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: 50-88 parts of a biodegradable polyester, 2-15 parts of a polylactic acid, and 10-35 parts of a mineral filler. The polyester composition of the present invention has good puncture strength, longitudinal tear strength and transverse tear strength when being prepared into thin films having different thicknesses, and can still maintain good puncture strength, longitudinal tear strength and transverse tear strength under the condition that the polyester composition has a high content of the mineral filler.

Description

Polyester composition, and preparation method and application thereof TECHNICAL FIELD

[0001] The present application relates to the technical field of high polymer material modification, and more particularly to a polyester composition, and a preparation method and application thereof. BACKGROUND

[0002] Flexible polyester generally refers to a copolymer of dibasic acid and / or its ester-forming derivative and dihydric alcohol, which has excellent toughness and high melt strength. Polylactic acid is a polymer obtained by polymerization of lactic acid or lactide, which has a biobased source and good rigidity. Both flexible polyester and polylactic acid are biodegradable, and the combination of the two can obtain a biodegradable material that combines the advantages of both. A certain amount of mineral filler is usually added to the biodegradable material to obtain a biodegradable composite material to meet one of the main application scenarios of the biodegradable composite material: biodegradable film. The addition of mineral filler can improve the bubble stability of the biodegradable composite material when it is prepared into a film, i.e., improve the processability of film production; on the other hand, it can reduce the raw material cost of production. In order to achieve good bubble stability and control the raw material cost of production within a reasonable range, the amount of mineral filler added is usually 10-35wt% of the biodegradable composite material.

[0003] The further popularization of biodegradable film puts forward higher requirements for its performance. Compared with traditional PE film, the puncture resistance of biodegradable film is relatively weak; and with the development of the industry, lightweight thinning is a trend of biodegradable film, and under this trend, the puncture resistance of biodegradable film is further weakened, which limits the application of biodegradable film in scenarios that carry certain sharp objects, such as logistics express bags, industrial packaging bags, etc.

[0004] To improve the puncture strength of biodegradable film, there are currently two ways in the industry: one is to reduce the mineral filler content of biodegradable composite material or even use a filling-free scheme, and the other is to use a multi-layer film structure. Reducing the mineral filler content of biodegradable composite material obviously has a negative impact on bubble stability and increases the raw material cost of production. Using a multi-layer film structure requires high equipment, high equipment cost and low efficiency. Therefore, more technologies that can improve the puncture resistance of biodegradable film with high mineral filler content are needed.

[0005] Patent CN115637023A provides an anti-puncture biodegradable blown film, and obviously, the amount of filler added is very small, and it does not focus on the puncture resistance of biodegradable film with high mineral filler content (10-35wt%).

[0006] In addition to the puncture resistance performance, the machine direction and cross direction tear resistance performance of the biodegradable film also needs to be concerned, if the machine direction and cross direction tear resistance performance is too low, the film bag will be easily torn further when subjected to external force once a notch occurs when carrying articles, resulting in a situation that cannot be used. Therefore, the puncture resistance performance and the machine direction and cross direction tear resistance performance of the biodegradable film need to be improved at the same time. SUMMARY

[0007] The primary object of the present application is to overcome the problem of poor puncture resistance performance and poor machine direction and cross direction tear resistance performance of the biodegradable film prepared from the biodegradable composite material with high mineral filler content in the prior art, and to provide a polyester composition.

[0008] A further object of the present application is to provide a preparation method of the polyester composition.

[0009] A further object of the present application is to provide the use of the polyester composition in the preparation of a film.

[0010] The above objects of the present application are achieved by the following technical solutions:

[0011] A polyester composition comprising the following components in parts by weight: biodegradable polyester 50-88 parts, polylactic acid 2-15 parts, and mineral filler 10-35 parts.

[0012] The biodegradable polyester is a copolymer of a dibasic acid and / or an ester-forming derivative thereof and a dihydric alcohol, and the Z-average molecular weight of the biodegradable polyester is 180000-400000.

[0013] The content of D-lactic acid units in the polylactic acid is 3-50 mol%.

[0014] The particle size D98 of the mineral filler is ≤15 μm.

[0015] The components of the polyester composition of the present application include biodegradable polyester and polylactic acid, and the combination of the two imparts the polyester composition with basic toughness and rigidity. A certain amount of mineral filler is also added to impart the polyester composition with certain rigidity and to improve the processing performance of the polyester composition when prepared into a film.

[0016] The inventors of the present application have found through research that by regulating the Z-average molecular weight of the biodegradable polyester within a specific range, the puncture strength, the machine direction tear strength and the cross direction tear strength of the polyester composition can be improved through the entanglement of the long biodegradable polyester molecular chains. If the Z-average molecular weight is too small, the properties are difficult to improve; if the Z-average molecular weight is too high, the flowability of the biodegradable polyester will be poor, which will further result in poor compatibility with other components, thereby deteriorating the machine direction tear strength and the cross direction tear strength.

[0017] If the content of D-lactic acid units is too low, the crystallinity of the polylactic acid is improved, and separation occurs when the polylactic acid is blended with the semi-crystalline biodegradable polyester, thereby deteriorating the properties; if the content of D-lactic acid units is too high, the polylactic acid becomes an amorphous polymer, and also separates from the semi-crystalline biodegradable polyester, thereby deteriorating the properties.

[0018] In addition, the particle size D98 of the mineral filler also needs to be controlled within a specific range, so as to ensure that the polyester composition has good puncture strength, longitudinal tear strength and transverse tear strength.

[0019] That is, the polyester composition obtained by the combination of the biodegradable polyester with a specific Z-average molecular weight, the polylactic acid with a specific content of D-lactic acid units and the mineral filler with a specific particle size D98 has good puncture strength, longitudinal tear strength and transverse tear strength when the polyester composition is made into a film with different thicknesses, and the polyester composition can still maintain good puncture strength, longitudinal tear strength and transverse tear strength even when the polyester composition has a high content of mineral filler.

[0020] In the present application, the content of the biodegradable polyester as the main resin is more than 45 wt% of the polyester composition.

[0021] In the present application, the biodegradable polyester can be used in an amount of 50, 55, 28, 60, 62, 65, 68, 70, 75, 78, 80, 85 or 88 parts by weight; the polylactic acid can be used in an amount of 2, 3, 5, 6, 8, 9, 10, 12 or 15 parts by weight; and the mineral filler can be used in an amount of 10, 12, 15, 18, 20, 24, 25, 28, 30, 32 or 35 parts by weight.

[0022] Preferably, the polyester composition comprises the following components in the following amounts by weight: biodegradable polyester 74-88 parts, polylactic acid 2-6 parts, and mineral filler 10-20 parts.

[0023] By controlling the amounts of the components within the range, the puncture strength and transverse tear strength of the polyester composition are better.

[0024] In the present application, the Z-average molecular weight of the biodegradable polyester can be 180000, 185000, 190000, 200000, 240000, 250000, 270000, 280000, 300000, 320000, 350000, 360000, 380000 or 400000.

[0025] Preferably, the biodegradable polyester has a Z-average molecular weight of 210,000 to 300,000. In this range, the polyester composition has better longitudinal and transverse tear strength.

[0026] Preferably, the biodegradable polyester has a Z-average molecular weight of 210,000 to 400,000. In this range, the polyester composition has better puncture strength.

[0027] The biodegradable polyester used in the present application can be synthesized by copolymerization of a commonly used diacid and / or ester-forming derivative thereof and a commonly used diol.

[0028] The biodegradable polyester used in the present application can be commercially available or self-made. The self-made biodegradable polyester can be prepared by mixing a diacid and / or ester-forming derivative thereof, a diol and a branching agent, and then reacting at 180 to 200°C for 2 to 8 hours, adding a catalyst, and then reacting at 230 to 250°C and 150 to 250 Pa for 8 to 18 hours.

[0029] Preferably, the branching agent includes, but is not limited to, glycerol. The amount of the branching agent is 0.03% to 0.06% based on the mass of the diacid and / or ester-forming derivative thereof.

[0030] Preferably, the catalyst includes, but is not limited to, tetrabutyl titanate. The amount of the catalyst is 0.005% to 0.015% based on the sum of the mass of the diacid and / or ester-forming derivative thereof and the diol.

[0031] Preferably, the molar ratio of the diacid and / or ester-forming derivative thereof to the diol is 1:(1.05 to 1.2).

[0032] Preferably, the diacid is at least one of an aliphatic diacid or an aromatic diacid.

[0033] More preferably, the aliphatic diacid is at least one of succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid or dodecanedioic acid.

[0034] More preferably, the aromatic diacid is terephthalic acid.

[0035] More preferably, the diacid is an aliphatic diacid and an aromatic diacid, and the molar ratio of the aromatic diacid to the aliphatic diacid is 1:(0.80 to 1.20); specifically, 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 1.20.

[0036] More preferably, the dihydric alcohol is at least one of butanediol, propanediol, ethylene glycol or pentanediol.

[0037] Specifically, the biodegradable polyester can be at least one of polybutylene adipate terephthalate (PBAT), polybutylene sebacate terephthalate (PBSeT), polybutylene succinate terephthalate (PBST), polybutylene adipate sebacate terephthalate (PBSeAT), polybutylene succinate sebacate terephthalate (PBSeST), polybutylene succinate adipate terephthalate (PBSAT) or polypropylene adipate terephthalate (PDAT).

[0038] Preferably, the poly-lactic acid has a melt index of 2-30 g / 10 min measured at 190℃ under 2.16 kg.

[0039] In the present application, the melt index of the poly-lactic acid can be measured by the standard of ISO 1133-1:2022.

[0040] In the present application, the poly-lactic acid can be commercially available or self-made. The self-made method can be as follows: adding lactide raw materials containing L-lactide and meso-lactide and / or lactic acid into a solvent to occur ring-opening polymerization reaction, and the poly-lactic acid is obtained.

[0041] Preferably, the lactide raw materials containing L-lactide and meso-lactide are added into a solvent to occur ring-opening polymerization reaction, and the poly-lactic acid is obtained.

[0042] More preferably, the mass ratio of the L-lactide and meso-lactide is 1-92:8-99; further preferably 1-90:10-99.

[0043] More preferably, the solvent includes but is not limited to hexanediol.

[0044] More preferably, the ring-opening polymerization reaction is carried out in the presence of a catalyst, which includes but is not limited to stannous octoate.

[0045] More preferably, the process of the ring-opening polymerization reaction is as follows: first reacting at 130-140℃ and 1100-1300 pa for 3-4 hours, and then reacting at 160-180℃ and 250-350 pa for 4-6 hours.

[0046] Preferably, the molecules of the poly-lactic acid are composed of left-handed lactic acid units and right-handed lactic acid units.

[0047] In the present application, the content of D-lactic acid units in the polylactic acid can be specifically 3, 3.5, 4, 5, 8, 10, 12, 15, 18, 20, 24, 25, 28, 30, 33, 35, 36, 38, 40, 42, 45, 48 or 50 mol%.

[0048] Preferably, the content of D-lactic acid units in the polylactic acid is 10-35 mol%. Within this range, the puncture strength, the longitudinal tear strength and the transverse tear strength of the polyester composition are all better.

[0049] Preferably, the glass transition temperature (Tg) of the polylactic acid is ≤65℃.

[0050] More preferably, the glass transition temperature of the polylactic acid is ≤62℃.

[0051] Further preferably, the glass transition temperature of the polylactic acid is ≤60℃.

[0052] Preferably, the content of the mineral filler of the polyester composition is 10-35 wt%. Specifically, it can be 10, 12, 15, 18, 20, 24, 26, 28, 30, 32 or 35 wt%.

[0053] Preferably, the mineral filler is at least one of calcium carbonate, talc or montmorillonite.

[0054] When the mineral filler is calcium carbonate, the longitudinal tear strength and the transverse tear strength of the polyester composition are both better; when the mineral filler is talc, the puncture strength of the polyester composition is better.

[0055] In the present application, the particle size D98 of the mineral filler can be specifically 3, 5, 7, 8, 9, 10, 11, 12, 13, 14 or 15 μm.

[0056] Preferably, the particle size D98 of the mineral filler is 7 μm≤D98≤15 μm.

[0057] Preferably, the polyester composition further comprises other auxiliary agents 0.2-2 parts.

[0058] Optionally, the other auxiliary agent is at least one of an antioxidant, a UV stabilizer or a UV absorber.

[0059] Generally, the amount of each other auxiliary agent is: antioxidant 0.01-0.3 parts by weight, UV absorber 0.05-2 parts by weight, and UV stabilizer 0.1-3 parts by weight.

[0060] Optionally, the antioxidant is at least one of antioxidant 1010 or antioxidant 168.

[0061] Optionally, the UV stabilizer is at least one of bis(1-octyloxy-2,2,6,6-tetramethyl-4-piperidyl) sebacate or 2-(2-hydroxy-3-tert-butyl-5-methylphenyl)-5-(2,4-dimethylphenyl)-2H-benzotriazol-4-one.

[0062] Optionally, the UV absorber is at least one of 2,4-dihydroxybenzophenone, phenyl salicylate, 2-hydroxy-4-methoxybenzophenone or 2-hydroxy-4-n-octyloxybenzophenone.

[0063] The preparation method of the polyester composition comprises the following steps: mixing the components, melt extruding, and granulating, to obtain the polyester composition.

[0064] Preferably, the temperature of the melt extrusion is 160-180℃; the screw length-diameter ratio of the extruder for the melt extrusion is 30-50:1, and the screw rotation speed is 250-400rpm.

[0065] The application of the polyester composition in preparing a film is also within the protection scope of the present application.

[0066] A film prepared by the polyester composition.

[0067] Compared with the prior art, the present application has the following beneficial effects:

[0068] The present application uses a biodegradable polyester with a specific Z-average molecular weight, polylactic acid with a specific content of D-lactic acid units, and a mineral filler with a specific particle size D98, and the polyester composition obtained by the combination has good puncture strength, longitudinal tear strength and transverse tear strength when it is made into a film with different thicknesses, and the polyester composition can maintain good puncture strength, longitudinal tear strength and transverse tear strength even when it contains a high content of mineral filler. DETAILED DESCRIPTION

[0069] In order to more clearly and completely describe the technical solutions of the present application, the present application is further described in detail below through specific examples, and it should be understood that the specific examples described herein are only used to explain the present application and are not used to limit the present application, and various changes can be made within the scope of the present application.

[0070] Some reagents selected by the embodiments and comparative examples of the present application are described as follows:

[0071] Biodegradable polyester 1#: self-made, PBAT, and the preparation method is as follows:

[0072] terephthalic acid 2.0 kg, adipic acid 2.0 kg, 1,4-butanediol 2.6 kg (excess), and glycerol 2.0 g were added to a 20 L reaction kettle, stirred at 190 °C (denoted as temperature T1) for 3 hours (denoted as time t1), then 0.01% of tetrabutyl titanate based on the total mass of the diacid and diol was added as a catalyst, the temperature was raised to 240 °C (denoted as temperature T2), the vacuum was opened, the vacuum degree was 200 Pa, and the reaction was carried out for 8 hours (denoted as time t2) to obtain biodegradable polyester 1#. The Z-average molecular weight of biodegradable polyester 1# was 231600 Da.

[0073] Biodegradable polyester 2#: self-made, PBAT, the difference between its preparation method and that of biodegradable polyester 1# is that time t1 is 5 hours and time t2 is 12 hours. The Z-average molecular weight of biodegradable polyester 2# is 297800 Da.

[0074] Biodegradable polyester 3#: self-made, PBAT, the difference between its preparation method and that of biodegradable polyester 1# is that time t1 is 8 hours and time t2 is 18 hours. The Z-average molecular weight of biodegradable polyester 3# is 398040 Da.

[0075] Biodegradable polyester 4#: self-made, PBAT, the difference between its preparation method and that of biodegradable polyester 1# is that time t1 is 2 hours and time t2 is 14 hours. The Z-average molecular weight of biodegradable polyester 4# is 187607 Da.

[0076] Biodegradable polyester 5#: self-made, PBSeT, the difference between its preparation method and that of biodegradable polyester 1# is that adipic acid 2.0 kg is replaced by sebacic acid 3.2 kg. The Z-average molecular weight of biodegradable polyester 5# is 234895 Da.

[0077] Biodegradable polyester 6#: self-made, PDAT, the difference between its preparation method and that of biodegradable polyester 1# is 1,4-butanediol 2.6 kg is replaced by propylene glycol 2.2 kg (excess). The Z-average molecular weight of biodegradable polyester 6# is 225898 Da.

[0078] Biodegradable polyester 7#: self-made, PBAT, the difference between its preparation method and that of biodegradable Polyester 1# is that time t1 is 1 hour and time t2 is 2 hours. The Z-average molecular weight of biodegradable polyester 7# is 159632 Da.

[0079] Biodegradable polyester 8#: self-made, PBAT, the difference between its preparation method and that of biodegradable polymer 1# is that time t1 is 8 hours and time t2 is 24 hours. The Z-average molecular weight of biodegradable polyester 8# is 416232 Da.

[0080] Z average molecular weight test method:

[0081] The GPC test method is: GPC uses Waters Corporation's ACQUITY APC TM The equipment is tested, the test temperature is 40℃, XT45, XT200 and XT459 chromatographic column are used, the solvent is tetrahydrofuran, the flow rate of mobile phase is 0.5mL / min. Polystyrene standard is used as a standard sample. The results are the average of three times.

[0082] Polylactic acid 1#: self-made, the preparation method is as follows: 90 parts by weight of L-lactide (L content is greater than or equal to 99.5%, the same below) and 10 parts by weight of meso-lactide (D content is about 50%, the same below) are dissolved in hexanediol, stannous octoate is added, and ring opening polymerization is carried out: first 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 to obtain polylactic acid 1#. The D content of polylactic acid 1# is 4.9%, the glass transition temperature is 59℃, and the melt index is 4.2g / 10min.

[0083] Polylactic acid 2#: self-made, the difference between its preparation method and that of polylactic acid 1# is that the amount of L-lactide is 84 parts by weight, and the amount of meso-lactide is 16 parts by weight. The D content of polylactic acid 2# is 8.1%, the glass transition temperature is 55℃, and the melt index is 3.9g / 10min.

[0084] Polylactic acid 3#: self-made, the difference between its preparation method and that of polylactic acid 1 # is that the amount of L-lactide is 30 parts by weight, and the amount of meso-lactide is 70 parts by weight. The D content of polylactic acid 3# is 34.6%, the glass transition temperature is 50℃, and the melt index is 4.1g / 10min.

[0085] Polylactic acid 4#: self-made, the difference between its preparation method and that of polylactic acid 1 is that the amount of L-lactide is 1 part by weight, and the amount of meso-lactide is 99 parts by weight. The D content of polylactic acid 4# is 49.8%, the glass transition temperature is 48.1℃, and the melt index is 4.0g / 10min.

[0086] Polylactic acid 5#: self-made, the difference between its preparation method and that of polylactic acid 1is that first at a reaction temperature of 135℃ and a reaction pressure of 1200pa for3 hours, and then at a reaction temperature of 170℃ and a reaction pressure of 300 pa for 4 hours. The D content of polylactic acid 5# is 4.0%, the glass transition temperature is 60℃, and the melt index is 7.7g / 10min.

[0087] Poly(lactic acid) 6: self-made, the difference between the preparation method and poly(lactic acid) 1 is that the amount of L-lactide is 98 parts by weight, and the amount of meso-lactide is 2 parts by weight. The D content of poly(lactic acid) 6 is 1%, the glass transition temperature is 60.5°C, and the melt index is 4.1 g / 10 min.

[0088] Poly(lactic acid) 7: self-made, the difference between the preparation method and poly(lactic acid) 1 is that 10 parts by weight of D-lactide (D content ≥ 99.5%) is added, and the amount of meso-lactide is 90 parts by weight. The D content of poly(lactic acid) 7 is 54.6%, the glass transition temperature is 47.0°C, and the melt index is 3.9 g / 10 min.

[0089] The D content of poly(lactic acid) can be detected according to the following steps: (1) weigh 100 ± 10 mg of ground and crushed poly(lactic acid) sample into a 25 mL pressure container inner tank; (2) add 10 mL of methanol and 1 drop of dilute sulfuric acid; (3) seal the pressure container and place it in a 150°C thermostat for 4 hours; (4) remove the pressure container and open the cover after the container cools to room temperature; (5) filter the sample solution through a membrane filter (pore size 0.22 or 0.45 μm) and transfer it to a gas chromatograph (Agilent 8860 gas chromatograph, CP7502 chromatographic column), and operate according to the manufacturer's instructions; (6) calculate the D content according to the peak area ratio.

[0090] The test method of the glass transition temperature Tg of poly(lactic acid) is as follows: using a DSC204 thermal analyzer of Netzsch Company in Germany, with nitrogen protection, the sample with a mass of 5 ± 1 mg is first heated from 30°C to 160°C at a rate of 10°C / min, and then kept at 160°C for 3 min, then cooled to -110°C at a rate of 20°C / min, and then heated to 150°C at a rate of 10°C / min; the glass transition temperature Tg of the sample is taken from the second heating curve, and the intersection of the extrapolation line with the baseline at the inflection point is taken as the value of the glass transition temperature Tg.

[0091] Mineral filler 1#: calcium carbonate, Omya, 1T-JI, D98: 7.8 μm;

[0092] Mineral filler 2#: calcium carbonate, Omya, 2T-JI, D98: 14.3 μm;

[0093] Mineral filler 3#: talcum powder, Aiha, AHCP 250, D98: 8.0 μm;

[0094] Mineral filler 4#: calcium carbonate, Omya, 5T-JI, D98: 16.7 μm;

[0095] The D98 of mineral fillers can be determined by referring to the method in GB / T 19077.1 "Particle size analysis by laser diffraction".

[0096] Other additives #1: Composed of antioxidant 168 and antioxidant 1010 in a 1:1 mass ratio, both of which are commercially available.

[0097] Unless otherwise specified, all components (e.g., other additives 1#) used in the parallel examples and comparative examples are the same commercially available products.

[0098] The polyester compositions provided in the embodiments and comparative examples of the present invention were first processed into films with thicknesses of 30 μm and 50 μm respectively using a blown film machine with controlled excitation speed. Their performance was then determined according to the following test methods:

[0099] 1) Puncture strength: The puncture performance of the film bag was tested using a universal testing machine for thin films, according to GB / T21302-2007. The film was fixed on the universal testing machine, and a puncture test needle with a diameter of 1 mm was used. The test was conducted at a speed of 50 mm / min, and the maximum force value was recorded. The average value of 5 tests was taken.

[0100] 2) Longitudinal tear strength: The longitudinal direction of the film is taken, and the tear performance of the film is tested according to GB / T 16578.2-2009.

[0101] 3) Transverse tear strength: The tear strength of the film is measured in the transverse direction. The tear performance of the film is tested according to GB / T 16578.2-2009.

[0102] The polyester compositions of the embodiments and comparative examples of the present invention were prepared by the following preparation method:

[0103] Weigh each component according to the formula, mix them evenly, and then feed them into a twin-screw extruder for melt extrusion and granulation to obtain a polyester composition. The temperatures of the twin-screw extruder from zone one to zone ten are 160℃, 170℃, 180℃, 180℃, 180℃, 180℃, 180℃, 180℃, and 180℃ respectively. The screw length-to-diameter ratio is 40:1, and the screw speed is 300 rpm.

[0104] Examples 1-14

[0105] Examples 1-14 provide a series of polyester compositions, the formulations of which are shown in Tables 1 and 2.

[0106] Table 1. Formulations (parts by weight) for Examples 1-8

[0107] Table 2. Formulations (parts by weight) for Examples 9-14

[0108] Comparative Examples 1-5

[0109] Comparative Examples 1-5 provide a series of polyester compositions whose formulations are shown in Table 3.

[0110] Table 3 Formulations (parts by weight) of Comparative Examples 1-5

[0111] The properties of the polyester compositions of each example and comparative example were determined according to the test methods mentioned above, and the test results are shown in Table 4.

[0112] Table 4 Test results of the properties of the polyester compositions of each example and comparative example

[0113] From Table 4, it can be seen that:

[0114] When the polyester compositions of each example were made into films with a thickness of 30 μm, the puncture strength was all above 1.1 N, the longitudinal tear strength was all above 1000 mN, and the transverse tear strength was all above 1800 mN; when the polyester compositions were made into films with a thickness of 50 μm, the puncture strength was all above 1.7 N, the longitudinal tear strength was all above 2400 mN, and the transverse tear strength was all above 3800 mN, indicating that the polyester compositions of the present application have good puncture strength, longitudinal tear strength and transverse tear strength when made into films with different thicknesses.

[0115] The biodegradable polyester added in Comparative Example 1 had too small a molecular weight, and the puncture strength and longitudinal tear strength of the polyester composition were poor after the polyester composition was made into a film, and the transverse tear strength was lower than that of Example 1 and Examples 4-6. The biodegradable polyester added in Comparative Example 2 had too large a molecular weight, and the puncture strength and longitudinal tear strength of the polyester composition were poor after the polyester composition was made into a film, and the transverse tear strength was lower than that of Example 1 and Examples 4-6. The D content of the polylactic acid added in Comparative Example 3 was too small, and the D content of the polylactic acid added in Comparative Example 4 was too large, and the puncture strength and longitudinal tear strength of the polyester composition were poor after the polyester composition was made into a film, and the transverse tear strength was lower than that of Example 1 and Example 9-11. The particle size D98 of the mineral filler added in Comparative Example 5 was too large, and the puncture strength and longitudinal tear strength of the polyester composition were poor, and the transverse tear strength was lower than that of Example 1 and Examples 13-14 after the polyester composition was made into a film.

[0116] Obviously, the above embodiments of the present application are merely exemplary but not intended to limit the embodiments of the present application. Based on the above description, any other variations or changes can be made by those skilled in the art without departing from the spirit and principles of the present application. It is not necessary to list all the embodiments here. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present application shall fall within the scope of the claims of the present application.

Claims

1. A polyester composition, characterized in that, The components include the following parts by weight: 50-88 parts of biodegradable polyester Polylactic acid 2-15 parts, 10-35 parts of mineral filler; The biodegradable polyester is a copolymer of a diacid and / or its ester derivatives and a diol, and the Z-average molecular weight of the biodegradable polyester is 180,000 to 400,000. The content of D-lactic acid units in the polylactic acid is 3-50 mol%. The particle size D98 of the mineral filler is ≤15μm.

2. The polyester composition according to claim 1, characterized in that, The dicarboxylic acid is an aliphatic dicarboxylic acid and / or an aromatic dicarboxylic acid.

3. The polyester composition according to claim 2, characterized in that, The aliphatic dicarboxylic acid is at least one of succinic acid, glutaric acid, adipic acid, pimelic acid, octanoic acid, azelaic acid, sebacic acid, undecanoic acid, or dodecanoic acid; the aromatic dicarboxylic acid is terephthalic acid.

4. The polyester composition according to claim 1, characterized in that, The melt index of the polylactic acid measured at 190°C and 2.16 kg was 2–30 g / 10 min.

5. The polyester composition according to claim 1, characterized in that, The mineral filler is at least one of calcium carbonate, talc, or montmorillonite.

6. The polyester composition according to claim 1, characterized in that, The particle size D98 of the mineral filler is 5μm≤D98≤15μm.

7. The polyester composition according to claim 1, characterized in that, The glass transition temperature of the polylactic acid is ≤65℃.

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. Use of the polyester composition according to any one of claims 1 to 7 in the preparation of films.

10. A thin film, characterized in that, It is prepared by any of the polyester compositions according to claims 1 to 7.

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