Preparation method of biodegradable composite material

Abstract

The invention relates to a preparation method of a biodegradable composite material, and belongs to the technical field of compositions of high-molecular compounds. The preparation method of the biodegradable composite material comprises the following steps: adding molten biodegradable resin I from an upper screw cylinder opening of an extruder, mixing with other components, melting and extruding to obtain the biodegradable composite material, the other components comprise biodegradable resin II, a filler and a processing aid; the biodegradable resin I is PBAT (poly (butylene adipate-co-terephthalate)), and the biodegradable resin II comprises at least one of PLA (polylactic acid), PBS (poly (butylene succinate)), PBSeT and PHA (polyhydroxyalkanoate). The biodegradable composite material prepared by the preparation method disclosed by the invention has excellent mechanical properties and low odor.

Description

Technical Field

[0001] The present invention relates to the technical field of compositions of polymer compounds, and particularly to a preparation method of a biodegradable composite material. Background Art

[0002] The preparation process of modified plastics mainly includes the following steps: material mixing → material weighing → material metering → kneading and processing → extrusion and pelletizing. Among them, the kneading and processing step is the key step to ensure uniform kneading of materials and plays an important role in the performance of products. At present, internal mixers or extruders (single-screw extruders, twin-screw extruders, multi-screw extruders) are mainly used for kneading and processing; compared with internal mixers, extruders are more suitable for continuous kneading and processing of multi-component, multi-form, and multi-physical property materials.

[0003] There are mainly two feeding methods for the materials processed by existing extruders. One is to mix all the used materials evenly in a mixing device and then meter and feed them into the extruder for kneading and extrusion. For example, the modified plastic extruder disclosed in Chinese Patent CN214082240U performs kneading and processing in this way, but this method is not suitable for a formulation system with multiple components and large differences in the proportions, physical properties, and forms of each component, which will directly lead to problems such as uneven material stratification and poor continuous production stability.

[0004] The other feeding method is to separately meter each component material into a hopper, or meter the mixed materials of some small-proportion components and other components together separately into a hopper, and then feed them together from one extruder feeding port for kneading and extrusion or feed them sequentially from multiple extruder feeding ports for kneading and extrusion. For example, the twin-screw side feeder disclosed in Chinese Patent CN209365320U adopts a method of feeding materials into the extruder in sections. Some materials enter the extruder from the front main feeding port for melting and plasticizing first, and other materials enter the extruder from the side feeding port at the rear section of the extruder and are kneaded and extruded with the materials that have been melted or semi-melted and entered from the front section.

[0005] Compared with mixing all the used materials evenly in a mixing device and then metering and feeding them into the extruder for kneading and extrusion, this processing method can not only solve the problems of material stratification during the feeding process and the difficulty of powder materials being eaten by the powder, but also reduce the wear of extrusion equipment such as the screw barrel and screw to a certain extent. However, this processing method has the problem that the plasticization conditions of different materials do not match the plasticization ability of the screw arrangement, which easily leads to poor plasticization or over-plasticization of materials during continuous production; especially for biodegradable composite materials, which include different biodegradable resins, it is extremely easy to cause uneven distribution of filled powder due to poor plasticization, and the mechanical properties of the composite material are poor and the odor is large due to over-plasticization. Summary of the Invention

[0006] The object of the present invention is to overcome the deficiencies of the prior art and provide a method for preparing a biodegradable composite material.

[0007] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] The present invention provides a method for preparing a biodegradable composite material, comprising the following steps:

[0009] Add the molten biodegradable resin I from the upper barrel opening of the extruder, mix and melt-extrude it with other components to obtain a biodegradable composite material;

[0010] The other components include biodegradable resin II, filler, and processing aid;

[0011] The biodegradable resin I is PBAT (polybutylene adipate-co-terephthalate);

[0012] The biodegradable resin II includes at least one of PLA (polylactic acid), PBS (polybutylene succinate), PBSeT (polybutylene sebacate-co-terephthalate), and PHA (polyhydroxyalkanoate).

[0013] Compared with the prior art of adding PBAT pellets from the main feeding port or side feeding port of the extruder, the present invention directly adds the PBAT melt from the upper barrel opening of the extruder, which can not only be fully mixed with other resin components that have been preliminarily sheared, melted, and plasticized and added from the main feeding port of the extruder to ensure good plasticization effect, thereby enabling the filler to be evenly distributed in the resin melt, thus improving the product quality stability during continuous production; but also effectively avoid over-plasticization of PBAT, thereby improving the mechanical properties of the biodegradable composite material and being beneficial to reducing the odor of the biodegradable composite material.

[0014] It should be noted that the extruder in the above preparation method is a common extruder such as a single-screw extruder, a twin-screw extruder, or a planetary screw extruder; preferably a twin-screw extruder, such as a 65-type extruder, a 75-type extruder, a 95-type extruder, etc. (the numbers are the nominal diameters of the screws), and the total length of the barrel is 32D to 64D (D is the nominal diameter of the screw).

[0015] The upper barrel opening of the extruder refers to the top opening of the barrel located between the main feeding port and the side feeding port (the side feeding port adjacent to the main feeding port) of the extruder; this barrel can generally specifically be the third barrel, the fourth barrel, or the fifth barrel of the extruder.

[0016] As a preferred embodiment of the preparation method of the biodegradable composite material of the present invention, the mass fraction of the biodegradable resin I in the biodegradable composite material is ≥50%. Optionally, the mass fraction of the biodegradable resin I in the biodegradable composite material can specifically be any one or the range value of any two of 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 99%.

[0017] As a preferred embodiment of the preparation method of the biodegradable composite material of the present invention, the mass fraction of the biodegradable resin I in the biodegradable composite material is 70% - 90%.

[0018] As a preferred embodiment of the preparation method of the biodegradable composite material of the present invention, the mass fraction of the biodegradable resin II in the biodegradable composite material is 1% - 30%. Optionally, the mass fraction of the biodegradable resin II in the biodegradable composite material can specifically be any one or the range value of any two of 1%, 5%, 10%, 15%, 20%, 25%, 30%.

[0019] As a preferred embodiment of the preparation method of the biodegradable composite material of the present invention, the biodegradable resin II and the processing aid are added from the main feeding port of the extruder, and the filler is added from the side feeding port of the extruder. Specifically, the main feeding port is generally located in the first or second barrel of the extruder, and the side feeding port is generally located in the fifth, sixth, seventh or eighth barrel of the extruder.

[0020] As a preferred embodiment of the preparation method of the biodegradable composite material of the present invention, the PBAT has a melt mass flow rate of 3 - 15 g / 10 min under the conditions of 190°C and 2.16 kg according to the ISO 1133-2011 standard; specifically, it can be any one or the range value of any two of 3 g / 10 min, 4 g / 10 min, 5 g / 10 min, 6 g / 10 min, 7 g / 10 min, 8 g / 10 min, 9 g / 10 min, 10 g / 10 min, 11 g / 10 min, 12 g / 10 min, 13 g / 10 min, 14 g / 10 min, 15 g / 10 min; preferably, the melt mass flow rate of the PBAT is 3.5 - 8.5 g / 10 min.

[0021] In the above preparation method, conventional biodegradable resin I pellets can be melted and then added to the extruder, or the melt polymerized from terephthalic acid, adipic acid and 1,4-butanediol can be directly added to the extruder; compared with the former, the latter can omit the intermediate stages of synthetic resin cooling and pelletizing, packaging and transportation, and plasticizing and melting, and directly modify the synthesized resin melt to achieve integrated production of polymerization and modification.

[0022] As a preferred embodiment of the preparation method of the biodegradable composite material of the present invention, the biodegradable resin I is added to the extruder through a metering melt pump.

[0023] The biodegradable resin II and processing aids in the biodegradable composite material can be metered and fed through a loss-in-weight weigher, enter and undergo preliminary shear melting and plasticization in the front section of the extruder, and then meet and mix with the molten material (biodegradable resin I) pumped through the melt pipeline in the middle section of the extruder; while the filler in the biodegradable composite material is fed into the extruder through one or two side feeders in the rear section of the extruder and kneaded with all the materials that entered the extruder before; the kneaded material is granulated through vacuum devolatilization of the extruder, stable pumping of the melt pump, impurity filtration of the screen changer, and underwater pelletizing system to complete the product processing process.

[0024] As Figure 1 shown, waste can be discharged by switching the discharge valve, weighing the weight of the discharged waste melt per unit time, and then calculating the flow rate at different melt pump speeds to achieve precise matching of the flow rate of the loss-in-weight weigher and the metering flow rate of the melt pump. In addition, considering the safety of melt metering and injection, multiple pressure gauges can be set on the pipeline where the melt enters to monitor the melt pressure; when the pressure value of pressure gauge 1 monitored by the system is greater than the warning value, the discharge valve will automatically open to discharge waste. At the same time, to avoid errors in the startup process caused by human factors, the operating state of the extruder and the opening and closing of the discharge valve can be interlocked, and only when the extruder is started and the rotation speed reaches a certain value, the discharge valve will be allowed to close and feed. The same is true for the startup and shutdown of the loss-in-weight weigher. Only when the discharge valve closes and feeds, the weigher will be allowed to start, and at the same time, if the discharge valve opens to discharge waste automatically / manually, the weigher will immediately stop feeding to prevent the modified filler from blocking the screw.

[0025] As a preferred embodiment of the preparation method of the biodegradable composite material of the present invention, the aspect ratio of the extruder is (32 - 64):1.

[0026] As a preferred embodiment of the preparation method of the biodegradable composite material of the present invention, the filler includes at least one of glass fiber, calcium carbonate, talcum powder, titanium dioxide, kaolin; preferably calcium carbonate and / or talcum powder, and its average particle size is 1 - 4μm;

[0027] And / or, the processing aid includes at least one of a lubricant, a nucleating agent, a compatibilizer, a dispersant, and an antiblocking agent.

[0028] Optionally, the above-mentioned lubricant may specifically be at least one of erucamide, polyethylene wax, N,N'-ethylenebisstearamide, and stearic acid; the nucleating agent may specifically be at least one of talcum powder and phosphate ester salt nucleating agent; the dispersant may specifically be at least one of polyethylene wax and N,N'-ethylenebisstearamide; the antiblocking agent may specifically be at least one of silica, Fischer-Tropsch wax, and oleamide.

[0029] As a preferred embodiment of the preparation method of the biodegradable composite material of the present invention, the lubricant includes one or more of erucamide and polyethylene wax; the mass percentage content of the lubricant is 0.1% to 2%. Preferably, the lubricant is polyethylene wax, and the melt mass flow rate of the polyethylene wax is ≥ 30 g / 10 min under the conditions of 190 °C and 2.16 kg according to the ISO 1133-2011 standard. Compared with other lubricants, polyethylene wax not only has a good lubrication effect but also has an excellent dispersion effect.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] In the present invention, the PBAT melt is directly added from the middle upper barrel opening of the extruder, which can not only be fully mixed with other resin components that have been preliminarily sheared, melted, and plasticized and added from the main feeding port of the extruder to ensure a good plasticization effect, thereby enabling the filler to be evenly distributed in the resin melt, and thus improving the product quality stability during continuous production; but also effectively avoid over-plasticization of PBAT, thereby improving the mechanical properties of the biodegradable composite material and being beneficial to reducing the odor of the biodegradable composite material. Description of the Drawings

[0032] Figure 1 It is a process schematic diagram of the preparation method of the biodegradable composite material in Example 1. Detailed Embodiments

[0033] To better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0034] Other materials, reagents, etc. used in the examples can be obtained from commercial channels without special instructions.

[0035] 1) In the example, the twin-screw extruder is the 75D model of Nanjing Ouli Extrusion Machinery Co., Ltd. The screw diameter of this twin-screw extruder is 71 mm, the length-diameter ratio is 48:1, and the barrel temperatures of each zone are as follows: the temperature of zone 1 is 80 °C, the temperature of zone 2 is 160 °C, the temperature of zone 3 is 160 °C, the temperature of zone 4 is 160 °C, the temperature of zone 5 is 160 °C, the temperature of zone 6 is 160 °C, the temperature of zone 7 is 160 °C, the temperature of zone 8 is 160 °C, and the temperature from zone 9 to the last zone is 180 °C.

[0036] The process parameters adopted in the example are as follows: the screw speed of the extruder is fixed at 350 rpm, and the total flow rate of the formulated materials is 870 kg / h. The flow rate of the melt part is calibrated by controlling the different output efficiencies of the metering melt pump to obtain the pumping parameters of the melt pump at different melt pump speeds for the corresponding melt flow rates.

[0037] The materials are mixed and extruded by the twin-screw extruder and pelletized by underwater pelletizing to obtain the finished materials.

[0038] 2) Raw materials and reagents

[0039] PBAT resin: Manufacturer is Wanhua Chemical, grade is T16. The melt mass flow rate measured at 190 °C and 2.16 kg according to the ISO 1133-2011 standard is 3.9 g / 10 min;

[0040] PLA resin: Manufacturer is Jinfa Biology, grade is KB600 NF20. The melt mass flow rate at 190 °C and 2.16 kg according to the ISO 1133-2011 standard is 6 g / 10 min, and the D content ≤ 2%;

[0041] N,N'-ethylenebisstearamide: Manufacturer is Dow Chemical, grade is EBS B50;

[0042] Erucamide: Manufacturer is Croda Chemical Europe, grade is CH-BE-(SI);

[0043] Polyethylene wax: Manufacturer is Guangdong Weilinna, grade is PE-S105;

[0044] Calcium carbonate 1: Manufacturer is Lianzhou Xinrong, grade is ACC-815, average particle size is 2.5 μm;

[0045] Calcium carbonate 2: Manufacturer is Lianzhou Xinrong, grade is ACC-812, average particle size is 1.8 μm;

[0046] Calcium carbonate 3: Manufacturer is Lianzhou Xinrong, grade is ACC-818, average particle size is 3.1 μm;

[0047] Talc powder: Manufacturer is Tianyuan Chemical Industry, grade is TYT-777A, average particle size is 3.5 μm.

[0048] Example 1

[0049] This example provides a method for preparing a biodegradable composite material (as shown in Figure 1 ), which includes the following steps:

[0050] S1. Add terephthalic acid and 1,4-butanediol into an esterification reactor according to a molar ratio of 1:1.5, and add 1% of the total mass of the raw materials of tetrabutyl titanate as a catalyst. React for 2.5 h at a temperature of 230 °C and a pressure of 40 KPa to obtain an esterified product A1;

[0051] Add adipic acid and 1,4-butanediol into an esterification reactor according to a molar ratio of 1:1.67. React for 2.5 h at a temperature of 200 °C and a pressure of 40 KPa to obtain an esterified product A2;

[0052] Continuously feed the esterified product A1 and the esterified product A2 into a mixer according to a molar ratio of 44:56 to calculate the feed liquid flow rate and mix. React for 2.5 h at a temperature of 240 °C and a pressure of 4 KPa to obtain a prepolymer, and then continue to polymerize at a temperature of 240 °C and a pressure of 120 Pa until the melt flow rate of the polyester reaches 4 g / 10 min (sampling, cooling, pelletizing, measured at 190 °C and 2.16 kg according to the ISO1133-2011 standard) to obtain a polybutylene adipate / terephthalate (PBAT) melt;

[0053] S2. Mix PLA resin, a dispersant (N,N'-ethylenebisstearamide), and a lubricant (erucamide) evenly and add them into a twin-screw extruder from the main feed port. At the same time, use a melt pump to add the PBAT melt in S1 (feeding temperature is 160 °C) into the twin-screw extruder from the middle upper barrel port, and add a filler (calcium carbonate 1) into the twin-screw extruder from the side feed port, and mix and melt-extrude to obtain a biodegradable composite material (where the mass ratio of the PBAT melt, PLA resin, dispersant, lubricant, and filler is 70:7:0.5:0.5:22).

[0054] Example 2

[0055] This example provides a method for preparing a biodegradable composite material. The S1 and S2 steps are the same as those in Example 1. The difference from Example 1 is that the mass ratio of the PBAT melt, PLA resin, dispersant, lubricant, and filler is 80:7:0.5:0.5:12.

[0056] Example 3

[0057] This example provides a method for preparing a biodegradable composite material, which includes the following steps:

[0058] S1. Extrude and melt - plasticize PBAT resin (Wanhua Chemical, grade T16) through a single - screw feeder, and add a screen changer at the end of the single - screw feeder to filter impurities in the PBAT resin to obtain a PBAT melt;

[0059] S2. Mix PLA resin, dispersant (N,N'-ethylenebisstearamide) and lubricant (erucamide) evenly and add them into the twin - screw extruder from the main feed port. At the same time, use a melt pump to add the PBAT melt in S1 (feeding temperature is 160 °C) into the twin - screw extruder from the middle upper barrel port, and add filler (calcium carbonate 1) into the twin - screw extruder from the side feed port, then mix, melt and extrude to obtain a biodegradable composite material (where the mass ratio of PBAT melt, PLA resin, dispersant, lubricant and filler is 70:7:0.5:0.5:22).

[0060] Example 4

[0061] This example provides a preparation method of a biodegradable composite material. The difference from Example 1 is only that the melt mass flow rate of the PBAT melt prepared in step S1 is 5.5 g / 10 min (measured at 190 °C and 2.16 kg according to the ISO 1133 - 2011 standard).

[0062] Example 5

[0063] This example provides a preparation method of a biodegradable composite material. The difference from Example 1 is only that the melt mass flow rate of the PBAT melt prepared in step S1 is 8 g / 10 min (measured at 190 °C and 2.16 kg according to the ISO 1133 - 2011 standard).

[0064] Example 6

[0065] This example provides a preparation method of a biodegradable composite material. The difference from Example 1 is only that the melt mass flow rate of the PBAT melt prepared in step S1 is 12 g / 10 min (measured at 190 °C and 2.16 kg according to the ISO 1133 - 2011 standard).

[0066] Example 7

[0067] This example provides a preparation method of a biodegradable composite material. The difference from Example 1 is only that the filler in step S2 is calcium carbonate 2.

[0068] Example 8

[0069] This example provides a preparation method of a biodegradable composite material. The difference from Example 1 is only that the filler in step S2 is calcium carbonate 3.

[0070] Example 9

[0071] This example provides a method for preparing a biodegradable composite material, which is only different from Example 1 in that the filler in step S2 is talc powder.

[0072] Example 10

[0073] This example provides a method for preparing a biodegradable composite material, which is only different from Example 1 in that the lubricant in step S2 is polyethylene wax.

[0074] Comparative Example 1

[0075] This comparative example provides a method for preparing a biodegradable composite material, including the following steps:

[0076] S1. Add terephthalic acid and 1,4-butanediol into an esterification reactor according to a molar ratio of 1:1.5, and add 1% of the total mass of the raw materials of tetrabutyl titanate as a catalyst. React at a temperature of 230°C and a pressure of 40 KPa for 2.5 h to obtain an esterified product A1;

[0077] Add adipic acid and 1,4-butanediol into an esterification reactor according to a molar ratio of 1:1.67, and react at a temperature of 200°C and a pressure of 40 KPa for 2.5 h to obtain an esterified product A2;

[0078] Continuously feed the esterified product A1 and the esterified product A2 into a mixer according to a molar ratio of 44:56 to calculate the feed liquid flow rate, and react at a temperature of 240°C and a pressure of 4 KPa for 2.5 h to obtain a prepolymer. Then continue to polymerize at a temperature of 240°C and a pressure of 120 Pa until the melt flow rate of the polyester reaches 4 g / 10 min (sampling, cooling, pelletizing, measured according to the ISO1133-2011 standard at 190°C and 2.16 kg) to obtain a poly(butylene adipate-co-terephthalate) PBAT melt. Introduce the melt into an underwater pelletizing system through one end of a three-way valve, cool and pelletize to obtain granular PBAT;

[0079] S2. Mix the granular PBAT, PLA resin, dispersant (N,N'-ethylenebisstearamide), and lubricant (erucamide) in S1 evenly and add them into a twin-screw extruder from the main feed port. At the same time, add the filler (calcium carbonate 1) into the twin-screw extruder from the side feed port, mix, melt, and extrude to obtain a biodegradable composite material (where the mass ratio of the granular PBAT, PLA resin, dispersant, lubricant, and filler is 70:7:0.5:0.5:22).

[0080] Comparative Example 2

[0081] This comparative example provides a method for preparing a biodegradable composite material, which includes the following steps:

[0082] S1. Add terephthalic acid and 1,4-butanediol into an esterification reactor according to a molar ratio of 1:1.5, and add 1% (by total mass of raw materials) of the catalyst tetrabutyl titanate. React at a temperature of 230 °C and a pressure of 40 KPa for 2.5 h to obtain esterified product A1;

[0083] Add adipic acid and 1,4-butanediol into an esterification reactor according to a molar ratio of 1:1.67. React at a temperature of 200 °C and a pressure of 40 KPa for 2.5 h to obtain esterified product A2;

[0084] Continuously feed the esterified product A1 and the esterified product A2 into a mixer according to the calculated feed liquid flow rate at a molar ratio of 44:56. React at a temperature of 240 °C and a pressure of 4 KPa for 2.5 h to obtain a prepolymer, and then continue to polymerize at a temperature of 240 °C and a pressure of 120 Pa until the melt flow rate of the polyester reaches 4 g / 10 min (sampling, cooling, pelletizing, measured at 190 °C and 2.16 kg according to the ISO 1133-2011 standard) to obtain a polybutylene adipate / terephthalate (PBAT) melt. Introduce the melt into an underwater pelletizing system through one end of a three-way valve, cool and pelletize to obtain granular PBAT;

[0085] S2. Mix PLA resin, dispersant (N,N'-ethylenebisstearamide) and lubricant (erucamide) evenly and add them into a twin-screw extruder from the main feed port. At the same time, add the granular PBAT in S1 into the twin-screw extruder from the middle side feed port 1 (side feed port 1 is located between the main feed port and side feed port 2), and add the filler (calcium carbonate 1) into the twin-screw extruder from side feed port 2. Mix, melt and extrude to obtain a biodegradable composite material (where the mass ratio of granular PBAT, PLA resin, dispersant, lubricant to filler is 70:7:0.5:0.5:22).

[0086] Comparative Example 3

[0087] This comparative example provides a method for preparing a biodegradable composite material, which is only different from Comparative Example 1 in that the melt mass flow rate of the granular PBAT prepared in step S1 is 5.5 g / 10 min (measured at 190 °C and 2.16 kg according to the ISO 1133-2011 standard).

[0088] Comparative Example 4

[0089] This comparative example provides a method for preparing a biodegradable composite material, which is only different from Comparative Example 1 in that the melt mass flow rate of the granular PBAT obtained in step S1 is 8 g / 10 min (measured at 190 °C and 2.16 kg according to the ISO 1133-2011 standard).

[0090] Comparative Example 5

[0091] This comparative example provides a method for preparing a biodegradable composite material, which is only different from Comparative Example 1 in that the melt mass flow rate of the granular PBAT obtained in step S1 is 12 g / 10 min (measured at 190 °C and 2.16 kg according to the ISO 1133-2011 standard).

[0092] Performance test

[0093] 1) Stability test: Starting from the time when the material is added to the twin-screw extruder, the biodegradable composite materials obtained at the 1st h, 2nd h, 3rd h, 4th h, 5th h, 6th h, 7th h, 8th h, and 9th h are respectively taken, and the calcium carbonate content in the biodegradable composite material is measured according to the GB / T 9345.1-2008 standard to evaluate the stability of the biodegradable composite material. The test results are shown in Table 1.

[0094] Table 1 Ash content of the biodegradable composite materials in each example and comparative example

[0095]

[0096]

[0097] According to the data in Table 1, the fluctuations of the ash content data of Examples 1 to 3 are all within ±1%, which is basically equivalent to those of Comparative Examples 1 and 2, indicating that compared with the current conventional extrusion process, directly adding the PBAT melt into the extruder in the present invention can maintain the production stability.

[0098] 2) Mechanical properties: The biodegradable composite materials in each example and comparative example are blown into films with a thickness of 20 μm. The tensile strength of the films is tested according to GB / T 1040.3-2006, the gauge length is 100 mm, and the tensile speed is 500 mm / min; the tear resistance of the films is tested according to GB / T 16578.2-2009. The test results are shown in Table 2.

[0099] 3) Odor level: The biodegradable composite materials in each example and comparative example are injection molded into standard square plates with a size of 100 mm × 100 mm × 2 mm, and then tested according to the VW AUTO PV3900 standard. The test results are shown in Table 2.

[0100] Table 2 Properties of the biodegradable composite materials in each example and comparative example

[0101]

[0102]

[0103] According to the data in Table 2, it can be seen that for the films made of the biodegradable composite materials in Examples 1 to 10, the longitudinal tensile strength ≥ 23 MPa, the transverse tensile strength ≥ 11 MPa, the longitudinal tear strength ≥ 1500 MPa, the transverse tear strength ≥ 2100 MPa, and the odor level ≤ 3.9. That is, the mechanical properties and odor properties are significantly better than those of Comparative Examples 1 to 5. This is mainly because the addition of the melt can reduce the shear friction of the extruder on the material, and also reduce the residence time of the resin under high temperature and high shear during the whole production and processing, retaining the integrity of the resin microstructure. Therefore, the biodegradable composite material prepared by the preparation method of the present invention has both excellent mechanical properties and low odor.

[0104] It can be seen from Examples 1, 4, 5 and 6 that as the melt mass flow rate of the PBAT melt increases, the tensile strength and tear strength of the films made of the biodegradable composite materials both decrease with the increase of the melt mass flow rate of the PBAT melt. At the same time, it is found that increasing the melt mass flow rate of the PBAT melt is beneficial to reducing the odor level of the biodegradable composite material.

[0105] It can be seen from Examples 7, 1 and 8 that as the average particle size of calcium carbonate increases, the tensile strength and tear strength of the films made of the biodegradable composite materials gradually decrease. The influence of the average particle size of the filler on the odor level of the biodegradable composite material is small. At the same time, it can be found from Examples 8 and 9 that compared with granular calcium carbonate, when flaky talc is used as the inorganic filler, since it will increase the friction with the screw, to a certain extent, it will reduce the tensile strength and tear strength of the biodegradable composite material film and increase the odor level.

[0106] It can be found from Examples 1 and 10 that compared with erucamide, using polyethylene wax as the lubricant is more beneficial to the uniform dispersion of the filler in the resin, and thus better improves the tear mechanical properties of the biodegradable composite material film.

[0107] It can be seen from Examples 1 and Comparative Example 1, Examples 4 and Comparative Example 3, Examples 5 and Comparative Example 4, Examples 6 and Comparative Example 5 that when the melt mass flow rate of PBAT is 3.5 - 8.5 g / 10 min, the preparation method of the present invention can better improve the mechanical properties and odor properties of the biodegradable composite material film.

[0108] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a biodegradable composite material, characterized in that: The following steps are involved: Adding the molten biodegradable resin I from the upper screw port of the extruder, mixing with other components and melt-extruded to obtain a biodegradable composite material; The other components include biodegradable resin II, fillers, and processing aids; The biodegradable resin I is PBAT, and the biodegradable resin II includes at least one of PLA, PBS, PBSeT, and PHA.

2. The preparation method according to claim 1, characterized in that The mass percentage of the biodegradable resin I in the biodegradable composite material is ≥50%.

3. The preparation method according to claim 2, characterized in that: The mass percentage of the biodegradable resin I in the biodegradable composite material is 70% to 90%.

4. The preparation method according to claim 1, characterized in that: The mass percentage of the biodegradable resin II in the biodegradable composite material is 1% to 30%.

5. The preparation method according to claim 1, characterized in that: The biodegradable resin II and the processing aid are added from the main feeding port of the extruder, and the filler is added from the side feeding port of the extruder.

6. The preparation method according to claim 1, characterized in that: The melt mass flow rate of the PBAT at 190° C. and 2.16 kg is 3 to 15 g / 10 min.

7. The preparation method according to claim 1, characterized in that: The biodegradable resin I is added to the extruder via a metering melt pump.

8. The preparation method according to claim 1, characterized in that: The screw length-to-diameter ratio of the extruder is (32-64):

1.

9. The preparation method according to claim 1, characterized in that: The filler comprises at least one of glass fiber, calcium carbonate, talcum powder, titanium dioxide, and kaolin; And / or, the processing aid includes at least one of a lubricant, a nucleating agent, a compatibilizer, a dispersant, and an opening agent.

10. The preparation method according to claim 9, characterized in that: The lubricant comprises one or more of erucamide and polyethylene wax; the mass percentage of the lubricant is 0.1% to 2%.

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