Biodegradable composition and preparation method thereof

Abstract

The invention relates to a biodegradable composition and a preparation method thereof, belongs to the technical field of degradable materials, and aims to overcome the defects of the traditional biodegradable material in the aspects of tensile strength, edge sealing strength and puncture strength. The composition comprises flexible biodegradable polyester, polylactic acid and inorganic filler, the flexible biodegradable polyester has a specific melting point, melting range and Mz / Mw, the polylactic acid has a certain D-lactic acid unit content so as to achieve high tensile strength, edge sealing strength and puncture strength, and the composition is suitable for preparing full-biodegradable film bags and packaging bags. Comprising food packaging bags, agricultural films and disposable articles, and has excellent biodegradability and mechanical properties.

Description

Technical Field

[0001] The present invention belongs to the technical field of degradable materials, and particularly relates to a biodegradable composition and a preparation method thereof. Background Art

[0002] With the increasing global awareness of environmental protection, biodegradable materials have received more and more attention because they can be decomposed by microorganisms in the natural environment without producing persistent pollution. In the field of polymer modification, biodegradable polyesters and polylactic acid (PLA) are two main biodegradable materials. However, compared with traditional polyethylene (PE), these biodegradable materials have deficiencies in terms of tensile strength, side seal strength, etc. Especially in the trend of light weight and thinning, the deficiencies of these properties are more obvious, which limits their application fields with higher requirements for side seal strength, such as logistics express bags, side-sealed clothing bags, side-sealed food bags, etc. To solve such problems, there are currently two methods in the industry. One is to use a dull knife for side sealing, and the other is to use a flexible biodegradable polyester with a higher content of terephthalic acid units (T content). Using a dull knife for side sealing will cause serious wire drawing of the seal line, uneven and unbeautiful appearance, affecting the consumer experience, while using a flexible biodegradable polyester with a high T will have a negative impact on the biodegradation rate. Even in the traditional PE industry, part of the HDPE component with stronger mechanical properties or other non-degradable reinforcing and toughening agents can be added, but this is not allowed in the biodegradable industry. Therefore, there are research difficulties in biodegradable polyester + PLA-MD materials with high tensile strength and high side seal strength under the conventional T content.

[0003] The prior art discloses a biodegradable material, in which the molar content of D-lactic acid in polylactic acid is 3-15%, and the melt index at 190 °C and 2.16 kg load according to ISO 1133-2011 is 1-30 g / 10 min; the particle size D50 of the filler ≤ 5 μm, and a biodegradable side-sealed bag is prepared. At the same time, this product effectively solves the problem of delayed failure, and has high delayed strength, but its tensile strength and side seal strength still need to be further improved, and the puncture strength of the material has not been studied, so the application range is limited.

[0004] Therefore, it is of great research significance and application value to develop a biodegradable composition with balanced tensile strength, side seal strength and puncture strength. Summary of the Invention

[0005] To address the challenge in the prior art that it is difficult to achieve a balance among tensile strength, side seal strength, and puncture strength of biodegradable materials, the primary objective of the present invention is to provide a biodegradable composition. The biodegradable composition provided by the present invention controls the melting point, melting range, and molecular weight of the flexible biodegradable polyester, as well as the content of D-lactic acid units in polylactic acid, and conducts comprehensive modification to obtain a biodegradable composition with both high tensile strength, side seal strength, and puncture strength.

[0006] Another objective of the present invention is to provide a preparation method for the above-mentioned biodegradable composition.

[0007] Another objective of the present invention is to provide the application of the above-mentioned biodegradable composition in the preparation of fully biodegradable film bags.

[0008] Another objective of the present invention is to provide a film or bag prepared from the above-mentioned biodegradable composition.

[0009] To achieve the above-mentioned invention objectives, the present invention adopts the following technical solutions:

[0010] The present invention protects a biodegradable composition, which comprises the following components in parts by weight:

[0011] 58 - 97 parts of flexible biodegradable polyester, 1 - 10 parts of polylactic acid, and 2 - 32 parts of inorganic filler;

[0012] Among them, the melting point of the flexible biodegradable polyester is 110 - 120 °C, the melting range is 22 - 40 °C, the Mz range is 160,000 - 300,000 g / mol, and Mz / Mw is 1.50 - 2.30;

[0013] The content of D-lactic acid units in the polylactic acid is 2 - 32%.

[0014] The present invention selects flexible biodegradable polyester, polylactic acid, and inorganic filler. When the melting point, melting range, and molecular weight distribution of the flexible biodegradable polyester are within a certain range, the flexible biodegradable polyester has a certain molecular chain branching structure. The branching structure of the molecular chain can cause certain entanglement between the molecular segments during the blending process, so that the material or film can withstand greater force when subjected to force, and then the edge sealing strength, tensile strength, and puncture strength are improved macroscopically. Flexible biodegradable polyester is a semi-crystalline polyester that crystallizes slowly. Polylactic acid with weaker crystallization performance has better compatibility with flexible biodegradable polyester, and similar compatibility is further improved. The improvement of compatibility further improves the strength of the blend, including edge sealing strength, tensile strength, and puncture strength. The D-lactic acid unit content of polylactic acid is controlled within a suitable range, and the various properties of the polyester composition can be further improved. If the content of D-lactic acid units is too low, the molecular chain of polylactic acid is relatively regular, so the crystallinity is strong, and separation will occur when blended with semi-crystalline biodegradable polyester, thereby deteriorating various properties; if the content of D-lactic acid units is too high, polylactic acid will become an amorphous polymer, and D-lactic acid segments will begin to replace L-lactic acid segments as the main body. When the content of D-lactic acid units is increased by 100% at a certain ratio, the molecular chain will gradually become regular, thereby deteriorating various properties. Therefore, it is necessary to control the content of D-lactic acid units within a certain range to promote its compatibility with semi-crystalline polyester.

[0015] In the biodegradable combination, the weight percentage of the flexible biodegradable polyester is not less than 58%.

[0016] Specifically, the flexible biodegradable polyester is a copolymer of a dibasic acid and / or an ester-forming derivative thereof and a diol.

[0017] Preferably, the dibasic acid is at least one of an aliphatic dibasic acid or an aromatic dibasic acid.

[0018] More preferably, the aliphatic dibasic acid is at least one of succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid or dodecanedioic acid.

[0019] More preferably, the aromatic dibasic acid is terephthalic acid.

[0020] More preferably, the dibasic acid is an aliphatic dibasic acid and an aromatic dibasic acid, and the molar ratio of the aromatic dibasic acid to the aliphatic dibasic acid is 1:(0.80-1.20); specifically, it can be one of 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.

[0021] More preferably, the diol is at least one of 1,4-butanediol, propylene glycol, ethylene glycol or pentylene glycol.

[0022] Specifically, the flexible biodegradable polyester may be at least one of poly(butylene adipate terephthalate) (PBAT), poly(butylene terephthalate sebacate) (PBSeT), poly(butylene terephthalate succinate) (PBST), poly(butylene terephthalate sebacate adipate) (PBSeAT), poly(butylene terephthalate sebacate succinate) (PBSeST), poly(butylene succinate adipate terephthalate) (PBSAT) or poly(propylene glycol adipate terephthalate) (PDAT).

[0023] Preferably, the Mz / Mw of the flexible biodegradable polyester is 1.60 - 2.20.

[0024] Preferably, the melting point of the flexible biodegradable polyester is 110 - 118 °C.

[0025] Preferably, the melting range of the flexible biodegradable polyester is 26 - 40 °C.

[0026] More preferably, the melting point of the flexible biodegradable polyester is 112 - 118 °C, the melting range is 28 - 38 °C, and the Mz / Mw is 1.65 - 2.15.

[0027] Among them, the test method for Mz / Mw: GPC test. GPC is tested using the ACQUITY APC TM equipment of Waters Corporation, the test temperature is 40 °C, XT45, XT200 and XT459 chromatographic columns are used, the solvent: tetrahydrofuran, the mobile phase flow rate: 0.5 mL / min. Polystyrene standard is used as the standard sample. The result is the average value of three times, and the Z-average molecular weight Mz is divided by the weight-average molecular weight Mw to obtain the Mz / Mw ratio.

[0028] The test method for the melting point Tm: DSC test. The sample is first heated from 30 °C to 220 °C at a heating rate of 10 °C / min and held at 220 °C for 3 min to eliminate the thermal history, then cooled to 30 °C at a rate of 10 °C / min, and then heated to 220 °C at a rate of 10 °C / min to obtain the second melting curve of the sample. The melting peak of this curve is selected as the melting point, and the melting range is the temperature difference from the start to the end of the melting peak. The starting point and the ending point are taken as the intersection points of the extrapolated line at the turning point and the baseline.

[0029] Preferably, the polylactic acid is a PLLA / PDLA copolymer.

[0030] Preferably, the D content of the polylactic acid is 2 - 25%.

[0031] Test method for D content of polylactic acid (PLA): (1) Weigh 100 ± 10 mg of ground and pulverized polylactic acid sample and place it in the inner container of a 25 mL pressure vessel; (2) Add 10 mL of methanol and 1 drop of dilute sulfuric acid; (3) Seal the pressure vessel and place it in a thermostat at 150 °C for 4 h; (4) Take out the pressure vessel and open the lid after the container has cooled to room temperature; (5) Filter the sample solution through a membrane filter (pore size 0.22 or 0.45 μm), transfer it to a special injection vial for gas chromatography, and operate according to the instructions of the equipment manufacturer; (6) Calculate the D-type content based on the peak area ratio.

[0032] Preferably, the inorganic filler is one or more of calcium carbonate, talcum powder, and montmorillonite.

[0033] More preferably, the inorganic filler is one or two of calcium carbonate and talcum powder.

[0034] Preferably, the biodegradable composition further comprises a processing aid.

[0035] Specifically, the processing aid includes a slip agent.

[0036] Preferably, the slip agent is selected from one or two of erucamide or oleamide.

[0037] More preferably, the weight of the additive is 0.1 - 0.5 parts.

[0038] Preferably, the biodegradable composition has a melt index of 0.5 - 8 g / 10 min at 190 °C under a load of 2.16 kg.

[0039] In the present invention, the melt index of the biodegradable composition can be measured according to the ISO 1133-1:2022 standard.

[0040] The present invention also provides a method for preparing a biodegradable composition, comprising the following steps:

[0041] Mix the components evenly and then melt-extrude and pelletize to obtain the biodegradable material.

[0042] Preferably, the melt-extrusion pelletization is carried out using a twin-screw extruder, with the temperature set at 150 - 180 °C, the rotation speed set at 300 - 400 rpm, and the feeding rate set at 600 - 1000 kg / h.

[0043] In the present invention, the flexible biodegradable polyester can be either commercially available or self-made. The self-making method is as follows:

[0044] Mix a dibasic acid and / or its ester derivative and a diol with a branching agent, first react at 180-200 °C under a pressure of 50-150 Pa for 1-8 hours, add a catalyst, and then react at 230-250 °C and 150-250 Pa for 2-18 hours to obtain the biodegradable polyester.

[0045] Preferably, the branching agent includes but is not limited to glycerol. The dosage of the branching agent is: 0.03% to 0.06% of the mass of the dibasic acid and / or its ester derivative.

[0046] Preferably, the catalyst includes but is not limited to tetrabutyl titanate. The dosage of the catalyst is: 0.005% to 0.015% of the sum of the masses of the dibasic acid and / or its ester derivative and the diol.

[0047] Preferably, the molar ratio of the dibasic acid and / or its ester derivative to the diol is 1:(1.05-1.4).

[0048] Preferably, the melt index of the polylactic acid measured at 190 °C and 2.16 kg is 2-30 g / 10 min.

[0049] In the present invention, the melt index of the polylactic acid can be measured according to the ISO 1133-1:2022 standard.

[0050] In the present invention, the polylactic acid can be obtained either commercially or prepared by oneself. The self-preparation method can be as follows: Add a lactide raw material containing L-lactide and meso-lactide and / or lactic acid to a solvent, and carry out a ring-opening polymerization reaction to obtain the polylactic acid.

[0051] Preferably, the solvent includes but is not limited to hexanediol.

[0052] Preferably, the mass ratio of L-lactide to meso-lactide is 30-98:2-70; more preferably 40-96:4-60.

[0053] More preferably, the ring-opening polymerization reaction is carried out in the presence of a catalyst, and the catalyst includes but is not limited to stannous octoate.

[0054] Even more preferably, the process of the ring-opening polymerization reaction is: first react at 120-150 °C and 1000-1500 Pa for 2-5 hours, and then react at 160-180 °C and 250-350 Pa for 3-7 hours.

[0055] Without affecting the effects of the present invention, the biodegradable composition of the present invention can also be added with one or more of a colorant, an antiblocking agent, an antistatic agent or an odor eliminator as needed.

[0056] The present invention also protects a film or a bag prepared from the above biodegradable composition.

[0057] Compared with the prior art, the present invention has the following beneficial effects:

[0058] The biodegradable composition provided by the present invention selects a flexible biodegradable polyester with a certain melting point, melting range and Mz / Mw, polylactic acid with a certain D content, and an inorganic filler. The prepared biodegradable composition achieves a balance of tensile strength, side seal strength and puncture strength. Under a film with a thickness of 50±2um, the longitudinal tensile strength ≥ 20MPa, the transverse tensile strength ≥ 20MPa, the side seal strength ≥ 15N / 15mm, and the puncture strength at 1mm ≥ 2N. Detailed embodiments

[0059] The present invention will be further described below in conjunction with embodiments. These embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. For the experimental methods without specific conditions in the following examples, they are generally carried out according to the conventional conditions in the art or according to the conditions recommended by the manufacturer; the raw materials, reagents, etc. used, unless otherwise specified, are all raw materials and reagents that can be obtained from commercial channels such as the conventional market. Any non-substantive changes and substitutions made by those skilled in the art based on the present invention fall within the scope of protection required by the present invention.

[0060] Some of the reagents selected in the examples and comparative examples of the present invention are described as follows:

[0061] Examples:

[0062] Flexible biodegradable polyester 1#: melting point is 118.0°C, melting range is 37°C, and Mz / Mw is 1.85:

[0063] Self-made. Add 2.0 kg of terephthalic acid, 2.0 kg of adipic acid, 2.6 kg (in excess) of 1,4-butanediol, and 2.0 g of glycerol into a 20L reaction kettle, stir at 190°C (denoted as temperature T1) for 3 hours (denoted as time t1), then add tetrabutyl titanate accounting for 0.01% of the total mass of the dibasic acid and diol as a catalyst, raise the temperature to 240°C (denoted as temperature T2), turn on the vacuum, the vacuum degree is 200 Pa, and react for 8 hours (denoted as time t2) to obtain biodegradable polyester 1#. The Z-average molecular weight (Mz) of biodegradable polyester 1# is 231600 Da;

[0064] Flexible biodegradable polyester 2#: melting point is 110.0°C, melting range is 35°C, and Mz / Mw is 1.99:

[0065] Self-made, PBAT. The difference in its preparation method from biodegradable polyester 1# is as follows: the amount of terephthalic acid is reduced to 1.8 kg, the amount of adipic acid is reduced to 1.8 kg, 2.6 kg of 1,4-butanediol (in excess), time t1 is 5 hours, and time t2 is 12 hours. The Z-average molecular weight (Mz) of biodegradable polyester 2# is 297800 Da;

[0066] Flexible biodegradable polyester 3#: melting point is 120.0 °C, melting range is 35 °C, Mz is 231458 g / mol, Mz / Mw is 1.78:

[0067] Commercially available, PBAT, A400, Zhuhai Jinfa Biomaterials Co., Ltd.;

[0068] Flexible biodegradable polyester 4#: melting point is 118.0 °C, melting range is 22 °C, Mz / Mw is 1.88:

[0069] Self-made, PBSeT. The difference in its preparation method from biodegradable polyester 1# is as follows: 2.0 kg of adipic acid is replaced with 3.0 kg of sebacic acid, 2.6 kg of 1,4-butanediol (in excess), time t1 is 4 hours, and time t2 is 9 hours. The Z-average molecular weight (Mz) of biodegradable polyester 4# is 248500 Da;

[0070] Flexible biodegradable polyester 5#: melting point is 118.3 °C, melting range is 35 °C, Mz / Mw is 1.69:

[0071] Self-made, PBAT. The difference in its preparation method from biodegradable polyester 1# is as follows: time t1 is 2 hours, and time t2 is 5.5 hours. The Z-average molecular weight (Mz) of biodegradable polyester 5# is 209300 Da;

[0072] Flexible biodegradable polyester 6#: melting point is 118.6 °C, melting range is 33 °C, Mz / Mw is 1.5:

[0073] Self-made, PBAT. The difference in its preparation method from biodegradable polyester 1# is as follows: time t1 is 1.5 hours, time t2 is 4 hours, and the usage amount of glycerol is reduced to 1.0 g. The Z-average molecular weight (Mz) of biodegradable polyester 6# is 178400 Da;

[0074] Flexible biodegradable polyester 7#: melting point is 118.1 °C, melting range is 36 °C, Mz / Mw is 2.3:

[0075] Self-made, PBAT. The difference in its preparation method from biodegradable polyester 1# is that: the time t1 is 3.5 hours, the time t2 is 5.5 hours, and the usage amount of glycerol is increased to 4.0 g. The Z-average molecular weight (Mz) of biodegradable polyester 7# is 180500 Da;

[0076] Comparative example:

[0077] Flexible biodegradable polyester 8#: The melting point is 100.0 °C, the melting range is 42 °C, and Mz / Mw is 1.80:

[0078] Self-made, PBAT. The difference in its preparation method from biodegradable polyester 1# is that: the time t1 is 1.5 hours, the time t2 is 3 hours, and the usage amount of glycerol is increased to 9.0 g. The Z-average molecular weight (Mz) of biodegradable polyester 8# is 160500 Da;

[0079] Flexible biodegradable polyester 9#: The melting point is 130.0 °C, the melting range is 35 °C, and Mz / Mw is 1.74:

[0080] Self-made, PBAT. The difference in its preparation method from biodegradable polyester 1# is that: the amount of terephthalic acid is increased to 2.5 kg, the amount of adipic acid is reduced to 1.5 kg, and 1,4-butanediol is 2.6 kg (in excess). The Z-average molecular weight (Mz) of biodegradable polyester 9# is 219700 Da;

[0081] Flexible biodegradable polyester 10#: The melting point is 119.0 °C, the melting range is 20 °C, and Mz / Mw is 1.91:

[0082] Self-made, PBAT. The difference in its preparation method from biodegradable polyester 1# is that: the amount of terephthalic acid is increased to 2.1 kg, the amount of adipic acid is reduced to 1.9 kg, 1,4-butanediol is 2.6 kg (in excess), the time t1 is 4 hours, the time t2 is 6 hours, and the usage amount of glycerol is increased to 3.0 g. The Z-average molecular weight of biodegradable polyester 10# is 220100 Da;

[0083] Flexible biodegradable polyester 11#: The melting point is 118.0 °C, the melting range is 45 °C, and Mz / Mw is 1.96:

[0084] Self-made, PBAT. The difference in its preparation method from biodegradable polyester 1# is that: the amount of terephthalic acid is reduced to 1.9 kg, the amount of adipic acid is increased to 2.1 kg, the time t1 is 5 hours, the time t2 is 12 hours, and the usage amount of glycerol is reduced to 0.2 g. The Z-average molecular weight of biodegradable polyester 11# is 288100 Da;

[0085] Flexible biodegradable polyester 12#: melting point is 118.8 °C, melting range is 32 °C, Mz / Mw is 1.0:

[0086] Self-made, PBAT. The difference in its preparation method from biodegradable polyester 1# is that: time t1 is 1 hour, time t2 is 2 hours, and the usage amount of glycerol is reduced to 0.1 g. The Z-average molecular weight of biodegradable polyester 13# is 111500 Da;

[0087] Flexible biodegradable polyester 13#: melting point is 117.0 °C, melting range is 41 °C, Mz / Mw is 2.5:

[0088] Self-made, PBAT. The difference in its preparation method from biodegradable polyester 1# is that: time t1 is 1.5 hours, time t2 is 5.5 hours, and the usage amount of glycerol is increased to 6.0 g. The Z-average molecular weight of biodegradable polyester 13# is 140900 Da;

[0089] Examples:

[0090] Polylactic acid 1#: grade PLA4060D, from Natureworks in the US, the content of D-lactic acid units is 12%, and the melt index is 4.9 g / 10 min;

[0091] Polylactic acid 2#: the content of D-lactic acid units is 2%;

[0092] Self-made. Its preparation method is as follows: Take 96 parts by weight of L-lactide (purity 99.6%) and 4 parts by weight of meso-lactide (purity 99.6%) and add them to a 20 L reaction kettle, add 0.002 parts by mass of stannous octoate, and carry out ring-opening polymerization: First, react at a reaction temperature of 135 °C and a reaction pressure of 1200 Pa for 4 hours, and then react at a reaction temperature of 170 °C and a reaction pressure of 300 Pa for 6 hours; underwater pelletize, crystallize, and dry to obtain polylactic acid. The content of D-lactic acid units in polylactic acid 2# is 2.0%, and the melt index is 4.6 g / 10 min;

[0093] Polylactic acid 3#: the content of D-lactic acid units is 25.1%;

[0094] Self-made. The difference in its preparation method from polylactic acid 2# is that: the usage amount of L-lactide is 50 parts by weight, and the usage amount of meso-lactide is 50 parts by weight. The content of D-lactic acid units in polylactic acid 3# is 25.1%, and the melt index is 6.4 g / 10 min;

[0095] Polylactic acid 4#: the content of D-lactic acid units is 30.9%;

[0096] Self-made. The difference in its preparation method from that of polylactic acid 1# lies in that the dosage of L-lactide is 40 parts by weight and the dosage of meso-lactide is 60 parts by weight. The content of D-lactic acid units in polylactic acid 4# is 30.9%, and the melt index is 6.9 g / 10 min;

[0097] Comparative example:

[0098] Polylactic acid 5#: The content of D-lactic acid units is 1.1%:

[0099] Self-made. The difference in its preparation method from that of polylactic acid 1# lies in that the dosage of L-lactide is 98 parts by weight and the dosage of meso-lactide is 2 parts by weight. The content of D-lactic acid units in polylactic acid 5# is 1.1%, and the melt index is 5.1 g / 10 min;

[0100] Polylactic acid 6#: The content of D-lactic acid units is 34.7%:

[0101] Self-made. The difference in its preparation method from that of polylactic acid 1# lies in that the dosage of L-lactide is 30 parts by weight and the dosage of meso-lactide is 70 parts by weight. The content of D-lactic acid units in polylactic acid 6# is 34.7%, and the melt index is 8.0 g / 10 min;

[0102] Inorganic filler 1#: Calcium carbonate and talc powder, with a ratio of 4:1;

[0103] Inorganic filler 2#: Barium sulfate;

[0104] Auxiliary agent: Oleic acid amide: Erucic acid amide = 2:1.

[0105] The biodegradable compositions of each example and comparative example of the present invention are prepared through the following process:

[0106] After mixing each component evenly, melt extrusion granulation is carried out by a twin-screw extruder to obtain the biodegradable material. The temperature is set at 170 °C, the rotation speed is set at 350 rpm, and the feeding rate is set at 700 kg / h.

[0107] The performance test methods and standards of the biodegradable composition materials of each example and comparative example of the present invention are as follows: The polyester compositions provided by each example and comparative example of the present invention are first blown into roll films by a film blowing machine, and then made into films with a thickness of 50 ± 2 μm by a side-sealing bag-making machine, and then the performance is measured according to the following test methods:

[0108] (1) Tensile strength: The tensile properties of the film bags were tested using a PARAM HST-H3 (Jinan Labthink) film tensile testing machine. The test was carried out in accordance with GB / T 1040.3-2006. Type 2 specimens were used, with a length of 150 mm and a width of 15 mm. The test speed was 500 mm / min;

[0109] (2) Side seal strength: The test was carried out in accordance with GB / T 1040.3-2006 at a speed of 300 mm / min;

[0110] (3) Puncture strength: The puncture properties of the film bags were tested using a universal film testing machine. The test was carried out in accordance with GB / T21302-2007. The film was fixed on the universal film testing machine, and a puncture test needle with a diameter of 1 mm was used for testing at a speed of 50 mm / min. The maximum force value was taken, and the test value was the average of 5 measurements.

[0111] Examples 1 to 14

[0112] This example provides a series of biodegradable compositions, and the weight parts of each component in the formula are shown in Table 1 and Table 2.

[0113] Table 1 Formulas of Examples 1 to 10 (parts)

[0114]

[0115]

[0116] Table 2 Formulas of Examples 11 to 14 (parts)

[0117]

[0118] Comparative Examples 1 to 10

[0119] This comparative example provides a series of biodegradable compositions, and the components in the formula are shown in Table 3.

[0120] Table 3 Formulas of Comparative Examples 1 to 10 (parts)

[0121]

[0122]

[0123] The performance test results of the biodegradable compositions in each example and comparative example according to the above-mentioned method are shown in Table 4.

[0124] Table 4 Performance test results of each example and comparative example

[0125] Examples / Comparative Examples Longitudinal Tensile Strength Transverse Tensile Strength Side Seal Strength 1mm Puncture Strength Example 1 29.9 32.4 19.7 3.12 Example 2 27.1 29.6 18.1 2.92 Example 3 21.5 21.0 15.2 2.11 Example 4 27.0 28.8 17.4 2.81 Example 5 28.1 27.1 17.5 2.77 Example 6 28.2 29.9 18.6 2.94 Example 7 26.8 28.1 16.9 2.70 Example 8 28.0 29.9 18.2 2.88 Example 9 26.4 27.6 16.7 2.63 Example 10 28.8 30.1 17.9 2.87 Example 11 23.5 22.0 15.8 2.23 Example 12 28.5 30.8 18.1 2.86 Example 13 26.9 29.8 17.2 2.67 Example 14 21.8 25.6 16.2 2.21 Comparative Example 1 19.2 18.6 14.5 1.84 Comparative Example 2 22.3 17.1 12.8 1.90 Comparative Example 3 18.3 16.5 12.3 1.70 Comparative Example 4 17.9 15.9 12.5 1.84 Comparative Example 5 16.5 15.3 12.2 1.58 Comparative Example 6 16.3 15.9 13.2 1.62 Comparative Example 7 21.3 12.6 11.6 1.98 Comparative Example 8 15.3 10.3 10.6 1.21 Comparative Example 9 23.3 12.6 12.6 1.65 Comparative Example 10 18.3 22.6 14.6 1.89

[0126] As can be seen from Table 4, the biodegradable compositions prepared in Examples 1 to 14 of the present invention all have the characteristics of high tensile strength, side seal strength and puncture strength. Among them, under the film with a thickness of 50±2um, the longitudinal tensile strength ≥ 20MPa, the transverse tensile strength ≥ 20MPa, the side seal strength ≥ 15N / 15mm, and the 1mm puncture strength ≥ 2N. Among them, the performance of Example 1 is the best.

[0127] In Comparative Example 1, the melting point of the flexible biodegradable polyester is too small. In Comparative Example 2, the melting point of the flexible biodegradable polyester is too large. In Comparative Example 3, the melting range of the flexible biodegradable polyester is too small. In Comparative Example 4, the melting range of the flexible biodegradable polyester is too large. In Comparative Example 5, the Mz / Mw of the flexible biodegradable polyester is too small. In Comparative Example 6, the Mz / Mw of the flexible biodegradable polyester is too large. Comparative Examples 1 to 6 all show that when the flexible biodegradable polyester has a certain molecular chain branching structure within the defined range of melting point, melting range and molecular weight distribution, the branching structure of the molecular chain can cause a certain entanglement between the molecular chain segments during the blending process, so that the material or film can withstand greater forces when stressed, and thus the side seal strength, tensile strength and puncture strength are improved macroscopically. In Comparative Example 7, the D content of polylactic acid is too small, and the side seal strength and puncture strength decrease. In Comparative Example 8, the D content of polylactic acid is too large. When the D content increases, the regularity of the molecular chain gradually decreases, the crystallization performance decreases, and the side seal strength, tensile strength and puncture strength all decrease. In Comparative Example 9, the amount of the flexible biodegradable polyester added is small. In Comparative Example 10, the amount of polylactic acid added is small, and excellent performance cannot be achieved.

[0128] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present invention rather than to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A biodegradable composition, characterized in that The composition comprises the following components in parts by weight: 58-97 parts of flexible biodegradable polyester, 1-10 parts of polylactic acid, 2-32 parts of inorganic filler; The melting point of the flexible biodegradable polyester is 110-120°C, the melting range is 22-40°C, the Mz range is 160000-300000 g / mol, and the Mz / Mw is 1.50-2.30; The content of D-lactic acid units in the polylactic acid is 2 to 32%.

2. The biodegradable composition according to claim 1, characterized in that: The flexible biodegradable polyester is an aliphatic-aromatic copolyester.

3. The biodegradable composition according to claim 1, characterized in that: The polylactic acid is selected from one or two of PDLA and PLLA / PDLA copolymer.

4. The biodegradable composition according to claim 1, characterized in that: The Mz / Mw of the flexible biodegradable polyester is 1.65-2.

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5. The biodegradable composition according to claim 1, characterized in that: The content of D-lactic acid units in the polylactic acid is 2-25%.

6. The biodegradable composition according to claim 1, characterized in that: The inorganic filler is one or more of calcium carbonate, talc and montmorillonite.

7. The biodegradable composition according to claim 1, characterized in that: The biodegradable composition also includes a processing aid.

8. The method for preparing the biodegradable composition according to any one of claims 1 to 7, characterized in that: The following steps are involved: After the components are uniformly mixed, they are melt-extruded and granulated to obtain the biodegradable material.

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

10. A film or bag prepared using the biodegradable composition according to any one of claims 1 to 7.

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