Low-temperature curing powder coating and preparation method thereof

Abstract

The invention relates to the technical field of powder coatings, and provides a low-temperature curing powder coating and a preparation method thereof.The low-temperature curing powder coating is prepared from, by weight, 80-100 parts of aliphatic epoxy resin, 15-20 parts of curing agent, 15-30 parts of filler, 1-2 parts of flatting agent and 0.5-1.5 parts of defoaming agent; the curing agent comprises diethylenetriamine and a piperazine thioamide compound, and the mass ratio of the diethylenetriamine to the piperazine thioamide compound is (1: 5)-(5: 1). Through the technical scheme, the problems of long curing time and low impact resistance of low-temperature curing powder coatings in related technologies are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of powder coatings, and in particular to a low-temperature curing powder coating and a preparation method thereof. Background Art

[0002] Powder coating is a new type of solid powder coating without solvent. With the continuous advancement of science and technology and the improvement of people's awareness of environmental protection, traditional solvent-based coatings are facing more and more restrictions because they contain a large amount of volatile organic compounds (VOC). Powder coatings have gradually become the development direction of the coatings industry with its advantages such as solvent-free, environmentally friendly and recyclable. However, traditional powder coatings usually require a higher curing temperature, which not only consumes a lot of energy, but also may cause damage to some heat-sensitive substrates. Low-temperature curing powder coatings overcome these disadvantages and can be cured quickly at a relatively low temperature.

[0003] Low-temperature curing powder coatings have a relatively slow chemical reaction rate due to their low curing temperature. Compared with high-temperature curing powder coatings, under the same production efficiency requirements, low-temperature curing powder coatings often require longer curing time, which will affect production efficiency in large-scale production processes, increase the residence time of products in curing equipment, and slow down the production rhythm of the production line, which in turn affects the overall production capacity and economic benefits of the enterprise. During the curing process of low-temperature curing powder coatings, due to the low temperature, the cross-linking network formed between the resin and the curing agent is not as dense and strong as that of high-temperature curing, which makes the coating more prone to cracking and peeling when subjected to external force impact. Therefore, the development of a low-temperature curing powder coating with a short curing time and high impact resistance is an urgent problem to be solved. Summary of the invention

[0004] The invention provides a low-temperature curing powder coating and a preparation method thereof, which solves the problems of long curing time and low impact resistance of the low-temperature curing powder coating in the related art.

[0005] The technical solution of the present invention is as follows: The present invention provides a low-temperature curing powder coating, comprising the following component raw materials in parts by weight: 80-100 parts of aliphatic epoxy resin, 15-20 parts of curing agent, 15-30 parts of filler, 1-2 parts of leveling agent, and 0.5-1.5 parts of defoaming agent; The curing agent comprises diethylenetriamine and a piperazine thioamide compound, and the mass ratio of the diethylenetriamine to the piperazine thioamide compound is 1:5 to 5:1.

[0006] As a further technical solution, the mass ratio of the diethylenetriamine to the piperazine thioamide compound is 2-3:1.

[0007] As a further technical solution, the piperazine thioamide compound includes one or more of N-ethyl-4-methyl-1-piperazine thiocarboxamide, 1-piperazine thiocarboxamide, and 4-(2-propenyl)-1-piperazine thiocarboxamide.

[0008] As a further technical solution, the raw material also includes: 5 to 10 parts of active diluent, and the active diluent is an aliphatic epoxy compound.

[0009] In the present invention, an aliphatic epoxy compound is added as an active diluent to accelerate the curing process of the system, reduce the viscosity of the system, improve the dispersibility of the curing agent, shorten the curing time of the low-temperature curing powder coating, and enhance the impact resistance of the powder coating.

[0010] As a further technical solution, the aliphatic epoxy compound includes one or more of 1,2-epoxyoctane, 1,2-epoxydodecane, and 1,2-epoxyeicosane.

[0011] As a further technical solution, the aliphatic epoxy compound is preferably 1,2-epoxydodecane.

[0012] In the present invention, 1,2-epoxydodecane is preferably used as the active diluent to promote the dissolution of the active diluent and the aliphatic epoxy resin, adjust the viscosity of the system, shorten the curing time of the low-temperature curing powder coating, and improve the impact resistance of the powder coating.

[0013] As a further technical solution, the filler includes one or more of calcium carbonate, kaolin, and talc.

[0014] As a further technical solution, the leveling agent includes one or more of leveling agent F-400, leveling agent F-401, and leveling agent DH-4036.

[0015] As a further technical solution, the defoamer includes one or more of an organosilicon defoamer, a mineral oil defoamer, and a polyether defoamer.

[0016] The present invention also provides a method for preparing a low-temperature curing powder coating, comprising the following steps: weighing the component raw materials by weight, mixing and then melt-extruding, cooling, crushing and sieving to obtain the low-temperature curing powder coating.

[0017] As a further technical solution, the mixing time is 15-30 minutes, and the sieving screen is 180-200 meshes.

[0018] The working principle and beneficial effects of the present invention are: In the present invention, diethylenetriamine and piperazine thioamide compound are added as curing agents at the same time, and the ratio of the two is adjusted to exert the synergistic effect of the two, thereby promoting the rapid and stable progress of the curing reaction, shortening the curing time of the low-temperature curing powder coating, and improving the impact resistance of the powder coating. DETAILED DESCRIPTION

[0019] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] In the following examples and comparative examples: Aliphatic epoxy resin: Model: Dow epoxy resin DER732; Silicone defoamer: Model: ACP-5500.

[0021] Example 1 A preparation method of a low-temperature curing powder coating comprises the following steps: weighing 80 parts of an aliphatic epoxy resin, 15 parts of a curing agent, 15 parts of calcium carbonate, 1 part of a leveling agent F-400, and 0.5 parts of an organosilicon defoaming agent, mixing and stirring for 15 minutes, heating to 100°C for melt extrusion, cooling, crushing, and sieving, wherein the sieve is 200 meshes, and the low-temperature curing powder coating is obtained; wherein the curing agent is composed of diethylenetriamine and N-ethyl-4-methyl-1-piperazinethiocarboxamide in a mass ratio of 2:1.

[0022] Example 2 A preparation method of a low-temperature curing powder coating comprises the following steps: weighing 90 parts of an aliphatic epoxy resin, 18 parts of a curing agent, 20 parts of calcium carbonate, 1.5 parts of a leveling agent F-401, and 1 part of an organosilicon defoamer, mixing and stirring for 20 minutes, heating to 100°C for melt extrusion, cooling, crushing, and sieving, wherein the sieve is 200 meshes, and the low-temperature curing powder coating is obtained; wherein the curing agent is composed of diethylenetriamine and N-ethyl-4-methyl-1-piperazinethiocarboxamide in a mass ratio of 5:1.

[0023] Example 3 A preparation method of a low-temperature curing powder coating comprises the following steps: weighing 100 parts of an aliphatic epoxy resin, 20 parts of a curing agent, 30 parts of calcium carbonate, 2 parts of a leveling agent DH-4036, and 1.5 parts of an organosilicon defoaming agent, mixing and stirring for 30 minutes, heating to 100°C for melt extrusion, cooling, crushing, and sieving, wherein the sieve is 200 meshes, and the low-temperature curing powder coating is obtained; wherein the curing agent is composed of diethylenetriamine and N-ethyl-4-methyl-1-piperazinethiocarboxamide in a mass ratio of 1:5.

[0024] Example 4 Compared with Example 1, the difference of Example 4 is that the curing agent consists of diethylenetriamine and N-ethyl-4-methyl-1-piperazinethiocarboxamide in a mass ratio of 3:1.

[0025] Example 5 Compared with Example 4, the difference of Example 5 is that the curing agent consists of diethylenetriamine and 1-piperazinethiocarboxamide in a mass ratio of 3:1.

[0026] Example 6 A preparation method of a low-temperature curing powder coating comprises the following steps: weighing 80 parts of aliphatic epoxy resin, 15 parts of curing agent, 15 parts of calcium carbonate, 1 part of leveling agent F-400, 0.5 parts of organosilicon defoaming agent and 5 parts of active diluent, mixing and stirring for 15 minutes, heating to 100°C for melt extrusion, cooling, crushing and sieving, wherein the sieve is 200 meshes, and the low-temperature curing powder coating is obtained; wherein the curing agent is composed of diethylenetriamine and N-ethyl-4-methyl-1-piperazinethiocarboxamide in a mass ratio of 3:1, and the active diluent is 1,2-octyl oxide.

[0027] Example 7 Compared with Example 6, Example 7 is different in that the active diluent is 1,2-epoxydodecane.

[0028] Example 8 Compared with Example 6, Example 8 is different in that the active diluent is 1,2-epoxyeicosane.

[0029] Comparative Example 1 Compared with Example 1, the difference of Comparative Example 1 is that the curing agent is diethylenetriamine.

[0030] Comparative Example 2 Compared with Example 1, the difference of Comparative Example 2 is that the curing agent is N-ethyl-4-methyl-1-piperazinethiocarboxamide.

[0031] The low-temperature curing powder coatings prepared in Examples 1 to 8 and Comparative Examples 1 to 2 were electrostatically sprayed on the surface of the aluminum plate at a curing temperature of 120° C. and tested according to the following method: 1. Curing time: Test the curing time of the sample according to the test method for surface drying time specified in GB / T 1728-2020 "Determination of Drying Time of Paint Film and Putty Film".

[0032] 2. Impact resistance: Test the impact resistance of the sample according to the test method specified in GB / T1732-2020 "Determination of impact resistance of paint film".

[0033] 3. Adhesion: Test the adhesion of the sample according to the test method specified in ISO 2409-2020 "Paints and varnishes - Cross-cut test".

[0034] The test results are shown in the following table: Table 1 Performance test results of low temperature curing powder coatings prepared in Examples 1 to 8 and Comparative Examples 1 to 2

[0035] Compared with Example 1, Comparative Example 1 only adds diethylenetriamine as a curing agent, and Comparative Example 2 only adds N-ethyl-4-methyl-1-piperazinethiocarboxamide as a curing agent. As a result, the curing time of Example 1 is shorter than that of Comparative Examples 1 and 2, and the impact resistance and adhesion performance are better than those of Comparative Examples 1 and 2, indicating that diethylenetriamine and N-ethyl-4-methyl-1-piperazinethiocarboxamide play a synergistic effect, which can shorten the curing time of the low-temperature curing powder coating, improve the impact resistance of the powder coating, and enhance the adhesion of the powder coating.

[0036] Compared with Example 4, Examples 6 to 8 added active diluents. As a result, the curing time of Examples 6 to 8 was shorter than that of Example 4, and the impact resistance was better than that of Examples 6 to 8, indicating that the addition of active diluents can shorten the curing time of low-temperature curing powder coatings and improve the impact resistance of powder coatings.

[0037] Compared with Example 6, Example 7 adds 1,2-epoxydodecane as an active diluent, and Example 8 adds 1,2-epoxyeicosane as an active diluent. As a result, the curing time of Example 7 is shorter than that of Examples 6 and 8, and the impact resistance is better than that of Examples 6 and 8, indicating that when the added active diluent is 1,2-epoxydodecane, the obtained low-temperature curing powder coating has a shorter curing time and better impact resistance.

[0038] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A low temperature curing powder coating, characterized in that: The invention comprises the following raw materials in parts by weight: 80-100 parts of aliphatic epoxy resin, 15-20 parts of curing agent, 15-30 parts of filler, 1-2 parts of leveling agent and 0.5-1.5 parts of defoaming agent; the curing agent comprises diethylenetriamine and piperazine thioamide compound, and the mass ratio of the diethylenetriamine to the piperazine thioamide compound is 1:5-5:

1.

2. A low temperature curing powder coating according to claim 1, characterized in that: The mass ratio of the diethylenetriamine to the piperazine thioamide compound is 2-3:

1.

3. A low temperature curing powder coating according to claim 1, characterized in that: The piperazine thioamide compound includes one or more of N-ethyl-4-methyl-1-piperazine thiocarboxamide, 1-piperazine thiocarboxamide, and 4-(2-propenyl)-1-piperazine thiocarboxamide.

4. A low temperature curing powder coating according to any one of claims 1 to 3, characterized in that: The raw materials also include: 5 to 10 parts of active diluent, and the active diluent is an aliphatic epoxy compound.

5. A low temperature curing powder coating according to claim 4, characterized in that: The aliphatic epoxy compound includes one or more of 1,2-epoxyoctane, 1,2-epoxydodecane, and 1,2-epoxyeicosane.

6. A low temperature curing powder coating according to claim 1, characterized in that: The filler includes one or more of calcium carbonate, kaolin and talc.

7. A low temperature curing powder coating according to claim 1, characterized in that: The leveling agent includes one or more of leveling agent F-400, leveling agent F-401, and leveling agent DH-4036.

8. The low temperature curing powder coating according to claim 1, characterized in that: The defoamer includes one or more of an organosilicon defoamer, a mineral oil defoamer, and a polyether defoamer.

9. The method for preparing a low temperature curing powder coating according to any one of claims 1 to 8, characterized in that: The method comprises the following steps: weighing the component raw materials by weight, mixing them, melting and extruding them, cooling, crushing and sieving them to obtain a low-temperature curing powder coating.

10. The method for preparing a low temperature curing powder coating according to claim 9, characterized in that: The mixing time is 15-30 minutes, and the sieving screen is 180-200 meshes.

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