High-transmittance agricultural greenhouse film and preparation method thereof

Abstract

This invention discloses a highly transparent agricultural greenhouse film and its preparation method, comprising the following components by weight: 50-70 parts siloxane-modified PBAT, 30-50 parts PLA, 2-5 parts chain extender, and 0.5-1 parts antioxidant. The invention modifies PBAT by inserting siloxane structures into the PBAT polymer molecular chains. The high flexibility of the siloxane segments (Si-O-Si) loosens the stacking of the PBAT molecular chains, reducing the proportion of crystalline regions in the polymer matrix. Crystalline regions scatter light, reducing light transmittance. The introduction of siloxane reduces the content of crystalline domains in PBAT, allowing light to penetrate the material more easily, thereby improving the light transmittance of the agricultural greenhouse film.

Description

Technical Field

[0001] The present invention belongs to the technical field of greenhouse films, and specifically relates to a high-light-transmittance agricultural greenhouse film and a preparation method thereof. Background Art

[0002] With the rapid development of modern agriculture, greenhouse technology is being used more and more widely in agricultural production. As the core construction material of greenhouses, greenhouse film plays an important role in protecting crop growth, improving the growth environment, and increasing crop yield and quality. However, traditional greenhouse films often have problems such as insufficient light transmittance, poor mechanical properties, low anti-aging performance, and susceptibility to pollution, which makes it difficult to meet the demand of modern agricultural production for high-quality agricultural greenhouse films.

[0003] Light transmittance is a key performance indicator for agricultural greenhouse films, directly impacting crop photosynthesis efficiency and growth quality. Generally speaking, the higher the light transmittance of a greenhouse film, the better the lighting conditions within the greenhouse, faster crop growth, and correspondingly higher yield and quality. However, while traditional polyethylene (PE) and ethylene-vinyl acetate copolymer (EVA) greenhouse films are inexpensive and flexible, their optical properties are less than ideal. This is particularly true under conditions of high light scattering or light attenuation, which can easily lead to uneven lighting within the greenhouse. Furthermore, traditional greenhouse films are susceptible to aging under prolonged exposure to ultraviolet light, shortening their service life and increasing agricultural production costs.

[0004] To address insufficient light transmittance, several greenhouse films with higher light transmittance have emerged on the market in recent years. These films are typically created by adding light-transmitting additives or modified materials to the base resin, or through multi-layer co-extrusion technology. However, while these films improve light transmittance to a certain extent, they are susceptible to accumulation of dust, water, and contaminants over long-term use, which can reduce light transmission. Furthermore, these modification techniques can also reduce the film's mechanical properties, such as tear resistance and impact resistance, making it unsuitable for complex agricultural environments and long-term use.

[0005] To further enhance the performance of greenhouse films, some research has focused on incorporating functional materials, such as nanotechnology-based modifications or the addition of specialized optical materials (such as UV inhibitors and near-infrared shielding agents) to the film. Nanomaterials, with their large surface area and unique optical properties, can significantly enhance the film's light transmittance, UV resistance, and anti-fog properties. However, current nanotechnology-modified greenhouse films are subject to high production costs and complex manufacturing processes, and have yet to achieve full industrialization.

[0006] Surface treatment technology for greenhouse films is also an important approach to improving light transmittance. For example, applying anti-fog and anti-drip coatings to the film surface can effectively reduce light scattering or obstruction caused by water droplets. However, the adhesion and durability of these coatings remain technical challenges, and they are prone to detachment or failure after long-term use.

[0007] In summary, developing agricultural greenhouse films with high light transmittance, aging resistance, excellent mechanical properties, and strong pollution resistance has become a critical need for modern agricultural development. Research on new high-transmittance agricultural greenhouse films requires not only breakthroughs in material selection and modification, but also a combination of cost-effective and manufacturable manufacturing processes to meet the requirements of large-scale production and application. The development of such new greenhouse films not only effectively increases crop yield and quality but also reduces agricultural production costs, thus having significant economic and social significance. Summary of the Invention

[0008] In response to the above situation and to overcome the shortcomings of the prior art, the present invention provides a highly light-transmitting agricultural greenhouse film and a method for preparing the same. The present invention modifies PBAT (polybutylene adipate / terephthalate) by inserting a siloxane structure into the PBAT polymer molecular chain. The high flexibility of the siloxane segment (Si-O-Si) makes the stacking between the PBAT molecular chains looser, reducing the proportion of crystalline regions in the polymer matrix; the crystalline region will scatter light and reduce light transmittance. The introduction of siloxane reduces the content of crystalline domains in PBAT, making it easier for light to penetrate the material, thereby improving the light transmittance of the agricultural greenhouse film.

[0009] To achieve the above-mentioned object, the technical solution adopted by the present invention is as follows: The present invention proposes a high-transmittance agricultural greenhouse film, which comprises the following components in parts by weight: 50-70 parts of siloxane-modified PBAT, 30-50 parts of PLA (polylactic acid), 2-5 parts of a chain extender, and 0.5-1 part of an antioxidant;

[0010] Preferably, the raw materials for preparing the siloxane-modified PBAT specifically include the following components in parts by weight: 20-23 parts of dichlorosiloxane, 17.5-26.5 parts of ethylene carbonate, 33-41.5 parts of p-dibenzoic acid, 16.5-25.5 parts of 1,4-butanediol, and 30-36.5 parts of adipic acid;

[0011] Preferably, the dichlorosiloxane includes at least one of 1,3-dichlorotetramethyldisiloxane, 1,3-bis(3-chloropropyl)tetramethyldisiloxane, and 1,3-bis(chloromethyl)tetramethyldisiloxane;

[0012] Preferably, the chain extender includes at least one of PDI (1,5-pentane diisocyanate), LDI (L-lysine diisocyanate), and HDI (hexamethylene diisocyanate);

[0013] Preferably, the antioxidant includes at least one of antioxidant 1010, antioxidant 1076, antioxidant 1035, and antioxidant 1330;

[0014] Preferably, the preparation method of the siloxane-modified PBAT specifically comprises the following steps:

[0015] S1. Dissolve dichlorosiloxane in tetrahydrofuran (THE), add ethylene carbonate, mix well, add a basic catalyst, and stir at 50-80 rpm. After the reaction system is uniform, introduce flowing argon gas, raise the temperature to 60-70°C, continue the reaction for 4-8 hours, cool, remove excess solvent by distillation under reduced pressure, and vacuum dry to obtain hydroxylated siloxane;

[0016] Preferably, in step S1, the mass concentration of the dichlorosiloxane in THE is 0.1-0.2 g / mL;

[0017] Preferably, in step S1, the alkaline catalyst includes at least one of pyridine, triethylamine, potassium hydroxide, potassium carbonate, and calcium carbonate;

[0018] Preferably, in step S1, the added mass of the alkaline catalyst is 5-10% of the mass of dichlorosiloxane;

[0019] Under the action of alkaline catalyst, ethylene carbonate undergoes a ring-opening reaction to form an intermediate, which then undergoes a nucleophilic substitution reaction with dichlorosiloxane, introducing hydroxyl groups at both ends of the siloxane structure to form a diol-like structure.

[0020] S2. The hydroxylated siloxane prepared in step S1 is placed in a flask, p-dibenzoic acid, adipic acid and 1,4-butanediol are added, flowing argon is introduced, tetrabutyl titanate is added, the temperature is increased to 180-200° C., and the reaction is carried out for 8-12 hours. After the reaction is cooled to room temperature, a PBAT polymer monomer is obtained;

[0021] Preferably, in step S2, the added mass of tetrabutyl titanate is 0.75%-0.9% of the mass of terephthalic acid;

[0022] Tetrabutyl titanate is a Lewis acid catalyst that promotes nucleophilic attack by activating the carboxyl group (-COOH). The hydroxyl group (-OH) of the hydroxylated siloxane attacks the carboxyl group of terephthalic acid to generate a siloxane-ester bond intermediate while removing water. The hydroxylated siloxane acts as a flexible segment in the reaction, forming an alternating microphase structure with the rigid terephthalic acid-1,4-butanediol segment of PBAT. This flexible-rigid coexistence structure improves the toughness and flexibility of PBAT.

[0023] S3, adding stannous octoate to the PBAT polymer monomer prepared in step S2, introducing flowing argon, raising the temperature to 230-250° C., and carrying out a pre-polycondensation reaction for 2-3 hours, then raising the temperature to 250-270° C., and carrying out a polycondensation reaction for 6-8 hours. The reaction mixture was cooled to room temperature, washed with anhydrous methanol, and dried to obtain a siloxane-modified PBAT;

[0024] Preferably, in step S3, the added mass of stannous octoate is 0.6%-0.8% of the mass of terephthalic acid;

[0025] By further polycondensation reaction to increase the molecular weight of the polymer while retaining the flexibility of the siloxane segment, the final PBAT material has higher mechanical strength, flexibility and thermal stability.

[0026] The present invention also provides a method for preparing a high-transmittance agricultural greenhouse film, which specifically comprises the following steps:

[0027] S4. Vacuum-dry the siloxane-modified PBAT and PLA, raise the temperature to 160-180° C. under vacuum conditions, stir at 60-80 rpm, add a chain extender, continue to raise the temperature to 180-190° C., and blend for 20-30 minutes to obtain a copolymer;

[0028] Siloxane-modified PBAT has a cross-linked structure of flexible Si-O-Si segments. As a dispersed phase in the PBAT-PLA matrix, it absorbs stress and guides crack propagation, preventing rapid crack propagation and causing brittle fracture of the material. The partial compatibility of siloxane segments with PLA (through intermolecular forces) further alleviates interfacial stress concentration, thereby improving the overall toughness of the material.

[0029] S5. Place the copolymer prepared in step S4 in an internal mixer, add an antioxidant, increase the temperature to 130-150° C., melt blend at a speed of 60-80 rpm, mix for 40-60 minutes, cool to 40-50° C., place in a mold, and hot-press mold at 180-200° C. After cooling, obtain an agricultural greenhouse film.

[0030] The beneficial effects achieved by the present invention are as follows:

[0031] The present invention provides a high-transmittance agricultural greenhouse film and a preparation method thereof. The present invention modifies PBAT and inserts a siloxane structure into the PBAT polymer molecular chain. The high flexibility of the siloxane segment (Si-O-Si) makes the stacking between the PBAT molecular chains looser, reducing the proportion of crystalline regions in the polymer matrix; the crystalline region scatters light and reduces light transmittance. The introduction of siloxane reduces the content of crystalline domains in PBAT, making it easier for light to penetrate the material, thereby improving the light transmittance of the agricultural greenhouse film; the present invention adopts a siloxane structure with a halogen structure, introduces hydroxyl groups to both ends of the siloxane structure through a nucleophilic substitution reaction of ethylene carbonate on the halogen, forming a diol structure, and undergoes a condensation reaction with terephthalic acid and 1,4-butanediol to form a PBAT polymer with a siloxane segment; in P In the amorphous phase of BAT, the presence of siloxane makes the molecular chain segments move more freely, improves the uniformity of the amorphous region, reduces the scattering points of light, and improves the light transmittance of the greenhouse film. During the modification process, siloxane and PBAT are chemically bonded to achieve a uniform distribution of the two components on the molecular scale. The compatibility of siloxane improves the optical uniformity of the material and further reduces light scattering. In step S1 of the present invention, siloxane reacts with ethylene carbonate to generate hydroxylated siloxane, which can react with terephthalic acid or 1,4-butanediol in the subsequent polymerization reaction to form a covalently bonded structure. The introduction of covalent bonds forms a certain degree of chemical cross-linking network between the PBAT molecular chains. This cross-linking structure enhances the tensile strength and impact resistance of the material. The Si-O bond of siloxane has a low bond energy (about 445 kJ / mol) and a large bond angle (Si-O-Si bond angle can reach over 130°), which endows siloxane molecules with high flexibility. The introduction of siloxane makes the PBAT molecular chain more flexible, reduces stress concentration, and improves the material's elongation at break and toughness. Siloxane-modified PBAT exhibits improved tensile properties. Due to the presence of reactive groups such as hydroxyl groups on the surface of siloxane-modified PBAT, these groups interact with polar groups of PLA (such as carbonyl and hydroxyl groups) through hydrogen bonding or van der Waals forces to enhance the compatibility between PLA and PBAT. Within the PLA matrix, modified PBAT typically exists as a microphase distribution, forming a composite structure of a flexible PBAT dispersed phase and a rigid PLA matrix phase. When subjected to stress, the flexible PBAT phase acts as a barrier to crack propagation, slowing crack growth and increasing elongation at break. The stress buffer formed by the microphase dispersion absorbs external forces and enhances mechanical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a hydrogen nuclear magnetic resonance spectrum image of the siloxane-modified PBAT prepared in step S3 of Example 1-3 of the present invention;

[0033] Figure 2 Graph showing light transmittance performance of agricultural greenhouse films prepared in Examples 1-3 and Comparative Examples 1-3 of the present invention;

[0034] Figure 3 The mechanical properties of the agricultural greenhouse films prepared in Examples 1-3 and Comparative Examples 1-3 of the present invention are shown in FIG.

[0035] Figure 4 This is a graph showing the thermal stability results of the agricultural greenhouse films prepared in Example 1 of the present invention and Comparative Examples 1-3.

[0036] The accompanying drawings are used to provide further understanding of the present invention and constitute a part of the specification. They are used to explain the present invention together with the embodiments of the present invention and do not constitute a limitation of the present invention. DETAILED DESCRIPTION

[0037] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0038] Unless otherwise defined, all technical and scientific terms used herein have the same meanings as those familiar to those skilled in the art. Furthermore, any methods and materials similar or equivalent to those described herein can be applied to the present invention. The preferred embodiments and materials described herein are for illustrative purposes only and are not intended to limit the scope of this application.

[0039] The experimental methods in the following examples, unless otherwise specified, are conventional methods; the test materials and test strains used in the following examples, unless otherwise specified, are purchased from commercial channels.

[0040] Example 1

[0041] This embodiment provides a high-transmittance agricultural greenhouse film, which includes the following components in parts by weight: 50 parts of siloxane-modified PBAT, 50 parts of PLA, 2 parts of PDI, and 0.5 parts of antioxidant 1010;

[0042] The raw materials for preparing siloxane-modified PBAT specifically include the following components in parts by weight: 20 parts of 1,3-dichlorotetramethyldisiloxane, 17.5 parts of ethylene carbonate, 33.5 parts of p-dibenzoic acid, 20.7 parts of 1,4-butanediol, and 30 parts of adipic acid;

[0043] The preparation method of siloxane-modified PBAT specifically comprises the following steps:

[0044] S1. Add molecular sieves to a drying bottle, add THE, place the bottle on a vacuum pump and evacuate the vacuum to dry the THE, take 2g of 1,3-dichlorotetramethyldisiloxane and place it in a round-bottom flask, add 10mL of THE after dehydration, mix until 1,3-dichlorotetramethyldisiloxane is completely dissolved, add 1.76g of ethylene carbonate, mix well, introduce flowing nitrogen, mix pyridine and tetrahydrofuran, and prepare a 1mol / L pyridine solution. Take 0.3mL of pyridine solution and add it to the reaction system, stir at 80rpm, after the reaction system is uniform, raise the temperature to 60℃, continue the reaction for 8h, cool the reaction to room temperature, remove excess solvent by distillation under reduced pressure, wash repeatedly with dichloromethane three times, and place it at 40℃ and vacuum dry for 24h to obtain hydroxylated siloxane;

[0045] S2. The hydroxylated siloxane prepared in step S1 was placed in a three-necked flask, vacuum-dried at 40° C. for 1 hour, and then 2.0 g of 1,4-butanediol was added. After mixing, 3.3 g of terephthalic acid and 3.0 g of adipic acid were added. Under a flowing argon atmosphere, 25 mg of tetrabutyl titanate was added, and the temperature was raised to 200° C. for 8 hours. After the reaction mixture was cooled to room temperature, it was washed three times with anhydrous ethanol and deionized water in sequence, and then vacuum-dried at 50° C. for 12 hours to obtain a PBAT polymer monomer.

[0046] S3. The PBAT polymer monomer prepared in step S3 was placed in a flask, and after flowing nitrogen, the reaction system was fully dried. 20 mg of stannous octoate was added, and the temperature was raised to 250° C. for a preliminary polycondensation reaction for 2 hours. The temperature was then continuously raised to 270° C. for a further polycondensation reaction. After the reaction was allowed to react for 6 hours, the reaction mixture was cooled to room temperature, washed repeatedly with anhydrous ethanol three times, and then dried in vacuum at 60° C. for 12 hours to obtain a siloxane-modified PBAT.

[0047] This embodiment also provides a method for preparing a high-transmittance agricultural greenhouse film, which specifically includes the following steps:

[0048] S4. Accurately weigh 10 g of siloxane-modified PBAT and 10 g of PLA, dry them at 60° C. for 2 h, transfer them to a dry flask, raise the temperature to 180° C., stir at 60 rpm, mix thoroughly, add 0.4 g of PDI, raise the temperature to 190° C., and blend for 20 min to obtain a copolymer;

[0049] S5. The copolymer prepared in step S4 was placed in an internal mixer, 0.1 g of antioxidant 1010 was added, the temperature was raised to 150° C., melt blended at 60 rpm, mixed for 40 min, cooled to 40° C., and placed on a flat fluidizer for hot pressing. The hot pressing temperature was adjusted to 200° C., hot pressed for 10 min, and then cold pressed to obtain an agricultural greenhouse film.

[0050] Example 2

[0051] This embodiment provides a high-transmittance agricultural greenhouse film, which includes the following components in parts by weight: 60 parts of siloxane-modified PBAT, 40 parts of PLA, 3.5 parts of LDI, and 0.8 parts of antioxidant 1076;

[0052] The raw materials for preparing siloxane-modified PBAT specifically include the following components in parts by weight: 23 parts of 1,3-bis(3-chloropropyl)tetramethyldisiloxane, 26.5 parts of ethylene carbonate, 41.5 parts of p-dibenzoic acid, 16.5 parts of 1,4-butanediol, and 36.5 parts of adipic acid;

[0053] The preparation method of siloxane-modified PBAT specifically comprises the following steps:

[0054] S1. Add molecular sieves to a drying bottle, add THE, place the mixture on a vacuum pump and evacuate the mixture to dry the mixture. Take 2.3 g of 1,3-bis(3-chloropropyl)tetramethyldisiloxane and place it in a round-bottom flask. Add 23 mL of THE after dehydration and mix until 1,3-dichlorotetramethyldisiloxane is completely dissolved. Then, add 2.65 g of ethylene carbonate and mix well. Then, introduce flowing nitrogen and add 0.26 g of potassium carbonate. Stir at 50 rpm. After the reaction system is uniform, raise the temperature to 70°C and continue the reaction for 4 hours. After the reaction is cooled to room temperature, remove the excess solvent by distillation under reduced pressure. After washing three times with dichloromethane, place the mixture at 40°C and vacuum dry for 24 hours to obtain hydroxylated siloxane.

[0055] S2. The hydroxylated siloxane prepared in step S1 was placed in a three-necked flask, vacuum-dried at 40° C. for 1 hour, and then 1.65 g of 1,4-butanediol was added. After mixing, 4.15 g of terephthalic acid and 3.65 g of adipic acid were added. Under a flowing argon atmosphere, 35 mg of tetrabutyl titanate was added, and the temperature was raised to 180° C. for 12 hours. After the reaction mixture was cooled to room temperature, it was washed three times with anhydrous ethanol and deionized water in sequence, and then vacuum-dried at 50° C. for 12 hours to obtain a PBAT polymer monomer.

[0056] S3. The PBAT polymer monomer prepared in step S3 was placed in a flask, and after flowing nitrogen, the reaction system was fully dried. 33 mg of stannous octoate was added, and the temperature was raised to 230° C. for a pre-polycondensation reaction for 3 hours. The temperature was then continuously raised to 250° C. for a further polycondensation reaction. After the reaction was allowed to react for 8 hours, the reaction mixture was cooled to room temperature, washed repeatedly with anhydrous ethanol three times, and then dried in vacuo at 60° C. for 12 hours to obtain a siloxane-modified PBAT.

[0057] The present invention also provides a method for preparing a high-transmittance agricultural greenhouse film, which specifically comprises the following steps:

[0058] S4. Accurately weigh 12 g of siloxane-modified PBAT and 8 g of PLA, dry them at 60° C. for 2 h, transfer them to a dry flask, raise the temperature to 160° C., stir at 70 rpm, mix thoroughly, add 0.7 g of LDI, raise the temperature to 180° C., and blend for 30 min to obtain a copolymer;

[0059] S5. The copolymer prepared in step S4 was placed in an internal mixer, 0.16 g of antioxidant 1076 was added, the temperature was raised to 130° C., melt blended at 80 rpm, mixed for 60 min, cooled to 50° C., and placed on a flat fluidizer for hot pressing. The hot pressing temperature was adjusted to 190° C., hot pressed for 10 min, and then cold pressed to obtain an agricultural greenhouse film.

[0060] Example 3

[0061] This embodiment provides a high-transmittance agricultural greenhouse film, which includes the following components in parts by weight: 70 parts of siloxane-modified PBAT, 30 parts of PLA, 5 parts of PDI, and 1 part of antioxidant 1035;

[0062] The raw materials for preparing siloxane-modified PBAT specifically include the following components in parts by weight: 23 parts of 1,3-bis(chloromethyl)tetramethyldisiloxane, 22 parts of ethylene carbonate, 37 parts of p-dibenzoic acid, 25.5 parts of 1,4-butanediol, and 32.5 parts of adipic acid;

[0063] The preparation method of siloxane-modified PBAT specifically comprises the following steps:

[0064] S1. Add molecular sieves to a drying bottle, add THE and place it on a vacuum pump to evacuate and dry THE. Take 2.3g of 1,3-bis(chloromethyl)tetramethyldisiloxane and place it in a round-bottom flask. Add 15mL of THE after dehydration and mix until 1,3-dichlorotetramethyldisiloxane is completely dissolved. Then, add 2.2g of ethylene carbonate. After mixing evenly, introduce flowing nitrogen. Mix triethylamine and tetrahydrofuran to prepare a 1mol / L triethylamine solution. Take 2mL of the triethylamine solution and add it to the reaction system. Stir at 80rpm. After the reaction system is uniform, raise the temperature to 65°C and continue the reaction for 6h. After the reaction is cooled to room temperature, remove the excess solvent by distillation under reduced pressure. After washing three times with dichloromethane, place it at 40°C and vacuum dry for 24h to obtain hydroxylated siloxane.

[0065] S2. The hydroxylated siloxane prepared in step S1 was placed in a three-necked flask, vacuum-dried at 40° C. for 1 hour, and then 2.55 g of 1,4-butanediol was added. After mixing evenly, 3.7 g of terephthalic acid and 3.25 g of adipic acid were added. Under a flowing argon atmosphere, 33 mg of tetrabutyl titanate was added, and the temperature was raised to 190° C. for 10 hours. After the reaction mixture was cooled to room temperature, it was washed three times with anhydrous ethanol and deionized water in sequence, and then vacuum-dried at 50° C. for 12 hours to obtain a PBAT polymer monomer.

[0066] S3. The PBAT polymer monomer prepared in step S3 was placed in a flask, and after flowing nitrogen, the reaction system was fully dried. 26 mg of stannous octoate was added, and the temperature was raised to 240° C. for a preliminary polycondensation reaction for 2 hours. The temperature was then continuously raised to 260° C. for a further polycondensation reaction. After the reaction was allowed to react for 7 hours, the reaction mixture was cooled to room temperature, washed repeatedly with anhydrous ethanol three times, and then dried in vacuo at 60° C. for 12 hours to obtain a siloxane-modified PBAT.

[0067] This embodiment also provides a method for preparing a high-transmittance agricultural greenhouse film, which specifically includes the following steps:

[0068] S4. Accurately weigh 14 g of siloxane-modified PBAT and 6 g of PLA, dry them at 60° C. for 2 h, transfer them to a dry flask, raise the temperature to 170° C., stir at 80 rpm, mix thoroughly, add 1 g of PDI, raise the temperature to 190° C., and blend for 30 min to obtain a copolymer;

[0069] S5. Place the copolymer prepared in step S4 in an internal mixer, add 0.2 g of antioxidant 1035, increase the temperature to 140° C., perform melt blending at 70 rpm, mix for 50 min, cool to 45° C., place on a flat fluidizer for hot pressing, adjust the hot pressing temperature to 180° C., hot press for 10 min, and then cold press to obtain an agricultural greenhouse film.

[0070] Comparative Example 1

[0071] This comparative example provides an agricultural greenhouse film and a preparation method thereof. The only difference between the comparative example and Example 1 is that PLA is not included in the components and is replaced by PBAT in equal parts by weight. The remaining components and component contents are the same as those in Example 1.

[0072] Comparative Example 2

[0073] This comparative example provides an agricultural greenhouse film and a preparation method thereof. The difference between the comparative example and Example 1 is that the siloxane-modified PBAT in the components is replaced by the same weight portion of PBAT, and the remaining components and component contents are the same as those in Example 1.

[0074] Comparative Example 3

[0075] This comparative example provides an agricultural greenhouse film and a preparation method thereof, which differs from Example 1 only in that the siloxane-modified PBAT in the components is replaced by the same weight portions of PBAT and terminal hydroxyl polydimethylsiloxane, the mass ratio between the PBAT and the terminal hydroxyl polydimethylsiloxane is 2:1, and the terminal hydroxyl polydimethylsiloxane (CasNo: 156327-07-0) is purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. with the product number C303003. The remaining components and component contents are the same as those in Example 1.

[0076] Experimental Example 1

[0077] In this experimental example, the structure of the siloxane-modified PBAT prepared in step S3 of Example 1-3 was characterized. The siloxane-modified PBAT was measured by hydrogen nuclear magnetic resonance spectroscopy. A 15 mg sample was dissolved at room temperature in deuterated chloroform as a solvent and tetramethylsilane as an internal standard for 4 h. The test was performed using a solid-liquid dual-purpose nuclear magnetic resonance instrument.

[0078] Figure 1 This is the nuclear magnetic resonance hydrogen spectrum image of the siloxane-modified PBAT prepared in step S3 of Examples 1-3 of the present invention, wherein A is Example 1, B is Example 2, and C is Example 3. As shown in the figure, the absorption bands at δ = 7.83 and δ = 8.03 correspond to the resonance absorption of the four H atoms on the benzene ring, and the absorption band at δ = 0.15 corresponds to the resonance absorption of the hydrogen atoms in the methyl CH3- connected to Si in the Si-O-Si structure, indicating that the siloxane is connected to the polymer molecule of PBAT. In the chain, the difference between A, B, and C is that in B, absorption vibration peaks of methylene appear at δ=0.67, δ=1.53, and δ=4.13, corresponding to the resonance absorption of the three methylene hydrogen atoms on the three chloropropyl groups in the raw material 1,3-bis(3-chloropropyl)tetramethyldisiloxane; in C, the resonance absorption of the methylene hydrogen atoms on the chloromethyl group in 1,3-bis(chloromethyl)tetramethyldisiloxane appears at δ=3.42, while there is no resonance absorption peak corresponding to the hydrogen atom in A.

[0079] Experimental Example 2

[0080] This experiment tests the light transmittance of the agricultural greenhouse films prepared in Examples 1-3 and Comparative Examples 1-3 using an ultraviolet spectrophotometer. The wavelength is set to 500 nm, and a black opaque baffle is used as a reference to establish a baseline. Three replicates are performed.

[0081] Figure 2This is a graph showing the light transmittance results of the agricultural greenhouse films prepared by Examples 1-3 of the present invention and Comparative Examples 1-3. As shown in the figure, the light transmittance of the agricultural greenhouse films prepared by Examples 1-3 is between 72.7% and 75.2%, the light transmittance of the agricultural greenhouse film prepared by Comparative Example 1 is 55.7%, the light transmittance of the agricultural greenhouse film prepared by Comparative Example 2 is 48.6%, and the light transmittance of the agricultural greenhouse film prepared by Comparative Example 3 is 52.6%. The light transmittance of PBAT film is poor, generally between 40%-50%, while the light transmittance of PLA is better, generally above 80%. After blending PLA and PBAT, the optical properties of PBAT can be improved. However, due to the poor compatibility between PBAT and PLA, the improvement in optical properties after blending the two is not obvious. Embedding siloxane molecules into the PBAT polymer molecular chain can improve the interface performance between PLA and PBAT through polar groups. In the process of forming the greenhouse film, it can increase the entanglement between the molecular chains, hinder the crystallization during the film formation process, and thus improve the light transmittance of the film.

[0082] Experimental Example 3

[0083] In this experimental example, the mechanical properties of the agricultural greenhouse films prepared in Examples 1-3 and Comparative Examples 1-3 were tested. According to the provisions of GB / T 1040.1-2006 and GB / T 1040.3-2006, the tensile strength and elongation at break of the samples were measured according to the dumbbell shape. The tensile speed was set at 100 mm / min until the sample was broken.

[0084] Figure 3 The mechanical properties of agricultural greenhouse films prepared according to Examples 1-3 and Comparative Examples 1-3 of the present invention are shown in the figure. As shown in the figure, the agricultural greenhouse films prepared according to Examples 1-3 have outstanding mechanical properties. In the present invention, the polymer molecular chain of PBAT is modified to introduce a siloxane structure (Si-O-Si), providing a flexible chain end, which can significantly improve the toughness of the film. At the same time, it also solves the problem of poor compatibility between PLA and PBAT, thereby achieving a balance in various performance aspects of the agricultural greenhouse film.

[0085] Experimental Example 4

[0086] In this experimental example, the thermal stability of the agricultural greenhouse films prepared in Example 1 and Comparative Examples 1-3 was tested using a thermal synchronous analyzer to record the thermal weight loss.

[0087] Figure 4The thermal stability results of the agricultural greenhouse films prepared according to Example 1 of the present invention and Comparative Examples 1-3 are shown. As shown in the figure, the agricultural greenhouse film prepared according to Example 1 of the present invention has significantly higher thermal stability than that of Comparative Examples 1-3. Examples 1-3 of the present invention introduce Si-O-Si segment structures into the PBAT molecular chain. The main chain of PBAT is mainly composed of structures such as ester groups (-COO-), alkyl groups (CC), and aromatic groups (benzene rings). The carbon-carbon bond is an important component of the polymer backbone. The introduction of the Si-O-Si structure may have a certain steric effect and intermolecular interaction, and the Si-O bond has a higher bond energy and stronger stability.

[0088] While the embodiments of the present invention have been shown and described, it will be apparent to those skilled in the art that various changes, modifications, substitutions, and alterations can be made to the embodiments without departing from the principles and spirit of the invention.

[0089] The present invention and its embodiments are described above. Such description is not restrictive. The drawings show only one embodiment of the present invention, and actual applications are not limited thereto. In short, if a person skilled in the art is inspired by the above, and does not deviate from the purpose of the present invention, any method and embodiment similar to the technical solution without creative design shall fall within the scope of protection of the present invention.

Claims

1. A high-light-transmittance agricultural greenhouse film, characterized by: The agricultural greenhouse film comprises the following components in parts by weight: 50-70 parts of silicone-modified PBAT, 30-50 parts of PLA, 2-5 parts of chain extender, and 0.5-1 part of antioxidant; The raw materials for preparing the siloxane-modified PBAT specifically include the following components in parts by weight: 20-23 parts of dichlorosiloxane, 17.5-26.5 parts of ethylene carbonate, 33-41.5 parts of p-dibenzoic acid, 16.5-25.5 parts of 1,4-butanediol, and 30-36.5 parts of adipic acid; The preparation method of the siloxane-modified PBAT specifically comprises the following steps: S1. Dissolve dichlorosiloxane in THF, add ethylene carbonate, mix well, add a basic catalyst, and stir at 50-80 rpm. After the reaction system is uniform, introduce flowing argon gas, raise the temperature to 60-70° C., continue the reaction for 4-8 hours, cool, remove excess solvent by distillation under reduced pressure, and vacuum dry to obtain hydroxylated siloxane; S2. The hydroxylated siloxane prepared in step S1 is placed in a flask, p-dibenzoic acid, adipic acid and 1,4-butanediol are added, flowing argon is introduced, tetrabutyl titanate is added, the temperature is increased to 180-200° C., and the reaction is carried out for 8-12 hours. After the reaction is cooled to room temperature, a PBAT polymer monomer is obtained; S3. Add stannous octoate to the PBAT polymer monomer prepared in step S2, introduce flowing argon, raise the temperature to 230-250° C., and carry out a pre-polycondensation reaction for 2-3 hours. Then, raise the temperature to 250-270° C. and carry out a polycondensation reaction for 6-8 hours. The reaction mixture is cooled to room temperature, washed with anhydrous methanol, and dried to obtain a siloxane-modified PBAT.

2. The high-transmittance agricultural greenhouse film according to claim 1, characterized in that: The dichlorosiloxane includes at least one of 1,3-dichlorotetramethyldisiloxane, 1,3-bis(3-chloropropyl)tetramethyldisiloxane and 1,3-bis(chloromethyl)tetramethyldisiloxane.

3. The high-transmittance agricultural greenhouse film according to claim 2, characterized in that: The antioxidant includes at least one of antioxidant 1010 , antioxidant 1076 , antioxidant 1035 , and antioxidant 1330 .

4. The high-transmittance agricultural greenhouse film according to claim 3, characterized in that: The chain extender includes at least one of PDI, LDI, and HDI.

5. The high-transmittance agricultural greenhouse film according to claim 4, characterized in that: In step S1, the alkaline catalyst includes at least one of pyridine, triethylamine, potassium hydroxide, and potassium carbonate.

6. The high-transmittance agricultural greenhouse film according to claim 5, characterized in that: In step S1, the mass concentration of the dichlorosiloxane in THF is 0.1-0.2 g / mL; the added mass of the alkaline catalyst is 5-10% of the mass of the dichlorosiloxane.

7. The high-transmittance agricultural greenhouse film according to claim 6, characterized in that: In step S2, the added mass of tetrabutyl titanate is 0.75%-0.9% of the mass of terephthalic acid.

8. The high-transmittance agricultural greenhouse film according to claim 7, characterized in that: In step S3, the added mass of stannous octoate is 0.6%-0.8% of the mass of terephthalic acid.

9. A method for preparing a high-transmittance agricultural greenhouse film according to any one of claims 1 to 8, characterized in that: The specific steps include: S4. Vacuum-dry the siloxane-modified PBAT and PLA, raise the temperature to 160-180° C. under vacuum conditions, stir at 60-80 rpm, add a chain extender, continue to raise the temperature to 180-190° C., and blend for 20-30 minutes to obtain a copolymer; S5. Place the copolymer prepared in step S4 in an internal mixer, add an antioxidant, increase the temperature to 130-150° C., melt blend at a speed of 60-80 rpm, mix for 40-60 minutes, cool to 40-50° C., place in a mold, and hot-press mold at 180-200° C. After cooling, obtain an agricultural greenhouse film.

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