A bio-based polyester latex, its preparation method and its application in crosslinking film formation

Abstract

The application discloses a kind of bio-based polyester latex and its preparation method and its application in crosslinking film formation.The bio-based polyester latex of the application includes solvent, emulsifier and the polyester of the structural unit shown in formula (I).The application successfully prepares a kind of polyester latex and polyester film with high bio-based content and excellent mechanical properties by innovative "copolymerization internal toughening" and "crosslinking network enhancement" synergistic strategy, solves many pain points of prior art, and has significant innovation and practical value.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials science and engineering, specifically relating to a bio-based polyester latex, its preparation method, and its application in crosslinking film formation. In particular, it relates to a method for obtaining a high-performance polyester film by introducing a terminal hydroxyl telechelic polymer containing C=C bonds to pre-embed crosslinking sites and using peroxides for efficient crosslinking. Background Technology

[0002] With increasing global awareness of sustainable development and environmental protection, the development of bio-based polymer materials made from renewable resources to replace traditional petroleum-based materials has become a research hotspot and important development direction in the fields of chemistry and materials science. Polyester elastomers (TPEEs), due to their combination of the high elasticity of rubber and the ease of processing of plastics, have been widely used in the automotive, electronics, medical, and consumer goods industries. However, the vast majority of currently commercially available polyester elastomers rely on non-renewable fossil resources, and their production and disposal processes place enormous pressure on the environment. Therefore, the development of bio-based polyester elastomers has significant social and economic value.

[0003] Currently, researchers have attempted to synthesize bio-based polyesters using biologically derived diols (such as 1,3-propanediol and 1,4-butanediol) and diacids (such as succinic acid, sebacic acid, and itaconic acid). However, existing bio-based polyester elastomer preparation technologies still face numerous bottlenecks and challenges: (1) Insufficient elasticity: Many bio-based polyesters, such as polylactic acid (PLA) or polybutylene succinate (PBS), although biodegradable, often exhibit high crystallinity and rigidity, resulting in brittle materials with insufficient flexibility and elasticity, and generally low elongation at break, making it difficult to meet the requirements of high-elasticity applications. To improve their flexibility, blending modification is usually adopted, such as blending with natural rubber or other elastomers, but this often leads to problems such as poor compatibility, weak interfacial bonding, and unstable performance.

[0004] (2) Limited molecular structure design: Existing bio-based polyester synthesis mainly focuses on combinations of several specific monomers, lacking a systematic approach to finely control the polymer chain structure to achieve performance optimization. In particular, how to introduce "flexible segments" into the molecular chain through copolymerization modification to construct a microphase separation structure similar to the "soft and hard segments" in polyurethane elastomers, thereby fundamentally improving the intrinsic elasticity and toughness of the material, is a difficult problem that urgently needs to be overcome in current technology.

[0005] (3) Poor latex preparation and stability: Preparing stable water-based latex from polyester is crucial for applications such as coatings, adhesives, and impregnated products. However, when traditional solvent emulsification is applied to highly hydrophobic polyesters, problems such as complex processes, high energy consumption, uneven latex particle size, and poor storage stability often arise. In particular, for high molecular weight elastomers, their high viscosity makes effective dispersion difficult, resulting in low emulsification efficiency.

[0006] (4) Limited post-processing and performance improvement: The mechanical strength of synthesized linear or branched bio-based polyester elastomers is usually difficult to match that of chemically cross-linked traditional rubber. Although some studies have attempted to introduce cross-linking structures, they often face problems such as low cross-linking efficiency, uneven cross-linking networks, or the introduction of cross-linking agents affecting the bio-based content of the material. There is a lack of an integrated technical solution that starts from polymer molecular design, pre-embeds cross-linking sites, and achieves efficient post-cross-linking.

[0007] In summary, how to develop a method that endows materials with excellent elasticity and toughness from the source through innovative molecular structure design, and combines it with efficient emulsification and crosslinking technologies to prepare bio-based polyester latexes and films with excellent comprehensive performance, is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0008] To solve the above-mentioned technical problems, the present invention provides the following technical solution: A bio-based polyester latex, the bio-based polyester latex comprising a solvent, an emulsifier, and a polyester containing structural units of formula (I): (I) U1, U2, U3, and U4 may be the same or different, and are independently selected from C1, U2, U3, and U4 that are chemically bonded, unsubstituted, or substituted by at least one group represented by formula (A). 1-10 alkylene, unsubstituted or substituted with at least one group of formula (A) 2-10 alkenyl; (A) Each Q may be the same or different, and each is independently selected from chemical bonds or C. 1-10 Alkylene; Each R m They are the same or different, and are selected independently from H or C. 1-10 alkyl; Each R n They are the same or different, and are selected independently from H or C. 1-10 alkyl; Z1, Z2, Z3, and Z4 may be the same or different, and are independently selected from chemical bonds or C bonds. 1-10 Alkylene; Represents chemical bonds; 'a' represents a number from 6 to 30; b represents a number between 8 and 35; c represents a number from 16 to 65; d represents a number from 0 to 5; The condition is that two, three, or four of U1, U2, U3, and U4 are selected from C1, U2, U3, and U4 that are unsubstituted or substituted by at least one group represented by formula (A). 2-10 It is an alkenyl group, and at most one of U1, U2, U3 and U4 is a chemical bond.

[0009] According to embodiments of the present invention, the solvent is selected from water, and optionally includes or excludes organic solvents. Preferably, the solvent is selected from water. Further, the organic solvent is selected from, but not limited to, one, two, or more of dichloromethane, trichloromethane, and tetrahydrofuran.

[0010] According to an embodiment of the present invention, the emulsifier is selected from, but not limited to, one, two, or more of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, and polyethylene glycol octylphenyl ether.

[0011] According to an embodiment of the present invention, the weight ratio of the polyester, emulsifier and solvent is 10:(0.1~0.5):(10~100), preferably 10:(0.2~0.4):(20~50), for example 10:0.2:50, 10:0.3:50, 10:0.4:50.

[0012] According to an embodiment of the present invention, the structural unit shown in formula (I) has the structure shown in formula (II): (II) Among them, Y1, Y2, Y6, Y7, Y8, and Y9 are the same or different, and are independently selected from C. 1-10 Alkylene; Y3, Y4, and Y9 may be the same or different, and are independently selected from chemical bonds, C, and D. 1-10 Alkylene or C 2-10 alkenyl; Y5 is selected from C 1-10 Mesenchymal or carbon atom; Y6 is selected from C 1-10 Alkylene or C 1-10 Phenyl group; Indicates a single or double bond, provided that when When representing a single bond, Y5 is C. 1-10 Phenylene group, Y6 is C 1-10 alkylene; when When representing a double bond, Y5 represents a carbon atom and Y6 represents a carbon atom. 1-10 Phenyl group; Z1, Z2, Z3, and Z4 may be the same or different, and are independently selected from chemical bonds or C bonds. 1-10 Alkylene; R1, R2, R3, and R4 may be the same or different, and are independently selected from H or C. 1-10 alkyl; Q1 is selected from chemical bonds or C. 1-10 Alkylene; Each R a They are the same or different, and are selected independently from H or C. 1-10 alkyl; Each R b They are the same or different, and are selected independently from H or C. 1-10 alkyl; R5 and R6 may be the same or different, and are independently selected from H and C. 1-10 Alkyl groups or groups represented by formula (B): (B) Q2 is selected from chemical bonds or C. 1-10 Alkylene; Each R c They are the same or different, and are selected independently from H or C. 1-10 alkyl; Each R d They are the same or different, and are selected independently from H or C. 1-10 alkyl; Represents chemical bonds; 'a' represents a number from 6 to 30; b represents a number between 8 and 35; c represents a number from 16 to 65; d represents a number from 0 to 5.

[0013] According to an embodiment of the present invention, the polyester further comprises a structural unit as shown in formula (III): (III) Among them, Alk1, Alk2, and Alk3 may be the same or different, and are independently selected from C. 1-12 Alkylene.

[0014] Preferably, the polyester comprises the structural unit shown in formula (D) and the structural unit shown in formula (E): (D) (E) Among them, D1, D2, D3, E1, E2, and E3 are the same or different, and are independently selected from C. 1-12 Alkylene; The condition is that one, two, or three of the following conditions are met: (1) D1 and E1 are not the same; (2) D2 and E2 are not the same; (3) D3 and E3 are not the same.

[0015] According to an embodiment of the present invention, the polyester is obtained by a reaction between a saturated diol, a saturated diacid, and a molecular structure modifier; wherein the molecular structure modifier is selected from a double-terminated hydroxyl telechelic polymer containing C=C bonds.

[0016] Preferably, the polyester has structural units represented by formula (I) as described above (such as structural units represented by formula (II), (i), (ii) or (iii); and structural units represented by formula (III) (such as structural units represented by formula (D) and formula (E)).

[0017] According to an embodiment of the present invention, the reaction between the saturated diol, the saturated diacid, and the molecular structure modifier is an esterification reaction and a polycondensation reaction.

[0018] According to an embodiment of the present invention, the C=C bond-containing dual-hydroxyl telechelic polymer is selected from one of dual-hydroxyl polybutadiene (HTPB), dual-hydroxyl polyisoprene, and dual-hydroxyl myrcene, preferably dual-hydroxyl polybutadiene.

[0019] According to embodiments of the present invention, the hydroxyl values ​​of the C=C-terminated hydroxyl telechelic polymers are the same or different, and are independently selected from 0.1-1 mmol / g, for example 0.47-0.53 mmol / g, 0.54-0.64 mmol / g, 0.65-0.70 mmol / g or 0.71-0.80 mmol / g.

[0020] According to an embodiment of the present invention, the saturated diol is selected from at least two of ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, and 1,6-hexanediol, preferably 1,2-propanediol and 1,4-butanediol.

[0021] According to an embodiment of the present invention, the saturated dicarboxylic acid is selected from at least two of succinic acid, glutaric acid, adipic acid, and sebacic acid, preferably 1,6-adipic acid and 1,10-sebacic acid.

[0022] According to an embodiment of the present invention, the molar ratio of the total molar amount of -OH in the saturated diol and the C=C-terminated hydroxyl telechelic polymer to the molar amount of -COOH in the saturated dicarboxylic acid is (1.05~1.8):1.

[0023] According to an embodiment of the present invention, the amount of -OH in the C=C-containing double-terminated hydroxyl telechelic polymer is 0.1% to 1.0% of the total molar number of -OH in the saturated diol and the C=C-containing double-terminated hydroxyl telechelic polymer, preferably 0.15% to 0.50%.

[0024] According to an embodiment of the present invention, the C=C double bond content in the polyester is 0.5 mol% to 15.0 mol%, preferably 0.9 mol% to 10 mol%, more preferably 0.9 mol% to 5.0 mol%, for example, 1 mol%, 1.5 mol%, 2 mol%, 2.5 mol%, 3 mol%, 3.5 mol%, or any two of the above values.

[0025] According to an embodiment of the present invention, an antioxidant and a polymerization inhibitor are also added during the esterification reaction.

[0026] According to an embodiment of the present invention, the antioxidant is selected from one or two of antioxidant 1010, antioxidant 245, phosphoric acid, phosphorous acid, and phosphate ester.

[0027] According to an embodiment of the present invention, the amount of antioxidant used is 0.01% to 0.6% of the total mass of diol and diacid, preferably 0.01% to 0.2%.

[0028] According to an embodiment of the present invention, the polymerization inhibitor is selected from at least one of hydroquinone, benzoquinone, tetrachlorobenzoquinone, 1,3,5-trinitrobenzene, and 1,1-diphenyl-2-trinitrobenzylhydrazine.

[0029] According to an embodiment of the present invention, the amount of the polymerization inhibitor is 0.01% to 0.6% of the total mass of the diol and diacid, preferably 0.01% to 0.2%.

[0030] According to an embodiment of the present invention, a catalyst is also added during the polycondensation reaction.

[0031] According to an embodiment of the present invention, the catalyst is selected from titanium-based catalysts, antimony-based catalysts, and tin-based catalysts, such as at least one of tetrabutyl titanate, tetraisopropyl titanate, antimony trioxide, stannous octoate, and stannous chloride.

[0032] According to an embodiment of the present invention, the amount of catalyst used is 0.05% to 1.5% of the total mass of the diol and the dicarboxylic acid, for example, 0.1%, 0.5%, 1% or any two of the above values.

[0033] According to an embodiment of the present invention, the number average molecular weight (Mn) of the polyester is not less than 10,000, for example, 10,000, 12,000, 14,000, 16,000, 18,000, 20,000, 25,000, 30,000, 35,000, 40,000, 45,000, 50,000 or a range between any two of the above values.

[0034] According to an embodiment of the present invention, the weight-average molecular weight (Mw) of the polyester is not less than 20,000, for example, 20,000, 25,000, 30,000, 35,000, 40,000, 45,000, 50,000, 55,000, 60,000, 70,000, 80,000, 90,000 or a range between any two of the above values.

[0035] According to an embodiment of the present invention, the polydispersity index (PDI) of the polyester is less than 5, preferably 1 to 3, for example 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9 or any two of the above values.

[0036] According to an embodiment of the present invention, the glass transition temperature of the polyester is -25°C to -60°C.

[0037] According to an embodiment of the present invention, the polyester is a bio-based polyester, which is prepared using at least one bio-based source raw material. Preferably, one, two, or all of the saturated diol, saturated diacid, and molecular structure modifier are bio-based.

[0038] According to an embodiment of the present invention, the polyester is an elastomer, preferably a bio-based polyester elastomer.

[0039] The present invention also provides a method for preparing the above-mentioned bio-based polyester latex, the method comprising the following steps: (S1) Synthesis of polyester: The polyester is obtained by reacting saturated diol, saturated diacid and molecular structure modifier; (S2) Preparation of bio-based polyester latex: The polyester obtained in step (S1) is dissolved in an organic solvent, and then an emulsifier and water are added. The mixture is emulsified under high-speed shearing. After removing the organic solvent, bio-based polyester latex is obtained.

[0040] According to an embodiment of the present invention, in step (S1), the reaction between the saturated diol, the saturated diacid, and the molecular structure modifier is an esterification reaction and a polycondensation reaction.

[0041] According to an embodiment of the present invention, step (S1) of the method for synthesizing polyester specifically includes the following steps: (1) Mix saturated diol, saturated diacid, molecular structure modifier, antioxidant and polymerization inhibitor, and carry out esterification reaction in an inert atmosphere; (2) After the esterification reaction is completed, a catalyst is added under an inert atmosphere, the temperature is raised to the temperature of the polycondensation reaction, and the polycondensation reaction is carried out under vacuum to obtain the polyester.

[0042] According to embodiments of the present invention, the saturated diol, saturated dicarboxylic acid, molecular structure modifier, antioxidant, polymerization inhibitor, and catalyst described above have the meanings as stated above.

[0043] According to an embodiment of the present invention, in step (1), the esterification reaction is carried out under normal pressure.

[0044] According to an embodiment of the present invention, in step (1), the inert atmosphere refers to an atmosphere that is inert to the reaction, such as N2.

[0045] According to an embodiment of the present invention, in step (1), the temperature of the esterification reaction is 160~200℃, preferably 170~190℃; the time of the esterification reaction is 2~4 h, preferably 2.5~3.5 h.

[0046] According to an embodiment of the present invention, in step (2), the temperature of the polycondensation reaction is 200~240℃, preferably 210~230℃; the time of the polycondensation reaction is 2~10 h, preferably 3~8 h.

[0047] According to an embodiment of the present invention, in step (2), the polycondensation reaction is carried out in a vacuum state, and a vacuum state known in the art can be selected, such as a pressure of less than 800 Pa, preferably less than 500 Pa.

[0048] According to an embodiment of the present invention, in step (2), during the polycondensation reaction, small molecules and water in the system are removed.

[0049] According to an embodiment of the present invention, in step (2), after the polycondensation reaction is completed, the polyester is collected by a method known in the art; for example, an inert gas is introduced to expel the polyester from the reaction apparatus.

[0050] According to an embodiment of the present invention, in step (S2), the organic solvent is selected from, but not limited to, one, two or more of dichloromethane, trichloromethane, and tetrahydrofuran.

[0051] According to an embodiment of the present invention, in step (S2), the emulsifier is selected from, but not limited to, one, two or more of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, and polyethylene glycol octylphenyl ether.

[0052] According to an embodiment of the present invention, in step (S2), the weight ratio of polyester, emulsifier, organic solvent and water is 10:(0.1~0.5):(30~100):(10~100), preferably 10:(0.2~0.4):(40~50):(20~50), for example 10:0.2:40:50, 10:0.3:45:50, 10:0.4:50:50.

[0053] According to an embodiment of the present invention, in step (S2), the water is preferably deionized water.

[0054] According to an embodiment of the present invention, in step (S2), the high-speed shearing action refers to a rotational speed of 1000-10000 rpm, for example 5000 rpm.

[0055] The present invention also provides the application of the above-mentioned bio-based polyester latex in crosslinking film formation, for example, for the preparation of bio-based polyester films.

[0056] The present invention also provides a bio-based polyester film, wherein the raw material of the polyester film includes the above-mentioned bio-based polyester latex.

[0057] The present invention also provides a method for forming the above-mentioned bio-based polyester film, the method comprising: mixing the above-mentioned bio-based polyester latex and crosslinking agent, laying the film, and curing it at 120~180°C for 10~30 min to obtain the bio-based polyester film.

[0058] According to an embodiment of the present invention, the crosslinking agent is selected from, but not limited to, at least one of dicumyl peroxide and 2,4-di-tert-butyl peroxide.

[0059] According to an embodiment of the present invention, the amount of crosslinking agent added is 0.5% to 10% of the mass of polyester in the bio-based polyester latex, for example, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or any two of the above values.

[0060] Beneficial effects: (1) Excellent elasticity and toughness are achieved, fundamentally overcoming the brittleness of bio-based polyesters. The core of this invention lies in constructing a microphase structure with distinct "soft and hard segments". Among them, the short-chain ester units formed by bio-based diols and diacids, due to their strong regularity and high cohesive energy, tend to aggregate in the polymer to form "hard segments", which act as physical crosslinking points and provide the necessary strength and modulus for the material. The introduced molecular structure regulator chain segment has a low glass transition temperature (usually below -70℃) and the main chain is composed of flexible C-C single bonds, which act as "soft segments" in the polymer. The thermodynamic incompatibility between soft and hard segments leads to microphase separation. The flexible soft segments endow the material with excellent elongation and low-temperature toughness, while the hard segments ensure that the material can effectively rebound after stretching. Unlike the existing technology that relies on physical blending to introduce a flexible phase, the molecular structure regulator of this invention avoids macroscopic phase separation through covalent chemical bonding, ensuring the uniformity and performance stability of the material. Furthermore, the introduction of bio-based diols containing side methyl groups further disrupts the chain symmetry and works synergistically with long-chain bio-based dicarboxylic acids to effectively reduce the overall crystallinity of the polymer and increase the proportion of amorphous regions, thus providing a structural basis for high elasticity.

[0061] (2) Mechanical strength is improved by pre-embedded crosslinking sites and efficient crosslinking. Another major innovation of this invention is the "dual-function" design of the molecular structure regulator. It not only acts as a flexible segment for internal toughening during the polymerization stage, but more importantly, the unsaturated C=C double bonds on its main chain pre-embed active sites for the subsequent crosslinking reaction. Free radical crosslinking initiated by peroxides (such as dicumyl peroxide) is a highly efficient crosslinking technology. When the free radicals generated by the thermal decomposition of peroxides attack the molecular structure regulator chain segments, the resulting macromolecular free radicals can combine with each other or attack the double bonds on other chains to form a stable chemical crosslinking network. The formation of this three-dimensional network binds the linear macromolecular chains that could originally slide relatively together. When the material is subjected to force, the deformation mainly comes from the extension of the flexible chain segments, while the crosslinking points effectively prevent the chain slippage, thereby ensuring the tensile strength, elongation and elasticity of the material.

[0062] (3) This provides a stable and environmentally friendly method for latex preparation, broadening its application areas. The introduction of non-polar molecular structure modifier segments into the polymer molecular chain enhances the overall hydrophobicity of the polymer. However, due to its unique soft and hard segment structure, under suitable emulsifier and shearing action, it can form a stable micelle structure with hydrophobic segments as the core and hydrophilic groups (emulsifiers) on the outside. By precisely controlling the solvent evaporation rate, water-based latex with narrow particle size distribution and good storage stability can be obtained. This latex form is not only environmentally friendly (using water as the dispersion medium) but also greatly expands the application range of this bio-based polyester, enabling the preparation of environmentally friendly coatings, dipped gloves, water-based adhesives, etc.

[0063] (4) The process flow is reasonable and has good prospects for industrial application. The esterification-polymerization reaction adopted in this invention is a mature process route in the polyester industry, and the equipment is highly versatile. Latex preparation and peroxide crosslinking are also commonly used industrial technologies. The entire method route is clear, the conditions are mild and controllable, and it is easy to achieve large-scale production, providing a practical and feasible technical path for the industrialization of high-performance bio-based polyesters.

[0064] In summary, this invention, through an innovative synergistic strategy of "copolymer internal toughening" and "crosslinking network enhancement," successfully prepared a polyester latex and polyester film that possess both high bio-based content and excellent mechanical properties, solving many pain points of existing technologies and demonstrating significant innovation and practical value. Attached Figure Description

[0065] Figure 1 The infrared spectrum of the bio-based polyester prepared in Example 1 is shown.

[0066] Figure 2 The bio-based polyester of Example 1 1 H-NMR spectrum.

[0067] Figure 3 For the polyester of Comparative Example 1 1 H-NMR spectrum.

[0068] Figure 4 The image shows the DSC curve of the bio-based polyester from Example 1. Detailed Implementation

[0069] Polyester A polyester comprising the structural unit shown in formula (I): (I) U1, U2, U3, and U4 may be the same or different, and are independently selected from C1, U2, U3, and U4 that are chemically bonded, unsubstituted, or substituted by at least one group represented by formula (A). 1-10 alkylene, unsubstituted or substituted with at least one group of formula (A) 2-10 alkenyl; (A) Each Q may be the same or different, and each is independently selected from chemical bonds or C. 1-10 Alkylene; Each R m They are the same or different, and are selected independently from H or C. 1-10 alkyl; Each R n They are the same or different, and are selected independently from H or C. 1-10 alkyl; Z1, Z2, Z3, and Z4 may be the same or different, and are independently selected from chemical bonds or C bonds. 1-10 Alkylene; Represents chemical bonds; 'a' represents a number from 6 to 30; b represents a number between 8 and 35; c represents a number from 16 to 65; d represents a number from 0 to 5; The condition is that two, three, or four of U1, U2, U3, and U4 are selected from C1, U2, U3, and U4 that are unsubstituted or substituted by at least one group represented by formula (A). 2-10 It is an alkenyl group, and at most one of U1, U2, U3 and U4 is a chemical bond.

[0070] According to an embodiment of the present invention, the structural unit shown in formula (I) has the structure shown in formula (II): (II) Among them, Y1, Y2, Y6, Y7, Y8, and Y9 are the same or different, and are independently selected from C. 1-10 Alkylene; Y3, Y4, and Y9 may be the same or different, and are independently selected from chemical bonds, C, and D. 1-10 Alkylene or C 2-10 alkenyl; Y5 is selected from C 1-10 Mesenchymal or carbon atom; Y6 is selected from C 1-10 Alkylene or C 1-10 Phenyl group; Indicates a single or double bond, provided that when When representing a single bond, Y5 is C. 1-10 Phenylene group, Y6 is C 1-10 alkylene; when When representing a double bond, Y5 represents a carbon atom and Y6 represents a carbon atom. 1-10 Phenyl group; Z1, Z2, Z3, and Z4 may be the same or different, and are independently selected from chemical bonds or C bonds. 1-10 Alkylene; R1, R2, R3, and R4 may be the same or different, and are independently selected from H or C. 1-10 alkyl; Q1 is selected from chemical bonds or C. 1-10 Alkylene; Each R a They are the same or different, and are selected independently from H or C. 1-10 alkyl; Each R bThey are the same or different, and are selected independently from H or C. 1-10 alkyl; R5 and R6 may be the same or different, and are independently selected from H and C. 1-10 Alkyl groups or groups represented by formula (B): (B) Q2 is selected from chemical bonds or C. 1-10 Alkylene; Each R c They are the same or different, and are selected independently from H or C. 1-10 alkyl; Each R d They are the same or different, and are selected independently from H or C. 1-10 alkyl; Represents chemical bonds; 'a' represents a number from 6 to 30; b represents a number between 8 and 35; c represents a number from 16 to 65; d represents a number from 0 to 5.

[0071] According to an embodiment of the present invention, 'a' represents a number from 6 to 30, such as 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30.

[0072] b represents a number from 8 to 35, such as 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35.

[0073] c represents a number from 16 to 65, for example, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65.

[0074] d represents a number from 0 to 5, such as 0, 1, 2, 3, 4, 5.

[0075] As an example, the structural unit shown in equation (I) is selected from at least one of the following structural units (i), (ii) and (iii): (i) wherein, a represents a number of 15 to 30, b represents a number of 20 to 35, and c represents a number of 40 to 65; (ii) wherein, a represents a number of 12 to 24, b represents a number of 16 to 28, c represents a number of 32 to 52, and d represents a number of 0 to 5; (iii) wherein, a represents a number of 6 to 12, b represents a number of 8 to 14, and c represents a number of 16 to 26.

[0076] According to an embodiment of the present invention, the polyester further comprises a structural unit represented by the following formula (III): (III) wherein, Alk1, Alk2 and Alk3 are the same or different, and are each independently selected from C 1-12 alkylene.

[0077] Preferably, the polyester comprises a structural unit represented by formula (D) and a structural unit represented by formula (E): (D) (E) wherein, D1, D2, D3, E1, E2 and E3 are the same or different, and are each independently selected from C 1-12 alkylene; with the proviso that one, two or three of the following conditions are satisfied: (1) D1 is different from E1; (2) D2 is different from E2; (3) D3 is different from E3.

[0078] As an example, the number of carbon atoms of D1 < the number of carbon atoms of E1, for example, D1 is selected from C 1-3 alkyl, and E1 is selected from C 4-10 alkyl; and / or, the number of carbon atoms of D3 < the number of carbon atoms of E3, for example, D3 is selected from C 1-3 alkyl, and E3 is selected from C 4-10 alkyl.

[0079] As an example, the number of carbon atoms of D1 > the number of carbon atoms of E1, for example, D1 is selected from C 4-10 alkyl, and E1 is selected from C 1-3 alkyl; and / or, the number of carbon atoms of D3 > the number of carbon atoms of E3, for example, D3 is selected from C 4-10 alkyl, and E3 is selected from C 1-3 alkyl.

[0080] As an example, the number of carbon atoms in D2 is less than the number of carbon atoms in E2, for example D2 is selected from C 1-6 alkyl, and E2 is selected from C 7-12 alkyl.

[0081] As an example, the number of carbon atoms in D2 is greater than the number of carbon atoms in E2, for example D2 is selected from C 7-12 alkyl, and E2 is selected from C 1-6 alkyl.

[0082] According to an embodiment of the present invention, the polyester is obtained by the reaction among a saturated diol, a saturated dibasic acid and a molecular structure modifier; wherein the molecular structure modifier is selected from telechelic polymers with hydroxyl groups at both ends containing a C=C bond.

[0083] Preferably, the polyester has the structural unit represented by formula (I) as described above (such as the structural unit represented by formula (II), (i), (ii) or (iii)); and the structural unit represented by formula (III) (such as the structural unit represented by formula (D) and the structural unit represented by formula (E)).

[0084] According to an embodiment of the present invention, the reaction among the saturated diol, the saturated dibasic acid and the molecular structure modifier is an esterification reaction and a polycondensation reaction.

[0085] According to an embodiment of the present invention, the telechelic polymer with hydroxyl groups at both ends containing a C=C bond is selected from one of hydroxyl-terminated polybutadiene (HTPB), hydroxyl-terminated polyisoprene, and hydroxyl-terminated myrcene, preferably hydroxyl-terminated polybutadiene.

[0086] According to an embodiment of the present invention, the hydroxyl values of the telechelic polymer with hydroxyl groups at both ends containing a C=C bond are the same or different, and are independently selected from 0.1-1 mmol / g, for example 0.47-0.53 mmol / g, 0.54-0.64 mmol / g, 0.65~0.70 mmol / g or 0.71-0.80 mmol / g.

[0087] According to an embodiment of the present invention, the saturated diol is selected from at least two of ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol and 1,6-hexanediol, preferably 1,2-propanediol and 1,4-butanediol.

[0088] According to an embodiment of the present invention, the saturated dibasic acid is selected from at least two of succinic acid, glutaric acid, adipic acid and sebacic acid, preferably 1,6-adipic acid and 1,10-sebacic acid.

[0089] According to an embodiment of the present invention, the molar ratio of the total molar amount of -OH in the saturated diol and the C=C-terminated hydroxyl telechelic polymer to the molar amount of -COOH in the saturated dicarboxylic acid is (1.05~1.8):1, preferably (1.1~1.4):1, for example 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1.

[0090] According to an embodiment of the present invention, the amount of -OH in the C=C-containing double-terminated hydroxyl telechelic polymer is 0.1% to 1.0% of the total molar amount of -OH in the saturated diol and the C=C-containing double-terminated hydroxyl telechelic polymer, preferably 0.15% to 0.50%, for example 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%.

[0091] According to an embodiment of the present invention, the C=C double bond content in the polyester is 1.0 mol% to 15.0 mol%, preferably 2.0 mol% to 15.0 mol%, more preferably 6 mol% to 15.0 mol%. For example, the C=C double bond content in the polyester is 1.0 mol%, 1.5 mol%, 1.6 mol%, 1.7 mol%, 1.8 mol%, 1.9 mol%, 2.0 mol%, 2.1 mol%, 2.2 mol%, 2.3 mol%, 2.4 mol%, 2.5 mol%, 2.6 mol%, 2.7 mol%, 2.8 mol%, 2.9 mol%, 3.0 mol%, 3.5 mol%, 4.0 mol%, 4.5 mol%, 5.0 mol%, 5.5 mol%, 6.0 mol%, 6.5 mol%, 7.0 mol%, 7.5 mol%, 8.0 mol%, 8.5 mol%, 9.0 mol%, 9.5 mol%, 10.0 mol%, 10.5 mol%, 11.0 mol%, 11.5 mol%, 12.0 mol%, 12.5 mol%, 13.0 mol%, 13.5 mol%. mol%, 14.0 mol%, 14.5 mol%, 15.0 mol%.

[0092] According to an embodiment of the present invention, an antioxidant and a polymerization inhibitor are also added during the esterification reaction.

[0093] According to an embodiment of the present invention, the antioxidant is selected from one or two of antioxidant 1010, antioxidant 245, phosphoric acid, phosphorous acid, and phosphate ester.

[0094] According to an embodiment of the present invention, the amount of antioxidant used is 0.01% to 0.6% of the total mass of diol and diacid, preferably 0.01% to 0.2%.

[0095] According to an embodiment of the present invention, the polymerization inhibitor is selected from at least one of hydroquinone, benzoquinone, tetrachlorobenzoquinone, 1,3,5-trinitrobenzene, and 1,1-diphenyl-2-trinitrobenzylhydrazine.

[0096] According to an embodiment of the present invention, the amount of the polymerization inhibitor is 0.01% to 0.6% of the total mass of the diol and diacid, preferably 0.01% to 0.2%.

[0097] According to an embodiment of the present invention, a catalyst is also added during the polycondensation reaction.

[0098] According to an embodiment of the present invention, the catalyst is selected from titanium-based catalysts, antimony-based catalysts, and tin-based catalysts, such as at least one of tetrabutyl titanate, tetraisopropyl titanate, antimony trioxide, stannous octoate, and stannous chloride.

[0099] According to an embodiment of the present invention, the amount of catalyst used is 0.05% to 1.5% of the total mass of the diol and diacid, preferably 0.1% to 0.5%, for example 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%.

[0100] According to an embodiment of the present invention, the number average molecular weight of the polyester is greater than 15,000, for example, 20,000, 25,000, 30,000, 35,000, 40,000, 45,000, 50,000, 60,000, 70,000, 80,000, 90,000, 100,000 or a range between any two of the above values.

[0101] According to an embodiment of the present invention, the polydispersity index of the polyester is less than 5, for example, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.5, 3.0, or 4.0.

[0102] According to an embodiment of the present invention, the glass transition temperature of the polyester is -25°C to -60°C, for example -26°C, -30°C, -35°C, -40°C, -45°C, -50°C, -54°C, and -58°C.

[0103] According to an embodiment of the present invention, the polyester is a bio-based polyester, which is prepared using at least one bio-based source raw material. Preferably, one, two, or all of the saturated diol, saturated diacid, and molecular structure modifier are bio-based.

[0104] According to an embodiment of the present invention, the polyester is an elastomer, preferably a bio-based polyester elastomer.

[0105] [Preparation methods of polyester] The above-mentioned method for preparing polyester includes reacting saturated diol, saturated diacid and molecular structure modifier.

[0106] According to an embodiment of the present invention, the reaction between the saturated diol, the saturated diacid, and the molecular structure modifier is an esterification reaction and a polycondensation reaction.

[0107] According to an embodiment of the present invention, the preparation method includes the following steps: (1) Mix saturated diol, saturated diacid, molecular structure modifier, antioxidant and polymerization inhibitor, and carry out esterification reaction in an inert atmosphere; (2) After the esterification reaction is completed, a catalyst is added under an inert atmosphere, the temperature is raised to the temperature of the polycondensation reaction, and the polycondensation reaction is carried out under vacuum to obtain the polyester.

[0108] According to embodiments of the present invention, the saturated diol, saturated dicarboxylic acid, molecular structure modifier, antioxidant, polymerization inhibitor, and catalyst described above have the meanings as stated above.

[0109] According to an embodiment of the present invention, in step (1), the esterification reaction is carried out under normal pressure.

[0110] According to an embodiment of the present invention, in step (1), the inert atmosphere refers to an atmosphere that is inert to the reaction, such as N2.

[0111] According to an embodiment of the present invention, in step (1), the temperature of the esterification reaction is 160~200℃, preferably 170~190℃; the time of the esterification reaction is 2~4 h, preferably 2.5~3.5 h.

[0112] According to an embodiment of the present invention, in step (2), the temperature of the polycondensation reaction is 200~240℃, preferably 210~230℃; the time of the polycondensation reaction is 2~10 h, preferably 3~8 h.

[0113] According to an embodiment of the present invention, in step (2), the polycondensation reaction is carried out in a vacuum state, and a vacuum state known in the art can be selected, such as a pressure of less than 800 Pa, preferably less than 500 Pa.

[0114] According to an embodiment of the present invention, in step (2), during the polycondensation reaction, small molecules and water in the system are removed.

[0115] According to an embodiment of the present invention, in step (2), after the polycondensation reaction is completed, the polyester is collected by a method known in the art; for example, an inert gas is introduced to expel the polyester from the reaction apparatus.

[0116] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention, and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0117] Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available products or can be prepared by known methods.

[0118] The test methods in the following embodiments include: Mechanical property testing: The tensile strength and elongation at break of the specimen were tested using an electronic universal tensile testing machine in accordance with GB / T 1040.1-2006 standard.

[0119] Example 1 (1) Synthesis of bio-based polyester: In a reaction apparatus equipped with a mechanical stirrer, nitrogen inlet and outlet, heating device, thermometer and condenser, 0.41 mol of 1,2-propanediol, 0.41 mol of 1,4-butanediol, 0.32 mol of sebacic acid, 0.36 mol of succinic acid, approximately 0.00137 mol of hydroxyl-terminated polybutadiene, and 0.1 wt% of antioxidant 1010 and 0.01 wt% of hydroquinone were added sequentially; stirring was started and nitrogen was introduced for 30 min to purge the air from the apparatus; under nitrogen atmosphere protection, the temperature was raised to 180℃ and esterification reaction was carried out for 4 h; after the reaction was completed, 0.2 wt% of tetrabutyl titanate was added, and then the pressure was gradually reduced to below 800 Pa while the temperature was slowly raised to 220℃ to carry out polycondensation reaction for 5 h. h; After the reaction is complete, heating is stopped, nitrogen gas is introduced to restore normal pressure, and the material is discharged while hot to obtain a light yellow transparent viscous bio-based polyester with Mn of 40214, Mw of 75602, PDI of 1.88, double bond content of 3.49 mol%, and Tg of -58.89℃. (2) Preparation of bio-based polyester latex: Weigh 10 parts (here, 10 parts refers to parts by weight; unless otherwise specified, "parts" in the following examples all refer to parts by weight) of the bio-based polyester elastomer obtained in step 1, add it to a beaker containing 40 parts of dichloromethane, and stir magnetically until the elastomer is completely dissolved; take another beaker, dissolve 0.2 parts of sodium dodecylbenzenesulfonate in 50 parts of deionized water; slowly add the dichloromethane polyester solution dropwise to the sodium dodecylbenzenesulfonate aqueous solution, and at the same time use a high-speed shear emulsifier to shear at a speed of 5000 rpm for 10 min to form a uniform milky white emulsion; transfer the emulsion to a round-bottom flask, place it in a 45℃ water bath for rotary evaporation for 4 h to remove dichloromethane; after the solvent is basically removed, let it stand to stabilize, and skim off the small amount of clear liquid that may exist on the upper layer to obtain the bio-based polyester latex; (3) Crosslinking film formation: Take 100 parts of the bio-based polyester latex prepared in step 2, add 1% of dicumyl peroxide by weight of polyester, and stir to disperse it evenly; pour the mixed latex evenly into a horizontally placed polytetrafluoroethylene mold to form a liquid film with a thickness of about 2 mm; let it stand at room temperature for one day to allow the liquid film to level; then, put the mold with the film in a vacuum oven and vacuum it at room temperature for 5 h to remove air bubbles, repeating this process twice; then, vulcanize the mold with the film at 120℃ for 30 min; after cooling and demolding, the bio-based polyester film is obtained. The tensile strength is 15 N and the elongation at break is 500%.

[0120] Example 2 (1) Synthesis of bio-based polyester: In a reaction apparatus equipped with a mechanical stirrer, nitrogen inlet and outlet, heating device, thermometer and condenser, 0.356 mol of ethylene glycol, 0.178 mol of 1,3-propanediol, 0.178 mol of 1,4-butanediol, 0.32 mol of glutaric acid, 0.36 mol of succinic acid, approximately 0.0014 mol of hydroxyl-terminated polyisoprene, and 0.1 wt% of antioxidant 245 and 0.05 wt% of benzoquinone were added sequentially; stirring was started, and nitrogen was introduced for 30 min to purge the air from the apparatus; under nitrogen atmosphere protection, the temperature was raised to 190℃ and esterification reaction was carried out for 5 h; after the reaction was completed, 0.5 wt% of tetraisopropyl titanate was added, and then the pressure was gradually reduced to below 800 Pa, while the temperature was slowly raised to 230℃ to carry out polycondensation reaction 2 h. h; After the reaction is complete, heating is stopped, nitrogen gas is introduced to restore normal pressure, and the material is discharged while hot to obtain a light yellow transparent viscous bio-based polyester with Mn of 12043, Mw of 25488, PDI of 1.95, double bond content of 0.98 mol%, and Tg of -18.06℃. (2) Preparation of bio-based polyester latex: Weigh 10 parts of the bio-based polyester elastomer obtained in step 1 and add it to a beaker containing 45 parts of chloroform. Stir magnetically until the elastomer is completely dissolved. Take another beaker and dissolve 0.3 parts of sodium dodecyl sulfate in 50 parts of deionized water. Slowly add the chloroform polyester solution to the sodium dodecyl sulfate aqueous solution and simultaneously use a high-speed shear emulsifier at 5000 rpm for 10 min to form a uniform milky white emulsion. Transfer the emulsion to a round-bottom flask and place it in a 45℃ water bath for rotary evaporation for 4 h to remove chloroform. After the solvent is basically removed, let it stand to stabilize and skim off any small amount of clear liquid that may be present on the upper layer to obtain the bio-based polyester latex. (3) Crosslinking film formation: Take 100 parts of the latex prepared in step 2, add 0.5% of 2,4-di-tert-butyl peroxide by weight of polyester, and stir to disperse it evenly; pour the mixed latex evenly into a horizontally placed polytetrafluoroethylene mold to form a liquid film with a thickness of about 2 mm; let it stand at room temperature for one day to allow the liquid film to level; then, put the mold with the film in a vacuum oven and vacuum it at room temperature for 5 h to remove air bubbles, repeating this process twice; then, vulcanize the mold with the film at 160℃ for 20 min; after cooling and demolding, a bio-based polyester film is obtained, which is tested to have a tensile strength of 10 N and an elongation at break of 450%.

[0121] Example 3 (1) Synthesis of bio-based polyester: In a reaction apparatus equipped with a mechanical stirrer, nitrogen inlet and outlet, heating device, thermometer and condenser, 0.4 mol of 1,5-pentanediol, 0.4 mol of 1,6-hexanediol, 0.18 mol of adipic acid, 0.18 mol of succinic acid, 0.37 mol of sebacic acid, approximately 0.004 mol of hydroxyl-terminated polybutadiene-acrylonitrile rubber, 0.004 mol of hydroxyl-terminated polyisoprene, and 0.1 wt% of phosphoric acid and 0.1 wt% of tetrachlorobenzoquinone by total monomer mass were added sequentially; stirring was started and nitrogen was introduced for 30 min to purge the air in the apparatus; under nitrogen atmosphere protection, the temperature was raised to 160℃ and esterification reaction was carried out for 6 h; after the reaction was completed, 0.05 wt% of antimony trioxide by total monomer mass was added, and then the pressure was gradually reduced to below 800 Pa, while the temperature was slowly raised to 170℃ to carry out polycondensation reaction for 10 h. h; After the reaction is complete, heating is stopped, nitrogen gas is introduced to restore normal pressure, and the material is discharged while hot to obtain a light yellow transparent viscous bio-based polyester with Mn of 11697, Mw of 27687, PDI of 2.37, double bond content of 1.9 mol%, and Tg of -39.46℃. (2) Preparation of bio-based polyester latex: Weigh 10 parts of the bio-based polyester elastomer obtained in step 1 and add it to a beaker containing 50 parts of dichloromethane. Stir magnetically until the elastomer is completely dissolved. Take another beaker and dissolve 0.4 parts of sodium dodecylbenzenesulfonate in 50 parts of deionized water. Slowly add the dichloromethane polyester solution to the sodium dodecylbenzenesulfonate aqueous solution. At the same time, use a high-speed shear emulsifier to shear at 5000 rpm for 10 min to form a uniform milky white emulsion. Transfer the emulsion to a round-bottom flask and place it in a 45℃ water bath for rotary evaporation for 4 h to remove dichloromethane. After the solvent is basically removed, let it stand to stabilize and skim off any small amount of clear liquid that may be present on the upper layer to obtain the bio-based polyester latex. (3) Crosslinking film formation: Take 100 parts of the latex prepared in step 2, add 2% of dicumyl peroxide by weight of polyester, and stir to disperse it evenly; pour the mixed latex evenly into a horizontally placed polytetrafluoroethylene mold to form a liquid film with a thickness of about 2 mm; let it stand at room temperature for one day to allow the liquid film to level; then, put the mold with the film in a vacuum oven and vacuum it at room temperature for 5 h to remove air bubbles, repeating this process twice; then, vulcanize the mold with the film at 180℃ for 10 min; after cooling and demolding, a bio-based polyester film is obtained, which is tested to have a tensile strength of 30 N and an elongation at break of 800%.

[0122] Example 4 (1) Synthesis of bio-based polyester: In a reaction apparatus equipped with a mechanical stirrer, nitrogen inlet and outlet, heating device, thermometer and condenser, 0.61 mol of 1,2-propanediol, 0.61 mol of 1,4-butanediol, 0.32 mol of adipic acid, 0.36 mol of sebacic acid, about 0.01 mol of dihydroxymyrcene, and 0.1 wt% of antioxidant 1010 and 0.6 wt% of hydroquinone were added sequentially; stirring was started and nitrogen was introduced for 30 min to purge the air in the apparatus; under nitrogen atmosphere protection, the temperature was raised to 200℃ and esterification reaction was carried out for 2 h; after the reaction was completed, 1.0 wt% of tetrabutyl titanate and 0.5 wt% of tetraisopropyl titanate were added, and then the pressure was gradually reduced to below 800 Pa, while the temperature was slowly raised to 200℃ to carry out polycondensation reaction for 4 h. h; After the reaction is complete, heating is stopped, nitrogen gas is introduced to restore normal pressure, and the material is discharged while hot to obtain a light yellow transparent viscous bio-based polyester with Mn of 19756, Mw of 42653, PDI of 2.16, double bond content of 3.2 mol%, and Tg of -34.26℃. (2) Preparation of bio-based polyester latex: Weigh 10 parts of the bio-based polyester elastomer obtained in step 1 and add it to a beaker containing 40 parts of dichloromethane. Stir magnetically until the elastomer is completely dissolved. Take another beaker and dissolve 0.2 parts of sodium dodecylbenzenesulfonate and 0.2 parts of sodium dodecyl sulfate in 20 parts of deionized water. Slowly add the dichloromethane polyester solution to the sodium dodecylbenzenesulfonate aqueous solution. At the same time, use a high-speed shear emulsifier to shear at 5000 rpm for 10 min to form a uniform milky white emulsion. Transfer the emulsion to a round-bottom flask and place it in a 45℃ water bath for rotary evaporation for 4 h to remove dichloromethane. After the solvent is basically removed, let it stand to stabilize and skim off any small amount of clear liquid that may be present on the upper layer to obtain the bio-based polyester latex. (3) Crosslinking film formation: Take 100 parts of the latex prepared in step 2, add 2% dicumyl peroxide and 8% 2,4-di-tert-butyl peroxide by weight of polyester, and stir to disperse evenly; pour the mixed latex evenly into a horizontally placed polytetrafluoroethylene mold to form a liquid film with a thickness of about 2 mm; let it stand at room temperature for one day to allow the liquid film to level; then, put the mold with the film in a vacuum oven and vacuum it at room temperature for 5 h to remove air bubbles, repeating this process twice; then, vulcanize the mold with the film at 140℃ for 25 min; after cooling and demolding, a bio-based polyester film is obtained, which is tested to have a tensile strength of 40 N and an elongation at break of 300%.

[0123] Example 5 (1) Synthesis of bio-based polyester: In a reaction apparatus equipped with a mechanical stirrer, nitrogen inlet and outlet, heating device, thermometer and condenser, 0.47 mol of 1,2-propanediol, 0.47 mol of 1,4-butanediol, 0.36 mol of adipic acid, 0.32 mol of sebacic acid, approximately 0.0047 mol of hydroxyl-terminated polybutadiene, and 0.1 wt% of antioxidant 245 and 0.2 wt% of 1,3,5-trinitrobenzene were added sequentially; stirring was started and nitrogen was introduced for 30 min to purge the air from the apparatus; under nitrogen atmosphere protection, the temperature was raised to 170℃ and esterification reaction was carried out for 4.5 h; after the reaction was completed, 1.0 wt% of tetraisopropyl titanate was added, and then the pressure was gradually reduced to below 800 Pa while the temperature was slowly raised to 210℃ to carry out polycondensation reaction for 3 h. h; After the reaction is complete, heating is stopped, nitrogen gas is introduced to restore normal pressure, and the material is discharged while hot to obtain a light yellow transparent viscous bio-based polyester with Mn of 16589, Mw of 34165, PDI of 2.06, double bond content of 2.2 mol%, and Tg of -28.28℃. (2) Preparation of bio-based polyester latex: Weigh 10 parts of the bio-based polyester elastomer obtained in step 1 and add it to a beaker containing 45 parts of chloroform. Stir magnetically until the elastomer is completely dissolved. Take another beaker and dissolve 0.3 parts of sodium dodecylbenzenesulfonate in 30 parts of deionized water. Slowly add the chloroform polyester solution to the sodium dodecylbenzenesulfonate aqueous solution and simultaneously use a high-speed shear emulsifier at 5000 rpm for 10 min to form a uniform milky white emulsion. Transfer the emulsion to a round-bottom flask and place it in a 45℃ water bath for rotary evaporation for 4 h to remove chloroform. After the solvent is basically removed, let it stand to stabilize and skim off any small amount of clear liquid that may be present on the upper layer to obtain the bio-based polyester latex. (3) Crosslinking film formation: Take 100 parts of the latex prepared in step 2, add 8% by weight of polyester 2,4-di-tert-butyl peroxide isopropylbenzene, stir to disperse it evenly; pour the mixed latex evenly into a horizontally placed polytetrafluoroethylene mold to form a liquid film with a thickness of about 2 mm; let it stand at room temperature for one day to allow the liquid film to level; then, put the mold with the film in a vacuum oven and vacuum it at room temperature for 5 h to remove air bubbles, repeat this process twice; then, vulcanize the mold with the film at 170℃ for 10 min; after cooling and demolding, a bio-based polyester film is obtained, and its tensile strength is 35 N and its elongation at break is 200%.

[0124] Example 6 (1) Synthesis of bio-based polyester: In a reaction apparatus equipped with a mechanical stirrer, nitrogen inlet and outlet, heating device, thermometer and condenser, 0.44 mol of 1,2-propanediol, 0.44 mol of 1,4-butanediol, 0.36 mol of adipic acid, 0.32 mol of sebacic acid, about 0.0035 mol of hydroxyl-terminated polybutadiene, and 0.1 wt% of antioxidant 245 and 0.2 wt% of 1,3,5-trinitrobenzene were added sequentially; stirring was started and nitrogen was introduced for 30 min to purge the air in the apparatus; under nitrogen atmosphere protection, the temperature was raised to 180℃ and esterification reaction was carried out for 5.5 h; after the reaction was completed, 0.1 wt% of tetrabutyl titanate was added, and then the pressure was gradually reduced to below 800 Pa, while the temperature was slowly raised to 200℃ to carry out polycondensation reaction for 8 h. h; After the reaction is complete, heating is stopped, nitrogen gas is introduced to restore normal pressure, and the material is discharged while hot to obtain a light yellow transparent viscous bio-based polyester with Mn of 17086, Mw of 36861, PDI of 2.16, double bond content of 2.97 mol%, and Tg of -26.44℃. (2) Preparation of bio-based polyester latex: Weigh 10 parts of the bio-based polyester elastomer obtained in step 1 and add it to a beaker containing 50 parts of chloroform. Stir magnetically until the elastomer is completely dissolved. Take another beaker and dissolve 0.2 parts of sodium dodecylbenzenesulfonate in 20 parts of deionized water. Slowly add the chloroform polyester solution to the sodium dodecylbenzenesulfonate aqueous solution and simultaneously use a high-speed shear emulsifier at 5000 rpm for 10 min to form a uniform milky white emulsion. Transfer the emulsion to a round-bottom flask and place it in a 45℃ water bath for rotary evaporation for 4 h to remove chloroform. After the solvent is basically removed, let it stand to stabilize and skim off any small amount of clear liquid that may be present on the upper layer to obtain the bio-based polyester latex. (3) Crosslinking film formation: Take 100 parts of the latex prepared in step 2, add 4% of dicumyl peroxide by weight of polyester, and stir to disperse it evenly; pour the mixed latex evenly into a horizontally placed polytetrafluoroethylene mold to form a liquid film with a thickness of about 2 mm; let it stand at room temperature for one day to allow the liquid film to level; then, put the mold with the film in a vacuum oven and vacuum it at room temperature for 5 h to remove air bubbles, repeating this process twice; then, vulcanize the mold with the film at 165℃ for 15 min; after cooling and demolding, a bio-based polyester film is obtained, which is tested to have a tensile strength of 30 N and an elongation at break of 700%.

[0125] Example 7 The only difference from Example 6 is that the amount of -OH in the molecular structure modifier in step (1) is 0.1% of the total molar number of -OH in the bio-based diol and the molecular structure modifier, for comparison; all other steps and parameters are exactly the same as in Example 6. The bio-based polyester has Mn of 21766, Mw of 46569, PDI of 2.14, double bond content of 1.12 mol%, and Tg of -24.65℃. The bio-based polyester film obtained was tested and found to have a tensile strength of 35 N and an elongation at break of 650%.

[0126] Example 8 The only difference from Example 6 is that the amount of crosslinking agent added in step (3) is 1% of the polyester mass, for comparison; all other steps and parameters are exactly the same as in Example 6. The resulting bio-based polyester has Mn of 17458, Mw of 38661, PDI of 2.21, double bond content of 3.02 mol%, and Tg of -26.79℃. The bio-based polyester film obtained was tested and found to have a tensile strength of 25 N and an elongation at break of 800%.

[0127] Comparative Example 1 The only difference from Example 6 is that no molecular structure modifier is added in step (1), and the total molar ratio of dicarboxylic acid and diol remains close for comparison; all other steps and parameters are exactly the same as in Example 6. The resulting bio-based polyester has a Mn of 9824, a Mw of 17854, a PDI of 1.82, a double bond content of 0.12 mol%, and a Tg of -22.58℃. The bio-based polyester film obtained was tested and found to have a tensile strength of 10 N and an elongation at break of 80%.

[0128] Comparative Example 2 The only difference from Example 6 is that no crosslinking agent is added in step (3) for comparison; all other steps and parameters are exactly the same as in Example 6; ultimately, the bio-based polyester latex obtained cannot form a film.

[0129] The performance of the bio-based polyester films prepared in Examples 6-8 and Comparative Examples 1-2 was tested, and the results are shown in Table 1.

[0130] Table 1. Performance comparison of bio-based polyester films obtained from different embodiments

[0131] Comparing Example 6 and Comparative Example 1, the only variable was the addition of a molecular structure modifier (hydroxyl-terminated polybutadiene). As shown in Table 1, the Comparative Example 1 sample without the molecular structure modifier exhibited typical brittle polyester characteristics: low breaking force (10 N) and poor elongation at break (80%). In contrast, Example 6, after introducing a small amount of the molecular structure modifier, showed an increase in elongation at break to 700% and a breaking force to 30 N, exhibiting excellent elastomer behavior. This demonstrates that the present invention, by introducing a molecular structure modifier as a flexible soft segment through copolymerization, can effectively improve the toughness and elasticity of the material at the molecular chain level, solving the brittleness problem of traditional bio-based polyesters and proving the decisive role of the creative introduction of a molecular structure modifier in the mechanical strength of bio-based polyester films.

[0132] Comparing Examples 6 and 7, when the amount of molecular structure modifier added increased from 0.1 mol% to 0.3 mol%, the elongation at break of the material further increased to 700%, but the tensile strength decreased slightly. This is because the content of dihydroxyl-terminated polybutadiene, as a soft segment, makes the material more flexible and easier to stretch when its content increases, but at the same time, it sacrifices some strength due to the relative decrease in the content of hard segments. This shows that by controlling the amount of molecular structure modifier, the mechanical properties of the material can be easily adjusted to meet different application requirements.

[0133] Comparing Example 6 and Comparative Example 2, the only variable was the addition of a crosslinking agent. As shown in Table 1, without the addition of a crosslinking agent, the resulting bio-based polyester latex could not form a film. Comparing Example 6 and Example 8, when the amount of dicumyl peroxide crosslinking agent increased from 1% to 4%, the tensile strength of the material increased from 25 N to 30 N, but the elongation at break decreased. This is because increasing the amount of DCP increased the crosslinking density, forming a denser and more stable three-dimensional crosslinked network, effectively improving the strength of the material. This confirms that the strategy of using molecular structure adjustment to pre-embed crosslinking sites and performing peroxide crosslinking is an effective means to improve the overall performance of materials.

[0134] In summary, this invention, through innovative formulation design, successfully prepared a high-performance bio-based polyester elastomer material, demonstrating significant technical advantages and application potential.

[0135] The exemplary embodiments of the present invention have been described above. However, the scope of protection of the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made by those skilled in the art within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A bio-based polyester latex, characterized in that, The bio-based polyester latex comprises a solvent, an emulsifier, and a polyester containing structural units of formula (I): （I） U1, U2, U3, and U4 may be the same or different, and are independently selected from C1, U2, U3, and U4 that are chemically bonded, unsubstituted, or substituted by at least one group represented by formula (A). 1-10 alkylene, unsubstituted or substituted with at least one group of formula (A) 2-10 alkenyl; （A） Each Q may be the same or different, and each is independently selected from chemical bonds or C. 1-10 Alkylene; Each R m They are the same or different, and are selected independently from H or C. 1-10 alkyl; Each R n They are the same or different, and are selected independently from H or C. 1-10 alkyl; Z1, Z2, Z3, and Z4 may be the same or different, and are independently selected from chemical bonds or C bonds. 1-10 Alkylene; Represents chemical bonds; 'a' represents a number from 6 to 30; b represents a number between 8 and 35; c represents a number from 16 to 65; d represents a number from 0 to 5; The condition is that two, three, or four of U1, U2, U3, and U4 are selected from C1, U2, U3, and U4 that are unsubstituted or substituted by at least one group represented by formula (A). 2-10 It is an alkenyl group, and at most one of U1, U2, U3 and U4 is a chemical bond.

2. The bio-based polyester latex according to claim 1, characterized in that, The solvent is selected from water, and optionally includes or excludes organic solvents; the solvent is selected from water; the organic solvent is selected from one, two or more of dichloromethane, trichloromethane, and tetrahydrofuran; The emulsifier is selected from one, two or more of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, and polyethylene glycol octylphenyl ether; The weight ratio of the polyester, emulsifier and solvent is 10:(0.1~0.5):(10~100).

3. The bio-based polyester latex according to claim 1, characterized in that, The structural unit shown in equation (I) has the structure shown in equation (II): (II) Among them, Y1, Y2, Y6, Y7, Y8, and Y9 are the same or different, and are independently selected from C. 1-10 Alkylene; Y3, Y4, and Y9 may be the same or different, and are independently selected from chemical bonds, C... 1-10 Alkylene or C 2-10 alkenyl; Y5 is selected from C 1-10 Mesenchymal or carbon atom; Y6 is selected from C 1-10 Alkylene or C 1-10 Phenyl group; Indicates a single or double bond, provided that when When representing a single bond, Y5 is C. 1-10 Phenylene group, Y6 is C 1-10 alkylene; when When representing a double bond, Y5 represents a carbon atom and Y6 represents a carbon atom. 1-10 Phenyl group; Z1, Z2, Z3, and Z4 may be the same or different, and are independently selected from chemical bonds or C bonds. 1-10 Alkylene; R1, R2, R3, and R4 may be the same or different, and are independently selected from H or C. 1-10 alkyl; Q1 is selected from chemical bonds or C. 1-10 Alkylene; Each R a They are the same or different, and are selected independently from H or C. 1-10 alkyl; Each R b They are the same or different, and are selected independently from H or C. 1-10 alkyl; R5 and R6 may be the same or different, and are independently selected from H and C. 1-10 Alkyl groups or groups represented by formula (B): （B） Q2 is selected from chemical bonds or C. 1-10 Alkylene; Each R c They are the same or different, and are selected independently from H or C. 1-10 alkyl; Each R d They are the same or different, and are selected independently from H or C. 1-10 alkyl; Represents chemical bonds; 'a' represents a number from 6 to 30; b represents a number between 8 and 35; c represents a number from 16 to 65; d represents a number from 0 to 5; The polyester further comprises the structural unit shown in formula (III): (III) Among them, Alk1, Alk2, and Alk3 may be the same or different, and are independently selected from C. 1-12 Alkylene; Optionally, the polyester comprises the structural unit shown in formula (D) and the structural unit shown in formula (E): （D） （E） Among them, D1, D2, D3, E1, E2, and E3 are the same or different, and are independently selected from C. 1-12 Alkylene; The condition is that one, two, or three of the following conditions are met: (1) D1 and E1 are not the same; (2) D2 and E2 are not the same; (3) D3 and E3 are not the same.

4. The bio-based polyester latex according to claim 1, characterized in that, The polyester is obtained by the reaction between a saturated diol, a saturated diacid, and a molecular structure modifier; wherein the molecular structure modifier is selected from a double-terminated hydroxyl telechelic polymer containing C=C bonds. The reaction between the saturated diol, the saturated dicarboxylic acid and the molecular structure modifier is an esterification reaction and a polycondensation reaction. The C=C bond-containing dual-hydroxyl telechelic polymer is selected from one of dual-hydroxyl polybutadiene (HTPB), dual-hydroxyl polyisoprene, and dual-hydroxyl myrcene. The hydroxyl values ​​of the C=C terminal hydroxyl telechelic polymers are the same or different, and are independently selected from 0.1-1 mmol / g; The saturated diol is selected from at least two of ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, and 1,6-hexanediol; The saturated dicarboxylic acid is selected from at least two of succinic acid, glutaric acid, adipic acid, and sebacic acid; The molar ratio of the total molar amount of -OH in the saturated diol and the C=C-terminated hydroxyl telechelic polymer to the molar amount of -COOH in the saturated dicarboxylic acid is (1.05~1.8):1; The amount of -OH in the C=C-terminated hydroxyl telechelic polymer is 0.1% to 1.0% of the total molar number of -OH in the saturated diol and the C=C-terminated hydroxyl telechelic polymer.

5. The bio-based polyester latex according to claim 1, characterized in that, The C=C double bond content in the polyester is 0.5 mol% to 15.0 mol%; The number-average molecular weight of the polyester is not less than 10,000; The weight-average molecular weight of the polyester is not less than 20,000; The polydispersity index of the polyester is less than 5; The glass transition temperature of the polyester is -25℃ to -60℃; The polyester is a bio-based polyester, which is prepared using at least one bio-based raw material; one, two, or all of the saturated diol, saturated dicarboxylic acid, and molecular structure modifier are bio-based.

6. The method for preparing the bio-based polyester latex according to any one of claims 1-5, characterized in that, The preparation method includes the following steps: (S1) Synthesis of polyester: The polyester is obtained by reacting saturated diol, saturated diacid and molecular structure modifier; (S2) Preparation of bio-based polyester latex: The polyester obtained in step (S1) is dissolved in an organic solvent, and then an emulsifier and water are added. The mixture is emulsified under high-speed shearing. After removing the organic solvent, bio-based polyester latex is obtained.

7. The preparation method according to claim 6, characterized in that, In step (S1), the reaction between the saturated diol, the saturated diacid, and the molecular structure regulator is an esterification reaction and a polycondensation reaction; In step (S2), the organic solvent is selected from one, two or more of dichloromethane, trichloromethane, and tetrahydrofuran; In step (S2), the emulsifier is selected from one, two or more of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, and polyethylene glycol octylphenyl ether; In step (S2), the weight ratio of polyester, emulsifier, organic solvent and water is 10:(0.1~0.5):(30~100):(10~100).

8. The use of the bio-based polyester latex according to any one of claims 1-5 in crosslinking film formation.

9. A bio-based polyester film, characterized in that, The raw material for the polyester film includes the bio-based polyester latex as described in any one of claims 1-5.

10. The method for forming the bio-based polyester film according to claim 9, characterized in that, The film-forming method includes: mixing the bio-based polyester latex according to any one of claims 1-5 with a crosslinking agent, laying the mixture into a film, and curing it at 120-180°C for 10-30 min to obtain the bio-based polyester film.

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