Multi-layer same-furnace composite production process for paint with different thermal levels

Abstract

The invention relates to a multi-layer same-furnace composite production process for paint with different thermal levels. The multi-layer same-furnace composite production process comprises the following steps: a, providing at least two kinds of insulating paint with different temperature-resistant levels; b, multi-pass coating is conducted on the metal wire, and the thickness of a single-side paint film of the first paint with the low temperature resistance grade is controlled to range from 5 micrometers to 7 micrometers; the thickness of a single-side paint film of the second paint with a higher temperature resistance grade is controlled to be 3-4 microns; c, under the condition that the oven temperature and the line speed of the production line are kept constant, idle running treatment is carried out on the paint layer needing to be more sufficiently crosslinked and cured; and repeating the steps b and c until the required enameled wire with the multi-layer composite paint film is obtained. According to the method, on the premise that the oven temperature and the linear speed are constant, the high-temperature-resistant-level paint obtains extra baking time to complete sufficient crosslinking through idle running treatment, and the problems that equipment is complex and energy consumption is high due to traditional multi-oven segmented curing are solved; multi-layer compounding can be achieved through single-furnace operation, and equipment investment and energy consumption are saved; the process is simple and is easy to transform and implement on the existing enameled wire production line.

Description

Technical Field

[0001] The invention relates to the technical field of enameled wire production, in particular to a composite production process for multiple layers of paints with different thermal grades in the same furnace. Background Art

[0002] Enameled wire is a key insulating material for motor windings, and its performance directly affects the motor's reliability and lifespan. Modern high-efficiency motors place higher demands on insulation systems, often requiring a multi-layer composite coating process that combines paints of varying temperature resistance levels to achieve a balance of mechanical strength, heat resistance, and dielectric properties. However, current mainstream production equipment has significant limitations: Inherent limitations of oven temperature distribution: Existing painting equipment mostly utilizes a single-chamber oven, which offers uniform but unadjustable horizontal temperature distribution. While vertical temperature distribution can be adjusted to a limited extent using heating units, it is difficult to create differentiated temperature zones. This structure is only suitable for the production of a single paint or paints with similar thermal ratings, and is not suitable for multi-material composite coatings with a temperature range greater than 30°C. The varying curing temperature windows of different paints can lead to both over-baking and brittleness of low-temperature materials and under-baking and adhesion of high-temperature materials.

[0003] Synchronized production restricts baking control: Enameled wire coating is performed on a continuous assembly line, with consistent line speeds across all passes. Traditionally, each coat of paint must be immediately placed in an oven for curing, forcing each paint layer to undergo a synchronized baking time. For highly heat-resistant materials requiring a deep cure, extending the thermal crosslinking time is impossible; for heat-sensitive materials, shortening the baking time to prevent decomposition is difficult.

[0004] Existing technologies attempt to achieve temperature differentiation through segmented ovens or multiple ovens in series, but these modifications are costly and still fail to resolve the core issue of forcing uniform baking times within the same temperature zone. Therefore, a cost-effective solution for multi-material composite coating, based on existing single-oven equipment and through process innovation, is urgently needed. Summary of the Invention

[0005] The purpose of the present invention is to provide a multi-layer composite production process of paints with different thermal grades in the same furnace to solve the problems raised in the background technology.

[0006] The above object of the present invention is achieved by the following technical solution: a multi-layer composite production process of different thermal grade paints in the same furnace, comprising the following steps: a. Provide at least two insulating paints with different temperature resistance grades; b. Use die coating to coat the metal wires in sequence, The single-side paint film thickness of the first paint with a lower temperature resistance grade is controlled at 5-7μm; The single-side paint film thickness of the second paint with a higher temperature resistance grade is controlled at 3-4μm; c. Under the condition that the oven temperature and production line speed are kept constant, the paint layer that needs more thorough crosslinking and curing is subjected to an idle treatment, that is, no painting is performed within N consecutive passes after the paint layer is applied, so that the applied paint film is only baked in the oven without adding new paint; Repeat steps b and c until the desired enameled wire with a multi-layer composite paint film is obtained.

[0007] Preferably, the mold design for mold painting achieves thickness control of different thermal grade paints in step b by adjusting the mold gap.

[0008] Preferably, the first paint material with a lower thermal level is selected from polyesterimide paint, and the second paint material with a higher thermal level is selected from polyamideimide paint.

[0009] Preferably, the enameled wire comprises at least one layer of low thermal grade paint with a thickness of 5-7 μm and at least one layer of high thermal grade paint with a thickness of 3-4 μm, and the curing degree of the high thermal grade paint layer is higher than that of the low thermal grade paint layer.

[0010] Preferably, after the air passage is completed, the surface of the enameled wire is subjected to plasma treatment.

[0011] Preferably, nitrogen is introduced into the furnace in the empty aisle sub-section to maintain the oxygen content at 2-5% to inhibit oxidation and scaling of the surface of the high-heat-grade paint.

[0012] Preferably, in the empty walkway subsection, the tension of the enameled wire is reduced to 70-80% of that in the painting pass.

[0013] Preferably, the oven is divided into a plurality of independent temperature zones along the traveling direction of the metal wire, and the temperature of each temperature zone can be adjusted independently.

[0014] Preferably, the mold includes a paint mold sleeve, a paint mold core and a porous rectifier block. A channel is provided in the paint mold sleeve, the channel is connected to a paint inlet, a guide ring is embedded in the front end of the channel, and a pressure equalizing cavity is provided at the rear end thereof. The paint mold core and the porous rectifier block are arranged in the pressure equalizing cavity, the porous rectifier block is arranged at the front end of the paint mold core, and a threading hole is provided in the paint mold core.

[0015] Preferably, the front end of the threading hole is provided with a first conical inlet and a second conical inlet in a stepped distribution, the taper of the first conical inlet is greater than the taper of the second conical inlet, and the inner wall of the second conical inlet is provided with a spirally distributed guide groove.

[0016] Beneficial effects of the present invention: Under the premise that the oven temperature and line speed remain constant, the present invention utilizes "idle running treatment" to allow high-temperature-resistant paint to obtain additional baking time to complete sufficient cross-linking, thereby avoiding the problems of complex equipment and high energy consumption caused by traditional multi-furnace segmented curing; multi-layer composite can be achieved by single-furnace operation, saving equipment investment and energy consumption; the process is simple and can be easily modified and implemented on existing enameled wire production lines. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a cross-sectional structural diagram of an enameled wire in an embodiment of the present invention; Figure 2 Schematic diagram of the distribution of molds in an embodiment of the present invention; Figure 3 is a cross-sectional view of a mold in an embodiment of the present invention; In the figure: 1- enameled wire, 1a- metal wire, 1b- first paint, 1c- second paint, 2- bracket, 3- mold, 301- paint mold sleeve, 3011- channel, 3012- paint inlet, 3013- pressure equalizing chamber, 3014- conical outlet, 302- paint mold core, 3021- threading hole, 3022- first conical inlet, 3023- second conical inlet, 3024- guide groove, 303- porous rectifier block, 304- guide ring. DETAILED DESCRIPTION

[0018] The present invention will be further described in detail below with reference to the accompanying drawings.

[0019] This specific embodiment is merely an explanation of the present invention and is not intended to limit the present invention. After reading this specification, those skilled in the art may make non-creative modifications to this embodiment as needed. However, as long as such modifications are within the scope of the claims of the present invention, they are protected by patent law.

[0020] Example: A multi-layer composite production process for different thermal grade paints in the same furnace for producing enameled wires, comprising the following steps: Step a, equipment and material preparation Metal conductor 1a: 1.0 mm diameter copper wire, cleaned, pickled, and boronized to remove surface impurities and oxides; The first paint 1b: low heat resistant polyester imide paint PEI-1801 with temperature grade 180.

[0021] Second paint 1c: high heat grade, temperature resistance grade 220 polyamide-imide paint PAI-2201.

[0022] Drying furnace: vertical catalytic combustion hot air circulation drying furnace, divided into 5 independent temperature zones T1-T5 along the direction of wire travel, and the temperature can be independently adjusted; Auxiliary equipment: plasma surface treatment machine, nitrogen supply system, tension control system; Production line speed: Constantly set at 4.5 m / min.

[0023] Painting equipment: such as Figure 2 As shown, it includes a bracket and a mold 3. A plurality of wire grooves are arranged horizontally on the bracket, and a plurality of groups of molds 3 are distributed at a part of the wire grooves.

[0024] like Figure 3 As shown, the painting mold 3 includes a painting mold sleeve 301, a painting mold core 302 and a porous rectifier block 303. A channel 3011 is provided in the painting mold sleeve 301, and the channel 3011 is connected to the paint inlet 3012. A guide ring 304 is embedded in the front end of the channel 3011, and a pressure equalizing chamber 3013 is provided at the rear end thereof. The painting mold core 302 and the porous rectifier block 303 are arranged in the pressure equalizing chamber 3013, and the porous rectifier block 303 is arranged at the front end of the painting mold core 302. A threading hole 3021 is provided in the painting mold core 302.

[0025] A conical outlet 3014 is provided at the rear end of the channel 3011 and the pressure equalizing chamber 3013, and the caliber of the conical outlet 3014 gradually increases along the direction of travel of the metal wire 1a. The function of the conical outlet 3014 is to achieve a smooth and efficient transition of the paint liquid from the channel 3011 to the pressure equalizing chamber 301. Its gradually expanding caliber design causes the flow rate of the high-speed flowing paint liquid to decrease slowly, and efficiently converts kinetic energy into static pressure energy. This process effectively suppresses the generation of turbulence and eddy currents, and ensures that the paint liquid enters the pressure equalizing chamber 3013 in a uniform and stable laminar state. This lays a key foundation for the subsequent porous rectifier block 303 to play the role of uniformly distributing pressure / flow, and improves the uniformity and precise control capability of the paint film thickness distribution in the circumferential and axial directions of the metal wire.

[0026] The front end of the threading hole 3021 is provided with a first conical inlet 3022 and a second conical inlet 3023 in a stepped distribution. The taper of the first conical inlet 3022 is greater than the taper of the second conical inlet 3023. The inner wall of the second conical inlet 3023 is provided with a spirally distributed guide groove 3024.

[0027] The first conical inlet 3022 quickly establishes the foundation of an annular paint flow through steep convergence, achieving initial guidance and acceleration of the paint liquid; the second conical inlet 3023 stabilizes the flow rate and pressure gradient with a smooth transition, ensuring the uniformity of the axial thickness of the paint film; the spiral guide groove 3024 forces the paint liquid to be evenly distributed circumferentially and form a vortex wrapping, completely eliminating the thickness deviation caused by gravity segregation, and at the same time enhancing the surface wettability of the wire through centrifugal adsorption.

[0028] Step b, applying a first paint layer of PEI-180 and a second paint layer of PAI-2201: The metal wires 1a that are not coated with the first paint 1b are passed through the mold 3 and coated with the first paint layer PEI-180 with a single-side wet film thickness of 5-7 μm, and then enter the drying oven; The metal wire 1a coated with the second paint 1c and having a single-side wet film thickness of 3-4 μm directly passes through the wire duct and enters the drying oven.

[0029] Among them, the thickness control of different thermal grade paints is achieved by adjusting the mold gap.

[0030] Step c, paint layer baking and curing: The PEI-180 coated conductor enters the oven with the following temperature zones set: T1 = 300°C, T2 = 320°C, T3 = 330°C, T4 = 320°C, and T5 = 280°C. The conductor stays in the oven for approximately 8 minutes based on the line speed to allow the PEI-180 layer to undergo initial crosslinking and curing.

[0031] Repeat steps b and c so that the metal wire is coated with three layers of the first paint 1b.

[0032] The wires coated with PAI-220 are then fed into the oven together. No further coating is performed during the next two consecutive passes (N=2). The wires circulate in the oven at a speed of only 4.5 m / min.

[0033] Nitrogen is introduced into the furnace section corresponding to the empty pass, precisely controlling the oxygen content within a range of 3% to 2-5% to prevent high-temperature oxidation and scaling of the PAI-220 surface. During the empty pass, the conductor tension is reduced to 70-80% of the tension used during the paint pass to minimize the effects of stress on the incompletely cured paint layer. During this stage, the total baking time is increased by approximately 16 minutes, with two passes of 8 minutes each. This allows the PAI-220 layer to achieve more complete crosslinking and curing, achieving a significantly higher degree of cure than the underlying PEI-180 layer.

[0034] At the end of the second empty pass and just before the wire leaves the oven, the surface of the enameled wire is treated with atmospheric pressure plasma. The purpose is to increase the surface energy of the paint film, improve subsequent processing properties such as impregnation, and remove any trace volatiles or weak boundary layers that may exist.

[0035] After the second paint 1c is cured, it is re-coated and steps b and c are repeated, so that the metal wire is coated with three layers of the second paint 1c.

[0036] Final enameled wire structure: Copper conductor 1a diameter: 1.0mm; Inner insulation layer 1b: 6μm thick 180 grade polyester imide paint PEI-180; Outer insulation layer 1c: 3.5 μm thick 220 grade polyamide-imide paint PAI-220, and its curing degree is higher than that of the inner layer PEI-180.

Claims

1. A multi-layer composite production process for different thermal grade paints in the same furnace, characterized in that: The following steps are involved: a. Provide at least two insulating paints with different temperature resistance grades; b. coating the metal wires (1a) in sequence by die coating, wherein: The single-side paint film thickness of the first paint (1b) with a lower temperature resistance grade is controlled at 5-7 μm; The single-side paint film thickness of the second paint (1c) with a higher temperature resistance grade is controlled at 3-4 μm; c. Under the condition that the oven temperature and production line speed remain constant, the paint layer that needs more thorough crosslinking and curing is subjected to an idle treatment, that is, no painting is performed within N consecutive passes after the paint layer is applied, so that the applied paint film is only baked in the oven without adding new paint; Repeat steps b and c until the desired enameled wire with a multi-layer composite paint film is obtained.

2. The process for producing multiple layers of paints with different thermal grades in the same furnace according to claim 1, characterized in that: The mold design of the mold painting realizes the thickness control of the different thermal grade paints in step b by adjusting the mold gap.

3. The process for producing multiple layers of paints with different thermal grades in the same furnace according to claim 1, characterized in that: The material of the first paint (1b) with a lower thermal grade is selected from polyesterimide paint, and the material of the second paint (1c) with a higher thermal grade is selected from polyamideimide paint.

4. The process for producing multiple layers of paints with different thermal grades in the same furnace according to claim 3, characterized in that: The enameled wire comprises at least one low-heat-grade paint layer with a thickness of 5-7 μm and at least one high-heat-grade paint layer with a thickness of 3-4 μm, and the curing degree of the high-heat-grade paint layer is higher than that of the low-heat-grade paint layer.

5. The process for producing multiple layers of paints with different thermal grades in the same furnace according to claim 1, characterized in that: After the air walk, the surface of the enameled wire is treated with plasma.

6. The process for producing multiple layers of paints with different thermal grades in the same furnace according to claim 5, characterized in that: In the empty aisle sub-section, nitrogen is introduced into the furnace to maintain the oxygen content at 2-5% to inhibit oxidation and scaling of the surface of high-heat-grade paint.

7. The process for producing multiple layers of paints with different thermal grades in the same furnace according to claim 6, characterized in that: In the empty walkway section, the tension of the enameled wire is reduced to 70-80% of that in the painting pass.

8. The process for producing multiple layers of paints with different thermal grades in the same furnace according to claim 1, characterized in that: The oven is divided into a plurality of independent temperature zones along the traveling direction of the metal wire (1a), and the temperature of each temperature zone can be adjusted independently.

9. The process for producing multiple layers of paints with different thermal grades in the same furnace according to claim 1, characterized in that: The mold (3) comprises a paint mold sleeve (301), a paint mold core (302) and a porous rectifying block (303); a channel (3011) is provided in the paint mold sleeve (301); the channel (3011) is connected to a paint inlet (3012); a guide ring (304) is embedded in the front end of the channel (3011); a pressure equalizing cavity (3013) is provided at the rear end thereof; the paint mold core (302) and the porous rectifying block (303) are arranged in the pressure equalizing cavity (3013); the porous rectifying block (303) is arranged at the front end of the paint mold core (302); and a threading hole (3021) is provided in the paint mold core (302).

10. The process for producing multiple layers of paints with different thermal grades in the same furnace according to claim 9, characterized in that: The front end of the threading hole (3021) is provided with a first conical inlet (3022) and a second conical inlet (3023) distributed in a stepped manner, the taper of the first conical inlet (3022) is greater than the taper of the second conical inlet (3023), and the inner wall of the second conical inlet (3023) is provided with a spirally distributed guide groove (3024).

Images