Biodegradable composition as well as preparation method and application thereof

Abstract

The invention relates to a biodegradable composition as well as a preparation method and application thereof, and the biodegradable composition comprises the following components in parts by weight: 41-97 parts of biodegradable polyester, 1-10 parts of polylactic acid, 1-15 parts of flaky mineral powder and 1-34 parts of calcium carbonate. The relaxation time of the biodegradable polyester is 0.1 to 10 seconds. The biodegradable composition provided by the invention has relatively high 10% tensile strength, can avoid the problem of rupture in a bag making process, and meets the requirement of rapid forming of an ultrathin film.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a biodegradable composition, its preparation method, and its application. Background Technology

[0002] With increasing environmental awareness, the problem of "white pollution" (plastic pollution) has garnered growing attention. White pollution primarily originates from non-degradable plastic products, such as polyethylene (PE) and polypropylene (PP), which are difficult to break down in the natural environment and severely impact ecosystems. Therefore, gradually replacing traditional plastics with biodegradable materials is the current development trend.

[0003] In the field of biodegradable materials, polybutylene adipate terephthalate (PBAT) and polylactic acid (PLA) are common biodegradable materials that, when combined with mineral powder, can be used to manufacture film bags. However, with the trend towards lower basis weight, lighter weight, and rapid prototyping of films, film thickness is constantly decreasing, even reaching 10 μm. Such ultra-thin films require rapid prototyping, thus significantly increasing the bag-making pressure on the film. The tensile deformation of the bag-making machine is generally controlled within 10%, making the 10% tensile strength a key indicator of the bag's deformation capacity. The film needs to possess good deformation resistance during the bag-making process to meet the requirements of rapid prototyping; otherwise, problems such as film rupture can easily occur, affecting production efficiency and product quality.

[0004] Therefore, providing a biodegradable material with good 10% tensile strength is a technical problem that needs to be solved. Summary of the Invention

[0005] To address the above problems, the present invention aims to provide a biodegradable composition, its preparation method, and its application. Compared with the prior art, the biodegradable composition provided by the present invention has a higher tensile strength of 10%, which can avoid the problem of rupture during the bag making process and meet the needs of rapid prototyping of ultra-thin films.

[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 41 to 97 parts of biodegradable polyester, 1 to 10 parts of polylactic acid, 1 to 15 parts of flake mineral powder and 1 to 34 parts of calcium carbonate. The relaxation time of the biodegradable polyester is 0.1~10s.

[0007] In this invention, 41 to 97 parts of biodegradable polyester can be, for example, 41 parts, 42 parts, 44 parts, 46 parts, 48 ​​parts, 50 parts, 52 parts, 54 parts, 56 parts, 58 parts, 60 parts, 62 parts, 64 parts, 66 parts, 68 parts, 70 parts, 72 parts, 74 parts, 76 parts, 78 parts, 80 parts, 82 parts, 84 parts, 86 parts, 88 parts, 90 parts, 92 parts, 94 parts, 96 parts, 97 parts, or any range of the above values.

[0008] In this invention, 1 to 10 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, or any range between the above values.

[0009] In this invention, 1 to 15 parts of flake mineral powder 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.

[0010] In this invention, 1 to 34 parts of calcium carbonate can be, for example, 1 part, 2 parts, 4 parts, 6 parts, 8 parts, 10 parts, 12 parts, 14 parts, 16 parts, 18 parts, 20 parts, 22 parts, 24 parts, 26 parts, 28 parts, 30 parts, 32 parts, 34 parts, or any range of the above values.

[0011] In this invention, the relaxation time of the biodegradable polyester is 0.1~10s, for example, it can be 0.1s, 0.2s, 0.4s, 0.6s, 0.8s, 1s, 1.2s, 1.4s, 1.6s, 1.8s, 2s, 2.2s, 2.4s, 2.6s, 2.8s, 3s, 3.2s, 3.4s, 3.6s, 3.8s, 4s, 4.2s, 4.4s, etc. 4.6s, 4.8s, 5s, 5.2s, 5.4s, 5.6s, 5.8s, 6s, 6.2s, 6.4s, 6.6s, 6.8s, 7s, 7.2s, 7.4s, 7.6s, 7.8s, 8s, 8.2s, 8.4s, 8.6s, 8.8s, 9s, 9.2s, 9.4s, 9.6s, 9.8s, 10s, or any of the above values.

[0012] In the biodegradable composition provided by this invention, biodegradable polyester, polylactic acid, flake mineral powder, and calcium carbonate, among other components, work synergistically. By controlling the relaxation time of the biodegradable polyester, the entanglement characteristics of the polyester molecular chains can be effectively regulated. When the relaxation time is too short, the chain segments of the polyester molecular chains have excessive freedom of movement, resulting in excessively rapid entanglement under shearing action. This makes it difficult to effectively coat and disperse the flake mineral powder and calcium carbonate, leading to agglomeration of the inorganic fillers and enhancing the grinding effect of the system. This makes the molecular chains more prone to breakage, ultimately resulting in a decrease in the 10% tensile strength of the biodegradable composition. When the relaxation time is too long, the chain segments of the polyester molecular chains have difficulty moving, reducing the deentanglement efficiency. This not only increases the viscosity of the system but also makes the molecular chains more prone to breakage under the blending shear effect, similarly leading to a decrease in the 10% tensile strength.

[0013] In this invention, the biodegradable composition contains a biodegradable polyester content of not less than 40% by weight.

[0014] In this invention, the method for testing the relaxation time of the biodegradable polyester is as follows: The biodegradable polyester granules are dried at 80°C for 10 hours to ensure a moisture content below 500 ppm, thus avoiding interference with the test results. The dried granules are then placed in a 100mm × 100mm × 2mm frame mold, with the top and bottom of the mold separated by PET film to prevent direct contact between the polyester granules and the mold. A flatbed vulcanizing apparatus is used for molding. The temperature is raised to 150°C, pressure is applied for 3 minutes, followed by one deflation, then pressure is applied again for 0.5 minutes, followed by another deflation, and finally pressure is applied for 2 minutes. After the pressure is applied, the molded sample is placed at 30°C. The sample was cooled on a 5℃ cooling plate for 5 minutes. The cooled sample was then separated from the PET film to obtain a sheet measuring 100mm × 100mm × 2mm, which was then cut into 10mm × 10mm × 2mm pieces. The pieces were placed in a rheometer and equilibrated at 150℃ for 5 minutes. A strain scanning experiment was then performed with a strain of 1%, scanning from 0.01Hz to 100Hz shear rates. The apparent viscosity data of the sample at different shear rates was recorded, and the results were analyzed according to the Cross equation: ; in, or Indicates apparent viscosity; or 0 represents zero-shear viscosity (viscosity when the shear rate approaches 0), and the initial value is taken in the low shear rate region (e.g., The viscosity plateau value (=0.01Hz); or ∞This represents infinite shear viscosity (viscosity when the shear rate approaches ∞), with an initial value of 0.001 Pa·s (approximate value). λ represents the relaxation time (s), with an initial estimated value of 0.1~50s; m This represents the dimensionless exponent (reflecting the degree of shear thinning), with an initial value set to 0.1~2.0 (empirical value). Shear rate (s) -1 ).

[0015] Set constraints or 0> or ∞ If λ > 0, substitute the obtained shear rate and apparent viscosity data into the Cross equation and fit it. Check the goodness of fit (R²). 2 (A value greater than 0.99 is preferred), and observe whether the residuals are randomly distributed. A randomly distributed residual indicates that the fitting result is reliable. or 0, λ, m Parameters such as relaxation time λ are selected.

[0016] Preferably, the biodegradable polyester is obtained by polycondensation of a diacid and a diol, wherein the diacid includes aromatic diacids and / or aliphatic diacids. The aromatic diacids include, but are not limited to, at least one of terephthalic acid, furanyl dicarboxylic acid, esters of the aforementioned substances, ester derivatives, or acid anhydride derivatives; the aliphatic diacids include, but are not limited to, at least one of adipic acid, succinic acid, azelaic acid, sebacic acid, brassic acid, esters of the aforementioned substances, ester derivatives, or acid anhydride derivatives; and the diols include, but are not limited to, propylene glycol and / or butanediol.

[0017] Preferably, the biodegradable polyester comprises an aliphatic-aromatic copolyester.

[0018] In this invention, the molar ratio of the diacid to the diol is 1:1; the molar percentage of the aromatic diacid in the diacid is ≥5%, more preferably ≥30%, and particularly preferably 45~70%.

[0019] Preferably, the aliphatic-aromatic copolyester includes at least one of polybutylene adipate terephthalate, polybutylene sebacate terephthalate, or polybutylene succinate terephthalate.

[0020] Preferably, the relaxation time of the biodegradable polyester is 0.2~8s, more preferably 0.35~5s.

[0021] In this invention, the biodegradable polyester can be obtained commercially or prepared using conventional methods. The preparation methods of the biodegradable polyester include, but are not limited to, the following: mixing a diacid, a diol, and a catalyst to carry out a first esterification reaction to obtain a first oligomer; mixing another diacid, a diol, and a catalyst to carry out a second esterification reaction to obtain a second oligomer; and carrying out a third reaction with the first and second oligomers and a catalyst to obtain the biodegradable polyester. Those skilled in the art can adjust the conditions of the first, second, and third esterification reactions, such as reaction time, temperature, and pressure, depending on the selected diacid and / or diol, to obtain the biodegradable polyester with the desired relaxation time.

[0022] For example, when terephthalic acid is selected as the diacid, 1,4-butanediol as the diol, and diphenylmethane diisocyanate as the catalyst in the first esterification reaction, and adipic acid, 1,4-butanediol, and diphenylmethane diisocyanate as the diacid, and diphenylmethane diisocyanate as the diol, in the second esterification reaction, the preparation method includes: First, mixing terephthalic acid, 1,4-butanediol, and diphenylmethane diisocyanate, and adding them to an esterification reactor for a first esterification reaction, continuously removing the water generated during the reaction to obtain a first oligomer; Second, mixing adipic acid, 1,4-butanediol, and diphenylmethane diisocyanate, and adding them to an esterification reactor for a second esterification reaction, continuously removing the water generated during the reaction to obtain a second oligomer; Third, reacting the first and second oligomers with tetrabutyl titanate catalyst to obtain a biodegradable polyester. The temperature of the first esterification reaction is 190~200℃, for example, it can be 190℃, 192℃, 194℃, 196℃, 198℃, 200℃ or any range between the above values. The time of the first esterification reaction is 0.1~8h, for example, it can be 0.1h, 0.5h, 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h or any range between the above values, preferably 2~3h. The raw materials for the first esterification reaction, by mass parts, include 15 to 30 parts of terephthalic acid, for example, 15, 20, 22, 24, 26, 28, 30 parts, or any range thereof; 10 to 15 parts of 1,4-butanediol, for example, 10, 11, 12, 13, 14, 15 parts, or any range thereof; and 0.001 to 0.005 parts of diphenylmethane diisocyanate, for example, 0.001, 0.002, 0.003, 0.004, 0.005 parts, or any range thereof. The temperature for the second esterification reaction is 190 to 200°C, for example, 190°C, 192°C, 194°C, 196°C, 198°C, 200°C, or any range thereof. The second esterification reaction takes 0.1 to 8 hours, for example, 0.1 hours, 0.5 hours, 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours or any range of the above values, preferably 2 to 3 hours. The raw materials for the second esterification reaction, by mass parts, include 10 to 20 parts of adipic acid, for example, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 parts or any range of the above values; 10 to 15 parts of 1,4-butanediol, for example, 10, 11, 12, 13, 14, 15 parts or any range of the above values; and 0.001 to 0.005 parts of diphenylmethane diisocyanate, for example, 0.001, 0.002, 0.003, 0.004, 0.005 parts or any range of the above values.The temperature of the third reaction is 220~260℃, for example, it can be 220℃, 225℃, 230℃, 235℃, 240℃, 245℃, 250℃, 255℃, 260℃ or any range between the above values, preferably 235~245℃. The pressure of the third reaction is 260~330Pa, for example, it can be 260Pa, 270Pa, 280Pa, 282Pa, 284Pa, 286Pa, 288Pa, 290Pa, 292Pa, 294Pa, ​​296Pa, 298Pa, 300Pa, 310Pa, 320Pa, 330Pa or any range between the above values, preferably 280~300Pa. The time of the third reaction is 2~12h, for example, it can be 2h, 4h, 5h, 6h, 8h, 10h, 12h or any range between the above values, preferably 5~6h.

[0023] Preferably, the polylactic acid comprises a PLLA / PDLA copolymer.

[0024] In this invention, the molar percentage of D-type lactic acid in the PLLA / PDLA copolymer is 0.5% to 30%, for example, it can be 0.5%, 1%, 2%, 4%, 6%, 8%, 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 28%, 30%, or any of the above values.

[0025] In this invention, the method for determining the molar content of D-type lactic acid in the PLLA / PDLA copolymer is as follows: The PLLA / PDLA copolymer sample is subjected to transesterification with methanol in a pressure vessel at 150°C to degrade the PLLA / PDLA copolymer. Gas chromatography (GC) is used to analyze the degraded sample. The molar content of D-type lactic acid in the PLLA / PDLA copolymer is calculated by detecting the peak areas of L-type methyl lactate and D-type methyl lactate, using the following formula: ; in, D-Lactic Acid This indicates the molar content of D-type lactic acid in the PLLA / PDLA copolymer; A DML This indicates the peak area of ​​methyl lactate D; A LML This represents the peak area of ​​L-type methyl lactate.

[0026] Three samples were taken, and the molar content of D-type lactic acid obtained from each gas chromatography run was statistically analyzed. The molar content of D-type lactic acid in the PLLA / PDLA copolymer was taken as the average value of the three test results.

[0027] Preferably, the intrinsic viscosity of the polylactic acid is 0.9~2.0 dL / g, for example, it can be 0.9 dL / g, 1 dL / g, 1.1 dL / g, 1.2 dL / g, 1.3 dL / g, 1.4 dL / g, 1.5 dL / g, 1.6 dL / g, 1.7 dL / g, 1.8 dL / g, 1.9 dL / g, 2.0 dL / g or any of the above values, preferably 1.0~1.8 dL / g, and more preferably 1.1~1.7 dL / g.

[0028] In this invention, by optimally controlling the intrinsic viscosity of polylactic acid (PLA), the 10% tensile strength of the biodegradable composition can be further improved. If the intrinsic viscosity of PLA is too low, the PLA molecular chains are relatively short, leading to reduced compatibility with polyester and a tendency to induce microphase separation. In this case, the gap at the phase interface is large, causing stress concentration under stress, which in turn leads to a decrease in the 10% tensile strength. If the intrinsic viscosity of PLA is too high, the entanglement effect between PLA molecular chains and between PLA and polyester is significantly enhanced, and the viscosity of the system also increases. During the blending and shearing process, the strong entanglement effect easily leads to molecular chain breakage, which also leads to a decrease in the 10% tensile strength.

[0029] In this invention, the method for testing the intrinsic viscosity of polylactic acid includes: accurately weighing 0.1250 g of the polylactic acid at 25°C. 0.0005 g of sample was dissolved in 25 mL of a mixed solution prepared by o-dichlorobenzene and phenol in a mass ratio of 2:3. The solution was heated and stirred at 110 °C until completely dissolved, and the viscosity was measured using a viscometer.

[0030] In this invention, the polylactic acid (PLLA) can be obtained commercially or prepared using conventional methods. The preparation method of the PLA includes, but is not limited to, the following: L-lactide, meso-lactide, and a catalyst undergo a ring-opening polymerization reaction, which is carried out in three steps: Step 1, L-lactide, meso-lactide, and stannous octoate catalyst undergo a first-step reaction to obtain a PLA oligomer; Step 2, a second-step reaction is carried out to remove the byproduct lactide, shifting the equilibrium towards polymerization; Step 3, a third-step reaction is carried out, followed by passivation treatment with a passivating agent, zinc phosphate, and then underwater pelletizing, crystallization, and drying to obtain the PLLA / PDLA copolymer. The temperature of the first-step reaction is 140~150℃, for example, 140℃, 142℃, 144℃, 146℃, 148℃, 150℃, or any range between these values. The reaction time for the first step is 0.8 to 7 hours, for example, it can be 0.8 hours, 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, or any range between these values. The vacuum degree for the first step reaction is 1800 to 2200 Pa, for example, it can be 1800 Pa, 1900 Pa, 2000 Pa, 2100 Pa, 2200 Pa, or any range between these values. Based on mass parts, in the first step reaction, L-lactide is 75-85 parts, for example, 75 parts, 78 parts, 80 parts, 82 parts, 84 parts, 85 parts, or any range between the above values; meso-lactide is 15-25 parts, for example, 15 parts, 16 parts, 18 parts, 20 parts, 22 parts, 24 parts, 25 parts, or any range between the above values; the catalyst includes stannous octoate, which is 0.002-0.006 parts, for example, 0.002 parts, 0.003 parts, 0.004 parts, 0.005 parts, 0.006 parts, or any range between the above values, preferably 0.004-0.006 parts. The temperature for the second step reaction is 160~180℃, for example, it can be 160℃, 162℃, 164℃, 166℃, 168℃, 170℃, 172℃, 174℃, 176℃, 178℃, 180℃, or any range between the above values. The initial vacuum degree in the second step reaction is 50~150Pa, and the vacuum degree is increased by 40~60Pa every 60 minutes until the final vacuum degree is 400~600Pa. The reaction time at the final vacuum degree is 1.5~7 hours, for example, it can be 1.5 hours, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, or any range between the above values. The temperature for the third reaction step is 140~160℃, for example, it can be 140℃, 142℃, 144℃, 146℃, 148℃, 150℃, 152℃, 154℃, 156℃, 158℃, 160℃ or any of the above values.In the third step of the reaction, the initial vacuum level is 400-600 Pa, and the vacuum level is controlled to decrease by 50-150 Pa every 60 minutes until the final vacuum level is 200-400 Pa. The passivation treatment time is 10-50 minutes, for example, it can be 10 minutes, 20 minutes, 30 minutes, 40 minutes, 50 minutes or any range between the above values, preferably 40-50 minutes. The passivating agent is 0.0003-0.0006 parts by mass, for example, it can be 0.0003 parts, 0.00035 parts, 0.0004 parts, 0.00045 parts, 0.0005 parts, 0.00055 parts, 0.0006 parts or any range between the above values, preferably 0.00045-0.00055 parts.

[0031] Preferably, the flaky mineral powder includes at least one of talc, montmorillonite, or mica, and is more preferably talc and / or montmorillonite.

[0032] In this invention, the D50 particle size of the flaky mineral powder 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.

[0033] In this invention, the D50 particle size of the calcium carbonate 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.

[0034] 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".

[0035] Preferably, the biodegradable composition further includes 0.1 to 2 parts by weight of an opening agent, for example, 0.1, 0.2, 0.4, 0.6, 0.8, 1, 1.2, 1.4, 1.6, 1.8, 2 parts or any range of the above values.

[0036] Preferably, the opening agent includes at least one of silicon dioxide, zeolite, barium sulfate, or polyethylene wax, and more preferably at least one of silicon dioxide, barium sulfate, or polyethylene wax.

[0037] Preferably, the biodegradable composition further includes 0.1 to 2 parts of lubricant by weight, for example, 0.1, 0.2, 0.4, 0.6, 0.8, 1, 1.2, 1.4, 1.6, 1.8, 2 parts or any range of the above values.

[0038] Preferably, the lubricant comprises at least one of erucamide, oleamide, glyceryl monostearate, pentaerythritol stearate, polyethylene wax, ethylene bis-stearamide, or silicone lubricant.

[0039] In this invention, the silicon-based lubricant can be any commonly used silicon-based lubricant in the art, such as polydimethylsiloxane, silicone powder, silicone ester, etc.

[0040] In a second aspect, the present invention provides a method for preparing a biodegradable composition as described in the first aspect of the present invention, the method comprising the following steps: The components are melt-blended and then extruded and granulated to obtain the biodegradable composition.

[0041] In this invention, the melt blending is not limited to being carried out in an extruder, which generally includes a first feeding section, a second feeding section and a melt blending section arranged in sequence.

[0042] Preferably, the temperature of the first feeding section is 80~90℃, for example, it can be 80℃, 82℃, 84℃, 86℃, 88℃, 90℃ or any of the above values.

[0043] Preferably, the temperature of the second feeding section is 90~150℃, for example, it can be 90℃, 95℃, 100℃, 105℃, 110℃, 120℃, 130℃, 140℃, 150℃ or any of the above values.

[0044] Preferably, the melt blending temperature is 180~210℃, for example, it can be 180℃, 190℃, 200℃, 210℃ or any range between the above values.

[0045] Thirdly, the present invention provides a biodegradable product formed from the biodegradable composition described in the first aspect of the present invention.

[0046] Preferably, the biodegradable product includes a membrane or bag.

[0047] Preferably, the membrane or bag has a thickness of ≤30mm, more preferably ≤20μm, more preferably ≤15μm, and even more preferably ≤12μm.

[0048] Preferably, the membrane is formed by using the biodegradable composition via melt blow molding.

[0049] Preferably, the bag is obtained by heat sealing with a film.

[0050] 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.

[0051] Compared with the prior art, the present invention has the following beneficial effects: In the biodegradable composition provided by this invention, the components such as biodegradable polyester, polylactic acid, flake mineral powder, and calcium carbonate work together synergistically. By controlling the relaxation time of the biodegradable polyester, the entanglement characteristics of the polyester molecular chains can be effectively regulated. Further optimization of the intrinsic viscosity of polylactic acid can further improve the compatibility between polylactic acid and polyester. Ultimately, the biodegradable composition has a high tensile strength of 10%, which can avoid the problem of breakage during the bag making process and meet the needs of rapid forming of ultra-thin films. Detailed Implementation

[0052] 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.

[0053] 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: PBAT1, Hangzhou Xinfu Technology Co., Ltd., Biosafe 2003F, relaxation time is 0.79s, molar percentage of terephthalic acid is 47.1% based on the total molar amount of terephthalic acid and adipic acid.

[0054] PBAT2, homemade, based on a three-step synthesis: Step 1: 20 kg of terephthalic acid, 13 kg of 1,4-butanediol, and 0.001 kg of diphenylmethane diisocyanate were esterified at 195°C for 2 hours, with continuous removal of the generated water during the process, to obtain butylene terephthalate oligomer; Step 2: 20 kg of adipic acid, 13 kg of... 1,4-Butanediol was esterified with 0.002 kg of diphenylmethane diisocyanate at 195 °C for 2 h, during which water was continuously removed to obtain butylene adipate oligomer. In the third step, butylene terephthalate oligomer, butylene adipate oligomer, and 0.3 kg of tetrabutyl titanate catalyst were added to a 200 L reactor and reacted at 240 °C and a vacuum pressure of 290 Pa for 6 h to obtain PBAT2. The relaxation time was 1.35 s. Based on the total molar amount of terephthalic acid and adipic acid, the molar percentage of terephthalic acid was 46.8%.

[0055] PBAT3, homemade, based on a three-step synthesis: Step 1: 23 kg of terephthalic acid, 13 kg of 1,4-butanediol, and 0.001 kg of diphenylmethane diisocyanate were esterified at 195°C for 2 hours, with continuous removal of the generated water during the process to obtain butylene terephthalate oligomer; Step 2: 17 kg of adipic acid, 13 kg of... 1,4-Butanediol was esterified with 0.002 kg of diphenylmethane diisocyanate at 195 °C for 2 h, during which water was continuously removed to obtain butylene adipate oligomer. In the third step, butylene terephthalate oligomer, butylene adipate oligomer, and 0.3 kg of tetrabutyl titanate catalyst were added to a 200 L reactor and reacted at 240 °C and a vacuum pressure of 290 Pa for 6 h to obtain PBAT3. The relaxation time was 1.69 s, and the molar percentage of terephthalic acid was 54.4% based on the total molar amount of terephthalic acid and adipic acid.

[0056] PBAT4, homemade, based on a three-step synthesis: Step 1: 20 kg of terephthalic acid, 13 kg of 1,4-butanediol, and 0.001 kg of diphenylmethane diisocyanate were esterified at 195°C for 0.5 h, with continuous removal of the generated water during the process to obtain butylene terephthalate oligomer; Step 2: 20 kg of adipic acid, 13 kg of... 1,4-Butanediol and 0.002 kg of diphenylmethane diisocyanate were esterified at 195 °C for 0.5 h, with the generated water being continuously removed during the process to obtain butylene adipate oligomer. In the third step, butylene terephthalate oligomer, butylene adipate oligomer, and 0.3 kg of tetrabutyl titanate catalyst were added to a 200 L reactor and reacted at 240 °C and a vacuum pressure of 290 Pa for 4 h to obtain PBAT3. The relaxation time was 0.18 s, and the molar percentage of terephthalic acid was 46.7% based on the total molar amount of terephthalic acid and adipic acid.

[0057] PBAT5, homemade, based on a three-step synthesis: Step 1: 20 kg of terephthalic acid, 13 kg of 1,4-butanediol, and 0.001 kg of diphenylmethane diisocyanate were esterified at 195°C for 4 hours, with continuous removal of the generated water during the process to obtain butylene terephthalate oligomer; Step 2: 20 kg of adipic acid, 13 kg of... 1,4-Butanediol was esterified with 0.002 kg of diphenylmethane diisocyanate at 195 °C for 4 h, with continuous removal of the generated water during the process, to obtain butylene adipate oligomer. In the third step, butylene terephthalate oligomer, butylene adipate oligomer, and 0.3 kg of tetrabutyl titanate catalyst were added to a 200 L reactor and reacted at 240 °C and a vacuum pressure of 290 Pa for 8 h to obtain PBAT4. The relaxation time was 8.24 s, and the molar percentage of terephthalic acid was 46.9% based on the total molar amount of terephthalic acid and adipic acid.

[0058] PBAT6, homemade, based on a three-step synthesis: Step 1: 20 kg of terephthalic acid, 13 kg of 1,4-butanediol, and 0.001 kg of diphenylmethane diisocyanate were esterified at 195°C for 0.1 h, with continuous removal of the generated water during the process to obtain butylene terephthalate oligomer; Step 2: 20 kg of adipic acid, 13 kg of... 1,4-Butanediol and 0.002 kg of diphenylmethane diisocyanate were esterified at 195 °C for 0.1 h, with the generated water being continuously removed during the process to obtain butylene adipate oligomer. In the third step, butylene terephthalate oligomer, butylene adipate oligomer, and 0.3 kg of tetrabutyl titanate catalyst were added to a 200 L reactor and reacted at 230 °C and a vacuum pressure of 260 Pa for 2 h to obtain PBAT5. The relaxation time was 0.08 s, and the molar percentage of terephthalic acid was 46.8% based on the total molar amount of terephthalic acid and adipic acid.

[0059] PBAT7, homemade, based on a three-step synthesis: Step 1: 20 kg of terephthalic acid, 13 kg of 1,4-butanediol, and 0.001 kg of diphenylmethane diisocyanate were esterified at 195°C for 8 hours, with continuous removal of the generated water during the process to obtain butylene terephthalate oligomer; Step 2: 20 kg of adipic acid, 13 kg of... 1,4-Butanediol was esterified with 0.002 kg of diphenylmethane diisocyanate at 195 °C for 8 h, during which water was continuously removed to obtain butylene adipate oligomer. In the third step, butylene terephthalate oligomer, butylene adipate oligomer, and 0.3 kg of tetrabutyl titanate catalyst were added to a 200 L reactor and reacted at 250 °C and a vacuum pressure of 330 Pa for 12 h to obtain PBAT6. The relaxation time was 13.2 s, and the molar percentage of terephthalic acid was 47.1% based on the total molar amount of terephthalic acid and adipic acid.

[0060] PBAT8, Zhuhai Kingfa Biomaterials Co., Ltd., A400 CF, relaxation time is 0.09s, molar percentage of terephthalic acid is 46.9% based on the total molar amount of terephthalic acid and adipic acid.

[0061] Polylactic acid: Polylactic acid 1, PLLA / PDLA copolymer, Nature Works, USA, 4043D, intrinsic viscosity of 1.58 dL / g, wherein the molar percentage of D-type lactic acid in the PLLA / PDLA copolymer is 4.6%.

[0062] Polylactic acid 2, PLLA / PDLA copolymer, Anhui Fengyuan Biotechnology Co., Ltd., FY 804, intrinsic viscosity is 1.42 dL / g, and the molar percentage of D-type lactic acid in the PLLA / PDLA copolymer is 3.6%.

[0063] Polylactic acid 3 (PLLA / PDLA) copolymer, prepared in-house, was prepared by means of: bulk ring-opening polymerization of 80 parts by weight of L-type lactide (purity 99.6%), 20 parts by weight of meso-lactide (purity 99.6%), and 0.005 parts by weight of stannous octoate in a 200L reactor, in three steps: First, the reaction was carried out for 2 hours at a temperature of 145℃ and a vacuum of 2000Pa to synthesize the polylactic acid oligomer; Second, the initial vacuum was set at 100Pa at 170℃, and the vacuum was increased every 60 minutes using a dynamic vacuum gradient control. The vacuum level was initially set at 50 Pa, then increased to 500 Pa. The reaction was carried out at 500 Pa for 3 hours to remove the byproduct lactide and shift the equilibrium towards polymerization. In the third step, the temperature was lowered to 150°C, and the initial vacuum level was set at 500 Pa. The vacuum level was decreased by 100 Pa every 60 minutes until it reached 300 Pa. At this point, 0.0005 parts by mass of zinc phosphate passivating agent was added, and the passivation treatment was carried out for 50 minutes. Then, the product was granulated underwater, crystallized, and dried to obtain the PLLA / PDLA copolymer with an intrinsic viscosity of 1.59 dL / g. The molar percentage of D-type lactic acid in the PLLA / PDLA copolymer was 9.8%.

[0064] Polylactic acid 4 (PLLA / PDLA) copolymer, self-made, preparation method includes: bulk ring-opening polymerization of 80 parts by mass of L-type lactide (purity 99.6%), 20 parts by mass of meso-lactide (purity 99.6%), and 0.002 parts by mass of stannous octoate in a 200L reactor, divided into three steps: First, the reaction is carried out for 2 hours at a reaction temperature of 145℃ and a reaction vacuum of 2000Pa to synthesize polylactic acid oligomer; Second, at 170℃, the initial vacuum is set to 100Pa, and the vacuum is increased every 60 minutes using dynamic vacuum gradient control. The vacuum level was initially set at 50 Pa, then increased to 500 Pa. The reaction was carried out at 500 Pa for 3 hours to remove the byproduct lactide and shift the equilibrium towards polymerization. In the third step, the temperature was lowered to 150°C, and the initial vacuum level was set at 500 Pa. The vacuum level was decreased by 100 Pa every 60 minutes until it reached 300 Pa. At this point, 0.0003 parts by mass of zinc phosphate passivating agent was added, and the passivation treatment was carried out for 30 minutes. Then, the product was granulated underwater, crystallized, and dried to obtain a PLLA / PDLA copolymer with an intrinsic viscosity of 0.96 dL / g. The molar percentage of D-type lactic acid in the PLLA / PDLA copolymer was 9.9%.

[0065] Polylactic acid 5 (PLLA / PDLA) copolymer, prepared in-house, was prepared by means of: bulk ring-opening polymerization of 80 parts by mass of L-type lactide (purity 99.6%), 20 parts by mass of meso-lactide (purity 99.6%), and 0.002 parts by mass of stannous octoate in a 200L reactor, in three steps: First, the reaction was carried out for 5 hours at a temperature of 145℃ and a vacuum of 2000Pa to synthesize the polylactic acid oligomer; Second, the initial vacuum was set at 100Pa at 170℃, and the vacuum was increased every 60 minutes using a dynamic vacuum gradient control. The vacuum level was initially set at 50 Pa, then increased to 500 Pa. The reaction was carried out at 500 Pa for 5 hours to remove the byproduct lactide and shift the equilibrium towards polymerization. In the third step, the temperature was lowered to 150°C, and the initial vacuum level was set at 500 Pa. The vacuum level was decreased by 100 Pa every 60 minutes until it reached 300 Pa. At this point, 0.0003 parts by mass of zinc phosphate passivating agent was added, and the passivation treatment was carried out for 20 minutes. Then, the product was granulated underwater, crystallized, and dried to obtain the PLLA / PDLA copolymer with an intrinsic viscosity of 1.86 dL / g. The molar percentage of D-type lactic acid in the PLLA / PDLA copolymer was 9.8%.

[0066] Polylactic acid 6 (PLLA / PDLA) copolymer, prepared in-house, was prepared by means of: bulk ring-opening polymerization of 80 parts by mass of L-lactide (99.6% purity), 20 parts by mass of meso-lactide (99.6% purity), and 0.002 parts by mass of stannous octoate in a 200L reactor, in three steps: First, the reaction was carried out at 145℃ and a vacuum of 2000Pa for 0.8h to synthesize the polylactic acid oligomer; Second, at 170℃, with an initial vacuum of 100Pa, the vacuum was increased every 60min using dynamic vacuum gradient control. The vacuum level was initially set at 50 Pa, then increased to 500 Pa. The reaction was carried out at 500 Pa for 1.5 hours to remove the byproduct lactide and shift the equilibrium towards polymerization. In the third step, the temperature was lowered to 150°C, and the initial vacuum level was set at 500 Pa. The vacuum level was decreased by 100 Pa every 60 minutes until it reached 300 Pa. At this point, 0.0003 parts by mass of zinc phosphate passivating agent was added, and the passivation treatment was carried out for 50 minutes. Then, the product was granulated underwater, crystallized, and dried to obtain a PLLA / PDLA copolymer with an intrinsic viscosity of 0.81 dL / g. The molar percentage of D-type lactic acid in the PLLA / PDLA copolymer was 10.1%.

[0067] Polylactic acid 7 (PLLA / PDLA copolymer), self-made, preparation method includes: bulk ring-opening polymerization of 80 parts by mass of L-type lactide (purity 99.6%), 20 parts by mass of meso-lactide (purity 99.6%), and 0.002 parts by mass of stannous octoate in a 200L reactor, divided into three steps: First, the reaction is carried out for 7 hours at a reaction temperature of 145℃ and a reaction vacuum of 2000Pa to synthesize polylactic acid oligomer; Second, at 170℃, the initial vacuum is set to 100Pa, and the vacuum is increased every 60 minutes using dynamic vacuum gradient control. The vacuum level was initially set at 50 Pa, then increased to 500 Pa. The reaction was carried out at 500 Pa for 7 hours to remove the byproduct lactide and shift the equilibrium towards polymerization. In the third step, the temperature was lowered to 150°C, and the initial vacuum level was set at 500 Pa. The vacuum level was decreased by 100 Pa every 60 minutes until it reached 300 Pa. At this point, 0.0003 parts by mass of zinc phosphate passivating agent was added, and the passivation treatment was carried out for 10 minutes. Then, the product was granulated underwater, crystallized, and dried to obtain the PLLA / PDLA copolymer with an intrinsic viscosity of 2.11 dL / g. The molar percentage of D-type lactic acid in the PLLA / PDLA copolymer was 9.9%.

[0068] Flaky mineral powder: Flaky mineral powder 1, talc powder, Liaoning Aihai Talc Company, D50 particle size is 1.5μm.

[0069] Flaky mineral powder 2, montmorillonite, Zhejiang Fenghong New Materials, D50 particle size is 4.5μm.

[0070] Calcium carbonate: Omia Technologies, D50 particle size is 1.8μm.

[0071] Opening agent: Fumed silica, Wacker Chemie Ltd.

[0072] Lubricant: Polydimethylsiloxane, Wanhua Chemical.

[0073] Examples 1-15 and Comparative Examples 1-3 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.

[0074] Unless otherwise specified, the preparation method of the biodegradable composition in this invention includes: melting and blending the components in an extruder and then extruding and granulating them, wherein the extruder temperature from the feed port to the die head is set to 80°C, 120°C, 150°C, 180°C, 180°C, 180°C, 190°C and 200°C respectively, to obtain the biodegradable composition.

[0075] Table 1 Table 2 Table 3 Performance testing: The biodegradable composition was melt-blown to form a film using a blown film extrusion machine with a die diameter of 50 mm. The blown film extrusion machine temperature was set at 50°C, 80°C, 150°C, 150°C, 150°C, and 160°C from the feed port to the die head, respectively. The blown film frequency was 25 Hz, resulting in a film with a thickness of 10 mm. A 1μm thin film with a width of 350mm.

[0076] According to GB / T 1040.3-2006 standard, a 10μm thick film was tested at a tensile speed of 500mm / min based on the film tensile test standard. The tensile strength when the film elongation reached 10% was recorded, i.e., the 10% constant elongation strength. The test was performed five times, and the average value was taken.

[0077] The specific test results are shown in Table 4.

[0078] Table 4 As shown in Table 4, in the biodegradable composition provided by this invention, the components such as biodegradable polyester, polylactic acid, flake mineral powder, and calcium carbonate work together synergistically. By controlling the relaxation time of the biodegradable polyester, the entanglement characteristics of the polyester molecular chains can be effectively regulated. Further optimization of the intrinsic viscosity of polylactic acid can improve the compatibility between polylactic acid and polyester. Ultimately, the biodegradable composition has a high 10% tensile strength, reaching above 8.62 MPa, and under optimal conditions, above 10.44 MPa. This can avoid the problem of breakage during bag making and meet the needs of rapid forming of ultra-thin films.

[0079] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A biodegradable composition, characterized in that, The biodegradable composition comprises, by weight, 41-97 parts of biodegradable polyester, 1-10 parts of polylactic acid, 1-15 parts of flake mineral powder and 1-34 parts of calcium carbonate; The relaxation time of the biodegradable polyester is 0.1~10s.

2. The biodegradable composition according to claim 1, characterized in that, The biodegradable polyester includes aliphatic-aromatic copolyesters; Preferably, the aliphatic-aromatic copolyester includes at least one of polybutylene adipate terephthalate, polybutylene sebacate terephthalate, or polybutylene succinate terephthalate.

3. The biodegradable composition according to claim 1, characterized in that, The relaxation time of the biodegradable polyester is 0.2~8s, preferably 0.35~5s.

4. The biodegradable composition according to claim 1, characterized in that, The polylactic acid includes a PLLA / PDLA copolymer; Preferably, the intrinsic viscosity of the polylactic acid is 0.9~2.0 dL / g, more preferably 1.0~1.8 dL / g, and even more preferably 1.1~1.7 dL / g.

5. The biodegradable composition according to claim 1, characterized in that, The flaky mineral powder includes at least one of talc, montmorillonite, or mica, preferably talc and / or montmorillonite.

6. The biodegradable composition according to claim 1, characterized in that, The biodegradable composition further includes, by weight, 0.1 to 2 parts of an opening agent; Preferably, the opening agent includes at least one of silicon dioxide, zeolite, barium sulfate, or polyethylene wax, and more preferably at least one of silicon dioxide, barium sulfate, or polyethylene wax.

7. The biodegradable composition according to claim 1, characterized in that, The biodegradable composition further includes, by weight, 0.1 to 2 parts of lubricant; Preferably, the lubricant comprises at least one of erucamide, oleamide, glyceryl monostearate, pentaerythritol stearate, polyethylene wax, ethylene bis-stearamide, or silicone lubricant.

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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