Polyester resin for high-gloss powder coating and preparation method thereof

Abstract

The invention relates to the technical field of high polymer materials, and discloses polyester resin for a high-gloss powder coating and a preparation method of the polyester resin. The polyester resin for the high-gloss powder coating is prepared from the following preparation raw materials: aliphatic polyol, S (-)-1, 1-diphenyl-1, 2-propylene glycol and a first polyacid composition, the first polyacid composition includes biphenyl dicarboxylic acid and a bio-based dibasic acid. According to the polyester resin for the high-gloss powder coating, provided by the invention, S (-)-1, 1-diphenyl-1, 2-propylene glycol, diphenyldicarboxylic acid and bio-based binary acid are introduced into a main chain structure, so that winding of a molecular chain of the polyester resin can be reduced, and reflection of the polyester resin to light rays can be greatly improved; the powder coating prepared from 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-based raw materials.

Description

Technical Field

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

[0002] Powder coating is a new type of solid coating that does not contain solvents and is more environmentally friendly. It is widely used in home appliances, automobiles, aluminum profiles and other fields. Powder coatings can be divided into high-gloss powder coatings and matte powder coatings according to the gloss of the coating. In the field of high-gloss coatings, powder coatings still have a certain gap in surface decoration compared with traditional paints, mainly manifested in insufficient leveling and insufficient gloss.

[0003] Polyester resin is the main raw material of powder coating and the key component for making the coating film have high gloss. CN103613744 A discloses a TGIC-cured polyester resin for high-adhesion and high-leveling powder coating and a preparation method thereof. The polyester resin can make the coating have high leveling, but the gloss of the coating is not high enough, below 94%. CN 102127212 A discloses a carboxyl-terminated polyester resin for weather-resistant high-gloss powder coating and a preparation method thereof. The carboxyl-terminated polyester resin can make the gloss of the coating reach between 96-98%, but the glass transition temperature of the polyester resin is not high enough and the storage performance is not good enough. CN 103642014A discloses an epoxy-cured polyester resin for high-gloss and high-leveling powder coating and a preparation method thereof. The polyester resin can make the coating have high gloss, but it uses epoxy resin as a curing agent, and the weather resistance of the coating is insufficient, and it is mainly used indoors. Providing a polyester resin that can make the coating have high gloss, excellent storage stability and weather resistance is of great significance to broadening the application range of powder coatings. 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, one of the objects of the present invention is to provide a polyester resin for high-gloss powder coating; the second object of the present invention is to provide a method for preparing the polyester resin for high-gloss powder coating; the third object of the present invention is to provide a high-gloss powder coating; the fourth object of the present invention is to provide a coating; the fifth object of the present invention is to provide a polyester resin for high-gloss powder coating, or the application of high-gloss powder coating.

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

[0006] Introducing S(-)-1,1-diphenyl-1,2-propanediol, biphenyl dicarboxylic acid and bio-based dibasic acid into the main chain structure of polyester resin can reduce the entanglement of polyester resin molecular chains, increase the rigidity of polyester resin, and greatly enhance the reflection of light by polyester resin.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is:

[0008] The first aspect of the present invention 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 a first polyacid composition; the first polyacid composition comprises biphenyl dicarboxylic acid and a bio-based dibasic acid.

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

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

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

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

[0013] Preferably, the raw materials for preparing the polyester resin for high-gloss powder coating further include a second polyacid, an acidolysis agent, an esterification catalyst and a curing accelerator.

[0014] Preferably, the second polyacid includes terephthalic acid, or terephthalic acid and at least one of adipic acid, succinic acid, isophthalic acid, and 1,4-cyclohexanedicarboxylic acid; further preferably, the second polyacid includes terephthalic acid, or terephthalic acid and at least one of adipic acid and succinic acid.

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

[0016] Preferably, the acidolysis agent includes at least one of isophthalic acid, 1,4-cyclohexanedicarboxylic acid, and pyromellitic acid.

[0017] Preferably, the esterification catalyst includes at least one of monobutyl dihydroxytin chloride, monobutyl tin oxide, tin oxalate, germanium dioxide, activated titanium dioxide, and an organic titanium-phosphorus complex.

[0018] Preferably, the curing accelerator includes at least one of triphenylbutylphosphonium bromide and benzyltributylammonium chloride.

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

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

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

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

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

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

[0025] S3, subjecting the acidolysis product to a vacuum polycondensation reaction, adding a curing accelerator, and obtaining the polyester resin for high-gloss powder coating.

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

[0027] Preferably, the heating and melting comprises heating to 130-140° C. and keeping warm for 25-35 min; further preferably, the heating and melting comprises heating to 133-137° C. and keeping warm for 28-32 min.

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

[0029] Preferably, the conditions for the polycondensation reaction include heating to 240-250° C. and keeping warm for 2-7 hours; further preferably, the conditions for the polycondensation reaction include heating to 242-246° C. and keeping warm for 2-6 hours.

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

[0031] Preferably, in step S2, after the temperature of the reaction system drops to 220-230° C., the esterification product and the bio-based dibasic acid are mixed and reacted for 1-4 hours; further preferably, after the temperature of the reaction system drops to 220-225° C., the esterification product and the bio-based dibasic acid are mixed and reacted for 1-3 hours.

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

[0033] Preferably, in step S2, after the temperature of the reaction system rises to 225-235°C, an acidolysis agent is added to continue the reaction for 2-6 hours; further preferably, after the temperature of the reaction system rises to 226-231°C, an acidolysis agent is added to continue the reaction for 3-5 hours.

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

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

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

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

[0038] The third aspect of the present invention provides a high gloss powder coating, comprising the polyester resin for high gloss powder coating according to the first aspect of the present invention; 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, by mass percentage: 2-6% curing agent, 40-45% processing aid.

[0041] Preferably, the curing agent includes at least one of triglycidyl isocyanurate (TGIC), triglycidyl trimellitate (PT910), triglycidyl trimellitate (Aplus101), and β-hydroxyalkylamide (HAA); more preferably, the curing agent is triglycidyl isocyanurate (TGIC).

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

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

[0044] Preferably, the leveling agent comprises an organic silicon 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, extruding after melting using a twin-screw extruder, tableting, crushing, and sieving to obtain the high-gloss powder coating.

[0047] A fourth aspect of the present invention provides a coating formed by the high gloss powder coating according to the third aspect of the present invention.

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

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

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

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

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

[0053] 1) The polyester resin for high-gloss powder coating provided by the present invention 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, biphenyl dicarboxylic acid and bio-based dibasic acid into the main chain structure, so that the powder coating prepared with the polyester resin can form a high-gloss coating with good storage stability and weather resistance; the use of bio-based dibasic acid can also reduce dependence on traditional petrochemical-based raw materials.

[0054] 2) The method for preparing the polyester resin for high-gloss powder coating provided by the present invention is simple and suitable for industrial use.

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

[0056] 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.

[0057] Example 1

[0058] This embodiment provides a polyester resin for high gloss powder coating, and the raw materials and amounts thereof are shown in Table 1:

[0059] Table 1 Preparation raw materials and dosage of polyester resin for high gloss powder coating in Example 1

[0060]

[0061]

[0062] The preparation steps are:

[0063] S11, adding aliphatic polyol and S(-)-1,1-diphenyl-1,2-propanediol according to the proportion, heating until the materials are melted, then adding biphenyl dicarboxylic acid, the second polyacid and an esterification catalyst, passing nitrogen and gradually raising the temperature to 242-246° C. for heat preservation reaction, controlling the acid value of the reactant to 8-12 mgKOH / g, to obtain an esterification product;

[0064] S21, lowering the temperature of the reaction system to 220-225° C. and adding a bio-based dibasic acid to react, controlling the acid value of the product to be 15-20 mgKOH / g;

[0065] S22, raising the temperature of the reaction system to 226-231° C., adding an acidolysis agent to react, and controlling the acid value of the acidolysis product to be 41-47 mgKOH / g;

[0066] S31, performing vacuum polycondensation reaction on the acidolysis product, controlling the acid value of the vacuum polycondensation product to be 30-36 mgKOH / g, and the melt viscosity at 200° C. to be 5000-7000 mPa·s;

[0067] S32, adding a curing accelerator, stirring for 15-25 minutes, and stopping the reaction to obtain a polyester resin for high-gloss powder coating.

[0068] Example 2

[0069] This embodiment provides a polyester resin for high gloss powder coating, and the raw materials and amounts used are shown in Table 2:

[0070] Table 2 Preparation raw materials and dosage of polyester resin for high gloss powder coating in Example 2

[0071]

[0072]

[0073] The preparation steps are:

[0074] S11, adding aliphatic polyol and S(-)-1,1-diphenyl-1,2-propanediol according to the proportion, heating until the materials are melted, then adding biphenyl dicarboxylic acid, the second polyacid and an esterification catalyst, passing nitrogen and gradually raising the temperature to 242-246° C. for heat preservation reaction, controlling the acid value of the reactant to 8-12 mgKOH / g, to obtain an esterification product;

[0075] S21, lowering the temperature of the reaction system to 220-225° C. and adding a bio-based dibasic acid to react, controlling the acid value of the product to be 15-20 mgKOH / g;

[0076] S22, raising the temperature of the reaction system to 226-231° C., adding an acidolysis agent to react, and controlling the acid value of the acidolysis product to be 41-47 mgKOH / g;

[0077] S31, performing vacuum polycondensation reaction on the acidolysis product, controlling the acid value of the vacuum polycondensation product to be 30-36 mgKOH / g, and the melt viscosity at 200° C. to be 5000-7000 mPa·s;

[0078] S32, adding a curing accelerator, stirring for 15-25 minutes, and stopping the reaction to obtain a polyester resin for high-gloss powder coating.

[0079] Example 3

[0080] This embodiment provides a polyester resin for high gloss powder coating, and the raw materials and amounts used are shown in Table 3:

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

[0082]

[0083] The preparation steps are:

[0084] S11, adding aliphatic polyol and S(-)-1,1-diphenyl-1,2-propanediol according to the proportion, heating until the materials are melted, then adding biphenyl dicarboxylic acid, the second polyacid and an esterification catalyst, passing nitrogen and gradually raising the temperature to 242-246° C. for heat preservation reaction, controlling the acid value of the reactant to 8-12 mgKOH / g, to obtain an esterification product;

[0085] S21, lowering the temperature of the reaction system to 220-225° C. and adding a bio-based dibasic acid to react, controlling the acid value of the product to be 15-20 mgKOH / g;

[0086] S22, raising the temperature of the reaction system to 226-231° C., adding an acidolysis agent to react, and controlling the acid value of the acidolysis product to be 41-47 mgKOH / g;

[0087] S31, performing vacuum polycondensation reaction on the acidolysis product, controlling the acid value of the vacuum polycondensation product to be 30-36 mgKOH / g, and the melt viscosity at 200° C. to be 5000-7000 mPa·s;

[0088] S32, adding a curing accelerator, stirring for 15-25 minutes, and stopping the reaction to obtain a polyester resin for high-gloss powder coating.

[0089] Example 4

[0090] This embodiment provides a polyester resin for high gloss powder coating, and the raw materials and amounts used are shown in Table 4:

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

[0092]

[0093] The preparation steps are:

[0094] S11, adding aliphatic polyol and S(-)-1,1-diphenyl-1,2-propanediol according to the proportion, heating until the materials are melted, then adding biphenyl dicarboxylic acid, the second polyacid and an esterification catalyst, passing nitrogen and gradually raising the temperature to 242-246° C. for heat preservation reaction, controlling the acid value of the reactant to 8-12 mgKOH / g, to obtain an esterification product;

[0095] S21, lowering the temperature of the reaction system to 220-225° C. and adding a bio-based dibasic acid to react, controlling the acid value of the product to be 15-20 mgKOH / g;

[0096] S22, raising the temperature of the reaction system to 226-231° C., adding an acidolysis agent to react, and controlling the acid value of the acidolysis product to be 41-47 mgKOH / g;

[0097] S31, performing vacuum polycondensation reaction on the acidolysis product, controlling the acid value of the vacuum polycondensation product to be 30-36 mgKOH / g, and the melt viscosity at 200° C. to be 5000-7000 mPa·s;

[0098] S32, adding a curing accelerator, stirring for 15-25 minutes, and stopping the reaction to obtain a polyester resin for high-gloss powder coating.

[0099] Example 5

[0100] This embodiment provides a polyester resin for high gloss powder coating, and the raw materials and amounts used are shown in Table 5:

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

[0102]

[0103] The preparation steps are:

[0104] S11, adding aliphatic polyol and S(-)-1,1-diphenyl-1,2-propanediol according to the proportion, heating until the materials are melted, then adding biphenyl dicarboxylic acid, the second polyacid and an esterification catalyst, passing nitrogen and gradually raising the temperature to 242-246° C. for heat preservation reaction, controlling the acid value of the reactant to 8-12 mgKOH / g, to obtain an esterification product;

[0105] S21, lowering the temperature of the reaction system to 220-225° C. and adding a bio-based dibasic acid to react, controlling the acid value of the product to be 15-20 mgKOH / g;

[0106] S22, raising the temperature of the reaction system to 226-231° C., adding an acidolysis agent to react, and controlling the acid value of the acidolysis product to be 41-47 mgKOH / g;

[0107] S31, performing vacuum polycondensation reaction on the acidolysis product, controlling the acid value of the vacuum polycondensation product to be 30-36 mgKOH / g, and the melt viscosity at 200° C. to be 5000-7000 mPa·s;

[0108] S32, adding a curing accelerator, stirring for 15-25 minutes, and stopping the reaction to obtain a polyester resin for high-gloss powder coating.

[0109] Comparative Example 1

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

[0111] Table 6 Preparation raw materials and dosage of polyester resin in comparative example 1

[0112]

[0113] The preparation steps are:

[0114] S11, adding aliphatic polyol according to the proportion, heating until the material is melted, then adding biphenyl dicarboxylic acid, the second polyacid and the esterification catalyst, passing nitrogen and gradually heating to 242-246° C. for heat preservation reaction, controlling the acid value of the reactant to 8-12 mgKOH / g, to obtain an esterification product;

[0115] S21, lowering the temperature of the reaction system to 220-225° C. and adding a bio-based dibasic acid to react, controlling the acid value of the product to be 15-20 mgKOH / g;

[0116] S22, raising the temperature of the reaction system to 226-231° C., adding an acidolysis agent to react, and controlling the acid value of the acidolysis product to be 41-47 mgKOH / g;

[0117] S31, performing vacuum polycondensation reaction on the acidolysis product, controlling the acid value of the vacuum polycondensation product to be 30-36 mgKOH / g, and the melt viscosity at 200° C. to be 5000-7000 mPa·s;

[0118] S32, adding a curing accelerator, stirring for 15-25 minutes, and stopping the reaction to obtain a polyester resin.

[0119] Comparative Example 2

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

[0121] Table 7 Preparation raw materials and dosage of polyester resin in comparative example 2

[0122]

[0123] The preparation steps are:

[0124] S11, adding aliphatic polyol and S(-)-1,1-diphenyl-1,2-propanediol according to the proportion, heating until the materials are melted, then adding the second polyacid and the esterification catalyst, passing nitrogen and gradually raising the temperature to 242-246° C. for heat preservation reaction, controlling the acid value of the reactant to 8-12 mgKOH / g, and obtaining an esterification product;

[0125] S21, lowering the temperature of the reaction system to 220-225° C. and adding a bio-based dibasic acid to react, controlling the acid value of the product to be 15-20 mgKOH / g;

[0126] S22, raising the temperature of the reaction system to 226-231° C., adding an acidolysis agent to react, and controlling the acid value of the acidolysis product to be 41-47 mgKOH / g;

[0127] S31, performing vacuum polycondensation reaction on the acidolysis product, controlling the acid value of the vacuum polycondensation product to be 30-36 mgKOH / g, and the melt viscosity at 200° C. to be 5000-7000 mPa·s;

[0128] S32, adding a curing accelerator, stirring for 15-25 minutes, and stopping the reaction to obtain a polyester resin.

[0129] Comparative Example 3

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

[0131] Table 8 Preparation raw materials and dosage of polyester resin in comparative example 3

[0132]

[0133] The preparation steps are:

[0134] S11, adding aliphatic polyol and S(-)-1,1-diphenyl-1,2-propanediol according to the proportion, heating until the materials are melted, then adding biphenyl dicarboxylic acid, the second polyacid and an esterification catalyst, passing nitrogen and gradually raising the temperature to 242-246° C. for heat preservation reaction, controlling the acid value of the reactant to 8-12 mgKOH / g, to obtain an esterification product;

[0135] S21, raising the temperature of the reaction system to 226-231° C., adding an acidolysis agent to react, and controlling the acid value of the acidolysis product to be 41-47 mgKOH / g;

[0136] S31, performing vacuum polycondensation reaction on the acidolysis product, controlling the acid value of the vacuum polycondensation product to be 30-36 mgKOH / g, and the melt viscosity at 200° C. to be 5000-7000 mPa·s;

[0137] S32, adding a curing accelerator, stirring for 15-25 minutes, and stopping the reaction to obtain a polyester resin.

[0138] Application Example 1

[0139] Powder coatings were prepared using the polyester resins in Examples 1-5 and Comparative Examples 1-3 as raw materials. The compositions of the powder coatings are shown in Table 9 below:

[0140] Table 9 Application Example 1 Powder coating components and contents (g)

[0141]

[0142] The steps for preparing powder coating are:

[0143] The components are mixed, melted and extruded using a twin-screw extruder to obtain a polyester resin composition, which is then tableted and crushed. The tablets are pulverized and sieved to obtain powder coatings 1-8.

[0144] Application Example 2

[0145] The powder coating 1-8 prepared in Application Example 1 was coated on the surface of the tinplate substrate by electrostatic spraying and cured at 200° C. for 10 min to obtain coating 1-8.

[0146] Performance Testing

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

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

[0149]

[0150] Table 10 shows the test results of the acid value, viscosity and glass transition temperature of the polyester resin in Examples 1-5 and Comparative Examples 1-3. It can be seen from Table 10 that 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°C is 5000-7000 mPa·s, and the glass transition temperature (TG) is 67-75°C. In Comparative Example 1, S(-)-1,1-diphenyl-1,2-propanediol was not added, in Comparative Example 2, biphenyl dicarboxylic acid was not added, and in Comparative Example 3, bio-based dibasic acid was not added, and the glass transition temperature of the obtained polyester resin was significantly reduced.

[0151] 2. The 60° gloss, impact resistance, storage gloss stability and xenon lamp aging gloss retention rate of coatings 1-8 in Application Example 2 were tested. The gloss test was carried out in accordance with GB / T 9754-2007, the impact resistance test was carried out in accordance with GB / T1732-1993, and the xenon lamp aging gloss retention rate test was carried out in accordance with 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 shows the performance test results of coating 1-8 in Application Example 2. It can be seen from Table 11 that the high gloss powder coating 1-5 prepared with the polyester resin for high gloss powder coating in Example 1-5 as raw material and cured after electrostatic spraying has a 60° gloss of more than 110%, and the coating has high gloss; the coating has good impact resistance; after an accelerated storage test at 42°C*24h, the gloss of the coating changes very little, and the stability reaches more than 110%, indicating that the storage stability and gloss stability of the coating are excellent; after a 1000h xenon lamp aging test, the gloss retention rate can reach 86% or more, indicating that the coating has good weather resistance.

[0155] In Comparative Example 1, no S(-)-1,1-diphenyl-1,2-propanediol was added to the polyester resin, in Comparative Example 2, no diphenyl dicarboxylic acid was added to the polyester resin, and in Comparative Example 3, no bio-based dibasic acid was added to the polyester resin. It can be seen that the 60° gloss of the corresponding coatings is lower than 96%, and the coating has qualified impact resistance, but poor storage stability and gloss stability. The gloss decreases significantly after 1000h xenon lamp aging, and the gloss retention rate is only close to 70%, indicating that S(-)-1,1-diphenyl-1,2-propanediol, diphenyl dicarboxylic acid and bio-based dibasic acid are important components for preparing polyester resins for high-gloss powder coatings. The lack of any one of them will affect the gloss, storage stability or weather resistance of the coating formed by the powder coating, and deteriorate the comprehensive performance of the powder coating.

Claims

1. A polyester resin for high gloss powder coating, characterized in that: The invention comprises the following raw materials: aliphatic polyol, S(-)-1,1-diphenyl-1,2-propanediol and a first polyacid composition; the first polyacid composition comprises biphenyl dicarboxylic acid and bio-based dibasic acid.

2. The polyester resin for high gloss powder coating according to claim 1, characterized in that: The aliphatic polyol includes neopentyl glycol, or neopentyl glycol and at least one of 1,4-cyclohexanedimethanol, 1,2-butanediol, 1,4-butanediol, and 1,6-hexanediol; Preferably, the mass percentage of the neopentyl glycol in the aliphatic polyol is ≥85%.

3. The polyester resin for high gloss powder coating according to claim 1, characterized in that: The mass ratio of the biphenyl dicarboxylic acid to the bio-based dibasic acid is 1:(0.5-8); Preferably, the bio-based dibasic acid includes at least one of 2,5-furandicarboxylic acid, itaconic acid, maleic acid, fumaric acid and citraconic acid.

4. The polyester resin for high gloss powder coating according to any one of claims 1 to 3, characterized in that: The raw materials for preparing the polyester resin also include a second polyacid, an acidolysis agent, an esterification catalyst and a curing accelerator.

5. The polyester resin for high gloss powder coating according to claim 4, characterized in that: The second polyacid includes terephthalic acid, or terephthalic acid and at least one of adipic acid, succinic acid, isophthalic acid, and 1,4-cyclohexanedicarboxylic acid; Preferably, the mass percentage of terephthalic acid in the second polyacid is ≥90%.

6. The polyester resin for high gloss powder coating according to claim 4, characterized in that: The polyester resin comprises the following raw materials by mass percentage: 20-35% aliphatic polyol, 2-8% S(-)-1,1-diphenyl-1,2-propylene glycol, 4-15% first polyacid, 35-60% second polyacid, 5-15% acidolysis agent, 0.1-0.5% esterification catalyst and 0.01-0.1% curing accelerator.

7. The method for preparing the polyester resin for high gloss powder coating according to claim 6, characterized in that: The following steps are involved: S1, mixing aliphatic polyol, S(-)-1,1-diphenyl-1,2-propanediol, biphenyl dicarboxylic acid, and a second polyacid, adding an esterification catalyst, and performing polycondensation reaction to obtain an esterification product; S2, mixing the esterification product with a bio-based dibasic acid for reaction, adding an acidolysis agent for further reaction, and obtaining an acidolysis product; S3, subjecting the acidolysis product to a vacuum polycondensation reaction, adding a curing accelerator, and obtaining the polyester resin for high-gloss powder coating.

8. A high gloss powder coating, characterized in that: A polyester resin for high gloss powder coating comprising any one of claims 1 to 6; The mass percentage of the polyester resin for the high gloss powder coating is 50-60%.

9. A coating, characterized in that: The invention is formed by comprising the high gloss powder coating according to claim 8.

10. Use of the polyester resin for high gloss powder coating according to any one of claims 1 to 6, or the high gloss powder coating according to claim 8 in coating of electrical appliances, automobiles, office appliances, metal materials, and outdoor building surfaces.

Images