A polyester resin for high-gloss powder coating and a method for preparing the same

Abstract

The application relates to the technical field of high polymer materials, and discloses a polyester resin for high-gloss powder coating and a preparation method thereof.The polyester resin for high-gloss powder coating comprises the following preparation raw materials: aliphatic polyol, S(-)-1,1-diphenyl-1,2-propanediol and a first polyacid composition; the first polyacid composition comprises diphenyldicarboxylic acid and bio-based dibasic acid.The polyester resin for high-gloss powder coating provided by the application can reduce the entanglement of polyester resin molecular chains and greatly improve the reflection of polyester resin to light by introducing S(-)-1,1-diphenyl-1,2-propanediol, diphenyldicarboxylic acid and bio-based dibasic acid into the main chain structure, so that the powder coating prepared by using the polyester resin can form a high-gloss coating, and has good storage stability and weather resistance; the use of bio-based dibasic acid can also reduce the dependence on traditional petrochemical raw materials.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high polymer materials, in particular to a polyester resin for high-gloss powder coating and a preparation method thereof. BACKGROUND

[0002] Powder coating is a new type of solid coating, which does not contain solvent and is more in line with environmental protection requirements, and is widely used in the fields of household appliances, automobiles, aluminum profiles and the like. According to the gloss of the coating layer, powder coating can be divided into high-gloss powder coating and matt powder coating. In the field of high-gloss coating, powder coating still has certain gap compared with traditional paint in terms of surface decoration, mainly manifested in insufficient leveling and insufficient gloss.

[0003] Polyester resin is the main raw material of powder coating and is the key component for making the coating film have high gloss. CN103613744A discloses a polyester resin for TGIC-cured high-adhesion high-leveling powder coating and a preparation method thereof, which can make the coating layer have high leveling, but the gloss of the coating layer is not high enough, being below 94%. CN102127212A discloses a carboxyl-terminated polyester resin for weather-resistant high-gloss powder coating and a preparation method thereof, which can make the gloss of the coating layer reach between 96-98%, but the glass transition temperature of the polyester resin is not high enough and the storage property is not good enough. CN103642014A discloses a polyester resin for epoxy-cured high-gloss high-leveling powder coating and a preparation method thereof, which can make the coating layer have high gloss, but it uses epoxy resin as a curing agent, and the weather resistance of the coating layer is not enough, mainly being applied indoors. It is of great significance to provide a polyester resin which can make the coating layer have high gloss, excellent storage stability and weather resistance, and to broaden the application range of powder coating. SUMMARY

[0004] The present application aims at solving at least one of the above technical problems existing in the prior art. To this end, one of the objects of the present application is to provide a polyester resin for high-gloss powder coating; the second object of the present application is to provide a preparation method of the polyester resin for high-gloss powder coating; the third object of the present application is to provide a high-gloss powder coating; the fourth object of the present application is to provide a coating layer; the fifth object of the present application is to provide the application of the polyester resin for high-gloss powder coating or the high-gloss powder coating.

[0005] The basic principle of the present application is described as follows:

[0006] The introduction of S(-)-1,1-diphenyl-1,2-propanediol, diphenyldicarboxylic acid and bio-based dibasic acid into the main chain structure of the polyester resin can reduce the entanglement of the polyester resin molecular chain, improve the rigidity of the polyester resin and greatly improve the reflection of the polyester resin to light.

[0007] To achieve the above object, the technical scheme adopted by the present application is:

[0008] The first aspect of the present application provides a polyester resin for high-gloss powder coating, comprising the following preparation raw materials: aliphatic polyol, S(-)-1,1-diphenyl-1,2-propanediol and first polybasic acid composition; the first polybasic acid composition comprises biphenyldicarboxylic acid and bio-based dibasic acid.

[0009] Preferably, the aliphatic polyol comprises neopentyl glycol, or is at least one of neopentyl glycol and 1,4-cyclohexane dimethanol, 1,2-butanediol, 1,4-butanediol, 1,6-hexanediol; further preferably, the aliphatic polyol comprises neopentyl glycol, or is at least one of neopentyl glycol and 1,4-cyclohexane dimethanol, 1,2-butanediol.

[0010] Preferably, the mass percentage of neopentyl glycol in the aliphatic polyol is ≥85%; further preferably, the mass percentage of neopentyl glycol in the aliphatic polyol is 85-97%.

[0011] Preferably, the mass ratio of biphenyldicarboxylic acid to bio-based dibasic acid is 1:(0.5-8); further preferably, the mass ratio of biphenyldicarboxylic acid to bio-based dibasic acid is 1:(0.75-7).

[0012] Preferably, the bio-based dibasic acid comprises at least one of 2,5-furandicarboxylic acid, itaconic acid, maleic acid, fumaric acid, citraconic acid; further preferably, the bio-based dibasic acid is 2,5-furandicarboxylic acid. The introduction of furandicarboxylic acid can give the coating better fullness, helping the coating to show higher gloss.

[0013] Preferably, the preparation raw materials of the polyester resin for high-gloss powder coating further comprise second polybasic acid, acidolysis agent, esterification catalyst and curing accelerator.

[0014] Preferably, the second polybasic acid comprises terephthalic acid, or is at least one of terephthalic acid and adipic acid, succinic acid, isophthalic acid, 1,4-cyclohexane dicarboxylic acid; further preferably, the second polybasic acid comprises terephthalic acid, or is at least one of terephthalic acid and adipic acid, succinic acid.

[0015] Preferably, the mass percentage of terephthalic acid in the second polybasic acid is ≥90%; further preferably, the mass percentage of terephthalic acid in the second polybasic acid is 95-100%.

[0016] Preferably, the acidolysis agent comprises at least one of isophthalic acid, 1,4-cyclohexane dicarboxylic acid, pyromellitic acid.

[0017] Preferably, the esterification catalyst comprises at least one of monobutyl tin dichloride, monobutyl tin oxide, tin oxalate, germanium dioxide, active titanium dioxide, organic titanium phosphorus complex.

[0018] Preferably, the curing promoter comprises at least one of triphenylbutyl phosphonium bromide, benzyl tributyl ammonium chloride.

[0019] Preferably, the high-gloss powder coating polyester resin comprises the following raw materials in percentage by mass: 20-35% aliphatic polyol, 2-8% S(-)-1,1-diphenyl-1,2-propanediol, 4-15% first polyacid, 35-60% second polyacid, 5-15% acidolysis agent, 0.1-0.5% esterification catalyst, 0.01-0.1% curing promoter; further preferably, the high-gloss powder coating polyester resin comprises the following raw materials: 23-33% aliphatic polyol, 2-6% S(-)-1,1-diphenyl-1,2-propanediol, 4-11% first polyacid, 35-56% second polyacid, 5-13% acidolysis agent, 0.1-0.2% esterification catalyst, 0.01-0.05% curing promoter.

[0020] Preferably, the acid value of the high-gloss powder coating polyester resin is 30-40 mgKOH / g; further preferably, the acid value of the high-gloss powder coating polyester resin is 30-36 mgKOH / g.

[0021] Preferably, the melt viscosity of the high-gloss powder coating polyester resin at 200℃ is 4000-8000 mPa·s; further preferably, the melt viscosity of the high-gloss powder coating polyester resin at 200℃ is 5000-7000 mPa·s.

[0022] The second aspect of the present application provides a preparation method of the high-gloss powder coating polyester resin according to the first aspect of the present application, comprising the following steps:

[0023] S1, mixing aliphatic polyol, S(-)-1,1-diphenyl-1,2-propanediol, diphenyldicarboxylic acid, and second polyacid, adding esterification catalyst, and performing polycondensation reaction to obtain an esterification product;

[0024] S2, mixing the esterification product with bio-based dibasic acid, adding acidolysis agent for further reaction to obtain an acidolysis product;

[0025] S3, performing vacuum polycondensation reaction on the acidolysis product, adding curing promoter to obtain the high-gloss powder coating polyester resin.

[0026] Preferably, in the step S1, the aliphatic polyol, S(-)-1,1-diphenyl-1,2-propanediol are mixed and heated to melt, and then the diphenic acid, the second polybasic acid and the esterification catalyst are added.

[0027] Preferably, the heating and melting includes heating to 130-140℃ and holding for 25-35min; further preferably, the heating and melting includes heating to 133-137℃ and holding for 28-32min.

[0028] Preferably, in the step S1, the polycondensation reaction is carried out in a protective atmosphere; the protective atmosphere includes helium.

[0029] Preferably, the conditions of the polycondensation reaction include heating to 240-250℃ and holding for 2-7h; further preferably, the conditions of the polycondensation reaction include heating to 242-246℃ and holding for 2-6h.

[0030] Preferably, in the step S1, the acid value of the esterification product is 8-15mgKOH / g; further preferably, the acid value of the esterification product is 8-12mgKOH / g.

[0031] Preferably, in the step S2, after the temperature of the reaction system is reduced to 220-230℃, the esterification product is mixed with the bio-based dibasic acid for 1-4h; further preferably, after the temperature of the reaction system is reduced to 220-225℃, the esterification product is mixed with the bio-based dibasic acid for 1-3h.

[0032] Preferably, in the step S2, the acid value of the product obtained by mixing the esterification product with the bio-based dibasic acid is 15-20mgKOH / g.

[0033] Preferably, in the step S2, after the temperature of the reaction system is increased to 225-235℃, an acidolysis agent is added and the reaction is continued for 2-6h; further preferably, after the temperature of the reaction system is increased to 226-231℃, an acidolysis agent is added and the reaction is continued for 3-5h.

[0034] Preferably, in the step S2, the acid value of the acidolysis product is 40-50mgKOH / g; further preferably, the acid value of the acidolysis product is 41-47mgKOH / g.

[0035] Preferably, in the step S3, the acid value of the product obtained by the vacuum polycondensation reaction is 30-36mgKOH / g.

[0036] Preferably, in the step S3, the melt viscosity of the product obtained by the vacuum polycondensation reaction is 5000-7000mPa·s at 200℃.

[0037] Preferably, in the step S3, after the curing accelerator is added, the stirring is performed for 15-25 minutes to obtain the polyester resin for high-gloss powder coating.

[0038] The third aspect of the present application provides a high-gloss powder coating, comprising the polyester resin for high-gloss powder coating according to the first aspect of the present application; the mass percentage of the polyester resin for high-gloss powder coating is 50-60%.

[0039] Preferably, the mass percentage of the polyester resin for high-gloss powder coating is 50-55%.

[0040] Preferably, the high-gloss powder coating further comprises the following raw materials by mass percentage: 2-8% curing agent, 35-45% processing aid; further preferably, the high-gloss powder coating further comprises the following raw materials: 2-6% curing agent, 40-45% processing aid.

[0041] Preferably, the curing agent comprises at least one of tri-glycidyl isocyanurate (TGIC), tri-glycidyl trimellitate (PT910), tri-glycidyl benzene-1,3,5-tricarboxylate (Aplus101), and β-hydroxyalkylamide (HAA); further preferably, the curing agent is tri-glycidyl isocyanurate (TGIC).

[0042] Preferably, the processing aid comprises the following components by mass parts: 35-45 parts of inorganic filler, 0.5-1.5 parts of leveling agent, 0.2-1 part of degassing agent, and 0.2-1 part of wetting promoter; further preferably, the processing aid comprises the following components: 38-42 parts of inorganic filler, 0.5-1 part of leveling agent, 0.2-0.5 part of degassing agent, and 0.2-0.5 part of wetting promoter.

[0043] Preferably, the inorganic filler comprises at least one of titanium white and barium sulfate.

[0044] Preferably, the leveling agent comprises a silicone leveling agent.

[0045] Preferably, the degassing agent comprises benzoin.

[0046] Preferably, the high-gloss powder coating is prepared by a method comprising the following steps: mixing the raw materials, melting and extruding by a double-screw extruder, tabletting, crushing, and sieving to obtain the high-gloss powder coating.

[0047] The fourth aspect of the present application provides a coating layer formed by the high-gloss powder coating according to the third aspect of the present application.

[0048] Preferably, the curing temperature of the high-gloss powder coating is 190-210℃ during the coating forming process; further preferably, the curing temperature of the high-gloss powder coating is 195-205℃.

[0049] Preferably, the curing time of the high-gloss powder coating is 5-15min during the coating forming process; further preferably, the curing time of the high-gloss powder coating is 8-12min.

[0050] Preferably, the glossiness of the coating at 60° angle is 110-120%; further preferably, the glossiness of the coating at 60° angle is 110-115%.

[0051] The fifth aspect of the present application provides the application of the high-gloss powder coating polyester resin of the first aspect of the present application, or the high-gloss powder coating of the third aspect of the present application in electrical appliances, automobiles, office appliances, metal materials, and outdoor building surface coating.

[0052] Compared with the prior art, the present application has the following beneficial effects:

[0053] 1) The high-gloss powder coating polyester resin provided by the present application can reduce the entanglement of the polyester resin molecular chain and greatly improve the reflection of light by introducing S(-)-1,1-diphenyl-1,2-propanediol, diphenyldicarboxylic acid, and bio-based diacid into the main chain structure, so that the powder coating prepared by using the polyester resin can form a high-gloss coating with good storage stability and weather resistance; the use of bio-based diacid can also reduce the dependence on traditional petrochemical-based raw materials.

[0054] 2) The high-gloss powder coating polyester resin provided by the present application has a simple preparation method and is suitable for industrial application.

[0055] 3) The coating formed by the high-gloss powder coating provided by the present application has high glossiness, with 60° glossiness reaching more than 110%, good storage stability and gloss stability, good weather resistance, and can meet the application requirements of electrical appliances, automobiles, office appliances, metal materials, and outdoor building surface coating. DETAILED DESCRIPTION

[0056] The content of the present application will be further described in detail through specific examples. Unless otherwise specified, the raw materials, reagents or devices used in the examples and comparative examples can be obtained from conventional commercial channels or can be obtained by existing technical methods. Unless otherwise specified, the test or test method is a conventional method in the art.

[0057] Example 1

[0058] The embodiment provides a polyester resin for high-gloss powder coating, and raw materials and dosages in preparation are shown in Table 1.

[0059] Table 1 shows raw materials and dosages in preparation of the polyester resin for high-gloss powder coating in Example 1.

[0060]

[0061]

[0062] The preparation steps are as follows:

[0063] S11, aliphatic polyols, S(-)-1,1-diphenyl-1,2-propanediol, biphenyl dicarboxylic acid, the second polybasic acid and esterification catalyst are added according to the proportion, heated to melt the materials, then nitrogen is passed and gradually heated to 242-246 DEG C for reaction, the acid value of the reactants is controlled to be 8-12 mgKOH / g, and an esterification product is obtained;

[0064] S21, the reaction system is cooled to 220-225 DEG C, then bio-based dibasic acid is added for reaction, and the acid value of the product is controlled to be 15-20 mgKOH / g;

[0065] S22, the reaction system is heated to 226-231 DEG C, then acidolysis agent is added for reaction, and the acid value of the acidolysis product is controlled to be 41-47 mgKOH / g;

[0066] S31, vacuum polycondensation reaction is carried out on the acidolysis product, the acid value of the vacuum polycondensation product is controlled to be 30-36 mgKOH / g, and the melt viscosity at 200 DEG C reaches 5000-7000 mPa·s;

[0067] S32, a curing accelerator is added, stirring is carried out for 15-25 min, and the reaction is stopped to obtain the polyester resin for high-gloss powder coating.

[0068] Example 2

[0069] The embodiment provides a polyester resin for high-gloss powder coating, and raw materials and dosages in preparation are shown in Table 2.

[0070] Table 2 shows raw materials and dosages in preparation of the polyester resin for high-gloss powder coating in Example 2.

[0071]

[0072]

[0073] The preparation steps are as follows:

[0074] S11, add aliphatic polyols, S(-)-1,1-diphenyl-1,2-propanediol according to the proportion, heat to melt the material, then add diphenic acid, second polybasic acid and esterification catalyst, pass nitrogen and gradually heat to 242-246℃ for heat preservation reaction, control the acid value of the reactants to be 8-12mgKOH / g, to obtain the esterification product;

[0075] S21, after the temperature of the reaction system is reduced to 220-225℃, add bio-based dibasic acid to react, control the acid value of the product to be 15-20mgKOH / g;

[0076] S22, after the temperature of the reaction system is raised to 226-231℃, add acidolysis agent to react, control the acid value of the acidolysis product to be 41-47mgKOH / g;

[0077] S31, vacuum polycondensation reaction is carried out on the acidolysis product, control the acid value of the vacuum polycondensation product to be 30-36mgKOH / g, and the melt viscosity at 200℃ reaches 5000-7000mPa·s;

[0078] S32, add curing accelerator, stir for 15-25min, stop the reaction to obtain the polyester resin for high-gloss powder coating.

[0079] Example 3

[0080] The example provides a polyester resin for high-gloss powder coating, the preparation raw materials and the amount are shown in Table 3:

[0081] Table 3 Preparation raw materials and amount of polyester resin for high-gloss powder coating in Example 3

[0082]

[0083] The preparation steps are:

[0084] S11, add aliphatic polyols, S(-)-1,1-diphenyl-1,2-propanediol according to the proportion, heat to melt the material, then add diphenic acid, second polybasic acid and esterification catalyst, pass nitrogen and gradually heat to 242-246℃ for heat preservation reaction, control the acid value of the reactants to be 8-12mgKOH / g, to obtain the esterification product;

[0085] S21, after the temperature of the reaction system is reduced to 220-225℃, add bio-based dibasic acid to react, control the acid value of the product to be 15-20mgKOH / g;

[0086] S22, after the temperature of the reaction system is raised to 226-231℃, add acidolysis agent to react, control the acid value of the acidolysis product to be 41-47mgKOH / g;

[0087] S31, vacuum polycondensation reaction is carried out on the acidolysis product, the acid value of the vacuum polycondensation product is controlled to be 30-36 mgKOH / g, and the melt viscosity at 200 DEG C reaches 5000-7000 mPa s;

[0088] S32, a curing accelerator is added, stirring for 15-25 min, and the reaction is stopped to obtain a high-gloss powder coating polyester resin.

[0089] Example 4

[0090] The example provides a high-gloss powder coating polyester resin, and the preparation raw materials and amounts are shown in Table 4:

[0091] Table 4 Preparation raw materials and amounts of high-gloss powder coating polyester resin in Example 4

[0092]

[0093] The preparation steps are:

[0094] S11, the aliphatic polyol, S(-)-1,1-diphenyl-1,2-propanediol are added according to the ratio, heated to melt the material, then diphenic acid, the second polybasic acid and esterification catalyst are added, nitrogen is passed and gradually heated to 242-246 DEG C for holding reaction, the acid value of the reactant is controlled to be 8-12 mgKOH / g, and the esterification product is obtained;

[0095] S21, the reaction system temperature is reduced to 220-225 DEG C, then the bio-based dibasic acid is added for reaction, and the acid value of the product is controlled to be 15-20 mgKOH / g;

[0096] S22, the reaction system temperature is raised to 226-231 DEG C, then the acidolysis agent is added for reaction, and the acid value of the acidolysis product is controlled to be 41-47 mgKOH / g;

[0097] S31, vacuum polycondensation reaction is carried out on the acidolysis product, the acid value of the vacuum polycondensation product is controlled to be 30-36 mgKOH / g, and the melt viscosity at 200 DEG C reaches 5000-7000 mPa s;

[0098] S32, a curing accelerator is added, stirring for 15-25 min, and the reaction is stopped to obtain a high-gloss powder coating polyester resin.

[0099] Example 5

[0100] The example provides a high-gloss powder coating polyester resin, and the preparation raw materials and amounts are shown in Table 5:

[0101] Table 5 Preparation raw materials and amounts of high-gloss powder coating polyester resin in Example 5

[0102]

[0103] The preparation steps are:

[0104] S11, add aliphatic polyols, S(-)-1, 1-diphenyl-1, 2-propanediol according to the proportion, heat to melt the material, then add diphenic acid, the second polybasic acid and esterification catalyst, pass nitrogen and gradually heat to 242-246℃ for holding reaction, control the acid value of the reactants to be 8-12mgKOH / g, to obtain the esterification product;

[0105] S21, after the reaction system temperature is reduced to 220-225℃, add bio-based dibasic acid to react, control the acid value of the product to be 15-20mgKOH / g;

[0106] S22, after the reaction system temperature is raised to 226-231℃, add acidolysis agent to react, control the acid value of the acidolysis product to be 41-47mgKOH / g;

[0107] S31, vacuum polycondensation reaction is carried out on the acidolysis product, control the acid value of the vacuum polycondensation product to be 30-36mgKOH / g, and the melt viscosity at 200℃ reaches 5000-7000mPa·s;

[0108] S32, add curing accelerator, stir for 15-25min, stop the reaction to obtain the polyester resin for high-gloss powder coating.

[0109] Comparative Example 1

[0110] The comparative example provides a polyester resin, and the preparation raw materials and amounts are shown in Table 6:

[0111] Table 6 Preparation raw materials and amounts of the polyester resin in Comparative Example 1

[0112]

[0113] The preparation steps are:

[0114] S11, add aliphatic polyols, S(-)-1, 1-diphenyl-1, 2-propanediol according to the proportion, heat to melt the material, then add diphenic acid, the second polybasic acid and esterification catalyst, pass nitrogen and gradually heat to 242-246℃ for holding reaction, control the acid value of the reactants to be 8-12mgKOH / g, to obtain the esterification product;

[0115] S21, after the reaction system temperature is reduced to 220-225℃, add bio-based dibasic acid to react, control the acid value of the product to be 15-20mgKOH / g;

[0116] S22, after the reaction system temperature is raised to 226-231℃, add acidolysis agent to react, control the acid value of the acidolysis product to be 41-47mgKOH / g;

[0117] S31, vacuum polycondensation reaction is carried out on the acidolysis product, the acid value of the vacuum polycondensation product is controlled to be 30-36 mgKOH / g, and the melt viscosity at 200℃ reaches 5000-7000 mPa·s;

[0118] S32, a curing accelerator is added, stirring for 15-25 min, and the reaction is stopped to obtain a polyester resin.

[0119] Comparative Example 2

[0120] The comparative example provides a polyester resin, and the preparation raw materials and amounts are shown in Table 7:

[0121] Table 7 Preparation raw materials and amounts of polyester resin in Comparative Example 2

[0122]

[0123] The preparation steps are as follows:

[0124] S11, the aliphatic polyol and S(-)-1,1-diphenyl-1,2-propanediol are added according to the proportion, heated to melt the materials, then the second polybasic acid and esterification catalyst are added, nitrogen is passed and gradually heated to 242-246℃ for heat preservation reaction, the acid value of the reactant is controlled to be 8-12 mgKOH / g, and the esterification product is obtained;

[0125] S21, the reaction system temperature is reduced to 220-225℃, then the bio-based dibasic acid is added for reaction, and the acid value of the product is controlled to be 15-20 mgKOH / g;

[0126] S22, the reaction system temperature is raised to 226-231℃, then the acidolysis agent is added for reaction, and the acid value of the acidolysis product is controlled to be 41-47 mgKOH / g;

[0127] S31, vacuum polycondensation reaction is carried out on the acidolysis product, the acid value of the vacuum polycondensation product is controlled to be 30-36 mgKOH / g, and the melt viscosity at 200℃ reaches 5000-7000 mPa·s;

[0128] S32, a curing accelerator is added, stirring for 15-25 min, and the reaction is stopped to obtain a polyester resin.

[0129] Comparative Example 3

[0130] The comparative example provides a polyester resin, and the preparation raw materials and amounts are shown in Table 8:

[0131] Table 8 Preparation raw materials and amounts of polyester resin in Comparative Example 3

[0132]

[0133] The preparation steps are as follows:

[0134] S11, the aliphatic polyol, S(-)-1,1-diphenyl-1,2-propanediol, are added according to the proportion, heated to melt the material, then diphenic acid, the second polybasic acid and esterification catalyst are added, nitrogen is passed and gradually heated to 242-246℃ for reaction, the acid value of the reactants is controlled to be 8-12 mgKOH / g, and the esterification product is obtained;

[0135] S21, after the temperature of the reaction system is raised to 226-231℃, the acidolysis agent is added for reaction, and the acid value of the acidolysis product is controlled to be 41-47 mgKOH / g;

[0136] S31, the acidolysis product is subjected to vacuum polycondensation reaction, the acid value of the vacuum polycondensation product is controlled to be 30-36 mgKOH / g, and the melt viscosity at 200℃ reaches 5000-7000 mPa·s;

[0137] S32, the curing accelerator is added, stirred for 15-25 min, and the reaction is stopped to obtain the polyester resin.

[0138] Application Example 1

[0139] The polyester resins in Examples 1-5 and Comparative Examples 1-3 are used as raw materials to prepare powder coatings, and the compositions of the powder coatings are shown in Table 9 as follows:

[0140] Table 9 Powder coating components and contents (g) of application example 1

[0141]

[0142] The powder coating preparation steps are as follows:

[0143] The components are mixed, melted by a twin-screw extruder, extruded to obtain a polyester resin composition, tabletted, broken, and the tablet is crushed and sieved to obtain powder coatings 1-8.

[0144] Application Example 2

[0145] The powder coatings 1-8 prepared in application example 1 are coated on the surface of the substrate tinplate by electrostatic spraying, and the coating 1-8 is obtained by curing at 200℃ for 10 min.

[0146] Performance test

[0147] 1, the acid value, viscosity and glass transition temperature of the polyester resins in Examples 1-5 and Comparative Examples 1-3 are tested, wherein the acid value test refers to GB / T6743-2008, the viscosity test is the ICI cone and plate viscosity at 200℃ according to ASTM D4287-88, and the glass transition temperature test is carried out according to GB / T 19466.2, and the test results are shown in Table 10.

[0148] Table 10 Test results of acid value, viscosity and glass transition temperature of polyester resins in Examples 1-5 and Comparative Examples 1-3

[0149]

[0150] Table 10 is the test results of acid value, viscosity and glass transition temperature of polyester resins in Examples 1-5 and Comparative Examples 1-3. As can be seen from Table 10, in Examples 1-5, the acid value of the polyester resin for high-gloss powder coating is 30-36 mgKOH / g, the melt viscosity at 200℃ is 5000-7000 mPa·s, and the glass transition temperature (TG) is 67-75℃. In Comparative Example 1, S(-)-1,1-diphenyl-1,2-propanediol is not added, in Comparative Example 2, diphenyldicarboxylic acid is not added, and in Comparative Example 3, bio-based diacid is not added, and the glass transition temperature of the obtained polyester resin is significantly reduced.

[0151] 2, Test the 60° gloss, impact resistance, storage gloss stability and xenon lamp aging gloss retention of coatings 1-8 in Application Example 2. The gloss test refers to GB / T 9754-2007, the impact resistance test refers to GB / T 1732-1993, and the xenon lamp aging gloss retention test refers to GB / T 1865-2009. The test results are shown in Table 11.

[0152] Table 11 Performance test results of coatings 1-8 in Application Example 2

[0153]

[0154] Table 11 is the performance test results of coatings 1-8 in Application Example 2. As can be seen from Table 11, the high-gloss powder coatings 1-5 prepared from the polyester resins for high-gloss powder coating in Examples 1-5 have a 60° gloss of more than 110% after electrostatic spraying and curing to form coatings 1-5, the coatings have high gloss; the coatings have good impact resistance; after 42℃*24h accelerated storage test, the gloss of the coatings changes little, and the stability is more than 110%, indicating that the storage stability and gloss stability of the coatings are excellent; after 1000h xenon lamp aging test, the gloss retention can reach 86% and above, indicating that the coatings have good weather resistance.

[0155] The 60° gloss of the coating corresponding to the polyester resin without the addition of S(-)-1,1-diphenyl-1,2-propanediol in Comparative Example 1, without the addition of diphenyl dicarboxylic acid in Comparative Example 2, and without the addition of bio-based diacid in Comparative Example 3 is all lower than 96%, the impact resistance of the coating is qualified, but the storage stability and gloss stability are poor, the gloss significantly decreases after 1000 h xenon lamp aging, and the gloss retention is only close to 70%, indicating that S(-)-1,1-diphenyl-1,2-propanediol, diphenyl dicarboxylic acid and bio-based diacid are important components for preparing a polyester resin for high-gloss powder coating, and the lack of any one will affect the gloss, storage stability or weather resistance of the coating formed by the powder coating, and the comprehensive performance of the powder coating becomes poor.

Claims

1. A polyester resin for high-gloss powder coatings, characterized in that, The preparation materials, by mass percentage, include the following: 20-35% aliphatic polyol, 2-8% S(-)-1,1-diphenyl-1,2-propanediol, 4-15% primary polyacid and 35-60% secondary polyacid; The aliphatic polyol includes neopentyl glycol, and at least one of 1,4-cyclohexanediol and 1,2-butanediol; the neopentyl glycol accounts for ≥85% of the mass percentage of the aliphatic polyol. The first polycarboxylic acid comprises biphenyl dicarboxylic acid and a bio-based dicarboxylic acid in a mass ratio of 1:(0.5-8); the bio-based dicarboxylic acid comprises 2,5-furandicarboxylic acid; The second polybasic acid includes terephthalic acid, and at least one of adipic acid and succinic acid; the mass percentage of terephthalic acid in the second polybasic acid is ≥90%.

2. The polyester resin for high-gloss powder coating according to claim 1, characterized in that, The raw materials for preparing the polyester resin, by weight percentage, also include 5-15% acid hydrolysate, 0.1-0.5% esterification catalyst and 0.01-0.1% curing accelerator.

3. The method for preparing the polyester resin for high-gloss powder coatings according to claim 2, characterized in that, Includes the following steps: S1. Mix aliphatic polyol, S(-)-1,1-diphenyl-1,2-propanediol, biphenyl dicarboxylic acid, and second polyacid, add esterification catalyst, and perform polycondensation reaction to obtain esterification product. S2. The esterification product is mixed with a bio-based dicarboxylic acid and reacted. An acid hydrolysis agent is added to continue the reaction to obtain the acid hydrolysis product. S3. The acid hydrolysis product is subjected to vacuum polycondensation reaction, and a curing accelerator is added to obtain the high-gloss powder coating polyester resin.

4. A high-gloss powder coating, characterized in that, Includes the polyester resin for high-gloss powder coatings as described in claim 1 or 2; The polyester resin used in the high-gloss powder coating has a mass percentage of 50-60%.

5. A coating, characterized in that, It is formed from the high-gloss powder coating as described in claim 4.

6. The application of the polyester resin for high-gloss powder coating as described in claim 1 or 2, or the high-gloss powder coating as described in claim 4, in the surface coating of electrical appliances, automobiles, office supplies, metal materials, and outdoor buildings.

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