Biodegradable composition as well as preparation method and application thereof

Abstract

The invention provides a biodegradable composition as well as a preparation method and application thereof, and the biodegradable composition comprises the following components in parts by weight: 50-93 parts of biodegradable polyester, 1-15 parts of polylactic acid, 5-30 parts of starch and 1-10 parts of plasticizer. The glass transition temperature of the polylactic acid is less than or equal to 62 DEG C; the weight-average molecular weight of the biodegradable polyester is 100,000 to 200,000 Da; the intrinsic viscosity of the biodegradable polyester is 1.10-1.45 dL / g after the biodegradable polyester is boiled in water at 95 DEG C for 12 hours. According to the present invention, the biodegradable composition has good mechanical property, and the film prepared from the composition has excellent puncture resistance and excellent tear resistance, such that the durability of the film is improved.

Description

Technical Field

[0001] This invention belongs to the field of engineering plastics technology, specifically relating to a biodegradable composition, its preparation method, and its application. Background Technology

[0002] With increasing emphasis on environmental protection, the environmental problems caused by traditional non-degradable plastic materials such as polyethylene (PE) are becoming more and more prominent. Biodegradable materials, because they can be broken down by microorganisms into harmless substances such as carbon dioxide and water in the natural environment, have become an ideal alternative to traditional plastics. Among them, blends of biodegradable polyester, polylactic acid, and starch have received widespread attention because they combine biodegradability with a certain bio-based content, effectively contributing to carbon reduction.

[0003] However, in practical applications, the puncture resistance of such biodegradable materials is relatively weak. Furthermore, with industry development, lightweighting and thinning are major trends in the future production of biodegradable films. This trend further challenges the puncture resistance of biodegradable films, limiting their application in carrying items with a certain degree of sharpness, such as supermarket shopping bags, logistics and express delivery bags, garbage bags, and industrial packaging bags. While in the traditional PE industry, the puncture resistance of films can be improved by adding metallocene polyethylene (mPE) or irradiated linear low-density polyethylene (LLDPE, i.e., xPE) through blending, or by using other non-degradable reinforcing and toughening agents, this is not permitted in the biodegradable industry.

[0004] To address this issue, the industry currently employs two main approaches: reducing the starch content in degradable materials or even using starch-free fillers, and utilizing multilayer membrane structures. Reducing starch content directly lowers the bio-based content of the blend, weakening its carbon reduction properties and increasing costs. Multilayer membrane structures, on the other hand, place excessive demands on equipment, leading to high costs and reduced efficiency. Therefore, enhancing the puncture resistance of the membrane while maintaining puncture and tear strength has become a critical technical challenge. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a biodegradable composition, its preparation method, and its application. The biodegradable composition exhibits good puncture resistance and transverse and longitudinal tear resistance, and also demonstrates good biocompatibility.

[0006] To achieve this objective, the present invention adopts the following technical solution: In a first aspect, the present invention provides a biodegradable composition comprising, by weight, 50-93 parts of biodegradable polyester, 1-15 parts of polylactic acid, 5-30 parts of starch and 1-10 parts of plasticizer; wherein the glass transition temperature of the polylactic acid is ≤62°C; the weight-average molecular weight of the biodegradable polyester is 100,000-200,000 Da; and the intrinsic viscosity of the biodegradable polyester after boiling in water at 95°C for 12 hours is 1.10-1.45 dL / g.

[0007] In this invention, 50 to 93 parts of biodegradable polyester can be, for example, 50 parts, 55 parts, 60 parts, 65 parts, 70 parts, 75 parts, 80 parts, 85 parts, 90 parts, 93 parts, or any range of the above values.

[0008] In this invention, 1 to 15 parts of polylactic acid can be, for example, 1 part, 2 parts, 3 parts, 4 parts, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, 11 parts, 12 parts, 13 parts, 14 parts, 15 parts, or any range of the above values.

[0009] In this invention, 5 to 30 parts of starch can be, for example, 5 parts, 6 parts, 8 parts, 10 parts, 12 parts, 14 parts, 16 parts, 18 parts, 20 parts, 22 parts, 26 parts, 28 parts, 30 parts, or any range of the above values.

[0010] In this invention, 1 to 10 parts of plasticizer can be, for example, 1 part, 1.5 parts, 2 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts, 4.5 parts, 5 parts, 5.5 parts, 6 parts, 6.5 parts, 7 parts, 7.5 parts, 8 parts, 8.5 parts, 9 parts, 9.5 parts, 10 parts, or any range between the above values.

[0011] In this invention, the glass transition temperature of polylactic acid is ≤62℃, for example, it can be 62℃, 61℃, 60℃, 59℃, 58℃, 57℃, 56℃, 55℃ or any of the above values, preferably ≤60℃.

[0012] In this invention, by precisely controlling the glass transition temperature of polylactic acid (PLA), the movement state of its molecular chains can be adjusted. When controlled within a specific range, the PLA molecular chains can remain in an amorphous state. The biodegradable polyester used in this invention is in a semi-crystalline state. The amorphous state of PLA and the semi-crystalline state of polyester form a more compatible mixed system. The PLA molecular chains can form a tighter physical entanglement with the polyester molecular chains, effectively transferring stress and thus enhancing the overall mechanical properties of the material. Simultaneously, it can disperse stress, prevent stress concentration, and further improve the material's puncture resistance and tear strength.

[0013] In this invention, the glass transition temperature of polylactic acid can be determined by the following method: using a DSC204 thermal analyzer from Netzsch, Germany, under nitrogen protection, a sample with a mass of 5±1 mg is first heated from 30°C to 160°C at a heating rate of 10°C / min, held at 160°C for 3 min, then cooled to -110°C at a rate of 20°C / min, and then heated to 150°C at a rate of 10°C / min; the glass transition temperature Tg of the sample is taken from the curve of the second heating, and the intersection of the extrapolation line at the bend and the baseline is taken as the value of glass transition temperature Tg.

[0014] In this invention, the weight-average molecular weight of the biodegradable polyester is 100,000 to 200,000 Da, for example, it can be 100,000 Da, 110,000 Da, 120,000 Da, 130,000 Da, 140,000 Da, 150,000 Da, 160,000 Da, 170,000 Da, 180,000 Da, 190,000 Da, 200,000 Da or any of the above values.

[0015] In this invention, the weight-average molecular weight of the biodegradable polyester can be determined by GPC. GPC was performed using a Waters ACQUITY APC™ instrument at a test temperature of 40°C, using XT45, XT200, and XT459 columns, tetrahydrofuran as the solvent, a mobile phase flow rate of 0.5 mL / min, and polystyrene standards as the standard. The results were calculated as the average of three measurements.

[0016] In this invention, by controlling the weight-average molecular weight of biodegradable polyester, the molecular chain length can be adjusted, making the physical entanglement between chains denser. During puncture, the stress is dispersed through the entanglement network, improving the puncture strength and thus resulting in better mechanical properties.

[0017] In this invention, the intrinsic viscosity of the biodegradable polyester after boiling in water at 95°C for 12 hours is 1.10~1.45 dL / g, for example, it can be 1.10 dL / g, 1.12 dL / g, 1.14 dL / g, 1.16 dL / g, 1.18 dL / g, 1.20 dL / g, 1.22 dL / g, 1.24 dL / g, 1.26 dL / g, 1.28 dL / g, 1.30 dL / g, 1.32 dL / g, 1.34 dL / g, 1.36 dL / g, 1.38 dL / g, 1.40 dL / g, 1.42 dL / g, 1.44 dL / g, 1.45 dL / g, or any range between the above values.

[0018] In this invention, the intrinsic viscosity of the biodegradable polyester after boiling in water at 95°C for 12 hours can be determined using a viscometer. The test method is as follows: the biodegradable polyester is boiled in water at 95°C for 12 hours, then dried to obtain a sample. At 25°C, 0.1250±0.0005g of the sample is accurately weighed and dissolved in 25mL of a solution (o-dichlorobenzene:phenol = 2:3 mass ratio). The solution is heated and stirred at 110°C until the resin is completely dissolved, and the viscosity is measured using a viscometer.

[0019] In this invention, by controlling the intrinsic viscosity of biodegradable polyester after boiling in water at 95°C for 12 hours, the stability of its molecular chain can be enhanced, ensuring that the polymer molecular chain maintains appropriate strength during the blending process, and further improving puncture strength and tear strength.

[0020] That is, by controlling the weight-average molecular weight of biodegradable polyester, the present invention can ensure that the molecular chain has sufficient length, thereby providing good mechanical properties. By controlling the intrinsic viscosity after boiling in water at 95°C for 12 hours, the extent of molecular chain expansion during melt blending can be controlled. Through mutual cooperation, the puncture resistance and tear strength of the material are further improved.

[0021] Preferably, the polylactic acid includes at least one of PLLA, PDLA, or PLLA / PDLA copolymer.

[0022] In this invention, the melt index of the polylactic acid is 2-20 g / 10 min, for example, it can be 2 g / 10 min, 2.5 g / 10 min, 3 g / 10 min, 3.5 g / 10 min, 4 g / 10 min, 4.5 g / 10 min, 5 g / 10 min, 5.5 g / 10 min, 6 g / 10 min, 6.5 g / 10 min, 7 g / 10 min, 7.5 g / 10 min, 8 g / 10 min, 8.5 g / 10 min, 9 g / 10 min, 9.5 g / 10 min, 10 g / 10 min, 10.5 g / 10 min, 11 g / 10 min, or 11.5 g / 10 min. n, 12g / 10min, 12.5g / 10min, 13g / 10min, 13.5g / 10min, 14g / 10min, 14.5g / 10min, 15g / 10min, 15.5g / 10min, 16g / 10min, 16.5g / 10min, 17g / 10min, 17.5g / 10min, 18g / 10min, 18.5g / 10min, 19g / 10min, 19.5g / 10min, 20g / 10min or any of the above values, preferably 2.5-15g / 10min, more preferably 3-10g / 10min.

[0023] In this invention, the test method for the melt index of polylactic acid adopts the ISO 1133 standard, with a set temperature of 190°C and an applied load of 2.16 kg.

[0024] Preferably, the molar percentage of D-lactic acid in the PLLA / PDLA copolymer is 2-10%, for example, it can be 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or any of the above values.

[0025] In this invention, one way to control the glass transition temperature of polylactic acid is to control the use of PLLA / PDLA copolymer and control the molar percentage of D-type lactic acid, thereby promoting the compatibility of polylactic acid with polyester and improving mechanical properties.

[0026] Preferably, the polylactic acid includes plasticized polylactic acid.

[0027] In this invention, the plasticized polylactic acid is prepared using conventional methods. Exemplarily, the preparation method of the plasticized polylactic acid includes: mixing polylactic acid and ester plasticizer in a high-speed mixer for 0.5 to 3 minutes, performing melt blending using a twin-screw extruder, processing at a temperature of 150 to 220°C, granulating, and drying at 70 to 100°C for 2 to 8 hours to obtain plasticized polylactic acid.

[0028] Preferably, the plasticizer used to plasticize the polylactic acid includes ester plasticizers.

[0029] Preferably, the ester plasticizer includes at least one of tributyl citrate, dioctyl phthalate, or ethyl lactate, and more preferably tributyl citrate and / or dioctyl phthalate.

[0030] Preferably, based on the mass of polylactic acid before plasticization as 100%, the mass of the ester plasticizer is 1 to 10%, for example, it can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or any range between the above values, preferably 2 to 7%, and more preferably 3 to 5%.

[0031] In this invention, one method of controlling the glass transition temperature of polylactic acid is to control the plasticized polylactic acid obtained by melt blending polylactic acid with ester plasticizers, and to control the mass ratio of ester plasticizers. The plasticizer can reduce the inter-segment forces through the interaction between the ester groups and the polylactic acid molecular chains, thereby reducing the glass transition temperature through plasticizing. It also has good compatibility with polylactic acid, which can reduce melt viscosity and inhibit crystallization.

[0032] Preferably, the biodegradable polyester comprises an aliphatic-aromatic copolyester.

[0033] Preferably, the aliphatic-aromatic copolyester includes at least one of polybutylene adipate terephthalate, polybutylene sebacate terephthalate, or polybutylene succinate terephthalate.

[0034] Preferably, the biodegradable polyester has a weight-average molecular weight of 120,000 to 180,000 Da, and more preferably 130,000 to 170,000 Da.

[0035] Preferably, the intrinsic viscosity of the biodegradable polyester after boiling in water at 95°C for 12 hours is 1.15~1.40 dL / g, more preferably 1.20~1.38 dL / g.

[0036] Preferably, the plasticizer used in the biodegradable composition includes a polyhydroxy organic compound and / or water.

[0037] Preferably, the plasticizer used in the biodegradable composition is a polyhydroxy organic compound and water.

[0038] Preferably, the mass ratio of the polyhydroxy organic compound to water in the plasticizer used in the biodegradable composition is (0.2~4):1, for example, it can be 0.2:1, 0.4:1, 0.6:1, 0.8:1, 1:1, 1.2:1, 1.4:1, 1.6:1, 1.8:1, 2:1, 2.2:1, 2.4:1, 2.6:1, 2.8:1, 3:1, 3.2:1, 3.4:1, 3.6:1, 3.8:1, 4:1 or any range between the above values, preferably (0.3~3):1, more preferably (0.4~2):1.

[0039] Preferably, the polyhydroxy organic compound includes at least one of glycerol, diglycerol, triglycerol, tetraglycerol, ethylene glycol, or sorbitol.

[0040] Preferably, the plasticizer accounts for 10-50% of the starch mass, for example, it can be 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50% or any of the above values, preferably 15-40%, and more preferably 18-35%.

[0041] Preferably, the biodegradable composition further includes an inorganic filler.

[0042] Preferably, the biodegradable composition comprises 1 to 5 parts by weight of inorganic filler, for example, 1 part, 2 parts, 3 parts, 4 parts, 5 parts or any range between the above values.

[0043] Preferably, the inorganic packing includes spherical inorganic packing and / or sheet-like inorganic packing.

[0044] Preferably, the spherical inorganic filler comprises calcium carbonate.

[0045] Preferably, the D50 particle size of the spherical inorganic filler is 1~3μm, for example, it can be 1μm, 1.2μm, 1.4μm, 1.5μm, 1.6μm, 1.8μm, 2μm, 2.2μm, 2.4μm, 2.5μm, 2.6μm, 2.8μm, 3μm or any of the above values.

[0046] In this invention, the D50 particle size is determined in accordance with the method of GB / T 19077.1-2016 "Particle Size Analysis by Laser Diffraction".

[0047] Preferably, the sheet-like inorganic filler includes at least one of talc, montmorillonite, or barium sulfate.

[0048] Preferably, the D50 particle size of the sheet-like inorganic filler is ≤5μm, for example, it can be 5μm, 4.8μm, 4.5μm, 4.2μm, 4μm, 3.8μm, 3.5μm, 3.2μm, 3μm, 2.8μm, 2.5μm, 2.2μm, 2μm, 1.8μm, 1.5μm, 1.2μm, 1μm, 0.8μm, 0.5μm, 0.2μm or any of the above values, preferably ≤4μm, and more preferably ≤2μm.

[0049] Preferably, the mass ratio of spherical inorganic packing to sheet-like inorganic packing in the inorganic packing is (0.1~1.2):1, for example, it can be 0.1:1, 0.2:1, 0.4:1, 0.6:1, 0.8:1, 1:1, 1.2:1 or any range between the above values, preferably (0.2~1.1):1, and more preferably (0.3~1.0):1.

[0050] In this invention, the inorganic filler is a combination of spherical and sheet-like inorganic fillers. During the dispersion process, the spherical and sheet-like inorganic fillers interact to generate van der Waals forces, and friction is generated during shear dispersion. This effectively promotes the dispersion of the spherical and sheet-like inorganic fillers, thereby enabling the film prepared by blending to better resist punctures and tears.

[0051] In a second aspect, the present invention provides a method for preparing the biodegradable composition according to the first aspect, the method comprising the following steps: The components are melt-blended and then extruded and granulated to obtain the biodegradable composition.

[0052] Preferably, the melt blending temperature is 150~210℃, for example, it can be 150℃, 160℃, 170℃, 180℃, 190℃, 200℃, 210℃ or any range between the above values, preferably 160~200℃.

[0053] Thirdly, the present invention provides a biodegradable product formed from the biodegradable composition described in the first aspect of the present invention.

[0054] Preferably, the biodegradable product includes a membrane or bag.

[0055] Preferably, the membrane is formed by using the biodegradable composition via melt blow molding.

[0056] Preferably, the bag is obtained by heat sealing with a film.

[0057] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0058] Compared with the prior art, the beneficial effects of the present invention are as follows: The biodegradable composition provided by this invention, through the compounding of biodegradable polyester, polylactic acid, starch, and plasticizer, and by controlling the glass transition temperature of polylactic acid, can be adjusted to an amorphous state. The amorphous state of polylactic acid and the semi-crystalline state of polyester form a more compatible mixed system. The molecular chains of polylactic acid can form a tighter physical entanglement with the molecular chains of polyester, which can effectively transfer stress, thereby enhancing the overall mechanical properties of the material. At the same time, it can also disperse stress and prevent stress concentration. By controlling the weight-average molecular weight of biodegradable polyester and the intrinsic viscosity after boiling in water at 95°C for 12 hours, the degree of molecular chain expansion during the melt blending process can be controlled. Through mutual cooperation, the puncture resistance and tear strength of the material are further improved. Detailed Implementation

[0059] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0060] In this invention, the materials used in the examples and comparative examples are all commercially available or prepared using conventional methods. Unless otherwise specified, the materials used in this invention are as follows: Biodegradable polyester: Polyester 1, polybutylene adipate terephthalate (PBAT), Zhuhai Kingfa Biomaterials Co., Ltd., KB100LF, weight-average molecular weight 169481 Da, intrinsic viscosity after boiling in water at 95℃ for 12 h is 1.321 dL / g. Polyester 2, polybutylene sebacic acid terephthalate PBSeT, Zhuhai Kingfa Biomaterials Co., Ltd., A300LF, weight average molecular weight 157892 Da, intrinsic viscosity after boiling in water at 95℃ for 12 h is 1.362 dL / g. Polyester 3, polybutylene adipate terephthalate (PBAT), Zhuhai Kingfa Biomaterials Co., Ltd., KB100HF, weight-average molecular weight 99523 Da, intrinsic viscosity after boiling in water at 95℃ for 12 h is 1.053 dL / g. Polyester 4, polybutylene adipate terephthalate (PBAT), Zhuhai Kingfa Biomaterials Co., Ltd., KB100SF, weight-average molecular weight 89865 Da, intrinsic viscosity after boiling in water at 95℃ for 12 h is 0.957 dL / g. Polyester 5 was synthesized using a two-step method. First, 20 kg of terephthalic acid and 13 kg of 1,4-butanediol were added to an esterification reactor (1#) and esterified at 185°C for 4 hours. During the reaction, the generated water was continuously drained to produce butylene terephthalate and its oligomers, which were then cooled and set aside. The butylene terephthalate and its oligomers, 20 kg of adipic acid, 15 kg of 1,4-butanediol, 0.3 kg of glycerol, and 0.3 kg of catalyst (tetrabutyl titanate) were added to a 200 L polymerization reactor and subjected to transesterification and polycondensation reactions at 245°C and a vacuum pressure of 300 Pa for 12 hours to obtain polybutylene adipate terephthalate (PBAT) with a weight-average molecular weight of 154530 Da and an intrinsic viscosity of 1.083 after boiling in water at 95°C for 12 hours.

[0061] Polylactic acid: Polylactic acid 1, PLLA / PDLA copolymer, Natureworks, USA, PLA 4060D, with a molar percentage of D-type lactic acid of 11.8%, a glass transition temperature of 58.4℃, and a melt index of 4.32 g / 10 min; Polylactic acid 2, plasticized polylactic acid PLLA, self-made, with ester plasticizer tributyl acetylacetic acid in a mass ratio of 3%, is prepared as follows: PLLA and ester plasticizer are mixed in a high-speed mixer for 1 minute, melt-blended using a twin-screw extruder, processed at 200℃, granulated and dried at 100℃ for 6 hours to obtain plasticized polylactic acid PLLA with a glass transition temperature of 59.1℃ and a melt index of 5.02 g / 10min; Polylactic acid 3, PLLA / PDLA copolymer, Anhui Fengyuan Biotechnology Co., Ltd., PLA FY801, with a molar percentage of D-type lactic acid of 0.79%, a glass transition temperature of 62.2℃, and a melt index of 4.12 g / 10 min; Polylactic acid 4 (PLLA), prepared in-house, is prepared as follows: 100 parts by weight of L-lactide (purity 99.6%) is added to a 20L reactor, along with 0.002 parts by weight of stannous octoate. Ring-opening polymerization is then carried out: first, the reaction is carried out at 135℃ and 1200Pa for 4 hours, then at 170℃ and 300Pa for 6 hours. Afterwards, the mixture is granulated underwater, crystallized, and dried to obtain polylactic acid. The glass transition temperature of polylactic acid 4 is 64.3℃, and the melt index is 7.12 g / 10min.

[0062] starch: Henan Jindan, edible corn starch.

[0063] Plasticizers: Plasticizer 1, glycerin aqueous solution, with a glycerin to water mass ratio of 0.5:1; Plasticizer 2, ethylene glycol aqueous solution, with a mass ratio of ethylene glycol to water of 0.8:1; Plasticizer 3, glycerin.

[0064] Spherical inorganic packing: Spherical inorganic filler, calcium carbonate, Omia Corporation, 1T-CU, D50 particle size is 1.52μm.

[0065] Flaky inorganic packing: Flaky inorganic filler 1, talc powder, Liaoning Aihai Company, HTPULtra5L, D50 particle size is 2.5μm; 2. Flaky inorganic filler, montmorillonite, Zhejiang Fenghong Company, DK10, D50 particle size is 4.3μm.

[0066] Examples 1-14 and Comparative Examples 1-5 each provide a biodegradable composition. The composition of the biodegradable composition is shown in Tables 1-3 by weight, where " / " indicates that the component is not in the formulation.

[0067] Unless otherwise specified, the preparation method of the biodegradable composition in this invention includes: weighing each raw material and then melting and blending them at 180°C, followed by extrusion granulation to obtain the biodegradable composition.

[0068] Table 1 Table 2 Table 3 Performance testing: (1) Puncture strength and puncture displacement: The biodegradable compositions provided in Examples 1-14 and Comparative Examples 1-5 were blown into films with a thickness of 12±1μm by a blown film machine and bagged by a bag cutting machine. Then, the puncture performance of the film bags was tested by a universal film testing machine. According to GB / T 21302-2007, the film was fixed on the universal film testing machine and a puncture test needle with a diameter of 1mm was used to test at a speed of 50mm / min. The maximum force value was taken and the average value of 5 tests was taken. The puncture displacement was the displacement at the maximum force.

[0069] (2) Longitudinal tear strength: The test was conducted according to GB / T 16578.2-2009. The samples were placed in a standard environment (23±2℃, 50±5%RH) for 24 hours before testing. The data of the longitudinal tear strength of the samples were obtained.

[0070] (3) Transverse tear strength: Tested according to GB / T 16578.2-2009. The samples were placed in a standard environment (23±2℃, 50±5%RH) for 24 hours before testing. Data on the transverse tear strength of the samples were obtained.

[0071] The specific test results are shown in Table 4.

[0072] Table 4 As shown in Table 4, the biodegradable composition provided by the present invention is made by compounding biodegradable polyester, polylactic acid, starch, inorganic filler and plasticizer, and by controlling the glass transition temperature of polylactic acid and the weight-average molecular weight of biodegradable polyester and the intrinsic viscosity after boiling in water at 95°C for 12 hours within a specific range, thereby enhancing the overall mechanical properties of the material and improving the puncture resistance and tear strength of the material.

[0073] Specifically, the biodegradable composition provided by the present invention has a puncture strength of 4.1 N or more, a puncture displacement of 7.1 mm or more, a longitudinal tear strength of 1254 mN or more, and a transverse tear strength of 1998 mN or more. Under preferred conditions, the puncture strength is 4.8 N or more, the puncture displacement is 8.3 mm or more, the longitudinal tear strength is 1528 mN or more, and the transverse tear strength is 2014 mN or more.

[0074] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A biodegradable composition, characterized in that, The biodegradable composition comprises, by weight, 50-93 parts of biodegradable polyester, 1-15 parts of polylactic acid, 5-30 parts of starch and 1-10 parts of plasticizer; The glass transition temperature of the polylactic acid is ≤62℃; The weight-average molecular weight of the biodegradable polyester is 100,000 to 200,000 Da; The intrinsic viscosity of the biodegradable polyester after boiling in water at 95°C for 12 hours is 1.10~1.45 dL / g.

2. The biodegradable composition according to claim 1, characterized in that, The glass transition temperature of the polylactic acid is ≤60℃.

3. The biodegradable composition according to claim 1, characterized in that, The polylactic acid includes at least one of PLLA, PDLA, or PLLA / PDLA copolymer; Preferably, the molar percentage of D-type lactic acid in the PLLA / PDLA copolymer is 2-20%; Preferably, the polylactic acid includes plasticized polylactic acid; Preferably, the plasticizer used to plasticize the polylactic acid includes ester plasticizers; Preferably, the ester plasticizer includes at least one of tributyl citrate, dioctyl phthalate, or ethyl lactate; Preferably, based on the mass of polylactic acid before plasticization as 100%, the mass of the ester plasticizer is 1~10%, more preferably 2~7%, and even more preferably 3~5%.

4. The biodegradable composition according to claim 1, characterized in that, The biodegradable polyester includes aliphatic-aromatic copolyesters; Preferably, the aliphatic-aromatic copolyester comprises at least one of polybutylene adipate terephthalate, polybutylene sebacic acid terephthalate, or polybutylene terephthalate succinate. Preferably, the biodegradable polyester has a weight-average molecular weight of 120,000 to 180,000 Da, and more preferably 130,000 to 170,000 Da.

5. The biodegradable composition according to claim 1, characterized in that, The intrinsic viscosity of the biodegradable polyester after boiling in water at 95°C for 12 hours is 1.15~1.40 dL / g, preferably 1.20~1.38 dL / g.

6. The biodegradable composition according to claim 1, characterized in that, The plasticizers used in the biodegradable composition include polyhydroxy organic compounds and / or water; Preferably, the plasticizer used in the biodegradable composition is a polyhydroxy organic compound and water; Preferably, the mass ratio of the polyhydroxy organic compound to water in the plasticizer used in the biodegradable composition is (0.2~4):1, more preferably (0.3~3):1, and even more preferably (0.4~2):1; Preferably, the polyhydroxy organic compound includes at least one of glycerol, diglycerol, triglycerol, tetraglycerol, ethylene glycol, or sorbitol; Preferably, the plasticizer accounts for 10-50% of the starch mass, more preferably 15-40%, and even more preferably 18-35%.

7. The biodegradable composition according to claim 1, characterized in that, The biodegradable composition also includes inorganic fillers; Preferably, the biodegradable composition comprises 1 to 5 parts by weight of inorganic filler; Preferably, the inorganic packing includes spherical inorganic packing and / or sheet-like inorganic packing; Preferably, the spherical inorganic filler comprises calcium carbonate; Preferably, the D50 particle size of the spherical inorganic filler is 1~3μm; Preferably, the sheet-like inorganic filler includes at least one of talc, montmorillonite, or barium sulfate; Preferably, the D50 particle size of the sheet-like inorganic filler is ≤5μm, more preferably ≤4μm, and even more preferably ≤2μm; Preferably, the mass ratio of spherical inorganic packing to sheet-like inorganic packing in the inorganic packing is (0.1~1.2):1, more preferably (0.2~1.1):1, and even more preferably (0.3~1.0):

1.

8. A method for preparing a biodegradable composition according to any one of claims 1 to 7, characterized in that, The preparation method includes the following steps: The components are melt-blended and then extruded and granulated to obtain the biodegradable composition.

9. A biodegradable product, characterized in that, The biodegradable product is formed from the biodegradable composition according to any one of claims 1 to 7.

10. The biodegradable product according to claim 9, characterized in that, The biodegradable products include films or bags.

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