Stretch-resistant and tear-resistant biodegradable copolyester with shape memory characteristic as well as preparation method and application of biodegradable copolyester

Abstract

The invention relates to the field of biodegradable high polymer materials, in particular to biodegradable copolyester with stretch resistance, tear resistance and shape memory characteristics and a preparation method and application thereof.The copolyester is prepared from, by mole, 4.2 parts of poly (terephthalic acid), 2.8 parts of adipic acid, 9.8 parts of 1, 4-butanediol, 0.8 part of an antioxidant, 0.8 part of a lubricant and 0.8 part of a lubricant. 0 to 0.06 mol part of tetrabutyl titanate, and 0 to 0.1 mol part of D-mannitol; hydroxyl groups of D-mannitol form hydrogen bonds in molecules and among molecules, and through the entanglement synergistic effect among the molecules, the mechanical strength of the polyester material is improved, the service life of the polyester material is prolonged, and polyester is endowed with a certain shape memory characteristic; when the addition amount of D-mannitol accounts for 1.4%, the tensile strength of the copolyester is 27.75 MPa, the tear strength is 73.57 KN / m, the recovery rate is 793.80%, and the modified copolyester still has biodegradability.

Description

Technical Field

[0001] The present invention relates to the field of biodegradable polymer materials, and relates to the synthesis and chemical modification of biodegradable PBAT copolyesters. Specifically, it relates to a biodegradable copolyester with tensile strength, tear resistance and shape memory properties, and its preparation method and application. Background Art

[0002] With the increasing attention of countries around the world to environmental protection issues, the development and research of biodegradable materials and bio-based materials have received more and more attention from researchers. Aliphatic-aromatic copolyesters, composed of aromatic polyester segments and aliphatic polyester chains, have become the central research focus of green material development due to their ideal properties, including biodegradability and improved mechanical and processing properties. Poly(butylene adipate-co-terephthalate) (PBAT), as a representative product of aliphatic-aromatic copolyesters, combines the beneficial properties of PBA and PBT, such as high elongation at break, heat resistance and significant biodegradability. It is recognized as a leading and commercially promising degradable material in the field of biodegradable polyester research. PBAT has a wide range of applications, from garbage bags and food packaging to agricultural films. Nevertheless, due to the low tear strength and tensile strength, poor water vapor barrier performance, high production cost, etc. of PBAT, the application of PBAT is still limited and cannot be fully promoted. Summary of the Invention

[0003] The present invention overcomes the deficiencies of the prior art and provides a biodegradable copolyester with tensile strength, tear resistance and shape memory properties. The present invention effectively enhances the mechanical strength of PBAT by the synergistic action of hydrogen bond and molecular chain entanglement. The modified copolyester still has a certain degradation rate, and at the same time endows the material with certain shape memory properties by the crosslinking of hydrogen bonds, providing a new idea for the preparation of high-strength biodegradable shape memory materials, and providing a new path for the research of fully bio-based PBAT.

[0004] To solve the above technical problems, the technical solution adopted by the present invention is: a biodegradable copolyester with tensile strength, tear resistance and shape memory properties, which is made from the following raw materials in molar ratio: 4.2 mol of terephthalic acid (TPA), 2.8 mol of adipic acid (AA), 9.8 mol of 1,4-butanediol (BDO), 0 to 0.06 mol of tetrabutyl titanate (but not 0), 0 to 0.1 mol of D-mannitol (but not 0).

[0005] The present invention also provides a method for preparing the above-mentioned biodegradable copolyester with anti-tensile, anti-tearing and shape memory properties, which is prepared by a two-stage esterification and one-step polycondensation method, and includes the following steps: Weigh adipic acid, terephthalic acid, 1,4-butanediol, and D-mannitol in molar proportions, mix the raw materials evenly and add them to a reaction kettle. The first-stage esterification starts under normal pressure. After the esterification is completed, the second-stage esterification starts. Add tetrabutyl titanate as a catalyst for the second-stage esterification. When the mass of the water generated by the esterification is equivalent to the theoretical value, the second-stage esterification is completed. The polycondensation stage starts. Add tetrabutyl titanate as a catalyst for polycondensation. Observe the torque change on the equipment. When the torque drops to 0 and then rises from 0 and no longer changes, the polycondensation is completed. Use the water-cooling method to granulate the polymer melt and vacuum dry it at 60 °C to complete the preparation.

[0006] As a further limitation of the technical solution of the present invention, the temperature of the first-stage esterification reaction is 120-180 °C, mixed at a stirring speed of 90 rpm, and the esterification time is 1-1.5 h.

[0007] As a further limitation of the technical solution of the present invention, when the temperature of the second-stage esterification reaction is 200-230 °C, the normal pressure condition remains unchanged, and it is carried out at a stirring speed of 100 rpm for at least 3.5 h.

[0008] As a further limitation of the technical solution of the present invention, the temperature of the polycondensation reaction is 230-250 °C, the pressure is within 500 Pa, and the polycondensation reaction is at least 5 h.

[0009] As a further limitation of the technical solution of the present invention, the molar ratio of tetrabutyl titanate added in the second-stage esterification reaction and the polycondensation reaction is 2:1.

[0010] As a further limitation of the technical solution of the present invention, the D-mannitol can be replaced by similar sugar alcohols, and the D-mannitol is replaced by sorbitol, maltitol or lactitol.

[0011] In addition, the present invention also provides the application of the above-mentioned biodegradable copolyester with anti-tensile, anti-tearing and shape memory properties in the preparation of packaging bags, garbage bags, lunch boxes, agricultural films and mulch films.

[0012] In addition, the present invention also provides the application of the above-mentioned biodegradable copolyester with anti-tensile, anti-tearing and shape memory properties in the preparation of intelligent materials.

[0013] Compared with the prior art, the present invention has the following beneficial effects: 1. The PBAT copolyester with tensile strength, tear strength and shape memory properties prepared by the present invention is achieved by introducing D-mannitol into the main chain of the PBAT molecule. First of all, D-mannitol is a bio-based polyhydroxy sugar alcohol, and introducing it into PBAT can improve the biocompatibility of the PBAT copolyester. Secondly, D-mannitol has a lower cost than 1,4-butanediol, and replacing a part of DM can reduce the cost of the PBAT copolyester. Moreover, the PBAT shape memory material prepared by modifying with D-mannitol has a lower cost than other shape memory materials.

[0014] 2. The PBAT copolyester with tensile strength, tear strength and shape memory properties prepared by the present invention utilizes the hydroxyl groups of D-mannitol to form hydrogen bonds within and between molecules, which synergistically acts with the entanglement between molecules to improve the mechanical strength of the polyester material, extend its service life, and endow the polyester with certain shape memory properties. The one-pot preparation process is relatively simple and easy to industrialize.

[0015] 3. The experimental results show that for the PBAT copolyester with tensile strength, tear strength and shape memory properties provided by the present invention, when the addition ratio of D-mannitol is 1.4%, its tensile strength is 27.75 MPa, the tear strength is 73.57 KN / m, the recovery rate is 793.80%, and obvious holes can be observed on the surface of the material by SEM after degradation, indicating that the modified copolyester still has biodegradable properties. Description of the Drawings

[0016] Figure 1 It is a comparative diagram of the tensile strengths of the CS, MA-1, MA-2, MA-3, MA-4, and MA-5 copolyesters prepared in the examples of the present invention.

[0017] Figure 2 It is a comparative diagram of the tear strengths of the CS, MA-1, MA-2, MA-3, MA-4, and MA-5 copolyesters prepared in the examples of the present invention.

[0018] Figure 3 It is a comparative diagram of the shape memory recovery rates of the CS, MA-1, MA-2, MA-3, MA-4, and MA-5 copolyesters prepared in the examples of the present invention.

[0019] Figure 4 It is an SEM result diagram of the CS, MA-1, MA-2, MA-3, MA-4, and MA-5 copolyesters after degradation prepared in the examples of the present invention.

[0020] Figure 5 It is an infrared detection experimental result diagram of the CS, MA-1, MA-2, MA-3, MA-4, and MA-5 copolyesters prepared in the examples of the present invention. Detailed implementation manners

[0021] The present invention will be further described below in conjunction with specific embodiments.

[0022] A biodegradable copolyester with tensile strength, tear resistance and shape memory properties, namely D-mannitol modified PBAT copolyester, is made from the following raw materials in mole parts: terephthalic acid (TPA) 4.2 mole parts, adipic acid (AA) 2.8 mole parts, 1,4-butanediol (BDO) 9.8 mole parts, tetrabutyl titanate 0 - 0.06 mole parts, D-mannitol 0 - 0.1 mole parts. The PBMAT copolyester is prepared by a one-pot method.

[0023] The copolyester poly(butylene adipate-co-butylene terephthalate) (PBMAT) modified with D-mannitol as the fourth monomer is synthesized by a method involving two esterification stages and one polycondensation stage (acid:alcohol = 1:1.4, PTA:AA = 6:4). The content of D-mannitol varies between 0 and 3.5%, while the catalyst dosage is fixed at 0.2% relative to the total stoichiometric acid amount. Groups with D-mannitol contents of 0.7%, 1.4%, 2.1%, 2.8% and 3.5% are established and named MA-1, MA-2, MA-3, MA-4 and MA-5 respectively. The control group without D-mannitol is called CS.

[0024] Atmospheric pressure and low-temperature esterification involve introducing terephthalic acid (TPA), adipic acid (AA), 1,4-butanediol (BDO) and D-mannitol (DA) into a 5 L stainless steel reactor. The reactants are mixed at 120 - 180 °C with a stirring speed of 90 rpm for 1 to 1.5 h to complete the initial esterification, ensuring complete reaction between AA and DA. Then the temperature is raised to 200 - 230 °C, and the stirring speed is increased to 100 rpm during the subsequent esterification stage, during which tetrabutyl titanate (TBOT) is added as a catalyst. Water is continuously removed by distillation, and the volume is monitored every half hour. Once the water volume matches the theoretical yield, it indicates that the esterification is complete.

[0025] Vacuum and high-temperature polycondensation: First, TBOT was added to the reaction mixture, and then a vacuum was applied to reduce the pressure below 500 Pa to promote polycondensation. The temperature was carefully adjusted within the range of 230–250 °C. The motor torque was closely observed and it was noted that it initially decreased and then increased. After reaching a stable maximum torque value in the reactor, the polycondensation was considered complete. Subsequently, the polymer melt was granulated using the water-cooling method and vacuum dried at 60 °C for at least 24 h. Then the dried granules were stored in a desiccator for further analysis.

[0026] The parameters of TPA are as follows: Yangzi Petrochemical Co., Ltd., Sinopec, industrial grade; The parameters of AA are as follows: Hengshui Jinghua Chemical Co., Ltd., industrial grade; The parameters of BDO are as follows: Guangzhou Haosheng Chemical Co., Ltd., industrial grade; The parameters of tetrabutyl titanate are as follows: Aladdin Co., Ltd., Shanghai, China, analytical pure; The parameters of D-mannitol are as follows: Jinan Yucheng Biotechnology Co., Ltd., food grade. Example 1

[0027] By the method of two-stage esterification and one-step polycondensation, 409.19 g of adipic acid (AA), 697.75 g of terephthalic acid (TPA), 883.18 g of 1,4-butanediol (BDO), and 3.64 g of D-mannitol were weighed. The raw materials were uniformly blended at 190 °C and added to the reaction kettle. The first-stage esterification was started under atmospheric pressure. After 1.5 h of esterification; the second-stage esterification began. When the temperature was raised to 210 °C while keeping the pressure constant, 6 g of the catalyst tetrabutyl titanate was added for the second-stage esterification, and the reaction was carried out for at least 3.5 h or more. When the mass of the water generated by esterification was equivalent to the theoretical value; the polycondensation stage began. 3 g of the catalyst tetrabutyl titanate was added and the temperature was raised to 235 °C, with the pressure within 500 Pa. After 5 h of polycondensation, the torque change on the equipment was observed. When the torque dropped to 0 and then rose from 0 and no longer changed, the experiment ended and was recorded as MA-1. Example 2

[0028] By the method of two-stage esterification and one-step polycondensation, weigh 409.19 g of adipic acid (AA), 697.75 g of terephthalic acid (TPA), 883.18 g of 1,4-butanediol (BDO), and 7.2 g of D-mannitol. At a temperature of 190 °C, mix the raw materials evenly and add them to the reaction kettle. Start the first-stage esterification under normal pressure conditions. After 1.5 h of esterification; start the second-stage esterification. When the temperature is raised to 210 °C, keep the pressure unchanged, and add 6 g of tetrabutyl titanate as a catalyst for the second-stage esterification. React for at least 3.5 h or more. When the mass of the water produced by esterification is equivalent to the theoretical value; start the polycondensation stage, add 3 g of tetrabutyl titanate as a catalyst and raise the temperature to 235 °C, with the pressure within 1000 Pa. After polycondensation for 5 h, observe the torque change on the equipment. When the torque drops to 0 and then rises from 0 and approaches a stable value, the experiment ends and is recorded as MA-2. Example 3

[0029] By the method of two-stage esterification and one-step polycondensation, weigh 409.19 g of adipic acid (AA), 697.75 g of terephthalic acid (TPA), 883.18 g of 1,4-butanediol (BDO), and 10.93 g of D-mannitol. At a temperature of 190 °C, mix the raw materials evenly and add them to the reaction kettle. Start the first-stage esterification under normal pressure conditions. After 1.5 h of esterification; start the second-stage esterification. When the temperature is raised to 210 °C, keep the pressure unchanged, and add 6 g of tetrabutyl titanate as a catalyst for the second-stage esterification. React for at least 3.5 h or more. When the mass of the water produced by esterification is equivalent to the theoretical value; start the polycondensation stage, add 3 g of tetrabutyl titanate as a catalyst and raise the temperature to 235 °C, with the pressure within 1000 Pa. After polycondensation for 5 h, observe the torque change on the equipment. When the torque drops to 0 and then rises from 0 and approaches a stable value, the experiment ends and is recorded as MA-3. Example 4

[0030] By means of two-stage esterification and one-step polycondensation, weigh 409.19 g of adipic acid (AA), 697.75 g of terephthalic acid (TPA), 883.18 g of 1,4-butanediol (BDO), and 14.57 g of D-mannitol. At a temperature of 190 °C, mix the raw materials evenly and add them to the reaction kettle. Start the first-stage esterification under normal pressure conditions. After 1.5 h of esterification; start the second-stage esterification. When the temperature is raised to 210 °C and the pressure is kept constant, add 6 g of tetrabutyl titanate as a catalyst for the second-stage esterification. React for at least 3.5 h or more. When the mass of the water generated by esterification is equivalent to the theoretical value; start the polycondensation stage. Add 3 g of tetrabutyl titanate as a catalyst and raise the temperature to 235 °C. The pressure is within 1000 Pa. After polycondensation for 5 h, observe the torque change on the equipment. When the torque drops to 0 and then rises from 0 and approaches a stable value, the experiment ends and is recorded as MA-4. Example 5

[0031] By means of two-stage esterification and one-step polycondensation, weigh 409.19 g of adipic acid (AA), 697.75 g of terephthalic acid (TPA), 883.18 g of 1,4-butanediol (BDO), and 18.21 g of D-mannitol. At a temperature of 190 °C, mix the raw materials evenly and add them to the reaction kettle. Start the first-stage esterification under normal pressure conditions. After 1.5 h of esterification; start the second-stage esterification. When the temperature is raised to 210 °C and the pressure is kept constant, add 6 g of tetrabutyl titanate as a catalyst for the second-stage esterification. React for at least 3.5 h or more. When the mass of the water generated by esterification is equivalent to the theoretical value; start the polycondensation stage. Add 3 g of tetrabutyl titanate as a catalyst and raise the temperature to 235 °C. The pressure is within 1000 Pa. After polycondensation for 5 h, observe the torque change on the equipment. When the torque drops to 0 and then rises from 0 and approaches a stable value, the experiment ends and is recorded as MA-5.

[0032] Control Group 1 By means of two-stage esterification and one-step polycondensation, 409.19 g of adipic acid (AA), 697.75 g of terephthalic acid (TPA), and 883.18 g of 1,4-butanediol (BDO) were weighed. At a temperature of 190 °C, the raw materials were blended evenly and added to the reaction kettle. The first-stage esterification was started under normal pressure. After 1.5 h of esterification; the second-stage esterification began. When the temperature was raised to 210 °C while keeping the pressure unchanged, 6 g of tetrabutyl titanate was added as a catalyst for the second-stage esterification, and the reaction was carried out for at least 3.5 h or more. When the mass of the water generated by esterification was equivalent to the theoretical value; the polycondensation stage began. 3 g of tetrabutyl titanate was added as a catalyst and the temperature was raised to 235 °C, with the pressure within 500 Pa. After 5 h of polycondensation, the torque change on the equipment was observed. When the torque dropped to 0 and then rose from 0 to no longer change, the experiment ended and was recorded as CS.

[0033] Test results: Tensile strength, tear strength, water contact angle test, water vapor barrier test, FTIR, and SEM were used to characterize the CS, MA-1, MA-2, MA-3, MA-4, and MA-5 polyesters of Comparative Example 1 and Examples 1 to 5. The results are as Figures 1 to 4 shown.

[0034] The results show that: Figure 1 As shown in Table 1, when mannitol is appropriate, it can improve the toughness of the polymer, but when it is excessive, it may cause over-plasticization, reducing the rigidity and strength of the material, thus resulting in a decrease in tensile strength. When 1.4% D-mannitol is added, the tensile strength is significantly improved. Figure 2 The results show that when 1.4% D-mannitol is added, the tear strength shows an enhancement effect, which is consistent with the enhancement result of the tensile strength. Figure 3 The results show that adding mannitol can significantly improve the recovery rate of PBAT. Hydrogen bonds will form between mannitol and PBAT, improving the compatibility of the material. This compatibility improves the overall mechanical properties of PBAT, enabling the material to recover better after an external force is applied. And mannitol, as a polyhydroxy sugar alcohol, has good thermoplasticity and can maintain fluidity at high temperatures, helping the material to disperse evenly during the processing. This uniform dispersion promotes the slippage of PBAT chain segments to a certain extent, enhancing its recovery. Figure 4 In the figure, Figure a shows the SEM result diagram before degradation. It can be clearly seen that the image is relatively smooth, while in Figures b, c, and d, it can be clearly seen that there are holes and grooves in the image, indicating that the polymer chains are broken. Adding mannitol does not affect its degradation performance. As Figure 5As shown, the broad stretching vibration peak shown in the red-framed area is the associated hydroxyl group. This is because the free hydroxyl groups after D-mannitol is incorporated into the main chain form hydrogen bonds between the copolyester molecules. Based on the synthetic raw material PBAT, we compared the recovery rates of PBAT with PBAT added with 0.7% - 3.5% D-mannitol. It can be seen that the recovery rates of the materials added with 0.7% (MA-1), 1.4% (MA-2), 2.8% (MA-4), and 3.5% (MA-5) D-mannitol have been significantly improved, proving that the addition of mannitol will further improve the shape memory function of the PBAT material.

[0035] Table 1 Detection Results

Claims

1. A biodegradable copolyester having tensile and tear resistance and shape memory properties, characterized in that: The invention is prepared from the following raw materials in the following molar proportions: 4.2 molar parts of polyethylene terephthalate, 2.8 molar parts of adipic acid, 9.8 molar parts of 1,4-butanediol, 0-0.06 molar parts of tetrabutyl titanate and not 0, and 0-0.1 molar parts of D-mannitol and not 0.

2. The method for preparing a biodegradable copolyester having tensile and tear resistance and shape memory properties according to claim 1, characterized in that: The method is prepared by a two-stage esterification and one-step polycondensation method, comprising the following steps: weighing adipic acid, terephthalic acid, 1,4-butanediol, and D-mannitol in molar proportions, uniformly blending the raw materials and adding them into a reactor, starting the first stage of esterification under normal pressure, and after the esterification is completed; starting the second stage of esterification, adding a catalyst tetrabutyl titanate for the second stage of esterification, and completing the second stage of esterification when the mass of water produced by the esterification is equivalent to the theoretical value; starting the polycondensation stage, adding a catalyst tetrabutyl titanate for polycondensation, observing the torque change on the equipment, and when the torque drops to 0 and then increases from 0 to no longer change, the polycondensation is completed, granulating the polymer melt by a water cooling method, and vacuum drying at 60°C to complete the preparation.

3. The method for preparing a biodegradable copolyester having tensile and tear resistance and shape memory properties according to claim 2, characterized in that: The temperature of the first stage esterification reaction is 120-180°C, the mixing is carried out at a stirring speed of 90 rpm, and the esterification time is 1-1.5h.

4. The method for preparing a biodegradable copolyester having tensile strength, tear resistance and shape memory properties according to claim 2, characterized in that: When the temperature of the second stage esterification reaction is 200-230°C, the normal pressure condition remains unchanged, the stirring speed is 100 rpm, and the reaction is carried out for at least 3.5 hours.

5. The method for preparing a biodegradable copolyester having tensile and tear resistance and shape memory properties according to claim 2, characterized in that: The temperature of the polycondensation reaction is 230-250°C, the pressure is within 500Pa, and the polycondensation reaction lasts for at least 5 hours.

6. The method for preparing a biodegradable copolyester having tensile and tear resistance and shape memory properties according to claim 2 is characterized in that: The molar ratio of the catalyst tetrabutyl titanate added in the second stage esterification reaction and the polycondensation reaction is 2:

1.

7. The biodegradable copolyester having tensile and tear resistance and shape memory properties according to claim 1, characterized in that: The D-mannitol is replaced by sorbitol, maltitol or lactitol.

8. Use of the biodegradable copolyester having tensile and tear resistance and shape memory properties according to claim 1 in the preparation of packaging bags, garbage bags, lunch box agricultural films and mulch films.

9. Use of the biodegradable copolyester having tensile and tear resistance and shape memory properties according to claim 1 in the preparation of smart materials.

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