Biodegradable composition as well as preparation method and application thereof

Abstract

The invention discloses a biodegradable composition as well as a preparation method and application thereof, and belongs to the technical field of polymer engineering plastics. The biodegradable composition provided by the invention is prepared from the following components in parts by mass: 48 to 72 parts of poly (butylene terephthalate)-adipate, 2 to 10 parts of polylactic acid, 18 to 42 parts of calcium carbonate, 1 to 9 parts of talcum powder and 0.3 to 1.2 parts of slipping agent, the calcium carbonate comprises first calcium carbonate and second calcium carbonate. The product prepared by the invention has excellent puncture performance and relatively low film blowing apparent density; therefore, the method can be widely applied to preparation of packaging bags. In addition, the preparation method of the biodegradable composition provided by the invention is simple to operate and beneficial to actual production.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of high molecular engineering plastics, and particularly relates to a biodegradable composition and a preparation method and application thereof. BACKGROUND

[0002] Polybutylene adipate terephthalate (PBAT) is the most mature flexible biodegradable polyester at present, and has similar performance to PE and can be used for film blowing molding. At present, it has been widely used in shopping bags, milk tea bags, express bags and other fields.

[0003] There are two types of PBAT film modification products, namely mineral powder filling and starch filling. The cost of mineral powder is lower, and the cost performance is higher. In the actual film blowing process, the real thickness of the film is lower than the thickness measured by the gauge due to the roughness of the filler on the surface of the film. The rougher the surface of the film, the lower the apparent density (gram weight of the film per unit volume) calculated. This is a desirable result in production, as low apparent density means that the same weight of raw material can produce a larger area of film, which helps to reduce production costs. However, too low apparent density will result in a decrease in the puncture performance of the film. How to maintain the puncture performance of the film while keeping low apparent density is a key research content in the industry. SUMMARY

[0004] The present application aims to overcome the shortcomings of the prior art and provide a biodegradable composition with good puncture performance and low apparent density, as well as a preparation method and application thereof.

[0005] To achieve the above-mentioned purpose, in the first aspect of the present application, the present application provides a biodegradable composition, which comprises the following components by mass fraction: 48-72 parts of polybutylene adipate terephthalate, 2-10 parts of polylactic acid, 18-42 parts of calcium carbonate, 1-9 parts of talc, and 0.3-1.2 parts of a slip agent. The calcium carbonate comprises first calcium carbonate and second calcium carbonate. The first calcium carbonate satisfies 0.6 pm≤Dv50≤1.3 pm and 1.4 pm≤Dv90≤4.1 pm. The second calcium carbonate satisfies 1.7 pm≤Dv50≤2.8 pm and 8.3 pm≤Dv90≤13.4 pm. The talc satisfies 0.6 pm≤Dv50≤8.2 pm and 1.8 pm≤Dv90≤14.2 pm.

[0006] The biodegradable composition provided by the application selects a first calcium carbonate and a second calcium carbonate with specific Dv50 particle sizes and Dv90 particle sizes, and simultaneously compounding talc with specific Dv50 particle sizes and Dv90 particle sizes, further adding polylactic acid and a slip agent, which can effectively realize good puncture performance and low apparent density of the biodegradable composition.

[0007] The Dv50 particle sizes and Dv90 particle sizes of the calcium carbonate and talc are tested by the laser particle size analyzer method in GB / T 19281-2014 standard. The specific test conditions are as follows: According to the requirements of the laser particle size analyzer, 2g of sample is taken and added into 400mL of water, then 2.0mL of sodium hexametaphosphate solution (200g / L) is added to obtain a sample solution. The sample solution is placed on the instrument and ultrasonic dispersed for 10min, and the particle size of the sample is measured according to the test steps specified by the laser particle size analyzer.

[0008] Exemplarily, the mass parts of the PBAT can be any point value or any two-point range value between 48-72 parts, such as 50-70 parts, or 48 parts, 50 parts, 52 parts, 55 parts, 58 parts, 60 parts, 62 parts, 65 parts, 68 parts, 70 parts, 72 parts, etc.; the polylactic acid can be any point value or any two-point range value between 2-10 parts, such as 3-9 parts, or 2 parts, 3 parts, 4 parts, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, etc.; the calcium carbonate can be any point value or any two-point range value between 18-42 parts, such as 20-40 parts, or 18 parts, 20 parts, 22 parts, 24 parts, 26 parts, 28 parts, 30 parts, 32 parts, 34 parts, 36 parts, 38 parts, 40 parts, 42 parts, etc.; the talc can be any point value or any two-point range value between 1-9 parts, such as 2-8 parts, or 1 part, 2 parts, 3 parts, 4 parts, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, etc.; the slip agent can be any point value or any two-point range value between 0.3-1.2 parts, such as 0.5-1 part, or 0.3 part, 0.5 part, 0.8 part, 1 part, 1.2 part, etc.

[0009] Preferably, the mass percentage of PBAT in the biodegradable composition is ≥42%.

[0010] More preferably, the mass percentage of PBAT in the biodegradable composition is 55-65%.

[0011] As a preferred embodiment of the biodegradable composition, the biodegradable composition comprises the following components by mass: 60-65 parts of polybutylene adipate terephthalate, 5-8 parts of polylactic acid, 25-30 parts of calcium carbonate, 4-6 parts of talc, and 0.5-0.8 parts of a slip agent.

[0012] The present application finds that the mass of the components in the biodegradable composition affects the overall performance of the composition. When the mass of the components in the composition is further selected within the above range, the obtained composition has a lower apparent density of the blown film and better puncture performance.

[0013] Exemplarily, the Dv50 of the first calcium carbonate can be any point value or any two-point range value between 0.6-1.3 μm, such as 0.75-1.2 μm, or can be 0.6 μm, 0.7 μm, 0.75 μm, 0.8 μm, 0.9 μm, 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, etc.; the Dv90 can be any point value or any two-point range value between 1.4-4.1 μm, such as 1.5-4.0 μm, or can be 1.4 μm, 1.5 μm, 1.8 μm, 2 μm, 2.2 μm, 2.5 μm, 2.8 μm, 3 μm, 3.2 μm, 3.4 μm, 3.6 μm, 3.8 μm, 4 μm, 4.1 μm, etc.

[0014] Exemplarily, the Dv50 of the second calcium carbonate can be any point value or any two-point range value between 1.7-2.8 μm, such as 1.8-2.6 μm, or can be 1.7 μm, 1.8 μm, 2.0 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, 2.5 μm, 2.6 μm, 2.7 μm, 2.8 μm, etc.; the Dv90 can be any point value or any two-point range value between 8.3-13.4 μm, such as 8.5-13.2 μm, or can be 8.3 μm, 8.5 μm, 8.8 μm, 9 μm, 9.2 μm, 9.5 μm, 9.8 μm, 10 μm, 10.2 μm, 10.5 μm, 10.8 μm, 11 μm, 11.2 μm, 11.5 μm, 11.8 μm, 12 μm, 12.2 μm, 12.5 μm, 12.8 μm, 13 μm, 13.2 μm, 13.4 μm, etc.

[0015] Exemplarily, the Dv50 of the talc powder can be any point value or range value between any two points of 0.6-8.2 μm, such as 0.7-8.0 μm, 0.7-4.5 μm, 4.5-8.0 μm, etc., or can be 0.6 μm, 0.7 μm, 1 μm, 1.3 μm, 1.5 μm, 1.8 μm, 2 μm, 2.2 μm, 2.5 μm, 2.8 μm, 3 μm, 3.2 μm, 3.5 μm, 3.8 μm, 4 μm, 4.2 μm, 4.5 μm, 4.8 μm, 5 μm, 5.2 μm, 5.5 μm, 5.8 μm, 6.2 μm, 6.5 μm, 6.8 μm, 7 μm, 7.2 μm, 7.5 μm, 7.8 μm, 8 μm, 8.2 μm, etc.; the Dv90 can be any point value or range value between any two points of 1.8-14.2 μm, such as 2-14 μm, 2-11.5 μm, 11.5-14 μm, etc., or can be 1.8 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 11.8 μm, 12 μm, 12.2 μm, 12.5 μm, 12.8 μm, 13 μm, 13.2 μm, 13.4 μm, 13.6 μm, 13.8 μm, 14 μm, 14.2 μm, etc.

[0016] As a preferred embodiment of the biodegradable composition of the present application, the mass ratio of the first calcium carbonate and the second calcium carbonate is (1.5-7.5):1.

[0017] Exemplarily, the mass ratio of the first calcium carbonate and the second calcium carbonate can be any point value or range value between any two points of (1.5-7.5):1, such as (2-7):1, (2-4):1, (4-7):1, etc., or can be 1.5:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 7.5:1, etc.

[0018] The present application has found that the combination of the first calcium carbonate and the second calcium carbonate can affect the apparent density and the puncture performance of the product in cooperation with the talc powder; specifically, the Dv50 and Dv90 values of the first calcium carbonate are relatively small, which can effectively improve the puncture strength of the product to a certain extent; the Dv50 and Dv90 values of the second calcium carbonate are relatively large, which can better reduce the surface density of the product to a certain extent; when the above two are compounded in the above mass ratio, the comprehensive performance of the product is better.

[0019] As a preferred embodiment of the biodegradable composition of the present invention, the talc powder satisfies: 4.3μm≤Dv50≤8.2μm, 11.2μm≤Dv90≤14.2μm.

[0020] The present invention has found that the Dv50 and Dv90 values ​​of talc affect its dispersion performance in PBAT, as well as its interaction with the first and second calcium carbonates. When the Dv50 and Dv90 values ​​of talc are further selected to be within the above ranges, the resulting composition has a lower apparent density in blown film and also has good puncture resistance.

[0021] As a preferred embodiment of the biodegradable composition of the present invention, the molar percentage of the terephthalic acid monomer unit is 46-48% based on the total molar amount of terephthalic acid monomer units and adipic acid monomer units in the polybutylene terephthalate-adipate.

[0022] For example, based on the total molar amount of terephthalic acid monomer units and adipic acid monomer units in the polybutylene terephthalate-adipate, the molar percentage of the terephthalic acid monomer units can be any point value or any two-point range value between 46% and 48%, such as 46%, 46.5%, 47%, 47.5%, 48%, etc.

[0023] It should be noted that, based on the total molar amount of terephthalic acid monomer units and adipic acid monomer units in the polybutylene terephthalate-adipate, the method for testing the molar percentage of the terephthalic acid monomer units is as follows: 20 mg of PBAT resin sample was dissolved in 0.6 mL of deuterated chloroform, and then 1H NMR was measured at room temperature using a Bruker AV 500 NMR spectrometer. The chloroform solvent peak was calibrated to around 7.26 ppm. Based on the shift of hydrogen under different chemical environments, for aromatic diacids such as terephthalic acid in PBAT, the four hydrogen atoms on the benzene ring in the repeating unit appear around 8.10 ppm; for aliphatic diacids such as adipic acid, the four hydrogen atoms in the two CH2 units adjacent to the carbonyl group in the repeating unit appear around 2.33 ppm. Thus, the molar content of the diacid component can be represented by the integrated areas (IT and IA) of the two peaks at 8.10 ppm and 2.33 ppm. Subsequently, the molar percentage of the terephthalic acid monomer unit was calculated: molar percentage of the terephthalic acid monomer unit in PBAT = IT / (IT+IA)×100%.

[0024] As a preferred embodiment of the biodegradable composition of the present invention, the polybutylene terephthalate has a melt index of 3-5 g / 10 min.

[0025] For example, the melt index of the polybutylene terephthalate can be any point value or any two-point range between 3 and 5 g / 10 min, such as 3 g / 10 min, 3.5 g / 10 min, 4 g / 10 min, 4.5 g / 10 min, 5 g / 10 min, etc.

[0026] It should be noted that the melt flow index of the PBAT was tested according to the ISO 1133-2011 standard, and the test conditions were 190℃ / 2.16kg.

[0027] The present invention has found that when the molar percentage of terephthalic acid monomer units in PBAT and the melt index of PBAT are further selected within the above range, the resulting biodegradable composition has better puncture performance and lower blown film apparent density.

[0028] It should be noted that the PBAT of this invention can be obtained commercially or prepared in-house. If prepared in-house, this invention does not impose any particular restrictions on the preparation method.

[0029] For example, the preparation method of PBAT includes the following steps: adding terephthalic acid, adipic acid, 1,4-butanediol and a branching agent into a reaction vessel, performing a first heating and stirring, then adding a catalyst, raising the temperature for a second heating and stirring, and then raising the temperature for a third heating and stirring. After the reaction is completed, PBAT is obtained.

[0030] The branching agent may be glycerol, etc.; the catalyst may be tetrabutyl titanate, etc.

[0031] The temperature of the first heating and stirring is 180-200℃, and the time of the first heating and stirring is 1-8h; the temperature of the second heating and stirring is 210-230℃, and the time of the second heating and stirring is 1-5h; the temperature of the third heating and stirring is 240-260℃, and the time of the third heating and stirring is 2-8h.

[0032] The ratio of the total molar amount of terephthalic acid and adipic acid to the molar amount of 1,4-butanediol is 1:(1.3-1.5).

[0033] It should be noted that the molar ratio of terephthalic acid in terephthalic acid and adipic acid can be adjusted to control the range of terephthalic acid monomer units. Different melt indices of PBAT can be prepared by adjusting the temperature and time of the first and second heating and stirring processes.

[0034] As a preferred embodiment of the biodegradable composition of the present invention, the molar content of D-lactic acid in the polylactic acid is ≥7%.

[0035] For example, the molar content of D-lactic acid in the polylactic acid can be any point value or any two points within the range of ≥7%, such as 7-10%, 7-8%, 8-10%, etc., or 7%, 8%, 9%, 10%, etc.

[0036] It should be noted that the molar content of L-lactic acid in the polylactic acid is ≤94%.

[0037] It should be noted that the molar content of D-lactic acid in polylactic acid (PLA) is determined as follows: PLA samples are subjected to transesterification degradation with methanol at 150°C in a pressure vessel, followed by analysis using gas chromatography. The D-lactic acid content in PLA is calculated by the ratio of the sum of the peak areas of L- and D-lactic acid methyl esters to the peak area of ​​D-lactic acid methyl ester, as shown in the following formula: For each GC run, the D-lactic acid content of the sample solution is calculated as follows: A DML : Peak area of ​​D-methyl lactate; A LML : Peak area of ​​L-lactic acid methyl ester; Calculate the average D-lactic acid content of the sample solution from the obtained single-value D-lactic acid content. Report the D-lactic acid content in the PLA sample as the average of the D-lactic acid content found in all sample solutions prepared from the PLA sample.

[0038] Preferably, the molar content of D-lactic acid in the polylactic acid is 7-8%.

[0039] The present invention has found that further limiting the molar content of D-lactic acid in polylactic acid within the above-mentioned range can better achieve good puncture performance and lower blown film apparent density of the product.

[0040] It should be noted that the polylactic acid provided by this invention can be obtained commercially or prepared in-house. If prepared in-house, this invention does not impose any particular restrictions on the preparation method.

[0041] As a preferred embodiment of the biodegradable composition of the present invention, the slip agent includes at least one of oleamide, erucamide, monoglycine ester, N,N'-ethylenebisstearamide, and Fischer-Tropsch wax.

[0042] Preferably, the slip agent comprises oleamide.

[0043] In a second aspect, the present invention provides a method for preparing the biodegradable composition, the method comprising the following steps: After drying, the raw materials are weighed and mixed, then fed into a twin-screw extruder. The mixture is melt-extruded, drawn into strands, cooled, pelletized, and dried to obtain a biodegradable composition.

[0044] In a preferred embodiment of the preparation method described in this invention, the temperature of the melt extrusion is 120-160°C.

[0045] In a third aspect, the present invention provides the use of the biodegradable composition in the preparation of packaging bags.

[0046] In a fourth aspect, the present invention provides a packaging bag prepared using the biodegradable composition described herein.

[0047] For example, the packaging bag includes shopping bags, milk tea bags, express delivery bags, etc.

[0048] Compared with the prior art, the beneficial effects of the present invention are as follows: The biodegradable composition provided by this invention, through the selection of appropriate mass proportions of components, exhibits good interactions between the components, resulting in a product with excellent puncture resistance and low blown film apparent density; thus, it can be widely used in the preparation of packaging bags. Furthermore, the preparation method of the biodegradable composition provided by this invention is simple to operate and beneficial for practical production. Detailed Implementation

[0049] 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.

[0050] Unless otherwise specified, the reagents, methods and equipment used in this invention are all conventional reagents, methods and equipment in the field.

[0051] PBAT1: Based on the total molar amount of terephthalic acid monomer units and adipic acid monomer units in PBAT, the molar proportion of terephthalic acid monomer units is 47%, the melt index is 3.8 g / 10 min, it is self-made, and the preparation method includes the following steps: 1.9 kg of terephthalic acid, 1.9 kg of adipic acid, 3.0 kg of 1,4-butanediol, and a branching agent (glycerol, with a molar addition of 0.05% based on the total molar amount of terephthalic acid, adipic acid, and 1,4-butanediol) were added to a reaction vessel. The mixture was heated to 190 °C and stirred for 1 h. Then, tetrabutyl titanate was added as a catalyst, and the mixture was heated to 220 °C and stirred for another 3 h. Finally, the mixture was heated to 250 °C and stirred for 4 h to obtain PBAT1. PBAT2: Based on the total molar amount of terephthalic acid monomer units and adipic acid monomer units in PBAT, the molar proportion of terephthalic acid monomer units is 47%, the melt index is 4.9 g / 10 min, it is self-made, and the preparation method is different from PBAT1 in that after adding the catalyst, the temperature is raised to 220℃ and the reaction continues for 3 h, then the temperature is raised to 250℃ and the reaction is stirred for 3.5 h. PBAT3: Based on the total molar amount of terephthalic acid monomer units and adipic acid monomer units in PBAT, the molar proportion of terephthalic acid monomer units is 47%, the melt index is 2.1 g / 10 min, it is prepared in-house, and the preparation method is different from PBAT1 in that after adding the catalyst, the temperature is raised to 220℃ and stirred for 4 h, and then the temperature is raised to 240℃ and stirred for 5 h. PBAT4: Based on the total molar amount of terephthalic acid monomer units and adipic acid monomer units in PBAT, the molar proportion of terephthalic acid monomer units is 47%, the melt index is 6.0 g / 10 min, it is self-made, and the preparation method is different from PBAT1 in that after adding the catalyst, the temperature is raised to 220℃ and stirred for 2.5 h, and then the temperature is raised to 240℃ and stirred for 3 h. PBAT5: Based on the total molar amount of terephthalic acid monomer units and adipic acid monomer units in PBAT, the molar proportion of terephthalic acid monomer units is 45%, the melt index is 4.0 g / 10 min, it is prepared in-house, and the preparation method differs from PBAT1 in that the amount of terephthalic acid and adipic acid added is adjusted; specifically, terephthalic acid is 1.83 kg and adipic acid is 1.97 kg. PBAT6: Based on the total molar amount of terephthalic acid monomer units and adipic acid monomer units in PBAT, the molar proportion of terephthalic acid monomer units is 49%, the melt index is 4.1 g / 10 min, it is self-made, and the preparation method differs from PBAT1 in that the amount of terephthalic acid and adipic acid added is adjusted; specifically, terephthalic acid is 1.98 kg and adipic acid is 1.82 kg.

[0052] PLA1: The molar content of D-lactic acid is 8%, prepared in-house, and the preparation method includes the following steps: L,L-lactide (92% L, 8% D) was added to a reactor along with stannous octoate for ring-opening polymerization: the reaction was first carried out at 150℃ and 5000 Pa for 2 hours, and then at 180℃ and 10000 Pa for 4 hours. After the reaction was completed, the product was granulated underwater, crystallized, and dried to obtain PLA1. PLA2: D-lactic acid molar content is 10%, Jinfa Biotechnology, brand name KB600 NF50; PLA3: D-lactic acid molar content is 4%, Jinfeng Biotechnology, brand name KB600 NF30; First calcium carbonate 1: Dv50 is 1.2μm, Dv90 is 4.0μm, Guangdong Xinrong, grade ACC-812; First calcium carbonate 2: Dv50 is 0.75μm, Dv90 is 1.5μm, Omia, grade Hydrocarb® 95T; Second calcium carbonate 1: Dv50 is 1.8μm, Dv90 is 8.5μm, Guangdong Xinrong, grade ACC-818; Second calcium carbonate 2: Dv50 is 2.6μm, Dv90 is 13.2μm, Guangdong Dongyuan, grade DY-33838; Talc 1: Dv50 is 8.0μm, Dv90 is 14.0μm, Guangxi Longsheng Huamei, brand name AH-1250N6; Talc 2: Dv50 is 4.5μm, Dv90 is 11.5μm, Liaoning Xinda, brand name SDC-F7; Talc 3: Dv50 is 0.7μm, Dv90 is 2.0μm, Liaoning Aihaiyimi, brand name HTPultra5 L; Talc 4: Dv50 is 10.5μm, Dv90 is 26.0μm, Yirui Stone, brand name HAR T84; Slip agent 1: Oleamide, commercially available; Slip agent 2: N,N'-ethylene bis-stearamide, commercially available; Slip agent 3: Fischer-Tropsch wax, commercially available.

[0053] Examples 1-18 and Comparative Examples 1-8 The present invention provides a biodegradable composition in the embodiments and comparative examples, wherein the component content (parts by weight) of the biodegradable composition is shown in Tables 1-3; Table 1 Table 2 Table 3 The preparation methods for the examples and comparative examples are as follows: After drying, the raw materials are weighed and added to a mixer for uniform mixing. Then, the mixture is fed into a twin-screw extruder, and the feed rate of the twin-screw extruder is adjusted to 200 kg / hour. After extrusion, stranding, cooling, pelletizing, and drying, a biodegradable composition is obtained. The parameters of the twin-screw extruder are as follows: the temperature of each screw section from the feed port to the die head is 120℃, 160℃, 160℃, 160℃, 160℃, 160℃, respectively; the screw speed is 300 rpm.

[0054] Example of effect The performance of the product prepared by the comparative example of the effect verification of the present invention was achieved by drying the biodegradable composition and controlling the moisture content to be below 500 ppm. The dried biodegradable composition was then subjected to blown film treatment to obtain a biodegradable film. The temperature of the blown film treatment was 145°C. The resulting biodegradable film had a perimeter of 660 mm (blown film die diameter of 70 mm, blow-up ratio of 3.0) and a thickness of 18 ± 2 μm. Subsequently, corresponding tests were performed. The test items include the following aspects: 1. Apparent density test The area of ​​the film cut using a standard cutting tool is S (6.3 * 7.5 cm = 47.25 cm²). 2 The film was weighed to obtain its mass M, and its thickness D was measured using a micrometer. The apparent density was calculated as M / (D*S).

[0055] 2. Membrane puncture strength test It was carried out in accordance with the GB / T 37841-2019 standard.

[0056] The test results are shown in Table 4. Table 4 As can be seen from Table 4, when the technical solution of the present invention is adopted, the obtained product has excellent puncture performance and low apparent density. Specifically, the apparent density of the blown film of the obtained product is 1.356 kg / m³. 3 Below this, the puncture force is above 0.81N; As can be seen from Examples 1 and 3-8, the molar percentage of terephthalic acid and its melt index in PBAT affect the puncture performance and blown film apparent density of the product; as can be seen from Examples 1 and 9-10, the molar content of D-lactic acid in polylactic acid also has a certain impact on the puncture performance and blown film apparent density of the product; as can be seen from Examples 1, 11-12, and Comparative Examples 7-8, the Dv50 and Dv90 values ​​of the first and second calcium carbonates also affect the puncture performance and blown film apparent density of the product; when the Dv50 and Dv90 values ​​of the first and second calcium carbonates in Comparative Examples 7-8 are not within the range given in this invention, the overall performance of the obtained product decreases significantly; as can be seen from Examples 1, 13-14, and Comparative Example 3, the slip... The Dv50 and Dv90 values ​​of the talc powder also affect the puncture performance and blown film apparent density of the product. When the Dv50 and Dv90 values ​​of the talc powder in Comparative Example 3 are not within the range given in this invention, the puncture force of the obtained product decreases significantly. As can be seen from Examples 1, 17-18 and Comparative Examples 1-2, the mass ratio of the first calcium carbonate and the second calcium carbonate also affects the performance of the product. When only the second calcium carbonate is present in Comparative Example 1, the puncture force of the obtained product decreases significantly. When only the first calcium carbonate is present in Comparative Example 2, the surface density of the obtained product increases significantly. As can be seen from Examples 1 and Comparative Examples 4-6, when neither calcium carbonate nor talc powder is added, or when the mass fractions of calcium carbonate and talc powder are not within the range given in this invention, the overall performance of the obtained product deteriorates significantly.

[0057] Finally, it should be noted that the above embodiments are used to illustrate the technical solutions of the present invention and not to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A biodegradable composition, characterized in that, The biodegradable composition comprises the following components by mass fraction: 48-72 parts of polybutylene terephthalate-adipate, 2-10 parts of polylactic acid, 18-42 parts of calcium carbonate, 1-9 parts of talc, 0.3-1.2 parts of a slip agent; The calcium carbonate comprises a first calcium carbonate and a second calcium carbonate; The first calcium carbonate satisfies: 0.6 μm≤Dv50≤1.3 μm, 1.4 μm≤Dv90≤4.1 μm; The second calcium carbonate satisfies: 1.7 μm≤Dv50≤2.8 μm, 8.3 μm≤Dv90≤13.4 μm; The talc satisfies: 0.6 μm≤Dv50≤8.2 μm, 1.8 μm≤Dv90≤14.2 μm.

2. The biodegradable composition according to claim 1, characterized in that, The biodegradable composition comprises the following components by mass fraction: 60-65 parts of polybutylene terephthalate-adipate, 5-8 parts of polylactic acid, 25-30 parts of calcium carbonate, 4-6 parts of talc, 0.5-0.8 parts of a slip agent.

3. The biodegradable composition according to claim 1, characterized in that, The mass ratio of the first calcium carbonate and the second calcium carbonate is (1.5-7.5):

1.

4. The biodegradable composition according to claim 1, characterized in that, The talc satisfies: 4.3 μm≤Dv50≤8.2 μm, 11.2 μm≤Dv90≤14.2 μm.

5. The biodegradable composition according to claim 1, characterized in that, Based on the total molar amount of terephthalic acid monomer units and adipic acid monomer units in the polybutylene terephthalate-adipate, the mole percentage of the terephthalic acid monomer units is 46-48%; And / or, the melt index of the polybutylene terephthalate-adipate is 3-5 g / 10 min.

6. The biodegradable composition according to claim 1, characterized in that, The mole content of D-lactic acid in the polylactic acid is ≥7%.

7. The biodegradable composition according to claim 1, characterized in that, The slip agent comprises at least one of oleic acid amide, erucic acid amide, monoglyceride ester, N,N'-ethylene bis-stearamide, and Fischer-Tropsch wax; preferably, the slip agent comprises oleic acid amide.

8. Process for the preparation of a biodegradable composition according to any one of claims 1 to 7, characterized in that, The preparation method comprises the following steps: after drying, each raw material is weighed and mixed and then sent into a twin-screw extruder, and then melt-extruded, drawn, cooled, granulated, and dried to obtain the biodegradable composition.

9. Use of the biodegradable composition according to any one of claims 1-7 in the preparation of a packaging bag.

10. A package, characterized in that Prepared by using the biodegradable composition according to any one of claims 1-7.

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