High heat-resistant low-volatile micro enameled wire for vehicle relay and preparation method thereof

Abstract

The application discloses a kind of high heat-resistant low volatile micro enameled wire for vehicle relay and preparation method thereof, relate to enameled wire production technical field, the enameled wire includes copper conductor and primer layer and topcoat layer successively coated on the surface of copper conductor;Primer layer is 200 grade straight welding polyurethane paint layer, and 80~95% of total paint film thickness;Topcoat layer is 200 grade self-lubricating straight welding polyurethane paint layer, and 5~20% of total paint film thickness, 0.5~1% vaseline is added in topcoat layer, and surface does not need additional coating lubricating oil.The application is designed by "high heat-resistant primer + self-lubricating upper coating" double coating without oil, so that the heat resistance grade of enameled wire reaches 200, the content of aromatic compound is less than 1mg / kg, the content of total volatile organic compounds is less than 10mg / kg, effectively solve the problem of relay contact corrosion failure caused by insufficient heat resistance and gas volatilization of existing enameled wire, especially suitable for harsh vehicle environment such as high temperature and high vibration.

Description

Technical Field

[0001] This invention relates to the field of enameled wire manufacturing technology, specifically to a high heat-resistant, low-volatility micro-enameled wire for automotive relays and its preparation method. Background Technology

[0002] With the rapid development of the new energy vehicle industry, the performance requirements for automotive electronic components are becoming increasingly stringent. As a core control component, automotive relays operate in extremely harsh environments, especially those in the engine compartment, which must withstand high and low temperature cycles of -40℃ to 125℃, vibration and shock, as well as corrosion from oil, salt, water, and dust. Furthermore, the automotive power system (typically a 12V battery) suffers from voltage instability and high coil power consumption (1.6~2W), leading to temperature rise. This places higher demands on the heat resistance and long-term reliability of the enameled wire.

[0003] Currently, the industry commonly uses 155-grade direct-welded polyurethane enameled wire (single-layer coating plus surface lubricant) to manufacture relay coils. This type of enameled wire has the following significant drawbacks: 1) It has a low heat resistance rating, and under long-term high temperature and high load conditions, it is prone to insulation aging and enamel film cracking, leading to coil short circuits or relay failure; 2) The surface-coated lubricant contains a large amount of aliphatic and aromatic volatile organic compounds (VOCs). In the confined space of the relay, these gases easily corrode the metal contacts after evaporation, leading to increased contact resistance, relay malfunction, and seriously affecting service life and driving safety. The small amount of 180-grade enameled wire used still cannot meet the stringent operating conditions of 200℃ and above, and the VOCs problem persists. It should be noted that, to address higher heat resistance requirements, there are reports in the field of technologies that introduce heat-resistant groups such as imide rings and oxazolidinone rings into the main chain to achieve a heat resistance rating of 200-grade polyurethane enameled wire. However, how to apply such coatings to fine enameled wires and simultaneously meet the stringent comprehensive performance requirements of high heat resistance, low volatility, and self-lubrication without relying on surface lubricating oil remains an unsolved technical challenge.

[0004] Therefore, developing an enameled wire that combines high heat resistance, low gas volatilization, and meets the requirements of high-speed automated winding has become a pressing technical challenge in the field of automotive relays. Summary of the Invention

[0005] To address the shortcomings of existing enameled wires used in automotive relays, such as low heat resistance, high volatile gas content, and reliance on surface lubricant leading to relay failure, this invention provides a high-heat-resistant, low-volatile micro-enameled wire for automotive relays and its preparation method. Through a double-coating, oil-free design, the heat resistance is increased to Class 200, the volatile gas content is reduced, and the self-lubricating properties of the wire are maintained, making it suitable for the harsh automotive environment.

[0006] The technical solution of the present invention is: a high heat-resistant and low-volatility automotive relay micro-enameled wire, comprising a copper conductor and a primer layer and a topcoat layer sequentially coated on the outer surface of the copper conductor.

[0007] The primer layer is a Grade 200 direct-soldering polyurethane varnish, accounting for 80-95% of the total varnish film thickness. The core function of the primer layer is to ensure a tight bond between the enameled wire and the copper conductor, improve insulation and winding performance, and reduce pinholes in the varnish film during winding. In this invention, "Grade 200" refers to the enameled wire product that, when tested according to GB / T 6109.20-2008 or IEC 60317-20 standards, can pass a thermal life assessment at 200°C for at least 20,000 hours. The Grade 200 direct-soldering polyurethane varnish can be a conventional direct-soldering polyurethane insulating varnish with a heat resistance rating meeting the aforementioned Grade 200 standard. Its typical composition includes polyurethane prepolymer, curing agent, solvent, etc., and the specific formula can be prepared using known technologies or obtained commercially.

[0008] The topcoat layer is a 200-grade self-lubricating direct-welding polyurethane varnish, accounting for 5-20% of the total film thickness. This topcoat layer contains 0.5-1 wt% petrolatum. The petrolatum is pharmaceutical-grade white petrolatum with a dropping point of 42°C to 60°C, volatility (weight loss <1% after 24 hours of heating at 140°C), and melting point of approximately 45-60°C. Petrolatum possesses excellent high-temperature resistance (weight loss <1% after 24 hours of heating at 140°C) and lubricating properties. When uniformly dispersed in the topcoat layer, it forms a micro-lubricating layer on the film surface, effectively reducing the winding friction coefficient and thus completely replacing traditional surface lubricants, reducing VOCs generation at the source.

[0009] The enameled wire has no additional lubricating oil coating on its surface. Testing revealed that its aromatic compound content is less than 1 mg / kg, its total volatile organic compound content is less than 10 mg / kg, and its heat resistance rating reaches Class 200, allowing it to withstand ambient temperatures from -40℃ to 125℃.

[0010] Furthermore, the copper conductor is a high-purity, low-oxygen copper wire with a diameter of 0.025~0.15 mm to ensure conductivity and processing performance.

[0011] Furthermore, the total varnish thickness is 3~12 μm, which ensures insulation performance without affecting winding flexibility due to excessive varnish thickness.

[0012] This invention also discloses a method for preparing the above-mentioned high heat-resistant, low-volatility micro-enameled wire for automotive relays, comprising the following steps: (1) Laying out: Select a fine copper conductor with a conductor diameter of 0.025~0.15mm, and feed it at a constant speed through the guide wheel to ensure no deviation and no sudden tension change; The wire tension is controlled at 0.03~0.5N, and finely adjusted according to the actual conductor diameter of the copper conductor; the wire speed is continuously adjustable from 150~500m / min, without sudden speed changes; (2) Annealing: The copper conductor is annealed in an annealing furnace at a speed of 150~500m / min to eliminate internal stress and remove oil; The annealing process uses a tubular steam annealing furnace, which introduces steam for protection to prevent high-temperature oxidation of the copper conductor and improve the adhesion between the varnish and the conductor. Annealing process parameters: Annealing temperature 450~500℃, annealing speed and wire feeding speed are completely synchronized; temperature uniformity error in the annealing furnace ≤±10℃, to avoid local overheating that could lead to conductor embrittlement; Post-processing: After the copper conductor is discharged from the annealing furnace, it is pre-cooled to 100~120℃ by ambient dry air before entering the coating process. This is to prevent the high-temperature conductor from directly contacting the paint liquid, which would cause the paint liquid to solidify instantly and affect the coating effect.

[0013] (3) Primer coating and baking: Dip the copper conductor in 200 grade direct soldering polyurethane paint, and bake and cure it in a firing oven at 200~600℃ at a speed of 150~500m / min. Repeat the coating until the thickness of the primer layer accounts for 80~95% of the total paint film. (4) Topcoat coating and baking: Dip the primer layer with 200 grade self-lubricating direct welding polyurethane paint, bake and cure in a firing oven at 200~600℃ at a speed of 150~500m / min, and apply multiple times until the thickness of the topcoat layer accounts for 5~20% of the total paint film; after the primer layer is cured, dry air dust removal treatment is carried out to remove floating dust on the paint film surface, and then the topcoat coating process is carried out to improve the bonding force between the primer and topcoat layers and avoid the layers from falling off.

[0014] (5) Cooling and winding: After the enameled wire is cooled naturally, it is wound up under constant tension to obtain the finished product.

[0015] Furthermore, in step (3), the coating method adopts a capillary dip coater (adapted to a micro-conductor), and the paint tank is kept at a constant temperature (temperature 25±2℃) to prevent the paint viscosity from changing and causing uneven coating thickness. Furthermore, in step (3), the paint liquid control is as follows: the viscosity of the primer layer paint liquid is controlled at 15~40s (Ford-4 cup, 25℃), preferably 18~25s (Ford-4 cup, 25℃), and it is filtered regularly (filter screen precision 100 mesh) to remove impurities in the paint liquid and avoid paint film particles; a filter cartridge (precision 100 mesh) is used for filtration, and the paint liquid is filtered in real time and transmitted to the liquid tank by a motor. The filter cartridge is replaced once a week.

[0016] Furthermore, in step (3), the coating thickness is: the thickness of the paint film on one side of a single dip coating is 0.3~0.5μm, and the thickness of the primer layer accounts for 80~95% of the total paint film through 6~12 dip coatings. The thickness of a single dip coating can be finely adjusted according to the target thickness of the total paint film, and the number of dip coatings can be finely adjusted according to the target thickness of the total paint film.

[0017] Furthermore, in step (3), the baking process adopts a three-stage gradient firing furnace, which is divided into a preheating stage, a curing stage, and a ripening stage, to precisely control the baking process; the baking speed is synchronized with the annealing speed, and the three-stage temperature gradient is 200~300℃ for the preheating stage → 380~450℃ for the curing stage → 300~350℃ for the ripening stage; the hot air circulation speed in the furnace is 0.8~1.2m / s to ensure that the paint film is heated evenly; After each dip coating, the paint should be baked in a firing oven immediately to prevent paint dripping; after the primer layer is finally cured, the paint film surface should be free of pinholes and flow marks, and the adhesion should be ≥ Grade 1 (cross-cut test).

[0018] Furthermore, in step (4), the painting method is the same as that for the primer layer, using a capillary dip coater, which is used separately from the primer layer dip coater to prevent cross-contamination of the paint.

[0019] Furthermore, in step (4), the viscosity of the topcoat layer is controlled to be 15~40s (Ford-4 cup, 25°C), preferably 20~28s (Ford-4 cup, 25°C).

[0020] Furthermore, the petrolatum lubricant is uniformly dispersed using a high-speed stirring process. Specific process conditions are: stirring temperature 23~27℃, preferably 25℃; stirring speed 800~1200 r / min, preferably 1000 r / min; stirring time 20~30 min, preferably 25 min; and standing for 5~10 min after stirring to allow the dispersion system to reach a stable state. The stirred petrolatum should present a uniform and fine slurry state, without particle agglomeration or sedimentation. After adding the topcoat, there should be no floating oil or oil spots, ensuring its uniform and stable dispersion in the paint film.

[0021] Furthermore, in step (4), the coating thickness is: the thickness of the paint film on one side of a single dip coating is 0.1~0.4μm. The thickness of the topcoat layer accounts for 5~20% of the total paint film through 1~5 dip coatings. In combination with the primer layer, the thickness of the total paint film on one side is ≥1.5μm. The thickness of a single dip coating can be finely adjusted according to the target thickness of the total paint film.

[0022] Furthermore, the baking process parameters in step (4) are as follows: the baking adopts a three-stage gradient baking furnace, the three-stage temperature gradient is 200~300℃ for the preheating stage → 350~420℃ for the curing stage → 280~320℃ for the ripening stage, which is lower than the curing temperature of the primer layer, so as to avoid the internal stress generated by the secondary curing of the primer layer; after the topcoat layer is cured, the surface of the paint film is smooth, which meets the requirements of self-lubricating winding.

[0023] Furthermore, in step (5), a micro-tension winding machine is used for winding, with a winding tension of 0.5~0.6N, which is slightly higher than the unwinding tension, to ensure that the enameled wire is tightly wound but not stretched; the winding reel is chamfered (chamfer radius ≥0.5mm) to avoid damage to the edge of the enameled wire due to pressure.

[0024] In this invention, the total coating thickness refers to the total thickness of the coating on both sides of the copper conductor, and the single-side coating thickness refers to the coating thickness on one side only; the thickness of the primer layer and the topcoat layer are both the total thickness (the sum of both sides), and the single-dip coating thickness is the dry film thickness on one side only.

[0025] It is important to emphasize that the key to achieving the aforementioned technical effects of this invention lies not in the specific chemical formulation of the polyurethane varnish used in the primer and topcoat layers, but in the dual-layer structure design of "thick primer layer + thin self-lubricating topcoat layer" proposed for the first time in this invention, the concept of replacing traditional surface lubricants with specific low-volatility petrolatum, and the precisely matched specific preparation process (especially the control of the segmented baking temperature curve). It can be understood that the synergistic combination of the above structure, raw materials, and processes enables the use of any commercially available or self-formulated direct-soldering polyurethane insulating varnish that can pass the aforementioned 200°C thermal life test to achieve the inventive objective of this invention, obtaining micro-enameled wires with the aforementioned high heat resistance, low volatility, and self-lubricating properties.

[0026] The beneficial effects of this invention are: 1. This invention uses 200-grade direct-welding polyurethane as the primer and topcoat material. The enameled wire has a heat resistance rating of 200, which can withstand the harsh temperature environment of -40℃ to 125℃ in the vehicle, effectively resisting the temperature rise caused by the high power consumption of the relay, avoiding aging and cracking of the paint film, and extending the service life of the relay.

[0027] 2. By completely replacing traditional surface lubricating oil with a self-lubricating topcoat layer, the source of VOCs in the lubricating oil is fundamentally eliminated. Combined with a specific paint formula, the aromatic compound content of the finished enameled wire is less than 1 mg / kg, and the total volatile organic compound content is less than 10 mg / kg, resulting in extremely low gas volatilization of the enameled wire and effectively preventing corrosion failure of relay contacts.

[0028] 3. The petroleum jelly added to the topcoat layer of this invention gives the wire good wear resistance and lubrication. The friction is small during the winding process, which can meet the needs of rapid winding. There is no need to apply additional lubricating oil, which simplifies the production process and improves product reliability.

[0029] 4. The primer layer is tightly bonded to the copper conductor, ensuring the adhesion and insulation of the enamel film to the copper conductor. The topcoat layer provides protection and lubrication. The synergistic effect of the double-layer structure significantly improves the long-term reliability of the enameled wire under harsh conditions such as vibration and thermal shock, ensuring that the enameled wire has excellent insulation performance and is suitable for the electrical performance requirements of vehicle relays. Attached Figure Description

[0030] none Detailed Implementation

[0031] The invention is further illustrated below by means of non-limiting embodiments. Experimental methods not specifically described in the embodiments are generally performed under conventional conditions or as recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products. Example 1

[0032] A high heat-resistant, low-volatility automotive relay uses a fine enameled wire with a copper conductor of 0.08 mm diameter and low oxygen copper wire. The total coating thickness is 8 μm (4 μm on each side), of which the primer layer is 7.2 μm thick (accounting for 90% of the total coating thickness) and the topcoat layer is 0.8 μm thick (accounting for 10% of the total coating thickness).

[0033] In this embodiment, both the primer and topcoat layers are commercially available direct-soldering polyurethane enameled wire enamels that meet the 200-level heat resistance requirements (i.e., pass the 200℃, 20000h thermal life test according to GB / T 6109.20-2008 standard). Vaseline is added to the topcoat liquid at a mass ratio of 1%.

[0034] Preparation method: 1. Wire feeding: The low-oxygen copper wire with a diameter of 0.08 mm is fed at a constant speed with a feeding tension of 0.4 N and a feeding speed of 300 m / min.

[0035] 2. Annealing: A tubular steam annealing furnace is used, with an annealing temperature of 500℃, an annealing speed of 300 m / min, and a furnace temperature uniformity error of ±8℃. After annealing, the furnace is pre-cooled with dry air to 110℃.

[0036] 3. Primer Coating and Baking: Capillary dip coating, paint viscosity 22 s (Ford cup 4, 25℃), paint temperature 25℃, single dip coating single-side dry film thickness 0.4 μm, 9 dip coating-baking cycles. The baking oven adopts a three-stage gradient firing oven: preheating section 250℃ → curing section 420℃ → ripening section 320℃, hot air velocity 1.0 m / s.

[0037] 4. Topcoat Coating and Baking: After the primer layer surface is dried and dust-free, the topcoat layer is dip-coated. Vaseline pretreatment: Stir at 25℃ and 1000 r / min for 25 min, then let stand for 5 min. Topcoat viscosity is 25 s (Ford cup 4, 25℃), single dip coating thickness is 0.4 μm on one side, followed by one dip coating and baking. Baking oven temperature gradient: preheating section 250℃ → curing section 380℃ → ripening section 300℃, hot air velocity 1.0 m / s.

[0038] 5. Cooling and winding: After natural cooling, the low-tension winding machine winds up the yarn with a winding tension of 0.55 N and a spool chamfer radius of 0.6 mm.

[0039] Finished product performance testing: Adhesion grade 0 (cross-cut test), dynamic friction coefficient 0.12, heat resistance grade 200, total film thickness 8μm, elongation 28%, softening temperature 292℃; thermal shock resistance (260℃×20%×3D×1h and 220℃×0.5h): no cracking of the film; breaking voltage 2.66 kV, no weld slag after direct welding at 420℃×1.5s; no defects in the continuity of the film and 0 pinholes when tested at 350V×30M.

[0040] Volatile organic compound (VOC) detection: Headspace gas chromatography / mass spectrometry (headspace conditions: heating at 180℃ for 1 h; GC-MS conditions: holding at 40℃ for 1 min, increasing to 280℃ at 10℃ / min and holding for 10 min, split ratio 10:1; calculated using the peak area of ​​10 μL phenol (1000 mg / L) as a reference). Results: Aromatic compound content was 0.721 mg / kg, and total VOC content was 3.174 mg / kg.

[0041] Outsourced testing for semi-quantitative analysis of volatile organic compounds in samples; some test conditions are as follows: 1. Headspace conditions: Heat the sample at 180℃ for 1 hour.

[0042] 2. Gas chromatography / mass spectrometry analysis conditions: Hold at 40°C for 1 minute, then increase to 280°C at a rate of 10°C per minute and hold for 10 minutes; split ratio: 10:1; spectral library: NIST23 library.

[0043] 3. Result Calculation: The peak area response value of 10 μL phenol (concentration of 1000 mg / L) was used as a reference for the calculation results.

[0044] The test results are as follows: aromatic compound content 0.721 mg / kg, total volatile organic compound content 3.174 mg / kg.

[0045] The specific performance comparison between the enameled wire (200-grade polyurethane) prepared in Example 1 of this invention and the conventional wire (180-grade polyurethane) is as follows:

[0046] The conventional use conditions for thermal shock resistance in this invention are 220℃×0.5h, and the accelerated aging conditions are 260℃×20%×3D×1h. The accelerated aging conditions are subject to the stringent testing standards of the enameled wire industry. The product of this invention meets the performance requirements under both conditions, proving its excellent high-temperature shock resistance. Example 2

[0047] A high heat-resistant, low-volatility automotive relay uses a fine enameled wire with a copper conductor of 0.12 mm diameter low-oxygen copper wire and a total enamel film thickness of 10 μm (5 μm on one side). The primer layer is 8 μm thick (accounting for 80% of the total enamel film thickness), and the topcoat layer is 2 μm thick (accounting for 20% of the total enamel film thickness).

[0048] In this embodiment, both the primer and topcoat layers are commercially available direct-soldering polyurethane enameled wire enamels that meet the 200-level heat resistance requirements (i.e., pass the 200℃, 20000h thermal life test according to GB / T 6109.20-2008 standard). Vaseline is added to the topcoat liquid at a mass ratio of 1%.

[0049] Preparation method: 1. Wire feeding: Feed low-oxygen copper wire with a diameter of 0.12mm at a uniform speed, with a feeding tension of 0.35N and a feeding speed of 300m / min; 2. Annealing: A tubular steam annealing furnace is used, with an annealing temperature of 480℃, an annealing speed of 300m / min, and a furnace temperature uniformity error of ±9℃. After annealing, the furnace is pre-cooled with dry air to 105℃. 3. Primer coating and baking: Capillary dip coating, paint viscosity 20s (Ford cup 4, 25℃), paint temperature 25℃, single dip coating single-side dry film thickness 0.4μm, 8~9 dip coating-baking, baking oven temperature gradient: preheating section 230℃ → curing section 400℃ → ripening section 310℃, hot air velocity 0.9m / s; 4. Topcoat Coating and Baking: After dust removal, the primer layer is dip-coated with a viscosity of 23s (Ford Cup 4, 25℃). Vaseline is pre-treated by high-speed stirring at a temperature of 25℃, a speed of 1000r / min, and a stirring time of 25min. After stirring, it is allowed to stand for 5min to ensure that the Vaseline is evenly dispersed in the paint without agglomeration. The paint temperature is 25℃. The dry film thickness on one side of a single dip coating is 0.2μm. After 5 dip coatings and baking, the temperature gradient of the baking oven is 230℃ for the preheating section, 370℃ for the curing section, and 290℃ for the ripening section, with a hot air velocity of 0.9m / s. 5. Cooling and winding: After natural cooling, the low-tension winding machine winds up the yarn with a winding tension of 0.5N and a spool chamfer radius of 0.5mm.

[0050] Finished product inspection: Adhesion grade 0 (cross-cut test), dynamic friction coefficient 0.13, heat resistance grade 200, softening temperature 295℃, direct welding at 420℃ for 1.5s with no weld slag; paint film continuity test at 350V×30M with no defects and 0 pinholes; good lubrication performance.

[0051]

[0052] The detection method was the same as in Example 1, and the detection results are as follows: aromatic compound content was 0.379 mg / kg, and total volatile organic compound content was 1.662 mg / kg. Example 3

[0053] A high heat-resistant, low-volatility automotive relay uses a fine enameled wire with a copper conductor of 0.05 mm diameter low-oxygen copper wire and a total enamel film thickness of 6 μm (3 μm on one side); the primer layer is 5.6 μm thick (accounting for 93% of the total enamel film thickness) and the topcoat layer is 0.4 μm thick (accounting for 7% of the total enamel film thickness).

[0054] In this embodiment, both the primer and topcoat layers are commercially available direct-soldering polyurethane enameled wire enamels that meet the 200-level heat resistance requirements (i.e., pass the 200℃, 20000h thermal life test according to GB / T 6109.20-2008 standard). Vaseline is added to the topcoat liquid at a mass ratio of 0.5%.

[0055] Preparation method: 1. Wire feeding: Feed low-oxygen copper wire with a diameter of 0.05mm at a uniform speed, with a wire feeding tension of 0.3N and a wire feeding speed of 300m / min; 2. Annealing: A tubular steam annealing furnace is used, with an annealing temperature of 450℃, an annealing speed of 300m / min, and a furnace temperature uniformity error of ±7℃. After annealing, the furnace is pre-cooled with dry air to 120℃. 3. Primer coating and baking: Capillary dip coating, paint viscosity 18s (Ford cup 4, 25℃), paint temperature 25℃, single dip coating single-side dry film thickness 0.4μm, after 7 dip coating-baking cycles, baking oven temperature gradient is preheating section 200℃ → curing section 380℃ → ripening section 300℃, hot air velocity 0.8m / s; 4. Topcoat Coating and Baking: After dust removal, the primer layer is dip-coated with a viscosity of 20s (Ford Cup 4, 25℃). Vaseline is pre-treated by high-speed stirring at a temperature of 25℃, a speed of 1000r / min, and a stirring time of 25min. After stirring, the mixture is allowed to stand for 5min to ensure that the Vaseline is evenly dispersed in the paint without agglomeration. The paint temperature is 25℃. The dry film thickness on one side of a single dip coating is 0.4μm. The process involves one dip coating and baking. The oven temperature gradient is: preheating section 200℃ → curing section 350℃ → ripening section 280℃, with a hot air velocity of 0.8m / s. 5. Cooling and winding: After natural cooling, the low-tension winding machine winds up the yarn with a winding tension of 0.6N and a spool chamfer radius of 0.7mm.

[0056] Finished product testing: Adhesion grade 1, dynamic friction coefficient 0.14, heat resistance grade 200, softening temperature 305℃, direct welding at 420℃ for 1.5s yielded no weld slag; paint film continuity was tested at 350V×30M with no defects and 0 pinholes; tested at -40℃, the paint film showed no cracking, suitable for extreme low-temperature automotive conditions. Specific performance indicators are as follows:

[0057] The detection method was the same as in Example 1, and the detection results are as follows: aromatic compound content was 0.068 mg / kg, and total volatile organic compound content was 3.672 mg / kg.

[0058] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any equivalent modifications, substitutions, and improvements made to the above embodiments within the technical concept of the present invention should be included within the protection scope of the present invention.

Claims

1. A type of fine enameled wire for high heat resistance and low volatility automotive relays, characterized in that, The product includes a copper conductor and a primer layer and a topcoat layer sequentially coated on the outer surface of the copper conductor; the primer layer is a 200-grade direct-soldering polyurethane varnish, accounting for 80-95% of the total varnish film thickness; the topcoat layer is a 200-grade self-lubricating direct-soldering polyurethane varnish, accounting for 5-20% of the total varnish film thickness, and the topcoat layer contains 0.5-1 wt% petrolatum; the surface of the enameled wire is not coated with any additional lubricating oil, and the aromatic compound content of the enameled wire is less than 1 mg / kg, and the total volatile organic compound content is less than 10 mg / kg.

2. The micro-fine enameled wire for high heat resistance and low volatility automotive relays according to claim 1, characterized in that, The petrolatum is pharmaceutical grade white petrolatum with a dropping point of 42°C to 60°C, volatility of <1% after 24 hours of heating at 140°C, and melting point of approximately 45-60°C.

3. The micro-fine enameled wire for high heat resistance and low volatility automotive relays according to claim 1, characterized in that, The copper conductor is a low-oxygen copper wire with a diameter of 0.025~0.15 mm.

4. The micro-fine enameled wire for high heat resistance and low volatility automotive relays according to claim 1, characterized in that, The total paint film thickness is 3~12 μm.

5. A method for preparing a high-heat-resistant, low-volatility micro-enameled wire for an automotive relay as described in any one of claims 1 to 4, characterized in that, Includes the following steps: (1) Wire feeding: The fine copper conductor is fed at a constant speed, the wire feeding tension is controlled at 0.03~0.5 N, and the wire feeding speed is 150~500m / min; (2) Annealing: The copper conductor is annealed in an annealing furnace at 400-650℃ at a speed of 150-500 m / min to eliminate internal stress and remove oil; (3) Primer coating and baking: Dip the copper conductor in 200 grade direct soldering polyurethane paint, and bake and cure it in a firing oven at 200~600℃ at a speed of 150~500 m / min. Repeat the coating until the thickness of the primer layer accounts for 80~95% of the total paint film. (4) Topcoat coating and baking: Dip the primer layer with 200 grade self-lubricating direct welding polyurethane paint, the topcoat layer contains 0.5~1wt% lubricant, and bake and cure in a firing oven at 200~600℃ at a speed of 150~500 m / min. Repeat the coating until the thickness of the topcoat layer accounts for 5~20% of the total paint film; (5) Cooling and winding: After the enameled wire is cooled naturally, it is wound up under constant tension to obtain the finished product.

6. The preparation method according to claim 5, characterized in that, In step (2), the annealing temperature is 450~500℃ and the annealing speed is 200~350 m / min; the temperature uniformity error in the annealing furnace is ≤±10℃.

7. The preparation method according to claim 5, characterized in that, In steps (3) and (4), the coating method uses a capillary dip coater, the viscosity of the primer layer is controlled at 15~40 s, and the viscosity of the topcoat layer is controlled at 15~40 s. The viscosity is the value measured by a Forte-4 cup at 25°C.

8. The preparation method according to claim 7, characterized in that, In step (3), the dry film thickness of the paint film on one side of a single dip coating is 0.3~0.5 μm, and the thickness of the primer layer accounts for 80~95% of the total paint film through 6~12 dip coatings; in step (4), the dry film thickness of the paint film on one side of a single dip coating is 0.1~0.4 μm, and the thickness of the topcoat layer accounts for 5~20% of the total paint film through 1~5 dip coatings.

9. The preparation method according to claim 7, characterized in that, In step (4), the lubricant is petrolatum, which is uniformly dispersed by high-speed stirring. The specific process conditions are: stirring temperature 23~27℃; stirring speed 800~1200 r / min; stirring time 20~30 min.

10. The preparation method according to claim 7, characterized in that, In step (4), the topcoat layer is baked using a three-stage gradient firing furnace, with a preheating stage of 200~300℃, a curing stage of 350~420℃, and a maturation stage of 280~320℃. The curing temperature is lower than the curing temperature of the primer layer in step (3).

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