CN113845644A - Low-chlorine branched epoxy resin for powder coating and preparation method and application thereof - Google Patents
Low-chlorine branched epoxy resin for powder coating and preparation method and application thereof Download PDFInfo
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Abstract
The invention belongs to the technical field of powder coatings, and particularly relates to a low-chlorine branched epoxy resin for a powder coating, and a preparation method and application thereof. The low-chlorine branched epoxy resin for the powder is obtained by carrying out polymerization reaction on oxalic acid, 1, 4-succinic acid, 1, 3-propanediol, trimethylolpropane, pyromellitic acid, methanol, glycidyl oil and the like serving as raw materials. The epoxy resin final product has extremely low chloride ion content and high branching degree and epoxy activity, can be suitable for coating the surfaces of special fields with high requirements on chloride ions, such as engines, oil tanks and the like, can also be used as an additive in outdoor weather-resistant powder coatings, has the effects of enhancing the crosslinking density to improve the boiling water boiling resistance of the coating film, and can effectively improve the film performance of the outdoor weather-resistant powder coatings.
Description
Technical Field
The invention belongs to the technical field of powder coatings, and particularly relates to a low-chlorine branched epoxy resin for a powder coating, and a preparation method and application thereof.
Background
The powder coating is 100% solid powder without organic solvent, which is different from oil-based coating and water-based coating, and the powder coating is a novel environment-friendly coating which does not use solvent or water as a dispersion medium but uses air as a dispersion medium, is uniformly coated on the surface of a workpiece and forms a coating film with special purpose after being heated. The powder coating has the advantages of no VOC, environmental protection, energy conservation, high construction efficiency, wide application range and the like, and gradually replaces organic solvent type coatings with the advantages of economy, environmental protection, high efficiency, excellent performance and the like, thereby becoming an important development direction in the coating industry and keeping a faster growth rate all the time.
The powder coating has good protective performance and decorative performance, so that the powder coating is widely applied in the conventional coating industry at present, and the powder coating is applied to common fields such as guardrails of highways, air-conditioning outdoor units and the like, and is applied to special fields such as engine parts, automobile oil tanks and the like. Generally, due to the particularity of these special application fields, the requirement for chloride ions is very strict, and the total chlorine is generally required to be less than 500ppm so as to ensure the safety and durability of the application.
At present, epoxy resins applied in the field of powder coatings are mainly E-12 epoxy resins, which are synthesized by epichlorohydrin and bisphenol A under the action of strong base, a large amount of sodium chloride is generated in the process, although the epoxy resins are subjected to water washing treatment, the total chlorine content of final products is still high and generally reaches more than 5000ppm, and the application requirements of the special fields are far from being met. In addition, for outdoor weather-resistant powder coating products such as TGIC powder coatings, the requirement on the water resistance of a coating film is high due to more rainwater in part of application areas of customers all the year round, and the common TGIC type powder coatings have certain defects in long-time boiling resistance due to relatively low crosslinking density. Therefore, how to increase the crosslinking density of TGIC powder coatings and enhance the long-lasting boiling resistance is also a direction of continuous efforts in the industry.
Disclosure of Invention
Therefore, the invention aims to provide a low-chlorine branched epoxy resin for powder coating, so as to solve the problem that the application of E-12 epoxy resin is influenced by high chlorine content in the prior art;
the second technical problem to be solved by the present invention is to provide a preparation method of the low-chlorine branched epoxy resin and the application of the low-chlorine branched epoxy resin in the preparation of powder coating.
In order to solve the technical problems, the low-chlorine branched epoxy resin for the powder coating comprises the following components in molar weight:
specifically, the preparation raw materials also comprise a catalyst, and the molar amount of the catalyst accounts for 0.01-0.03% of the total molar amount of the preparation raw materials.
Specifically, the catalyst comprises dibutyltin oxide.
The invention also discloses a method for preparing the low-chlorine branched epoxy resin for the powder coating, which comprises the following steps:
(1) uniformly mixing the oxalic acid, the 1, 3-propanediol, the 1, 4-succinic acid and the catalyst according to the formula ratio, and controlling the temperature of a material system to 210-220 ℃ for polymerization reaction;
(2) when the acid value of the polymer to be detected in the reaction system reaches 35-45mgKOH/g, adding the trimethylolpropane with the formula amount, and heating to 230-235 ℃ for chain extension reaction;
(3) when the acid value of the polymer of the reaction system to be detected reaches 15-20mgKOH/g, adding the pyromellitic acid with the formula amount, and continuing to perform carboxyl end-capping reaction at 230-235 ℃;
(4) when the hydroxyl value of the polymer of the reaction system to be detected is reduced to be below 5mgKOH/g, quickly cooling the reaction material to 55-60 ℃, and then adding the methanol with the formula amount to perform methyl esterification reaction on the polymer;
(5) when the acid value of the polymer to be detected in the reaction system is lower than 2mgKOH/g, starting a vacuum program, heating to 80-85 ℃, and removing excessive methanol and micromolecular water under reduced pressure;
(6) stopping the vacuum process when no obvious distillate is evaporated, adding the glycidol in the formula amount, uniformly mixing, starting the vacuum process again for vacuum ester exchange reaction, and distilling out methanol generated by the ester exchange reaction;
(7) when the collected methanol amount reaches more than 80% of the theoretical amount, heating the reaction system materials to 110-115 ℃ to remove excessive glycidol, stopping the reaction when no obvious distillate is evaporated, discharging at high temperature while the reaction system materials are hot, cooling, crushing and granulating to obtain the catalyst.
Specifically, in the step (1), the temperature rise rate of the temperature rise step is controlled to be 15-18 ℃/h.
Specifically, in the step (2), the temperature rise rate of the temperature rise step is controlled to be 6-8 ℃/h.
Specifically, in the steps (5) and (6), the vacuum degree of the vacuum program is controlled to be-0.097 MPa to-0.099 MPa.
Specifically, in the step (7), the temperature rise rate of the temperature rise step is controlled to be 5-8 ℃/h.
The invention also discloses application of the low-chlorine branched epoxy resin in preparing powder coating.
The invention also discloses application of the low-chlorine branched epoxy resin in preparing a boiling-water-resistant auxiliary agent for outdoor TGIC powder coating.
The invention also discloses a powder coating prepared from the low-chlorine branched epoxy resin.
The low-chlorine branched epoxy resin for the powder is obtained by carrying out polymerization reaction on oxalic acid, 1, 4-succinic acid, 1, 3-propanediol, trimethylolpropane, pyromellitic acid, methanol, glycidyl oil and the like serving as raw materials. The epoxy equivalent of the epoxy resin final product is 350-400g/mol, the total chlorine is basically below 300ppm, the content of chloride ions is extremely low, and the epoxy resin final product can be suitable for coating the surfaces of special fields such as engines, oil tanks and the like with high requirements on the chloride ions.
The epoxy resin has high branching degree and epoxy activity, can realize low-temperature full curing (150 ℃/10min), and the cured coating has excellent impact resistance and boiling water resistance, can be used as an additive in outdoor weather-resistant powder coatings, has the effect of enhancing the crosslinking density to improve the boiling water resistance of the coating, and can effectively improve the coating performance of the outdoor weather-resistant powder coatings, particularly the boiling water resistance.
Detailed Description
Example 1
The preparation of the low-chlorine branched epoxy resin for the powder coating of this example comprises the following components in molar amounts:
dibutyl tin oxide accounting for 0.01 percent of the total molar weight of the raw materials for preparation.
The preparation method of the low-chlorine branched epoxy resin for the powder coating comprises the following steps:
(1) adding the oxalic acid, the 1, 3-propanediol, the 1, 4-succinic acid and the catalyst dibutyltin oxide into a reaction kettle according to the formula ratio, starting stirring and uniformly mixing, gradually heating to 210 ℃ at a heating rate of 15 ℃/h, and carrying out heat preservation polymerization reaction;
(2) detecting, adding the trimethylolpropane with the formula amount when the acid value of the polymer of the reaction system is 35-45mgKOH/g, and gradually heating to 230 ℃ at the heating rate of 6 ℃/h to perform heat preservation chain extension reaction;
(3) detecting that when the acid value of the polymer in the reaction system reaches 15-20mgKOH/g, adding the pyromellitic acid with the formula amount, and continuing to perform carboxyl end-capping reaction at 230 ℃;
(4) through detection, when the hydroxyl value of the polymer in the reaction system is reduced to be below 5mgKOH/g, the material is quickly cooled to 55 ℃, and then the methanol with the formula amount is added to carry out sufficient methyl esterification reaction on the polymer;
(5) detecting that the methyl esterification is basically finished when the acid value of the polymer of the reaction system is lower than 2mgKOH/g, then starting vacuum, controlling the vacuum degree to be between-0.097 Mpa and-0.099 Mpa, and heating to 80 ℃ to remove excessive methanol and micromolecular water by decompression;
(6) stopping the vacuum process when no obvious distillate is distilled out (less than 1 drop of distillate in 30 s), adding the glycidol with the formula amount, uniformly stirring, starting the vacuum process again, controlling the vacuum degree to be between-0.097 Mpa and-0.099 Mpa, and carrying out vacuum ester exchange reaction to distill out methanol generated by the ester exchange reaction;
(7) when the amount of the collected methanol reaches more than 80% of the theoretical amount, gradually heating to 110 ℃ at the heating rate of 5 ℃/h to remove excessive glycidol, stopping reaction after no obvious distillate is evaporated (the distillate is less than 1 drop in 30 s), discharging at high temperature while the mixture is hot, cooling the epoxy resin by using a steel belt with condensed water, and then crushing and granulating to obtain the required low-chlorine branched epoxy resin.
The epoxy resin prepared in this example was tested as colorless transparent particles having an epoxy equivalent of 408g/mol, a softening point of 82 ℃ and a total chlorine content of 210 ppm.
Example 2
The preparation of the low-chlorine branched epoxy resin for the powder coating of this example comprises the following components in molar amounts:
dibutyl tin oxide accounting for 0.03 percent of the total molar weight of the raw materials for preparation.
The preparation method of the low-chlorine branched epoxy resin for the powder coating comprises the following steps:
(1) adding the oxalic acid, the 1, 3-propanediol, the 1, 4-succinic acid and the catalyst dibutyltin oxide into a reaction kettle according to the formula ratio, starting stirring and uniformly mixing, gradually heating to 220 ℃ at a heating rate of 18 ℃/h, and carrying out heat preservation polymerization reaction;
(2) detecting, adding the trimethylolpropane with the formula amount when the acid value of the polymer of the reaction system is 35-45mgKOH/g, and gradually heating to 235 ℃ at the heating rate of 8 ℃/h to perform heat preservation chain extension reaction;
(3) detecting, when the acid value of the polymer in the reaction system reaches 15-20mgKOH/g, adding the pyromellitic acid with the formula amount, and continuing to perform carboxyl end-capping reaction at 235 ℃;
(4) through detection, when the hydroxyl value of the polymer in the reaction system is reduced to be below 5mgKOH/g, the material is quickly cooled to 60 ℃, and then the methanol with the formula amount is added to carry out sufficient methyl esterification reaction on the polymer;
(5) detecting that the methyl esterification is basically finished when the acid value of the polymer of the reaction system is lower than 2mgKOH/g, then starting vacuum, controlling the vacuum degree to be between-0.097 Mpa and-0.099 Mpa, and heating to 85 ℃ to remove excessive methanol and micromolecular water by decompression;
(6) stopping the vacuum process when no obvious distillate is distilled out (less than 1 drop of distillate in 30 s), adding the glycidol with the formula amount, uniformly stirring, starting the vacuum process again, controlling the vacuum degree to be between-0.097 Mpa and-0.099 Mpa, and carrying out vacuum ester exchange reaction to distill out methanol generated by the ester exchange reaction;
(7) when the amount of the collected methanol reaches more than 80% of the theoretical amount, gradually heating to 115 ℃ at the heating rate of 8 ℃/h to remove excessive glycidol, stopping reaction after no obvious distillate is evaporated (the distillate is less than 1 drop in 30 s), discharging at high temperature while the mixture is hot, cooling the epoxy resin by using a steel belt with condensed water, and then crushing and granulating to obtain the required low-chlorine branched epoxy resin.
The epoxy resin prepared in this example was tested as colorless transparent particles having an epoxy equivalent of 453g/mol, a softening point of 75 ℃ and a total chlorine content of 195 ppm.
Example 3
The preparation of the low-chlorine branched epoxy resin for the powder coating of this example comprises the following components in molar amounts:
dibutyl tin oxide accounting for 0.02 percent of the total molar weight of the raw materials for preparation.
The preparation method of the low-chlorine branched epoxy resin for the powder coating comprises the following steps:
(1) adding the oxalic acid, the 1, 3-propanediol, the 1, 4-succinic acid and the catalyst dibutyltin oxide into a reaction kettle according to the formula ratio, starting stirring and uniformly mixing, gradually heating to 215 ℃ at a heating rate of 16 ℃/h, and carrying out heat preservation polymerization reaction;
(2) detecting, adding the trimethylolpropane with the formula amount when the acid value of the polymer of the reaction system is 35-45mgKOH/g, and gradually heating to 232 ℃ at the heating rate of 7 ℃/h to perform heat preservation chain extension reaction;
(3) detecting, when the acid value of the polymer in the reaction system reaches 15-20mgKOH/g, adding the pyromellitic acid with the formula amount, and continuing to perform carboxyl end-capping reaction at 232 ℃;
(4) through detection, when the hydroxyl value of the polymer in the reaction system is reduced to be below 5mgKOH/g, the material is quickly cooled to 58 ℃, and then the methanol with the formula amount is added to carry out sufficient methyl esterification reaction on the polymer;
(5) after detection, when the acid value of the polymer of the reaction system is lower than 2mgKOH/g, the methyl esterification is basically finished, then the vacuum is started, the vacuum degree is controlled to be between-0.097 Mpa and-0.099 Mpa, and the temperature is increased to 82 ℃ for decompression and removal of excessive methanol and micromolecular water;
(6) stopping the vacuum process when no obvious distillate is distilled out (less than 1 drop of distillate in 30 s), adding the glycidol with the formula amount, uniformly stirring, starting the vacuum process again, controlling the vacuum degree to be between-0.097 Mpa and-0.099 Mpa, and carrying out vacuum ester exchange reaction to distill out methanol generated by the ester exchange reaction;
(7) when the amount of the collected methanol reaches more than 80% of the theoretical amount, gradually heating to 112 ℃ at the heating rate of 6 ℃/h to remove excessive glycidol, stopping reaction after no obvious distillate is evaporated (the distillate is less than 1 drop in 30 s), discharging at high temperature while the mixture is hot, cooling the epoxy resin by using a steel belt with condensed water, and then crushing and granulating to obtain the required low-chlorine branched epoxy resin.
The epoxy resin prepared in this example was tested as colorless transparent particles having an epoxy equivalent of 437g/mol, a softening point of 78 ℃ and a total chlorine content of 228 ppm.
Example 4
The preparation of the low-chlorine branched epoxy resin for the powder coating of this example comprises the following components in molar amounts:
dibutyl tin oxide accounting for 0.02 percent of the total molar weight of the raw materials for preparation.
The preparation method of the low-chlorine branched epoxy resin for the powder coating comprises the following steps:
(1) adding the oxalic acid, the 1, 3-propanediol, the 1, 4-succinic acid and the catalyst dibutyltin oxide into a reaction kettle according to the formula ratio, starting stirring and uniformly mixing, gradually heating to 215 ℃ at a heating rate of 16 ℃/h, and carrying out heat preservation polymerization reaction;
(2) detecting, adding the trimethylolpropane with the formula amount when the acid value of the polymer of the reaction system is 35-45mgKOH/g, and gradually heating to 232 ℃ at the heating rate of 7 ℃/h to perform heat preservation chain extension reaction;
(3) detecting, when the acid value of the polymer in the reaction system reaches 15-20mgKOH/g, adding the pyromellitic acid with the formula amount, and continuing to perform carboxyl end-capping reaction at 232 ℃;
(4) through detection, when the hydroxyl value of the polymer in the reaction system is reduced to be below 5mgKOH/g, the material is quickly cooled to 58 ℃, and then the methanol with the formula amount is added to carry out sufficient methyl esterification reaction on the polymer;
(5) after detection, when the acid value of the polymer of the reaction system is lower than 2mgKOH/g, the methyl esterification is basically finished, then the vacuum is started, the vacuum degree is controlled to be between-0.097 Mpa and-0.099 Mpa, and the temperature is increased to 82 ℃ for decompression and removal of excessive methanol and micromolecular water;
(6) stopping the vacuum process when no obvious distillate is distilled out (less than 1 drop of distillate in 30 s), adding the glycidol with the formula amount, uniformly stirring, starting the vacuum process again, controlling the vacuum degree to be between-0.097 Mpa and-0.099 Mpa, and carrying out vacuum ester exchange reaction to distill out methanol generated by the ester exchange reaction;
(7) when the amount of the collected methanol reaches more than 80% of the theoretical amount, gradually heating to 112 ℃ at the heating rate of 6 ℃/h to remove excessive glycidol, stopping reaction after no obvious distillate is evaporated (the distillate is less than 1 drop in 30 s), discharging at high temperature while the mixture is hot, cooling the epoxy resin by using a steel belt with condensed water, and then crushing and granulating to obtain the required low-chlorine branched epoxy resin.
The epoxy resin prepared in this example was tested as colorless transparent particles with an epoxy equivalent of 446g/mol, a softening point of 80 ℃ and a total chlorine content of 215 ppm.
Examples of the experiments
1. Pure epoxy resin system powder coating
The epoxy resin prepared in the embodiments 1-4 of the invention is respectively taken and prepared into pure epoxy resin system powder coating according to the following components, and the specific formula is as follows:
among them, JG803A was obtained from Ningbo south sea chemical Co.
Preparing a coating layer: mixing the materials uniformly according to the requirements of the powder coating formula, 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 70-80 mu m, and then the powder coating is baked and cured at 150 ℃/10min to obtain the coating film of the coating.
The low-chlorine epoxy resin of the present invention (the amount of the JG803A curing agent was adjusted to 40g due to the difference in epoxy equivalent) was replaced with a commercially available ordinary E-12 epoxy resin (having an epoxy equivalent of 824g/mol, a softening point of 92 ℃ C., a total chlorine of 5180ppm, available from Huangshan pentacyclic technologies, Ltd.) and cured by baking at 150 ℃ for 10min as comparative example 1.
The low-chlorine epoxy resin of the present invention was cured by baking at 180 ℃ for 10min in place of a commercially available ordinary E-12 epoxy resin (having an epoxy equivalent of 824g/mol, a softening point of 92 ℃ C., and a total chlorine of 5180ppm, available from Huangshan pentacyclic technologies, Ltd.) as comparative example 2.
The method for measuring the total chlorine is based on GB/T12007.3-1989 method for measuring the total chlorine content of epoxy resin and detection of coating indexes based on GB/T21776 2008 standard guidelines for detecting powder coatings and coatings thereof.
Epoxy resins prepared by the above examples and comparative examples coating formulations according to the invention were prepared and tested for coating properties as shown in table 1 below.
TABLE 1 pure epoxy powder coating Performance test data
As can be seen from the data in Table 1, the low-chlorine branched epoxy resin for powder has the advantages that under the coordination action of the components, the total chlorine of the product is lower than 300ppm, the final product also has a better application effect, the appearance, impact and gloss of the coating film are better after the low-temperature curing at 150 ℃/10min, and particularly, the coating film shows excellent boiling water resistance and can be used in special fields such as engines, vehicle fuel tanks and other special fields with higher requirements on chlorine ions;
while the comparative examples 1-2 adopt the common E-12 epoxy resin, the total chlorine content is higher and reaches about 5000ppm, and the boiling water resistance of the final coating film is still insufficient even under the condition of adopting high-temperature curing (180 ℃/10 min).
2. Outdoor TGIC system powder coating
In this experimental example, the performance of the low-chlorine branched epoxy resin of the present invention as a boiling water resistant additive for outdoor TGIC powder coatings was verified based on the epoxy resins prepared in examples 1-4, respectively.
The outdoor TGIC system powder coating formulations of examples 5-8 and comparative example 3 were formed in the respective proportions shown in table 2 below.
TABLE 2 outdoor TGIC system powder coating formulation
Wherein the polyester resin is purchased from Zhejiang Guanghua New materials GmbH, model number GH-2200.
Preparing a coating layer: mixing the materials uniformly according to the requirements of the powder coating formula, 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 70-80 mu m, and then the powder coating is baked and cured at 200 ℃/10min to obtain the coating film of the coating.
The detection of the coating index is in accordance with GB/T21776 2008 'Standard guide for powder coating and coating detection'.
The results of testing the coating properties of the coatings prepared in examples 5 to 8 and comparative example 3 are shown in Table 3 below.
TABLE 3 outdoor TGIC powder coating Performance test data
As can be seen from the data in Table 3 above, when the epoxy resin of the present invention is used as an additive in combination with a conventional polyester resin, the durable boiling water resistance of the coating film product is greatly improved with the increase of the crosslinking density. In comparative example 3, the TGIC powder coating product prepared from the common polyester resin has good comprehensive performance, but the boiling water resistance of the TGIC powder coating product needs to be further improved due to insufficient crosslinking density. The low-chlorine branched epoxy resin can also be used as a boiling water resistant additive in outdoor TGIC powder coatings.
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.
Claims (10)
1. The low-chlorine branched epoxy resin for the powder coating is characterized by comprising the following components in molar weight:
2. the low-chlorine branched epoxy resin for powder coating according to claim 1, wherein the raw materials for preparation further comprise a catalyst, and the molar amount of the catalyst is 0.01-0.03% of the total molar amount of the raw materials for preparation.
3. The low-chlorine branched epoxy resin for powder coating according to claim 2, wherein the catalyst comprises dibutyltin oxide.
4. A process for preparing a low-chlorine branched epoxy resin for powder coatings according to any of claims 1 to 3, comprising the steps of:
(1) uniformly mixing the oxalic acid, the 1, 3-propanediol, the 1, 4-succinic acid and the catalyst according to the formula ratio, and controlling the temperature of a material system to 210-220 ℃ for polymerization reaction;
(2) when the acid value of the polymer to be detected in the reaction system reaches 35-45mgKOH/g, adding the trimethylolpropane with the formula amount, and heating to 230-235 ℃ for chain extension reaction;
(3) when the acid value of the polymer of the reaction system to be detected reaches 15-20mgKOH/g, adding the pyromellitic acid with the formula amount, and continuing to perform carboxyl end-capping reaction at 230-235 ℃;
(4) when the hydroxyl value of the polymer of the reaction system to be detected is reduced to be below 5mgKOH/g, quickly cooling the reaction material to 55-60 ℃, and then adding the methanol with the formula amount to perform methyl esterification reaction on the polymer;
(5) when the acid value of the polymer to be detected in the reaction system is lower than 2mgKOH/g, starting a vacuum program, heating to 80-85 ℃, and removing excessive methanol and micromolecular water under reduced pressure;
(6) stopping the vacuum process when no obvious distillate is evaporated, adding the glycidol in the formula amount, uniformly mixing, starting the vacuum process again for vacuum ester exchange reaction, and distilling out methanol generated by the ester exchange reaction;
(7) when the collected methanol amount reaches more than 80% of the theoretical amount, heating the reaction system materials to 110-115 ℃ to remove excessive glycidol, stopping the reaction when no obvious distillate is evaporated, discharging at high temperature while the reaction system materials are hot, cooling, crushing and granulating to obtain the catalyst.
5. The method for preparing a low-chlorine branched epoxy resin for powder coating according to claim 4, wherein in the step (1), the temperature increase rate of the temperature increase step is controlled to be 15 to 18 ℃/h.
6. The method for producing a low-chlorine branched epoxy resin for powder coating according to claim 4 or 5, wherein in the step (2), the temperature-raising rate in the temperature-raising step is controlled to 6 to 8 ℃/h.
7. The method for preparing a low-chlorine branched epoxy resin for powder coating according to any one of claims 4 to 6, wherein in the steps (5) and (6), the degree of vacuum of the vacuum process is controlled to be-0.097 MPa to-0.099 MPa.
8. The method for producing a low-chlorine branched epoxy resin for powder coating according to any one of claims 4 to 7, wherein in the step (7), the temperature-raising step is controlled at a temperature-raising rate of 5 to 8 ℃/h.
9. Use of a low-chlorine branched epoxy resin as claimed in any of claims 1 to 3 for the preparation of powder coatings.
10. Use of the low chlorine branched epoxy resin of any one of claims 1 to 3 for the preparation of a boil-off resistant aid for outdoor TGIC powder coatings.
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| CN202111287828.6A CN113845644B (en) | 2021-11-02 | 2021-11-02 | Low-chlorine branched epoxy resin for powder coating and preparation method and application thereof |
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| CN113845644B CN113845644B (en) | 2023-08-15 |
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