A modified polybutylene terephthalate-co-adipate and a method for its preparation

Abstract

The application relates to the technical field of biodegradable polyesters, and provides a modified polybutylene terephthalate-co-adipate and a preparation method thereof. The repeating structural unit of the modified polybutylene terephthalate-co-adipate comprises a terephthalic acid structural unit, an adipic acid structural unit, a 1,4-butanediol structural unit and a fourth monomer structural unit; the fourth monomer comprises at least one of oxalic acid, dimethyl oxalate, furan dicarboxylic acid, dimethyl furan dicarboxylic acid, malonic acid, dimethyl malonic acid, methylmalonic acid and diethyl methylmalonic acid. The modified polybutylene terephthalate-co-adipate provided by the application has higher glass transition temperature and breaking strength, lower melt index and better product hue than conventional pure PBAT, can meet the use requirements of PBAT, and effectively solves various problems caused by poor heat resistance and strength of conventional PBAT products in the processing process and subsequent application.

Description

Technical Field

[0001] This invention relates to the field of biodegradable polyester technology, and more specifically, to a modified polybutylene terephthalate-co-adipate and its preparation method. Background Technology

[0002] Polybutylene terephthalate (PBAT) is prepared from terephthalic acid (PTA), adipic acid (AA), and 1,4-butanediol (BDO) through esterification and polycondensation reactions. It is an aliphatic-aromatic copolyester with the biodegradability of aliphatic polyesters, and is easily decomposed by various microorganisms or enzymes in plants and animals in nature, ultimately producing carbon dioxide and water.

[0003] PBAT is a semi-crystalline polymer, typically with a melting point of 120–130°C and a density of 1.17–1.30 g / cm³. 3 PBAT has a glass transition temperature of approximately -33℃ and a tensile strength of 20–30 MPa. Its advantages lie in its status as a thermoplastic biodegradable material, which can help address the problem of white pollution, and its good ductility, elongation at break, and impact resistance. However, its disadvantages include a low glass transition temperature and poor heat resistance. Furthermore, PBAT prepared using a one-step direct polycondensation method has a melt flow index (MFR) (190℃, 2.16 kg) exceeding 10 g / 10 min. While further processing PBAT using chain extension or liquid-phase thickening methods can increase the MFR to around 5 g / 10 min, it cannot raise the glass transition temperature, and the improvement in tensile strength is very limited, leading to defects and shortcomings in processing and subsequent applications.

[0004] Currently, blending modification is generally used to improve the properties of PBAT, which involves adding a certain proportion of other polymers or inorganic substances to PBAT to improve the properties of PBAT blends. Some researchers have also attempted to add other reactants during the PBAT polymerization process to synthesize modified PBAT through copolymerization, thereby improving certain performance defects of PBAT. However, existing PBAT modification methods have not effectively solved the shortcomings of PBAT, such as low glass transition temperature, poor heat resistance, and low strength. In processing and subsequent applications, PBAT products still suffer from insufficient heat resistance and low strength.

[0005] Patent CN114561000A discloses a method for preparing polybutylene terephthalate (PBAT) modified with 1,4-cyclohexanedicarboxylic acid. The method involves reacting 1,4-cyclohexanedicarboxylic acid and 1,4-butanediol to obtain a third esterification intermediate. Then, the first and second esterification intermediates obtained from the esterification reactions of terephthalic acid and adipic acid are fed together into a polymerization reactor for polycondensation. The resulting modified PBAT polymer exhibits enhanced tensile strength and elastic modulus, but the intrinsic viscosity of the synthesized modified PBAT polymer is low, affecting its actual mechanical properties. Furthermore, no experimental research information is available regarding its heat resistance.

[0006] Patent CN113861399A discloses a method for preparing a biodegradable polyester PBIAT. A certain proportion of isosorbide is added to terephthalic acid, adipic acid, and 1,4-butanediol, and a catalyst is added to raise the temperature for a polycondensation reaction, synthesizing poly(adipate-terephthalic acid-isosorbide-butanediol). This copolymer exhibits good barrier properties and toughness, but its thermal properties, tensile strength, etc., are not disclosed. The description of the synthesis process is very general. Based on the synthesis method used, the resulting copolymer has a low molecular weight, which is clearly detrimental to improving its mechanical properties.

[0007] Patent CN113512187A discloses a transparent and biodegradable PBAT material, its preparation method, and its uses. In the PBAT preparation process, isosorbide and isohexol are added for prepolymerization, and a chain extender is added to synthesize a copolymer with a higher molecular weight. The transparency of the copolymer is improved, but the heat resistance and mechanical properties of the copolymer are not disclosed.

[0008] Patent CN110591057B discloses a method for synthesizing a biodegradable aliphatic-aromatic copolyester. In the esterification process of PTA and adipic acid, epoxidized soybean oil is added to the PBAT molecular chain through transesterification and polycondensation at a higher temperature to achieve the target values ​​for molecular weight and intrinsic viscosity. This method solves the problem of more easily achieving high target viscosity and molecular weight, reducing side reactions and lowering the end carboxyl groups of the product. However, it does not disclose the heat resistance and mechanical properties of the copolymer. Summary of the Invention

[0009] The purpose of this invention is to provide a modified polybutylene terephthalate-co-adipate and its preparation method, so as to solve the technical problems of insufficient heat resistance and strength in the prior art.

[0010] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0011] In a first aspect, the present invention provides a modified polybutylene terephthalate-co-adipate, wherein the repeating structural units include terephthalic acid structural units, adipic acid structural units, 1,4-butanediol structural units and a fourth monomer structural unit; the fourth monomer includes at least one of oxalic acid, dimethyl oxalate, furanyl dicarboxylic acid, dimethyl furanyl dicarboxylate, malonic acid, dimethyl malonate, methylmalonic acid, and diethyl methylmalonic acid.

[0012] According to some embodiments of the present invention, the molar ratio of the terephthalic acid structural unit, the adipic acid structural unit and the fourth monomer structural unit is 50:(30-45):(5-20), and the molar ratio of the sum of the moles of the terephthalic acid structural unit, the adipic acid structural unit and the fourth monomer structural unit to the molar ratio of the 1,4-butanediol structural unit is 1:(1.2-2).

[0013] According to some embodiments of the present invention, the modified polybutylene terephthalate-co-adipate has a melt flow index (MFR) ≤ 11.1 g / 10 min at 190 °C and 2.16 kg, a glass transition temperature (Tg) > 10 °C, a tensile strength ≥ 27.5 MPa, and a hue (b) value of 3.0 to 9.6.

[0014] The glass transition temperature (Tg) of typical pure PBAT products is around -30℃, and the tensile strength is around 20MPa. The modified PBAT provided by this invention has a significantly higher glass transition temperature (Tg) than pure PBAT products, exhibiting significantly improved heat resistance and a certain degree of increase in tensile strength. This overcomes the shortcomings of conventional pure PBAT products, such as low glass transition temperature, poor heat resistance, and low tensile strength, and also results in a better product color.

[0015] According to some preferred embodiments of the present invention, the modified polybutylene terephthalate-co-adipate has a melt flow index (MFR) of 3.0 to 10.0 g / 10 min at 190°C and 2.16 kg, a glass transition temperature (Tg) of 20.4 to 50.1°C, a tensile strength of 40.1 to 50.3 MPa, and a hue (b) value of 3.0 to 7.0.

[0016] In a second aspect, the present invention provides a method for preparing modified polybutylene terephthalate-co-adipate, comprising: mixing terephthalic acid (PTA), adipic acid (AA), 1,4-butanediol (BDO) and a fourth monomer, and sequentially subjecting them to esterification and polycondensation reactions to obtain the modified polybutylene terephthalate-co-adipate;

[0017] The fourth monomer includes at least one of oxalic acid, dimethyl oxalate, furanyl dicarboxylic acid, dimethyl furanyl dicarboxylate, malonic acid, dimethyl malonate, methylmalonic acid, and diethyl methylmalonic acid.

[0018] In existing methods for preparing pure PBAT, in addition to catalysts, stabilizers and other auxiliaries are required during esterification and polycondensation reactions. PBAT products obtained through direct one-step polycondensation often have unsatisfactory performance. However, the modified PBAT preparation method provided by this invention eliminates the need for additional stabilizers and chain extenders. It can directly produce modified PBAT products with low melt index, high tensile strength, good heat resistance, and favorable color through a one-step polycondensation process, fully meeting the application requirements.

[0019] According to some embodiments of the present invention, the molar ratio of terephthalic acid, adipic acid and the fourth monomer is 50:(30-45):(5-20), and the molar ratio of the sum of the moles of terephthalic acid, adipic acid and the fourth monomer to the molar ratio of 1,4-butanediol is 1:(1.2-2).

[0020] According to some embodiments of the present invention, the esterification catalyst added in the esterification reaction includes titanate and phosphate; preferably, the molar ratio of the titanate (calculated by the amount of titanium contained) to the phosphate (calculated by the amount of phosphorus contained) is (5-10):1, and / or the titanate includes at least one of tetrabutyl titanate and tetraisopropyl titanate, and / or the phosphate includes at least one of trimethyl phosphate, triethyl phosphate, and triphenyl phosphite.

[0021] According to some embodiments of the present invention, the polycondensation catalyst added in the polycondensation reaction includes titanate and acetate; preferably, the molar ratio of the titanate, calculated by the amount of titanium contained, to the acetate, calculated by the amount of metal element contained, is (1-5):1, and / or the titanate includes at least one of tetrabutyl titanate and tetraisopropyl titanate, and / or the acetate includes at least one of magnesium acetate, zinc acetate, aluminum acetate, and lithium acetate.

[0022] According to some embodiments of the present invention, the molar ratio of the esterification catalyst, calculated based on the amount of titanium contained, to the sum of the molar amounts of the terephthalic acid, adipic acid, and the fourth monomer is 1:(1×10⁻⁶). 3 ~10×10 3 ).

[0023] According to some embodiments of the present invention, the molar ratio of the polycondensation catalyst, calculated based on the amount of titanium contained, to the sum of the molar amounts of the terephthalic acid, adipic acid, and the fourth monomer is 1:(1×10⁻⁶). 3 ~10×10 3 ).

[0024] According to some embodiments of the present invention, the conditions for the esterification reaction include: a temperature of 170–240°C, a gauge pressure of 0–0.3 MPa, and a time of 3–5 hours.

[0025] According to some embodiments of the present invention, the conditions for the polycondensation reaction are: temperature of 240-260°C, absolute pressure of 40-400 Pa, and time of 1-5 hours.

[0026] According to some embodiments of the present invention, the preparation method further includes: discharging the material after the polycondensation reaction, water cooling, casting into strips, and pelletizing to obtain the modified polybutylene terephthalate-co-adipate.

[0027] Thirdly, the present invention provides a modified polybutylene terephthalate-co-adipate, which is prepared by the preparation method described in the second aspect.

[0028] Fourthly, the present invention provides the application of the modified polybutylene terephthalate (PET) described in the first or third aspect in biodegradable materials.

[0029] The beneficial effects of this invention are at least as follows:

[0030] (1) The modified PBAT provided by this invention has a glass transition temperature (Tg) that is significantly higher than that of pure PBAT products, and its heat resistance is significantly improved; at the same time, it has a lower melt index and a higher fracture strength. The modified PBAT provided by this invention can effectively solve the problems and shortcomings of pure PBAT products in the current processing and subsequent applications due to poor heat resistance and strength.

[0031] (2) The modified PBAT provided by the present invention has a better product hue than pure PBAT.

[0032] (3) The modified PBAT preparation method provided by the present invention does not require the addition of stabilizers or chain extenders. The final modified PBAT product can be obtained directly through one-step polycondensation, which is simpler and more convenient than the currently used PBAT blending modification method.

[0033] (4) The modified PBAT provided by the present invention has good biodegradability and can be completely degraded into harmless small molecules in nature. It can be widely used in the fields of lunch boxes, film bags, foam materials, and disposable plastic products. Detailed Implementation

[0034] To make the technical problem to be solved, the technical solution, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely for illustrating this patent and do not limit the scope of protection of this invention in any way.

[0035] Unless otherwise defined, the technical terms used in the following embodiments have the same meaning as commonly understood by those skilled in the art. Unless otherwise specified, the reagents used in the following embodiments are conventional biochemical reagents; the raw materials, instruments, and equipment used in the following embodiments can all be obtained commercially or by existing methods; unless otherwise specified, the reagent dosages are those used in routine experimental operations; unless otherwise specified, the experimental methods are conventional methods.

[0036] In the various embodiments and comparative examples of the present invention, the performance data were tested according to the following test methods:

[0037] (1) Melt flow index (MFR): The MFR was measured using a GT-7100 melt flow indexer manufactured by High-speed Rail Testing Instruments Co., Ltd., in accordance with GB / T3682.1-2018 at a temperature of 190℃ and a weight mass of 2.16kg.

[0038] (2) Glass transition temperature: The glass transition temperature was measured using a DSC 131 differential thermal scanner (with refrigeration accessories) manufactured by Setaram. The specific method included: weighing about 10 mg of sample and placing it into the DSC sample cell, and gradually increasing the temperature to 150 °C at a rate of 10 °C / min starting at -50 °C under N2 protection, and recording the heating curve.

[0039] (3) Hue b value: Measured using a TC-PⅡG type fully automatic colorimeter.

[0040] (4) Fracture strength: The fracture strength was determined by a universal testing machine according to the method and conditions specified in GB / T1040.1-2018.

[0041] Example 1

[0042] Esterification catalyst C1: Tetrabutyl titanate (based on the molar amount of Ti) / Trimethyl phosphate (based on the molar amount of P) = 5:1;

[0043] Polycondensation catalyst S1: Tetrabutyl titanate (based on the molar amount of Ti) / Magnesium acetate (based on the molar amount of Mg) = 1:1;

[0044] Preparation process:

[0045] S1. Weigh 332g (2mol) PTA, 263g (1.8mol) AA, 18g (0.2mol) oxalic acid (fourth monomer), and 432g (4.8mol) BDO, and add them to the reaction vessel. Add 4×10 -3 mol (based on titanium element) of esterification catalyst C1 was added to obtain a mixture;

[0046] Molar ratio: C1 (based on titanium) / (PTA + AA + fourth monomer) = 1 : (1 × 103 ),

[0047] Fourth monomer / (PTA + AA + fourth monomer) = 5%;

[0048] S2. Stir the mixture evenly and heat it from room temperature to 170°C under a reaction pressure of 0 (gauge pressure); control the mixture to carry out the esterification reaction for 5 hours at a temperature of 170°C and a pressure of 0 (gauge pressure). When the distillate reaches more than 95% of the theoretical value, the esterification reaction ends and the esterification intermediate product is obtained.

[0049] S3. Add 4×10 to the esterification intermediate. -3 The polycondensation catalyst S1 was stirred evenly and subjected to a polycondensation reaction for 5 hours at a temperature of 240℃ and a pressure of 40Pa (absolute pressure) to obtain a polycondensation product liquid.

[0050] Molar ratio: S1 (based on titanium) / (PTA + AA + fourth monomer) = 1:(1×10 3 ).

[0051] S4. The molten material is discharged, water-cooled, cast into bars, and granulated to obtain modified PBAT.

[0052] Example 2

[0053] Esterification catalyst C2: Tetraisopropyl titanate (based on the molar amount of Ti) / Triethyl phosphate (based on the molar amount of P) = 10:1;

[0054] Polycondensation catalyst S2: Tetraisopropyl titanate (based on the molar amount of Ti) / Zinc acetate (based on the molar amount of Zn) = 5:1;

[0055] Preparation process:

[0056] S1. Weigh 332g (2mol) PTA, 234g (1.6mol) AA, 47g (0.4mol) dimethyl oxalate (fourth monomer) and 540g (6mol) BDO, and put them into the reaction vessel. Add 4×10 -4 mol (based on titanium element) of esterification catalyst C2 was used to obtain a mixture;

[0057] Molar ratio: C2 (based on titanium) / (PTA + AA + fourth monomer) = 1 : (10 × 10 3 ),

[0058] Fourth monomer / (PTA + AA + fourth monomer) = 10%;

[0059] S2. Stir the mixture evenly and heat it from room temperature to 240°C under a reaction pressure of 0 (gauge pressure); control the mixture to carry out the esterification reaction for 5 hours at a temperature of 240°C and a pressure of 0.3 (gauge pressure). When the distillate reaches more than 95% of the theoretical value, the esterification reaction ends and the esterification intermediate product is obtained.

[0060] S3. Add 4×10 to the esterification intermediate. -4 The polycondensation catalyst S2 was stirred evenly and subjected to a polycondensation reaction for 1 hour at a temperature of 260℃ and a pressure of 400Pa (absolute pressure) to obtain a polycondensation product liquid.

[0061] Molar ratio: S2 (based on titanium) / (PTA + AA + fourth monomer) = 1 : (10 × 10 3 ).

[0062] S4. The molten material is discharged, water-cooled, cast into bars, and granulated to obtain modified PBAT.

[0063] Example 3

[0064] Esterification catalyst C3: Tetraisopropyl titanate (based on the molar amount of Ti) / Triphenyl phosphite (based on the molar amount of P) = 5:1;

[0065] Polycondensation catalyst S3: Tetrabutyl titanate (based on the molar amount of Ti) / Aluminum acetate (based on the molar amount of Al) = 2:1;

[0066] Preparation process:

[0067] S1. Weigh 332g (2mol) PTA, 175g (1.2mol) AA, 125g (0.8mol) furanyl dicarboxylic acid (fourth monomer) and 720g (8mol) BDO, add them to the reaction vessel, and add 4×10 -3 mol (based on titanium element) of esterification catalyst C3 was added to obtain a mixture;

[0068] Molar ratio: C3 (based on titanium) / (PTA + AA + fourth monomer) = 1 : (1 × 10 3 ),

[0069] Fourth monomer / (PTA + AA + fourth monomer) = 20%;

[0070] S2. Stir the mixture evenly and heat it from room temperature to 240°C under a reaction pressure of 0 (gauge pressure); control the mixture to carry out the esterification reaction for 3 hours at a temperature of 240°C and a pressure of 0.3 (gauge pressure). When the distillate reaches more than 95% of the theoretical value, the esterification reaction ends and the esterification intermediate product is obtained.

[0071] S3. Add 4×10 to the esterification intermediate. -3 The polycondensation catalyst S3 was stirred evenly and subjected to a polycondensation reaction for 5 hours at a temperature of 260℃ and a pressure of 40Pa (absolute pressure) to obtain a polycondensation product liquid.

[0072] Molar ratio: S3 (based on titanium) / (PTA + AA + fourth monomer) = 1:(1×10 3 ).

[0073] S4. The molten material is discharged, water-cooled, cast into bars, and granulated to obtain modified PBAT.

[0074] Example 4

[0075] Esterification catalyst C4: Tetrabutyl titanate (based on the molar amount of Ti) / Triphenyl phosphite (based on the molar amount of P) = 8:1;

[0076] Polycondensation catalyst S4: Tetraisopropyl titanate (based on the molar amount of Ti) / Lithium acetate (based on the molar amount of Li) = 5:1;

[0077] Preparation process:

[0078] S1. Weigh 332g (2mol) PTA, 234g (1.6mol) AA, 74g (0.4mol) dimethyl furanate (fourth monomer) and 540g (6mol) BDO, add them to the reactor, and add 4×10 -3 mol (based on titanium element) of esterification catalyst C4 was used to obtain a mixture;

[0079] Molar ratio: C4 (based on titanium) / (PTA + AA + fourth monomer) = 1:(1×10 3 ),

[0080] Fourth monomer / (PTA + AA + fourth monomer) = 10%;

[0081] S2. Stir the mixture evenly and heat it from room temperature to 170°C under a reaction pressure of 0 (gauge pressure); control the mixture to carry out the esterification reaction for 5 hours at a temperature of 170°C and a pressure of 0 (gauge pressure). When the distillate reaches more than 95% of the theoretical value, the esterification reaction ends and the esterification intermediate product is obtained.

[0082] S3. Add 4×10 to the esterification intermediate. -3 The polycondensation catalyst S4 was stirred evenly and subjected to a polycondensation reaction for 4 hours at a temperature of 250℃ and a pressure of 200Pa (absolute pressure) to obtain a polycondensation product liquid.

[0083] Molar ratio: S4 (based on titanium) / (PTA + AA + fourth monomer) = 1:(1×10 3 ).

[0084] S4. The molten material is discharged, water-cooled, cast into bars, and granulated to obtain modified PBAT.

[0085] Example 5

[0086] Esterification catalyst C5: Tetraisopropyl titanate (based on the molar amount of Ti) / Trimethyl phosphate (based on the molar amount of P) = 5:1;

[0087] Polycondensation catalyst S5: Tetraisopropyl titanate (based on the molar amount of Ti) / Zinc acetate (based on the molar amount of ZN) = 1:1;

[0088] Preparation process:

[0089] S1. Weigh 332g (2mol) PTA, 263g (1.8mol) AA, 21g (0.2mol) malonic acid (fourth monomer), and 432g (4.8mol) BDO, and add them to the reaction vessel. Add 4×10 -3 mol (based on titanium element) of esterification catalyst C5 was used to obtain a mixture;

[0090] Molar ratio: C5 (based on titanium) / (PTA + AA + fourth monomer) = 1 : (1 × 10 3 ),

[0091] Fourth monomer / (PTA + AA + fourth monomer) = 5%;

[0092] S2. Stir the mixture evenly and heat it from room temperature to 240°C under a reaction pressure of 0 (gauge pressure); control the mixture to carry out the esterification reaction for 3 hours at a temperature of 240°C and a pressure of 0.3 (gauge pressure). When the distillate reaches more than 95% of the theoretical value, the esterification reaction ends and the esterification intermediate product is obtained.

[0093] S3. Add 4×10 to the esterification intermediate. -4 The polycondensation catalyst S5 was stirred evenly and subjected to a polycondensation reaction for 4 hours at a temperature of 260℃ and a pressure of 40Pa (absolute pressure) to obtain a polycondensation product liquid.

[0094] Molar ratio: S5 (based on titanium) / (PTA + AA + fourth monomer) = 1 : (10 × 10 3 ).

[0095] S4. The molten material is discharged, water-cooled, cast into bars, and granulated to obtain modified PBAT.

[0096] Example 6

[0097] Esterification catalyst C6: Tetraisopropyl titanate (based on the molar amount of Ti) / Trimethyl phosphate (based on the molar amount of P) = 10:1;

[0098] Polycondensation catalyst S6: Tetrabutyl titanate (based on the molar amount of Ti) / Aluminum acetate (based on the molar amount of Al) = 5:1;

[0099] Preparation process:

[0100] S1. Weigh 332g (2mol) PTA, 263g (1.8mol) AA, 26g (0.2mol) dimethyl malonate (fourth monomer) and 540g (6mol) BDO, add them to the reaction vessel, and add 4×10 -4 mol (based on titanium element) of esterification catalyst C6 was used to obtain a mixture;

[0101] Molar ratio: C6 (based on titanium) / (PTA + AA + fourth monomer) = 1 : (10 × 10 3 ),

[0102] Fourth monomer / (PTA + AA + fourth monomer) = 5%;

[0103] S2. Stir the mixture evenly and heat it from room temperature to 240°C under a reaction pressure of 0 (gauge pressure); control the mixture to carry out the esterification reaction for 3 hours at a temperature of 240°C and a pressure of 0.3 MPa (gauge pressure). When the distillate reaches more than 95% of the theoretical value, the esterification reaction ends and the esterification intermediate product is obtained.

[0104] S3. Add 4×10 to the esterification intermediate. -3 The polycondensation catalyst S6 was stirred evenly and subjected to a polycondensation reaction for 5 hours at a temperature of 260℃ and a pressure of 100Pa (absolute pressure) to obtain a polycondensation product liquid.

[0105] Molar ratio: S6 (based on titanium) / (PTA + AA + fourth monomer) = 1:(1×10 3 ).

[0106] S4. The molten material is discharged, water-cooled, cast into bars, and granulated to obtain modified PBAT.

[0107] Example 7

[0108] Esterification catalyst C7: Tetrabutyl titanate (based on the molar amount of Ti) / Triethyl phosphate (based on the molar amount of P) = 5:1;

[0109] Polycondensation catalyst S7: Tetraisopropyl titanate (based on the molar amount of Ti) / Magnesium acetate (based on the molar amount of Mg) = 1:1;

[0110] Preparation process:

[0111] S1. Weigh 332g (2mol) PTA, 234g (1.6mol) AA, 47g (0.4mol) methylmalonic acid (fourth monomer), and 540g (6mol) BDO, and add them to the reaction vessel. Add 4×10 -3 mol (based on titanium element) of esterification catalyst C7 was used to obtain a mixture;

[0112] Molar ratio: C7 (based on titanium) / (PTA + AA + fourth monomer) = 1:(1×10 3 ),

[0113] Fourth monomer / (PTA + AA + fourth monomer) = 10%;

[0114] S2. Stir the mixture evenly and heat it from room temperature to 240°C under a reaction pressure of 0 (gauge pressure); control the mixture to carry out the esterification reaction for 3 hours at a temperature of 240°C and a pressure of 0.3 MPa (gauge pressure). When the distillate reaches more than 95% of the theoretical value, the esterification reaction ends and the esterification intermediate product is obtained.

[0115] S3. Add 4×10 to the esterification intermediate. -3 The polycondensation catalyst S7 was stirred evenly and subjected to a polycondensation reaction for 4 hours at a temperature of 250℃ and a pressure of 40Pa (absolute pressure) to obtain a polycondensation product liquid.

[0116] Molar ratio: S7 (based on titanium) / (PTA + AA + fourth monomer) = 1:(1×10 3 ).

[0117] S4. The molten material is discharged, water-cooled, cast into bars, and granulated to obtain modified PBAT.

[0118] Example 8

[0119] Esterification catalyst C8: Tetrabutyl titanate (based on the molar amount of Ti) / Trimethyl phosphate (based on the molar amount of P) = 10:1;

[0120] Polycondensation catalyst S8: Tetrabutyl titanate (based on Ti molar amount) / Lithium acetate (based on Li molar amount) = 3:1;

[0121] Preparation process:

[0122] S1. Weigh 332g (2mol) PTA, 234g (1.6mol) AA, 70g (0.4mol) diethyl methylmalonate (fourth monomer) and 540g (6mol) BDO, add them to the reaction vessel, and add 4×10 -3 mol (based on titanium element) of esterification catalyst C8 was used to obtain a mixture;

[0123] Molar ratio: C8 (based on titanium) / (PTA + AA + fourth monomer) = 1 : (1 × 10 3 ),

[0124] Fourth monomer / (PTA + AA + fourth monomer) = 10%;

[0125] S2. Stir the mixture evenly and heat it from room temperature to 240°C under a reaction pressure of 0 (gauge pressure); control the mixture to carry out the esterification reaction for 3 hours at a temperature of 240°C and a pressure of 0.3 MPa (gauge pressure). When the distillate reaches more than 95% of the theoretical value, the esterification reaction ends and the esterification intermediate product is obtained.

[0126] S3. Add 4×10 to the esterification intermediate. -3 The polycondensation catalyst S8 was stirred evenly and subjected to a polycondensation reaction for 5 hours at a temperature of 260℃ and a pressure of 100Pa (absolute pressure) to obtain a polycondensation product liquid.

[0127] Molar ratio: S8 (based on titanium) / (PTA + AA + fourth monomer) = 1:(1×10 3 ).

[0128] S4. The molten material is discharged, cooled by water, cast into bars, and granulated to obtain modified PBAT.

[0129] Example 9

[0130] The preparation process is the same as in Example 1, except that the amount of AA and oxalic acid (fourth monomer) was changed to: fourth monomer / (PTA+AA+fourth monomer)=20%.

[0131] Example 10

[0132] The preparation process is the same as in Example 2, except that the amount of polycondensation catalyst S2 added is 4 × 10⁻⁶. -3 mol (based on titanium element), S2 (based on titanium element) / (PTA + AA + fourth monomer) = 1:(1 × 10 3 ).

[0133] Example 11

[0134] The preparation process is the same as in Example 1, except that the amount of AA and oxalic acid (fourth monomer) was changed to: fourth monomer / (PTA+AA+fourth monomer)=30%.

[0135] Example 12

[0136] The preparation process is the same as in Example 1, except that the esterification catalyst C1 is replaced with tetrabutyl titanate (TBT) in equimolar amounts based on titanium.

[0137] Example 13

[0138] The preparation process is the same as in Example 1, except that the esterification catalyst C1 is replaced with an esterification catalyst C9 in an equimolar amount based on titanium.

[0139] Esterification catalyst C9: Tetrabutyl titanate (based on the molar amount of Ti) / Trimethyl phosphate (based on the molar amount of P) = 3:1.

[0140] Example 14

[0141] The preparation process is the same as in Example 1, except that the esterification catalyst C1 is replaced with an esterification catalyst C in an equimolar amount based on titanium. 10 ;

[0142] Esterification catalyst C 10 Tetrabutyl titanate (based on the molar amount of Ti) / Trimethyl phosphate (based on the molar amount of P) = 15:1.

[0143] Example 15

[0144] The preparation process is the same as in Example 1, except that the polycondensation catalyst S1 is replaced with tetrabutyl titanate in an equimolar amount based on titanium.

[0145] Example 16

[0146] The preparation process is the same as in Example 1, except that the polycondensation catalyst S1 is replaced with a polycondensation catalyst S9 in an equimolar amount based on titanium.

[0147] Polycondensation catalyst S9: Tetrabutyl titanate (based on the molar amount of Ti) / Magnesium acetate (based on the molar amount of Mg) = 1:2.

[0148] Example 17

[0149] The preparation process is the same as in Example 1, except that the polycondensation catalyst S1 is replaced with a polycondensation catalyst S in an equimolar amount based on titanium. 10 ;

[0150] Polycondensation catalyst S 10Tetrabutyl titanate (based on the molar amount of Ti) / magnesium acetate (based on the molar amount of Mg) = 8:1.

[0151] Comparative Example 1

[0152] The preparation process is the same as in Example 1, except that:

[0153] S1. Weigh 332g (2mol) PTA, 292g (2mol) AA and 432g (4.8mol) BDO, add them to the reactor, and add 4×10 -3 mol (based on titanium element) of esterification catalyst C1 was added to obtain a mixture;

[0154] Molar ratio: C1 (based on titanium) / (PTA + AA) = 1 : (1 × 10 3 ).

[0155] Comparative Example 2

[0156] The preparation process was the same as in Example 1, except that 18 g (0.2 mol) of oxalic acid was replaced with 34.4 g (0.2 mol) of 1,4-cyclohexanedicarboxylic acid.

[0157] Performance Evaluation

[0158] The PBAT products prepared in Examples 1-17 and Comparative Examples 1-2 were tested for melt flow index (MFR) (190℃, 2.16kg), glass transition temperature (Tg), hue b-value, and fracture strength. The results are shown in the table below:

[0159]

[0160] The experimental results of Example 1 and Comparative Examples 1-2 show that adding a fourth monomer during the preparation of modified polybutylene terephthalate-co-adipate can reduce the melt index of PBAT products, significantly improve their fracture strength and glass transition temperature, and also improve their hue b value to a certain extent.

[0161] The experimental results from Examples 1, 9, and 11 show that a higher amount of the fourth monomer is not necessarily better. When the molar ratio of the fourth monomer to (PTA + AA + fourth monomer) is between 5% and 20%, increasing the amount of the fourth monomer helps to further increase the glass transition temperature of the PBAT product and improve its heat resistance. However, when the molar ratio of the fourth monomer to (PTA + AA + fourth monomer) increases to 30%, it can actually lead to a smaller molecular weight of the polymerized product due to polymerization difficulties, resulting in a larger melt index and a significantly reduced tensile strength of the PBAT product.

[0162] The experimental results from Examples 1 and 12-14 show that using a combination of titanate and phosphate esters as the esterification catalyst, compared to using titanate alone, can reduce the melt index of the PBAT product and improve its fracture strength. Furthermore, the ratio of titanate to phosphate ester in the esterification catalyst also affects the performance of the prepared PBAT product. Too little phosphate ester will not reduce the melt index or improve the fracture strength of the PBAT product; too much phosphate ester will adversely affect the melt index, fracture strength, glass transition temperature, and color of the PBAT product.

[0163] The experimental results from Examples 1 and 15-17 show that using a combination of titanate and acetate in the polycondensation catalyst, compared to using titanate alone, can reduce the melt index of PBAT products to a certain extent, improve their fracture strength, and significantly improve their color. Furthermore, the ratio of titanate to acetate in the polycondensation catalyst also affects the performance of the prepared PBAT products. A molar ratio of titanate (calculated by the amount of titanium) to acetate (calculated by the amount of metal element) within the range of (1-5):1 is most suitable. Insufficient acetate dosage cannot reduce the melt index, improve the fracture strength, or improve the color of PBAT products; further increasing the acetate dosage also fails to improve the performance of PBAT products.

[0164] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A modified polybutylene terephthalate-co-adipate, characterized in that, The modified polybutylene terephthalate-co-butylene adipate has repeating structural units including terephthalic acid structural units, adipic acid structural units, 1,4-butanediol structural units, and a fourth monomer structural unit; the fourth monomer includes at least one of oxalic acid, dimethyl oxalate, furanyl dicarboxylic acid, dimethyl furanyl dicarboxylate, malonic acid, dimethyl malonate, methylmalonic acid, and diethyl methylmalonic acid. The molar ratio of the terephthalic acid structural unit, the adipic acid structural unit, and the fourth monomer structural unit is 50:(30-45):(5-20), and the molar ratio of the sum of the molars of the terephthalic acid structural unit, the adipic acid structural unit, and the fourth monomer structural unit to the molar ratio of the 1,4-butanediol structural unit is 1:(1.2-2). The method for preparing the modified polybutylene terephthalate-co-butylene adipate includes: mixing terephthalic acid, adipic acid, 1,4-butanediol and a fourth monomer, and sequentially undergoing esterification and polycondensation reactions to obtain the modified polybutylene terephthalate-co-butylene adipate. The esterification catalyst added in the esterification reaction includes titanate and phosphate ester; the molar ratio of titanate (calculated based on the amount of titanium contained) to phosphate ester (calculated based on the amount of phosphorus contained) is (5-10):

1. The polycondensation catalyst added in the polycondensation reaction includes titanate and acetate; the molar ratio of titanate (calculated by the amount of titanium contained) to acetate (calculated by the amount of metal element contained) is (1-5):

1.

2. A method for preparing modified polybutylene terephthalate-co-butylene adipate, characterized in that, include: Terephthalic acid, adipic acid, 1,4-butanediol and a fourth monomer are mixed and subjected to esterification and polycondensation reactions in sequence to obtain the modified poly(butylene terephthalate-co-adipate). The fourth monomer includes at least one of oxalic acid, dimethyl oxalate, furanyl dicarboxylic acid, dimethyl furanyl dicarboxylate, malonic acid, dimethyl malonate, methylmalonic acid, and diethyl methylmalonic acid. The molar ratio of terephthalic acid, adipic acid and the fourth monomer is 50:(30-45):(5-20), and the molar ratio of the sum of the moles of terephthalic acid, adipic acid and the fourth monomer to the molar ratio of 1,4-butanediol is 1:(1.2-2). The esterification catalyst added in the esterification reaction includes titanate and phosphate ester; the molar ratio of titanate (calculated based on the amount of titanium contained) to phosphate ester (calculated based on the amount of phosphorus contained) is (5-10):

1. The polycondensation catalyst added in the polycondensation reaction includes titanate and acetate; the molar ratio of titanate (calculated by the amount of titanium contained) to acetate (calculated by the amount of metal element contained) is (1-5):

1.

3. The preparation method according to claim 2, characterized in that, The titanate includes at least one of tetrabutyl titanate and tetraisopropyl titanate; And / or the phosphate ester includes at least one of trimethyl phosphate, triethyl phosphate, and triphenyl phosphite; And / or the acetate includes at least one of magnesium acetate, zinc acetate, aluminum acetate, and lithium acetate.

4. The preparation method according to claim 2 or 3, characterized in that, The molar ratio of the esterification catalyst, calculated based on the amount of titanium it contains, to the sum of the molar amounts of the terephthalic acid, adipic acid, and the fourth monomer is 1:(1×10⁻⁶). 3 ~10×10 3 ); And / or, the molar ratio of the polycondensation catalyst, calculated based on the amount of titanium contained, to the sum of the molar amounts of the terephthalic acid, adipic acid, and the fourth monomer is 1:(1×10⁻⁶). 3 ~10×10 3 ).

5. The preparation method according to claim 2 or 3, characterized in that, The conditions for the esterification reaction include: a temperature of 170–240°C, a gauge pressure of 0–0.3 MPa, and a time of 3–5 hours; And / or, the conditions for the polycondensation reaction are: temperature of 240–260°C, absolute pressure of 40–400 Pa, and time of 1–5 hours.

6. The preparation method according to claim 2 or 3, characterized in that, The preparation method further includes: discharging the material after the polycondensation reaction, water cooling, casting into strips, and pelletizing to obtain the modified polybutylene terephthalate-co-adipate.

7. A modified polybutylene terephthalate-co-adipate, prepared by any one of claims 3-6.

8. The application of the modified polybutylene terephthalate as described in claim 1 or claim 7 in biodegradable materials.

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