An insulating epoxy powder coating and a method for producing the same

Abstract

The application relates to the technical field of insulating coating preparation.The insulating epoxy powder coating is prepared from an epoxy resin, a phenolic epoxy resin, a modified curing agent, a curing accelerator, a leveling agent, a degassing agent, polyvinylidene, a filler, a pigment, a flow aid, an anti-caking agent and a nano carbon tube; wherein the modified curing agent is prepared from dicyandiamide, dodecyl glycidyl ether, triethylamine, diaminodiphenyl sulfone and concentrated hydrochloric acid.The epoxy resin is matched with the phenolic epoxy resin, the overall functionality is improved, the crosslinking density after film formation of the curing agent is high, the chemical resistance and the insulating voltage resistance are excellent, the epoxy curing agent is prepared through a chemical modification method, active groups are introduced to replace the amino groups of dicyandiamide, the reaction activity is moderate, the solubility with the epoxy resin is good, the reaction temperature can be obviously reduced, and the surface smoothness of the coating film is improved.

Description

Technical Field

[0001] This invention relates to the field of coating preparation technology, and more specifically to a powder coating applied to the field of insulating coating for electronic components. Background Technology

[0002] Traditional solvent-based insulating varnishes release large amounts of volatile organic solvents into the environment during baking, imposing strict requirements on the application environment and posing significant safety hazards during production. Powder coatings, on the other hand, contain no chemical solvents, causing less environmental pollution and are considered one of the most environmentally friendly coating products. Therefore, in the field of insulating coating for electronic components, powder coatings will increasingly replace liquid coatings, becoming an industry trend.

[0003] When coating magnetic rings, the low melt viscosity and slow curing rate of currently available insulating powder coatings cause severe shrinkage during curing. The coating flows away from sharp angles, exposing sharp metal edges and creating defects. Furthermore, many insulating powder manufacturers use dicyandiamide as a curing agent, with curing temperatures typically between 180 and 220°C. At low temperatures, the coating often fails to fully cure, making it unsuitable for workpieces with poor heat resistance and resulting in high energy consumption. Existing invention patent CN 107513334A provides a low-temperature, rapid-curing insulating epoxy powder coating process that uses a mixture of epoxy resin and carboxylated polyester resin to lower the curing temperature and achieves better insulation strength. However, due to the structural influence of the polyester resin, the chemical resistance of the coating film decreases.

[0004] Therefore, the insulating epoxy powder coatings for magnetic rings currently still have problems such as poor edge and corner coverage and incomplete curing under medium and low temperature conditions. Summary of the Invention

[0005] The purpose of this invention is to address the problems of high baking temperature and poor edge coverage in existing insulating powder technologies by providing a green and environmentally friendly insulating epoxy powder coating that can achieve complete curing at medium and low temperatures (140℃~160℃) and has excellent edge coverage.

[0006] An insulating epoxy powder coating is prepared from the following components in parts by weight:

[0007]

[0008] The sum of the weight parts of the above components is 100 parts;

[0009] The modified curing agent is prepared from the following components in parts by weight:

[0010] 35-50 parts of prepolymerized liquefied dicyandiamide

[0011] 45-55 parts of diaminodiphenyl sulfone

[0012] 10-20 parts concentrated hydrochloric acid

[0013] The prepolymerized liquefied dicyandiamide is prepared from the following components in parts by weight:

[0014] 30-40 parts of dicyandiamide

[0015] 50-60 parts of dodecyl glycidyl ether

[0016] Triethylamine 0.1-0.5 parts

[0017] Preferably, the epoxy resin is one or more of the two-step process E-12, E-14, and E-20;

[0018] Preferably, the phenolic epoxy resin is o-cresol formaldehyde epoxy resin;

[0019] Preferably, the curing accelerator is one or both of 2-methylimidazole and triphenylphosphine;

[0020] Preferably, the leveling agent is a silicone-free acrylate.

[0021] Preferably, the degassing agent is one or both of benzoin and polyamide wax;

[0022] Preferably, the flow aid is one or both of fumed silica and nano-sized alumina;

[0023] Preferably, the anti-caking agent is one or both of polyethylene wax and polyamide wax;

[0024] Preferably, the filler is one or more of feldspar powder, silica powder, and mica powder;

[0025] Preferably, the pigment is one or more of carbon black, titanium dioxide, iron oxide red, iron oxide yellow, permanent violet, and phthalocyanine blue;

[0026] Preferably, the carbon nanotubes are silica-coated carbon nanotubes with a diameter of 2 to 20 nm.

[0027] Another object of the present invention is to provide a method for preparing the above-mentioned insulating epoxy powder coating, specifically including the following steps:

[0028] Step 1: Modified curing agent

[0029] In a reactor equipped with a stirring device, a reflux condenser, a dropping device, a temperature control device, and a vacuum device, (30-40) parts of dicyandiamide and (50-60) parts of dodecyl glycidyl ether are ultrasonically dispersed. The reflux condenser is turned on, argon gas is introduced, and the temperature is raised to 130℃±5℃. (0.1-0.5) parts of triethylamine are added as a catalyst, and the mixture is kept at this temperature and refluxed for 6 hours until no liquid is extracted, thus obtaining prepolymerized liquefied dicyandiamide. (35-50) parts of prepolymerized liquefied dicyandiamide and (45-55) parts of diaminodiphenyl sulfone are dissolved in (10-20) parts of concentrated hydrochloric acid. The reflux condenser is turned on, argon gas is introduced, and the temperature is raised to 120℃±5℃ and kept at this temperature for 4 hours. After the reaction, the mixture is filtered and washed with water 3-4 times. After purification, it is vacuum dried to obtain a modified curing agent for dicyandiamide.

[0030] Step 2: Preparation of insulating epoxy powder coating

[0031] Add (30-50) parts epoxy resin, (5-15) parts phenolic epoxy resin, (1.5-4.5) parts modified curing agent, (0.3-1) parts curing accelerator, (35-50) parts filler, (2-15) parts pigment, (0.2-0.6) parts degassing agent, (0.3-1) parts leveling agent, (2-6) parts polyvinyl butyral, and (0.02-0.1) parts carbon nanotubes to a mixing pot and stir at a speed of (400-600) rpm for (5- After 10 minutes, the uniformly mixed material is fed into a twin-screw extruder. The temperature of zone 1 is set to 90°C, the temperature of zone 2 is set to 100°C, and the screw frequency is set to 45 Hz. The material is melt-extruded into flakes. The extruded flakes are crushed, and 0.2 to 0.7 parts of flow aid and 0.3 to 0.8 parts of anti-caking agent are added in sequence. The material is fed into a grinding mill. The main mill is set to 50 Hz, the auxiliary mill is set to 40 Hz, and the material is sieved through a 180-mesh screen.

[0032] This invention uses o-cresol formaldehyde epoxy resin combined with two-step bisphenol A type epoxy resin as the main film-forming material. From the molecular structure of o-cresol formaldehyde epoxy resin, each benzene ring is connected to an epoxy group, which can provide more than 2.5 times the number of crosslinking sites during curing, making it easy to form a three-dimensional structure with ultra-high crosslinking density. In addition, the film-forming material is rich in phenolic skeleton, which can provide excellent thermal stability, water resistance, insulation performance and chemical resistance. The coating can still maintain good performance in harsh environments with high temperature and humidity.

[0033] This invention utilizes modified dicyandiamide. Because the cyano group in dicyandiamide has strong electron-withdrawing properties, it greatly restricts the activity of the amino group, leading to weakened curing reactivity and easy recrystallization at high temperatures, reducing coating performance and affecting the coating appearance. Therefore, a chemical modification method is used to first modify dicyandiamide molecules with dodecyl glycerol ether to generate a prepolymerized dicyandiamide containing a dodecyl chain and hydroxyl groups. This prepolymer then reacts with diaminodiphenyl sulfone to generate a crosslinked product containing sulfone groups and benzene ring structures. By introducing active groups, the structure of dicyandiamide itself and the strong electron-withdrawing properties of the cyano group are altered, releasing the amino group's activity, thereby lowering the onset temperature of the curing reaction. Furthermore, the introduction of similar groups such as ether bonds and benzene rings improves the solubility of dicyandiamide in epoxy resins.

[0034] This invention utilizes polyvinyl butyral to increase the melt viscosity of the coating, reduce thinning at the edges caused by surface tension differences, and improve the coating's edge coverage. Silica-coated carbon nanotubes are used as a reinforcing phase to improve the mechanical and thermal properties of the coating film, increasing mechanical strength and modulus; the modulus of a single multi-walled carbon nanotube can reach 950 GPa. The hydroxyl groups, carbonyl groups, and coordination unsaturated sites on the surface of the carbon nanotubes interact with the epoxy resin through hydrogen bonds or van der Waals forces, forming additional physical crosslinking points. This allows for greater deformation under external stress, improving the coating's toughness.

[0035] The beneficial effects of this invention are:

[0036] 1. This invention uses epoxy resin combined with phenolic epoxy resin, which improves the overall functionality and the crosslinking density after curing film formation, resulting in excellent chemical resistance and insulation and voltage resistance.

[0037] 2. The epoxy curing agent prepared by the present invention introduces active groups to replace the amino groups of dicyandiamide through chemical modification. It has moderate reactivity, good solubility with epoxy resin, can significantly reduce reaction temperature, and improve the surface smoothness of the coating film.

[0038] 3. The epoxy insulating powder coating prepared by this invention uses halogen-free and heavy metal-free pigments and fillers, is non-toxic, odorless, and pollution-free, and has extremely low halogen content, fully meeting the RoHS directive and environmental protection requirements. Detailed Implementation

[0039] Example 1: Preparation of modified curing agent

[0040] In a reactor equipped with a stirring device, a reflux condenser, a dropping device, a temperature control device, and a vacuum device, 35 parts of dicyandiamide and 55 parts of dodecyl glycidyl ether were ultrasonically dispersed. The reflux condenser was turned on, argon gas was introduced, and the temperature was raised to 130℃±5℃. 0.3 parts of triethylamine were added as a catalyst, and the mixture was kept at this temperature and refluxed for 6 hours until no liquid was extracted, thus obtaining prepolymerized liquefied dicyandiamide. 35 parts of prepolymerized liquefied dicyandiamide and 55 parts of diaminodiphenyl sulfone were dissolved in 10 parts of concentrated hydrochloric acid. The reflux condenser was turned on, argon gas was introduced, and the temperature was raised to 120℃±5℃ and kept at this temperature for 4 hours. After the reaction, the mixture was filtered and washed with water 3-4 times. After purification, it was vacuum dried to obtain a dicyandiamide-type modified curing agent.

[0041] Example 2: Preparation of modified curing agent

[0042] In a reactor equipped with a stirring device, a reflux condenser, a dropping device, a temperature control device, and a vacuum device, 40 parts of dicyandiamide and 50 parts of dodecyl glycidyl ether were ultrasonically dispersed. The reflux condenser was turned on, argon gas was introduced, and the temperature was raised to 130℃±5℃. 0.4 parts of triethylamine were added as a catalyst, and the mixture was kept at this temperature and refluxed for 6 hours until no liquid was extracted, thus obtaining prepolymerized liquefied dicyandiamide. 35 parts of prepolymerized liquefied dicyandiamide and 50 parts of diaminodiphenyl sulfone were dissolved in 15 parts of concentrated hydrochloric acid. The reflux condenser was turned on, argon gas was introduced, and the temperature was raised to 120℃±5℃ and kept at this temperature for 4 hours. After the reaction, the mixture was filtered and washed with water 3-4 times. After purification, it was vacuum dried to obtain a dicyandiamide-type modified curing agent.

[0043] Example 3: Preparation of Insulating Epoxy Powder Coating

[0044] 40 parts of E-12 epoxy resin, 10 parts of phenolic epoxy resin, 2.2 parts of the modified curing agent prepared in Example 1, 0.3 parts of curing accelerator, 40 parts of filler, 4 parts of pigment, 0.3 parts of degassing agent, 0.37 parts of leveling agent, 2 parts of polyvinyl butyral, and 0.03 parts of carbon nanotubes were added to a mixing pot and stirred at a speed of (400-600) rpm for (5-10) minutes. Then, the uniformly mixed material was fed into a twin-screw extruder. The temperature of zone 1 was set to (90) ℃, the temperature of zone 2 was set to (100) ℃, and the screw frequency was set to (45) Hz. The material was melt-extruded into sheet material. The extruded sheet material was crushed, and 0.3 parts of flow aid and 0.5 parts of anti-caking agent were added in sequence. The material was fed into a grinding mill. The power of the main mill was set to (50) Hz, the power of the auxiliary mill was set to (40) Hz, and the feed power was set to (15) Hz. The material was sieved through a 180-mesh sieve.

[0045] Example 4: Preparation of Insulating Epoxy Powder Coating

[0046] 42.5 parts of E-14 epoxy resin, 7.5 parts of phenolic epoxy resin, 2.8 parts of the modified curing agent prepared in Example 1, 0.3 parts of curing accelerator, 42 parts of filler, 2 parts of pigment, 0.3 parts of degassing agent, 0.37 parts of leveling agent, 3 parts of polyvinyl butyral, and 0.03 parts of carbon nanotubes were added to a mixing pot and stirred at a speed of (400-600) rpm for (5-10) minutes. Then, the uniformly mixed material was fed into a twin-screw extruder. The temperature of zone 1 was set to (90) ℃, the temperature of zone 2 was set to (100) ℃, and the screw frequency was set to (45) Hz. The material was melt-extruded into sheet material. The extruded sheet material was crushed, and 0.3 parts of flow aid and 0.5 parts of anti-caking agent were added in sequence. The material was fed into a grinding mill. The power of the main mill was set to (50) Hz, the power of the auxiliary mill was set to (40) Hz, and the feed power was set to (15) Hz. The material was sieved through a 180-mesh sieve.

[0047] Example 5: Preparation of Insulating Epoxy Powder Coating

[0048] 45 parts of E-20 epoxy resin, 5 parts of phenolic epoxy resin, 3.2 parts of the modified curing agent prepared in Example 2, 0.3 parts of curing accelerator, 38 parts of filler, 6 parts of pigment, 0.37 parts of degassing agent, 0.37 parts of leveling agent, 3 parts of polyvinyl butyral, and 0.03 parts of carbon nanotubes were stirred at a speed of (400-600) rpm for (5-10) minutes. The uniformly mixed material was then fed into a twin-screw extruder. The temperature of zone 1 was set to (90) ℃, the temperature of zone 2 was set to (100) ℃, and the screw frequency was set to (45) Hz. The material was melt-extruded into sheet material. The extruded sheet material was crushed, and 0.3 parts of flow aid and 0.5 parts of anti-caking agent were added in sequence. The material was then fed into a grinding mill. The power of the main mill was set to (50) Hz, the power of the auxiliary mill was set to (40) Hz, and the feed power was set to (15) Hz. The material was sieved through a 180-mesh sieve.

[0049] Example for comparison:

[0050] Add 50 parts of E-12 epoxy resin, 2 parts of curing agent, 0.3 parts of curing accelerator, 40 parts of filler, 6 parts of pigment, 0.3 parts of degassing agent, and 0.4 parts of leveling agent to a mixing pot and stir at a speed of (400-600) rpm for (5-10) minutes. Then, feed the uniformly mixed material into a twin-screw extruder. Set the temperature of zone 1 to (90) ℃, the temperature of zone 2 to (100) ℃, and the screw frequency to (45) Hz. Melt and extrude the material into sheet form. Crush the extruded sheet and add 0.3 parts of flow aid and 0.5 parts of anti-caking agent in sequence. Feed the material into a grinding mill. Set the power of the main mill to (50) Hz, the power of the auxiliary mill to (40) Hz, and the feed power to (15) Hz. Sieve the material through a 180-mesh sieve.

[0051]

[0052]

[0053] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. An insulating epoxy powder coating, characterized in that: It was prepared from the following components in parts by weight: 30-50 parts of epoxy resin 5-15 parts of phenolic epoxy resin Modified curing agent 1.5 to 4.5 parts Curing accelerator 0.3 to 1 part Leveling agent 0.3 to 1 part Degassing agent 0.2-0.6 parts 2-6 parts of polyvinyl butyral 35-50 parts of filler 2-15 parts of pigment 0.2–0.7 parts of flow aid. Anti-caking agent 0.3-0.8 parts 0.02–0.1 parts of carbon nanotubes The sum of the weight parts of the above components is 100 parts; The modified curing agent is prepared from the following components in parts by weight: 35-50 parts of prepolymerized liquefied dicyandiamide 45-55 parts of diaminodiphenyl sulfone 10-20 parts concentrated hydrochloric acid The prepolymerized liquefied dicyandiamide is prepared from the following components in parts by weight: 30-40 parts of dicyandiamide 50-60 parts of dodecyl glycidyl ether Triethylamine 0.1-0.5 parts The epoxy resin is one or more of the two-step method E-12, two-step method E-14, and two-step method E-20; The phenolic epoxy resin mentioned is o-cresol formaldehyde epoxy resin.

2. A method for preparing the insulating epoxy powder coating according to claim 1, characterized in that: Includes the following steps: Step 1: Modified curing agent In a reactor equipped with a stirring device, a reflux condenser, a dropping device, a temperature control device, and a vacuum device, 30-40 parts of dicyandiamide and 50-60 parts of dodecyl glycidyl ether are ultrasonically dispersed. The reflux condenser is turned on, argon gas is introduced, and the temperature is raised to 130℃±5℃. 0.1-0.5 parts of triethylamine are added as a catalyst, and the mixture is kept at this temperature and refluxed for 6 hours until no liquid is extracted, thus obtaining prepolymerized liquefied dicyandiamide. 35-50 parts of prepolymerized liquefied dicyandiamide and 45-55 parts of diaminodiphenyl sulfone are dissolved in 10-20 parts of concentrated hydrochloric acid. The reflux condenser is turned on, argon gas is introduced, and the temperature is raised to 120℃±5℃ and kept at this temperature for 4 hours. After the reaction, the mixture is filtered and washed with water 3-4 times. After purification, it is vacuum dried to obtain a modified curing agent for dicyandiamide. Step 2: Preparation of insulating epoxy powder coating Add 30-50 parts epoxy resin, 5-15 parts phenolic epoxy resin, 1.5-4.5 parts modified curing agent, 0.3-1 part curing accelerator, 35-50 parts filler, 2-15 parts pigment, 0.2-0.6 parts degassing agent, 0.3-1 part leveling agent, 2-6 parts polyvinyl butyral, and 0.02-0.1 parts carbon nanotubes to a mixing pot and stir at 400-600 rpm for 5-10 minutes. Then, feed the uniformly mixed material into a twin-screw extruder, set the temperature of zone 1 to 90℃, the temperature of zone 2 to 100℃, and the screw frequency to 45Hz, and melt-extrude into sheet material. Crush the extruded sheet material, add 0.2-0.7 parts flow aid and 0.3-0.8 parts anti-caking agent in sequence, and feed it into a grinding mill, set the main mill to 50Hz and the auxiliary mill to 40Hz, and sieve it through a 180-mesh screen.

3. The insulating epoxy powder coating according to claim 1, characterized in that: The curing accelerator is one or both of 2-methylimidazole and triphenylphosphine.

4. The insulating epoxy powder coating according to claim 1, characterized in that: The leveling agent is a silicone-free acrylate.

5. The insulating epoxy powder coating according to claim 1, characterized in that: The degassing agent is one or both of benzoin and polyamide wax.

6. The insulating epoxy powder coating according to claim 1, characterized in that: The flow aid is one or both of fumed silica and nano-sized alumina.

7. The insulating epoxy powder coating according to claim 1, characterized in that: The anti-caking agent is one or both of polyethylene wax and polyamide wax.

8. The insulating epoxy powder coating according to claim 1, characterized in that: The carbon nanotubes are carbon nanotubes with a diameter of 2 to 20 nm coated with silica.

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