Polyester composition, and preparation method therefor and use thereof

Abstract

The present invention relates to a polyester composition, and a preparation method therefor and the use thereof. The polyester composition comprises the following components in parts by weight: 40-91 parts of a biodegradable polyester, 2-20 parts of polylactic acid, 1-30 parts of calcium carbonate, 0.1-10 parts of a flaky inorganic filler, and 0.1-2 parts of an organic anti-blocking agent. A film bag prepared from the polyester composition of the present invention by means of a high-speed ultrathin film blowing technique has good resistance to "the blocking of die-cut openings' and dart drop impact.

Description

A polyester composition, its preparation method and application Technical Field

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

[0002] Compared to traditional polyethylene plastics, flexible biodegradable polyesters are mostly semi-crystalline materials (such as PBAT). Biodegradable plastics with flexible biodegradable polyesters, polylactic acid and mineral fillers as the main components often crystallize more slowly during blown film production, resulting in slow film cooling. This often leads to the problem of "punching sticking" when cutting bags and punching, which affects the consumer experience.

[0003] With the development of the biodegradable plastics industry, high-speed blown film and lightweight thinning are major trends in the future production of biodegradable films. Under this trend, the problem of "punch adhesion" will become more severe and urgently needs to be overcome. The traditional polyethylene industry can enhance film bubble stability by adding polyethylene components with stronger crystallinity. However, the biodegradable industry does not allow the addition of recalcitrant polyethylene to biodegradable plastics, and highly crystalline resins generally have weaker degradation performance; therefore, other highly crystalline resins are also unsuitable for the biodegradable industry.

[0004] Currently, the industry typically employs several methods to address the issue of punch adhesion. From a manufacturing process perspective, this can be achieved by reducing the blown film speed to enhance crystallization cooling, allowing the film to rest for two or three days before bag cutting, or raising the height of the blown film machine to 6 meters or even 7 meters or more to provide powerful cooling to the workshop, thereby lowering the temperature and improving the film's cooling effect. However, the first two methods both impact production efficiency to varying degrees, while the last method, by modifying the height of the blown film machine or providing powerful cooling to the workshop, leads to space constraints and wasted costs.

[0005] Therefore, addressing the issue of punch adhesion at the formulation level is a more feasible solution for industrial production. Currently, the industry often solves the problem by adding large amounts of opening agents to increase slip properties. However, opening agents are mostly small molecules with poor compatibility with polymers, which can easily lead to a decrease in dart impact performance. Summary of the Invention

[0006] To overcome the problem of insufficient balance between anti-sticking performance and film dart impact performance in the prior art, the primary objective of this invention is to provide a polyester composition.

[0007] A further object of the present invention is to provide a method for preparing the above-described polyester composition.

[0008] A further object of the present invention is to provide the use of the above-described polyester composition in the preparation of films.

[0009] This invention protects a polyester composition comprising the following components in parts by weight:

[0010] 40-91 parts by weight of biodegradable polyester

[0011] Polylactic acid 2-20 parts by weight

[0012] Calcium carbonate 1-30 parts by weight

[0013] 0.1-10 parts by weight of flake-shaped inorganic filler.

[0014] 0.1-2 parts by weight of organic opening agent;

[0015] The D98 particle size of the sheet-like inorganic filler is ≤16μm;

[0016] The supercooling degree of the polylactic acid is 80~115℃;

[0017] The organic opening agent has a melting point of 55~120℃.

[0018] The polyester composition of the present invention comprises biodegradable polyester and polylactic acid. The combination of the two imparts basic toughness and rigidity to the polyester composition, while a certain amount of calcium carbonate imparts processing stability. To improve the anti-blocking properties of the polyester composition, the present invention further incorporates sheet-like inorganic fillers and organic opening agents.

[0019] For the polyester composition of this invention, which is mainly composed of biodegradable polyester and supplemented with polylactic acid, the sheet-like inorganic filler is a key component for resisting impact adhesion. Specifically, the D98 particle size of the sheet-like inorganic filler needs to be controlled within a certain range to ensure that the filler is layered, stacked, and uniformly dispersed in the polyester composition. This reduces the interaction between molecular chains in the biodegradable polyester, preventing adhesion and ensuring that the films prepared from the polyester composition do not stick together. Furthermore, it minimizes the impact on the impact resistance of the polyester composition.

[0020] The melting point of the organic opening agent needs to be controlled within a suitable range so that the compatibility between the organic opening agent and the polyester composition is within an appropriate range. This avoids difficulties in sealing and drop impact caused by insufficient compatibility or excessive precipitation, or sticking at the opening caused by excessive compatibility or inability to precipitate.

[0021] The polyester composition of this invention is primarily a semi-crystalline biodegradable polyester polymer, which has poor crystallization and shaping properties, easily leading to sticking at the punching point. This invention improves these defects by adding polylactic acid with a specific degree of supercooling to the biodegradable polyester, resulting in a polyester composition with good crystallization and shaping properties, thus exhibiting appropriate anti-sticking properties, while also imparting suitable rigidity to the polyester composition.

[0022] As can be seen, the present invention, through the combination of a sheet-like inorganic filler with a specific D98 particle size, an organic opening agent with a specific melting point, and polylactic acid with a specific supercooling degree, achieves a polyester composition with the dual synergistic effect of promoting crystallization and promoting slippage. During the high-speed blown film process of ultra-thin films, the film bubble can be rapidly crystallized and shaped, and the film surface has a slippage layer. At the same time, it satisfies the balance between the anti-"punch adhesion" performance and the film drop impact performance after high-speed blown film production of ultra-thin films.

[0023] The supercooling described in this invention is the difference between the melting point (Tm) and the glass transition temperature (Tg), i.e., supercooling = Tm - Tg.

[0024] The melting point Tm was determined using a DSC204 thermal analyzer from Netzsch, Germany. The sample was first heated from 30°C to 220°C at a rate of 10°C / min, and held at 220°C for 3 minutes to eliminate thermal history. Then, it was cooled to 30°C at a rate of 10°C / min, and then heated to 220°C at a rate of 10°C / min. The second melting curve of the sample was obtained, and the melting peak of this curve was taken as the melting point.

[0025] The glass transition temperature (Tg) was determined using a DSC204 thermal analyzer from Netzsch, Germany, under nitrogen protection. A sample with a mass of 5 ± 1 mg was heated from 30 °C to 160 °C at a heating rate of 10 °C / min and held at 160 °C for 3 min. Then, the sample was cooled to -110 °C at a heating rate of 20 °C / min and then heated to 150 °C at a heating rate of 10 °C / min. The glass transition temperature (Tg) of the sample was obtained from the curve of the second heating, and the intersection of the extrapolation line at the bend and the baseline was taken as the value of the glass transition temperature (Tg).

[0026] The test method for D98 particle size described in this invention is performed in accordance with the method of GB / T 19077.1 "Particle size analysis by laser diffraction".

[0027] Specifically, the flaky inorganic filler is at least one of flaky talc, flaky montmorillonite, and flaky mica, more preferably flaky talc, flaky montmorillonite, or a combination thereof, and more preferably talc.

[0028] Preferably, the D98 particle size of the sheet-like inorganic filler is ≤13μm.

[0029] Preferably, the organic opening agent is one or more of the following: glyceryl monostearate, stearyl erucamide, oleamide, erucamide, stearamide, behenamide, and synthetic wax.

[0030] Preferably, the organic opening agent has a melting point of 60~115℃.

[0031] Preferably, the supercooling degree of the polylactic acid is 85~105°C.

[0032] Specifically, the polylactic acid is selected from one or more of PLLA, PDLA, or PLLA / PDLA copolymer, more preferably PLLA / PDLA copolymer.

[0033] Preferably, the content of D-lactic acid in the polylactic acid is 0.1~10 mol% or 90-100% mol%, more preferably 0.1~8 mol% or 92-100 mol%, and even more preferably 0.1~5 mol% or 95-100 mol%.

[0034] In this invention, polylactic acid can be either commercially available or prepared in-house. The preparation method is as follows:

[0035] Polylactic acid is obtained by using a bulk polymerization method to induce ring-opening polymerization of lactide.

[0036] Specifically, the polylactic acid is PLLA, PDLA, or a PLLA / PDLA copolymer.

[0037] More specifically, when the polylactic acid is PLLA, the lactide is L-lactide; when the polylactic acid is PDLA, the lactide is D-lactide; when the polylactic acid is a PLLA / PDLA copolymer, the lactide is L-lactide and meso-lactide.

[0038] Preferably, the ring-opening polymerization reaction is carried out in the presence of a catalyst, which includes, but is not limited to, stannous octoate.

[0039] Specifically, the mass ratio of the catalyst to the lactide is 0.0001 to 0.01:100.

[0040] Preferably, the ring-opening polymerization process is as follows: first, react at 130~140℃ and 1100~1300Pa for 3~4 hours, and then react at 160~180℃ and 250~350Pa for 4~6 hours.

[0041] Preferably, the polylactic acid has a melt flow rate of 2~12 g / 10min measured at 190℃ and 2.16kg.

[0042] In this invention, the melt flow rate can be measured using the ISO 1133 standard.

[0043] Specifically, the biodegradable polyester is an aliphatic-aromatic copolyester.

[0044] Specifically, the biodegradable polyester is a copolymer of a diacid and / or its ester derivatives and a diol.

[0045] Biodegradable polyesters copolymerized from commonly used diacids and / or their ester derivatives and commonly used diols can all be used in this invention.

[0046] The present invention provides a biodegradable polyester that is either commercially available or can be prepared in-house. The preparation method is as follows: a diacid and / or its esterification derivative, a diol, and a branching agent are mixed and reacted at 180-200°C for 2-8 hours. A catalyst is then added, and the mixture is reacted again at 230-250°C and 250-350 Pa for 6-18 hours to obtain the biodegradable polyester.

[0047] Specifically, the branching agent includes, but is not limited to, glycerol. The amount of the branching agent used is 0.03% to 0.06% of the mass of the diacid and / or its esterified derivatives.

[0048] Preferably, the catalyst includes, but is not limited to, tetrabutyl titanate. The amount of the catalyst is 0.01% to 0.03% of the sum of the molar amounts of the diacid and / or its ester derivatives and diols.

[0049] Preferably, the molar ratio of the dicarboxylic acid and / or its ester derivative to the diol is 1:(1.05~1.2).

[0050] Preferably, the dicarboxylic acid is at least one of an aliphatic dicarboxylic acid or an aromatic dicarboxylic acid.

[0051] More preferably, the aliphatic dicarboxylic acid is at least one selected from succinic acid, glutaric acid, adipic acid, pimelic acid, octanoic acid, azelaic acid, sebacic acid, undecanoic acid, or dodecanoic acid.

[0052] More preferably, the aromatic dicarboxylic acid is terephthalic acid.

[0053] More preferably, the dicarboxylic acid is an aliphatic dicarboxylic acid and an aromatic dicarboxylic acid, and the molar ratio of the aromatic dicarboxylic acid to the aliphatic dicarboxylic acid is 1:(0.80~1.20); specifically, it can be 1:0.8, 1:0.85, 1:0.87, 1:0.90, 1:0.95, 1:1, 1:1.05, 1:1.1, 1:1.15, 1:1.16 or 1:1.20.

[0054] Preferably, the diol is at least one of butanediol, propylene glycol, ethylene glycol, or pentanediol.

[0055] Specifically, the biodegradable polyester may be at least one of polybutylene terephthalate (PBAT), polybutylene sebacic acid terephthalate (PBSeT), polybutylene succinate terephthalate (PBST), polybutylene sebacic acid adipate terephthalate (PBSeAT), polybutylene sebacic acid adipate terephthalate (PBSeST), polybutylene succinate adipate terephthalate (PBSAT), or polypropylene adipate terephthalate (PDAT).

[0056] The present invention also found that the content of terephthalic acid units in biodegradable polyester is best controlled within a certain range, which can improve the crystallinity of biodegradable polyester, obtain good anti-blocking properties, and ensure that the drop performance and biodegradation rate do not fail to meet the requirements of biodegradable film.

[0057] Preferably, the content (T content) of terephthalic acid units in the biodegradable polyester is 45~55 mol%, more preferably 48~50 mol%.

[0058] Specifically, the melt flow rate of the biodegradable polyester at 190°C and 2.16 kg is 2~10 g / 10 min.

[0059] Preferably, the D50 particle size of the calcium carbonate is 1~5μm, more preferably 2.3~5μm.

[0060] Specifically, the melt flow rate of the polyester composition measured at 190°C and 2.16 kg is 2~10 g / 10 min.

[0061] The present invention also protects a method for preparing the above-mentioned polyester composition, comprising the following steps: mixing the components, melt extruding, and granulating to obtain the polyester composition.

[0062] The application of the above-mentioned polyester composition in the preparation of fully biodegradable film bags is also within the scope of protection of this invention.

[0063] A fully biodegradable membrane bag is prepared from the above-mentioned polyester composition.

[0064] Compared with the prior art, the present invention has the following beneficial effects:

[0065] The present invention combines a sheet-like inorganic filler with a specific D98 particle size, an organic opening agent with a specific melting point, and polylactic acid with a specific supercooling degree to obtain a polyester composition. The resulting film bag, prepared by ultra-thin film high-speed blown film technology, has good anti-"punch-off adhesion" and film drop impact resistance. Embodiments of the present invention

[0066] The present invention is further illustrated below with reference to specific embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions in the art or as recommended by the manufacturer; the raw materials and reagents used, unless otherwise specified, are all commercially available from the conventional market. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention are within the scope of protection claimed by the present invention.

[0067] The reagents used in the various embodiments and comparative examples of this invention are described below:

[0068] Biodegradable polyester 1#: self-made, PBAT, prepared as follows: 1.919 kg of terephthalic acid, 1.966 kg of adipic acid, and excess 2.548 kg of 1,4-butanediol and 2.3 g of glycerol were added to a 20 L reactor, stirred at 190 °C for 3 hours, then tetrabutyl titanate (0.02% of the total acid-to-alcohol molar ratio) was added as a catalyst, the temperature was raised to 240 °C, and the reaction was carried out under a vacuum pressure of 300 Pa for 7 hours to obtain PBAT. The melt flow rate of biodegradable polyester 1# was 3.8 g / 10 min, and the terephthalic acid content was 46.2 mol%.

[0069] Biodegradable polyester 2#: self-made, PBAT. Its preparation method differs from biodegradable polyester 1# in that it uses 1.994 kg of terephthalic acid and 1.901 kg of adipic acid. Biodegradable polyester 1# has a melt flow rate of 4.1 g / 10 min and a terephthalic acid content of 49.8 mol%.

[0070] Polylactic acid 1#: Self-made, prepared as follows: Bulk polymerization was carried out using 80 parts by weight of L-lactide (purity 99.6%) and 20 parts by weight of meso-lactide (purity 99.6%), with 0.002 parts by weight of stannous octoate added for ring-opening polymerization: first, the reaction was carried out at a reaction temperature of 135℃ and a reaction pressure of 1200Pa for 4 hours, and then at a reaction temperature of 170℃ and a reaction pressure of 300Pa for 6 hours; underwater pelletizing, crystallization, and drying were performed to obtain polylactic acid 1#. The supercooling degree of polylactic acid 1# was 82.9℃, the type was PDLA / PLLA copolymer, and the melt flow rate was 4.2 g / 10min.

[0071] Polylactic acid 2#: Prepared in-house, its preparation method differs from that of polylactic acid 1# in that: 82 parts by weight of L-type lactide (purity 99.6%) and 18 parts by weight of meso-lactide (purity 99.6%) are added, along with 0.002 parts by weight of stannous octoate, and ring-opening polymerization is carried out. The supercooling temperature of polylactic acid 2# is 86.7℃, it is a PDLA / PLLA copolymer, and the melt flow rate is 4.5 g / 10min.

[0072] Polylactic acid 3#: In-house prepared, its preparation method differs from that of polylactic acid 1# in that: 92 parts by weight of L-type lactide (purity 99.6%) and 8 parts by weight of meso-lactide (purity 99.6%) are added, along with 0.002 parts by weight of stannous octoate, and ring-opening polymerization is carried out. The supercooling temperature of polylactic acid 3# is 102.4℃, it is a PDLA / PLLA copolymer, and the melt flow rate is 3.9 g / 10 min.

[0073] Polylactic acid 4#: In-house prepared, its preparation method differs from that of polylactic acid 1# in that: 99 parts by weight of L-type lactide (purity 99.6%) and 1 part by weight of meso-lactide (purity 99.6%) are added, along with 0.002 parts by weight of stannous octoate, for ring-opening polymerization. The reaction is first carried out at 135℃ and 1200 Pa for 5 hours, and then at 170℃ and 300 Pa for 9 hours. The supercooling of polylactic acid 4# is 104.8℃, the type is PLLA, and the melt flow rate is 2.1 g / 10 min.

[0074] Polylactic acid (PLA) 5#: Prepared in-house, its preparation method differs from PLA 1# in that: 100 parts by weight of D-type lactide (purity 99.6%) are added to 0.002 parts by weight of stannous octoate for ring-opening polymerization. The reaction is first carried out at 135℃ and 1200 Pa for 3 hours, then at 170℃ and 300 Pa for 5 hours. PLA 5# has a supercooling of 114.7℃, is PDLA, and has a melt flow rate of 6.4 g / 10 min.

[0075] Polylactic acid 6#: In-house prepared, its preparation method differs from that of polylactic acid 1# in that: 74 parts by weight of L-type lactide (purity 99.6%) and 26 parts by weight of meso-lactide (purity 99.6%) are added, along with 0.002 parts by weight of stannous octoate, for ring-opening polymerization. The reaction is first carried out at a reaction temperature of 135℃ and a reaction pressure of 1200 Pa for 3 hours, and then at a reaction temperature of 170℃ and a reaction pressure of 300 Pa for 7 hours. The supercooling of polylactic acid 6# is 78.8℃, it is a PDLA / PLLA copolymer, and the melt flow rate is 4.3 g / 10 min.

[0076] Polylactic acid 7#: In-house prepared, its preparation method differs from that of polylactic acid 1# in that: 100 parts by weight of L-lactide (purity 99.9%) are added to 0.002 parts by weight of stannous octoate for ring-opening polymerization. The supercooling temperature of polylactic acid 7# is 116.8℃, the type is PLLA, and the melt flow rate is 4.1 g / 10 min.

[0077] Polylactic acid 8#: Manufacturer: Anhui Fengyuan, Grade: FY804, Subcooling: 101.2℃, Type: PLLA / PDLA, Melt flow rate: 4.1g / 10min.

[0078] Calcium carbonate #1: Manufacturer: Omia, Brand: 2T-JI, D50 particle size: 2.5μm.

[0079] Calcium carbonate #2: Manufacturer: Omia, Grade: 1T-CU, D50 particle size: 1.8μm.

[0080] Flaky inorganic filler #1: Talc, manufactured by Liaoning Haiyuan Tiancheng, grade HTPUHItra5L, D98 particle size 8.1μm.

[0081] Flaky inorganic filler #2: Talc, manufactured by Liaoning Aihai, grade AH-3000N9, D98 particle size 14.3μm.

[0082] Flaky inorganic filler #3: Talc, manufactured by Liaoning Aihai, grade AH-1250N6, D98 particle size 19.8μm.

[0083] Organic opening agent #1: Glyceryl monostearate, manufactured by Binzhou Jinsheng, brand name ST-101, melting point 58.5℃.

[0084] Organic opening agent #2: Synthetic wax, manufacturer: SHELL, brand name: Callista 144, melting point: 61.3℃.

[0085] Organic opening agent #3: Erucamide, manufactured by Croda Chemical, brand name CRODAMIDE ER-CH-MB-(SI), melting point 80.1℃.

[0086] Organic opening agent #4: behenamide, manufactured by THIAI (Shanghai) Chemical Industry Development Co., Ltd., grade D1007, melting point 112.8℃.

[0087] Organic opening agent #5: Synthetic wax, manufactured by Sasol, brand name Spray 105, melting point 117.2℃.

[0088] Organic opening agent #6: Synthetic wax, manufactured by Shell, brand name Callista 122, melting point 54.1℃.

[0089] Organic opening agent 7#: Vinyl bis-stearamide, manufactured by Zhuhai Kingfa Supply Chain Management Co., Ltd., grade ES B50, melting point 142.0℃.

[0090] The polyester compositions of the embodiments and comparative examples of the present invention were prepared by the following process:

[0091] Weigh each component according to the formula, mix them evenly, and then put them into a twin-screw extruder for melt extrusion and granulation at 180°C to obtain a polyester composition.

[0092] The performance testing methods and standards for the polyester compositions of the various embodiments and comparative examples of the present invention are as follows:

[0093] The melting point Tm was determined using a DSC204 thermal analyzer from Netzsch, Germany. The sample was first heated from 30°C to 220°C at a rate of 10°C / min, and held at 220°C for 3 min to eliminate thermal history. Then, it was cooled to 30°C at a rate of 10°C / min, and then heated to 220°C at a rate of 10°C / min. The second melting curve of the sample was obtained, and the melting peak of this curve was selected as the melting point.

[0094] The glass transition temperature (Tg) was determined using a DSC204 thermal analyzer from Netzsch, Germany, under nitrogen protection. A sample with a mass of 5 ± 1 mg was heated from 30 °C to 160 °C at a heating rate of 10 °C / min and held at 160 °C for 3 min. Then, the sample was cooled to -110 °C at a heating rate of 20 °C / min and then heated to 150 °C at a heating rate of 10 °C / min. The glass transition temperature (Tg) of the sample was obtained from the curve of the second heating, and the intersection of the extrapolation line at the bend and the baseline was taken as the value of the glass transition temperature (Tg).

[0095] The D98 particle size was determined according to the method in GB / T 19077.1-2016 "Particle Size Analysis by Laser Diffraction".

[0096] The melt flow rate was measured according to ISO 1133-1-2011 standard. The melt flow rate test conditions were 190℃ and 2.16kg.

[0097] The test method for punching adhesion is as follows: A single-screw blown film machine is used with a die gap of 2.0 mm, a die diameter of 70 mm, a blow-up ratio of 3.0, a temperature of 150℃, a blown film frequency of 40 Hz, and a film thickness controlled at 25 ± 2 μm. Bags are cut within one hour of blown film production, with a punch tip thickness of 0.1-0.2 mm. After punching, the film is graded according to the criteria described in Table 1. A mid-level grade can be assigned; for example, a grade between 1 and 2 can be assigned as 1.5, and so on. Five people are involved in the grading, and the average of the five grades is taken as the final grade.

[0098] Table 1. Criteria for Determining the Grade of Adhesion at the Punch Point

[0099]

[0100] The test method for dart impact strength is as follows: refer to GB / T 9639.1-2008 standard.

[0101] Examples 1-15

[0102] Examples 1-15 provide a series of polyester compositions, the weight parts of each component in the formulations are shown in Tables 2 and 3.

[0103] Table 2 Formulations (parts by weight) for Examples 1-8

[0104]

[0105] Table 3. Formulations (parts by weight) for Examples 9-15

[0106]

[0107] Comparative Examples 1-7

[0108] Comparative Examples 1 to 7 provide a series of polyester compositions, the weight parts of each component in the formulation of which are shown in Table 4.

[0109] Table 4. Formulations (parts by weight) for Comparative Examples 1-7

[0110]

[0111] The properties of the polyester compositions of each embodiment and comparative example were determined according to the test methods mentioned above, and the test results are shown in Table 5.

[0112] Table 5 Performance test results of the polyester compositions in each example and comparative example

[0113]

[0114] As can be seen from Table 5:

[0115] When the polyester compositions of each embodiment are made into film bags with a film thickness controlled at 25±2μm using ultra-thin high-speed blown film technology, the punch adhesion level is ≤N2 and the dart impact strength is ≥100 g, indicating that the ultra-thin film bags made from the polyester compositions of the present invention have good anti-punch adhesion performance and dart impact strength.

[0116] The supercooling of the polylactic acid added in Comparative Example 1 was too low. Although polylactic acid has good compatibility with the blend system, the viscosity of the system was too high, resulting in a poor anti-blocking grade of 3.9, which is unacceptable. The supercooling of the polylactic acid added in Comparative Example 2 was too high. The compatibility of polylactic acid with the blend system was poor, and the dart drop performance was significantly reduced to only 58.2g, which is also unacceptable. The D98 particle size of the sheet-like inorganic filler added in Comparative Example 3 was too large, resulting in numerous microscopic defects in the film prepared from the blend material, and a significant reduction in dart drop performance to only 38.9g, which is also unacceptable. The melting point of the organic opening agent added in Comparative Example 4 was too low, resulting in poor compatibility with the system and rapid precipitation onto the film surface. Although it provided some help in preventing adhesion, the thin dart impact strength was only 35.9g, which is also unacceptable. The organic opening agent added in Comparative Example 5 has a melting point that is too high, making it difficult to precipitate into a film to achieve a smooth effect. Its anti-blocking effect is poor, with a grade of only 4.5, which is not satisfactory for use. Comparative Example 6 does not contain calcium carbonate and only contains flake-shaped inorganic fillers. The dispersibility of flake-shaped inorganic fillers is not as good as that of calcium carbonate, so its dart drop performance is poor. Comparative Example 7 does not contain flake-shaped inorganic fillers, and the powder content on the surface of the film is low, so its anti-blocking effect is poor.

[0117] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A polyester composition, characterized in that, The components include the following parts by weight: 40-91 parts by weight of biodegradable polyester Polylactic acid 2-20 parts by weight Calcium carbonate 1-30 parts by weight 0.1-10 parts by weight of flake-shaped inorganic filler. 0.1-2 parts by weight of organic opening agent; The D98 particle size of the sheet-like inorganic filler is ≤16μm; The supercooling degree of the polylactic acid is 80~115℃; The organic opening agent has a melting point of 55~120℃.

2. The polyester composition according to claim 1, characterized in that, The sheet-like inorganic filler is one or more of talc, montmorillonite, and mica.

3. The polyester composition according to claim 1 or 2, characterized in that, The D98 particle size of the sheet-like inorganic filler is ≤13μm.

4. The polyester composition according to claim 1, characterized in that, The organic opening agent is one or more of the following: glyceryl monostearate, stearyl erucamide, oleamide, erucamide, stearamide, behenamide, and synthetic wax.

5. The polyester composition according to claim 1 or 4, characterized in that, The organic opening agent has a melting point of 60~115℃.

6. The polyester composition according to claim 1, characterized in that, The polylactic acid is selected from one or more of PLLA, PDLA, or PLLA / PDLA copolymer.

7. The polyester composition according to claim 1 or 6, characterized in that, The supercooling degree of the polylactic acid is 85~105℃.

8. A method for preparing the polyester composition according to any one of claims 1 to 7, characterized in that, The process includes the following steps: mixing the components, melt extruding, and granulating to obtain the polyester composition.

9. The use of the polyester composition according to any one of claims 1 to 7 in the preparation of fully biodegradable film bags.

10. A fully biodegradable membrane bag, characterized in that, It is prepared by any of the polyester compositions according to claims 1 to 7.

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