Water-based polyester as well as preparation method and application thereof

Abstract

The invention discloses waterborne polyester as well as a preparation method and application thereof. The preparation method comprises the following steps: putting an intermediate compound into a pre-polycondensation product to carry out polycondensation reaction; wherein the pre-polycondensation product is a product obtained by adding an auxiliary agent into an ester and carrying out polycondensation reaction until the hydroxyl value reaches 80 mgKOH / g-100 mgKOH / g, the chemical structural formula of the ester is shown in the specification, R1, R2 and R3 are independently selected from C4-C12 alkyl groups or aryl groups, R4 and R5 are independently selected from C2-C9 alkyl groups; the chemical structural formula of the intermediate compound is shown in the specification, R6 is C3-C6 alkyl, and R7 is methyl or ethyl. The super-hydrophilic coating prepared from the water-based polyester prepared by the method has super-hydrophilicity, high wear resistance and long service life, and is suitable for the fields of building glass, medical equipment, automobile glass, electronic screens and the like which require antifogging, self-cleaning and durability requirements.

Description

Technical Field

[0001] This invention relates to the field of polymer technology, and more specifically, to an aqueous polyester, its preparation method, and its application. Background Technology

[0002] Superhydrophilic coatings, as an important branch of functional surface treatment technology, possess a water contact angle close to 0°, enabling water droplets to spread instantly and form a uniform water film. This characteristic makes them widely applicable in fields such as anti-fogging, self-cleaning, and anti-fouling. Waterborne polyester resins have become a research hotspot in this field due to their environmentally friendly properties. Introducing sulfonate or carboxyl-based ionic hydrophilic monomers through molecular design can endow materials with excellent water dispersibility. Existing research shows that increasing the acid value of polyester resin (reaching above 20 mg KOH / g) can significantly enhance the hydrophilicity of the coating. However, traditional high-acid-value polyester systems generally face technical bottlenecks such as decreased water resistance, insufficient mechanical strength, and short service life.

[0003] To address these shortcomings, existing technologies have proposed various solutions: these include a combination of block polymerization and crosslinking reactions, using components such as methylated amino resins and polyether-modified polydimethylsiloxane to balance hydrophilicity and water resistance; or constructing a chemically bonded network using PEG-modified polymers and acrylic compounds to enhance adhesion; and some technologies employ multi-component formulations to achieve superhydrophilic properties through precise control of the synergistic effect of surfactants and functional additives. However, these existing technologies either suffer from complex synthesis processes and insufficient durability, or face problems such as decreased water resistance and difficulty in controlling the production process, thus limiting their industrial application.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] The purpose of this invention is to provide an aqueous polyester, its preparation method, and its application, so as to improve the above-mentioned technical problems.

[0006] This invention is implemented as follows: In a first aspect, the present invention provides a method for preparing an aqueous polyester, comprising: adding an intermediate compound to a prepolymerization product for a polycondensation reaction; wherein the prepolymerization product is obtained by adding an auxiliary agent to an ester and carrying out a polycondensation reaction until the hydroxyl value reaches 80 mg KOH / g to 100 mg KOH / g, and the chemical structural formula of the esterization product is: R1, R2, and R3 are each independently selected from C4-C12 alkyl or aryl groups, and R4 and R5 are each independently selected from C2-C9 alkyl groups; the chemical structural formula of the intermediate compound is: R6 is a C3-C6 alkyl group, and R7 is a methyl or ethyl group.

[0007] In an optional embodiment, the preparation of the esterified product includes the following steps: reacting a diacid, a diamine, a diol, a branched monomer, and a first catalyst in a reaction vessel to generate a carboxyl-terminated intermediate, followed by esterification to form the esterified product, wherein the chemical structural formula of the carboxyl-terminated intermediate is as follows: .

[0008] In an optional embodiment, the reaction to generate the carboxyl-terminated intermediate includes: reacting at an inert atmosphere of 150°C to 170°C for 1.5 h to 2.5 h. Preferably, the temperature is first increased to 115°C to 125°C at a heating rate of 1.5°C / min to 2.5°C / min, then stirred, and then increased to 150°C to 170°C at a heating rate of 0.4°C / min to 0.6°C / min, and the temperature is maintained for the reaction. In an optional embodiment, the esterification to form the esterified product includes reacting at a temperature of 220°C to 240°C and an inert gas pressure of 0.08 MPa to 0.12 MPa until the esterification byproduct yield exceeds 90% of the theoretical yield. Preferably, the heating rate to 220°C to 240°C is 0.4°C / min to 0.6°C / min.

[0009] In optional embodiments, the molar ratio of the diol to the diacid is 0.8 to 1.2; and / or, the molar ratio of the diamine to the diacid is 0.2 to 0.4; and / or, the molar ratio of the branched monomer to the diacid is 0.02 to 0.04; and / or, based on the total mass of the reaction system, the amount of catalyst used is 50 ppm to 200 ppm; and / or, the diacid includes one or more of terephthalic acid, isophthalic acid, succinic acid, adipic acid, sebacic acid, dodecanoic acid, and 1,4-cyclohexanedicarboxylic acid. ; and / or, the diamine comprises one or more of hexamethylenediamine, 2-methylpentanediamine, decanediamine, and isophoronediamine; and / or, the diol comprises one or more of neopentyl glycol, 2-methyl-1,3-propanediol, 1,2-propanediol, 2-butyl-2-ethyl-1,3-propanediol, and 2,2,4-trimethyl-1,3-pentanediol; and / or, the branched monomer comprises trimethylolpropane; and / or, the first catalyst comprises one or more of lithium acetylacetonate, 4-dimethylaminopyridine, tetrabutyl titanate, zinc acetate, and germanium oxide.

[0010] In an optional embodiment, the polycondensation temperature for adding an auxiliary agent to the esterified compound is 240°C to 260°C; preferably, the polycondensation reaction is carried out under stirring conditions at a stirring speed of 60 r / min to 120 r / min; and / or, the auxiliary agent includes one or more of trimethyl phosphate, triethyl phosphate, and triethyl phosphonoacetate; and / or, the amount of the auxiliary agent added is 50 ppm to 200 ppm.

[0011] In an optional embodiment, the preparation of the intermediate compound includes the following steps: reacting an acidified monomer with a chain extender and a second catalyst to obtain the intermediate compound.

[0012] In an optional embodiment, the reaction temperature for preparing the intermediate compound is 170°C to 175°C, and the reaction continues until the esterification byproduct reaches more than 90% of the theoretical value. Preferably, the temperature is first increased to 115°C to 125°C at a heating rate of 1.5°C / min to 2.5°C / min, and then increased to 170°C to 175°C at a heating rate of 0.4°C / min to 0.6°C / min. In an optional embodiment, the molar ratio of the acidified monomer to the chain extender is 0.4 to 0.6; In an optional embodiment, the amount of the second catalyst is 20 ppm to 100 ppm; In an optional embodiment, the second catalyst comprises one or more of tetrabutyl titanate, zinc acetate, and germanium oxide.

[0013] In an optional embodiment, adding the intermediate compound to the prepolymerization product for polycondensation reaction includes: under an inert atmosphere, adding the intermediate compound to the prepolymerization product and mixing it evenly, then turning off the inert atmosphere, heating to 210℃~230℃, then evacuating to a vacuum degree ≤100Pa, and continuing polycondensation for 50min~70min as the reaction endpoint.

[0014] In an optional embodiment, the temperature is increased to 210°C to 230°C at a heating rate of 0.8°C / min to 1.2°C / min; In an optional implementation, the vacuum is gradually evacuated to a vacuum level of ≤100Pa within 25 to 35 minutes.

[0015] Secondly, the present invention provides an aqueous polyester, which is prepared by the method for preparing aqueous polyester as described in any of the foregoing embodiments.

[0016] Thirdly, the present invention provides the application of waterborne polyester as described in the foregoing embodiments in the preparation of superhydrophilic coatings.

[0017] The present invention has the following beneficial effects: By rationally designing the molecular structure of waterborne polyester and introducing a certain amount of amide bonds into the polymer backbone, the wear resistance of the coating film is effectively enhanced. Simultaneously, by selecting a branched diol as a comonomer and precisely introducing carboxyl functional groups using an intermediate method, not only is quantitative control of the acid value achieved, thus endowing the resin with good water dispersibility and hydrophilicity, but the branched structure also forms a spatial shielding effect at the molecular level, protecting the ester bonds and significantly improving the polyester's hydrolysis resistance. This technical solution overcomes the technical challenge of traditional waterborne polyester coatings in balancing durability and hydrophilicity. The resulting coating possesses both excellent superhydrophilic properties and mechanical durability, significantly expanding its application range in functional surface coatings and extending its service life. Furthermore, the waterborne polyester preparation process provided by this invention is simple, has low production costs, requires no organic solvents throughout the process, and has no VOC emissions, meeting the environmental protection requirements of green manufacturing and sustainable development.

[0018] The superhydrophilic coating prepared from this waterborne polyester has superhydrophilicity, high abrasion resistance and long service life, and is suitable for fields that require anti-fog, self-cleaning and durability, such as architectural glass, medical devices, automotive glass and electronic screens. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0020] Various embodiments of the present invention may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible subranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the range referred to.

[0021] In the description of this invention, the terms "comprising," "including," etc., mean "including but not limited to." In this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this document, "and / or" describes the relationship between related objects, indicating that three relationships may exist; for example, A and / or B can represent: A alone, A and B simultaneously, or B alone. A and B can be singular or plural. In this document, "at least one" means one or more, and "more than one" means two or more. "At least one," "at least one of the following," or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c" or "at least one of a, b, and c" can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be a single or multiple.

[0022] The following is a detailed description of an aqueous polyester, its preparation method, and its application provided by the present invention.

[0023] Some embodiments of the present invention provide a method for preparing an aqueous polyester, comprising: adding an intermediate compound to a prepolymerization product for a polycondensation reaction; wherein the prepolymerization product is obtained by adding an auxiliary agent to an ester and carrying out a polycondensation reaction until the hydroxyl value reaches 80 mg KOH / g to 100 mg KOH / g, and the chemical structural formula of the esterization product is as follows: R1, R2, and R3 are each independently selected from C4-C12 alkyl or aryl groups, and R4 and R5 are each independently selected from C2-C9 alkyl groups; the chemical structural formula of the intermediate compound is: R6 is a C3-C6 alkyl group, and R7 is a methyl or ethyl group.

[0024] Specifically, in some embodiments, the preparation method of waterborne polyester includes the following steps: S1. Preparation of carboxyl-terminated intermediates.

[0025] In some embodiments, a diacid, a diamine, a diol, a branched monomer, and a first catalyst are reacted in a reaction vessel to generate a carboxyl-terminated intermediate. The reaction vessel may be a stainless steel reactor.

[0026] In some embodiments, the reaction is carried out at 150°C to 170°C under an inert atmosphere for 1.5 to 2.5 hours.

[0027] By controlling the reaction temperature, the diacid and diamine undergo an amidation reaction at low temperatures, prepolymerizing to obtain a carboxyl-terminated intermediate. It should be noted that during this process, a small amount of the diacid and diol also undergo esterification (the reaction rate is slower at low temperatures). Simultaneously, only a small number of functional groups of the branched monomer react, laying "active sites" for subsequent branching and preventing excessive cross-linking at low temperatures that could lead to gelation. By generating a carboxyl-terminated intermediate with a lower molecular weight, the uniform concentration of functional groups is ensured during subsequent high-temperature esterification. Furthermore, the gradual release of water molecules generated during amidation at low temperatures prevents excessive moisture from causing a reverse reaction at high temperatures.

[0028] In some embodiments, the temperature is first increased to 115°C to 125°C at a heating rate of 1.5°C / min to 2.5°C / min, then stirring is started, and then the temperature is increased to 150°C to 170°C at a heating rate of 0.4°C / min to 0.6°C / min, and the temperature is maintained for the reaction.

[0029] Rapid heating first melts the raw materials quickly and reduces the volatilization loss of the diamine, while avoiding stratification caused by prolonged static storage at low temperatures. Since there is no stirring, monomer molecules have limited contact, resulting in only a small number of localized functional group reactions. Subsequent stirring during slow heating prevents localized cross-linking; rapid reaction of the multifunctional groups of branched monomers easily forms localized "micro-crosslinking points," leading to a sharp increase in system viscosity. Slow heating allows the functional groups of the branched monomers to react gradually with the linear monomers, distributing them evenly in the intermediate. The water generated in the amidation reaction gradually volatilizes with increasing temperature, and slow heating ensures stable water removal. It should be noted that the entire heating and reaction process is carried out under an inert atmosphere. The inert gas facilitates the removal of air, prevents oxidation of the diamine and diol, and also removes the water generated in the reaction, promoting the forward reaction.

[0030] To ensure the reaction proceeds effectively and yields the desired product, some embodiments optimize the dosage of each raw material. The molar ratio of diol to diacid is 0.8–1.2, for example, 0.8, 0.9, 1.0, 1.1, or 1.2; the molar ratio of diamine to diacid is 0.2–0.4, for example, 0.2, 0.3, or 0.4; the molar ratio of branched monomer to diacid is 0.02–0.04, for example, 0.02, 0.03, or 0.04; and the amount of catalyst used, based on the total mass of the reaction system, is 50 ppm–200 ppm, for example, 50 ppm, 80 ppm, 100 ppm, 150 ppm, or 200 ppm.

[0031] For example, a diacid, a diamine, a diol, and a branched monomer are added to a stainless steel reactor at an alcohol-to-acid molar ratio of 0.8 to 1.2, wherein the diamine accounts for 0.2 to 0.4 of the diacid molar ratio. A catalyst is added, and the reactor is maintained under a normal pressure and an N2 atmosphere. The temperature is increased to 120°C at 2°C / min, and then stirred at a stirring speed of 60 to 100 r / min. The temperature is increased to 160°C at a programmed rate of 0.5°C / min, and the reaction is maintained at this temperature for 2 hours to obtain a carboxyl-terminated intermediate.

[0032] In some embodiments, the dicarboxylic acid includes, but is not limited to, one or more of terephthalic acid, isophthalic acid, succinic acid, adipic acid, sebacic acid, dodecanoic acid, and 1,4-cyclohexanedicarboxylic acid.

[0033] In some embodiments, the diamine includes, but is not limited to, one or more of hexamethylenediamine, 2-methylpentanediamine, decanediamine, and isophoronediamine.

[0034] In some embodiments, the diol includes, but is not limited to, one or more of neopentyl glycol, 2-methyl-1,3-propanediol, 1,2-propanediol, 2-butyl-2-ethyl-1,3-propanediol, and 2,2,4-trimethyl-1,3-pentanediol.

[0035] In some embodiments, the branched monomer includes, but is not limited to, trimethylolpropane; and / or, the first catalyst includes one or more of lithium acetylacetonate, 4-dimethylaminopyridine, tetrabutyl titanate, zinc acetate, and germanium oxide.

[0036] S2, Preparation of esterified products.

[0037] Specifically, in some embodiments, the reaction is carried out at a temperature of 220°C to 240°C and an inert gas pressure of 0.08 MPa to 0.12 MPa until the esterification byproduct exceeds 90% of the theoretical yield, and the temperature at the top of the reaction vessel is reduced to below 110°C, i.e., under normal pressure, to obtain the esterified product.

[0038] Under the above temperature and pressure, the esterification and branching reactions proceed synergistically, which is beneficial to improving reaction efficiency and can also promote water removal and inhibit the reverse reaction.

[0039] In some embodiments, the heating rate to 220°C to 240°C is 0.4°C / min to 0.6°C / min.

[0040] S3. Prepare prepolymerization products.

[0041] Specifically, an auxiliary agent is added to the esterified compound to carry out a polycondensation reaction until the hydroxyl value reaches 80mgKOH / g~100mgKOH / g. The polycondensation is then stopped, and the temperature is lowered to 200℃ while maintaining an N2 atmosphere to obtain the pre-polycondensation product.

[0042] In some embodiments, the polycondensation temperature for adding an auxiliary agent to the esterified compound is 240°C to 260°C, such as 240°C, 242°C, 245°C, 250°C, 255°C, or 260°C.

[0043] In some embodiments, the adjuvant includes one or more of trimethyl phosphate, triethyl phosphate, and triethyl phosphonoacetate; the amount of adjuvant added is 50 ppm to 200 ppm.

[0044] At 240~260℃, through transesterification and coordination crosslinking, phosphorus-based auxiliaries act as "chain growth bridges" to increase the molecular weight of the product, thereby achieving precise control of the hydroxyl value.

[0045] In some embodiments, the polycondensation reaction is carried out under stirring conditions at a stirring speed of 60 r / min to 120 r / min. High stirring speed ensures uniform mixing of the phosphorus-based additives and the esterified product, avoiding uneven crosslinking caused by excessively high local concentrations; it also promotes heat transfer and avoids temperature gradients in the system.

[0046] S4. Preparation of intermediate compounds.

[0047] In some embodiments, the acidified monomer is reacted with a chain extender and a second catalyst to obtain an intermediate compound.

[0048] In some embodiments, the reaction temperature for preparing the intermediate compound is 170°C to 175°C, and the reaction ends when the esterification byproducts reach more than 90% of the theoretical value and the temperature at the top of the reaction vessel drops below 60°C.

[0049] In some embodiments, the temperature is first increased to 115°C to 125°C at a heating rate of 1.5°C / min to 2.5°C / min, and then increased to 170°C to 175°C at a heating rate of 0.4°C / min to 0.6°C / min.

[0050] In some embodiments, the acidifying monomer is dimethylolpropionic acid; the molar ratio of the acidifying monomer to the chain extender is 0.4 to 0.6; and the amount of the second catalyst is 20 ppm to 100 ppm. In some embodiments, the second catalyst includes one or more of tetrabutyl titanate, zinc acetate, and germanium oxide.

[0051] It should be noted that the order of steps S4 can be interchanged with or performed in parallel with steps S1 to S3.

[0052] S5. Preparation of waterborne polyester.

[0053] Specifically, the process of adding the intermediate compound to the prepolymerization product for polycondensation reaction includes: under an inert atmosphere, adding the intermediate compound to the prepolymerization product and mixing it evenly, then turning off the inert atmosphere, heating to 210℃~230℃, then evacuating to a vacuum degree ≤100Pa, and continuing polycondensation for 50min~70min as the reaction endpoint.

[0054] The intermediate compound is added to the prepolymerization product and mixed under normal pressure with stirring to achieve molecular-level mixing of the intermediate and the prepolymerization product. The highly active carboxyl group of the intermediate is used to form a "functional group match" with the residual hydroxyl group and the alkoxy group of the phosphorus group in the prepolymerization product, laying the foundation for subsequent chain growth.

[0055] In some embodiments, heating to 210°C to 230°C at a heating rate of 0.8°C / min to 1.2°C / min can slowly activate the transesterification and esterification reactions, avoiding chain entanglement or gelation caused by violent local reactions.

[0056] In some implementations, the vacuum level is gradually reduced to ≤100 Pa over 25-35 minutes. This gradual transition from atmospheric pressure to high vacuum removes reaction byproducts in stages, shifting the equilibrium towards polycondensation while preventing system boiling or small molecule entrainment under high vacuum.

[0057] Continuing polycondensation for 50-70 minutes can complete the final growth and branching of molecular chains, reducing the content of residual monomers and small molecules.

[0058] Some embodiments of the present invention also provide an aqueous polyester, which is prepared by the preparation method of the aqueous polyester described in any of the foregoing embodiments.

[0059] Some embodiments of the present invention also provide the application of the waterborne polyester as described in the foregoing embodiments in the preparation of superhydrophilic coatings. The superhydrophilic coating based on the above-mentioned waterborne polyester possesses superhydrophilicity, high abrasion resistance, and long service life, making it suitable for applications requiring anti-fogging, self-cleaning, and durability, such as architectural glass, medical devices, automotive glass, and electronic screens.

[0060] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0061] Preparation of intermediate compounds: The intermediates obtained by reacting diethyl malonate, dimethyl succinate, and dimethyl adipate with dimethylolpropionic acid are of similar quality, with the only difference being the amount added according to the equivalent of the carboxyl group during the reaction. The following examples only use the intermediate generated by dimethyl succinate and dimethylolpropionic acid as an example. Dimethyl succinate and dimethylolpropionic acid were added to the reaction vessel at a molar ratio of 2:1. 50 ppm of tetrabutyl titanate was added by weight. Under a nitrogen atmosphere, the temperature was gradually increased to 120°C at 2°C / min. Stirring was started and the stirring speed was 100 min. Then, the temperature was gradually increased to 175°C at 0.5°C / min. The reaction was terminated when the esterification byproducts reached more than 90% of the theoretical value and the temperature at the top of the reactor column dropped below 60°C, yielding the intermediate compound.

[0062] Example 1 This embodiment provides a method for preparing waterborne polyester, which includes the following steps: Add 193.23g isophthalic acid, 313.65g sebacic acid, 200.27g 1,4-cyclohexanedicarboxylic acid, 135.15g 2-methylpentanediamine, 121.14g neopentanediol, 139.76g 2-methyl-1,3-propanediol, 186.39g 2-butyl-2-ethyl-1,3-propanediol, and 10.40g trimethylolpropane to a 2L reactor, and add 0.13g... 4-Dimethylaminopyridine and 0.13 g tetrabutyl titanate were mixed under a nitrogen atmosphere and atmospheric pressure. The temperature was increased to 120 °C at a programmed rate of 2 °C / min, and then stirred at 100 r / min. The temperature was then increased to 160 °C at a programmed rate of 0.5 °C / min and maintained for 2 h. After the reaction was completed, the pressure was increased to 0.1 MPa by introducing nitrogen and maintained. The temperature was increased to 240 °C at a programmed rate of 0.5 °C / min. When the esterification byproduct exceeded the theoretical yield by more than 90% and the temperature at the top of the column dropped below 110 °C, the temperature was reduced to normal pressure to obtain the esterified product. Add 0.1g of trimethyl phosphate to the reactor to start the polycondensation reaction. Maintain the polycondensation temperature at 250℃ and the stirring speed at 60r / min. Polycondense until the hydroxyl value reaches 92mgKOH / g, then stop the polycondensation. Maintain the N2 atmosphere under normal pressure and lower the temperature to 200℃. Add 180g of intermediate compound and stir at 60r / min for 20min. Turn off the N2 and start the polycondensation reaction. Increase the temperature to 220℃ in a programmed manner at 1℃ / min. Gradually increase the vacuum to below 100Pa within 30min. Adjust the stirring speed to 120r / min and continue polycondensation for 60min as the reaction endpoint. Discharge the reactor to obtain the target waterborne polyester.

[0063] Example 2 This embodiment provides a method for preparing waterborne polyester, which includes the following steps: Add 188.67g isophthalic acid, 267.97g sebacic acid, 228.13g 1,4-cyclohexanedicarboxylic acid, 131.98g hexamethylenediamine, 118.28g neopentyl glycol, 172.83g 1,2-propanediol, 181.99g 2-butyl-2-ethyl-1,3-propanediol, and 10.16g trimethylolpropane to a 2L reactor, and add 0.13g... 4-Dimethylaminopyridine and 0.13 g tetrabutyl titanate were mixed under a nitrogen atmosphere and atmospheric pressure. The temperature was increased to 120 °C at a programmed rate of 2 °C / min, and then stirred at 100 r / min. The temperature was then increased to 160 °C at a programmed rate of 0.5 °C / min and maintained for 2 h. After the reaction was completed, the pressure was increased to 0.1 MPa by introducing nitrogen and maintained. The temperature was increased to 240 °C at a programmed rate of 0.5 °C / min. When the esterification byproduct exceeded the theoretical yield by more than 90% and the temperature at the top of the column dropped below 110 °C, the temperature was reduced to normal pressure to obtain the esterified product.

[0064] Add 0.1g of trimethyl phosphate to the reactor to start the polycondensation reaction. Maintain the polycondensation temperature at 250℃ and the stirring speed at 60r / min. When the hydroxyl value of the polycondensation is 86mgKOH / g, stop the polycondensation. Maintain the N2 atmosphere under normal pressure and lower the temperature to 200℃. Add 180g of intermediate and stir at 60r / min for 20min. Turn off the N2 and start the polycondensation reaction. Increase the temperature to 220℃ in a programmed manner at 1℃ / min. Gradually increase the vacuum degree to below 100Pa within 30min. Adjust the stirring speed to 120r / min and continue the polycondensation for 60min as the reaction endpoint. Discharge the reactor to obtain the target waterborne polyester.

[0065] Example 3 This embodiment provides a method for preparing waterborne polyester, which includes the following steps: Add 143.67g terephthalic acid, 143.67g isophthalic acid, 252.77g adipic acid, 148.91g 1,4-cyclohexanedicarboxylic acid, 175.88g hexamethylenediamine, 98.71g 1,2-propanediol, 116.91g 2-methyl-1,3-propanediol, 207.88g 2-butyl-2-ethyl-1,3-propanediol, and 11.60g trimethylolpropane to a 2L reactor, and add 0.13g... Lithium acetylacetone and 0.13 g tetrabutyl titanate were mixed under a nitrogen atmosphere and atmospheric pressure. The temperature was increased to 120 °C at a rate of 2 °C / min, and then stirred at 100 r / min. The temperature was then increased to 160 °C at a rate of 0.5 °C / min and maintained for 2 h. After the reaction was completed, the pressure was increased to 0.1 MPa by introducing nitrogen and maintained. The temperature was increased to 240 °C at a rate of 0.5 °C / min. When the esterification byproduct yield exceeded 90% of the theoretical yield and the temperature at the top of the column dropped below 110 °C, the reaction was stopped at normal pressure to obtain the esterified product. Add 0.1g of triethyl phosphate to the reactor to start the polycondensation reaction. Maintain the polycondensation temperature at 250℃ and the stirring speed at 60r / min. The hydroxyl value of the polycondensation is 94mgKOH / g. Stop the polycondensation. Maintain the N2 atmosphere under normal pressure and lower the temperature to 200℃. Add 180g of intermediate and stir at 60r / min for 20min. Turn off the N2 and start the polycondensation reaction. Increase the temperature to 220℃ in a programmed manner at 1℃ / min. Gradually increase the vacuum degree to below 100Pa within 30min. Adjust the stirring speed to 120r / min and continue the polycondensation for 60min as the reaction endpoint. Discharge the reactor to obtain the target waterborne polyester.

[0066] Example 4 This embodiment provides a method for preparing waterborne polyester, which includes the following steps: Add 132.63g terephthalic acid, 132.63g isophthalic acid, 188.55g succinic acid, 183.85g dodecanoic acid, 171.95g decanediamine, 124.72g neopentyl glycol, 179.86g 2-methyl-1,3-propanediol, 175.11g 2,2,4-trimethyl-1,3-pentanediol, and 10.71g trimethylolpropane to a 2L reactor, and add 0.13g... 4-Dimethylaminopyridine and 0.13 g tetrabutyl titanate were mixed under a nitrogen atmosphere and atmospheric pressure. The temperature was increased to 120 °C at a programmed rate of 2 °C / min, and then stirred at 100 r / min. The temperature was then increased to 160 °C at a programmed rate of 0.5 °C / min and maintained for 2 h. After the reaction was completed, the pressure was increased to 0.1 MPa by introducing nitrogen and maintained. The temperature was increased to 240 °C at a programmed rate of 0.5 °C / min. When the esterification byproduct exceeded the theoretical yield by more than 90% and the temperature at the top of the column dropped below 110 °C, the temperature was reduced to normal pressure to obtain the esterified product. Add 0.1g of triethyl phosphonoacetate to the reactor to start the polycondensation reaction. Maintain the polycondensation temperature at 250℃ and the stirring speed at 60r / min. When the hydroxyl value of the polycondensation is 95mgKOH / g, stop the polycondensation. Maintain the N2 atmosphere under normal pressure and lower the temperature to 200℃. Add 180g of intermediate and stir at 60r / min for 20min. Turn off the N2 and start the polycondensation reaction. Increase the temperature to 220℃ in a programmed manner at 1℃ / min. Gradually increase the vacuum degree to below 100Pa within 30min. Adjust the stirring speed to 120r / min and continue the polycondensation for 60min as the reaction endpoint. Discharge the reactor to obtain the target waterborne polyester.

[0067] Example 5 This embodiment provides a method for preparing waterborne polyester, which includes the following steps: Add 202.42g isophthalic acid, 328.57g sebacic acid, 209.79g 1,4-cyclohexanedicarboxylic acid, 94.39g 2-methylpentanediamine, 138.33g isophoronediamine, 169.20g neopentanediol, 146.41g 2-methyl-1,3-propanediol, and 10.90g trimethylolpropane to a 2L reactor, along with 0.13g... 4-Dimethylaminopyridine and 0.13 g tetrabutyl titanate were mixed under a nitrogen atmosphere and atmospheric pressure. The temperature was increased to 120 °C at a programmed rate of 2 °C / min, and then stirred at 100 r / min. The temperature was then increased to 160 °C at a programmed rate of 0.5 °C / min and maintained for 2 h. After the reaction was completed, the pressure was increased to 0.1 MPa by introducing nitrogen and maintained. The temperature was increased to 240 °C at a programmed rate of 0.5 °C / min. When the esterification byproduct exceeded the theoretical yield by more than 90% and the temperature at the top of the column dropped below 110 °C, the temperature was reduced to normal pressure to obtain the esterified product. Add 0.1g of trimethyl phosphate to the reactor to start the polycondensation reaction. Maintain the polycondensation temperature at 250℃ and the stirring speed at 60r / min. When the hydroxyl value of the polycondensation is 88mgKOH / g, stop the polycondensation. Maintain the N2 atmosphere under normal pressure and lower the temperature to 200℃. Add 180g of intermediate and stir at 60r / min for 20min. Turn off the N2 and start the polycondensation reaction. Increase the temperature to 220℃ in a programmed manner at 1℃ / min. Gradually increase the vacuum degree to below 100Pa within 30min. Adjust the stirring speed to 120r / min and continue the polycondensation for 60min as the reaction endpoint. Discharge the reactor to obtain the target waterborne polyester.

[0068] Example 6 This embodiment provides a method for preparing waterborne polyester, which includes the following steps: Add 127.53g terephthalic acid, 127.53g isophthalic acid, 168.27g adipic acid, 232.88g sebacic acid, 89.21g hexamethylenediamine, 159.90g neopentyl glycol, 138.36g 2-methyl-1,3-propanediol, 246.03g 2-butyl-2-ethyl-1,3-propanediol, and 10.30g trimethylolpropane to a 2L reactor, and add 0.13g... Lithium acetylacetone and 0.13 g tetrabutyl titanate were mixed under a nitrogen atmosphere and atmospheric pressure. The temperature was increased to 120 °C at a rate of 2 °C / min, and then stirred at 100 r / min. The temperature was then increased to 160 °C at a rate of 0.5 °C / min and maintained for 2 h. After the reaction was completed, the pressure was increased to 0.1 MPa by introducing nitrogen and maintained. The temperature was increased to 240 °C at a rate of 0.5 °C / min. When the esterification byproduct yield exceeded 90% of the theoretical yield and the temperature at the top of the column dropped below 110 °C, the reaction was stopped at normal pressure to obtain the esterified product. Add 0.1g of trimethyl phosphate to the reactor to start the polycondensation reaction. Maintain the polycondensation temperature at 250℃ and the stirring speed at 60r / min. When the hydroxyl value of the polycondensation is 85mgKOH / g, stop the polycondensation. Maintain the N2 atmosphere under normal pressure and lower the temperature to 200℃. Add 180g of intermediate and stir at 60r / min for 20min. Turn off the N2 and start the polycondensation reaction. Increase the temperature to 220℃ in a programmed manner at 1℃ / min. Gradually increase the vacuum degree to below 100Pa within 30min. Adjust the stirring speed to 120r / min and continue the polycondensation for 60min as the reaction endpoint. Discharge the reactor to obtain the target waterborne polyester.

[0069] Example 7 This embodiment provides a method for preparing waterborne polyester, which includes the following steps: Add 198.87g isophthalic acid, 188.49g succinic acid, 242.11g sebacic acid, 103.14g decanediamine, 101.93g isophorone diamine, 91.09g 1,2-propanediol, 107.88g 2-methyl-1,3-propanediol, 255.78g 2-butyl-2-ethyl-1,3-propanediol, and 10.71g trimethylolpropane to a 2L reactor, along with 0.13g... 4-Dimethylaminopyridine and 0.13 g tetrabutyl titanate were mixed under a nitrogen atmosphere and atmospheric pressure. The temperature was increased to 120 °C at a programmed rate of 2 °C / min, and then stirred at 100 r / min. The temperature was then increased to 160 °C at a programmed rate of 0.5 °C / min and maintained for 2 h. After the reaction was completed, the pressure was increased to 0.1 MPa by introducing nitrogen and maintained. The temperature was increased to 240 °C at a programmed rate of 0.5 °C / min. When the esterification byproduct exceeded the theoretical yield by more than 90% and the temperature at the top of the column dropped below 110 °C, the temperature was reduced to normal pressure to obtain the esterified product. Add 0.1g of triethyl phosphonoacetate to the reactor to start the polycondensation reaction. Maintain the polycondensation temperature at 250℃ and the stirring speed at 60r / min. When the hydroxyl value of the polycondensation is 90mgKOH / g, stop the polycondensation. Maintain the N2 atmosphere under normal pressure and lower the temperature to 200℃. Add 180g of intermediate and stir at 60r / min for 20min. Turn off the N2 and start the polycondensation reaction. Increase the temperature to 220℃ in a programmed manner at 1℃ / min. Gradually increase the vacuum degree to below 100Pa within 30min. Adjust the stirring speed to 120r / min and continue the polycondensation for 60min as the reaction endpoint. Discharge the reactor to obtain the target waterborne polyester.

[0070] Comparative Example 1 Based on Example 1, the amount of intermediate added was adjusted to 120g, and other conditions were the same as in Example 1.

[0071] Comparative Example 2 Based on Example 1, the amount of intermediate added was adjusted to 240g, and other conditions were the same as in Example 1.

[0072] Comparative Example 3 Based on Example 1, the molar ratio of 2-methylpentanediamine to total acid was adjusted from 30% to 18%, while other conditions remained the same as in Example 1.

[0073] Comparative Example 4 Based on Example 1, except for the removal of trihydroxypropane, all other conditions are the same as in Example 1.

[0074] Comparative Example 5 Based on Example 1, the total alcohol-acid ratio was adjusted from 1 to 0.7, while other conditions remained the same as in Example 1.

[0075] Comparative Example 6 Based on Example 1, all total alcohols were replaced with equimolar amounts of 1,3-propanediol, while other conditions remained the same as in Example 1.

[0076] The waterborne polyesters obtained in the examples and comparative examples were tested for performance using the following methods: Intrinsic viscosity (IV) test: Measured using an Ubbelohde viscometer with o-chlorophenol as the solvent at 35°C. The formula for calculating intrinsic viscosity is: =

[0077] In the formula: η: intrinsic viscosity, mL / g; : Increased specific viscosity; : Viscosity ratio; c: Polymer concentration, mol / L; t: Sample eluent time, s; t0: Blank sample eluent time, s.

[0078] Acid value test: GB / T 33371.1-2016 Paint and varnish base alkyd resins - Part 1: General test methods.

[0079] Hydroxyl value test: GB / T 31412-2015 Determination of hydroxyl value of paint base in varnishes and varnishes by titration.

[0080] The test results are shown in Table 1.

[0081] Table 1. Test results of waterborne polyester

[0082] By weight, 60 parts of the aqueous polyester from the above examples and comparative examples were dissolved in 120 parts of deionized water and 6 parts of N,N-dimethylethanolamine to obtain a polyester dispersion. Separately, 3 parts of PVP K-30 were dissolved in 8 parts of deionized water and then slowly added to the continuously stirred polyester dispersion. Then, 3 parts of WS-500 were added sequentially, followed by 0.2 parts of BYK-345. After thorough mixing and filtration, a 30% aqueous coating solution was obtained. The resulting coating solution was coated onto a PET film and baked at 160°C for 15 minutes to obtain a superhydrophilic coating.

[0083] The prepared superhydrophilic coating was subjected to performance tests. Water contact angle test: GB / T 30693-2014 Measurement of water contact angle between plastic films. Abrasion resistance test: HG-T 4303-2012 Method for determining the abrasion resistance of surface-hardened polyester films. The abrasion resistance effect was determined by testing the abrasion resistance limit of the coating surface with or without scratches; the higher the abrasion resistance limit, the better the effect. The test results are shown in Table 2.

[0084] Table 2. Test results of superhydrophilic coating performance

[0085] As can be seen from the results in Tables 1 and 2, the waterborne polyesters in Examples 1-7 possess both superhydrophilicity and good abrasion resistance. The adjustment of the amount of intermediates in Comparative Examples 1 and 2 affected the acid hydroxyl value of the waterborne polyester, resulting in either insufficient hydrophilicity or excessive addition of intermediates, leading to a relatively low hydroxyl value and affecting the increase of the intrinsic viscosity (IV) of the polyester. Comparative Example 3, due to the reduction of the amide structure, had a certain impact on the abrasion resistance of the coating. Comparative Example 4 lacked branching, resulting in a low total acid hydroxyl value of the final waterborne polyester and insufficient hydrophilicity. Comparative Example 5 also involved a low overall hydroxyl value, which had a certain impact on the hydrophilicity of the final coating. Comparative Example 6 removed the alcohol containing the side chain, which could not provide protection for the ester bond, affecting the subsequent water resistance and storage stability. In addition, the abrasion resistance also decreased in this test.

[0086] In summary, the method for preparing waterborne polyester provided by this invention introduces acid value through an intermediate method, resulting in higher stability of the synthesis process. By introducing a specific proportion of amide bond structures, the wear resistance of the material is effectively improved. Simultaneously, the introduction of an appropriate amount of branched structure enhances the degree of crosslinking during the subsequent coating curing process, thereby further optimizing the wear resistance of the coating. Furthermore, the diol component containing side chains can protect the ester bonds of the polyester backbone, significantly improving the water resistance and durability of the coating. Based on the above technical features, the resulting coating not only possesses excellent superhydrophilic properties but also exhibits good wear resistance and water resistance. Moreover, this preparation process has advantages such as simple operation and low cost, which is conducive to large-scale production and shows broad market prospects in industrial applications.

[0087] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing an aqueous polyester, characterized in that, It includes: The intermediate compound is added to the pre-condensation product for a condensation reaction; wherein, the pre-condensation product is obtained by adding an auxiliary agent to the ester and carrying out a condensation reaction until the hydroxyl value reaches 80 mg KOH / g~100 mg KOH / g, and the chemical structural formula of the ester is: R1, R2, and R3 are each independently selected from C4-C12 alkyl or aryl groups, and R4 and R5 are each independently selected from C2-C9 alkyl groups; the chemical structural formula of the intermediate compound is: R6 is a C3-C6 alkyl group, and R7 is a methyl or ethyl group.

2. The method for preparing waterborne polyester according to claim 1, characterized in that, The preparation of the esterified compound includes the following steps: A diacid, a diamine, a diol, a branched monomer, and a first catalyst are reacted in a reaction vessel to generate a carboxyl-terminated intermediate, which is then esterified to form the esterified product. The chemical structural formula of the carboxyl-terminated intermediate is as follows: .

3. The method for preparing waterborne polyester according to claim 2, characterized in that, The reaction to generate the carboxyl-terminated intermediate includes: reacting at an inert atmosphere of 150°C to 170°C for 1.5 h to 2.5 h. Preferably, the temperature is first increased to 115°C to 125°C at a heating rate of 1.5°C / min to 2.5°C / min, then stirred, and then increased to 150°C to 170°C at a heating rate of 0.4°C / min to 0.6°C / min, and the temperature is maintained for the reaction. And / or, the esterification to form the esterified product includes: reacting at a temperature of 220°C to 240°C and an inert gas pressure of 0.08 MPa to 0.12 MPa until the esterification byproduct yield exceeds 90% of the theoretical yield, preferably, the heating rate to 220°C to 240°C is 0.4°C / min to 0.6°C / min.

4. The method for preparing waterborne polyester according to claim 2 or 3, characterized in that, The molar ratio of the diol to the diacid is 0.8 to 1.2; And / or, the molar ratio of the diamine to the diacid is 0.2 to 0.4; And / or, the molar ratio of the branched monomer to the dicarboxylic acid is 0.02 to 0.04; And / or, based on the total mass of the reaction system, the amount of the catalyst used is 50 ppm to 200 ppm; And / or, the dicarboxylic acid includes one or more of terephthalic acid, isophthalic acid, succinic acid, adipic acid, sebacic acid, dodecanoic acid and 1,4-cyclohexanedicarboxylic acid; And / or, the diamine includes one or more of hexamethylenediamine, 2-methylpentanediamine, decanediamine, and isophoronediamine; And / or, the diol includes one or more of neopentyl glycol, 2-methyl-1,3-propanediol, 1,2-propanediol, 2-butyl-2-ethyl-1,3-propanediol and 2,2,4-trimethyl-1,3-pentanediol; And / or, the branched monomer includes trimethylolpropane; And / or, the first catalyst comprises one or more of lithium acetylacetonate, 4-dimethylaminopyridine, tetrabutyl titanate, zinc acetate, and germanium oxide.

5. The method for preparing waterborne polyester according to claim 1, characterized in that, The polycondensation temperature of the esterified compound with added additives is 240℃~260℃; preferably, the polycondensation reaction is carried out under stirring conditions, and the stirring speed is 60r / min~120r / min. And / or, the adjuvant includes one or more of trimethyl phosphate, triethyl phosphate, and triethyl phosphonoacetate; And / or, the amount of the additive is 50ppm to 200ppm.

6. The method for preparing waterborne polyester according to claim 1, characterized in that, The preparation of the intermediate compound includes the following steps: reacting an acidified monomer with a chain extender and a second catalyst to obtain the intermediate compound.

7. The method for preparing waterborne polyester according to claim 6, characterized in that, The reaction temperature for preparing the intermediate compound is 170℃~175℃, and the reaction continues until the esterification byproduct reaches more than 90% of the theoretical value. Preferably, the temperature is first increased to 115℃~125℃ at a heating rate of 1.5℃ / min~2.5℃ / min, and then increased to 170℃~175℃ at a heating rate of 0.4℃ / min~0.6℃ / min. And / or, the molar ratio of the acidified monomer to the chain extender is 0.4 to 0.6; And / or, the amount of the second catalyst is 20ppm to 100ppm; And / or, the second catalyst comprises one or more of tetrabutyl titanate, zinc acetate, and germanium oxide; And / or, the chain extender includes one or more of diethyl malonate, dimethyl succinate, and dimethyl adipate; And / or, the acidified monomer is dimethylolpropionic acid.

8. The method for preparing waterborne polyester according to claim 1, characterized in that, The intermediate compound is added to the prepolymerization product for polycondensation reaction, which includes: under an inert atmosphere, the intermediate compound is added to the prepolymerization product and mixed evenly, the inert atmosphere is turned off, the temperature is raised to 210℃~230℃, then the vacuum is drawn to a vacuum degree ≤100Pa, and polycondensation is continued for 50min~70min as the reaction endpoint. Preferably, the temperature is increased to 210℃~230℃ at a heating rate of 0.8℃ / min~1.2℃ / min; Preferably, the vacuum is gradually evacuated to a vacuum level of ≤100Pa within 25 to 35 minutes.

9. A waterborne polyester, characterized in that, It is prepared by the method for preparing waterborne polyester according to any one of claims 1 to 8.

10. The application of the waterborne polyester as described in claim 9 in the preparation of superhydrophilic coatings.

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