Isosorbide-based copolyester as well as preparation method and application thereof

Abstract

The invention provides isosorbide-based copolyester as well as a preparation method and application thereof, and relates to the technical field of high polymer materials. According to the preparation method, a step-by-step esterification method is adopted, firstly, isosorbide, excessive aromatic dicarboxylic acid and an acylating agent are subjected to a first esterification reaction, so that the acylating agent can efficiently and specifically activate secondary hydroxyl of isosorbide, and the initial esterification rate of isosorbide is greatly increased. Meanwhile, the excessive aromatic dicarboxylic acid ensures that the generated isosorbide prepolymer takes carboxyl as a terminal group, so that isosorbide molecules are'locked 'in the middle of a polymer chain segment. Due to the fact that the isosorbide is embedded in the middle of the chain segment in advance, the problem that the isosorbide falls off in the ester exchange reaction due to the fact that the isosorbide is located at the chain end and low in reaction activity in the subsequent polycondensation stage is effectively solved, and therefore the retention rate of the isosorbide in the final polymer is greatly increased, and the glass-transition temperature of the isosorbide is greatly increased.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and in particular to an isosorbide-based copolyester, its preparation method, and its application. Background Technology

[0002] Polyethylene terephthalate (PET), as an important semi-crystalline thermoplastic polyester, is widely used in industries such as textiles, packaging, and electronics due to its excellent mechanical properties, abrasion resistance, low water absorption, and electrical insulation. However, the relatively low glass transition temperature (Tg ~ 78°C) of traditional PET limits its application in applications requiring high heat resistance.

[0003] Isosorbide (ISB) is a rigid diol derived from biomass. Its unique V-shaped rigid structure can effectively increase the glass transition temperature (Tg) of polymers and regulate crystallization behavior, making it an ideal monomer for preparing high-performance bio-based polyesters. However, the widespread application of ISB faces two major technical bottlenecks: First, the hydroxyl groups in ISB molecules are all secondary hydroxyl groups, whose reactivity is much lower than that of primary alcohols such as ethylene glycol, resulting in a slow esterification reaction rate and difficulty in integrating them into the polymer chain; Second, in the high-temperature, high-vacuum polycondensation stage, ISB monomers located at the ends of the molecular chain are prone to detach from the polymer molecular chain during transesterification, resulting in a low residual rate of ISB in the final polymer, which cannot effectively exert its role in increasing Tg.

[0004] In existing technologies, pre-activation or in-situ acylation methods are commonly used to address the low reactivity of ISB. For example, some improved schemes involve pre-chemical modification of the hydroxyl groups of ISB, but this process is cumbersome, costly, and not conducive to industrial production. Another approach uses bis(2-hydroxyethyl)isosorbide as a monomer, but its preparation is complex. Other literature reports the synthesis of ISB copolyesters in the presence of in-situ acylation; however, in systems containing multiple diols, the acylating agent preferentially reacts with the more reactive primary alcohol, resulting in minimal activation of ISB and failing to effectively address the issues of low ISB insertion and retention rates.

[0005] Therefore, developing a simple and cost-effective preparation method that can effectively improve the reactivity of ISB and its retention rate in the final polymer is of great significance for promoting the practical application of high-performance bio-based polyesters.

[0006] In view of this, the present invention is hereby proposed. Summary of the Invention

[0007] The first objective of this invention is to provide a method for preparing isosorbide-based copolyesters, wherein the method significantly improves the retention rate of isosorbide in the final polymer and the glass transition temperature by performing a stepwise esterification reaction.

[0008] A second objective of this invention is to provide an isosorbide-based copolyester.

[0009] A third objective of this invention is to provide an application of isosorbide-based copolyesters.

[0010] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted: This invention provides a method for preparing isosorbide-based copolyesters, the method comprising the following steps: (A) First esterification reaction: Isosorbide, a portion of aromatic dicarboxylic acid, acylating agent and catalyst are mixed and esterified to obtain isosorbide prepolymer with carboxyl-terminated group; In the first esterification reaction, the molar ratio of isosorbide to aromatic dicarboxylic acid is 1:1.1~2; (B) Second esterification reaction: The isosorbide prepolymer obtained in step (A) is mixed with the remaining aromatic dicarboxylic acid and one or more non-isosorbide diols and then subjected to esterification reaction. (C) Polycondensation: The product of the second esterification reaction is subjected to melt polycondensation to obtain isosorbide-based copolyester.

[0011] Furthermore, the aromatic dicarboxylic acid includes at least one of terephthalic acid, isophthalic acid, naphthalic acid, and cyclohexanedicarboxylic acid; Preferably, the aromatic dicarboxylic acid is terephthalic acid.

[0012] Furthermore, the non-isosorbitol diol is an aliphatic diol with 2-12 carbon atoms or an alicyclic diol with 3-20 carbon atoms. Preferably, the non-isosorbitol diol includes at least one selected from ethylene glycol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, and 1,4-cyclohexanediethanol. Preferably, the molar ratio of the non-isosorbitol diol to isosorbitol is 10~95:90~5, and the total molar ratio of all diols to all aromatic dicarboxylic acids is 1.1~1.8:1.

[0013] Furthermore, the acylating agent is an acid anhydride compound; Preferably, the acylating agent includes one or more of acetic anhydride, propionic anhydride, succinic anhydride, and phthalic anhydride; Preferably, the amount of the acylating agent is 0.1 to 75 mol of isosorbide.

[0014] Furthermore, the catalyst is a germanium-based catalyst or an antimony-based catalyst; Preferably, the amount of catalyst used is 0.01% to 0.1% of the total mass of all reactants; Preferably, the total mass of all reactants is the sum of the masses of isosorbide, all aromatic dicarboxylic acids, and all diols.

[0015] Furthermore, the temperature of the first esterification reaction is 180~260℃, and the pressure is 100~400 kPa; Preferably, the temperature of the second esterification reaction is 180~260℃ and the pressure is 100~400 kPa.

[0016] Furthermore, step (C) polycondensation is carried out under a pressure of 0~100 Pa; Preferably, the temperature of the melt polycondensation is 255~280℃, and the reaction is stopped when the reaction torque reaches 25~35 N•m.

[0017] The isosorbide-based copolyester obtained by the above preparation method provided by the present invention.

[0018] Furthermore, the isosorbide structure in the isosorbide-based copolyester is retained at a rate of 83-91%, and the glass transition temperature is 96-109°C.

[0019] This invention provides the application of the above-mentioned isosorbide-based copolyester in the preparation of polymer material products.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention provides a method for preparing isosorbide-based copolyesters. This method employs a stepwise esterification reaction. First, isosorbide monophosphate (ISB) undergoes a first esterification reaction with excess diacid and an acylating agent. This creates an environment free from competition from other highly reactive alcohols, allowing the acylating agent to efficiently and specifically activate the secondary hydroxyl groups of ISB, significantly increasing the initial esterification rate of ISB. Furthermore, the excess diacid ensures that the resulting ISB ester has a carboxyl group as the terminal group, thus locking the ISB molecule in the middle of the polymer chain. In addition, because the ISB is pre-embedded in the middle of the chain segment, it effectively avoids the problem of ISB detachment during the transesterification reaction in the subsequent polycondensation stage due to its low reactivity at the chain end. This significantly improves the retention rate of ISB in the final polymer. The high ISB retention rate directly leads to a significant increase in the glass transition temperature, broadening the application temperature range of the isosorbide-based copolyester of the present invention.

[0021] The isosorbide-based copolyester provided by the present invention is prepared by the above preparation method. Due to the advantages of the preparation method, the isosorbide structure retention rate in the isosorbide-based copolyester of this application is ≥80%, and the glass transition temperature is ≥85℃.

[0022] The isosorbide-based copolyester provided by this invention can be widely used in the preparation of polymer materials. Detailed Implementation

[0023] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] According to one aspect of the present invention, a method for preparing an isosorbide-based copolyester, the method comprising the following steps: (A) First esterification reaction: Isosorbide, a portion of aromatic dicarboxylic acid, acylating agent and catalyst are mixed and esterified to obtain isosorbide prepolymer with carboxyl-terminated group; In the first esterification reaction, the molar ratio of isosorbide to aromatic dicarboxylic acid is 1:1.1~2; (B) Second esterification reaction: The isosorbide prepolymer obtained in step (A) is mixed with the remaining aromatic dicarboxylic acid and one or more non-isosorbide diols and then subjected to esterification reaction. (C) Polycondensation: The product of the second esterification reaction is subjected to melt polycondensation to obtain isosorbide-based copolyester.

[0025] The present invention provides a method for preparing isosorbide-based copolyesters. This method employs a stepwise esterification reaction. First, isosorbide monophosphate (ISB) undergoes a first esterification reaction with excess diacid and an acylating agent. This creates an environment free from competition from other highly reactive alcohols, allowing the acylating agent to efficiently and specifically activate the secondary hydroxyl groups of ISB, significantly increasing the initial esterification rate of ISB. Furthermore, the excess diacid ensures that the resulting ISB ester has a carboxyl group as the terminal group, thus locking the ISB molecule in the middle of the polymer chain. In addition, because the ISB is pre-embedded in the middle of the chain segment, it effectively avoids the problem of ISB detachment during the transesterification reaction in the subsequent polycondensation stage due to its low reactivity at the chain end. This significantly improves the retention rate of ISB in the final polymer. The high ISB retention rate directly leads to a significant increase in the glass transition temperature, broadening the application temperature range of the isosorbide-based copolyester of the present invention.

[0026] Furthermore, it should be noted that the preparation method of the isosorbide-based copolyester of the present invention does not require complicated pre-separation and pre-activation steps, and can be achieved using conventional polyester production equipment. The process is simple and easy to operate.

[0027] In a preferred embodiment of the present invention, the aromatic dicarboxylic acid includes at least one selected from terephthalic acid, isophthalic acid, naphthalic acid, and cyclohexanedicarboxylic acid; In a preferred embodiment of the present invention, the non-isosorbitol diol is an aliphatic diol with 2-12 carbon atoms or an alicyclic diol with 3-20 carbon atoms. Preferably, the non-isosorbitol diol includes at least one selected from ethylene glycol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, and 1,4-cyclohexanediethanol. In a preferred embodiment of the present invention, the molar ratio of the non-isosorbitol diol to isosorbitol is 10~95:90~5, and the total molar ratio of all diols to all aromatic dicarboxylic acids is 1.1~1.8:1.

[0028] In a preferred embodiment, the molar ratio of non-isosorbitol diol to isosorbitol in this invention is 10~95:90~5. Within this ratio range, the isosorbitol-based copolyester of this application has a better glass transition temperature. The total molar ratio of all diols to all aromatic dicarboxylic acids is 1.1~1.8:1, which can ensure efficient conversion in the preparation process.

[0029] In a preferred embodiment of the present invention, the acylating agent is an acid anhydride compound; Preferably, the acylating agent includes one or more of acetic anhydride, propionic anhydride, succinic anhydride, and phthalic anhydride; In a preferred embodiment of the present invention, the amount of the acylating agent is 0.1 to 75 mol of isosorbide.

[0030] In a preferred embodiment of the present invention, the catalyst is a germanium-based catalyst or an antimony-based catalyst; Preferably, the amount of catalyst used is 0.01% to 0.1% of the total mass of all reactants; Preferably, the total mass of all reactants is the sum of the masses of isosorbide, all aromatic dicarboxylic acids, and all diols.

[0031] In a preferred embodiment of the present invention, the temperature of the first esterification reaction is 180~260°C and the pressure is 100~400 kPa. In a preferred embodiment of the present invention, the temperature of the second esterification reaction is 180~260°C and the pressure is 100~400 kPa.

[0032] In a preferred embodiment of the present invention, step (C) polycondensation is carried out under a pressure of 0~100 Pa; Preferably, the temperature of the melt polycondensation is 255~280℃, and the reaction is stopped when the reaction torque reaches 25~35 N•m.

[0033] According to one aspect of the present invention, the isosorbide-based copolyester obtained by the above preparation method.

[0034] The isosorbide-based copolyester provided by the present invention is prepared by the above preparation method. Due to the advantages of the preparation method, the isosorbide structure retention rate in the isosorbide-based copolyester of this application is 83-91%, and the glass transition temperature is 96-109℃.

[0035] According to one aspect of the present invention, the application of the above-mentioned isosorbide-based copolyester in the preparation of polymer material articles.

[0036] The isosorbide-based copolyester provided by this invention can be widely used in the preparation of polymer materials.

[0037] Preferably, the polymer material product is a fiber, film, packaging material, or engineering plastic product.

[0038] The technical solution of the present invention will be further described below with reference to the embodiments.

[0039] Example 1 A method for preparing an isosorbide-based copolyester, the method comprising: (1) Raw material preparation: Preparation of Slurry 1: Accurately weigh 174g of isosorbide, 230g of terephthalic acid, 0.06g of acetic anhydride, 0.27g of germanium oxide catalyst, 0.003g of blue colorant, and 0.0012g of red colorant. Place the above materials in a container and stir thoroughly until uniformly mixed to obtain slurry 1.

[0040] Preparation of slurry 2: Accurately weigh 1420 g of terephthalic acid, 296 g of ethylene glycol, 858 g of 1,4-cyclohexanediethanol, 1.87 g of germanium oxide catalyst, and 0.19 g of phosphoric acid stabilizer. Mix the above materials in another container to obtain slurry 2.

[0041] (2) Esterification reaction: (2.1) First esterification stage: The prepared slurry 1 is transferred to a 5-liter polymerization reactor equipped with a reflux condenser. The reactor is sealed and subjected to three nitrogen pressurization and purging cycles to replace the air inside the reactor, ultimately maintaining the pressure inside the reactor at 0.2 MPa.

[0042] Subsequently, stirring was started and the temperature was increased, with the reaction temperature controlled at 245 °C and the reaction pressure maintained at 280 kPa, to carry out the first stage of esterification reaction.

[0043] During esterification, the water generated by the esterification reaction is continuously distilled off and condensed for removal. The reaction progress is monitored by metering the amount of water discharged, and the first esterification stage is considered complete when the amount of water discharged reaches 80% of the theoretically calculated value.

[0044] (2.1) Second esterification stage: Add the pre-prepared slurry 2 to the reaction system that has completed the first esterification, and continue the second esterification reaction under the conditions of 245 ℃ and 280 kPa pressure.

[0045] Continue to monitor the water output. When the total water output reaches the theoretical calculation value, it indicates that the esterification reaction is basically complete. Release the pressure inside the reactor and drain the residual water.

[0046] (3) Condensation polymerization: After the esterification reaction was completed, the temperature was raised to 270 °C, and then the pressure of the reaction system was gradually reduced to below 60 Pa absolute pressure over 30 minutes to carry out the melt polycondensation reaction. The monitoring system tracked the stirring torque in real time, and when the torque value rose to 30 N, isosorbide-based copolyester was obtained.

[0047] (4) Discharge and post-processing: After the reaction is complete, the molten polymer stream is extruded through a casting head under nitrogen protection to form strips.

[0048] The strips are cooled and solidified in a water tank, and then cut into uniform particles by a pelletizer to obtain the isosorbide-based copolyester of this embodiment.

[0049] Example 2 Except for the composition of the slurry in step (1) of raw material preparation, this embodiment is the same as that in embodiment 1, as detailed below: "(1) Raw material preparation: Preparation of Slurry 1: Accurately weigh 260 g of isosorbide, 345 g of terephthalic acid, 0.09 g of acetic anhydride, 0.41 g of germanium oxide catalyst, 0.003 g of blue colorant, and 0.0012 g of red colorant. Thoroughly mix the above materials to obtain slurry 1.

[0050] Preparation of slurry 2: Accurately weigh 1305 g of terephthalic acid, 258 g of ethylene glycol, 858 g of 1,4-cyclohexanediethanol, 1.77 g of germanium oxide catalyst, and 0.19 g of phosphoric acid stabilizer. Mix the above materials thoroughly to obtain slurry 2.

[0051] Example 3 Except for the composition of the slurry in step (1) of raw material preparation, this embodiment is the same as that in embodiment 1, as detailed below: "(1) Raw material preparation: Preparation of Slurry 1: Accurately weigh 226 g of isosorbide, 300 g of terephthalic acid, 0.075 g of acetic anhydride, 0.34 g of germanium oxide catalyst, 0.003 g of blue colorant, and 0.0012 g of red colorant. Mix the above materials thoroughly to obtain slurry 1.

[0052] Preparation of slurry 2: Accurately weigh 1350 g of terephthalic acid, 273 g of ethylene glycol, 858 g of 1,4-cyclohexanediethanol, 1.77 g of germanium oxide catalyst, and 0.19 g of phosphoric acid stabilizer. Mix the above materials thoroughly to obtain slurry 2.

[0053] Example 4 Except for step (1) where the acetic anhydride content in slurry 1 is 0.09g, this embodiment is the same as in embodiment 1, as detailed below: "Preparation of slurry 1: Accurately weigh 174g of isosorbide, 230g of terephthalic acid, 0.09g of acetic anhydride, 0.27g of germanium oxide catalyst, 0.003g of blue colorant and 0.0012g of red colorant. Place the above materials in a container and stir thoroughly until they are mixed evenly to obtain slurry 1."

[0054] Example 5 Except for step (1) where the acetic anhydride content in slurry 1 is 0.12g, this embodiment is the same as in embodiment 1, as detailed below: "Preparation of slurry 1: Accurately weigh 174g of isosorbide, 230g of terephthalic acid, 0.12g of acetic anhydride, 0.27g of germanium oxide catalyst, 0.003g of blue colorant and 0.0012g of red colorant. Place the above materials in a container and stir thoroughly until they are mixed evenly to obtain slurry 1."

[0055] Comparative Example 1 (No acylating agent was added to this comparative example slurry 1) A method for preparing an isosorbide-based copolyester, the method comprising: (1) Raw material preparation: Preparation of Slurry 1: Accurately weigh 174 g of isosorbide, 230 g of terephthalic acid, 0.27 g of germanium oxide as a catalyst, 0.003 g of blue colorant, and 0.0012 g of red colorant. Thoroughly mix the above materials to obtain slurry 1. Preparation of slurry 2: Accurately weigh 1420 g of terephthalic acid, 296 g of ethylene glycol, 858 g of 1,4-cyclohexanediethanol, 1.87 g of germanium oxide catalyst, and 0.19 g of phosphoric acid stabilizer. Mix the above materials in another container to obtain slurry 2.

[0056] (2) Esterification reaction: Performed according to Example 1; (3) Polycondensation reaction: carried out as in Example 1; (4) Discharge and post-processing: Refer to Example 1.

[0057] Comparative Example 2 (This comparative example uses a one-step feeding method and does not use an acylation agent) A method for preparing an isosorbide-based copolyester, the method comprising: (1) Preparation of slurry: Accurately weigh 174 g of isosorbide, 1650 g of terephthalic acid, 296 g of ethylene glycol, 858 g of 1,4-cyclohexanediethanol, 2.14 g of germanium oxide catalyst, 0.19 g of phosphoric acid stabilizer, 0.003 g of blue colorant and 0.0012 g of red colorant. Put all the above materials into a container at once and stir thoroughly to make a slurry.

[0058] (2) Esterification reaction: All the prepared slurry was added to the polymerization reactor. The subsequent esterification reaction and polycondensation reaction process conditions, steps and parameter control were the same as in Example 1. (3) Polycondensation reaction: carried out as in Example 1; (4) Discharge and post-processing: Refer to Example 1.

[0059] Comparative Example 3 (This comparative example uses a one-step feeding method and an acylating agent) A method for preparing an isosorbide-based copolyester, the method comprising: (1) Preparation of slurry: Accurately weigh 174 g of isosorbide, 1650 g of total terephthalic acid, 296 g of ethylene glycol, 858 g of 1,4-cyclohexanediethanol, 0.06 g of acetic anhydride as an acylating agent, 2.14 g of germanium oxide catalyst, 0.19 g of phosphoric acid stabilizer, 0.003 g of blue colorant and 0.0012 g of red colorant. Put all the above materials into a container at once and stir thoroughly to make a slurry.

[0060] (2) Esterification reaction: All the prepared slurry was added to the polymerization reactor. The subsequent esterification reaction and polycondensation reaction process conditions, steps and parameter control were the same as in Example 1. (3) Polycondensation reaction: carried out as in Example 1; (4) Discharge and post-processing: Refer to Example 1.

[0061] Comparative Example 4 (In this comparative example, the molar ratio of PTA to ISB is approximately 0.5:1, and the amount of diacid is insufficient in the first esterification reaction) A method for preparing an isosorbide-based copolyester, the method comprising: (1) Raw material preparation: Preparation of Slurry 1: Accurately weigh 174 g of isosorbide, 83.2 g of terephthalic acid, 0.06 g of acetic anhydride, 0.27 g of germanium oxide catalyst, 0.003 g of blue colorant, and 0.0012 g of red colorant. Mix the above materials thoroughly to obtain slurry 1.

[0062] Note: The molar ratio of terephthalic acid (PTA) to isosorbide (ISB) used in this amount is 0.5:1, which means that the amount of acid is insufficient.

[0063] Preparation of slurry 2: Accurately weigh 1566.8 g of terephthalic acid, 296 g of ethylene glycol, 858 g of 1,4-cyclohexanediethanol, 1.87 g of germanium oxide catalyst, and 0.19 g of phosphoric acid stabilizer. Mix the above materials thoroughly to obtain slurry 2.

[0064] (2) Esterification reaction: Performed according to Example 1; (3) Polycondensation reaction: carried out as in Example 1; (4) Discharge and post-processing: Refer to Example 1.

[0065] Experimental Example 1 To objectively evaluate the performance of the isosorbide-based copolyester prepared by the method of the present invention, a series of standard tests were performed on the copolymer particles obtained in Examples 1-5 and Comparative Examples 1-4. The test methods and results are as follows.

[0066] (I) Test methods and standards 1. Intrinsic viscosity: Tested according to national standard GB / T 14190-2008, using a mixed solvent of phenol and tetrachloroethane in a weight ratio of 60 / 40, at a test temperature of 25 °C, and with a copolyester concentration of 5 mg / mL. In this application, this index is used to characterize the molecular weight of the polymer.

[0067] 2. Isosorbide retention rate: determined by proton nuclear magnetic resonance spectroscopy.

[0068] 3. Glass transition temperature: Tested according to national standard GB / T 19466.2-2004. This temperature is a key indicator for evaluating the heat resistance of polymers.

[0069] (ii) The test results are shown in Table 1.

[0070] Table 1: Performance Test Results of Isosorbide-Based Copolyesters

[0071] (III) Results Analysis: The test data above show that the isosorbide-based copolyesters prepared by the isosorbide-based copolyester preparation method of the present invention in Examples 1 to 5 have an excellent ISB retention rate of 83% to 91%, and the glass transition temperature is significantly higher than that of traditional PET (78°C), reaching up to 109°C.

[0072] This fully demonstrates that the method of the present invention can significantly improve the retention rate of isosorbide in the final polymer and the glass transition temperature. In contrast, the ISB retention rates of Comparative Examples 2 and 3 dropped sharply to 54% and 56%, respectively, showing a significant difference from the results of the examples. Therefore, it can be seen that the stepwise esterification process of this application is the key to ensuring a high ISB retention rate, and its effect is far superior to simply adding an acylation agent.

[0073] Comparing Example 1 and Comparative Example 1, it can be seen that, under the same stepwise process, Example 1, which uses an acylation agent, has a higher ISB retention rate (86%) than Comparative Example 1 (80%) without acylation, and a shorter polycondensation time. This indicates that combining the acylation reaction with the stepwise esterification process in this application can further optimize the reaction efficiency and effect.

[0074] Comparing Example 1 (ISB ratio 10%) with Examples 2 and 3 (ISB ratio 15% and 13%), it can be seen that appropriately increasing the ISB feed ratio can further increase the glass transition temperature of the copolyester.

[0075] Comparing Examples 1 with Examples 4 and 5, it can be seen that appropriately increasing the amount of acylating agent can effectively accelerate the polymerization reaction rate and improve the retention rate of ISB within a certain range (such as increasing to 0.075% in Example 4). However, when the amount of acylating agent is increased to 0.1%, the Tg value decreases significantly.

[0076] In contrast, in Comparative Example 4, the amount of isosorbide was higher than that of aromatic dicarboxylic acids during the first esterification reaction, which prevented the effective formation of terminal carboxyl isosorbide esters, resulting in a significant decrease in isosorbide retention.

[0077] In summary, the method for preparing isosorbide-based copolyesters in this application can significantly improve the reaction efficiency of isosorbide and its retention rate in the polymer, thereby successfully obtaining high-performance bio-based copolyesters with high glass transition temperatures.

[0078] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing an isosorbide-based copolyester, characterized in that, The preparation method includes the following steps: (A) First esterification reaction: Isosorbide, a portion of aromatic dicarboxylic acid, acylating agent and catalyst are mixed and esterified to obtain isosorbide prepolymer with carboxyl-terminated group; In the first esterification reaction, the molar ratio of isosorbide to aromatic dicarboxylic acid is 1:1.1~2; (B) Second esterification reaction: The isosorbide prepolymer obtained in step (A) is mixed with the remaining aromatic dicarboxylic acid and one or more non-isosorbide diols and then subjected to esterification reaction. (C) Polycondensation: The product of the second esterification reaction is subjected to melt polycondensation to obtain isosorbide-based copolyester.

2. The method for preparing isosorbide-based copolyester according to claim 1, characterized in that, The aromatic dicarboxylic acid includes at least one of terephthalic acid, isophthalic acid, naphthalic acid, and cyclohexanedicarboxylic acid.

3. The method for preparing isosorbide-based copolyester according to claim 1, characterized in that, The non-isosorbitol diol is an aliphatic diol with 2-12 carbon atoms or an alicyclic diol with 3-20 carbon atoms. Preferably, the non-isosorbitol diol includes at least one selected from ethylene glycol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, and 1,4-cyclohexanediethanol. Preferably, the molar ratio of the non-isosorbitol diol to isosorbitol is 10~95:90~5, and the molar ratio of the total amount of the diol to the total amount of the aromatic dicarboxylic acid is 1.1~1.8:

1.

4. The method for preparing isosorbide-based copolyester according to claim 1, characterized in that, The acylating agent is an acid anhydride compound; Preferably, the acylating agent includes one or more of acetic anhydride, propionic anhydride, succinic anhydride, and phthalic anhydride; Preferably, the amount of the acylating agent is 0.1 to 75 mol of isosorbide.

5. The method for preparing isosorbide-based copolyester according to claim 1, characterized in that, The catalyst is a germanium-based catalyst or an antimony-based catalyst; Preferably, the amount of catalyst used is 0.01% to 0.1% of the total mass of all reactants; Preferably, the total mass of all reactants is the sum of the masses of isosorbide, all aromatic dicarboxylic acids, and all diols.

6. The method for preparing isosorbide-based copolyester according to claim 1, characterized in that, The temperature of the first esterification reaction is 180~260℃, and the pressure is 100~400 kPa; Preferably, the temperature of the second esterification reaction is 180~260℃ and the pressure is 100~400 kPa.

7. The method for preparing isosorbide-based copolyester according to claim 1, characterized in that, The polycondensation in step (C) is carried out under a pressure of 0~100 Pa; Preferably, the temperature of the melt polycondensation is 255~280℃, and the reaction is stopped when the reaction torque reaches 25~35 N•m.

8. The isosorbide-based copolyester obtained by the preparation method according to any one of claims 1 to 7.

9. The isosorbide-based copolyester according to claim 8, characterized in that, The isosorbide-based copolyester retains 83-91% of the isosorbide structure and has a glass transition temperature of 96-109℃.

10. The use of an isosorbide-based copolyester according to claim 8 or 9 in the preparation of polymeric material articles.

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