Modified saturated polyester resins, methods for their preparation, and metallic coatings

Abstract

The application discloses a modified saturated polyester resin and a preparation method thereof and a metal coating, and relates to the technical field of coating resins.The raw material of the modified saturated polyester resin comprises the following components in mass fractions: 70-90 parts of isophthalic acid; 75-150 parts of glycidyl neodecanoate; 0.1-0.5 parts of a pre-reaction catalyst; main materials, including 300-400 parts of neopentyl glycol, 15-25 parts of trimethylolpropane, 400-500 parts of terephthalic acid, 30-50 parts of isophthalic acid, 0.1-1.0 parts of monobutyl tin oxide; and 0.5-1.0 parts of an antioxidant.The modified saturated polyester resin prepared by the application can be applied to the metal coating, has the advantages that metal powder arrangement can be supported, a metallic luster is good, and the flexibility and the hardness can be well balanced.

Description

Technical Field

[0001] This invention relates to the field of coating resin technology, and particularly to a modified saturated polyester resin and its preparation method, as well as metallic coatings. Background Technology

[0002] Saturated polyester resins are widely used as film-forming substances in high-performance industrial coatings, especially metallic effect coatings, due to their excellent adhesion, flexibility, weather resistance, and good pigment wetting properties. The core of metallic effect coatings lies in enabling metallic pigments to form a parallel-to-substrate oriented arrangement in the coating film, thereby producing a metallic shimmering effect with different colors at different angles.

[0003] Existing carboxyl-containing saturated polyester resins often suffer from high viscosity, slow solvent evaporation, and difficulty in balancing leveling and anti-sagging properties when preparing metallic paints. Traditional saturated polyester resins typically have high molecular weights and strong intermolecular interactions, resulting in high solution viscosity. When formulating high-solids metallic coatings, large amounts of volatile organic solvents must be used to reduce application viscosity. This not only increases VOC emissions but also reduces the fluidity of the wet film during drying due to slow solvent evaporation. The metallic pigments lack sufficient rearrangement time, leading to disordered arrangement and resulting in "blackening" or "cloudiness," severely weakening the metallic luster. In traditional saturated polyester systems, large amounts of leveling agents or thixotropic additives are usually added to improve the orientation of metallic powders, sacrificing the paint film's water resistance, chemical resistance, or interlayer adhesion.

[0004] Therefore, providing a novel saturated polyester resin that can be structurally designed at the molecular chain level, so that it can maintain low viscosity while possessing excellent metal powder orientation ability and a good balance between film hardness and flexibility, has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] The main objective of this invention is to propose a modified saturated polyester resin and its preparation method, as well as a metallic coating, in order to solve the problems of high viscosity, slow solvent evaporation, difficulty in balancing leveling and anti-sagging properties, disordered metal powder arrangement, and poor metallic luster when using carboxyl-containing saturated polyester resins to prepare metallic paints in the prior art.

[0006] To achieve the above objectives, the present invention provides a modified saturated polyester resin, wherein the raw materials of the modified saturated polyester resin comprise the following components in parts by weight: 70-90 parts isophthalic acid; 75-150 parts of glycidyl neodecanoate; 0.1-0.5 parts of pre-reaction catalyst; The main ingredients include 300-400 parts neopentyl glycol, 15-25 parts trimethylolpropane, 400-500 parts terephthalic acid, 30-50 parts isophthalic acid, and 0.1-1.0 parts monobutyltin oxide; and, 0.5-1.0 parts antioxidant.

[0007] This invention proposes a method for preparing a modified saturated polyester resin, comprising the following steps: Step S10, mixing 70-90 parts of isophthalic acid and 75-150 parts of glycidyl neodecanoate, adding 0.1-0.5 parts of a pre-reaction catalyst to carry out a pre-reaction, and preparing a modified intermediate; Step S20: The modified intermediate and the main material undergo an esterification reaction to uniformly connect the modified intermediate to the polyester main chain. After the esterification reaction is completed, vacuum polycondensation is performed, and the material is discharged to obtain the modified saturated polyester resin. The main ingredients include 300-400 parts neopentyl glycol, 15-25 parts trimethylolpropane, 400-500 parts terephthalic acid, 30-50 parts isophthalic acid, and 0.1-1.0 parts monobutyltin oxide.

[0008] In one embodiment, step S10 specifically includes the following steps: under a nitrogen atmosphere, 70-90 parts of isophthalic acid and 75-150 parts of neodecanoic acid glycidyl ester are added to a reaction vessel, stirred, heated to 120-140°C, 0.1-0.3 parts of pre-reaction catalyst are added, the temperature is raised to 145-155°C, and the reaction is carried out for 2-3 hours. When the acid value of the reaction system drops to 135-140 mg KOH / g, the intermediate is considered to be obtained.

[0009] In one embodiment, step S20, the esterification reaction between the intermediate and the main material includes the following steps: adding the main material to the intermediate reaction vessel, heating to 175-185°C, controlling the heating rate at 5-15°C / hour, and ensuring the top temperature does not exceed 102°C, gradually heating to 230-240°C, during which water is distilled off; maintaining the temperature until the acid value of the reaction system drops to 25-30 mgKOH / g, and the amount of water distilled off reaches more than 95% of the theoretical value, confirming that the esterification is complete.

[0010] In one embodiment, step S20, the vacuum polycondensation includes the following steps: adding an antioxidant, starting to gradually reduce the pressure, reducing the vacuum from atmospheric pressure to below -0.098 MPa within 60 minutes, while maintaining the temperature at 240-245°C, stopping the vacuum when the acid value of the system reaches 14-16 mg KOH / g and the melt viscosity reaches 3000-4000 mPa·s, and introducing nitrogen gas to break the vacuum.

[0011] In one embodiment, the antioxidant includes at least one of butylated hydroxytoluene, Irganox 1010, Irganox 1076, and Irganox 1098.

[0012] In one embodiment, step S20 includes the following steps for discharging: rapidly cooling to below 180°C, filtering through a 200-mesh filter bag, and then extruding through a granulator to obtain transparent, light yellow granular modified saturated polyester resin.

[0013] The present invention also provides a metallic coating comprising the following components in parts by weight: 50-70 parts of film-forming substance, 15-25 parts of organic solvent, 5-15 parts of metal powder, 0.1-1.0 parts of defoamer, 0.1-1.0 parts of leveling agent, 1-5 parts of adhesion promoter, and 3-8 parts of curing agent; The film-forming substance comprises: 59-61% modified saturated polyester resin and 39-41% solvent; The solvent includes ethyl 3-ethoxypropionate.

[0014] In the technical solution of the present invention, the raw materials of the modified saturated polyester resin include the following components in parts by weight: 70-90 parts isophthalic acid; 75-150 parts glycidyl neodecanoate; 0.1-0.5 parts pre-reaction catalyst; main material, including 300-400 parts neopentyl glycol, 15-25 parts trimethylolpropane, 400-500 parts terephthalic acid, 30-50 parts isophthalic acid, 0.1-1.0 parts monobutyltin oxide; and 0.5-1.0 parts antioxidant.

[0015] This invention provides a method for preparing a modified saturated polyester resin. The modified saturated polyester resin prepared by this invention can be applied to metal coatings. When applied to metal paint, the modified saturated polyester resin of this invention has the advantages of supporting the arrangement of metal powder, good metallic gloss, and a good balance between flexibility and hardness. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially. Furthermore, the meaning of "and / or" throughout the text includes three parallel solutions; for example, "A and / or B" includes solution A, or solution B, or a solution where both A and B are satisfied simultaneously. In addition, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] Existing carboxyl-containing saturated polyester resins often suffer from high viscosity, slow solvent evaporation, and difficulty in balancing leveling and anti-sagging properties when preparing metallic paints. This results in disordered aluminum powder arrangement (blackening, cloudiness), poor metallic luster, and other drawbacks. Traditional improvement methods involve directly adding large amounts of leveling or thixotropic additives, which can affect the water resistance or interlayer adhesion of the paint film. Alternatively, adding CAB resin can improve the directional arrangement of silver powder, but the poor compatibility between saturated polyester resin and CAB resin can lead to coating clumping or haziness, ultimately causing a decline in the overall performance of the paint film.

[0018] In view of this, the present invention provides a modified saturated polyester resin, wherein the raw material of the modified saturated polyester resin comprises the following components in parts by weight: 70-90 parts isophthalic acid; 75-150 parts of glycidyl neodecanoate; 0.1-0.5 parts of pre-reaction catalyst; The main ingredients include 300-400 parts neopentyl glycol, 15-25 parts trimethylolpropane, 400-500 parts terephthalic acid, 30-50 parts isophthalic acid, and 0.1-1.0 parts monobutyltin oxide; and, 0.5-1.0 parts antioxidant.

[0019] When applied to metallic paints, the modified saturated polyester resin of this invention offers advantages such as supporting the arrangement of metallic powders, providing a good metallic luster, and effectively balancing flexibility and hardness. Utilizing the sterically hindered neodecanoic acid side groups uniformly distributed along the resin molecular chain, the modified saturated polyester resin significantly improves the orientation and leveling effect of metallic pigments during the coating film formation process. The modified saturated resin allows metallic powders to rotate more freely and align parallel to the substrate in the wet film. Simultaneously, during solvent evaporation and curing crosslinking, the sterically hindered side groups act as a scaffold, inhibiting excessive collapse of the polymer chains, thereby significantly improving the angle-dependent color difference and the metallic luster on the front side, avoiding defects such as blackening and clouding. Furthermore, this resin also balances the hardness, flexibility, and chemical resistance of the paint film, and crosslinks well with the curing agent in the formulation, ultimately obtaining a metallic effect coating that combines high decorative properties, high protective properties, and good application performance.

[0020] The present invention also provides a method for preparing a modified saturated polyester resin, comprising the following steps: Step S10: Mix 70-90 parts of isophthalic acid and 75-150 parts of neodecanoic acid glycidyl ester, add 0.1-0.5 parts of pre-reaction catalyst to carry out pre-reaction, and prepare modified intermediate; Step S20: The modified intermediate and the main material undergo an esterification reaction to uniformly connect the modified intermediate to the polyester main chain. After the esterification reaction is completed, vacuum polycondensation is performed, and the material is discharged to obtain the modified saturated polyester resin. The main ingredients include 300-400 parts neopentyl glycol, 15-25 parts trimethylolpropane, 400-500 parts terephthalic acid, 30-50 parts isophthalic acid, and 0.1-1.0 parts monobutyltin oxide.

[0021] This invention first performs a pre-reaction to generate a semi-ester intermediate with sterically hindered side chains, and then introduces the semi-ester intermediate into the polyester backbone polycondensation reaction. Compared with traditional physical blending or later end-capping, this can ensure that the sterically hindered tertiary carbon groups are more evenly distributed in the molecular chain segments.

[0022] In some embodiments of the present invention, step S10 specifically includes the following steps: under a nitrogen atmosphere, 70-90 parts of isophthalic acid and 75-150 parts of neodecanoic acid glycidyl ester are added to a reaction vessel, stirred, heated to 120-140°C, 0.1-0.3 parts of pre-reaction catalyst are added, the temperature is raised to 145-155°C, and the reaction is carried out for 2-3 hours. When the acid value of the reaction system drops to the range of 135-140 mgKOH / g, it is considered that an intermediate is obtained.

[0023] It is understood that in the pre-reaction of the present invention, glycidyl neodecanoate is reacted with isophthalic acid to generate a semi-ester intermediate with a sterically hindered side chain. This intermediate contains a carboxyl group at one end and a secondary hydroxyl group at the other end, which allows the tertiary carbon groups to be evenly distributed in the middle segment of the polymer backbone in a comb-like manner, rather than being randomly distributed.

[0024] In some embodiments of the present invention, the pre-reaction catalyst may be at least one, or a combination of two or all of tetrabutylammonium bromide, tetramethylammonium bromide and trioctylmethylammonium chloride.

[0025] Understandably, the pre-reaction catalyst is used to activate the epoxy group of neodecanoic acid glycidyl ester, promoting its selective ring-opening esterification with isophthalic acid to generate a structurally uniform terminal carboxyl-terminal secondary hydroxyl half-ester intermediate. It not only effectively inhibits side reactions such as epoxy self-polymerization, ensuring the stable progress of the reaction and precisely controlling the acid value to the target range of 135-140 mgKOH / g, but more importantly, this intermediate enables the sterically hindered tertiary carbon side chains to be uniformly distributed in a comb shape on the polymer backbone during subsequent polycondensation, thereby ensuring that the final product has excellent processing stability and physical and mechanical properties.

[0026] In some embodiments of the present invention, step S20, the esterification reaction of the intermediate and the excipients includes the following steps: adding 300-400 parts of neopentyl glycol, 15-25 parts of trimethylolpropane, 400-500 parts of terephthalic acid, and 0.1-1.0 parts of monobutyltin oxide to the intermediate reaction vessel, heating to 175-185°C, controlling the heating rate at 5-15°C / hour, with the top temperature not exceeding 102°C, and gradually heating to 230-240°C, during which water generated is distilled off; maintaining the temperature until the acid value of the reaction system drops to 25-30 mg KOH / g, and the amount of water distilled off reaches more than 95% of the theoretical value, confirming that the esterification is complete.

[0027] Understandably, by performing melt polycondensation of the pre-reacted semi-ester intermediate with sterically hindered side chains and monomers such as neopentyl glycol, trimethylolpropane, and terephthalic acid under the catalysis of monobutyltin oxide, the sterically hindered tertiary carbon structure of the pre-reacted semi-ester intermediate with sterically hindered side chains, namely the tertiary carbon structure of neodecanoic acid glycidyl ester, can be uniformly embedded into the polyester backbone. By controlling the top temperature of the column to not exceed 102℃, it is ensured that only the water generated in the reaction is removed, avoiding the loss of alcohols. By monitoring the acid value to drop to 25-30 mg KOH / g and the distillate water volume to reach more than 95% of the theoretical value, the high degree of completion of the esterification reaction and the controllable increase of molecular weight can be ensured.

[0028] In some embodiments of the present invention, step S20, the vacuum polycondensation includes the following steps: adding an antioxidant, starting to gradually reduce the pressure, reducing the vacuum degree from atmospheric pressure to below -0.098 MPa within 60 minutes, while maintaining the temperature at 240-245°C; when the acid value of the system reaches 14-16 mg KOH / g and the melt viscosity reaches 3000-4000 mPa·s, stopping the vacuum and introducing nitrogen gas to break the air.

[0029] Understandably, by fully extending the chain under high vacuum and gradually reducing the pressure over 60 minutes, the small molecule byproducts remaining in the esterification reaction equilibrium are effectively removed, driving the polymerization equilibrium towards higher molecular weight. This allows the sterically hindered side group structure uniformly embedded in the main chain to be retained and stabilized during the molecular weight increase. By precisely controlling the endpoint conditions, when the acid value of the system reaches 14-16 mg KOH / g and the melt viscosity reaches 3000-4000 mPa·s, the resin is ultimately endowed with high solids content, low viscosity, excellent metal powder orientation, and a good balance between hardness and flexibility, providing an ideal resin skeleton for subsequent coating applications.

[0030] In some embodiments of the present invention, the antioxidant includes at least one of butylated hydroxytoluene, Irganox 1010, Irganox 1076, and Irganox 1098, and the antioxidant may be a combination or all of these.

[0031] It is understood that the antioxidant is used to capture and quench free radicals / peroxides generated by heat and trace metal ions in the resin system under high temperature and vacuum polycondensation conditions of 240-245℃, inhibit the oxidation, thermo-oxidative degradation and yellowing of the polyester main chain and neodecanoic acid tertiary carbon side chain, and prevent the molecular chain from undergoing thermal oxidative chain breakage or excessive cross-linking.

[0032] In some embodiments of the present invention, step S20 includes the following steps: rapidly cooling to below 180°C, filtering through a 200-mesh filter bag, and then extruding through a granulator to obtain transparent, light yellow granular modified saturated polyester resin.

[0033] Understandably, by rapidly cooling to below 180°C, the high-temperature polycondensation reaction is terminated in time, preventing further cross-linking or degradation of the resin, thereby locking in the optimal molecular weight and viscosity characteristics obtained by vacuum polycondensation in step S30. Subsequently, filtration through a 200-mesh filter bag effectively removes trace amounts of gel, mechanical impurities, or unreacted solid particles that may be generated during the reaction, ensuring the purity and batch stability of the resin. Finally, the molten resin is extruded through a granulator to transform it into transparent, light yellow granular solids, facilitating subsequent packaging, transportation, storage, and rapid feeding and uniform dissolution during use.

[0034] The present invention also provides a metallic coating comprising any of the modified saturated polyester resins described above.

[0035] In some embodiments of the present invention, the metallic coating comprises the following components in parts by weight: 50-70 parts of film-forming substance, 15-25 parts of organic solvent, 5-15 parts of metal powder, 0.1-1.0 parts of defoamer, 0.1-1.0 parts of leveling agent, 1-5 parts of adhesion promoter, and 3-8 parts of curing agent; the film-forming substance comprises: 59-61% of modified saturated polyester resin and 39-41% of solvent; the solvent comprises ethyl 3-ethoxypropionate.

[0036] It is understood that the modified saturated polyester resin preferably has a number-average molecular weight (Mn) of 3500-5500, a weight-average molecular weight (Mw) of 8000-15000, and a molecular weight distribution index (PDI) of 2.0-3.0. Within this molecular weight range, the resin can maintain excellent mechanical strength while ensuring low application viscosity under high solids content. Adding modified saturated polyester resin utilizes the sterically hindered neodecanoic acid side groups uniformly distributed on the resin molecular chain to significantly improve the orientation and leveling effect of metallic pigments during the coating film formation process. Modified saturated resin allows metal powder to rotate more freely and align parallel to the substrate in the wet film. Meanwhile, during solvent evaporation and curing crosslinking, the sterically hindered side groups act as a scaffold, inhibiting excessive collapse of the polymer chains. This significantly improves the angle-dependent color value and the metallic luster on the front side, avoiding defects such as blackening and clouding. In addition, the resin also takes into account the hardness, flexibility, and chemical resistance of the coating film, and crosslinks well with the curing agent in the formulation, ultimately obtaining a metallic effect coating that combines high decorativeness, high protection, and good workability.

[0037] In some embodiments of the present invention, the organic solvent may be butyl acetate; the metal powder may be at least one or all of silver powder and aluminum powder; the defoamer may be BYK-1790; the leveling agent may be Levaslip432; the adhesion promoter may be Changxing / 4901-B-72; and the curing agent may be Desmodur 3175.

[0038] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are only used to explain the present invention and are not intended to limit the present invention.

[0039] Example 1 A metallic coating comprises the following components: 60 parts of film-forming substance, 21.5 parts of butyl acetate, 10 parts of silver powder, 0.5 parts of BYK-1790, 0.5 parts of Levaslip 432, 2.5 parts of Changxing / 4901-B-72, and 5 parts of Desmodur 3175; the film-forming substance comprises 60% of modified saturated polyester resin and 40% of ethyl 3-ethoxypropionate solvent.

[0040] The method for preparing the modified saturated polyester resin includes the following steps: Step S10: Under a nitrogen atmosphere, 83 parts of isophthalic acid and 125 parts of neodecanoic acid glycidyl ester were added to a reaction vessel, stirred, heated to 130°C, 0.2 parts of tetrabutylammonium bromide were added, the temperature was raised to 150°C, and the reaction was carried out for 3 hours. When the acid value of the reaction system dropped to 140 mg KOH / g, the intermediate was considered to be obtained. Step S20: Add 340 parts neopentyl glycol, 18 parts trimethylolpropane, 460 parts terephthalic acid, and 0.5 parts monobutyltin oxide to the intermediate reaction vessel. Heat to 180°C, controlling the heating rate at 10°C / hour, with the top temperature not exceeding 102°C. Gradually increase the temperature to 235°C, distilling off the generated water during this process. Maintain the temperature until the acid value of the reaction system drops to 30 mg KOH / g, and the amount of distilled water reaches more than 95% of the theoretical value, confirming the completion of esterification. Add 1.0 part dibutylhydroxytoluene and begin gradually reducing the pressure, lowering the vacuum from atmospheric pressure to below -0.098 MPa within 60 minutes while maintaining the temperature at 245°C. When the acid value of the system reaches 16 mg KOH / g... When the KOH concentration is 1 / g and the melt viscosity reaches 3500 mPa·s, the vacuum is stopped and nitrogen is introduced to break the air vent. The temperature is then rapidly reduced to below 180°C, filtered through a 200-mesh filter bag, and extruded through a granulator to obtain transparent, light yellow granular modified saturated polyester resin.

[0041] Example 2 The difference between this metallic coating and Example 1 lies only in step S10: under a nitrogen atmosphere, 83 parts of isophthalic acid and 75 parts of neodecanoic acid glycidyl ester are added to a reaction vessel, stirred, heated to 130°C, 0.2 parts of tetrabutylammonium bromide are added, the temperature is raised to 150°C, and the reaction is carried out for 3 hours; when the acid value of the reaction system drops to 140 mg KOH / g, the intermediate is considered to be obtained.

[0042] Example 3 The difference between this metallic coating and Example 1 lies only in step S10: under a nitrogen atmosphere, 83 parts of isophthalic acid and 150 parts of neodecanoic acid glycidyl ester are added to a reaction vessel, stirred, heated to 130°C, 0.2 parts of tetrabutylammonium bromide are added, the temperature is raised to 150°C, and the reaction is carried out for 3 hours; when the acid value of the reaction system drops to 140 mg KOH / g, the intermediate is considered to be obtained.

[0043] Example 4 A metallic coating comprises the following components: 50 parts of film-forming substance, 25 parts of butyl acetate, 10 parts of silver powder, 0.1 parts of BYK-1790, 0.1 parts of Levaslip 432, 1 part of Changxing / 4901-B-72, and 5 parts of Desmodur 3175; the film-forming substance comprises 60% of modified saturated polyester resin and 40% of ethyl 3-ethoxypropionate solvent.

[0044] The method for preparing the modified saturated polyester resin includes the following steps: Step S10: Under a nitrogen atmosphere, 70 parts of isophthalic acid and 75 parts of neodecanoic acid glycidyl ester were added to a reaction vessel, stirred, heated to 130°C, 0.1 parts of tetrabutylammonium bromide were added, the temperature was raised to 150°C, and the reaction was carried out for 3 hours. When the acid value of the reaction system dropped to 138 mg KOH / g, the intermediate was considered to be obtained. Step S20: Add 300 parts neopentyl glycol, 15 parts trimethylolpropane, 400 parts terephthalic acid, and 0.1 parts monobutyltin oxide to the intermediate reaction vessel. Heat to 180°C, controlling the heating rate at 10°C / hour, with the top temperature not exceeding 102°C. Gradually increase the temperature to 235°C, distilling off the generated water during this process. Maintain the temperature until the acid value of the reaction system drops to 28 mg KOH / g, and the amount of distilled water reaches more than 95% of the theoretical value, confirming the esterification is complete. Add 0.5 parts dibutylhydroxytoluene and begin gradually reducing the pressure, lowering the vacuum from atmospheric pressure to below -0.098 MPa within 60 minutes while maintaining the temperature at 245°C. When the acid value of the system reaches 15.5 mg KOH / g... When the KOH concentration is 1 / g and the melt viscosity reaches 3600 mPa·s, the vacuum is stopped and nitrogen is introduced to break the air vent. The temperature is then rapidly reduced to below 180°C, filtered through a 200-mesh filter bag, and extruded through a granulator to obtain transparent, light yellow granular modified saturated polyester resin.

[0045] Example 5 A metallic coating comprises the following components: 70 parts of film-forming substance, 15 parts of butyl acetate, 5 parts of silver powder, 1.0 part of BYK-1790, 3 parts of Levaslip 432, 2 parts of Changxing / 4901-B-72, and 6 parts of Desmodur 3175; the film-forming substance comprises 60% modified saturated polyester resin and 40% ethyl 3-ethoxypropionate solvent.

[0046] The method for preparing the modified saturated polyester resin includes the following steps: Step S10: Under a nitrogen atmosphere, 90 parts of isophthalic acid and 150 parts of neodecanoic acid glycidyl ester were added to a reaction vessel, stirred, and heated to 130°C. Then, 0.5 parts of tetrabutylammonium bromide were added, and the temperature was raised to 150°C. The reaction was carried out for 3 hours. When the acid value of the reaction system dropped to 135 mg KOH / g, the intermediate was considered to be obtained. Step S20: Add 400 parts neopentyl glycol, 25 parts trimethylolpropane, 500 parts terephthalic acid, and 1.0 part monobutyltin oxide to the intermediate reaction vessel. Heat to 180°C, controlling the heating rate at 10°C / hour, with the top temperature not exceeding 102°C. Gradually increase the temperature to 235°C, distilling off the generated water during this process. Maintain the temperature until the acid value of the reaction system drops to 26 mg KOH / g, and the amount of distilled water reaches more than 95% of the theoretical value, confirming the esterification is complete. Add 1.0 part dibutylhydroxytoluene and begin gradually reducing the pressure, lowering the vacuum from atmospheric pressure to below -0.098 MPa within 60 minutes while maintaining the temperature at 245°C. When the acid value of the system reaches 14.5 mg KOH / g... When the KOH concentration is 1 / g and the melt viscosity reaches 3800 mPa·s, the vacuum is stopped and nitrogen is introduced to break the air vent. The temperature is then rapidly reduced to below 180°C, filtered through a 200-mesh filter bag, and extruded through a granulator to obtain transparent, light yellow granular modified saturated polyester resin.

[0047] Example 6 A metallic coating comprises the following components: 65 parts of film-forming substance, 20 parts of butyl acetate, 15 parts of silver powder, 1.0 part of BYK-1790, 3 parts of Levaslip 432, 5 parts of Changxing / 4901-B-72, and 4 parts of Desmodur 3175; the film-forming substance comprises 60% modified saturated polyester resin and 40% ethyl 3-ethoxypropionate solvent.

[0048] The method for preparing the modified saturated polyester resin includes the following steps: Step S10: Under a nitrogen atmosphere, 90 parts of isophthalic acid and 75 parts of neodecanoic acid glycidyl ester were added to a reaction vessel, stirred, heated to 130°C, 0.1 parts of tetrabutylammonium bromide were added, the temperature was raised to 150°C, and the reaction was carried out for 3 hours. When the acid value of the reaction system dropped to 140 mg KOH / g, the intermediate was considered to be obtained. Step S20: Add 300 parts neopentyl glycol, 25 parts trimethylolpropane, 400 parts terephthalic acid, and 1.0 part monobutyltin oxide to the intermediate reaction vessel. Heat to 180°C, controlling the heating rate at 10°C / hour, with the top temperature not exceeding 102°C. Gradually increase the temperature to 235°C, distilling off the generated water during this process. Maintain the temperature until the acid value of the reaction system drops to 27 mg KOH / g, and the amount of distilled water reaches more than 95% of the theoretical value, confirming that esterification is complete. Add 0.5 parts dibutylhydroxytoluene and begin gradually reducing the pressure, lowering the vacuum from atmospheric pressure to below -0.098 MPa within 60 minutes while maintaining the temperature at 245°C. When the acid value of the system reaches 15 mg KOH / g... When the KOH concentration is 1 / g and the melt viscosity reaches 3500 mPa·s, the vacuum is stopped and nitrogen is introduced to break the air vent. The temperature is then rapidly reduced to below 180°C, filtered through a 200-mesh filter bag, and extruded through a granulator to obtain transparent, light yellow granular modified saturated polyester resin.

[0049] Comparative Example 1 The difference between this metallic coating and Example 1 is that the 60%wt modified saturated polyester resin is replaced with an equal amount of 60%wt ordinary saturated polyester resin.

[0050] The preparation method of the ordinary saturated resin includes the following steps: Under nitrogen protection, 365 parts of neopentyl glycol, 22 parts of trimethylolpropane, 470 parts of terephthalic acid, 143 parts of isophthalic acid, and 0.5 parts of monobutyltin oxide catalyst were added to the reactor. The temperature was raised to 180°C, with the heating rate controlled at 10°C / hour, and the top temperature not exceeding 102°C. The temperature was gradually increased to 235°C, during which water was distilled off. The temperature was maintained until the acid value of the reaction system dropped to 25 mg KOH / g, and the amount of water distilled off reached more than 95% of the theoretical value. 1.0 part of dibutylhydroxytoluene was added, and the pressure was gradually reduced. The vacuum degree was reduced from atmospheric pressure to below -0.098 MPa within 60 minutes. When the acid value of the system reached 15 mg KOH / g and the melt viscosity reached 3500 mPa·s, the vacuum was stopped, and nitrogen was introduced to break the air vent. The temperature was rapidly reduced to below 180°C, and the mixture was granulated to obtain ordinary saturated polyester resin.

[0051] Comparative Example 2 The difference between this metallic coating and Example 1 is that, in step S10, under a nitrogen atmosphere, 83 parts of isophthalic acid and 115 parts of allyl glycidyl ester are added to a reaction vessel, stirred, heated to 130°C, 0.2 parts of tetrabutylammonium bromide are added, the temperature is raised to 150°C, and the reaction is carried out for 3 hours. When the acid value of the reaction system drops to 140 mg KOH / g, the intermediate is considered to be obtained.

[0052] Performance testing The modified saturated polyester resins obtained in Examples 1-6 were subjected to performance tests.

[0053] The modified saturated polyester resins of Examples 1-6 underwent basic physicochemical tests, and the test results are shown in Table 1. The resins obtained in Examples 1-6 and Comparative Examples 1-2 were subjected to liquid performance tests. The performance of the metallic coatings obtained in Examples 1-6 and Comparative Examples 1-2 was tested. The substrates were tinplate and black and white cardboard, and the curing conditions were 160℃ for 20 minutes. The test results are shown in Tables 3-5. The molecular weight of the modified saturated polyester resins of Examples 1-3 was tested using the GPC method, and the test results are shown in Table 6.

[0054] Table 1. Performance test results of modified saturated polyester resins in Examples 1-3

[0055] Table 2. Test results of resin liquid properties

[0056] Table 3. Results of Coating Appearance Performance Tests

[0057] Table 4. Test results of the physical and mechanical properties of the coating film

[0058] Table 5 Chemical Resistance Tests

[0059] Table 6. Molecular weight test results of modified saturated polyester resins

[0060] The modified saturated polyester resin prepared by this invention maintains the expected excellent performance in terms of molecular weight distribution (Mn between 3500-5500, PDI between 2.0-3.0), resin viscosity (3700-5300 mPa·s), and the orientation of metal powder (Flop Index is maintained above 14.5, and the silver powder is visually well arranged / strong metallic feel). At the same time, it also balances the hardness, flexibility (T-bend test reaches 0T-1T), and chemical resistance such as water boiling resistance of the coating film.

[0061] Comparing Example 1 and Comparative Example 1, the angle-dependent colorimetric value of Example 1 (15.8) is significantly higher than that of Comparative Example 1 (11.7). This is because Comparative Example 1 has an excessively high viscosity (7300 mPa·s), resulting in poor resin flowability during solvent evaporation, preventing the silver powder from freely rotating to a parallel state during film shrinkage. In contrast, Example 1, by introducing the neodecanoic acid structure, utilizes its large side chain volume to reduce intermolecular forces, significantly lowering viscosity and providing the silver powder with an excellent orientation environment.

[0062] Comparing Example 1 and Comparative Example 2, although Comparative Example 2 has a lower viscosity of 3900 mPa·s, its angle-dependent colorimetric value of 12.5 is also lower than that of Example 1. This indicates that simply reducing viscosity cannot improve the appearance of the paint film. In Example 1, the tertiary carbon steric hindrance structure of neodecanoic acid acts as a micro-scaffold between polymer chains, preventing excessive collapse and curling of the polymer chains during drying, thus more effectively supporting the silver powder to maintain parallel alignment. In contrast, the straight-chain alkyl group in Comparative Example 2 is too soft and prone to chain segment entanglement, resulting in a weaker ability to support and orient the silver powder.

[0063] Compared with Comparative Example 2, Comparative Example 2, which uses a linear long-chain epoxy, showed a significant decrease in hardness to HB and a deterioration in solvent resistance (MEK) (from >100 to 80). This is because the flexible segments are easily swollen by the solvent. Example 1 utilizes the rigidity of the neodecanoic acid structure, where the tertiary carbon atoms are not easily rotated. While providing flexibility (OT), it maintains good hardness (H) and solvent resistance, achieving a good balance between rigidity and flexibility.

[0064] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the patent protection scope of the present invention.

Claims

1. A modified saturated polyester resin, characterized in that, The raw material of the modified saturated polyester resin includes the following components in parts by weight: The main ingredients include 300-400 parts neopentyl glycol, 15-25 parts trimethylolpropane, 400-500 parts terephthalic acid, 30-50 parts isophthalic acid, and 0.1-1.0 parts monobutyltin oxide; 70-90 parts isophthalic acid; 75-150 parts of glycidyl neodecanoate; 0.1-0.5 parts of pre-reaction catalyst; as well as, 0.5-1.0 parts antioxidant.

2. A method for preparing a modified saturated polyester resin, characterized in that, Includes the following steps: Step S10: Mix 70-90 parts of isophthalic acid and 75-150 parts of neodecanoic acid glycidyl ester, add 0.1-0.5 parts of pre-reaction catalyst to carry out pre-reaction, and prepare modified intermediate; Step S20: The modified intermediate and the main material undergo an esterification reaction to uniformly connect the modified intermediate to the polyester main chain. After the esterification reaction is completed, vacuum polycondensation is performed, and the material is discharged to obtain the modified saturated polyester resin. The main ingredients include 300-400 parts neopentyl glycol, 15-25 parts trimethylolpropane, 400-500 parts terephthalic acid, 30-50 parts isophthalic acid, and 0.1-1.0 parts monobutyltin oxide.

3. The method for preparing the modified saturated polyester resin as described in claim 2, characterized in that, Step S10 specifically includes the following steps: Under a nitrogen atmosphere, 70-90 parts of isophthalic acid and 75-150 parts of neodecanoic acid glycidyl ester are added to a reaction vessel, stirred, heated to 120-140℃, 0.1-0.3 parts of pre-reaction catalyst are added, the temperature is raised to 145-155℃, and the reaction is carried out for 2-3 hours. When the acid value of the reaction system drops to 135-140 mg KOH / g, the intermediate is considered to be obtained.

4. The method for preparing the modified saturated polyester resin as described in claim 2, characterized in that, In step S20, the esterification reaction between the intermediate and the main material includes the following steps: adding the main material to the intermediate reaction vessel, heating to 175-185℃, controlling the heating rate at 5-15℃ / hour, and keeping the top temperature below 102℃, gradually heating to 230-240℃, distilling off the generated water during this period, and maintaining the temperature until the acid value of the reaction system drops to 25-30mg KOH / g, and the amount of distilled water reaches more than 95% of the theoretical value, confirming that the esterification is complete.

5. The method for preparing the modified saturated polyester resin as described in claim 2, characterized in that, In step S20, the vacuum polycondensation includes the following steps: adding an antioxidant, starting to gradually reduce the pressure, reducing the vacuum from atmospheric pressure to below -0.098 MPa within 60 minutes, while maintaining the temperature at 240-245℃, stopping the vacuum when the acid value of the system reaches 14-16 mg KOH / g and the melt viscosity reaches 3000-4000 mPa·s, and introducing nitrogen gas to break the vacuum.

6. The method for preparing the modified saturated polyester resin according to claim 5, characterized in that, The antioxidant includes at least one of butylated hydroxytoluene, Irganox 1010, Irganox 1076, and Irganox 1098.

7. The method for preparing the modified saturated polyester resin according to claim 2, characterized in that, In step S20, the discharge includes the following steps: rapidly cooling to below 180°C, filtering through a 200-mesh filter bag, and then extruding through a granulator to obtain transparent, light yellow granular modified saturated polyester resin.

8. A metallic coating, characterized in that, The metallic coating comprises the modified saturated polyester resin as described in claim 1 or the modified saturated polyester resin prepared by the method described in any one of claims 2-7.

9. The metallic coating as described in claim 8, characterized in that, The film-forming agent comprises the following components in parts by weight: 50-70 parts film-forming substance, 15-25 parts organic solvent, 5-15 parts metal powder, 0.1-1.0 parts defoamer, 0.1-1.0 parts leveling agent, 1-5 parts adhesion promoter, and 3-8 parts curing agent; wherein the film-forming substance comprises 59-61% modified saturated polyester resin and 39-41% solvent. The solvent includes ethyl 3-ethoxypropionate.

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