Biodegradable ground film and preparation method thereof

Abstract

The present application relates to the field of degradable plastics, and specifically discloses a biodegradable mulch film and a preparation method thereof; a biodegradable mulch film comprises an upper layer, an adhesive liquid and a lower layer; the upper layer is a silk fibroin fiber membrane, and the lower layer is a PBAT membrane; the PBAT membrane comprises the following raw materials in parts by weight: 80-100 parts of PBAT, 25-35 parts of PHB, 5-15 parts of coated biochar, and 5-10 parts of coated bamboo powder; the preparation method thereof is as follows: S1, weighing PBAT, PHB, coated biochar, and coated bamboo powder, mixing and stirring evenly, and extruding to form a PBAT membrane; S2, preparing a silk fibroin fiber membrane; S3, evenly applying an adhesive liquid on the surface of the PBAT membrane, and then covering it with a silk fibroin fiber membrane, and drying it, so that the PBAT membrane is the upper layer, the adhesive liquid forms an adhesive layer after drying, and the silk fibroin fiber membrane is the lower layer, thereby preparing a finished mulch film; the mulch film has the advantages of being degradable and ensuring the growth of crops.

Description

Technical Field

[0001] The present application relates to the field of degradable plastics, and more specifically, to a biodegradable ground film and a preparation method thereof. Background Art

[0002] Ground film is a ground covering film, including polyvinyl chloride film, polyvinyl chloride drip-free film, ordinary polyethylene film, polyethylene drip-free film, polyethylene multifunctional composite film and EVA multifunctional composite film, etc.; it is usually a transparent or black film, and some are green or silver; ground film has the advantages of increasing soil temperature, retaining soil moisture, maintaining soil structure, preventing pests from invading crops, and promoting crop growth.

[0003] Ordinary mulch film is blown with polyethylene from petrochemical products as the main component. It contains high-molecular polyethylene compounds and their resins, and is not easy to rot and is extremely difficult to decompose. Residual film will affect soil properties and reduce soil fertility. In severe cases, it will cause poor migration of water and nutrients in the soil, causing secondary salinization in local areas. At the same time, the harm to crop growth will be aggravated, mainly manifested in the possible obstruction of crop root growth, reducing the ability of crops to obtain water and nutrients, and leading to lower yields.

[0004] Therefore, how to prepare a biodegradable mulch film that can ensure the growth of crops is a problem to be solved. Summary of the Invention

[0005] In order to prepare a biodegradable mulch film and ensure the growth of crops, the present application provides a biodegradable mulch film and a preparation method thereof.

[0006] In a first aspect, the present application provides a biodegradable ground film, which adopts the following technical solution:

[0007] A biodegradable ground film comprises an upper layer, an adhesive liquid and a lower layer; the upper layer is a silk fibroin fiber film, and the lower layer is a PBAT film; the PBAT film contains the following raw materials in parts by weight: 80-100 parts of PBAT, 25-35 parts of PHB, 5-15 parts of coated biochar, and 5-10 parts of coated bamboo powder.

[0008] By adopting the above technical solution, the silk fibroin fiber membrane and the PBAT membrane can be biodegraded, so that the ground film has good biodegradability, and the silk fibroin fiber membrane and the PBAT membrane have good air permeability, which facilitates the contact between the roots of crops and oxygen, thereby ensuring the growth of crops.

[0009] PBAT, PHB, coated biochar, and coated bamboo powder are combined, and the excellent biocompatibility of PHB can improve the compatibility and bonding effect between the coated biochar, coated bamboo powder, and PBAT. When biodegrading the PBAT film, the excellent hydrophilic adhesion of the coated biochar and coated bamboo powder first facilitates the rapid attachment of bacteria to the surfaces of the biochar and bamboo powder, while PHB serves as a connecting bridge between the biochar, bamboo powder, and PBAT. Bacterial secretions are first used to degrade the biochar and bamboo powder. Then, the alkaline substances generated by the degradation of the biochar and bamboo powder can promote the degradation of PHB. After the degradation of PHB, the PBAT is exposed, that is, there is no adhesive around the PBAT, thereby increasing the contact area between the PBAT and the bacteria. At the same time, the degradation of the biochar, bamboo powder, and PHB can provide nutrients to the bacteria, promote bacterial growth and reproduction, and further promote the bacterial degradation of the PBAT film. The good hydrophilic and hygroscopic properties of silk fibroin fibers facilitate the attachment of bacteria to the surface of the silk fibroin fiber membrane for degradation, making the finished mulch film have a good biodegradable effect.

[0010] The upper and lower layers cooperate with each other and utilize a double-layer two-color structure, so that the silk fibroin fiber membrane of the upper layer has better light reflectivity, which increases the photosynthesis of crops. At the same time, the PBAT membrane of the lower layer is black, which is convenient for absorbing solar energy to increase ground temperature, inhibiting the growth of light-loving weeds, and can also ensure the growth of crop roots, thereby ensuring the growth of crops.

[0011] Preferably, the coated biochar is prepared by loading biochar with plant extract and then coating it with a polylysine membrane.

[0012] By adopting the above technical solution, biochar, plant extract and polylysine film are matched together, and the porous structure of biochar is utilized to facilitate the loading of plant extract, combined with the coating effect of the polylysine film. On the one hand, the sustained-release effect of the plant extract is prolonged, and the action time of the plant extract in the soil is prolonged. On the other hand, the amino and carboxyl groups in polylysine are combined with the hydroxyl groups in PHB to further promote PHB to bond the coated biochar with PBAT, thereby improving the bonding stability of the coated biochar in the PBAT film, thereby ensuring the mechanical strength of the mulch film; and the degradation effect of the coated biochar is utilized to further promote the degradation of the mulch film.

[0013] During the use of the mulch film, the coating effect of the polylysine film is utilized to gradually release the effective ingredients in the plant extract, and the insect repellent and harmful bacteria growth inhibition effects of the effective ingredients are utilized to prevent crops from being damaged by pests and affecting the growth of crops. During the degradation of the mulch film, the polylysine film is first utilized to attract and adhere to bacteria, making it easier for bacteria to attach to the surface of the polylysine film. Then, the bacteria are used to decompose the polylysine and biochar in turn, so that the mulch film can be biodegraded. That is, the finished mulch film has a degradable effect and can promote the growth and reproduction of crops at the same time.

[0014] Preferably, the coated bamboo powder is prepared by loading bamboo powder with plant extract and then coating it with a polydopamine film.

[0015] By adopting the above technical solution, bamboo powder, plant extract and polydopamine membrane are coordinated, and the porous adsorption effect of bamboo powder is utilized to facilitate bamboo powder to adsorb plant extract, and then the coating effect of polydopamine membrane is utilized to achieve slow release of plant extract.

[0016] When the mulch is buried in the soil for degradation, the coated bamboo powder and the coated biochar are combined to form a cross-linked network by utilizing the amino group of polydopamine on the surface of the bamboo powder and the carboxyl group of polylysine on the surface of the coated biochar, so as to facilitate the rapid entry of bacteria into the network pores and accelerate the rate of biodegradation. At the same time, after the bacteria degrade polydopamine, bamboo powder and other raw materials, the nutrients produced can supply the growth and reproduction of bacteria, thereby utilizing more bacteria to degrade PBAT and PHB, accelerating the degradation rate of the mulch and improving the degradation efficiency of the mulch.

[0017] Preferably, the plant extract consists of lemon balm ethanol solution and marigold ethanol solution in a weight ratio of 1:0.2-0.5.

[0018] By adopting the above technical solution, lemon balm and marigold are extracted using ethanol as the extraction solvent. The extracted substances such as citronellol and citral can not only repel insects but also purify the air through their fragrance. Moreover, the two substances are not easy to inhibit beneficial bacteria in the soil, but can inhibit harmful bacteria in the soil, thereby ensuring the growth of crops.

[0019] Polylysine and polydopamine are slightly soluble in ethanol. The plant extract loaded inside the biochar and bamboo powder can be blocked inside the envelope, and the plant extract remaining on the surface of the biochar and bamboo powder can also tightly adhere to the polylysine membrane and polydopamine membrane, improving the stability of the envelope, thereby ensuring that the effective insect repellent ingredients in the plant extract are slowly released.

[0020] Preferably, the silk fibroin fiber membrane comprises the following raw materials in parts by weight:

[0021] 20-32 parts of silk fibroin fiber, 1-2 parts of color fixing agent, 35-50 parts of PBAT, 1-3 parts of compatibilizer, 2-4 parts of plasticizer, and 5-10 parts of maleic anhydride grafted EVA.

[0022] By adopting the above technical solution, silk fibroin fiber, a color fixing agent, PBAT, a compatibilizer, a plasticizer, and maleic anhydride grafted EVA are combined, with silk fibroin fiber and PBAT as the matrix, the silk fibroin fiber is evenly dispersed in the PBAT, under the connecting effect of the maleic anhydride grafted EVA, the compatibilizer and the plasticizer are combined to ensure that the silk fibroin fiber is relatively stably dispersed and bonded in the PBAT, and the color fixing agent is combined to make the silk fibroin fiber film appear gray. The gray film layer has good light reflectivity, can increase the photosynthesis of crops, and ensure the growth of crops.

[0023] When the mulch film is degraded, the silk fibroin fiber is hydrophilic, and the bacteria in the soil can quickly attach to the surface of the silk fibroin fiber. As the bacterial secretions degrade the silk fibroin fiber, the degradation products of the silk fibroin fiber provide energy for the bacteria, promote bacterial reproduction, and increase the number of bacteria. After the silk fibroin fiber is degraded, the PBAT is in a state of fault splitting, which increases the contact area with bacteria, making it easier to be decomposed by bacteria, ensuring that the silk fibroin fiber film is biodegraded, thereby accelerating the degradation rate of the mulch film.

[0024] Preferably, the silk fibroin fibers are prepared by soaking silk fibroin fibers in a Cineraria extract solution and then coating them with a polyvinyl alcohol film.

[0025] By adopting the above technical scheme, the silk fibroin fiber utilizes its good adsorption effect to facilitate the adsorption of the cinnamon extract, and then utilizes the film-forming effect of polyvinyl alcohol to coat the surface of the silk fibroin fiber; utilizes flavonoids, alkaloids and other substances in cinnamon to improve the insect repellent effect of the silk fibroin fiber membrane and improve the antibacterial effect of the silk fibroin fiber membrane; and utilizes the silver-gray reflective and antioxidant effects of cinnamon to ensure the mechanical strength of the mulch film while ensuring photosynthesis during use; at the same time, utilizes the hydroxyl groups in polyvinyl alcohol to further promote the decomposition of silk fibroin fibers by microorganisms, thereby increasing the degradation rate of the mulch film.

[0026] Preferably, the compatibilizer is polyethylene glycol.

[0027] By adopting the above technical solution, polyethylene glycol and silk fibroin fibers are combined, and the hydroxyl groups in polyethylene glycol are combined with the hydroxyl groups in polyvinyl alcohol on the surface of the silk fibroin fibers, so that the compatibilizer can improve the bonding compatibility between the silk fibroin fibers and PBAT, thereby improving the mechanical strength of the silk fibroin fiber membrane; and the hydroxyl groups of polyethylene glycol can promote the attachment of bacteria to the surface of the silk fibroin fiber membrane, making it easier for bacteria to degrade the silk fibroin fiber membrane, thereby improving the degradation efficiency of the ground film.

[0028] Preferably, the plasticizer is hydrogenated castor oil.

[0029] By adopting the above technical solution, hydrogenated castor oil, a compatibilizer, and silk fibroin fibers are combined, and the hydroxyl groups in hydrogenated castor oil and the compatibilizer are used to combine with the silk fibroin fibers, the stable bonding between the silk fibroin fibers and PBAT is further promoted, thereby improving the mechanical strength of the mulch film while improving the biodegradation efficiency of the mulch film.

[0030] Preferably, the adhesive solution is composed of sodium alginate solution, nano boron nitride and polyglutamic acid in a weight ratio of 1:0.02-0.08:0.05-0.15.

[0031] By adopting the above technical solution, sodium alginate solution, nano-boron nitride and polyglutamic acid are combined, and microorganisms in the soil can degrade sodium alginate and polyglutamic acid, while nano-boron nitride can loosen the soil, thereby degrading the ground film while promoting crop growth.

[0032] The adhesive liquid, PBAT membrane and silk fibroin fiber membrane are matched. The polylysine and polydopamine in the PBAT membrane are easily soluble in water, and the solvent in the sodium alginate solution is water, so that the coated biochar and coated bamboo powder on the PBAT membrane that are in direct contact with the adhesive liquid are more tightly bonded to the sodium alginate solution, thereby improving the bonding stability between PBAT and the adhesive liquid; and the polyvinyl alcohol on the silk fibroin fiber membrane is soluble in water, which can also improve the bonding effect between the silk fibroin fiber and the adhesive layer; when the ground film is degraded, the nano-boron nitride and polyglutamic acid particles in the adhesive liquid are used as filling materials and the layer structure is formed. The gaps, combined with the high water absorption of sodium alginate, promote the rapid entry of bacteria into the bonding layer to achieve degradation. At the same time, the coated biochar and coated bamboo powder on the PBAT membrane that are in direct contact with the bonding liquid are also degraded, and the silk fibroin fibers on the silk fibroin fiber membrane that are in direct contact with the bonding liquid are also degraded. Then, the coated biochar and coated bamboo powder at other positions on the PBAT membrane are gradually degraded, and the silk fibroin fibers at other positions on the silk fibroin fiber membrane are gradually degraded. When the bonding layer is degraded, the upper and lower layers are separated, which further increases the contact area with bacteria and further accelerates the degradation rate of the film.

[0033] The adhesive liquid, PBAT membrane, and silk fibroin fiber membrane work together. Under low temperature conditions, solar energy can penetrate the silk fibroin fiber membrane and reach the adhesive liquid. The nano-boron nitride in the adhesive liquid has a good thermal conductivity, which facilitates the transfer of solar energy to the PBAT layer. The black color of the PBAT layer is used to further absorb heat and increase the ground temperature, thereby inhibiting the growth of light-loving weeds and maintaining the ground temperature to ensure the health of the crop roots.

[0034] In a second aspect, the present application provides a method for preparing a biodegradable ground film, which adopts the following technical solution:

[0035] A method for preparing a biodegradable ground film comprises the following steps:

[0036] S1. Weigh PBAT, PHB, coated biochar, and coated bamboo powder, mix and stir evenly, and extrude to form a PBAT film; S2. Prepare a silk fibroin fiber film;

[0037] S3. Evenly apply adhesive liquid on the surface of the PBAT film, and then cover it with silk fibroin fiber membrane. After drying, the PBAT film is the upper layer, the adhesive liquid forms an adhesive layer after drying, and the silk fibroin fiber membrane is the lower layer to obtain a finished ground film.

[0038] By adopting the above technical solution, the PBAT film, adhesive liquid and silk fibroin fiber membrane are combined to make the ground film have good elasticity and toughness, thereby ensuring the mechanical strength of the ground film.

[0039] In summary, this application has the following beneficial effects:

[0040] 1. Silk fibroin fiber membrane and PBAT membrane can be biodegraded, so that the ground film has good biodegradability, and the silk fibroin fiber membrane and PBAT membrane have good air permeability, which facilitates the contact between crop roots and oxygen, thereby ensuring the growth of crops.

[0041] 2. The combination of coated biochar and coated bamboo powder ensures the strength of the mulch film during its use. When the mulch film is degraded, since polylysine and polydopamine are hydrophilic and water-soluble, they are more easily promoted to be decomposed by organisms under the action of moisture in the soil, thereby quickly disintegrating the PBAT film and promoting the degradation of the mulch film.

[0042] 3. The adhesive liquid, PBAT membrane and silk fibroin fiber membrane are combined. Under low temperature conditions, solar energy can penetrate the silk fibroin fiber membrane and reach the adhesive liquid. The nano-boron nitride in the adhesive liquid has a good thermal conductivity, which facilitates the transfer of solar energy to the PBAT layer. The black color of the PBAT layer is used to further absorb heat and increase the ground temperature, thereby inhibiting the growth of light-loving weeds and maintaining the ground temperature to ensure the health of the crop roots.

[0043] 4. The bonding layer, upper layer and lower layer cooperate with each other, and the bonding layer is degraded first, and then the PBAT membrane and silk fibroin fiber membrane in contact with the bonding layer are degraded. As the substances produced by degradation increase, the growth and reproduction of bacteria are promoted, and the contact area between the PBAT membrane and silk fibroin fiber membrane and bacteria is increased, thereby accelerating the degradation rate of the ground film.

[0044] 5. The combination of coated biochar, coated bamboo powder, nano-boron nitride and silk fibroin fiber forms a network structure that facilitates the rapid entry of bacteria to achieve degradation; and nano-boron nitride can loosen the soil, increase the oxygen content in the soil, further promote the reproduction and growth of beneficial bacteria, and accelerate the biodegradation of the film. DETAILED DESCRIPTION

[0045] The present application is further described in detail below with reference to examples.

[0046] Preparation example of plant extract

[0047] Preparation Example 1: The plant extract was prepared by the following method:

[0048] Weigh 1 kg of lemon balm and place it in 200 kg of 75% ethanol for 24 hours, then filter the filtrate and concentrate it to 1 / 10 of the volume of the filtrate to prepare a lemon balm ethanol solution for later use;

[0049] Weigh 1 kg of marigolds and place them in 200 kg of 75% ethanol for 24 hours, then filter the filtrate and concentrate it to 1 / 10 of the volume of the filtrate to prepare a marigold ethanol solution for later use;

[0050] 1 kg of lemon balm ethanol solution and 0.4 kg of calendula ethanol solution were weighed and mixed to obtain a finished plant extract.

[0051] Preparation Example 2: This preparation example differs from Preparation Example 1 in that:

[0052] Weigh 1 kg of lemon balm ethanol solution and 0.2 kg of calendula ethanol solution, mix and stir evenly to prepare a finished plant extract.

[0053] Preparation Example 3: This preparation example differs from Preparation Example 1 in that:

[0054] Weigh 1 kg of lemon balm ethanol solution and 0.5 kg of calendula ethanol solution, mix and stir evenly to prepare a finished plant extract.

[0055] Preparation example of coated biochar

[0056] Preparation Example 4: Coated biochar was prepared by the following method:

[0057] Weigh 1 kg of biochar and place it in 10 kg of the plant extract prepared in Preparation Example 1, immerse and stir, ultrasonically disperse it at 20 kHz for 30 minutes, then stir it at 500 r / min for 1 hour, filter out the biochar, and prepare loaded biochar; the biochar is 200 nm;

[0058] Polylysine was placed in water and stirred to dissolve to prepare a 10% by mass polylysine aqueous solution, and sodium alginate was placed in water and stirred to dissolve to prepare a 1% by mass sodium alginate aqueous solution; 1 kg of the polylysine aqueous solution and 0.3 kg of the sodium alginate aqueous solution were mixed and stirred to prepare a composite solution;

[0059] 0.32 kg of the composite liquid was evenly sprayed on the surface of 1 kg of loaded biochar, and then quickly dried, and the composite liquid formed a polylysine film to obtain a finished coated biochar.

[0060] Preparation Example 5: This preparation example differs from Preparation Example 4 in that:

[0061] The plant extract was the plant extract prepared in Preparation Example 2.

[0062] Preparation Example 6: This preparation example differs from Preparation Example 4 in that:

[0063] The plant extract was the plant extract prepared in Preparation Example 3.

[0064] Preparation example of coated bamboo powder

[0065] Preparation Example 7: Coated bamboo powder was prepared by the following method:

[0066] 1 kg of bamboo powder was weighed and placed in 10 kg of the plant extract prepared in Preparation Example 1, immersed and stirred, ultrasonically dispersed at 20 kHz for 30 minutes, and then stirred at 500 r / min for 1 hour. The bamboo powder was filtered to obtain loaded bamboo powder; the bamboo powder was 300 nm; polydopamine was placed in water and stirred and dissolved to obtain a 10% polydopamine aqueous solution; sodium hydroxymethyl cellulose was placed in water and stirred and dissolved to obtain a 1% sodium hydroxymethyl cellulose aqueous solution; 1 kg of the polydopamine aqueous solution and 0.2 kg of the sodium hydroxymethyl cellulose aqueous solution were mixed and stirred to obtain a mixed solution;

[0067] 0.36 kg of the mixed liquid was evenly sprayed on the surface of 1 kg of loaded bamboo powder, and then quickly dried to form a polydopamine film to obtain a finished coated bamboo powder.

[0068] Preparation Example 8: This preparation example differs from Preparation Example 7 in that:

[0069] The plant extract was the plant extract prepared in Preparation Example 2.

[0070] Preparation Example 9: This preparation example differs from Preparation Example 7 in that:

[0071] The plant extract was the plant extract prepared in Preparation Example 3.

[0072] Preparation example of silk fibroin fiber

[0073] Preparation Example 10: Silk fibroin fibers were prepared by the following method:

[0074] Weigh 1 kg of Cineraria japonica and place it in 200 kg of 75% ethanol for 24 hours, then filter the filtrate and concentrate it to 1 / 10 of the volume of the filtrate to obtain the Cineraria japonica extract for later use;

[0075] 1 kg of silk fibroin fiber whiskers were weighed and immersed in 10 kg of Cineraria extract to disperse the whiskers. The length of the silk fibroin fiber whiskers was 300 nm. The whiskers were dispersed at 20 kHz for 10 min, then stirred at 250 r / min for 1 h to separate the silk fibroin fiber whiskers. 0.2 kg of a 2% by mass polyvinyl alcohol aqueous solution was evenly sprayed on the surface. After drying, the polyvinyl alcohol aqueous solution formed a polyvinyl alcohol film to obtain silk fibroin fibers.

[0076] Preparation example of adhesive solution

[0077] Preparation Example 11: The adhesive solution was prepared by the following method:

[0078] Weigh sodium alginate, place it in water, stir and dissolve it, and prepare a sodium alginate solution with a mass fraction of 2%. Weigh 0.05 kg of nano-boron nitride and add it to 1 kg of the sodium alginate solution at a rate of 2 g / s, stir evenly, and finally add 0.1 kg of polyglutamic acid at an addition rate of 2 g / s, mix and stir evenly, and prepare a finished adhesive solution; the particle size of the nano-boron nitride is 80 nm, and the particle size of the polyglutamic acid is 200 nm.

[0079] Preparation Example 12: This preparation example differs from Preparation Example 11 in that:

[0080] Weigh sodium alginate, place it in water and stir to dissolve it to prepare a 2% sodium alginate solution by mass. Weigh 0.02 kg of nano-boron nitride and add it to 1 kg of the sodium alginate solution at a rate of 2 g / s, stir evenly, and finally add 0.05 kg of polyglutamic acid at a rate of 2 g / s, mix and stir evenly to prepare a finished adhesive solution.

[0081] Preparation Example 13: This preparation example differs from Preparation Example 11 in that:

[0082] Weigh sodium alginate, place it in water and stir to dissolve it to prepare a 2% sodium alginate solution by mass. Weigh 0.08 kg of nano-boron nitride and add it to 1 kg of the sodium alginate solution at a rate of 2 g / s, stir evenly, and finally add 0.15 kg of polyglutamic acid at a rate of 2 g / s, mix and stir evenly to prepare a finished adhesive solution.

[0083] Example

[0084] Example 1: A biodegradable ground film:

[0085] It includes an upper layer, a bonding liquid and a lower layer, wherein the upper layer is a silk fibroin fiber membrane and the lower layer is a PBAT membrane; the bonding liquid is the bonding liquid prepared in Preparation Example 11;

[0086] In the PBAT film: 90kg PBAT, 30kg PHB, 10kg coated biochar, 8kg coated bamboo powder; the coated biochar is the coated biochar prepared in Preparation Example 4; the coated bamboo powder is the coated bamboo powder prepared in Preparation Example 7;

[0087] The silk fibroin fiber membrane comprises: 26 kg of silk fibroin fiber, 1.5 kg of color fixing agent, 42 kg of PBAT, 2 kg of compatibilizer, 3 kg of plasticizer, and 8 kg of maleic anhydride-grafted EVA; the silk fibroin fiber is the silk fibroin fiber prepared in Preparation Example 10, the color fixing agent is sodium chloride, the compatibilizer is polyethylene glycol, the polyethylene glycol is polyethylene glycol 2000, and the plasticizer is hydrogenated castor oil;

[0088] The preparation method is as follows:

[0089] S1. PHB, coated biochar, and coated bamboo powder were weighed and mixed evenly, and then PBAT was added and mixed evenly, and melt-extruded to obtain a PBAT film with a thickness of 0.004 mm.

[0090] S2. Weigh silk fibroin fiber, color fixing agent, PBAT, compatibilizer, plasticizer, and maleic anhydride grafted EVA, mix and stir evenly, and melt-extrude to form a silk fibroin fiber membrane; the thickness of the silk fibroin fiber membrane is 0.003 cm;

[0091] S3. Evenly apply adhesive liquid on the surface of the PBAT film, and then cover it with silk fibroin fiber membrane. After drying, the PBAT film is the upper layer, the adhesive liquid forms an adhesive layer after drying, and the thickness of the adhesive layer is 0.001 mm. The silk fibroin fiber membrane is the lower layer to obtain a finished ground film.

[0092] Example 2: This example differs from Example 1 in that:

[0093] The bonding liquid is the bonding liquid prepared in Preparation Example 12;

[0094] In the PBAT film: 80kg of PBAT, 25kg of PHB, 5kg of coated biochar, and 5kg of coated bamboo powder; the coated biochar is the coated biochar prepared in Preparation Example 5; the coated bamboo powder is the coated bamboo powder prepared in Preparation Example 8;

[0095] The silk fibroin fiber membrane contains: 20 kg of silk fibroin fiber, 1 kg of color fixing agent, 35 kg of PBAT, 1 kg of compatibilizer, 2 kg of plasticizer, and 5 kg of maleic anhydride-grafted EVA; the silk fibroin fiber is the silk fibroin fiber prepared in Preparation Example 10.

[0096] Example 3: This example differs from Example 1 in that:

[0097] The bonding liquid is the bonding liquid prepared in Preparation Example 13;

[0098] In the PBAT film: 100 kg of PBAT, 35 kg of PHB, 15 kg of coated biochar, and 10 kg of coated bamboo powder; the coated biochar is the coated biochar prepared in Preparation Example 6; the coated bamboo powder is the coated bamboo powder prepared in Preparation Example 9;

[0099] The silk fibroin fiber membrane contains: 32 kg of silk fibroin fiber, 2 kg of color fixing agent, 50 kg of PBAT, 3 kg of compatibilizer, 4 kg of plasticizer, and 10 kg of maleic anhydride-grafted EVA; the silk fibroin fiber is the silk fibroin fiber prepared in Preparation Example 10.

[0100] Example 4: This example differs from Example 1 in that:

[0101] The coated biochar in the PBAT membrane replaces the polylysine membrane with an ethyl cellulose membrane;

[0102] The preparation method is as follows:

[0103] 1 kg of ethyl cellulose was placed in 99 kg of 99% by mass anhydrous ethanol and stirred to dissolve to prepare a composite liquid;

[0104] 0.32 kg of the composite liquid was evenly sprayed on the surface of 1 kg of loaded biochar, and then quickly dried to form an ethyl cellulose film to obtain a finished coated biochar.

[0105] Example 5: This example differs from Example 1 in that:

[0106] No sodium alginate aqueous solution was added to the PBAT membrane-coated biochar composite solution.

[0107] Example 6: This example differs from Example 1 in that:

[0108] The bamboo powder coated in the PBAT membrane is replaced by the polydopamine membrane with ethyl cellulose membrane;

[0109] The preparation method is as follows:

[0110] 1 kg of ethyl cellulose was placed in 99 kg of 99% by mass anhydrous ethanol and stirred to dissolve to prepare a composite liquid;

[0111] 0.36 kg of the mixed liquid was evenly sprayed on the surface of 1 kg of loaded bamboo powder, and then quickly dried to form an ethyl cellulose film to obtain a finished coated bamboo powder.

[0112] Example 7: This example differs from Example 1 in that:

[0113] No sodium hydroxymethyl cellulose aqueous solution was added during the preparation of the coated bamboo powder.

[0114] Example 8: This example differs from Example 1 in that:

[0115] The plant extract is an aqueous solution of mugwort;

[0116] Weigh 1 kg of mugwort and place it in 200 kg of water for 24 hours, then filter the filtrate and concentrate it to 1 / 10 of the volume of the filtrate to obtain a mugwort aqueous solution.

[0117] Example 9: This example differs from Example 1 in that:

[0118] The silk fibroin fibers in the silk fibroin fiber membrane were not soaked in Cineraria extract during the preparation process.

[0119] Example 10: This example differs from Example 1 in that:

[0120] No compatibilizer or plasticizer was added during the preparation of silk fibroin fibers.

[0121] Example 11: This example differs from Example 1 in that:

[0122] Nano boron nitride and polyglutamic acid are not added to the adhesive solution.

[0123] Example 12: This example differs from Example 1 in that:

[0124] The adhesive liquid is an ethyl cellulose ethanol solution with a mass fraction of 1%.

[0125] Comparative Example

[0126] Comparative Example 1: The difference between this comparative example and Example 1 is that:

[0127] The biochar in the PBAT film was not coated;

[0128] 1 kg of biochar particles were weighed and placed in 10 kg of plant extract, immersed and stirred, ultrasonically dispersed at 20 kHz for 30 minutes, and then stirred at a speed of 500 r / min for 1 hour. The biochar particles were filtered out to obtain biochar.

[0129] Comparative Example 2: This comparative example differs from Example 1 in that:

[0130] The bamboo powder in the PBAT film is not coated;

[0131] 1 kg of bamboo powder particles were weighed and placed in 10 kg of plant extract, immersed and stirred, ultrasonically dispersed at 20 kHz for 30 minutes, then stirred at a speed of 500 r / min for 1 hour, and the bamboo powder particles were filtered out to obtain bamboo powder.

[0132] Comparative Example 3: This comparative example differs from Example 1 in that:

[0133] The ground film is polyethylene film with a thickness of 0.01mm.

[0134] Performance testing

[0135] 1. Degradation efficiency test

[0136] The finished mulch films were prepared by the preparation methods of Examples 1-12 and Comparative Examples 1-3, and the mulch films were used for mulch application. The number of days of the mulch film degradation period was recorded. 80-90 days was sufficient for 100

[0137] 2. Insect repellent performance test

[0138] Finished mulch films were prepared using the preparation methods of Examples 1-3 and 8-9, respectively. The mulch films were applied on eggplant seedlings, with each group corresponding to 10 seedlings. After 20 days, the area of ​​the eggplant seedlings bitten by insects was recorded, and the data was recorded.

[0139] 3. Crop growth detection

[0140] Finished mulch films were prepared using the preparation methods of Examples 1-8, 11 and Comparative Examples 1-3, respectively. The mulch films were applied to eggplant seedlings. The eggplant seedlings were 10-12 cm tall. Each group corresponded to 10 seedlings. The growth lengths of the 10 seedlings were recorded after 7 days. Except for the different biofilms, all other soil conditions, temperature, humidity, etc. were the same for all groups.

[0141] 4. Strength detection

[0142] Finished mulch films were prepared using the preparation methods of Examples 1-12 and Comparative Examples 1-2, respectively. The tensile strength was tested according to GB / T1040-2006, and the data were recorded.

[0143] 5. UV resistance test

[0144] Finished mulch films were prepared using the preparation methods of Examples 1-3 and 9, respectively. The elongation at break retention rate after 480 hours of ultraviolet aging was tested with reference to GB / T16422-2006, and the data were recorded.

[0145] Table 1 Performance test table

[0146]

[0147]

[0148] From Examples 1-3 and Table 1, it can be seen that the finished mulch film prepared in the present application has a good degradation effect, can prevent insects, promote crop growth, and has good mechanical properties, so that the mulch film has a long service life.

[0149] Combining Example 1 and Examples 4-12 and Table 1, it can be seen that in Example 4, the coated biochar in the PBAT membrane replaces the polylysine membrane with an ethyl cellulose membrane, and no sodium alginate aqueous solution is added to the composite liquid of the coated biochar in the PBAT membrane in Example 5. Compared with Example 1, the degradation time of the mulch films prepared in Examples 4 and 5 is longer than that in Example 1, the crop growth is slower than that in Example 1, and the tensile strength is less than that in Example 1; this indicates that the combination of polylysine and sodium alginate aqueous solutions can promote the compatibility and adhesion of the coated biochar with the coated bamboo powder and PBAT and PHB, thereby improving the mechanical strength of the mulch film, and the network structure formed by cross-linking polylysine and sodium alginate can promote bacterial attachment to the surface of the coated biochar. The bacteria first degrade polylysine and sodium alginate and then provide nutrients for bacterial growth, further promoting the degradation of the mulch film by bacteria; at the same time, the pores of the network structure cooperate with the pores of the biochar to facilitate the ventilation of the mulch film, thereby ensuring the oxygen content in the soil, thereby ensuring the growth of crops.

[0150] In Example 6, the polydopamine film was replaced by ethyl cellulose film in the PBAT film for the coated bamboo powder. In Example 7, no sodium hydroxymethyl cellulose aqueous solution was added during the preparation of the coated bamboo powder. Compared with Example 1, the degradation time of the mulch films prepared in Examples 6 and 7 was longer than that in Example 1, the crop growth was slower than that in Example 1, and the tensile strength was lower than that in Example 1. This indicates that polydopamine, sodium hydroxymethyl cellulose, polylysine, and sodium alginate can be cross-linked to form a network structure, which is not only breathable and promotes crop growth, but also can attract bacteria to attach and promote the degradation of the mulch film.

[0151] The plant extract in Example 8 is an aqueous solution of mugwort. Compared with Example 1, the insect bite area of ​​the ground film prepared in Example 8 is larger than that in Example 1, the crop growth is slower than that in Example 1, and the tensile strength is lower than that in Example 1. This indicates that the solvent of the aqueous solution of mugwort is water, which can easily affect the effective concentration of the mugwort extract when coated with polylysine and polydopamine, not only easily affecting the stability of the coating, but also affecting the sustained-release effect, thereby affecting the insect repellent effect.

[0152] In Example 9, the silk fibroin fibers in the silk fibroin fiber membrane were not soaked in Cineraria extract during the preparation process. Compared with Example 1, the degradation rate of the mulch film prepared in Example 9 was slower than that in Example 1, the insect bite area was larger than that in Example 1, the tensile strength was smaller than that in Example 1, and the retention rate of elongation at break was smaller than that in Example 1. This indicates that the flavonoids, alkaloids and other substances in Cineraria improve the insect repellent effect of the silk fibroin fiber membrane and the antibacterial effect of the silk fibroin fiber membrane. The silver-gray reflective and antioxidant effects of Cineraria can ensure the mechanical strength of the mulch film while ensuring photosynthesis during use. At the same time, the hydroxyl groups in polyvinyl alcohol can further promote the decomposition of silk fibroin fibers by microorganisms, thereby increasing the degradation rate of the mulch film.

[0153] In the preparation process of the silk fibroin fiber in Example 10, no compatibilizer and plasticizer were added. Compared with Example 1, the tensile strength of the mulch film prepared in Example 10 was lower than that in Example 1. This indicates that the combination of hydrogenated castor oil, compatibilizer, and silk fibroin fiber, and the use of hydroxyl groups in hydrogenated castor oil and the compatibilizer to combine with the silk fibroin fiber, further promote the stable bonding between the silk fibroin fiber and PBAT, thereby improving the mechanical strength of the mulch film while improving the biodegradation efficiency of the mulch film.

[0154] In Example 11, nano boron nitride and polyglutamic acid were not added to the adhesive solution. In Example 12, the adhesive solution was a 1% by mass ethyl cellulose ethanol solution. Compared with Example 1, the degradation time of the mulch film prepared in Example 11 was longer than that in Example 1, the crop growth was slower than that in Example 1, and the tensile strength was less than that in Example 1. The degradation time of the mulch film prepared in Example 12 was longer than that in Example 1, and the tensile strength was less than that in Example 1. This indicates that the sodium alginate solution, nano boron nitride and polyglutamic acid are combined, and the microorganisms in the soil can degrade the sodium alginate and polyglutamic acid, while the nano boron nitride can loosen the soil, thereby degrading the mulch film while promoting the growth of crops. In addition, the ethyl cellulose ethanol solution cannot be combined with the PBAT film and the silk fibroin fiber film, which is likely to affect the properties of the mulch film.

[0155] Combining Example 1 and Comparative Examples 1-3 and Table 1, it can be seen that the biochar in the PBAT film of Comparative Example 1 is not coated, and the bamboo powder in the PBAT film of Comparative Example 2 is not coated. Compared with Example 1, the degradation time of the mulch films prepared in Comparative Examples 1 and 2 is longer than that in Example 1, the crop growth is slower than that in Example 1, and the tensile strength is less than that in Example 1; this shows that the combination of the film biochar and the coated bamboo powder ensures the strength of the mulch film during its use. When the mulch film is degraded, since polylysine and polydopamine are hydrophilic and water-soluble, under the action of moisture in the soil, it is easier to promote the decomposition of polylysine and polydopamine by organisms, thereby quickly disintegrating the PBAT film and promoting the degradation of the mulch film; and the silk fibroin fiber film and the PBAT film have good air permeability, which facilitates the contact of crop roots with oxygen, thereby ensuring the growth of crops; at the same time, the layered structure film has good mechanical properties.

[0156] The mulch film in comparative example 3, which is made of polyethylene mulch film, has a longer degradation time than that in example 1, slower crop growth than that in example 1, and a lower tensile strength than that in example 1; this indicates that the mulch film prepared in this application replaces the polyethylene mulch film, making the mulch film have the advantages of being degradable, insect-repellent, and breathable, and can ensure the growth of crops.

[0157] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A biodegradable ground film, characterized in that: It includes an upper layer, an adhesive liquid and a lower layer; the upper layer is a silk fibroin fiber membrane, and the lower layer is a PBAT membrane; The PBAT film contains the following raw materials in parts by weight: 80-100 parts of PBAT, 25-35 parts of PHB, 5-15 parts of coated biochar, and 5-10 parts of coated bamboo powder; the silk fibroin fiber film contains the following raw materials in parts by weight: 20-32 parts of silk fibroin fiber, 1-2 parts of color fixing agent, 35-50 parts of PBAT, 1-3 parts of compatibilizer, 2-4 parts of plasticizer, and 5-10 parts of maleic anhydride grafted EVA; the silk fibroin fiber is prepared by soaking the silk fibroin fiber in a Cineraria extract and then coating it with a polyvinyl alcohol film; the coated biochar is prepared by loading the biochar with a plant extract and then coating it with a polylysine film; and the coated bamboo powder is prepared by loading the bamboo powder with a plant extract and then coating it with a polydopamine film.

2. The biodegradable ground film according to claim 1, characterized in that: The plant extract consists of lemon balm ethanol solution and marigold ethanol solution in a weight ratio of 1:0.2-0.

5.

3. The biodegradable ground film according to claim 1, characterized in that: The compatibilizer is polyethylene glycol.

4. The biodegradable ground film according to claim 1, characterized in that: The plasticizer is hydrogenated castor oil.

5. The biodegradable ground film according to claim 1, characterized in that: The adhesive solution consists of sodium alginate solution, nano boron nitride and polyglutamic acid in a weight ratio of 1:0.02-0.08:0.05-0.

15.

6. The method for preparing a biodegradable ground film according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1. Weigh PBAT, PHB, coated biochar, and coated bamboo powder, mix and stir evenly, and extrude to form a PBAT film; S2, preparing silk fibroin fiber membrane; S3. Evenly apply adhesive liquid on the surface of the PBAT film, and then cover it with silk fibroin fiber membrane. After drying, the PBAT film is the upper layer, the adhesive liquid forms an adhesive layer after drying, and the silk fibroin fiber membrane is the lower layer to obtain a finished ground film.

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