Degradable resin material, optical property regulator, optically-adjustable environment-friendly mulching film and processing method of optically-adjustable environment-friendly mulching film

Abstract

The invention discloses a degradable resin material, an optical property regulator, an optically-adjustable environment-friendly mulching film and a processing method of the optically-adjustable environment-friendly mulching film, and belongs to the field of degradable environment-friendly materials. The invention provides a degradable polyester resin material with a novel structure, namely polycaprolactone-co-lactide. The degradable polyester resin material is formed by performing ring-opening copolymerization on epsilon-caprolactone and lactide under the catalytic action of a symmetric binuclear Schiff base complex; the ratio of the average chain segment length of caprolactone to the average chain segment length of lactide in the resin material is (2-2.2): (2-2.2), which is close to that of an alternating copolymer. The compound can be used as an optical property regulator, and preparation of an environment-friendly mulching film with adjustable optical properties such as ultraviolet light absorbance, infrared light transmittance and haze can be realized under the condition that no dye or other coloring additives are used.

Description

Technical Field

[0001] The present invention belongs to the field of degradable environmentally friendly materials, and in particular relates to a degradable resin material, an optical property regulator, an optically adjustable environmentally friendly ground film and a processing method thereof. Background Art

[0002] As an essential piece of modern agricultural technology, mulch films improve the growing environment and significantly increase crop yields and product quality. With the advancement of science and technology and society, the performance requirements for mulch films are becoming increasingly stringent. In particular, with the continuous advancement of agricultural planting technology, it has been discovered that different crops have varying requirements for light intensity and soil temperature due to their different growth habits. For example, crops like corn, green peppers, watermelon, and eggplant are sun-loving and thrive in strong sunlight. Meanwhile, crops like cilantro, leeks, onions, ginger, wood ear mushrooms, mushrooms, and lettuce are shade-loving and thrive in low light conditions. They cannot tolerate strong sunlight. To meet the varying light intensity requirements of different crops, researchers have developed a range of mulch film products with varying colors and optical properties by adding dyes or other coloring additives to traditional mulch films. These products have, for a time, met the diverse needs of crops with different growth habits.

[0003] Traditional mulch films are typically made from non-degradable polyolefin polymers such as polyethylene and polyvinyl chloride. However, these films are thin, lightweight, difficult to recycle, and difficult to degrade. Long-term use of these materials creates an increasingly prominent "white pollution" problem. To mitigate the environmental impact of non-degradable mulch films, research and development of biodegradable and environmentally friendly mulch films has begun. In recent years, a growing number of biodegradable mulch film varieties have been developed, including polyester-based biodegradable mulch films. Building on the experience gained in developing traditional mulch films with varying colors, the addition of dyes or other coloring additives has enabled the development of environmentally friendly mulch films with varying optical properties.

[0004] However, there are also some problems with degradable mulch films prepared by adding dyes or other coloring additives. Among them, the addition of dyes or other coloring additives has a significant impact on the processing performance and mechanical properties of the degradable mulch film. Generally speaking, the existing degradable resin materials that can meet the requirements of mulch film processing have inferior film-forming performance and mechanical properties compared to non-degradable resin materials. The addition of dyes or other coloring additives will further reduce the processing and mechanical properties of the mulch film. It can be seen that the traditional process of adding dyes or other coloring additives has obvious shortcomings in producing degradable mulch films with adjustable optical properties. The development of degradable resin materials with adjustable optical properties and the finding of more economical, safe, and environmentally friendly methods for regulating the optical properties of degradable mulch films have important social value and economic significance. Summary of the Invention

[0005] In view of this, the present invention provides a degradable resin material, an optical property regulator, an optically adjustable environmentally friendly mulch film and a processing method thereof. The degradable resin material provided by the present invention can be used to make an optical property regulator for a degradable mulch film, and further can be processed to prepare a degradable mulch film with adjustable optical properties and good mechanical properties.

[0006] The present invention provides a degradable resin material, which is polycaprolactone-co-lactide, formed by ring-opening copolymerization of ε-caprolactone and lactide under the catalysis of a symmetrical binuclear Schiff base complex;

[0007] In the degradable resin material, the ratio of the average chain length of caprolactone to the average chain length of lactide is 2-2.2:2-2.2.

[0008] In an embodiment of the present invention, the symmetric binuclear Schiff base complex is a symmetric binuclear Schiff base aluminum complex, preferably having a structure of Formula 1:

[0009]

[0010] In an embodiment of the present invention, the ring-opening copolymerization is carried out in the presence of an initiator, the reaction temperature of the ring-opening copolymerization is 120-130° C., and the reaction time is 6-8 hours.

[0011] The present invention provides an optical property modifier, comprising a degradable base resin and an optical functional component; the degradable base resin is one or more of PCL, PLA and PBAT;

[0012] The optical functional component is the degradable resin material mentioned above.

[0013] In an embodiment of the present invention, the optical property modifier further comprises a filler, and the filler is preferably nano-montmorillonite.

[0014] In an embodiment of the present invention, the optical property modifier is prepared by screw melt blending and extrusion granulation.

[0015] The present invention provides an optically adjustable environmentally friendly ground film, comprising a degradable polyester and an additive; the degradable polyester is one or more of PCL, PLA and PBAT;

[0016] The additive is the optical property modifier mentioned above.

[0017] In an embodiment of the present invention, the mass ratio of the degradable polyester to the optical property additive is 17-100:30-83.

[0018] In an embodiment of the present invention, the thickness of the environmentally friendly ground film is 10 to 15 microns; the haze of the environmentally friendly ground film is 69% to 91%.

[0019] The present invention provides a method for processing the aforementioned environmentally friendly mulch film, comprising the following steps:

[0020] The optical property regulator and the degradable polyester resin particles are weighed and mixed, and then subjected to film blowing processing to obtain the optically adjustable environmentally friendly ground film.

[0021] The present invention provides a novel biodegradable polyester resin material - polycaprolactone-co-lactide (PCLA), which is formed by ring-opening copolymerization of ε-caprolactone and lactide under the catalysis of a symmetrical binuclear Schiff base complex; the ratio of the average chain length of caprolactone to the average chain length of lactide in the resin material is 2-2.2:2-2.2, approaching that of an alternating copolymer. It can be used as an optical property modifier, and can achieve the preparation of environmentally friendly ground films with adjustable optical properties such as ultraviolet light absorbance, infrared light transmittance, and haze without the use of dyes or other coloring additives. The present invention regulates the average intramolecular chain length of the caprolactone-lactide copolymer, which can inhibit the microscopic phase separation behavior of the copolymer molecules, making this copolymer PCLA, as a solubilizer in the blending system, have better compatibility with biodegradable polyesters such as PLA, PCL, and PBAT, thereby enabling the optical property modifier obtained by blending the PCLA described in this application with the biodegradable polyester to regulate the optical properties of the film material.

[0022] Finally, the present invention can adjust the optical properties of the blow-molded mulch film by varying the mixing ratio of the optical property modifier and a resin such as PBAT. Therefore, the environmentally friendly mulch film based on the biodegradable resin material of the present invention exhibits excellent mechanical properties and adjustable optical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Comparative Example 1: Stannous octoate catalyzes the copolymerization of caprolactone and lactide at a ratio of 50:50 to synthesize PCLA. 13 C NMR spectrum;

[0024] Figure 2 The copolymerization of caprolactone and lactide in a ratio of 50:50 catalyzed by the large sterically hindered binuclear aluminum complex in Example 1 to synthesize PCLA 13 C NMR spectrum;

[0025] Figure 3 The UV-visible absorption spectra of the degradable mulch films with different contents of the optical property modifiers in the examples are shown;

[0026] Figure 4 The infrared light transmittance spectra of the degradable mulch films with different contents of the optical property regulator in the examples are shown. DETAILED DESCRIPTION

[0027] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, the technical solutions of the present invention are described in detail below in conjunction with specific embodiments. The described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0028] The present invention provides a biodegradable resin material, which is polycaprolactone-co-lactide, formed by ring-opening copolymerization of ε-caprolactone and lactide under the catalysis of a symmetrical binuclear Schiff base complex;

[0029] In the degradable resin material, the ratio of the average chain length of caprolactone to the average chain length of lactide is 2-2.2:2-2.2.

[0030] The degradable resin material provided by the present invention is a polycaprolactone-co-lactide with a new structure, which can be used to make an optical property regulator for degradable mulch, and further can be processed to prepare degradable and environmentally friendly mulch products with adjustable optical properties and good mechanical properties.

[0031] In the embodiment of the present invention, a symmetrical binuclear Schiff base complex (mainly a binuclear aluminum complex) is used to catalyze the ring-opening copolymerization of ε-caprolactone (ε-CL) and lactide (LA) to obtain a novel copolyester biodegradable material, namely the biodegradable resin material, which has a caprolactone ring-opening structure repeating unit (caprolactone unit) and a lactide ring-opening structure repeating unit (lactide unit). The molecular structure is shown below, where x and y are both the degree of polymerization;

[0032]

[0033] The lactide can be divided into left-handed lactide (L-lactide), D-lactide, and meso-lactide (meso-lactide). The symmetrical binuclear Schiff base complex is preferably a highly sterically hindered binuclear aluminum complex, with aluminum (Al) as the central metal ion and ligands containing Schiff base structures (imino group -CH=N-), benzene rings, and other groups. This can inhibit the polymerization activity of lactide and reduce the difference in reactivity between lactide and caprolactone.

[0034] Furthermore, the symmetrical binuclear Schiff base complex has a structure of Formula 1. The specific preparation process is as follows: 40 ml of an ethanol solution of substituted salicylaldehyde (0.4 mol / L) is dropwise added to 40 ml of an ethanol solution of pentaerythritol (0.1 mol / L) under magnetic stirring. After the dropwise addition is completed, the mixture is heated under reflux and reacted for 12 hours to allow the pentaerythritol (a commercially available analytically pure reagent) and substituted salicylidine aldehydes (a commercially available analytically pure reagent) with different substituent groups to fully react and synthesize the Schiff base ligand. After the reaction is completed, the solvent is removed by rotary evaporation and the complex is further purified by recrystallization from a mixed solvent of ethanol and dichloromethane. The substituent group at the ortho position of the ligand can be different: it can be tert-butyl, trimethylsilyl, or tert-butyldimethylsilyl (TBDMS), and is preferably tert-butyldimethylsilyl. Take 1 ml of toluene solution (0.1 mol / L) of Schiff base ligand, add 5 ml of toluene solution (0.04 mol / L) of triethylaluminum AlEt3 (commercial analytical grade reagent) under magnetic stirring at room temperature, then heat the system to 70 ° C and stir for 12 hours to obtain

[0035] The catalyst shown in Formula 1;

[0036]

[0037] Specifically, in an embodiment of the present invention, ε-caprolactone and lactide monomers can be added to a polymerization reactor, preferably repeatedly vacuuming and nitrogen-filling operations to fully replace the air in the reactor. Then, the reactor is preferably heated until the temperature of the material in the reactor reaches 120-130°C, preferably 130°C, and the catalyst represented by Formula 1 and the initiator (preferably n-butanol) are injected into the reactor, and the mixture is fully mixed to initiate the ring-opening copolymerization reaction. The ring-opening polymerization time can be controlled to be 6-8 hours. The amount of the catalyst can be 0.01% to 0.1% of the total mass of the monomers, for example, 0.05%. The amount of the initiator can be 0.01% to 0.05% of the total mass of the monomers, for example, 0.02%. In a preferred embodiment, the molar ratio of the monomers ε-caprolactone to lactide is 1:1.

[0038] After the polymerization reaction is completed, an oil pump can be used to evacuate the product to remove unreacted ε-caprolactone and lactide monomers, and then the product can be extruded and granulated to obtain a biodegradable polyester material PCLA with a new structure.

[0039] In the new structure PCLA synthesized in the embodiment of the present invention, the two monomers are more evenly distributed; wherein the ratio of the average segment length of caprolactone to the average segment length of lactide is 2-2.2:2-2.2.

[0040] In some specific examples, the PCLA (50:50) synthesized by this method has a number-average molecular weight of 79 kg / mol, a weight-average molecular weight of 130 kg / mol, and a molecular weight distribution index (PDI) of ≈1.66. The measured molar ratio of CL:LA in the copolymer is 51:49, with an average LA segment length of 2.1 and an average CL segment length of 2.2. The PCLA prepared in the present invention using a highly hindered binuclear aluminum complex catalyst has a significant proportion of LA and CL molecular segment lengths approaching 2, similar to an alternating copolymer, which is beneficial for applications in membrane materials and other applications.

[0041] Alternating copolymers are copolymers in which two monomers are arranged in a strictly alternating pattern along the macromolecular chain. The reactivity ratio of the copolymerization reaction, r1 = r2 = 1, means the mole fraction of each monomer in the copolymer is 0.5. The reactivity ratio is the ratio of the two reactivity factors in competitive polymerization.

[0042] The present invention provides an optical property modifier, comprising a degradable base resin and an optical functional component; the degradable base resin is one or more of polycaprolactone (PCL), polylactic acid (PLA), and polybutylene terephthalate-adipate (PBAT); and the optical functional component is the degradable resin material described above.

[0043] By using the optical property regulator of the present invention, it is possible to prepare an environmentally friendly ground film with adjustable optical properties such as ultraviolet light absorbance, infrared light transmittance and haze without using dyes or other coloring additives.

[0044] The optical property modifier described in the embodiment of the present invention includes a degradable matrix resin, which is preferably a matrix resin material composed of three types of PCL, PLA and PBAT. In a preferred embodiment, the mass ratio of PBAT, PLA and PCL can be 70:10:5.

[0045] In this embodiment of the present invention, the aforementioned biodegradable resin material PCLA is blended with PCL, PLA, PBAT, and nano-montmorillonite in appropriate proportions, and then extruded and granulated to produce a novel biodegradable resin masterbatch, which can be used as an optical property modifier for biodegradable mulch films. For example, the molecular weight of PCL is 50,000-100,000, the molecular weight of PLA is 50,000-200,000, and the molecular weight of PBAT is 50,000-200,000.

[0046] Preferably, the optical property modifier also includes a filler to enhance performance and reduce costs. The filler is preferably nano-montmorillonite. The present invention does not specifically limit its specific type; conventional nanoparticles can be used. In a preferred embodiment, the mass ratio of the filler to the optically functional component PCLA is 2:1. The preferred nano-montmorillonite can be 400 to 6000 mesh. All raw materials, including the matrix resin, are commercially available and are not specifically limited.

[0047] After the above raw materials are stirred and mixed, a twin-screw extruder can be used in a specific embodiment of the present invention for melt blending and extrusion granulation, with the melt temperature preferably being 135-170°C. Preferably, the twin-screw extruder has 1-11 sections, with temperatures of 135°C, 145°C, 165°C, 170°C, 170°C, 170°C, 170°C, 170°C, 170°C, 170°C, and 167°C, respectively. The die temperature is 165°C, and the screw speed is 150-155 rpm. After stable operation, the extruder melt pressure can be 10-15 MPa. The melt-extruded blended resin material is subjected to conventional strand drawing, air cooling and pelletizing to obtain the resin masterbatch of the optical property modifier. The resin masterbatch particle size can be 3-6 mm, which can meet the processing requirements of conventional processing equipment. The preferred proportion of PCLA in the masterbatch is 5%.

[0048] An embodiment of the present invention provides an optically adjustable environmentally friendly ground film, comprising a degradable polyester and an additive; the degradable polyester is one or more of PCL, PLA and PBAT, preferably PBAT; and the additive is the optical property modifier described above.

[0049] The present invention preferably utilizes such an optical property modifier to be blended with a degradable polyester (PBAT) and then blown into a film to form a degradable mulch film with adjustable optical properties (referred to as an optically adjustable environmentally friendly mulch film). By varying the ratio of the optical property modifier to PBAT, degradable mulch films with varying optical properties can be prepared. Accordingly, an embodiment of the present invention provides a method for processing the environmentally friendly mulch film as described above, comprising the following steps: weighing and mixing the optical property modifier with degradable polyester resin particles, such as PBAT, and performing a film blowing process to produce the optically adjustable environmentally friendly mulch film.

[0050] PLA, also known as polylactide, is biodegradable, just like polycaprolactone. However, the present invention prefers biodegradable PBAT, which exhibits excellent mechanical and processing properties, particularly relatively good toughness. In the embodiments of the present invention, the PBAT typically has a molecular weight distribution in the range of 50,000 to 200,000, and commercially available PBAT suitable for blown film processing is preferred.

[0051] Moreover, the mass ratio of the degradable polyester and the optical property additive is preferably 17-100:30-83, for example, 17:83, 30:70, 50:50, 70:30, etc. The optical property regulator is used in degradable mulch films to adjust the optical properties of the mulch films obtained by blow molding the blended materials at different mixing ratios, wherein the new structural polymer PCLA can also act as a compatibilizer. For example, if the melt strength is large and the rebound is high, the film bubble cannot be blown up. The embodiment of the present invention improves the film blowing effect through formula adjustment, and can be used for film blowing processing. Preferably, the film blowing temperature is 170-230°C; the screw speed is 25-150rpm; the residence time is 1-3.5min; and the pulling speed is 5-12 m / min.

[0052] Under other conditions, problems such as uneven film thickness, unstable bubbles, easy rupture, and poor opening can easily arise. The present invention, through extensive formulation development and testing, combined with exploration and optimization of film blowing processes, ultimately achieves optimized performance while simultaneously controlling film processing costs. In some embodiments, the environmentally friendly film can be 10 to 15 microns thick, or even 11 to 14 microns thick; the width is not limited.

[0053] Traditionally, biodegradable mulch films with adjustable optical properties are prepared by adding dyes or other coloring additives. This, on the one hand, affects the film's mechanical properties. More importantly, the organic luminescent molecules or metal ions contained in these additives can remain in the soil after the mulch's resin degrades. Over time, these organic luminescent molecules and metal ions accumulate and contaminate the soil microenvironment. Furthermore, these organic luminescent molecules and metal ions are washed away by rainwater and enter the water cycle, including rivers, lakes, and even the ocean, posing unforeseen environmental risks.

[0054] The environmentally friendly ground film described in the embodiment of the present invention has good mechanical properties. In addition, it does not contain coloring additives such as dyes, the haze can be 69% to 91%, and the optical properties such as light absorption transmittance can be adjusted; it is degradable, more environmentally friendly, safe and economical.

[0055] To further illustrate the present invention, the present invention is described in detail below with reference to the following examples. In the examples, all raw reagents and materials are commercially available, and the experimental methods without specific experimental conditions are conventional methods and conditions well known in the art.

[0056] Comparative Example 1

[0057] Experiments on ring-opening polymerization of caprolactone and lactide using stannous octoate catalyst:

[0058] 44.2 kg of ε-caprolactone and 55.8 g of lactide were added to a 200 L polymerization reactor. Vacuuming and nitrogen filling were repeated several times to fully replace the air in the reactor. The reactor was then heated to a temperature of 130°C. 50 g of stannous octoate catalyst and 20 g of n-butanol were added to the reactor and thoroughly mixed to initiate a ring-opening copolymerization reaction. The polymerization was controlled to proceed for 7.5 hours.

[0059] according to Figure 1 The carbon NMR spectrum shown ( 13 C NMR analysis reveals that the ratio of CCC and LLLLLL in this catalytic system is significantly greater than the alternating segments of the two, demonstrating that the PCLA copolymer obtained from this system contains longer PLA and PCL segments. Table 1 shows that the PCLA (50:50) synthesized using this method has a number-average molecular weight of 69 kg / mol, a weight-average molecular weight of 117 kg / mol, a molecular weight distribution index (PDI) of ≈1.7, a measured CL:LA monomer ratio of 51:49, an average LA segment length of 3.9, and an average CL segment length of 4.2. This indicates that PCLA produced using stannous octoate catalysis has a significant proportion of LA and CL molecular segments with lengths exceeding 4, with the presence of two longer segments within the molecule, which readily forms a phase-separated structure.

[0060] Under the catalysis of stannous octoate, the polymerization reaction reactivity rates of the two monomers are quite different, with lactide reacting faster and caprolactone reacting slower. Most of the polymerization in the early stage is lactide, and most of the polymerization in the later stage is caprolactone. The resulting copolymer structure is: one end is mainly PLA molecular chain fragments, the other end is mainly PCL molecular chain fragments, and some irregular gradient molecular structures with alternating structures of the two monomers are doped in the middle.

[0061] Table 1. Molecular weight and molecular structure of PCLA synthesized by stannous octoate-catalyzed copolymerization of caprolactone and lactide (50:50)

[0062]

[0063] Further experimental results show that the PCLA obtained by stannous octoate catalyzed copolymerization, when added to the PLA and PCL blend system, has unsatisfactory compatibility and toughening effects and is difficult to meet the requirements of ground film processing.

[0064] Example 1

[0065] The typical PCLA preparation and synthesis process is as follows: 44.2 kg of ε-caprolactone and 55.8 kg of lactide are added to a 200-liter polymerization reactor. The reactor is then vacuumed and filled with nitrogen three times to fully displace the air in the reactor. The reactor is then heated to a temperature of 130°C. 50 g of the catalyst represented by Molecular Formula 1 and 20 g of n-butanol initiator are then injected into the reactor and thoroughly mixed to initiate a copolymerization reaction. The polymerization time is controlled to 7.5 hours. After the polymerization reaction is completed, an oil pump is used to vacuumize the product and devolatilize it to remove unreacted ε-caprolactone and lactide monomers. The product is then extruded and pelletized to produce the novel structurally biodegradable polyester material, PCLA.

[0066] The two monomers in the synthesized new structure PCLA are more evenly distributed, e.g. Figure 2 shown 13 C NMR. It can be seen that the ratio of CCC and LLLLLL under the action of this catalyst is significantly reduced, indicating that the degree of alternation of the two monomers in the new structure PCLA molecular chain is significantly higher than that of the stannous octoate catalytic system.

[0067] Table 2 shows that the PCLA (50:50) synthesized using this method has a number-average molecular weight of 79 kg / mol, a weight-average molecular weight of 130 kg / mol, a molecular weight distribution index (PDI) of 1.65, a measured CL:LA monomer ratio of 51:49, an average LA segment length of 2.1, and an average CL segment length of 2.2. These results indicate that PCLA produced by copolymerization catalyzed by a highly hindered binuclear aluminum complex has a significant proportion of LA and CL molecular segment lengths approaching 2, similar to an alternating copolymer.

[0068] Table 2. Molecular weight and molecular structure of PCLA catalyzed by large steric hindrance binuclear aluminum complexes

[0069]

[0070] Example 2

[0071] A typical preparation process for the optical property modifier is as follows: 5 kg of PCLA (homemade, molecular weight 80,000-100,000) prepared in Example 1, 5 kg of PCL (commercially available, molecular weight 50,000-80,000), 10 kg of PLA (commercially available, molecular weight 120,000-150,000), 70 kg of PBAT (commercially available, molecular weight 80,000-100,000), and 10 kg of nano-montmorillonite (commercially available, 1000-1500 mesh) are stirred and mixed, and then added to a Nanjing Keya AK36 twin-screw extruder for melt extrusion and granulation. The temperatures of extruder sections 1-11 are 135° C., 145° C., 165° C., 170° C., 170° C., 170° C., 170° C., 170° C., 170° C., 170° C., and 167° C., respectively; the die temperature is 165° C., the screw speed is 154 rpm, and after stable operation, the extruder melt pressure is 12 MPa. The melt-extruded blended resin is subjected to strip drawing, air cooling and pelletizing to obtain the resin masterbatch of the optical property modifier; the particle size of the resin masterbatch is 3-6 mm.

[0072] Example 3

[0073] Environmentally friendly mulch film with adjustable optical properties (1): 83 parts by weight of optical property modifier resin masterbatch and 17 parts by weight of PBAT resin particles (commercially available, molecular weight ~100,000) were uniformly mixed, added to an extruder for hot melt extrusion, blown into a 1.2-meter-wide degradable mulch film, and rolled. The thickness of the obtained degradable mulch film was 11 microns, and its mechanical properties, haze, and visible light transmittance were detailed in Table 3. The film blowing temperature was 170-230°C; the screw speed was 25-150 rpm; the residence time was 1-3.5 min; and the pulling speed was 5-12 m / min. The following processes were the same.

[0074] Example 4

[0075] Environmentally friendly mulch film with adjustable optical properties (2): 70 parts by weight of optical property modifier resin masterbatch and 30 parts by weight of PBAT resin particles were uniformly blended, added to an extruder for hot melt extrusion, blown into a 1.2-meter-wide degradable mulch film, and rolled. The resulting degradable mulch film had a thickness of 12 μm. Details of mechanical properties, haze, and visible light transmittance are shown in Table 3.

[0076] Example 5

[0077] Environmentally friendly mulch film with adjustable optical properties (3): 50 parts by weight of optical property modifier resin masterbatch and 50 parts by weight of PBAT resin particles were uniformly blended, added to an extruder for hot melt extrusion, blown into a 1.2-meter-wide degradable mulch film, and rolled. The resulting degradable mulch film had a thickness of 13 μm. Mechanical properties, haze, and visible light transmittance are detailed in Table 3.

[0078] Example 6

[0079] Environmentally friendly mulch film with adjustable optical properties (4): 30 parts by weight of optical property modifier resin masterbatch and 70 parts by weight of PBAT resin particles were uniformly blended, added to an extruder for hot melt extrusion, blown into a 1.2-meter-wide degradable mulch film, and rolled. The resulting degradable mulch film had a thickness of 14 μm. Mechanical properties, haze, and visible light transmittance are detailed in Table 3.

[0080] Comparative Example 2 (Comparative Example)

[0081] 100 parts by weight of PBAT resin particles were added to an extruder for hot melt extrusion, blown, and processed into a 1.2-meter-wide biodegradable mulch film, which was then rolled. The resulting biodegradable mulch film had a thickness of 12 microns. Mechanical properties (electronic tensile testing machine), haze (TH-100 haze meter), and visible light transmittance (UV-visible spectrometer) were measured using conventional methods in the field, as shown in Table 3.

[0082] Table 3. Thickness, mechanical properties, haze, and visible light transmittance of biodegradable mulch films with different component ratios

[0083] Sample name Example 3 Example 4 Example 5 Example 6 Comparative Example 2 Optical property modifiers 83 copies 70 servings 50 servings 30 servings 0 copies PBAT 17 servings 30 servings 50 servings 70 servings 100 copies thickness 11 microns 12 microns 13 microns 14 microns 12 microns Longitudinal tensile strength 15.2MPa 14.8MPa 15.1MPa 13.2MPa 12.9MPa Longitudinal elongation at break 370％ 342％ 295％ 269％ 243％ Transverse tensile strength 15.9MPa 14.2MPa 15.4MPa 13.1MPa 10.1MPa Transverse elongation at break 568％ 538％ 499％ 467％ 412％ Visible light transmittance 89.8％ 90.0％ 90.0％ 89.2％ 89.5％ Haze 69.3％ 79.2％ 85.3％ 90.4％ 90.9％

[0084] Table 3 shows that the novel biodegradable resin material PCLA provided by the present invention, as a functional component of an optical property modifier, has little effect on the visible light transmittance of biodegradable mulch films, but can alter the haze of the biodegradable mulch films. As the amount of the added optical property modifier of the biodegradable resin material decreases from 83 parts to 0 parts, the haze of the biodegradable mulch films obtained by blown film processing increases from 69.3% to 90.9%. This demonstrates that the novel biodegradable resin material provided by the present invention, when used as an optical property modifier, can modulate the haze of biodegradable mulch films.

[0085] Figure 3 The UV-visible absorption spectra of degradable mulch films containing different amounts of optical property modifiers are given. Figure 3It can be seen that within the wavelength range of 200-300nm, as the addition amount of the optical property regulator decreases from 83 parts to 0 parts, the ultraviolet light absorption of the degradable mulch gradually decreases; within the wavelength range of 300-400nm, as the addition amount of the optical property regulator decreases from 83 parts to 50 parts, the ultraviolet light absorption of the degradable mulch first increases, and then the addition amount of the optical property regulator further decreases from 50 parts to 0 parts, the ultraviolet light absorption of the degradable mulch gradually decreases; within the wavelength range of 400-520nm, as the addition amount of the optical property regulator decreases from 83 parts to 50 parts, the ultraviolet light absorption of the degradable mulch first increases, and then the addition amount of the optical property regulator further decreases from 50 parts to 0 parts, the ultraviolet light absorption of the degradable mulch gradually decreases. Within the wavelength range of 520-800nm, as the added amount of optical property regulator decreases from 83 parts to 50 parts, the ultraviolet light absorption of the degradable mulch film is basically the same, and when the added amount of optical property regulator further decreases from 30 parts to 0 parts, the ultraviolet light absorption of the degradable mulch film is basically the same, and slightly lower than that of the degradable mulch film samples with the added amount of optical property regulator ≥50 parts; within the wavelength range of 520-800nm, as the added amount of optical property regulator decreases from 83 parts to 0 parts, the ultraviolet light absorption of the degradable mulch film is basically the same.

[0086] Figure 4 The changes in infrared light transmittance of degradable mulch films containing different amounts of optical property modifiers are given. Figure 4 You can see: wave number 400~1800cm -1 Within the range, the change of the added amount of optical property modifier has little effect on the infrared light transmittance of the degradable mulch film; the wave number is 1800~2800cm -1 In the range of 2800-3050 cm-1, as the addition amount of optical property modifier decreases from 83 to 0, the infrared transmittance of the degradable mulch film gradually decreases. -1 In the range of 1.5-2.5 nm, as the addition amount of optical property modifier decreases from 83 to 0, the infrared transmittance of the degradable mulch film decreases, but not significantly; the wave number is 3050-800 cm -1 Within this range, as the amount of optical property regulator added decreased from 83 parts to 0 parts, the infrared light transmittance of the degradable mulch film showed a significant downward trend.

[0087] The present invention can prepare a biodegradable mulch film with an optical property adjustment function without adding dyes or other coloring additives, and has important social value and economic significance.

[0088] The description of the above embodiments is only used to help understand the method of the present invention and its core idea. It should be noted that for those skilled in the art, without departing from the principles of the present invention, several improvements and modifications may be made to the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention. The above description of the disclosed embodiments enables professionals in this field to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A biodegradable resin material, polycaprolactone-co-lactide, characterized in that: It is formed by the ring-opening copolymerization of ε-caprolactone and lactide under the catalysis of a symmetrical binuclear Schiff base complex; In the degradable resin material, the ratio of the average segment length of caprolactone to the average segment length of lactide is 2-2.2:2-2.

2.

2. The degradable resin material according to claim 1, characterized in that: The symmetrical binuclear Schiff base complex is a symmetrical binuclear Schiff base aluminum complex, preferably having a structure of Formula 1:

3. The degradable resin material according to claim 2, characterized in that: The ring-opening copolymerization is carried out in the presence of an initiator, the reaction temperature of the ring-opening copolymerization is 120-130° C., and the reaction time is 6-8 hours.

4. An optical property modifier, characterized in that: It includes a degradable matrix resin and an optical functional component; the degradable matrix resin is one or more of PCL, PLA and PBAT; The optical functional component is the degradable resin material according to any one of claims 1 to 3.

5. The optical property modifier according to claim 4, characterized in that The optical property modifier further comprises a filler, and the filler is preferably nano-montmorillonite.

6. The optical property modifier according to claim 4, characterized in that The optical property regulator is prepared by screw melt blending and extrusion granulation.

7. An optically adjustable environmentally friendly ground film, characterized in that: Comprising a degradable polyester and an additive; the degradable polyester is one or more of PCL, PLA and PBAT; The additive is the optical property modifier according to any one of claims 4 to 6.

8. The environmentally friendly ground film according to claim 7, characterized in that: The mass ratio of the degradable polyester to the optical property additive is 17-100:30-83.

9. The environmentally friendly ground film according to claim 7, characterized in that: The thickness of the environmentally friendly ground film is 10 to 15 microns; the haze of the environmentally friendly ground film is 69% to 91%.

10. The method for processing the environmentally friendly ground film according to any one of claims 7 to 9, comprising the following steps: The optical property regulator and the degradable polyester resin particles are weighed and mixed, and then subjected to film blowing processing to obtain the optically adjustable environmentally friendly ground film.

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