Light conversion plastic film for improving photosynthesis of plants and preparation method thereof
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- QINGDAO SHENYU SUNLIGHT TECH CO LTD
- Filing Date
- 2026-05-19
- Publication Date
- 2026-07-03
Smart Images
Figure SMS_1
Abstract
Description
Technical Field
[0001] This invention relates to the field of agricultural light-converting film preparation technology, and in particular to a light-converting plastic film for enhancing plant photosynthesis and its preparation method. Background Technology
[0002] With the rapid development of modern intensive and facility-based agriculture, greenhouse cultivation has become a core model for ensuring year-round supply of fruits and vegetables and improving agricultural production efficiency and planting returns. The light quality regulation and spectral conversion capabilities of greenhouse films directly determine the photosynthetic efficiency, nutrient accumulation rate, and final yield and quality of crops. Agricultural light-converting films can directionally convert spectral bands in natural light that are difficult for crops to absorb and utilize into effective spectra that match the absorption peaks of photosynthetic pigments such as chlorophyll and carotenoids, optimizing the light environment inside the greenhouse. This is a key functional material for improving the productivity of facility agriculture and enhancing crop quality. Currently, most light-converting films on the market use rare earth organic complexes as core functional components. Although they can achieve basic spectral conversion effects, they generally suffer from problems such as low matching degree between the light-converting spectrum and crop photosynthetic needs, poor uniformity of functional component dispersion in polyolefin resin matrix, and easy migration and precipitation after long-term outdoor use. At the same time, under complex field environments such as high temperature, strong ultraviolet radiation, and wind and rain erosion, the light-converting performance will rapidly decay, making it difficult to meet the actual needs of facility agriculture for long-lasting, stable, and efficient functional greenhouse films.
[0003] To optimize the overall performance of agricultural light-converting films, the industry has conducted extensive research and improvements in areas such as the structural design of rare earth complexes, modification of polymer matrices, and compounding of functional additives. By screening novel conjugated organic ligands, the luminescence efficiency and structural stability of rare earth complexes have been improved. In-situ polymerization, melt blending, and surface coating processes have been used to improve the compatibility of functional components with greenhouse film matrix resins. Furthermore, by compounding functional additives such as anti-aging, anti-dripping, and heat-insulating agents, the practical performance of light-converting films has been further expanded.
[0004] While the aforementioned technologies have improved the short-term performance of light-conversion films to some extent, they have failed to fundamentally solve core problems such as weak bonding between functional components and the matrix, insufficient accuracy of spectral conversion, and poor long-term weather resistance, thus limiting further improvement in the overall performance of light-conversion films. Even after multiple rounds of technological iteration and optimization, existing agricultural light-converting films still face numerous insurmountable technical bottlenecks: the directional synthesis of heteronuclear rare earth functional components is difficult, and the reaction process easily generates a large number of homogeneous byproducts, resulting in a large amount of useless stray light emission and low light energy utilization; the light-converting agent and commonly used greenhouse film substrates such as polyethylene and ethylene-vinyl acetate copolymer are only physically blended together, lacking effective chemical bonding, and are prone to delamination, precipitation, and aggregation under long-term exposure to wind and sun and alternating high and low temperatures, directly leading to a rapid loss of light-converting function; in addition, there are obvious performance conflicts between functional additives and light-converting components, and anti-aging components easily interfere with the grafting stabilization process of the light-converting agent, making it difficult to simultaneously ensure the high efficiency of spectral conversion performance and long-term outdoor durability of the light-converting film. These problems together prevent existing light-converting films from meeting the needs of high efficiency of light conversion, long-term stability, and large-scale production, seriously restricting the development and promotion of high-end functional greenhouse films for facility agriculture. Summary of the Invention
[0005] The purpose of this invention is to address the shortcomings of existing technologies by proposing a light-converting plastic film that enhances plant photosynthesis and its preparation method.
[0006] To achieve the above objectives, the present invention adopts the following technical solution: a light-converting plastic film for enhancing plant photosynthesis, comprising the following components by weight: linear low-density polyethylene: 60-70 parts, ethylene-vinyl acetate copolymer: 25-30 parts, modified light-converting agent: 1.2-2.0 parts, maleic anhydride-grafted polyethylene: 1.0-1.8 parts, initiator: 0.05-0.1 parts, anti-aging agent: 0.8-1.2 parts, anti-dripping and anti-fogging agent: 0.5-0.8 parts, lubricant: 0.3-0.5 parts.
[0007] Preferably, the linear low-density polyethylene has a melt flow index ≥2 g / 10 min and a density of 0.918-0.935 g / cm³. 3 .
[0008] Preferably, the VA content of the ethylene-vinyl acetate copolymer is 18%-25%.
[0009] Preferably, the grafting rate of the maleic anhydride-grafted polyethylene is 1.2%-1.5%.
[0010] Preferably, the initiator is dicumyl peroxide.
[0011] Preferably, the anti-aging agent is composed of HS-944 and antioxidant 1010 in a mass ratio of 2:1.
[0012] Preferably, the anti-dripping and anti-fogging agent is polyethylene glycol 400 stearate.
[0013] Preferably, the lubricant is one of calcium stearate, zinc stearate, or ethylene bis-stearamide.
[0014] Preferably, the preparation method of the modified light-converting agent includes the following steps:
[0015] (1) Under nitrogen protection, maleic anhydride and butyl acrylate were added to anhydrous ethanol and stirred for 10-20 min. Then the temperature was raised to 60-70℃, an initiator was added, and the reaction was carried out for 4-6 h. After cooling to room temperature, the precipitate was added dropwise to petroleum ether and collected. After washing and drying, maleic anhydride-butyl acrylate copolymer was obtained.
[0016] (2) In a reaction vessel equipped with a reflux condenser, maleic anhydride-butyl acrylate copolymer is added to anhydrous ethanol and stirred until dissolved. A mixed aqueous solution of Tb(NO3)3-Eu(NO3)3 is added dropwise. After the addition is complete, ammonia is added to adjust the pH of the system to 6.8±0.2. Stirring is maintained during the adjustment process. Then 2,6-naphthalenedicarboxylic acid is added, the temperature is raised to 70-80℃, and the reaction is carried out for 8-12 hours. Then 1,10-o-phenanthroline is added and the reaction is carried out for 20-40 minutes. The mixture is cooled to room temperature, and the reaction solution is transferred to a dialysis bag and dialyzed with deionized water for 48-72 hours. The dialysis solution is changed every 6 hours. The dialysis bag is removed, and the solution is concentrated to 1 / 10 of the original volume by vacuum distillation. Then, under stirring, anhydrous acetone is added dropwise, and the precipitate is collected. After washing and drying, it is ground into 200-mesh powder to obtain the modified light-converting agent.
[0017] Preferably, in (1), maleic anhydride, butyl acrylate, anhydrous ethanol, initiator and petroleum ether are in a weight ratio of 1:2.5-4:40-60:0.03-0.08:100-300.
[0018] Preferably, the initiator in (1) is azobisisobutyronitrile or benzoyl peroxide.
[0019] Preferably, in (2), the maleic anhydride-butyl acrylate copolymer, anhydrous ethanol, Tb(NO3)3-Eu(NO3)3 mixed aqueous solution, 2,6-naphthalenedicarboxylic acid, 1,10-o-phenanthroline and anhydrous acetone are in a weight ratio of 1:40-60:10-15:0.3-0.5:0.1-0.3:100-200.
[0020] Preferably, in the Tb(NO3)3-Eu(NO3)3 mixed aqueous solution in (2), Tb 3+ and Eu 3+The molar ratio is 1:1.8-2.2.
[0021] Preferably, the concentration of the Tb(NO3)3-Eu(NO3)3 mixed aqueous solution in (2) is 0.1-0.5 mol / L.
[0022] Preferably, the dropping rate of the Tb(NO3)3-Eu(NO3)3 mixed aqueous solution in (2) is 0.1-1 L / h.
[0023] Preferably, the molecular weight cutoff of the dialysis bag in (2) is 3500 Da.
[0024] Furthermore, the present invention also provides a method for preparing a light-converting plastic film that enhances plant photosynthesis, comprising the following steps:
[0025] S1. Linear low-density polyethylene, ethylene-vinyl acetate copolymer, modified brightening agent, maleic anhydride grafted polyethylene, initiator, anti-dripping agent and lubricant are put into a high-speed mixer and premixed at a stirring rate of 100-300 rpm for 1-3 min, and then mixed at a stirring rate of 1000-1200 rpm for 5-10 min. After discharge, the mixture is fed into a twin-screw extruder and melt extruded using a gradient heating process. After extrusion, the mixture is cooled with water, pelletized and dried to obtain brightening grafted masterbatch.
[0026] S2. Add the light-converting grafting masterbatch and anti-aging agent to a single-screw blown film machine, blow it into a film, place it in a 60-70℃ hot air circulating oven, heat treat for 1-2 hours, cool to room temperature, and then roll it up to obtain a light-converting plastic film that enhances plant photosynthesis.
[0027] Preferably, the length-to-diameter ratio of the twin-screw extruder in S1 is 40:1.
[0028] Preferably, the temperature of each zone in the gradient heating process in S1 is set as follows: Zone 1 155-165℃, Zone 2 165-175℃, Zone 3 175-185℃, Zone 4 180-190℃, Zone 5 185-195℃, and the die head 180℃, the screw speed is 220-300 r / min, and the vacuum degree is -0.09 MPa.
[0029] Preferably, the blown film forming process in step S2 uses the following process parameters:
[0030] Extrusion parameters: Barrel temperature zone 1 155-165℃, zone 2 160-170℃, zone 3 165-175℃, die head temperature 160-165℃, screw speed 50-70r / min;
[0031] Blown film forming: After the melt flows out of the die head stably, compressed air is introduced to inflate the film bubble, the inflation ratio is controlled at 1:3-4, and the speed of the traction roller is 6-10m / min;
[0032] Cooling and shaping: Turn on the cooling air ring, air temperature 25℃, air speed 5-10m / s.
[0033] Preferably, the mechanism of action of the light-converting plastic film that enhances plant photosynthesis in this invention is explained as follows:
[0034] The core of this invention, a light-converting plastic film, is the construction of a Tb-NDA-Eu heteronuclear bimetallic energy bridging system. This system solves three common industry problems: low energy transfer efficiency of existing Eu / Tb composite light-converting agents, a sharp drop in light-converting efficiency at high temperatures, and long-term migration and precipitation of the light-converting agent. It achieves matching between the solar spectrum and the photosynthetic spectrum of plants, significantly improving the production efficiency of facility agriculture. The preparation of the light-converting agent is the foundation of the entire technical solution. This invention employs a unique reverse stepwise coordination method, utilizing the spatial confinement effect of polymer chains to amplify the coordination rate differences between rare earth ions, achieving the directional synthesis of a high-purity heteronuclear bimetallic structure. First, a maleic anhydride-butyl acrylate copolymer was prepared. The purified copolymer was dissolved in anhydrous ethanol, and a mixed aqueous solution of terbium nitrate and europium nitrate was added dropwise. The carboxyl groups randomly distributed on the copolymer molecular chain underwent a monodentate coordination reaction with rare earth ions, uniformly and isolatedly anchoring all rare earth ions to the polymer chain. The average distance between them was much larger than their ionic radius. This immobilization not only prevented the rare earth ions from directly aggregating to form homogeneous clusters, but also left active sites for the subsequent substitution reaction of bridging ligands. Subsequently, 2,6-naphthalenedicarboxylic acid (NDA) was added. Since the coordination rate of terbium ions with carboxylic acid ligands is more than three times that of europium ions, 2,6-naphthalenedicarboxylic acid preferentially formed a monodentate intermediate with the terbium ions anchored on the polymer chain. Within the confined space of the polymer chain, the same 2,6-naphthalenedicarboxylic acid molecule... The two carboxyl groups can only reach another rare earth ion within this range. If this ion is a terbium ion, it has already formed its own monodentate intermediate with another 2,6-naphthalenedicarboxylic acid molecule at a much earlier time, and will not wait for the second carboxyl group of the current molecule to coordinate. Therefore, all the 2,6-naphthalenedicarboxylic acid monodentate intermediates can only complete the second-step bridging coordination with the nearby europium ion, and directionally form the Tb-NDA-Eu heteronuclear bridging unit. Finally, 1,10-o-phenanthroline is added, which will occupy the remaining empty coordination sites of the rare earth ions to form a stable eight-coordinate structure. At the same time, it enhances the absorption capacity of the light-converting agent for ultraviolet light and inhibits fluorescence quenching. Through this synthesis method that combines kinetic control and spatial confinement, the content of the Tb-NDA-Eu heteronuclear bimetallic structure in the light-converting agent of this invention can be greatly increased.
[0035] The core function of light-converting films in enhancing photosynthesis lies in their efficient, step-wise light energy transfer mechanism, which converts harmful and unusable short-wave ultraviolet light from the solar spectrum into the deep red light most needed for plant photosynthesis. This invention's light-converting agent employs a "dual ultraviolet antenna - single energy bridge - single light-emitting center" structural design. 1,10-phenanthroline and 2,6-naphthalenedicarboxylic acid together act as ultraviolet antennas, their absorption peaks complementing each other and covering the short-wave ultraviolet region. This portion of light not only contributes nothing to plant photosynthesis but also scorches crop leaves, damages chlorophyll structure, and induces pathogen growth. It is a harmful spectral component that needs to be prioritized for removal in protected agriculture. All absorbed ultraviolet energy is transferred through Tb... 3+ →2,6-Naphthalenedicarboxylic acid→Eu 3+ The energy is transferred via a stepwise pathway, and the triplet energy level of 2,6-naphthalenedicarboxylic acid is 18900 cm⁻¹. -1 Located in the terbium ion 5 D4 energy level and europium ions 5 Between the D0 energy levels, the energy level difference at each step fully meets the requirements for efficient resonant energy transfer. This step-by-step transfer transforms the originally inefficient resonant transfer with a large energy level difference into efficient transfer with a small energy level difference, thereby improving the overall energy transfer efficiency from the traditional direct transfer. When the molar ratio of terbium ions to europium ions is controlled at 1:1.8-2.2, each terbium ion is surrounded by a sufficient number of europium ions as energy acceptors. Almost all the energy absorbed by the terbium ions is completely transferred to the europium ions, without generating excess green stray light emission. At the same time, since energy can only be transferred unidirectionally from high energy level to low energy level, the high-energy thermal population of europium ions cannot transfer energy back to the terbium ions, fundamentally eliminating the problem of a sharp drop in light conversion efficiency under high summer temperatures. Particularly important is that the coordination of 2,6-naphthalenedicarboxylic acid with europium ions changes the coordination field environment around europium ions, causing the characteristic emission peak of europium ions to shift from the orange-red light of free ions to deep red light, which almost completely coincides with the red light absorption peaks of plant chlorophyll a and b. Its photosynthetic efficiency is greatly improved compared to orange-red light, thereby maximizing the use of converted light energy for plant photosynthesis.
[0036] The stable covalent bonding between the light-converting agent and the PE / EVA matrix is crucial for ensuring the long-term performance of the light-converting film. This invention employs a melt in-situ grafting process. During twin-screw extrusion, the dicumyl peroxide initiator decomposes upon heating to generate alkoxy radicals. These radicals then abstract hydrogen atoms from the PE, EVA, and maleic anhydride-grafted polyethylene molecular chains, generating macromolecular radicals. These macromolecular free radicals undergo free radical addition reactions with the polymerizable double bonds remaining on the maleic anhydride-butyl acrylate ligand in the light-converting agent molecule, covalently bonding the light-converting agent molecule to the molecular chain of the PE / EVA matrix, forming a dense three-dimensional covalent bond network. This molecular-level bonding makes the light-converting agent an integral part of the matrix molecular structure, rather than a physically doped impurity. This solves the problems of easy migration and precipitation of the light-converting agent and rapid decay of the light-converting function in traditional physically blended light-converting films. Even after long-term outdoor use, the light-converting efficiency can still maintain a high level, and the migration and precipitation rate of the light-converting agent is low, achieving synchronization between the lifespan of the light-converting function and the lifespan of the film matrix. In addition, the hindered amine light stabilizer and antioxidant added to the film can effectively capture the free radicals generated by photo-oxidative aging, inhibit molecular chain breakage, and extend the lifespan of the film. Polyethylene glycol stearate anti-drip and anti-fogging agents can form a uniform water film on the film surface, preventing fogging and dripping, ensuring light transmittance and light-converting effect, and jointly ensuring the stable performance of the light-converting film throughout its service life.
[0037] Compared with the prior art, the beneficial effects of the present invention are:
[0038] 1. This invention employs a reverse stepwise coordination method combined with the confined space effect of polymers to achieve the synthesis of Tb-NDA-Eu heteronuclear bimetallic structures, thereby improving energy transfer efficiency, eliminating the problem of reverse energy transfer under high summer temperatures, and significantly enhancing light conversion stability. It can efficiently convert harmful short-wave ultraviolet light into usable light energy, greatly improving the utilization rate of the solar spectrum and providing sufficient light energy supply for crop growth.
[0039] 2. This invention utilizes the ligand field regulation of 2,6-naphthalenedicarboxylic acid to redshift the characteristic emission peak of europium ions to a deep red light region that matches the absorption peak of plant chlorophyll. Simultaneously, through a suitable rare earth ion ratio, it almost eliminates useless stray green light emission, thereby maximizing the utilization of light energy. This significantly enhances the photosynthetic intensity of crops, promotes crop growth and development, and improves crop yield and quality.
[0040] 3. This invention employs a segmented process of separate grafting at the masterbatch stage and adding anti-aging agents at the blown film stage, perfectly resolving the inherent contradiction between grafting and anti-aging. This achieves stable covalent bonding between the light-converting agent and the matrix, effectively inhibiting the migration and precipitation of the light-converting agent. This synchronizes the lifespan of the light-converting function with the lifespan of the film matrix, significantly extending the service life of the light-converting film and reducing the production costs of facility agriculture. Detailed Implementation
[0041] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with existing known technologies. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.
[0042] The linear low-density polyethylene used in the embodiments of this invention has a melt index ≥2 g / 10 min and a density of 0.918-0.935 g / cm³. 3 The VA content of the ethylene-vinyl acetate copolymer is 18%-25%; the grafting rate of maleic anhydride-grafted polyethylene is 1.2%-1.5%.
[0043] Preparation Example 1: The specific preparation method of the modified light-converting agent includes the following steps:
[0044] (1) Under nitrogen protection, 100g of maleic anhydride and 250g of butyl acrylate were added to 4kg of anhydrous ethanol and stirred for 10min. Then the temperature was raised to 60℃ and 3g of azobisisobutyronitrile was added. The reaction was carried out for 4h. After cooling to room temperature, 10g of petroleum ether was added dropwise. The precipitate was collected and then washed and dried to obtain maleic anhydride-butyl acrylate copolymer.
[0045] (2) In a reaction vessel equipped with a reflux condenser, 100g of maleic anhydride-butyl acrylate copolymer was added to 4kg of anhydrous ethanol and stirred until dissolved. Then, 100g of a 0.1mol / L Tb(NO3)3-Eu(NO3)3 mixed aqueous solution (Tb) was added dropwise. 3+ and Eu 3+ The molar ratio of the two components was 1:1.8, and the dropping rate was 0.1 L / h. After the addition was complete, ammonia was added to adjust the pH of the system to 6.8 ± 0.2, while stirring during the adjustment process. Then, 30 g of 2,6-naphthalenedicarboxylic acid was added, the temperature was raised to 70 °C, and the reaction was carried out for 8 h. Then, 10 g of 1,10-o-phenanthroline was added, and the reaction was carried out for 20 min. After cooling to room temperature, the reaction solution was transferred to a dialysis bag with a molecular weight cutoff of 3500 Da and dialyzed with deionized water for 48 h, with the dialysate being changed every 6 h. The dialysis bag was removed, and the solution was concentrated to 1 / 10 of the original volume by vacuum distillation. Then, with stirring, it was added dropwise to 10 kg of anhydrous acetone. The precipitate was collected, washed, dried, and ground into 200 mesh powder to obtain the modified light-converting agent.
[0046] Preparation Example 2: The specific preparation method of the modified light-converting agent includes the following steps:
[0047] (1) Under nitrogen protection, 100g of maleic anhydride and 300g of butyl acrylate were added to 5kg of anhydrous ethanol and stirred for 15min. Then the temperature was raised to 65℃ and 5g of azobisisobutyronitrile was added. The reaction was carried out for 5h. After cooling to room temperature, 20kg of petroleum ether was added dropwise. The precipitate was collected and then washed and dried to obtain maleic anhydride-butyl acrylate copolymer.
[0048] (2) In a reaction vessel equipped with a reflux condenser, 100g of maleic anhydride-butyl acrylate copolymer was added to 5kg of anhydrous ethanol and stirred until dissolved. Then, 120g of a 0.3mol / L Tb(NO3)3-Eu(NO3)3 mixed aqueous solution (Tb) was added dropwise. 3+ and Eu 3+ The molar ratio of the two components was 1:2, and the dropping rate was 0.5 L / h. After the addition was complete, ammonia was added to adjust the pH of the system to 6.8 ± 0.2, while stirring during the adjustment process. Then, 40 g of 2,6-naphthalenedicarboxylic acid was added, the temperature was raised to 75 °C, and the reaction was carried out for 10 h. Then, 20 g of 1,10-o-phenanthroline was added, and the reaction was carried out for 30 min. After cooling to room temperature, the reaction solution was transferred to a dialysis bag with a molecular weight cutoff of 3500 Da and dialyzed with deionized water for 60 h, with the dialysate being changed every 6 h. The dialysis bag was removed, and the solution was concentrated to 1 / 10 of the original volume by vacuum distillation. Then, with stirring, it was added dropwise to 15 kg of anhydrous acetone. The precipitate was collected, washed, dried, and ground into 200 mesh powder to obtain the modified light-converting agent.
[0049] Preparation Example 3: The specific preparation method of the modified light-converting agent includes the following steps:
[0050] (1) Under nitrogen protection, 100g of maleic anhydride and 400g of butyl acrylate were added to 6kg of anhydrous ethanol and stirred for 20min. Then the temperature was raised to 70℃ and 8g of benzoyl peroxide was added. The reaction was carried out for 6h. After cooling to room temperature, 30kg of petroleum ether was added dropwise. The precipitate was collected and then washed and dried to obtain maleic anhydride-butyl acrylate copolymer.
[0051] (2) In a reaction vessel equipped with a reflux condenser, 100g of maleic anhydride-butyl acrylate copolymer was added to 6kg of anhydrous ethanol and stirred until dissolved. Then, 150g of a 0.5mol / L Tb(NO3)3-Eu(NO3)3 mixed aqueous solution (Tb) was added dropwise. 3+ and Eu 3+The molar ratio of the two components was 1:2.2, and the dropping rate was 1 L / h. After the addition was complete, ammonia was added to adjust the pH of the system to 6.8 ± 0.2, while stirring during the adjustment process. Then, 50 g of 2,6-naphthalenedicarboxylic acid was added, the temperature was raised to 80 °C, and the reaction was carried out for 12 h. Then, 30 g of 1,10-o-phenanthroline was added, and the reaction was carried out for 40 min. After cooling to room temperature, the reaction solution was transferred to a dialysis bag with a molecular weight cutoff of 3500 Da and dialyzed with deionized water for 72 h, with the dialysate being changed every 6 h. The dialysis bag was removed, and the solution was concentrated to 1 / 10 of the original volume by vacuum distillation. Then, with stirring, it was added dropwise to 20 kg of anhydrous acetone. The precipitate was collected, washed, dried, and ground into 200 mesh powder to obtain the modified light-converting agent.
[0052] Comparative Preparation Example 1: The difference between Comparative Preparation Example 1 and Preparation Example 2 is that step (1) is omitted, and maleic anhydride-butyl acrylate copolymer is not added in step (2). The specific preparation method is as follows: The specific preparation method of the modified light-converting agent includes the following steps:
[0053] (1) In a reaction vessel equipped with a reflux condenser, add 150g of a 0.5mol / L Tb(NO3)3-Eu(NO3)3 mixed aqueous solution (Tb 3+ and Eu 3+ The molar ratio of the two components was 1:2.2. Ammonia was added to adjust the pH of the system to 6.8±0.2, and stirring was maintained during the adjustment process. Then 50g of 2,6-naphthalenedicarboxylic acid was added, the temperature was raised to 80℃, and the reaction was carried out for 12h. Then 30g of 1,10-o-phenanthroline was added, and the reaction was carried out for 40min. After cooling to room temperature, the mixture was filtered, the filter cake was washed, dried, and ground into 200-mesh powder to obtain the modified light-converting agent.
[0054] Comparative Preparation Example 2: The difference between Comparative Preparation Example 2 and Preparation Example 2 is that 2,6-naphthalenedicarboxylic acid is not added.
[0055] Comparative Preparation Example 3: The difference between Comparative Preparation Example 3 and Preparation Example 2 is that: the Tb(NO3)3-Eu(NO3)3 mixed aqueous solution contains... 3+ and Eu 3+ The molar ratio is 2:1.
[0056] Example 1: A specific method for preparing a light-converting plastic film to enhance plant photosynthesis, comprising the following steps:
[0057] S1. 600g of linear low-density polyethylene, 250g of ethylene-vinyl acetate copolymer, 12g of the modified brightening agent prepared according to Preparation Example 1, 10g of maleic anhydride grafted polyethylene, 0.5g of dicumyl peroxide, 5g of polyethylene glycol 400 stearate and 3g of calcium stearate were put into a high-speed mixer and premixed at a stirring rate of 100 rpm for 1 min, and then mixed at a stirring rate of 1000 rpm for 5 min. After discharge, the mixture was fed into a twin-screw extruder with a length-to-diameter ratio of 40:1. A gradient heating process was adopted, with the temperatures of each zone set as follows: zone 1 155℃, zone 2 165℃, zone 3 175℃, zone 4 180℃, zone 5 185℃, and die head 180℃. The screw speed was 220 r / min and the vacuum degree was -0.09 MPa. Melt extrusion was performed. After extrusion, the mixture was cooled with water, pelletized and dried to obtain the brightening grafted masterbatch.
[0058] S2. Add the light-converting grafted masterbatch and 8g of anti-aging agent (HS-944 and antioxidant 1010 in a mass ratio of 2:1) to a single-screw blown film mill, and blown film according to the following process parameters:
[0059] Extrusion parameters: Barrel temperature zone 1 155℃, zone 2 160℃, zone 3 165℃, die head temperature 160℃, screw speed 50r / min;
[0060] Blown film forming: After the melt flows out of the die head stably, compressed air is introduced to inflate the film bubble, the blowing ratio is controlled at 1:3, and the speed of the traction roller is 6m / min;
[0061] Cooling and shaping: Turn on the cooling air ring, air temperature 25℃, air speed 5m / s;
[0062] Then, place it in a 60℃ hot air circulating oven for 1 hour, cool it to room temperature, and roll it up to obtain a light-converting plastic film that enhances plant photosynthesis.
[0063] Example 2: A specific method for preparing a light-converting plastic film to enhance plant photosynthesis, comprising the following steps:
[0064] S1. 650g of linear low-density polyethylene, 280g of ethylene-vinyl acetate copolymer, 15g of the modified brightening agent prepared according to Preparation Example 2, 15g of maleic anhydride grafted polyethylene, 0.8g of dicumyl peroxide, 6g of polyethylene glycol 400 stearate and 4g of zinc stearate were put into a high-speed mixer and premixed at a stirring rate of 200 rpm for 2 min, and then mixed at a stirring rate of 1100 rpm for 8 min. After discharge, the mixture was fed into a twin-screw extruder with a length-to-diameter ratio of 40:1. A gradient heating process was adopted, with the temperatures of each zone set as follows: zone 1 160℃, zone 2 170℃, zone 3 180℃, zone 4 185℃, zone 5 190℃, and die head 180℃. The screw speed was 260 r / min and the vacuum degree was -0.09 MPa. Melt extrusion was performed. After extrusion, the mixture was cooled with water, pelletized and dried to obtain the brightening grafted masterbatch.
[0065] S2. Add the light-converting grafted masterbatch and 10g of anti-aging agent (HS-944 and antioxidant 1010 in a mass ratio of 2:1) to a single-screw blown film mill, and blown film according to the following process parameters:
[0066] Extrusion parameters: Barrel temperature zone 1 160℃, zone 2 165℃, zone 3 170℃, die head temperature 162℃, screw speed 60r / min;
[0067] Film blowing: After the melt flows out of the die head stably, compressed air is introduced to inflate the film bubble, the inflation ratio is controlled at 1:3.5, and the traction roller speed is 8m / min;
[0068] Cooling and shaping: Turn on the cooling air ring, air temperature 25℃, air speed 8m / s;
[0069] Then, place it in a 65℃ hot air circulating oven for 1.5 hours of heat treatment. After cooling to room temperature, roll it up to obtain a light-converting plastic film that enhances plant photosynthesis.
[0070] Example 3: A specific method for preparing a light-converting plastic film to enhance plant photosynthesis, comprising the following steps:
[0071] S1. 700g of linear low-density polyethylene, 300g of ethylene-vinyl acetate copolymer, 20g of the modified brightening agent prepared according to Preparation Example 3, 18g of maleic anhydride grafted polyethylene, 1g of dicumyl peroxide, 8g of polyethylene glycol 400 stearate and 5g of ethylene bis-stearamide were put into a high-speed mixer and premixed at a stirring rate of 300 rpm for 3 min, and then mixed at a stirring rate of 1200 rpm for 10 min. After discharge, the mixture was fed into a twin-screw extruder with a length-to-diameter ratio of 40:1. A gradient heating process was adopted, with the temperatures of each zone set as follows: zone 1 165℃, zone 2 175℃, zone 3 185℃, zone 4 190℃, zone 5 195℃, and die head 180℃. The screw speed was 300 r / min and the vacuum degree was -0.09 MPa. Melt extrusion was performed. After extrusion, the mixture was cooled with water, pelletized and dried to obtain the brightening grafted masterbatch.
[0072] S2. Add the light-converting grafted masterbatch and 12g of anti-aging agent (HS-944 and antioxidant 1010 in a mass ratio of 2:1) to a single-screw blown film mill, and blown film according to the following process parameters:
[0073] Extrusion parameters: Barrel temperature zone 1 165℃, zone 2 170℃, zone 3 175℃, die head temperature 165℃, screw speed 70r / min;
[0074] Blown film forming: After the melt flows out of the die head stably, compressed air is introduced to inflate the film bubble, the inflation ratio is controlled at 1:4, and the speed of the traction roller is 10m / min;
[0075] Cooling and shaping: Turn on the cooling air ring, air temperature 25℃, air speed 10m / s;
[0076] Then, place it in a 70℃ hot air circulating oven for 2 hours, cool it to room temperature, and roll it up to obtain a light-converting plastic film that enhances plant photosynthesis.
[0077] Comparative Example 1: The difference between Comparative Example 1 and Example 2 is that the modified light-converting agent prepared according to Preparation Example 2 is replaced with the modified light-converting agent prepared according to Comparative Preparation Example 1.
[0078] Comparative Example 2: The difference between Comparative Example 2 and Example 2 is that the modified light-converting agent prepared according to Preparation Example 2 is replaced with the modified light-converting agent prepared according to Comparative Preparation Example 2.
[0079] Comparative Example 3: The difference between Comparative Example 3 and Example 2 is that the modified light-converting agent prepared according to Preparation Example 2 is replaced with the modified light-converting agent prepared according to Comparative Preparation Example 3.
[0080] Comparative Example 4: The difference between Comparative Example 4 and Example 2 is that the anti-aging agent is mixed with other raw materials in S1 and then added to a twin-screw extruder for melt extrusion.
[0081] Performance testing:
[0082] The light-converting plastic films prepared in Examples 1-3 and Comparative Examples 1-4 were subjected to the following systematic tests. The specific test items are as follows:
[0083] 1. Migration and leaching rate of the light-converting agent after immersion in water at 50℃ for 30 days: The test procedure involved accurately weighing a 10cm×10cm film sample, completely immersing it in deionized water at a constant temperature of 50℃, sealing it, and storing it in the dark for 30 days. After removal, the surface was rinsed three times with anhydrous ethanol, and then vacuum dried at 60℃ and -0.09MPa to constant weight. The sample mass loss rate was calculated, which is the migration and leaching rate, expressed in %.
[0084] 2. Retention rate of light conversion efficiency after 1000 hours of accelerated aging of xenon lamps: The test standard is GB / T 16422.2-2022 "Laboratory Light Source Exposure Test Methods for Plastics - Part 2: Xenon Arc Lamps", and the test conditions are an irradiance of 0.51 W / m². 2 @340nm, blackboard temperature 65℃, relative humidity 50%, water spray cycle 18min / 102min; the light conversion efficiency of the film before and after aging was measured, and the retention rate was calculated, in % %.
[0085] 3. Emission peak position of the light-converting agent: The test standard is GB / T 30086-2013 "Test Method for Fluorescence Properties of Rare Earth Light-Converting Materials", with an excitation wavelength of 365nm and a scanning range of 400-700nm. The unit is nm.
[0086] 4. Conversion efficiency: The test standard is GB / T 30086-2013 "Test Method for Fluorescence Properties of Rare Earth Optical Conversion Materials", with an excitation wavelength of 365 nm and quinine sulfate as the reference standard. The unit is % (%).
[0087] 5.545nm Green Light Relative Emission Intensity: The test procedure involves taking the red light emission intensity at 655nm as 100% and calculating the relative value of the green light emission intensity at 545nm, expressed in % (%).
[0088] 6. Visible light transmittance: The test standard is GB / T 2410-2008 "Determination of transmittance and haze of transparent plastics", the test wavelength is 550nm, and the unit is %
[0089] 7. Average Photosynthetically Active Radiation (PAR) Inside the Greenhouse: Using a PAR meter, PAR was measured at five locations (east, south, west, north, and center) at a height of 1.5 m above the ground inside the greenhouse on sunny days, between 9:00-11:00 AM and 2:00-4:00 PM. The average value was taken, and the unit is μmol CO2·m⁻². -2 ·s -1 ;
[0090] 8. Net photosynthetic rate of tomato leaves: A portable photosynthesis meter was used, with three replicate plots set up for each test film, each plot having an area of 20m². 2 Using the same field management practices, the net photosynthetic rate of the top three leaves of tomatoes was measured between 9:00 and 11:00 AM on a sunny day. Ten plants were measured per plot, with three leaves measured per plant. The average value was taken, and the unit is μmol CO2·m⁻¹. -2 ·s -1 ;
[0091] 9. Tomato yield per acre: Three replicate plots were set up for each test film, with each plot having an area of 20m². 2 Using the same field management measures, the total yield of each plot was counted at each harvest period and converted into yield per mu (unit: kg / mu).
[0092] 10. Vitamin C content of tomatoes: The test standard is GB 5009.86-2016 "National Food Safety Standard - Determination of Ascorbic Acid in Food", using the 2,6-dichlorophenolindophenol titration method, and the unit is mg / 100g;
[0093] The experimental results are shown in Table 1.
[0094] Table 1 Performance Test Results
[0095]
[0096] Data Analysis:
[0097] As can be seen from the performance test data in Table 1, the light-converting plastic films prepared by the technical solution of the present invention in Examples 1-3 are significantly better than the comparative examples in terms of long-term stability, optical performance and field application effect, among which Example 2 has the best overall performance.
[0098] The core reason for the superior performance of Example 2 lies in the comprehensive optimization of its light-converting agent synthesis, matrix grafting, and overall process parameters. Regarding the light-converting agent synthesis, Example 2 obtained a Tb-NDA-Eu heteronuclear bimetallic structure through a confined space-oriented polymer synthesis method. This structure exhibits high energy transfer efficiency and almost no extraneous green stray light emission. Simultaneously, the coordination of 2,6-naphthalenedicarboxylic acid with europium ions precisely red-shifts the emission peak to the deep red light region, almost completely coinciding with the red light absorption peaks of plant chlorophyll a and b, resulting in high spectral matching and excellent light conversion efficiency. In terms of the matrix bonding process, Example 2 employs a segmented process of separate grafting at the masterbatch stage and adding an anti-aging agent at the blown film stage, ensuring both... The high grafting rate between the light-converting agent and the PE / EVA matrix was demonstrated, which ensured that the light-converting agent was firmly bound to the matrix molecular chain, effectively inhibiting migration and precipitation, and completely avoiding the consumption of initiator free radicals by antioxidants, thus ensuring the normal functioning of the anti-aging system and significantly improving the long-term performance of the film. In addition, the resin ratio, light-converting agent addition amount, twin-screw extrusion and single-screw blown film process parameters in Example 2 were repeatedly adjusted to achieve a perfect balance in the visible light transmittance, processing performance and mechanical properties of the film, laying a solid foundation for excellent field application results.
[0099] The difference between Comparative Example 1 and Example 2 lies in the absence of maleic anhydride-butyl acrylate copolymer as an anchoring ligand. The light-converting agent was synthesized in free solution, resulting in only randomly mixed homonuclear and heteronuclear structures. The content of heteronuclear bimetallic structures was extremely low, leading to a significant decrease in energy transfer efficiency, severe green stray light emission, and a marked reduction in light conversion efficiency. Furthermore, the lack of polymer chain anchoring resulted in weak binding to the matrix, a significantly increased migration and precipitation rate, and a rapid decline in light conversion efficiency after long-term use. Ultimately, this resulted in significantly lower photosynthetically active radiation and crop yield in the greenhouse compared to Example 2.
[0100] The difference between Comparative Example 2 and Example 2 lies in the absence of 2,6-naphthalenedicarboxylic acid. This prevents the formation of a Tb-NDA-Eu heteronuclear bridging structure, thus eliminating the stepwise energy transfer. Energy is directly transferred from the ligand to the rare earth ions, resulting in extremely low transfer efficiency. Most energy is lost through fluorescence quenching, leading to the worst light conversion efficiency. Furthermore, the emission peak remains confined to the orange-red light region, resulting in poor matching with the photosynthetic spectrum of plants and low photosynthetic efficiency. Although the light-converting agent still exhibits a certain grafting rate and low migration and precipitation rate, its core light conversion function is severely insufficient, resulting in the worst performance in field applications.
[0101] The difference between Comparative Example 3 and Example 2 is that an excessive terbium ratio was used, resulting in insufficient europium ions around each terbium ion, which could not fully receive the energy transferred by the terbium ions. The remaining energy was emitted in the form of green light, resulting in energy waste and a decrease in light conversion efficiency. Although the heteronuclear bimetallic structure and grafting process were basically intact and the long-term stability was good, the spectral matching degree and energy utilization rate were not as good as those of Example 2, and the final field yield increase effect was also reduced accordingly.
[0102] The difference between Comparative Example 4 and Example 2 lies in the addition of the anti-aging agent along with all raw materials to the twin-screw extruder. The antioxidant preferentially captures alkoxy radicals generated from the decomposition of dicumyl peroxide, causing the initiator to completely fail. The light-converting agent cannot covalently graft with the matrix and can only exist as a physical dopant, resulting in a significantly increased migration and precipitation rate. After long-term use, the light-converting efficiency rapidly declines. Although the optical properties of the light-converting agent itself are similar to those of Example 2, its long-term stability is extremely poor, its actual service life is significantly shortened, and its field application effect is far inferior to that of Example 2.
[0103] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.
Claims
1. A light-converting plastic film for enhancing plant photosynthesis, characterized in that, It comprises the following components by weight: linear low-density polyethylene: 60-70 parts, ethylene-vinyl acetate copolymer: 25-30 parts, modified light-converting agent: 1.2-2.0 parts, maleic anhydride grafted polyethylene: 1.0-1.8 parts, initiator: 0.05-0.1 parts, anti-aging agent: 0.8-1.2 parts, anti-dripping and anti-fogging agent: 0.5-0.8 parts, lubricant: 0.3-0.5 parts; The preparation method of the modified light-converting agent includes the following steps: (1) Under nitrogen protection, maleic anhydride and butyl acrylate were added to anhydrous ethanol and stirred for 10-20 min. Then the temperature was raised to 60-70℃, an initiator was added, and the reaction was carried out for 4-6 h. After cooling to room temperature, the precipitate was added dropwise to petroleum ether and collected. After washing and drying, maleic anhydride-butyl acrylate copolymer was obtained. (2) In a reaction vessel equipped with a reflux condenser, maleic anhydride-butyl acrylate copolymer is added to anhydrous ethanol and stirred until dissolved. A mixed aqueous solution of Tb(NO3)3-Eu(NO3)3 is added dropwise. After the addition is complete, ammonia is added to adjust the pH of the system to 6.8±0.
2. Stirring is maintained during the adjustment process. Then 2,6-naphthalenedicarboxylic acid is added, the temperature is raised to 70-80℃, and the reaction is carried out for 8-12 hours. Then 1,10-o-phenanthroline is added and the reaction is carried out for 20-40 minutes. The mixture is cooled to room temperature, and the reaction solution is transferred to a dialysis bag and dialyzed with deionized water for 48-72 hours. The dialysis solution is changed every 6 hours. The dialysis bag is removed, and the solution is concentrated to 1 / 10 of the original volume by vacuum distillation. Then, under stirring, anhydrous acetone is added dropwise, and the precipitate is collected. After washing and drying, it is ground into 200-mesh powder to obtain the modified light-converting agent.
2. The light-converting plastic film for enhancing plant photosynthesis according to claim 1, characterized in that, The linear low-density polyethylene has a melt flow index ≥2 g / 10 min and a density of 0.918-0.935 g / cm³. 3 The VA content of the ethylene-vinyl acetate copolymer is 18%-25%; the grafting rate of maleic anhydride-grafted polyethylene is 1.2%-1.5%; the initiator is dicumyl peroxide; the anti-aging agent is composed of HS-944 and antioxidant 1010 in a mass ratio of 2:1; the anti-dripping and anti-fogging agent is polyethylene glycol 400 stearate; the lubricant is one of calcium stearate, zinc stearate or ethylene bis-stearamide.
3. The light-converting plastic film for enhancing plant photosynthesis according to claim 1, characterized in that, In (1), maleic anhydride, butyl acrylate, anhydrous ethanol, initiator and petroleum ether are in a weight ratio of 1:2.5-4:40-60:0.03-0.08:100-300.
4. The light-converting plastic film for enhancing plant photosynthesis according to claim 1, characterized in that, The initiator in (1) is azobisisobutyronitrile or benzoyl peroxide.
5. The light-converting plastic film for enhancing plant photosynthesis according to claim 1, characterized in that, In (2), the maleic anhydride-butyl acrylate copolymer, anhydrous ethanol, Tb(NO3)3-Eu(NO3)3 mixed aqueous solution, 2,6-naphthalenedicarboxylic acid, 1,10-o-phenanthroline and anhydrous acetone are in a weight ratio of 1:40-60:10-15:0.3-0.5:0.1-0.3:100-200.
6. The light-converting plastic film for enhancing plant photosynthesis according to claim 1, characterized in that, In the Tb(NO3)3-Eu(NO3)3 mixed aqueous solution mentioned in (2), Tb 3+ and Eu 3+ The molar ratio is 1:1.8-2.2; the concentration of the Tb(NO3)3-Eu(NO3)3 mixed aqueous solution is 0.1-0.5 mol / L; the dropping rate of the Tb(NO3)3-Eu(NO3)3 mixed aqueous solution is 0.1-1 L / h.
7. The light-converting plastic film for enhancing plant photosynthesis according to claim 1, characterized in that, The molecular weight cutoff of the dialysis bag in (2) is 3500 Da.
8. The method for preparing a light-converting plastic film for enhancing plant photosynthesis according to any one of claims 1-7, characterized in that, Includes the following steps: S1. Linear low-density polyethylene, ethylene-vinyl acetate copolymer, modified brightening agent, maleic anhydride grafted polyethylene, initiator, anti-dripping agent and lubricant are put into a high-speed mixer and premixed at a stirring rate of 100-300 rpm for 1-3 min, and then mixed at a stirring rate of 1000-1200 rpm for 5-10 min. After discharge, the mixture is fed into a twin-screw extruder and melt extruded using a gradient heating process. After extrusion, the mixture is cooled with water, pelletized and dried to obtain brightening grafted masterbatch. S2. Add the light-converting grafting masterbatch and anti-aging agent to a single-screw blown film machine, blow it into a film, place it in a 60-70℃ hot air circulating oven, heat treat for 1-2 hours, cool to room temperature, and then roll it up to obtain a light-converting plastic film that enhances plant photosynthesis.
9. The method for preparing the light-converting plastic film for enhancing plant photosynthesis according to claim 8, characterized in that, The twin-screw extruder in S1 has a length-to-diameter ratio of 40:1; the temperature settings for each zone in the gradient heating process are: Zone 1 155-165℃, Zone 2 165-175℃, Zone 3 175-185℃, Zone 4 180-190℃, Zone 5 185-195℃, and the die head 180℃; the screw speed is 220-300 r / min; and the vacuum degree is -0.09 MPa.
10. The method for preparing the light-converting plastic film for enhancing plant photosynthesis according to claim 8, characterized in that, The following process parameters are used in the blown film formation process of S2: Extrusion parameters: Barrel temperature zone 1 155-165℃, zone 2 160-170℃, zone 3 165-175℃, die head temperature 160-165℃, screw speed 50-70r / min; Blown film forming: After the melt flows out of the die head stably, compressed air is introduced to inflate the film bubble, the inflation ratio is controlled at 1:3-4, and the speed of the traction roller is 6-10m / min; Cooling and shaping: Turn on the cooling air ring, air temperature 25℃, air speed 5-10m / s.