A high molecular weight polyester resin for primer coating, its preparation method and application

Abstract

This invention discloses a high-molecular-weight polyester resin for primers, its preparation method, and its application. By molar parts, it comprises the following components: 16-26 parts terephthalic acid, 8-14 parts isophthalic acid, 25-40 parts neopentyl glycol, 4-5 parts 1,4-cyclohexanediethanol, 2-5 parts ethylene glycol, 1-3 parts diethylene glycol, 1-4 parts glycerol, 2-3 parts trimethylolpropane, 0.04-0.06 parts catalyst, 0.1-0.3 parts antioxidant, and 0.1-0.2 parts auxiliary antioxidant. The high-molecular-weight polyester resin used for this primer has a glass transition temperature of ≥60℃, a surface drying time of ≤5 minutes at room temperature, and good solubility in common ink solvents. The coating exhibits excellent mechanical properties, scratch resistance, good flexibility, and a peel rate of ≤5%. It also demonstrates excellent adhesion to the substrate, tensile strength retention of over 85%, and excellent hydrolysis resistance. Furthermore, the synthesis process is simple, the reaction conditions are mild, the performance has a wide range of adjustable properties, and it has strong application potential, making it highly valuable for industrial promotion.

Description

Technical Field

[0001] This invention relates to the field of primer technology, specifically to a high molecular weight polyester resin for primers, its preparation method, and its application. Background Technology

[0002] Primers, also known as undercoats or adhesion promoters, are diluted solutions or emulsions applied to the surface of a substrate before printing to improve the adhesion between ink and the substrate. As the printing and packaging industry moves towards high-speed, environmentally friendly, and diversified substrates, the requirements for primers are increasing. Currently, industrially used ink primers are mainly divided into three categories: general-purpose solvent-based primers, two-component reactive primers, and radiation-cured primers.

[0003] General-purpose primers typically use polyester resins, alkyd resins, acrylic resins, or vinyl resins as the main film-forming agents, relying on physical drying through solvent evaporation to form a film. These primers are easy to apply, cost-effective, and suitable for various conventional substrates such as paper and treated plastics. However, they have poor chemical and heat resistance, insufficient adhesion to some non-polar substrates, and their drying speed is greatly affected by the environment, making it difficult to meet the efficiency requirements of high-speed printing production lines.

[0004] Two-component reactive primers consist of a base agent and a curing agent (e.g., a hydroxyl-containing resin base agent and an isocyanate curing agent). They are mixed before use and form a cross-linked network through a chemical reaction, exhibiting excellent adhesion, solvent resistance, and mechanical strength, making them suitable for almost all substrates. However, their application convenience is limited by process defects such as the need for on-site mixing before use, short pot life, harsh drying / curing conditions, and narrow application window. Furthermore, quality control is difficult, costs are high, and some cross-linked systems cannot be recycled after curing.

[0005] Radiation-cured primers consist of prepolymers, reactive diluents, and photoinitiators. They utilize ultraviolet (UV) light or electron beam (EB) irradiation to instantly transform from liquid to solid, offering environmental friendliness, energy efficiency, and excellent coating performance. However, their substrate limitations are significant, making them unsuitable for materials with shadows, depressions, or complex three-dimensional structures. Furthermore, the high cost of equipment and operating principles greatly restricts their applications.

[0006] In summary, general-purpose primers remain the most suitable for low-cost, high-volume printing production lines with simple substrates. High-speed printing lines require primers to dry rapidly at room temperature (typically ≤10 minutes) to avoid sticking during winding and post-printing defects. Increasing the glass transition temperature (Tg) of the primer resin is an effective way to accelerate the drying speed of general-purpose primers. However, high-Tg resins often have low solubility in common ink solvents such as ethyl acetate and methyl ethyl ketone, resulting in reduced adhesion to the substrate and a brittle coating that is not scratch-resistant and has poor flexibility. Balancing the fast drying speed, solubility, adhesion, and coating performance of primer resins has become a major research focus in ink primer technology.

[0007] Chinese patent CN104231879A, "Waterborne Polyester Primer for Reinforced Printing and Metallization and its Preparation Method," discloses a water-soluble polyester polyol resin comprising terephthalic acid, isophthalic acid, sodium isophthalate-5-sulfonate, ethylene glycol, 1,3-propanediol, catalyst one, catalyst two, and an antioxidant. By synthesizing a polyester polyol resin with a specific molecular structure and introducing sulfonate groups, a water-soluble polyester polyol resin with a relative molecular mass of 12000-18000, an acid value of less than 2 mgKOH / g, a hydroxyl value of 5-10 mgKOH / g, and a glass transition temperature of 60-70℃ is obtained. The resulting primer exhibits self-emulsifying ability, good solubility, and excellent adhesion to the substrate. However, the resin synthesis process is complex, the raw material cost is high, and hydrolysis side reactions are easily triggered during production. Furthermore, the coating performance still needs further improvement.

[0008] Therefore, it is of great significance to develop a primer polymer polyester resin that does not require the introduction of sulfonate groups, still has good solubility, excellent adhesion to the substrate, and excellent coating performance, as well as its preparation method and application. Summary of the Invention

[0009] The purpose of this invention is to provide a high molecular weight polyester resin for primer coating, its preparation method, and its application, in order to solve the problems mentioned in the background art, such as the need to introduce sulfonate groups into existing primer coating resins with high Tg, good solubility, and excellent adhesion to the substrate, complex synthesis process, high raw material cost, easy to cause hydrolysis side reactions during production, and the need for further improvement in coating performance.

[0010] To achieve the above objectives, the present invention provides the following technical solution:

[0011] A primer-grade high-molecular-weight polyester resin, by molar parts, comprises the following components: 16-26 parts terephthalic acid, 8-14 parts isophthalic acid, 25-40 parts neopentyl glycol, 4-5 parts 1,4-cyclohexanediethanol, 2-5 parts ethylene glycol, 1-3 parts diethylene glycol, 1-4 parts glycerol, 2-3 parts trimethylolpropane, 0.04-0.06 parts catalyst, 0.1-0.3 parts antioxidant, and 0.1-0.2 parts auxiliary antioxidant.

[0012] The primer-grade polyester resin of the present invention is prepared from components including terephthalic acid, isophthalic acid, neopentyl glycol, 1,4-cyclohexanediethanol, ethylene glycol, diethylene glycol, glycerol, trimethylolpropane, catalyst, antioxidant, and auxiliary antioxidant. Terephthalic acid and isophthalic acid provide rigid segments with appropriate amorphous structures; neopentyl glycol and 1,4-cyclohexanediethanol synergistically improve the rigidity of the molecular chain; ethylene glycol, diethylene glycol, and glycerol provide necessary flexible units for the molecular chain; and the hydroxyl content is increased. Simultaneously, glycerol and trimethylolpropane are used to construct a bibranched system, forming a network structure with moderate crosslinking density, improving crosslinking density and hydroxyl functionality. This results in a primer polymer polyester resin that not only has a glass transition temperature of ≥60℃ and a surface drying time of ≤5 minutes at room temperature, but also exhibits good solubility in common ink solvents, excellent coating mechanical properties, scratch resistance, good flexibility, peel rate of ≤5%, excellent adhesion to the substrate, tensile strength retention rate of over 85%, and excellent hydrolysis resistance.

[0013] Preferably, the molar ratio of the total molar fractions of terephthalic acid and isophthalic acid to the total molar fractions of neopentyl glycol, 1,4-cyclohexanediol, ethylene glycol, diethylene glycol, glycerol, and trimethylolpropane is (1.4-1.7):1.

[0014] The present invention preferably controls the total molar ratio of terephthalic acid and isophthalic acid to the total molar ratio of neopentyl glycol, 1,4-cyclohexanediol, ethylene glycol, diethylene glycol, glycerol, and trimethylolpropane to (1.4-1.7):1, which can effectively improve the solubility and hydrolysis resistance of the polymer polyester resin used for primer coating.

[0015] More preferably, the molar ratio of the total molar fractions of terephthalic acid and isophthalic acid to the total molar fractions of neopentyl glycol, 1,4-cyclohexanediol, ethylene glycol, diethylene glycol, glycerol, and trimethylolpropane is (1.5-1.6):1.

[0016] Preferably, the molar ratio of terephthalic acid to isophthalic acid is 1:(0.3-0.5).

[0017] The present invention preferably controls the molar ratio of terephthalic acid to isophthalic acid to be 1:(0.3-0.5), which is beneficial to control the content of amorphous structure in the polymer polyester resin used for primer, increase the glass transition temperature, shorten the surface drying time, and improve the hydrolysis resistance.

[0018] Preferably, the molar ratio of ethylene glycol, diethylene glycol, and glycerol is 2:1:(1-2).

[0019] Preferably, the molar ratio of glycerol to trimethylolpropane is (1-2):1.

[0020] The present invention preferably controls the molar ratio of glycerol to trimethylolpropane to be (1-2):1, which is beneficial to control the crosslinking density and hydroxyl functionality of the polymer polyester resin for the primer, and improves the glass transition temperature, hydrolysis resistance and adhesion of the polymer polyester resin for the primer to the substrate.

[0021] Preferably, the catalyst is one or more of tetrabutyl titanate, isopropyl titanate, antimony trioxide, and antimony glycolate.

[0022] More preferably, the catalyst is tetrabutyl titanate.

[0023] Preferably, the antioxidant is one or more of antioxidant 1010, antioxidant 1076, and antioxidant 1098.

[0024] More preferably, the antioxidant is antioxidant 1010.

[0025] Preferably, the auxiliary antioxidant is one or more of trimethyl phosphite, triethyl phosphite, and triisopropyl phosphite.

[0026] More preferably, the auxiliary antioxidant is trimethyl phosphite.

[0027] In addition, the present invention also provides a method for preparing a polymeric polyester resin for primer coating.

[0028] A method for preparing a primer polyester resin according to any one of the above claims includes the following steps:

[0029] S1. Feeding: Weigh each component according to the required ratio, and add terephthalic acid, isophthalic acid, neopentyl glycol, 1,4-cyclohexanediol, ethylene glycol, diethylene glycol, glycerol, trimethylolpropane and catalyst into the reaction vessel;

[0030] S2. Esterification reaction: Slowly heat to 150℃, and start stirring after the material begins to melt; gradually increase the temperature to 230-235℃, and keep the reaction at this temperature until the reactants are clear;

[0031] S3. Vacuum polycondensation reaction: After sampling and testing to ensure the acid value meets the standard, the temperature is lowered to 200-220℃, and antioxidants and auxiliary antioxidants are added; the temperature is raised to 250-255℃, and vacuum is slowly drawn. After testing that the viscosity and molecular weight meet the standard, the material is discharged to obtain the high molecular weight polyester resin for the primer.

[0032] Preferably, the reaction is carried out under the protection of an inert gas.

[0033] Preferably, the stirring speed in S2 is 200-300 r / min.

[0034] Preferably, the gradual heating rate in S2 is 10℃ / h.

[0035] Preferably, the sampling and acid value detection in S3 also includes recording the outflow volume, and sampling and acid value detection when the outflow volume is close to 90% of the theoretical value.

[0036] Preferably, the slow vacuuming described in S3 refers to gradually reducing the vacuum level to <100Pa within 30-60 minutes.

[0037] More preferably, the slow vacuuming described in S3 refers to gradually reducing the vacuum level to 60-95 Pa over 30-60 minutes.

[0038] Preferably, the viscosity detected in S3 is determined by changes in stirring current / torque.

[0039] In addition, the present invention also provides an application of a polymeric polyester resin for a primer.

[0040] An application of a polymeric polyester resin for primer according to any one of the preceding claims, used in an ink primer.

[0041] Compared with the prior art, the beneficial effects of the present invention are:

[0042] (1) The primer polyester resin of the present invention is prepared from components including terephthalic acid, isophthalic acid, neopentyl glycol, 1,4-cyclohexanediol, ethylene glycol, diethylene glycol, glycerol, trimethylolpropane, catalyst, antioxidant, and auxiliary antioxidant. By designing the synergistic ratio of rigid monomers and flexible monomers, the alkyd molar ratio of polyacids and polyols is controlled, which can effectively improve the problems of existing primer resins that require the introduction of sulfonate groups, have complex synthesis processes, high raw material costs, are prone to hydrolysis side reactions during production, and whose coating performance still needs further improvement. The resulting primer, a high-molecular-weight polyester resin, does not require the introduction of sulfonate groups. It not only possesses a glass transition temperature of ≥60℃ and a surface drying time of ≤5 minutes at room temperature, but also exhibits good solubility in common ink solvents. The coating demonstrates excellent mechanical properties, scratch resistance, good flexibility, and a peel rate of ≤5%. It exhibits excellent adhesion to the substrate, with tensile strength retention exceeding 85%, and excellent hydrolysis resistance, allowing for long-term stable storage. Furthermore, the synthesis process is simple, the reaction conditions are mild, the cost is low, the performance has a wide adjustable range, and the application scope is strong, making it highly valuable for industrial promotion.

[0043] (2) The primer polyester resin of the present invention uses terephthalic acid (PTA) and isophthalic acid (IPA) as rigid dicarboxylic acid components. The meta-substitution structure of IPA hinders the close stacking of molecular chains, which can effectively destroy the regularity of molecular chains and obtain a primer polyester resin with appropriate amorphous structure. While having a glass transition temperature of ≥60℃, it can still be completely dissolved in common ink solvents such as esters and ketones, and has excellent hydrolysis resistance.

[0044] (3) The primer polyester resin of the present invention utilizes neopentyl glycol (NPG) and 1,4-cyclohexanediethanol (CHDM) to enhance the rigidity of the molecular chain by using the side methyl structure of NPG and the saturated six-membered ring structure of CHDM, which significantly increases the glass transition temperature of the polyester. At the same time, ethylene glycol (EG), diethylene glycol (DEG), and glycerol (GLY) are introduced to regulate the molecular chain, providing necessary flexible units, increasing the hydroxyl content, and improving the adhesion between the primer polyester resin and the substrate surface. This allows the product to have a glass transition temperature of ≥60℃ while still possessing good flexibility and excellent adhesion to the substrate, enabling it to adapt to the deformation of the substrate during post-processing. By adjusting the ratio of EG, DEG, and GLY, the flexibility of the coating and its adhesion to the substrate can be controlled within a certain range to adapt to different post-processing requirements. The resulting primer polyester resin has a wide range of adjustable properties, strong application expansion, and good industrial promotion value.

[0045] (4) The primer polyester resin of the present invention is constructed by glycerol and trimethylolpropane (TMP), which both have trifunctionality, to form a dual-branching point system, forming a network structure with medium crosslinking density, thereby improving the crosslinking density and hydroxyl functionality, and improving the glass transition temperature, hydrolysis resistance and adhesion to the substrate of the primer polyester resin.

[0046] (5) The polymer polyester resin for the primer of the present invention remains stable under high temperature polycondensation conditions through the compound system of antioxidant and auxiliary antioxidant, without affecting the polymerization reaction rate, effectively inhibiting thermal oxidative degradation during the synthesis process, reducing resin yellowing, and having good compatibility with polyester resin, without migration or precipitation, thus improving the long-term storage stability of the resin, and without gelation or stratification after long-term storage.

[0047] (6) The polymer polyester resin for primer of the present invention does not require the use of special solvents with strong corrosiveness or high toxicity, nor does it require the introduction of sulfonate groups. Through the synergistic regulation of polyacid components and polyol components, the resin performance can be designed, which can meet the differentiated needs of different substrates and different printing processes for primer. The synthesis process is simple to operate, the reaction conditions are mild, the cost is low, the performance is adjustable in a wide range, the application is highly expandable, the product has good stability, no gelation or stratification after long-term storage, it can be used immediately after opening the can, the construction is simple, and there is no limitation on the applicable period. The coating can be dissolved in the solvent again after drying, and the printing waste can be recycled, which meets the requirements of green environmental protection and is suitable for industrial-scale production. Attached Figure Description

[0048] Figure 1 This is a sample of the polymer polyester resin for primer obtained in Example 1 of the present invention. Detailed Implementation

[0049] To better illustrate the objectives, technical solutions, and advantages of this invention, the following embodiments are provided. Obviously, the following embodiments are only a part of the embodiments of this invention, and not all of them; these embodiments do not imply any limitation on this invention. Those skilled in the art should understand that these embodiments are only used to illustrate the technical effects of this invention, and not to limit the scope of protection of this invention.

[0050] Experimental methods in the following examples, unless otherwise specified, are generally performed under standard conditions or as recommended by the manufacturer. These examples are primarily intended to provide a better understanding of the analytical methods of this invention and do not exhaustively cover all possible procedures.

[0051] All raw materials used in the examples are commercially available; unless otherwise specified, the reagents, methods and equipment used in this invention are conventional reagents, methods and equipment in this technical field.

[0052] Example 1

[0053] A method for preparing a primer polymer polyester resin includes the following steps:

[0054] S1. Feeding: Weigh each component according to the required ratio, by molar parts, including the following components: 20 parts terephthalic acid, 8 parts isophthalic acid, 29 parts neopentyl glycol, 5 parts 1,4-cyclohexanediethanol, 2 parts ethylene glycol, 1 part diethylene glycol, 2 parts glycerol, 2 parts trimethylolpropane, 0.05 parts tetrabutyl titanate, 0.2 parts antioxidant 1010, and 0.1 parts trimethyl phosphite; add terephthalic acid, isophthalic acid, neopentyl glycol, 1,4-cyclohexanediethanol, ethylene glycol, diethylene glycol, glycerol, trimethylolpropane, and tetrabutyl titanate to the reaction vessel;

[0055] S2. Esterification reaction: Turn on nitrogen protection (weak gas flow) to remove air from the reaction system, slowly heat to 150°C, and start stirring after the material begins to melt, with the speed controlled at 250 r / min; gradually increase the temperature to 235°C at a rate of 10°C / h, and keep the reaction at this temperature until the reactants are clear.

[0056] S3. Vacuum polycondensation reaction: Record the water output. When the water output is close to 90% of the theoretical value, take a sample to measure the acid value. After the acid value meets the standard, cool down to 210℃ and add antioxidant 1010 and trimethyl phosphite. Heat up to 250-255℃ and slowly evacuate the vacuum. Gradually reduce the vacuum to 90 Pa within 30-60 minutes. Detect the viscosity by changing the stirring current / torque. Take samples periodically to measure the molecular weight. After the viscosity and molecular weight meet the standards, discharge the material to obtain the high molecular weight polyester resin for the primer.

[0057] Example 2

[0058] A method for preparing a primer polymer polyester resin includes the following steps:

[0059] S1. Feeding: Weigh each component according to the required ratio, by molar parts, including the following components: 18 parts terephthalic acid, 8 parts isophthalic acid, 27 parts neopentyl glycol, 4 parts 1,4-cyclohexanediethanol, 3 parts ethylene glycol, 2 parts diethylene glycol, 3 parts glycerol, 3 parts trimethylolpropane, 0.06 parts tetrabutyl titanate, 0.2 parts antioxidant 1010, and 0.1 parts trimethyl phosphite; add terephthalic acid, isophthalic acid, neopentyl glycol, 1,4-cyclohexanediethanol, ethylene glycol, diethylene glycol, glycerol, trimethylolpropane, and tetrabutyl titanate to the reaction vessel;

[0060] S2. Esterification reaction: Turn on nitrogen protection (weak gas flow) to remove air from the reaction system, slowly heat to 150°C, and start stirring after the material begins to melt, with the speed controlled at 260 r / min; gradually increase the temperature to 235°C at a rate of 10°C / h, and keep the reaction at this temperature until the reactants are clear.

[0061] S3. Vacuum polycondensation reaction: Record the water output. When the water output is close to 90% of the theoretical value, take a sample to measure the acid value. After the acid value meets the standard, cool down to 212℃ and add antioxidant 1010 and trimethyl phosphite. Heat up to 255℃ and slowly evacuate the vacuum. Gradually reduce the vacuum to 95 Pa within 30-60 minutes. Detect the viscosity by changing the stirring current / torque. Take samples periodically to measure the molecular weight. After the viscosity and molecular weight meet the standards, discharge the material to obtain the high molecular weight polyester resin for the primer.

[0062] Example 3

[0063] A method for preparing a primer polymer polyester resin includes the following steps:

[0064] S1. Feeding: Weigh each component according to the required ratio, by molar parts, including the following components: 25 parts terephthalic acid, 12 parts isophthalic acid, 36 parts neopentyl glycol, 4 parts 1,4-cyclohexanediol, 4 parts ethylene glycol, 2 parts diethylene glycol, 3 parts glycerol, 3 parts trimethylolpropane, 0.05 parts antimony glycolide, 0.3 parts antioxidant 1010, and 0.2 parts trimethyl phosphite; add terephthalic acid, isophthalic acid, neopentyl glycol, 1,4-cyclohexanediol, ethylene glycol, diethylene glycol, glycerol, trimethylolpropane, and antimony glycolide to the reaction vessel;

[0065] S2. Esterification reaction: Turn on nitrogen protection (weak gas flow) to remove air from the reaction system, slowly heat to 150°C, and start stirring after the material begins to melt, with the speed controlled at 220 r / min; gradually increase the temperature to 230°C at a rate of 10°C / h, and keep the reaction at this temperature until the reactants are clear.

[0066] S3. Vacuum polycondensation reaction: Record the water output. When the water output is close to 90% of the theoretical value, take a sample to measure the acid value. After the acid value meets the standard, cool down to 200℃ and add antioxidant 1010 and trimethyl phosphite. Heat up to 250℃ and slowly evacuate the vacuum. Gradually reduce the vacuum to 88 Pa within 30-60 minutes. Detect the viscosity by changing the stirring current / torque. Take samples periodically to measure the molecular weight. After the viscosity and molecular weight meet the standards, discharge the material to obtain the high molecular weight polyester resin for the primer.

[0067] Example 4

[0068] A method for preparing a primer polymer polyester resin includes the following steps:

[0069] S1. Feeding: Weigh each component according to the required ratio, by molar parts, including the following components: 22 parts terephthalic acid, 9 parts isophthalic acid, 30 parts neopentyl glycol, 5 parts 1,4-cyclohexanediol, 3 parts ethylene glycol, 1 part diethylene glycol, 4 parts glycerol, 3 parts trimethylolpropane, 0.04 parts tetrabutyl titanate, 0.2 parts antioxidant 1076, and 0.1 parts triethyl phosphite; add terephthalic acid, isophthalic acid, neopentyl glycol, 1,4-cyclohexanediol, ethylene glycol, diethylene glycol, glycerol, trimethylolpropane, and tetrabutyl titanate to the reaction vessel;

[0070] S2. Esterification reaction: Turn on nitrogen protection (weak gas flow) to remove air from the reaction system, slowly heat to 150°C, and start stirring after the material begins to melt, with the speed controlled at 230 r / min; gradually increase the temperature to 230°C at a rate of 10°C / h, and keep the reaction at this temperature until the reactants are clear.

[0071] S3. Vacuum polycondensation reaction: Record the water output. When the water output is close to 90% of the theoretical value, take a sample to measure the acid value. After the acid value meets the standard, cool down to 216℃ and add antioxidant 1076 and triethyl phosphite. Heat up to 251℃ and slowly evacuate the vacuum. Gradually reduce the vacuum to 81 Pa within 30-60 minutes. Detect the viscosity by changing the stirring current / torque. Take samples periodically to measure the molecular weight. After the viscosity and molecular weight meet the standards, discharge the material to obtain the high molecular weight polyester resin for the primer.

[0072] Example 5

[0073] A method for preparing a primer polymer polyester resin includes the following steps:

[0074] S1. Feeding: Weigh each component according to the required ratio, by molar parts, including the following components: 17 parts terephthalic acid, 8 parts isophthalic acid, 26 parts neopentyl glycol, 5 parts 1,4-cyclohexanediethanol, 2 parts ethylene glycol, 1 part diethylene glycol, 2 parts glycerol, 2 parts trimethylolpropane, 0.05 parts tetrabutyl titanate, 0.2 parts antioxidant 1010, and 0.2 parts triethyl phosphite; add terephthalic acid, isophthalic acid, neopentyl glycol, 1,4-cyclohexanediethanol, ethylene glycol, diethylene glycol, glycerol, trimethylolpropane, and tetrabutyl titanate to the reaction vessel;

[0075] S2. Esterification reaction: Turn on nitrogen protection (weak gas flow) to remove air from the reaction system, slowly heat to 150°C, and start stirring after the material begins to melt, with the speed controlled at 280 r / min; gradually increase the temperature to 235°C at a rate of 10°C / h, and keep the reaction at this temperature until the reactants are clear.

[0076] S3. Vacuum polycondensation reaction: Record the water output. When the water output is close to 90% of the theoretical value, take a sample to measure the acid value. After the acid value meets the standard, cool down to 202℃ and add antioxidant 1010 and triethyl phosphite. Heat up to 252℃ and slowly evacuate the vacuum. Gradually reduce the vacuum to 76 Pa within 30-60 minutes. Detect the viscosity by changing the stirring current / torque. Take samples periodically to measure the molecular weight. After the viscosity and molecular weight meet the standards, discharge the material to obtain the high molecular weight polyester resin for the primer.

[0077] Comparative Example 1

[0078] A method for preparing a primer polymer polyester resin includes the following steps:

[0079] S1. Feeding: Weigh each component according to the required ratio, by molar parts, including the following components: 8 parts terephthalic acid, 20 parts isophthalic acid, 29 parts neopentyl glycol, 5 parts 1,4-cyclohexanediethanol, 2 parts ethylene glycol, 1 part diethylene glycol, 2 parts glycerol, 2 parts trimethylolpropane, 0.05 parts tetrabutyl titanate, 0.2 parts antioxidant 1010, and 0.1 parts trimethyl phosphite; add terephthalic acid, isophthalic acid, neopentyl glycol, 1,4-cyclohexanediethanol, ethylene glycol, diethylene glycol, glycerol, trimethylolpropane, and tetrabutyl titanate to the reaction vessel;

[0080] S2. Esterification reaction: Turn on nitrogen protection (weak gas flow) to remove air from the reaction system, slowly heat to 150°C, and start stirring after the material begins to melt, with the speed controlled at 240 r / min; gradually increase the temperature to 235°C at a rate of 10°C / h, and keep the reaction at this temperature until the reactants are clear.

[0081] S3. Vacuum polycondensation reaction: Record the water output. When the water output is close to 90% of the theoretical value, take a sample to measure the acid value. After the acid value meets the standard, cool down to 210℃ and add antioxidant 1010 and trimethyl phosphite. Heat up to 255℃ and slowly evacuate the vacuum. Gradually reduce the vacuum to 90 Pa within 30-60 minutes. Detect the viscosity by changing the stirring current / torque. Take samples periodically to measure the molecular weight. After the viscosity and molecular weight meet the standards, discharge the material to obtain the high molecular weight polyester resin for the primer.

[0082] The main difference between this comparative example and Example 1 is that the proportions of terephthalic acid and isophthalic acid are interchanged.

[0083] Comparative Example 2

[0084] A method for preparing a primer polymer polyester resin includes the following steps:

[0085] S1. Feeding: Weigh each component according to the required ratio, by molar parts, including the following components: 14 parts terephthalic acid, 14 parts isophthalic acid, 29 parts neopentyl glycol, 5 parts 1,4-cyclohexanediethanol, 2 parts ethylene glycol, 1 part diethylene glycol, 2 parts glycerol, 2 parts trimethylolpropane, 0.05 parts tetrabutyl titanate, 0.2 parts antioxidant 1010, and 0.1 parts trimethyl phosphite; add terephthalic acid, isophthalic acid, neopentyl glycol, 1,4-cyclohexanediethanol, ethylene glycol, diethylene glycol, glycerol, trimethylolpropane, and tetrabutyl titanate to the reaction vessel;

[0086] S2. Esterification reaction: Turn on nitrogen protection (weak gas flow) to remove air from the reaction system, slowly heat to 150°C, and start stirring after the material begins to melt, with the speed controlled at 250 r / min; gradually increase the temperature to 235°C at a rate of 10°C / h, and keep the reaction at this temperature until the reactants are clear.

[0087] S3. Vacuum polycondensation reaction: Record the water output. When the water output is close to 90% of the theoretical value, take a sample to measure the acid value. After the acid value meets the standard, cool down to 200℃ and add antioxidant 1010 and trimethyl phosphite. Heat up to 250℃ and slowly evacuate the vacuum. Gradually reduce the vacuum to 91 Pa within 30-60 minutes. Detect the viscosity by changing the stirring current / torque. Take samples periodically to measure the molecular weight. After the viscosity and molecular weight meet the standards, discharge the material to obtain the high molecular weight polyester resin for the primer.

[0088] The main difference between this comparative example and Example 1 is that the ratio of terephthalic acid to isophthalic acid is 1:1 and the amount of terephthalic acid used is less than the range value.

[0089] Comparative Example 3

[0090] A method for preparing a primer polymer polyester resin includes the following steps:

[0091] S1. Feeding: Weigh each component according to the required ratio, by molar parts, including the following components: 20 parts terephthalic acid, 8 parts isophthalic acid, 34 parts neopentyl glycol, 2 parts ethylene glycol, 1 part diethylene glycol, 2 parts glycerol, 2 parts trimethylolpropane, 0.05 parts tetrabutyl titanate, 0.2 parts antioxidant 1010, and 0.1 parts trimethyl phosphite; add terephthalic acid, isophthalic acid, neopentyl glycol, ethylene glycol, diethylene glycol, glycerol, trimethylolpropane, and tetrabutyl titanate to the reaction vessel;

[0092] S2. Esterification reaction: Turn on nitrogen protection (weak gas flow) to remove air from the reaction system, slowly heat to 150°C, and start stirring after the material begins to melt, with the speed controlled at 280 r / min; gradually increase the temperature to 235°C at a rate of 10°C / h, and keep the reaction at this temperature until the reactants are clear.

[0093] S3. Vacuum polycondensation reaction: Record the water output. When the water output is close to 90% of the theoretical value, take a sample to measure the acid value. After the acid value meets the standard, cool down to 210℃ and add antioxidant 1010 and trimethyl phosphite. Heat up to 251℃ and slowly evacuate the vacuum. Gradually reduce the vacuum to 90 Pa within 30-60 minutes. Detect the viscosity by changing the stirring current / torque. Take samples periodically to measure the molecular weight. After the viscosity and molecular weight meet the standards, discharge the material to obtain the high molecular weight polyester resin for the primer.

[0094] The main difference between this comparative example and Example 1 is that 1,4-cyclohexanediethanol is not added, and the insufficient part is supplemented by neopentyl glycol.

[0095] Comparative Example 4

[0096] A method for preparing a primer polymer polyester resin includes the following steps:

[0097] S1. Feeding: Weigh each component according to the required ratio, by molar parts, including the following components: 20 parts terephthalic acid, 8 parts isophthalic acid, 31 parts neopentyl glycol, 5 parts 1,4-cyclohexanediol, 1 part diethylene glycol, 2 parts glycerol, 2 parts trimethylolpropane, 0.05 parts tetrabutyl titanate, 0.2 parts antioxidant 1010, and 0.1 parts trimethyl phosphite; add terephthalic acid, isophthalic acid, neopentyl glycol, 1,4-cyclohexanediol, diethylene glycol, glycerol, trimethylolpropane, and tetrabutyl titanate to the reaction vessel;

[0098] S2. Esterification reaction: Turn on nitrogen protection (weak gas flow) to remove air from the reaction system, slowly heat to 150°C, and start stirring after the material begins to melt, with the speed controlled at 280 r / min; gradually increase the temperature to 235°C at a rate of 10°C / h, and keep the reaction at this temperature until the reactants are clear.

[0099] S3. Vacuum polycondensation reaction: Record the water output. When the water output is close to 90% of the theoretical value, take a sample to measure the acid value. After the acid value meets the standard, cool down to 210℃ and add antioxidant 1010 and trimethyl phosphite. Heat up to 251℃ and slowly evacuate the vacuum. Gradually reduce the vacuum to 90 Pa within 30-60 minutes. Detect the viscosity by changing the stirring current / torque. Take samples periodically to measure the molecular weight. After the viscosity and molecular weight meet the standards, discharge the material to obtain the high molecular weight polyester resin for the primer.

[0100] The main difference between this comparative example and Example 1 is that ethylene glycol is not added, and the insufficient part is supplemented by neopentyl glycol.

[0101] Comparative Example 5

[0102] A method for preparing a primer polymer polyester resin includes the following steps:

[0103] S1. Feeding: Weigh each component according to the required ratio, by molar parts, including the following components: 20 parts terephthalic acid, 8 parts isophthalic acid, 30 parts neopentyl glycol, 5 parts 1,4-cyclohexanediethanol, 2 parts ethylene glycol, 2 parts glycerol, 2 parts trimethylolpropane, 0.05 parts tetrabutyl titanate, 0.2 parts antioxidant 1010, and 0.1 parts trimethyl phosphite; add terephthalic acid, isophthalic acid, neopentyl glycol, 1,4-cyclohexanediethanol, ethylene glycol, glycerol, trimethylolpropane, and tetrabutyl titanate to the reaction vessel;

[0104] S2. Esterification reaction: Turn on nitrogen protection (weak gas flow) to remove air from the reaction system, slowly heat to 150°C, and start stirring after the material begins to melt, with the speed controlled at 250 r / min; gradually increase the temperature to 232°C at a rate of 10°C / h, and keep the reaction at this temperature until the reactants are clear.

[0105] S3. Vacuum polycondensation reaction: Record the water output. When the water output is close to 90% of the theoretical value, take a sample to measure the acid value. After the acid value meets the standard, cool down to 210℃ and add antioxidant 1010 and trimethyl phosphite. Heat up to 255℃ and slowly evacuate the vacuum. Gradually reduce the vacuum to 90 Pa within 30-60 minutes. Detect the viscosity by changing the stirring current / torque. Take samples periodically to measure the molecular weight. After the viscosity and molecular weight meet the standards, discharge the material to obtain the high molecular weight polyester resin for the primer.

[0106] The main difference between this comparative example and Example 1 is that diethylene glycol is not added, and the insufficient part is supplemented by neopentyl glycol.

[0107] Comparative Example 6

[0108] A method for preparing a primer polymer polyester resin includes the following steps:

[0109] S1. Feeding: Weigh each component according to the required ratio, by molar parts, including the following components: 20 parts terephthalic acid, 8 parts isophthalic acid, 32 parts neopentyl glycol, 5 parts 1,4-cyclohexanediethanol, 2 parts ethylene glycol, 1 part diethylene glycol, 2 parts trimethylolpropane, 0.05 parts tetrabutyl titanate, 0.2 parts antioxidant 1010, and 0.1 parts trimethyl phosphite; add terephthalic acid, isophthalic acid, neopentyl glycol, 1,4-cyclohexanediethanol, ethylene glycol, diethylene glycol, trimethylolpropane, and tetrabutyl titanate to the reaction vessel;

[0110] S2. Esterification reaction: Turn on nitrogen protection (weak gas flow) to remove air from the reaction system, slowly heat to 150°C, and start stirring after the material begins to melt, with the speed controlled at 250 r / min; gradually increase the temperature to 235°C at a rate of 10°C / h, and keep the reaction at this temperature until the reactants are clear.

[0111] S3. Vacuum polycondensation reaction: Record the water output. When the water output is close to 90% of the theoretical value, take a sample to measure the acid value. After the acid value meets the standard, cool down to 220℃ and add antioxidant 1010 and trimethyl phosphite. Heat up to 251℃ and slowly evacuate the vacuum. Gradually reduce the vacuum to 92 Pa within 30-60 minutes. Detect the viscosity by changing the stirring current / torque. Take samples periodically to measure the molecular weight. After the viscosity and molecular weight meet the standards, discharge the material to obtain the high molecular weight polyester resin for the primer.

[0112] The main difference between this comparative example and Example 1 is that glycerol is not added, and the insufficient part is supplemented by neopentyl glycol.

[0113] Comparative Example 7

[0114] A method for preparing a primer polymer polyester resin includes the following steps:

[0115] S1. Feeding: Weigh each component according to the required ratio, by molar parts, including the following components: 20 parts terephthalic acid, 8 parts isophthalic acid, 29 parts neopentyl glycol, 5 parts 1,4-cyclohexanediethanol, 2 parts ethylene glycol, 1 part diethylene glycol, 5 parts glycerol, 2 parts trimethylolpropane, 0.05 parts tetrabutyl titanate, 0.2 parts antioxidant 1010, and 0.1 parts trimethyl phosphite; add terephthalic acid, isophthalic acid, neopentyl glycol, 1,4-cyclohexanediethanol, ethylene glycol, diethylene glycol, glycerol, trimethylolpropane, and tetrabutyl titanate to the reaction vessel;

[0116] S2. Esterification reaction: Turn on nitrogen protection (weak gas flow) to remove air from the reaction system, slowly heat to 150°C, and start stirring after the material begins to melt, with the speed controlled at 250 r / min; gradually increase the temperature to 235°C at a rate of 10°C / h, and keep the reaction at this temperature until the reactants are clear.

[0117] S3. Vacuum polycondensation reaction: Record the water output. When the water output is close to 90% of the theoretical value, take a sample to measure the acid value. After the acid value meets the standard, cool down to 210℃ and add antioxidant 1010 and trimethyl phosphite. Heat up to 250-255℃ and slowly evacuate the vacuum. Gradually reduce the vacuum to 90 Pa within 30-60 minutes. Detect the viscosity by changing the stirring current / torque. Take samples periodically to measure the molecular weight. After the viscosity and molecular weight meet the standards, discharge the material to obtain the high molecular weight polyester resin for the primer.

[0118] The main difference between this comparative example and Example 1 is that an excess of glycerol was added.

[0119] Comparative Example 8

[0120] A method for preparing a primer polymer polyester resin includes the following steps:

[0121] S1. Feeding: Weigh each component according to the required ratio, by molar parts, including the following components: 20 parts terephthalic acid, 8 parts isophthalic acid, 32 parts neopentyl glycol, 5 parts 1,4-cyclohexanediethanol, 2 parts ethylene glycol, 1 part diethylene glycol, 2 parts glycerol, 0.05 parts tetrabutyl titanate, 0.2 parts antioxidant 1010, and 0.1 parts trimethyl phosphite; add terephthalic acid, isophthalic acid, neopentyl glycol, 1,4-cyclohexanediethanol, ethylene glycol, diethylene glycol, glycerol, and tetrabutyl titanate to the reaction vessel;

[0122] S2. Esterification reaction: Turn on nitrogen protection (weak gas flow) to remove air from the reaction system, slowly heat to 150°C, and start stirring after the material begins to melt, with the speed controlled at 230 r / min; gradually increase the temperature to 235°C at a rate of 10°C / h, and keep the reaction at this temperature until the reactants are clear.

[0123] S3. Vacuum polycondensation reaction: Record the water output. When the water output is close to 90% of the theoretical value, take a sample to measure the acid value. After the acid value meets the standard, cool down to 210℃ and add antioxidant 1010 and trimethyl phosphite. Heat up to 251℃ and slowly evacuate the vacuum. Gradually reduce the vacuum to 90 Pa within 30-60 minutes. Detect the viscosity by changing the stirring current / torque. Take samples periodically to measure the molecular weight. After the viscosity and molecular weight meet the standards, discharge the material to obtain the high molecular weight polyester resin for the primer.

[0124] The main difference between this comparative example and Example 1 is that trimethylolpropane is not added, and the insufficient part is supplemented by neopentyl glycol.

[0125] Comparative Example 9

[0126] A water-soluble polyester polyol resin was prepared by the preparation method described in CN104231879A.

[0127] Comparative Example 10

[0128] A commercially available polyester resin for primer application.

[0129] The main component allocation of the above embodiments and comparative examples is shown in the table below:

[0130] Table 1. Proportions of main components in Examples 1-5 and Comparative Examples 1-8

[0131] PTA IPA NPG CHDM EG DEG GLY TMP catalyst antioxidants Co-oxidants Example 1 20 8 29 5 2 1 2 2 0.05 0.2 0.1 Example 2 18 8 27 4 3 2 3 3 0.06 0.2 0.1 Example 3 25 12 36 4 4 2 3 3 0.05 0.3 0.2 Example 4 22 9 30 5 3 1 4 3 0.04 0.2 0.1 Example 5 17 8 26 5 2 1 2 2 0.05 0.2 0.2 Comparative Example 1 8 20 29 5 2 1 2 2 0.05 0.2 0.1 Comparative Example 2 14 14 29 5 2 1 2 2 0.05 0.2 0.1 Comparative Example 3 20 8 34 0 2 1 2 2 0.05 0.2 0.1 Comparative Example 4 20 8 31 5 0 1 2 2 0.05 0.2 0.1 Comparative Example 5 20 8 30 5 2 0 2 2 0.05 0.2 0.1 Comparative Example 6 20 8 32 5 2 1 0 2 0.05 0.2 0.1 Comparative Example 7 20 8 32 5 2 1 5 2 0.05 0.2 0.1 Comparative Example 8 20 8 32 5 2 1 2 0 0.05 0.2 0.1

[0132] Performance testing:

[0133] Performance tests were conducted on Examples 1-5 and Comparative Examples 1-10, and the specific test methods are as follows:

[0134] The glass transition temperature (Tg) was measured by differential scanning calorimetry (DSC) at a heating rate of 10 °C / min.

[0135] Hydroxyl value and acid value were tested by titration.

[0136] Number average molecular weight (Mn) was determined by gel permeation chromatography (GPC).

[0137] Solubility was tested by visual inspection after dissolving the prepared polyester resin in 40% by mass in methyl ethyl ketone and ethyl acetate solvents, respectively.

[0138] The surface drying time should be tested according to GB / T 1728-2020 "Determination of Drying Time of Paint Film and Putty Film". For high-speed printing, the surface drying time of the primer at room temperature should be ≤10 minutes.

[0139] The scratch resistance performance is tested according to the test method of GB / T 6739-2022 "Determination of Hardness of Paint Film by Pencil Method".

[0140] Flexibility is tested through a T-bend test; the smaller the T-bend rating number, the better the flexibility.

[0141] Adhesion is tested according to the cross-cut test method of GB / T 9286-2021 "Paints and Varnishes", and is expressed as peel rate. The smaller the peel rate, the stronger the adhesion.

[0142] Hydrolysis resistance was tested by accelerated aging at 85℃ / 85%RH and expressed as tensile strength retention rate. The higher the tensile strength retention rate, the better the hydrolysis resistance.

[0143] The specific performance test results of Examples 1-5 and Comparative Examples 1-10 are shown in the table below:

[0144] Table 2 Performance test results of Examples 1-5

[0145] Example 1 Example 2 Example 3 Example 4 Example 5 Tg (°C) 62 60 61 64 62 Hydroxyl value (mgKOH / g) 15 12 14 17 13 Acid value (mgKOH / g) 1.8 1.6 1.8 2.1 1.9 Mn 15000 12000 14000 16000 14000 Solubility (butanone) Completely dissolved, clear solution Completely dissolved, clear solution Completely dissolved, clear solution Completely dissolved, clear solution Completely dissolved, clear solution Solubility (ethyl acetate) Completely dissolved, clear solution Completely dissolved, clear solution Completely dissolved, clear solution Completely dissolved, clear solution Completely dissolved, clear solution Surface drying time (min) ≤5 ≤5 ≤5 ≤5 ≤5 Pencil hardness 2H 3H 2H 2H 2H T-bend level 1T 1T 1T 1T 1T Peeling rate (%) ≤5 ≤5 ≤5 ≤5 ≤5 Tensile strength retention rate (%) 90 87 88 91 90

[0146] Table 3 Performance test results of Comparative Examples 1-10

[0147] Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Comparative Example 7 Comparative Example 8 Comparative Example 9 Comparative Example 10 Tg (°C) 46 51 42 68 70 44 71 43 69 35 Hydroxyl value (mgKOH / g) 14 15 10 12 17 9 20 9 6 10 Acid value (mgKOH / g) 1.8 1.9 2.0 1.6 0.9 1.8 0.9 2.3 1.0 3.5 Mn 10000 11000 17000 16000 18000 9000 18000 8000 18000 12000 Solubility (butanone) Dissolved, the solution is slightly turbid. Completely dissolved, clear solution Completely dissolved, clear solution Completely dissolved, clear solution Dissolved, the solution is slightly turbid. Completely dissolved, clear solution Dissolved, the solution is slightly turbid. Completely dissolved, clear solution Completely dissolved, clear solution Dissolved, the solution is slightly turbid. Solubility (ethyl acetate) Dissolved, the solution is slightly turbid. Dissolved, the solution is slightly turbid. Completely dissolved, clear solution Completely dissolved, clear solution Dissolved, the solution is slightly turbid. Completely dissolved, clear solution Dissolved, the solution is slightly turbid. Completely dissolved, clear solution Completely dissolved, clear solution Dissolved, the solution is slightly turbid. Surface drying time (min) >10 ≤10 >10 ≤5 ≤5 >20 ≤5 >20 ≤5 >20 Pencil hardness B HB HB 2H 3H HB 3H B H B T-bend level 0T 0T 0T 3T 3T 1T 4T 0T 3T 2T Peeling rate (%) ≤5 ≤5 ≤5 ≤10 ≤10 ≤5 ≤10 ≤5 ≤10 ≤10 Tensile strength retention rate (%) 75 81 92 91 95 92 80 82 69 80

[0148] As shown in Table 2, the polymeric polyester resins for primers prepared in Examples 1-5 of this invention not only have a glass transition temperature of ≥60℃ and a surface drying time of ≤5 minutes at room temperature, but also exhibit good solubility in common ink solvents, excellent coating mechanical properties, scratch resistance, good flexibility, peel rate of ≤5%, excellent adhesion to the substrate, tensile strength retention rate of ≤85%, and excellent hydrolysis resistance. Furthermore, the synthesis process is simple, the reaction conditions are mild, the cost is low, the performance has a wide range of adjustable properties, and the application scope is strong, making it of good industrial promotion value.

[0149] As shown in Table 3, compared with Example 1, Comparative Example 1, by exchanging the proportions of terephthalic acid and isophthalic acid, increased the amorphous structure in the polyester resin, significantly lowered the glass transition temperature, prolonged the surface drying time, and simultaneously reduced the hydrolysis resistance. Comparative Example 2, with a 1:1 ratio of terephthalic acid and isophthalic acid, showed a slight improvement in overall performance compared to Comparative Example 1, but the amorphous regions in the molecular chain were more susceptible to water molecule attack, resulting in poor solubility and hydrolysis resistance, and still could not compare with Example 1. Comparative Example 3, without the addition of 1,4-cyclohexanediethanol, significantly reduced the crosslinking density of the polyester resin, resulting in a substantial decrease in the glass transition temperature and a longer surface drying time. Comparative Example 4, without the addition of ethylene glycol, reduced the flexible symmetrical segments in the molecular chain, significantly decreasing flexibility. Comparative Example 5, without the addition of diethylene glycol, provided highly flexible chains through ether bonds. The disappearance of the segment increases the rigidity of the molecular chain, resulting in a greater decrease in flexibility compared to Comparative Example 4. Comparative Example 6, without the addition of glycerol, has a lower hydroxyl content and loses the bibranched point system with trimethylolpropane, leading to decreased adhesion, a significant decrease in glass transition temperature, and a longer surface drying time. Comparative Example 7, with the addition of excessive glycerol, suffers from an imbalance in the bibranched point system, resulting in excessive crosslinking density and a significant decrease in flexibility. Comparative Example 8, without the addition of trimethylolpropane, has a lower crosslinking density, lower number-average molecular weight, a significant decrease in glass transition temperature, and easier penetration of water molecules into the ester bond region, resulting in decreased hydrolysis resistance. Comparative Example 9, by introducing sulfonate groups, obtains a high molecular weight, high Tg resin, but with poor flexibility and a significant decrease in hydrolysis resistance. Comparative Example 10, using commercially available resin, has a surface drying time far from meeting the requirements of high-speed printing.

[0150] In summary, this invention provides a primer-grade polymer polyester resin prepared from components including terephthalic acid, isophthalic acid, neopentyl glycol, 1,4-cyclohexanediol, ethylene glycol, diethylene glycol, glycerol, trimethylolpropane, a catalyst, an antioxidant, and an auxiliary antioxidant. Through the synergistic design of rigid and flexible monomers and the control of the alkyd molar ratio of polyacids and polyols, this invention effectively improves upon existing primer resins that require the introduction of sulfonate groups, have complex synthesis processes, high raw material costs, are prone to hydrolysis side reactions during production, and whose coating performance still needs improvement. Further improvements are made without introducing sulfonate groups. The coating not only has a glass transition temperature of ≥60℃ and a surface drying time of ≤5 minutes at room temperature, but also exhibits good solubility in common ink solvents. It possesses excellent mechanical properties, scratch resistance, good flexibility, and a peel rate of ≤5%. It also demonstrates excellent adhesion to the substrate, tensile strength retention of over 85%, and superior hydrolysis resistance, allowing for long-term stable storage. Furthermore, the synthesis process is simple, the reaction conditions are mild, the cost is low, the performance has a wide adjustable range, and the application scope is broad, making it highly valuable for industrial promotion.

[0151] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A polymeric polyester resin for primer coating, characterized in that, The product comprises the following components by molar amount: 16-26 parts terephthalic acid, 8-14 parts isophthalic acid, 25-40 parts neopentyl glycol, 4-5 parts 1,4-cyclohexanediethanol, 2-5 parts ethylene glycol, 1-3 parts diethylene glycol, 1-4 parts glycerol, 2-3 parts trimethylolpropane, 0.04-0.06 parts catalyst, 0.1-0.3 parts antioxidant, and 0.1-0.2 parts auxiliary antioxidant.

2. The polymeric polyester resin for primer according to claim 1, characterized in that: The total molar ratio of terephthalic acid and isophthalic acid to the total molar ratio of neopentyl glycol, 1,4-cyclohexanediol, ethylene glycol, diethylene glycol, glycerol, and trimethylolpropane is (1.4-1.7):

1.

3. The polymeric polyester resin for primer according to claim 1, characterized in that: The molar ratio of ethylene glycol, diethylene glycol, and glycerol is 2:1:(1-2).

4. The polymeric polyester resin for primer according to claim 1, characterized in that: The catalyst is one or more of tetrabutyl titanate, isopropyl titanate, antimony trioxide, and antimony glycolate.

5. The polymeric polyester resin for primer according to claim 1, characterized in that: The antioxidant is one or more of antioxidant 1010, antioxidant 1076, and antioxidant 1098.

6. The polymeric polyester resin for primer according to claim 1, characterized in that: The auxiliary antioxidant is one or more of trimethyl phosphite, triethyl phosphite, and triisopropyl phosphite.

7. A method for preparing a primer polymer polyester resin according to any one of claims 1-6, characterized in that, Includes the following steps: S1. Feeding: Weigh each component according to the required ratio, and add terephthalic acid, isophthalic acid, neopentyl glycol, 1,4-cyclohexanediol, ethylene glycol, diethylene glycol, glycerol, trimethylolpropane and catalyst into the reaction vessel; S2. Esterification reaction: Slowly heat to 150℃, and start stirring after the material begins to melt; gradually increase the temperature to 230-235℃, and keep the reaction at this temperature until the reactants are clear; S3. Vacuum polycondensation reaction: After sampling and testing to ensure the acid value meets the standard, the temperature is lowered to 200-220℃, and antioxidants and auxiliary antioxidants are added; the temperature is raised to 250-255℃, and vacuum is slowly drawn. After testing that the viscosity and molecular weight meet the standard, the material is discharged to obtain the high molecular weight polyester resin for the primer.

8. The method for preparing a primer polymer polyester resin according to claim 7, characterized in that: The reaction is carried out under the protection of an inert gas.

9. The method for preparing a primer polymer polyester resin according to claim 7, characterized in that: The slow vacuuming described in S3 refers to gradually reducing the vacuum level to <100 Pa within 30-60 minutes.

10. An application of the polymeric polyester resin for primer according to any one of claims 1-6, characterized in that, Used as a primer for inks.

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