Reversible crosslinking polyester resin, and preparation method and application thereof

Abstract

The application discloses a kind of reversible crosslinking polyester resin and its preparation method and application, belong to printing consumables technical field.The preparation method of reversible crosslinking polyester resin provided by the present application first synthesizes linear prepolymer of high molecular weight, then forms the polyester resin with reversible crosslinking network by the Diels-Alder reaction of furan group and maleimide group.Reversible crosslinking polyester resin in the instant of heating, DA bond occurs reversible fracture, make the network structure of originally high molecular weight, high crosslinking degree rapidly dissociate into low molecular weight, low viscosity linear segment, to realize fast melting, flow flat and firmly combined with paper fiber under lower temperature and pressure;After cooling, DA bond is reformed, and the strength of the material is restored, which skillfully solves the technical contradiction that high molecular weight resin is difficult to fix at low temperature.Meanwhile, it has low-temperature fixing property, high self-repairing rate, excellent anti-blocking property and recyclability.

Description

Technical Field

[0001] This invention relates to the field of printing consumables technology, and in particular to a reversible crosslinked polyester resin, its preparation method, and its application. Background Technology

[0002] Polyester resin, as the core binder material for color toners, is the cornerstone of modern high-speed, high-quality, and low-energy digital printing technology. With its excellent low-temperature fixing properties, high gloss, outstanding color performance, and high molecular designability, polyester resin perfectly meets the stringent requirements of color toners for image quality and printing performance. The performance of polyester resin directly determines the fixing temperature, printing speed, anti-blocking properties, and environmental friendliness of color toners.

[0003] With the technological development in the field of color toner, existing polyester resins have encountered performance bottlenecks in application, such as high fixing temperature and energy consumption; narrow molecular weight distribution leading to performance contradictions; and insufficient anti-blocking properties. In order to reduce the fixing temperature, low Tg resins or low molecular weight waxes are often used, but this increases non-recyclability and environmental pressure.

[0004] To address the aforementioned issues, the industry has explored various improvement solutions, such as the development of low-temperature fixing resins, the exploration of dynamic covalent bonds, and the design of environmentally friendly resins. However, in pursuing low-temperature fixing performance, excellent anti-blocking properties, and good recyclability, improving any one performance trait may come at the expense of another, leading to a predicament in existing technological approaches. Therefore, given the current core technological challenges faced by polyester resins in color toner applications, there is an urgent need for a polyester resin that can effectively solve the synergistic problems of low-temperature fixing, anti-blocking, and recyclability, providing an innovative solution for the greening and high-performance of high-end printing consumables. Summary of the Invention

[0005] In view of the problems existing in the prior art, the purpose of this invention is to provide a method for preparing a reversible cross-linked polyester resin that can be fixed at low temperature, has anti-blocking properties, and is recyclable; another purpose of this invention is to provide a reversible cross-linked polyester resin with low temperature fixing properties, wide molecular weight distribution properties, anti-blocking properties, and recyclability.

[0006] This invention discloses a method for preparing a reversible crosslinked polyester resin, comprising the following steps:

[0007] S1 Esterification reaction: In a protective gas atmosphere, the organic carboxylic acid component, polyol component and catalyst are mixed, the temperature of the mixture is raised to the esterification temperature, and the esterification reaction is carried out. After the reaction is complete, the esterified product is obtained.

[0008] S2 prepolymer synthesis: The esterified compound is mixed with furan dicarboxylic acid and maleimide-modified butanediol, and the temperature is adjusted to 170℃-190℃. The reaction is carried out for 1.5h-2.5h to obtain a linear prepolymer with furan and / or maleimide end groups.

[0009] S3 Polycondensation: The temperature of the prepolymer is adjusted to the polymerization temperature, a vacuum is drawn, and a polycondensation reaction is carried out. The reaction is stopped after the target degree of polymerization is reached, and the resin particles are obtained through post-processing.

[0010] When the temperature at the top of the distillation column drops below 70°C during the esterification reaction, it indicates that the esterification water has completely flowed out, and the esterification reaction is considered to be complete.

[0011] Furan dicarboxylic acid (FDCA) is a bio-based aromatic diacid, generally less reactive than conventional terephthalic acid (PTA). Higher temperatures (170℃-190℃) help overcome its steric hindrance and the stability of its aromatic ring, promoting efficient reaction between the carboxyl group and the alcohol hydroxyl group. In maleimide-modified butanediol, the maleimide group contains a carbon-carbon double bond (C=C), which may lead to undesirable side reactions (such as self-polymerization or decomposition) at excessively high temperatures. 170℃-190℃ is a trade-off point, sufficient to drive the desired Diels-Alder reaction or copolymerization with the furan ring while minimizing its thermal degradation.

[0012] Within this temperature range, reactants (such as FDCA, glycols, and esterification intermediates) typically remain in a molten state or are well dispersed, ensuring a homogeneous reaction and preventing excessively wide molecular weight distribution of the product due to localized inhomogeneities. Furthermore, it promotes selective reactions of functional groups (-COOH and -OH) and suppresses side reactions such as oxidation, decarboxylation, or etherification that may occur at high temperatures. These side reactions could lead to molecular chain branching or gelation. Precise control of temperature and time ensures that furan and maleimide groups are primarily located at the ends of the prepolymer chains, rather than embedded within them. This is a crucial prerequisite for subsequent thermally reversible crosslinking (e.g., based on the Diels-Alder reaction) or functionalization.

[0013] During the polycondensation process, furan and maleimide groups on the linear prepolymer chain undergo a Diels-Alder reaction to form a reversible cross-linked network structure.

[0014] The post-processing steps include: stopping heating and vacuuming, releasing the vacuum with N2, discharging the molten resin, and then cooling, pelletizing, and drying to obtain light yellow transparent resin particles.

[0015] Furthermore, the organic carboxylic acid component includes isophthalic acid, terephthalic acid, adipic acid, maleic anhydride, trimellitic anhydride, stearic acid, and benzoic acid.

[0016] Trimeric triphthalic anhydride (TMA) and trimethylolpropane (TMP) are branching agents, while terephthalic acid (PTA) and isophthalic acid (IPA) are rigid units. Adipic acid (AA) is a flexible unit, imparting mobility to polymer chain segments, improving toughness, and lowering the glass transition temperature.

[0017] Furthermore, the acid component includes the organic carboxylic acid component and the furanyl dicarboxylic acid; wherein, in the acid component, by molar percentage, terephthalic acid accounts for 30%-40%, isophthalic acid accounts for 15-25%, adipic acid accounts for 4%-8%, maleic anhydride accounts for 9%-12%, furanyl dicarboxylic acid accounts for 12%-20%, trimellitic anhydride accounts for 2%-5%; benzoic acid accounts for 3%-5%, and stearic acid accounts for 3%-5%.

[0018] Furthermore, the polyol components include ethylene glycol, 1,4-butanediol, trimethylolpropane (TMP), high molecular weight alcohol ether D33, and high molecular weight alcohol ether D22.

[0019] The polymeric alcohol ether D33 is propoxylated bisphenol A; the polymeric alcohol ether D22 is polyether diol.

[0020] Furthermore, the alcohol component includes the polyol component and the maleimide-modified butanediol; in the alcohol component, by molar percentage, ethylene glycol accounts for 25%-40%, 1,4-butanediol accounts for 33%-40%, maleimide-modified butanediol accounts for 14%-20%, and trimethylolpropane accounts for 1%-3%; high molecular weight alcohol ether D33 accounts for 8%-11%, and high molecular weight alcohol ether D22 accounts for 6%-10%.

[0021] Furthermore, the catalyst comprises tetraisopropyl titanate, and the added mass of the catalyst is 0.03%-0.05% of the sum of the masses of the alcohol component and the acid component; the esterification temperature is 190℃-210℃.

[0022] Using furanyl dicarboxylic acid (12mol%-20mol%) as the donor and maleimide-modified butylene glycol (14mol%-20mol%) as the acceptor, Diels-Alder (DA) dynamic covalent bonds are formed during the polycondensation process. The DA bonds dissociate at 90℃-140℃ (resin viscosity decreases, achieving low-temperature fixing), and recombine at 60℃-90℃ to restore the crosslinked network and improve fixing strength.

[0023] Furthermore, the polymerization temperature is 230℃-240℃; the absolute pressure during vacuuming is below 100Pa; the target degree of polymerization is characterized by viscosity, and the reaction stops when the viscosity reaches 0.80dL / g-0.85dL / g.

[0024] Furthermore, in the alcohol component and the acid component, the molar ratio of hydroxyl to carboxyl groups is (1.02-1.05):1; the molar ratio of furanyl dicarboxylic acid to maleimide-modified butanediol is 0.6-1.45.

[0025] The present invention also discloses a reversible crosslinked polyester resin, which is prepared by the preparation method described above; the reversible crosslinked polyester resin has a number average molecular weight range (Mn) of 20,000-30,000, a molecular weight distribution (PDI) of 3.8 ≥ 3.0, a glass transition temperature (Tg) of 55℃-65℃, and a resin surface contact angle of 103° ≥ 98°.

[0026] By introducing branching points such as trimellitic anhydride (TMA), the molecular weight distribution of the resin was precisely controlled (PDI can reach 3.0 – 3.8), achieving a perfect balance between "low melt viscosity" and "high strength." The wide molecular weight distribution forms a "multi-level synergistic" chain structure. The low molecular weight portion acts as a "plasticizer," primarily responsible for reducing melt viscosity, which is key to achieving low-temperature fixing and high gloss. The high molecular weight portion and branched chains form physical entanglement points, providing melt strength and toughness, effectively preventing "thermal shift" during fixing, and endowing the toner with excellent mechanical properties.

[0027] By optimizing the ratio of rigid monomers (such as terephthalic acid), the resin Tg was stably controlled at a high level of 55℃-65℃, preventing adhesion at its source. A strategy of synergistic end-capping with stearic acid and benzoic acid was adopted to introduce long-chain alkyl groups and benzene rings at the ends of the molecular chains, effectively reducing the surface energy of the resin and achieving a contact angle ≥98°, significantly improving its hydrophobic and moisture-resistant properties.

[0028] The cross-linked monomer furanyl dicarboxylic acid (FDCA) is derived from biomass resources such as corn cobs and straw, reducing dependence on petroleum resources. The preparation process involves melt polycondensation, eliminating the need for organic solvents and preventing VOC (volatile organic compound) emissions and residues from the source. Compared to some traditional additives, the dynamic cross-linking system used is more environmentally friendly.

[0029] The present invention also discloses a colored toner comprising the reversible crosslinked polyester resin as described above.

[0030] Color toner has successfully achieved low-temperature fixing at ≤110℃, which is significantly lower than the fixing temperature of traditional petroleum-based polyester resins (which typically require ≥130℃). This characteristic stems from the Diels-Alder (DA) dynamic reversible covalent bond network introduced into the resin.

[0031] This invention discloses a method for preparing a reversible crosslinked polyester resin. First, a high-molecular-weight linear prepolymer is synthesized, and then a reversible crosslinked network is formed through the Diels-Alder reaction of furan and maleimide groups. Upon heating, the DA bonds in the synthesized reversible crosslinked polyester resin undergo reversible breakage, causing the originally high-molecular-weight, highly crosslinked network structure to rapidly dissociate into low-molecular-weight, low-viscosity linear segments. This allows for rapid melting, leveling, and strong bonding with paper fibers at relatively low temperatures and pressures. Upon cooling, the DA bonds reform, restoring the material's strength, cleverly solving the technical challenge of low-temperature fixing of high-molecular-weight resins. It also possesses low-temperature fixing properties, high self-healing rate, excellent anti-blocking properties, and recyclability. Detailed Implementation

[0032] To make the technical solution of the present invention clearer, the present invention will be further described in detail below with reference to specific embodiments.

[0033] Polymer alcohol ether D33 is propoxylated bisphenol A; polymer alcohol ether D22 is polyether diol. Example 1

[0034] Preparation of reversible crosslinked polyester resin:

[0035] S1 Esterification reaction: According to the proportions shown in Table 1, organic carboxylic acids, polyol components, and catalyst (tetraisopropyl titanate, amounting to 0.04% of the total feed mass) other than furanyl dicarboxylic acid and maleimide-modified butanediol were added to the reactor. Under N2 protection, the temperature was slowly raised to 200°C with stirring to carry out the esterification reaction until the top temperature of the fractionation column dropped below 70°C (indicating that the water output was complete).

[0036] S2 prepolymer synthesis: Add furan dicarboxylic acid and maleimide-modified butanediol in the proportions shown in the table, maintain the temperature at 180℃, and continue the reaction for 2 hours to form a linear prepolymer with furan and / or maleimide end groups.

[0037] S3 Polycondensation: The temperature of the prepolymer is gradually raised to 235℃, and a vacuum is slowly applied until the absolute pressure of the system is below 100 Pa. The polycondensation reaction is carried out under these conditions. The reaction endpoint is controlled by monitoring the stirring motor torque or intrinsic viscosity ([η]). The reaction is stopped when [η] reaches 0.80-0.85 dL / g (measured by a rotational viscometer at 25℃, using a mixed solvent of phenol and tetrachloroethane, where the mass ratio of phenol to tetrachloroethane is 1:1). Heating and vacuuming are stopped, the vacuum is released with N2, the molten resin is discharged, and after water cooling, pelletizing, and drying, pale yellow transparent resin particles are obtained.

[0038] During this process, furan and maleimide groups on the prepolymer chain undergo a Diels-Alder reaction to form a reversible cross-linked network structure.

[0039] Table 1. Materials and proportions for Example 1 (where the total molar ratio of organic carboxylic acid components and polyol components is 1:1).

[0040] Example 2

[0041] The only difference between Example 2 and Example 1 is the proportion of materials used; all other steps are the same. The specific proportions of materials used are shown in Table 2.

[0042] Table 2 shows the materials and proportions for Example 2 (where the total molar ratio of organic carboxylic acid components and polyol components is 1:1).

[0043] Example 3

[0044] The only difference between Example 3 and Example 1 is the proportion of materials used; all other steps are the same. The specific proportions of materials used are shown in Table 3.

[0045] Table 3 shows the materials and proportions for Example 3 (where the total molar ratio of organic carboxylic acid components and polyol components is 1:1).

[0046] Example 4

[0047] The only difference between Example 4 and Example 1 is the proportion of materials used; all other steps are the same. The specific proportions of materials used are shown in Table 4.

[0048] Table 4 shows the materials and proportions for Example 4 (where the total molar ratio of organic carboxylic acid components and polyol components is 1:1).

[0049] Example 5

[0050] The only difference between Example 5 and Example 1 is the proportion of materials used; all other steps are the same. The specific proportions of materials used are shown in Table 5.

[0051] Table 5 shows the materials and proportions for Example 5 (where the total molar ratio of organic carboxylic acid components and polyol components is 1:1).

[0052] Example 6

[0053] The only difference between Example 6 and Example 1 is the proportion of materials used; all other steps are the same. The specific proportions of materials used are shown in Table 6.

[0054] Table 6 shows the materials and proportions for Example 6 (where the molar ratio of organic carboxylic acid component to polyol component is 1:1).

[0055]

[0056] Comparative Example

[0057] The main difference between the comparative example and the embodiment is that the traditional, performance-balanced commercially available polyester resin for toner is used, and no synthetic DA dynamic bonds are introduced. The specific material ratios are shown in Table 7.

[0058] Table 7 shows the materials and proportions for the comparative examples (where the molar ratio of organic carboxylic acid components to polyol components is 1:1).

[0059]

[0060] Performance testing:

[0061] The polyester resins used in the examples and comparative examples were subjected to acid value testing, gel permeation chromatography (GPC), differential scanning calorimetry (DSC), and static water droplet method to test their contact angle. The test methods and results are shown in Table 8.

[0062] The polyester resins obtained in the examples and comparative examples were mixed with colorants (pigments), charge control agents, and release agents in a high-speed mixer in proportion and mixed evenly. The premix was then fed into an internal mixer and melt-mixed at 90-120°C to ensure uniform dispersion of the components. Subsequently, the mixture was cooled, coarsely crushed, finely crushed, and finely graded to obtain a basic powder (masterbatch) with a volume average particle size (D50) of 5-12 μm. Finally, hydrophobic nano-silica and other external additives were quantitatively added to the surface of the masterbatch in a high-speed mixer for surface coating treatment to obtain colored toner. The fixing temperature, self-healing rate, and whether the colored toner agglomerated after being stored at (45°C, 80%RH) for more than 6 months were then tested. The test results are shown in Table 8.

[0063] Table 8 Test results of the embodiments and comparative examples

[0064]

[0065] Examples 1-6: Even after being stored for more than 6 months in harsh environments with high temperature and humidity (45°C, 80%RH), the toner showed no clumping, demonstrating excellent storage stability. By optimizing the ratio of rigid monomers (such as terephthalic acid), the resin Tg was stably controlled at a high level of 55°C-60°C, preventing adhesion at the root of molecular chain mobility.

[0066] The resin prepared in Example 1 is of a balanced type with moderate branching, using moderate amounts of TMA (trimethoate anhydride) 3 mol% and TMP (trimethylolpropane) 2 mol%. The functional group ratio (OH / COOH) is 1.03, which is moderate. The dynamic crosslinking monomers, FDCA (furandicarboxylic acid) 18 mol% and MI-BDO (maleimide-modified butylene glycol) 15 mol%, are balanced in a molar ratio of approximately 1.2:1. A balance between rigidity and flexibility is achieved, with PTA (terephthalic acid) 35 mol% and IPA (isophthalic acid) 20 mol% providing rigidity, and AA (adipic acid) 5 mol% and MAH (maleic anhydride) 10 mol% providing adequate flexibility.

[0067] Example 1 successfully synthesized a resin with an Mn of 22500 g / mol and a PDI of 3.2. This indicates that moderate branching and functional group ratios effectively promote molecular chain growth and result in a broad molecular weight distribution. Example 1 has a Tg of 59°C and a fixing temperature of 108°C. Its performance is in the middle range among several examples, reflecting its "balanced" design intent. The melt viscosity of 400 mPa·s and self-healing rate of 88% are both good, but not optimal. The contact angle is 101°, indicating that stearic acid end-capping and the resin structure impart excellent hydrophobicity. Example 1 is a robust and balanced formulation with no obvious weaknesses, suitable for general-purpose high-performance color toners, and serves as a benchmark for subsequent optimization.

[0068] Example 2, with high branching degree, used the highest combination of TMA (5 mol%) and TMP (3 mol%). The functional group ratio was the highest, with OH / COOH = 1.05. The amount of MI-BDO (18 mol%) was the highest among all examples, while the amount of FDCA (12 mol%) was relatively low, with a molar ratio of approximately 0.67:1. For highly flexible segments, a relatively high amount of AA (8 mol%) and MAH (12 mol%) was used.

[0069] Example 2 achieved the highest Mn content of 28800 g / mol and the widest PDI of 3.8. This is attributed to the synergistic effect of high branching degree and high functional group ratio, which greatly promoted molecular chain growth and distribution broadening. Example 2 had a Tg of 57°C, the lowest among all examples, but achieved the lowest fixing temperature of 105°C. This demonstrates that the low molecular weight fraction played a strong role in internal plasticizing and viscosity reduction within its extremely wide molecular weight distribution, perfectly reflecting the contribution of the wide distribution to low-temperature fixing. It achieved the lowest melt viscosity of 290 mPa·s and the highest self-healing rate of 92%. The low viscosity is due to the wide distribution, while the high self-healing rate directly stems from the highest dynamic crosslinking point density (MI-BDO) content. Example 2 had the lowest acid value of 14.0 mg KOH / g, directly due to the highest excess hydroxyl group ratio, ensuring complete reaction of the carboxyl groups. Example 2, by maximizing the degree of branching and the ratio of functional groups, and combining it with the amount of highly dynamic crosslinking monomers, successfully integrates the highest molecular weight, the lowest fixing temperature, the best flowability and the strongest self-healing ability, making it the formulation with the best overall performance.

[0070] Example 3 exhibits a high dynamic bond density. Branching degree: the amounts of TMA (4 mol%) and TMP (2.5 mol%) are relatively high, but slightly lower than in Example 2. Functional group ratio: OH / COOH = 1.04, which is relatively high. Dynamic crosslinking monomers: the amounts of FDCA (16 mol%) and MI-BDO (16 mol%) are relatively high, with a perfect molar ratio of 1:1, designed to maximize the density and integrity of the dynamic crosslinking network. Rigidity / flexibility: the ratio of PTA (32 mol%) and IPA (22 mol%) is balanced, while AA (6 mol%) and MAH (11 mol%) provide flexibility.

[0071] Molecular weight and distribution of Example 3: Mn was 25100 g / mol, and PDI was 3.4. Its molecular weight is lower than that of Example 2, indicating that at similar degrees of branching, the functional group ratio has a more significant impact on molecular weight. Thermal properties and fixing: Tg was 58℃, and fixing temperature was 107℃. Its performance is very close to that of Example 1, indicating that the equimolar ratio of dynamically crosslinking monomers has a controllable effect on Tg and fixing temperature. Flowability and self-healing: The melt viscosity of 350 mPa·s was good, and the self-healing rate of 90% was very high, second only to Example 2. This verifies that a 1:1 FDA / MI-BDO ratio helps to form a more complete and efficient reversible crosslinking network, thereby obtaining excellent self-healing performance. The acid value was 15.2 mgKOH / g, lower than that of Example 1, reflecting the advantage of a higher functional group ratio of 1.04. The core advantage of Example 3 lies in the fact that by using an equimolar ratio of dynamically crosslinked monomers, while maintaining excellent comprehensive performance (high molecular weight, low temperature fixing), it achieves excellent self-healing efficiency and network reversibility, demonstrating outstanding reliability.

[0072] Example 4 is a high-rigidity and high-Tg type, using the highest PTA content of 38 mol%, while using the lowest TMA content of 2 mol% and TMP content of 1.5 mol%, aiming to reduce branching and increase linear rigid segments.

[0073] Example 4 exhibits the lowest Mn value (20300) and the narrowest PDI (2.9). It has low branching, limited molecular chain growth, and a more uniform distribution. It also has the highest Tg (61°C) and fixing temperature of 110°C. The high content of rigid PTA segments and the more linear structure reduce segment mobility, leading to a higher Tg, poorer melt flowability, and the highest required fixing temperature. It also has the highest contact angle (103°), due to the high PTA content and lower surface energy after stearic acid end-capping. Furthermore, it has the lowest self-healing rate of 85% and a relatively low content of dynamically crosslinking monomers (FDCA 20 mol%, MI-BDO 14 mol%). Example 4 sacrifices some flowability and fixing performance in exchange for the highest heat resistance and storage stability.

[0074] Example 5 is a high-flowability formulation, employing a high content of flexible segments (7 mol% AA and 10 mol% MAH), combined with a high TMA (4 mol%) and OH / COOH ratio (1.04) to broaden its distribution. It features a high molecular weight (Mn) of 26500 and a wide PDI (3.6), ensuring strength. It also exhibits a low melt viscosity of 320 mPa·s and a fixing temperature of 106°C. The introduction and broad distribution of flexible segments significantly improve flowability at high temperatures. A high self-healing rate of 91% and a high content of dynamically crosslinking monomers (MI-BDO 17 mol%) ensure good repair capabilities. Example 5 achieves excellent processing flowability while maintaining a high molecular weight through the synergy of flexible segments and branched structures.

[0075] Example 6 is a balanced example, with parameters falling between those of other examples, exhibiting no extreme values, aiming to find the optimal balance. All performance indicators are in the middle range, with no significant weaknesses, demonstrating the robustness and versatility of the formulation. Example 6 is a representative of balanced performance and is suitable for general scenarios requiring comprehensive performance.

[0076] The comparative sample lacks any self-healing or low-temperature fixing capabilities, a fundamental limitation of its linear and irreversible chemical structure. At 110°C, the comparative sample resin has extremely high viscosity, making it impossible to flow and difficult to measure, while the fixing temperature needs to be above 120°C, resulting in high energy consumption and unsuitability for high-speed printing. Its molecular weight, Tg, acid value, and other indicators are all at a medium to low level in the industry, offering no outstanding advantages in strength, durability, or storage stability. Example 2 has four core advantages as the best solution:

[0077] 1. The perfect combination of ultra-high molecular weight and low-temperature fixing properties

[0078] Example 2 achieves a perfect combination of the highest molecular weight (28800) and the lowest fixing temperature (105°C), which is the core technical breakthrough of this invention.

[0079] This is due to the extremely high degree of branching (TMA=5mol%, TMP=3mol%) and the widest molecular weight distribution (PDI=3.8). The high molecular weight fraction ensures strength, while the large number of low molecular weight segments in the wide distribution act as "highly efficient plasticizers" upon heating, significantly reducing melt viscosity and allowing it to flow fully at 105°C. This is something that cannot be achieved by relying solely on linear structures or narrow distribution resins.

[0080] 2. Excellent self-healing ability and reliability

[0081] Example 2 exhibits the highest self-healing rate of 92% among all examples, signifying that the toner possesses near-perfect damage self-healing capabilities. This stems directly from its highest maleimide-modified butanediol content (18 mol%). The higher dynamic crosslink density translates to a denser DA bond network, enabling the formation of more reversible "solder joints" at the crack interface upon heating, thereby achieving the most efficient repair and significantly improving the reliability and lifespan of the toner product.

[0082] 3. Good processing fluidity and energy-saving effect

[0083] Example 2 has the lowest melt viscosity of 290 mPa·s, which gives it unparalleled fluidity and leveling properties during fixing, while the lowest fixing temperature (105°C) brings significant energy savings.

[0084] This is due to the combined effect of the widest molecular weight distribution (PDI=3.8) and an appropriate amount of flexible monomers (AA=8mol%, MAH=12mol%), ensuring excellent high-temperature rheological properties. This is crucial for adapting to next-generation ultra-high-speed printers (>120 pages / minute) and reducing device energy consumption.

[0085] 4. Highest conversion rate and product stability

[0086] Example 2, with its lowest acid value (14.0 mg KOH / g), indicates the highest reaction conversion rate and the most complete end-capping reaction. This is because Example 2 has the highest functional group ratio (OH / COOH = 1.05), ensuring that the carboxyl functional groups are completely reacted, thus reducing the acid value to its limit from the source. A low acid value means the resin has more stable charge properties (for toner charging) and better storage stability (slower hydrolytic aging), directly improving the consistency of the final toner product quality.

[0087] Because of the introduction of DA bonds into the resin molecules, waste toner or resin fragments are recyclable. The specific procedure involves heating the waste toner or resin fragments above the temperature at which the DA bonds completely dissociate (typically >130°C). At this point, the DA cross-linking network within the material fully opens, temporarily transforming the originally insoluble and infusible thermosetting material into a flowable, reprocessable thermoplastic state. With the DA bonds in an "open" state, the melt can be reshaped, for example, by hot pressing into new sheets or by extrusion and regranulation. Recombination is also possible; after molding, the material is cooled to room temperature or lower. The furan and maleimide groups react again, and the DA bonds "close" again, reforming a stable three-dimensional cross-linking network in the new product shape, restoring its original mechanical strength and thermal properties.

[0088] This invention, by adjusting the PTA / IPA ratio (rigidity / randomness), AA / MAH ratio (flexibility), TMA / TMP ratio (branching degree and molecular weight distribution), FDA / MI-BDO ratio (dynamic bond density), and functional group ratio, can "precisely tune" a series of high molecular weight polyester resins with different performance focuses to meet the stringent requirements of various application scenarios such as high speed, high gloss, high durability, and high stability. All embodiments possess the core properties of high molecular weight (Mn>20000) and low-temperature fixing (≤110℃), and compared with the comparative examples, they exhibit better low-temperature fixing performance, wider molecular weight distribution, anti-blocking properties, and recyclability.

[0089] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for preparing a reversible crosslinked polyester resin, characterized in that, Includes the following steps: S1 Esterification reaction: In a protective gas atmosphere, the organic carboxylic acid component, polyol component and catalyst are mixed, the temperature of the mixture is raised to the esterification temperature, and the esterification reaction is carried out. After the reaction is complete, the esterified product is obtained. S2 prepolymer synthesis: The esterified compound is mixed with furan dicarboxylic acid and maleimide-modified butanediol, and the temperature is adjusted to 170℃-190℃. The reaction is carried out for 1.5h-2.5h to obtain a linear prepolymer with furan and / or maleimide end groups. S3 Polycondensation: The temperature of the prepolymer is adjusted to the polymerization temperature, a vacuum is drawn, and a polycondensation reaction is carried out. The reaction is stopped after the target degree of polymerization is reached, and the resin particles are obtained through post-processing.

2. The method for preparing the reversible crosslinked polyester resin according to claim 1, characterized in that, The organic carboxylic acid components include isophthalic acid, terephthalic acid, adipic acid, maleic anhydride, trimellitic anhydride, stearic acid, and benzoic acid.

3. The method for preparing the reversible crosslinked polyester resin according to claim 2, characterized in that, The acid component includes the organic carboxylic acid component and the furanyl dicarboxylic acid; in the acid component, by molar percentage, terephthalic acid accounts for 30%-40%, isophthalic acid accounts for 15-25%, adipic acid accounts for 4%-8%, maleic anhydride accounts for 9%-12%, furanyl dicarboxylic acid accounts for 12%-20%, trimellitic anhydride accounts for 2%-5%; benzoic acid accounts for 3%-5%, and stearic acid accounts for 3%-5%.

4. The method for preparing the reversible crosslinked polyester resin according to claim 3, characterized in that, The polyol components include ethylene glycol, 1,4-butanediol, trimethylolpropane, high molecular weight alcohol ether D33, and high molecular weight alcohol ether D22.

5. The method for preparing the reversible crosslinked polyester resin according to claim 4, characterized in that, The alcohol component includes the polyol component and the maleimide-modified butanediol; in the alcohol component, by molar percentage, ethylene glycol accounts for 25%-40%, 1,4-butanediol accounts for 33%-40%, maleimide-modified butanediol accounts for 14%-20%, and trimethylolpropane accounts for 1%-3%; high molecular weight alcohol ether D33 accounts for 8%-11%, and high molecular weight alcohol ether D22 accounts for 6%-10%.

6. The method for preparing the reversible crosslinked polyester resin according to claim 5, characterized in that, The catalyst includes tetraisopropyl titanate, and the added mass of the catalyst is 0.03%-0.05% of the sum of the masses of the alcohol component and the acid component; the esterification temperature is 190℃-210℃.

7. The method for preparing the reversible crosslinked polyester resin according to claim 1, characterized in that, The polymerization temperature is 230℃-240℃; the absolute pressure during vacuuming is below 100Pa; the target degree of polymerization is characterized by viscosity, and the reaction stops when the viscosity reaches 0.80dL / g - 0.85dL / g.

8. The method for preparing the reversible crosslinked polyester resin according to claim 1, characterized in that, In the alcohol component and the acid component, the molar ratio of hydroxyl to carboxyl groups is 1.02-1.05:1; the molar ratio of furanyl dicarboxylic acid to maleimide-modified butanediol is 0.6-1.

45.

9. A reversible crosslinked polyester resin, characterized in that, The reversible crosslinked polyester resin is prepared by the preparation method described in any one of claims 1-8; the number average molecular weight range is 20,000-30,000, the molecular weight distribution is 3.8 ≥ 3.0, the glass transition temperature is 55℃-65℃, and the resin surface contact angle is 103° ≥ 98°.

10. A colored toner, characterized in that, Includes the reversible crosslinked polyester resin as described in claim 9.

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