Hydroponic foam matrix as well as preparation method and application thereof

Abstract

The invention provides a hydroponic foam matrix as well as a preparation method and application thereof. The hydroponic foam matrix comprises at least one layer of surface layer material, at least one layer of middle layer material and at least one layer of deep layer material from top to bottom, the surface layer material comprises the following components in parts by weight: 30-80 parts of a vinyl aromatic compound, 5-30 parts of hydroxyl acrylate, 10-35 parts of an acrylic compound and 5-25 parts of a cross-linking agent; the middle layer material comprises the following components in parts by weight: 40-80 parts of a vinyl aromatic compound, 10-40 parts of a vinyl imidazole compound and 5-20 parts of a cross-linking agent; the deep layer material comprises the following components in parts by weight: 20-50 parts of a vinyl aromatic compound, 10-40 parts of a vinyl imidazole compound, 10-35 parts of an acrylic acid compound and 5-20 parts of a cross-linking agent. The hydroponic foam matrix can adsorb different nutrients in a nutrient solution in a targeted mode, and the nutrient requirements of plants in different growth stages are met.

Description

Technical Field

[0001] This invention belongs to the technical field of porous polymer foam materials, and particularly relates to a hydroponic foam matrix, its preparation method and application. Background Technology

[0002] Hydroponics is one of the core cultivation methods in modern agriculture, providing nutrients for crop growth by directly delivering nutrient solution to the roots. Traditional hydroponic systems mainly rely on the circulation of pre-prepared nutrient solutions to meet the needs of plants throughout their entire growth cycle, and use inert substrates such as rock wool and sponges to fix the roots. Although this model has the advantages of water conservation and high yield, its nutrient supply method is mostly "uniform adsorption," making it difficult to adapt to the dynamic needs of plants for different types and concentrations of nutrients at different growth stages. For example, the absorption characteristics of elements such as nitrogen, phosphorus, and potassium differ significantly between the seed germination period, seedling stage, and vigorous seedling stage. Traditional substrates cannot achieve precise stage-specific nutrient control, often requiring frequent manual adjustments or replacements of the nutrient solution, which is not only cumbersome but also prone to root damage, seedling burn, or stage-specific nutrient deficiencies.

[0003] Furthermore, this technology has inherent limitations in oxygen supply. Plant roots are constantly submerged in a liquid environment, and especially when the root system is dense, insufficient dissolved oxygen can lead to root hypoxia, affecting crop growth. At the same time, commonly used hydroponic substrates such as rock wool and sponge blocks have limited functions, only providing physical support and unable to actively participate in nutrient regulation or improve the root zone environment, further limiting the nutrient supply efficiency of the hydroponic system.

[0004] CN110268964A discloses a method for cultivating high-quality, low-potassium lettuce, comprising: preparing a 1 / 2 Japanese garden trial formula nutrient solution containing potassium and a 1 / 2 Japanese garden trial formula nutrient solution without potassium; after the lettuce seeds germinate, the seedlings are transplanted into sponge blocks and placed in a hydroponic trough for cultivation, the hydroponic trough containing the 1 / 2 Japanese garden trial formula nutrient solution; after the seedlings are transplanted, the hydroponic trough is placed in a natural light environment, and the plants grow by relying on natural light; two weeks after transplanting, the nutrient solution in the hydroponic trough is replaced with the potassium-free 1 / 2 Japanese garden trial formula nutrient solution, and after the solution replacement, the hydroponic trough is still placed in a natural light environment, and the plants grow by relying on natural light; an LED supplemental light is installed above the hydroponic trough, and the LED supplemental light is turned on 48 hours before harvest, the light quality of the supplemental light is blue light, and the supplemental light is continuously provided for 48 hours until harvest. This patent meets the nutritional needs of plants at different growth stages by changing the nutrient solution, and the sponge blocks only serve a fixing function.

[0005] CN203597195U discloses a planting board for hydroponics, which can be continuously extended horizontally and vertically to form a larger planting board. A sponge hemisphere serves to fix the plant, quickly achieving the planting of hydroponic plants. This patent solves the problems of conventional foam board hydroponics, such as insufficient flexibility in the shape and size of the water container, easy damage to the root system, plant root and stem rot, and unstable plant fixation. However, it requires changing the nutrient solution with different nutrients according to different growth stages of the plant, which can easily cause root damage, seedling burn, or nutrient deficiency.

[0006] CN110291977A discloses a hydroponic sponge assembly for easy sowing, comprising a lower sponge section and an upper sponge section. The upper sponge section has blind holes on its upper side, and the upper sponge section has a slit. The upper sponge section is placed on the lower sponge section, with the slit located above the blind holes. This hydroponic sponge assembly covers the top of the blind holes with the upper sponge section, meeting the light-sensitive requirement. Simultaneously, seeds can grow upwards without needing to be inserted into the slit, making sowing simpler and more efficient. However, this sponge cannot target specific nutrients, requiring regular replacement of the nutrient solution.

[0007] High internal phase emulsion foams, with their high porosity, three-dimensional interconnected pore structure, and excellent liquid adsorption and slow-release properties, are increasingly widely used in functional materials, especially showing potential value in hydroponic plant technology. In hydroponic plant technology, high internal phase emulsion foams, as a novel porous material, allow for precise control of pore structure and porosity through the regulation of emulsion formulation and preparation processes. This enables efficient adsorption and controlled, slow release of nutrient solutions while ensuring the aerobic respiration needs of the roots. However, the application of this technology in hydroponics is still in the exploratory stage and has not yet been widely adopted.

[0008] In addition, high internal phase emulsion porous foam materials can also be applied in the field of daily chemical hygiene products, such as sanitary napkins and dressings. Their porous structure gives the materials excellent absorption, flow conduction, water retention, anti-backflow and slow release advantages, which helps to improve the user experience and functionality of the products.

[0009] Therefore, developing a layered, targeted hydroponic foam substrate for adsorbing specific nutrients, enabling precise nutrient supply at different growth stages of plants and meeting their needs throughout the entire growth cycle, has become a pressing technical problem in this field. Summary of the Invention

[0010] To address the shortcomings of existing technologies, the present invention aims to provide a hydroponic foam substrate, its preparation method, and its application. The hydroponic foam substrate adopts a layered structure design. By selectively choosing the material components of each layer, each layer can target and adsorb different nutrients in the nutrient solution to meet the nutrient requirements of different growth stages and parts of the plant. This avoids the need for frequent replacement of substrate or nutrient solution during plant cultivation, as well as the mechanical damage and environmental stress to the roots caused by such replacement.

[0011] To achieve this objective, the present invention adopts the following technical solution:

[0012] In a first aspect, the present invention provides a hydroponic foam substrate, wherein the hydroponic foam substrate comprises, from top to bottom, at least one surface material, at least one intermediate material and at least one deep material;

[0013] The surface material comprises the following components by weight:

[0014] Vinyl aromatic compounds 30-80 parts, hydroxy acrylate 5-30 parts, acrylic acid compounds 10-35 parts, crosslinking agent 5-25 parts;

[0015] The intermediate layer material comprises the following components by weight:

[0016] 40-80 parts of vinyl aromatic compounds, 10-40 parts of vinyl imidazole compounds, and 5-20 parts of crosslinking agents;

[0017] The deep material comprises the following components by weight:

[0018] 20-50 parts of vinyl aromatic compounds, 10-40 parts of vinyl imidazole compounds, 10-35 parts of acrylic compounds, and 5-20 parts of crosslinking agents.

[0019] In this invention, sufficient water is required during seed germination. The surface material is selected to contain hydroxyl monomers to enhance its hydrophilicity, providing enough water for seed germination and promoting root development. During the seedling stage, the plant roots grow downwards continuously, requiring sufficient potassium and nitrogen elements. The intermediate layer material is selected from vinylimidazolium compounds, which target and adsorb anionic nutrients PO4 through the coordination of the imidazole ring. 3- NO3 - During the seedling stage, as the root system matures, the plant requires large amounts of nitrogen, phosphorus, potassium, and trace elements. For deep-penetration materials, vinylimidazole compounds and acrylic acid compounds are selected. Vinylimidazole compounds adsorb large amounts of phosphorus and nitrogen, while the carboxyl groups in acrylic acid compounds target and adsorb cationic nutrients (Ca) through electrostatic interactions. 2+ Fe 2+ Zn 2+Trace elements are also present. Vinyl aromatic compounds in each layer of the material construct the polymer skeleton, providing the necessary mechanical strength and structural stability for each layer. Crosslinking agents enable effective control over the pore size of the foam material. This invention prepares foam material layers with different properties through the selection of polymer monomers, endowing different layers with specific functional groups and surface characteristics. This allows them to selectively adsorb and store different nutrients from the same nutrient solution. When plant roots grow to the corresponding depth, the nutrients absorbed by the foam material are preferentially absorbed and utilized. This achieves "one-time construction, no need to change the substrate, precise fertilization, and full-cycle use," avoiding the mechanical damage and environmental stress to the roots caused by frequent changes in substrate or nutrient solution during cultivation.

[0020] The amount of vinyl aromatic compounds used in the surface material can be 30 parts, 32 parts, 34 parts, 36 parts, 38 parts, 40 parts, 42 parts, 44 parts, 46 parts, 48 ​​parts, 50 parts, 52 parts, 54 parts, 56 parts, 58 parts, 60 parts, 62 parts, 64 parts, 66 parts, 68 parts, 70 parts, 72 parts, 74 parts, 76 parts, 78 parts, or 80 parts, etc.

[0021] The amount of hydroxyl acrylate used in the surface material can be 5 parts, 6 parts, 8 parts, 10 parts, 12 parts, 14 parts, 16 parts, 18 parts, 20 parts, 22 parts, 24 parts, 26 parts, 28 parts, or 30 parts, etc.

[0022] The amount of acrylic compound used in the surface material and the deep material can be independently 10 parts, 12 parts, 14 parts, 16 parts, 18 parts, 20 parts, 22 parts, 24 parts, 26 parts, 28 parts, 30 parts, 32 parts, 34 parts or 35 parts, etc.

[0023] The amount of crosslinking agent used in the surface material can be 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, 11 parts, 12 parts, 13 parts, 14 parts, 15 parts, 16 parts, 17 parts, 18 parts, 19 parts, 20 parts, 21 parts, 22 parts, 23 parts, 24 parts, or 25 parts, etc.

[0024] The amount of vinyl aromatic compounds used in the intermediate layer material can be 40 parts, 42 parts, 44 parts, 46 parts, 48 ​​parts, 50 parts, 52 parts, 54 parts, 56 parts, 58 parts, 60 parts, 62 parts, 64 parts, 66 parts, 68 parts, 70 parts, 72 parts, 74 parts, 76 parts, 78 parts, or 80 parts, etc.

[0025] The amount of vinylimidazole compounds used in the intermediate layer material and the deep layer material can be independently 10 parts, 12 parts, 14 parts, 16 parts, 18 parts, 20 parts, 22 parts, 24 parts, 26 parts, 28 parts, 30 parts, 32 parts, 34 parts, 36 parts, 38 parts or 40 parts, etc.

[0026] The amount of crosslinking agent used in the intermediate layer material and the deep layer material can be independently 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, 11 parts, 12 parts, 13 parts, 14 parts, 15 parts, 16 parts, 17 parts, 18 parts, 19 parts or 20 parts, etc.

[0027] The amount of vinyl aromatic compounds used in the deep material can be 20 parts, 22 parts, 24 parts, 26 parts, 28 parts, 30 parts, 32 parts, 34 parts, 36 parts, 38 parts, 40 parts, 42 parts, 44 parts, 46 parts, 48 ​​parts, or 50 parts, etc.

[0028] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The purpose and beneficial effects of the present invention can be better achieved and realized through the following preferred technical solutions.

[0029] Preferably, the compressive strength of the surface material is 0.1-0.2 MPa, such as 0.1 MPa, 0.11 MPa, 0.12 MPa, 0.13 MPa, 0.14 MPa, 0.15 MPa, 0.16 MPa, 0.17 MPa, 0.18 MPa, 0.19 MPa, or 0.2 MPa.

[0030] Preferably, the compressive strength of the intermediate layer material is 0.3-0.4 MPa, such as 0.3 MPa, 0.31 MPa, 0.32 MPa, 0.33 MPa, 0.34 MPa, 0.35 MPa, 0.36 MPa, 0.37 MPa, 0.38 MPa, 0.39 MPa, or 0.4 MPa.

[0031] Preferably, the compressive strength of the deep material is 0.4-0.5 MPa, such as 0.4 MPa, 0.41 MPa, 0.42 MPa, 0.43 MPa, 0.44 MPa, 0.45 MPa, 0.46 MPa, 0.47 MPa, 0.48 MPa, 0.49 MPa, or 0.5 MPa.

[0032] In this invention, the hydroponic foam substrate employs a gradient compressive strength design, with the compressive strength gradually increasing from the surface to the deep layers. The surface material has lower compressive strength and a softer texture to minimize mechanical damage to young roots; the middle layer material has moderate toughness and compressive strength, providing stable mechanical support for the root system; and the deep layer material has higher compressive strength, providing strong support for deep root development and promoting robust root growth.

[0033] Preferably, the pore size of the surface material is 10-20 μm, such as 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm or 20 μm.

[0034] Preferably, the pore size of the intermediate layer material is 20-40 μm, such as 20 μm, 22 μm, 24 μm, 26 μm, 28 μm, 30 μm, 32 μm, 34 μm, 36 μm, 38 μm or 40 μm.

[0035] Preferably, the pore size of the deep material is 40-100μm, such as 40μm, 45μm, 50μm, 55μm, 60μm, 65μm, 70μm, 75μm, 80μm, 85μm, 90μm, 95μm or 100μm.

[0036] Preferably, the vinyl aromatic compound includes styrene and / or vinyltoluene.

[0037] Preferably, the hydroxy acrylate includes any one or a combination of at least two of hydroxyethyl methacrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, or hydroxypropyl methacrylate.

[0038] Preferably, the acrylic compound includes any one or a combination of at least two of acrylic acid, methacrylic acid, or ethyl acrylate.

[0039] Preferably, the crosslinking agent comprises any one or a combination of at least two of the following: divinylbenzene, 1,6-hexanediol diacrylate, 1,4-butanediol dimethacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, 1,12-dodecyl dimethacrylate, 1,14-tetradecanediol dimethacrylate, ethylene glycol dimethacrylate, neopentyl glycol diacrylate, 2,2-dimethylpropylene glycol diacrylate, hexanediol diacrylate, methacrylate, or sorbitol pentaacrylate.

[0040] Preferably, the vinylimidazole compound includes any one or a combination of at least two of vinylimidazole, 2-methylvinylimidazole, or 4-methylvinylimidazole.

[0041] Preferably, the surface material, intermediate material, and deep material each independently further include any one or a combination of at least two of the following: an initiator, a surfactant, a solvent, or an electrolyte.

[0042] Preferably, the initiator includes a persulfate initiator.

[0043] Preferably, the persulfate initiator includes any one or a combination of at least two of ammonium persulfate, sodium persulfate, or potassium persulfate.

[0044] Preferably, the amount of initiator in each of the surface material, intermediate layer material and deep layer material is 1-3 parts, for example, 1 part, 2 parts or 3 parts.

[0045] Preferably, the surfactant comprises any one or a combination of at least two of the following: Span 80, organically modified montmorillonite, nano-silica, polyglycerol ricinoleate, sorbitol monooleate, sorbitol monomyristate, sorbitol monoester, sorbitol monolaurate, dipolyglycerol monooleate, polyglycerol isostearate, polyglycerol monomyristate, diglycerol monooleate, diglycerol monomyristate, diglycerol monoisostearate, diglycerol monoester, sterols, triterpenoid alcohols, palmitenol, oleyl alcohol, isostearyl alcohol, lauryl alcohol, myristyl alcohol, or coconut oil alcohol.

[0046] Preferably, the amount of surfactant used in the surface material, intermediate layer material and deep layer material is 4-6 parts each, for example 4 parts, 5 parts or 6 parts.

[0047] Preferably, the solvent includes water.

[0048] Preferably, the electrolyte comprises any one or a combination of at least two of calcium chloride, sodium chloride, sodium sulfate, or calcium sulfate.

[0049] Preferably, the amount of electrolyte in the surface material, intermediate layer material and deep layer material is independently 2-4 parts, for example 2 parts, 3 parts or 4 parts.

[0050] In a second aspect, the present invention provides a method for preparing a hydroponic foam substrate as described in the first aspect, the method comprising the following steps:

[0051] (1) Mix vinyl aromatic compounds, hydroxy acrylates, acrylic compounds and crosslinking agents to obtain oil phase component A;

[0052] Vinyl aromatic compounds, vinyl imidazole compounds, and crosslinking agents are mixed to obtain oil phase component B;

[0053] Vinyl aromatic compounds, vinyl imidazole compounds, acrylic compounds, and crosslinking agents are mixed to obtain oil phase component C;

[0054] (2) The initiator, solvent and electrolyte are mixed to obtain an aqueous phase component;

[0055] (3) Mix oil phase component A, oil phase component B, and oil phase component C with aqueous phase component respectively, emulsify, and react to obtain the surface material, intermediate layer material, and deep layer material;

[0056] (4) At least one surface material, at least one intermediate material and at least one deep material are stacked to obtain the hydroponic foam substrate.

[0057] This invention regulates the functional groups and surface properties of each layer of material by selecting specific functional monomers; and fully utilizes the adjustability of the high internal phase emulsion template method in terms of pore size, physical properties and porosity to prepare foam materials with high porosity and suitable pore size. The gradient nutrient adsorption and strength design of this foam material in the vertical direction can accurately match the needs of different growth stages of plant roots, creating the best growth environment for plant roots.

[0058] The hydroponic foam substrate of this invention has a surface material suitable for seed germination, containing a large number of hydroxyl groups, which has a water-retaining effect and also resists NH4+. + It exhibits weak adsorption capacity, thus avoiding salt stress; the intermediate layer material is suitable for plant seedlings and contains imidazole groups, enabling it to adsorb large amounts of NO3. - and PO4 3- It promotes rapid plant growth; the deep-layer material is suitable for the vigorous seedling stage of plants, enhances salt tolerance, and the carboxyl groups contained in the deep-layer material can adsorb a large amount of Ca. 2+ Fe 2+ K + The material contains isocations to meet the growth needs of plants during their vigorous seedling stage. The pre-load of each layer of material is slightly higher than the amount that the plant needs to absorb, to prevent nutrient depletion midway.

[0059] Preferably, the mixture of oil phase component A, oil phase component B and oil phase component C further includes a surfactant.

[0060] Preferably, the volume ratio of oil phase component A, oil phase component B, and oil phase component C to the aqueous phase component is independently 1:(10-40), for example, 1:10, 1:12, 1:14, 1:16, 1:18, 1:20, 1:22, 1:24, 1:26, 1:28, 1:30, 1:32, 1:34, 1:36, 1:38, or 1:40, etc.

[0061] Preferably, the emulsification time is 20-30 minutes, such as 20 minutes, 21 minutes, 22 minutes, 23 minutes, 24 minutes, 25 minutes, 26 minutes, 27 minutes, 28 minutes, 29 minutes, or 30 minutes.

[0062] Preferably, the reaction is carried out in a polytetrafluoroethylene mold.

[0063] Preferably, the reaction includes a first-stage polymerization and a second-stage polymerization.

[0064] Preferably, the polymerization temperature in the first stage is 55-65℃, such as 55℃, 56℃, 57℃, 58℃, 59℃, 60℃, 61℃, 62℃, 63℃, 64℃ or 65℃.

[0065] Preferably, the polymerization time in the first stage is 1-1.5 hours, such as 1 hour, 1.1 hours, 1.2 hours, 1.3 hours, 1.4 hours, or 1.5 hours.

[0066] Preferably, the polymerization temperature in the second stage is 75-85℃, such as 75℃, 76℃, 77℃, 78℃, 79℃, 80℃, 81℃, 82℃, 83℃, 84℃ or 85℃.

[0067] Preferably, the polymerization time in the second stage is 2-3 hours, such as 2 hours, 2.2 hours, 2.4 hours, 2.6 hours, 2.8 hours, or 3 hours.

[0068] Preferably, step (4) further includes impregnation and drying before the lamination.

[0069] Preferably, the impregnation includes immersing the surface material, intermediate material and deep material in a nutrient solution.

[0070] Preferably, the impregnation is carried out under vacuum conditions.

[0071] Preferably, the soaking time is 2-3 hours, such as 2 hours, 2.2 hours, 2.4 hours, 2.6 hours, 2.8 hours, or 3 hours.

[0072] Preferably, the nutrient solution contains any one or a combination of at least two of the elements nitrogen, phosphorus, potassium, calcium, iron, or zinc.

[0073] Thirdly, the present invention provides an application of the hydroponic foam substrate as described in the first aspect in plant cultivation or daily chemical hygiene products.

[0074] Preferably, the plants used in the plant cultivation include at least one of leafy vegetables, melons and fruits, or flowers.

[0075] Preferably, the multilayer high internal phase emulsion foam preparation technology of the present invention is also applicable to the preparation of multilayer absorbent foam materials. This material can be used in the field of sanitary napkins, medical dressings, and other daily chemical hygiene products. By using one or more layers of absorbent foam material as the core of sanitary napkins, medical dressings, and other daily chemical hygiene products, its high porosity, high connectivity, and controllable pore size enable rapid absorption, diversion, water retention, anti-backflow, and slow release of liquids such as moisture, menstrual blood, blood, body fluids, and nutrients. This results in hygiene products that are thin, dry, long-lasting, and have a slow-release effect.

[0076] Compared with the prior art, the present invention has the following beneficial effects:

[0077] (1) The foam material with vertical gradient nutrient adsorption function provided by the present invention achieves automatic matching and synchronization of nutrient supply and different root growth depths by targeting the adsorption of different nutrients. It is suitable for the whole cycle cultivation of plants from seed rooting to complete root development. At the same time, it has physical support, water retention and air permeability functions, realizing "one-time construction, no need to change substrate, precise fertilization, and full cycle use", avoiding mechanical damage and environmental stress to the root system caused by frequent replacement of substrate or nutrient solution during cultivation.

[0078] (2) The hydroponic foam substrate prepared by the present invention has a surface material with a pore size of 10-20 μm and a compressive strength of 0.1-0.2 MPa, a middle layer material with a pore size of 20-40 μm and a compressive strength of 0.3-0.4 MPa, and a deep layer material with a pore size of 40-100 μm and a compressive strength of 0.4-0.5 MPa. This gradient design enables the physical properties of the material at different depths to be precisely matched with the growth requirements of the root system, and has a high water retention rate of ≥90%.

[0079] (3) Plants were cultured using the hydroponic foam substrate provided by this invention, and all growth indicators showed excellent performance. Specifically, the seed germination rate of the three plants was 92%-95% (except for the rose), the root system integrity was 96%-98%, the plant height was 18.5-42.6cm, the number of lettuce leaves was 8, the number of tomato fruits was 3, and the number of rose flowers was 2. Attached Figure Description

[0080] Figure 1 This is a scanning electron microscope image of the microstructure of the surface material of the hydroponic foam substrate prepared in Example 1;

[0081] Figure 2 This is a scanning electron microscope image of the microstructure of the intermediate layer material of the hydroponic foam substrate prepared in Example 1;

[0082] Figure 3 This is a scanning electron microscope image of the microstructure of the deep hydroponic foam substrate material prepared in Example 1;

[0083] Figure 4 This is a scanning electron microscope image of the transition between the intermediate and surface layers of the hydroponic foam substrate prepared in Example 1. Detailed Implementation

[0084] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0085] Example 1 (High Nitrogen + High Calcium)

[0086] This embodiment provides a hydroponic foam substrate, the raw materials for which the hydroponic foam substrate is prepared are shown in Table 1:

[0087] Table 1

[0088]

[0089] The preparation method includes the following steps:

[0090] (1) According to the above formula dosage, styrene, hydroxyethyl methacrylate, acrylic acid, divinylbenzene and dehydrated sorbitol monooleate are mixed and stirred at room temperature for 30 min to obtain oil phase component A;

[0091] Styrene, vinylimidazole, divinylbenzene and dehydrated sorbitol monooleate were mixed and stirred at room temperature for 30 min to obtain oil phase component B;

[0092] Styrene, vinylimidazole, acrylic acid, divinylbenzene and dehydrated sorbitol monooleate were mixed and stirred at room temperature for 30 min to obtain oil phase component C;

[0093] (2) Sodium persulfate, water and calcium chloride in the surface material, intermediate material and deep material are mixed respectively to obtain the aqueous phase component;

[0094] (3) Mix oil phase component A, oil phase component B, and oil phase component C with water phase component in a stirred tank and stir at 100 rpm for 20 min to form a W / O type high internal phase emulsion. Pour the emulsion into a polytetrafluoroethylene mold in sequence and polymerize at 60°C for 1 h and then at 80°C for 2 h to obtain the surface material, intermediate layer material and deep layer material. Immerse the obtained surface material, intermediate layer material and deep layer material in nutrient solution under vacuum for 2 h, and take them out and drain the surface free liquid.

[0095] (4) The surface material, intermediate material and deep material after impregnation are stacked from top to bottom to obtain the hydroponic foam substrate.

[0096] Step (3) The method for preparing the nutrient solution includes:

[0097] Mother liquor A (macro elements): Dissolve 94.3g of calcium nitrate tetrahydrate and 60.8g of potassium nitrate together in 1L of water and stir until completely dissolved;

[0098] B. Mother liquor (phosphorus and trace elements): Dissolve 23g ammonium dihydrogen phosphate, 4.52g iron EDTA, and 0.57g boric acid together in 1L of water and stir until completely dissolved.

[0099] C. Mother liquor (organic components): Dissolve 0.5g glycine and 0.5g L-glutamic acid together in 1L of water and stir until completely dissolved;

[0100] Dilution and mixing: Add about 7L of water to a container, add 1L of stock solution A to the container, stir well, then add 0.5L of stock solution B, stir well, then add 0.2L of stock solution C, and finally add water to make up to 10L. Stir well to obtain the nutrient solution.

[0101] The microstructure of the hydroponic foam substrate provided in Example 1 was analyzed by scanning electron microscopy. Figure 1 In the middle, the surface material has a pore size of about 15μm, the pores are three-dimensionally connected, the surface is smooth, and it is suitable for the water retention requirements of seed germination; Figure 2 In the middle layer, the pore size is 25-30 μm and the pore walls are dense, which is conducive to the targeted adsorption of NO3 by imidazole groups. - PO4 3- ; Figure 3 The medium- and deep-layer materials have pore sizes of 55-60 μm and wide channels, making them suitable for cation adsorption and deep root penetration. Figure 4 In the middle layer, the intermediate layer material and the surface layer material are tightly bonded at the transition point without obvious gaps, and the pores are interconnected, which is conducive to nutrient conduction.

[0102] Example 2 (High phosphorus and potassium + high boron)

[0103] This embodiment provides a hydroponic foam substrate, the raw materials for which the hydroponic foam substrate is prepared are shown in Table 2:

[0104] Table 2

[0105]

[0106] The preparation method includes the following steps:

[0107] (1) According to the above formula dosage, styrene, hydroxyethyl acrylate, methacrylic acid, ethylene glycol dimethacrylate and Span 80 are mixed and stirred at room temperature for 25 min to obtain oil phase component A;

[0108] Styrene, vinylimidazole, ethylene glycol dimethacrylate and Span 80 were mixed and stirred at room temperature for 25 min to obtain oil phase component B;

[0109] Styrene, vinylimidazole, acrylic acid, ethylene glycol dimethacrylate and Span 80 were mixed and stirred at room temperature for 28 min to obtain oil phase component C;

[0110] (2) Sodium persulfate, water and calcium chloride in the surface material, intermediate material and deep material are mixed respectively to obtain the aqueous phase component;

[0111] (3) Mix oil phase component A, oil phase component B, and oil phase component C with water phase component in a stirred tank and stir at 120 rpm for 25 min to form a W / O type high internal phase emulsion. Pour the emulsion into a polytetrafluoroethylene mold in sequence and polymerize at 55°C for 1.5 h and then at 75°C for 3 h to obtain the surface material, intermediate layer material and deep layer material. Immerse the obtained surface material, intermediate layer material and deep layer material in a nutrient solution (same as in Example 1) under vacuum for 3 h, and take them out and drain the surface free liquid.

[0112] (4) The surface material, intermediate material and deep material after impregnation are stacked from top to bottom to obtain the hydroponic foam substrate.

[0113] Example 3 (High Potassium + Low Nitrogen)

[0114] This embodiment provides a hydroponic foam substrate, the raw materials for which the hydroponic foam substrate is prepared are shown in Table 3:

[0115] Table 3

[0116]

[0117] The preparation method includes the following steps:

[0118] (1) According to the above formula dosage, styrene, hydroxyethyl acrylate, acrylic acid, 1,4-butanediol dimethacrylate and Span 80 are mixed and stirred at room temperature for 35 min to obtain oil phase component A;

[0119] Styrene, vinylimidazole, 1,4-butanediol dimethacrylate and Span 80 were mixed and stirred at room temperature for 30 min to obtain oil phase component B;

[0120] Styrene, vinylimidazole, methacrylic acid, divinylbenzene and Span 80 were mixed and stirred at room temperature for 35 min to obtain oil phase component C;

[0121] (2) Sodium persulfate, water and calcium chloride in the surface material, intermediate material and deep material are mixed respectively to obtain the aqueous phase component;

[0122] (3) Mix oil phase component A, oil phase component B, and oil phase component C with water phase component in a stirred tank and stir at 110 rpm for 30 min to form a W / O type high internal phase emulsion. Pour the emulsion into a polytetrafluoroethylene mold in sequence and polymerize at 65°C for 1.5 h and then at 85°C for 2.5 h to obtain the surface material, intermediate layer material and deep layer material. Immerse the obtained surface material, intermediate layer material and deep layer material in nutrient solution (same as in Example 1) under vacuum for 2.5 h, and take them out and drain the surface free liquid.

[0123] (4) The surface material, intermediate material and deep material after impregnation are stacked from top to bottom to obtain the hydroponic foam substrate.

[0124] Comparative Example 1

[0125] The only difference from Example 1 is that the amount of hydroxyethyl methacrylate in the surface material is 1 part, while the amount of the remaining components and the preparation method are the same as in Example 1.

[0126] Comparative Example 2

[0127] The only difference from Example 1 is that the amount of hydroxyethyl methacrylate in the surface material is 50 parts, while the amount of the remaining components and the preparation method are the same as in Example 1.

[0128] Comparative Example 3

[0129] The only difference from Example 1 is that the amount of vinylimidazole in the intermediate layer material is 65 parts, while the amount of the remaining components and the preparation method are the same as in Example 1.

[0130] Comparative Example 4

[0131] The only difference from Example 1 is that the amount of vinylimidazole in the intermediate layer material is 6 parts, while the amount of the remaining components and the preparation method are the same as in Example 1.

[0132] Comparative Example 5

[0133] The only difference from Example 1 is that acrylic acid is not added to the deep material, while the amount of other components and the preparation method are the same as in Example 1.

[0134] Comparative Example 6

[0135] The only difference from Example 1 is that hydroxyethyl methacrylate in the surface material is replaced with an equal amount of vinylimidazole, while the amounts of the remaining components and the preparation methods are the same as in Example 1.

[0136] Performance testing

[0137] (1) Adsorption capacity: 1g of foam material matrix sample was dried to constant weight, impregnated with nutrient solution for 24h, and the supernatant was collected; centrifuged at 5000rpm for 10min. Total nitrogen was determined by Kjeldahl method; phosphorus was determined by molybdenum blue method (λ=700nm) using UV spectrophotometer (UV-2600); calcium / iron was measured by atomic absorption spectrometry using atomic absorption spectrometer (AA-6300).

[0138] Adsorption capacity (mg / g) = (initial concentration - equilibrium concentration) × solution volume / sample mass

[0139] (2) Average pore size: The cross-section of the foam was observed using a scanning electron microscope (SEM), and the diameter of 100 pores was measured to calculate the average pore diameter D50.

[0140] (3) Compression modulus: The compression modulus was tested using an MTS universal tensile tester. The foam was cut into cubic specimens of 10mm×10mm×10mm and compressed at 25℃ and a compression rate of 1mm / min. The compression modulus was extracted from the linear segment of the stress-strain curve. The test result was the average value of three parallel specimens.

[0141] (4) Water retention rate: Soak the foam material in water until it is saturated with water, weigh it and record it as m1; let it dry for 24 hours until it reaches constant weight, weigh it and record it as m2. Water retention rate (%) = (m1-m2) / m2×100%, take the average of 3 times.

[0142] The hydroponic foam substrates provided in the examples and comparative examples were tested according to the above test methods. The results are shown in Tables 4 and 5.

[0143] Table 4

[0144]

[0145] Table 5

[0146]

[0147] As shown in Tables 4-5, the hydroponic foam substrate provided by this invention adopts a gradient design, which precisely matches the physical properties of the material at different depths with the growth requirements of the root system. Specifically, the pore size of the surface material is 10-20 μm and the compressive strength is 0.1-0.2 MPa, the pore size of the middle layer material is 20-40 μm and the compressive strength is 0.3-0.4 MPa, and the pore size of the deep layer material is 40-100 μm and the compressive strength is 0.4-0.5 MPa. It has a high water retention rate of ≥90%.

[0148] Application Example 1

[0149] Lettuce seeds were cultured using the hydroponic foam substrate provided in Example 1.

[0150] The only difference between Application Examples 2-3 and Comparative Application Examples 1-6 and Application Example 1 is that the hydroponic foam substrates of Examples 2-3 and Comparative Examples 1-6 were used to cultivate tomatoes, roses or lettuce, respectively. All other aspects are the same as Application Example 1.

[0151] Performance testing

[0152] (1) Seed germination rate: 100 seeds of each plant were grouped into three groups. The seeds were evenly sown on the surface of the hydroponic foam substrate and placed in an environment with a temperature of 25℃ and a humidity of 70%. The plants were exposed to light for 12 hours a day and cultured for 7 days. The number of germinated seeds was recorded.

[0153] Germination rate (%) = number of germinated seeds / 100 × 100%, take the average of 3 groups.

[0154] (2) Root integrity: Continue cultivation for 30 days, remove the plant and rinse the root system; scan the root system and analyze the number of broken roots.

[0155] Root integrity (%) = (Total number of roots - Number of broken roots) / Total number of roots × 100%.

[0156] (3) Plant height and number of leaves: Continue cultivation for 30 days, measure plant height (from the base of the root to the growing point), and take the average value of 30 plants;

[0157] Count the number of unfolded lettuce leaves, the number of tomatoes, and the number of roses, and take the average value of 30 plants for each.

[0158] The plant growth was tested according to the test cases and comparative application examples described above, and the results are shown in Table 6:

[0159] Table 6

[0160]

[0161] As shown in Table 6, the hydroponic foam substrate provided by this invention achieves automatic matching and synchronization of nutrient supply and root growth at different depths through targeted adsorption of different nutrients. Plants grown using this hydroponic foam substrate exhibit excellent growth indicators across the board. Seed germination rates for the three plant species were 92%-95% (except for roses), root integrity was 96%-98%, plant height was 18.5-42.6 cm, lettuce had 8 leaves, tomatoes had 3 fruits, and roses had 2 flowers.

[0162] The comparison between Application Example 1 and Comparative Application Example 1-2 shows that if the amount of hydroxyethyl methacrylate in the surface material is too small, the amount of water adsorbed will be reduced, resulting in a decrease in seed germination rate; if the amount of hydroxyethyl methacrylate in the surface material is too large, the amount of water adsorbed will be too large, resulting in the seeds being unable to breathe, and the germination rate will decrease significantly.

[0163] The comparison between Application Example 1 and Comparative Application Examples 3-4 shows that if too much vinylimidazole is used in the intermediate layer material, the adsorption of phosphorus and nitrogen elements will be excessive, causing seedling burn, with a leaf scorch rate of 15%, root integrity decreasing from 98% to 85%, plant height decreasing from 18.5cm to 12.5cm, and fresh weight per plant decreasing by 38.3%. If too little vinylimidazole is used in the intermediate layer material, it cannot provide sufficient nutrients for plant growth, with a leaf yellowing rate of 10%, the number of lateral roots decreasing from 6 to 3, plant height growth limited (only 15.6cm), and fresh weight per plant decreasing by 20.7% compared to Example 1.

[0164] The comparison between Application Example 1 and Comparative Application Example 5 shows that if acrylic acid is not added to the deep layer material, sufficient Ca cannot be obtained. 2+ Fe 2+ The presence of trace elements caused the rate of dry heart burning in lettuce seedlings to rise from 0% to 25%, the yellowing area of ​​leaves to reach 18%, the root system's nutrient absorption efficiency to decrease, the plant height to drop from 18.5cm to 16.2cm, the fresh weight of a single plant to decrease by 16%, and the leaves to become less tough and more susceptible to mechanical damage, resulting in a significant deterioration in overall growth indicators.

[0165] As can be seen from the comparison between Application Example 1 and Comparative Application Example 6, if hydroxyethyl methacrylate in the surface material is replaced with vinylimidazole, the surface material will adsorb a large amount of salt. Excessive salt will inhibit seed germination, resulting in a decrease in germination rate.

[0166] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A hydroponic foam substrate, characterized by, The hydroponic foam substrate comprises at least one surface layer material, at least one intermediate layer material and at least one deep layer material from top to bottom; The surface layer material comprises the following components by weight parts: vinyl aromatic compound 30-80 parts, hydroxy acrylate 5-30 parts, acrylic compound 10-35 parts, crosslinking agent 5-25 parts; The intermediate layer material comprises the following components by weight parts: vinyl aromatic compound 40-80 parts, vinyl imidazole compound 10-40 parts, crosslinking agent 5-20 parts; The deep layer material comprises the following components by weight parts: vinyl aromatic compound 20-50 parts, vinyl imidazole compound 10-40 parts, acrylic compound 10-35 parts, crosslinking agent 5-20 parts.

2. The hydroponic foam substrate according to claim 1, characterized by, The compression strength of the surface layer material is 0.1-0.2 MPa; Preferably, the compression strength of the intermediate layer material is 0.3-0.4 MPa; Preferably, the compression strength of the deep layer material is 0.4-0.5 MPa; Preferably, the vinyl aromatic compound comprises styrene and / or vinyl toluene; Preferably, the hydroxy acrylate comprises any one or a combination of at least two of hydroxyethyl methacrylate, hydroxyethyl acrylate, hydroxypropyl acrylate or hydroxypropyl methacrylate; Preferably, the acrylic compound comprises any one or a combination of at least two of acrylic acid, methacrylic acid or ethyl acrylate.

3. The hydroponic foam substrate according to claim 1 or 2, characterized in that, The crosslinking agent comprises any one or a combination of at least two of divinyl benzene, 1,6-hexanediol diacrylate, 1,4-butanediol dimethacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, 1,12-dodecanediol dimethacrylate, 1,14-tetradecanediol dimethacrylate, ethylene glycol dimethacrylate, neopentyl glycol diacrylate, 2,2-dimethylpropanediol diacrylate, hexanediol diacrylate, methacrylate or sorbitol pentaacrylate; Preferably, the vinyl imidazole compound comprises any one or a combination of at least two of vinyl imidazole, 2-methyl vinyl imidazole or 4-methyl vinyl imidazole.

4. The hydroponic foam substrate according to any one of claims 1 to 3, characterized in that, The surface layer material, intermediate layer material and deep layer material each independently further comprise any one or a combination of at least two of initiator, surfactant, solvent or electrolyte; Preferably, the initiator comprises persulfate initiator; Preferably, the persulfate initiator comprises any one or a combination of at least two of ammonium persulfate, sodium persulfate or potassium persulfate; Preferably, the amount of initiator in the surface layer material, intermediate layer material and deep layer material is independently 1-3 parts. Preferably, the surfactant comprises any one or a combination of at least two of Span 80, organically modified montmorillonite, nano-silica, polyglyceryl ricinoleate, sorbitan monooleate, sorbitan monomyristate, sorbitan monoester, sorbitan monolaurate, diglyceryl monooleate, polyglyceryl isostearate, polyglyceryl monomyristate, diglyceryl monooleate, diglyceryl monomyristate, diglyceryl monoisostearate, diglyceryl monoester, sterol, triterpene alcohol, palmitelaidic alcohol, oleyl alcohol, isostearyl alcohol, lauryl alcohol, myristyl alcohol or coco alcohol; Preferably, the surfactant in the surface layer material, the intermediate layer material and the deep layer material is independently used in an amount of 4-6 parts; Preferably, the solvent comprises water; Preferably, the electrolyte comprises any one or a combination of at least two of calcium chloride, sodium chloride, sodium sulfate or calcium sulfate; Preferably, the electrolyte in the surface layer material, the intermediate layer material and the deep layer material is independently used in an amount of 2-4 parts.

5. A method for the production of a hydroponic foam substrate according to any one of claims 1 to 4, characterized in that, The preparation method comprises the following steps: (1) mixing a vinyl aromatic compound, a hydroxy acrylate, an acrylic compound and a crosslinking agent to obtain an oil phase component A; mixing a vinyl aromatic compound, a vinyl imidazole compound and a crosslinking agent to obtain an oil phase component B; mixing a vinyl aromatic compound, a vinyl imidazole compound, an acrylic compound and a crosslinking agent to obtain an oil phase component C; (2) mixing an initiator, a solvent and an electrolyte to obtain an aqueous phase component; (3) mixing the oil phase component A, the oil phase component B, the oil phase component C and the aqueous phase component respectively, emulsifying, reacting to obtain the surface layer material, the intermediate layer material and the deep layer material; (4) stacking at least one surface layer material, at least one intermediate layer material and at least one deep layer material to obtain the hydroponic foam substrate.

6. The preparation method according to claim 5, characterized in that, The materials mixed in the oil phase component A, the oil phase component B and the oil phase component C further comprise a surfactant; Preferably, the volume ratio of the oil phase component A, the oil phase component B and the oil phase component C to the aqueous phase component is independently 1:(10-40).

7. The production method according to claim 5 or 6, characterized by, The emulsifying time is 20-30 min; Preferably, the reaction is carried out in a polytetrafluoroethylene mold.

8. The method of any one of claims 5-7, wherein, The reaction comprises a first stage polymerization and a second stage polymerization; Preferably, the temperature of the first stage polymerization is 55-65℃; Preferably, the time of the first stage polymerization is 1-1.5 h; Preferably, the temperature of the second stage polymerization is 75-85℃; Preferably, the time of the second stage polymerization is 2-3 h.

9. The method of any one of claims 5-8, wherein, Step (4) further comprises impregnation and drying before stacking; Preferably, the impregnation comprises impregnating the surface layer material, the intermediate layer material and the deep layer material in a nutrient solution; Preferably, the impregnation is carried out under vacuum conditions; Preferably, the impregnation time is 2-3 h; Preferably, the nutrient solution comprises any one or a combination of at least two of nitrogen, phosphorus, potassium, calcium, iron or zinc elements.

10. Use of the hydroponic foam substrate according to any one of claims 1-4 in plant cultivation or daily hygiene products. Preferably, the plant in the plant cultivation includes at least one of a leafy vegetable, a fruit or a flower. Preferably, the plant in the plant cultivation includes at least one of a leafy vegetable, a fruit or a flower.

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