and 3.3 g of sodium hypophosphite (50% of the amount of citric acid), with a bath ratio of 1:20 (fiber mass: solution mass), and soaked at room temperature for 30 min. After removal, it was rolled to a roll yield of 80%, pre-dried at 85℃ for 10 min, then cured at 150℃ for 4 min, washed with deionized water for 10 min, and dried at 50℃ until the moisture content was <8%.

[0050] The wet web forming process has a net-connection concentration of 0.035%.

[0051] (2) Top coating: Disperse 3.89g of oxidized starch in 105g of deionized water, heat to 85℃ and gelatinize for 30min, cool and add 13.61g of barium sulfate powder (D50=0.8μm), stir and disperse evenly to obtain coating liquid.

[0052] The above coating liquid was applied to the upper surface of the upper cover layer base fabric using a metering rod, with a coating amount of 17.5 g / m² (dry weight). 2 The upper cover layer functional base fabric is obtained by drying at 105℃ for 15 minutes.

[0053] The mass ratio of barium sulfate to oxidized starch dry base is 3.5:1; the mass ratio of water to the total amount of reflective filler particles and oxidized starch dry base in the coating liquid is 6:1.

[0054] (3) Hot-pressing composite: The upper cover layer functional base fabric, the middle support layer base fabric, and the lower contact layer base fabric that has undergone cross-linking pretreatment are stacked, and polylactic acid hot melt mesh film (6 g / m² per layer) is placed between the layers. 2 The composite nonwoven fabric is obtained by hot pressing at 160℃, linear pressure of 35N / mm and linear speed of 5m / min.

[0055] (4) Wax layer application and water-absorbing coating crosslinking: Carnauba wax micropowder (D50 of 10-30 μm) and hydrophobic fumed silica (particle size of 100 nm) are applied to the upper surface of the composite nonwoven fabric cover layer. The mass ratio of the wax powder to the hydrophobic fumed silica is 60:1, and the amount of carnauba wax micropowder applied is 4 g / m². 2 The wax powder is heated to 100°C on the surface of the upper cover layer by mid-wave infrared heating, which melts the wax powder. Then it is naturally cooled to form a hydrophobic wax layer.

[0056] A coating solution containing 0.3g sodium carboxymethyl cellulose, 0.15g sodium alginate, 0.1g chitosan quaternary ammonium salt, and 100g water (mass ratio of sodium carboxymethyl cellulose, sodium alginate, chitosan quaternary ammonium salt, and water is 6:3:2:2000) was sprayed onto the lower surface of the lower contact layer of the composite nonwoven fabric. The wet weight of the sprayed solution was 25g / m². 2After drying to semi-dryness at 70℃, spray with a 1.0wt% calcium chloride solution at a rate of 5g / m³. 2 Let it stand for 5 minutes, rinse with deionized water, and then dry at 80℃ to obtain weed-removing and moisture-retaining non-woven fabric.

[0057] Example 3: A method for using a weed-controlling and moisture-retaining nonwoven fabric, comprising the following steps: (1) Wet web forming and crosslinking pretreatment: The upper cover layer fiber (45.5g jute fiber and 19.5g bleached sulfate wood pulp, mass ratio 70:30), the middle support layer fiber (105.3g jute fiber and 11.7g core-shell type polylactic acid bicomponent short fiber treated with 0.5% sodium carbonate solution soaked for 30min and saponified, mass ratio 90:10) and the lower contact layer fiber (65g cotton linter fiber) were dispersed in deionized water, and 0.05g of a composite dispersant of polyethylene oxide and sodium lignosulfonate (mass ratio 2:1) was added to each to prepare a suspension slurry with a web forming concentration of 0.05wt%.

[0058] The upper cover layer base fabric (65 g / m²) is obtained by forming and drying the fabric using a wet wire mesh forming machine. 2 ), intermediate support layer base fabric (weight 117g / m²) 2 ) and the lower contact layer base fabric (65 g / m²) 2 ).

[0059] The lower contact layer base fabric was impregnated in 1300 mL of an aqueous solution containing 11.05 g of citric acid (17% of the dry weight of the lower contact layer fiber) and 5.53 g of sodium hypophosphite (50% of the amount of citric acid), with a bath ratio of 1:20 (fiber mass: solution mass), and soaked at room temperature for 30 min. After removal, it was rolled to a roll yield of 80%, pre-dried at 85℃ for 10 min, then cured at 160℃ for 5 min, washed with deionized water for 10 min, and dried at 50℃ until the moisture content was <8%.

[0060] The wet-laid mesh concentration is 0.05%.

[0061] (2) Top coating: Disperse 3.33g of oxidized starch in 200g of deionized water, heat to 85℃ and gelatinize for 30min, cool and add 16.65g of barium sulfate powder (D50=0.8μm), stir and disperse evenly to obtain coating liquid.

[0062] The above coating liquid was applied to the upper surface of the upper cover layer base fabric using a metering rod, with a coating amount of 25 g / m² (dry weight). 2 The upper cover layer functional base fabric is obtained by drying at 105℃ for 15 minutes.

[0063] The mass ratio of barium sulfate to dry oxidized starch is 5:1; the mass ratio of water to the total amount of reflective filler particles and dry oxidized starch in the coating liquid is 10:1.

[0064] (3) Hot-pressing composite: The upper cover layer functional base fabric, the middle support layer base fabric, and the lower contact layer base fabric that has undergone cross-linking pretreatment are stacked, and polylactic acid hot melt mesh film (6 g / m² per layer) is placed between the layers. 2 The composite nonwoven fabric is obtained by hot pressing at 165℃, linear pressure of 35N / mm and linear speed of 5m / min.

[0065] (4) Wax layer application and water-absorbing coating crosslinking: Plant-derived fatty acid wax (D50 of 10-30 μm) and hydrophobic fumed silica (particle size of 100 nm) are applied to the upper surface of the composite nonwoven fabric's upper covering layer. The mass ratio of the wax powder to the hydrophobic fumed silica is 99:1, and the amount of carnauba wax micropowder applied is 6 g / m². 2 The wax powder is heated to 110°C on the surface of the upper cover layer by mid-wave infrared heating, which melts the wax powder. Then it is naturally cooled to form a hydrophobic wax layer.

[0066] A coating solution containing 0.3g sodium carboxymethyl cellulose, 0.15g sodium alginate, 0.1g chitosan, and 100g water (mass ratio of sodium carboxymethyl cellulose, sodium alginate, chitosan, and water is 6:3:2:2000) was sprayed onto the lower surface of the lower contact layer of the composite nonwoven fabric. The wet weight of the sprayed solution was 25g / m². 2 After drying to semi-dryness at 70℃, spray with a 1.0wt% calcium chloride solution at a rate of 5g / m³. 2 Let it stand for 5 minutes, rinse with deionized water, and then dry at 80℃ to obtain weed-removing and moisture-retaining non-woven fabric.

[0067] Example 4: The difference between Example 4 and Example 2 is that in step (2), the amount of barium sulfate powder is changed to 12g, and the amount of oxidized starch is still 3g, that is, the mass ratio of reflective filler particles to dry oxidized starch is 4:1; the rest is the same as in Example 2.

[0068] Example 5: The difference between Example 5 and Example 2 is that in step (2), the coating amount is changed to 15 g / m² (dry weight). 2 The rest is the same as in Example 2.

[0069] Example 6: The difference between Example 6 and Example 2 is that in step (1), the amount of citric acid is changed to 4.8g (8% of the dry weight of the lower contact layer fiber), and the amount of sodium hypophosphite is changed to 2.4g (50% of the amount of citric acid); the rest is the same as in Example 2.

[0070] Comparative Example 1: Based on Example 2, the difference is that: the upper surface of the upper cover layer is not sprinkled with carnauba wax powder and hydrophobic fumed silica, and the lower surface of the lower contact layer is not sprayed with a coating liquid containing sodium carboxymethyl cellulose, sodium alginate and antibacterial and anti-degradation agent. Both the upper cover layer and the lower contact layer are unmodified fiber base fabrics (the upper cover layer contains only jute / wood pulp, and the lower contact layer contains only cotton linters). The contact angle of the upper and lower surfaces is about 0°, with no contact angle difference. The rest is the same as in Example 2.

[0071] Comparative Example 2: Based on Example 2, the difference is that in step (2), the coating liquid contains only oxidized starch and no barium sulfate powder is added, and the coating amount is 3 g / m² on a dry weight basis. 2 The rest is the same as in Example 2.

[0072] Comparative Example 3: Based on Example 2, the difference is that in step (4), the upper surface of the upper cover layer is not sprinkled with carnauba wax powder and hydrophobic fumed silica, and the rest is the same as Example 2.

[0073] Comparative Example 4: Based on Example 2, the difference is that in step (4), the lower surface of the lower contact layer is not sprayed with a coating liquid containing sodium carboxymethyl cellulose, sodium alginate and antibacterial and anti-degradation agent, and only the intrinsic hydrophilicity of the cotton linter base fabric that has been pretreated by crosslinking is retained, and the rest is the same as in Example 2.

[0074] Comparative Example 5: Based on Example 2, the difference is that in step (1), after the lower contact layer base fabric is formed into a web, it is not impregnated with citric acid and sodium hypophosphite solution, but directly hot-pressed and composited with the upper cover layer and the middle support layer. The rest is the same as in Example 2.

[0075] Comparative Example 6: Based on Example 2, the difference is that the three-layer structure is cancelled and replaced with a single layer of PLA spunbond nonwoven fabric (25 g / m²). 2 (Black), without upper cover coating, without wax layer, without lower contact layer water-absorbing coating, without crosslinking pretreatment, otherwise the same as in Example 2.

[0076] Test Example: The weed-controlling and moisture-retaining nonwoven fabrics prepared in Examples 1-6 and Comparative Examples 1-6 above were subjected to the following tests, and the test methods are as follows: (1) Total weight: According to GB / T24218.1 standard, a 100cm section is cut from the nonwoven fabric to be tested. 2 Three samples were weighed using an electronic balance with an accuracy of not less than 0.001g. The arithmetic mean was taken and converted to the mass per unit area (g / m²) according to the formula. 2 ).

[0077] (2) Tensile strength: According to GB / T3923.1 standard, the non-woven fabric to be tested is cut into a sample strip with a width of 50mm and a length of 300mm. The clamping distance is 200mm. The fracture test is carried out on a universal testing machine at a constant tensile speed of 100mm / min. The maximum force value at the time of fracture is read. The result is expressed as N / 5cm.

[0078] (3) Interlayer peel strength: Referring to the FZ / T60011 standard, the nonwoven fabric to be tested was cut into strips with a width of 25mm and a length of 150mm. Along the longitudinal direction, the upper cover layer and the middle support layer, and the middle support layer and the lower contact layer were pre-peeled by about 50mm at one end of the sample. The unseparated part was placed in the upper clamp and the peeled layer was placed in the lower clamp. The 180° peel test was performed on the universal testing machine at a tensile speed of 100mm / min. The arithmetic mean of the peak peel force was recorded and the result was expressed in N / cm.

[0079] (4) Static water contact angle and roll-off angle of the upper and lower surfaces: Contact angle measurement: The non-woven fabric to be tested is flatly attached to a glass slide. Using a contact angle measuring instrument, 5 μL of deionized water is dropped onto the test surface at room temperature. After 10 s, the left and right contact angles are measured. The arithmetic mean of 5 different positions is taken for each sample. Roll-off angle measurement: 10 μL of deionized water is dropped onto the test surface. The sample stage is tilted at a rate of 1° / s, and the tilt angle when the water droplet begins to roll off is recorded. Because the lower surface of the lower contact layer has the characteristic of rapid water absorption, a high-speed camera is used to record the shape of the droplet within 0 to 1 s after contact with the surface at a frame rate of not less than 60 fps. The static contact angle at the moment of contact (<0.1 s) is recorded as the initial contact angle. The arithmetic mean of 5 different positions is taken for each group of samples.

[0080] (5) Photosynthetically active radiation transmittance: Referring to ASTM E903 standard, the spectral transmittance of the nonwoven fabric under test is scanned in the wavelength range of 300 to 2500 nm using an ultraviolet-visible-near-infrared spectrophotometer equipped with an integrating sphere. The transmittance data in the 400 to 700 nm band is extracted, and the weighted average transmittance is calculated using AM1.5 standard solar spectral irradiance as the weighting function. This is the photosynthetically active radiation transmittance.

[0081] (6) Weighted average reflectance and infrared emissivity of the upper cover layer: Solar reflectance measurement: Referring to ASTM E903 standard, the spectral reflectance of the upper cover layer was measured in the wavelength range of 300 to 2500 nm using an ultraviolet-visible-near-infrared spectrophotometer equipped with an integrating sphere. The weighted average reflectance was calculated using AM1.5 standard solar spectral irradiance as the weighting function.

[0082] Infrared emissivity measurement: The spectral radiance of the upper coating layer was measured in the wavelength range of 8 to 13 μm using a Fourier transform infrared spectrometer. The radiance was compared with that of a standard blackbody at the same temperature to calculate the average emissivity in this band.

[0083] (7) Water absorption ratio: Weigh the dry mass W0 of the nonwoven fabric lower contact layer sample (5cm×5cm), immerse it in deionized water for 30min, take it out and hang it to drain for 10min, weigh the wet mass W1, water absorption ratio = (W1-W0) / W0, and the result is expressed in g / g.

[0084] (8) Soil burial degradation half-life: Referring to GB / T 33616-2017, the nonwoven fabric to be tested was buried in standard active soil (temperature 25℃, humidity 60–80%). Samples were taken out periodically to determine its mass loss rate. The time taken for the mass loss to reach 50% of the initial mass was recorded as the degradation half-life.

[0085] The test results are shown in Tables 1 and 2.

[0086] Table 1: Performance Test Results of the Embodiments and Comparative Examples Note: Total basis weight of polylactic acid hot melt web film is 12g / m². 2 (Two layers) are included in the total weight of each embodiment; Comparative Example 6 is a single-layer PLA spunbond nonwoven fabric with no interlayer structure, and the peel strength is not measured.

[0087] Table 2: Functional Performance Test Results of Examples and Comparative Examples Data Analysis: Analysis of the data in Tables 1 and 2 shows that the total basis weight of the nonwoven fabrics prepared in Examples 1 to 3 ranges from 234 g / m². 2 Increased to 290g / m 2 The longitudinal tensile strength increased from 58 N / 5 cm to 85 N / 5 cm, and the interlayer peel strength also improved, indicating that increasing the basis weight and coating amount of the base cloth can enhance mechanical properties. The contact angle of the top cover layer increased from 132° to 141°, the roll-off angle decreased from 18° to 10°, and the contact angle of the bottom contact layer was close to 0°. The difference in contact angle between the two sides exceeded 130°, forming a stable asymmetric wettability gradient. Solar reflectance increased from 0.81 to 0.84, infrared emissivity increased from 0.86 to 0.90, photosynthetically active radiation transmittance decreased from 4.2% to 3.0%, water absorption ratio increased from 18 g / g to 26 g / g, and degradation half-life increased from 6 months to 12 months. It can be seen that by adjusting the coating amount of the top cover layer, the amount of wax powder, the amount of citric acid, and the curing conditions, the thickness of the base cloth can be increased to 230–290 g / m². 2Within a weight range, it achieves gradient regulation of mechanical strength, radiative cooling, shading and weed control, water absorption and retention, and degradation cycle to meet the needs of different seedling cultivation cycles for forest trees.

[0088] Example 4 changed the mass ratio of barium sulfate to oxidized starch from 3.5:1 to 4:1, while keeping the rest the same as in Example 2. The tensile strength decreased from 72 N / 5 cm to 68 N / 5 cm, and the interlayer peel strength slightly decreased, indicating that increasing the filler ratio slightly weakens the interfiber bonding force. The solar reflectance increased from 0.83 to 0.84, while the infrared emissivity remained unchanged, indicating that increasing the filler ratio has a marginal improvement on radiative cooling performance. Example 5 changed the top cover coating amount from 17.5 g / m². 2 Reduced to 15g / m 2 The total weight decreased to 257g / m³ 2 The tensile strength decreased to 70 N / 5 cm, the solar reflectance decreased to 0.82, the PAR transmittance increased to 3.7%, and the water absorption ratio decreased to 20 g / g. The coating amount is a key factor affecting optical performance and water retention capacity; even when reduced to 15 g / m², it still affects these properties. 2 All indicators still meet the basic requirements. In Example 6, the amount of citric acid in the lower contact layer was reduced from 11% to 8%, while the total basis weight remained unchanged. The tensile strength was basically the same as in Example 2, and the degradation half-life was shortened from 9 months to 8 months, indicating that reducing the degree of crosslinking can appropriately accelerate the degradation rate while maintaining stable mechanical and functional properties.

[0089] In Comparative Example 1, the contact angle of the upper cover layer is close to 0°, and the contact angle of the lower contact layer is 42°, with no wettability gradient on either side. The mechanical properties are similar to those of Example 2, and the optical properties remain unchanged, but the water absorption ratio decreases from 22 g / g to 5 g / g, relying solely on capillary water retention in the cotton fibers. This demonstrates the indispensability of the wax layer and the absorbent coating in constructing the Janus unidirectional hydrophobic structure: without the wax layer, the upper cover layer cannot be hydrophobic, making it difficult for irrigation water to penetrate downwards in a directional manner; without the absorbent coating, the lower contact layer lacks the function of actively absorbing and storing water, greatly weakening the evaporation inhibition effect.

[0090] Compared to Example 2, Comparative Example 2 showed a sharp decrease in solar reflectance from 0.83 to 0.42 and infrared emissivity from 0.89 to 0.87. This indicates that barium sulfate is the core filler for improving solar reflectance, while its contribution to infrared emissivity is relatively minor, as the cellulose matrix itself already has high emissivity within the atmospheric window. PAR transmittance, water absorption ratio, and degradation half-life were almost identical to those of Example 2, suggesting that physical shading mainly relies on the high basis weight fiber network, and the absence of the BaSO4 coating does not significantly affect the weeding effect.

[0091] In Comparative Example 3, the contact angle of both the upper and lower cover layers is close to 0°, and both surfaces are hydrophilic, thus losing the asymmetric wettability gradient. The mechanical, optical, and water-retention properties are similar to those of Example 2. Without the hydrophobic wax layer, although water can still penetrate downwards from the upper cover layer, the upward evaporation inhibition capacity is significantly reduced. Irrigation water will spread and form a water film on the upper cover layer, affecting air permeability and radiative cooling efficiency.

[0092] Comparative Example 4 was not coated with an absorbent coating, only retaining the cross-linked pretreated cotton linter base fabric. Compared to Example 2, the water absorption ratio decreased from 22 g / g to 4 g / g, while other indicators remained essentially unchanged. This indicates that the absorbent coating is crucial for active water retention; without it, the lower contact layer can only rely on the capillary force of the cotton fibers to retain water, resulting in extremely weak water absorption capacity and an inability to provide continuous moisture to seedlings under drought conditions.

[0093] Comparative Example 5 did not undergo crosslinking pretreatment with citric acid and sodium hypophosphite. Compared to Example 2, the tensile strength decreased from 72 N / 5 cm to 63 N / 5 cm, the interlayer peel strength decreased, and the degradation half-life plummeted from 9 months to 2 months. This indicates that crosslinking pretreatment not only enhances the bonding force between cellulose fibers, but more importantly, by introducing ester crosslinking points between molecular chains, it reduces the accessibility of glycosidic bonds to cellulase, significantly delaying the rate of microbial degradation of fibers in the soil environment. Without crosslinking pretreatment, the lower contact layer lost its structural integrity within 2 months, failing to match the seedling cultivation cycle of forest trees.

[0094] Comparative Example 6 is a commercially available single-layer black PLA spunbond nonwoven fabric with a basis weight of only 25 g / m². 2 This invention lacks a three-layer structure, coating, wax layer, and cross-linking pretreatment. Its tensile strength is only 15 N / 5 cm, far lower than other embodiments, failing to meet the requirements for film coating construction. The upper cover layer and lower contact layer are made of the same material, with a contact angle of 95° and no wettability gradient. Its solar reflectivity is only 0.06, infrared emissivity 0.87, and PAR transmittance 1.8%. While it offers extremely high shading effect, this comes at the cost of sacrificing water and air permeability. Its water absorption rate is only 1 g / g, exhibiting almost no water retention capacity, and its degradation half-life exceeds 24 months, making it virtually non-degradable in soil at room temperature. This comparative example has significant deficiencies in mechanical strength, water retention, and controllable degradation, and cannot replace the three-layer composite biodegradable nonwoven fabric of this invention.

[0095] Application Example 1: Pot Test on Water Retention Performance The purpose of this application example is to verify the inhibitory effect of the weed-controlling and moisture-retaining nonwoven fabric of the present invention on soil moisture evaporation and the one-way permeability of irrigation water.

[0096] The specific steps are as follows: (1) Experimental groups: A blank control group (bare soil, no cover) and a PP weed control group (covered with commercially available PP weed control fabric, weight 100g / m²) were set up.2 PLA mulch film kit (covering commercially available black PLA mulch film, 25g / m²) 2 The present invention group (covering the nonwoven fabric prepared in Example 2, with the upper covering layer facing upwards and the lower contact layer in contact with the soil). Each group has 3 replicates.

[0097] (2) Potting preparation: Take a plastic pot with an inner diameter of 25cm and a height of 30cm, make holes at the bottom and lay a mesh to prevent soil leakage. Fill each pot with an equal amount of sieved and air-dried soil (2.5kg, with the initial moisture content adjusted to 20%), cut each covering material into round pieces the same size as the pot opening, cover the soil surface tightly, and fix the edges with rubber bands.

[0098] (3) Moisture evaporation monitoring: All potted plants were placed in a constant temperature incubation room at 25±2℃ and relative humidity at 50±5%, without additional watering. They were weighed daily (accuracy ±1g) for 15 consecutive days. The cumulative evaporation was calculated using the following formula: Cumulative evaporation = initial mass - daily mass; Evaporation inhibition rate = (cumulative evaporation of blank group - cumulative evaporation of treatment group) / cumulative evaporation of blank group × 100%.

[0099] (4) One-way permeability verification: Slowly pour 50 mL of deionized water onto the surface of the covering material, record the time required for the water to completely infiltrate the soil, and observe whether there is surface water or runoff.

[0100] (5) Data collection: The soil surface (0-5cm) moisture content was measured every 3 days (by drying method or soil moisture meter) and a curve of soil moisture content change over time was plotted.

[0101] The results are as follows: Table 3: Cumulative evaporation and evaporation inhibition rate for each treatment group (15 days) Table 4: Changes in soil moisture content over time under different treatments (%, w / w) Data Analysis: Analysis of Tables 3 and 4 shows that the blank control group experienced a cumulative evaporation of 285.6g over 15 days, with an average daily evaporation of approximately 19.0g, and the soil moisture content decreased from 20.0% to 5.7%. The PP weed control fabric group experienced a cumulative evaporation of 234.2g, with an evaporation inhibition rate of 18.0%, and a moisture content of 7.1% on day 15. This indicates that ordinary PP weed control fabric has a certain but limited evaporation inhibition effect, as its porous structure allows water vapor to diffuse through the fiber gaps. The PLA mulch film group experienced a cumulative evaporation of only 28.5g, with an evaporation inhibition rate as high as 90.0%, and the moisture content remained at 17.5% on day 15. This is a typical characteristic of continuous film structures—water molecules cannot penetrate the polymer body and can only slowly escape through edge gaps. The present invention group experienced a cumulative evaporation of 167.2g, with an evaporation inhibition rate of 41.5%, falling between that of PP weed control fabric and PLA mulch film, and a moisture content of 11.3% on day 15. These data demonstrate that the asymmetric wettability gradient of the nonwoven fabric of this invention plays its intended role: the sodium carboxymethyl cellulose-sodium alginate water-absorbing coating in the lower contact layer actively retains irrigation water, while the hydrophobic wax layer in the upper cover layer effectively inhibits the upward diffusion of water vapor. Although the evaporation inhibition rate is not as high as that of continuously sealed plastic films, it is far superior to that of ordinary weed control fabrics. It is noteworthy that this invention achieves 41.5% evaporation inhibition while ensuring rapid downward penetration of irrigation water (see unidirectional permeability verification), which is direct evidence of the "forward conduction, reverse blocking" principle of the Janus structure.

[0102] Application Example 2: Field Trial of Weed Suppression The purpose of this application example is to verify the inhibitory effect of the weed-removing and moisture-retaining nonwoven fabric of the present invention on the germination and growth of weeds through physical shading.

[0103] The specific steps are as follows: (1) Experiment location and time: Select the summer (June to August) when weeds grow vigorously, and conduct the experiment in an open nursery or experimental base. Before the experiment, remove the surface stubble and level the land.

[0104] (2) Experimental groups: The experimental groups included a blank control group (no cover, allowing natural weed growth), a PP weed control fabric group (covered with commercially available PP weed control fabric), a PLA mulch film group (covered with commercially available black PLA mulch film), a BaSO4-free group (covered with the non-woven fabric prepared in Comparative Example 2), and the present invention group (covered with the non-woven fabric prepared in Example 2). Each treatment had 3 replicate plots, with a plot area of ​​4m × 5m, arranged in randomized blocks, and a 1m isolation strip between plots.

[0105] (3) Laying method: Each covering material is laid flat on the soil surface of the plot, and the edges are fixed with U-shaped nails or soil compaction. The present invention group keeps the upper covering layer facing upward and the lower contact layer in contact with the soil. No manual weeding or chemical weeding is required after laying.

[0106] (4) Weed survey: On the 30th, 60th and 90th day after laying, three 0.5m×0.5m quadrats were randomly set up in each plot. The number of weeds in the quadrats was counted, and the above-ground parts were cut at ground level and weighed. The inhibition rate was calculated according to the following formulas: Inhibition rate by number of plants (%) = (1 - number of weeds in the treatment area / number of weeds in the blank control group) × 100%; Inhibition rate by fresh weight (%) = (1 - fresh weight of weeds in the treatment area / fresh weight of weeds in the blank control group) × 100%.

[0107] (5) Correlation verification of photosynthetically active radiation transmittance: The PAR value (400-700nm) was measured above and below the cover material in each plot (close to the soil surface) using a photosynthetically active radiation sensor. The transmittance was calculated and the correlation between transmittance and weed suppression rate was analyzed.

[0108] The test results are as follows: Table 5: PAR transmittance of various covering materials Table 6: Weed Suppression Effect of Each Treatment Group Data Analysis: Analysis of Tables 5 and 6 shows a clear negative correlation between the PAR transmittance of each covering material and its weed suppression effect. The PLA mulch film group had a PAR transmittance of only 1.8%, achieving a 90-day weed fresh weight inhibition rate of 98.0%, almost completely suppressing weed growth, which meets the physical shading limit of black continuous film. The PP weed control fabric group had a PAR transmittance of 7.0%, with a 90-day fresh weight inhibition rate of only 58.0%, indicating that a considerable proportion of light still penetrated, allowing shade-tolerant weeds to survive. The present invention group had a PAR transmittance of 3.5%, and the group without the BaSO4 layer had a PAR transmittance of 3.6%, very close. Their 90-day fresh weight inhibition rates were 92.0% and 89.2%, respectively, also essentially equivalent. This verifies a key point: physical shading weed control mainly relies on the scattering and extinction of light by the high-basis-weight three-layer fiber network; the BaSO4 filler contributes little to the PAR transmittance, its core function being radiative cooling rather than weed control. From a time-dynamic perspective, the weed inhibition rate of each covering group decreased slightly with the extension of the laying time. This is because the covering material is subjected to wind and rain erosion and the influence of the field microenvironment for a long time outdoors. Local dust accumulation on the surface traps moisture and light and heat microenvironment for weed seeds, and small gaps easily form at the edges and seams of the material, allowing a small number of shade-tolerant weeds to germinate from these weak points. However, the group of this invention still maintained a fresh weight inhibition rate of 92.0% after 90 days, indicating that the three-layer composite structure maintained good integrity and light-blocking performance during the experimental period.

[0109] Application Example 3: Monitoring of Diurnal Variation of Soil Temperature The purpose of this application example is to verify the daytime radiative cooling effect of the reflective filler particles in the covering layer of the weed-removing and moisture-retaining nonwoven fabric of the present invention and their active cooling effect on the shallow soil temperature.

[0110] The specific steps are as follows: (1) Test time and location: Select a summer with continuous sunny weather (daily maximum temperature ≥35℃, no precipitation, lasting for at least 5 days) and conduct the test at an open-air test site.

[0111] (2) Experimental groups: The experiment included a blank control group (bare soil), a PP weed control fabric group (covered with commercially available PP weed control fabric), a PLA mulch film group (covered with commercially available black PLA mulch film), a BaSO4-free layer group (covered with the non-woven fabric prepared in Comparative Example 2), and the present invention group (covered with the non-woven fabric prepared in Example 2). Each group had 3 replicate plots with a plot area of ​​2m×2m.

[0112] (3) Temperature sensor deployment: At the center of each plot, soil temperature sensors (accuracy ±0.1℃) were buried at the surface (the surface of the covering material in contact with the soil), 5cm underground, and 15cm underground, respectively. In addition, Stevenson screens were set up in an open area of ​​the test site to record the ambient temperature.

[0113] (4) Data acquisition: Temperature values ​​of each sensor were read at 06:00, 10:00, 14:00, 18:00 and 00:00 every day during the monitoring period, and recorded continuously for 5 days. The soil temperature at 14:00 (the highest temperature period during the day) at a depth of 5cm was analyzed in detail.

[0114] (5) Evaluation of cooling effect: Calculate the soil temperature difference between each treatment group and the blank control group (ΔT=T 处理 -T 空白 (Negative values ​​indicate cooling.) The difference in cooling magnitude between the present invention group and the group without BaSO4 layer was compared to verify the contribution of reflective filler particles to radiative cooling.

[0115] The test results are as follows: Table 7: Soil temperature (°C) at 14:00 for each treatment group Table 8: Diurnal variation of soil temperature at 5cm depth in each treatment group (°C) Data Analysis: Analysis of Tables 7 and 8 shows that on hot, sunny summer days (daily maximum temperature ≥35℃), the surface temperature of the bare soil in the control group reached 52.3℃, and the temperature at a depth of 5cm was 45.3℃. High temperature stress inhibits the root vitality of shallow-rooted seedlings. The PP weed control fabric group and the PLA mulch film group, due to heat absorption by their black surfaces, had surface temperatures as high as 54.0℃ and 55.5℃ respectively, higher than the bare soil. This is a common drawback of dark-colored covering materials—although they provide shade, they themselves significantly increase temperature. The surface temperature of the group without a BaSO4 layer was 50.5℃, 1.8℃ lower than the control group, due to the shading and evaporative cooling of the fiber mesh itself. The surface temperature of the group using this invention was 46.2℃, 6.1℃ lower than the control group, 7.8℃ lower than the PP weed control fabric group, and 4.3℃ lower than the group without a BaSO4 layer. The additional 4.3℃ cooling is due to the radiative cooling contribution of the BaSO4 filler – high solar reflectivity reduces radiative heat gain, while the high infrared emission of the fiber matrix and wax layer through the atmospheric window radiates heat into outer space. At a depth of 5cm, the soil temperature in the invention group was 40.5℃, 4.8℃ lower than the control group and 7.7℃ lower than the PP weed control group. Regarding diurnal temperature fluctuations, the diurnal range of the invention group was only 9.7℃, the smallest among all treatments, indicating that the high-reflectivity top cover layer reduced daytime heat absorption, while the thermal inertia of the fiber network and water-absorbing coating delayed nighttime heat dissipation, keeping the rhizosphere temperature relatively stable. Compared with the PP weed control group (diurnal range 14.4℃) and the PLA mulch film group (diurnal range 14.3℃), the black material absorbed heat intensely during the day and dissipated heat rapidly at night, resulting in large temperature fluctuations, which is not conducive to continuous root growth. The above data fully verify the diurnal radiative cooling effect of the reflective filler particles in the top cover layer of this invention and its active cooling effect on shallow soil temperature.

[0116] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for manufacturing a weed-controlling and moisture-retaining nonwoven fabric, characterized in that, Includes the following steps: (1) Wet web forming and crosslinking pretreatment: The upper cover layer fiber, the middle support layer fiber and the lower contact layer fiber are wet web formed to obtain the upper cover layer base fabric, the middle support layer base fabric and the lower contact layer base fabric; wherein, after the lower contact layer base fabric is web formed, it is subjected to crosslinking pretreatment to obtain the crosslinked pretreated lower contact layer base fabric. (2) Top Cover Coating: A coating liquid containing reflective filler particles and oxidized starch is coated on the upper surface of the top cover base fabric and dried to obtain the top cover functional base fabric; in the coating liquid, the mass ratio of reflective filler particles to oxidized starch dry base is (2-5):1, the mass ratio of water to the total mass of reflective filler particles and oxidized starch dry base is (4-10):1, and the coating amount is 10-25 g / m² (dry weight). 2 The reflective filler particles are BaSO4 with a particle size of 200 nm to 2 μm. (3) Hot pressing composite: The upper cover layer functional base fabric, the middle support layer base fabric and the cross-linked pretreated lower contact layer base fabric are stacked, and polylactic acid hot melt mesh film is placed between the layers. The composite nonwoven fabric is obtained by hot pressing at 155-165℃. (4) Wax layer application and water-absorbing coating crosslinking: Wax powder and hydrophobic fumed silica are applied to the upper surface of the upper cover layer of the composite nonwoven fabric. The mass ratio of wax powder to hydrophobic fumed silica is (19-99):

1. After being melted by infrared heating, the wax layer is naturally cooled to form a hydrophobic wax layer. A coating liquid containing sodium carboxymethyl cellulose, sodium alginate and antibacterial and anti-degradation agent is applied to the lower surface of the lower contact layer of the composite nonwoven fabric. Then, CaCl2 solution is used for ion crosslinking and curing to obtain the weed-removing and moisture-retaining nonwoven fabric.

2. The method for manufacturing weed-controlling and moisture-retaining nonwoven fabric according to claim 1, characterized in that, In step (1), the upper covering layer fiber comprises jute fiber and wood pulp fiber in a mass ratio of 70:30; the middle support layer fiber comprises jute fiber and core-sheath type polylactic acid bicomponent short fiber in a mass ratio of 90:10; and the lower contact layer fiber comprises cotton linter fiber.

3. The method for manufacturing weed-controlling and moisture-retaining nonwoven fabric according to claim 1, characterized in that, In step (1), the concentration of the wet web forming is 0.02-0.05%; the crosslinking pretreatment involves immersing the lower contact layer base fabric after wet web forming in an aqueous solution containing citric acid and sodium hypophosphite, curing it at 140-160℃ for 3-5 minutes, and then washing and drying it; the amount of citric acid used is 5-17% of the dry weight of the lower contact layer fiber, and the amount of sodium hypophosphite used is 50% of the amount of citric acid used; the bath ratio of the impregnation is 1:

20.

4. The method for manufacturing weed-controlling and moisture-retaining nonwoven fabric according to claim 1, characterized in that, In step (3), the polylactic acid hot melt web film has a basis weight of 6 g / m². 2 .

5. The method for manufacturing weed-controlling and moisture-retaining nonwoven fabric according to claim 1, characterized in that, In step (4), the wax powder is either carnauba wax or plant-derived fatty acid wax, the particle size D50 of the wax powder is 10-30 μm, and the spreading amount is 2-6 g / m³. 2 The hydrophobic fumed silica has a particle size of 50–200 nm.

6. The method for manufacturing weed-controlling and moisture-retaining nonwoven fabric according to claim 1, characterized in that, In step (4), the infrared heating is to control the temperature of the fabric surface at 90-110°C, and the wax powder melts and then slowly cools and crystallizes at room temperature.

7. The method for manufacturing weed-controlling and moisture-retaining nonwoven fabric according to claim 1, characterized in that, In step (4), the coating liquid is composed of sodium carboxymethyl cellulose, sodium alginate, antibacterial and anti-degradation agent and water in a mass ratio of 6:3:2:2000; the antibacterial and anti-degradation agent is any one of tannic acid, chitosan or chitosan quaternary ammonium salt.

8. The method for manufacturing weed-controlling and moisture-retaining nonwoven fabric according to claim 1, characterized in that, In step (4), the specification of the weed-controlling and moisture-retaining nonwoven fabric is 230-290 g / m². 2 The photosynthetically active radiation transmittance is <5%.

9. The method for manufacturing weed-controlling and moisture-retaining nonwoven fabric according to claim 1, characterized in that, In step (4), the weighted average reflectance of the upper cover layer of the weed-removing and moisture-retaining nonwoven fabric under the AM1.5 standard solar spectrum is ≥0.80, and the infrared emissivity in the atmospheric window 8-13μm band is ≥0.85; the static water contact angle of the upper cover layer of the weed-removing and moisture-retaining nonwoven fabric is ≥130°, and the roll-off angle is <20°; the difference in static water contact angle between the upper surface of the upper cover layer and the lower surface of the lower contact layer of the weed-removing and moisture-retaining nonwoven fabric is ≥80°, forming an asymmetric wettability gradient.

10. The application of the weed-controlling and moisture-retaining nonwoven fabric manufactured by the manufacturing method according to any one of claims 1 to 9 in forest tree seedling cultivation and / or seed and seedling cultivation, characterized in that, The weed-controlling and moisture-retaining non-woven fabric is laid in the seedbed or between planting rows with the upper covering layer facing upwards and the lower contact layer in contact with the soil. The asymmetric wettability gradient enables irrigation water to penetrate downwards and inhibits soil moisture from evaporating upwards.

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