Preparation method of light conversion agricultural film

Abstract

The present application relates to the technical field of light conversion agricultural film, and particularly relates to a preparation method of light conversion agricultural film. The preparation method of light conversion agricultural film comprises the following steps: S1, adding a light conversion agent and a base into a banbury mixer, and carrying out banburying at 125-135 DEG C for 1-2 hours to obtain a mixed uniform block polymer melt; S2, adding the block polymer melt into a forced feeder, adjusting the temperature to 180-185 DEG C, and extruding a strip polymer by using a single screw extruder; S3, adding the strip polymer into a pelletizer, rotating the pelletizer at a frequency of 20.00 Hz to obtain a light conversion master batch; S4, mixing the light conversion master batch, the base and an additive, and adding them into a hopper of a film blowing machine, adjusting the temperature of three temperature zones of the hopper to 130 DEG C, 150 DEG C and 165 DEG C respectively, adjusting the temperature of a die head to 160 DEG C, rotating a screw at a frequency of 12.00 Hz, and adjusting the winding speed to 160 rpm to prepare the light conversion agricultural film.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of light conversion agricultural film, in particular to a preparation method of light conversion agricultural film. BACKGROUND

[0002] With the increase of world population, the food supply has been in a tense situation. With the large use of pesticides and fertilizers, the potential for increasing food production is becoming more and more limited, and the environment has also been greatly polluted. Therefore, it is necessary to seek other pollution-free and effective ways to increase production. Using agricultural light conversion film to improve plant photosynthesis is an environmentally friendly and effective way. Light conversion film can increase light conversion function by adding light conversion agent to polyethylene, polyvinyl chloride and other shed film which has the functions of heat preservation, cold prevention, wind and rain prevention, to improve the light quality of shed film, absorb the unnecessary purple light and green light in sunlight for plant photosynthesis, emit blue light or red light, strengthen plant photosynthesis, promote the growth and development of crops, promote the photosynthesis of greenhouse crops, and have a positive influence on plant growth and development, nutrient absorption, chlorophyll content and agricultural product quality, etc., to improve crop quality and achieve the effect of increasing yield.

[0003] The light stability of different light conversion agents themselves under sunlight exposure is directly related to its actual application value, and affects the promotion and application of light conversion film. At present, the main light conversion agents are organic light conversion agents and inorganic light conversion agents. When the organic fluorescent dye fluorescent substance is used as a light conversion agent for agricultural film, it has good compatibility with resin, and the film is easy to make. However, it is easy to oxidize and decompose, has a short service life, has low absorption and conversion efficiency of sunlight, affects the light transmission properties of agricultural film, and has a higher price and cost than inorganic light conversion agents.

[0004] In order to improve the performance of light conversion film, inorganic and organic light conversion agents can be used at the same time for mixed compounding, which can not only improve the filtering and absorption of light at different wavelengths of light conversion film, make the transmission wavelength more reasonable, but also reduce the reduction of film strength caused by single inorganic light conversion agent. In addition, in order to make the light conversion film have certain heat preservation performance, a certain amount of hydrotalcite needs to be added to block infrared rays and achieve heat preservation. Hydrotalcite can also improve the durability of light conversion film to a certain extent, and the light conversion performance decays more slowly. However, due to the hygroscopicity of hydrotalcite, when it is compounded with inorganic light conversion agent of hygroscopic metal sulfide system, the service life of light conversion film in a humid environment will be greatly reduced.

[0005] The present application aims to replace the traditional rare earth luminescent material with an environmentally friendly carbon-based nanomaterial, which can not rely on rare earth, a strategic mineral resource, and the supply chain is safer, and the entire preparation process is more green and sustainable. SUMMARY

[0006] To solve the problems mentioned in the above background art, the present application provides a preparation method of light conversion agricultural film.

[0007] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0008] A preparation method of light conversion agricultural film, comprising the following steps:

[0009] S1, add light conversion agent and base to the internal mixer, and mix at 125-135℃ for 1-2h to obtain a mixed uniform block polymer melt;

[0010] S2, add the block polymer melt to the forced feeder, adjust the temperature to 180-185℃, and use a single screw extruder to extrude a strip-shaped polymer;

[0011] S3, add the strip-shaped polymer to the granulator, and set the rotation frequency of the granulator to 20.00Hz to obtain a light conversion master batch;

[0012] S4, mix the light conversion master batch, base and auxiliary agent, and add them to the hopper of the film blowing machine, set the temperature of the three temperature zones of the barrel of the film blowing machine to 130℃, 150℃ and 165℃ respectively, set the temperature of the die head to 160℃, set the rotation frequency of the screw to 12.00Hz, and set the winding speed to 160rpm to prepare a light conversion agricultural film.

[0013] Preferably, the preparation method of the light conversion agent comprises the following steps:

[0014] S1-1, take graphene and add it to 1% chitosan acetic acid solution (acetic acid concentration 1%, pH 3-4), ultrasonic dispersion for 30-45min (power 300W, frequency 40kHz) to form a uniform suspension;

[0015] S1-2, add modified carbon quantum dot powder to the suspension, and continue ultrasonic dispersion for 15-30min to obtain a dispersion liquid;

[0016] S1-3, add chitosan powder to the above dispersion liquid, and magnetically stir at 30-40℃ for 1-2h (rotation speed 300r / min) until the powder is completely dissolved;

[0017] Add corn starch and citric acid, and continue stirring for 30-45min to prepare a mixed liquid (citric acid also acts as a crosslinking agent, promoting the hydroxyl reaction of chitosan and starch);

[0018] S1-4, dropwise adding dilute alkali solution to the above mixed solution while continuously stirring with a magnetic stirrer, adjusting the pH value to 7-9, pouring the adjusted mixed solution into a horizontal glass plate mold, controlling the thickness to be 0.1-0.2mm with a spatula, standing for 1-2h at room temperature, and then transferring to a vacuum drying oven for vacuum drying at 45℃ for 4.5h (vacuum degree: -0.08MPa, to avoid high temperature leading to fluorescence attenuation of carbon quantum dots);

[0019] S1-5, taking out the film after drying, soaking in deionized water (25℃) for 1-2h (washing away unreacted citric acid and acetic acid), and then naturally airing for 20-24h at room temperature to obtain the light conversion agent.

[0020] Preferably, the preparation method of the modified carbon quantum dot powder comprises the following steps:

[0021] mixing citric acid with deionized water, stirring with a magnetic stirrer until dissolved, transferring to a polytetrafluoroethylene reaction kettle, hydrothermal reaction at 170-190℃ for 3-4h, naturally cooling to room temperature after reaction, centrifuging (8000r / min, 10min) to take the supernatant, dropwise adding dilute sodium hydroxide solution to the supernatant, adjusting the pH value to 9-10, and then adding KH550, stirring at 50-60℃ for 1-2h, and then freeze-drying to obtain the modified carbon quantum dot powder, so that the amino group of the silane coupling agent reacts with the hydroxyl group on the surface of the carbon quantum dots, improving the dispersibility in the chitosan matrix.

[0022] Preferably, the base body is at least one of low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, high-density polyethylene, polypropylene and ethylene-vinyl acetate resin.

[0023] Preferably, the auxiliary agent is at least one of polyethylene wax, vinyl bis-stearamide, zinc stearate, pentaerythritol stearate, titanate coupling agent and aluminate coupling agent.

[0024] A light conversion agricultural film prepared by the preparation method.

[0025] Compared with the prior art, the present application has the following beneficial effects:

[0026] 1. The light conversion agent prepared by the present application takes carbon quantum dots (CQDs) modified by KH550 as the core, is loaded in a stable composite matrix formed by a chitosan-graphene-citric acid crosslinked network, and forms a solid film light conversion agent; and takes CQDs / graphene as the core and a crosslinked chitosan-starch network as the shell. This shell not only solves the problems of dispersion and compatibility, but also plays a protective and fixing role. The light conversion agent is well dispersed in the matrix and is firmly combined with the matrix, avoiding becoming a stress defect point due to agglomeration, so as to ensure the tensile strength and tear strength of the agricultural film.

[0027] 2. In this invention, the biopolymer matrix coats the CQDs, effectively isolating them from external environmental factors (such as oxygen and humidity) and high processing temperatures that could damage their fluorescence properties. The CQDs and graphene are locked within a cross-linked network, preventing their migration and precipitation from the agricultural film during subsequent processing or use. Although CS / starch is hydrophilic, its surface polarity is reduced after cross-linking and subsequent washing. More importantly, the prior modification with KH550 has already given the CQDs a PE-compatible coating, improving the interfacial compatibility between the entire light-converting agent particle and PE. Simultaneously, the addition of graphene not only enhances mechanical properties, but its excellent thermal conductivity may also contribute to the thermal uniformity of the agricultural film during processing and use. Detailed Implementation

[0028] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] Unless otherwise specified, the raw materials used in this invention are all from commercially available conventional products.

[0030] The graphene was purchased from Zhengzhou Wanchuang Chemical Products Co., Ltd., CAS No.: 7782-42-5;

[0031] Chitosan powder was purchased from Xi'an Weisbo Biotechnology Co., Ltd., CAS No.: 9012-76-4;

[0032] KH550 was purchased from Shandong Shuntai New Materials Co., Ltd., CAS No.: 919-30-2.

[0033] Preparation Example 1

[0034] The preparation method of the modified carbon quantum dot powder includes the following steps:

[0035] Mix 5g of citric acid with 50mL of deionized water, stir magnetically until dissolved, and then transfer to a polytetrafluoroethylene reactor. React hydrothermally at 170℃ for 3h. After the reaction, allow to cool naturally to room temperature, centrifuge (8000r / min, 10min) to collect the supernatant, and add 1M dilute sodium hydroxide solution dropwise to the supernatant to adjust the pH to 9. Then add 0.5g of KH550, stir at 50℃ for 1h, and freeze-dry to obtain modified carbon quantum dot powder.

[0036] The preparation method of the light-converting agent includes the following steps:

[0037] S1-1, take 0.5g graphene into 100mL 1% chitosan acetic acid solution (acetic acid concentration 1%, pH 3), ultrasonic dispersion 30min (power 300W, frequency 40kHz), form a uniform suspension;

[0038] S1-2, add 1g of the modified carbon quantum dot powder to the suspension, continue to ultrasonic for 15min, to obtain a dispersion;

[0039] S1-3, add 5g chitosan powder to the above dispersion, 30℃ magnetic stirring 1h (speed 300r / min), until the powder is completely dissolved;

[0040] Add 10g corn starch and 3g citric acid, continue to stir for 30min to prepare a mixed solution.

[0041] S1-4, add 1M sodium hydroxide solution dropwise to the above mixed solution while continuously stirring, adjust the pH value to 7, pour the adjusted mixed solution into a horizontal glass plate mold, control the thickness to be 0.1mm with a spatula, room temperature standing for 1h, transfer to a vacuum drying oven, vacuum drying at 45℃ for 4.5h, vacuum degree-0.08MPa;

[0042] S1-5, after drying, take out the film, soak in 25℃ deionized water for 1h, then air dry at room temperature for 20h, to obtain a light conversion agent.

[0043] Preparation Example 2

[0044] The preparation method of the modified carbon quantum dot powder comprises the following steps:

[0045] Mix 6g citric acid with 55mL deionized water, magnetically stir until dissolved, then transfer to a polytetrafluoroethylene reaction kettle, hydrothermal reaction at 180℃ for 3h, after reaction, naturally cool to room temperature, centrifuge (8000r / min, 10min) to take the supernatant, add 1M dilute sodium hydroxide solution dropwise to the supernatant with a dropper, adjust the pH value to 9, then add 0.5g KH550, stir at 50℃ for 1h, freeze-dried to obtain modified carbon quantum dot powder.

[0046] The preparation method of the light conversion agent comprises the following steps:

[0047] S1-1, take 0.5g graphene into 100mL 1% chitosan acetic acid solution (acetic acid concentration 1%, pH 3), ultrasonic dispersion 30min (power 300W, frequency 40kHz), form a uniform suspension;

[0048] S1-2, add 1g of the modified carbon quantum dot powder to the suspension, continue to ultrasonic for 15min, to obtain a dispersion;

[0049] S1-3, 6 g of chitosan powder was added to the dispersion liquid, and magnetic stirring was performed at 30°C for 1 h (rotation speed 300 r / min) until the powder was completely dissolved;

[0050] 10 g of corn starch and 3 g of citric acid were added, and stirring was continued for 30 min to prepare a mixed solution.

[0051] S1-4, 1M sodium hydroxide solution was added dropwise to the mixed solution while continuously performing magnetic stirring, and the pH value was adjusted to 8. The adjusted mixed solution was poured into a horizontal glass plate mold, the thickness was controlled to be 0.1 mm using a spatula, and the solution was left to flow at room temperature for 1 h. Then, the solution was transferred to a vacuum drying oven, and vacuum drying was performed at 45°C for 4.5 h at a vacuum degree of -0.08 MPa.

[0052] S1-5, after drying, the film was taken out, soaked in deionized water at 25°C for 1 h, and then naturally air-dried at room temperature for 20 h to obtain a light conversion agent.

[0053] Preparation Example 3

[0054] The preparation method of the modified carbon quantum dot powder comprises the following steps:

[0055] 7 g of citric acid was mixed with 55 mL of deionized water, and after magnetic stirring until dissolution, the solution was transferred to a polytetrafluoroethylene reaction kettle. Hydrothermal reaction was performed at 190°C for 4 h. After reaction, the solution was naturally cooled to room temperature, centrifuged (8000 r / min, 10 min), and the supernatant was taken. A 1M dilute sodium hydroxide solution was added dropwise to the supernatant using a dropper, the pH value was adjusted to 9, and then 0.8 g of KH550 was added. Stirring was performed at 55°C for 2 h, and then freeze-drying was performed to obtain a modified carbon quantum dot powder.

[0056] The preparation method of the light conversion agent comprises the following steps:

[0057] S1-1, 0.5 g of graphene was added to 100 mL of 1% chitosan acetic acid solution (acetic acid concentration 1%, pH 4), and ultrasonic dispersion was performed for 30 min (power 300 W, frequency 40 kHz) to form a uniform suspension;

[0058] S1-2, 3 g of the modified carbon quantum dot powder was added to the suspension, and ultrasonic dispersion was continued for 15 min to obtain a dispersion liquid;

[0059] S1-3, 6 g of chitosan powder was added to the dispersion liquid, and magnetic stirring was performed at 30°C for 1 h (rotation speed 300 r / min) until the powder was completely dissolved;

[0060] 10 g of corn starch and 3 g of citric acid were added, and stirring was continued for 30 min to prepare a mixed solution.

[0061] S1-4, 1M sodium hydroxide solution was added dropwise to the above mixed solution while continuously stirring with a magnetic stirrer, the pH value was adjusted to 9, the adjusted mixed solution was poured into a horizontal glass plate mold, the thickness was controlled to be 0.1mm with a scraper, and the solution was cast at room temperature for 1h, then transferred to a vacuum drying oven, dried at 45℃ for 4.5h under a vacuum degree of-0.08MPa;

[0062] S1-5, after drying, the film was taken out, soaked in 25℃ deionized water for 1h, then naturally air-dried at room temperature for 20h to obtain the light conversion agent.

[0063] Preparation Example 4

[0064] The preparation method of the modified carbon quantum dot powder comprises the following steps:

[0065] 8g of citric acid was mixed with 60mL of deionized water, and after magnetic stirring until dissolution, it was transferred to a polytetrafluoroethylene reaction kettle, and hydrothermal reaction was carried out at 190℃ for 4h. After reaction, it was naturally cooled to room temperature, centrifuged (8000r / min, 10min) to take the supernatant, and 1M dilute sodium hydroxide solution was added dropwise to the supernatant with a dropper, the pH value was adjusted to 9.5, and then 1g of KH550 was added, and stirred at 60℃ for 2h. After freeze-drying, the modified carbon quantum dot powder was obtained.

[0066] The preparation method of the light conversion agent comprises the following steps:

[0067] S1-1, 0.5g of graphene was added to 100mL of 1% chitosan acetic acid solution (acetic acid concentration 1%, pH 3), and ultrasonic dispersion was carried out for 30min (power 300W, frequency 40kHz) to form a uniform suspension;

[0068] S1-2, 1g of the modified carbon quantum dot powder was added to the suspension, and ultrasonic dispersion was continued for 15min to obtain a dispersion liquid;

[0069] S1-3, 5g of chitosan powder was added to the above dispersion liquid, and magnetic stirring was carried out at 30℃ for 1h (rotation speed 300r / min) until the powder was completely dissolved;

[0070] 10g of corn starch and 3g of citric acid were added, and stirring was continued for 30min to prepare a mixed solution.

[0071] S1-4, 1M sodium hydroxide solution was added dropwise to the above mixed solution while continuously stirring with a magnetic stirrer, the pH value was adjusted to 7, the adjusted mixed solution was poured into a horizontal glass plate mold, the thickness was controlled to be 0.1mm with a scraper, and the solution was cast at room temperature for 1h, then transferred to a vacuum drying oven, dried at 45℃ for 4.5h under a vacuum degree of-0.08MPa;

[0072] S1-5, the film is taken out after drying, soaked in 25℃ deionized water for 1h, then naturally air dried at room temperature for 20h, to obtain the light conversion agent.

[0073] Preparation Example 5

[0074] The preparation method of the modified carbon quantum dot powder comprises the following steps:

[0075] 8g of citric acid is mixed with 55mL of deionized water, magnetically stirred until dissolved, then transferred to a polytetrafluoroethylene reaction kettle, hydrothermally reacted at 185℃ for 4h, naturally cooled to room temperature after reaction, centrifuged (8000r / min, 10min) to take the supernatant, 1M dilute sodium hydroxide solution is added dropwise to the supernatant, the pH value is adjusted to 9.5, then 1g of KH550 is added, stirred at 50℃ for 1h, and then freeze-dried to obtain the modified carbon quantum dot powder.

[0076] The preparation method of the light conversion agent comprises the following steps:

[0077] S1-1, 0.5g of graphene is added to 100mL of 1% chitosan acetic acid solution (acetic acid concentration 1%, pH 3), ultrasonically dispersed for 40min (power 300W, frequency 40kHz), to form a uniform suspension;

[0078] S1-2, 2g of the modified carbon quantum dot powder is added to the suspension, and ultrasonic dispersion is continued for 25min to obtain a dispersion liquid;

[0079] S1-3, 8g of chitosan powder is added to the above dispersion liquid, and magnetically stirred at 35℃ for 1h (rotation speed 300r / min) until the powder is completely dissolved;

[0080] 15g of corn starch and 3g of citric acid are added, and the stirring is continued for 35min to prepare a mixed solution.

[0081] S1-4, 1M sodium hydroxide solution is added dropwise to the above mixed solution while continuously magnetically stirring, and the pH value is adjusted to 8, the adjusted mixed solution is poured into a horizontal glass plate mold, the thickness is controlled to be 0.2mm by a scraper, and the solution is cast at room temperature for 1h, then transferred to a vacuum drying oven, and vacuum dried at 45℃ for 4.5h, the vacuum degree is-0.08MPa;

[0082] S1-5, the film is taken out after drying, soaked in 25℃ deionized water for 1h, then naturally air dried at room temperature for 20h, to obtain the light conversion agent.

[0083] Preparation Example 5

[0084] The preparation method of the modified carbon quantum dot powder comprises the following steps:

[0085] 7g citric acid was mixed with 55mL deionized water, and after magnetic stirring until dissolution, it was transferred to a polytetrafluoroethylene reaction kettle for hydrothermal reaction at 190℃ for 4h. After the reaction, it was naturally cooled to room temperature, centrifuged (8000r / min, 10min) to take the supernatant, and 1M dilute sodium hydroxide solution was added dropwise to the supernatant with a dropper. The pH value was adjusted to 9.5, and then 1g KH550 was added. After stirring at 60℃ for 2h, the modified carbon quantum dot powder was obtained after freeze-drying.

[0086] The preparation method of the light conversion agent comprises the following steps:

[0087] S1-1, 0.5g graphene was added to 100mL 1% chitosan acetic acid solution (acetic acid concentration 1%, pH 3), and ultrasonic dispersion was carried out for 45min (power 300W, frequency 40kHz) to form a uniform suspension;

[0088] S1-2, 3g of the modified carbon quantum dot powder was added to the suspension, and ultrasonic dispersion was continued for 25min to obtain a dispersion liquid;

[0089] S1-3, 5g of chitosan powder was added to the above dispersion liquid, and magnetic stirring was carried out at 30℃ for 1h (rotation speed 300r / min) until the powder was completely dissolved;

[0090] 15g of corn starch and 4g of citric acid were added, and stirring was continued for 30min to prepare a mixed solution.

[0091] S1-4, 1M sodium hydroxide solution was added dropwise to the above mixed solution while continuously stirring magnetically, and the pH value was adjusted to 9. The adjusted mixed solution was poured into a horizontal glass plate mold, the thickness was controlled to be 0.1mm with a spatula, and the solution was left to flow cast at room temperature for 1h. Then it was transferred to a vacuum drying oven, and vacuum drying was carried out at 45℃ for 4.5h at a vacuum degree of-0.08MPa.

[0092] S1-5, after drying, the film was taken out, soaked in 25℃ deionized water for 1h, and then naturally air-dried at room temperature for 20h to obtain the light conversion agent.

[0093] Preparation Example 7

[0094] The preparation method of the modified carbon quantum dot powder comprises the following steps:

[0095] 6g citric acid was mixed with 50mL deionized water, and after magnetic stirring until dissolution, it was transferred to a polytetrafluoroethylene reaction kettle for hydrothermal reaction at 180℃ for 3h. After the reaction, it was naturally cooled to room temperature, centrifuged (8000r / min, 10min) to take the supernatant, and 1M dilute sodium hydroxide solution was added dropwise to the supernatant with a dropper. The pH value was adjusted to 10, and then 0.8g KH550 was added. After stirring at 50℃ for 2h, the modified carbon quantum dot powder was obtained after freeze-drying.

[0096] The preparation method of the light conversion agent comprises the following steps:

[0097] S1-1, take 0.5g graphene and add it to 100mL 1% chitosan acetic acid solution (acetic acid concentration 1%, pH 3), ultrasonic dispersion for 30min (power 300W, frequency 40kHz), to form a uniform suspension;

[0098] S1-2, add 2g of the modified carbon quantum dot powder to the suspension, and continue to ultrasonic for 15min to obtain a dispersion;

[0099] S1-3, add 5g chitosan powder to the above dispersion, and magnetically stir at 30℃ for 1h (rotation speed 300r / min) until the powder is completely dissolved;

[0100] Add 10g corn starch and 3g citric acid, and continue to stir for 30min to prepare a mixed solution.

[0101] S1-4, add 1M sodium hydroxide solution dropwise to the above mixed solution while continuously magnetically stirring, and adjust the pH value to 7, pour the adjusted mixed solution into a horizontal glass plate mold, control the thickness to be 0.1mm with a scraper, and let it flow at room temperature for 1h, then transfer it to a vacuum drying oven, and dry it at 45℃ for 4.5h under a vacuum degree of-0.08MPa;

[0102] S1-5, after drying, take out the film, soak it in 25℃ deionized water for 1h, then naturally air dry it at room temperature for 20h, and obtain the light conversion agent.

[0103] Preparation Example 8

[0104] The preparation method of the modified carbon quantum dot powder comprises the following steps:

[0105] Mix 8g citric acid with 60mL deionized water, magnetically stir until dissolved, then transfer it to a polytetrafluoroethylene reaction kettle, and hydrothermally react at 190℃ for 4h, after reaction, naturally cool to room temperature, centrifuge (8000r / min, 10min) to take the supernatant, add 1M dilute sodium hydroxide solution dropwise to the supernatant with a dropper, adjust the pH value to 10, then add 1g KH550, and stir at 60℃ for 2h, and freeze-dry to obtain the modified carbon quantum dot powder.

[0106] The preparation method of the light conversion agent comprises the following steps:

[0107] S1-1, take 0.5g graphene and add it to 100mL 1% chitosan acetic acid solution (acetic acid concentration 1%, pH 3), ultrasonic dispersion for 30min (power 300W, frequency 40kHz), to form a uniform suspension;

[0108] S1-2, 3g of the modified carbon quantum dot powder was added to the suspension, and ultrasonic treatment was continued for 30 min to obtain a dispersion liquid;

[0109] S1-3, 8g of chitosan powder was added to the dispersion liquid, and magnetic stirring was continued at 40°C for 2h (rotation speed 300r / min) until the powder was completely dissolved;

[0110] 20g of corn starch and 5g of citric acid were added, and stirring was continued for 30 min to prepare a mixed solution.

[0111] S1-4, 1M sodium hydroxide solution was added dropwise to the mixed solution, and magnetic stirring was continued, and the pH value was adjusted to 8. The adjusted mixed solution was poured into a horizontal glass plate mold, the thickness was controlled to be 0.1mm with a scraper, and the solution was left to flow at room temperature for 1h. Then, the solution was transferred to a vacuum drying oven, and vacuum drying was carried out at 45°C for 4.5h, and the vacuum degree was -0.08MPa;

[0112] S1-5, after drying, the film was taken out, soaked in 25°C deionized water for 1h, and then naturally air-dried at room temperature for 20h to obtain a light conversion agent.

[0113] Preparation Example 9

[0114] The preparation method of the modified carbon quantum dot powder comprises the following steps:

[0115] 8g of citric acid was mixed with 55mL of deionized water, and magnetic stirring was continued until the powder was completely dissolved. Then, the solution was transferred to a polytetrafluoroethylene reaction kettle, and hydrothermal reaction was carried out at 185°C for 4h. After reaction, the solution was naturally cooled to room temperature, centrifuged (8000r / min, 10min), and the supernatant was taken. 1M dilute sodium hydroxide solution was added dropwise to the supernatant, the pH value was adjusted to 10, and then 1g of KH550 was added. Stirring was continued at 60°C for 1h, and then freeze-drying was carried out to obtain a modified carbon quantum dot powder.

[0116] The preparation method of the light conversion agent comprises the following steps:

[0117] S1-1, 0.5g of graphene was added to 100mL of 1% chitosan acetic acid solution (acetic acid concentration 1%, pH 3), and ultrasonic dispersion was carried out for 30min (power 300W, frequency 40kHz) to form a uniform suspension;

[0118] S1-2, 1g of the modified carbon quantum dot powder was added to the suspension, and ultrasonic treatment was continued for 15min to obtain a dispersion liquid;

[0119] S1-3, 5g of chitosan powder was added to the dispersion liquid, and magnetic stirring was continued at 30°C for 1h (rotation speed 300r / min) until the powder was completely dissolved;

[0120] 18g of corn starch and 4g of citric acid were added, and stirring was continued for 30 min to prepare a mixed solution.

[0121] S1-4, drop 1M sodium hydroxide solution into the above mixed solution while continuously stirring with a magnetic stirrer, adjust the pH value to 9, pour the adjusted mixed solution into a horizontal glass plate mold, control the thickness to be 0.1mm with a spatula, stand for 1h at room temperature, transfer to a vacuum drying oven, and dry at 45℃ for 4.5h at a vacuum degree of -0.08MPa;

[0122] S1-5, after drying, immerse the film in 25℃ deionized water for 2h, then naturally air dry at room temperature for 24h, to obtain the light conversion agent.

[0123] Example 1

[0124] A method for preparing a light conversion agricultural film, comprising the following steps:

[0125] S1, add 1g of the light conversion agent prepared in Preparation Example 1 and 50g of low-density polyethylene into a Banbury mixer, and mix at 125℃ for 1h to obtain a mixed and uniform block polymer melt;

[0126] S2, add the block polymer melt into a forced feeder, adjust the temperature to 180℃, and use a single-screw extruder to extrude a strip-shaped polymer;

[0127] S3, add the strip-shaped polymer into a pelletizer, set the rotation frequency of the pelletizer to 20.00Hz, and obtain a light conversion master batch;

[0128] S4, mix 2g of the light conversion master batch, 50g of low-density polyethylene, and 1g of polyethylene wax, and add them into a hopper of a film blowing machine, set the temperatures of the three temperature zones of the barrel of the film blowing machine to be 130℃, 150℃, and 165℃ respectively, set the temperature of the die head to be 160℃, set the rotation frequency of the screw to be 12.00Hz, and set the winding speed to be 160rpm, to prepare a light conversion agricultural film.

[0129] Example 2

[0130] A method for preparing a light conversion agricultural film, comprising the following steps:

[0131] S1, add 1g of the light conversion agent prepared in Preparation Example 2 and 50g of linear low-density polyethylene into a Banbury mixer, and mix at 125℃ for 2h to obtain a mixed and uniform block polymer melt;

[0132] S2, add the block polymer melt into a forced feeder, adjust the temperature to 185℃, and use a single-screw extruder to extrude a strip-shaped polymer;

[0133] S3, add the strip-shaped polymer into a pelletizer, set the rotation frequency of the pelletizer to 20.00Hz, and obtain a light conversion master batch;

[0134] S4. Mix 3g of light-converting masterbatch, 50g of linear low-density polyethylene and 1.5g of vinyl bis-stearamide, and add them to the hopper of the blown film machine. The temperature of the blown film machine's three-temperature zone barrel is 130℃, 150℃ and 165℃, the die head temperature is 160℃, the screw rotation frequency is 12.00Hz and the winding speed is 160rpm to prepare light-converting agricultural film.

[0135] Example 3

[0136] A method for preparing a light-converting agricultural film includes the following steps:

[0137] S1. Add 1.5g of the light-converting agent prepared in Preparation Example 3 and 50g of medium-density polyethylene to a mixer and mix at 135°C for 2 hours to obtain a uniformly mixed block polymer melt.

[0138] S2. Add the block polymer melt to the forced feeder, adjust the temperature to 185℃, and extrude the strip polymer using a single screw extruder;

[0139] S3. Add the strip polymer to a pelletizer with a rotation frequency of 20.00 Hz to obtain optical conversion masterbatch;

[0140] S4. Mix 4g of light-converting masterbatch, 50g of medium-density polyethylene and 2g of vinyl bis-stearamide, and add them to the hopper of the blown film machine. The temperature of the blown film machine's three-temperature zone barrel is 130℃, 150℃ and 165℃, the die head temperature is 160℃, the screw rotation frequency is 12.00Hz and the winding speed is 160rpm to prepare light-converting agricultural film.

[0141] Example 4

[0142] A method for preparing a light-converting agricultural film includes the following steps:

[0143] S1. Add 1.5g of the light-converting agent prepared in Preparation Example 4 and 50g of high-density polyethylene to a mixer and mix at 135°C for 2 hours to obtain a uniformly mixed block polymer melt.

[0144] S2. Add the block polymer melt to the forced feeder, adjust the temperature to 185℃, and extrude the strip polymer using a single screw extruder;

[0145] S3. Add the strip polymer to a pelletizer with a rotation frequency of 20.00 Hz to obtain optical conversion masterbatch;

[0146] S4, 4 g of the light conversion master batch, 50 g of polypropylene and 1 g of pentaerythritol stearate were mixed and added to the hopper of the film blowing machine, the three temperature zone barrel temperatures of the film blowing machine were 130 DEG C, 150 DEG C and 165 DEG C respectively, the die head temperature was 160 DEG C, the screw rotation frequency was 12.00 Hz, and the winding speed was 160 rpm, to obtain the light conversion agricultural film.

[0147] Example 5

[0148] A method for preparing a light conversion agricultural film, comprising the following steps:

[0149] S1, 1.5 g of the light conversion agent prepared in Preparation Example 5 and 50 g of polypropylene were added to the internal mixer, and mixed at 135 DEG C for 1 h to obtain a block polymer melt;

[0150] S2, the block polymer melt was added to the forced feeder, the temperature was adjusted to 180 DEG C, and a single screw extruder was used to extrude a strip-shaped polymer;

[0151] S3, the strip-shaped polymer was added to the granulator, the rotation frequency of the granulator was 20.00 Hz, and the light conversion master batch was obtained;

[0152] S4, 4 g of the light conversion master batch, 50 g of polypropylene and 1 g of pentaerythritol stearate were mixed and added to the hopper of the film blowing machine, the three temperature zone barrel temperatures of the film blowing machine were 130 DEG C, 150 DEG C and 165 DEG C respectively, the die head temperature was 160 DEG C, the screw rotation frequency was 12.00 Hz, and the winding speed was 160 rpm, to obtain the light conversion agricultural film.

[0153] Example 6

[0154] A method for preparing a light conversion agricultural film, comprising the following steps:

[0155] S1, 1.5 g of the light conversion agent prepared in Preparation Example 6 and 50 g of ethylene-vinyl acetate resin were added to the internal mixer, and mixed at 130 DEG C for 1 h to obtain a block polymer melt;

[0156] S2, the block polymer melt was added to the forced feeder, the temperature was adjusted to 185 DEG C, and a single screw extruder was used to extrude a strip-shaped polymer;

[0157] S3, the strip-shaped polymer was added to the granulator, the rotation frequency of the granulator was 20.00 Hz, and the light conversion master batch was obtained;

[0158] S4, 3g of the light conversion master batch, 50g of ethylene-vinyl acetate resin and 1g of aluminate coupling agent were mixed and added to the hopper of the film blowing machine, the three temperature zone barrel temperatures of the film blowing machine were 130 DEG C, 150 DEG C and 165 DEG C respectively, the die head temperature was 160 DEG C, the screw rotation frequency was 12.00 Hz, and the winding speed was 160 rpm, to obtain the light conversion agricultural film.

[0159] Example 7

[0160] A method for preparing a light conversion agricultural film, comprising the following steps:

[0161] S1, 1g of the light conversion agent prepared in Preparation Example 7 and 50g of high density polyethylene were added to a Banbury mixer, and mixed at 135 DEG C for 2h to obtain a mixed and uniform block polymer melt;

[0162] S2, the block polymer melt was added to a forced feeder, the temperature was adjusted to 185 DEG C, and a single screw extruder was used to extrude a strip-shaped polymer;

[0163] S3, the strip-shaped polymer was added to a pelletizer, the rotation frequency of the pelletizer was 20.00 Hz, and a light conversion master batch was obtained;

[0164] S4, 3g of the light conversion master batch, 50g of high density polyethylene and 2g of aluminate coupling agent were mixed and added to the hopper of the film blowing machine, the three temperature zone barrel temperatures of the film blowing machine were 130 DEG C, 150 DEG C and 165 DEG C respectively, the die head temperature was 160 DEG C, the screw rotation frequency was 12.00 Hz, and the winding speed was 160 rpm, to obtain the light conversion agricultural film.

[0165] Example 8

[0166] A method for preparing a light conversion agricultural film, comprising the following steps:

[0167] S1, 1g of the light conversion agent prepared in Preparation Example 8 and 50g of polypropylene were added to a Banbury mixer, and mixed at 130 DEG C for 2h to obtain a mixed and uniform block polymer melt;

[0168] S2, the block polymer melt was added to a forced feeder, the temperature was adjusted to 185 DEG C, and a single screw extruder was used to extrude a strip-shaped polymer;

[0169] S3, the strip-shaped polymer was added to a pelletizer, the rotation frequency of the pelletizer was 20.00 Hz, and a light conversion master batch was obtained;

[0170] S4, 3g of the light conversion master batch, 50g of polypropylene and 1g of aluminate coupling agent were mixed and added to the hopper of the film blowing machine, the three temperature zone barrel temperatures of the film blowing machine were 130 DEG C, 150 DEG C and 165 DEG C respectively, the die head temperature was 160 DEG C, the screw rotation frequency was 12.00 Hz, and the winding speed was 160 rpm, to obtain the light conversion agricultural film.

[0171] Example 9

[0172] A preparation method of a light conversion agricultural film, comprising the following steps:

[0173] S1, 1.5 g of light conversion agent prepared in Preparation Example 9 and 50 g of linear low density polyethylene were added to a banbury mixer, and mixed at 125°C for 1 h to obtain a mixed block polymer melt;

[0174] S2, the block polymer melt was added to a forced feeder, and the temperature was adjusted to 185°C, and a single screw extruder was used to extrude a strip-shaped polymer;

[0175] S3, the strip-shaped polymer was added to a pelletizer, the pelletizer was rotated at a frequency of 20.00 Hz, and a light conversion master batch was obtained;

[0176] S4, 3 g of the light conversion master batch, 50 g of linear low density polyethylene and 2 g of vinyl bis-stearamide were mixed and added to the hopper of a film blowing machine, the temperature of the three-zone barrel of the film blowing machine was 130°C, 150°C and 165°C respectively, the die head temperature was 160°C, the screw rotation frequency was 12.00 Hz, and the winding speed was 160 rpm, to prepare a light conversion agricultural film.

[0177] Comparative Example 1

[0178] The difference between this comparative example and Example 1 is that no light conversion agent prepared in Preparation Example 1 is added.

[0179] Comparative Example 2

[0180] The difference between this comparative example and Example 1 is that the light conversion agent prepared in Preparation Example 1 is replaced by a commonly used light conversion agent purchased from Hubei Xingyan New Material Technology Co., Ltd.

[0181] Comparative Example 3

[0182] The difference between this comparative example and Example 1 is that no modified carbon quantum dot powder is added during the preparation of the light conversion agent in Preparation Example 1.

[0183] The light conversion agricultural films prepared in Examples 1-9 and Comparative Examples 1-3 were detected for light transmittance and haze according to the method in GB / T2410-2008.

[0184] Meanwhile, a transmission photometer was used to detect the ultraviolet blocking rate of the light conversion film at a wavelength of 300 nm.

[0185] A universal tensile testing machine was used to test the tensile properties and tear strength of the light conversion agricultural film, the thickness of the film sample was 0.06 mm, the width was 12 mm, the tensile rate was 50 mm / min, and each group of samples was tested 5 times to take the average value.

[0186] The performance test results are shown in Table 1:

[0187] Table 1

[0188] Test item Transmittance (%) Haze (%) UV blocking rate (%) Transverse tensile strength (MPa) Longitudinal tensile strength (MPa) Transverse tear strength (kN / m) Longitudinal tear strength (kN / m) Example 1 83.2 46.12 87.2 36.5 34.2 205 193 Example 2 83.1 46.15 87.5 36.6 34.1 203 192 Example 3 83.3 46.02 87.3 36.3 34.2 202 194 Example 4 82.7 46.07 87.4 35.9 34.3 206 193 Example 5 82.8 45.85 88.1 35.5 34.2 208 195 Example 6 83.5 46.11 88.2 36.2 34.1 206 194 Example 7 83.3 46.13 87.8 36.2 33.8 204 191 Example 8 83.1 46.11 88.2 36.1 33.9 205 192 Example 9 83.5 45.58 87.7 36.3 34.2 204 190 Comparative Example 1 93.6 27.56 58.3 28.9 25.6 156 147 Comparative Example 2 88.5 33.82 69.2 30.5 28.7 178 166 Comparative Example 3 88.6 34.18 68.5 30.8 28.3 181 169

[0189] In summary: the light conversion agricultural film prepared in examples 1-9, due to the addition of carbon quantum dots (CQDs) as the core modified by KH550, and through the cross-linking network of chitosan-graphene-lactic acid to form a stable composite matrix for loading, the solid film light conversion agent can be prepared into a functional agricultural film with high haze and high scattering type. This is usually beneficial for agricultural applications, because the diffuse light can more evenly illuminate the plant canopy and the lower leaves, improve the photosynthesis efficiency, and at the same time greatly improve the mechanical properties such as tensile strength and tear strength of the agricultural film.

[0190] The above merely provides the preferred but non-limiting embodiments of the present application, and the protection scope of the present application is not limited thereto. Any person skilled in the art, according to the technical range disclosed in the present application and the inventive concept, makes equivalent replacement or change, should be covered within the protection scope of the present application.

Claims

1. A method for preparing a light converting agricultural film, characterized by, The method comprises the following steps: S1, adding the light conversion agent and the base into a banbury mixer to obtain a mixed block polymer melt; S2, adding the block polymer melt into a forced feeder, and extruding a strip polymer by using a single screw extruder; S3, adding the strip polymer into a pelletizer to obtain the light conversion master batch; S4, mixing the light conversion master batch, the base and the additive, and adding them into a hopper of a film blowing machine to prepare the light conversion agricultural film by controlling the temperature of the three temperature zones of the film blowing machine; The preparation method of the light conversion agent comprises the following steps: S1-1, adding graphene into a 1% chitosan acetic acid solution, adjusting the pH, and ultrasonic dispersing to form a uniform suspension; S1-2, adding modified carbon quantum dot powder into the suspension, and continuing to ultrasonic to obtain a dispersion liquid; S1-3, adding chitosan powder into the dispersion liquid, magnetically stirring until the powder is completely dissolved, adding corn starch and citric acid, and continuing to stir for 30-45 min to prepare a mixed liquid; S1-4, adding a dilute alkali solution drop by drop into the mixed liquid while continuously magnetically stirring, adjusting the pH to 7-9, pouring the adjusted mixed liquid into a horizontal glass plate mold, controlling the thickness to be 0.1-0.2 mm by using a scraper, and standing for 1-2 h at room temperature, and then transferring to a vacuum drying oven, and vacuum drying at 45°C for 4.5 h; S1-5, taking out the film after drying, soaking in 25°C deionized water for 1-2 h, and then naturally air-drying at room temperature for 20-24 h to obtain the light conversion agent.

2. The method of preparing a light conversion agricultural film according to claim 1, characterized in that, The acetic acid concentration in S1-1 is 1%, and the pH is 3-4.

3. The method of preparing a light conversion agricultural film according to claim 1, characterized in that, The ultrasonic dispersing time in S1-1 is 30-45 min, the ultrasonic power is 300 W, and the frequency is 40 kHz.

4. The method of preparing a light conversion agricultural film according to claim 1, characterized in that, The magnetic stirring condition in S1-3 is 1-2 h at 30-40°C, and the rotating speed is 300 r / min.

5. The method of preparing a light conversion agricultural film according to claim 1, characterized in that, The preparation method of the modified carbon quantum dot powder comprises the following steps: Mixing citric acid and deionized water, magnetically stirring until dissolved, and then transferring into a polytetrafluoroethylene reaction kettle, and hydrothermal reaction at 170-190°C for 3-4 h, and then naturally cooling to room temperature, and then centrifuging to take the supernatant, and then adding a dilute sodium hydroxide solution drop by drop into the supernatant by using a dropper, and adjusting the pH to 9-10, and then adding KH550, and stirring at 50-60°C for 1-2 h, and then freeze-drying to obtain the modified carbon quantum dot powder.

6. The method of preparing a light conversion agricultural film according to claim 5, wherein, The centrifuging time is 10-15 min, and the rotating speed is 8000-8500 r / min.

7. The method of preparing a light conversion agricultural film according to claim 1, wherein, The base is at least one of low density polyethylene, linear low density polyethylene, medium density polyethylene, high density polyethylene, polypropylene and ethylene-vinyl acetate resin.

8. The method of preparing a light conversion agricultural film according to claim 1, wherein, The additive is at least one of polyethylene wax, vinyl bis stearyl amide, zinc stearate, pentaerythritol stearate, titanate coupling agent and aluminate coupling agent.

9. A light conversion agricultural film prepared by the preparation method of any one of claims 1-8.