Low-temperature curing powder coating and preparation method thereof

Abstract

The present 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 comprises the following raw materials by weight: 80-100 parts of an aliphatic epoxy resin, 15-20 parts of a curing agent, 15-30 parts of a filler, 1-2 parts of a leveling agent, and 0.5-1.5 parts of a defoaming agent. The curing agent comprises diethylenetriamine and a piperazine thioamide compound, with the mass ratio of diethylenetriamine to piperazine thioamide being 1:5 to 5:1. This technical solution solves the problems of long curing time and low impact resistance of low-temperature curing powder coatings in related technologies.

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 solvent-free, solid powder coating. With the continuous advancement of technology and growing awareness of environmental protection, traditional solvent-based coatings are facing increasing restrictions due to their high levels of volatile organic compounds (VOCs). Powder coatings, with their solvent-free, environmentally friendly, and recyclable advantages, are gradually becoming the development direction of the coatings industry. However, traditional powder coatings typically require high curing temperatures, which not only consumes a lot of energy but can also damage some heat-sensitive substrates. Low-temperature curing powder coatings, on the other hand, overcome these drawbacks, rapidly curing at relatively low temperatures.

[0003] Due to the low curing temperature, low-temperature curing powder coatings have a relatively slow chemical reaction rate. Compared with high-temperature curing powder coatings, under the same production efficiency requirements, low-temperature curing powder coatings often require longer curing times. This affects production efficiency during large-scale production, increases the residence time of the product in the curing equipment, and slows the production cycle 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 lower temperature, the cross-linked network formed between the resin and the curing agent is not as dense and strong as that of high-temperature curing. This makes the coating more prone to cracking and flaking when subjected to external impact. Therefore, the development of a low-temperature curing powder coating with a short curing time and high impact resistance is an urgent problem that needs to be solved. Summary of the Invention

[0004] The present 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 low-temperature curing powder coatings in related technologies.

[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;

[0006] The curing agent includes diethylenetriamine and a piperazine thioamide compound, and the mass ratio of the diethylenetriamine to the piperazine thioamide compound is 1:5 to 5:1.

[0007] As a further technical solution, the mass ratio of the diethylenetriamine to the piperazine thioamide compound is 2-3:1.

[0008] 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.

[0009] As a further technical solution, the raw materials further include: 5 to 10 parts of a reactive diluent, which is an aliphatic epoxy compound.

[0010] In the present invention, an aliphatic epoxy compound is added as a reactive 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.

[0011] As a further technical solution, the aliphatic epoxy compound includes one or more of 1,2-epoxyoctane, 1,2-epoxydodecane, and 1,2-epoxyeicosane.

[0012] As a further technical solution, the aliphatic epoxy compound is preferably 1,2-epoxydodecane.

[0013] 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.

[0014] As a further technical solution, the filler includes one or more of calcium carbonate, kaolin, and talc.

[0015] 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.

[0016] As a further technical solution, the defoaming agent includes one or more of an organosilicon defoaming agent, a mineral oil defoaming agent, and a polyether defoaming agent.

[0017] The present invention also provides a method for preparing a low-temperature curing powder coating, comprising the following steps: weighing the component raw materials in parts by weight, mixing and then melt-extruding, cooling, crushing and sieving to obtain the low-temperature curing powder coating.

[0018] As a further technical solution, the mixing time is 15 to 30 minutes, and the sieving screen is 180 to 200 meshes.

[0019] The working principle and beneficial effects of the present invention are:

[0020] In the present invention, diethylenetriamine and piperazine thioamide compound are added simultaneously as curing agents, and by adjusting the ratio between the two, the synergistic effect of the two is exerted to promote the rapid and stable progress of the curing reaction, shorten the curing time of the low-temperature curing powder coating, and improve the impact resistance of the powder coating. DETAILED DESCRIPTION

[0021] 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 embodiments described 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 making any creative efforts are within the scope of protection of the present invention.

[0022] In the following examples and comparative examples:

[0023] Aliphatic epoxy resin: Model: Dow epoxy resin DER732;

[0024] Silicone defoamer: Model ACP-5500.

[0025] Example 1

[0026] A method for preparing 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 defoamer, stirring and mixing them for 15 minutes, heating them to 100° C., melt-extruding them, cooling them, crushing them, and sieving them through a 200-mesh sieve to obtain the low-temperature curing powder coating; wherein the curing agent comprises diethylenetriamine and N-ethyl-4-methyl-1-piperazinethiocarboxamide in a mass ratio of 2:1.

[0027] Example 2

[0028] A method for preparing 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, melt-extruding, cooling, crushing, and sieving using a 200-mesh sieve to obtain the low-temperature curing powder coating; wherein the curing agent comprises diethylenetriamine and N-ethyl-4-methyl-1-piperazinethiocarboxamide in a mass ratio of 5:1.

[0029] Example 3

[0030] A method for preparing 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 defoamer, stirring and mixing them for 30 minutes, heating them to 100° C., melt-extruding them, cooling them, crushing them, and sieving them through a 200-mesh sieve to obtain the low-temperature curing powder coating; wherein the curing agent comprises diethylenetriamine and N-ethyl-4-methyl-1-piperazinethiocarboxamide in a mass ratio of 1:5.

[0031] Example 4

[0032] Compared with Example 1, Example 4 is different in that the curing agent consists of diethylenetriamine and N-ethyl-4-methyl-1-piperazinethiocarboxamide in a mass ratio of 3:1.

[0033] Example 5

[0034] 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.

[0035] Example 6

[0036] A method for preparing 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, 0.5 parts of an organosilicon defoaming agent, and 5 parts of a reactive diluent, stirring and mixing them for 15 minutes, heating them to 100° C. for melt extrusion, cooling, crushing, and sieving the mixture through a 200-mesh screen to obtain the low-temperature curing powder coating; wherein the curing agent comprises diethylenetriamine and N-ethyl-4-methyl-1-piperazinethiocarboxamide in a mass ratio of 3:1, and the reactive diluent is 1,2-octyl oxide.

[0037] Example 7

[0038] Compared with Example 6, Example 7 is different in that the active diluent is 1,2-epoxydodecane.

[0039] Example 8

[0040] Compared with Example 6, Example 8 is different in that the active diluent is 1,2-epoxyeicosane.

[0041] Comparative Example 1

[0042] Compared with Example 1, the difference in Comparative Example 1 is that the curing agent is diethylenetriamine.

[0043] Comparative Example 2

[0044] Compared with Example 1, the difference in Comparative Example 2 is that the curing agent is N-ethyl-4-methyl-1-piperazinethiocarboxamide.

[0045] 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 an aluminum plate at a curing temperature of 120° C. and tested as follows:

[0046] 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".

[0047] 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".

[0048] 3. Adhesion: Test the adhesion of the sample according to the test method specified in ISO 2409:2020 "Paints and varnishes - Cross-cut test".

[0049] The test results are shown in the following table:

[0050] Table 1 Performance test results of low temperature curing powder coatings prepared in Examples 1 to 8 and Comparative Examples 1 to 2

[0051]

[0052] Compared with Example 1, Comparative Example 1 only added diethylenetriamine as a curing agent, and Comparative Example 2 only added N-ethyl-4-methyl-1-piperazinethiocarboxamide as a curing agent. The results show that 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, 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.

[0053] Compared with Example 4, Examples 6 to 8 added reactive 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 reactive diluents can shorten the curing time of low-temperature curing powder coatings and improve the impact resistance of powder coatings.

[0054] Compared with Example 6, Example 7 adds 1,2-epoxydodecane as a reactive diluent, and Example 8 adds 1,2-epoxyeicosane as a reactive 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 reactive diluent is 1,2-epoxydodecane, the obtained low-temperature curing powder coating has a shorter curing time and better impact resistance.

[0055] 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 scope of protection 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, 0.5-1.5 parts of defoaming agent, and 5-10 parts of reactive diluent; 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; 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; The active diluent is an aliphatic epoxy compound, and the aliphatic epoxy compound is 1,2-epoxydodecane.

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 filler includes one or more of calcium carbonate, kaolin, and talc.

4. 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.

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

6. The method for preparing a low-temperature curing powder coating according to any one of claims 1 to 5, characterized in that: The method comprises the following steps: weighing the component raw materials in parts by weight, mixing them, melting and extruding them, cooling, crushing and sieving to obtain a low-temperature curing powder coating.

7. The method for preparing a low-temperature curing powder coating according to claim 6, characterized in that: The mixing time is 15-30 min, and the sieve mesh is 180-200 mesh.

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