Beta-hydroxy fatty acid ester polymers and process for preparing beta-hydroxy fatty acid ester polymers by polycondensation of transesterification

Abstract

The present application relates to the field of beta-hydroxy fatty acid ester polymer preparation, further to a kind of beta-hydroxy fatty acid ester polymer and the method for preparing the polymer.The structural formula of the polymer is as shown in formula 1:Wherein, R1 is H or C1-C12 alkyl, R2 is C1-C6 alkyl;The weight average molecular weight of the polymer is 8000-200000;The number average molecular weight of the polymer is 5000-180000;Polydispersity index is 1-2.5.The beta-hydroxy fatty acid ester polymer of the present application has higher molecular weight, narrower molecular weight distribution, has the performance of corresponding biofermentation synthesis beta-hydroxy fatty acid ester polymer, and does not contain the impurity that bio-synthesis beta-hydroxy fatty acid ester polymer is difficult to remove, has higher application value.The preparation method of the present application, reaction condition is relatively mild, process is simple, and has higher process safety.

Description

Technical Field

[0001] This invention relates to the field of β-hydroxy fatty acid ester polymer preparation, and more specifically, to a method for preparing β-hydroxy fatty acid ester polymers by transesterification polycondensation. Background Technology

[0002] Biodegradable materials can rival traditional polymer materials in terms of mechanical and thermal properties. They can be completely degraded under certain conditions. As a high-tech and environmentally friendly material, they have become a hot research topic in the field of materials science and are recognized as one of the effective ways to solve the pollution and sustainable development problems of traditional polymer materials.

[0003] β-hydroxy fatty acid ester polymers (PHAs) are a class of thermoplastic polyesters initially synthesized by microbial fermentation. They possess properties similar to traditional polymers, while also exhibiting excellent biocompatibility, biodegradability, optical activity, and gas barrier properties—qualities not found in traditional polymers. This makes them promising for applications in biodegradable medical materials, packaging materials, tissue engineering materials, sustained-release materials, and electrical materials. By altering the chemical composition of PHA, various structures can be easily formed; over 150 types of PHA polymers have been discovered, each offering different properties and functions. Therefore, compared to chemically synthesized biodegradable materials such as PLA and PCL, PHA structures are more diverse, leading to a wider range of performance and thus greater advantages in applications. Traditionally, PHA synthesis has relied primarily on microbial methods, which suffer from drawbacks such as long synthesis cycles, complex extraction processes, high synthesis costs, and low yields. Chemical synthesis methods can significantly shorten the PHA synthesis cycle, reduce costs, and increase yields, thereby greatly enhancing PHA's competitiveness in practical applications. Currently, there are few literature reports on the chemical synthesis of PHA, and the following three methods are the main ones:

[0004] 1. Direct polycondensation of β-hydroxycarboxylic acids

[0005] This method is relatively simple, but hydroxycarboxylic acids are very unstable and prone to hydrolysis and intramolecular condensation, making it difficult to increase the degree of polymerization of the condensation reaction and obtain higher molecular weight PHA.

[0006] 2. Ring-opening polymerization of lactones

[0007] This method can relatively easily synthesize high molecular weight PHAs, with commonly used lactones including butyrolactone, lactide, and glycolide. However, due to the difficulty in preparing these lactone monomers, the monomers are hard to obtain, industrialization is challenging, and some lactone monomers are highly carcinogenic, thus greatly limiting their application.

[0008] 3. Self-transesterification polycondensation of β-hydroxycarboxylic acid esters

[0009] The condensation monomer hydroxycarboxylic acid ester produced by this method is relatively stable, easy to purify, and the reaction process is relatively simple. It is an environmentally friendly and efficient method for synthesizing PHA. However, under low catalyst concentrations, existing preparation methods cannot obtain high molecular weight β-hydroxy fatty acid ester polymers. Summary of the Invention

[0010] To address the shortcomings of existing technologies for synthesizing β-hydroxy fatty acid ester polymers, such as the long cycle, complex extraction process, high synthesis cost, and low yield of biosynthesis methods, and the difficulty in increasing the degree of polymerization in chemical synthesis methods and the low process safety, this paper provides a method for preparing β-hydroxy fatty acid ester polymers by transesterification polycondensation.

[0011] One objective of this invention is to provide a β-hydroxy fatty acid ester polymer, the polymer having the structural formula shown in Formula 1:

[0012]

[0013] Wherein, R1 is H or a C1-C12 alkyl group, and R2 is a C1-C6 alkyl group;

[0014] The polymer has a weight-average molecular weight of 8,000-200,000; a number-average molecular weight of 5,000-180,000; a dispersibility index of 1-2.5; and n is the degree of polymerization.

[0015] According to the present invention, R1 and R2 in Formula 1 can be either straight-chain alkyl or branched-chain alkyl, and the present invention has no particular limitation.

[0016] According to the present invention, R1 can be selected from a wide range. In a preferred embodiment of the present invention, R1 is H or a C1-C4 alkyl group. More preferably, R1 is one of -CH2CH2CH3, -CH2CH3, -CH3 or H.

[0017] According to the present invention, R2 can be selected from a wide range. In a preferred embodiment of the present invention, R2 is a C1-C2 alkyl group, that is, R2 is either -CH3 or -CH2CH3.

[0018] According to the present invention, the weight-average molecular weight of the polymer can be selected within a wide range. In a preferred embodiment of the present invention, the weight-average molecular weight of the polymer is 10,000-50,000, for example, it can be 10,000, 12,000, 15,000, 20,000, 25,000, 30,000, 35,000, 40,000, 45,000, 50,000, or any two values ​​or any range of any two values.

[0019] According to the present invention, the number-average molecular weight of the polymer can be selected within a wide range. In a preferred embodiment of the present invention, the number-average molecular weight of the polymer is 4,000-30,000; for example, it can be 4,000, 8,000, 12,000, 15,000, 20,000, 25,000, 30,000, or any two values ​​or any range of any two values.

[0020] According to the present invention, the dispersibility index of the polymer can be selected within a wide range. In a preferred embodiment of the present invention, the dispersibility index of the polymer is 1-2.2.

[0021] In a more preferred embodiment of the present invention, the polymer is prepared by transesterification polycondensation of β-hydroxy fatty acid esters themselves.

[0022] The second objective of this invention is to provide a method for preparing the β-hydroxy fatty acid ester polymer described above, comprising prepolymerizing the β-hydroxy fatty acid ester shown in Formula 2 in the presence of a catalyst, and then subjecting the prepolymer to an ester exchange polycondensation reaction.

[0023]

[0024] According to the present invention, R1 and R2 in Formula 2 can be, for example, those listed in Formula 1 above, and there can be a variety of choices.

[0025] According to the present invention, in Formula 2, R1 is H or a C1-C12 alkyl group, and R2 is a C1-C6 alkyl group.

[0026] According to the present invention, R1 and R2 in Formula 2 can be either straight-chain alkyl or branched-chain alkyl, and the present invention has no particular limitation.

[0027] According to the present invention, R1 in Formula 2 can be selected from a wide range. In a preferred embodiment of the present invention, R1 is H or a C1-C4 alkyl group.

[0028] According to the present invention, R2 in Formula 2 can be selected from a wide range. In a preferred embodiment of the present invention, R2 is a C1-C2 alkyl group.

[0029] In a preferred embodiment of the present invention, the preparation method includes the following steps:

[0030] (a) Under a protective atmosphere, the β-hydroxy fatty acid ester is mixed with a catalyst and subjected to a prepolymerization reaction to obtain a prepolymer;

[0031] (b) Remove the byproducts of the prepolymer in step (a) to obtain the purified prepolymer, and then carry out the polycondensation reaction of the purified prepolymer under high vacuum to obtain the β-hydroxy fatty acid ester polymer.

[0032] According to the present invention, the prepolymerization reaction conditions in step (a) can be selected within a wide range. In a preferred embodiment of the present invention, the prepolymerization reaction conditions in step (a) include a temperature of 130-160°C, preferably 140-150°C.

[0033] According to the present invention, the prepolymerization reaction time in step (a) can be selected within a wide range. In a preferred embodiment of the present invention, the reaction time is 1-4 hours, preferably 1-2 hours.

[0034] In a more preferred embodiment of the present invention, the prepolymerization reaction conditions in step (a) include: a temperature of 130-160°C, preferably 140-150°C, and a reaction time of 1-4 hours, preferably 1-2 hours.

[0035] According to the present invention, the method for removing the byproducts of the prepolymer in step (b) can be selected from a wide range. In a preferred embodiment of the present invention, the method for removing the byproducts of the prepolymer in step (b) is vacuum distillation.

[0036] According to the present invention, the conditions for removing the byproducts of the prepolymer by vacuum distillation in step (b) can be selected in a wide range, preferably at 160-200°C.

[0037] According to the present invention, the conditions for removing the byproducts of the prepolymer by vacuum distillation in step (b) can be selected in a wide range, preferably vacuum distillation is carried out under the conditions of 1-1.5 kPa until the fraction no longer flows out.

[0038] In a more preferred embodiment of the present invention, step (b) involves vacuum distillation to remove the byproducts of the prepolymer, including vacuum distillation at 160-200°C and 1-1.5 kPa until no more fractions flow out.

[0039] According to the present invention, the polycondensation reaction conditions in step (b) can be selected within a wide range. In a preferred embodiment of the present invention, the polycondensation reaction conditions in step (b) include: a temperature of 160-200°C, preferably 170-180°C.

[0040] According to the present invention, the polycondensation reaction pressure in step (b) can be selected within a wide range. In a preferred embodiment of the present invention, the pressure is not higher than 200 Pa, and preferably 50-180 Pa.

[0041] According to the present invention, the polycondensation reaction time in step (b) can be selected within a wide range. In a preferred embodiment of the present invention, the reaction time is 5-8 hours, preferably 6-8 hours.

[0042] In a more preferred embodiment of the present invention, the polycondensation reaction conditions in step (b) include: a temperature of 160-200°C, preferably 170-180°C; a pressure not exceeding 200 Pa, preferably 50-180 Pa; and a reaction time of 5-8 hours, preferably 6-8 hours.

[0043] According to the present invention, the catalyst can be selected from a wide range. In a preferred embodiment of the present invention, the catalyst is selected from compounds or mixtures based on at least one element selected from Ti, Sn, and Sb, preferably at least one of antimony trioxide, tetrabutyl titanate, dibutyltin dilaurate, dibutyltin oxide, stannous octoate, stannous oxalate, and stannous chloride.

[0044] According to the present invention, the molar ratio of the catalyst to the total amount of the β-hydroxy fatty acid ester can be selected within a wide range. In a preferred embodiment of the present invention, the molar ratio of the catalyst to the total amount of the β-hydroxy fatty acid ester is (0.1-1):100, preferably (0.3-0.6):100. For example, it can be a ratio of 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6 to 100, or any number between 0.3 and 0.6 or any range of two values ​​to 100. The present invention can prepare β-hydroxy fatty acid ester polymers at low catalyst concentrations, and has superior technical effects.

[0045] According to the present invention, the β-hydroxy fatty acid ester can be a compound represented by Formula 2. In a preferred embodiment of the present invention, the β-hydroxy fatty acid ester is selected from at least one of methyl β-hydroxypropionate, ethyl β-hydroxypropionate, methyl β-hydroxybutyrate, ethyl β-hydroxybutyrate, methyl β-hydroxyvalerate, ethyl β-hydroxyvalerate, methyl β-hydroxyhexanoate, and ethyl β-hydroxyhexanoate.

[0046] In a preferred embodiment of the present invention, the method for preparing the β-hydroxy fatty acid ester polymer includes the following steps:

[0047] (a) Mix β-hydroxy fatty acid ester monomers and catalysts in a certain proportion, heat to melt, raise the temperature to 130-160℃, and react for 1-4 hours under nitrogen protection to obtain prepolymer;

[0048] (b) The prepolymer obtained in step (a) above is heated, and byproducts are removed by vacuum distillation. The temperature is raised to 160-200℃, and the pressure is reduced to below 200Pa. The reaction is carried out for 5-8 hours to obtain β-hydroxy fatty acid ester polymer.

[0049] Compared with the prior art, the present invention has the following advantages due to the use of the above-mentioned chemical synthesis method:

[0050] The preparation method of this invention features relatively mild reaction conditions, a simple process, and high process safety. This invention can be used to prepare the product under low catalyst concentrations, with relatively mild reaction conditions, a simple process, and a relatively short reaction time. Compared with existing bio-fermentation synthesis technologies, it significantly shortens the production synthesis cycle and reduces production synthesis costs.

[0051] The β-hydroxy fatty acid ester polymer synthesized by condensation polymerization has a higher molecular weight and a narrower molecular weight distribution. It possesses the properties of β-hydroxy fatty acid ester polymers synthesized by bio-fermentation, and does not contain impurities that are difficult to remove from bio-synthesized β-hydroxy fatty acid ester polymers, thus having higher application value. Detailed Implementation

[0052] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0053] The embodiments of the present invention are illustrated with specific examples, and the results of each example are tested accordingly. The weight-average molecular weight, number-average molecular weight, and polydispersity index (PDI) of the polymer are determined using gel permeation chromatography (GPC).

[0054] Example 1

[0055] (1) Using methyl β-hydroxypropionate as its own transesterification condensation monomer and tetrabutyl titanate as a catalyst, the two (molar ratio 1:0.005) were placed in a reactor, heated to melt and stirred thoroughly, and then heated to 150°C. Prepolymerization was carried out under nitrogen protection for 2 hours.

[0056] (2) After cooling the prepolymer obtained in (1), heat it to 170°C, slowly reduce the pressure of the reaction system to 1.2 kPa until the fraction no longer flows out to remove the byproducts, and then slowly reduce the pressure to 150 Pa to carry out the polycondensation reaction. After reacting for 6 hours, poly(β-hydroxypropionate) methyl ester is obtained.

[0057] GPC testing showed that the polymer had a weight-average molecular weight (Mw) of 12065 g / mol, a number-average molecular weight (Mn) of 8861 g / mol, and a PDI (Polymer dispersity index) of 1.36.

[0058] Example 2

[0059] (1) Using ethyl β-hydroxybutyrate as its own transesterification monomer and dibutyltin dilaurate as a catalyst, the two (molar ratio 1:0.008) were placed in a reactor, heated to melt and stirred thoroughly, and then heated to 160°C. Prepolymerization was carried out under nitrogen protection for 1 hour.

[0060] (2) After cooling the prepolymer obtained in (1), heat it to 180°C, slowly reduce the pressure of the reaction system to 1.3 kPa until the fraction no longer flows out to remove the byproducts, and then slowly reduce the pressure to 200 Pa to carry out the polycondensation reaction. After reacting for 7 hours, poly(β-hydroxybutyrate) ethyl ester is obtained.

[0061] GPC testing showed that the polymer had a weight-average molecular weight (Mw) of 19694 g / mol, a number-average molecular weight (Mn) of 9544 g / mol, and a PDI of 2.06.

[0062] Example 3

[0063] (1) Using β-hydroxyvalerate ethyl ester as its own transesterification condensation monomer and dibutyltin oxide as catalyst, the two (molar ratio 1:0.003) were placed in a reactor, heated to melt and stirred thoroughly, and then heated to 150°C. Prepolymerization was carried out under nitrogen protection for 4 hours.

[0064] (2) After cooling the prepolymer obtained in (1), heat it to 180°C, slowly reduce the pressure of the reaction system to 1.2 kPa until the fraction no longer flows out to remove the byproducts, and then slowly reduce the pressure to 170 Pa to carry out the polycondensation reaction. After reacting for 8 hours, poly(β-hydroxyvalerate) ethyl ester is obtained.

[0065] GPC testing showed that the polymer had a weight-average molecular weight (Mw) of 28,751 g / mol, a number-average molecular weight (Mn) of 13,768 g / mol, and a PDI of 2.09.

[0066] Example 4

[0067] (1) Using methyl β-hydroxyhexanoate as its own transesterification monomer and stannous octoate as a catalyst, the two (molar ratio 1:0.005) were placed in a reactor, heated to melt and stirred thoroughly, and then heated to 140°C. Prepolymerization was carried out under nitrogen protection for 2 hours.

[0068] (2) After cooling the prepolymer obtained in (1), heat it to 180°C, slowly reduce the pressure of the reaction system to 1.1 kPa until the fraction no longer flows out to remove the byproducts, and then slowly reduce the pressure to 100 Pa to carry out the polycondensation reaction. After reacting for 6 hours, poly(β-hydroxyhexanoate) methyl ester is obtained.

[0069] GPC testing showed that the polymer had a weight-average molecular weight (Mw) of 39695 g / mol, a number-average molecular weight (Mn) of 21039 g / mol, and a PDI of 1.89.

[0070] Example 5

[0071] (1) Using β-hydroxypropionate as its own transesterification condensation monomer and stannous chloride as a catalyst, the two (molar ratio 1:0.002) were placed in a reactor, heated to melt and stirred thoroughly, and then heated to 160°C for prepolymerization under nitrogen protection for 3 hours.

[0072] (2) After cooling the prepolymer obtained in (1), heat it to 180°C, slowly reduce the pressure of the reaction system to 1.1 kPa until the fraction no longer flows out to remove the byproducts, and then slowly reduce the pressure to 110 Pa to carry out the polycondensation reaction. After reacting for 7 hours, poly(β-hydroxypropionate) ethyl ester is obtained.

[0073] GPC testing showed that the polymer had a weight-average molecular weight (Mw) of 20199 g / mol, a number-average molecular weight (Mn) of 9316 g / mol, and a PDI of 2.17.

[0074] Example 6

[0075] (1) Using methyl β-hydroxybutyrate as its own transesterification monomer and stannous oxalate as a catalyst, the two (molar ratio 1:0.006) were placed in a reactor, heated to melt and stirred thoroughly, and then heated to 150°C for prepolymerization under nitrogen protection for 2 hours.

[0076] (2) After cooling the prepolymer obtained in (1), heat it to 170°C, slowly reduce the pressure of the reaction system to 1.0 kPa until the fraction no longer flows out to remove the byproducts, and then slowly reduce the pressure to 100 Pa to carry out the polycondensation reaction. After reacting for 8 hours, poly(β-hydroxybutyrate) methyl ester is obtained.

[0077] GPC testing showed that the polymer had a weight-average molecular weight (Mw) of 23,825 g / mol, a number-average molecular weight (Mn) of 14,788 g / mol, and a PDI of 1.61.

[0078] Comparative Example 1

[0079] (1) Using methyl β-hydroxyhexanoate as its own transesterification monomer and stannous octoate as a catalyst, the two (molar ratio 1:0.005) were placed in a reactor, heated to melt and stirred thoroughly, and then heated to 140°C. Prepolymerization was carried out under nitrogen protection for 2 hours.

[0080] (2) After cooling the prepolymer obtained in (1), heat it to 180°C for polycondensation reaction and react for 6 hours to obtain poly(β-hydroxyhexanoate).

[0081] GPC testing showed that the polymer had a weight-average molecular weight (Mw) of 4874 g / mol, a number-average molecular weight (Mn) of 2534 g / mol, and a PDI of 1.92.

[0082] Comparative Example 2

[0083] (1) Using methyl β-hydroxyhexanoate as its own transesterification monomer and stannous octoate as a catalyst, the two (molar ratio 1:0.005) were placed in a reactor, heated to melt and stirred thoroughly, and then heated to 140°C. Prepolymerization was carried out under nitrogen protection for 2 hours.

[0084] (2) After cooling the prepolymer obtained in (1), heat it to 180°C and then slowly reduce the pressure to 100Pa to carry out polycondensation reaction. After reacting for 6 hours, poly(β-hydroxyhexanoate) methyl ester is obtained.

[0085] GPC testing showed that the polymer had a weight-average molecular weight (Mw) of 6028 g / mol, a number-average molecular weight (Mn) of 2725 g / mol, and a PDI of 2.21.

[0086] Comparative Example 3

[0087] (1) Using methyl β-hydroxyhexanoate as its own transesterification monomer and stannous octoate as a catalyst, the two (molar ratio 1:0.005) were placed in a reactor, heated to melt and stirred thoroughly, and then heated to 140°C. Prepolymerization was carried out under nitrogen protection for 2 hours.

[0088] (2) After cooling the prepolymer obtained in (1), heat it to 160°C, slowly reduce the pressure of the reaction system to 1.1 kPa until the fraction no longer flows out to remove the byproducts, and then slowly reduce the pressure to 300 Pa to carry out the polycondensation reaction. After reacting for 6 hours, poly(β-hydroxyhexanoate) methyl ester is obtained.

[0089] GPC testing showed that the polymer had a weight-average molecular weight (Mw) of 8749 g / mol, a number-average molecular weight (Mn) of 4642 g / mol, and a PDI of 1.88.

[0090] Currently, the main assessment of the properties of β-hydroxy fatty acid ester polymers is based on their molecular weight. Existing similar technologies synthesize β-hydroxy fatty acid ester polymers with relatively low molecular weights. The β-hydroxy fatty acid ester polymer synthesized by the technology of this invention has a higher molecular weight, a lower PDI, and does not contain impurities that are difficult to remove in biosynthesized β-hydroxy fatty acid ester polymers, thus having higher application value.

[0091] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

[0092] All publications, patent applications, patents, and other references mentioned in this specification are incorporated herein by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings commonly understood by those skilled in the art. In case of conflict, the definitions in this specification shall prevail.

[0093] When this specification uses the prefixes “known to those skilled in the art,” “prior art,” or similar terms to derive materials, substances, methods, steps, apparatus, or components, the objects derived from such prefixes cover those commonly used in the art at the time of this application, but also include those that are not currently commonly used but will become generally recognized in the art as suitable for similar purposes.

[0094] The endpoints and any values ​​of the ranges disclosed in this application are not limited to the precise ranges or values; such ranges or values ​​should be understood to include values ​​close to them. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. In principle, various technical solutions can be combined with each other to obtain new technical solutions, which should also be considered as specifically disclosed herein.

[0095] In the context of this specification, except where expressly stated otherwise, any matters or issues not mentioned shall apply directly to those known in the art without any modification.

[0096] Furthermore, any implementation described herein can be freely combined with one or more other implementations described herein, and the resulting technical solutions or technical ideas shall be regarded as part of the original disclosure or original record of the present invention, and should not be regarded as new content not disclosed or anticipated herein, unless those skilled in the art consider the combination to be obviously unreasonable.

Claims

1. A method for preparing a β-hydroxy fatty acid ester polymer, the β-hydroxy fatty acid ester polymer having a structural formula as shown in Formula 1: ###0001### Formula 1 wherein R1 is H or a C1-C12 alkyl group, and R2 is a C1-C6 alkyl group; the polymer having a weight average molecular weight of 8000-200000; the polymer having a number average molecular weight of 5000-180000; the polymer having a dispersity index of 1-2.5; and n being a polymerization degree; the method comprising: first, pre-polymerizing a β-hydroxy fatty acid ester represented by Formula 2 in the presence of a catalyst, and then, performing an ester exchange polycondensation reaction on the pre-polymer. Formula 1; wherein 2. The method according to claim 1, wherein: the pre-polymerization reaction in step (a) is performed at a temperature of 130-160°C; and / or, the reaction time is 1-4 hours.

3. The method according to claim 1, wherein: the pre-polymerization reaction in step (a) is performed at a temperature of 140-150°C; and / or, the reaction time is 1-2 hours.

4. The method according to claim 1, wherein: the by-product of the pre-polymer is removed by vacuum distillation in step (b); the vacuum distillation is performed at a temperature of 160-200°C and / or a pressure of 1-1.5 KPa until no distillate is obtained; and / or, the polycondensation reaction in step (b) is performed at a temperature of 160-200°C; and / or, the reaction time is 5-8 hours.

5. The method according to claim 1, wherein: the polycondensation reaction in step (b) is performed at a temperature of 170-180°C; a pressure of 50-180 Pa; and / or, the reaction time is 6-8 hours. Formula 2; 6. The method according to any one of claims 1-5, wherein: the catalyst is selected from a compound or mixture based on at least one element of Ti, Sn, and Sb; and / or, the molar ratio of the catalyst to the total amount of the β-hydroxy fatty acid ester is (0.1-1):

100.

7. The method according to any one of claims 1-5, wherein: the catalyst is selected from at least one of antimony trioxide, tetrabutyl titanate, dibutyltin dilaurate, dibutyltin oxide, stannous octoate, stannous oxalate, and stannous chloride; and / or, the molar ratio of the catalyst to the total amount of the β-hydroxy fatty acid ester is (0.3-0.6):

100.

8. The method according to any one of claims 1-5, wherein: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The beta-hydroxy fatty acid ester is at least one selected from the group consisting of beta-hydroxy propionic acid methyl ester, beta-hydroxy propionic acid ethyl ester, beta-hydroxy butyric acid methyl ester, beta-hydroxy butyric acid ethyl ester, beta-hydroxy valeric acid methyl ester, beta-hydroxy valeric acid ethyl ester, beta-hydroxy caproic acid methyl ester and beta-hydroxy caproic acid ethyl ester.

9. A beta-hydroxy fatty acid ester polymer obtained by the preparation method of the beta-hydroxy fatty acid ester polymer according to any one of claims 1-8, and the structure of the polymer is shown as formula 1: Formula 1 wherein R1 is H or C1-C12 alkyl, and R2 is C1-C6 alkyl; the weight average molecular weight of the polymer is 8000-200000; the number average molecular weight of the polymer is 5000-180000; the dispersity index of the polymer is 1-2.5; and n is the degree of polymerization. Formula 1; wherein 9. The beta-hydroxy fatty acid ester polymer of claim 9, wherein: R1 is H or C1-C4 alkyl; and / or, R2 is C1-C2 alkyl.

11. The beta-hydroxy fatty acid ester polymer of claim 9, wherein: the weight average molecular weight of the polymer is 10000-50000; and / or, the number average molecular weight of the polymer is 5000-30000; and / or, the dispersity index of the polymer is 1-2.

2.

11. The beta-hydroxy fatty acid ester polymer of claim 9, wherein: the weight average molecular weight of the polymer is 10000-50000; and / or, the number average molecular weight of the polymer is 5000-30000; and / or, the dispersity index of the polymer is 1-2.

2. ​ ​ ​ ​ ​ ​

Images