CN115109259A

CN115109259A - Polyester resin, low-temperature curing powder coating composition, and preparation method and application thereof

Info

Publication number: CN115109259A
Application number: CN202210711642.7A
Authority: CN
Inventors: 王韶顺; 马志平; 李勇; 顾宇昕; 李诗乐
Original assignee: Qingtian Material Technology Co ltd
Current assignee: Qingtian Material Technology Co ltd
Priority date: 2022-06-22
Filing date: 2022-06-22
Publication date: 2022-09-27

Abstract

The invention relates to the technical field of high polymer materials, in particular to a polyester resin, a low-temperature curing powder coating composition, and a preparation method and application thereof. The polyester resin of the present invention comprises a block structure segment derived from a hyperbranched polyester prepolymer and a prepolymer containing a reactive group; the end group of the hyperbranched polyester prepolymer is carboxyl and/or hydroxyl, and is composed of C ₃ ～C ₃₀ Dibasic or polybasic acids or derivatives thereof, C ₂ ～C ₃₀ A dihydric or polyhydric alcohol or a derivative thereof, C ₁₀ ～C ₄₂ Long-chain alkane monobasic acid or dibasic acid is obtained by polycondensation; the prepolymer containing reactive groups comprises at least one of polyester resin prepolymer, acrylic resin prepolymer and polyurethane resin prepolymer, and the reactive groups comprise at least one of carboxyl, hydroxyl, epoxy, isocyanate, ester, amino, amide and halogenated alkyl. The powder coating prepared from the polyester resin can be cured at low temperature and has excellent weather resistance and leveling property.

Description

Polyester resin, low-temperature curing powder coating composition, and preparation method and application thereof

Technical Field

The invention belongs to the technical field of high polymer materials, and particularly relates to a polyester resin, a low-temperature curing powder coating composition, and a preparation method and application thereof.

Background

The polyester powder coating has excellent leveling property, mechanical property and storage stability, and excellent weather resistance, and is widely used for coating outdoor building profiles. Experimental data show that 10% of energy can be saved when the curing temperature of the powder coating is reduced by 10 ℃, so that the development of low-temperature curing powder coating has a wide market prospect.

The greenhouse effect causes global warming and acid rain caused by environmental pollution, a new challenge is provided for the weather resistance of the powder coating, meanwhile, the requirement on the leveling property of the powder coating is higher due to the improvement of the aesthetic level, and the existing polyester resin for the low-temperature curing powder coating is difficult to simultaneously consider the aspects of ultrahigh weather resistance and high leveling property. In the prior art, polyester resin is synthesized by high-activity monomers such as cyclohexane-1, 2-dicarboxylic acid diglycidyl ester, estradiol, citric acid and the like, the prepared powder coating can be fully cured at 140/20min, the energy consumption in the production process of the powder coating is greatly reduced, the performance in all aspects meets the use requirement of the common polyester powder coating, but the weather resistance is the conventional weather resistance level and cannot reach the super weather resistance level. In the prior art, neopentyl glycol, ethyl butyl propylene glycol, isophthalic acid, cyclohexanedicarboxylic acid and other synthetic polyester resins are adopted, and the prepared powder coating has excellent mechanical properties, excellent weather resistance and high glossiness of surface gloss of more than 90 degrees, but the curing condition of the powder coating is 200 ℃/15min, and the powder coating cannot meet the low-temperature curing requirement.

Disclosure of Invention

The present invention is directed to solving at least one of the problems of the prior art described above. Therefore, the invention provides a preparation method of polyester resin, and low-temperature curing powder coating containing the polyester resin has excellent weather resistance and leveling property.

The invention provides a polyester resin obtained by the preparation method.

The invention also provides a low-temperature curing powder coating containing the polyester resin, and a preparation method and application thereof.

In a first aspect of the present invention, a polyester resin is provided, the polyester resin comprising a block structure segment derived from a hyperbranched polyester prepolymer and a prepolymer containing a reactive group; the end group of the hyperbranched polyester prepolymer is carboxyl and/or hydroxyl, and is composed of C ₃ ～C ₃₀ Dibasic or polybasic acids or derivatives thereof, C ₂ ～C ₃₀ A dihydric or polyhydric alcohol or a derivative thereof, C ₁₀ ～C ₄₂ Long-chain alkane monobasic acid or dibasic acid is obtained by polycondensation; the prepolymer containing reactive groups comprises at least one of polyester resin prepolymer, acrylic resin prepolymer and polyurethane resin prepolymer, and the reactive groupsComprises at least one of carboxyl, hydroxyl, epoxy, isocyanate, ester, amino, amido and halogenated alkyl.

According to the first aspect of the present invention, at least the following advantageous effects are obtained:

the polyester resin of the invention is a block copolymer formed by hyperbranched polyester prepolymer and prepolymer containing reactive groups, wherein the hyperbranched polyester prepolymer is formed by C ₃ ～C ₃₀ Dibasic or polybasic acids or derivatives thereof, C ₂ ～C ₃₀ A dihydric or polyhydric alcohol or a derivative thereof, C ₁₀ ～C ₄₂ The long-chain alkane monobasic acid or dibasic acid is obtained by polycondensation and has a hyperbranched structure shown in the formula (I) or (II), the powder coating prepared from the polyester resin has excellent weather resistance and leveling property and excellent mechanical property, and the coating can be cured at a low temperature of 130-160 ℃, so that the energy consumption generated in the curing process of the powder coating is greatly reduced.

S in the formula (I) and the formula (II) is carboxyl, and Q is hydroxyl;

preferably, the polyester resin has any one or more of the following properties: (1) an acid value of 15 to 350mgKOH/g, preferably 20 to 50mgKOH/g, more preferably 30 to 33 mgKOH/g; (2) a hydroxyl value of 20 to 350mgKOH/g, more preferably 20 to 100mgKOH/g, still more preferably 35 to 45 mgKOH/g; (3) the content of the isocyanate matrix is 1-10%, and more preferably 5-10%; (4) the epoxy value is 0.1 to 1.0mol/100 g.

Preferably, the mass ratio of the hyperbranched polyester prepolymer to the prepolymer containing reactive groups is 1: 0.2 to 5, more preferably 1: 1-2, more preferably 1: 1.1 to 1.2.

Preferably, the hyperbranched polyester prepolymer has a weight average molecular weight Mw of less than 2500 g/mol; more preferably, the Mw is less than 2000 g/mol.

Preferably, the hyperbranched polyester prepolymer has any one or more of the following properties: (1) an acid value of 0 to 400mgKOH/g, preferably 20 to 380mgKOH/g, more preferably 200 to 220 mgKOH/g; (2) the hydroxyl value is 0 to 400mgKOH/mg, more preferably 20 to 380mgKOH/g, still more preferably 40 to 90 mgKOH/g.

Preferably, when the reactive group-containing prepolymer is a reactive group-containing polyester resin prepolymer, the reactive group-containing polyester resin prepolymer has any one or more of the following properties: (1) an acid value of 20 to 400mgKOH/g, preferably 110 to 120mgKOH/g, and (2) a hydroxyl value of 20 to 400 mgKOH/g; (3) the epoxy value is 0.1 to 1.0mol/100 g.

Preferably, the terminal group of the polyester resin prepolymer containing a reactive group includes at least one of a carboxyl group, a hydroxyl group, or an epoxy group.

Preferably, the theoretical glass transition temperature of the acrylic resin prepolymer containing the reactive group is 30-100 ℃. The ratio of each olefin monomer in the acrylic resin prepolymer containing the reactive group can be calculated by designing a theoretical glass transition temperature, and the theoretical glass transition temperature of the copolymer is calculated according to a FOX equation, wherein the specific calculation formula is as follows:

in the above formula, the first and second carbon atoms are,

is the theoretical Tg of each homopolymer of monomers; w ₁ …W _n The percentage of each monomer in the total mass is shown.

Preferably, when the prepolymer containing the reactive group is a polyurethane resin prepolymer containing the reactive group, the content of the isocyanate matrix in the polyurethane resin prepolymer containing the reactive group is 1-10% by weight.

Preferably, the raw materials for preparing the polyester resin comprise: a hyperbranched polyester prepolymer, a prepolymer containing reactive groups and an esterification catalyst.

Preferably, the esterification catalyst accounts for 0.01-0.02% of the total mass of the polyester resin raw materials, and more preferably 0.017-0.019%.

Preferably, the esterification catalyst comprises at least one of p-toluenesulfonic acid, ethylene glycol antimony, stannous oxalate, tetrabutyl titanate, tetraisopropyl titanate, monobutyl tin oxide.

Preferably, the raw materials for preparing the polyester resin further comprise one of an antioxidant and a curing accelerator.

Preferably, the antioxidant comprises at least one of a primary antioxidant and a secondary antioxidant. The primary antioxidant can capture free radicals generated in the aging process, so that the oxidative decomposition of the polymer is inhibited; the auxiliary antioxidant can decompose unstable polymers into stable inactive free radicals, so that new active free radicals are prevented from being generated, and the purpose of slowing down aging is achieved; the primary and secondary antioxidants can be used independently or in combination.

Preferably, the primary antioxidant comprises at least one of hindered phenol antioxidants and aromatic amine antioxidants, and more preferably, the antioxidant comprises at least one of antioxidant 1010, antioxidant 1076, antioxidant 264, antioxidant CA, antioxidant 330, antioxidant MEB, antioxidant HBP, antioxidant TBM, antioxidant 3114, antioxidant HLS, antioxidant HSS, antioxidant 300, antioxidant 2246, antioxidant DOD and antioxidant EBP.

Preferably, the primary antioxidant comprises at least one of antioxidant 1010, antioxidant 1076, antioxidant CA, antioxidant 264 and antioxidant 3114.

The auxiliary antioxidant comprises at least one of phosphite antioxidant and thioether antioxidant, and comprises at least one of antioxidant 168, antioxidant DLTDP, antioxidant DSTDP, antioxidant TPP, antioxidant TNP, antioxidant TBP, antioxidant DPD, antioxidant PS802, antioxidant PS800, antioxidant 1098, antioxidant 626, antioxidant 4500, antioxidant 323, antioxidant 9228 and antioxidant PEP 36.

Preferably, the secondary antioxidant comprises at least one of antioxidant 168, antioxidant 626, antioxidant TPP, antioxidant 4500, and antioxidant DLTDP.

Preferably, the mass ratio of the antioxidant in the polyester resin is 0.01-0.1%, more preferably 0.01-0.06%, and further preferably 0.016-0.056%.

Preferably, the curing accelerator comprises at least one of phosphines, ammonium salts, tertiary amines and imidazoles curing accelerators; more preferred curing accelerators include at least one of triphenylphosphine, triphenylethylphosphonium bromide, butyltriphenylphosphonium bromide, benzyltriphenylphosphonium bromide, triethylphosphine boron trifluoride, triisopropylphosphine boron trifluoride, trimethylphosphine, benzyltrimethylammonium bromide, dioctadecyldimethylammonium bromide, benzyltriethylammonium chloride, tert-butylamine, triethylamine, triethanolamine, BMDA, DBU, DMP-10, pyridine, 2-methylimidazole, 2-ethylimidazole, 2-ethyl-4-methylimidazole, 2-isopropylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, dimethylimidazole. The curing accelerator can accelerate the crosslinking reaction between the resin and the curing agent, reduce the curing temperature of the powder coating, shorten the curing time, and simultaneously improve the mechanical property, the solvent resistance and the weather resistance of the thermosetting resin.

Preferably, the curing accelerator accounts for 0.001-0.01%, more preferably 0.005-0.01%, and even more preferably 0.005-0.007% of the total mass of the raw materials of the polyester resin.

Preferably, the preparation raw material of the hyperbranched polyester prepolymer comprises C ₃ ～C ₃₀ Dibasic or polybasic acids or derivatives thereof, C ₂ ～C ₃₀ A dihydric or polyhydric alcohol or a derivative thereof, C ₁₀ ～C ₄₂ Long-chain alkane monobasic acid or dibasic acid and an esterification catalyst.

Preferably, said C ₃ ～C ₃₀ Dibasic or polybasic acids or derivatives thereof, C ₂ ～C ₃₀ Dihydric or polyhydric alcohol or derivatives thereof, C ₁₀ ～C ₄₂ The mole ratio of the long-chain alkane monoacid or the diacid is 1: 0.2-2.0: 0.05-3.0, and the more preferable molar ratio is 1: 0.3-1.5: 0.05 to 0.2, and more preferably in a molar ratio of 1: 0.46-1.12: 0.07 to 0.15.

Preferably, the esterification catalyst accounts for 0.05-0.2 mol%, more preferably 0.1-0.2 mol% of the total mol of the raw materials of the hyperbranched polyester prepolymer.

Preferably, said C ₃ ～C ₃₀ The dibasic acid is a compound having two carboxyl groups in the molecule, and includes at least one of isophthalic acid, terephthalic acid, naphthalenedicarboxylic acid, cyclohexanedicarboxylic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, hexadecanedioic acid, heptadecanedioic acid, octadecanedioic acid, eicosanedioic acid, docosanedioic acid, tetracosanedioic acid, pentacosanedioic acid, and tridecanedioic acid.

Preferably, said C ₃ ～C ₃₀ The polybasic acid is a compound having three or more carboxyl groups in the molecule, and comprises at least one of benzene tricarboxylic acid, citric acid, ethylene diamine tetraacetic acid and butane tetracarboxylic acid, and more preferably citric acid and ethylene diamine tetraacetic acid; further preferred is ethylenediaminetetraacetic acid.

Preferably, said C ₃ ～C ₃₀ The derivative of a dibasic acid means C ₃ ～C ₃₀ The compound formed by partially substituting dibasic acid comprises at least one of 2-fluoroisophthalic acid, 5-fluoroisophthalic acid, 3-hydroxy-1, 8-naphthalic anhydride, 1, 2-cyclohexanedicarboxylic acid diglycidyl ester, phthalic acid, butylmalonic acid, methylmalonic acid, 3-thiophenepropanedioic acid, succinic anhydride, tetrafluorosuccinic acid, phenylsuccinic acid, maleic anhydride, glutaric anhydride, hexafluoroglutaric acid, 3-aminoglutaric acid, adipic anhydride, octafluoroadipic acid, perfluorosuberic acid, perfluorosebacic acid, 4-oxododecanedioic acid and 3-hydroxytetradecanedioic acid.

Preferably, said C ₃ ～C ₃₀ The derivative of a polybasic acid means C ₃ ～C ₃₀ The compound in which the polybasic acid is partially substituted comprises at least one of trimellitic anhydride, 5-nitro-1, 2, 3-benzenetricarboxylic acid, 2-hydroxycitric acid, triallyl citrate, ethylenediaminetetraacetic dianhydride, 1,2,3, 4-cyclobutanetetracarboxylic acid and 1,2,3, 4-tetramethyl-1, 2,3, 4-cyclobutanetetracarboxylic dianhydride, and trimellitic anhydride is more preferable.

Preferably, said C ₂ ～C ₃₀ By glycol is meant a compound having two atoms in the moleculeHydroxyl alcohol compounds including at least one of neopentyl glycol, ethylene glycol, diethylene glycol, cyclohexanedimethanol, trimethylpentanediol, bisphenol A, hexanediol, propylene glycol, butanediol, pentanediol, heptanediol, octanediol, decanediol, undecanediol, dodecanediol, tridecanediol, tetradecanediol, pentadecanediol, hexadecanediol, octadecanediol, eicosanediol, docosanediol, and hexacosanediol; more preferred are neopentyl glycol and cyclohexanedimethanol.

Preferably, said C ₂ ～C ₃₀ The polyhydric alcohol of (a) is an alcohol compound having three or more hydroxyl groups in the molecule, and includes at least one of trimethylolpropane, pentaerythritol, dipentaerythritol, trimethylolethane, glycerol, xylitol, sorbitol, glucose, fructose, maltose, starch, lignin, and cellulose; more preferably trimethylolpropane, xylitol, or sorbitol.

Preferably, said C ₂ ～C ₃₀ The derivative of a glycol means C ₂ ～C ₃₀ The diol of (a) is partially substituted to form a compound comprising neopentyl glycol diglycidyl ether, neopentyl glycol 9-phenanthreneborate, neopentyl glycol 1-phenylethenylborate, polyethylene glycol-200, polyethylene glycol-400, polyethylene glycol-600, polyethylene glycol-800, polyethylene glycol-1000, polyethylene glycol-2000, (+ -) -1-phenyl-1, 2-ethanediol, dimethyl diglycolate, 1, 4-cyclohexanedimethanol diisovalerate, polypropylene glycol-400, dipropylene glycol, glycidylpropylene glycol, 1, 4-dibromo-2, 3-butanediol, 2-methyl-2, 4-pentanediol, 3, 6-dithia-1, 8-octanediol, 3, 7-dimethyl-1, 7-octanediol, 1, 2-cyclododecanediol, 1H,12H, 12H-icosyl-1, 12-dodecanediol.

Preferably, said C ₂ ～C ₃₀ The derivative of a polyhydric alcohol means C ₂ ～C ₃₀ The polyol of (1) is partially substituted to produce a compound comprising trimethylolpropane triacrylate, trimethylolpropane triglycidyl ether, trimethylolpropane tris (3-mercaptopropionate), tripentaerythritol, dipentaerythritol, pentaerythritol phosphate, triglycerolAt least one of hexaglycerol, 1, 4-anhydride-D-xylitol, span 20, tween 20, lactulose and hydroxyethyl cellulose.

Preferably, said C ₁₀ ～C ₄₂ The long-chain alkane mono-or dibasic acid refers to a compound having 10 to 42 carbon atoms and having one or two carboxyl groups, and includes at least one of stearic acid, undecanoic acid, lauric acid, myristic acid, margaric acid, eicosanoic acid, behenic acid, montanic acid, melissic acid, lacceric acid, triacontanoic acid, tetracosanoic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, hexadecanedioic acid, heptadecanedioic acid, octadecanedioic acid, eicosanedioic acid, docosanedioic acid, pentacosanedioic acid, and tridecanedioic acid; more preferably at least one of stearic acid, palmitic acid, dodecanedioic acid, tridecanedioic acid.

Preferably, the raw materials for preparing the hyperbranched polyester prepolymer further comprise at least one of an antioxidant and a curing accelerator. The antioxidant accounts for 0.2-2.0 mol%, more preferably 0.2-1.5 mol%, and even more preferably 0.47-0.92 mol% of the total molar amount of the hyperbranched polyester prepolymer raw materials. The curing accelerator accounts for 0.01-0.5 mol%, more preferably 0.02-0.40 mol% of the total molar amount of the hyperbranched polyester prepolymer raw materials.

Preferably, the antioxidant comprises a main antioxidant and an auxiliary antioxidant, and the molar ratio of the main antioxidant to the auxiliary antioxidant is 1: 1-3, and more preferably 1: 1-2. The types of the primary antioxidant and the secondary antioxidant are as described above, and are not described in detail herein.

Preferably, the type of cure accelerator is as described above and will not be described in detail herein.

Preferably, the raw materials for preparing the hyperbranched polyester prepolymer also comprise an organic solvent. The organic solvent and C ₂ ～C ₃₀ And mixing dihydric alcohol or polyhydric alcohol or derivatives thereof and then dropwise adding the mixture into a reaction system. The organic solvent has the functions of keeping the reaction heated uniformly, controlling the reaction temperature of the system more easily and avoiding polymer gel caused by viscosity shock under the high-temperature condition.

Preferably, the mass molar ratio of the organic solvent to the hyperbranched polyester prepolymer raw material is 50-350 g/mol, and more preferably 76-330 g/mol.

Preferably, the organic solvent comprises at least one of an alkane, an alkene, an alcohol, an ether, an ester, a ketone, an aldehyde, an amine, a halogenated hydrocarbon, a heterocyclic compound, a nitrogen-containing compound, a sulfur-containing compound.

Preferably, the organic solvent includes at least one of petroleum ether, gasoline, kerosene, diesel oil, lubricating oil, paraffin, asphalt, cyclohexane, benzene, toluene, xylene, N-hexane, N-heptane, N-octane, methanol, ethanol, isopropanol, butanol, cyclohexanol, benzyl alcohol, terpineol, ethylene glycol, propylene glycol monomethyl ether, ethylene glycol monoethyl ether and ethylene glycol mono-N-butyl ether, acetone, methyl ethyl ketone, methyl acetate, ethyl acetate, N-propyl acetate, propylene glycol methyl ether acetate, ethylene glycol monomethyl ether acetate, phenol, cresol, terpinene, limonene, acetal, furfural, ethylenediamine, oleylamine, chlorobenzene, dichlorobenzene, dichloromethane, tetrahydrofuran, N-dimethylformamide, pyridine, dimethyl sulfoxide.

Preferably, the organic solvent includes at least one of propylene glycol methyl ether acetate, ethylene glycol monomethyl ether acetate, N-dimethylformamide, ethyl acetate, N-hexane, N-heptane, and N-octane.

Preferably, when the reactive group-containing prepolymer is a reactive group-containing polyester resin prepolymer, the raw material for preparing the reactive group-containing polyester resin prepolymer comprises a diol or a polyol and/or a derivative thereof, a diacid or a polyacid or a derivative thereof, and an esterification catalyst.

Preferably, the diol or polyol or derivative thereof is C ₂ ～C ₃₀ A dihydric or polyhydric alcohol or a derivative thereof, said C ₂ ～C ₃₀ The types of diols or polyols or derivatives thereof are as described above.

Preferably, the dibasic or polybasic acid or derivative thereof is C ₃ ～C ₃₀ A dibasic or polybasic acid or derivative thereof, said C ₃ ～C ₃₀ Dibasic acidOr the type of polyacid or derivative thereof is as described above.

Preferably, the molar ratio of the dihydric alcohol or the polyhydric alcohol or the derivative thereof to the dibasic acid or the polybasic acid or the derivative thereof for preparing the polyester resin prepolymer containing the reactive group is 0.7-1.5: 1, more preferably 0.9 to 1: 1.

preferably, the esterification catalyst accounts for 0.05-0.1 mol% of the total molar amount of the raw materials of the polyester resin prepolymer containing the reactive group, and more preferably 0.08-0.1 mol%.

Preferably, the raw material for preparing the polyester resin prepolymer containing the reactive group further comprises a glycidyl ether compound and a derivative thereof, wherein the glycidyl ether compound and the derivative thereof comprise at least one of triglycidyl isocyanurate, tert-butyl glycidyl ether, o-toluene glycidyl ether, maleic anhydride, glutaconic acid, fumaric anhydride, chloromaleic acid, itaconic acid, citraconic acid and mesaconic acid.

Preferably, the molar ratio of the glycidyl ether compound and the derivative thereof to the dibasic acid or the polybasic acid or the derivative thereof is 0.2-2.0: 1.

preferably, the raw materials for preparing the polyester resin prepolymer containing the reactive group further comprise an acid hydrolysis agent, wherein the acid hydrolysis agent accounts for 3-10 mol%, more preferably 4.2-6.5 mol% of the total molar amount of the raw materials of the polyester resin prepolymer containing the reactive group. The acidolysis agent can adjust the number of terminal groups.

Preferably, the acidolysis agent is C ₂ ～C ₃₀ A diol or polyol or a derivative thereof, C ₂ ～C ₃₀ The specific types of the diols or polyols or derivatives thereof are as described above.

Preferably, the reactive polyester resin-containing prepolymer further comprises at least one of an antioxidant and a curing accelerator. The antioxidant accounts for 0.02-0.1 mol%, more preferably 0.04-0.05 mol% of the total molar weight of the prepolymer raw materials of the polyester resin containing reactive groups. The curing accelerator accounts for 0.01-0.05 mol%, more preferably 0.03-0.04 mol% of the total molar amount of the raw materials of the reactive group-containing polyester resin prepolymer.

The antioxidant comprises a main antioxidant and an auxiliary antioxidant, and the molar ratio of the main antioxidant to the auxiliary antioxidant is 1: 0.8 to 1.5; more preferably 1: about 1. The type of antioxidant is as described above.

Preferably, the curing accelerator species are as described hereinbefore.

Preferably, when the prepolymer containing the reactive group is an acrylic resin prepolymer containing the reactive group, the raw materials for preparing the acrylic resin prepolymer containing the reactive group include an olefin monomer and an initiator.

Preferably, the raw materials for preparing the acrylic resin prepolymer containing the reactive group further comprise at least one of a molecular regulator and an organic solvent.

Preferably, the amount of the molecular regulator is 1-5%, more preferably 2-3% of the total mass of the alkene monomers. The molecular weight regulator can control the molecular weight and the molecular weight distribution of the acrylic resin prepolymer containing the reactive group.

Preferably, the amount of the initiator is 2 to 8%, more preferably 3 to 5% of the total mass of the ethylenic monomer.

Preferably, the raw materials for preparing the acrylic resin prepolymer containing the reactive group further comprise an organic solvent, and the mass ratio of the organic solvent to the vinyl monomer is 0.5-2: 1, more preferably 0.8: about 1. The kind of the organic solvent is as described above, and is not described herein again.

Preferably, the olefinic monomer includes at least one of acrylic acid, methacrylic acid, methacrylate ester, glycidyl ester and derivatives thereof, specifically including acrylic acid, methyl methacrylate, butyl methacrylate, glycidyl methacrylate, methyl acrylate, butyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, styrene, isodecyl acrylate, heptadecyl acrylate, isobutyl acrylate, tert-butyl methacrylate, cyclohexyl methacrylate, dicyclopentadienyl acrylate, hydroxybutyl acrylate, hydroxyethyl caprolactone acrylate, lauryl acrylate, stearyl acrylate, lauryl methacrylate, stearyl methacrylate, behenyl acrylate, behenyl methacrylate, ureido methyl acrylate, and derivatives thereof, At least one of ethyl diethylene glycol acrylate, polyethylene glycol (350) methacrylate, polyethylene glycol (2000) methacrylate, long-chain alkyl alcohol polyoxyethylene ether acrylate, and long-chain alkyl alcohol polyoxyethylene ether methacrylate.

Preferably, the molecular weight regulator is a compound having a large chain transfer constant, including aliphatic thiols, xanthogen disulfides, polyphenols, sulfur, halides and nitroso compounds, and specifically includes at least one of n-dodecyl mercaptan, sec-dodecyl mercaptan, mercaptoethanol, thioglycolic acid, isooctyl 3-mercaptopropionate, tert-dodecyl mercaptan, diisopropyl xanthogen disulfide, chloroform, carbon tetrachloride, carbon tetrabromide, tert-butyl mercaptan, n-butyl mercaptan, octadecyl mercaptan, pyrogallol, sulfur, dimethyl nitrosamine, nitrosamide, and alpha-methyl styrene linear dimer.

Preferably, the initiator is an initiator which can be decomposed into free radicals when heated and can initiate the free radical polymerization of the monomer, and the initiator comprises at least one of peroxide initiators, azo initiators and redox initiators.

Preferably, the peroxy compound initiator comprises benzoyl peroxide, lauroyl peroxide, t-amyl peroxypivalate, t-amyl peroxy-2-ethylhexanoate, t-butyl peroxy-2-ethylhexanoate, 1 '-bis (t-amylperoxy) cyclohexane, 1' -bis (t-butylperoxy) -3,3, 5-trimethylcyclohexane, t-butyl peroxy-2-ethylhexylcarbonate, at least one of tert-amyl peroxyacetate, tert-butyl peroxy-3, 3, 5-trimethylhexanoate, tert-butyl peroxybenzoate, dicumyl peroxide, di-tert-amyl peroxide, di-tert-butyl peroxide, cumene hydroperoxide, tert-amyl hydroperoxide and tert-butyl hydroperoxide.

Preferably, the azo initiator includes at least one of azobisisobutyronitrile, azobisisovaleronitrile, azobisisoheptonitrile, azobisisobutyronitrile formamide, azobisdicyclohexylcarbonitrile, dimethyl azobisisobutyrate, azobisisobutyramidine hydrochloride, azobisisopropylimidazoline hydrochloride, and azobiscyanovaleric acid.

Preferably, the redox initiator comprises at least one combination of dibenzoyl peroxide and N, N-dimethylaniline, dibenzoyl peroxide and N, N-dimethyl-p-toluidine, cyclohexanone peroxide and N, N-diethylaniline, methyl ethyl ketone peroxide and a thiol, dibenzophthalein peroxide and N, N-diethylaniline.

Preferably, when the reactive group-containing prepolymer is a reactive group-containing polyurethane resin prepolymer, the raw materials for preparing the reactive group-containing polyurethane resin prepolymer include a diol or a polyol or a derivative thereof, a diacid or a polyacid or a derivative thereof, an isocyanate compound, and an esterification catalyst.

Preferably, the molar ratio of the dihydric alcohol or the polyhydric alcohol or the derivative thereof, the dibasic acid or the polybasic acid or the derivative thereof and the isocyanate compound for preparing the polyurethane resin prepolymer containing the reactive group is 25-30: 15-20: 1, more preferably 30: 20: about 1.

Preferably, the molar percentage of the esterification catalyst in the reactive group-containing polyurethane resin prepolymer raw material is 0.05-0.1 mol%.

Preferably, the isocyanate-based compound includes at least one of toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, and lysine diisocyanate.

Preferably, the diol or polyol or derivative thereof is C ₂ ～C ₃₀ A diol or polyol or a derivative thereof, C ₂ ～C ₃₀ The diol or polyol or derivative thereof of (3) is as described above.

Preferably, the dibasic or polybasic acid or derivative thereof is C ₃ ～C ₃₀ A dibasic or polybasic acid or derivative thereof, said C ₃ ～C ₃₀ The kinds of the dibasic or polybasic acids or derivatives thereof are as defined aboveThe following steps are carried out.

In a second aspect of the present invention, a method for preparing a polyester resin is provided, which comprises the following steps: and mixing the hyperbranched polyester prepolymer, the prepolymer containing reactive groups and an esterification catalyst, and carrying out polycondensation reaction to obtain the polyester resin.

Preferably, the polycondensation reaction is carried out in stages, comprising a first stage: reacting for 1-3 h at 160-190 ℃; and a second stage: reacting for 2-5 h at 210-240 ℃; and a third stage: reacting for 2-5 h at 210-240 ℃ in a vacuum state.

Preferably, the polycondensation reaction comprises a first stage: reacting for 2-3 h at 160-180 ℃; and a second stage: reacting for 4 hours at 220 ℃; and a third stage: reacting for 2 hours at 220-240 ℃ in a vacuum state.

Preferably, the temperature rise rate of the second stage of the polycondensation reaction is 1-5 ℃/15min, more preferably 1-3 ℃/15 min.

Preferably, the degree of vacuum in the third stage of the polycondensation reaction is in the range of-0.085 to-0.1 MPa, more preferably in the range of-0.096 to-0.098 MPa.

Preferably, the preparation method of the polyester resin further comprises a premixing treatment before the polycondensation reaction, specifically, the hyperbranched polyester prepolymer, the polyester resin prepolymer containing reactive groups and the catalyst are mixed, heated to 60-140 ℃, and melted and mixed; more preferably, the mixing temperature is 80 to 120 ℃.

Preferably, after the polycondensation reaction is finished, adding an antioxidant and a curing accelerator, preserving the heat for 10-30 min, and discharging to obtain the polyester resin.

Preferably, the preparation method of the hyperbranched polyester prepolymer comprises the following steps: c is to be ₃ ～C ₃₀ Dibasic or polybasic acid or derivative thereof, C ₂ ～C ₃₀ A dihydric or polyhydric alcohol or a derivative thereof, C ₁₀ ～C ₄₂ And mixing long-chain alkane monobasic acid or dibasic acid and an esterification catalyst, and reacting to obtain the hyperbranched polyester prepolymer.

Preferably, the reaction includes at least one of a polycondensation method, a ring-opening polymerization method, and a living radical polymerization method, and more preferably, a polycondensation method.

Preferably, the preparation method of the hyperbranched polyester prepolymer comprises the following steps: c is to be ₃ ～C ₃₀ Dibasic or polybasic acids or derivatives thereof, C ₂ ～C ₃₀ Mixing dihydric alcohol or polyhydric alcohol or its derivative with esterification catalyst, adding C ₁₀ ～C ₄₂ And (3) carrying out heat preservation reaction on long-chain alkane monoacid or diacid, and carrying out reduced pressure reaction after the acid value or the hydroxyl value reaches the standard to obtain the hyperbranched polyester prepolymer.

Preferably, said C ₃ ～C ₃₀ Dibasic or polybasic acids or derivatives thereof, C ₂ ～C ₃₀ The reaction temperature of the dihydric alcohol or the polyhydric alcohol or the derivative thereof is divided into two stages, the reaction temperature of the first stage is 100-130 ℃, more preferably 120-130 ℃, and the reaction time of the first stage is 1-5 h; the reaction temperature of the second stage is 140-180 ℃, more preferably 150-180 ℃, the temperature rise rate of the second stage is 1-5 ℃/30min, more preferably 1-2 ℃/30min, and the reaction time of the second stage is 1-5 h, more preferably 2-4 h.

Preferably, the addition of C ₁₀ ～C ₄₂ The long-chain alkane monobasic acid or dibasic acid is subjected to heat preservation reaction for 1-5 hours. More preferably 3 to 4 hours.

Preferably, the acid value reaching the standard is 200-300 mgKOH/g, more preferably 220-240 mgKOH/g; the hydroxyl value reaching the standard is 50-150 mgKOH/g, and more preferably 60-110 mgKOH/g.

Preferably, the vacuum degree of the decompression reaction after the acid value or the hydroxyl value reaches the standard is-0.09 MPa to-0.1 MPa, and more preferably-0.096 MPa to-0.098 MPa.

Preferably, at said C ₃ ～C ₃₀ Dibasic or polybasic acid or derivative thereof, C ₂ ～C ₃₀ Before the reaction of the dihydric alcohol or the polyhydric alcohol or the derivative thereof, the C is also included ₃ ～C ₃₀ Pre-mixing the dibasic acid or polybasic acid or derivative thereof and the esterification catalyst at the mixing temperature of 60-120 ℃, preferably 80-100 ℃, and then adding C in a dropwise manner ₂ ～C ₃₀ The dropping time of the solution of the dihydric alcohol or the polyhydric alcohol or the derivative thereof is 2 to 8 hours, and the preferable time is 2.5 to 6 hours.

Preferably, an antioxidant and a curing accelerator are added after the pressure reduction reaction, and specifically, when the hydroxyl value is 40-120 mgKOH/g or the acid value is 180-300 mgKOH/g, the antioxidant and the curing accelerator are added and mixed, and the hyperbranched polyester prepolymer is obtained after discharging; more preferably, when the hydroxyl value is 40-90 mgKOH/g or the acid value is 200-220 mgKOH/g, adding an antioxidant and a curing accelerator, mixing, and discharging to obtain the hyperbranched polyester prepolymer.

Preferably, the time for mixing after adding the antioxidant and the curing accelerator is 0.2-2 hours, and more preferably 0.3-1 hour.

Preferably, the preparation process of the hyperbranched polyester prepolymer further comprises adding an organic solvent. The organic solvent and C ₂ ～C ₃₀ And mixing dihydric alcohol or polyhydric alcohol or derivatives thereof and then dropwise adding the mixture into a reaction system. The organic solvent has the functions of keeping the reaction heated uniformly, controlling the reaction temperature of the system more easily and avoiding polymer gel caused by viscosity shock under the high-temperature condition.

Preferably, when the prepolymer containing the reactive group is a polyester resin prepolymer containing the reactive group, the preparation method of the polyester resin prepolymer containing the reactive group comprises the following steps:

mixing dihydric alcohol or polyhydric alcohol or derivatives thereof, dibasic acid or polybasic acid or derivatives thereof, glycidyl ether compounds or derivatives thereof and an esterification catalyst, and carrying out polycondensation reaction;

adding an acidolysis agent, carrying out heat preservation reaction, and discharging to obtain the polyester resin prepolymer containing the reactive group.

Preferably, the mixing temperature of the dihydric alcohol or the polyhydric alcohol or the derivative thereof, the dibasic acid or the polybasic acid or the derivative thereof, the glycidyl ether compound or the derivative thereof and the esterification catalyst is 80-120 ℃, and more preferably 100-120 ℃.

Preferably, the polycondensation reaction of the reactive group-containing polyester resin prepolymer is performed under an inert gas atmosphere, such as nitrogen, argon, and the like. The polycondensation reaction is carried out in two stages, wherein the reaction temperature in the first stage is 170-190 ℃, and 180-190 ℃ is more preferable; the reaction time in the first stage is 1 to 5 hours, and more preferably 3 to 4 hours. The reaction temperature in the second stage is 230-255 ℃, and 240-250 ℃ is more preferable; the reaction time of the second stage is 1-5 h, and preferably 2-4 h; the temperature rise rate in the second stage is 2-5 ℃/30min, and more preferably 2-3 ℃/30 min.

Preferably, when the reactive group-containing prepolymer is a reactive group-containing acrylic resin prepolymer, the method for preparing the reactive group-containing acrylic resin prepolymer comprises the following steps: and (3) mixing an olefin monomer and an initiator to perform solution polymerization reaction to obtain the acrylic resin prepolymer containing the reactive group.

The preparation process of the acrylic resin mainly comprises the following steps: solution polymerization, bulk polymerization, emulsion polymerization, and suspension polymerization; the solution polymerization refers to that a monomer and an initiator are mixed and dissolved in a proper solvent to carry out polymerization reaction in a dropwise adding mode, the prepared acrylic resin has proper molecular weight and molecular weight distribution, the product quality is stable, and the subsequent solvent treatment is troublesome; the bulk polymerization is obtained by directly polymerizing a monomer and a small amount of initiator, the prepared acrylic resin product has high purity, simple process and simple post-treatment, but the viscosity is higher during resin synthesis, heat cannot be transferred in time, and the reaction is easy to implode; the emulsion polymerization means that the monomer is dispersed in water to form emulsion under the action of an emulsifier, and then an initiator is added to initiate the polymerization of the monomer, so that the prepared acrylic resin does not contain an organic solvent, the reaction is easy to control, but the emulsifier remained in the product is difficult to remove, and the performance of the polymer is influenced; the suspension polymerization refers to that a monomer dissolved with an initiator is suspended in water in a droplet shape for polymerization, the prepared acrylic resin has low viscosity, the relative molecular weight and distribution are easy to control, the polymerization heat is easy to be led out, but a dispersant remained in the product is difficult to be led out, and the performance of the polymer is influenced; the invention considers the performance, cost and quality stability of the product, and selects solution polymerization as the production process for preparing the acrylic resin.

Preferably, the preparation method of the acrylic resin prepolymer containing reactive groups comprises the following steps:

s1, mixing part of the organic solvent with part of the initiator to obtain initiator mixed solution;

s2, adding the mixture of olefin monomer, molecular weight regulator and partial initiator dropwise into the initiator mixture, and reacting;

and S3, adding the residual organic solvent and initiator mixed solution, and carrying out heat preservation reaction to obtain the acrylic resin prepolymer containing the reactive groups.

Preferably, the reaction temperature of step S2 is 50 to 160 ℃, more preferably 130 to 150 ℃, and even more preferably about 138 ℃. The reaction time of the step S2 is 1-10 h, and more preferably 1-8 h.

Preferably, in the step S2, the dropping time of the mixed solution of the olefin monomer, the molecular weight regulator and the partial initiator is 2-5 hours, and the reaction is carried out for 1-3 hours under heat preservation after the dropping is completed.

Preferably, the time of the heat preservation reaction in the step S3 is 3 to 6 hours, and more preferably about 6 hours.

Preferably, the initiator is added in three times, and the mass ratio of the initiator in the steps S1, S2 and S3 is 1-5: 4-7: 1, more preferably 3: 6: about 1. The stepwise addition of the initiator can effectively improve the conversion rate of the monomer.

Preferably, the solvent is added in two times, and the mass ratio of the solvent in the steps S1 and S3 is 5-12: 1, more preferably 9 to 10: 1.

preferably, the step S3 is followed by a post-treatment step, specifically, the temperature is raised to 160 to 210 ℃, most of the organic solvent in the system is removed, the pressure is reduced, the vacuum operation is performed to remove the residual organic solvent and small molecules, and the acrylic resin prepolymer containing the reactive group is obtained after discharging. The vacuum degree of the vacuum operation is-0.009-0.1 MPa, and the vacuum operation time is 1-3 h.

Preferably, when the reactive group-containing prepolymer is a reactive group-containing polyurethane resin prepolymer, the method for preparing the reactive group-containing polyurethane resin prepolymer comprises the following steps:

mixing dihydric alcohol or polyhydric alcohol or derivatives thereof, dibasic acid or polybasic acid or derivatives thereof and an esterification catalyst, and reacting to obtain a mixture;

and dripping the isocyanate compound into the mixture to react to obtain the polyurethane prepolymer containing the reactive group.

The reactive group-containing polyurethane resin prepolymer is a polymer with a molecular main chain having-NH-COO-characteristic group, and the current preparation method mainly uses phosgene as a raw material and then reacts with diamine or dihydric alcohol to obtain the reactive group-containing polyurethane resin prepolymer, so that the synthesis route is divided into two routes, and the synthesis principle is as follows:

(1) reaction of Dichloroformate with diamine

(2) Addition reaction of diisocyanate with diol

Among these, the production method (2) is preferred because hydrogen on the alcoholic hydroxyl group is directly added to the nitrogen atom of the isocyanate group, the reaction does not produce by-products, and the subsequent treatment is small.

Preferably, the reaction temperature of the dihydric alcohol or the polyhydric alcohol or the derivative thereof and the dibasic acid or the polybasic acid or the derivative thereof is 60-120 ℃, and more preferably 80-100 ℃; the reaction time is 1-5, and more preferably 4-5 h.

Preferably, the isocyanate compound is dripped into the mixture for 2-8 hours, and more preferably 2.5-6 hours. And reacting for 3-6 h after the dropwise adding is finished, and preferably reacting for 4-6 h.

In a third aspect of the invention, a low temperature curing powder coating composition is provided, comprising the polyester resin.

Preferably, the low temperature curing powder coating composition comprises the following components in parts by weight:

preferably, the low-temperature curing powder coating composition comprises the following components in parts by weight:

preferably, the crosslinking agent comprises dicyandiamide, substituted dicyandiamide, aromatic amines, dicarboxylic acid dihydrazide, acid anhydrides, imidazoles, imidazolines, cyclic amidines, boron trifluoride amine complexes, phenolic hydroxyl resins, polyester resins, acrylic resins, triglycidyl isocyanurate, polyepoxy compounds PT910, PT710, PT810, PT912, tetramethylolglycoluril, Primid XL 552, Primid QM 1260, Primid SF 4510, T-105M, SJ-552, amino resins, HF3180, blocked isophorone diisocyanate, caprolactam blocked isophorone diisocyanate trimer, caprolactam blocked trimethylolpropane and isophorone diisocyanate adduct, isophorone diisocyanate and pentaerythritol prepolymer, isophorone diisocyanate and ethylene glycol prepolymer, polycarboxylic acids, polyamines, polyphenols, imidazoles, imidazolines, cyclic amidines, borazoles, phenoxyamines, polyoxyalkylenes PT910, PT710, PT810, Primid QMs, Primid, and their derivatives, At least one of carboxylic acid anhydride, polybasic carboxyl compound and epoxy resin.

Preferably, the pigment and filler comprises at least one of titanium dioxide and barium sulfate.

Preferably, the defoamer comprises benzoin.

Preferably, the leveling agent includes at least one of 701 and 703.

In a fourth aspect of the present invention, a method for preparing a low temperature curing powder coating is provided, which comprises the following steps: and mixing the components to obtain the low-temperature curing powder coating.

Preferably, the preparation method of the low-temperature curing powder coating comprises the following steps: mixing the components, performing melt extrusion through an extruder, tabletting, cooling, crushing, sieving and mixing to obtain the low-temperature curing powder coating.

In a fifth aspect of the present invention, a method for applying a low-temperature curing powder coating is provided, which includes the steps of applying the low-temperature curing powder coating to a surface of a substrate, and heating and curing to form a coating on the surface of the substrate.

Preferably, the curing temperature is 80-150 ℃, and more preferably about 130 ℃; the curing time is 5-20 min, and more preferably about 10 min.

Compared with the prior art, the invention at least has the following beneficial effects:

the novel polyester resin of the invention adopts hyperbranched polyester prepolymer and prepolymer containing reactive groups to form two-block copolymer, and the finally synthesized novel polyester resin has the advantages of both the hyperbranched polyester prepolymer and the prepolymer containing reactive groups; the prepolymer containing the reactive group improves the weather resistance of the powder coating and improves the weather resistance of the coating to an ultra-weather resistance level while not influencing the leveling property of the powder coating prepared from the novel polyester resin; the hyperbranched polyester prepolymer is prepared by a multifunctional monomer copolymerization method, a core-carrying hyperbranched polyester prepolymer is formed by phase-change ABx type monomer self-polycondensation, and long-chain alkane dibasic acid is used for modification, so that the synthesized hyperbranched polyester prepolymer has higher crystallinity and lower viscosity, and meanwhile, the synthesized hyperbranched polyester prepolymer contains more multifunctional monomers, provides more reaction active sites for the tail end of a polyester main chain, and the prepared polyester powder coating has better leveling property and can be fully cured at 130 ℃/10 min.

The novel polyester resin for the low-temperature curing, super-weather-proof and high-leveling powder coating is synthesized by adopting the prepolymer containing the reactive group with better weather resistance and the hyperbranched polyester prepolymer with high reactivity and low viscosity, compared with the performance of the traditional super-weather-proof polyester resin, the novel polyester resin synthesized by the invention has lower viscosity and higher reactivity, and the correspondingly prepared powder coating has higher leveling property, can realize low-temperature curing and saves the energy consumption in the curing process of the powder coating. In conclusion, the powder coating prepared from the novel polyester resin synthesized by the invention has excellent weather resistance and leveling property, and can be fully cured at 130 ℃/10 min.

Drawings

The invention is further described with reference to the following figures and examples, in which:

FIG. 1 is AB _x A monomer self-condensed non-nucleated and nucleated monomer polymer;

FIG. 2 is A ₃ And B ₄ Self-polycondensation of monomers to AB ₂ A monomer;

FIG. 3 is a ring-opening polymerization process for preparing hyperbranched polymers;

FIG. 4 is a self-condensing vinyl polymerization to produce a hyperbranched polymer;

FIG. 5 preparation of hyperbranched polymers by proton transfer radical polymerization;

FIG. 6 preparation of hyperbranched polymer by atom transfer radical polymerization;

FIG. 7 preparation of hyperbranched polymers by reversible addition-fragmentation transfer polymerization.

Detailed Description

The concept and technical effects of the present invention will be clearly and completely described below in conjunction with the embodiments to fully understand the objects, features and effects of the present invention. It is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments, and those skilled in the art can obtain other embodiments without inventive effort based on the embodiments of the present invention, and all embodiments are within the protection scope of the present invention.

In order to illustrate the hyperbranched polyester prepolymer (A) of the present invention in more detail, the following will develop a detailed description of the specific synthetic principle or method thereof. The hyperbranched polyester prepolymer of the invention is prepared from ₃ ～C ₃₀ Dibasic or polybasic acids or derivatives thereof, C ₂ ～C ₃₀ A dihydric or polyhydric alcohol or a derivative thereof, C ₁₀ ～C ₄₂ Long-chain alkane monobasic acid or dibasic acid; the reaction comprises at least one of a polycondensation method, a ring-opening polymerization method and a living radical polymerization method, and the specific mechanism of each method is as follows:

as illustrated in FIG. 1, the polycondensation process generally employs AB _x The monomers are self-condensed to form hyperbranched polyester, wherein x is more than or equal to 2, and the functional group A and the functional group B are differentThe reactive group, and the functional group A and the functional group B can perform polycondensation reaction, so that the molecule can be continuously polymerized; wherein B is _x The monomer can be used as nuclear monomer for regulating molecular weight distribution of polymer and preventing AB _x Excessive polycondensation of the monomers results in polymer gels.

In particular, as shown in FIG. 2, at AB _x On the monomer self-polycondensation method, scientific researchers propose A _n +B _m Monomer copolymerization by self-synthesis of AB _x The method is simple to operate, and the available polymerization monomers have wider sources and wider selectivity.

As shown in FIG. 3, the ring-opening polymerization method is strictly speaking also a phase-change AB _x Self-polycondensation of type monomers to form AB by ring opening of cyclic monomers _x Compared with a polycondensation method, the method has the advantages that the reaction speed is high, the prepared polymer has higher molecular weight, small molecules and the like are not generated in the reaction process, and the molecular weight distribution of the polymer is more uniform. But has the defects of complicated process, high cost and the like.

The living radical polymerization process comprises: self-condensing vinyl (SCVP) polymerization, Proton Transfer (PTP) radical polymerization, Atom Transfer (ATRP) radical polymerization, and reversible addition-fragmentation transfer (RAFT) method.

As shown in FIG. 4, the self-condensing vinyl (SCVP) polymerization method uses monomers as both an initiator and a polymerization point for hyper-branching, and R groups on the vinyl groups are activated under external action to generate a plurality of active free radicals to form new activation centers to generate a monomer similar to AB ₂ And the dimer of the monomer is continuously initiated to polymerize to form the hyperbranched polymer. The method can keep the concentration of the active chain constant all the time, and realize the precise control of the molecular weight, the structure and the polymerization rate of the polymer, but has the defect that the polymerization degree and the branching degree of the polymer cannot be controlled.

The Proton Transfer (PTP) free radical polymerization method is to utilize AB containing active hydrogen ₂ The monomer continuously transfers protons and then uses AB ₂ The nucleophilic property of the monomer forms hyperbranched polymer, and the principle of the proton transfer radical polymerization method is shown in figure 5, and the method is an acidThe base-controlled reaction, the nucleophilicity and acidity of the monomer or intermediate dominate the reaction, which also results in the restriction of the reactive monomer and a narrower application range.

The reaction principle of Atom Transfer (ATRP) free radical polymerization is that cuprous abstracts halogen atoms to form high-valence copper and simultaneously generates free radical R, which can initiate monomer synthesis to grow into free radical P _n A free radical P _n By obtaining halogen atoms from higher-valent copper halides to form P _n and-X, so as to achieve dynamic reversible equilibrium with the active species, and the reaction principle of the atom transfer radical polymerization method is shown in figure 6. The atom transfer radical polymerization method has wide monomer application range, controllable reaction temperature and high controllability of molecular structure design.

The reaction principle of the reversible addition-fragmentation transfer (RAFT) method is shown in figure 7, an initiator is heated and decomposed into a primary free radical, the primary free radical is polymerized with a monomer to form a growing free radical, the growing free radical is reversibly added with a C ═ S double bond in a special chain transfer agent dithioester, an addition product can be further cracked with an S-R bond in dithioester to form a new active species R, and then the new active species R and the monomer are initiated to polymerize, so that the high-molecular polymer is formed in a circulating and reciprocating manner. The method has wide monomer selection range and strong molecular design capability, but the preparation of a special chain transfer agent in the method is very difficult.

The following examples were prepared by a polycondensation method in consideration of the production cost of the hyperbranched polyester prepolymer and the ease of handling.

Example 1

This example prepares a polyester resin (C1) by the specific process of:

preparing hyperbranched polyester prepolymer (A1):

(1) adding 12.3mol of isophthalic acid and 1.0mol of trimellitic anhydride and 0.03mol of p-toluenesulfonic acid into a reaction kettle, and heating to 100 ℃;

(2) adding 12.0mol of neopentyl glycol, 2.2mol of trimethylolpropane and 0.7mol of xylitol into 30.4mol of N, N-dimethylformamide for dissolving, after the alcohol is completely dissolved, dropwise adding the mixture into the reaction kettle in the step (1) within 2.5h, introducing nitrogen and condensed water, quickly heating to 120 ℃, and preserving heat for 5h after the temperature is set;

(3) then the temperature is programmed to be raised to 150 ℃, the temperature raising rate is 2 ℃/30min, and the temperature is preserved for 3h after the set temperature is reached;

(4) adding 1.0mol of stearic acid, and keeping the temperature for 3 hours; and when the hydroxyl value is reduced to 110mgKOH/g, carrying out vacuum reduction reaction, removing micromolecules and solvents in the reaction kettle, adding 0.07mol of antioxidant 1076, 0.07mol of antioxidant 626 and 0.006mol of triphenyl ethyl phosphine bromide when the vacuum degree is-0.096 MPa and the hydroxyl value is 80-90 mgKOH/g, stirring for 0.3h, and stopping the reaction to obtain the hyperbranched polyester prepolymer (A1).

(II) preparing a polyester resin prepolymer (B1) containing reactive groups:

(1) adding 11mol of neopentyl glycol, 2.1mol of 1, 4-cyclohexanedimethanol, 13.5mol of isophthalic acid and 1.0mol of tetrafluorosuccinic acid into a reaction kettle, adding 0.03mol of monobutyl tin oxide, and heating to 120 ℃;

(2) after the materials are completely melted, stirring, condensing water, introducing nitrogen, rapidly heating to 190 ℃, preserving heat for 3 hours, then programming to 243 ℃, heating at the rate of 2 ℃/30min, and preserving heat for 4 hours after the materials reach the set temperature;

(3) adding 1.8mol of isophthalic acid into a reaction kettle, preserving heat for 3h, adding 0.007mol of antioxidant 1010, 0.007mol of antioxidant 168 and 0.009mol of dimethyl imidazole when the acid value is 110-120 mgKOH/g, stirring for 1.0h, and stopping reaction to obtain a polyester prepolymer (B1).

(III) preparation of polyester resin (C1):

(1) adding 10.0kg of hyperbranched polyester prepolymer (A1), 11.0kg of polyester resin prepolymer (B1) containing reactive groups and 0.02mol (3.86g) of monobutyl tin oxide into a reaction kettle, heating to 120 ℃, starting stirring after materials are completely melted, introducing nitrogen and condensed water, quickly heating to 180 ℃, and preserving heat for 3 hours after the temperature is set;

(2) then the temperature is programmed to be increased to 220 ℃, the temperature increase rate is 2 ℃/15min, and the temperature is maintained for 4h after the temperature reaches the set temperature;

(3) carrying out vacuum polycondensation reaction, wherein the vacuum degree is-0.098 MPa, and the vacuumizing time is 2 h.

(4) Adding 0.01mol (11.78g) of antioxidant 1010 and 0.004mol (1.49g) of triphenyl ethyl phosphine bromide, preserving the heat for 30min, and discharging to obtain the polyester resin (C1) with the acid value of 30-33 mgKOH/g.

Example 2

This example prepared a polyester resin (C2) by the specific process of:

preparing hyperbranched polyester prepolymer (A2):

(1) adding 7.2mol of isophthalic acid, 2.1mol of adipic acid and 3.9mol of citric acid, and adding 0.03mol of p-toluenesulfonic acid into a reaction kettle, and heating to 100 ℃;

(2) adding 7.2mol of neopentyl glycol, 3.0mol of trimethylolpropane and 2.4mol of dipentaerythritol into 31.5mol of ethylene glycol monomethyl ether acetate for dissolving, after the alcohol is completely dissolved, dropwise adding the mixture into the reaction kettle in the step (1) within 3h, introducing nitrogen and condensed water, quickly heating to 120 ℃, keeping the temperature for 4h after the temperature reaches a set temperature;

(3) then the temperature is programmed to 160 ℃, the heating rate is 1 ℃/30min, and the temperature is kept for 2h after the temperature reaches the set temperature;

(4) adding 1.6mol of palmitic acid, and keeping the temperature for 3 hours; and when the hydroxyl value is reduced to 110mgKOH/g, carrying out vacuum reduction reaction, removing micromolecules and solvents in the reaction kettle, adding 0.07mol of antioxidant 1076, 0.07mol of antioxidant 626 and 0.006mol of triphenyl ethyl phosphine bromide when the vacuum degree is-0.096 MPa and the hydroxyl value is 80-90 mgKOH/g, stirring for 0.3h, and stopping the reaction to obtain the hyperbranched polyester prepolymer (A2).

(II) preparing a polyester resin prepolymer (B2) containing reactive groups:

(1) adding 11.0mol of neopentyl glycol, 3.5mol of 1, 4-cyclohexanedimethanol, 7.2mol of isophthalic acid and 6.7mol of 1, 4-cyclohexanedicarboxylic acid into a reaction kettle, adding 0.03mol of monobutyl tin oxide, and heating to 120 ℃;

(2) after the materials are completely melted, stirring, condensing water, introducing nitrogen, rapidly heating to 180 ℃, preserving heat for 4 hours, then programming to 240 ℃, heating at the rate of 2 ℃/30min, and preserving heat for 4 hours after the materials reach the set temperature;

(3) adding 1.2mol of isophthalic acid into a reaction kettle, preserving heat for 2h, adding 0.007mol of antioxidant 1010, 0.007mol of antioxidant 168 and 0.009mol of dimethyl imidazole when the acid value is 110-120 mgKOH/g, stirring for 1.0h, and stopping reaction to obtain a polyester prepolymer (B2).

(III) preparation of polyester resin (C2):

(1) adding 10.0kg of hyperbranched polyester prepolymer (A2), 11.0kg of polyester resin prepolymer (B2) containing reactive groups and 0.02mol (3.86g) of monobutyl tin oxide into a reaction kettle, heating to 120 ℃, starting stirring after materials are completely melted, introducing nitrogen and condensed water, quickly heating to 180 ℃, and preserving heat for 3 hours after the set temperature is reached;

(2) then the temperature is programmed to be increased to 220 ℃, the temperature increase rate is 2 ℃/15min, and the temperature is maintained for 4h after the temperature is increased to the set temperature;

(4) Adding 0.01mol (11.78g) of antioxidant 1010 and 0.004mol (1.49g) of triphenyl ethyl phosphine bromide, preserving the temperature for 30min, and discharging to obtain polyester resin (C2) with the acid value of 30-33 mgKOH/g.

Example 3

This example prepares a polyester resin (C3) by the specific process of:

preparing hyperbranched polyester prepolymer (A3):

(1) adding 13.5mol of isophthalic acid and 2.1mol of ethylenediamine tetraacetic acid into a reaction kettle, adding 0.038mol of tetrabutyl titanate, and heating to 100 ℃;

(2) adding 6.2mol of neopentyl glycol and 1.1mol of sorbitol into 62.8mol of propylene glycol methyl ether acetate for dissolving, after the alcohol is completely dissolved, dropwise adding the mixture into the reaction kettle in the step (1) within 4h, introducing nitrogen and condensed water, rapidly heating to 120 ℃, and preserving heat for 4h after the temperature is set;

(3) then the temperature is programmed to 180 ℃, the heating rate is 2 ℃/30min, and the temperature is kept for 3h after the set temperature is reached;

(4) then 2.2mol of dodecanedioic acid is added, and the heat preservation is continued for 3 hours; and (3) when the acid value is 220-240 mgKOH/g, carrying out vacuum reduction reaction, removing small molecules and solvents in the reaction kettle, keeping the vacuum degree at-0.098 MPa, adding 0.08mol of antioxidant 2246, 0.15mol of antioxidant 4500 and 0.01mol of dioctadecyl dimethyl ammonium bromide after the acid value is 200-220 mgKOH/g, stirring for 0.5h, and stopping the reaction to obtain the hyperbranched polyester prepolymer (A3).

(II) preparing an acrylic resin prepolymer (B3) containing reactive groups:

(1) 1080.0g of dimethylbenzene and 17.0g of di-tert-amyl peroxide are put into a reaction kettle, the temperature is rapidly raised to 138 ℃, and the temperature is kept for 1h under the reflux state of an organic solvent;

(2) 507.0g of methyl methacrylate, 416.0g of acrylic acid-2-hydroxypropyl ester, 577.0g of styrene, 30.0g of mercaptoethanol and 34.0g of di-tert-amyl peroxide are mixed and dripped into a reaction kettle, the dripping time is 5 hours, and the mixed solution is kept warm for 3 hours after the dripping is finished;

(3) adding the rest 120.0g of dimethylbenzene and 5.7g of di-tert-amyl peroxide initiator into a reaction kettle, and preserving heat for 6 hours;

(3) quickly heating the reaction kettle to 190 ℃, and removing most of the organic solvent in the system;

(4) removing residual organic solvent and micromolecules by vacuum decompression operation, wherein the vacuum degree is-0.098 MPa, the vacuumizing time is 2h, and discharging while the acrylic resin prepolymer (B3) is obtained.

(III) preparation of polyester resin (C3):

(1) adding 10.0kg of hyperbranched polyester resin (A3), 11.2kg of acrylic resin prepolymer (B3) containing reactive groups and 0.02mol (3.86g) of monobutyl tin oxide into a reaction kettle, heating to 100 ℃, starting stirring after materials are completely melted, introducing nitrogen and condensed water, quickly heating to 180 ℃, and preserving heat for 3 hours after the temperature is set;

(2) then the temperature is programmed to 240 ℃, the heating rate is 3 ℃/15min, and the temperature is kept for 3h after the temperature reaches the set temperature;

(3) carrying out vacuum polycondensation reaction, wherein the vacuum degree is-0.096 MPa, and the vacuumizing time is 3 h.

(4) Adding 0.01mol (3.47g) of antioxidant 1076 and 0.004mol (1.49g) of triphenyl ethyl phosphine bromide, preserving the temperature for 40min, and discharging to obtain polyester resin (C3), wherein the hydroxyl value is 35-45 mgKOH/g.

Example 4

This example prepares a polyester resin (C4) by the specific process of:

preparing hyperbranched polyester prepolymer (A4):

(1) adding 2.1mol of butanetetracarboxylic acid, 6.3mol of isophthalic acid and 4.2mol of adipic acid into a reaction kettle, adding 0.03mol of tetraisopropyl titanate, and heating to 100 ℃;

(2) adding 2.0mol of dipentaerythritol and 10.8mol of neopentyl glycol into 26.0mol of ethylene glycol monomethyl ether acetate for dissolving, after the alcohol is completely dissolved, dropwise adding the mixture into the reaction kettle in the step (1) within 3.5h, introducing nitrogen and condensed water, rapidly heating to 130 ℃, and preserving heat for 1h after the temperature is set;

(3) then the temperature is programmed to 160 ℃, the heating rate is 2 ℃/30min, and the temperature is kept for 4h after the set temperature is reached;

(4) then adding 1.4mol of tetradecanedioic acid, and continuing to keep the temperature for 4 h; and (3) carrying out reduced pressure vacuum reaction when the hydroxyl value is 60-70 mgKOH/g, removing small molecules and solvents in the reaction kettle, adding 0.07mol of antioxidant CA, 0.14mol of antioxidant TPP and 0.008mol of benzyl trimethyl ammonium bromide when the vacuum degree is-0.098 MPa and the hydroxyl value is 40-50 mgKOH/g, stirring for 1.0h, and stopping the reaction to obtain the hyperbranched polyester prepolymer (A4).

(II) preparing a polyurethane resin prepolymer (B4) containing reactive groups:

(1) adding 19.6mol of ethylene glycol, 9.9mol of diethylene glycol, 9.8mol of oxalic acid, 10.1mol of malonic acid and 0.05mol of p-toluenesulfonic acid into a reaction kettle, heating to 80 ℃, and preserving heat for 4 hours after the temperature reaches a set temperature;

(2) and (2) dropwise adding 1.0mol of isophorone diisocyanate into the reaction kettle in the step (1), keeping the temperature for 6h, and discharging while the solution is hot to obtain a polyurethane resin prepolymer (B4).

(III) preparation of polyester resin (C4):

(1) adding 10.0kg of hyperbranched polyester resin prepolymer (A4), 11.5kg of polyurethane resin prepolymer (B4) containing reactive groups and 0.02mol of monobutyl tin oxide into a reaction kettle, heating to 80 ℃, starting stirring after materials are completely melted, introducing nitrogen and condensed water, quickly heating to 160 ℃, and keeping the temperature for 2 hours after the temperature reaches a set temperature;

(2) then the temperature is programmed to be increased to 220 ℃, the temperature increasing rate is 1 ℃/15min, and the temperature is kept for 4h after the temperature reaches the set temperature;

(3) carrying out vacuum polycondensation reaction, wherein the vacuum degree is-0.096 MPa, and the vacuumizing time is 2 h.

(4) Adding 0.01mol (3.47g) of antioxidant 1076 and 0.005mol (1.15g) of benzyl trimethyl ammonium bromide, preserving the temperature for 20min, and discharging to obtain the polyester resin (C4), wherein the content of the isocyanate matrix is 6%.

Comparative example 1

This comparative example prepared a polyester resin (C5), which was a polyester resin without hyperbranched structures (C5), by the specific process of:

adding 48mol of neopentyl glycol and 5mol of 1, 4-cyclohexanedimethanol into a reaction kettle, heating to 110 ℃, introducing nitrogen for protection after the alcohol is dissolved, adding 35mol of isophthalic acid, 12mol of 1, 4-cyclohexanedicarboxylic acid and 0.1mol of monobutyltin oxide, quickly heating to 170 ℃, preserving heat for 3 hours, heating to 240 ℃ according to a temperature rise rate program of 2 ℃/hour, and preserving heat for 4 hours; when the acid value is reduced to be below 16mg/KOH, 9mol of isophthalic acid is added, and the temperature is kept for 3 hours; and (3) when the acid value is reduced to be below 45mg/KOH, carrying out reduced pressure reaction, wherein the vacuum degree is-0.096 MPa, when the acid value is 30-35 mg/KOH, adding an antioxidant and a curing accelerator, stirring for 20min, and discharging at high temperature while the mixture is hot to obtain the polyester resin (C5).

Wherein the using amount of the antioxidant accounts for 0.2 mol% of the total molar amount of the raw materials, and the mass of the antioxidant 1076 and the antioxidant 168 is 2: 1; the curing accelerator is triphenyl ethyl phosphonium bromide, and the using amount of the curing accelerator accounts for 0.02 mol% of the total molar amount of the raw materials.

Comparative example 2

The comparative example prepares the polyester resin (C6), and the polyester resin (C6) is a hyperbranched polyester resin without a prepolymer segment containing a reactive group, and the specific process is as follows:

adding 12.6mol of isophthalic acid and 2.6mol of trimellitic anhydride and 0.03mol of p-toluenesulfonic acid into a reaction kettle, and heating to 120 ℃; adding 1.9mol of neopentyl glycol, 4.5mol of trimethylolpropane and 3.7mol of pentaerythritol into 64.2mol of N, N-dimethylformamide for dissolving, after the alcohol is completely dissolved, dropwise adding the mixture into the reaction kettle in the step (1) within 5h, introducing nitrogen and condensed water, quickly heating to 140 ℃, and preserving heat for 4h after the temperature is set; then the temperature is programmed to 170 ℃, the heating rate is 1 ℃/30min, and the temperature is kept for 4h after the temperature reaches the set temperature; then adding 0.4mol of stearic acid, and continuing to preserve heat for 3 hours; and (3) when the acid value is reduced to 45mgKOH/g, carrying out vacuum reaction under reduced pressure, removing micromolecules and solvents in the reaction kettle, adding an antioxidant and a curing accelerator when the vacuum degree is-0.098 MPa and the acid value is 30-35 mgKOH/g, stirring for 20min, and discharging at high temperature while the mixture is hot to obtain the polyester resin (C6).

Wherein the using amount of the antioxidant accounts for 0.2 mol% of the total molar amount of the raw materials, and the mass of the antioxidant 1076 and the antioxidant 626 is 2: 1; the curing accelerator is tert-butylamine, and the using amount of the curing accelerator accounts for 0.02 mol% of the total molar amount of raw materials.

Comparative example 3

This comparative example prepared a hyperbranched polyester prepolymer (a7), a polyester resin in a prepolymer containing reactive groups (B7) by the following specific procedure:

the preparation method of the hyperbranched polyester prepolymer (A7) comprises the following specific steps:

(1) adding 12.3mol of isophthalic acid and 1.0mol of trimellitic anhydride and 0.03mol of p-toluenesulfonic acid into a reaction kettle, and heating to 110 ℃;

(2) adding 12.0mol of neopentyl glycol, 2.2mol of trimethylolpropane and 0.7mol of xylitol into 30.4mol of N, N-dimethylformamide for dissolving, after the alcohol is completely dissolved, dropwise adding the mixture into the reaction kettle in the step (1) within 6h, introducing nitrogen and condensed water, quickly heating to 120 ℃, and preserving heat for 4h after the temperature reaches a set temperature;

(3) then the temperature is programmed to 160 ℃, the heating rate is 2 ℃/30min, and the temperature is kept for 3h after the temperature reaches the set temperature;

(4) then adding 1.0mol of stearic acid, and continuing to preserve heat for 4 hours; and when the hydroxyl value is reduced to 110mgKOH/g, carrying out vacuum reduction reaction, removing micromolecules and solvents in the reaction kettle, adding 0.07mol of antioxidant 1076, 0.07mol of antioxidant 626 and 0.006mol of triphenyl ethyl phosphine bromide when the vacuum degree is-0.096 MPa and the hydroxyl value is 80-90 mgKOH/g, stirring for 0.2h, and stopping the reaction to obtain the hyperbranched polyester prepolymer (A7).

(II) preparing a polyester resin prepolymer (B7) containing reactive groups, which comprises the following specific steps:

(1) adding 11mol of neopentyl glycol, 2.1mol of 1, 4-cyclohexanedimethanol, 13.5mol of isophthalic acid and 1.0mol of tetrafluorosuccinic acid into a reaction kettle, adding 0.03mol of monobutyl tin oxide, and heating to 110 ℃;

(2) after the materials are completely melted, stirring, condensing water, introducing nitrogen, rapidly heating to 190 ℃, preserving heat for 4 hours, then programming to 240 ℃, heating at the rate of 2 ℃/30min, and preserving heat for 3 hours when the set temperature is reached;

(3) adding 1.8mol of isophthalic acid into a reaction kettle, preserving heat for 3h, adding 0.007mol of antioxidant 1010, 0.007mol of antioxidant 168 and 0.009mol of dimethyl imidazole when the acid value is 110-120 mgKOH/g, stirring for 1.0h, and stopping reaction to obtain a polyester prepolymer (B7).

Test examples

The polyester resins (C1-C6) prepared in examples 1-4 and comparative examples 1-2, and the hyperbranched polyester prepolymer (A7) and the polyester prepolymer (B7) prepared in comparative example 3 were applied to a powder coating according to the components and amounts shown in Table 1, and the powder coating was prepared as follows:

the components are uniformly mixed according to the formula of the polyester resin powder coating shown in the table 1, and the mixture is subjected to melt extrusion, tabletting, cooling crushing and sieving by a double-screw extruder, sprayed on a galvanized iron substrate subjected to surface treatment by using an electrostatic spray gun, and cured for 10min at 130 ℃ to obtain the polyester powder coating.

And (3) coating detection standard:

the 60 DEG gloss is tested according to GB/T9754-2007;

the test of the impact strength is based on T/GDTL 004-2019;

the test of the leveling grade is that the leveling grade is carried out according to the leveling performance grade and according to the standard edition of the leveling effect grade of the American PCI: in comparison to the standard panel, 1 is poor and 10 is excellent;

the coating film appearance was tested according to visual observation, with the following evaluation criteria: the method is poor when more orange peels (the orange peels account for more than 30 percent) appear on the board surface, common when a small amount of orange peels (the orange peels account for 10 to 30 percent) appear on the board surface, and excellent when no orange peels (the orange peels account for less than 5 percent) appear on the board surface;

the gel time was tested according to GB/T1699-1997;

the weather resistance test of the coating is in accordance with GB/T14522-2008.

TABLE 1 amounts of the components of the powder coatings prepared in the examples and comparative examples and the properties of the coatings

As can be seen from Table 1, the hyperbranched polyester prepolymer and the reactive group-containing prepolymer are adopted to obtain the polyester resin through block copolymerization as the matrix resin, so that the prepared powder coating has excellent film appearance and high glossiness, and the 60-degree gloss is more than or equal to 86.8 degrees; the leveling property is good, the leveling grade reaches more than 7 grade, the weather resistance is good, the leveling degree is still more than 57.9 percent after UVB 313/700h test, the curing property is excellent, and the gelling time is less than or equal to 112 s. The powder coating prepared from the synthesized polyester resin still maintains more than 50% of light-retaining rate through UVB 313/700h test, and meanwhile, the prepared powder coating has shorter gelling time, so that the coating can be cured at low temperature under the curing condition of 130 ℃/10min, and the comprehensive performance is excellent.

Compared with the example 1, the polyester resin (C5) prepared in the comparative example 1 does not contain a hyperbranched structure, the coating film appearance of the obtained powder coating is general, the curing performance is poor, the gel time is more than 3 times that of the powder coating prepared in the example 1, the impact strength is poor, the front side and the back side are uniformly cracked, the leveling grade is only 5 grade, the weather resistance is poor, and the light retention rate is only 24.3 percent after the UVB 313/700h test. The polyester (C6) prepared in comparative example 2 contained no reactive group-containing prepolymer segment, and only a hyperbranched structure; the prepared powder coating has poor appearance of a coating film; the 60-degree gloss and the weather resistance are also obviously reduced, the 60-degree gloss is only 67.8 percent, the gloss retention after UVB 313/700h test is only 32.5 percent, and the curing performance and the impact strength are also deteriorated. Comparative example 3 a hyperbranched prepolymer (a7) and a polyester resin containing a reactive group prepolymer (B7) were physically mixed directly as a matrix resin for a powder coating, and the resulting powder coating had poor leveling properties, poor film appearance, low gloss, long gel time, and poor impact strength and weatherability.

According to the invention, the hyperbranched polyester prepolymer and the prepolymer containing reactive groups are subjected to graft copolymerization to form a block copolymer, chain segments of the polymer are linked through chemical bonds, the structure and the physical and chemical properties are more stable, and the simple physical blending of the hyperbranched polyester prepolymer and the prepolymer containing reactive groups can cause uneven mixing and also reduce the performance of the powder coating; in addition, the hyperbranched polyester without the prepolymer chain segment containing the reactive group has higher reactivity, and the direct preparation of the powder coating can reduce the leveling property, the glossiness, the mechanical property and the like of the coating.

Claims

1. A polyester resin characterized by comprising the steps of: the polyester resin comprises a block structure chain segment derived from a hyperbranched polyester prepolymer and a prepolymer containing a reactive group; the end group of the hyperbranched polyester prepolymer is carboxyl and/or hydroxyl, and is composed of C ₃ ～C ₃₀ Dibasic or polybasic acids or derivatives thereof, C ₂ ～C ₃₀ A dihydric or polyhydric alcohol or a derivative thereof, C ₁₀ ～C ₄₂ Long-chain alkane monobasic acid or dibasic acid is obtained by polycondensation; the prepolymer containing reactive groups comprises at least one of polyester resin prepolymer, acrylic resin prepolymer and polyurethane resin prepolymer, and the reactive groups comprise at least one of carboxyl, hydroxyl, epoxy, isocyanate, ester, amino, amide and halogenated alkyl.

2. The polyester resin of claim 1, wherein the polyester resin has any one or more of the following properties: (1) the acid value is 15-350 mgKOH/g; (2) the hydroxyl value is 20-350 mgKOH/g; (3) the content of the isocyanate matrix is 1-10%; (4) the epoxy value is 0.1 to 1.0mol/100 g.

3. The polyester resin according to claim 1, wherein the mass ratio of the hyperbranched polyester prepolymer to the reactive group-containing prepolymer is 1: 0.2 to 5.

4. The polyester resin of claim 1, wherein the hyperbranched polyester prepolymer has any one or more of the following properties: (1) the acid value is 0-400 mgKOH/g; (2) a hydroxyl value of 0 to 400 mgKOH/g.

5. The polyester resin according to claim 1, wherein C is ₃ ～C ₃₀ Dibasic or polybasic acids or derivatives thereof, C ₂ ～C ₃₀ Dihydric or polyhydric alcohol or derivatives thereof, C ₁₀ ～C ₄₂ The mole ratio of the long-chain alkane monoacid or the diacid is 1: 0.2 to 2.0: 0.05 to 3.0.

6. The method for preparing a polyester resin according to any one of claims 1 to 5, comprising the steps of: and mixing the hyperbranched polyester prepolymer, the prepolymer containing reactive groups and an esterification catalyst, and carrying out polycondensation reaction to obtain the polyester resin.

7. A low temperature curing powder coating comprising the polyester resin according to any one of claims 1 to 6.

8. The low temperature curing powder coating of claim 7, comprising the following components in parts by weight:

9. a process for preparing a low temperature curing powder coating according to claim 8, characterized in that it comprises the steps of: and mixing the components to obtain the low-temperature curing powder coating.

10. A method for applying a low-temperature curing powder coating, comprising the steps of applying the low-temperature curing powder coating according to claim 8 to a surface of a substrate, and heating and curing the coating to form a coating layer on the surface of the substrate.