Highly aging-resistant enameled wire varnish, enameled stranded wire, and preparation method thereof

Abstract

The present application relates to the technical field of enameled wires, and specifically to a highly aging-resistant enameled wire varnish, an enameled stranded wire, and a method for preparing the same. The method for preparing the highly aging-resistant enameled wire varnish of the present application is as follows: first, an isocyanate-terminated polyurethane prepolymer is prepared, then epoxy-modified nano-titanium dioxide is prepared, and finally the polyurethane prepolymer, modified nano-titanium dioxide, aminopolysiloxane, and polyamine are cross-linked. The enameled wire varnish obtained by the above method tends to be enriched in polysiloxane on the surface during curing, so it has good hydrophobic properties, and the bonding strength between polysiloxane and polyurethane is high, so it has excellent heat resistance, aging resistance, and mechanical properties. The above-mentioned wire varnish is applied to the surface of a metal wire core to prepare an enameled stranded wire, which also has good heat resistance, aging resistance, and mechanical properties.

Description

Technical Field

[0001] The present application relates to the technical field of enameled wires, and in particular to a highly aging-resistant enameled wire varnish, an enameled stranded wire, and a preparation method thereof. Background Art

[0002] Enameled wire is a conductive material made by coating the core of a copper or aluminum wire with a layer of enameled varnish through a baking process. It is a core component of motors, electrical appliances, and electronic equipment, and its performance directly determines the reliability and safety of these devices. As industrial technology evolves toward higher power and smaller components, motors, transformers, and other equipment are placing higher demands on the heat and aging resistance of enameled wire. However, enameled wire, exposed to long-term high temperatures, electric fields, and harsh environmental conditions, commonly experiences aging issues such as decreased insulation performance and weakened mechanical strength. This leads to increased equipment failure rates and increased maintenance costs.

[0003] Wire enamel, as part of the enameled wire, has a significant impact on its aging resistance. Currently, the most commonly used wire enamels include polyester, polyurethane, polyamide, and polyimide. Polyimide enamels offer excellent aging resistance and high heat resistance, but they are expensive and require complex production processes. Polyester, polyurethane, and polyamide enamels, on the other hand, all suffer from poor aging resistance.

[0004] The above-mentioned polyurethane enameled wire enamel has strong adhesion, high frequency resistance, good corrosion resistance, and direct solderability. In order to improve its aging resistance, a composite coating method is often used. For example, the patent application document with application publication number CN106519649A discloses an aging-resistant insulating enameled wire, including a metal wire core and an insulating layer wrapped around the outer layer of the metal wire core. The insulating layer is composed of a polyurethane insulating layer attached to the surface of the metal wire core and an insulating varnish layer brushed on the outer surface of the polyurethane insulating layer. The polyurethane insulating layer is made of polyether polyol, toluene diisocyanate, epoxy resin, propylene glycol and modified filler, and the insulating varnish layer is made of epoxy-modified silicone resin, acrylic resin, pigment, modified filler and dispersant. By sequentially coating the polyurethane insulating layer and the insulating varnish layer on the surface of the metal wire core, the aging resistance, wear resistance and corrosion resistance of the enameled wire are improved. However, the use of this composite coating method not only has a complex coating process and high cost, but also may have poor bonding strength between the two layers, which also affects the aging resistance of the enameled wire. Summary of the Invention

[0005] In order to improve the aging resistance of polyurethane wire enamel, the present application provides a high aging resistance wire enamel, enameled stranded wire and a preparation method thereof.

[0006] An enameled stranded wire is made by twisting enameled wires, the enameled wire comprising a metal wire core and a paint film covering the metal wire core, the paint film being formed by curing a high-aging-resistant enameled wire varnish. The preparation method of the high-aging-resistant enameled wire varnish comprises the following steps:

[0007] S1: reacting diol and diisocyanate under nitrogen protection to obtain a polyurethane prepolymer;

[0008] S2: dispersing nano-titanium dioxide in DMF, adding epoxysilane to react, and obtaining modified nano-titanium dioxide;

[0009] S3: Mix the polyurethane prepolymer and modified nano titanium dioxide, add aminopolysiloxane, react at room temperature, then heat to 55-70°C, add polyamine, and continue the reaction to obtain the product.

[0010] In the above technical solution, the polyurethane prepolymer contains a large number of isocyanate groups, and the surface of the modified nano-titanium dioxide contains epoxy groups. The polyurethane prepolymer and the modified nano-titanium dioxide are reacted with aminopolysiloxane, and the isocyanate groups in the polyurethane prepolymer react with the amino groups of the aminopolysiloxane to introduce the polysiloxane into the polyurethane. Due to the different surface tensions of polysiloxane and polyurethane, the surface tension of the polysiloxane chain segment is smaller and tends to be enriched on the surface, while the surface tension of the polyurethane is larger and tends to form a stronger force with the surface of the substrate. Therefore, the surface of the formed paint film exhibits excellent hydrophobicity, heat resistance, weather resistance and insulation due to the enrichment of more polysiloxane chain segments, and the bottom of the formed paint film exhibits good adhesion due to the enrichment of more polyurethane chain segments.

[0011] Moreover, the amino group of aminopolysiloxane not only reacts with isocyanate groups, but also reacts with epoxy groups in titanium dioxide, thereby introducing polysiloxane chain segments into the surface of nano-titanium dioxide; after adding polyamine, the amino group of polyamine further reacts with isocyanate groups and epoxy groups on the surface of nano-titanium dioxide to form a mutually penetrating and cross-linked network structure, which not only improves the aging resistance and heat resistance of the paint film, but also increases the interaction force between polysiloxane and polyurethane, reduces the risk of phase separation between polyurethane segments and polysiloxane segments due to poor compatibility, enhances the strength of the paint film, and further improves the aging resistance, heat resistance and mechanical properties of the paint film.

[0012] In addition, the wire enamel obtained by the above method, after coating and curing, forms a paint film that reduces at least one coating process compared with the composite coating, and the coating process is simpler and reduces the cost; and the introduced nano titanium dioxide is also beneficial to improving the aging resistance, heat resistance and mechanical properties of the paint film.

[0013] Preferably, the enameled stranded wire is a spirally twisted body formed by twisting multiple enameled single wires with a certain structure and a specific lay length according to certain rules, such as concentric twisting, bundle twisting, etc., once or multiple times. Generally, the diameter of the metal wire core and the thickness of the enameled wire paint film are different according to different insulation levels and usage requirements.

[0014] Further preferably, the twisting requirements are: a maximum twisting number of 4 times, a maximum number of strands of 7200 strands, a maximum finished outer diameter of 8 mm, and a minimum lay length of 2.2 mm.

[0015] Preferably, in step S1, the molar ratio of diol to diisocyanate is 1:(1.4-2).

[0016] The polyurethane prepolymer prepared by adopting the above technical solution contains a large number of isocyanate groups, which is conducive to the subsequent reaction with the amino groups in aminopolysiloxane and polyamine, introducing polysiloxane segments with better weather resistance, heat resistance and hydrophobicity, and forming a cross-linked network, effectively reducing the phase separation of polysiloxane segments and polyurethane segments.

[0017] In some specific embodiments, in step S1, the molar ratio of diol to diisocyanate can be 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, or 1:2. Generally, in step S1, when the molar ratio of diol to diisocyanate is 1:1.7, better experimental results can be obtained.

[0018] Preferably, in step S2, the mass ratio of nano-titanium dioxide to epoxysilane is 1:(0.3-0.6).

[0019] In some specific embodiments, in step S2, the mass ratio of nano-titanium dioxide to epoxysilane can be 1:0.3, 1:0.35, 1:0.4, 1:0.45, 1:0.5, 1:0.55, or 1:0.6. Generally, in step S2, when the mass ratio of nano-titanium dioxide to epoxysilane is 1:0.5, better experimental results can be obtained.

[0020] Preferably, in step S3, the aminopolysiloxane is prepared by reacting an organosiloxane monomer with an aminosilane coupling agent, and the mass ratio of the organosiloxane monomer to the aminosilane coupling agent is 1:(0.2-0.5).

[0021] In the above technical solution, the more aminosilane coupling agent is added, the higher the amino content in the aminopolysiloxane is, and the more polysiloxane segments are introduced into the polyurethane.

[0022] In some specific embodiments, in step S3, the mass ratio of the organosiloxane monomer to the aminosilane coupling agent can be 1:0.2, 1:0.25, 1:0.3, 1:0.35, 1:0.4, 1:0.45, or 1:0.5. Generally, in step S3, when the mass ratio of the organosiloxane monomer to the aminosilane coupling agent is 1:0.35, better experimental results can be obtained.

[0023] Preferably, the organosiloxane monomer is one or more of diphenyldimethoxysilane, phenyltrimethoxysilane, and phenyltriethoxysilane;

[0024] And / or, the aminosilane coupling agent is one or more of γ-aminopropyltriethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane and N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane.

[0025] Preferably, in step S3, the polyamine is one or more of ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine and p-phenylenediamine.

[0026] By adopting the above technical solution, the addition of polyamine can form a cross-linked network structure, improve the bonding strength between polyurethane and polysiloxane, reduce the phase separation between the two, and thus improve heat resistance, aging resistance, mechanical properties, etc.

[0027] Further preferably, in step S3, a curing agent is added after adding the polyamine, and the curing agent is tetrabutyl titanate or dibutyltin oxalate; and the mass ratio of the aminopolysiloxane to the curing agent is 100:(1-5).

[0028] In the above technical solution, the addition of a curing agent is beneficial to increasing the curing rate of polysiloxane and reducing the curing temperature of polysiloxane, thereby reducing paint film defects caused by different curing processes of polyurethane and polysiloxane, such as incomplete curing of polysiloxane under polyurethane curing conditions or stress concentration inside polyurethane under polysiloxane curing conditions.

[0029] In some specific embodiments, in step S3, the mass ratio of the aminopolysiloxane to the curing agent can be 100:1, 100:2, 100:2.5, 100:3, 100:3.5, 100:4, 100:4.5, or 100:5. Generally, in step S3, when the mass ratio of the aminopolysiloxane to the curing agent is 100:3, better experimental results can be obtained.

[0030] Further preferably, in step S3, the mass ratio of the sum of the mass of the polyurethane prepolymer and the modified nano-titanium dioxide to the mass of the aminopolysiloxane is 100:(10-30);

[0031] And / or, in step S3, the mass ratio of the sum of the mass of the polyurethane prepolymer and the modified nano-titanium dioxide to the mass of the polyamine is 100:(1-5).

[0032] When the above technical solution is adopted, when the amount of aminopolysiloxane added is small, the polysiloxane chain segments introduced into the polyurethane are small, and then the polysiloxane chain segments enriched on the surface are small, which is not conducive to improving the hydrophobicity, heat resistance, aging resistance, etc. of the paint film; if the amount of aminopolysiloxane added is too much, the flexibility of the paint film increases, but the hardness is insufficient, which will also affect the mechanical properties and aging resistance of the enameled wire.

[0033] When the amount of polyamine added is large, the cross-linking rate is accelerated and the degree of cross-linking increases. Conversely, if the amount of polyamine added is small, the cross-linking rate is slowed down and the degree of cross-linking decreases.

[0034] In some specific embodiments, in step S3, the mass ratio of the sum of the masses of the polyurethane prepolymer and the modified nano-titanium dioxide to the aminopolysiloxane can be 100:10, 100:12, 100:15, 100:18, 100:20, 100:22, 100:25, 100:28, or 100:30. Generally, in step S3, when the mass ratio of the sum of the masses of the polyurethane prepolymer and the modified nano-titanium dioxide to the aminopolysiloxane is 100:18, better experimental results can be obtained.

[0035] In some specific embodiments, in step S3, the mass ratio of the sum of the masses of the polyurethane prepolymer and the modified nano-titanium dioxide to the polyamine can be 100:1, 100:1.5, 100:2, 100:2.5, 100:3, 100:3.5, 100:4, 100:4.5, or 100:5. Generally, in step S3, when the mass ratio of the sum of the masses of the polyurethane prepolymer and the modified nano-titanium dioxide to the polyamine is 100:3, better experimental results can be obtained.

[0036] Preferably, the curing conditions of the high aging-resistant wire enamel are: furnace temperature of 280-380° C., softening temperature of 410-460° C., and wire speed of 115-285 m / min.

[0037] In the above technical solution, the paint drying operation is carried out fully automatically through a fully automatic paint drying machine. First, before starting the machine, clean all the guide wheels and the sand guide grooves and nylon splints in front and behind the guide wheels on the machine to keep the guide wheels, sand guide grooves and nylon splints smooth, flexible and clean; secondly, after starting the machine, after the temperature reaches the set temperature, turn on the exhaust gas switch to discharge the waste in advance. As the vehicle speed gradually increases, the exhaust fan speed is gradually increased; thirdly, the vehicle speed cannot be too fast, otherwise it is easy to produce defective products and increase waste silk. If the vehicle speed is too slow, the take-up head cannot move the spool, affecting normal take-up; finally, the finished products should be placed with care to avoid surface scratches or abrasions.

[0038] A highly aging-resistant wire enamel is prepared by adopting the above preparation method.

[0039] In the above technical solution, the wire enamel is polysiloxane-modified polyurethane, and forms an interpenetrating cross-linked network. At the same time, nano-titanium dioxide is introduced to improve the aging resistance, heat resistance, mechanical properties, hydrophobic properties, etc. of the wire enamel.

[0040] Compared with the prior art, this application has the following beneficial effects:

[0041] 1. This application introduces polysiloxane into polyurethane. Since polysiloxane has good heat resistance, weather resistance, and hydrophobicity, and tends to be enriched on the surface, and polyurethane has strong adhesion, the enameled wire paint film formed not only has strong adhesion, but also has good aging resistance, heat resistance, hydrophobicity, and mechanical properties.

[0042] 2. This application modifies nano-titanium dioxide and introduces epoxy groups on the surface of titanium dioxide, which can react with aminopolysiloxane and polyamine to form an interpenetrating cross-linked network with polyurethane chains. This not only improves the heat resistance and aging resistance of polyurethane, but also limits the microphase separation of polysiloxane segments and polyurethane segments, thereby improving the strength of the enameled wire paint film, thereby improving the aging resistance, heat resistance, hydrophobicity, mechanical properties, etc. of the enameled wire paint.

[0043] 3. The present application increases the cross-linking rate of the polysiloxane chain segments by adding a curing agent, so that the polysiloxane is cured at a lower temperature, thereby reducing the performance degradation of the enameled wire film caused by poor curing. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 is the water contact angle of the enameled wire film.

[0045] Figure 2 The cross-sectional micromorphology of the enameled wire film of Comparative Example 1 and Example 3 is shown.

[0046] Figure 3 Schematic diagram of enameled stranded wire.

[0047] Figure 4 This is the process flow chart for enameled stranded wire production. DETAILED DESCRIPTION

[0048] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0049] Example 1

[0050] The preparation method of the wire enamel of this embodiment comprises the following steps:

[0051] S1: Add 50 g of polyoxypropylene glycol (Mn: 1000) to a three-necked flask, then place the flask in an 80°C water bath with stirring. Add 11.8 g of hexamethylene diisocyanate, introduce nitrogen, and react for 2.5 h to obtain a polyurethane prepolymer.

[0052] S2: Weigh 10 mL of isopropyl titanate and 100 mL of glacial acetic acid, stir for 15 min, add to 500 mL of deionized water, stir and react at 75 ° C for 0.5 h, heat to 95 ° C for 1 h, dilute the reaction solution 3 times with deionized water and transfer it to a hydrothermal autoclave, react at 150 ° C for 8 h, cool to room temperature after the reaction, and vacuum dry at 80 ° C to obtain powder. Weigh 10 g of the powder and ultrasonically disperse it in 400 mL of DMF. Add 3 g of β-(3,4-epoxycyclohexane)ethyltrimethoxysilane, disperse it evenly, place it in a three-necked flask, and react at 75 ° C under nitrogen protection for 20 h. After the reaction, precipitate with ethyl acetate to obtain modified nano-titanium dioxide;

[0053] S3: Weigh 95g of polyurethane prepolymer and 5g of modified nano-titanium dioxide, mix thoroughly, and slowly add 10g of bisaminopropyl polydimethylsiloxane. Under nitrogen protection, react at room temperature for 1h. Then, heat to 55°C, add 1g of p-phenylenediamine, continue to react for 2h, and vacuum to remove foam.

[0054] The preparation process of the enameled stranded wire of this embodiment is as follows:

[0055] 1) Liquid enamel preparation: Mix the prepared wire enamel with phenol, cresol, and xylene, and stir at high speed for 30 minutes to obtain a liquid enamel with a solid content of 35%, which is set aside.

[0056] 2) Preparation before starting the machine: First, use cotton wool cloth and a brush to scrub all the guide wheels, the sand guide grooves and nylon splints in front and behind the guide wheels, all the heads on the locomotive, the furnace inlet and outlet, the paint tank, the nylon shelf and nylon block above the paint tank, and the paint roller, etc. Then scrub them again with a small amount of acetone until they are clean and smooth; install a finished product bobbin and a waste silk bobbin on each group of heads, replace the nylon on time, then check and record the spool identification on the wire record sheet, place the spool under the wire positioning steel ring, align it with the positioning steel ring, and cover it with a brush;

[0057] 3) Start the machine: Turn on the power, set the furnace entry temperature to 300℃ and the furnace exit temperature to 360℃. After the temperature reaches the set temperature, turn on the exhaust gas switch, set the exhaust fan speed to 200r / min, set the traction speed to 40m / min, turn on the waxing device power, let the white wax enter the waxing box and the nylon strip, and let the whole nylon strip be soaked with white wax; transport the wire spool to the wire-paying section, pass the wire through the felt pressing plate, wire groove, and guide wheel, and then to the annealing furnace mouth, use steel wire to thread the wire into the annealing furnace tube, after the wire passes through the annealing furnace, pass through the wire hook and guide wheel to enter the oven mouth, divide the wire back and forth, and bring it out of the oven mouth in 8 lanes.

[0058] 4) Painting: Pass the 0.2mm copper wire through the white wax nylon strip, insert it into the wire guide wheel and wrap it around the waste wire bobbin of the take-up reel. Turn on the power of the reel and slowly turn it on. After all the wire ends are wrapped around the take-up reel, turn on the paint pump power to fill the paint tank with paint liquid; place the dry nylon strips and painted nylon strips neatly and flatly on the nylon strip shelf, and press on the nylon pressure plate that meets the wire gauge, turn on all the take-up reels, slowly increase the speed to 60m / min, turn on the paint tank, paint the copper wire, slowly increase the speed to 120m / min, measure the diameter with a laser diameter gauge, and record the outer diameter of each shaft, which is 0.27±0.01mm.

[0059] Example 2

[0060] The preparation method of the wire enamel of this embodiment comprises the following steps:

[0061] S1: Add 50 g of polytetramethylene glycol (Mn: 1000) to a three-necked flask, then place the flask in an 80°C water bath with stirring, add 17.4 g of toluene-2,4-diisocyanate, introduce nitrogen, and react for 2.5 h to obtain a polyurethane prepolymer;

[0062] S2: Weigh 10 mL of isopropyl titanate and 100 mL of glacial acetic acid, stir for 15 min, add to 500 mL of deionized water, stir and react at 75 ° C for 0.5 h, heat to 95 ° C for 1 h, dilute the reaction solution 3 times with deionized water and transfer it to a hydrothermal autoclave, react at 150 ° C for 8 h, cool to room temperature after the reaction, and vacuum dry at 80 ° C to obtain powder. Weigh 10 g of the powder and ultrasonically disperse it in 400 mL of DMF. Add 6 g of γ-glycidyloxypropyltrimethoxysilane, disperse evenly, place in a three-necked flask, and react at 75 ° C under nitrogen protection for 20 h. After the reaction, precipitate with ethyl acetate to obtain modified nano-titanium dioxide;

[0063] S3: Weigh 95g of polyurethane prepolymer and 5g of modified nano-titanium dioxide, mix thoroughly, slowly add 30g of aminopolysiloxane, pass nitrogen protection, react at room temperature for 1h, then raise the temperature to 70°C, add 5g of diethylenetriamine, continue to react for 1h, and vacuum to remove foam;

[0064] The preparation method of aminopolysiloxane of this embodiment comprises the following steps:

[0065] Weigh 20 g of phenyltrimethoxysilane and 4 g of N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, place in a three-necked flask, add 1% hydrochloric acid aqueous solution, react at room temperature for 15 min, then heat to 80 ° C and react for 6 h, then rotary evaporate and separate;

[0066] The preparation process of the enameled stranded wire in this embodiment is the same as that in Example 1.

[0067] Example 3

[0068] The preparation method of the wire enamel of this embodiment comprises the following steps:

[0069] S1: 50 g of poly(1,4-butylene adipate) diol (Mn: 1000) was added to a three-necked flask, which was then placed in an 80°C water bath with stirring. 21.3 g of diphenylmethane diisocyanate was added, and nitrogen was introduced. The reaction was continued for 2.5 h to obtain a polyurethane prepolymer.

[0070] S2: Weigh 10 mL of isopropyl titanate and 100 mL of glacial acetic acid, stir for 15 min, add to 500 mL of deionized water, stir and react at 75 ° C for 0.5 h, heat to 95 ° C for 1 h, dilute the reaction solution 3 times with deionized water and transfer it to a hydrothermal autoclave, react at 150 ° C for 8 h, cool to room temperature after the reaction, and vacuum dry at 80 ° C to obtain powder. Weigh 10 g of the powder and ultrasonically disperse it in 400 mL of DMF. Add 5 g of γ-glycidyloxypropyltrimethoxysilane, disperse evenly, place in a three-necked flask, and react at 75 ° C under nitrogen protection for 20 h. After the reaction, precipitate with ethyl acetate to obtain modified nano-titanium dioxide;

[0071] S3: Weigh 95g of polyurethane prepolymer and 5g of modified nano-titanium dioxide, mix thoroughly, slowly add 18g of aminopolysiloxane, pass nitrogen protection, react at room temperature for 1h, then heat to 60°C, add 3g of tetraethylenepentamine, continue to react for 1h, add 0.54g of tetrabutyl titanate, mix well, and vacuum to remove bubbles;

[0072] The preparation method of aminopolysiloxane of this embodiment comprises the following steps:

[0073] Weigh 20g of diphenyldimethoxysilane and 7g of γ-aminopropyltriethoxysilane, place in a three-necked flask, add 1% hydrochloric acid aqueous solution, react at room temperature for 15min, then heat to 80℃ and react for 6h, then rotary evaporate and separate;

[0074] The preparation process of the enameled stranded wire in this embodiment is the same as that in Example 1.

[0075] Comparative Example 1

[0076] The preparation method of the wire enamel of this comparative example comprises the following steps:

[0077] S1: Add 50 g of polyoxypropylene glycol (Mn: 1000) to a three-necked flask, then place the flask in an 80°C water bath with stirring. Add 11.8 g of hexamethylene diisocyanate, introduce nitrogen, and react for 2.5 h to obtain a polyurethane prepolymer.

[0078] S2: Weigh 95g of polyurethane prepolymer and 5g of nano-silica, slowly add 10g of bis-aminopropyl polydimethylsiloxane, pass nitrogen protection, react at room temperature for 1h, then raise the temperature to 60°C, add 1g of p-phenylenediamine, continue to react for 1h, and vacuum to remove foam;

[0079] The preparation process of the enameled stranded wire in this comparative example is the same as that in Example 1.

[0080] Performance testing

[0081] Enameled wire paint film preparation

[0082] The wire enamels of Examples 1-3 and Comparative Example 1 were mixed with phenol, cresol and xylene, and stirred at high speed for 30 minutes to obtain a paint solution with a solid content of 35%. The mixture was then spread on a polytetrafluoroethylene plate and naturally dried at room temperature for 24 hours. The mixture was then placed in a blast drying oven and dried at 65°C for 6 hours. The mixture was then placed in a vacuum drying oven and dried at 65°C for 6 hours. The mixture was cut into dumbbell-shaped standard specimens with a length of 40 mm and a width of 10 mm for later use. The paint film thickness was measured to be 0.3±0.1 mm.

[0083] 1. Mechanical properties test

[0084] Test method: A desktop electronic precision universal testing machine was used to measure the tensile strength and elongation at break of the standard specimens. A 500N sensor was used for the tensile test at a tensile rate of 100mm / min. The average value of the three tensile specimens was taken as the test result.

[0085] ① Heat aging test: Take the cut standard specimens and place them in a muffle furnace, heat them to 180℃ and keep them warm for 12 hours, then take samples to test the tensile strength and elongation at break.

[0086] ② High temperature and high humidity test: Place the cut standard specimens in a constant temperature and humidity test chamber with a temperature of 85±2℃ and a humidity of 95±5% for 7 days. After taking them out, wipe them dry and vacuum dry them at 60℃ for 24 hours before conducting a tensile performance test.

[0087] At the same time, a blank test was performed to test the mechanical properties without any aging test. The results are shown in Table 1.

[0088] Table 1 Mechanical properties test results of the enameled wire paint films of Examples 1-3 and Comparative Example 1

[0089]

[0090] 2. Water contact angle test

[0091] Place the newly prepared enameled wire film on the contact angle tester, drip 300μL of water each time, and measure the contact angle of water on the film. The results are as follows: Figure 1 shown.

[0092] 3. Scanning electron microscopy observation

[0093] The cross sections of the enameled wire films of Example 3 and Comparative Example 1 were observed using a scanning electron microscope. The microscopic morphologies are as follows: Figure 2 shown.

[0094] 4. Thermal performance test

[0095] With reference to the standard GB / T 4074.6-2008, a softening breakdown test was performed on the enameled wire using a softening breakdown tester, with the test conditions being 220°C, 4.5N, and 2 min. A thermal shock test was performed on the enameled wire using a heated blast drying oven, with the oven temperature being 200°C and the thermal shock time being 30 min. The surface cracking of the paint film was observed using a magnifying glass, and it was found that the enameled wires of Examples 1-3 did not crack, and the temperature grade met the 155 grade, while the surface of the enameled wire of Comparative Example 1 had cracks.

[0096] Result Analysis

[0097] As can be seen from Table 1, after heat aging or high temperature and high humidity treatment, the tensile strength and elongation at break of the enameled wire paint film of Comparative Example 1 are greatly reduced, indicating that the aging resistance is poor, while the aging resistance of the enameled wire paint film of the embodiment is better.

[0098] from Figure 1 It can be seen that the hydrophobic properties of the wire enamel films of Examples 1-3 and the comparative example are better, which may be because the polysiloxane segments tend to be enriched on the surface during the curing process of the wire enamel.

[0099] from Figure 2 It can be seen that the enameled wire paint film of the comparative example has a more serious phase separation phenomenon, while the phase separation phenomenon of the enameled wire paint film of Example 3 is weakened. Combined with the mechanical property analysis, it can be seen that the polyurethane and polysiloxane in Example 3 have a stronger bonding strength.

[0100] Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments, or make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application should be included in the scope of protection of the present invention.

Claims

1. An enameled stranded wire, characterized in that: The enameled wire is made by twisting, and the enameled wire includes a metal wire core and a paint film covering the metal wire core. The paint film is formed by curing a high-aging-resistant enameled wire varnish. The preparation method of the high-aging-resistant enameled wire varnish includes the following steps: S1: reacting diol and diisocyanate under nitrogen protection to obtain a polyurethane prepolymer; the molar ratio of diol to diisocyanate is 1:(1.4-2); S2: dispersing nano-titanium dioxide in DMF, adding epoxysilane to react, and obtaining modified nano-titanium dioxide; the mass ratio of nano-titanium dioxide to epoxysilane is 1:(0.3-0.6); S3: Mix the polyurethane prepolymer and modified nano-titanium dioxide, add aminopolysiloxane, react at room temperature, then heat to 55-70°C, add polyamine, and continue to react to obtain the product; the aminopolysiloxane is prepared by reacting an organic siloxane monomer with an aminosilane coupling agent, and the mass ratio of the organic siloxane monomer to the aminosilane coupling agent is 1:(0.2-0.5); the mass ratio of the sum of the mass of the polyurethane prepolymer and the modified nano-titanium dioxide to the aminopolysiloxane is 100:(10-30); the mass ratio of the sum of the mass of the polyurethane prepolymer and the modified nano-titanium dioxide to the polyamine is 100:(1-5).

2. The enameled stranded wire according to claim 1, characterized in that The organosiloxane monomer is one or more of diphenyldimethoxysilane, phenyltrimethoxysilane, and phenyltriethoxysilane; And / or, the aminosilane coupling agent is one or more of γ-aminopropyltriethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane and N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane.

3. The enameled stranded wire according to claim 1, characterized in that In step S3, the polyamine is one or more of ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine and p-phenylenediamine.

4. The enameled stranded wire according to claim 1, characterized in that In step S3, a curing agent is added after adding the polyamine, and the curing agent is tetrabutyl titanate or dibutyltin oxalate; And / or, the mass ratio of the aminopolysiloxane to the curing agent is 100:(1-5).

5. The enameled stranded wire according to claim 1, characterized in that The curing conditions of the high-aging-resistant wire enamel are: furnace temperature of 280-380° C., softening temperature of 410-460° C., and wire speed of 115-285 m / min.

6. A highly aging-resistant wire enamel, characterized in that: The preparation method of the highly aging-resistant wire enamel comprises the following steps: S1: reacting diol and diisocyanate under nitrogen protection to obtain a polyurethane prepolymer; the molar ratio of diol to diisocyanate is 1:(1.4-2); S2: dispersing nano-titanium dioxide in DMF, adding epoxysilane to react, and obtaining modified nano-titanium dioxide; the mass ratio of nano-titanium dioxide to epoxysilane is 1:(0.3-0.6); S3: Mix the polyurethane prepolymer and modified nano-titanium dioxide, add aminopolysiloxane, react at room temperature, then heat to 55-70°C, add polyamine, and continue to react to obtain the product; the aminopolysiloxane is prepared by reacting an organic siloxane monomer with an aminosilane coupling agent, and the mass ratio of the organic siloxane monomer to the aminosilane coupling agent is 1:(0.2-0.5); the mass ratio of the sum of the mass of the polyurethane prepolymer and the modified nano-titanium dioxide to the aminopolysiloxane is 100:(10-30); the mass ratio of the sum of the mass of the polyurethane prepolymer and the modified nano-titanium dioxide to the polyamine is 100:(1-5).

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