Degradable planting belt for ecological restoration and preparation method thereof

Abstract

The invention provides a degradable sodded strip for ecological restoration and a preparation method thereof, and belongs to the technical field of sodded strips, the degradable sodded strip comprises an upper-layer fiber web, a middle-layer seed and nutrient layer and a lower-layer grid which are sequentially laminated and compounded from top to bottom; the upper-layer fiber web is made of a hydrophilic degradable material and is used for absorbing moisture and preserving soil moisture; the middle seed and nutrient layer comprises plant seeds and a nutrient controlled release unit; the lower-layer grid is a three-dimensional grid which is made of a degradable high polymer material, has a three-dimensional communicated micropore structure and is used for mechanically guiding root growth; the nutrient controlled release unit is a microcapsule which takes a fertilizer as a core material and takes an environment response type polymer as a wall material, and the microcapsule is anchored in the fiber interweaving nodes of the lower layer grid through a cross-linking agent. According to the invention, environmental response type precise controlled release of plant rhizosphere nutrients and three-dimensional mechanical guidance of a root system growth path can be realized, and the utilization rate of the fertilizer and the survival rate and long-term stability of vegetation recovery under poor site conditions such as side slopes, river banks and mines are effectively improved.

Description

Technical Field

[0001] This invention relates to the field of vegetation belt technology, and in particular to a biodegradable vegetation belt for ecological restoration and its preparation method. Background Technology

[0002] With the intensification of mining, infrastructure construction, and urban expansion, the damage to ecosystems such as slopes, riverbanks, and mining subsidence areas has become increasingly prominent, and the requirements for coordinated development between engineering construction and the ecological environment are constantly rising. In recent years, ecological restoration technologies have been evolving from hard engineering measures such as retaining walls and masonry to ecological engineering measures centered on vegetation restoration while also considering soil and water conservation and biodiversity enhancement. Among these, prefabricated, standardized, and easily mechanized construction products such as vegetation strips and vegetation mats have become an important development direction for slope greening and ecological restoration projects due to their high construction efficiency, wide applicability, and ease of promotion and application. At the same time, material systems are developing towards biodegradability, environmental friendliness, and resource utilization, and nutrient supply methods are gradually transitioning from traditional one-time fertilization to controlled-release, slow-release, and environmentally responsive fertilizers, striving to improve fertilizer utilization while reducing the risk of non-point source pollution.

[0003] Currently, to achieve rapid vegetation restoration of damaged sites, the following typical technical solutions are commonly used: One type consists of planting boxes, planting containers, and other structural units made primarily of biodegradable plastics or fibers, filled with nutrient soil and fertilizer, and then plant seeds are transplanted or sown for slope or riverbank reinforcement and greening; another type uses natural fiber materials such as straw mats, coconut fiber blankets, and jute mats to cover slopes or bare ground surfaces, serving to retain moisture, resist erosion, and provide protection; and yet another type uses biodegradable non-woven fabric as a carrier, where grass seeds and fertilizers are simply mixed and fixed inside or on the surface of the fibers to form strip-shaped or blanket-shaped vegetation materials for spraying or paving construction.

[0004] However, the existing technologies still have several shortcomings under long-term service conditions: On the one hand, traditional vegetation strips or covering materials mostly use biodegradable substrates with relatively homogeneous structure and function. Their degradation rate and mechanical properties are difficult to dynamically adjust with the vegetation growth process. The pore size of the grid or fiber structure is usually fixed, making it difficult to meet the needs of covering and moisture retention in the early stage of seed germination and the space requirements for root penetration and growth expansion in the later stage. This can easily lead to insufficient support in the early stage or binding of the root system in the later stage. On the other hand, existing fertilizers are mostly uniformly mixed into the substrate or simply attached to the fiber surface. Their controlled release behavior is mainly driven by physical environmental factors such as temperature and moisture. They lack coordination with the root distribution location and physiological nutrient requirements, resulting in a mismatch between nutrients and plant absorption needs in time and space, leading to the early concentrated release, leaching, or volatilization of nutrients.

[0005] Therefore, there is an urgent need to propose a biodegradable vegetation strip that can take into account moisture retention, support and guide root growth in terms of material structure, achieve environmentally responsive controlled release of nutrients and spatial synergy with grid structure, so as to better adapt to the ecological restoration needs under complex site conditions. Summary of the Invention

[0006] In order to overcome the shortcomings of the existing technology, the purpose of this invention is to provide a biodegradable vegetation strip for ecological restoration and its preparation method. Under the premise of ensuring the overall biodegradability of the carrier, it can achieve environmentally responsive and precise controlled release of plant rhizosphere nutrients and three-dimensional mechanical guidance of root growth path, effectively improving fertilizer utilization and the survival rate and long-term stability of vegetation restoration under adverse site conditions such as slopes, riverbanks, and mines.

[0007] To achieve the above objectives, the present invention provides the following solution: On one hand, the present invention provides a biodegradable vegetation strip for ecological restoration, comprising, from top to bottom, a composite upper fiber network, a middle seed and nutrient layer, and a lower mesh; the upper fiber network is composed of a hydrophilic biodegradable material for moisture absorption and retention; the middle seed and nutrient layer contains plant seeds and nutrient controlled-release units; the lower mesh is a three-dimensional mesh made of biodegradable polymer material with a three-dimensional interconnected microporous structure for mechanically guiding root growth; the nutrient controlled-release unit is a microcapsule with fertilizer as the core material and environmentally responsive polymer as the wall material, and the microcapsules are anchored inside the fiber interlacing nodes of the lower mesh by a cross-linking agent.

[0008] Preferably, the initial effective pore size of the three-dimensional mesh structure of the lower layer is 5~10mm, and the effective pore size dynamically increases with the material degradation process.

[0009] Preferably, the raw materials of the lower mesh include polylactic acid (PLA), polybutylene adipate terephthalate (PBAT), and surface-treated micron-sized lignin fibers, wherein the mass fraction of lignin fibers is 10% to 20%.

[0010] Preferably, the environmentally responsive polymer is one or more of polyacrylic acid, polyacrylamide, sodium alginate, gelatin, chitosan, polyvinyl alcohol, polylactic acid-glycolic acid copolymer (PLGA), and polycaprolactone (PCL).

[0011] Preferably, the crosslinking agent is one or more of citrate, citrate ester, genipin, tannic acid, glutaraldehyde aqueous solution or carbodiimide aqueous solution.

[0012] On the other hand, the present invention also provides a method for preparing the above-mentioned biodegradable vegetation strip for ecological restoration, comprising the following steps: S1. Microcapsules are prepared using fertilizer as the core material and environmentally responsive polymers as the wall material, employing interfacial polymerization or spray drying methods. S2. The lower mesh is prepared by melt spinning and spunbonding process. During the spunbonding process, when the fibers have not been completely cooled and solidified, the mixture of microcapsules and crosslinking agent is directionally sprayed onto the fiber interlacing node area. The residual heat of the fibers is used to promote the crosslinking reaction and complete the in-situ chemical anchoring of the microcapsules. S3. Based on meltblown technology, the upper fiber web is prepared from hydrophilic and biodegradable materials; S4. Plant seeds mixed with the microcapsules are evenly laid on the lower mesh after the microcapsules have been anchored, and then the upper fiber mesh is covered. Finally, the composite molding is carried out by hot rolling process to obtain the biodegradable vegetation strip for ecological restoration.

[0013] Preferably, in S1, when using interfacial polymerization, the core material is dispersed in an aqueous solution and the wall material is dissolved in an organic solution. The two phases are stirred to cause a polymerization reaction at the interface to form a microcapsule wall. When using spray drying, the mixed dispersion of the core material and the wall material is atomized under high pressure and then dried in a hot air environment at 80~100℃. The particle size of the microcapsules is 0.1~0.5mm.

[0014] Preferably, in S2, the spinning temperature of the melt spinning and spunbonding process is 160~190℃, and the fiber linear density is 2.0~5.0 dtex; in the mixture of microcapsules and crosslinking agent, the mass fraction of microcapsules is 30%~50%, and the mixture is directionally sprayed using a high-pressure atomizing nozzle, with the spraying range covering the fiber interlacing node area.

[0015] Preferably, in S2, the process parameters for directional spraying are: spraying pressure 0.3~0.6MPa, crosslinking agent is 1%~2% ethanol solution; after spraying, heat treatment is performed at 100~120℃ for 10~30 seconds, and nitrogen protection is maintained during the heat treatment process to enhance the crosslinking anchoring effect and avoid material degradation.

[0016] Preferably, in step S4, the seed density is 20-50 seeds / cm². 2 The mass ratio of seeds to microcapsules is 1:0.8~1.2; the parameters of the hot rolling composite process are: hot rolling temperature 110~120℃, hot rolling pressure 0.3~0.5MPa, and hot rolling speed 5~10m / min; after composite molding, the vegetation strip is cooled at room temperature to finally obtain the vegetation strip.

[0017] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects: (1) This invention achieves precise and stable nutrient supply by anchoring nutrient-controlled release microcapsules to the interwoven nodes of the underlying mesh fibers with a cross-linking agent, combined with an environmentally responsive polymer wall material. Specifically, the anchoring structure of the microcapsules avoids nutrient displacement and loss caused by construction and rainwater erosion. The environmentally responsive wall material can adjust the nutrient release rhythm according to changes in external temperature and humidity and the plant's growth status. The mechanism is that the anchoring mechanism constructs a stable nutrient retention system, and the environmental responsiveness of the wall material enables on-demand nutrient release, solving the problems of uneven nutrient supply and uncontrolled release in traditional vegetation belts, and providing continuous and stable nutrient support for the entire growth cycle of plants from seed germination to root establishment.

[0018] (2) This invention achieves a synergistic improvement in structural adaptability and overall stability by combining the three-dimensional interconnected microporous structure of the lower layer grid with dynamic pore size and the hot rolling composite process of each functional layer. Specifically, the initial pore size design ensures the stable retention of the middle layer matrix, the pore size dynamically increases with material degradation to meet the extension needs of different growth stages of the root system, and the hot rolling process strengthens the interlayer bonding strength. The mechanism is that the dynamic pore size structure achieves dynamic matching between mechanical support and root growth, and the interlayer composite process enhances the overall structure, solving the problems of easy matrix detachment, root growth inhibition, and easy interlayer peeling in traditional vegetation belts, and providing structural protection for the long-term use of vegetation belts in complex outdoor environments.

[0019] (3) This invention achieves a unity of ecological environmental protection and functional synergy. Specifically, the upper fiber mesh, lower mesh, microcapsule wall material and crosslinking agent are all made of biodegradable materials. The process parameters are adapted to the material characteristics to avoid premature degradation. The mechanism is that the fully biodegradable material system eliminates the risk of secondary pollution. The compatibility between the process and the materials ensures that each functional layer plays a synergistic role. It solves the problems of insufficient environmental protection and incoordination between material degradation and functional performance in traditional vegetation belts, and provides efficient technical support for the green and sustainable development of ecological restoration projects. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic cross-sectional view of a biodegradable vegetation strip for ecological restoration according to the present invention. Figure 2 This is a flowchart of a method for preparing a biodegradable vegetation strip for ecological restoration according to the present invention.

[0022] Explanation of reference numerals in the attached figures: 1. Upper fiber mesh; 2. Middle seed and nutrient layer; 3. Lower mesh; 4. Microcapsules. Detailed Implementation

[0023] The technical solutions of 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.

[0024] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0025] like Figure 1 As shown, this invention provides a biodegradable vegetation strip for ecological restoration, characterized by comprising, from top to bottom, a layered composite structure: an upper fiber mesh 1, a middle seed and nutrient layer 2, and a lower mesh 3; the upper fiber mesh 1 is composed of a hydrophilic biodegradable material for moisture absorption and retention; the middle seed and nutrient layer 2 contains plant seeds and nutrient controlled-release units; the lower mesh 3 is a three-dimensional mesh made of biodegradable polymer material with a three-dimensional interconnected microporous structure for mechanically guiding root growth; the nutrient controlled-release units are microcapsules 4 with fertilizer as the core material and environmentally responsive polymer as the wall material, and the microcapsules 4 are anchored inside the fiber interlacing nodes of the lower mesh 3 by a cross-linking agent.

[0026] The upper fiber web 1 is a continuous fiber web structure made of hydrophilic biodegradable material through melt-blowing process. It forms uniform and interconnected microporous channels inside, with a thickness controlled at 0.1~0.3mm and a porosity maintained at 60%~70%. Its mechanism lies in the fact that the surface of hydrophilic biodegradable materials, such as biodegradable cellulose fibers and polylactic acid modified hydrophilic fibers, is rich in hydrophilic groups such as hydroxyl and carboxyl groups. On the one hand, it efficiently adsorbs water vapor in the air and surface soil moisture through intermolecular forces. On the other hand, it locks the adsorbed water in the fiber gaps through the capillary effect inside the fiber web, significantly reducing the rapid evaporation of water. Ultimately, it provides a continuous and stable humid environment for seed germination and seedling growth, giving full play to the function of moisture absorption and retention, and effectively avoiding the problem of seed dehydration and necrosis under drought conditions.

[0027] The middle layer, consisting of seeds and nutrients (layer 2), is a loosely packed layer. Inside, plant seeds and nutrient-controlled release units (microcapsules 4) are evenly dispersed. The mass ratio of seeds to microcapsules 4 is controlled at 1:0.8~1.2, with an overall thickness of 0.5~1.0 mm. Microcapsules 4 employ a core-shell structure, with the core material being a nitrogen-phosphorus-potassium compound fertilizer or slow-release organic fertilizer, and the wall material being an environmentally responsive polymer with a precisely controlled particle size of 0.1~0.5 mm. The core mechanism involves environmentally responsive polymer wall materials such as polyacrylic acid, chitosan, PLGA, and PCL, which are sensitive to temperature and humidity. When the ambient temperature and humidity reach the suitable range for seed germination or seedling growth, the wall material molecular chains swell or degrade, gradually releasing the fertilizer from the core material. Simultaneously, microcapsules 4 form a stable chemical bond with the interwoven nodes of the lower mesh 3 through a cross-linking agent, effectively preventing displacement and loss. This achieves a stepped nutrient supply from germination to seedling to growth, ensuring the uniformity and continuity of nutrient supply.

[0028] In the above content, the selection and design of environmentally responsive polymers fully consider the differentiated needs of different ecological restoration scenarios. Hydrophilic polymers such as polyacrylic acid and polyacrylamide can quickly respond to changes in soil moisture, rapidly swell and release nutrients when humidity increases, and are suitable for plant growth in humid environments. Natural polymers such as sodium alginate, gelatin, and chitosan have excellent biocompatibility, their degradation products are non-toxic and harmless, and they are sensitive to pH values, making them suitable for soil environments with different acidity and alkalinity. The degradation cycle of synthetic polymers such as PLGA and PCL can be precisely controlled, and the nutrient release time can be designed according to the plant growth cycle. The selection space of multiple polymers ensures the applicability of vegetation strips in various ecological restoration scenarios. The selection of crosslinking agents has also been optimized. Natural crosslinking agents such as citrate, citric acid ester, and genipin have good biocompatibility, leave no residual pollution after degradation, and will not have a negative impact on the soil environment. Synthetic crosslinking agents such as glutaraldehyde aqueous solution and carbodiimide aqueous solution have high crosslinking efficiency and can achieve chemical bonding between microcapsules 4 and mesh fibers in a short time. Moreover, all crosslinking agents can react with the active groups on the surface of environmentally responsive polymer wall materials and mesh fibers to form stable chemical bonds, ensuring that microcapsules 4 are firmly anchored, while not affecting the biodegradability of the material.

[0029] In addition, the microcapsule size is controlled within the range of 0.1~0.5mm, which allows it to be evenly dispersed in the middle layer of the matrix and form close contact with the plant seeds. This ensures that nutrients are accurately supplied to the seeds and the roots of the seedlings during release. At the same time, the particle size is smaller than the seed size, i.e., 0.5~2mm, so it will not affect the normal breakthrough of the radicle during seed germination. It is also easy to anchor to the nodes of the lower grid 3 through directional spraying process, avoiding the problem of weak anchoring caused by excessively large particle size.

[0030] The lower mesh 3 is a three-dimensional interconnected microporous mesh made of biodegradable polymer materials through melt spinning and spunbonding processes. The initial effective pore size is 5~10mm, the fiber linear density is 2.0~5.0dtex, and the overall thickness is 1.0~2.0mm. Its mechanism lies in the fact that PLA in the mesh raw materials provides excellent mechanical strength, PBAT enhances the material's flexibility, and the surface-treated micron-sized lignin fibers enhance the bonding force between fibers through physical entanglement and chemical action, forming a stable three-dimensional support structure. As the material gradually degrades in the natural environment, the polymer molecular chains break, resulting in a dynamic increase in the mesh pore size, which can accurately adapt to the spatial needs of root growth, ultimately providing overall mechanical support for the vegetation strip, preventing deformation and collapse during construction and use, while guiding plant roots to extend into deeper soil layers and enhancing plant rooting stability.

[0031] Specifically, the initial effective pore size of the lower mesh 3, ranging from 5 to 10 mm, can firmly fix the middle layer seeds and the substrate of the nutrient layer 2 through the physical limiting effect of the mesh pores, preventing the substrate from falling off during construction and laying. It can also provide sufficient initial growth space for the seedling roots in the early stage of germination. As the material gradually degrades in the natural environment, the polymer molecular chain breaks, causing the mesh pore size to dynamically increase. This can simultaneously meet the growth needs of the root system from delicate seedling roots to robust mature roots, effectively solving the contradiction that the fixed pore size mesh cannot protect the roots in the early stage and restricts growth in the later stage, further improving the adaptability of plants at different growth stages.

[0032] Furthermore, the lower mesh 3 uses a blend of PLA, PBAT, and 10%~20% lignin fiber. The combination of PLA and PBAT balances the rigidity and toughness of the materials, ensuring that the mesh has sufficient mechanical strength to withstand external impacts during construction, while also possessing good construction flexibility for easy laying. The addition of 10%~20% micron-sized lignin fiber has several advantages. First, the rigid structure of the lignin fiber significantly enhances the mesh's tensile and tear resistance, extending its service life. Second, as a natural biodegradable material, lignin can effectively regulate the degradation rate of the mesh, precisely matching it with the plant growth cycle. This also reduces material costs and improves overall environmental friendliness.

[0033] Based on the above, such as Figure 2 As shown, the present invention also provides a method for preparing the above-mentioned biodegradable vegetation strip for ecological restoration, comprising the following steps: S1. Microcapsules are prepared using fertilizer as the core material and environmentally responsive polymers as the wall material, employing interfacial polymerization or spray drying methods.

[0034] In the interfacial polymerization method, nitrogen, phosphorus, and potassium compound fertilizer is dispersed in deionized water at a mass fraction of 20%–30%, and 0.5%–1% Tween-80 is added as an emulsifier. The mixture is stirred at 500–800 rpm to form a stable aqueous emulsion. Then, an environmentally responsive polymer such as PLGA is dissolved in dichloromethane at a mass fraction of 5%–10% as the organic phase. The aqueous emulsion is slowly added dropwise while maintaining a stirring speed of 1000–1500 rpm to allow polymerization at the interface between the two phases to form a dense microcapsule wall. After the reaction continues for 2–4 hours, the microcapsules are collected by filtration and washed 3–5 times with anhydrous ethanol to remove residual impurities. Subsequently, they are dried in a vacuum drying oven at 40–60°C for 8–12 hours to finally obtain core-shell structured microcapsules with a particle size of 0.1–0.5 mm.

[0035] If spray drying is used, fertilizer and environmentally responsive polymers such as chitosan are mixed at a mass ratio of 3:1, and deionized water is added to make a mixed dispersion with a mass fraction of 15% to 25%. The dispersion is then atomized into tiny droplets through a high-pressure atomizing nozzle with an atomization pressure of 0.8 to 1.0 MPa. The atomized droplets are then passed into a hot air drying tower, and the hot air temperature is controlled at 80 to 100°C and the drying time is 10 to 15 seconds. The droplets lose moisture rapidly in the hot air environment, and the wall material is simultaneously solidified to form microcapsules that encapsulate the core material. After collection, nutrient controlled-release units with the target particle size can be obtained.

[0036] In S1, interfacial polymerization utilizes the interfacial tension difference between the water and oil phases to directionally polymerize wall material molecules on the core material surface, forming a uniform and dense film that effectively encapsulates the fertilizer core material. The stirring speed and reaction time allow for precise control of the microcapsule wall thickness and density. Vacuum drying temperature is strictly controlled below the polymer's glass transition temperature to prevent wall material deformation and maintain controlled-release performance. Spray drying, on the other hand, disperses the mixture into tiny droplets through high-pressure atomization, increasing the surface area for water evaporation. A hot air temperature of 80-100°C ensures rapid water evaporation for molding while preventing fertilizer decomposition at high temperatures and premature degradation of the wall material, thus ensuring the structural integrity and nutrient retention rate of the microcapsules.

[0037] S2. The lower mesh is prepared by melt spinning and spunbonding process. During the spunbonding process, when the fibers have not been completely cooled and solidified, the mixture of microcapsules and crosslinking agent is directionally sprayed onto the fiber interlacing node area. The residual heat of the fibers is used to promote the crosslinking reaction and complete the in-situ chemical anchoring of the microcapsules.

[0038] In this step, the raw materials are first weighed according to the mass ratio of PLA:PBAT:lignin fiber of 60%~70%:20%~30%:10%~20%, and fed into a twin-screw extruder. The extrusion temperature is set to 160~190℃, with 160℃ in zone 1, 175℃ in zone 2, and 190℃ in zone 3. The screw speed is 300~400rpm. After the raw materials are melt-blended, they are extruded from the spinning nozzle to form continuous fibers. After the fibers are drawn, they are laid into a preliminary mesh preform by a web laying machine to ensure that the mesh has a three-dimensional interconnected microporous structure. The fiber linear density is controlled to be 2.0~5.0dtex. Subsequently, during the spunbond molding process, before the fibers have completely cooled and solidified, a mixture of microcapsules and crosslinking agent is directionally sprayed through a high-pressure atomizing nozzle. The mass fraction of microcapsules in the mixture is 30%~50%, the spraying pressure is controlled at 0.3~0.6MPa, and a 1%~2% ethanol solution is used as the crosslinking agent. The spraying range precisely covers the fiber interlacing node area, and the residual heat of the fibers is used to promote the crosslinking reaction. After the spraying is completed, the mesh preform is placed at 100~120℃ for 10~30 seconds for heat treatment. Nitrogen protection is maintained during the heat treatment process, and finally the in-situ chemical anchoring of microcapsules is completed.

[0039] In this step, the temperature gradient setting of the melt spinning and spunbonding process ensures that the raw materials are fully melted and do not degrade. The matching of screw speed and drawing speed can precisely control the fiber linear density, thereby ensuring the mechanical strength and pore structure of the mesh. The directional spraying is carried out when the fibers are not completely cooled and solidified. At this time, the fiber surface still has a certain degree of activity, which facilitates the reaction with the crosslinking agent. The spraying pressure of 0.3~0.6MPa can ensure that the mixture uniformly covers the fiber interlacing nodes. The crosslinking agent concentration of 1%~2% ensures the efficiency of the crosslinking reaction and avoids fiber embrittlement due to excessive concentration. The heat treatment temperature of 100~120℃ and the treatment time of 10~30 seconds can further enhance the crosslinking anchoring effect. Nitrogen protection effectively prevents the biodegradable material from degrading prematurely during the heat treatment process, ensuring the structural stability and service life of the mesh.

[0040] S3. Based on meltblown technology, the upper fiber web is prepared from hydrophilic and biodegradable materials.

[0041] In this step, based on the meltblown process, hydrophilic biodegradable materials such as biodegradable cellulose fibers and polylactic acid-modified hydrophilic fibers are selected as raw materials and fed into the meltblown machine. The meltblown temperature is set to 150~170℃, and the spinneret pressure is 0.2~0.4MPa. After melting, the raw materials are extruded from the spinneret orifices to form ultrafine fibers. Under the action of airflow, the ultrafine fibers are laid together to form a web, which is then cooled and solidified to form the upper fiber web. The thickness of the fiber web is controlled to be 0.1~0.3mm, and the porosity is maintained at 60%~70%. The optimized matching of meltblown temperature and spinneret pressure in this step ensures that the raw materials are fully melted and uniform ultrafine fibers are formed. The interwoven structure of the ultrafine fibers gives the fiber web good moisture absorption and retention properties, while ensuring that the fiber web has sufficient air permeability, providing a suitable gaseous environment for seed germination.

[0042] S4. Plant seeds mixed with the microcapsules are evenly laid on the lower mesh after the microcapsules have been anchored, and then the upper fiber mesh is covered. Finally, the composite molding is carried out by hot rolling process to obtain the biodegradable vegetation strip for ecological restoration.

[0043] Specifically, on the lower grid layer where microcapsules have been anchored, apply 20-50 capsules / cm. 2 Plant seeds mixed with microcapsules are evenly laid at a density of 1:0.8~1.2 (seed to microcapsule mass ratio). This is then covered with an upper fiber web prepared by S3. The three-layer structure is fed into a hot rolling mill for composite forming. The hot rolling temperature is controlled at 110~120℃, the hot rolling pressure at 0.3~0.5MPa, and the hot rolling speed at 5~10m / min. After composite forming, the vegetation strip is cooled at room temperature to below 30℃, finally obtaining a biodegradable vegetation strip for ecological restoration. In this step, the density is 20~50 seeds / cm². 2 The seed density ensures adequate coverage after plant growth, and a seed-to-microcapsule mixing ratio of 1:0.8~1.2 ensures sufficient nutrient supply around each seed. Controlling the hot rolling temperature and pressure is crucial; a temperature of 110~120℃ allows for slight melting of the material surfaces to achieve interlayer bonding without causing material degradation or seed inactivation. A pressure of 0.3~0.5MPa and a speed of 5~10m / min ensure uniform interlayer bonding strength and prevent delamination.

[0044] To verify the technical effects of the present invention, two specific embodiments are described below, wherein the listed embodiments are only some embodiments of the present invention.

[0045] Example 1 In this embodiment, the preparation of biodegradable vegetation strips for ecological restoration includes the following steps: Microcapsule preparation: Microcapsules were prepared using NPK compound fertilizer as the core material and polylactic acid-glycolic acid copolymer (PLGA) as the wall material via interfacial polymerization. 0.3 kg of NPK compound fertilizer (core material) was dispersed at 25% by mass in 1.2 L of deionized water, and 0.0075 kg of Tween-80 was added as an emulsifier. The mixture was ultrasonically stirred at 600 rpm for 30 min to form a stable aqueous emulsion. 0.05 kg of PLGA (wall material) was dissolved at 8% by mass in 0.625 L of dichloromethane and slowly added dropwise to the aqueous emulsion as the organic phase. The reaction was maintained at 1200 rpm for 3 h to allow polymerization at the interface between the two phases, forming the microcapsule wall. After the reaction, the microcapsules were collected by filtration, washed four times with anhydrous ethanol, and dried in a vacuum drying oven at 50℃ for 10 h to obtain microcapsules with a particle size of 0.2–0.3 mm.

[0046] Lower-layer mesh preparation and in-situ microcapsule anchoring: Raw materials were weighed according to a mass ratio of PLA:PBAT:lignin fiber = 65%:25%:10%, including 1.3 kg of PLA, 0.5 kg of PBAT, and 0.2 kg of surface-treated micron-sized lignin fiber. These were fed into a twin-screw extruder, with zone 1 temperatures set to 160℃, zone 2 to 175℃, and zone 3 to 190℃, and a screw speed of 350 rpm. After the raw materials were melted and mixed, they were extruded from the spinning nozzle to form continuous fibers. The fibers were then drawn and laid into a mesh preform using a web-laying machine. The fiber linear density was controlled at 3.0 dtex. Before the fibers were completely cooled and solidified, a mixture of microcapsules and crosslinking agent (microcapsule mass fraction 40%, crosslinking agent is genipin prepared with 1% ethanol solution) was directionally sprayed through a high-pressure atomizing nozzle at a spraying pressure of 0.4 MPa, covering the fiber interlacing node area. After spraying, the mesh blank was placed at 110℃ for 20 seconds for heat treatment, and nitrogen protection was maintained during the heat treatment to complete the in-situ anchoring of microcapsules, resulting in a lower mesh with an initial effective pore size of 5~8 mm.

[0047] Upper layer fiber web preparation: Based on meltblown process, biodegradable cellulose fiber is selected as raw material, put into meltblown machine, meltblown temperature is set to 160℃, spinneret pressure is 0.3MPa, after the raw material melts, it is sprayed out from the spinneret to form ultrafine fiber. The ultrafine fiber lays up into a web under the action of airflow. After cooling and solidification, an upper layer fiber web with a thickness of 0.2mm and a porosity of 65% is obtained.

[0048] Composite molding: On the lower mesh layer where microcapsules have been anchored, at a density of 30 capsules / cm 2Alfalfa seeds mixed with microcapsules (seed to microcapsule mass ratio 1:1) are evenly laid at a uniform density, and then covered with the upper fiber web prepared in step three. The three-layer structure is then fed into a hot rolling mill, with the hot rolling temperature set at 115℃, pressure at 0.4MPa, and speed at 8m / min for composite molding. After composite molding, the vegetation strip is cooled to below 30℃ at room temperature to finally obtain a biodegradable vegetation strip for ecological restoration.

[0049] The vegetation strip prepared in Example 1 was used in an outdoor slope ecological restoration scenario, and its performance was tested for 3 months. The test indicators included seed germination rate, seedling survival rate, nutrient retention rate, root penetration depth, interlayer peeling strength, change in the pore size of the lower layer grid, material degradation rate, and soil pH range. The test methods are as follows: Seed germination rate: The percentage of seeds that germinated within 3 months out of the total number of seeds laid. Seedling survival rate: The percentage of seedlings that survive after germination out of the total number of germinated seeds. Nutrient retention rate: calculated by measuring the ratio of the remaining fertilizer content in the intermediate substrate to the initial fertilizer content; Root penetration depth: Randomly select 10 seedlings and measure the depth to which the roots vertically penetrate the vegetation zone and extend into the soil, and take the average value; Material degradation rate: The proportion of the vegetation strip's mass loss to its initial mass after 3 months was calculated by weighing. Suitable pH range for soil: Vegetation strips were laid in soil samples with different pH values, and the pH range in which seeds could germinate normally was recorded.

[0050] Example 2 In this embodiment, the preparation of biodegradable vegetation strips for ecological restoration includes the following steps: Microcapsule preparation: Microcapsules were prepared using slow-release organic fertilizer as the core material and chitosan as the wall material via spray drying. 0.4 kg of slow-release organic fertilizer and 0.167 kg of chitosan were mixed at a mass ratio of 3:1, and 1.86 L of deionized water was added. The mixture was stirred to prepare a 25% (w / w) mixed dispersion. The dispersion was atomized through a high-pressure atomizing nozzle (0.9 MPa) and passed into a hot air drying tower. The hot air temperature was controlled at 90℃ and the drying time was 12 seconds. After drying, the droplets formed core-shell structured microcapsules, which were collected to obtain microcapsules with a particle size of 0.3–0.4 mm.

[0051] Lower-layer mesh preparation and in-situ microcapsule anchoring: Raw materials were weighed according to a mass ratio of PLA:PBAT:lignin fiber = 60%:20%:20%, including 1.2 kg of PLA, 0.4 kg of PBAT, and 0.4 kg of surface-treated micron-sized lignin fiber. These were fed into a twin-screw extruder with zone 1 temperatures of 165℃, zone 2 temperatures of 180℃, and zone 3 temperatures of 190℃, and a screw speed of 380 rpm. After melt mixing, the raw materials were spun, drawn, and web-laid, with the fiber linear density controlled at 4.0 dtex. Before the fibers were completely cooled and solidified, a mixture of microcapsules and a crosslinking agent (microcapsule mass fraction 45%, crosslinking agent being carbodiimide prepared with a 2% ethanol solution) was directionally sprayed through a high-pressure atomizing nozzle at a pressure of 0.5 MPa. After spraying, the mixture was heat-treated at 115℃ for 15 seconds under nitrogen protection to complete the anchoring, resulting in a lower-layer mesh with an initial effective pore size of 7-10 mm.

[0052] Upper layer fiber web preparation: Polylactic acid modified hydrophilic fiber was selected as raw material. Based on the meltblown process, the meltblown temperature was set at 165℃ and the spinning pressure was 0.35MPa to prepare an upper layer fiber web with a thickness of 0.25mm and a porosity of 68%.

[0053] Composite molding: 40 particles / cm on the lower mesh layer 2 Seeds mixed with microcapsules (seed to microcapsule mass ratio 1:1.2) are laid at a density of 1, covered with an upper fiber mesh, and then fed into a hot rolling mill. The hot rolling temperature is set at 120℃, the pressure at 0.3MPa, and the speed at 6m / min. After composite molding, the mixture is cooled to below 30℃ at room temperature to obtain a biodegradable vegetation strip for ecological restoration.

[0054] The vegetation strip prepared in Example 2 was used in an ecological restoration scenario of a mining wasteland, and its performance was tested for 3 months using the same testing method as in Example 1.

[0055] Comparative Example 1 In this comparative example, the preparation of a traditional biodegradable vegetation strip includes the following steps: Microcapsule preparation: Microcapsules of PLGA wall material and nitrogen-phosphorus-potassium compound fertilizer core material were prepared using the same raw materials and methods as in Example 1, with a particle size of 0.2~0.3 mm.

[0056] Lower layer mesh preparation: The raw materials were weighed at a mass ratio of PLA:PBAT=75%:25%, without the addition of lignin fiber, and a lower layer mesh with a fixed pore size of 8mm was prepared by melt spinning and spunbonding process. The fiber linear density was 3.0dtex, and no microcapsule anchoring treatment was performed.

[0057] Preparation of upper fiber web: Same as in Example 1, prepare a biodegradable cellulose fiber upper fiber web with a thickness of 0.2 mm and a porosity of 65%.

[0058] Composite molding: Alfalfa seeds mixed with microcapsules are laid on the lower grid (seed to microcapsule mass ratio 1:1, laying density 30 seeds / cm). 2 After covering with an upper layer of fiber mesh, it is hot-rolled and composited at parameters of 115℃, 0.4MPa, and 8m / min. After cooling, a traditional biodegradable vegetation strip (without microcapsule anchoring and fixed pore size mesh) is obtained.

[0059] The vegetation strip prepared in Comparative Example 1 was placed in the same outdoor slope scenario as in Example 1, and its performance was tested for 3 months using the same testing method.

[0060] Comparative Example 2 In this comparative example, the preparation of a traditional biodegradable vegetation strip includes the following steps: Microcapsule preparation: Chitosan wall material and slow-release organic fertilizer core material microcapsules were prepared using the same raw materials and methods as in Example 2, with a particle size of 0.3~0.4 mm.

[0061] Lower layer mesh preparation: The raw materials were weighed according to the mass ratio of PLA:PBAT=80%:20%, without the addition of lignin fiber, to prepare a lower layer mesh with a fixed pore size of 8mm and a fiber linear density of 4.0dtex, without microcapsule anchoring treatment.

[0062] Preparation of upper fiber web: Same as in Example 2, a polylactic acid modified hydrophilic fiber upper fiber web with a thickness of 0.25 mm and a porosity of 68% was prepared.

[0063] Composite molding: Bermuda grass seeds mixed with microcapsules are laid on the lower grid (seed to microcapsule mass ratio 1:1.2, laying density 40 seeds / cm²). 2 After covering with an upper layer of fiber mesh, it is hot-rolled and composited at parameters of 120℃, 0.3MPa, and 6m / min, and then cooled to obtain a traditional biodegradable vegetation strip (without microcapsule anchoring and fixed pore size mesh).

[0064] The vegetation strip prepared in Comparative Example 2 was placed in the same mine wasteland scenario as in Example 2, and its performance was tested for 3 months using the same testing method.

[0065] Based on the above-mentioned Examples 1-2 and Comparative Examples 1-2, the corresponding performance test results are summarized, and the results are shown in Table 1.

[0066] Table 1 Performance Test Results

[0067] Table 1 shows that, in terms of basic plant growth performance, the seed germination rate and seedling survival rate of Example 1 were increased by 3.7 and 4.4 percentage points respectively compared to Comparative Example 1, while the corresponding indicators of Example 2 were increased by 7.9 and 9.2 percentage points respectively compared to Comparative Example 2. This indicates that the structural and process design of the present invention can provide more stable support for seed germination and seedling growth. Regarding nutrient retention rate, Examples 1 and 2 reached 62.8% and 65.3% respectively, an increase of 9.6 and 13.6 percentage points respectively compared to Comparative Examples 1 and 2, demonstrating that the microcapsule anchoring mechanism effectively reduces nutrient loss and increases nutrient retention. The continuous supply of nutrients was enhanced. In terms of root growth adaptability, the root penetration depth of Examples 1 and 2 was 13.5 cm and 14.2 cm, respectively, which was 2.3 cm and 3.4 cm higher than that of the comparative examples 1 and 2. This confirms that the dynamic pore size of the lower layer grid provided by the present invention can adapt to the needs of root growth and avoid the limitation of root extension by the traditional fixed pore size grid. The slightly higher degradation rate of the materials in Examples 1 and 2 and the wider range of soil pH adaptability indicate that the material selection and process optimization of the present invention not only ensure the matching of degradation rhythm with plant growth, but also broaden the applicable soil environment of the vegetation zone.

[0068] Therefore, the above-mentioned biodegradable vegetation strip for ecological restoration and its preparation method can achieve precise controlled release of plant rhizosphere nutrients and three-dimensional mechanical guidance of root growth paths while ensuring the overall biodegradability of the carrier. This effectively improves fertilizer utilization and the survival rate and long-term stability of vegetation restoration under adverse site conditions such as slopes, riverbanks, and mines.

[0069] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0070] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A degradable vegetation belt for ecological restoration, characterized in that, The composite includes an upper layer of fiber net, a middle layer of seed and nutrient layer, and a lower layer of grid, which are stacked in sequence from top to bottom; the upper layer of fiber net is made of hydrophilic degradable material and is used for moisture absorption and soil conservation; the middle layer of seed and nutrient layer contains plant seeds and nutrient controlled release units; the lower layer of grid is a three-dimensional grid made of degradable polymer material and has a three-dimensional interconnected microporous structure, which is used for mechanical guiding of root growth; the nutrient controlled release unit is a microcapsule with fertilizer as the core material and environment-responsive polymer as the wall material, and the microcapsule is anchored inside the fiber interlacing nodes of the lower layer of grid by a crosslinking agent.

2. The degradable vegetation belt for ecological restoration according to claim 1, characterized in that, The initial effective pore size of the three-dimensional grid structure of the lower layer of grid is 5-10 mm, and the effective pore size dynamically increases with the degradation process of the material.

3. The degradable vegetation belt for ecological restoration according to claim 1, characterized in that, The raw material of the lower layer of grid includes polylactic acid (PLA), polybutylene adipate terephthalate (PBAT), and micron-sized lignin fibers treated on the surface, wherein the mass fraction of the lignin fibers is 10%-20%.

4. The degradable vegetation belt for ecological restoration according to claim 1, characterized in that, The environment-responsive polymer is one or more of polyacrylic acid, polyacrylamide, sodium alginate, gelatin, chitosan, polyvinyl alcohol, polylactic acid-glycolic acid copolymer (PLGA), and polycaprolactone (PCL).

5. The degradable vegetation belt for ecological restoration according to claim 1, characterized in that, The crosslinking agent is one or more of citrate, citrate ester, genipin, tannic acid, glutaraldehyde aqueous solution, or carbodiimide aqueous solution.

6. A method for preparing the degradable vegetated strip for ecological restoration according to any one of claims 1 to 5, characterized in that, The method includes the following steps: S1. A microcapsule is prepared by using an interface polymerization method or a spray drying method, with fertilizer as the core material and environment-responsive polymer as the wall material. S2. The lower layer of grid is prepared by a melt spinning and spun-bonding process, and when the fibers have not yet completely cooled and solidified during the spun-bonding forming process, a mixed solution of the microcapsule and the crosslinking agent is sprayed to the fiber interlacing node area in a directional manner, and the crosslinking reaction is promoted to occur by using the residual heat of the fibers to complete the in-situ chemical anchoring of the microcapsule. S3. An upper layer of fiber net is prepared from a hydrophilic degradable material based on a melt blowing process. S4. On the lower layer of grid on which the anchoring of the microcapsule has been completed, plant seeds mixed with the microcapsule are uniformly laid, and then the upper layer of fiber net is covered, and finally a hot rolling process is performed for composite forming to obtain the degradable vegetation belt for ecological restoration.

7. The method of claim 6, wherein, In S1, when the interface polymerization method is used, the core material is dispersed in an aqueous solution, the wall material is dissolved in an organic phase solution, and the interface of the two phases is subjected to a polymerization reaction to form a microcapsule wall by stirring; when the spray drying method is used, a mixed dispersion liquid of the core material and the wall material is subjected to high-pressure atomization, and then dried and formed in a hot air environment at 80-100℃; the particle size of the microcapsule is 0.1-0.5 mm.

8. The method of claim 6, wherein, In S2, the spinning temperature of the melt spinning and spun-bonding process is 160-190℃, and the fiber linear density is 2.0-5.0 dtex; in the mixed solution of the microcapsule and the crosslinking agent, the mass fraction of the microcapsule is 30%-50%, and the mixed solution is sprayed in a directional manner by using a high-pressure atomization nozzle, and the spraying range can cover the fiber interlacing node area.

9. The method of claim 8, wherein, In S2, the process parameters of the directional spraying are as follows: spraying pressure 0.3-0.6 MPa, and the crosslinking agent is an ethanol solution with a concentration of 1%-2%. After the spraying is completed, heat treatment is performed at 100-120 DEG C for 10-30 seconds, and nitrogen protection is maintained during the heat treatment, so as to strengthen the cross-linking anchoring effect and avoid material degradation.

10. The method of claim 6, wherein, In S4, the laying density of the plant seeds is 20-50 grains / cm 2 The mixing mass ratio of the seeds and the microcapsules is 1:0.8-1.2; the parameters of the hot rolling composite process are as follows: hot rolling temperature 110-120 DEG C, hot rolling pressure 0.3-0.5 MPa, and hot rolling speed 5-10 m / min. After the composite molding, the vegetation belt is cooled at room temperature, and finally the vegetation belt is obtained.

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