Low-temperature curing high-toughness polyester resin as well as preparation method and application thereof

Abstract

The invention discloses low-temperature curing high-toughness polyester resin as well as a preparation method and application thereof, and relates to the technical field of high-molecular polymer materials. The polyester resin is prepared from the following raw materials: a prepolymer A, a prepolymer B and an end-capping reagent, the prepolymer A is a hydroxyl-terminated prepolymer containing one or more cycloalkyl groups; and the prepolymer B is a carboxyl-terminated prepolymer containing a borneol structure. The polyester resin has relatively low melt viscosity and relatively high glass transition temperature, is good in leveling property and flexibility, can realize low-temperature curing and is suitable for preparing a powder coating, and the obtained powder coating not only has low-temperature curing performance, but also has relatively low cost compared with a conventional polyester powder coating obtained by low-temperature curing. The leveling property, the flexibility and the storage stability can be considered, and the better comprehensive performance is achieved. The powder coating is particularly suitable for coating thermosensitive substrates, such as substrates such as wood and plastic.

Description

Technical Field

[0001] The invention relates to the technical field of high molecular polymer materials, and in particular to a low temperature curing high toughness polyester resin and a preparation method and application thereof. Background Art

[0002] Polyester resin is a healthy and environmentally friendly polymer material and an important component of powder coatings. Powder coatings are environmentally friendly coatings that exist in the form of solid powders. No solvent is required when using them. The powder is melted by heating and forms a uniform film on the surface of the substrate. Powder coatings do not contain volatile organic compounds (VOCs), which reduces the impact on the environment. All ingredients participate in the film-forming process, which improves resource utilization. They also have excellent mechanical properties, chemical resistance and decorative properties, and are widely used in all walks of life. However, the high-temperature curing conditions required for powder coatings limit their application on heat-sensitive substrates. For example, heat-sensitive substrates such as wood, plastics and other non-metallic materials cannot withstand traditional high-temperature curing conditions (usually 180-200°C), and often deform or discolor during the curing process, resulting in quality problems in powder coatings. In comparison, low-temperature curing can not only expand the application range of powder coatings, but also reduce energy consumption and improve production efficiency. Although there are some low-temperature curing products on the market, they often face the problem of poor coating performance, especially in terms of toughness and leveling.

[0003] At present, the key to solving the problems of flexibility and low-temperature curability of powder coatings lies in polyester resins, and there are mainly two ways: 1) adding semi-crystalline polyester during powder making, the amount of which is usually more than 10%. This method can improve the leveling performance and flexibility of the coating, but it will significantly reduce the glass transition temperature of the powder coating and affect its storage stability; 2) increasing the acid value of the polyester resin and introducing highly active monomers, but the powder coating prepared by this method has poor chemical stability, is easy to self-crosslink, and the increase in acid value will increase the production cost of the powder coating. In addition, the existing technology also attempts to solve the problems of powder coatings by increasing the amount of curing accelerator, but this method can only improve the mechanical properties to a certain extent, barely achieve the low-temperature curing effect, and the leveling appearance is poor. Summary of the invention

[0004] The present invention aims to solve at least one of the above-mentioned technical problems existing in the prior art. To this end, the purpose of the present invention is to provide a polyester resin, which uses a cycloalkyl-containing terminal hydroxyl prepolymer, a borneol-containing terminal carboxyl prepolymer and a capping agent as raw materials, and the obtained polyester resin has a high glass transition temperature, a low melt viscosity, and has low temperature curing property and high toughness.

[0005] The second aspect of the present invention is to provide a method for preparing a polyester resin.

[0006] A third aspect of the present invention is to provide a powder coating.

[0007] A fourth aspect of the present invention is to provide an application of a polyester resin or a powder coating.

[0008] In order to achieve the above object, the technical solution adopted by the present invention is:

[0009] The first aspect of the present invention provides a polyester resin, wherein the raw materials for preparing the polyester resin include prepolymer A, prepolymer B and a capping agent; the prepolymer A is a terminal hydroxyl prepolymer containing one or more cycloalkyl groups; the prepolymer B is a terminal carboxyl prepolymer containing a borneol structure.

[0010] The present invention selects specific prepolymer A and prepolymer B. Prepolymer A is a terminal hydroxyl prepolymer containing one or more cycloalkyl groups. Compared with the straight-chain alkane structure, the main chain containing the cycloalkyl structure gives the polyester higher rigidity and shows a higher glass transition temperature. At the same time, the cycloalkane is a chair structure, which basically does not have angular tension and torsional tension, and the molecular structure is stable, which can greatly alleviate the huge impact force and show higher toughness. Prepolymer B is a terminal carboxyl prepolymer containing a borneol structure. The borneol structure is introduced into the polyester chain segment, and the random arrangement of the bulky side groups increases the free rotation of the main chain, which helps to reduce the viscosity of the resin system.

[0011] The polyester resin obtained by using prepolymer A and prepolymer B as raw materials exhibits better flexibility and leveling, higher glass transition temperature, and can achieve low-temperature curing. This is because the terminal hydroxyl prepolymer A containing one or more cycloalkyl groups has a very low viscosity and a relatively low glass transition temperature, while the terminal carboxyl prepolymer B containing a borneol structure has a higher glass transition temperature and reaction activity, but a relatively high viscosity. After the two are grafted, the obtained polyester resin can take into account the advantages of both.

[0012] In some embodiments of the present invention, the molar ratio of the prepolymer A to the prepolymer B is (1-1.2):1.

[0013] In some embodiments of the present invention, the molar ratio of the prepolymer A to the prepolymer B is (1.08-1.15):1.

[0014] In some embodiments of the present invention, the capping agent includes a capping agent C1 and a capping agent C2; the capping agent C1 contains a carboxyl structure; and the capping agent C2 contains an amino structure and / or an aminocarboxyl structure.

[0015] The amino-carboxyl structure refers to a structure containing both an amino group and a carboxyl group.

[0016] In the present invention, the product after esterification and grafting of prepolymer A and prepolymer B is capped with a capping agent containing an amino structure and / or an aminocarboxyl structure. On the one hand, the amino / aminocarboxyl structure at the end of the polyester resin main chain can form a hydrogen bond or a chemical bond with the surface of the substrate, thereby enhancing the interaction between the coating formed by the polyester resin as a coating and the substrate, which can significantly improve the adhesion of the coating and further enhance the flexibility of the polyester resin. On the other hand, the amino / aminocarboxyl structure itself has a high reactivity. The introduction of a multifunctional amino structure can further improve the reactivity of the polyester resin, better realize the low-temperature curing performance of the polyester resin, and can be cured at 130° C., and has excellent comprehensive performance.

[0017] In some embodiments of the present invention, the capping agent C1 includes one or more of cyclopentanetetracarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,3,4-butanetetracarboxylic acid, 1,3,5-pentanetricarboxylic acid, 3,4,9,10-pyrenetetracarboxylic acid, aurinetricarboxylic acid, 1,3,5-cyclohexanetricarboxylic acid, and 1,3,5,7-adamantanetetracarboxylic acid.

[0018] In some specific embodiments of the present invention, the end-capping agent C1 includes one or more of cyclopentanetetracarboxylic acid, 1,2,3,4-butanetetracarboxylic acid, aurine tricarboxylic acid, 1,3,5-cyclohexane tricarboxylic acid, and 1,3,5,7-adamantane tetracarboxylic acid.

[0019] In some embodiments of the present invention, the capping agent C2 includes one or more of N,N,N",N"-tetrabutyldiethylenetriamine, N,N-dimethyldipropylenetriamine, diethylenetriamine, isomeric ditridecylamine, bis(hexamethylene)triamine, diethylenetriaminepentaacetic acid, and diethylenetriaminepentaacetic acid dianhydride.

[0020] In some specific embodiments of the present invention, the end-capping agent C2 includes one or more of N,N,N",N"-tetrabutyldiethylenetriamine, isomeric ditridecylamine, diethylenetriaminepentaacetic acid, and diethylenetriaminepentaacetic acid dianhydride.

[0021] In some examples of the present invention, the end-capping agent C2 includes N,N,N",N"-tetrabutyldiethylenetriamine and isomeric ditridecylamine, or diethylenetriaminepentaacetic acid and diethylenetriaminepentaacetic dianhydride.

[0022] In some specific examples of the present invention, the molar ratio of the N,N,N",N"-tetrabutyldiethylenetriamine and isomeric ditridecylamine, or the diethylenetriaminepentaacetic acid and diethylenetriaminepentaacetic dianhydride is 1:(3-5).

[0023] In some embodiments of the present invention, the molar ratio of the total molar amount of the capping agent C2 and the prepolymer B to the prepolymer A is (1.02-1.04):1.

[0024] In some embodiments of the present invention, the raw materials for preparing the prepolymer A include a first alcohol and a first acid; the first alcohol includes one or more of cyclohexanedimethanol, cyclopropane dimethanol, cyclobutane dimethanol, cyclopentane dimethanol, dicycloheptane-2,3-dimethanol, tricyclodecane dimethanol, and bicyclooctanedimethanol; the first acid includes one or more of cyclohexanedicarboxylic acid, cyclopropanedicarboxylic acid, cyclobutanedicarboxylic acid, cyclopentanedicarboxylic acid, bicycloheptane-2,3-dicarboxylic acid, bicyclooctane dicarboxylic acid, and cyclohexanediacetic acid.

[0025] Prepolymer A is prepared using cyclic structure monomers with good symmetry, and the synthesized polyester resin has a lower melt viscosity and a relatively high glass transition temperature. This is mainly because the first alcohol and the first acid monomers are structurally symmetrical, the synthesized polyester resin chain segments have a certain regularity, and the interaction force between non-polar structure molecules is relatively weak, and the specific physical property is a lower viscosity.

[0026] In some embodiments of the present invention, the first alcohol includes one or more of cyclohexanedimethanol, cyclobutane dimethanol, dicycloheptane-2,3-dimethanol, and bicyclooctanedimethanol.

[0027] In some specific embodiments of the present invention, the first alcohol includes two or three of cyclobutane dimethanol, dicycloheptane-2,3-dimethanol, and bicyclooctanedimethanol.

[0028] In some examples of the present invention, the molar ratio of cyclobutane dimethanol, dicycloheptane-2,3-dimethanol and bicyclooctanedimethanol is (45-65): (0-20): (30-60).

[0029] In some specific examples of the present invention, the molar ratio of cyclobutane dimethanol, dicycloheptane-2,3-dimethanol and bicyclooctanedimethanol is (48-55): (0-15): (35-55).

[0030] Furthermore, the dicycloheptane-2,3-dimethanol is not zero.

[0031] In some embodiments of the present invention, the first acid includes one or more of cyclohexanedicarboxylic acid, cyclobutanedicarboxylic acid, bicyclooctanedicarboxylic acid, and cyclohexanediacetic acid.

[0032] In some specific embodiments of the present invention, the first acid includes two or three of cyclobutanedicarboxylic acid, bicyclooctanedicarboxylic acid, and cyclohexanediacetic acid.

[0033] In some examples of the present invention, the molar ratio of cyclobutanedicarboxylic acid, bicyclooctanedicarboxylic acid and cyclohexanediacetic acid is (40-60): (0-30): (35-60).

[0034] In some specific examples of the present invention, the molar ratio of cyclobutanedicarboxylic acid, bicyclooctanedicarboxylic acid and cyclohexanediacetic acid is (45-52): (0-15): (36-52).

[0035] Furthermore, the bicyclooctane dicarboxylic acid is not zero.

[0036] In some embodiments of the present invention, the raw materials for preparing the prepolymer B include second alcohols and second acids; the second alcohols include one or more of neopentyl glycol, bornyl alcohol, isoborneol, exo-borneol, 3,6-dihydroxybenzonorbornene, 5-norbornene-2,2-dimethanol, and 5-norbornene-2,3-dimethanol; the second acids include one or more of isophthalic acid, nadic anhydride, 5-norbornene-2-carboxylic acid, exo-5-norbornene carboxylic acid, norbornene-2,3-dicarboxylic acid, cis-2,3-norbornene dicarboxylic anhydride, oxacarboxylic anhydride, and cis-5-norbornene-endo-2,3-dicarboxylic acid.

[0037] In some embodiments of the present invention, the second alcohol includes one or more of neopentyl glycol, bornyl alcohol, isobornyl alcohol, exo-norborneol, and 3,6-dihydroxybenzonorbornane.

[0038] In some specific embodiments of the present invention, the second alcohols include two or three of neopentyl glycol, bornyl alcohol, and 3,6-dihydroxybenzonorbornane.

[0039] In some examples of the present invention, the molar ratio of neopentyl glycol, bornyl alcohol and 3,6-dihydroxybenzonorbornane is (45-65): (30-55): (0-10).

[0040] In some specific examples of the present invention, the molar ratio of neopentyl glycol, bornyl alcohol and 3,6-dihydroxybenzonorbornane is (49-60): (34-51): (0-8).

[0041] Furthermore, the 3,6-dihydroxybenzonorbornane is not zero.

[0042] In some embodiments of the present invention, the second acid includes one or more of isophthalic acid, nadic anhydride, 2,3-dicarboxylic acid, cis-2,3-dicarboxylic anhydride, and heteroacid anhydrides.

[0043] In some specific embodiments of the present invention, the second acid includes two or three of isophthalic acid, nadic anhydride, and cis-2,3-nadic anhydride.

[0044] In some examples of the present invention, the molar ratio of isophthalic acid, nadic anhydride, and cis-2,3-norbornane dicarboxylic anhydride is (40-65): (30-50): (0-20).

[0045] In some specific examples of the present invention, the molar ratio of isophthalic acid, nadic anhydride, and cis-2,3-nadic anhydride is (44-57): (40-45): (0-14).

[0046] Furthermore, the cis-2,3-norbornane dicarboxylic anhydride is not zero.

[0047] In some embodiments of the present invention, the molar ratio of the total molar amount of the capping agent C1 and the second acid to the second alcohol is (1.03-1.05):1.

[0048] In some embodiments of the present invention, the molar ratio of the first alcohol to the first acid in the prepolymer A is (1-1.06):1.

[0049] In some specific embodiments of the present invention, the molar ratio of the first alcohol to the first acid in the prepolymer A is (1.01-1.05):1.

[0050] In some examples of the present invention, the molar ratio of the first alcohol to the first acid in the prepolymer A is (1.02-1.04):1.

[0051] In some embodiments of the present invention, the molar ratio of the second alcohol to the second acid in the prepolymer B is (1.05-1.2):1.

[0052] In some specific embodiments of the present invention, the molar ratio of the second alcohol to the second acid in the prepolymer B is (1.07-1.15):1.

[0053] In some embodiments of the present invention, the acid value of the polyester resin is 30 to 35 mgKOH / g.

[0054] In some embodiments of the present invention, the polyester resin has a melt viscosity of 1800 to 2200 mPa·s at 200° C.

[0055] In some embodiments of the present invention, the glass transition temperature of the polyester resin is 60 to 70°C, further 65 to 67°C.

[0056] The second aspect of the present invention provides a method for preparing the polyester resin according to the first aspect of the present invention, comprising the following steps:

[0057] The prepolymer A and the prepolymer B are mixed to carry out an esterification reaction, and after the reaction, the end-capping agent is added to carry out a constant temperature reaction, and then a polycondensation reaction is carried out to obtain the polyester resin.

[0058] In some embodiments of the present invention, the method for preparing the prepolymer A comprises the following steps:

[0059] The first alcohol and the first acid are subjected to an esterification reaction and then to a polycondensation reaction to obtain the prepolymer A.

[0060] In some embodiments of the present invention, during the preparation of the prepolymer A, the temperature of the esterification reaction is 130-150° C.; the heating rate is 1.5-8.5° C. / h, further 1.6-8.3° C. / h.

[0061] In some embodiments of the present invention, during the preparation of the prepolymer A, the temperature of the polycondensation reaction is 180-200° C.; the heating rate is 5-12° C. / h, further 5-11.6° C. / h.

[0062] In some embodiments of the present invention, during the preparation of the prepolymer A, the polycondensation reaction time is 6 to 8 hours.

[0063] In some embodiments of the present invention, during the preparation of the prepolymer A, the polycondensation reaction is a reduced pressure polycondensation reaction.

[0064] In some specific embodiments of the present invention, the vacuum degree of the reduced pressure polycondensation reaction is -0.09 to -0.1 MPa.

[0065] In some embodiments of the present invention, during the preparation of the prepolymer A, the polycondensation reaction further includes a process of cooling and discharging the material; the temperature of the cooling and discharging the material is 160-180°C.

[0066] In some embodiments of the present invention, the preparation method of the prepolymer B comprises the following steps:

[0067] After the second alcohol and the second acid are subjected to esterification reaction, the end-capping agent C1 is added to react at a constant temperature to obtain the prepolymer B.

[0068] Introducing a multifunctional monomer end-capping agent C1 containing a cyclic structure at the end of the prepolymer B can not only further increase the glass transition temperature, but the multifunctional carboxylic acid structure can also increase the reactivity of the polyester resin, thereby better achieving the low-temperature curing performance of the polyester resin.

[0069] In some embodiments of the present invention, during the preparation of the prepolymer B, the temperature of the esterification reaction is 220-240° C.; the heating rate is 0.5-1.5° C. / h, further 0.7-1.4° C. / h.

[0070] In some embodiments of the present invention, during the preparation of the prepolymer B, the temperature of the isothermal reaction is 210-230° C. and the insulation time is 2-4 hours.

[0071] In some embodiments of the present invention, during the preparation of the prepolymer B, the polycondensation reaction further includes a process of cooling and discharging the material; the temperature of the cooling and discharging the material is 190-210°C.

[0072] In some embodiments of the present invention, an esterification catalyst is added to the esterification reaction of the first acid and the first alcohol, and the esterification reaction of the second acid and the second alcohol.

[0073] In some embodiments of the present invention, during the preparation of the prepolymer A and the prepolymer B, the first alcohol or the second alcohol is first dissolved; the dissolution temperature is 100 to 120° C.; and the heating rate is 70 to 90° C. / h.

[0074] In some embodiments of the present invention, the esterification reaction is carried out until the theoretical water output is 94-98%.

[0075] In some embodiments of the present invention, an esterification catalyst is also added during the esterification reaction of the prepolymer A and the prepolymer B.

[0076] In some embodiments of the present invention, the esterification catalyst comprises monobutyltin oxide; the amount of the esterification catalyst used is 0.08 to 0.1 mol% of the total molar amount of the raw materials for the esterification reaction.

[0077] In some embodiments of the present invention, during the preparation of the polyester resin, a curing accelerator and an antioxidant are added after the polycondensation reaction.

[0078] In some embodiments of the present invention, the curing accelerator includes triphenylethylphosphonium bromide; the amount of the curing accelerator is 0.02 to 0.05 mol% of the total molar amount of the raw materials.

[0079] In some embodiments of the present invention, the antioxidant includes at least two of antioxidant 1010, antioxidant 1076, and antioxidant 168; the amount of the antioxidant is 0.3-0.5 mol% of the total molar amount of the raw materials.

[0080] In some embodiments of the present invention, the temperature of the esterification reaction of the prepolymer A and the prepolymer B is 225-245° C.; the heating rate is 9-13° C. / h, further 9.5-12.5° C. / h.

[0081] In some embodiments of the present invention, during the preparation of the polyester resin, the end-capping agent added is end-capping agent C2.

[0082] In some embodiments of the present invention, during the preparation of the polyester resin, the temperature of the isothermal reaction is 195-215° C.; the insulation time is gradually reduced to 0.5-2 hours, and further to 0.5-1.5 hours.

[0083] In some embodiments of the present invention, during the preparation of the polyester resin, the temperature of the polycondensation reaction is 180 to 210°C, further 185 to 205°C.

[0084] In some embodiments of the present invention, during the preparation of the polyester resin, the polycondensation reaction time is 0.1 to 1 h, further 0.3 to 0.8 h.

[0085] In some embodiments of the present invention, during the preparation of the polyester resin, the polycondensation reaction is a reduced pressure polycondensation reaction.

[0086] In some embodiments of the present invention, the vacuum degree of the reduced pressure polycondensation reaction is -0.03 to -0.08 MPa.

[0087] In some embodiments of the present invention, during the preparation of the polyester resin, the polycondensation reaction further includes a process of cooling and discharging the material; the temperature of the cooling and discharging the material is 170-190°C.

[0088] The third aspect of the present invention provides a powder coating comprising the polyester resin described in the first aspect of the present invention.

[0089] In some embodiments of the present invention, the powder coating further comprises a curing agent, a pigment, a filler and an auxiliary agent.

[0090] In some embodiments of the present invention, the curing temperature of the powder coating is 120-130°C.

[0091] In some embodiments of the present invention, the bending axis diameter of the powder coating is 2 to 4 mm.

[0092] The polyester resin of the present invention has low-temperature curing property and high toughness, and can be cured at 120-130° C. The powder coating formed by the polyester resin also has low-temperature curing property and high toughness.

[0093] The fourth aspect of the present invention provides a use of the polyester resin described in the first aspect of the present invention or the powder coating described in the second aspect of the present invention in the field of coating of heat-sensitive substrates.

[0094] In some embodiments of the present invention, the heat-sensitive substrate includes non-metallic materials; for example, it may be wood, plastic, etc.

[0095] Compared with the prior art, the present invention has the following beneficial effects:

[0096] (1) The polyester resin of the present invention uses a terminal hydroxyl prepolymer A containing one or more cycloalkyl groups, a terminal carboxyl prepolymer B containing a borneol structure, and a capping agent as raw materials. The obtained polyester resin has a lower melt viscosity and a higher glass transition temperature, good leveling and flexibility, and can be cured at low temperature.

[0097] (2) The polyester resin of the present invention has low melt viscosity and high glass transition temperature, can be cured at a low temperature of 130°C, and is suitable for preparing powder coatings. The obtained powder coatings not only have low temperature curing properties, but also, compared with conventional low temperature cured polyester powder coatings, the powder coatings prepared from the polyester resin of the present invention can take into account leveling properties, flexibility and storage stability, and have better comprehensive properties.

[0098] (3) The polyester resin of the present invention has good comprehensive properties. The powder coating prepared therefrom has excellent leveling, flexibility and storage temperature resistance, and can be cured at low temperature. It is particularly suitable for coating heat-sensitive substrates, such as wood, plastic and other substrates. DETAILED DESCRIPTION

[0099] The present invention is further described in detail below by specific examples. Unless otherwise specified, the raw materials, reagents or devices used in the examples and comparative examples can be obtained from conventional commercial sources or can be obtained by prior art methods. Unless otherwise specified, the experiments or test methods are conventional methods in the art.

[0100] The following is a detailed description with reference to the embodiments and comparative examples.

[0101] Example 1

[0102] A polyester resin, the preparation raw materials include prepolymer A1, prepolymer B1 and a capping agent; prepolymer A1 is a terminal hydroxyl prepolymer containing multiple cycloalkyl groups; prepolymer B1 is a terminal carboxyl prepolymer containing a borneol structure;

[0103] Specific preparation materials and preparation methods refer to the following steps:

[0104] Step I: 0.49 mol of cyclobutane dimethanol and 0.52 mol of bicyclooctanedimethanol are added to a reaction kettle, and the temperature is quickly raised to 100° C. to dissolve them at a heating rate of 70° C. / h, and then stirring and nitrogen are turned on, followed by adding 0.49 mol of cyclobutane dicarboxylic acid, 0.49 mol of cyclohexane diacetic acid and 0.0016 mol of monobutyltin oxide, and then the temperature is programmed to 130° C. for esterification reaction at a heating rate of 1.6° C. / h. When the theoretical water output reaches more than 96%, the temperature is raised to 180° C. for reduced pressure polyurethane reaction at a heating rate of 5.0° C. / h, and finally the temperature is lowered to 160° C. to obtain a terminal hydroxyl prepolymer (A1) containing multiple cycloalkyl groups;

[0105] Step II: Add 0.49 mol of neopentyl glycol and 0.51 mol of borneol into a reaction kettle, quickly heat it to 100°C to dissolve them, then start stirring and nitrogen, then add 0.53 mol of isophthalic acid, 0.40 mol of nadic anhydride and 0.0016 mol of monobutyltin oxide, and then program the temperature to 220°C for esterification reaction at a heating rate of 0.7°C / h. When the theoretical water output reaches more than 96%, add 0.1 mol of cyclopentanetetracarboxylic acid at 210°C, keep the temperature for reaction for 2h, and finally cool it to 190°C to obtain a terminal carboxyl prepolymer (B1) containing a borneol structure;

[0106] Step III: 1.08 mol of the hydroxyl-terminated prepolymer (A1) containing multiple cycloalkyl groups prepared in step I, 1.0 mol of the carboxyl-terminated prepolymer (B1) containing borneol structure prepared in step II and 0.0017 mol of monobutyltin oxide are added to the reaction kettle, and then the temperature is raised to 225°C for esterification reaction at a heating rate of 9.5°C / h. When the theoretical water output reaches more than 96%, 0.025 mol of N,N,N",N"-tetrabutyldiethylenetriamine and 0.075 mol of diethylenetriaminepentaacetic acid were kept warm for reaction for 0.5 h, then cooled to 185°C for reduced pressure polycondensation, the vacuum degree was -0.03 MPa, the reduced pressure polycondensation time was 0.3 h, and finally cooled to 170°C, 0.0005 mol of triphenylethylphosphonium bromide, 0.0044 mol of antioxidant 1076 and 0.0022 mol of antioxidant 168 were added, and the polyester resin for low-temperature curing and high-toughness powder coatings was obtained.

[0107] The polyester resin had an acid value of 33 mgKOH / g, a melt viscosity of 2200 mPa·s (200° C.), and a glass transition temperature of 66.2° C.

[0108] Example 2

[0109] A polyester resin, the preparation raw materials include prepolymer A2, prepolymer B2 and a capping agent; prepolymer A2 is a terminal hydroxyl prepolymer containing multiple cycloalkyl groups; prepolymer B2 is a terminal carboxyl prepolymer containing a borneol structure;

[0110] Specific preparation materials and preparation methods refer to the following steps:

[0111] Step I: 0.55 mol of cyclobutane dimethanol, 0.08 mol of dicycloheptane-2,3-dimethanol and 0.45 mol of bicyclooctanedimethanol are added to a reaction kettle, and the temperature is quickly raised to 110° C. to dissolve them at a heating rate of 80° C. / h, and then stirring and nitrogen are turned on, followed by adding 0.5 mol of cyclobutane dicarboxylic acid, 0.15 mol of bicyclooctanedicarboxylic acid, 0.4 mol of cyclohexane diacetic acid and 0.002 mol of monobutyltin oxide, and then the temperature is programmed to 140° C. for esterification reaction at a heating rate of 5.0° C. / h. When the theoretical water output reaches more than 96%, the temperature is raised to 190° C. for reduced pressure polyurethane reaction at a heating rate of 8.3° C. / h, and finally the temperature is lowered to 170° C. to obtain a terminal hydroxyl prepolymer (A2) containing multiple cycloalkyl groups;

[0112] Step II: 0.55 mol of neopentyl glycol, 0.45 mol of borneol and 0.05 mol of 3,6-dihydroxybenzonorbornane are added to the reaction kettle, and the temperature is quickly raised to 110° C. to dissolve them, and then stirring and nitrogen are turned on. Then, 0.47 mol of isophthalic acid, 0.41 mol of nadic anhydride and 0.06 mol of cis-2,3-norbornane dicarboxylic anhydride and 0.0019 mol of monobutyltin oxide are added, and then the temperature is programmed to 230° C. for esterification reaction at a heating rate of 1.1° C. / h. When the theoretical water output reaches more than 96%, 0.15 mol of 1,2,3,4-butanetetracarboxylic acid is added at 220° C., and the reaction is kept warm for 3 hours. Finally, the temperature is lowered to 200° C. to obtain a terminal carboxyl prepolymer (B2) containing a borneol structure;

[0113] Step III: Add 1.1 mol of the hydroxyl-terminated prepolymer (A2) containing multiple cycloalkyl groups prepared in step I, 1.0 mol of the carboxyl-terminated prepolymer (B2) containing a borneol structure prepared in step II, and 0.0019 mol of monobutyltin oxide into the reaction kettle, and then heat the temperature to 235°C for esterification reaction at a heating rate of 11.0°C / h. When the theoretical water output reaches more than 96%, add 0.026 mol of N,N,N",N"-tetrabutyldiethylenetriamine and 0.104 mol of diethylenetriaminepentaacetic dianhydride were kept warm for reaction for 1.0 h, then cooled to 195°C for reduced pressure polycondensation, the vacuum degree was -0.05 MPa, the reduced pressure polycondensation time was 0.5 h, and finally cooled to 180°C, 0.0008 mol of triphenylethylphosphonium bromide, 0.0045 mol of antioxidant 1010 and 0.0045 mol of antioxidant 168 were added, and the polyester resin for low-temperature curing and high-toughness powder coatings was obtained.

[0114] The polyester resin had an acid value of 32.5 mgKOH / g, a melt viscosity of 1800 mPa·s (200° C.), and a glass transition temperature of 65.8° C.

[0115] Example 3

[0116] A polyester resin, the preparation raw materials include prepolymer A3, prepolymer B3 and a capping agent; prepolymer A3 is a terminal hydroxyl prepolymer containing multiple cycloalkyl groups; prepolymer B3 is a terminal carboxyl prepolymer containing a borneol structure;

[0117] Specific preparation materials and preparation methods refer to the following steps:

[0118] Step I: 0.58 mol of cyclobutane dimethanol, 0.15 mol of dicycloheptane-2,3-dimethanol and 0.42 mol of bicyclooctanedimethanol are added to a reaction kettle, and the temperature is quickly raised to 120° C. to dissolve them at a heating rate of 90° C. / h, and then stirring and nitrogen are turned on, followed by adding 0.53 mol of cyclobutane dicarboxylic acid, 0.15 mol of bicyclooctanedicarboxylic acid and 0.43 mol of cyclohexane diacetic acid and 0.002 mol of monobutyltin oxide, and then the temperature is programmed to 150° C. for esterification reaction at a heating rate of 8.3° C. / h. When the theoretical water output reaches more than 96%, the temperature is raised to 200° C. for reduced pressure polycondensation reaction at a heating rate of 11.6° C. / h, and finally the temperature is lowered to 180° C. to obtain a terminal hydroxyl prepolymer (A3) containing multiple cycloalkyl groups;

[0119] Step II: 0.58 mol of neopentyl glycol, 0.34 mol of borneol and 0.08 mol of 3,6-dihydroxybenzonorbornane are added to the reactor, and the temperature is quickly raised to 120° C. to dissolve them, and then stirring and nitrogen are turned on. Then, 0.4 mol of isophthalic acid, 0.35 mol of nadic anhydride and 0.12 mol of cis-2,3-norbornane dicarboxylic anhydride and 0.0019 mol of monobutyltin oxide are added, and then the temperature is programmed to 240° C. for esterification reaction at a heating rate of 1.4° C. / h. When the theoretical water output reaches more than 96%, 0.09 mol of aurintricarboxylic acid and 0.09 mol of 1,3,5-cyclohexanetricarboxylic acid are added at 230° C., and the reaction is kept warm for 4 hours. Finally, the temperature is lowered to 210° C. to obtain a terminal carboxyl prepolymer (B3) containing a borneol structure;

[0120] Step III: 1.15 mol of the hydroxyl-terminated prepolymer (A3) containing multiple cycloalkyl groups prepared in step I, 1.0 mol of the carboxyl-terminated prepolymer (B3) containing borneol structure prepared in step II and 0.0022 mol of monobutyltin oxide are added to the reaction kettle, and then the temperature is raised to 245°C for esterification reaction at a heating rate of 12.5°C / h. When the theoretical water output reaches more than 96%, 0.032 mol of isomeric tridecylamine and 0.158 mol of diethylenetriaminepentaacetic dianhydride was reacted at the temperature for 1.5 hours, then the temperature was lowered to 205°C for reduced pressure polycondensation, the vacuum degree was -0.08 MPa, the reduced pressure polycondensation time was 0.8 hours, and finally the temperature was lowered to 190°C, 0.0011 mol of triphenylethylphosphonium bromide, 0.0078 mol of antioxidant 1076 and 0.0039 mol of antioxidant 168 were added, and the polyester resin for low temperature curing and high toughness powder coating was obtained.

[0121] The polyester resin had an acid value of 32 mgKOH / g, a melt viscosity of 2000 mPa·s (200° C.), and a glass transition temperature of 66.5° C.

[0122] Example 4

[0123] A polyester resin, which is the same as that in Example 2, except that:

[0124] The cyclobutanedicarboxylic acid in the prepolymer A2 in Example 2 was replaced with cyclohexanedicarboxylic acid in an equal molar amount to synthesize a polyester resin for low-temperature curing and high-toughness powder coating.

[0125] The polyester resin had an acid value of 33.5 mgKOH / g, a melt viscosity of 1850 mPa·s (200° C.), and a glass transition temperature of 65.1° C.

[0126] Example 5

[0127] A polyester resin, the preparation raw materials include prepolymer A5, prepolymer B5 and a capping agent; prepolymer A5 is a terminal hydroxyl prepolymer containing multiple cycloalkyl groups; prepolymer B5 is a terminal carboxyl prepolymer containing a borneol structure;

[0128] Specific preparation materials and preparation methods refer to the following steps:

[0129] Step I: 0.55 mol of cyclobutane dimethanol, 0.08 mol of dicycloheptane-2,3-dimethanol and 0.45 mol of bicyclooctanedimethanol are added to a reaction kettle, and the temperature is quickly raised to 110° C. to dissolve them at a heating rate of 80° C. / h, and then stirring and nitrogen are turned on, followed by adding 0.5 mol of cyclobutane dicarboxylic acid, 0.15 mol of bicyclooctanedicarboxylic acid, 0.4 mol of cyclohexane diacetic acid and 0.002 mol of monobutyltin oxide, and then the temperature is programmed to 140° C. for esterification reaction at a heating rate of 5.0° C. / h. When the theoretical water output reaches more than 96%, the temperature is raised to 190° C. for reduced pressure polyurethane reaction at a heating rate of 8.3° C. / h, and finally the temperature is lowered to 170° C. to obtain a terminal hydroxyl prepolymer (A5) containing multiple cycloalkyl groups;

[0130] Step II: 0.55 mol of neopentyl glycol, 0.45 mol of borneol and 0.05 mol of 3,6-dihydroxybenzonorbornane are added to the reactor, and the temperature is quickly raised to 110° C. to dissolve them, and then stirring and nitrogen are turned on. Then, 0.47 mol of isophthalic acid, 0.41 mol of nadic anhydride and 0.06 mol of cis-2,3-norbornane dicarboxylic anhydride and 0.0019 mol of monobutyltin oxide are added, and then the temperature is programmed to 230° C. for esterification reaction at a heating rate of 1.1° C. / h. When the theoretical water output reaches more than 96%, 0.15 mol of 1,3,5,7-adamantane tetracarboxylic acid is added at 220° C., and the reaction is kept warm for 3 hours. Finally, the temperature is lowered to 200° C. to obtain a terminal carboxyl prepolymer (B5) containing a borneol structure;

[0131] Step III: 1.1 mol of the hydroxyl-terminated prepolymer (A5) containing multiple cycloalkyl groups prepared in step I, 1.0 mol of the carboxyl-terminated prepolymer (B5) containing a borneol structure prepared in step II and 0.0019 mol of monobutyltin oxide are added to the reaction kettle, and then the temperature is raised to 235°C for esterification reaction at a heating rate of 11.0°C / h. When the theoretical water output reaches more than 96%, 0.026 mol of isomeric tridecylamine and 0.0019 mol of monobutyltin oxide are added at 205°C. .104mol of diethylenetriaminepentaacetic dianhydride, keep warm for reaction for 1.0h, then cool to 195℃ for reduced pressure polycondensation, vacuum degree is -0.05MPa, reduced pressure polycondensation time is 0.5h, finally cool to 180℃, add 0.0008mol of triphenylethylphosphonium bromide, 0.0045mol of antioxidant 1010 and 0.0045mol of antioxidant 168, and obtain polyester resin for low temperature curing and high toughness powder coating.

[0132] The polyester resin had an acid value of 33.2 mgKOH / g, a melt viscosity of 1900 mPa·s (200° C.), and a glass transition temperature of 65.2° C.

[0133] Example 6

[0134] A polyester resin, the preparation raw materials include prepolymer A6, prepolymer B6 and a capping agent; prepolymer A6 is a terminal hydroxyl prepolymer containing multiple cycloalkyl groups; prepolymer B6 is a terminal carboxyl prepolymer containing a borneol structure;

[0135] Specific preparation materials and preparation methods refer to the following steps:

[0136] Step I: 0.55 mol of cyclobutane dimethanol, 0.08 mol of dicycloheptane-2,3-dimethanol and 0.45 mol of bicyclooctanedimethanol are added to a reaction kettle, and the temperature is quickly raised to 110° C. to dissolve them at a heating rate of 80° C. / h, and then stirring and nitrogen are turned on, followed by adding 0.5 mol of cyclohexanedicarboxylic acid, 0.15 mol of bicyclooctanedicarboxylic acid, 0.4 mol of cyclohexanediacetic acid and 0.002 mol of monobutyltin oxide, and then the temperature is programmed to 140° C. for esterification reaction at a heating rate of 5.0° C. / h. When the theoretical water output reaches more than 96%, the temperature is raised to 190° C. for reduced pressure polyurethane reaction at a heating rate of 8.3° C. / h, and finally the temperature is lowered to 170° C. to obtain a terminal hydroxyl prepolymer (A6) containing multiple cycloalkyl groups;

[0137] Step II: 0.55 mol of neopentyl glycol, 0.45 mol of borneol and 0.05 mol of 3,6-dihydroxybenzonorbornane are added to the reaction kettle, and the temperature is quickly raised to 110° C. to dissolve them, and then stirring and nitrogen are turned on. Then, 0.47 mol of isophthalic acid, 0.41 mol of nadic anhydride and 0.06 mol of cis-2,3-norbornane dicarboxylic anhydride and 0.0019 mol of monobutyltin oxide are added, and then the temperature is programmed to 230° C. for esterification reaction at a heating rate of 1.1° C. / h. When the theoretical water output reaches more than 96%, 0.1 mol of cyclopentane tetracarboxylic acid and 0.05 mol of 1,3,5,7-adamantane tetracarboxylic acid are added at 220° C., and the reaction is kept warm for 3 hours. Finally, the temperature is lowered to 200° C. to obtain a terminal carboxyl prepolymer (B6) containing a borneol structure;

[0138] Step III: 1.1 mol of the hydroxyl-terminated prepolymer (A6) containing multiple cycloalkyl groups prepared in step I, 1.0 mol of the carboxyl-terminated prepolymer (B6) containing a borneol structure prepared in step II and 0.0019 mol of monobutyltin oxide are added to the reaction kettle, and then the temperature is raised to 235°C for esterification reaction at a heating rate of 11.0°C / h. When the theoretical water output reaches more than 96%, 0.026 mol of isomeric tridecylamine and 0.0019 mol of monobutyltin oxide are added at 205°C. .104mol of diethylenetriaminepentaacetic dianhydride, keep warm for reaction for 1.0h, then cool to 195℃ for reduced pressure polycondensation, vacuum degree is -0.05MPa, reduced pressure polycondensation time is 0.5h, finally cool to 180℃, add 0.0008mol of triphenylethylphosphonium bromide, 0.0045mol of antioxidant 1010 and 0.0045mol of antioxidant 168, and obtain polyester resin for low temperature curing and high toughness powder coating.

[0139] The polyester resin had an acid value of 32.9 mgKOH / g, a melt viscosity of 1950 mPa·s (200° C.), and a glass transition temperature of 66.1° C.

[0140] Example 7

[0141] A polyester resin, the preparation raw materials include prepolymer A7, prepolymer B7 and a capping agent; prepolymer A7 is a terminal hydroxyl prepolymer containing multiple cycloalkyl groups; prepolymer B7 is a terminal carboxyl prepolymer containing a borneol structure;

[0142] Specific preparation materials and preparation methods refer to the following steps:

[0143] Step I: 0.55 mol of cyclobutane dimethanol, 0.08 mol of dicycloheptane-2,3-dimethanol and 0.45 mol of bicyclooctanedimethanol are added to a reaction kettle, and the temperature is quickly raised to 110° C. to dissolve them at a heating rate of 80° C. / h, and then stirring and nitrogen are turned on, followed by adding 0.5 mol of cyclobutane dicarboxylic acid, 0.15 mol of bicyclooctanedicarboxylic acid, 0.4 mol of cyclohexane diacetic acid and 0.002 mol of monobutyltin oxide, and then the temperature is programmed to 140° C. for esterification reaction at a heating rate of 5.0° C. / h. When the theoretical water output reaches more than 96%, the temperature is raised to 190° C. for reduced pressure polyurethane reaction at a heating rate of 8.3° C. / h, and finally the temperature is lowered to 170° C. to obtain a terminal hydroxyl prepolymer (A7) containing multiple cycloalkyl groups;

[0144] Step II: 0.55 mol of neopentyl glycol, 0.45 mol of borneol and 0.05 mol of 3,6-dihydroxybenzonorbornane are added to the reaction kettle, and the temperature is quickly raised to 110° C. to dissolve them, and then stirring and nitrogen are turned on. Then, 0.47 mol of isophthalic acid, 0.41 mol of nadic anhydride and 0.06 mol of cis-2,3-norbornane dicarboxylic anhydride and 0.0019 mol of monobutyltin oxide are added, and then the temperature is programmed to 230° C. for esterification reaction at a heating rate of 1.1° C. / h. When the theoretical water output reaches more than 96%, 0.1 mol of aurin tricarboxylic acid and 0.05 mol of 1,3,5,7-adamantane tetracarboxylic acid are added at 220° C., and the reaction is kept warm for 3 hours. Finally, the temperature is lowered to 200° C. to obtain a terminal carboxyl prepolymer (B7) containing a borneol structure;

[0145] Step III: Add 1.1 mol of the terminal hydroxyl prepolymer (A7) containing multiple cycloalkyl groups prepared in step I, 1.0 mol of the terminal carboxyl prepolymer (B7) containing borneol structure prepared in step II and 0.0019 mol of monobutyltin oxide into the reaction kettle, and then program the temperature to 235°C for esterification reaction at a heating rate of 11.0°C / h. When the theoretical water output reaches more than 96%, add 0.026 mol of isomeric ditridecylamine at 205°C. and 0.104 mol of diethylenetriaminepentaacetic acid, keep the temperature for reaction for 1.0 h, then cool to 195°C for reduced pressure polycondensation, the vacuum degree is -0.05 MPa, the reduced pressure polycondensation time is 0.5 h, finally cool to 180°C, add 0.0008 mol of triphenylethylphosphine bromide, 0.0045 mol of antioxidant 1010 and 0.0045 mol of antioxidant 168, and obtain polyester resin for low-temperature curing and high-toughness powder coating.

[0146] The polyester resin had an acid value of 33.1 mgKOH / g, a melt viscosity of 2010 mPa·s (200° C.), and a glass transition temperature of 65.9° C.

[0147] Example 8

[0148] A polyester resin, the preparation raw materials include prepolymer A8, prepolymer B8 and a capping agent; prepolymer A8 is a terminal hydroxyl prepolymer containing multiple cycloalkyl groups; prepolymer B8 is a terminal carboxyl prepolymer containing a borneol structure;

[0149] Specific preparation materials and preparation methods refer to the following steps:

[0150] Step I: 0.51 mol of cyclobutane dimethanol, 0.1 mol of dicycloheptane-2,3-dimethanol and 0.47 mol of bicyclooctanedimethanol are added to a reaction kettle, and the temperature is quickly raised to 110° C. to dissolve them at a heating rate of 80° C. / h, and then stirring and nitrogen are turned on, followed by adding 0.55 mol of cyclobutane dicarboxylic acid, 0.12 mol of bicyclooctanedicarboxylic acid, 0.38 mol of cyclohexane diacetic acid and 0.002 mol of monobutyltin oxide, and then the temperature is programmed to 140° C. for esterification reaction at a heating rate of 5.0° C. / h. When the theoretical water output reaches more than 96%, the temperature is raised to 190° C. for reduced pressure polyurethane reaction at a heating rate of 8.3° C. / h, and finally the temperature is lowered to 170° C. to obtain a terminal hydroxyl prepolymer (A8) containing multiple cycloalkyl groups;

[0151] Step II: 0.56 mol of neopentyl glycol, 0.42 mol of borneol and 0.07 mol of 3,6-dihydroxybenzonorbornane are added to the reaction kettle, and the temperature is quickly raised to 110° C. to dissolve them, and then stirring and nitrogen are turned on. Then, 0.48 mol of isophthalic acid, 0.4 mol of nadic anhydride and 0.06 mol of cis-2,3-norbornane dicarboxylic anhydride and 0.0019 mol of monobutyltin oxide are added, and then the temperature is programmed to 230° C. for esterification reaction at a heating rate of 1.1° C. / h. When the theoretical water output reaches more than 96%, 0.1 mol of aurin tricarboxylic acid and 0.05 mol of 1,3,5,7-adamantane tetracarboxylic acid are added at 220° C., and the reaction is kept warm for 3 hours. Finally, the temperature is lowered to 200° C. to obtain a terminal carboxyl prepolymer (B8) containing a borneol structure;

[0152] Step III: Add 1.1 mol of the hydroxy-terminated prepolymer (A8) containing multiple cycloalkyl groups prepared in step I, 1.0 mol of the carboxyl-terminated prepolymer (B8) containing a borneol structure prepared in step II, and 0.0019 mol of monobutyltin oxide into the reaction kettle, and then program the temperature to 235°C for esterification reaction at a heating rate of 11.0°C / h. When the theoretical water output reaches more than 96%, add 0.026 mol of isomeric ditridecylamine at 205°C. and 0.104 mol of diethylenetriaminepentaacetic acid, keep the temperature for reaction for 1.0 h, then cool to 195°C for reduced pressure polycondensation, the vacuum degree is -0.05 MPa, the reduced pressure polycondensation time is 0.5 h, finally cool to 180°C, add 0.0008 mol of triphenylethylphosphine bromide, 0.0045 mol of antioxidant 1010 and 0.0045 mol of antioxidant 168, and obtain polyester resin for low-temperature curing and high-toughness powder coating.

[0153] The polyester resin had an acid value of 33.2 mgKOH / g, a melt viscosity of 2050 mPa·s (200° C.), and a glass transition temperature of 66.1° C.

[0154] Example 9

[0155] A polyester resin, the preparation raw materials include prepolymer A9, prepolymer B9 and a capping agent; prepolymer A9 is a terminal hydroxyl prepolymer containing multiple cycloalkyl groups; prepolymer B9 is a terminal carboxyl prepolymer containing a borneol structure;

[0156] Specific preparation materials and preparation methods refer to the following steps:

[0157] Step I: 0.5 mol of cyclobutane dimethanol, 0.12 mol of dicycloheptane-2,3-dimethanol and 0.46 mol of bicyclooctanedimethanol are added to a reaction kettle, and the temperature is quickly raised to 110° C. to dissolve them at a heating rate of 80° C. / h, and then stirring and nitrogen are turned on, followed by adding 0.53 mol of cyclobutane dicarboxylic acid, 0.14 mol of bicyclooctanedicarboxylic acid, 0.38 mol of cyclohexane diacetic acid and 0.002 mol of monobutyltin oxide, and then the temperature is programmed to 140° C. for esterification reaction at a heating rate of 5.0° C. / h. When the theoretical water output reaches more than 96%, the temperature is raised to 190° C. for reduced pressure polyurethane reaction at a heating rate of 8.3° C. / h, and finally the temperature is lowered to 170° C. to obtain a terminal hydroxyl prepolymer (A9) containing multiple cycloalkyl groups;

[0158] Step II: 0.54 mol of neopentyl glycol, 0.44 mol of borneol and 0.07 mol of 3,6-dihydroxybenzonorbornane are added to the reaction kettle, and the temperature is quickly raised to 110° C. to dissolve them, and then stirring and nitrogen are turned on. Then, 0.48 mol of isophthalic acid, 0.38 mol of nadic anhydride and 0.08 mol of cis-2,3-norbornane dicarboxylic anhydride and 0.0019 mol of monobutyltin oxide are added, and then the temperature is programmed to 230° C. for esterification reaction at a heating rate of 1.1° C. / h. When the theoretical water output reaches more than 96%, 0.1 mol of aurin tricarboxylic acid and 0.05 mol of 1,3,5,7-adamantane tetracarboxylic acid are added at 220° C., and the reaction is kept warm for 3 hours. Finally, the temperature is lowered to 200° C. to obtain a terminal carboxyl prepolymer (B9) containing a borneol structure;

[0159] Step III: Add 1.1 mol of the terminal hydroxyl prepolymer (A9) containing multiple cycloalkyl groups prepared in step I, 1.0 mol of the terminal carboxyl prepolymer (B9) containing a borneol structure prepared in step II and 0.0019 mol of monobutyltin oxide into the reaction kettle, and then program the temperature to 235°C for esterification reaction at a heating rate of 11.0°C / h. When the theoretical water output reaches more than 96%, add 0.026 mol of isomeric ditridecylamine at 205°C. and 0.104 mol of diethylenetriaminepentaacetic acid, keep the temperature for reaction for 1.0 h, then cool to 195°C for reduced pressure polycondensation, the vacuum degree is -0.05 MPa, the reduced pressure polycondensation time is 0.5 h, finally cool to 180°C, add 0.0008 mol of triphenylethylphosphine bromide, 0.0045 mol of antioxidant 1010 and 0.0045 mol of antioxidant 168, and obtain polyester resin for low-temperature curing and high-toughness powder coating.

[0160] The polyester resin had an acid value of 33.4 mgKOH / g, a melt viscosity of 1960 mPa·s (200° C.), and a glass transition temperature of 65.8° C.

[0161] Comparative Example 1

[0162] A polyester resin, wherein the raw materials for preparing the polyester resin do not include a carboxyl-terminated prepolymer containing a borneol structure, and the preparation method comprises the following steps:

[0163] 0.58 mol of cyclobutane dimethanol, 0.15 mol of dicycloheptane-2,3-dimethanol and 0.42 mol of bicyclooctanedimethanol were added to the reactor, and the temperature was quickly raised to 120°C to dissolve them, and the heating rate was 90°C / h. Then stirring and nitrogen were turned on, and then 0.53 mol of cyclobutane dicarboxylic acid, 0.15 mol of bicyclooctanedicarboxylic acid and 0.43 mol of cyclohexane diacetic acid and 0.002 mol of monobutyltin oxide were added, and then the temperature was programmed to 150°C for esterification reaction, and the heating rate was The rate is 8.3℃ / h. When the theoretical water output reaches more than 96%, the temperature is raised to 200℃ for reduced pressure polyurethane reaction at a heating rate of 11.6℃ / h, then raised to 220℃ at a heating rate of 10.0℃ / h, 0.09mol of adipic acid is added for end-capping, and the reaction is kept warm for 4h, and then 0.0011mol of triphenylethylphosphine bromide, 0.0078mol of antioxidant 1076 and 0.0039mol of antioxidant 168 are added, and finally the temperature is lowered to 180℃ to obtain polyester resin.

[0164] The polyester resin had an acid value of 33.5 mgKOH / g, a melt viscosity of 500 mPa·s (130°C), and a melting point of 100°C.

[0165] Comparative Example 2

[0166] A polyester resin, wherein the raw materials for preparing the polyester resin do not include a terminal hydroxyl prepolymer containing one or more cycloalkyl groups, and the preparation method comprises the following steps:

[0167] 0.58 mol of neopentyl glycol, 0.34 mol of bornyl alcohol and 0.08 mol of 3,6-dihydroxybenzonorbornane were added to the reactor, and the temperature was quickly raised to 120°C to dissolve them. Then, stirring and nitrogen were turned on. Then, 0.4 mol of isophthalic acid, 0.35 mol of nadic anhydride and 0.12 mol of cis-2,3-norbornane dicarboxylic anhydride and 0.0019 mol of monobutyltin oxide were added. Then, the temperature was programmed to 240°C for esterification reaction. The heating rate was 1.4°C / h. When the theoretical water output reached more than 96%, 0.09 mol of aurintricarboxylic acid and 0.09 mol of chlorinated ... 1,3,5-cyclohexanetricarboxylic acid was reacted at the temperature for 4 hours, followed by the addition of 0.0011 mol of triphenylethylphosphonium bromide, 0.0078 mol of antioxidant 1076 and 0.0039 mol of antioxidant 168, and finally the temperature was lowered to 210°C to obtain polyester resin.

[0168] The polyester resin had an acid value of 33 mgKOH / g, a melt viscosity of 3500 mPa·s (200° C.), and a glass transition temperature of 64° C.

[0169] Comparative Example 3

[0170] A polyester resin, the preparation method comprises the following steps:

[0171] 0.58 mol of neopentyl glycol, 0.34 mol of bornyl alcohol and 0.08 mol of 3,6-dihydroxybenzonorbornane were added to the reactor, and the temperature was quickly raised to 120°C to dissolve them. Then, stirring and nitrogen were turned on. Then, 0.4 mol of isophthalic acid, 0.35 mol of nadic anhydride and 0.12 mol of cis-2,3-norbornane dicarboxylic anhydride and 0.0019 mol of monobutyltin oxide were added. Then, the temperature was programmed to 240°C for esterification reaction. The heating rate was 1.4°C / h. When the theoretical water output reached more than 96%, 0.09 mol of aurintricarboxylic acid and 0.09 mol of chlorinated ... 1,3,5-cyclohexanetricarboxylic acid was reacted at the temperature for 4 hours, followed by the addition of 0.02 mol of triphenylethylphosphonium bromide, 0.0078 mol of antioxidant 1076 and 0.0039 mol of antioxidant 168, and finally the temperature was lowered to 210°C to obtain polyester resin.

[0172] The polyester resin had an acid value of 33 mgKOH / g, a melt viscosity of 3400 mPa·s (200° C.), and a glass transition temperature of 64.2° C.

[0173] Comparative Example 4

[0174] A polyester resin, the same as that in Example 1, except that:

[0175] In Example 1, the end-capping agent C2 is isophthalic acid, and the other parts remain unchanged, and a polyester resin for low-temperature curing and high-toughness powder coating is synthesized.

[0176] The polyester resin had an acid value of 33.0 mgKOH / g, a melt viscosity of 3550 mPa·s (200° C.), and a glass transition temperature of 66.5° C.

[0177] Comparative Example 5

[0178] A polyester resin, the same as that in Example 1, except that:

[0179] In Example 1, the end-capping agent C2 is N,N,N",N"-tetrabutyldiethylenetriamine, and the other components remain unchanged to synthesize a polyester resin for low-temperature curing and high-toughness powder coating.

[0180] The polyester resin had an acid value of 32.8 mgKOH / g, a melt viscosity of 1560 mPa·s (200° C.), and a glass transition temperature of 64.2° C.

[0181] Comparative Example 6

[0182] A polyester resin, the same as that in Example 1, except that:

[0183] In Example 1, the end-capping agent C2 is isomeric ditridecylamine, and the other components remain unchanged, thereby synthesizing a polyester resin for low-temperature curing and high-toughness powder coating.

[0184] The polyester resin had an acid value of 33.1 mgKOH / g, a melt viscosity of 1640 mPa·s (200° C.), and a glass transition temperature of 64.5° C.

[0185] Comparative Example 7

[0186] A polyester resin, the same as that in Example 1, except that:

[0187] In Example 1, the end-capping agent C2 is diethylenetriaminepentaacetic acid, and the other components remain unchanged, thereby synthesizing a polyester resin for low-temperature curing and high-toughness powder coating.

[0188] The polyester resin had an acid value of 32.5 mgKOH / g, a melt viscosity of 2850 mPa·s (200° C.), and a glass transition temperature of 65.9° C.

[0189] Comparative Example 8

[0190] A polyester resin, the same as that in Example 1, except that:

[0191] In Example 1, the end-capping agent C2 is diethylenetriaminepentaacetic dianhydride, and the other parts remain unchanged, and a polyester resin for low-temperature curing and high-toughness powder coating is synthesized.

[0192] The polyester resin had an acid value of 32.8 mgKOH / g, a melt viscosity of 2650 mPa·s (200° C.), and a glass transition temperature of 65.7° C.

[0193] Performance Testing

[0194] The polyester resins of Examples 1 to 9 and Comparative Examples 1 to 8 were respectively applied to powder coatings, which were sequentially recorded as Application Examples 1 to 9 and Comparative Application Examples 1 to 8. The formulas of the powder coatings are shown in Tables 1 and 2 below.

[0195] Table 1 Application example powder coating formula (unit: g)

[0196]

[0197]

[0198] Table 2 Comparative application example powder coating formula (unit: g)

[0199]

[0200]

[0201] In Table 1 and Table 2, TGIC is triglycidyl isocyanurate, the leveling agent is GLP588 (silicon dioxide adsorbed polyacrylate) of Ningbo Nanhai Chemical, and 701 is an acrylic copolymer containing polar groups. It should be noted that the TGIC, titanium dioxide, barium sulfate, leveling agent, benzoin and 701 used in the above application examples and comparative application examples are all of the same kind.

[0202] The preparation method of the powder coating is as follows: the materials are weighed and premixed according to the polyester resin powder coating formula in Table 1, melt-extruded by a twin-screw extruder, tableted, cooled and crushed, and sieved to obtain the powder coating.

[0203] The powder coating was sprayed on the surface treated tinplate substrate using an electrostatic spray gun and cured at 130°C / 15min to obtain a polyester powder coating.

[0204] The coatings of the powder coatings obtained by using the polyester resins of Examples 1 to 9 and Comparative Examples 1 to 8 were tested, and the test method was as follows:

[0205] Impact strength: Tested in accordance with GB / T 1732-1993;

[0206] Bending test: Tested in accordance with GB / T 6742-2007, expressed in terms of bending shaft diameter. The smaller the shaft diameter, the better the toughness.

[0207] Leveling grade: Leveling performance rating is based on the leveling effect rating standard of the US PCI. The higher the grade, the better the leveling performance.

[0208] Coating appearance: visual observation;

[0209] Boiling performance: Tested in accordance with QUALICOAT standards, boiling water at high pressure for 2 hours, expressed by the degree of light retention rate;

[0210] Storage stability: Tested in accordance with GB / T 21782.8-2008. The lower the grade, the better the storage stability.

[0211] The test results are shown in Tables 3 and 4 below.

[0212] Table 3 Performance test results of application examples 1 to 9

[0213]

[0214] Table 4 Comparison of performance test results of application examples 1 to 8

[0215]

[0216] It can be seen from Table 3 and Table 4 that the powder coating prepared by the polyester resin of the present invention has good comprehensive performance. After low-temperature curing at 130°C, it can simultaneously ensure that the water boiling gloss retention rate is above 90%, the leveling grade is not less than 8, the bending axis diameter does not exceed 3mm, the coating has a flat and smooth appearance, and has good impact strength, that is, good flexibility, and the storage stability is maintained at level 0. Compared with traditional low-temperature curing powder coatings, it also takes into account the performance of leveling, flexibility, appearance and storage stability.

[0217] In Comparative Example 3, since the amount of the curing accelerator triphenylethylphosphonium bromide was changed, the curing speed of the coating was also changed, so the leveling, water boiling resistance and bending properties were all affected.

[0218] In summary, the polyester resin of the present invention has a low melt viscosity and a high glass transition temperature, good leveling and flexibility, and can be cured at low temperature, and is suitable for preparing powder coatings. The obtained powder coatings not only have low temperature curing performance, but also can take into account leveling, flexibility and storage stability compared with conventional low temperature cured polyester powder coatings, and have better comprehensive performance. The powder coating is particularly suitable for coating heat-sensitive substrates, such as wood, plastic and other substrates.

[0219] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A polyester resin, characterized in that The raw materials for preparing the polyester resin include prepolymer A, prepolymer B and a capping agent; the prepolymer A is a terminal hydroxyl prepolymer containing one or more cycloalkyl groups; and the prepolymer B is a terminal carboxyl prepolymer containing a borneol structure.

2. The polyester resin according to claim 1, characterized in that The molar ratio of the prepolymer A to the prepolymer B is (1-1.2):

1.

3. The polyester resin according to claim 1 or 2, characterized in that The end-capping agent includes an end-capping agent C1 and an end-capping agent C2; the end-capping agent C1 contains a carboxyl structure; and the end-capping agent C2 contains an amino structure and / or an aminocarboxyl structure.

4. The polyester resin according to claim 3, characterized in that The end-capping agent C1 includes one or more of cyclopentanetetracarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,3,4-butanetetracarboxylic acid, 1,3,5-pentanetricarboxylic acid, 3,4,9,10-pyrenetetracarboxylic acid, aurinetricarboxylic acid, 1,3,5-cyclohexanetricarboxylic acid, and 1,3,5,7-adamantanetetracarboxylic acid; And / or, the end-capping agent C2 includes one or more of N,N,N",N"-tetrabutyldiethylenetriamine, N,N-dimethyldipropylenetriamine, diethylenetriamine, isomeric ditridecylamine, bis(hexamethylene)triamine, diethylenetriaminepentaacetic acid, and diethylenetriaminepentaacetic dianhydride.

5. The polyester resin according to claim 1, characterized in that The raw materials for preparing the prepolymer A include first alcohols and first acids; the first alcohols include one or more of cyclohexanedimethanol, cyclopropane dimethanol, cyclobutane dimethanol, cyclopentane dimethanol, dicycloheptane-2,3-dimethanol, tricyclodecane dimethanol, and bicyclooctanedimethanol; the first acids include one or more of cyclohexanedicarboxylic acid, cyclopropanedicarboxylic acid, cyclobutanedicarboxylic acid, cyclopentanedicarboxylic acid, bicycloheptane-2,3-dicarboxylic acid, bicyclooctanedicarboxylic acid, and cyclohexanediacetic acid.

6. The polyester resin according to claim 5, characterized in that The raw materials for preparing the prepolymer B include second alcohols and second acids; the second alcohols include one or more of neopentyl glycol, bornyl alcohol, isoborneol, exo-norborneol, 3,6-dihydroxybenzonorbornene, 5-norbornene-2,2-dimethanol, and 5-norbornene-2,3-dimethanol; the second acids include one or more of isophthalic acid, nadic anhydride, 5-norbornene-2-carboxylic acid, exo-5-norbornene carboxylic acid, norbornene-2,3-dicarboxylic acid, cis-2,3-norbornene dicarboxylic anhydride, oxoacid anhydride, and cis-5-norbornene-endo-2,3-dicarboxylic acid.

7. The polyester resin according to claim 5 or 6, characterized in that The molar ratio of the first alcohol to the first acid in the prepolymer A is (1-1.06):1; And / or, the molar ratio of the second alcohol to the second acid in the prepolymer B is (1.05-1.2):

1.

8. A method for preparing a polyester resin according to any one of claims 1 to 7, characterized in that: The steps include: The prepolymer A and the prepolymer B are mixed to carry out an esterification reaction, and after the reaction, the end-capping agent is added to carry out a constant temperature reaction, and then a polycondensation reaction is carried out to obtain the polyester resin.

9. A powder coating, characterized in that: The polyester resin comprises the polyester resin according to any one of claims 1 to 7.

10. Use of the polyester resin according to any one of claims 1 to 7 or the powder coating according to claim 9 in the field of coating of heat-sensitive substrates.

Images