Butenediol-based bio-based polyester and preparation method thereof

Abstract

The invention discloses butenediol-based bio-polyester and a preparation method thereof, and relates to the technical field of high polymer materials. According to the invention, 3, 4-butylene glycol is adopted as a double bond donor, and the structural formula is shown in the specification, so that the risk of gelation in the high-temperature polycondensation process can be effectively reduced, and a relatively controllable cross-linking rate can be realized in the cross-linking process. Compared with itaconic acid-based polyester, the synthesized polyester elastomer has higher relative molecular mass and narrower molecular weight distribution, and the molecular weight distribution value is about 2.0 and is close to the level of saturated polyester plastic. Besides, isomerized 3, 4-butylene glycol is selected to replace traditional 1, 4-butylene glycol, and the crystal structure of a polyester molecular chain can be destroyed when only 5 wt% of 3, 4-butylene glycol is used, so that the polyester elastomer is obtained. The innovation not only improves the heat resistance of the polyester, but also significantly reduces the glass transition temperature, thereby effectively reducing the overall cost.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, in particular to a novel butene glycol-based bio-based polyester elastomer and a preparation method thereof. Background Art

[0002] Polyester, as a biodegradable polymer, is widely used in the field of polymer materials, but its application in the rubber field remains limited. In recent years, with the advent of "bio-based engineered elastomers," many new polyester materials have been gradually developed, especially polyester elastomers synthesized from bio-based raw materials. Despite this, existing polyester elastomers still face some challenges, such as insufficient control of crosslinking degree and a wide molecular weight distribution. In particular, when using itaconic acid as a double bond donor, due to its high double bond activity, side reactions are prone to occur, resulting in large fluctuations in product performance.

[0003] 3,4-Butenediol (3,4-BDO) is a bio-based diol with double bonds and hydroxyl functional groups. It can be efficiently synthesized through biofermentation or plant-based feedstock. Its unique molecular structure (such as the unsaturated double bond) can impart dynamic cross-linking capabilities and functional modification potential to polyester chains. However, its use as a primary monomer in polyester synthesis has not been systematically studied.

[0004] Current research attempts to construct polyester elastomer systems by introducing bio-based monomers such as itaconic acid or butenediol to achieve a balance between material reproducibility and performance. Patent CN101450985A utilizes the double bond properties of itaconic acid to construct polyester elastomers. While these systems exhibit a certain degree of reactivity and structural diversity, the high reactivity of the double bond in itaconic acid easily induces gelation during the polycondensation process, leading to uncontrollable molecular structures. Furthermore, the product of this system has a broad molecular weight distribution. Subsequent crosslinking with peroxides, due to the limited dosage of the crosslinking agent and the rapid reaction rate, further exacerbates the problems of insufficient crosslinking uniformity and poor structural stability.

[0005] In contrast, CN113136027A discloses a bio-based polyester synthesis route with 1,4-butenediol as the core building block, relying on a high-temperature polycondensation process to complete esterification and polymerization reactions under the action of catalysts and auxiliary additives. This method has advantages in terms of synthesis efficiency and molecular structure control. The resulting material has a narrow molecular weight distribution and a high degree of polymerization, and has a good mechanical basis. However, this technical solution is relatively complex in terms of the raw material system and the synthesis cost is high. At the same time, its research focus is on the construction path and feasibility verification of the elastomer, and no structural optimization design is given to improve the performance of the material in a low-temperature environment.

[0006] In summary, to achieve a synergistic breakthrough between the functional performance and green sustainability of bio-based polyester elastomers, it is urgent to develop a new type of butenediol-based polyester elastomer. This material should not only have excellent low-temperature resistance and biodegradability, but also possess good rubber processability to expand its practical application boundaries in low-temperature environments and fill a key gap in the existing technology system. Summary of the Invention

[0007] In order to solve the problems in the prior art, the present invention provides a butene glycol-based bio-based polyester elastomer and a preparation method thereof.

[0008] The purpose of the present invention is to provide a preparation method for a novel butene glycol-based bio-based polyester elastomer to solve the technical problems of existing polyester elastomer materials, especially itaconic acid-based polyesters, such as easy gelation during the polycondensation stage, wide molecular weight distribution, and poor cross-linking controllability.

[0009] The present invention selects 3,4-butenediol with highly stable non-conjugated double bonds as the double bond donor, ensuring that the polyester elastomer has a low gel risk during high-temperature polycondensation and a relatively controllable crosslinking speed during crosslinking.

[0010] One of the objects of the present invention is to provide a novel butene glycol-based bio-based polyester elastomer.

[0011]

[0012] The structure of the novel butene glycol-based polyester elastomer is shown below:

[0013] The total number of moles of each polymer unit in the structural formula is 1;

[0014] a, b, c, d are each 0 to 0.5 mole fractions; a, b, c, d are not all 0; preferably, a and b are 0, and at least one of c and d is not 0, the mole fraction of c is 0.01 to 0.5, preferably 0.1 to 0.5, and the mole fraction of d is 0.01 to 0.5, preferably 0.1 to 0.5;

[0015] u, v, w, j are respectively 0 to 0.5 mole fractions; u, v, w, j are not all 0; preferably, u is not 0, and one of v, w, and j is not 0, the mole fraction of u is 0.01 to 0.5, preferably 0.15 to 0.45, and the mole fraction of v+w+j is 0.01 to 0.5, preferably 0.05 to 0.15;

[0016] x is 0 to 0.5 mole fraction and x is not 0, the mole fraction of x is 0.05 to 0.2, more preferably 0.05 to 0.1;

[0017] In a preferred embodiment of the present invention;

[0018] The bio-based polyester elastomer of the present invention is prepared by polycondensation reaction of raw materials including dibasic acid, diol, polymerization inhibitor, antioxidant and catalyst; wherein,

[0019] Preferred dibasic acids are 1,4-butanedioic acid, 1,6-hexanedioic acid, 1,7-pimelic acid or 1,10-decanedioic acid.

[0020] As for diols, at least two of 3,4-butene glycol, ethylene glycol, 1,3-propylene glycol, 1,4-butanediol, and 1,5-pentanediol are selected, and a butene glycol monomer must be included.

[0021] In a preferred embodiment of the present invention;

[0022] The polymerization inhibitor may be a phenolic compound, specifically one or both of hydroquinone and 4-methoxyphenol.

[0023] The antioxidant may be phosphoric acid and / or phosphorous acid compounds, specifically one or both of phosphoric acid and phosphorous acid.

[0024] The catalyst can be a titanium-based catalyst, an organic tin catalyst and a solution thereof, specifically including one or two of tetrabutyl titanate and stannous octoate.

[0025] In a preferred embodiment of the present invention,

[0026] The molar ratio of diol to dibasic acid is (1.02-1.8):1; preferably (1.2-1.4):1;

[0027] The mass of the polymerization inhibitor is 0.01 to 0.2% of the total mass of the materials added to the reaction; preferably 0.01 to 0.08%;

[0028] The mass of the antioxidant is 0.01-0.2% of the total mass of the materials added to the reaction; preferably 0.01-0.05%;

[0029] The mass of the catalyst is 0.05% to 1% of the total mass of the materials added to the reaction, preferably 0.1 to 0.5%.

[0030] A second object of the present invention is to provide a method for preparing a novel butene glycol-based bio-based polyester elastomer, comprising the following steps:

[0031] (1) adding the dibasic acid, polymerization inhibitor, and antioxidant into the reactor according to the amounts described;

[0032] (2) adding diol under the protection of nitrogen to carry out esterification reaction;

[0033] (3) After the esterification is completed, a catalyst is added to carry out a polycondensation reaction to obtain the bio-based polyester elastomer.

[0034] In a preferred embodiment of the present invention, in step (1), a reactor equipped with a stainless steel stirrer, a nitrogen inlet, and a condenser is selected. A dibasic acid is added to the reactor, and a polymerization inhibitor and an antioxidant are weighed and added to the reactor. To prevent reactant powder from being carried away by airflow during subsequent operations, the reactants are lightly compacted.

[0035] In a preferred embodiment of the present invention, in step (2), the esterification reaction is heated; before heating, the system is first evacuated to a negative pressure on the gauge, maintained for 2 minutes, and then nitrogen is introduced until the vacuum gauge returns to zero; the above evacuation-nitrogen introduction steps are repeated at least 3 times to ensure that no oxygen remains in the reactor. After the deoxygenation treatment is completed, the diol is added under nitrogen countercurrent protection. The reaction system is heated and maintained under nitrogen atmosphere protection; the oil bath temperature is raised to 180°C and the reaction is carried out for 1 hour to allow the reactants to fully melt and initiate esterification; the temperature is then raised to 200°C and the reaction is continued for 2 hours, and then the temperature is raised to 210°C and the reaction is carried out for 1 hour.

[0036] In a preferred embodiment of the present invention, in step (3), after the esterification reaction is completed, a catalyst is added, and then the nitrogen is turned off and the vacuum is evacuated to -0.01atm to carry out a polycondensation reaction at a temperature of 220-235°C for 8-15 hours; when stirring is performed at a stirring rate of 30rpm, an obvious climbing pole effect (Weissenberg) appears, indicating that the reaction is complete; the heat source is turned off, and the vacuum state is continued to be maintained. The reaction is terminated after the reactor is naturally cooled, and the target polyester elastomer product is finally obtained.

[0037] The third object of the present invention is to provide a bio-based polyester elastomer prepared by the above method.

[0038] The present invention can specifically adopt the following technical solutions: In a preferred embodiment of the present invention,

[0039] During the polymerization step, a four-necked round-bottom flask equipped with a stainless steel stirrer, nitrogen inlet, and condenser was used as the reactor. The dibasic acid was added to the reactor, and 4-methoxyphenol and an aqueous phosphorous acid solution were weighed and added to the reactor using a pipette to act as a free radical inhibitor. The reactants were then gently compacted with a glass rod to prevent the reactant powder from being carried away by the airflow during the subsequent vacuum and nitrogen flow.

[0040] Before the esterification reaction, the system was pumped down to a negative pressure on the gauge, maintained for 2 minutes, and then nitrogen was introduced until the vacuum gauge returned to zero. This process was repeated at least three times to ensure that there was no oxygen in the reactor. After the deoxygenation operation was completed, the diol and 3,4-butenediol were added under nitrogen countercurrent protection, and heating was initiated. Nitrogen protection was maintained throughout the heating process. The oil bath temperature was raised to 180°C, and after reacting for 1 hour, the temperature was increased to 200°C and the reaction continued for 2 hours. The temperature was then raised to 210°C and the reaction continued for 1 hour. The catalyst, stannous octoate, was added, the nitrogen flow was stopped, and the vacuum was reduced to -0.01 atm. The polycondensation reaction continued for 8 to 15 hours. After the reaction, the heat source was turned off and the vacuum state was maintained until the reactor cooled, ultimately completing the polymerization reaction.

[0041] In the present invention, a direct esterification route is adopted, which has a simple process, is easy to implement and has strong operability.

[0042] Compared with the prior art, the present invention has the following advantages:

[0043] 1. The present invention introduces 3,4-butenediol into polyester elastomer for the first time and develops a new polyester elastomer.

[0044] 2. In the present invention, the double bonds in butenediol are highly stable during the polymerization process and are not prone to side reactions, thereby obtaining a polyester elastomer product with a high molecular weight and narrow molecular weight distribution.

[0045] Third, the polyester elastomer prepared by this invention has a lower glass transition temperature (down to over -50°C) and a higher molecular weight, resulting in superior low-temperature resistance. Furthermore, its high molecular weight structure enhances mechanical strength and processing stability, promising broad application prospects in the automotive, electronics, and medical device sectors.

[0046] Fourth, compared to itaconic acid-based polyesters, the resulting polyester elastomer has a higher relative molecular weight and a narrower molecular weight distribution, with a molecular weight distribution of approximately 2.0, approaching that of saturated polyester plastics. Furthermore, the use of isomerized 3,4-butenediol instead of traditional 1,4-butenediol, particularly when using only 5wt% of 3,4-butenediol, disrupts the crystalline structure of the polyester molecular chain, resulting in a polyester elastomer. This innovation not only improves the polyester's heat resistance but also significantly lowers the glass transition temperature, effectively reducing overall costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 is the FTIR spectrum of the novel butene glycol-based polyester elastomer prepared in Example 1;

[0048] Figure 2 is the H-NMR spectrum of the novel butene glycol-based polyester elastomer prepared in Example 1;

[0049] Figure 3 1 is the DSC secondary temperature rise curve of the novel butene glycol-based polyester elastomer prepared in Example 1, Comparative Example 1 and Comparative Example 2.

[0050] The chemical structure of the obtained butene glycol-based polyester was determined by Fourier transform infrared spectroscopy (FTIR) and H NMR spectroscopy ( 1 The sample exhibited distinct carbonyl (-C=O) stretching vibration peaks and ester group characteristic peaks (-C–O–C=O) in the FTIR spectrum, indicating that the polymer contained a large number of ester bond structures. The -CH2- absorption peak also indicated that the main chain was rich in aliphatic chains. Furthermore, the characteristic absorption peaks of -C=C- and -CH=CH- indicated that the butene glycol monomer was successfully introduced into the polyester side chain, confirming that the material was a butene glycol-based polyester. 1 In the H-NMR spectrum, peak f corresponds to the allylic hydrogen signal from the butenediol structure, further confirming the effective incorporation of butenediol. This peak is observed in all examples and is representative. Taking Example 1 as an example, peak a corresponds to a single hydrogen signal from succinic acid, peaks b and c are attributed to two types of hydrogen from adipic acid, and peaks d and e correspond to two hydrogen signals from 1,5-pentanediol. The one-to-one correspondence between these signals and structures further confirms that the composition of the target polyester is consistent with the expected structure.

[0051] As can be seen from the figure, the polyester material obtained in Example 1 has a glass transition temperature lower than room temperature, and is therefore an elastomeric material at room temperature; compared with Comparative Examples 1 and 2, the polyester elastomer prepared in Example 1 has a lower glass transition temperature. DETAILED DESCRIPTION

[0052] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. It is necessary to point out that the following embodiments are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art to the present invention based on the contents of the present invention still fall within the scope of protection of the present invention.

[0053] The raw materials used in the examples are all conventional commercially available raw materials.

[0054] GPC test (conventional, commonly used in existing technologies): using polystyrene as a standard and tetrahydrofuran as a mobile phase, the relative molecular mass and distribution of the obtained sample were determined. The experimental test results are shown in Table 1.

[0055] DSC test: DSC test (conventional, commonly used in existing technologies): Under a nitrogen atmosphere, the sample was heated from 25°C to 140°C at a rate of 10°C / min and held for 10 minutes; then the sample was cooled from 140°C to -70°C at a rate of 10°C / min and held for 10 minutes; then the temperature was raised from -70°C to 140°C at a rate of 10°C / min. The Tg and Tm values ​​of the sample were read from the second heating curve. The experimental test results are shown in Table 1.

[0056] Example 1

[0057] 1,4-Butanediol (0.319 mol) and 1,6-hexanediol (0.136 mol) were added to a 100 ml reactor. 0.05% wt of 4-methoxyphenol and 0.05% wt of phosphorous acid aqueous solution were weighed and 1 mL was taken with a pipette and added to the reactor as a free radical inhibitor. Subsequently, a glass rod was used to gently compact the reactants to prevent the reactant powder from being carried out by the airflow during the subsequent vacuum and nitrogen flow process. Before the reaction, the system was evacuated to a negative pressure on the gauge, maintained for 2 minutes, and then nitrogen was introduced until the vacuum gauge returned to zero. This operation was repeated at least 3 times to ensure that there was no oxygen in the reactor. After the deoxygenation operation was completed, 1,5-pentanediol (0.495 mol) and 3,4-butenediol (0.05 mol) were added under nitrogen countercurrent protection, and heating was started. Nitrogen protection was maintained throughout the heating process. The oil bath temperature was raised to 180°C for one hour, then raised to 200°C for another two hours. The temperature was then raised to 210°C for one hour, followed by the addition of 0.1% wt stannous octoate catalyst. The nitrogen flow was stopped, and the vacuum was reduced to -0.01 atm. The polycondensation reaction was continued for another 8-15 hours. After the reaction was complete, the heat source was turned off, and the vacuum state was maintained until the reactor cooled, ultimately completing the polymerization reaction.

[0058] The structure of the prepared polyester elastomer is as follows:

[0059]

[0060] Among them, d=0.495, u=0.319, x=0.05, v=0.136.

[0061] Example 2

[0062] 1,4-Butanediol (0.167 mol) and 1,6-hexanediol (0.167 mol) were added to a 100 ml reactor. 0.05% wt of 4-methoxyphenol and 0.05% wt of phosphorous acid aqueous solution were weighed and 1 mL was taken with a pipette and added to the reactor as a free radical inhibitor. Subsequently, a glass rod was used to gently compact the reactants to prevent the reactant powder from being carried away by the airflow during the subsequent vacuum and nitrogen flow process. Before the reaction, the system was evacuated to a negative pressure on the gauge, maintained for 2 minutes, and then nitrogen was introduced until the vacuum gauge returned to zero. This operation was repeated at least 3 times to ensure that there was no oxygen in the reactor. After the deoxygenation operation was completed, 1,4-butanediol (0.363 mol) and 3,4-butenediol (0.0366 mol) were added under nitrogen countercurrent protection, and heating was started. Nitrogen protection was maintained throughout the heating process. The oil bath temperature was raised to 180°C for one hour, then raised to 200°C for another two hours. The temperature was then raised to 210°C for one hour, followed by the addition of 0.1% wt stannous octoate catalyst. The nitrogen flow was stopped, and the vacuum was reduced to -0.01 atm. The polycondensation reaction was continued for another 8-15 hours. After the reaction was complete, the heat source was turned off, and the vacuum state was maintained until the reactor cooled, ultimately completing the polymerization reaction.

[0063] The structure of the prepared polyester elastomer is as follows:

[0064]

[0065] Among them, c=0.495, u=0.228, x=0.05, v=0.222.

[0066] Example 3

[0067] 1,4-Butanediol (0.16 mol) and 1,7-heptanedioic acid (0.16 mol) were added to a 100 ml reactor. 0.05% wt of 4-methoxyphenol and 0.05% wt of phosphorous acid aqueous solution were weighed, and 1 mL was taken with a pipette and added to the reactor as a free radical inhibitor. Subsequently, a glass rod was used to gently compact the reactants to prevent the reactant powder from being carried away by the airflow during the subsequent vacuum and nitrogen flow process. Before the reaction, the system was evacuated to a negative pressure on the gauge, maintained for 2 minutes, and then nitrogen was introduced until the vacuum gauge returned to zero. This operation was repeated at least 3 times to ensure that there was no oxygen in the reactor. After the deoxygenation operation was completed, 1,4-diol (0.349 mol) and 3,4-butenediol (0.0352 mol) were added under nitrogen countercurrent protection, and heating was started. Nitrogen protection was maintained throughout the heating process. The oil bath temperature was raised to 180°C for one hour, then raised to 200°C for another two hours. The temperature was then raised to 210°C for one hour, followed by the addition of 0.1% wt stannous octoate catalyst. The nitrogen flow was stopped, and the vacuum was reduced to -0.01 atm. The polycondensation reaction was continued for another 8-15 hours. After the reaction was complete, the heat source was turned off, and the vacuum state was maintained until the reactor cooled, ultimately completing the polymerization reaction.

[0068] The structure of the prepared polyester elastomer is as follows:

[0069]

[0070] Among them, c=0.496, u=0.227, x=0.05, w=0.227.

[0071] Example 4

[0072] 1,4-Butanediol (0.15 mol) and 1,10-decanedioic acid (0.15 mol) were added to a 100 ml reactor, 0.05% wt of 4-methoxyphenol and 0.05% wt of phosphorous acid aqueous solution were weighed, and 1 mL was taken with a pipette and added to the reactor as a free radical inhibitor. Subsequently, a glass rod was used to gently compact the reactants to prevent the reactant powder from being carried out by the airflow during the subsequent vacuum and nitrogen flow process. Before the reaction, the system was evacuated to a negative pressure on the gauge, maintained for 2 minutes, and then nitrogen was introduced until the vacuum gauge returned to zero. This operation was repeated at least 3 times to ensure that there was no oxygen in the reactor. After the deoxygenation operation was completed, 1,4-butanediol (0.327 mol) and 3,4-butenediol (0.033 mol) were added under nitrogen countercurrent protection, and heating was started. Nitrogen protection was maintained throughout the heating process. The oil bath temperature was raised to 180°C for one hour, then raised to 200°C for another two hours. The temperature was then raised to 210°C for one hour, followed by the addition of 0.1% wt stannous octoate catalyst. The nitrogen flow was stopped, and the vacuum was reduced to -0.01 atm. The polycondensation reaction was continued for another 8-15 hours. After the reaction was complete, the heat source was turned off, and the vacuum state was maintained until the reactor cooled, ultimately completing the polymerization reaction.

[0073]

[0074] The structure of the prepared polyester elastomer is as follows:

[0075] Among them, c=0.496, u=0.227, x=0.05, j=0.227.

[0076] Example 5

[0077] 1,4-Butanediol (0.167 mol) and 1,6-hexanediol (0.167 mol) were added to a 100 ml reactor. 0.05% wt of 4-methoxyphenol and 0.05% wt of phosphorous acid aqueous solution were weighed and 1 mL was taken with a pipette and added to the reactor as a free radical inhibitor. Subsequently, a glass rod was used to gently compact the reactants to prevent the reactant powder from being carried away by the airflow during the subsequent vacuum and nitrogen flow process. Before the reaction, the system was evacuated to a negative pressure on the gauge, maintained for 2 minutes, and then nitrogen was introduced until the vacuum gauge returned to zero. This operation was repeated at least 3 times to ensure that there was no oxygen in the reactor. After the deoxygenation operation was completed, 1,4-butanediol (0.327 mol) and 3,4-butenediol (0.0735 mol) were added under nitrogen countercurrent protection, and heating was started. Nitrogen protection was maintained throughout the heating process. The oil bath temperature was raised to 180°C for one hour, then raised to 200°C for another two hours. The temperature was then raised to 210°C for one hour, followed by the addition of 0.1% wt stannous octoate catalyst. The nitrogen flow was stopped, and the vacuum was reduced to -0.01 atm. The polycondensation reaction was continued for another 8-15 hours. After the reaction was complete, the heat source was turned off, and the vacuum state was maintained until the reactor cooled, ultimately completing the polymerization reaction.

[0078] The structure of the prepared polyester elastomer is as follows:

[0079]

[0080] Among them, c=0.445, u=0.227, x=0.1, v=0.228.

[0081] Example 6

[0082] 1,4-Butanediol (0.167 mol) and 1,6-hexanediol (0.167 mol) were added to a 100 ml reactor. 0.05% wt of 4-methoxyphenol and 0.05% wt of phosphorous acid aqueous solution were weighed and 1 mL was taken with a pipette and added to the reactor as a free radical inhibitor. Subsequently, a glass rod was used to gently compact the reactants to prevent the reactant powder from being carried away by the airflow during the subsequent vacuum and nitrogen flow process. Before the reaction, the system was evacuated to a negative pressure on the gauge, maintained for 2 minutes, and then nitrogen was introduced until the vacuum gauge returned to zero. This operation was repeated at least 3 times to ensure that there was no oxygen in the reactor. After the deoxygenation operation was completed, 1,4-butanediol (0.254 mol) and 3,4-butenediol (0.147 mol) were added under nitrogen countercurrent protection, and heating was started. Nitrogen protection was maintained throughout the heating process. The oil bath temperature was raised to 180°C for one hour, then raised to 200°C for another two hours. The temperature was then raised to 210°C for one hour, followed by the addition of 0.1% wt stannous octoate catalyst. The nitrogen flow was stopped, and the vacuum was reduced to -0.01 atm. The polycondensation reaction was continued for another 8-15 hours. After the reaction was complete, the heat source was turned off, and the vacuum state was maintained until the reactor cooled, ultimately completing the polymerization reaction.

[0083] The structure of the prepared polyester elastomer is as follows:

[0084]

[0085] Among them, c=0.346, u=0.227, x=0.2, v=0.227.

[0086] Comparative Example 1

[0087] The difference from Example 1 is that 3,4-butenediol is replaced by itaconic acid;

[0088] Itaconic acid (0.05 mol), 1,4-butanediol (0.319 mol), and 1,6-hexanedioic acid (0.136 mol) were added to a 100 ml reactor. 0.05% wt of 4-methoxyphenol and 0.05% wt of phosphorous acid aqueous solution were weighed, and 1 mL was taken with a pipette and added to the reactor as a free radical inhibitor. Subsequently, a glass rod was used to gently compact the reactants to prevent the reactant powder from being carried out by the airflow during the subsequent vacuum and nitrogen flow process. Before the reaction, the system was evacuated to a negative pressure on the gauge, maintained for 2 minutes, and then nitrogen was introduced until the vacuum gauge returned to zero. This operation was repeated at least 3 times to ensure that there was no oxygen in the reactor. After the deoxygenation operation was completed, 1,5-pentanediol (0.495 mol) was added under nitrogen countercurrent protection, and heating was started. Nitrogen protection was maintained throughout the heating process. The oil bath temperature was raised to 180°C, and after reacting for 1 hour, the temperature was raised to 200°C and the reaction was continued for 2 hours; then the temperature was raised to 210°C and the reaction was continued for 1 hour, 0.1% wt of the catalyst stannous octoate was added, the nitrogen flow was stopped and the vacuum was evacuated to -0.01 atm, and the polycondensation reaction was continued for 8 to 15 hours. After the reaction was completed, the heat source was turned off and the vacuum was maintained.

[0089]

[0090] The polymerization reaction is completed.

[0091] The structure of the prepared polyester elastomer is as follows:

[0092] Among them, d=0.495, u=0.319, x=0.05, v=0.136.

[0093] Comparative Example 2

[0094] The difference from Example 1 is that 3,4-butenediol (0.05 mol) is replaced by 1,4-butenediol (0.05 mol);

[0095] The rest is the same as in Example 1, and a bio-based polyester elastomer is obtained after the reaction.

[0096] The structure of the prepared polyester elastomer is as follows:

[0097]

[0098] Among them, d=0.495, u=0.319, x=0.05, v=0.136.

[0099] Table 1 Test results of polyester elastomers in Examples and Comparative Examples of the present invention

[0100]

[0101] a: BeDO% mol refers to the molar fraction of 3,4-butenediol in the total reactants; the total reactants include dibasic acid and diol.

[0102] b: 5% mol IA means that the molar fraction of itaconic acid in the total reactants is 5%.

[0103] Table 1 shows the Tg, Tm, Mn, Mw, and PDI test results for Examples 1 to 4. The data show that the melting point and crystallization temperature decrease with the increase of methylene groups, and the introduction of long carbon chain monomers inhibits the crystallization behavior of the copolyester to a certain extent, resulting in an elastomeric material.

[0104] Compared with Comparative Examples 1 and 2, the polyester elastomers prepared in Examples 1 to 4 exhibited higher relative molecular weights (Mn, Mw) and narrower molecular weight distributions (PDI). When the 3,4-butenediol content was 5 mol%, the prepared polyester elastomers exhibited higher relative molecular weights, significantly higher than those obtained with 10 and 20 mol% 3,4-butenediol content in Examples 5 and 6. As the amount of butenediol increased, the relative molecular weight gradually decreased; at the same time, the molecular weight distribution gradually increased, but overall, the results were still superior to those of the itaconic acid system in Comparative Example 1.

[0105] Compared with Comparative Example 2, the polyester elastomer prepared in Example 1 has a lower glass transition temperature. This also confirms that compared with 1,4-butenediol, the introduction of 3,4-butenediol gives the polyester elastomer a lower glass transition temperature, allowing it to maintain better performance in low temperature environments.

[0106] In summary, the novel butenediol polyester elastomers prepared in Examples 1-4 exhibit relatively low glass transition temperatures and relatively high molecular weights, demonstrating excellent low-temperature resistance and processability. This material combines excellent low-temperature resistance with biodegradability while also exhibiting good rubber processability, expanding its practical application in low-temperature environments and filling a key gap in the existing technology.

Claims

1. A butene glycol-based bio-based polyester elastomer, characterized in that: The structural formula is as follows: The total number of moles of each polymer unit in the structural formula is 1; a, b, c, d are each 0 to 0.5 mole fractions; a, b, c, d are not all 0; preferably, a and b are 0, and at least one of c and d is not 0, the mole fraction of c is 0.01 to 0.5, preferably 0.1 to 0.5, and the mole fraction of d is 0.01 to 0.5, preferably 0.1 to 0.5; u, v, w, j are respectively 0 to 0.5 mole fractions; u, v, w, j are not all 0; preferably, u is not 0, and one of v, w, and j is not 0, the mole fraction of u is 0.01 to 0.5, preferably 0.15 to 0.45, and the mole fraction of v+w+j is 0.01 to 0.5, preferably 0.05 to 0.15; x is 0 to 0.5 mole fraction and x is not 0. The mole fraction of x is 0.05 to 0.2, more preferably 0.05 to 0.

1.

2. A butene glycol-based bio-based polyester elastomer according to claim 1, characterized in that: The bio-based polyester elastomer is prepared by polycondensation reaction of raw materials including dibasic acid, diol, polymerization inhibitor, antioxidant and catalyst; wherein, Preferred dibasic acids are 1,4-butanedioic acid, 1,6-hexanedioic acid, 1,7-pimelic acid or 1,10-decanedioic acid. As for diols, at least two of 3,4-butene glycol, ethylene glycol, 1,3-propylene glycol, 1,4-butanediol, and 1,5-pentanediol are selected, and a butene glycol monomer must be included.

3. A butene glycol-based bio-based polyester elastomer according to claim 2, characterized in that: The polymerization inhibitor is a phenolic compound, specifically one or both of hydroquinone and 4-methoxyphenol; preferably, the polymerization inhibitor is one or both of hydroquinone and 4-methoxyphenol; The antioxidant is phosphoric acid and / or phosphorous acid compounds, preferably the antioxidant is one or both of phosphoric acid and phosphorous acid; The catalyst is a titanium-based, organic tin catalyst and its solution, preferably including one or two of tetrabutyl titanate and stannous octoate.

4. A butene glycol-based bio-based polyester elastomer according to claim 2, characterized in that: The molar ratio of the diol to the dibasic acid is (1.02-1.8):1, preferably (1.2-1.4):

1.

5. The butene glycol-based bio-based polyester elastomer according to claim 2, characterized in that: The mass of the polymerization inhibitor is 0.01 to 0.2% of the total mass of the materials added to the reaction; preferably 0.01 to 0.08%; The mass of the antioxidant is 0.01-0.2% of the total mass of the materials added to the reaction; preferably 0.01-0.05%; The mass of the catalyst is 0.05% to 1% of the total mass of the materials added to the reaction, preferably 0.1 to 0.5%.

6. The method for preparing a butene glycol-based bio-based polyester elastomer according to any one of claims 1 to 5, characterized in that: The following steps are involved: (1) adding the dibasic acid, polymerization inhibitor, and antioxidant into the reactor according to the amounts described; (2) adding diol under the protection of nitrogen to carry out esterification reaction; (3) After the esterification is completed, a catalyst is added to carry out a polycondensation reaction to obtain the bio-based polyester elastomer.

7. The method according to claim 6, characterized in that In step (1), a reactor equipped with a stainless steel stirrer, a nitrogen inlet, and a condenser is selected. A dibasic acid is added to the reactor, and a polymerization inhibitor and an antioxidant are weighed and added to the reactor. To prevent the reactant powder from being carried out by the airflow during subsequent operations, lightly compact the reactants.

8. The method according to claim 6, characterized in that Step (2), heating for the esterification reaction; before heating, first evacuate the system until the gauge shows negative pressure, maintain for 2 minutes, and then introduce nitrogen until the vacuum gauge returns to zero; repeat the above evacuation-nitrogenization steps at least 3 times to ensure that there is no residual oxygen in the reactor. After the deoxygenation treatment is completed, add the diol under nitrogen countercurrent protection. Start heating the reaction system, maintaining a nitrogen atmosphere; raise the oil bath temperature to 180°C, react for 1 hour to allow the reactants to fully melt and initiate esterification; then raise the temperature to 200°C and continue the reaction for 2 hours, and then raise the temperature to 210°C and react for 1 hour.

9. The method according to claim 6, characterized in that Step (3) after the esterification reaction is completed, a catalyst is added, and then the nitrogen is turned off and the vacuum is evacuated to -0.01 atm to carry out a polycondensation reaction at a temperature of 220 to 235° C. for 8 to 15 hours; stirring is performed when a significant climbing pole effect (Weissenberg) appears when the stirring rate is 30 rpm, indicating that the reaction is complete; the heat source is turned off, and the vacuum state is continued to be maintained. The reaction is terminated after the reactor is naturally cooled, and the target polyester elastomer product is finally obtained.

10. The method according to claim 6, characterized in that In the polymerization step, a four-necked round-bottom flask equipped with a stainless steel stirrer, a nitrogen inlet, and a condenser is used as a reactor. The dibasic acid is added to the reactor, and 4-methoxyphenol and an aqueous phosphorous acid solution are weighed and added to the reactor using a pipette to act as a free radical inhibitor. Subsequently, the reactants are gently compacted with a glass rod to prevent the reactant powder from being carried away by the airflow during the subsequent vacuum and nitrogen flow process. Before the esterification reaction, the system was evacuated to a negative pressure on the gauge, maintained for 2 minutes, and then nitrogen was introduced until the vacuum gauge returned to zero. This operation was repeated at least 3 times to ensure that there was no oxygen in the reactor. After the deoxygenation operation was completed, diol and 3,4-butenediol were added under nitrogen countercurrent protection, and heating was started. Nitrogen protection was maintained throughout the heating process. The oil bath temperature was raised to 180°C, reacted for 1 hour, and then heated to 200°C and continued to react for 2 hours. The temperature was then raised to 210°C and reacted for 1 hour. After that, the catalyst stannous octoate was added, the nitrogen was stopped, and the vacuum was evacuated to -0.01atm. The polycondensation reaction was continued for 8 to 15 hours. After the reaction was completed, the heat source was turned off and the vacuum state was maintained until the reactor cooled down to complete the polymerization reaction.

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