High performance eco-friendly polyester dispersion and method for preparing the same

Abstract

The application discloses a high-performance environment-friendly polyester dispersion and a preparation method thereof. The dispersion is prepared from a regenerated PET alcoholysis product, a dicarboxylic acid acid component, a dihydric alcohol alcohol component, an ionic hydrophilic monomer containing a sulfonate group, a polyether glycol and a hydrophobic modified monomer as raw materials, and is prepared through esterification or ester exchange and polycondensation reaction to obtain a water-dispersible polyester resin, and then is formed into a water continuous phase dispersion through a low-solvent phase reverse dispersion process or a melt direct dispersion process. The obtained dispersion has a solid content of 45-60 wt%, an additional small molecule emulsifier of not higher than 0.2 wt%, and a residual organic solvent of not higher than 0.3 wt%, and can be used in water-based ink, packaging coating, PET film primer, paper coating, aluminum foil coating, metal coating, water-based adhesive or water-based composite glue.

Description

Technical Field

[0001] This invention belongs to the field of water-based polymer materials technology, specifically relating to a high-performance environmentally friendly polyester dispersion and its preparation method. Background Technology

[0002] Polyester resins possess good film-forming properties, adhesion, flexibility, and chemical resistance, making them widely used in coatings, inks, adhesives, film treatment agents, and many other fields. Conventional polyester resins typically require organic solvents for dissolution, dilution, or dispersion during preparation or use. While water-based formulations can reduce solvent usage, under high solids content conditions, issues such as increased particle size, wider particle size distribution, increased viscosity, and decreased storage stability can still arise. To improve aqueous phase stability, current methods often involve increasing the content of hydrophilic groups in the polyester chain or adding small-molecule emulsifiers. The former may reduce the water resistance and damp heat resistance of the coating film, while the latter can easily lead to migration, precipitation, foaming, or bubbling during film formation and storage, affecting the long-term state of the dispersion and film layer.

[0003] Recycled PET can serve as a source of polyester segments; however, its raw material source, molecular weight, end-group composition, and impurity levels vary from batch to batch. Furthermore, its high proportion of terephthalic acid esters can lead to insufficient reaction uniformity, excessive segment rigidity, and difficulty in aqueous dispersion when directly used in water-dispersible polyesters. Therefore, a suitable water-based polyester dispersion for recycled PET is needed, simultaneously achieving the benefits of recycled PET utilization, high solids content dispersion, low levels of added small-molecule emulsifiers, and low residual organic solvents. Summary of the Invention

[0004] This invention provides a high-performance, environmentally friendly polyester dispersion and its preparation method, aiming to improve the problem of balancing high solids content dispersion stability with low solvent and low added emulsifier requirements when using recycled PET in water-based polyester systems.

[0005] To achieve the above objectives, the present invention adopts the following technical solution.

[0006] This invention provides a high-performance, environmentally friendly polyester dispersion, comprising an aqueous phase and a water-dispersible polyester resin dispersed in the aqueous phase. The water-dispersible polyester resin is obtained from polyester raw materials through esterification or transesterification followed by polycondensation. Based on a total polyester raw material mass of 100 wt%, the polyester raw material comprises 25–55 wt% recycled PET alcoholysis product, 1.0–5.5 wt% ionic hydrophilic monomers containing sulfonate groups, 0.8–4 wt% polyether diols with a number average molecular weight of 400–2000, 10–35 wt% hydrophobic modified monomers, 0–3 wt% branching regulator monomers and / or crosslinking regulator monomers, with the balance being dicarboxylic acid components and diol alcohol components; wherein the recycled PET alcoholysis product is obtained by alcoholysis of recycled PET with an alcoholysis agent in the presence of a catalyst. The total mass of polyester raw materials refers to the total mass of reactive raw materials that participate in the formation of the main chain, branched structure, or cross-linking adjustment structure of water-dispersible polyester resin. Water, pH adjusters, catalysts, and organic solvents used or removed during dispersion, dilution, solvent removal, or filtration are not included. Hydrophobic modified monomers can be monomers formed from the hydrophobic structure of dicarboxylic acid components and / or diol alcohol components; when they simultaneously participate in the polyester reaction as dicarboxylic acid components or diol alcohol components, they are counted once based on the actual feed mass and are not counted repeatedly. The solid content of the obtained polyester dispersion is 45–60 wt%; based on the total mass of the polyester dispersion, the content of added small molecule emulsifiers is not higher than 0.2 wt%, and the residual organic solvent content is not higher than 0.3 wt%.

[0007] Furthermore, the alcoholysis products of recycled PET are one or two of hydroxyl-terminated terephthalic acid ester oligomers and dialkyl terephthalate compounds; the alcoholysis agent is selected from at least one of ethylene glycol, diethylene glycol, neopentyl glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, and cyclohexanediol. Recycled PET can be selected from one or more of waste PET bottle flakes, waste PET films, waste PET fibers, waste PET sheets, and waste polyester packaging materials.

[0008] Furthermore, based on a total polyester raw material mass of 100wt%, the recycled PET alcoholysis products are 30-50wt%, the ionic hydrophilic monomers containing sulfonate groups are 1.2-5.0wt%, the polyether glycol is 1.2-3.0wt%, and the hydrophobic modified monomers are 18-30wt%.

[0009] Furthermore, the ionic hydrophilic monomer containing sulfonate groups is dimethyl isophthalate sodium 5-sulfonate, the polyether glycol is polyethylene glycol, the branching regulator monomer is trimethylolpropane, and the crosslinking regulator monomer is trimellitic anhydride. When the polyester raw material contains branching regulator monomers and / or crosslinking regulator monomers, the combined amount of the two is preferably 0.2–3 wt%, where wt% is based on the total mass of the polyester raw material.

[0010] Further, the dicarboxylic acid component includes one or more of aromatic or heteroaromatic dicarboxylic acids, aliphatic dicarboxylic acids, and dimer acids; the diol component includes aliphatic diols and / or alicyclic diols; the hydrophobically modified monomer includes one or more of branched aliphatic diols, alicyclic diols, long-chain aliphatic diols, long-chain aliphatic dicarboxylic acids, and dimer acids. Preferably, the aromatic or heteroaromatic dicarboxylic acid is selected from one or two of isophthalic acid and bio-based furanyldicarboxylic acid, and the aliphatic dicarboxylic acid is selected from one or two of bisaccharide and sebacic acid; the diol component is selected from one or more of ethylene glycol, diethylene glycol, neopentyl glycol, 1,4-butanediol, 1,6-hexanediol, and cyclohexanediol; the hydrophobically modified monomer is selected from one or more of neopentyl glycol, cyclohexanediol, 1,4-butanediol, 1,6-hexanediol, sebacic acid, and dimer acids.

[0011] This invention also provides a method for preparing the above-mentioned high-performance environmentally friendly polyester dispersion, comprising the following steps: S1, adding recycled PET, an alcoholysis agent, and a catalyst to a reaction system, and carrying out an alcoholysis reaction under nitrogen or inert gas protection to obtain recycled PET alcoholysis product; S2, taking 25-55 wt% of the recycled PET alcoholysis product obtained in S1 based on 100 wt% of the total mass of polyester raw materials, and adding 1.0-5.5 wt% of an ionic hydrophilic monomer containing sulfonate groups, 0.8-4 wt% of a polyether diol with a number average molecular weight of 400-2000, and 1 wt% of a hydrophobic modified monomer under stirring conditions. 0–35 wt%, optional branching regulator monomers and / or crosslinking regulator monomers 0–3 wt%, and the balance dicarboxylic acid components and diol alcohol components are added to form a polyester reaction system; subsequently, esterification or transesterification reaction and polycondensation reaction are carried out to obtain a water-dispersible polyester resin; S3, using a low-solvent phase inversion dispersion process or melt direct dispersion process, the water-dispersible polyester resin is mixed with the aqueous phase to form a continuous aqueous dispersion; S4, the continuous aqueous dispersion is subjected to solidification, pH adjustment, filtration, and solvent removal treatment according to the residual organic solvent content to obtain a high-performance environmentally friendly polyester dispersion.

[0012] Furthermore, in S1, the alcoholysis reaction temperature is 190–230℃, the reaction time is 2–4 h, and the catalyst dosage is 0.02–0.10 wt% based on the total mass of the polyester raw materials; in S2, the esterification or transesterification reaction temperature is 210–245℃, the polycondensation reaction temperature is 230–265℃, and the vacuum degree of the system during the polycondensation stage is -0.08 MPa to -0.10 MPa (gauge pressure). The catalyst can be selected from one or more of titanate catalysts, zinc salt catalysts, organobismuth catalysts, and tin salt catalysts.

[0013] Further, in S3, the low-solvent phase-inversion dispersion process is as follows: the water-dispersible polyester resin is softened, melted, or swollen at 75–105°C and then mixed with the aqueous phase, so that the system changes from a resin continuous phase to an aqueous continuous phase dispersion; wherein, the amount of organic solvent used is not more than 10 wt% based on the mass of the water-dispersible polyester resin; the melt direct dispersion process is as follows: after the polycondensation reaction, without cooling and granulation, the polyester melt is directly cooled to 110–150°C and mixed and dispersed with the preheated hot water phase to form an aqueous continuous phase dispersion. The aqueous phase can be deionized water or an aqueous solution containing a pH adjuster; the pH adjuster can be selected from one or more of ammonia, organic amines, alkali metal hydroxides, alkali metal carbonates, and alkali metal bicarbonates. The solvent removal treatment can be performed by one or more of vacuum distillation, vacuum removal, thin-film evaporation, and inert gas purging. Preferably, the preparation method does not use N-methylpyrrolidone, dimethylformamide, toluene, or xylene as a dispersion solvent.

[0014] The high-performance, environmentally friendly polyester dispersion of the present invention can be used in water-based inks, packaging coatings, PET film primers, paper coatings, aluminum foil coatings, metal coatings, water-based adhesives, or water-based composite adhesives.

[0015] Beneficial effects: 1. This invention addresses the problems that easily arise when recycled PET is used in aqueous polyester dispersions, such as insufficient reaction uniformity, difficulty in dispersion with high solids content, reliance on excessive external emulsifiers or organic solvents, and insufficient storage stability. By combining recycled PET alcoholysis products, ionic hydrophilic monomers containing sulfonate groups, polyether glycols, hydrophobically modified monomers, and branching and / or crosslinking regulating monomers, along with a low-solvent phase-inversion dispersion process or a melt direct dispersion process, an aqueous polyester dispersion is obtained that combines the characteristics of recycled resource utilization, high solids content, low external small-molecule emulsifier content, and low residual organic solvent content. The solids content of this polyester dispersion can reach 45–60 wt%, the content of external small-molecule emulsifier is no more than 0.2 wt%, and the residual organic solvent content is no more than 0.3 wt%, achieving a good overall balance between environmental friendliness, dispersion stability, and processing adaptability.

[0016] 2. This invention first performs alcoholysis on recycled PET to form one or both of the following: hydroxyl-terminated terephthalic acid ester oligomers and dialkyl terephthalate compounds. These then participate in subsequent esterification, transesterification, and polycondensation reactions. Compared to directly adding recycled PET to the polyester reaction system, the alcoholysis products have lower molecular weights and more defined end-group reactivity. This helps reduce the impact of insufficient melting, uneven local reactions, and source fluctuations of recycled PET on the polyester structure, thereby improving the effective utilization rate of recycled PET in water-dispersible polyester resins.

[0017] 3. This invention improves the hydrophilic / hydrophobic balance of water-dispersible polyester resins through the combination of ionic hydrophilic monomers containing sulfonate groups, polyether glycols, and hydrophobic modified monomers. Ionic hydrophilic monomers containing sulfonate groups enhance the resin's aqueous dispersion capability, polyether glycols improve chain segment flexibility and dispersion uniformity during dispersion, and hydrophobic modified monomers help adjust the hydrophobicity, film-forming properties, and application compatibility of the polyester segments. The combination of these components allows for better aqueous dispersion with lower amounts of added small-molecule emulsifiers, reducing the risk of decreased water resistance that might result from simply increasing the hydrophilic component.

[0018] 4. This invention primarily relies on the hydrophilic structure of the water-dispersible polyester resin itself to achieve aqueous phase dispersion, reducing dependence on externally added small-molecule emulsifiers. Compared to systems stabilized by high amounts of externally added emulsifiers, the polyester dispersion obtained by this invention helps reduce problems such as foaming, bubbling, emulsifier migration, particle size fluctuations, or stratification during preparation, storage, and use, thereby improving the bulk stability of the dispersion and enhancing its stability during subsequent film formation and application.

[0019] 5. This invention can introduce one or both of branching regulator monomers and crosslinking regulator monomers into polyester raw materials to adjust the molecular structure and molecular weight distribution of water-dispersible polyester resins. When the amount is controlled within 0 to 3 wt%, preferably within the range of 0.2 to 3 wt%, it is beneficial to improve the dispersion stability, storage stability and film-forming compatibility of the resin, while avoiding the increase in system viscosity, local gelation or difficulty in aqueous phase dispersion caused by excessive branching or crosslinking.

[0020] 6. The dispersion process used in this invention has good compatibility with the polyester formulation. When using a low-solvent phase-inversion dispersion process, the amount of organic solvent is controlled to be below 10 wt% of the mass of the water-dispersible polyester resin. This not only assists in resin softening, swelling, and phase-inversion dispersion, but also reduces the burden of subsequent solvent removal and helps to control the residual organic solvent content to below 0.3 wt%. When using a melt direct dispersion process, the polyester melt after polycondensation is not cooled and granulated, but is directly dispersed with the preheated hot water phase after cooling to 110–150°C. This reduces the dispersion resistance caused by resin cooling, crystallization, agglomeration, and secondary softening, thus making it easier to form a stable aqueous continuous phase dispersion.

[0021] 7. The high-performance environmentally friendly polyester dispersion obtained by this invention has the characteristics of recycled PET utilization, high solid content, low residual organic solvent, low added small molecule emulsifier, and good storage stability. It can be used as a waterborne polyester resin component in waterborne inks, packaging coatings, PET film primers, paper coatings, aluminum foil coatings, metal coatings, waterborne adhesives, or waterborne composite adhesives, and has good industrial application adaptability. Attached Figure Description

[0022] Figure 1 This is a process flow diagram of the high-performance environmentally friendly polyester dispersion of the present invention. Detailed Implementation

[0023] The present invention will be further described below with reference to embodiments and comparative examples. It should be understood that the following embodiments are only for illustrating the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Appropriate adjustments, substitutions, or equivalent modifications made by those skilled in the art without departing from the concept of the present invention should be considered to fall within the scope of protection of the present invention. In the following embodiments, the total mass of polyester raw materials refers to the total mass of reactive raw materials entering the esterification or transesterification reaction and the polycondensation reaction. Diols or dicarboxylic acids, which also serve as hydrophobic modifying monomers, are included in the total mass of polyester raw materials only once according to the actual mass fed.

[0024] Example 1

[0025] A high-performance, environmentally friendly polyester dispersion based on recycled PET comprises water and an aqueous polyester resin dispersed in the water, wherein the aqueous phase contains a small amount of pH adjuster. The aqueous polyester resin is prepared by esterification or transesterification and polycondensation reactions of recycled PET alcoholysis products, isophthalic acid, adipic acid, sodium 5-sulfonate dimethyl isophthalate, neopentyl glycol, diethylene glycol, cyclohexanediol, polyethylene glycol, and trimethylolpropane.

[0026] The following ingredients were used to prepare the mixture: 350g of recycled PET alcoholysis product, 180g of isophthalic acid, 90g of adipic acid, 30g of sodium 5-sulfonate dimethyl isophthalate, 100g of neopentyl glycol, 74g of diethylene glycol, 150g of cyclohexanediol, 20g of polyethylene glycol with a number average molecular weight of 1000, and 6g of trimethylolpropane. The recycled PET alcoholysis product accounted for 35wt%, sodium 5-sulfonate dimethyl isophthalate for 3.0wt%, polyethylene glycol for 2.0wt%, and trimethylolpropane for 0.6wt%; neopentyl glycol and cyclohexanediol were used as hydrophobic modifying monomers, totaling 25wt%. The mixture was prepared according to the following steps: S1, Recycled PET Alcohololysis: Clean, dry waste PET flakes, ethylene glycol, and neopentyl glycol are added to a reactor equipped with stirring, condensation, and nitrogen protection. A titanate catalyst is added, with a catalyst dosage of 0.05 wt% based on the total mass of the polyester raw materials. The mixture is heated to 210°C under nitrogen protection and maintained at this temperature for 3 hours for alcohololysis. After the reaction, infusible impurities are removed by filtration, and excess small molecule alcohols are removed under reduced pressure to obtain the recycled PET alcohololysis product. 350 g of the recycled PET alcohololysis product is used in the S2 stage.

[0027] S2. Esterification Polycondensation: Add 180g of isophthalic acid, 90g of adipic acid, 30g of sodium 5-sulfonate dimethyl isophthalate, 100g of neopentyl glycol, 74g of diethylene glycol, 150g of cyclohexanediethanol, 20g of polyethylene glycol with a number average molecular weight of 1000, and 6g of trimethylolpropane to 350g of recycled PET alcoholysis product. Stir until homogeneous to form a polyester reaction system. Under nitrogen protection, heat to 230℃ for esterification or transesterification reaction. After the theoretical water output or small molecule alcohol distillation amount is basically reached, heat to 255℃, gradually evacuate to -0.09MPa, and polycondense under this vacuum condition for 2h to obtain water-dispersible polyester resin.

[0028] S3. Aqueous phase dispersion: The water-dispersible polyester resin is cooled to 92°C, and an ethanol-n-butanol mixed solvent equivalent to 6 wt% of the resin mass is added to soften or swell the resin. Then, preheated deionized water containing triethylamine is added in batches under high-speed shear conditions to transform the system from a resin continuous phase to an aqueous continuous phase, thus obtaining an aqueous continuous phase dispersion.

[0029] S4. Post-treatment: The aqueous continuous phase dispersion obtained in S3 is subjected to depressurization desolventization, solidification, pH adjustment and filtration to obtain a recycled PET type high-performance environmentally friendly polyester dispersion.

[0030] Example 2

[0031] A flexible, high-performance, environmentally friendly polyester dispersion made from recycled PET is similar to Example 1 in that: the recycled PET raw materials are all first cleaned and dried before being used for alcoholysis; S1 is carried out in a reactor equipped with stirring, condensation, and nitrogen protection; after alcoholysis, insoluble impurities are removed by filtration, and excess small molecule alcohols are removed under reduced pressure to obtain the recycled PET alcoholysis product; S2 involves mixing the recycled PET alcoholysis product, dicarboxylic acid components, diol components, sodium 5-sulfonate dimethyl isophthalate, and polyethylene glycol to form a polyester reaction system, and then sequentially undergoing esterification or transesterification and polycondensation reactions under nitrogen protection to obtain a water-dispersible polyester resin; S3 employs a low-solvent phase-inversion dispersion process to soften or swell the water-dispersible polyester resin, and then adds preheated deionized water containing triethylamine in batches under shear conditions to form a continuous aqueous dispersion; S4 involves solvent removal, solidification, pH adjustment, and filtration. The differences lie in the polyester raw material composition, alcoholysis agent, catalyst, and process parameters of this embodiment, which are as follows.

[0032] Based on 1000g of polyester raw material: 250g of recycled PET alcoholysis product, 230g of isophthalic acid, 120g of adipic acid, 10g of sodium 5-sulfonate dimethyl isophthalate, 60g of neopentyl glycol, 40g of cyclohexanediol, 132g of ethylene glycol, 150g of diethylene glycol, and 8g of polyethylene glycol with a number average molecular weight of 400. The recycled PET alcoholysis product accounts for 25wt%, sodium 5-sulfonate dimethyl isophthalate accounts for 1.0wt%, and polyethylene glycol accounts for 0.8wt%; neopentyl glycol and cyclohexanediol together serve as hydrophobic modifying monomers, accounting for 10wt%.

[0033] In the preparation process, S1 uses ethylene glycol as the alcoholysis agent, a zinc salt catalyst, and a catalyst dosage of 0.02 wt% based on the total mass of the polyester raw materials. The alcoholysis temperature is 190°C, and the alcoholysis time is 2 h. In S2, the esterification or transesterification reaction temperature is 210°C, the polycondensation temperature is 230°C, and the polycondensation vacuum degree is -0.08 MPa. In S3, the softening or swelling temperature of the water-dispersible polyester resin is 75°C, and the amount of ethanol-n-butanol mixed solvent is 4 wt% of the resin mass. The remaining operations are carried out in the same manner as described in the previous embodiment. After post-treatment, a recycled PET-based waterborne polyester dispersion is obtained.

[0034] Example 3

[0035] A crosslinking-regulated high-performance environmentally friendly polyester dispersion of recycled PET is disclosed in this embodiment. Except for differences in polyester raw material composition, alcoholysis agent, catalyst, and process parameters, the pretreatment of recycled PET raw materials, filtration and de-alcoholization after S1 alcoholysis, the formation of the polyester reaction system in S2, the determination of the endpoint of esterification or transesterification reaction, the stepwise vacuum polycondensation method, the batch water addition method in the low-solvent phase inversion dispersion in S3, and the solvent removal, solidification, pH adjustment, and filtration methods in S4 are all the same as in Example 1. The difference lies in the polyester raw material composition, alcoholysis agent, catalyst, and process parameters of this embodiment, as follows.

[0036] Based on 1000g of polyester raw material, the composition includes: 550g of recycled PET alcoholysis products, 70g of isophthalic acid, 45g of adipic acid, 55g of sodium 5-sulfonate dimethyl isophthalate, 120g of neopentyl glycol, 60g of cyclohexanediol, 30g of diethylene glycol, 40g of polyethylene glycol with a number average molecular weight of 2000, and 30g of trimellitic anhydride. The recycled PET alcoholysis products account for 55wt%, sodium 5-sulfonate dimethyl isophthalate for 5.5wt%, polyethylene glycol for 4.0wt%, and trimellitic anhydride for 3.0wt%. Neopentyl glycol and cyclohexanediol, as hydrophobic modifying monomers, account for 18wt%.

[0037] In the preparation process, S1 uses diethylene glycol as the alcoholysis agent, an organic bismuth catalyst, and the catalyst dosage is 0.10 wt% based on the total mass of the polyester raw materials. The alcoholysis temperature is 230℃, and the alcoholysis time is 4 h. In S2, the esterification or transesterification reaction temperature is 245℃, the polycondensation temperature is 265℃, and the polycondensation vacuum degree is -0.10 MPa. In S3, the softening or swelling temperature of the water-dispersible polyester resin is 105℃, and the amount of ethanol-n-butanol mixed solvent is 10 wt% of the resin mass. The remaining operations are carried out as in Example 1 to obtain a crosslinking-regulated recycled PET high-performance environmentally friendly polyester dispersion.

[0038] Example 4

[0039] A branched-regulating high-performance environmentally friendly polyester dispersion of recycled PET is disclosed in this embodiment. Except for differences in polyester raw material composition, alcoholysis agent, catalyst, and process parameters, the pretreatment of recycled PET raw materials, filtration and de-alcoholization after S1 alcoholysis, the formation of the polyester reaction system in S2, the determination of the endpoint of esterification or transesterification reaction, the stepwise vacuum polycondensation method, the batch water addition method in the low-solvent phase inversion dispersion in S3, and the solvent removal, solidification, pH adjustment, and filtration methods in S4 are all the same as in Example 1. The difference lies in the polyester raw material composition, alcoholysis agent, catalyst, and process parameters of this embodiment, as follows.

[0040] The ingredients are formulated in 1000g batches, including 300g of recycled PET alcoholysis product, 220g of isophthalic acid, 100g of adipic acid, 12g of sodium 5-sulfonate dimethyl isophthalate, 100g of neopentyl glycol, 80g of cyclohexanediol, 174g of diethylene glycol, 12g of polyethylene glycol with a number average molecular weight of 600, and 2g of trimethylolpropane. Correspondingly, the recycled PET alcoholysis product accounts for 30wt%, sodium 5-sulfonate dimethyl isophthalate 1.2wt%, polyethylene glycol 1.2wt%, and trimethylolpropane 0.2wt%; neopentyl glycol and cyclohexanediol together account for 18wt%, serving as hydrophobic modifying monomers.

[0041] In the preparation process, S1 uses 1,3-propanediol as the alcoholysis agent and titanate catalyst, with a catalyst dosage of 0.04 wt% based on the total mass of polyester raw materials. The alcoholysis temperature is 205℃, and the alcoholysis time is 3 h. In S2, the esterification or transesterification reaction temperature is 225℃, the polycondensation temperature is 250℃, and the polycondensation vacuum degree is -0.09 MPa. In S3, the softening or swelling temperature of the water-dispersible polyester resin is 85℃, and the amount of ethanol-n-butanol mixed solvent is 5 wt% of the resin mass. The remaining operations are carried out as in Example 1, resulting in a branched-regulated recycled PET high-performance environmentally friendly polyester dispersion.

[0042] Example 5

[0043] A high-performance, environmentally friendly polyester dispersion of recycled PET using a melt direct dispersion method is disclosed in this embodiment. Except for differences in polyester raw material composition, alcoholysis agent, catalyst, S2 reaction parameters, and S3 dispersion process, the pretreatment of recycled PET raw materials, filtration and de-alcoholization after S1 alcoholysis, the formation of the polyester reaction system in S2, the determination of the esterification or transesterification reaction endpoint, the step-by-step vacuum polycondensation method, and the S4 solidification, pH adjustment, filtration, and defoaming treatment methods are all the same as in Example 1. The difference lies in the polyester raw material composition, alcoholysis agent, catalyst, and process parameters as follows.

[0044] The polyester raw material is 1000g, including 500g of recycled PET alcoholysis product, 70g of isophthalic acid, 30g of adipic acid, 50g of sodium 5-sulfonate dimethyl isophthalate, 120g of neopentyl glycol, 180g of cyclohexanediol, 20g of diethylene glycol, and 30g of polyethylene glycol with a number average molecular weight of 1000. The recycled PET alcoholysis product accounts for 50wt%, sodium 5-sulfonate dimethyl isophthalate for 5.0wt%, and polyethylene glycol for 3.0wt%; neopentyl glycol and cyclohexanediol together account for 30wt%, serving as hydrophobic modifying monomers.

[0045] In the preparation process, S1 uses cyclohexanediethanol as the alcoholysis agent, the catalyst is a tin salt catalyst, the catalyst dosage is 0.08 wt% based on the total mass of polyester raw materials, the alcoholysis temperature is 220℃, and the alcoholysis time is 3h; in S2, the esterification or transesterification reaction temperature is 240℃, the polycondensation temperature is 260℃, and the polycondensation vacuum degree is -0.09MPa.

[0046] In this embodiment, S3 employs a melt direct dispersion process. After polycondensation, the polyester melt is not cooled and granulated. Instead, it is directly cooled to 110°C, and a preheated (90°C) triethylamine-containing aqueous phase is added. The system then undergoes high-speed shearing and high-pressure homogenization to form a continuous aqueous dispersion. Subsequently, solids conditioning, pH adjustment, filtration, and defoaming are performed to obtain a melt direct dispersion type recycled PET high-performance environmentally friendly polyester dispersion.

[0047] Example 6

[0048] A hydrophobically modified high-performance environmentally friendly polyester dispersion of recycled PET is disclosed in this embodiment. Except for the differences in polyester raw material composition, alcoholysis agent, catalyst, and process parameters, the pretreatment of recycled PET raw materials, filtration and de-alcoholization after alcoholysis in S1, the formation of the polyester reaction system in S2, the determination of the endpoint of esterification or transesterification reaction, the stepwise vacuum polycondensation method, the batch water addition method in the low-solvent phase inversion dispersion in S3, and the solvent removal, solidification, pH adjustment, and filtration methods in S4 are all the same as in Example 1. The difference lies in the polyester raw material composition, alcoholysis agent, catalyst, and process parameters of this embodiment, as follows.

[0049] The formulation uses 1000g of polyester raw material, specifically: 320g of recycled PET alcoholysis product, 185g of isophthalic acid, 15g of sodium 5-sulfonate dimethyl isophthalate, 100g of diethylene glycol, 100g of neopentyl glycol, 100g of 1,6-hexanediol, 120g of sebacic acid, 30g of dimer acid, and 30g of polyethylene glycol with a number average molecular weight of 1000. The recycled PET alcoholysis product accounts for 32wt%, sodium 5-sulfonate dimethyl isophthalate for 1.5wt%, and polyethylene glycol for 3.0wt%; neopentyl glycol, 1,6-hexanediol, sebacic acid, and dimer acid together serve as hydrophobic modifying monomers, totaling 35wt%.

[0050] In the preparation process, S1 uses ethylene glycol and 1,6-hexanediol as alcoholysis agents, a zinc salt catalyst, and a catalyst dosage of 0.06 wt% based on the total mass of the polyester raw materials. The alcoholysis temperature is 215°C, and the alcoholysis time is 3 h. In S2, the esterification or transesterification reaction temperature is 235°C, the polycondensation temperature is 255°C, and the polycondensation vacuum degree is -0.09 MPa. In S3, the softening or swelling temperature of the water-dispersible polyester resin is 88°C, and the amount of ethanol-n-butanol mixed solvent is 4 wt% of the resin mass. The remaining operations are carried out as in Example 1 to obtain a hydrophobically modified recycled PET high-performance environmentally friendly polyester dispersion.

[0051] Example 7

[0052] A high-performance, environmentally friendly polyester dispersion of recycled PET modified with heteroaromatic dicarboxylic acids via melt direct dispersion. Except for the polyester raw material composition, alcoholysis agent, catalyst, S2 reaction parameters, and S3 dispersion process, the pretreatment of recycled PET raw materials, filtration and de-alcoholization after S1 alcoholysis, the formation of the polyester reaction system in S2, the determination of the esterification or transesterification reaction endpoint, and the step-by-step vacuum polycondensation method are all the same as in Example 1; the solidification, pH adjustment, and filtration treatment in S4 are performed according to Example 1. The difference lies in the polyester raw material composition, alcoholysis agent, catalyst, and process parameters of this embodiment, which are as follows.

[0053] The feed composition for 1000g of polyester raw material includes: 400g of recycled PET alcoholysis product, 100g of isophthalic acid, 80g of bio-based furanyl dicarboxylic acid, 20g of sodium 5-sulfonate dimethyl isophthalate, 100g of neopentyl glycol, 100g of cyclohexanediol, 40g of 1,4-butanediol, 130g of diethylene glycol, 25g of polyethylene glycol with a number average molecular weight of 1000, and 5g of trimethylolpropane. The recycled PET alcoholysis product accounts for 40wt%, sodium 5-sulfonate dimethyl isophthalate for 2.0wt%, polyethylene glycol for 2.5wt%, and trimethylolpropane for 0.5wt%. Neopentyl glycol, cyclohexanediol, and 1,4-butanediol are used as hydrophobic modifying monomers, totaling 24wt%.

[0054] In the preparation process, S1 uses 1,4-butanediol as the alcoholysis agent and titanate catalyst. The catalyst dosage is 0.05 wt% based on the total mass of polyester raw materials. The alcoholysis temperature is 220℃ and the alcoholysis time is 3h. In S2, the esterification or transesterification reaction temperature is 235℃, the polycondensation temperature is 250℃, and the polycondensation vacuum degree is -0.09MPa.

[0055] In this embodiment, S3 employs a melt direct dispersion process. After polycondensation, the polyester melt is not cooled and granulated. Instead, it is directly cooled to 150°C. Under closed or shear dispersion conditions with reflux condensation, a preheated aqueous phase containing a pH adjuster (95°C) is added. The system then undergoes high-speed shearing and high-pressure homogenization to form a continuous aqueous dispersion. Subsequently, solids conditioning, pH adjustment, filtration, and necessary defoaming are performed to obtain a high-performance, environmentally friendly melt direct dispersion of recycled PET modified with heteroaromatic dicarboxylic acids.

[0056] Comparative Example 1

[0057] A polyester dispersion lacking polyether glycol. This comparative example differs from Example 1 in that: polyethylene glycol is not added, and the diethylene glycol is adjusted from 74g to 94g to make up the total mass of the polyester raw material; the other raw material types, feeding methods, esterification or transesterification reactions, polycondensation reactions, aqueous dispersion and post-treatment steps are all performed in accordance with Example 1.

[0058] The mixture consists of 1000g of polyester raw materials, 350g of recycled PET alcoholysis product, 180g of isophthalic acid, 90g of adipic acid, 30g of sodium 5-sulfonate dimethyl isophthalate, 100g of neopentyl glycol, 94g of diethylene glycol, 150g of cyclohexanediethanol and 6g of trimethylolpropane.

[0059] Comparative Example 2

[0060] A polyester dispersion with a simple increase in the amount of ionic hydrophilic monomers. This comparative example differs from Example 1 in that: polyethylene glycol is not added, and the amount of sodium 5-sulfonate dimethyl isophthalate is increased from 30g to 55g; simultaneously, diethylene glycol is adjusted to 69g to make up the total mass of the polyester raw materials; the remaining raw material types, feeding methods, esterification or transesterification reactions, polycondensation reactions, aqueous dispersion, and post-treatment steps are all performed as in Example 1.

[0061] The mixture consists of 350g of recycled PET alcoholysis product, 180g of isophthalic acid, 90g of adipic acid, 55g of sodium 5-sulfonate dimethyl isophthalate, 100g of neopentyl glycol, 69g of diethylene glycol, 150g of cyclohexanediethanol and 6g of trimethylolpropane, based on a total mass of 1000g of polyester raw materials.

[0062] Comparative Example 3

[0063] A polyester dispersion with a relatively low amount of ionic hydrophilic monomers. This comparative example differs from Example 1 in that: the amount of dimethyl isophthalate sodium 5-sulfonate is reduced from 30g to 5g, and the amount of diethylene glycol is adjusted from 74g to 99g; no external small-molecule emulsifier is added during the dispersion stage; the remaining raw material types, feeding methods, esterification or transesterification reactions, polycondensation reactions, aqueous phase dispersion, and post-treatment steps are all performed in accordance with Example 1.

[0064] The mixture consists of 1000g of polyester raw materials, 350g of recycled PET alcoholysis product, 180g of isophthalic acid, 90g of adipic acid, 5g of sodium 5-sulfonate dimethyl isophthalate, 100g of neopentyl glycol, 99g of diethylene glycol, 150g of cyclohexanediethanol, 20g of polyethylene glycol with a number average molecular weight of 1000, and 6g of trimethylolpropane.

[0065] Comparative Example 4

[0066] A polyester dispersion stabilized by an added small molecule emulsifier. This comparative example differs from Example 1 in that: the amount of dimethyl isophthalate sodium 5-sulfonate is reduced to 5g, polyethylene glycol is not added, and an anionic small molecule emulsifier is added during the dispersion stage; simultaneously, diethylene glycol is adjusted to 119g to make up the total mass of the polyester raw materials; the remaining raw material types, feeding methods, esterification or transesterification reactions, polycondensation reactions, aqueous dispersion, and post-treatment steps are all performed as in Example 1.

[0067] The composition, based on a total polyester raw material mass of 1000g, includes 350g of recycled PET alcoholysis product, 180g of isophthalic acid, 90g of adipic acid, 5g of sodium 5-sulfonate dimethyl isophthalate, 100g of neopentyl glycol, 119g of diethylene glycol, 150g of cyclohexanediol, and 6g of trimethylolpropane. The amount of anionic small molecule emulsifier added is 2.0wt% based on the total mass of the polyester dispersion.

[0068] Comparative Example 5

[0069] A high solvent content polyester dispersion. This comparative example differs from Example 1 in that: the type and amount of polyester raw material are the same as in Example 1; before dispersion in the S3 aqueous phase, the resin is dissolved or swollen using an ethanol-n-butanol mixed solvent equivalent to 45 wt% of the mass of the water-dispersible polyester resin, followed by phase inversion dispersion and solvent removal; the remaining esterification or transesterification reactions, polycondensation reactions, and post-treatment steps are performed as in Example 1.

[0070] Comparative Example 6

[0071] A polyester dispersion without pre-alcoholization. This comparative example differs from Example 1 in that the recycled PET alcoholysis step in S1 is omitted; instead, clean, dry waste PET bottle flakes are directly added to the esterification and polycondensation reaction system to undergo esterification or transesterification and polycondensation reactions together with other polyester raw materials. The remaining aqueous dispersion and post-treatment steps are performed as in Example 1.

[0072] In this comparative example, based on a total polyester raw material weight of 1000g, the following were added: 350g of waste PET bottle flakes, 180g of isophthalic acid, 90g of adipic acid, 30g of sodium 5-sulfonate dimethyl isophthalate, 100g of neopentyl glycol, 74g of diethylene glycol, 150g of cyclohexanediol, 20g of polyethylene glycol with a number average molecular weight of 1000, and 6g of trimethylolpropane. In this example, the waste PET bottle flakes were not pre-converted into recycled PET alcoholysis products.

[0073] Comparative Example 7

[0074] A polyester dispersion with a high amount of alcoholysis product. This comparative example differs from Example 1 in that: the amount of recycled PET alcoholysis product is increased to 700g, and the amount of other acid and alcohol components is reduced accordingly; the other raw material addition methods, esterification or transesterification reactions, polycondensation reactions, aqueous phase dispersion, and post-treatment steps are all performed in accordance with Example 1.

[0075] The mixture consists of 700g of recycled PET alcoholysis product, 70g of isophthalic acid, 24g of adipic acid, 30g of sodium 5-sulfonate dimethyl isophthalate, 70g of neopentyl glycol, 80g of cyclohexanediethanol, 20g of polyethylene glycol with a number average molecular weight of 1000, and 6g of trimethylolpropane, based on a total mass of 1000g of polyester raw materials.

[0076] Comparative Example 8

[0077] A polyester dispersion that does not employ phase inversion or direct melt dispersion processes. This comparative example differs from Example 1 in that: in stage S3, neither a low-solvent phase inversion dispersion process nor a direct melt dispersion process is used. Instead, the water-dispersible polyester resin obtained from polycondensation is cooled to room temperature and then crushed. Room temperature deionized water is added all at once without allowing the resin to soften, melt, or swell, and dispersion is achieved using only ordinary mechanical stirring. The remaining polyester raw material composition, esterification or transesterification reaction, polycondensation reaction, and post-treatment steps are performed as in Example 1.

[0078] Comparative Example 9

[0079] A hydrophilic component-added polyester dispersion. This comparative example differs from Example 1 in that: sodium 5-sulfonate dimethyl isophthalate and polyethylene glycol do not participate in esterification, transesterification, or polycondensation reactions in the S2 stage, but are added to the system as hydrophilic components in the aqueous dispersion stage.

[0080] In stage S2, based on a total polyester raw material mass of 1000g, 350g of recycled PET alcoholysis product, 210g of isophthalic acid, 90g of adipic acid, 100g of neopentyl glycol, 94g of diethylene glycol, 150g of cyclohexanediol, and 6g of trimethylolpropane were added. The polyester resin was obtained through esterification or transesterification and polycondensation. Subsequently, in stage S3 (aqueous phase dispersion), 30g of sodium 5-sulfonate dimethyl isophthalate and 20g of polyethylene glycol with a number average molecular weight of 1000 were added to the preheated hot water phase, and then dispersed in aqueous phase with the aforementioned polyester resin. The remaining dispersion and post-treatment steps were performed as described in Example 1.

[0081] Performance testing

[0082] The bulk properties of the polyester dispersions obtained in Examples 1-7 and Comparative Examples 1-9 were tested. Solid content was determined by drying loss; average particle size and particle size distribution index (PDI) were determined by dynamic light scattering; viscosity at 25°C was determined by rotational viscometer; pH was determined by pH meter; residual organic solvent content was determined by gas chromatography; centrifugal stability was evaluated by observing the presence of obvious stratification, sedimentation, or flocculation after centrifuging the dispersion at 3000 r / min for 30 min; storage stability was evaluated by observing changes in appearance after placing the dispersion at 50°C for 7 days, and re-measuring changes in particle size and viscosity.

[0083] Table 1. Performance test results of polyester dispersions in Examples 1-7 and Comparative Examples 1-9

[0084] As can be seen from the data in Table 1, the samples obtained in Examples 1-7 showed good overall stability. The solid content of each sample ranged from 54.3% to 56.7 wt%, the average particle size was 114-146 nm, the PDI was 0.19-0.25, the viscosity at 25°C was 832-1483 mPa·s, and the residual organic solvent content was 0.13-0.24 wt%. After centrifuging the samples at 3000 r / min for 30 min, no obvious stratification was observed. After being placed at 50°C for 7 days, no significant changes were observed in the appearance of the samples, no obvious sedimentation occurred, and no abnormal changes were observed in particle size and viscosity.

[0085] Comparative Example 1, without the addition of polyether glycol, showed an increase in average particle size to 283 nm, a PDI of 0.38, and a viscosity of 3173 mPa·s at 25°C. A small amount of precipitation occurred after centrifugation. Compared to Example 1, it can be seen that without the polyether segment, relying solely on the sulfonate-type ionic hydrophilic structure to maintain aqueous phase dispersion makes it difficult to control particle size and viscosity. In Comparative Example 2, although the amount of sodium 5-sulfonate dimethyl isophthalate was increased to 55 g, resulting in a decrease in average particle size, the viscosity at 25°C increased to 3837 mPa·s. This means that while increasing the amount of ionic hydrophilic monomer can improve dispersion to some extent, it cannot replace the role of polyether glycol in regulating the particle interface and system viscosity; excessively high ionic hydrophilicity can actually increase system viscosity.

[0086] In Comparative Example 3, reducing the amount of sodium 5-sulfonate dimethyl isophthalate to 5g resulted in a decrease in the solid content of the dispersion, an increase in the average particle size to 421nm, and a PDI of 0.46. Precipitation or sedimentation occurred after centrifugation and storage at 50℃. This indicates that when the amount of ionic hydrophilic monomer is too low, the polyester resin cannot achieve sufficient aqueous dispersion. In Comparative Example 4, reducing the amount of ionic hydrophilic monomer and adding an anionic small molecule emulsifier to assist dispersion resulted in a lower initial average particle size, but the PDI reached 0.35. Excessive foaming occurred during centrifugation, and surface foam was present after storage. This result shows that adding a small molecule emulsifier can improve the initial dispersion state, but it easily introduces foam, foam, and interfacial fluctuations, which is detrimental to the long-term stability of the dispersion.

[0087] Comparative Example 5 employed a high solvent dosage phase-inversion dispersion process. The average particle size and viscosity of the resulting dispersion were similar to those of some examples, but the residual organic solvent content reached 0.82 wt%, significantly higher than the sample in the examples. This indicates that while increasing the amount of organic solvent is beneficial for resin softening and initial phase-inversion dispersion, it increases the subsequent solvent removal burden and makes it difficult to meet the requirement of low residual organic solvent.

[0088] The method of introducing recycled PET also significantly affects the dispersion state. In Comparative Example 6, no pre-alcoholization was performed; instead, waste PET bottle flakes were directly added to the esterification polycondensation system. The resulting dispersion showed a significant increase in average particle size, PDI, and viscosity, and sedimentation occurred after storage. This is related to insufficient melting, depolymerization, and reaction uniformity of the waste PET in the reaction system, ultimately affecting the structural uniformity and aqueous dispersion effect of the water-dispersible polyester resin. In Comparative Example 7, increasing the amount of recycled PET alcoholysis product to 700g resulted in a decrease in solid content to 46.2wt%, an increase in average particle size and PDI, and significant sedimentation and increased viscosity after storage. This indicates that when the proportion of recycled PET alcoholysis product is too high, the proportion of rigid terephthalate segments increases, consequently increasing the difficulty of aqueous dispersion.

[0089] Comparative Example 8 did not employ a low-solvent phase-inversion dispersion process or a direct melt dispersion process. Instead, it was dispersed directly with water under ordinary mechanical stirring conditions. The resulting dispersion had an average particle size of 497 nm and a PDI of 0.63. Significant precipitation or sedimentation was observed after centrifugation and storage. These results indicate that for the high-solids polyester system of this invention, it is difficult to form a stable, low-particle-size, narrowly distributed aqueous continuous phase dispersion using only ordinary mechanical stirring. The dispersion process needs to be matched with the resin structure.

[0090] In Comparative Example 9, sodium 5-sulfonate dimethyl isophthalate and polyethylene glycol did not participate in the construction of polyester segments during esterification, transesterification, or polycondensation; instead, they were added as hydrophilic components during the aqueous dispersion stage. The average particle size and PDI of the resulting dispersion were significantly higher than those in the Example. A small amount of precipitation occurred after centrifugation, and sedimentation occurred after storage at 50°C. These results indicate that ionic hydrophilic monomers and polyether glycols can more effectively form a stable intramolecular hydrophilic dispersion structure only after entering the resin molecular structure through the polyester reaction; simply adding them later cannot achieve the same stabilizing effect.

[0091] The results of the examples and comparative examples show that the present invention achieves synergistic optimization of resin structure and dispersion process through the combination of pre-alcoholization of recycled PET, synergistic introduction of ionic hydrophilic monomers and polyether glycols, appropriate adjustment of hydrophobic modified monomers, and low-solvent phase inversion dispersion or melt direct dispersion processes. Even under conditions of high solids content, low added small molecule emulsifiers, and low residual organic solvents, waterborne polyester dispersions with small particle size, moderate viscosity, and good storage stability can still be obtained.

[0092] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. All equivalent substitutions, parameter adjustments, or conventional improvements made based on the concept of the present invention should be included within the scope of protection of the present invention.

Claims

1. A high-performance, environmentally friendly polyester dispersion, characterized in that, It includes water and a water-dispersible polyester resin dispersed in water; the water-dispersible polyester resin is obtained from polyester raw materials through esterification or transesterification and polycondensation reactions; Based on a total polyester raw material mass of 100 wt%, the polyester raw material comprises the following components: 25-55 wt% of recycled PET alcoholysis product obtained by alcoholysis of recycled PET and an alcoholysis agent in the presence of a catalyst; 1.0-5.5 wt% of sodium isophthalate 5-sulfonate; 0.8-4 wt% of polyether glycol with a number average molecular weight of 400-2000; and at least one selected from neopentyl glycol, cyclohexanediol, 1,4-butanediol, 1,6-hexanediol, sebacic acid, and dimer acid. The mixture comprises 10-35 wt% of a hydrophobic modifying monomer, 0-3 wt% of a branching regulating monomer and / or a crosslinking regulating monomer, and the balance being at least one dicarboxylic acid component selected from isophthalic acid, bio-based furanyl dicarboxylic acid and adipic acid, and at least one diol component selected from ethylene glycol and diethylene glycol; wherein the sodium 5-sulfonate dimethyl isophthalate and the polyether diol are both added to the polyester reaction system before the esterification or transesterification reaction and the polycondensation reaction, and participate in the formation of polyester segments; The recycled PET alcoholysis product is one or two of hydroxyl-terminated terephthalate oligomers and terephthalic acid dihydroxyalkyl esters; the alcoholysis agent is selected from at least one of ethylene glycol, diethylene glycol, neopentyl glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol and cyclohexanediol. The polyester dispersion is formed into an aqueous continuous phase dispersion using any of the following dispersion processes: Low-solvent phase-conversion dispersion process: The water-dispersible polyester resin is added to a mixed solvent of ethanol and n-butanol at 75–105°C to soften or swell the water-dispersible polyester resin. Subsequently, an aqueous phase is added to the resulting system, causing the system to transform from a resin continuous phase to a water continuous phase. The total mass of ethanol and n-butanol added is 4–10 wt% of the mass of the water-dispersible polyester resin. Alternatively, the melt direct dispersion process involves cooling the polyester melt after polycondensation reaction without cooling and granulation to 110–150°C and mixing it with preheated hot water to form a continuous aqueous dispersion. The solid content of the polyester dispersion is 45-60 wt%; based on the total mass of the polyester dispersion, the content of added small molecule emulsifier is not higher than 0.2 wt%, and the total content of residual organic solvent is not higher than 0.3 wt%.

2. The high-performance environmentally friendly polyester dispersion according to claim 1, characterized in that, Based on a total polyester raw material mass of 100wt%, the recycled PET alcoholysis product is 30-50wt%, the sodium 5-sulfonate dimethyl isophthalate is 1.2-5.0wt%, the polyether glycol is 1.2-3.0wt%, and the hydrophobic modified monomer is 18-30wt%.

3. The high-performance environmentally friendly polyester dispersion according to claim 1, characterized in that, The polyether glycol is polyethylene glycol, the branching regulator is trimethylolpropane, and the crosslinking regulator is trimellitic anhydride; when the amount of the branching regulator and / or the crosslinking regulator is not 0, the total amount of the two is 0.2 to 3 wt%.

4. A method for preparing the high-performance environmentally friendly polyester dispersion according to any one of claims 1 to 3, characterized in that, Includes the following steps: S1. Add recycled PET, alcoholysis agent and catalyst to the reaction system, and carry out alcoholysis reaction under nitrogen or inert gas protection to obtain recycled PET alcoholysis product; S2. According to the polyester raw material composition and dosage defined in any one of claims 1 to 3, the recycled PET alcoholysis product obtained in S1, sodium 5-sulfonate dimethyl isophthalate, polyether glycol, hydrophobic modified monomer, optional branching regulating monomer and / or crosslinking regulating monomer, dicarboxylic acid component and diol alcohol component are added to the reaction system and mixed, and then esterification or transesterification reaction and polycondensation reaction are carried out, so that sodium 5-sulfonate dimethyl isophthalate and polyether glycol participate in the formation of polyester segments to obtain a water-dispersible polyester resin. S3. The water-dispersible polyester resin is mixed with an aqueous phase using any of the following dispersion processes to form a continuous aqueous dispersion: Low-solvent phase-conversion dispersion process: The water-dispersible polyester resin is added to a mixed solvent of ethanol and n-butanol at 75–105°C to soften or swell the water-dispersible polyester resin. Subsequently, an aqueous phase is added to the resulting system, causing the system to transform from a resin continuous phase to a water continuous phase. The total mass of ethanol and n-butanol added is 4–10 wt% of the mass of the water-dispersible polyester resin. Alternatively, the melt direct dispersion process involves cooling the polyester melt after polycondensation reaction without cooling and granulation to 110–150°C and mixing it with preheated hot water to form a continuous aqueous dispersion. S4. The aqueous continuous phase dispersion is subjected to solidification, pH adjustment, and filtration, and solvent removal treatment is performed according to the residual organic solvent content to obtain a high-performance environmentally friendly polyester dispersion; wherein, based on the total mass of the obtained high-performance environmentally friendly polyester dispersion, the residual organic solvent content is not higher than 0.3 wt%.

5. The preparation method according to claim 4, characterized in that, In S1, the alcoholysis reaction temperature is 190–230°C, the reaction time is 2–4 h, and the catalyst dosage is 0.02–0.10 wt% based on the total mass of the polyester raw materials; in S2, the esterification or transesterification reaction temperature is 210–245°C, the polycondensation reaction temperature is 230–265°C, and the vacuum degree of the system during the polycondensation stage is -0.08 MPa to -0.10 MPa using a gauge pressure gauge.

6. The preparation method according to claim 4, characterized in that, The aqueous phase is deionized water or an aqueous solution containing a pH adjuster, wherein the pH adjuster is selected from at least one of ammonia, organic amines, alkali metal hydroxides, alkali metal carbonates and alkali metal bicarbonates; The solvent removal process is selected from at least one of vacuum distillation, vacuum removal, thin-film evaporation, and inert gas purging; the preparation method does not use N-methylpyrrolidone, dimethylformamide, toluene, or xylene as a dispersion solvent.

7. The application of the high-performance environmentally friendly polyester dispersion according to any one of claims 1 to 3 in water-based inks, packaging coatings, PET film primers, paper coatings, metal coatings, and water-based adhesives.

Images