High-leveling storage-resistant polyester resin as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of coatings, and particularly relates to high-leveling storage-resistant polyester resin as well as a preparation method and application thereof. The high-leveling and storage-resistant polyester resin is prepared from the following raw materials: first polyhydric alcohol, second polyhydric alcohol, monohydric alcohol, polybasic acid, monobasic acid and an acidolysis agent. Through interaction of all the components, particularly, the fluorene-containing polyhydric alcohol, the monohydric alcohol and the monobasic acid are rigid high-steric-hindrance monomers, so that the positive correlation limitation between the glass transition temperature and the melting viscosity of the traditional amorphous polyester resin is well overcome to a certain extent, and good balance between the glass transition temperature and the melting viscosity is realized; and the prepared coating has relatively high glass transition temperature and relatively low melt viscosity, so that the prepared coating can give consideration to both storage stability and leveling property, and has good storage stability and leveling property.

Description

Technical Field

[0001] The invention belongs to the technical field of coatings, and particularly relates to a high-leveling, storage-resistant polyester resin and a preparation method and application thereof. Background Art

[0002] Triglycidyl isocyanurate (TGIC) high-leveling powder coating is a high-performance coating widely used on the surface of metal products. Its excellent leveling performance makes the coating surface smooth and flat, providing good decorative and protective properties. It is widely used in home appliances, auto parts, building hardware and other fields.

[0003] Balancing the leveling performance and storage performance of powder coatings has always been a major challenge faced by the industry. Leveling performance is directly related to the smoothness, flatness and aesthetics of the coating surface, and is a key indicator for evaluating the decorative effect of coatings; while storage performance determines the stability of powder coatings during long-term storage, which is crucial to reducing production costs and improving production efficiency. However, these two properties often restrict each other and it is difficult to achieve the optimal state at the same time. The main reason lies in the performance characteristics of polyester resin, the core component of powder coatings. At present, the main raw material of powder coatings is amorphous polyester resin. This type of resin has an inherent characteristic that its glass transition temperature (Tg) and melt viscosity show a positive correlation. This means that in order to obtain a higher Tg to ensure the storage stability of the coating, a higher melt viscosity has to be accepted, thereby sacrificing the leveling performance of the coating; conversely, if a low melt viscosity is pursued to optimize the leveling performance, the Tg will be reduced, affecting the storage stability of the coating. Therefore, it is difficult for amorphous polyester resins to find an ideal balance between the two.

[0004] Therefore, there is an urgent need to provide a polyester resin, the coating prepared by which can take into account both storage stability and leveling properties and has good storage stability and leveling properties. Summary of the invention

[0005] The present invention aims to solve one or more technical problems existing in the above-mentioned prior art, and at least provide a beneficial choice or create conditions. Specifically, the present invention provides a polyester resin, and the coating prepared by the polyester resin can take into account both storage stability and leveling properties, and has good storage stability and leveling properties.

[0006] The inventive concept of the present invention: The raw materials for preparing the high-leveling, storage-resistant polyester resin of the present invention include a first polyol, a second polyol, a monool, a polyacid, a monoacid, and an acidolysis agent, and the second polyol, the monool, and the monoacid are selected from specific types. The present invention overcomes the positive correlation limitation between the glass transition temperature and the melt viscosity of the traditional amorphous polyester resin by selecting specific types of second polyols, monools, and monoacids that have both rigidity and high steric hindrance properties, and through the interaction of each component, achieves a good balance between the two, has a higher glass transition temperature and a lower melt viscosity, so that the prepared coating can take into account both storage stability and leveling properties, and has good storage stability and leveling performance.

[0007] Therefore, a first aspect of the present invention provides a high-leveling, storage-resistant polyester resin.

[0008] Specifically, the raw materials for preparing the high-leveling and storage-resistant polyester resin include a first polyol, a second polyol, a monohydric alcohol, a polyacid, a monoacid, and an acidolysis agent;

[0009] The second polyol is a fluorene-containing polyol;

[0010] The monohydric alcohol is at least one selected from 9-hydroxyfluorene, 2-benzyloxyethanol, cyclododecanol, 9-phenyl-9-fluorenol, 4-isopropylbenzyl alcohol, p-fluorobenzyl alcohol, and m-methoxybenzyl alcohol;

[0011] The monoacid is selected from at least one of 9-fluorenecarboxylic acid, p-toluic acid, p-tert-butylbenzoic acid, 2,4-dimethylbenzoic acid, 3,4-dimethylbenzoic acid, 3-trifluoromethylbenzoic acid, 3-phenylpropionic acid, 4-phenylbutyric acid, 2,2-diphenylacetic acid, 4-phenylbenzoic acid, and cyclohexanecarboxylic acid.

[0012] Preferably, the second polyol is at least one selected from 9,9-fluorenedimethanol, 9,9-fluorenediethanol, and 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene.

[0013] Specifically, the second polyol is a fluorene-containing monomer. The present invention innovatively introduces a fluorene-containing rigid high steric hindrance monomer as a key component. The fluorene group, with its unique conjugated benzene ring structure, significantly enhances the rigidity of the polyester resin chain and effectively maintains the high glass transition temperature (Tg) of the polyester resin, thereby giving the powder coating excellent storage stability. In addition, the non-coplanar structural characteristics of fluorene make its suspended benzene ring side groups and the main chain present a vertical skew spatial conformation. This structural feature not only increases the spacing between polyester molecular chains and reduces the mutual entanglement between molecular chains, but also significantly reduces the viscosity of the polyester resin, so that the powder coating of the present invention has good leveling performance while maintaining good storage stability.

[0014] Specifically, the present invention introduces monohydric alcohol and monoacid with both rigidity and high steric hindrance characteristics, which can effectively reduce the resin viscosity and significantly enhance the leveling performance of the coating without sacrificing the Tg of the polyester resin and ensuring the storage stability of the coating. By accurately regulating the monofunctional monomer, the molecular weight of the polyester resin is finely controlled, and the processing performance of the coating is further improved. In addition, by utilizing the competition and steric hindrance effect between the monoacid and the acidolysis agent, the activity of the polyester resin end group is reduced, the melt leveling time is prolonged, and a smooth, uniform and high-performance coating surface can be formed after curing.

[0015] Preferably, the first polyol is selected from at least one of ethylene glycol, propylene glycol, diethylene glycol, methyl propanediol, neopentyl glycol, butylene glycol, 1,2-propylene glycol, 1,4-cyclohexanedimethanol, isosorbide, 2-methyl-2,4-pentanediol, ethyl butyl propanediol, trimethylolpropane, and pentaerythritol.

[0016] Preferably, the polyacid is selected from at least one of terephthalic acid, isophthalic acid, cyclohexanedicarboxylic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, dodecanedioic acid, phthalic anhydride and trimellitic anhydride.

[0017] Preferably, the acidolysis agent is selected from at least one of isophthalic acid, cyclohexanedicarboxylic acid, succinic acid, adipic acid, dodecanedioic acid, trimellitic anhydride, 9,9-bis(3,4-dicarboxyphenyl)fluorene anhydride, pyromellitic anhydride, and phenylmalonic acid.

[0018] Preferably, the raw materials for preparing the high-leveling, storage-resistant polyester resin include, by weight, 15-40 parts of a first polyol, 1-20 parts of a second polyol, 0.5-5 parts of a monohydric alcohol, 40-60 parts of a polyacid, 0.5-5 parts of a monoacid, and 5-15 parts of an acidolysis agent.

[0019] Further preferably, the raw materials for preparing the high-leveling, storage-resistant polyester resin include, by weight, 15-38 parts of a first polyol, 1-18 parts of a second polyol, 1-5 parts of a monohydric alcohol, 40-58 parts of a polyacid, 0.8-5 parts of a monoacid, and 5-13 parts of an acidolysis agent.

[0020] Preferably, the raw materials for preparing the high-leveling, storage-resistant polyester resin further include at least one of a catalyst and a curing accelerator.

[0021] Preferably, the raw materials for preparing the high-leveling, storage-resistant polyester resin also include an esterification catalyst and a curing accelerator, and in parts by weight, the raw materials for preparing the high-leveling, storage-resistant polyester resin include 15-40 parts of a first polyol, 1-20 parts of a second polyol, 0.5-5 parts of a monohydric alcohol, 40-60 parts of a polyacid, 0.5-5 parts of a monoacid, 5-15 parts of an acidolysis agent, 0.0001-0.002 parts of a catalyst, and 0.00010-0.0015 parts of a curing accelerator.

[0022] Further preferably, the raw materials for preparing the high-leveling, storage-resistant polyester resin also include an esterification catalyst and a curing accelerator, and in parts by weight, the raw materials for preparing the high-leveling, storage-resistant polyester resin include 15-38 parts of a first polyol, 1-18 parts of a second polyol, 1-5 parts of a monohydric alcohol, 40-58 parts of a polyacid, 0.8-5 parts of a monoacid, 5-13 parts of an acidolysis agent, 0.0001-0.0018 parts of a catalyst, and 0.00010-0.0012 parts of a curing accelerator.

[0023] Preferably, the catalyst comprises an esterification catalyst.

[0024] Preferably, the esterification catalyst includes at least one of a tin catalyst, a zinc catalyst, a bismuth catalyst and a titanium catalyst.

[0025] Preferably, the tin catalyst includes at least one of monobutyltin oxide, monobutyltin chloride, stannous oxalate, stannous octoate, stannous chloride, dibutyltin dilaurate, stannous octoate, dibutyltin didodecylsulfide, and dibutyltin diacetate.

[0026] Preferably, the zinc catalyst includes at least one of zinc isooctanoate and zinc oxalate.

[0027] Preferably, the bismuth catalyst comprises bismuth oxide.

[0028] Preferably, the titanium catalyst comprises n-butyl titanate.

[0029] Preferably, the curing accelerator includes at least one of triphenylethylphosphine bromide and triphenylphosphine.

[0030] Preferably, the acid value of the polyester resin is 24-40 mgKOH / g; more preferably, the acid value of the polyester resin is 26-40 mgKOH / g.

[0031] Preferably, the melt viscosity of the polyester resin is 1500-7000 mPa·s, and the glass transition temperature of the polyester resin is 58-80°C; further preferably, the melt viscosity of the polyester resin is 1800-6000 mPa·s, and the glass transition temperature of the polyester resin is 60-75°C.

[0032] Preferably, the number average molecular weight of the polyester resin is 1800-8000 g / mol; further preferably, the number average molecular weight of the polyester resin is 2000-7000 g / mol.

[0033] The second aspect of the present invention provides a method for preparing the high-leveling, storage-resistant polyester resin according to the first aspect of the present invention.

[0034] Specifically, the method for preparing the high-leveling and storage-resistant polyester resin comprises the following steps:

[0035] The raw material components are mixed and reacted to obtain the high-leveling and storage-resistant polyester resin.

[0036] Preferably, the method for preparing the high-leveling, storage-resistant polyester resin comprises the following steps:

[0037] (1) mixing the first polyol, the second polyol, the monohydric alcohol, and the polyacid, and reacting them to obtain a mixed material 1;

[0038] (2) mixing the mixed material 1 obtained in step (1) with the acidolysis agent and the monobasic acid, and reacting them to obtain a mixed material 2;

[0039] (3) The mixed material 2 obtained in step (2) is subjected to polycondensation to obtain the high-leveling, storage-resistant polyester resin.

[0040] Preferably, the reaction in step (1) is an esterification polycondensation reaction, and the esterification polycondensation reaction is carried out in the presence of an esterification catalyst.

[0041] Preferably, in step (1), the reaction temperature is 60-280°C, and the reaction time is 6-24h; further preferably, the reaction temperature is 60-260°C, and the reaction time is 8-24h.

[0042] Preferably, in step (2), the reaction temperature is 150-260°C, and the reaction time is 0.5-10h; further preferably, the reaction temperature is 150-250°C, and the reaction time is 0.5-10h.

[0043] Preferably, in step (3), the polycondensation is vacuum polycondensation.

[0044] Preferably, in step (3), the temperature of the vacuum polycondensation is 180-270°C, the vacuum degree is -0.08 to -0.099 MPa, and the time of the vacuum polycondensation is 25-260 min; further preferably, the temperature of the vacuum polycondensation is 200-250°C, the vacuum degree is -0.09 to -0.099 MPa, and the time of the vacuum polycondensation is 30-240 min.

[0045] Preferably, in step (3), the acid value of the system after the vacuum polycondensation is 25-40 mgKOH / g; further preferably, the acid value of the system after the vacuum polycondensation is 26-40 mgKOH / g.

[0046] Preferably, in step (3), after the vacuum polycondensation is completed, a curing accelerator is added to obtain the polyester resin.

[0047] A third aspect of the present invention provides a coating.

[0048] Specifically, the coating comprises the high-leveling, storage-resistant polyester resin described in the first aspect of the present invention.

[0049] Preferably, the coating is a powder coating.

[0050] Preferably, the coating further comprises a curing agent, a pigment, a filler and an auxiliary agent.

[0051] Preferably, the coating comprises, by weight, 50-75 parts of a high-leveling, storage-resistant polyester resin, 4.5-11 parts of a curing agent, 13-45 parts of a pigment and filler, and 0.25-5.5 parts of an auxiliary agent.

[0052] Further preferably, the coating comprises, by weight, 55-70 parts of a high-leveling, storage-resistant polyester resin, 5-10 parts of a curing agent, 15-40 parts of a pigment and filler, and 0.3-5 parts of an auxiliary agent.

[0053] Preferably, the curing agent is selected from at least one of triglycidyl isocyanurate and hydroxyalkylamide.

[0054] Specifically, the types and amounts of the pigments, fillers and additives can be determined according to actual needs in combination with the commonly used techniques in the field; the powder coating can also contain brighteners, pinhole eliminators or other additives as needed, and their types and amounts can also be determined according to actual needs in combination with the commonly used techniques in the field, without any special limitation.

[0055] Preferably, the pigment and filler include at least one of titanium dioxide and barium sulfate.

[0056] Preferably, the auxiliary agent includes at least one of a leveling agent, a brightening agent, and a pinhole eliminating agent.

[0057] The leveling agent includes at least one of an acrylic leveling agent, a silicone leveling agent, and a fluorocarbon leveling agent; more preferably, the leveling agent includes an acrylic leveling agent, such as the leveling agent GLP588.

[0058] Preferably, the brightener includes at least one of an acrylate brightener and a silicone brightener. Further preferably, the brightener includes an acrylate brightener, such as brightener 701.

[0059] Preferably, the pinhole eliminating agent includes benzoin.

[0060] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0061] (1) The raw materials for preparing the high-leveling, storage-resistant polyester resin of the present invention include a first polyol, a second polyol, a monohydric alcohol, a polyacid, a monoacid, and an acidolysis agent. The present invention overcomes the positive correlation limitation between the glass transition temperature and the melt viscosity of the traditional amorphous polyester resin through the interaction of the components, achieves a good balance between the two, has a higher glass transition temperature and a lower melt viscosity, so that the prepared coating can take into account both storage stability and leveling properties, and has good storage stability and leveling performance.

[0062] (2) The present invention innovatively introduces a rigid high steric hindrance monomer containing fluorene, which can significantly reduce the viscosity of the polyester resin while giving the powder coating good storage stability, so that the powder coating can take into account both leveling performance and storage stability, and has good leveling performance and storage stability. In addition, the monohydric alcohol and monoacid of the present invention are also rigid high steric hindrance monomers, which can effectively reduce the viscosity of the resin and improve the leveling performance of the coating without sacrificing the Tg of the polyester resin. At the same time, the monoacid can compete with the acidolysis agent, reduce the activity of the polyester resin end group, reduce the reaction activity of the polyester resin, and prolong the melt leveling time, so that the coating has good leveling performance.

[0063] (3) The preparation process of the present invention is simple and convenient for large-scale production and application. DETAILED DESCRIPTION

[0064] In order to make the technical scheme of the present invention more clearly understood by those skilled in the art, the following embodiments are listed for illustration. It should be pointed out that the following embodiments do not limit the protection scope of the present invention.

[0065] Unless otherwise specified, the raw materials, reagents or devices used in the following examples can be obtained from conventional commercial sources or by existing known methods.

[0066] The raw material components and amounts of the high-leveling, storage-resistant polyester resins of Examples 1-4 of the present invention are shown in Table 1.

[0067] Table 1: Raw material components and dosages (parts by weight) of high-leveling, storage-resistant polyester resins of Examples 1-4

[0068]

[0069] In Table 1, “-” means no addition.

[0070] Example 1

[0071] A high-leveling, storage-resistant polyester resin, whose raw material components and amounts are shown in Table 1 in parts by weight.

[0072] A method for preparing a high-leveling, storage-resistant polyester resin comprises the following steps:

[0073] (1) Add the first polyol, the second polyol and the monool into a reaction kettle, control the temperature in the kettle to 100° C., stir and melt, add the polyacid and the esterification catalyst after the materials are completely melted, gradually increase the temperature to 250° C. and keep the temperature for 2 hours until no obvious distillate is evaporated, to obtain a mixed material 1;

[0074] (2) adding an acidolysis agent and a monobasic acid to the mixed material obtained in step (1) in sequence, reacting at a temperature of 235° C. for 2 h until the acid value of the reactant reaches 46 mgKOH / g, to obtain a mixed material 2;

[0075] (3) The mixture 2 obtained in step (2) was cooled to 230° C., reacted at −0.098 MPa for 2 h until the acid value of the reactant reached 32.9 mgKOH / g, a curing accelerator was added, stirred for 30 min, and discharged to obtain a polyester resin with high leveling and storage resistance.

[0076] Example 2

[0077] A high-leveling, storage-resistant polyester resin, whose raw material components and amounts are shown in Table 1 in parts by weight.

[0078] In step (3) of the method for preparing a high-leveling, storage-resistant polyester resin in Example 2, the reaction is carried out at a temperature of 235° C. for 2 h (the vacuum degree is −0.096 MPa), and the acid value is controlled at 33.8 mg KOH / g. The rest is the same as in Example 1.

[0079] Example 3

[0080] A high-leveling, storage-resistant polyester resin, whose raw material components and amounts are shown in Table 1 in parts by weight.

[0081] In step (3) of the method for preparing a high-leveling, storage-resistant polyester resin in Example 3, the reaction is carried out at a temperature of 228° C. for 3 h (the vacuum degree is −0.096 MPa), and the acid value is controlled at 32.8 mg KOH / g. The rest is the same as in Example 1.

[0082] Example 4

[0083] A high-leveling, storage-resistant polyester resin, whose raw material components and amounts are shown in Table 1 in parts by weight.

[0084] In step (3) of the method for preparing a high-leveling, storage-resistant polyester resin in Example 4, the reaction is carried out at a temperature of 240° C. for 1 h (the vacuum degree is −0.096 MPa), and the acid value is controlled at 33.4 mgKOH / g. The rest is the same as in Example 1.

[0085] Comparative Example 1

[0086] The difference between Comparative Example 1 and Example 1 is that Comparative Example 1 uses an equal molar amount of neopentyl glycol to replace the second polyol 9,9-fluorenedimethanol, and the rest is the same as Example 1.

[0087] Comparative Example 2

[0088] The difference between Comparative Example 2 and Example 2 is that Comparative Example 2 uses an equal molar amount of neopentyl glycol to replace monohydric alcohol 9-hydroxyfluorene, and the rest is the same as Example 2.

[0089] Comparative Example 3

[0090] The difference between Comparative Example 3 and Example 3 is that Comparative Example 3 uses an equimolar amount of isophthalic acid to replace the monoacid p-tert-butylbenzoic acid, and the rest is the same as Example 3.

[0091] Comparative Example 4

[0092] Comparative Example 4 is a commercially available polyester resin NH3309 specially used for high-leveling powder coatings, purchased from Qingtian Material Technology Co., Ltd., with an acid value of 33 mgKOH / g and a viscosity of 3700 mPa·s.

[0093] Performance Testing

[0094] 1. Test of acid value, viscosity and glass transition temperature of polyester resin

[0095] According to T / GDTL 004-2019 standard, the acid value, viscosity and glass transition temperature of the polyester resins prepared in Examples 1-4 and Comparative Examples 1-4 were tested, and the results are shown in Table 2.

[0096] Table 2: Acid value, viscosity, glass transition temperature of polyester resins of Examples 1-4 and Comparative Examples 1-4

[0097]

[0098] It can be seen from Table 2 that the glass transition temperature of the polyester resin of the present invention is relatively high, all above 65°C, which ensures good storage stability of the powder coating, and the viscosity of the polyester resin is relatively low, which to a certain extent overcomes the positive correlation contradiction between the glass transition temperature and melt viscosity of traditional amorphous polyester, and achieves a good balance between the two. This characteristic enables the coating to have both good storage stability and leveling performance.

[0099] Although the glass transition temperatures of Comparative Examples 2 and 3 are higher than that of Example 1, their viscosities at 200° C. are also significantly higher than that of Example 1. Comparative Examples 2 and 3 cannot take into account both storage stability and leveling performance.

[0100] The glass transition temperatures of Comparative Examples 1 and 4 are lower than those of Example 1, and the viscosities at 200° C. are also higher than those of Example 1, so that Comparative Examples 2 and 3 cannot simultaneously take into account both storage stability and leveling performance.

[0101] 2. Coating performance test

[0102] Take 279 parts of each of the polyester resins of Examples 1-4, Comparative Examples 1-3, and the commercially available product of Comparative Example 4, and mix them evenly with 21 parts of triglycidyl isocyanurate (TGIC), 100 parts of titanium dioxide, 92 parts of barium sulfate, 2 parts of benzoin, 5 parts of Nanhai Chemical leveling agent GLP588, and 2 parts of Nanhai Chemical brightener 701, respectively, and use a screw extruder to melt, extrude, tablet, and crush, and crush the tablets to a 200-mesh screen to obtain a powder coating. The process parameters of the screw extruder are controlled as follows: the temperature of zone 1 is 100°C, the temperature of zone 2 is 105°C, and the screw speed is 40Hz.

[0103] The prepared powder coating was sprayed on the tinplate with degreasing and rust removal by using an electrostatic spray gun. The spraying parameters were: electrostatic voltage 70 kV, powder feeding pressure 0.05 MPa. After baking and curing at 200 ° C for 10 minutes, a coating with a thickness of 75 to 80 μm was obtained. Then the performance test was carried out. The test results are shown in Table 3.

[0104] Among them, the test items and test methods are as follows:

[0105] Surface appearance: visual inspection;

[0106] Storage stability: Tested in accordance with GB / T 21782.8-2008, the baking condition of the powder coating is 40°C / 7 days, and the storage stability of the powder coating is determined by the agglomeration level. The larger the number from 0 to 3, the worse the storage stability.

[0107] Glossiness (%): Tested in accordance with GB / T 9754-2007 standard, with an incident angle of 60°;

[0108] Impact performance (50cm): tested in accordance with T / GDTL004-2019 standard;

[0109] Horizontal fluidity (mm): tested in accordance with GB 6554-1986 standard;

[0110] Leveling: The PCI leveling grade standard board is used for comparison and rating. The larger the number, the better the leveling.

[0111] Among the above test items, storage stability and horizontal fluidity are tested for powder coatings, and other test items are tested for coatings.

[0112] Table 3: Performance test results of powder coatings prepared from the polyester resins of Examples 1-4, Comparative Examples 1-3, and the commercially available product of Comparative Example 4

[0113]

[0114] It can be seen from the test results in Table 3 that the coating obtained by the polyester resin of the present invention has good leveling performance, surface appearance and mechanical properties, the coating has high gloss, the PCI leveling grade is above level 7, the horizontal flow is above 30 mm, and the coating is baked at 40° C. for 7 days without agglomeration. At the same time, it has good leveling performance and storage stability.

[0115] Since no fluorene-containing polyol was added to Comparative Example 1, the glass transition temperature of the polyester resin synthesized in Comparative Example 1 was significantly lower than that in Example 1, and thus the leveling performance of the coating in Comparative Example 1 was worse than that in Example 1. This indicates that the fluorene-containing compound has the effect of simultaneously improving the rigid chain structure of the polyester resin and reducing the viscosity of the polyester, and thus the coating has both good leveling performance and storage stability.

[0116] Comparative Example 2 uses an equal amount of neopentyl glycol to replace 9-hydroxyfluorene. Although the polyester resin synthesized in Comparative Example 2 also has a higher glass transition temperature and thus has good storage stability, the appearance, gloss and leveling properties of the coating of Comparative Example 2 are significantly worse than those of Example 2, that is, Comparative Example 2 cannot take into account both leveling performance and storage stability. This indicates that monohydric alcohol 9-hydroxyfluorene has a significant end-capping effect, which can effectively regulate the functionality of the polyester resin, reduce the viscosity of the polyester resin, and ensure the storage stability of the coating while also allowing the coating to have excellent leveling properties.

[0117] Comparative Example 3 uses an equal amount of isophthalic acid to replace the monoacid p-tert-butylbenzoic acid, so that the leveling performance of Comparative Example 3 is worse than that of Example 3. Because when p-tert-butylbenzoic acid is absent, the functionality of the polyester resin is high, the melt viscosity is large, and the coating reaction speed is too fast, which greatly affects the leveling performance of the coating. The use of high steric hindrance monoacids such as p-tert-butylbenzoic acid can not only maintain the high viscosity of the polyester resin through the high steric hindrance effect to ensure the glass transition temperature, but also compete with the acidolysis agent to reduce the reactivity of the polyester resin and prolong the melt leveling time, so that the coating has good leveling performance.

[0118] Comparative Example 4 uses a conventional polyester resin on the market. Since it does not have a fluorene group and a capping structure, the leveling performance, glossiness, and storage stability of the coating obtained therefrom are significantly inferior to those of the coating prepared by the polyester resin of the present invention.

[0119] In summary, the fluorene-containing polyol, monohydric alcohol and monoacid of the present invention are all rigid high steric hindrance monomers, which work together to successfully overcome the positive correlation limitation between the glass transition temperature and melt viscosity of traditional amorphous polyester resins, and achieve a good balance between the two. Without sacrificing the glass transition temperature of the polyester resin, the resin viscosity can be effectively reduced and the leveling performance of the coating can be improved, so that the coating can have good storage stability and leveling performance at the same time.

[0120] The above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A polyester resin, characterized in that The raw materials for its preparation include a first polyol, a second polyol, a monool, a polyacid, a monoacid, and an acidolysis agent; The second polyol is a fluorene-containing polyol; The monohydric alcohol is at least one selected from 9-hydroxyfluorene, 2-benzyloxyethanol, cyclododecanol, 9-phenyl-9-fluorenol, 4-isopropylbenzyl alcohol, p-fluorobenzyl alcohol, and m-methoxybenzyl alcohol; The monoacid is selected from at least one of 9-fluorenecarboxylic acid, p-toluic acid, p-tert-butylbenzoic acid, 2,4-dimethylbenzoic acid, 3,4-dimethylbenzoic acid, 3-trifluoromethylbenzoic acid, 3-phenylpropionic acid, 4-phenylbutyric acid, 2,2-diphenylacetic acid, 4-phenylbenzoic acid, and cyclohexanecarboxylic acid.

2. The polyester resin according to claim 1, characterized in that The first polyol is selected from at least one of ethylene glycol, propylene glycol, diethylene glycol, methyl propanediol, neopentyl glycol, butylene glycol, 1,2-propylene glycol, 1,4-cyclohexanedimethanol, isosorbide, 2-methyl-2,4-pentanediol, ethyl butyl propanediol, trimethylolpropane, and pentaerythritol.

3. The polyester resin according to claim 1, characterized in that The polyacid is selected from at least one of terephthalic acid, isophthalic acid, cyclohexanedicarboxylic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, dodecanedioic acid, phthalic anhydride and trimellitic anhydride; And / or, the acidolysis agent is selected from at least one of isophthalic acid, cyclohexanedicarboxylic acid, succinic acid, adipic acid, dodecanedioic acid, trimellitic anhydride, 9,9-bis(3,4-dicarboxyphenyl)fluorene anhydride, pyromellitic anhydride, and phenylmalonic acid.

4. The polyester resin according to claim 1, characterized in that By weight, the raw materials for preparing the polyester resin include 15-40 parts of a first polyol, 1-20 parts of a second polyol, 0.5-5 parts of a monohydric alcohol, 40-60 parts of a polyacid, 0.5-5 parts of a monoacid, and 5-15 parts of an acidolysis agent.

5. The polyester resin according to any one of claims 1 to 4, characterized in that The raw materials for preparing the polyester resin also include at least one of a catalyst and a curing accelerator.

6. The polyester resin according to claim 5, characterized in that The raw materials for preparing the polyester resin also include a catalyst and a curing accelerator, and by weight, the raw materials for preparing the polyester resin include 15-40 parts of a first polyol, 1-20 parts of a second polyol, 0.5-5 parts of a monohydric alcohol, 40-60 parts of a polyacid, 0.5-5 parts of a monoacid, 5-15 parts of an acidolysis agent, 0.0001-0.002 parts of a catalyst, and 0.00010-0.0015 parts of a curing accelerator.

7. The polyester resin according to any one of claims 1 to 4, characterized in that The acid value of the polyester resin is 24-40 mgKOH / g; and / or the melt viscosity of the polyester resin is 1500-7000 mPa·s, the glass transition temperature of the polyester resin is 58-80° C.; and / or the number average molecular weight of the polyester resin is 1800-8000 g / mol.

8. The method for preparing a polyester resin according to any one of claims 1 to 7, characterized in that: The following steps are involved: The various raw material components are mixed and reacted to obtain the polyester resin.

9. The preparation method according to claim 8, characterized in that: The following steps are involved: (1) mixing the first polyol, the second polyol, the monohydric alcohol, and the polyacid, and reacting them to obtain a mixed material 1; (2) mixing the mixed material 1 obtained in step (1) with the acidolysis agent and the monobasic acid, and reacting them to obtain a mixed material 2; (3) The mixed material 2 obtained in step (2) is subjected to polycondensation to obtain the polyester resin.

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

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