Polyester composition as well as preparation method and application thereof

Abstract

The invention provides a polyester composition as well as a preparation method and application thereof, and belongs to the technical field of high polymer materials. The polyester composition is prepared from, by weight, 40-81 parts of PBAT resin, 15-35 parts of starch, 4-12 parts of plasticizer and 0.1-10 parts of flaky filler, and the content of terminal carboxyl groups of the PBAT resin is smaller than or equal to 35 mol / t. According to the invention, the sheet filler is added into the PBAT resin with specific terminal carboxyl group content, so that the polyester composition with good opening property and mechanical property is obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and particularly relates to a polyester composition, a preparation method thereof, and an application thereof. Background Art

[0002] PBAT resin (polybutylene adipate terephthalate copolymer) is a semi-crystalline material with a slow cooling crystallization rate, which results in slow cooling of the film surface during blown film winding. When cutting the tape or using it, problems such as "adhesion at the cut" or "inability to open" are likely to occur, especially for thinner film bag products, such as fruit and vegetable bags, where problems such as "adhesion at the cut" or "inability to open" are more serious, thus affecting the use and consumption experience of the product. To improve such problems, from the perspective of the material formula, a large amount of antiblocking agent is usually added to the PBAT resin. For example, in patent CN 117903584 A, a packaging film material with good antiblocking property is prepared by adding a large amount of PLA, PBS, and antiblocking agent, but this material is not suitable for making fruit and vegetable bag products with a lower thickness, and a large amount of PLA, PBS, and antiblocking agent will significantly increase the cost of the material; from the perspective of molding processing, the following methods are usually adopted: (1) reducing the blown film speed, (2) increasing the height between the die head of the blown film machine and the "herringbone clip", (3) inflating the wound film before cutting the bag and then cutting the bag; improving the problems of "adhesion at the cut" or "inability to open" of PBAT resin from the above-mentioned molding processing perspective requires modifying the production equipment or reducing the production efficiency.

[0003] With the development of the industry, the thinning and lightweighting of products have become a possible future trend. The thinner the product, the higher the requirements for the adhesiveness and antiblocking property of the product. Therefore, how to make good use of the existing factory buildings and equipment to improve the antiblocking property and dart impact resistance of PBAT resin without increasing costs and reducing production efficiency is an urgent problem to be solved at present. Summary of the Invention

[0004] The purpose of the present disclosure is to overcome the deficiencies of the prior art and provide a polyester composition, a preparation method thereof, and an application thereof.

[0005] To achieve the above purpose, the technical solutions adopted by the present disclosure are as follows: In the first aspect, the present invention provides a polyester composition, comprising the following components in parts by weight: 40 - 81 parts of PBAT resin, 15 - 35 parts of starch, 4 - 12 parts of plasticizer, 0.1 - 10 parts of flaky filler, wherein the terminal carboxyl group content of the PBAT resin ≤ 35 mol / t.

[0006] In some embodiments, the terminal carboxyl group content of the PBAT resin is 3 - 20 mol / t.

[0007] In some embodiments, the maximum crystallization temperature of the PBAT resin ≥ 30 °C.

[0008] In some embodiments, the maximum crystallization temperature of the PBAT resin is 35 - 55 °C.

[0009] In some embodiments, D98 of the flaky filler ≤ 15 μm.

[0010] In some embodiments, the flaky filler is at least one of talc, montmorillonite, and mica.

[0011] In some embodiments, the plasticizer is at least one of ethanol, glycerol, diglycerol, triglycerol, urea, or sorbitol.

[0012] In some embodiments, the polyester composition further comprises 0.1 - 2 parts by weight of an auxiliary agent, and the auxiliary agent is at least one of a lubricant and an antioxidant.

[0013] In a second aspect, a method for preparing the polyester composition is provided, comprising the following steps: after mixing each component evenly in proportion, the obtained premix is added to a screw extruder, melt-extruded and pelletized to obtain the polyester composition.

[0014] In some embodiments, the temperature of the melt-extrusion pelletization is 150 - 200 °C; and / or, the length-diameter ratio of the screw extruder ≤ 1:75.

[0015] In a third aspect, an application of the polyester composition in preparing a biodegradable film is provided.

[0016] In a fourth aspect, a film or bag is provided, and the film or bag is formed from the polyester composition.

[0017] Compared with the prior art, the beneficial effects of the present disclosure are as follows: in the present invention, a PBAT resin with a specific carboxyl end group content is selected and a flaky filler is added, so that the polyester composition can be quickly cooled and formed during film blowing, and has both soft toughness, so that the polyester composition has good opening properties and dart impact resistance. If the carboxyl end group content of the PBAT resin is too high, it will cause a sharp decline in the short-term properties of the PBAT resin in processing and the dart of the blown film product. Therefore, the present invention preferably selects the carboxyl end group content of the PBAT resin to be 3 - 20 mol / t to obtain a polyester composition with good opening properties and dart impact resistance. Specific Embodiments

[0018] To facilitate the understanding of the present disclosure, the present disclosure will be described more comprehensively below. However, the present disclosure can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the understanding of the disclosed content of the present disclosure more thorough and comprehensive.

[0019] As used herein, the terms:

[0020] "Prepared from..." is synonymous with "comprising". As used herein, the terms "comprising", "including", "having", "containing", or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that comprises the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.

[0021] The conjunctive "consisting of" excludes any unrecited element, step, or component. If used in a claim, this phrase renders the claim closed-ended, excluding materials other than those described, except for conventional impurities associated therewith. When the phrase "consisting of" appears in a clause of the claim body rather than immediately following the subject, it only limits the elements described in that clause; other elements are not excluded from the claim as a whole.

[0022] When an equivalent, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper preferred values and lower preferred values, this should be understood to specifically disclose all ranges formed by any pairing of any range upper limit or preferred value with any range lower limit or preferred value, whether or not those ranges are separately disclosed. For example, when the range "1-5" is disclosed, the described range should be interpreted to include ranges "1-4", "1-3", "1-2", "1-2 and 4-5", "1-3 and 5", etc. When a numerical range is described herein, unless otherwise stated, the range is intended to include its endpoint values and all integers and fractions within that range.

[0023] In these examples, unless otherwise specified, the parts and percentages are by mass.

[0024] "Parts by mass" refers to the basic measurement unit representing the mass ratio relationship of multiple components. 1 part can represent any unit mass, such as 1 g or 2.689 g, etc. If we say that the mass part of component A is a parts and the mass part of component B is b parts, it means the mass ratio of component A to component B is a:b. Or, it means the mass of component A is aK and the mass of component B is bK (K is any number representing a multiple factor). It should not be misunderstood that, different from the number of mass parts, the sum of the mass parts of all components is not limited to 100 parts.

[0025] "And / or" is used to indicate that either or both of the stated circumstances may occur. For example, A and / or B includes (A and B) and (A or B).

[0026] To solve the problem in the prior art that biodegradable films cannot have both good opening properties and dart impact resistance.

[0027] In a first aspect, the present invention provides a polyester composition comprising the following components in parts by weight: 40 - 81 parts of PBAT resin, 15 - 35 parts of starch, 4 - 12 parts of plasticizer, and 0.1 - 10 parts of flaky filler, wherein the terminal carboxyl group content of the PBAT resin is ≤ 35 mol / t.

[0028] In different embodiments, the parts by weight of the PBAT resin can be, but are not limited to, 40 parts, 42 parts, 45 parts, 50 parts, 55 parts, 60 parts, 65 parts, 70 parts, 75 parts, 78 parts, 81 parts;

[0029] In different embodiments, the parts by weight of the starch can be, but are not limited to, 15 parts, 18 parts, 20 parts, 22 parts, 25 parts, 27 parts, 30 parts, 33 parts, 35 parts;

[0030] In different embodiments, the parts by weight of the plasticizer can be, but are not limited to, 4 parts, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, 11 parts, 12 parts;

[0031] In different embodiments, the parts by weight of the flaky filler can be, but are not limited to, 0.1 parts, 0.5 parts, 1 part, 3 parts, 5 parts, 7 parts, 9 parts, 10 parts.

[0032] In different embodiments, the terminal carboxyl group content of the PBAT resin can be 1 mol / t, 3 mol / t, 5 mol / t, 7 mol / t, 9 mol / t, 11 mol / t, 13 mol / t, 15 mol / t, 17 mol / t, 19 mol / t, 21 mol / t, 23 mol / t, 25 mol / t, 27 mol / t, 29 mol / t, 31 mol / t, 33 mol / t, 35 mol / t; preferably 3 - 20 mol / t, and its test method is the chemical titration method in GB / T 32366 - 2015.

[0033] The present invention selects a PBAT resin with a specific terminal carboxyl group content and adds a flaky filler. Introducing a PBAT resin containing branched chain segments enables the polyester composition to be rapidly cooled and formed during blown film production through the side chain crystallization of the branched chain segments, and it also has a soft toughness, thereby making the polyester composition have good opening properties. At the same time, if the terminal carboxyl group content of the PBAT resin is too high, it will cause the polyester composition to decompose during forming processing or the aging degradation to accelerate during long - term use, resulting in a significant decrease in the dart impact performance. Therefore, the present invention preferably selects the terminal carboxyl group content of the PBAT resin to be 3 - 20 mol / t to obtain a polyester composition with good opening properties and dart impact resistance.

[0034] In some embodiments, the maximum crystallization temperature of the PBAT resin is ≥ 30°C, specifically 30 - 60°C, and for example, it can be but is not limited to 30°C, 33°C, 35°C, 38°C, 40°C, 42°C, 45°C, 47°C, 50°C, 53°C, 55°C, 60°C; preferably 35 - 55°C, and more preferably 38 - 50°C.

[0035] In the present invention, the maximum crystallization temperature of the PBAT resin is measured by DSC. The specific test method is as follows: 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 of the PBAT resin. Then, it is 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 crystallization peak of this curve is selected as the maximum crystallization temperature.

[0036] In the present invention, the maximum crystallization temperature of the PBAT resin affects the performance of the polyester composition. If the maximum crystallization temperature of the PBAT resin is too high, it will cause serious crystal points in blown film. If the maximum crystallization temperature of the PBAT resin is too low, it will cause poor mechanical properties and opening properties in blown film.

[0037] In the present invention, the PBAT resin can be a polymer prepared from a polymerizable composition by a conventional or well-known polymerization method of PBAT resin.

[0038] Specifically, in the present invention, the preparation method of the PBAT resin includes the following steps:

[0039] S1: React 1,4-butanediol, adipic acid, terephthalic acid, and a branching agent under the conditions of a catalyst, a temperature of 220 - 248°C, and a pressure of 68 - 82 kPa for 2.5 - 5.5 h to obtain a first product with an inherent viscosity of 20 - 35 mL / g;

[0040] S2: React the first product under the conditions of a catalyst, a temperature of 235 - 250°C, and a pressure of 90 - 150 kPa for 2.5 - 4.5 h to obtain a second product with an inherent viscosity of 70 - 92 mL / g;

[0041] S3: React the second product at a temperature of 240 - 249°C and a pressure of 110 - 200 Pa for 1 - 3 h to obtain the PBAT resin.

[0042] The present invention mainly obtains a PBAT resin with a high maximum crystallization rate and a low acid value by adjusting the inherent viscosities of the first product and the second product in the PBAT resin preparation method.

[0043] In the present invention, adipic acid and terephthalic acid are used as dicarboxylic acid compounds. Among the dicarboxylic acid compounds, the molar content of adipic acid is 48 - 60%, for example, it can be but not limited to 48%, 50%, 52%, 54%, 56%, 58%, 60%; the molar content of terephthalic acid is 40 - 52%, for example, it can be but not limited to 40%, 42%, 44%, 46%, 48%, 50%.

[0044] In some embodiments, the molar ratio of 1,4 - butanediol to the dicarboxylic acid compound is 1 - 3:1, preferably 1.25 - 2:1.

[0045] In some embodiments, the catalyst plays a role in reducing the free energy of the reaction and increasing the reaction rate. The catalyst is at least one of tetrabutyl titanate and tetraisopropyl titanate.

[0046] Specifically, relative to the PBAT resin, the content of the catalyst is 0.001 - 1 wt%.

[0047] In some embodiments, the branching agent can widely adjust the terminal carboxyl group content of the PBAT resin according to an embodiment of the present invention. In particular, the terminal carboxyl group content of the PBAT resin can be adjusted to ≤ 35 mol / t. The branching agent can have more than 3 functional groups. Specifically, the branching agent can be a polyol compound having more than 3 hydroxyl groups. More specifically, the branching agent can be a polyol compound having more than 4 hydroxyl groups. The branching agent can be selected from one or a combination of two or more of tartaric acid, citric acid, malic acid, trimethylolpropane, trimethylolethane, pentaerythritol, polyether triol, glycerol, trimesic acid, trimellitic acid, trimellitic anhydride, pyromellitic acid, and pyromellitic dianhydride, etc. More specifically, it can be glycerol or pentaerythritol.

[0048] Specifically, relative to the PBAT resin, the content of the branching agent is 2.05 - 4.5 wt%, for example, it can be but not limited to 2.05 wt%, 2.3 wt%, 2.5 wt%, 2.7 wt%, 3 wt%, 3.3 wt%, 3.5 wt%, 3.8 wt%, 4 wt%, 4.3 wt%, 4.5 wt%; preferably 2.5 - 4 wt%.

[0049] Specifically, in the polyester composition, the content of the PBAT resin is not less than 20%.

[0050] In some embodiments, D98 of the flaky filler is ≤ 15 μm, and for example, it may be but not limited to 0.1 μm, 0.5 μm, 1 μm, 3 μm, 5 μm, 7 μm, 9 μm, 11 μm, 13 μm, 15 μm; preferably, D98 of the flaky filler is ≤ 13 μm.

[0051] In the present invention, D98 of the flaky filler is obtained by testing according to the method of GB / T 19077.1 "Particle Size Analysis - Laser Diffraction Method".

[0052] In the present invention, the particle size D98 of the flaky filler is ≤ 15 μm. If the particle size of the flaky filler is too large, the mechanical properties of the polyester composition film will decrease significantly.

[0053] In some embodiments, the flaky filler is at least one of talc, montmorillonite, and mica.

[0054] In some embodiments, the plasticizer is at least one of ethanol, glycerol, diglycerol, triglycerol, urea, or sorbitol.

[0055] In some embodiments, the polyester composition further comprises 0.1 - 2 parts by weight of an auxiliary agent, and for example, it may be but not limited to 0.1 part by weight, 0.3 part by weight, 0.5 part by weight, 0.9 part by weight, 1.3 part by weight, 1.5 part by weight, 1.8 part by weight, 2.0 part by weight; the auxiliary agent is at least one of a lubricant and an antioxidant.

[0056] Specifically, the antioxidant is at least one of phenolic antioxidants, phosphite antioxidants, divalent sulfur antioxidants or hindered amine antioxidants. Among them, the phenolic antioxidants can be selected from at least one of 2,6-di-tert-butyl-4-methylphenol, pentaerythritol tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], n-octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, styrenated phenol, 2,2'-methylenebis(4-methyl-6-tert-butylphenol), 1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene and 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)isocyanuric acid; the phosphite antioxidants can be selected from at least one of tris(nonylphenyl) phosphite, the reaction product of N-phenylaniline and 2,4,4-trimethylpentene, tris[2,4-di-tert-butylphenyl] phosphite and diethyl (3,5-di-tert-butyl-4-hydroxybenzyl)phosphonate; the divalent sulfur antioxidants can be selected from at least one of dilauryl thiodipropionate (DLTP) and distearyl thiodipropionate (DSTP); the hindered amine antioxidants can be selected from at least one of 2,2,6,6-tetramethylpiperidinyl benzoate, bis(2,2,6,6-tetramethylpiperidinyl) sebacate and tris(1,2,2,6,6-pentamethylpiperidinol) phosphite.

[0057] Specifically, the lubricant is at least one of low molecular weight ester lubricants, metal soap lubricants, stearic acid composite ester lubricants, and amide lubricants. Among them, the low molecular weight ester lubricants can be selected from at least one of solid paraffin, liquid paraffin and low molecular weight polyolefin wax; the metal soap lubricants can be selected from at least one of calcium stearate, magnesium stearate, zinc stearate and barium stearate; the stearic acid composite ester lubricants can be selected from at least one of monoglyceride, ethylene glycol stearate, glycerol stearate and pentaerythritol stearate; the amide lubricants can be selected from at least one of oleic acid amide, erucic acid amide, methylene bis-stearic acid amide and N,N-ethylene bis-stearic acid amide.

[0058] There is no special limitation on the production method of the polyester composition of the present invention, and a blending device such as a mixer, a single-screw or twin-screw extruder is used. There is no particularly strict limitation on the addition order of the components. They can be added simultaneously or in a certain order. Two or more components can be selected from all components for pre-mixing or kneading. For example, titanium dioxide, benzotriazole compounds and polyphenylene ether can be pre-formed into a polyphenylene ether masterbatch, and then added to the melt of other components in the form of the masterbatch according to a set ratio for extrusion. Under the condition that the mixing capacity of the equipment permits, when molding or producing parts, the particles formed by the masterbatch and other components can also be mixed and melt-processed according to a set ratio.

[0059] In a second aspect, a method for preparing the polyester composition is provided, comprising the following steps: after mixing each component evenly in proportion, the obtained premix is added into a screw extruder, melt-extruded and pelletized to obtain the polyester composition.

[0060] In some embodiments, the temperature for the melt-extrusion pelletization is 150 - 200 °C, for example, it can be but is not limited to 150 °C, 160 °C, 170 °C, 180 °C, 190 °C, 200 °C.

[0061] In some embodiments, the length-diameter ratio of the screw extruder is ≤ 1:75, and preferably 1:60.

[0062] In a third aspect, the application of the polyester composition in preparing a biodegradable film is provided; for example, pharmaceutical packaging materials, food packaging materials, packaging films for product protection, agricultural mulch films, etc.; a more specific use is fruit and vegetable bags.

[0063] The raw materials used in the examples and comparative examples are described as follows, but are not limited to these materials:

[0064] PBAT resin A is self-made, and its preparation method comprises the following steps:

[0065] Mix 765 kg of 1,4-butanediol, 438 kg of adipic acid, 415 kg of terephthalic acid and 51.8 kg of trimethylolpropane evenly, and add 0.53 kg of tetrabutyl titanate. React at a temperature of 235 °C and a pressure of 72 kPa for 4.5 h to obtain a first product with an inherent viscosity of 30 mL / g;

[0066] S2: Add 0.27 kg of tetrabutyl titanate to the first product, and react at a temperature of 240 °C and a pressure of 115 kPa for 4.0 h to obtain a second product with an inherent viscosity of 80 mL / g;

[0067] S3: React the second product at a temperature of 245 °C and a pressure of 160 Pa for 1.8 h to obtain PBAT resin A; the end carboxyl group content of PBAT resin A is 10.1 mol / t, and the maximum crystallization temperature is 45.2 °C.

[0068] PBAT resin B is self-made, and its preparation method comprises the following steps:

[0069] Mix 748 kg of 1,4-butanediol, 438 kg of adipic acid, 415 kg of terephthalic acid and 49.5 kg of trimethylolpropane evenly, and add 0.52 kg of tetrabutyl titanate. React at a temperature of 235 °C and a pressure of 72 kPa for 4.5 h to obtain a first product with an inherent viscosity of 29 mL / g;

[0070] S2: Add 0.26 kg of tetrabutyl titanate to the first product, and react for 4.0 h under the conditions of a temperature of 240 °C and a pressure of 115 kPa to obtain a second product with an intrinsic viscosity of 78 mL / g;

[0071] S3: React the second product for 1.8 h under the conditions of a temperature of 245 °C and a pressure of 160 Pa to obtain PBAT resin B; The end carboxyl group content of PBAT resin B is 14.8 mol / t, and the maximum crystallization temperature is 45.0 °C.

[0072] PBAT resin C is self-made, and its preparation method includes the following steps:

[0073] Mix 730 kg of 1,4-butanediol, 438 kg of adipic acid, 415 kg of terephthalic acid, and 46.0 kg of trimethylolpropane evenly, and add 0.51 kg of tetrabutyl titanate. React for 4.0 h under the conditions of a temperature of 230 °C and a pressure of 74 kPa to obtain a first product with an intrinsic viscosity of 28 mL / g;

[0074] S2: Add 0.24 kg of tetrabutyl titanate to the first product, and react for 3.5 h under the conditions of a temperature of 240 °C and a pressure of 115 kPa to obtain a second product with an intrinsic viscosity of 75 mL / g;

[0075] S3: React the second product for 1.8 h under the conditions of a temperature of 245 °C and a pressure of 160 Pa to obtain PBAT resin C; The end carboxyl group content of PBAT resin C is 20.2 mol / t, and the maximum crystallization temperature is 44.9 °C.

[0076] PBAT resin D is self-made, and its preparation method includes the following steps:

[0077] Mix 901 kg of 1,4-butanediol, 438 kg of adipic acid, 415 kg of terephthalic acid, and 43.7 kg of trimethylolpropane evenly, and add 0.57 kg of tetrabutyl titanate. React for 4.0 h under the conditions of a temperature of 230 °C and a pressure of 74 kPa to obtain a first product with an intrinsic viscosity of 28 mL / g;

[0078] S2: Add 0.32 kg of tetrabutyl titanate to the first product, and react for 4.0 h under the conditions of a temperature of 240 °C and a pressure of 115 kPa to obtain a second product with an intrinsic viscosity of 83 mL / g;

[0079] S3: React the second product for 1.8 h under the conditions of a temperature of 245 °C and a pressure of 160 Pa to obtain PBAT resin D; The end carboxyl group content of PBAT resin D is 3.1 mol / t, and the maximum crystallization temperature is 45.0 °C.

[0080] PBAT resin E was self-made, and its preparation method included the following steps:

[0081] Mix 676 kg of 1,4-butanediol, 438 kg of adipic acid, 415 kg of terephthalic acid and 40.3 kg of trimethylolpropane evenly, and add 0.52 kg of tetrabutyl titanate. React for 4.5 h under the conditions of a temperature of 235 kg°C and a pressure of 72 kPa to obtain a first product with an inherent viscosity of 30 mL / g.

[0082] S2: Add 0.25 kg of tetrabutyl titanate to the first product, and react for 4.0 h under the conditions of a temperature of 240°C and a pressure of 115 kPa to obtain a second product with an inherent viscosity of 80 mL / g.

[0083] S3: React the second product for 1.8 h under the conditions of a temperature of 245°C and a pressure of 160 Pa to obtain PBAT resin E; the end carboxyl group content of PBAT resin E is 35.0 mol / t, and the maximum crystallization temperature is 45.3°C.

[0084] PBAT resin F was self-made, and its preparation method included the following steps:

[0085] Mix 765 kg of 1,4-butanediol, 438 kg of adipic acid, 415 kg of terephthalic acid and 36.8 kg of trimethylolpropane evenly, and add 0.58 kg of tetrabutyl titanate. React for 4.5 h under the conditions of a temperature of 240°C and a pressure of 70 kPa to obtain a first product with an inherent viscosity of 32 mL / g.

[0086] S2: Add 0.30 kg of tetrabutyl titanate to the first product, and react for 4.0 h under the conditions of a temperature of 242°C and a pressure of 110 kPa to obtain a second product with an inherent viscosity of 81 mL / g.

[0087] S3: React the second product for 2.0 h under the conditions of a temperature of 244°C and a pressure of 155 Pa to obtain PBAT resin F; the end carboxyl group content of PBAT resin F is 9.8 mol / t, and the maximum crystallization temperature is 50.2°C.

[0088] PBAT resin G was self-made, and its preparation method included the following steps:

[0089] Mix 765 kg of 1,4-butanediol, 438 kg of adipic acid, 415 kg of terephthalic acid and 34.5 kg of trimethylolpropane evenly, and add 0.47 kg of tetrabutyl titanate. React for 3.5 h under the conditions of a temperature of 225°C and a pressure of 76 kPa to obtain a first product with an inherent viscosity of 26 mL / g.

[0090] S2: Add 0.23 kg of tetrabutyl titanate to the first product, and react for 3.5 h under the conditions of a temperature of 238 °C and a pressure of 125 kPa to obtain a second product with an inherent viscosity of 74 mL / g;

[0091] S3: React the second product for 2.5 h under the conditions of a temperature of 247 °C and a pressure of 170 Pa to obtain PBAT resin G; The end carboxyl group content of PBAT resin G is 10.1 mol / t, and the maximum crystallization temperature is 38.1 °C.

[0092] PBAT resin H is self-made, and its preparation method includes the following steps:

[0093] Mix 765 kg of 1,4-butanediol, 438 kg of adipic acid, 415 kg of terephthalic acid and 31.1 kg of trimethylolpropane evenly, and add 0.40 kg of tetrabutyl titanate, and react for 3.5 h under the conditions of a temperature of 225 °C and a pressure of 78 kPa to obtain a first product with an inherent viscosity of 25 mL / g;

[0094] S2: Add 0.25 kg of tetrabutyl titanate to the first product, and react for 3.5 h under the conditions of a temperature of 238 °C and a pressure of 130 kPa to obtain a second product with an inherent viscosity of 76 mL / g;

[0095] S3: React the second product for 2.5 h under the conditions of a temperature of 247 °C and a pressure of 185 Pa to obtain PBAT resin H; The end carboxyl group content of PBAT resin H is 10.0 mol / t, and the maximum crystallization temperature is 34.8 °C.

[0096] PBAT resin I is self-made, and its preparation method includes the following steps:

[0097] Mix 765 kg of 1,4-butanediol, 438 kg of adipic acid, 415 kg of terephthalic acid and 28.8 kg of trimethylolpropane evenly, and add 0.61 kg of tetrabutyl titanate, and react for 5.0 h under the conditions of a temperature of 233 °C and a pressure of 70 kPa to obtain a first product with an inherent viscosity of 33 mL / g;

[0098] S2: Add 0.31 kg of tetrabutyl titanate to the first product, and react for 4.5 h under the conditions of a temperature of 246 °C and a pressure of 105 kPa to obtain a second product with an inherent viscosity of 83 mL / g;

[0099] S3: React the second product for 2.0 h under the conditions of a temperature of 243 °C and a pressure of 140 Pa to obtain PBAT resin I; The end carboxyl group content of PBAT resin I is 10.2 mol / t, and the maximum crystallization temperature is 55.2 °C.

[0100] PBAT resin J was self-made, and its preparation method included the following steps:

[0101] Mix 765 kg of 1,4-butanediol, 438 kg of adipic acid, 415 kg of terephthalic acid, and 26.5 kg of trimethylolpropane evenly, and add 0.37 kg of tetrabutyl titanate. React under the conditions of a temperature of 220 °C and a pressure of 78 kPa for 3.5 h to obtain a first product with an inherent viscosity of 24 mL / g.

[0102] S2: Add 0.2 kg of tetrabutyl titanate to the first product, and react under the conditions of a temperature of 235 °C and a pressure of 135 kPa for 3.0 h to obtain a second product with an inherent viscosity of 72 mL / g.

[0103] S3: React the second product under the conditions of a temperature of 248 °C and a pressure of 190 Pa for 2.5 h to obtain PBAT resin J; the end carboxyl group content of PBAT resin J is 9.9 mol / t, and the maximum crystallization temperature is 29.9 °C.

[0104] PBAT resin K was self-made, and its preparation method included the following steps:

[0105] Mix 765 kg of 1,4-butanediol, 438 kg of adipic acid, 451 kg of terephthalic acid, and 23.6 kg of trimethylolpropane evenly, and add 0.34 kg of tetrabutyl titanate. React under the conditions of a temperature of 220 °C and a pressure of 80 kPa for 3.0 h to obtain a first product with an inherent viscosity of 22 mL / g.

[0106] S2: Add 0.18 kg of tetrabutyl titanate to the first product, and react under the conditions of a temperature of 235 °C and a pressure of 140 kPa for 3.0 h to obtain a second product with an inherent viscosity of 70 mL / g.

[0107] S3: React the second product under the conditions of a temperature of 248 °C and a pressure of 195 Pa for 2.5 h to obtain PBAT resin K; the end carboxyl group content of PBAT resin K is 10.1 mol / t, and the maximum crystallization temperature is 24.8 °C.

[0108] PBAT resin L was self-made, and its preparation method included the following steps:

[0109] Mix 765 kg of 1,4-butanediol, 438 kg of adipic acid, 415 kg of terephthalic acid, and 43.7 kg of trimethylolpropane evenly, and add 0.68 kg of tetrabutyl titanate. React under the conditions of a temperature of 245 °C and a pressure of 68 kPa for 5.0 h to obtain a first product with an inherent viscosity of 34 mL / g.

[0110] S2: Add 0.32 kg of tetrabutyl titanate to the first product, and react for 4.5 h under the conditions of a temperature of 248 °C and a pressure of 100 kPa to obtain a second product with an inherent viscosity of 85 mL / g;

[0111] S3: React the second product for 2.0 h under the conditions of a temperature of 242 °C and a pressure of 125 Pa to obtain PBAT resin L; The carboxyl end group content of PBAT resin L is 10.0 mol / t, and the maximum crystallization temperature is 60.5 °C.

[0112] PBAT resin M is self-made, and its preparation method includes the following steps:

[0113] Mix 765 kg of 1,4-butanediol, 438 kg of adipic acid, 415 kg of terephthalic acid, and 43.7 kg of trimethylolpropane evenly, and add 0.52 kg of tetrabutyl titanate. React for 4.0 h under the conditions of a temperature of 230 °C and a pressure of 74 kPa to obtain a first product with an inherent viscosity of 28 mL / g;

[0114] S2: Add 0.26 kg of tetrabutyl titanate to the first product, and react for 3.5 h under the conditions of a temperature of 240 °C and a pressure of 115 kPa to obtain a second product with an inherent viscosity of 78 mL / g;

[0115] S3: React the second product for 1.8 h under the conditions of a temperature of 245 °C and a pressure of 160 Pa to obtain PBAT resin M; The carboxyl end group content of PBAT resin M is 39.6 mol / t, and the maximum crystallization temperature is 44.9 °C.

[0116] Flaky filler:

[0117] Talc powder A: D98 = 5 μm, HTP Ultra5L, Aihai Yimi talc powder;

[0118] Talc powder B: D98 = 13 μm, SDC-F7, Liaoning Xinda Talc Group Co., Ltd.;

[0119] Talc powder C: D98 = 15 μm, TYT-777A, Haicheng Tianyuan Chemical Co., Ltd.;

[0120] Talc powder D: D98 = 20 μm, TY90-13-A, Guilin Longwei New Materials Co., Ltd.;

[0121] Spherical calcium carbonate: D98 = 10 μm, ACC-815, Xinrong (Lianzhou) Powder Technology Co., Ltd.;

[0122] Starch: Corn starch, Shandong Shouguang Jueneng Golden Corn Development Co., Ltd.;

[0123] Plasticizer: Glycerol, commercially available;

[0124] Lubricant: Oleic acid amide, commercially available.

[0125] Examples and Comparative Examples

[0126] The composition components of the polyester compositions in the examples and comparative examples are shown in Tables 1 and 2;

[0127] The preparation method of the polyester compositions in the examples and comparative examples includes the following steps:

[0128] After mixing the components evenly according to the parts by weight in Tables 1 and 2, the obtained premix is added into a twin-screw extruder, melt-extruded and pelletized to obtain a polyester composition; wherein the temperature of the melt-extrusion pelletization is 150 - 200 °C, and the length-diameter ratio of the twin-screw extruder is 1:50.

[0129] The polyester compositions obtained in the examples and comparative examples were subjected to performance tests, and the test methods are as follows:

[0130] (1) Dart impact: Tested according to the free dart method of GB / T 9639.1 - 2008;

[0131] (2) Opening - adhesion: Using a single-screw blown film machine with a length-diameter ratio of 45:1, a die with a die gap of 2.0 mm, a die diameter of 70 mm, a blow-up ratio of 3.0, a set temperature of 150 °C, a blown film frequency of 40 Hz, the film thickness is controlled at 10 ± 2 μm, the bag is cut within 1 hour after blowing the film, the thickness of the cutting knife tip is 0.1 - 0.2 mm, and the evaluation is carried out according to the standard rating in Table 3 after punching; the test results are shown in Tables 1 - 2.

[0132] Table 1

[0133]

[0134]

[0135] Table 2

[0136]

[0137]

[0138] Grade determination criteria for opening - adhesion in Table 3

[0139] Level Definition Description N1 No adhesion The punched opening naturally spreads out, the film surface is not damaged, and no external force is required N2 Slight adhesion It can be spread out by gently rubbing with hands, the film surface is not damaged, and a small external force is required N3 Moderate adhesion It can be spread out by rubbing and pulling with hands, the film surface is not damaged, and a moderate external force is required N4 Obvious adhesion It can be spread out by rubbing and pulling with hands, the edge of the film surface is damaged, and a moderate external force is required N5 Severe adhesion Completely adhered and cannot be separated, and the film surface is significantly damaged by external force tearing

[0140] It can be seen from the experimental data in Tables 1 - 2 that the grade of the opening - adhesion of the polyester composition of the present invention ≤ N2 level, and the dart impact strength ≥ 280 g, indicating that the polyester composition of the present invention has high opening property and mechanical properties.

[0141] Comparing Comparative Examples 3-7 with Comparative Example 1, it can be seen that when the carboxyl end group content of the PBAT resin is 3-20 mol / t, the grade of the opening-adhesion of the obtained polyester composition is ≤ N1, and the dart impact strength is ≥ 330 g. This shows that when the carboxyl end group content of the PBAT resin is 3-20 mol / t, the obtained polyester composition has better opening properties and mechanical properties.

[0142] Comparing Example 3 with Examples 8-14, it can be seen that when the maximum crystallization temperature of the PBAT resin is 35-55 °C, the grade of the opening-adhesion of the obtained polyester composition is ≤ N2, and the dart impact strength is ≥ 310 g; when the maximum crystallization temperature of the PBAT resin is 38-50 °C, the grade of the opening-adhesion of the obtained polyester composition is ≤ N1, and the dart impact strength is ≥ 325 g. This shows that when the maximum crystallization temperature of the PBAT resin is 38-50 °C, the obtained polyester composition has higher opening properties and mechanical properties.

[0143] Comparing Example 3, Examples 15-17 with Comparative Example 2, it can be seen that when D98 of the flaky filler ≤ 13 μm, the grade of the opening-adhesion of the obtained polyester composition is ≤ N1, and the dart impact strength is ≥ 325 g. This shows that when D98 of the flaky filler ≤ 13 μm, the obtained polyester composition has higher opening properties and mechanical properties.

[0144] When the filler is spherical, the grade of the opening-adhesion of the obtained polyester composition is ≤ N4, and the dart impact strength is ≥ 235 g. This shows that when the filler is spherical, it will cause a decrease in the opening properties and mechanical properties of the polyester composition.

[0145] Finally, it should be noted that the above examples are used to illustrate the technical solutions of the present disclosure rather than to limit the protection scope of the present disclosure. Although the present disclosure 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 disclosure can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present disclosure.

Claims

1. A polyester composition, characterized in that The invention comprises the following components in parts by weight: 40-81 parts of PBAT resin, 15-35 parts of starch, 4-12 parts of plasticizer, and 0.1-10 parts of flaky filler, wherein the terminal carboxyl content of the PBAT resin is ≤35 mol / t.

2. The polyester composition according to claim 1, characterized in that The terminal carboxyl content of the PBAT resin is 3-20 mol / t.

3. The polyester composition according to claim 1, characterized in that The maximum crystallization temperature of the PBAT resin is ≥30°C.

4. The polyester composition according to claim 1, characterized in that The maximum crystallization temperature of the PBAT resin is 35-55°C.

5. The polyester composition according to claim 1, characterized in that The D98 of the plate-like filler is ≤15 μm.

6. The polyester composition according to claim 1, characterized in that The flaky filler is at least one of talc, montmorillonite and mica; And / or, the plasticizer is at least one of ethylene glycol, glycerol, diglycerol, triglycerol, urea or sorbitol.

7. The polyester composition according to claim 1, characterized in that The polyester composition further comprises 0.1-2 parts by weight of an auxiliary agent, wherein the auxiliary agent is at least one of a lubricant and an antioxidant.

8. A method for preparing a polyester composition according to any one of claims 1 to 7, characterized in that: The following steps are involved: After the components are uniformly mixed according to the proportion, the obtained premix is ​​added into a screw extruder, melt-extruded and granulated to obtain a polyester composition.

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

10. A film or bag, characterized in that The film or bag is formed from the polyester composition according to any one of claims 1 to 7.

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