Degradable copolyester, monomer used by degradable copolyester and preparation method of monomer

Abstract

The invention relates to a degradable copolyester, a monomer used by the degradable copolyester and a preparation method of the monomer, and the preparation method of the monomer comprises the following steps: adding protonic acid, halide and a compound as shown in a formula (1) into an organic solvent, carrying out heating reaction under a protective atmosphere, and after the reaction is finished, separating to obtain an intermediate product as shown in a formula (2); and adding the intermediate product, an alkaline compound, a transition metal catalyst and a phosphine ligand into a solvent, introducing CO, carrying out a heating reaction, and after the reaction is finished, carrying out separation to obtain the monomer as shown in a formula (3). According to the method, the monomer based on the terephthalic acid and propyl alcohol ester and shown in the formula (3) can be obtained through the halogenation reaction and the carbonyl insertion reaction, the raw materials used in the reaction are low in cost and safe, the reaction conversion rate, selectivity and stability are high, and the product is easy to purify and separate.

Description

Technical Field

[0001] This invention relates to the field of polyester materials technology, and in particular to biodegradable copolyesters, the monomers used therein, and methods for preparing the monomers. Background Technology

[0002] Polyesters are a class of polymeric materials formed by the condensation polymerization of polyols and polyacids. Among them, aromatic polyesters, represented by polyethylene terephthalate (PET), polypropylene terephthalate (PTT), and polybutylene terephthalate (PBT), are widely used in fields such as chemical fibers due to their excellent properties. However, these polyester materials are difficult to degrade in the natural environment, and the large amount of waste they produce puts enormous pressure on the ecological environment.

[0003] To address the aforementioned issues, improving the degradation performance of polyester materials through molecular structure design has become an important research direction. Control methods mainly include enhancing the hydrophilicity of polymer chains, lowering their glass transition temperature, and introducing biodegradable segments. Currently, by introducing aliphatic biodegradable units into aromatic polyesters, materials combining usability and degradation properties have been successfully developed, such as polybutylene terephthalate (PBAT), which has been industrially produced. Among the many aliphatic units that can be introduced, glycolic acid has attracted widespread attention due to its excellent biodegradability and molecular structural flexibility. However, glycolic acid has poor thermal stability and is prone to side reactions such as "ester chain scission" during high-temperature polymerization, resulting in low utilization in actual polymerization.

[0004] To incorporate biodegradable units such as glycolic acid into polyester chains, various methods for synthesizing the corresponding comonomers have been developed. These methods are typically based on the reaction of terephthalic acid or its derivatives with hydroxyl-containing carboxylic acids, but they generally suffer from significant drawbacks: for example, the need for stoichiometric strong oxidants, the use of highly toxic or expensive reagents, and the requirement to add large amounts of acid-binding agents to neutralize the acidic byproducts generated in the reaction. These factors result in poor economic efficiency of the synthetic routes, complex post-processing purification, and the generation of large amounts of waste, limiting their practical application. Summary of the Invention

[0005] Therefore, it is necessary to provide a biodegradable copolyester, its monomers, and a method for preparing the monomers, in order to address the above problems. The method for preparing the monomers is economical, efficient, environmentally friendly, and the products are easy to purify and separate.

[0006] A method for preparing a biodegradable copolyester monomer includes the following steps:

[0007] A protic acid, a halide, and the compound shown in formula (1) are added to an organic solvent and heated under a protective atmosphere. After the reaction is completed, the intermediate product shown in formula (2) is obtained by separation.

[0008] , ;

[0009] The intermediate product, basic compound, transition metal catalyst and phosphine ligand are added to a solvent and CO is introduced to carry out the heating reaction. After the reaction is completed, the monomer shown in formula (3) is separated.

[0010] ;

[0011] Wherein, R1 is selected from -COOH or -COOCH2CH2OH, R2 is selected from -COOH or -COOCH2CH2X, R3 is selected from -COOH or -COOCH2CH2COOR', X is selected from halogen atoms, and R' is selected from H, alkyl or benzyl.

[0012] In one embodiment, the step of adding the protic acid, halide, and compound of formula (1) to the organic solvent satisfies at least one of the following conditions:

[0013] (1) The protic acid is selected from at least one of acetic acid, trifluoroacetic acid, trifluoromethanesulfonic acid, p-toluenesulfonic acid, hydrochloric acid, sulfuric acid, and phosphoric acid;

[0014] (2) The halide is selected from iodides, and the iodide is selected from at least one of potassium iodide, sodium iodide, lithium iodide, ammonium iodide, and hydroiodic acid;

[0015] (3) The organic solvent is selected from at least one of ethyl acetate, propyl acetate, butyl acetate, γ-valerolactone, dichloromethane, chloroform, dioxane, tetrahydrofuran, 2-methyltetrahydrofuran, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, acetone, cyclohexanone, acetonitrile, tert-valeronitrile, benzonitrile, toluene, benzene, DMF, and DMSO;

[0016] (4) The molar ratio of the compound represented by formula (1) to the protic acid is 1:1~6;

[0017] (5) The molar ratio of the compound shown in formula (1) to the halide is 1:1~4.

[0018] In one embodiment, the step of carrying out the heating reaction under a protective atmosphere satisfies at least one of the following conditions:

[0019] (1) The temperature for heating the reaction is 60℃~150℃;

[0020] (2) The heating reaction time is 1h~8h;

[0021] (3) The protective atmosphere is selected from at least one of nitrogen and argon.

[0022] In one embodiment, the step of adding the intermediate product, the basic compound, the transition metal catalyst, and the phosphine ligand to the solvent satisfies at least one of the following conditions:

[0023] (1) The alkaline compound is selected from at least one of potassium carbonate, sodium carbonate, lithium carbonate, ammonium carbonate, sodium methoxide, sodium ethoxide, sodium tert-butoxide, potassium phosphate, sodium phosphate, lithium phosphate, and ammonia water;

[0024] (2) The transition metal catalyst is selected from at least one of Rh(acac)(CO)2, Rh(cod)2BF4, [Rh(cod)Cl]2, Rh(PPh3)3Cl, rhodium triiodide, and rhodium trichloride;

[0025] (3) The phosphine ligand is selected from compounds with the structural formula shown in formula (4) or formula (5);

[0026] , ;

[0027] Wherein, R is selected from at least one of H, methyl, isopropyl, phenyl, tert-butyl, and methoxy;

[0028] (4) The solvent is selected from at least one of water, acetic acid, and alcohol solvents;

[0029] (5) The mass ratio of the intermediate product to the transition metal catalyst is 100~10000:1;

[0030] (6) The molar ratio of the phosphine ligand to the transition metal catalyst is 1~100:1;

[0031] (7) The molar ratio of the intermediate product to the basic compound is 1:1 to 4.

[0032] In one embodiment, the step of introducing CO gas to carry out the heating reaction satisfies at least one of the following conditions:

[0033] (1) The pressure of the heating reaction is 3MPa~6MPa;

[0034] (2) The temperature of the heating reaction is 70℃~130℃;

[0035] (3) The heating reaction time is 2h~12h.

[0036] In one embodiment, the step of separating the intermediate product shown in formula (2) after the reaction is completed includes: after the reaction is completed, water is added to the reaction solution, the crude product is filtered to obtain the crude product, and then the crude product is added to a recrystallization solvent for cooling and recrystallization to obtain the intermediate product.

[0037] In one embodiment, the step of separating the monomer shown in formula (3) after the reaction is completed includes: after the reaction is completed, water and organic solvent are added to the reaction solution in sequence, and an aqueous phase and an organic phase are obtained after separation. Then, a halide is obtained from the aqueous phase and the monomer shown in formula (3) is obtained from the organic phase.

[0038] In one embodiment, the halide is recycled to prepare the intermediate product shown in formula (2).

[0039] A biodegradable copolyester monomer obtained by the preparation method described above.

[0040] A biodegradable copolyester prepared using the aforementioned monomer.

[0041] In the preparation method of this invention, the monomer based on terephthalic acid and propanol esterification, as shown in formula (3), can be obtained through halogenation and carbonyl insertion reactions. This method not only uses low-cost and safe raw materials, but also exhibits high reaction conversion rate, selectivity, and stability, and the product is easy to purify and separate. Furthermore, the biodegradable copolyester prepared using the monomer has excellent degradation performance. Attached Figure Description

[0042] To more clearly illustrate the technical solutions in the embodiments of this application or the conventional technology, the drawings used in the description of the embodiments or the conventional technology will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0043] Figure 1 The liquid chromatogram of the BHET iodide obtained in Example 1;

[0044] Figure 2 The 1H NMR spectrum of the BHET iodide obtained in Example 1;

[0045] Figure 3 The liquid chromatogram of the monomer obtained in Example 1;

[0046] Figure 4 The image shows the hydrogen nuclear magnetic resonance spectrum of the monomer obtained in Example 1. Detailed Implementation

[0047] To facilitate understanding of the present invention, it will be described in more detail below. However, it should be understood that the present invention can be implemented in many different forms and is not limited to the embodiments or examples described herein. Rather, these embodiments or examples are provided to make the disclosure of the present invention more thorough and complete.

[0048] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments or examples only and is not intended to limit the invention. The optional scope of the term "and / or" as used herein includes any one of two or more of the related listed items, as well as any and all combinations of the related listed items, including any two related listed items, any more related listed items, or a combination of all related listed items.

[0049] In this invention, numerical ranges are involved. Unless otherwise specified, the numerical ranges are considered continuous and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe features or characteristics, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are included.

[0050] The method for preparing biodegradable copolyester monomers provided by the present invention includes the following steps:

[0051] S1, add protic acid, halide and compound of formula (1) into organic solvent, heat the reaction under protective atmosphere, and separate the intermediate product of formula (2) after the reaction is completed;

[0052] S2, the intermediate product, basic compound, transition metal catalyst and phosphine ligand are added to the solvent and CO is introduced to carry out the heating reaction. After the reaction is completed, the monomer shown in formula (3) is separated.

[0053] Specifically, the compounds represented by formula (1) and formula (2) are as follows:

[0054] , .

[0055] In formula (1), R1 is selected from -COOH or -COOCH2CH2OH. When R1 is selected from -COOCH2CH2OH, the compound shown in formula (1) is bis(hydroxyethyl) terephthalate (BHET). BHET can be obtained by esterification reaction of terephthalic acid (PTA) and ethylene glycol (EG), or it can be obtained by recycling waste textiles, etc. It is preferred to use BHET obtained by recycling waste textiles, etc., so as to realize the resource utilization and recycling of raw materials.

[0056] It can be understood that R2 in equation (2) is related to R1. When R1 is selected from -COOH, R2 is also -COOH. When R1 is selected from -COOCH2CH2OH, R2 is -COOCH2CH2X, where X is a halogen atom.

[0057] In step S1, in order to better promote the reaction, the protic acid is preferably at least one of acetic acid, trifluoroacetic acid, trifluoromethanesulfonic acid, p-toluenesulfonic acid, hydrochloric acid, sulfuric acid, and phosphoric acid, and preferably the molar ratio of the compound shown in formula (1) to the protic acid is 1:1 to 6, such as 1:1, 1:2, 1:3, 1:4, 1:5 or 1:6, and more preferably 1:1 to 3.

[0058] It is understood that the halides include iodides, chlorides, bromides, and fluorides, all of which are inorganic compounds. To promote the reaction more efficiently, the halides are preferably iodides, and the iodides are selected from at least one of potassium iodide, sodium iodide, lithium iodide, ammonium iodide, and hydroiodic acid. Furthermore, the molar ratio of the compound shown in formula (1) to the halides is preferably 1:1 to 4, for example, 1:1, 1:2, 1:3, or 1:4, and more preferably 1:2 to 3.

[0059] The present invention does not limit the organic solvent used in step S1, and it can be selected from at least one of ethyl acetate, propyl acetate, butyl acetate, γ-valerolactone, dichloromethane, chloroform, dioxane, tetrahydrofuran, 2-methyltetrahydrofuran, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, acetone, cyclohexanone, acetonitrile, tert-valeronitrile, benzonitrile, toluene, benzene, DMF, and DMSO.

[0060] Taking BHET, sodium iodide, and sulfuric acid as examples, the reaction process under a protective atmosphere during heating is as follows:

[0061]

[0062] It is understood that the protective atmosphere during the heating reaction can be selected from nitrogen, argon, etc., and there are no specific requirements. In order to better promote the reaction, the preferred heating temperature is 60℃~150℃, such as 60℃, 70℃, 80℃, 90℃, 100℃, 110℃, 120℃, 130℃, 140℃ or 150℃, etc., and the preferred heating time is 1h~8h, such as 1h, 2h, 3h, 4h, 5h, 6h, 7h or 8h, etc.

[0063] In some embodiments, the step of separating the intermediate product shown in formula (2) after the reaction is completed includes: after the reaction is completed, adding water to the reaction solution, filtering to obtain a crude product, and then adding the crude product to a recrystallization solvent for cooling and recrystallization to obtain the intermediate product.

[0064] The recrystallization solvent is selected from at least one of ethyl acetate, propyl acetate, butyl acetate, dichloromethane, chloroform, dioxane, tetrahydrofuran, acetonitrile, tert-valerate, benzonitrile, acetone, methanol, ethanol, and isopropanol. The cooling rate of the cooling recrystallization is preferably 1℃ / h to 25℃ / h, more preferably 5℃ / h to 20℃ / h. The starting temperature is preferably lower than the boiling point of the recrystallization solvent, more preferably 5℃ to 10℃ lower than the boiling point of the recrystallization solvent. The ending temperature is preferably 0℃ to 40℃, more preferably 0℃ to 10℃. After completing the cooling recrystallization step, the obtained solid components are washed with a crystallization solvent at 0℃ to 10℃.

[0065] Specifically, the compounds represented by formula (3) are as follows:

[0066] .

[0067] It can be understood that R3 in formula (3) is related to R2. When R2 is selected from -COOH, R3 is also -COOH. When R2 is selected from -COOCH2CH2X, R3 is -COOCH2CH2COOR', and R' is selected from H, alkyl or benzyl.

[0068] In step S2, the alkaline compound is preferably selected from at least one of potassium carbonate, sodium carbonate, lithium carbonate, ammonium carbonate, sodium methoxide, sodium ethoxide, sodium tert-butoxide, potassium phosphate, sodium phosphate, lithium phosphate, and ammonia water. Furthermore, the molar ratio of the intermediate product to the alkaline compound is preferably 1:1 to 4, for example, 1:1, 1:2, 1:3, or 1:4, and more preferably 1:1 to 1:2.

[0069] In this invention, the transition metal catalyst can be selected from noble metal catalysts, and more preferably from rhodium catalysts, specifically at least one of Rh(acac)(CO)2, Rh(cod)2BF4, [Rh(cod)Cl]2, Rh(PPh3)3Cl, rhodium triiodide, and rhodium trichloride. Preferably, the mass ratio of the intermediate product to the transition metal catalyst is 100~10000:1, for example, 100:1, 200:1, 300:1, 400:1, 500:1, 600:1, 700:1, 800:1, 900:1, 1000:1, 2000:1, 3000:1, 4000:1, 5000:1, 6000:1, 7000:1, 8000:1, 9000:1, or 10000:1.

[0070] In some embodiments, the phosphine ligand is selected from compounds with the structural formulas shown in formula (4) or (5);

[0071] , ;

[0072] Wherein, R is selected from at least one of H, methyl, isopropyl, phenyl, tert-butyl, and methoxy. Preferably, the molar ratio of the phosphine ligand to the transition metal catalyst is 1 to 100:1, for example, 1:1, 5:1, 10:1, 20:1, 30:1, 40:1, 50:1, 60:1, 70:1, 80:1, 90:1, or 100:1.

[0073] In some embodiments, the solvent is selected from at least one of water, acetic acid, and alcohol solvents, preferably an alcohol solvent, and more preferably an alcohol solvent such as methanol, ethanol, isopropanol, tert-butanol, or benzyl alcohol.

[0074] Specifically, taking iodo-BHET, a basic compound selected from sodium carbonate, and a solvent selected from methanol as an example, the reaction process during heating with CO is as follows:

[0075]

[0076] Thus, when the solvent is selected from water and acetic acid, R' is -H; when the solvent is selected from aliphatic alcohol solvents such as methanol and ethanol, R' is alkyl such as methyl or ethyl; and when the solvent is selected from aromatic alcohol solvents such as benzyl alcohol, R' is benzyl.

[0077] To promote a more efficient reaction, in some embodiments, the heating pressure is preferably 3MPa to 6MPa, such as 3MPa, 4MPa, 5MPa or 6MPa, the heating temperature is preferably 70℃ to 130℃, such as 70℃, 80℃, 90℃, 100℃, 110℃, 120℃ or 130℃, and the heating time is preferably 2h to 12h, such as 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h or 12h.

[0078] In some embodiments, the step of separating the monomer shown in formula (3) after the reaction is completed includes: after the reaction is completed, water and an organic solvent are added sequentially to the reaction solution, and an aqueous phase and an organic phase are obtained after separation. Then, a halide is obtained from the aqueous phase and the monomer shown in formula (3) is obtained from the organic phase.

[0079] The halide can be obtained from the aqueous phase by concentration and cooling crystallization. The halide obtained can be purified and recycled to prepare the intermediate product shown in formula (2), thereby reducing costs.

[0080] The method for obtaining the monomer shown in formula (3) from the organic phase includes: first removing the organic solvent from the organic phase by means of drying to obtain a crude product, then dissolving the crude product in a solvent, and then cooling and crystallizing to obtain the monomer. The solvent is selected from toluene, benzene, n-hexane, cyclohexane, ethyl acetate, acetonitrile, etc. The cooling rate for crystallization is preferably 1℃ / h to 25℃ / h, more preferably 5℃ / h to 20℃ / h. The starting temperature is preferably lower than the boiling point of the recrystallization solvent, more preferably 5℃ to 10℃ lower than the boiling point of the recrystallization solvent. The ending temperature is preferably -10℃ to 40℃, more preferably -5℃ to 5℃. After completing the cooling and recrystallization step, the obtained solid component is washed with a crystallization solvent at approximately 0℃.

[0081] Therefore, the present invention can obtain the monomer based on terephthalic acid and propanol esters as shown in formula (3) through only the halogenation reaction in step S1 and the carbonyl insertion reaction in step S2. Not only are the raw materials used in the reaction low-cost and safe, but the reaction conversion rate, selectivity and stability are also high, and the product is easy to purify and separate.

[0082] The present invention also provides a monomer for a biodegradable copolyester obtained by the preparation method described above.

[0083] In addition, the present invention also provides a biodegradable copolyester prepared using the aforementioned monomer, wherein the biodegradable copolyester has excellent degradation performance.

[0084] The technical solution of the present invention will be further described below through specific embodiments. However, those skilled in the art will understand that the following embodiments are only for illustrating the present invention and should not be regarded as limiting the scope of the present invention. Unless otherwise specified, specific conditions in the embodiments are performed under conventional conditions or conditions recommended by the manufacturer. Reagents or instruments used without specified manufacturers are all commercially available conventional products.

[0085] Example 1

[0086] Under nitrogen protection, 25 g of BHET, 200 mL of dioxane, 30 g of sodium iodide, and 15 mL of phosphoric acid were added to a 500 mL three-necked flask equipped with a reflux condenser. After the addition was complete, the flask was placed at 100 °C and reacted for 4 hours. The flask was then cooled to room temperature, and the reaction solution was poured into a 1000 mL flask. Approximately 500 mL of deionized water was added, and the mixture was cooled thoroughly in an ice-water bath. After sufficient solid was precipitated, solid-liquid separation and filtration were performed. The resulting filter cake was washed with ice water and dried to obtain the crude product.

[0087] The dried crude product was transferred to a 500 mL crystallizer, and about 250 g of acetonitrile was added. The temperature was rapidly raised to 60 °C. After the crude product was completely dissolved, the temperature was lowered to 0 °C at a rate of 20 °C / h to crystallize. The product was then filtered, and the resulting filter cake was washed and dried to obtain the intermediate product.

[0088] After analysis and testing, such as Figure 1 and Figure 2 As shown, the intermediate product is BHET iodide. The conversion rate of the iodination reaction is greater than 99%, the selectivity is 92%, and after purification, the purity of BHET iodide is greater than 97%, and the separation yield is 85%.

[0089] In a 100 mL high-pressure reactor, 2.34 g of purified BHET iodide, 6 mg of Rh(acac)(CO)₂, 22 mg of triphenylphosphine, 1.06 g of sodium carbonate, and 30 mL of anhydrous methanol were added sequentially. The reactor was sealed, and CO was introduced into the reactor for three gas replacement cycles. The pressure inside the reactor was then maintained at 4 MPa, and the reaction was stirred at 100 °C for 4 hours. The reactor was then thoroughly cooled to room temperature, and the gas was slowly released to atmospheric pressure. The reaction solution was transferred to a separatory funnel, and a small amount of deionized water was added to dissolve the solid salts in the system. Then, approximately 30 mL of toluene was added, and the mixture was shaken and allowed to stand for separation. The toluene phase was collected, and the toluene solvent was removed by drying to obtain the crude product. The aqueous phase was concentrated and cooled to crystallize, yielding crude sodium iodide, which, after purification, can be directly recycled for the BHET iodination reaction.

[0090] The crude product was then transferred to a 100 mL crystallizer, an appropriate amount of anhydrous toluene was added, and the temperature was rapidly raised to 80 °C. After the solid was completely dissolved, the temperature was lowered to 0 °C at a rate of 20 °C / h for crystallization. The product was then filtered, and the resulting filter cake was washed and dried to obtain the purified monomer.

[0091] After analysis and testing, such as Figure 3 and Figure 4 As shown, the monomer is an esterification of terephthalic acid and methyl propionate. The conversion rate of the carbonyl insertion reaction is greater than 99%, the selectivity is 90%, and after purification, the purity of the monomer is greater than 98%, and the separation yield is 80%.

[0092] Example 2

[0093] The only difference between Example 2 and Example 1 is that the solvent for the iodination reaction is replaced with acetonitrile instead of dioxane.

[0094] Final analysis showed that the conversion rate of the iodination reaction was greater than 99% and the selectivity was 87%, while the conversion rate of the carbonyl insertion reaction was greater than 99% and the selectivity was 90%. After purification, the purity of the monomer was greater than 98%, and the separation yield was 80%.

[0095] Example 3

[0096] The only difference between Example 3 and Example 1 is that the solvent for the carbonyl insertion reaction is replaced with ethanol instead of methanol.

[0097] Final analysis showed that the conversion rate of the iodination reaction was greater than 99% and the selectivity was 92%, while the conversion rate of the carbonyl insertion reaction was greater than 99% and the selectivity was 86%. After purification, the purity of the monomer was greater than 98%, and the separation yield was 78%.

[0098] Example 4

[0099] The only difference between Example 4 and Example 1 is that the iodinated product of the iodination reaction is replaced with ammonium iodide instead of sodium iodide.

[0100] Final analysis showed that the conversion rate of the iodination reaction was greater than 99% and the selectivity was 80%, while the conversion rate of the carbonyl insertion reaction was greater than 99% and the selectivity was 89%. After purification, the purity of the monomer was greater than 98%, and the separation yield was 78%.

[0101] Example 5

[0102] The only difference between Example 5 and Example 1 is that the acid auxiliary agent in the iodination reaction is replaced by sulfuric acid instead of phosphoric acid.

[0103] Final analysis showed that the conversion rate of the iodination reaction was greater than 99% and the selectivity was 75%, while the conversion rate of the carbonyl insertion reaction was greater than 99% and the selectivity was 90%. After purification, the purity of the monomer was greater than 98%, and the separation yield was 80%.

[0104] Example 6

[0105] The only difference between Example 6 and Example 1 is that the solvent for the carbonylation reaction is replaced with water instead of methanol. The final product obtained in formula (3) has R' as H.

[0106] Final analysis showed that the conversion rate of the iodination reaction was greater than 99% and the selectivity was 92%, while the conversion rate of the carbonyl insertion reaction was 80% and the selectivity was 90%. After purification, the purity of the monomer was greater than 97% and the separation yield was 63%.

[0107] Example 7

[0108] The only difference between Example 7 and Example 1 is that the solvent for the carbonylation reaction is replaced with benzyl alcohol instead of methanol. Therefore, R' in the final formula (3) represents the benzyl product.

[0109] Final analysis showed that the conversion rate of the iodination reaction was greater than 99% and the selectivity was 92%, while the conversion rate of the carbonyl insertion reaction was greater than 99% and the selectivity was 89%. After purification, the purity of the monomer was greater than 98%, and the separation yield was 78%.

[0110] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0111] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing a monomer for a biodegradable copolyester, characterized in that, Includes the following steps: A protic acid, a halide, and the compound shown in formula (1) are added to an organic solvent and heated under a protective atmosphere. After the reaction is completed, the intermediate product shown in formula (2) is obtained by separation. 、 ； The intermediate product, basic compound, transition metal catalyst and phosphine ligand are added to a solvent and CO is introduced to carry out the heating reaction. After the reaction is completed, the monomer shown in formula (3) is separated. ； Wherein, R1 is selected from -COOH or -COOCH2CH2OH, R2 is selected from -COOH or -COOCH2CH2X, R3 is selected from -COOH or -COOCH2CH2COOR', X is selected from halogen atoms, and R' is selected from H, alkyl or benzyl.

2. The method for preparing the monomer for biodegradable copolyester according to claim 1, characterized in that, The step of adding a protic acid, a halide, and a compound of formula (1) to an organic solvent satisfies at least one of the following conditions: (1) The protic acid is selected from at least one of acetic acid, trifluoroacetic acid, trifluoromethanesulfonic acid, p-toluenesulfonic acid, hydrochloric acid, sulfuric acid, and phosphoric acid; (2) The halide is selected from iodides, and the iodide is selected from at least one of potassium iodide, sodium iodide, lithium iodide, ammonium iodide, and hydroiodic acid; (3) The organic solvent is selected from at least one of ethyl acetate, propyl acetate, butyl acetate, γ-valerolactone, dichloromethane, chloroform, dioxane, tetrahydrofuran, 2-methyltetrahydrofuran, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, acetone, cyclohexanone, acetonitrile, tert-valeronitrile, benzonitrile, toluene, benzene, DMF, and DMSO; (4) The molar ratio of the compound represented by formula (1) to the protic acid is 1:1~6; (5) The molar ratio of the compound shown in formula (1) to the halide is 1:1~4.

3. The method for preparing the monomer for biodegradable copolyester according to claim 1, characterized in that, The heating reaction step carried out under a protective atmosphere satisfies at least one of the following conditions: (1) The temperature for heating the reaction is 60℃~150℃; (2) The heating reaction time is 1h~8h; (3) The protective atmosphere is selected from at least one of nitrogen and argon.

4. The method for preparing the biodegradable copolyester monomer according to claim 1, characterized in that, The step of adding the intermediate product, basic compound, transition metal catalyst, and phosphine ligand to the solvent satisfies at least one of the following conditions: (1) The alkaline compound is selected from at least one of potassium carbonate, sodium carbonate, lithium carbonate, ammonium carbonate, sodium methoxide, sodium ethoxide, sodium tert-butoxide, potassium phosphate, sodium phosphate, lithium phosphate, and ammonia water; (2) The transition metal catalyst is selected from at least one of Rh(acac)(CO)2, Rh(cod)2BF4, [Rh(cod)Cl]2, Rh(PPh3)3Cl, rhodium triiodide, and rhodium trichloride; (3) The phosphine ligand is selected from compounds with the structural formula shown in formula (4) or formula (5); 、 ； Wherein, R is selected from at least one of H, methyl, isopropyl, phenyl, tert-butyl, and methoxy; (4) The solvent is selected from at least one of water, acetic acid, and alcohol solvents; (5) The mass ratio of the intermediate product to the transition metal catalyst is 100~10000:1; (6) The molar ratio of the phosphine ligand to the transition metal catalyst is 1~100:1; (7) The molar ratio of the intermediate product to the basic compound is 1:1 to 4.

5. The method for preparing the monomer for biodegradable copolyester according to claim 1, characterized in that, The step of introducing CO gas and heating the reaction satisfies at least one of the following conditions: (1) The pressure of the heating reaction is 3MPa~6MPa; (2) The temperature of the heating reaction is 70℃~130℃; (3) The heating reaction time is 2h~12h.

6. The method for preparing the monomer for the biodegradable copolyester according to any one of claims 1 to 5, characterized in that, The steps to separate the intermediate product shown in formula (2) after the reaction are completed include: after the reaction is completed, water is added to the reaction solution, the crude product is filtered to obtain the crude product, and then the crude product is added to a recrystallization solvent for cooling and recrystallization to obtain the intermediate product.

7. The method for preparing the monomer for the biodegradable copolyester according to any one of claims 1 to 5, characterized in that, The steps for separating the monomer shown in formula (3) after the reaction are completed include: after the reaction is completed, water and organic solvent are added to the reaction solution in sequence, and the aqueous phase and organic phase are obtained after separation. Then, the halide is obtained from the aqueous phase and the monomer shown in formula (3) is obtained from the organic phase.

8. The method for preparing the monomer for biodegradable copolyester according to claim 7, characterized in that, The halide recycling is used to prepare the intermediate product shown in formula (2).

9. A monomer for a biodegradable copolyester obtained by the preparation method according to any one of claims 1 to 8.

10. A biodegradable copolyester prepared using the monomer described in claim 9.

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