阅读说明：本技术 一种低温快速固化型聚酯树脂及其制备的卷材用粉末涂料 (Low-temperature fast-curing polyester resin and powder coating prepared from same and used for coiled material ) 是由 江建明 胡泽湘 江兴科 吴湧泉 于 2020-12-10 设计创作，主要内容包括：本发明属于粉末涂料技术领域,具体涉及一种低温快速固化型聚酯树脂,并进一步公开其制备的消光型卷材用粉末涂料。本发明所述低温快速固化型聚酯树脂,以3,3-二甲基戊二酸、对苯二甲酸、丙烯酸聚合物、己二酸二缩水甘油酯、新戊二醇、1,4-萘二甲醇、1,10-癸二胺、乙二胺-N,N’-二乙酸为原料聚合得到。本发明所述低温快速固化型聚酯树脂产品中含有活性氨基、不同结构的酰胺基及少量的羧基,最终酸值较低(小于12mgKOH/g)、总胺值较高(35-45mgKOH/g),便于实现低温快速固化完全,且具有自消光效果。(The invention belongs to the technical field of powder coatings, and particularly relates to a low-temperature fast-curing polyester resin, and further discloses a powder coating for a delustering type coiled material prepared from the polyester resin. The low-temperature fast curing polyester resin is obtained by polymerizing 3, 3-dimethylglutaric acid, terephthalic acid, acrylic polymer, adipic acid diglycidyl ester, neopentyl glycol, 1, 4-naphthalenediol, 1, 10-decanediamine and ethylenediamine-N, N' -diacetic acid serving as raw materials. The low-temperature fast curing polyester resin product contains active amino, acylamino with different structures and a small amount of carboxyl, has a low final acid value (less than 12mgKOH/g) and a high total amine value (35-45mgKOH/g), is convenient to realize complete low-temperature fast curing, and has a self-extinction effect.)

1. The low-temperature fast-curing polyester resin is characterized in that the preparation raw materials of the polyester resin comprise the following components in parts by weight:

2. the low-temperature fast-curing polyester resin as claimed in claim 1, wherein the acrylic polymer is a polymerization product of methacrylic acid, acrylamide and n-butyl acrylate, and has an acid value of 148-155 mgKOH/g.

3. The low-temperature fast-curing polyester resin according to claim 1 or 2, further comprising a polymerization catalyst, wherein the amount of the polymerization catalyst is 0.05 to 0.2 wt% of the total amount of the preparation raw materials;

the polymerization catalyst comprises monobutyl tin oxide.

4. The low-temperature fast-curing polyester resin according to any one of claims 1 to 3, further comprising an antioxidant in an amount of 0.3 to 0.5 wt% based on the total amount of the raw materials for preparation;

the antioxidant comprises tetra [ methyl-beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ] pentaerythritol ester, namely antioxidant 1010.

5. A method for preparing the low-temperature fast-curing polyester resin according to any one of claims 1 to 4, comprising the steps of:

(1) uniformly mixing the neopentyl glycol, the 1, 4-naphthalenediol and the diglycidyl adipate according to the formula ratio, and heating and melting for later use;

(2) adding the 3, 3-dimethyl glutaric acid, terephthalic acid and the catalyst into the mixed material according to the formula ratio, and carrying out heat preservation reaction at the temperature of 190-200 ℃ in a protective atmosphere;

(3) when the acid value of the system is reduced to 75-90mgKOH/g and the epoxy equivalent is more than 2000g/mol, adding the acrylic polymer, 1, 10-decamethylene diamine and ethylenediamine-N, N' -diacetic acid according to the formula amount, and continuing the heat preservation reaction at the temperature of 210-220 ℃;

(4) when the acid value of the system is reduced to 25-30mgKOH/g, adding the antioxidant with the formula amount, starting a vacuum system, and continuing to perform heat preservation reaction at the temperature of 210-220 ℃;

(5) stopping the reaction when the acid value of the system is reduced to be below 12mgKOH/g and the total amine value is 35-45mgKOH/g, discharging at high temperature while the system is hot, and cooling, crushing and granulating the discharged material to obtain the catalyst.

6. The method for preparing a low-temperature fast curing polyester resin as claimed in claim 5, wherein in the step (2), the temperature is gradually increased to 190-200 ℃ at 10-12 ℃/h in the heat preservation reaction.

7. The method for preparing a low-temperature fast curing polyester resin as claimed in claim 5 or 6, wherein in the step (3), the temperature is raised to 210-220 ℃ at a temperature raising rate of 6-8 ℃/h in the heat preservation reaction.

8. The method for preparing a low temperature fast curing type polyester resin according to any one of claims 5 to 7, further comprising a step of preparing the acrylic polymer by mixing the acrylic polymer in a mass ratio of 1: 0.3: 3, methacrylic acid, acrylamide and n-butyl acrylate are taken, BPO which accounts for 4 percent of the total mass of the three monomer raw materials is taken as an initiator, the polymerization reaction is carried out in a dimethylbenzene solvent at the temperature of 125-155 ℃, the reaction is stopped when the amount of free monomers is less than 3 percent of the total amount of the monomers, the dimethylbenzene solvent is removed under reduced pressure, the temperature is reduced, and the material is discharged, and the acid value is 148-155 mgKOH/g.

9. Use of the low temperature fast curing polyester resin according to any one of claims 1 to 4 for the preparation of powder coatings for matt coiled materials.

10. A powder coating for a low-temperature curing matting type coil, characterized in that a polyester resin for preparing the powder coating comprises the low-temperature fast curing type polyester resin according to any one of claims 1 to 4.

Technical Field

The invention belongs to the technical field of powder coatings, and particularly relates to a low-temperature fast-curing polyester resin, and further discloses a powder coating for a coil prepared from the same.

Background

The coating of the coil steel is a pre-coating method, is a coating mode different from the traditional 'post-coating', and is a development direction of the coating industry in the future no matter in the field of paint or other types of coatings because of a series of advantages of simplifying production process, efficiently constructing, saving investment and operating cost, meeting environmental protection regulations, having performance superior to that of the traditional method and the like. It is well known that conventional liquid coil coatings have been successfully developed and applied in the late 50 s and early 60 s of the 20 th century. To date, almost all pre-coated coil color sheets have been coated with liquid coil coatings. However, since the liquid coil coating contains organic solvents (VOC) harmful to the environment, and the like, countries such as europe and the united states continue to have stricter environmental regulations, and coating manufacturers are always looking for developing products and technologies capable of replacing the liquid coil coating. The powder coating has the advantage of zero VOC because of no solvent, and is the best choice for replacing the traditional liquid coil coating from the aspect of environmental protection. The coil powder coating mainly refers to the coating of color steel plates and the coating of color aluminum plates, and is a coating process of uniformly coating a coating on one side or two sides of a rolled planar substrate on a continuous coating production line running at a high speed, rapidly baking and solidifying the coating, and then cooling and rolling the coating. For decades, coil coating using powder coating materials has been developed, but the coating effect is not ideal due to the limitation of technical conditions. Generally, coil coating requires a high curing speed, but polyester resins used in general coil powder coatings mostly have carboxyl groups as end groups, and the curing temperature is high, mostly above 220 ℃, so that the problems of easy yellowing of high-temperature coating films and poor appearance fineness of the coating films are caused. Therefore, in order to increase the curing rate of the polyester resin and the curing agent, the activity of the polyester is generally increased by increasing the acid value of the polyester resin. However, the high acid value polyester resin has too many carboxyl groups, which can cause incomplete curing of the carboxyl end groups, and further affect the properties of the coating film such as hardness and the like; moreover, due to the excessive carboxyl, the requirements on the temperature and time of the process are high in the full curing process, rapid curing can hardly be realized under the low-temperature condition, and obvious energy consumption disadvantages are caused.

In addition, the powder coating of the TGIC (triglycidyl isocyanurate) curing system has excellent weather resistance and water resistance and excellent mechanical property, can be used for an outdoor weather-resistant system for a long time without yellowing, and is widely applied. In order to improve the decorativeness of powder coatings, a common method is to achieve a certain degree of matting by adding a matting agent, but the complexity of the system is increased to a certain extent, and the production cost is also increased.

Therefore, it is of positive significance to develop a powder coating for a coil material which can realize low-temperature curing and has self-extinction performance.

Disclosure of Invention

Therefore, the invention aims to provide a low-temperature fast curing polyester resin to solve the problem that the powder coating for the coiled material in the prior art can not realize low-temperature curing;

the second technical problem to be solved by the invention is to provide a powder coating for a low-temperature curing type extinction coiled material.

In order to solve the technical problems, the low-temperature fast curing polyester resin provided by the invention comprises the following raw materials in parts by weight:

specifically, the acrylic polymer is a polymerization product of methacrylic acid, acrylamide and n-butyl acrylate, and the acid value of the acrylic polymer is 148-155 mgKOH/g.

Specifically, the low-temperature fast curing polyester resin also comprises a polymerization catalyst, wherein the dosage of the polymerization catalyst is 0.05-0.1 wt% of the total amount of the preparation raw materials;

the polymerization catalyst comprises monobutyl tin oxide.

Specifically, the low-temperature fast curing polyester resin also comprises an antioxidant, and the dosage of the antioxidant is 0.3-0.5 wt% of the total amount of the preparation raw materials;

the antioxidant comprises tetra [ methyl-beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ] pentaerythritol ester.

The invention also discloses a method for preparing the low-temperature fast curing polyester resin, which comprises the following steps:

(1) uniformly mixing the neopentyl glycol, the 1, 4-naphthalenediol and the diglycidyl adipate according to the formula ratio, and heating and melting for later use;

(2) adding the 3, 3-dimethyl glutaric acid, terephthalic acid and the catalyst into the mixed material according to the formula ratio, and carrying out heat preservation reaction at the temperature of 190-200 ℃ in a protective atmosphere;

(3) when the acid value of the system is reduced to be below 75-90mgKOH/g and the epoxy equivalent is more than 2000g/mol, adding the acrylic polymer, 1, 10-decamethylene diamine and ethylenediamine-N, N' -diacetic acid according to the formula amount, and continuing the heat preservation reaction at the temperature of 210-220 ℃;

(4) when the acid value of the system is reduced to below 25-30mgKOH/g, adding the antioxidant with the formula amount, starting a vacuum system, and continuing to perform heat preservation reaction at the temperature of 210-220 ℃;

(5) stopping the reaction when the acid value of the system is reduced to be below 12mgKOH/g and the total amine value is 35-45mgKOH/g, discharging at high temperature while the system is hot, and cooling, crushing and granulating the discharged material to obtain the catalyst.

Specifically, in the step (2), the temperature is gradually increased to 190-200 ℃ at a rate of 10-12 ℃/h in the heat preservation reaction.

Specifically, in the step (3), the temperature is increased to 210-220 ℃ at a temperature increase rate of 6-8 ℃/h during the heat preservation reaction.

Specifically, the preparation method of the low-temperature fast curing polyester resin further comprises the step of preparing the acrylic polymer, namely, according to the mass ratio of 1: 0.3: 3, methacrylic acid, acrylamide and n-butyl acrylate are taken, BPO which accounts for 4 percent of the total mass of the three monomer raw materials is taken as an initiator, the polymerization reaction is carried out in a dimethylbenzene solvent at the temperature of 125-155 ℃, the reaction is stopped when the amount of free monomers is less than 3 percent of the total amount of the monomers, the dimethylbenzene solvent is removed under reduced pressure, the temperature is reduced, and the material is discharged, and the acid value is 148-155 mgKOH/g.

The invention also discloses application of the low-temperature fast curing polyester resin in preparing powder coating for coils.

The invention also discloses a low-temperature curing type extinction powder coating for the coiled material, and the polyester resin for preparing the powder coating comprises the low-temperature rapid curing type polyester resin.

The low-temperature fast curing polyester resin is obtained by polymerizing 3, 3-dimethylglutaric acid, terephthalic acid, acrylic polymer, adipic acid diglycidyl ester, neopentyl glycol, 1, 4-naphthalenediol, 1, 10-decanediamine and ethylenediamine-N, N' -diacetic acid serving as raw materials. The low-temperature fast curing polyester resin product contains active amino, amido with different structures and a small amount of carboxyl, and has low acid value (less than 12mgKOH/g) and high total amine value (35-45mgKOH/g), so that the low-temperature fast curing is completely realized. The active amino and amido groups of the polyester resin and the epoxy group of TGIC have extremely high curing activity, can be completely cured at a low temperature of 160 ℃/2min with a TGIC curing agent, and have certain difference in curing speed due to the activity difference of different functional groups, so that the whole system does not need to be additionally provided with a delustering agent, and can obtain a coating film with semi-gloss (50-70%) after being cured with the TGIC; due to the participation of the multifunctional acrylic polymer, especially the participation of leveling-assisting butyl acrylate, the surface fineness of the finally prepared coating is excellent, the multi-point of the polyester chain segment participates in curing, the hardness of the coating is higher and is more than 3H, other properties can completely meet various requirements of the conventional coil powder coating, and the coating can be used for preparing high-hardness, semi-gloss and low-temperature rapid curing coil powder coating.

Detailed Description

In the following examples of the present invention, the acrylic polymer is a copolymer of 1: 0.3: 3, taking methacrylic acid, acrylamide and n-butyl acrylate, taking BPO which is 4 percent of the total mass of the three monomer raw materials as an initiator, carrying out polymerization reaction in a xylene solvent at the temperature of 125-155 ℃, stopping the reaction when the amount of free monomers is less than 3 percent of the total amount of the monomers, reducing the pressure to remove the xylene solvent, cooling and discharging, and keeping the acid value at 155mgKOH/g for later use.

Example 1

The low-temperature fast-curing polyester resin comprises the following raw materials in parts by weight:

monobutyl tin oxide, the dosage of which is 0.05 wt% of the total amount of the preparation raw materials;

antioxidant 1010 in an amount of 0.5 wt% of the total amount of the raw materials.

The preparation method of the low-temperature fast curing polyester resin comprises the following steps:

(1) adding the neopentyl glycol, the 1, 4-naphthalenediol and the diglycidyl adipate with the formula ratio into a reactor, and heating and melting at the temperature of below 135 ℃;

(2) adding 3, 3-dimethyl glutaric acid and terephthalic acid in formula amount into the mixed material, simultaneously adding catalyst in formula amount, under the protection of nitrogen, gradually heating to react to 195 ℃ at 10 ℃/h, and keeping the temperature for reaction;

(3) when the acid value is reduced to 76mgKOH/g and the epoxy equivalent is more than 2000g/mol, adding the acrylic polymer, 1, 10-decamethylene diamine and ethylenediamine-N, N' -diacetic acid in the formula amount, continuously heating to 210 ℃ at the heating rate of 6 ℃/h, and continuously carrying out heat preservation reaction;

(4) when the acid value is reduced to 25mgKOH/g, adding antioxidant 1010 with the formula amount, starting a vacuum system, controlling the vacuum degree to be-0.098 Mpa, and continuing to perform heat preservation reaction at 210 ℃;

(5) stopping the reaction when the acid value is reduced to be below 12mgKOH/g and the total amine value is 35mgKOH/g, discharging at high temperature, cooling the polyester resin by using a steel belt with condensed water, and then crushing and granulating to obtain the polyester resin.

The polyester resin product described in this example is a colorless transparent particle, and has an acid value of 10mgKOH/g, a total amine value of 35mgKOH/g, and a softening point of 97 ℃.

Example 2

The low-temperature fast-curing polyester resin comprises the following raw materials in parts by weight:

monobutyl tin oxide, the dosage of which is 0.2 wt% of the total amount of the preparation raw materials;

antioxidant 1010 in an amount of 0.3 wt% of the total amount of the raw materials.

The preparation method of the low-temperature fast curing polyester resin comprises the following steps:

(1) adding the neopentyl glycol, the 1, 4-naphthalenediol and the diglycidyl adipate with the formula ratio into a reactor, and heating and melting at the temperature of below 135 ℃;

(2) adding 3, 3-dimethyl glutaric acid and terephthalic acid in formula amount into the mixed material, simultaneously adding catalyst in formula amount, under the protection of nitrogen, gradually heating to 190 ℃ at a speed of 12 ℃/h, and carrying out heat preservation reaction;

(3) when the acid value is reduced to 89mgKOH/g and the epoxy equivalent is more than 2000g/mol, adding acrylic polymer, 1, 10-decamethylene diamine and ethylenediamine-N, N' -diacetic acid according to the formula amount, continuously heating to 215 ℃ at the heating rate of 8 ℃/h, and continuously carrying out heat preservation reaction;

(4) when the acid value is reduced to 30mgKOH/g, adding antioxidant 1010 with the formula amount, starting a vacuum system, controlling the vacuum degree to be-0.097 Mpa, and continuing to perform heat preservation reaction at 215 ℃;

(5) stopping the reaction when the acid value is reduced to be below 12mgKOH/g and the total amine value is 45mgKOH/g, discharging at high temperature, cooling the polyester resin by using a steel belt with condensed water, and then crushing and granulating to obtain the polyester resin.

The polyester resin product described in this example was a colorless transparent particle having an acid value of 8mgKOH/g, a total amine value of 45mgKOH/g, and a softening point of 104 ℃.

Example 3

The low-temperature fast-curing polyester resin comprises the following raw materials in parts by weight:

monobutyl tin oxide, the dosage of which is 0.1 wt% of the total amount of the preparation raw materials;

antioxidant 1010 in an amount of 0.3 wt% of the total amount of the raw materials.

The preparation method of the low-temperature fast curing polyester resin comprises the following steps:

(1) adding the neopentyl glycol, the 1, 4-naphthalenediol and the diglycidyl adipate with the formula ratio into a reactor, and heating and melting at the temperature of below 135 ℃;

(2) adding 3, 3-dimethyl glutaric acid and terephthalic acid in formula amount into the mixed material, simultaneously adding catalyst in formula amount, under the protection of nitrogen, gradually heating to react to 200 ℃ at 11 ℃/h, and keeping the temperature for reaction;

(3) when the acid value is reduced to 83mgKOH/g and the epoxy equivalent is more than 2000g/mol, adding acrylic polymer, 1, 10-decamethylene diamine and ethylenediamine-N, N' -diacetic acid according to the formula amount, continuously heating to 218 ℃ at the heating rate of 7 ℃/h, and continuously carrying out heat preservation reaction;

(4) when the acid value is reduced to 27mgKOH/g, adding antioxidant 1010 with the formula amount, starting a vacuum system, controlling the vacuum degree to be-0.096 Mpa, and continuing to perform heat preservation reaction at 218 ℃;

(5) stopping the reaction when the acid value is reduced to be below 12mgKOH/g and the total amine value is 41mgKOH/g, discharging at high temperature, cooling the polyester resin by using a steel belt with condensed water, and then crushing and granulating to obtain the polyester resin.

The polyester resin product described in this example is a colorless transparent particle, and has an acid value of 9mgKOH/g, a total amine value of 41mgKOH/g, and a softening point of 99 ℃.

Example 4

The low-temperature fast-curing polyester resin comprises the following raw materials in parts by weight:

monobutyl tin oxide, the dosage of which is 0.15 wt% of the total amount of the preparation raw materials;

antioxidant 1010 in an amount of 0.4 wt% of the total amount of the raw materials for preparation.

The preparation method of the low-temperature fast curing polyester resin comprises the following steps:

(1) adding the neopentyl glycol, the 1, 4-naphthalenediol and the diglycidyl adipate with the formula ratio into a reactor, and heating and melting at the temperature of below 135 ℃;

(2) adding 3, 3-dimethyl glutaric acid and terephthalic acid in formula amount into the mixed material, simultaneously adding catalyst in formula amount, under the protection of nitrogen, gradually heating to 198 ℃ at 10 ℃/h, and keeping the temperature for reaction;

(3) when the acid value is reduced to 80mgKOH/g and the epoxy equivalent is more than 2000g/mol, adding the acrylic polymer, 1, 10-decamethylene diamine and ethylenediamine-N, N' -diacetic acid according to the formula amount, continuously heating to 213 ℃ at the heating rate of 7 ℃/h, and continuously carrying out heat preservation reaction;

(4) when the acid value is reduced to 28mgKOH/g, adding antioxidant 1010 with the formula amount, starting a vacuum system, controlling the vacuum degree to be-0.098 Mpa, and continuing to perform heat preservation reaction at 213 ℃;

(5) stopping the reaction when the acid value is reduced to be below 12mgKOH/g and the total amine value is 44mgKOH/g, discharging at high temperature, cooling the polyester resin by using a steel belt with condensed water, and then crushing and granulating to obtain the polyester resin.

The polyester resin product described in this example is a colorless transparent particle, and has an acid value of 11mgKOH/g, a total amine value of 44mgKOH/g, and a softening point of 103 ℃.

Example 5

The low-temperature fast-curing polyester resin comprises the following raw materials in parts by weight:

monobutyl tin oxide, the dosage of which is 0.08 wt% of the total amount of the preparation raw materials;

antioxidant 1010 in an amount of 0.4 wt% of the total amount of the raw materials for preparation.

The preparation method of the low-temperature fast curing polyester resin comprises the following steps:

(1) adding the neopentyl glycol, the 1, 4-naphthalenediol and the diglycidyl adipate with the formula ratio into a reactor, and heating and melting at the temperature of below 135 ℃;

(2) adding 3, 3-dimethyl glutaric acid and terephthalic acid in formula amount into the mixed material, simultaneously adding catalyst in formula amount, under the protection of nitrogen, gradually heating to react to 193 ℃ at the speed of 12 ℃/h, and keeping the temperature for reaction;

(3) when the acid value is reduced to 78mgKOH/g and the epoxy equivalent is more than 2000g/mol, adding acrylic polymer, 1, 10-decamethylene diamine and ethylenediamine-N, N' -diacetic acid according to the formula amount, continuously heating to 216 ℃ at the heating rate of 6 ℃/h, and continuously carrying out heat preservation reaction;

(4) when the acid value is reduced to 26mgKOH/g, adding antioxidant 1010 with the formula amount, starting a vacuum system, controlling the vacuum degree to be-0.097 Mpa, and continuing to perform heat preservation reaction at 216 ℃;

(5) stopping the reaction when the acid value is reduced to be below 12mgKOH/g and the total amine value is 37mgKOH/g, discharging at high temperature, cooling the polyester resin by using a steel belt with condensed water, and then crushing and granulating to obtain the polyester resin.

The polyester resin product described in this example is a colorless transparent particle, and has an acid value of 8mgKOH/g, a total amine value of 37mgKOH/g, and a softening point of 98 ℃.

Comparative example 1

The raw materials for preparing the polyester resin and the preparation method of the polyester resin according to this comparative example were the same as those of example 3 except that the acrylic polymer was not used as the raw material.

The polyester resin of this comparative example had an acid value of 5mgKOH/g, a total amine value of 48mgKOH/g, and a softening point of 93 ℃.

Examples of the experiments

The following powder coating formulations were used with the polyester resins of examples 1-5 and comparative example 1, respectively, and were generally as follows in parts by weight:

preparing a coating layer: mixing the materials according to the formula of the low-gloss powder coating, extruding, tabletting and crushing by using a double-screw extruder, and then crushing and sieving the tablets to prepare the powder coating. The powder coating is sprayed on the galvanized iron substrate after surface treatment by an electrostatic spray gun, the film thickness is 35-45 mu m, and the powder coating is cured at 160 ℃/2min to obtain the coating.

Comparative example 2

The polyester resin product prepared in example 1 of Chinese patent CN103755931B is used as a scheme of comparative example 2, and the acid value of the polyester resin product is 31mgKOH/g, and the softening point is 107 ℃.

The curing formula is the same as the scheme of the embodiment 1 in the Chinese patent CN103755931B, the film thickness is controlled to be 35-45 μm, and the curing conditions are as follows: 160 ℃/2 min.

Comparative example 3

The polyester resin product prepared in example 1 of Chinese patent CN103755931B is used as a proposal of comparative example 3, and the acid value of the polyester resin product is 31mgKOH/g, and the softening point is 107 ℃.

The curing formula is the same as the scheme of example 1 in patent CN103755931B, the film thickness is controlled to be 35-45 μm, and the curing conditions are as follows: 180 ℃/15 min.

Comparative example 4

The product of example 1 in Chinese patent CN105218795B is used as comparative example 4, and the acid value of the polyester resin is as follows: 69mgKOH/g, softening point 104 ℃.

The curing formula is the same as the formula of the embodiment of the invention, the film thickness is controlled to be 35-45 μm, and the curing conditions are as follows: 280 ℃/1 min.

Comparative example 5

The product of example 1 in Chinese patent CN105218795B is used as comparative example 5, and the acid value of the polyester resin is as follows: 69mgKOH/g, softening point 104 ℃.

The curing formula is the same as that of example 1 in Chinese patent CN105218795B, the film thickness is controlled to be 35-45 μm, and the curing conditions are as follows: 160 ℃/2 min.

Comparative example 6

The product of example 1 in Chinese patent CN105218795B is used as comparative example 5, and the acid value of the polyester resin is as follows: 69mgKOH/g, softening point 104 ℃.

The curing formula is the same as that of example 1 in Chinese patent CN105218795B, the film thickness is controlled to be 35-45 μm, and the curing conditions are as follows: 280 ℃/1 min.

The test basis is as follows: the total amine value was determined as described in ZB G71005-1989 octadecylamine;

the conventional indexes of the coating are carried out according to the method of GB/T21776-2008 'Standard guidelines for detection of powder coatings and coatings thereof'; the test standard of the adhesion force is in accordance with GB/T9286-1998 test of the grid test of paint films of colored paint and varnish; the hardness test is carried out according to GB/T6739-2006 paint film hardness determination by a color paint and varnish pencil method. The pencil hardness parameter is 5B-4B-3B-2B-B-HB-F-H-2H-3H-4H-5H, and the hardness grade gradually increases from left to right; the T-bend value test method is based on the seventh part (bending test) of GB/T13448-2006 test methods for color coated steel plates and steel strips.

TABLE 1 coating film Properties of examples and comparative examples

As can be seen from the data in the table above, the polyester resin product contains active amino, amido with different structures and a small amount of carboxyl, the final acid value is lower (less than 12mgKOH/g), the total amine value is higher (35-45mgKOH/g), and the polyester resin product and a TGIC curing agent can realize complete curing at the low temperature of 160 ℃/2 min; and because of the different activity of different functional groups, the curing speed of the polyester resin and TGIC generates a certain difference, the whole system does not need to be additionally provided with a flatting agent, and after the polyester resin and the TGIC are cured, a coating film with semi-gloss (50-70%) can be obtained; due to the participation of the multifunctional acrylic polymer, especially the participation of leveling-assisting butyl acrylate, the surface fineness of the finally prepared coating is excellent, the multi-point of the polyester chain segment participates in curing, the hardness of the coating is higher and is more than 3H, other properties can completely meet various requirements of the conventional coil powder coating, and the coating can be used for preparing high-hardness, semi-gloss and low-temperature rapid curing coil powder coating.

In the scheme of the comparative example 1, due to the lack of the acrylic polymer which is helpful for leveling and increases the compatibility, the fineness of the coating is deteriorated, the raw material is a multifunctional polymer, and the lack of the acrylic polymer can also cause the reduction of the crosslinking density, so that the boiling water boiling resistance and the hardness are reduced;

comparative example 2 and comparative example 3 are the same polyester product, but the product is only suitable for high-temperature long-time curing (180 ℃/15min) due to low activity, and the coating performance is poor, for example, the product can not be fully cured under the condition of low temperature and short time (160 ℃/2min) in the comparative example 2;

comparative examples 4-6 are the same polyester product, but the product is a polyester resin matched with HAA (also called N, N, N ', N' -tetrakis (2-hydroxyethyl) adipamide) hydroxyl curing agent, is not matched for TGIC curing agent system, can not achieve effective curing at 280 ℃ (see comparative example 4), and the product can not achieve sufficient curing even with its own formulation system under the low temperature fast curing (160 ℃/2min) condition of the present invention (see comparative example 5); the product is only suitable for ultra-high temperature curing (280 ℃) of an HAA system, the leveling of a coating film is insufficient due to the excessively high curing speed, the appearance fineness is poor, the coating film is easy to yellow at high temperature due to the adoption of an HAA (amide curing agent) curing system and the excessively high temperature, and the extinction effect of the product cannot be realized.

It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications therefrom are within the scope of the invention.