CN110760238A - A kind of powder coating and preparation method thereof - Google Patents

Abstract

The invention belongs to the field of materials, and discloses a powder coating, which comprises the following components in parts by weight: 150-200 parts of epoxy resin, 10-50 parts of modified epoxy resin, 5-20 parts of curing agent, curing accelerator 0.1-3 parts of agent, 50-150 parts of filler, 5-20 parts of auxiliary agent, 0.5-10 parts of pigment, the powder coating has good insulation, high pressure resistance, acid and alkali resistance, organic solvent resistance, spray the powder coating 200 ‑300μm, the coating will not break down under 5000V; after continuous baking at 155℃ for 400 hours, the coating will not break down under 5000V; the insulation class is F; the coating is immersed in acetone 2h, soaked in butanone for 4h, and soaked in xylene for 24h, the coating did not soften and fall off; the coating was soaked in 10% mass concentration hydrochloric acid solution or 10% mass concentration NaOH solution for 10 days, and the coating did not appear. Blistering phenomenon.

Description

A kind of powder coating and preparation method thereof

technical field

The invention belongs to the field of materials, in particular to a powder coating and a preparation method thereof.

Background technique

Powder coatings are solid powder resin coatings composed of resins, pigments, fillers, additives, etc. Compared with ordinary solvent-based coatings and water-based coatings, the dispersion medium is not solvent and water, but air. Therefore, it has the characteristics of no solvent pollution, 100% film formation, high coating efficiency, excellent coating performance and low energy consumption.

With the widespread use of powder coatings, powder coatings are also playing an increasingly important role in insulating materials for electronics and motors. Powder coatings are widely used in motors, electronics, automotive industry, aviation machinery and other fields. However, because high-voltage electrical appliances, high-voltage coils, inductor coils and other high-voltage machines or materials are in a high-voltage environment when working, the voltage reaches more than 5,000 volts, and at the same time, they may come into contact with organic solvents and acid-base solutions. Insulation, high pressure resistance, acid and alkali resistance, and organic solvent resistance have put forward higher requirements, but the current powder coatings cannot meet the above requirements at the same time, which greatly restricts the promotion and application of insulating powder coatings in this field.

Therefore, it is necessary to provide a powder coating that is resistant to high pressure, acid and alkali, and organic solvents.

SUMMARY OF THE INVENTION

The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention proposes a powder coating that can withstand high pressure, acid and alkali, and organic solvents.

A powder coating, by weight, comprises the following components:

Preferably, the powder coating, in parts by weight, comprises the following components:

The epoxy resin is a bisphenol A type epoxy resin.

Preferably, the epoxy equivalent of the bisphenol A epoxy resin is 400-1000 g/eq; further preferably, the epoxy equivalent of the bisphenol A epoxy resin is 600-900 g/eq; more preferably , the epoxy equivalent of the bisphenol A epoxy resin is 600-700 g/eq.

The modified epoxy resin is a silane-modified epoxy resin.

Preferably, the epoxy equivalent of the silane-modified epoxy resin is 100-500 g/eq; further preferably, the epoxy equivalent of the silane-modified epoxy resin is 200-350 g/eq.

The filler comprises mica powder, preferably, the mica powder accounts for 50%-100% of the mass of the filler.

The filler may also contain barium sulfate and/or silicon micropowder.

The curing agent is a cyanamide compound, preferably, the curing agent is dicyandiamide, and the melting point of the dicyandiamide is 209.5°C.

The curing accelerator is imidazole or imidazole derivatives, preferably, the curing accelerator is 2-methylimidazole.

The auxiliary agent is at least one of a leveling agent, an antioxidant, a defoaming agent or an adhesion enhancer.

The defoamer is benzoin (benzoin).

The pigments are general-purpose pigments for powder coatings, such as organic red, carbon black, iron yellow, and ultramarine blue.

The particle size of the powder coating is 10-50 μm; preferably, the particle size of the powder coating is 25-40 μm.

A preparation method of powder coating comprises the following steps: weighing each component in proportion, mixing, crushing, melting and extruding, tableting and crushing to obtain the powder coating.

Specifically, a preparation method of powder coating, comprising the following steps:

Weigh the components in proportion, and then place the materials in the mixer to fully mix and crush, and the mixing and crushing time is 5-15 minutes; the mixed materials are melted and extruded on the extruder, and pressed into tablets, and then the tablets are cooled. , crushing, sieving, passing the magnet at the powder outlet to remove metal impurities, and then the powder coating is obtained.

The temperature of the melt extrusion is 90-105°C in the first zone and 105-120°C in the second zone. Preferably, the melt extrusion temperature in step (2) is 100°C in the first zone and 110°C in the second zone.

A coating is prepared by spraying the powder coating and curing at 200° C. for 5-10 minutes. The thickness of the coating is 100-300 μm.

An electrical device includes the coating.

The powder coating is applied to high pressure machines or materials.

With respect to the prior art, the beneficial effects of the present invention are as follows:

The epoxy resin and silane modified epoxy resin are used as the main resin, and the cyanamide compound is used as the curing agent, and the reaction crosslinking density is high. After the siloxane structure in the silane-modified epoxy resin is cured by reaction, the siloxane part migrates to the surface, so that the surface of the coating has properties similar to silicone, which increases the hydrophobicity and thermal stability of the coating. At the same time, a large amount of mica powder is added to the powder coating as a filler, and the silica in the mica powder is compounded with aluminum oxide to form a composite silica layer, which has a macroscopic appearance of a sheet-like structure; during the coating process, the mica wafer is subjected to Under the action of surface tension, it will automatically form a structure that is parallel to each other and parallel to the surface of the paint film. Such layer-by-layer arrangement, its orientation is just perpendicular to the direction in which corrosive substances penetrate the paint film, and the barrier effect is strong; Mica itself has extremely high resistance and is an excellent insulating material. After mixing with resin, it strengthens the insulation and high pressure resistance of the coating.

Therefore, the powder coating has good insulation, high voltage resistance, acid and alkali resistance, and organic solvent resistance. When the powder coating is sprayed at 200-300 μm, the coating will not be broken down at 5000 volts; continuous baking at 155 ° C After 400 hours, the coating is not broken down under 5000 volts; the insulation class is F; the coating is soaked in acetone for 2 hours, butanone for 4 hours, and xylene for 24 hours. Softening and peeling phenomenon; the coating is soaked in 10% mass concentration hydrochloric acid solution or 10% mass concentration NaOH solution for 10 days, and the coating has no blistering and peeling phenomenon.

The powder coating of the invention has the advantages of simple formula, energy saving and environmental protection, can partially replace paint and coating products, and has zero organic volatile compounds (VOC).

Detailed ways

In order to make those skilled in the art understand the technical solutions of the present invention more clearly, the following examples are now given for illustration. It should be noted that the following examples do not limit the protection scope of the present invention.

Examples 1-6, according to the composition of the powder coating in Table 1, weigh each component, then place the material in a mixer to fully mix and crush, and the mixing and crushing time is 5-15min, and then the mixed material is melted on the extruder Extrusion, the temperature of melt extrusion is 90-105°C in the first zone and 105-120°C in the second zone. After melt extrusion, the tablet is pressed, and then the tablet is cooled, pulverized and sieved, and the powder outlet is magnetically passed. Remove metal impurities to obtain powder coating.

Table 1 Composition of powder coatings

Comparative Example 1

The 50 parts of mica powder in Example 1 were replaced with 30 parts, and the remaining raw materials and preparation methods were the same as those of Example 1.

Comparative Example 2

The 180 parts of bisphenol A epoxy resin in Example 1 were changed to 120 parts, and the remaining raw materials and preparation methods were the same as those of Example 1.

Comparative Example 3

The 20 parts of silane-modified epoxy resin in Example 1 were changed to 5 parts, and the remaining raw materials and preparation methods were the same as those of Example 1.

Comparative Example 4

Change 1.5 parts of 2-methylimidazole in Example 1 to 5 parts, and the remaining raw materials and preparation methods are the same as those of Example 1.

Comparative Example 5

In Example 1, 11.5 parts of micronized dicyandiamide were changed to 4.5 parts, and the rest of the raw materials and the preparation method were the same as those of Example 1.

Comparative Example 6

The temperature of melt extrusion in the preparation process of Example 1 was changed to 80°C from 90-105°C in the first zone, and 125°C from 105-120°C in the second zone. The remaining raw materials and preparation methods were the same as those in Example 1.

Product effect test

The powder coatings obtained in the above Examples 1-6 and Comparative Examples 1-6 were respectively sprayed on the ferrite coils preheated in a 200 ℃ oven by high-voltage electrostatic spraying, and the coating thickness was between 200-300 μm. The curing conditions are: 200℃, 5-10min.

The ferrite coils of the powder coatings obtained by spraying Examples 1-6 and Comparative Examples 1-6 are respectively tested for performance:

Among them, the adhesion is tested according to GB/T 9286; the impact resistance is tested according to GB/T 1732; the neutral salt spray is tested according to GB/T 1771-2007; the apparent density is tested according to GB/T 6554-2003; The breakdown strength (room temperature) is tested according to GB/T 6554-2003; the insulation grade is tested according to GB/T 11021-2007.

At the same time, perform the following tests on the ferrite coil:

(1) Test at 5000 volts;

(2) After continuous baking at 155°C for 400 hours, test at 5000 volts;

(3) soak in acetone for 2 hours, butanone for 4 hours, and xylene for 24 hours;

(4) soak in 10% mass concentration NaOH solution for 10 days;

(5) Soak in 10% mass concentration hydrochloric acid solution for 10 days.

The performance test results of Examples 1-6 are shown in Table 2, and the performance test results of Comparative Examples 1-6 are shown in Table 3.

Table 2 embodiment 1-6 performance test results

Among them, the insulation grades are divided into A, E, B, F, H, 5 grades: A grade insulation temperature resistance 105 ℃; E grade insulation temperature resistance 120 ℃; B grade insulation temperature resistance 130 ℃; F grade insulation temperature resistance 155 ℃; H-class insulation temperature resistance 180 ℃.

Table 3 Comparative Examples 1-6 Performance Test Results

It can be seen from the comparison of Table 2 and Table 3 that the performance of the ferrite coil of the powder coating obtained by spraying Example 1-6 is obviously better than that of Comparative Example 1-6, and the ferrite coil insulation of the powder coating obtained by spraying Example 1-6 All grades are F, the coating does not break down at 5000 volts; after continuous baking at 155 ° C for 400 hours, the coating still does not break down at 5000 volts; immersed in acetone for 2 hours, butanone for 4 hours No foaming and softening of the coating occurred in 24 hours and xylene for 24 hours; no foaming and softening occurred in the coating after immersion in 10% mass concentration NaOH solution for 10 days or in 10% mass concentration hydrochloric acid solution for 10 days. However, whether the ferrite coils of the powder coatings obtained by spraying Examples 1-6 were tested at a voltage of 5000 volts or after being continuously baked at 155°C for 400 hours, the coatings were all broken down; soaked in acetone for 2 hours, 4 hours in butanone, 24 hours in xylene, or immersed in 10% mass concentration NaOH solution/hydrochloric acid solution for 10 days, the coating will foam and soften.

Claims (10)

1. a powder coating is characterized in that, by weight, comprises the following components:

2 . The powder coating according to claim 1 , wherein the epoxy resin is a bisphenol A type epoxy resin. 3 . 3 . The powder coating according to claim 2 , wherein the epoxy equivalent of the bisphenol A epoxy resin is 400-1000 g/eq. 4 . 4. The powder coating according to claim 1, wherein the modified epoxy resin is a silane-modified epoxy resin. 5. The powder coating of claim 1, wherein the filler comprises mica powder. 6 . The powder coating according to claim 5 , wherein the mass of the mica powder accounts for 50%-100% of the mass of the filler. 7 . 7. The powder coating according to claim 1, wherein the curing agent is a cyanamide compound. 8. the preparation method of the powder coating described in any one of claim 1-7, is characterized in that, comprises the following steps: weighing each component in proportion, mixing, crushing, then melt extrusion, tabletting, pulverizing, That is, the powder coating is obtained. 9. A coating, characterized in that the coating is prepared by spraying and curing the powder coating according to any one of claims 1-7. 10. An electrical device, characterized by comprising the coating of claim 9.