Preparation method of anti-root penetration degradable film for rice seedling raising straw substrate tray without seedling tray

Abstract

The present application discloses a method for preparing a degradable film for preventing root penetration of a rice seedling raising straw substrate tray without a seedling tray, that is, the crop straw fibers that have been rubbed and crushed are subjected to steaming, composting, pulping and grafting treatment to obtain modified straw fibers, the modified straw fibers are pulped, put on a net to be formed, pressed and dried to form straw paper for coating, and then a polyadipate / butylene terephthalate mixture is coated on the straw paper, and the degradable film for preventing root penetration of a rice seedling raising straw substrate tray without a seedling tray is paved; the straw paper for coating ensures the strength and toughness of the material to facilitate the movement of a seeding tray placing machine, the coating layer ensures that the rice roots do not penetrate the substrate to facilitate the smooth lifting of the seedlings after the seedling raising is completed, the degradable film has a high longitudinal tear index, a high burst resistance and a high tensile index, and a simple preparation process, thereby realizing the recycling of agricultural straw waste straw resources, making up for the shortcomings of the existing mechanized tray placing operation, and being easy to promote and utilize.

Description

Technical Field

[0001] The invention relates to the technical field of rice seedling cultivation, and in particular to a degradable film for preventing root penetration for a rice seedling cultivation straw substrate tray without a seedling tray. Background Art

[0002] In recent years, with the rapid development of rice seedling raising technology, new rice seedling raising matrix trays with straw as the main raw material have become the main development direction of rice seedling raising trays, such as the multi-layer rice straw matrix block for machine transplanting disclosed in Chinese patent CN201910772006.3, which uses straw fibers of different degrees of maturity and different sizes to be pulped and dried to prepare multi-layer straw matrix blocks. The straw matrix block has a small bulk density, high water holding porosity, good mechanical properties during transplanting, and a high rice seedling rate, which is suitable for machine transplanting rice seedling raising. Another example is the straw degradable matrix tray for dry rice seedling raising disclosed in Chinese patent CN201920492583.2, which solves the problem of damage to the roots of rice seedlings during the process of rolling up the rice seedlings through the structural design of the upper surface of the matrix tray base. These straw matrix trays not only replace plastic seedling trays for carrying rice seeds and covering soil, but also partially replace seedling substrates, solving the problems of white pollution (plastic matrix trays) and farmland destruction. At the same time, the seedlings cultivated in straw matrix trays have good quality and strong root systems, which are conducive to machine transplanting and have broad application prospects.

[0003] However, the current seedling tray still needs plastic tray assistance during the sowing process. This is because the existing seedling sowing methods are divided into hard disk assembly line sowing and floppy disk self-propelled sowing. In the hard disk assembly line sowing process, water is sprayed synchronously to moisten the seedling substrate and then the tray needs to be placed. Plastic seedling trays are still needed to carry (the straw substrate tray absorbs water and softens, and cannot be mechanized). Otherwise, it is easy to miss the seeding caused by uneven sowing during the assembly line sowing process; and the floppy disk self-propelled sowing is usually in the field, without the coating of the plastic seedling tray, and the roots are easy to penetrate and entangle with each other, affecting the seedling after the seedling age expires (if the field seedlings are raised with straw substrate trays, a film must be used to cut off the contact between the root system and the soil), and in the seedling raising process, the root system on the side of the straw substrate tray is cross-linked, which makes it impossible to raise the seedlings into a blanket seedling of a specified size, whether it is late replanting or late cutting, which seriously affects the use efficiency of the straw substrate tray. Therefore, even if the straw substrate tray has the above-mentioned advantages, the non-degradable method of plastic seedling trays is still applicable in the current production practice.

[0004] In response to the above problems, Chinese patent CN110999676B discloses a straw-free degradable matrix block for rice dry seedling cultivation, which prevents root penetration by spraying nitrogen-rich slow-release nutrient-setting composite materials on the surrounding and lower surface of the matrix tray. Although this method has the effect of preventing root penetration, the cooling and shaping of the sprayed materials reduces production efficiency and is not conducive to the seedling separation step of the machine transplanting process. Chinese patent CN212436304U discloses a degradable matrix seedling tray swinging tray seeder, which can directly sow and cover the soil and swing the tray. After the matrix block is sown and covered with soil, the swing tray can be directly spaced at equal intervals, effectively avoiding the phenomenon of seedling rooting when the matrix block is raised. Although this method effectively avoids the rooting between the matrix blocks, the swing tray seeder needs to walk on a film that the roots cannot penetrate, so this method is only suitable for raising seedlings on cement ground, and non-degradable films are still required for field seedling raising.

[0005] At the same time, in the mechanized use of straw matrix trays for seedling-free trays, such as using a degradable matrix seedling tray swing seeder disclosed in Chinese patent CN212436304U to pave and place straw matrix trays, the film used in the straw matrix tray during the movement of the swing seeder has higher requirements than the conventional plastic agricultural film, such as: biodegradability to ensure that the film can be directly returned to the field after the seedling cultivation is completed (15-20 days), the film's load-bearing capacity during the movement of the swing seeder ensures that the film is not damaged, and the rice seedlings are not penetrated during the root growth process. These are still the key links and technical priorities that need to be solved urgently for the degradable film that prevents root penetration in the current straw matrix trays for seedling-free trays. Summary of the invention

[0006] In view of the above problems, the present invention provides a degradable film for preventing root penetration for a rice seedling raising straw matrix tray without a seedling tray. The film has biodegradability that is compatible with the rice seedling raising cycle, high bursting strength, and the degradation film is not damaged during the growth and penetration of the rice seedling roots. The film is suitable for use in a tray-raising seeder when raising rice seedlings in the field.

[0007] The purpose of the present invention is achieved through the following technical solution, and the specific operation steps are as follows:

[0008] First, the present application provides a method for preparing a root penetration-proof degradable film for a rice seedling raising straw substrate tray without a rice seedling tray, and the specific steps are as follows:

[0009] 1) Preparation of modified straw fiber / pulp:

[0010] The moisture content of the recycled crop straw is adjusted to 25% to 75%, and the straw is kneaded and crushed to prepare a fiber straw with a length of 2cm-8cm. The kneaded and crushed straw fiber is put into a conventional pulp fiber cooking pot, and the cooking pot contains 80°C hot water. After keeping the temperature for 0.5h to 1h, the temperature in the cooking pot is raised to 120°C to 160°C, and after keeping the temperature for 4h to 8h, the temperature is lowered and the material is discharged to obtain the cooked straw fiber;

[0011] The steamed straw fiber is mixed with a conventional straw composting agent, wherein the added straw composting agent accounts for 0.5% to 2% of the dry weight of the steamed straw fiber, and the fully mixed steamed straw fiber and the straw composting agent are filled into a fermentation tank with a mechanical vent at the bottom for fermentation, and the material is taken out after 5 days of aerobic fermentation to obtain the composted straw fiber;

[0012] The decomposed straw fibers are directly put into a conventional pulp refiner for pulping to obtain pulped straw fibers for standby use; a portion of the pulped straw fibers are weighed for conventional fiber esterification to obtain esterified straw fibers;

[0013] The modified straw fiber is obtained by mixing the esterified straw fiber and the pulped straw fiber. The lignin removal rate of the obtained modified straw fiber exceeds 30%, and the fiber yield exceeds 90%.

[0014] The purpose of fiber modification in this step is mainly to serve as a pre-treatment for step 2), i.e., pulp preparation. Straw fiber alone cannot be made into paper. The second traditional method is chemical mechanical method, i.e., using acid-base solution to delignify. In order to avoid chemical agents, this step uses biological pulping to soften the fiber to make paper and partially remove lignin.

[0015] In this step, rubbing and crushing the straw are conventional techniques in the art, such as the straw fiber processing method publicly reported in the reference "Research Status and Prospect of Straw Crusher in my country, Anhui Agricultural Science, 2012".

[0016] In this step, the fiber esterification treatment is a conventional technology in the art, such as the fiber esterification treatment method publicly reported in the Chinese patent "A method for esterification modification of lignocellulose and esterified modified lignocellulose, application number: CN201010548136.8".

[0017] In this step, the crop straw is preferably one or more of rice straw, corn straw, rape straw, and wheat straw.

[0018] In the modified straw fiber obtained in this step, the mass of the esterified fiber preferably accounts for 1-3% of the mass of the modified straw fiber.

[0019] 2) Preparation of straw paper for coating

[0020] The modified straw fiber prepared in step 1) is placed in a beating tank for 30 to 60 minutes, and the slurry concentration is 25% to 40% to ensure that the fiber is not completely cut to achieve fibrillation and obtain the beaten straw fiber;

[0021] Add wet strength agent and dry strength agent to the pulped straw fiber and stir evenly; then put it on the screen for forming, the concentration of the screen forming is 0.2%-0.5%, so as to avoid excessive weight of paper due to high concentration of the screen; after the screen forming, use an open press dehydrator for pressing, the first pressure line pressure is 30kN / m-40kN / m, the second pressure line pressure is 60kN / m-90kN / m, and the positive pressure line pressure is 90kN / m-120kN / m; after the pressing treatment, dry treatment is carried out to finally obtain the coated straw paper, and the moisture content of the coated straw paper is between 6% and 8%.

[0022] In this step, the thickness of the obtained straw paper for coating is preferably 0.1-0.6 mm.

[0023] The straw paper obtained in this step is used as the coated paper on which the plastic coating is coated in the coating process of step 3) to improve the overall strength of the material, especially the tensile strength and bursting strength.

[0024] In this step, the content of the wet strength agent added is 0.5-1% of the absolute dry weight of the straw paper for coating; the content of the dry strength agent added is 0.5-2.0% of the absolute dry weight of the straw paper for coating. In specific implementation, it can also be added according to actual conditions or the amount recommended in the wet strength agent / dry strength agent manual.

[0025] In this step, the wet strength agent used can be one or more of urea-formaldehyde resin, epichlorohydrin, and polyamide, and the dry strength agent can be one or more of polyacrylamide, cationic starch, and polyvinyl alcohol.

[0026] In the present application, the technical terms "beating, forming on the net, pressing, and drying" are conventional technologies (in the field of papermaking), and the contents disclosed in the reference "Clean Production Process of Unbleached Corrugated Paper from Wheat Straw Pulp, Environment and Development, 1999" can be seen.

[0027] 3) Laminating process

[0028] Polylactic acid PLA and polybutylene terephthalate PBAT are mixed and stirred uniformly to obtain a masterbatch, and then the masterbatch is mixed and stirred uniformly with zinc stearate, calcium carbonate, and erucamide (the stirring speed is preferably 500 r / min) to obtain a mixture;

[0029] The above mixture is added into a laminating machine, and is laminarized on the straw paper for laminating obtained in step 2), and the mixed material forms a laminating layer covering the straw paper during the laminating process to obtain a composite film; at the same time, a punching machine is used to uniformly punch through holes in the composite film in sequence to obtain the degradable film for preventing root penetration of the straw matrix tray for rice seedling cultivation without a rice seedling tray.

[0030] In this step, the temperature of the laminating machine is controlled to be 180°C to 280°C, and the thickness of the laminating layer is preferably 40um to 100um;

[0031] In this step, the coating layer prepared on the surface of the straw paper using degradable materials can not only ensure that the roots of the seedlings are blocked from penetrating into the soil during their growth, but can also be directly returned to the field for degradation after the seedlings are raised.

[0032] In this step, the mass ratio of the polylactic acid PLA to the polybutylene terephthalate PBAT is preferably 1:2-4.

[0033] In this step, the mass ratio of the masterbatch, zinc stearate, calcium carbonate and erucamide is preferably 100:1-2:5-10:2-5, respectively.

[0034] In this step, the above-mentioned drilling means that the hole spacing is 0.5cm~1cm and the hole diameter is 0.5mm~1mm. This hole diameter is conducive to water penetration and root respiration.

[0035] In this application, the technical term "coating" is a conventional technology (in the field of papermaking), as can be seen in the content published in the Chinese patent "A processing technology for coated kraft paper, application number: CN111335071A, 2020".

[0036] In the present application, the technical term "line pressure" is a conventional technology (in the field of papermaking), and the content disclosed in the reference "Application of high-concentration pulping technology to produce offset book paper with all-reed pulp", 1998.

[0037] In the anti-root penetration degradable film for rice seedling raising straw substrate tray obtained in this step, the thickness ratio of the straw paper for coating and the coating layer is preferably 5 to 10: 1. The mixture of PLA and PBAT used in the coating layer has low strength, and the strength is mainly provided by the paper base, while the modified straw fiber (slurry) prepared in this application has not been chemically treated, the fiber is well preserved, and the interweaving force is large. Therefore, the control of the thickness ratio ensures both the excellent mechanical properties of the degradable film and the faster degradation rate after the rice seedling raising is completed and abandoned and returned to the field.

[0038] The method for using the anti-root penetration degradable film for the rice seedling raising straw matrix tray obtained by the above method is as follows: the anti-root penetration degradable film for the rice seedling raising straw matrix tray without seedling tray is laid on the flattened farmland, the coating layer faces upward, the automatic sowing and plate-setting machine walks on the degradable film, the plate-setting, sowing and seed covering of the straw matrix tray are carried out synchronously, and the gap between the straw matrix trays is kept at 1cm to 3cm. After the plate is set, micro-spray or flood irrigation is performed until the straw matrix tray is completely soaked with water, and non-woven fabric is covered. No additional watering is required before the seeds emerge and turn white, and no fertilizer is applied during the 30-day seedling growth period, and the growth of the rice seedlings is completely provided by the matrix itself. The degradation period of the degradable film is about 20-30 days, that is, after the rice seedling raising is completed, it can be degraded and returned to the field, increasing the nutrients in the field, without causing pollution, but without consuming additional manual labor.

[0039] The present application is the first to prepare a degradable film that prevents root penetration for rice seedling raising straw substrate trays without seedling trays. The kneaded and crushed crop straw fibers are subjected to steaming, composting, grinding and grafting to obtain modified straw fibers. The modified straw fibers are pulped, formed on the net, pressed and dried to form straw paper for coating. The straw paper is then coated with a mixture of polybutylene adipate / terephthalate (PBAT) and polylactic acid (PLA) to form a degradable film that prevents root penetration for rice seedling raising straw substrate trays without seedling trays. The coating straw paper ensures the strength and toughness of the material to facilitate the movement of the seeding tray machine, and the coating layer ensures that the rice roots do not penetrate to facilitate the smooth lifting of the seedlings after the seedling raising is completed. According to the test in the embodiment, the degradable film has a high longitudinal tear index, a high burst resistance, and a high tensile index (longitudinal tear index 10-25mN·m 2 / g, bursting strength 5.1-11.3KPa·m 2 / g, tensile index 25-35N·m 2 / g), and the preparation process is simple, which realizes the recycling of agricultural straw waste straw resources, makes up for the shortcomings of existing mechanized plating operations, and is easy to promote and utilize. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 The schematic diagram of the application structure of the degradation film of the embodiment;

[0041] In the figure, A is a schematic diagram of the structure of the degradable film in use; B is a schematic diagram of the surface of the degradable film;

[0042] 1- straw substrate disc; 2- coating layer; 3. through hole; 4- straw paper for coating; 5- rice seedling.

[0043] Figure 2 The following are actual photos of the degradation films of the examples.

[0044] Figure 3 A conventional photograph of damaged agricultural film was used for the example.

[0045] Figure 4 This is a photo of the roots penetrating conventional agricultural film during the seedling lifting process.

[0046] Figure 5 The following are photos of the biodegradable film used in the examples. DETAILED DESCRIPTION

[0047] The technical solutions of the present invention will be more clearly described below in conjunction with the embodiments of the present invention. The embodiments are only some embodiments of the present invention, not all embodiments, and the specific embodiments are not used to limit the present invention.

[0048] Example 1 Preparation of a degradable film for preventing root penetration of rice seedling-raising straw substrate trays

[0049] 1) Preparation of modified straw fiber:

[0050] The recycled rice straw is adjusted to a moisture content of 25%, and a fiber straw with a length of 2 cm is prepared after the straw is rubbed and crushed. The rubbed and crushed straw fiber is put into a conventional pulp fiber cooking pot (model: HK-ZZ01, Dongguan Hengke Automation Equipment Co., Ltd.), the cooking pot contains 80°C hot water, and the temperature in the cooking pot is raised to 120°C after insulation for 0.5h, and the temperature is lowered and discharged after insulation for 4h to obtain the cooked straw fiber, and the cooked straw fiber is directly mixed with a straw composting agent (purchased from Ningliang Bioengineering Co., Ltd., the trade name is "organic material composting agent (straw quick-rotting agent)"), the amount of the straw composting agent added accounts for 0.5% of the dry mass of the cooked straw fiber (in specific implementation, the amount can be adjusted according to the composting agent manual), the fully mixed cooked straw fiber and the straw composting agent are filled into a fermentation tank with a mechanical vent at the bottom for fermentation, and the material is taken out after fermentation for 5 days to obtain the decomposed straw fiber;

[0051] The decomposed straw fibers are directly fed into a conventional pulp refiner (model GMM-600, Weifang Derui Biotechnology Co., Ltd., Shandong Province) for pulping to obtain refined straw fibers for later use;

[0052] Weigh a portion of the refined straw fibers and perform conventional fiber esterification treatment (this embodiment refers to the fiber esterification treatment method disclosed in patent CN201010548136.8) to obtain esterified straw fibers; the esterified straw fibers and the refined straw fibers are mixed to obtain modified straw fibers. In the modified straw fibers obtained in this embodiment, the esterified straw fibers account for 1% of the total mass of the modified straw fibers (in practical applications, the content range is controlled within the range of 1-3%, which can achieve the purpose of the invention).

[0053] According to the test, the lignin removal rate of the modified straw fiber obtained in this step exceeds 30%, and the fiber yield exceeds 90%.

[0054] 2) Preparation of straw paper for lamination:

[0055] The modified straw fiber obtained in step 1) is placed in a beating tank for beating for 30 minutes, with a slurry concentration of 25%, so as to achieve fibrillation without being completely cut, thereby obtaining beating straw fiber;

[0056] Add wet strength agent urea-formaldehyde resin and dry strength agent polyacrylamide to the pulped straw fiber and stir evenly, the amount of wet strength agent and dry strength agent added is 0.5% and 1% of the absolute dry mass of the straw paper for coating obtained in this step respectively; then put on the screen for forming, the concentration of the screen forming is 0.2%, to avoid excessive weight of paper due to high concentration of the screen; after the screen forming, press treatment is carried out, the first pressure line pressure is 30kN / m, the second pressure line pressure is 60kN / m, and the positive pressure line pressure is 90kN / m; after the pressing treatment, drying treatment is carried out to finally obtain the straw paper for coating, the thickness of which is 0.2mm and the moisture content is 6%. In the specific implementation, the thickness of the straw paper for coating can be controlled within the range of 0.1-0.6mm, which can achieve the purpose of the invention.

[0057] 3) Laminating process:

[0058] Polylactic acid PLA and polybutylene terephthalate PBAT are mixed evenly in a mass ratio of 1:4 to prepare a master batch for later use; then the master batch, zinc stearate, calcium carbonate, and erucamide are mixed evenly in a mass ratio of 100:1:5:2 to obtain a mixed material;

[0059] The mixed material was added into a laminating machine (Guangzhou Putong, model: FDSI-35 / 28); the temperature of the laminating machine was controlled at 180°C.

[0060] The mixed material is coated on the coating straw paper obtained in step 2), and the mixed material forms a coating layer covering the straw paper during the coating process to obtain a composite film; and then a puncher is used to uniformly punch through holes in the composite film in sequence, with a hole gap of 0.5 cm and a hole diameter of 0.5 mm to obtain a degradable film for preventing root penetration of rice straw substrate trays without rice seedling trays. The structural schematic diagram of its application is as follows Figure 1 As shown, Figure 1 A is a schematic diagram of the structure of the degradable film in use; B is a schematic diagram of the surface of the degradable film. Figure 2 shown.

[0061] In this embodiment, the ratio of the thickness of the straw paper for laminating to the laminating layer is 5:1.

[0062] The physical and chemical properties of the anti-root penetration degradable film for the rice seedling raising straw substrate tray prepared in this example and the conventional agricultural film are shown in Table 1.

[0063] The testing methods of bursting index, tensile strength and tearing index in Table 1 are published in the reference: "Jan-Erik Levlin. Pulp and Paper Testing [M], China Light Industry Press". The testing method of degradation cycle is published in the reference: "YOSHITO OTAKE, Biodegradation of low-density polythene, polystyrene, polyvinyl chloride, and urea formaldehyde resin buried under soil for over 32 years, journal of applied polymer science, 1995".

[0064] The “conventional agricultural film” in Table 1 was purchased from Linyi Senmao Plastic Products Factory, model: PE ground film, product thickness: 40um, color: white.

[0065] Table 1 Comparison of film properties

[0066]

[0067] As can be seen from Table 1, the degradable film obtained in Example 1 can significantly increase various mechanical properties, is beneficial to the movement of the swing disc seeder, has a short degradation cycle, and is beneficial to sufficient return to the field.

[0068] The multi-layer straw matrix block obtained in this example was used to carry out a seedling raising experiment, and the specific steps were as follows:

[0069] On the leveled farmland, a rice seedling-free straw substrate tray is laid with a root-proof degradable film, with the film layer facing upwards. The automatic sowing tray machine moves on the degradable film, and the straw substrate tray is placed, sown, and covered with seeds simultaneously, keeping the gap between the straw substrate trays at 1cm to 3cm. After placing the tray, micro-spray or flood irrigation is performed until the straw substrate tray is completely soaked with water, and then covered with non-woven fabric. No additional watering is required before the seeds emerge and turn white. No fertilizer is applied during the 30-day seedling growth period, and the growth of the rice seedlings is completely provided by the substrate itself.

[0070] The matrix block used in this embodiment is the multi-layer straw matrix block prepared in Example 1 of Chinese patent CN201910772006.3. The swing tray seeder used is the degradable matrix seedling tray swing tray seeder published in Chinese patent CN212436304U. In the specific implementation, other commercially available swing tray seeders (preferably interval swing tray seeders) can also be used. The conventional agricultural film used in Table 2 is the same as that in Table 1.

[0071] The damage of the film before and after raising the seedlings is shown in Table 2:

[0072] Table 2 Film damage before and after seedling raising

[0073]

[0074] Table 2 uses photos of conventional agricultural film damage. Figure 3 The root system penetrates the conventional agricultural film during the seedling lifting process. Figure 4 As shown in the figure, the conventional agricultural film is obviously damaged; the photo of using the degradable film to raise the seedlings is as follows Figure 5 It can be seen that when the degradable film obtained in this embodiment is used for transplanting seedlings, the root system does not penetrate the degradable film, which facilitates transplanting seedlings.

[0075] Example 2

[0076] 1) Preparation of modified straw fiber:

[0077] The recycled rice straw is adjusted to a moisture content of 75%, and is prepared into a fiber straw with a length of 6 cm after a straw kneading and crushing process. The kneaded and crushed straw fiber is put into a conventional pulp fiber cooking pot, and the cooking pot contains 80°C hot water. After keeping the temperature for 0.5 hours, the temperature in the cooking pot is raised to 160°C, and after keeping the temperature for 8 hours, the material is cooled and discharged to obtain the cooked straw fiber. The cooked straw fiber is directly mixed with a conventional straw composting agent, and the straw composting agent accounts for 2% of the dry weight of the cooked straw fiber. The fully mixed cooked straw fiber and the straw composting agent are filled into a fermentation tank with a mechanical vent at the bottom for fermentation. The material is taken out after fermentation for 5 days to obtain the decomposed straw fiber;

[0078] The decomposed straw fibers are directly put into a conventional pulp refiner for pulping to obtain pulped straw fibers; a portion of the pulped straw fibers are weighed for conventional fiber esterification to obtain esterified straw fibers; the esterified straw fibers and the pulped straw fibers are mixed to obtain modified straw fibers. In the modified straw fibers prepared in this embodiment, the esterified straw fibers account for 3% of the total mass of the modified straw fibers.

[0079] 2) Straw paper for laminating:

[0080] The modified straw fiber is placed in a beating tank and beaten for 60 minutes with a pulp concentration of 40% to ensure that the fibers are not completely cut and can be separated into fibers; the pulped straw fiber is mixed with a wet strength agent urea-formaldehyde resin and a dry strength agent polyacrylamide and stirred evenly; the wet strength agent and dry strength agent are added in an amount of 1% and 2% of the absolute dry mass of the straw paper for coating obtained in this step, respectively; it is then put on the screen for forming, and the concentration of the screen forming is 0.5% to avoid excessive weight of the paper due to a high screen concentration; after the screen forming, it is pressed, with a first pressure line pressure of 40kN / m, a second pressure line pressure of 90kN / m, and a positive pressure line pressure of 120kN / m; after the pressing treatment, it is dried to obtain the final straw paper for coating (thickness 0.25mm), and the moisture content of the final straw paper for coating is 8%.

[0081] 3) Laminating process:

[0082] Polylactic acid PLA and polybutylene terephthalate PBAT are mixed evenly in a mass ratio of 1:4 to form a masterbatch. The masterbatch and zinc stearate, calcium carbonate and erucamide are mixed evenly in a mass ratio of 100:2:10:5 in sequence and then added into a laminating machine; the temperature of the laminating machine is controlled at 280°C, and the thickness of the laminating layer is controlled at 100un.

[0083] The mixed material is coated on the coating straw paper in step 2), and holes are punched uniformly in sequence using a puncher, with a hole spacing of 1 cm and a hole diameter of 1 mm. The ratio of the coating straw paper to the coating layer thickness is 2.5:1, and the anti-root penetration degradable film for the rice seedling raising straw substrate tray without seedling tray is obtained. The obtained degradable film test data is shown in Table 3 below.

[0084] Table 3 Comparison of film performance

[0085]

[0086]

[0087] The above description is only a preferred embodiment of the present invention and is not intended to limit the protection scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention are included in the protection scope of the present invention.

Claims

1. A method for preparing a root penetration-proof degradable film for a rice seedling raising straw substrate tray without a rice seedling tray, characterized in that the specific steps are as follows: 1) Preparation of modified straw fiber 1.1) Adjust the moisture content of crop straw to 25% to 75%, rub and crush to obtain 2cm to 8cm long fiber straw; place the fiber straw in 80℃ hot water for 0.5h to 1h, and then keep it in 120℃ to 160℃ hot water for 4h to 8h to obtain cooked straw fiber; 1.2) Adding straw composting agent to the cooked straw fiber, and obtaining the decomposed straw fiber after aerobic fermentation; the added straw composting agent accounts for 0.5% to 2% of the dry mass of the cooked straw fiber; 1.3) Refining the decomposed straw fibers to obtain refined straw fibers for later use; 1.4) taking the refined straw fibers and performing fiber esterification treatment to obtain esterified straw fibers for later use; 1.5) mixing the esterified straw fiber and the refined straw fiber to obtain modified straw fiber; 2) Preparation of straw paper for coating 2.1) placing the modified straw fiber prepared in step 1) in a beating tank for beating to obtain beating straw fiber; 2.2) Add wet strength agent and dry strength agent to the pulped straw fiber, mix evenly, put it on the net to form, press and dry, and obtain straw paper for coating with a moisture content of 6% to 8%, which is set aside; 3) Laminating 3.1) Mix polylactic acid PLA and polybutylene terephthalate PBAT and stir them evenly to obtain a masterbatch; then mix the masterbatch with zinc stearate, calcium carbonate and erucamide to obtain a mixture; 3.2) adding the mixture into a laminating machine, laminating the composite film on the laminating straw paper obtained in step 2), wherein the mixed material forms a laminating layer covering the laminating straw paper in the laminating machine; 3.3) The composite film is evenly perforated to obtain the degradable film for preventing root penetration of the rice seedling raising straw substrate tray without seedling tray.

2. The method for preparing the anti-root penetration degradable film for the rice seedling raising straw substrate tray without seedling tray according to claim 1, characterized in that: In the modified straw fiber described in step 1), the mass of the esterified fiber accounts for 1-3% of the mass of the modified straw fiber.

3. The method for preparing the anti-root penetration degradable film for the rice seedling raising straw substrate tray without seedling tray according to claim 1, characterized in that: The crop straw in step 1) includes at least one of rice straw, corn straw, rape straw and wheat straw.

4. The method for preparing the anti-root penetration degradable film for the rice seedling raising straw substrate tray without seedling tray according to claim 1, characterized in that: The thickness of the straw paper for coating obtained in step 2) is 0.1-0.6 mm.

5. The method for preparing the anti-root penetration degradable film for the rice seedling raising straw substrate tray without seedling tray according to claim 1, characterized in that: The wet strength agent used in step 2) includes one or more of urea-formaldehyde resin, epichlorohydrin, and polyamide.

6. The method for preparing the anti-root penetration degradable film for the rice seedling raising straw substrate tray without seedling tray according to claim 1, characterized in that: The dry strength agent used in step 2) includes one or more of polyacrylamide, cationic starch, and polyvinyl alcohol.

7. The method for preparing the anti-root penetration degradable film for the rice seedling raising straw substrate tray without seedling tray according to claim 1, characterized in that: In step 3), the temperature of the laminating machine is 180°C to 280°C, and the thickness ratio of the straw paper for laminating to the laminating layer is 5 to 10:

1.

8. The method for preparing the anti-root penetration degradable film for the rice seedling raising straw substrate tray without seedling tray according to claim 1, characterized in that: In step 3), the mass ratio of polylactic acid PLA to polybutylene terephthalate PBAT is 1:2-4.

9. The method for preparing the anti-root penetration degradable film for the rice seedling raising straw substrate tray without seedling tray according to claim 1, characterized in that: In step 3), the mass ratios of masterbatch, zinc stearate, calcium carbonate and erucamide are 100:1-2:5-10:2-5 respectively.

10. The method for preparing the anti-root penetration degradable film for the rice seedling raising straw substrate tray without seedling tray according to claim 1, characterized in that: In step 3), the punching means that the hole spacing is 0.5cm to 1cm and the hole diameter is 0.5mm to 1mm.

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