A substrate, its preparation method and use thereof

Abstract

The application provides a substrate and a preparation method and application thereof, relates to the technical field of plant cultivation, and the preparation method of the substrate comprises the following steps: mixing 40-70 parts of wood fibers, 20-30 parts of peat and 10-25 parts of perlite according to volume fractions to obtain mixed raw materials; adjusting the water content of the mixed raw materials to 30wt%-40wt%, loading the mixed raw materials into a mold, heating the mold to 220-240 DEG C for hot pressing, and controlling the compression rate to be 0.4-0.45 to prepare the substrate. The preparation method of the substrate provided by the application can prepare a solidified substrate with suitable hardness, rich porosity and sufficient dry and wet strength without using an adhesive; on the other hand, only the surface layer of the raw materials needs to be heated to a plastic degree, and all the raw materials do not need to be heated, so that the heating energy consumption is reduced.

Description

Technical Field

[0001] This invention relates to the field of plant cultivation technology, and in particular to a substrate, its preparation method, and its application. Background Technology

[0002] Traditional granular bulk substrates, such as peat, perlite, vermiculite, and their mixtures, have uncontrollable pore structures, making it difficult to achieve a balance between water retention and aeration, and thus difficult to obtain substrate products with good water retention and aeration. Furthermore, their pore structures change significantly during the planting process, and sedimentation can easily occur later, leading to reduced aeration and affecting crop growth.

[0003] Curing the matrix material into a solid form can overcome the problems associated with loose particulate matrices to some extent. Existing curing processes include: (1) Adhesive curing and molding. Chinese patent application CN104529664A (Vegetable cultivation substrate and its preparation method) and Chinese patent application CN107602054A (A production process of a molded substrate) disclose curing and molding substrates and their production processes. First, the substrate raw materials containing adhesive are mixed, and then extruded and molded in a mold to finally obtain a substrate block with a stable appearance structure. Through curing and molding, the void structure of the substrate has a certain degree of controllability. However, these substrate blocks also have certain problems: they generally use water-soluble adhesives, the stability of the curing and molding substrate is poor, and it often expands after absorbing water, resulting in changes in appearance and uncontrollable micro void structure. Chinese Patent CN105367216B (A Plastic Fiber Culture Soil and Its Preparation Method) discloses a plastic fiber culture soil and its preparation method. The method involves mixing raw materials including substrate soil, plant fiber powder, perlite, peat moss, and a two-component thermoplastic adhesive composite fiber, followed by heating treatment to fuse the two-component thermoplastic adhesive composite fiber with the other raw materials. Specifically, to ensure the smooth fusion of the two-component thermoplastic adhesive composite fiber and to ensure the softening of the plant fiber powder in the activated fiber soil and the preparation of sterile culture soil, the melting point and softening point (i.e., melting point) of the polymer on the surface layer of the composite fiber are preferably above 130°C, and maintained for a sufficient time to ensure that the thermoplastic composite fiber inside the substrate block is basically melted, before molding. The disadvantages of the above adhesive-based curing process are: (1) additional adhesive is required, and many adhesives are not plant-friendly; (2) increased cost; (3) chemical adhesives often reduce the permeability of the substrate.

[0004] (2) High-pressure compression molding. The matrix raw material is compressed to solidify and form a solid. Due to the disadvantages of high-pressure compression molding: (1) high compression energy consumption; (2) the matrix block is dense and hard after compression; (3) lacks suitable porosity and is not suitable for plant growth; (4) it is easy to diffuse and lose strength after being soaked in water. Summary of the Invention

[0005] This invention provides a matrix, its preparation method, and its application, which solves the defects of the additional adhesive added in the existing adhesive-based matrix curing process, which is unfriendly to plants, reduces the permeability of the matrix, and increases costs. It realizes the preparation of a cured matrix with suitable dry and wet strength without adhesive, and with better pore distribution.

[0006] In a first aspect, the present invention provides a method for preparing a matrix, comprising the following steps: S1. By volume, mix 40-70 parts wood fiber, 20-30 parts peat and 10-25 parts perlite to obtain a mixed raw material; S2. Adjust the moisture content of the mixed raw materials to 30wt%~40wt%, load them into a mold, heat the mold to 220~240℃ for hot pressing, control the compression rate to 0.4~0.45, and obtain the matrix.

[0007] The present invention uses 40 to 70 parts by volume of wood fiber, for example, 40, 45, 50, 55, 60, 65, or 70 parts, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0008] The present invention uses 20 to 30 parts of peat by volume, for example, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, or 30 parts, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0009] The present invention uses 10 to 30 parts perlite by volume, for example, 10, 12, 15, 17, 20, 23, 25, 28, or 30 parts, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0010] The moisture content of the mixed raw materials of the present invention is 30wt%~40wt%, for example, it can be 30wt%, 31wt%, 32wt%, 33wt%, 34wt%, 35wt%, 36wt%, 37wt%, 38wt%, 39wt%, or 40wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0011] The mold temperature of this invention is 220~240 ℃, for example, it can be 220 ℃, 225 ℃, 230 ℃, 235 ℃, 240 ℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0012] The compression ratio of this invention is 0.4 to 0.45, for example, it can be 0.4, 0.41, 0.42, 0.43, 0.44, or 0.45, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0013] The matrix preparation method provided by this invention uses wood fiber as raw material, mixes it with peat and perlite in a specific ratio, and then heat-presses it under certain conditions to prepare a solidified matrix with suitable hardness, rich porosity, and sufficient dry and wet strength without the need for adhesives. Specifically, the moisture content of the mixed raw materials is controlled at 30wt%~40wt%. At this moisture content, the raw materials are easily mixed evenly, which can accelerate heat transfer and facilitate the softening and molding of wood fibers. Heating to 220~240℃ for hot pressing softens the wood fibers, giving them plasticity and achieving good molding results. Hot pressing at a compression ratio of 0.4~0.45 allows for bonding and molding without disintegration, and the matrix does not significantly expand or lose strength after absorbing water.

[0014] In the technical solution of this invention, the moisture content of the mixed raw materials is controlled at 30wt%~40wt%. At this moisture content, the raw materials are easy to mix evenly, and after solidification and molding, excess moisture can be evaporated using residual heat. Furthermore, if the moisture content of the mixed raw materials is too high, the material is difficult to gelatinize and mold, and it is easy to disperse during demolding. Moreover, because water has a high specific heat capacity, energy consumption is increased, and an additional drying process is required. If the moisture content of the mixed raw materials is too low, it is difficult to compress and mold, the matrix block has low strength, and the matrix block is prone to longitudinal rebound after demolding, forming transverse cracks.

[0015] In the technical solution of the present invention, the mold temperature is controlled at 220~240 ℃. If the temperature is too high, the material surface will carbonize, increase water repellency, and be difficult to wet. In addition, the wet and hot matrix mixture is prone to forming a fluid state, which is difficult to form, easy to disperse, and increases energy consumption.

[0016] In the technical solution of this invention, the purpose of compression is to shape the materials and bond them together. After compression, the materials will inevitably spring back, and after absorbing water and becoming wet, they will expand further. This rebound expansion will lead to a decrease in the strength of the matrix. However, this invention controls the compression ratio to be 0.4~0.45, so that the materials can be bonded and shaped without falling apart, and will not significantly expand and lose strength after absorbing water.

[0017] Preferably, in step S1, the wood fiber has a length of 5-20 mm and a diameter of 0.1-1 mm.

[0018] Preferably, in step S1, the wood fiber is selected from at least one of poplar fiber, pine fiber, and bamboo fiber.

[0019] More preferably, in step S1, the wood fiber is wood fiber after steam explosion treatment.

[0020] Preferably, in step S2, the moisture content of the mixed raw materials is 35wt%~40wt%.

[0021] Preferably, in step S2, the heating time to 220~240 ℃ is 30 seconds to 60 seconds, for example, it can be 30 seconds, 35 seconds, 40 seconds, 45 seconds, 50 seconds, 55 seconds, or 60 seconds, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0022] In step S2 of this scheme, the heating time to 220~240 ℃ is controlled within 30 seconds to 60 seconds. If the time is too short, the heating power requirement is high, the speed is fast, and the heat remains on the surface, resulting in insufficient softening depth of the raw material. If the time is too long, the heat transfer is too deep, the raw material is heated as a whole, resulting in excessive energy consumption.

[0023] Preferably, in step S2, the hot pressing time is 30 to 60 seconds, for example, 30 seconds, 35 seconds, 40 seconds, 45 seconds, 50 seconds, 55 seconds, or 60 seconds, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0024] Preferably, in step S2, the specific conditions for hot pressing are: holding the pressure for 10 to 20 seconds at a temperature of 220 to 240 ℃ and a compression ratio of 0.4 to 0.45, and then releasing the pressure, repeating the pressure holding and releasing process 3 to 5 times.

[0025] In step S2 of this scheme, the specific conditions for hot pressing are as described above. This allows the wood fibers to be fully plasticized and shaped while also fully releasing the stress between the raw materials, ensuring that the matrix does not crack after molding.

[0026] Preferably, in step S1, the mixed raw materials further include an adhesive, wherein the adhesive is selected from at least one of modified starch, polyvinyl alcohol, and white glue; The amount of the adhesive used is 1% to 3% of the total weight of wood fiber, peat and perlite, for example, it can be 1%, 1.2%, 1.5%, 1.7%, 2%, 2.3%, 2.5%, 2.8% or 3%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0027] The modified starch mentioned in this plan is at least one of modified corn starch and modified cassava starch.

[0028] In step S1 of this scheme, the mixed raw materials also include an adhesive. The adhesive is selected from at least one of modified starch, polyvinyl alcohol, and white glue. The amount of adhesive is controlled to be 1% to 3% of the total weight of wood fiber, peat, and perlite. This ensures that the adhesive has a low impact on plants, substrate permeability, and cost, while further increasing the strength of the solidified substrate.

[0029] Preferably, in step S1, the mixed raw materials further include bast fibers, which are selected from jute fiber, ramie fiber, hemp fiber, flax fiber, nettle fiber, and sisal fiber; The length of the bast fibers is 3-5 cm. The bast fiber is 1 to 3 parts by volume, for example, 1 part, 1.2 parts, 1.5 parts, 1.7 parts, 2 parts, 2.3 parts, 2.5 parts, 2.8 parts, or 3 parts, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0030] In step S1 of this scheme, the mixed raw materials also include bast fibers, and the bast fibers are selected from jute fibers, ramie fibers, hemp fibers, flax fibers, nettle fibers, and sisal fibers. The length of the bast fibers is controlled to be 3~5 cm, which can further increase the wet strength of the matrix.

[0031] In a second aspect, the present invention provides a matrix prepared by the matrix preparation method described in the first aspect above.

[0032] In a second aspect, the present invention provides a matrix prepared by the matrix preparation method described in the first aspect above.

[0033] A third aspect of the present invention provides the application of the substrate described in the second aspect above in plant cultivation.

[0034] Compared with the prior art, the beneficial technical effects of the present invention are as follows: The matrix preparation method provided by the present invention, on the one hand, can prepare a cured matrix with suitable dry and wet strength and good pore distribution without the need for adhesives; on the other hand, it only requires heating the surface raw material to a plastic degree, without heating all the raw materials, so as to reduce heating energy consumption. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0036] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values; these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and individual point values, and individual point values ​​can be combined to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this invention. Where specific techniques or conditions are not specified in the embodiments of this invention, they shall be performed in accordance with the techniques or conditions described in the literature in the art, or in accordance with the product instructions. Devices, instruments, reagents, etc., used without specified manufacturers are all conventional products that can be purchased through legitimate channels. All experimental reagents and raw materials involved are commercially available products.

[0037] Example 1 This embodiment provides a method for preparing a matrix, including the following steps: S1. By volume, 55 parts of steam-exploded poplar fiber (5-20 mm in length and 0.1-1 mm in diameter), 25 parts of peat, and 20 parts of perlite are uniformly mixed to obtain a mixed raw material; S2. Adjust the moisture content of the mixed raw materials to 35wt%, and put them into a cuboid mold of a high-frequency electromagnetic heating device (high-frequency heating curing matrix preparation equipment disclosed in CN222451484U). Heating coils are set on all 6 sides of the mold. The temperature is rapidly increased to 220℃ in 40 seconds. The upper panel is opened to move downwards and compress the raw materials. The compression ratio is controlled at 0.45 (compression ratio = height of compressed raw materials / original height of raw materials). The temperature is maintained at 220℃ and the compressed state for 20 seconds. Then the upper panel is moved upwards to completely release the pressure. The compressed state is maintained for another 20 seconds. The pressure is then completely released. This process is repeated 3 times to solidify and form a cured matrix.

[0038] Example 2 This embodiment provides a method for preparing a matrix, including the following steps: S1. By volume, 45 parts of steam-exploded bamboo fiber (5-20 mm in length and 0.1-1 mm in diameter), 30 parts of peat, and 25 parts of perlite are uniformly mixed. In addition, 1.5% of the total weight of the aforementioned raw materials (bamboo fiber, peat, and perlite) of a binder is added. The binder is a mixture of modified corn starch (commercially available, purchased from Shandong Jufuxinwang Chemical Co., Ltd.) and white latex of equal weight to obtain the mixed raw materials. S2. Adjust the moisture content of the mixed raw materials to 40wt%, and put them into a cuboid mold of a high-frequency electromagnetic heating device (high-frequency heating curing matrix preparation equipment disclosed in CN222451484U). Heating coils are set on all 6 sides of the mold. The temperature is rapidly increased to 240℃ in 60 seconds. The upper panel is opened to move downwards and compress the raw materials. The compression ratio is controlled at 0.40 (compression ratio = height of compressed raw materials / original height of raw materials). The temperature is maintained at 240℃ and the compressed state for 10 seconds. Then the upper panel is moved upwards to completely release the pressure. The compressed state is maintained for another 10 seconds. The pressure is then completely released. This process is repeated 4 times to solidify and form a cured matrix.

[0039] Example 3 This embodiment provides a method for preparing a matrix, including the following steps: S1. By volume, 58 parts of steam-exploded poplar fiber (5-20 mm in length and 0.1-1 mm in diameter), 2 parts of jute fiber (3-5 cm in length), 25 parts of peat, and 15 parts of perlite are uniformly mixed. In addition, 1.5% of the total weight of the aforementioned raw materials (poplar fiber, jute fiber, peat, and perlite) of a binder is added. The binder is composed of modified corn starch and white latex mixed by weight to obtain the mixed raw materials. S2. Adjust the moisture content of the mixed raw materials to 40wt%, and put them into a cuboid mold of a high-frequency electromagnetic heating device (high-frequency heating curing matrix preparation equipment disclosed in CN222451484U). Heating coils are set on all 6 sides of the mold. The temperature is rapidly increased to 230℃ in 30 seconds. The upper panel is opened to move downwards and compress the raw materials. The compression ratio is controlled at 0.43 (compression ratio = height of the raw materials after compression / original height of the raw materials). The temperature is maintained at 230℃ and the compressed state for 20 seconds. Then the upper panel is moved upwards to completely release the pressure. The compressed state is maintained for another 30 seconds. The pressure is then completely released. This process is repeated 3 times to solidify and form a cured matrix.

[0040] Example 4 The difference between the preparation method of the matrix provided in this embodiment and that in Example 1 is that the water content of the mixed raw materials is adjusted to 30 wt%.

[0041] Example 5 The difference between the matrix preparation method provided in this embodiment and that in Example 1 is that the inner surface temperature is raised to 220°C by rapid heating in 80 seconds.

[0042] Example 6 The difference between the preparation method of the matrix provided in this embodiment and that in Example 1 is that: the matrix is ​​kept at 220°C and under compression for 60 seconds (without repeated pressure holding and decompression), and then the pressure is completely released to solidify and form a cured matrix.

[0043] Comparative Example 1 The preparation method of the matrix provided in this comparative example differs from that in Example 1 in that: by volume, 30 parts of steam-exploded poplar fiber (5-20 mm in length and 0.1-1 mm in diameter), 35 parts of peat, and 35 parts of perlite are uniformly mixed to obtain a mixed raw material.

[0044] Comparative Example 2 The preparation method of the matrix provided in this comparative example differs from that in Example 1 in that: by volume, 80 parts of steam-exploded poplar fiber (5-20 mm in length and 0.1-1 mm in diameter), 10 parts of peat, and 10 parts of perlite are uniformly mixed to obtain a mixed raw material.

[0045] Comparative Example 3 The difference between the preparation method of the matrix provided in this comparative example and that in Example 1 is that the moisture content of the mixed raw materials is adjusted to 25 wt%.

[0046] Comparative Example 4 The difference between the preparation method of the matrix provided in this comparative example and that in Example 1 is that the moisture content of the mixed raw materials is adjusted to 50 wt%.

[0047] Comparative Example 5 The difference between the preparation method of the matrix provided in this comparative example and that in Example 1 is that the temperature of the inner surface is raised to 200°C.

[0048] Comparative Example 6 The difference between the preparation method of the matrix provided in this comparative example and that in Example 1 is that the inner surface temperature is raised to 270°C.

[0049] Comparative Example 7 The difference between the preparation method of the matrix provided in this comparative example and that in Example 1 is that the compression ratio is controlled at 0.3.

[0050] Comparative Example 8 The difference between the preparation method of the matrix provided in this comparative example and that in Example 1 is that the compression ratio is controlled at 0.6.

[0051] Performance testing (1) Porosity The measurement method using the reference ring cutter method was employed. After preparing the cured substrate, it was placed in an oven and dried at 80℃ for 24 hours; the weight was recorded as M1. Then, it was immersed in water to absorb water until a constant weight was reached; the weight was recorded as M2. Finally, the cured substrate was removed, placed on a standard mat for 1 hour, and the weight was recorded as M3. The porosity of the cured substrate was calculated using Formula 2.3. (2.3) *100% In the formula: TP is the total porosity of the cured matrix; AFP is the air porosity of the cured matrix; WHC is the water-holding porosity of the cured matrix; and V is the total volume of the cured matrix.

[0052] (2) Mechanical properties The mechanical properties of the cured substrate were tested using a push-pull force gauge. The cured substrate was immersed in water to absorb moisture, then removed and placed on a standard mat for 1 hour. The wet tensile strength was measured. After air-drying to constant weight at room temperature, the cured substrate was placed on a push-pull force gauge to test its dry tensile strength. The arithmetic mean of three samples was selected as the test result.

[0053] The porosity and mechanical properties of the cured matrices prepared in the above embodiments and comparative examples are shown in Table 1 below.

[0054] Table 1

[0055] Table 1 shows that the material composition of the matrix, especially the wood fiber content, significantly affects the water retention, air permeability, and dry and wet strength of the cured matrix. Furthermore, moisture content, curing compression ratio, and temperature all significantly affect the strength of the cured matrix. If the moisture content of the mixed raw materials is too high (>40%), the material gelatinizes poorly and is difficult to mold, easily disintegrating during demolding and increasing energy consumption. If the moisture content of the mixed raw materials is too low (<30%), the matrix block is prone to longitudinal rebound after demolding, forming transverse cracks and reducing the strength of the matrix block. If the compression degree is too low (compression ratio >0.45), the cured matrix strength is insufficient; if the compression degree is too high (compression ratio <0.4), although it can increase dry strength, it actually reduces wet strength. A mold surface temperature <220℃ results in poor wood fiber plasticization and molding, reducing the strength of the finished product. A temperature too high (>240℃) does not significantly increase strength but increases energy consumption and causes surface carbonization, increasing water repellency and hindering wetting of the matrix block. In addition, the heating time, pressure holding / depressurization time and frequency all have a significant impact on the dry and wet strength and energy consumption of the final product.

[0056] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a matrix, characterized in that, Includes the following steps: S1. By volume, mix 40-70 parts wood fiber, 20-30 parts peat and 10-25 parts perlite to obtain a mixed raw material; S2. Adjust the moisture content of the mixed raw materials to 30wt%~40wt%, load them into a mold, heat the mold to 220~240 ℃ for hot pressing, control the compression rate to 0.4~0.45, and obtain the matrix.

2. The method for preparing the matrix according to claim 1, characterized in that, In step S1, the wood fiber has a length of 5-20 mm and a diameter of 0.1-1 mm.

3. The method for preparing the matrix according to claim 1 or 2, characterized in that, In step S1, the wood fiber is selected from at least one of poplar fiber, pine fiber, and bamboo fiber.

4. The method for preparing the matrix according to any one of claims 1 to 3, characterized in that, In step S2, the moisture content of the mixed raw materials is 35wt%~40wt%.

5. The method for preparing the matrix according to claim 1 or 4, characterized in that, In step S2, the heating time to 220~240℃ is 30 seconds~60 seconds.

6. The method for preparing the matrix according to claim 1 or 5, characterized in that, In step S2, the hot pressing time is 30-60 seconds; Preferably, the specific conditions for hot pressing are as follows: holding pressure for 10 to 20 seconds at a temperature of 220 to 240 ℃ and a compression ratio of 0.4 to 0.45, and then releasing pressure, repeating the pressure holding and releasing process 3 to 5 times.

7. The method for preparing the matrix according to claim 1 or 6, characterized in that, In step S1, the mixed raw materials further include an adhesive, wherein the adhesive is selected from at least one of modified starch, polyvinyl alcohol, and white glue; The amount of the adhesive used is 1% to 3% of the total weight of wood fiber, peat, and perlite.

8. The method for preparing the matrix according to claim 1 or 7, characterized in that, In step S1, the mixed raw materials further include bast fibers, which are selected from jute fiber, ramie fiber, hemp fiber, flax fiber, nettle fiber, and sisal fiber; The length of the bast fibers is 3-5 cm. Bast fiber content: 1-3 parts by volume.

9. A matrix prepared by the method of any one of claims 1 to 8.

10. The application of the substrate as described in claim 9 in plant cultivation.

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