A process for the manufacture of an enameled wire

Abstract

The application discloses a processing technology for enameled wire and relates to the field of wire rods; the processing technology is applied to the manufacturing of XLPE insulated power cables and comprises the following steps: S1, extruding an XLPE insulation layer on the surface of a metal conductor and performing chemical crosslinking treatment to form the XLPE insulation layer; S2, performing atmospheric plasma surface pretreatment on the XLPE insulation layer; S3, coating a reactive paint liquid on the surface of the pretreated XLPE insulation layer to form a paint film; S4, synchronously completing the chemical crosslinking of the XLPE insulation layer and the curing reaction of the paint film through segmented temperature control; a. triggering the chemical crosslinking of the XLPE at 160-200 DEG C in the first stage; b. completing the curing of the paint film through a latent curing agent at 120-150 DEG C in the second stage. The application realizes the synchronization / step-by-step cooperation of the chemical crosslinking of the XLPE and the curing of the paint film by designing the reaction path cooperation and energy matching of the chemical crosslinking of the XLPE and the curing of the paint film, effectively solves the technical problems faced by the traditional XLPE cable when the enameled wire process is introduced, and improves the comprehensive performance of the cable.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wire rod, in particular to a method for manufacturing wire rod, and more particularly to a processing technology for enameled wire. BACKGROUND

[0002] In the field of power cable manufacturing, the selection and application of insulation materials are directly related to the electrical performance, heat resistance, mechanical strength, and service life of the cable. Cross-linked polyethylene (XLPE) has become the preferred material for the insulation layer of medium and high voltage power cables due to its excellent electrical insulation, heat aging resistance, and good mechanical properties.

[0003] However, with the development of the power industry, the transmission voltage level is continuously increasing, and there are challenges such as offshore wind power and direct current transmission in complex working conditions. The traditional XLPE cable gradually reveals its limitations. First, XLPE is prone to micro-cracks or impurity interfaces during extrusion cross-linking. These defects can reduce the partial discharge inception voltage (PDIV), especially in harsh environments such as humidity and salt spray, which can significantly degrade the insulation performance and affect the long-term stable operation of the cable. Second, the XLPE material itself has limited resistance to acid and alkali media, and relies on an outer sheath for additional protection, which not only increases the weight and cost of the cable, but also limits its application in certain special environments.

[0004] Therefore, it is necessary to improve the existing technology to solve the above problems. SUMMARY

[0005] The present application overcomes the shortcomings of the prior art and provides a processing technology for enameled wire.

[0006] To achieve the above purpose, the technical solution adopted by the present application is as follows: a processing technology for enameled wire applied to the manufacturing of XLPE insulated power cables, characterized by the following steps:

[0007] S1, extruding an XLPE insulation layer on the surface of a metal conductor and performing chemical cross-linking treatment to form an XLPE insulation layer;

[0008] S2, performing atmospheric plasma surface pretreatment on the XLPE insulation layer;

[0009] S3, coating a reactive paint solution on the surface of the pretreated XLPE insulation layer to form a paint film;

[0010] S4, synchronously completing the chemical cross-linking of the XLPE insulation layer and the curing reaction of the paint film through segmented temperature control;

[0011] a. The first stage triggers the chemical cross-linking of XLPE at 160-200℃;

[0012] b. The second stage is completed by a latent curing agent at 120-150℃ to cure the paint film.

[0013] In one preferred embodiment of the present application, in the step of S1, the XLPE base material comprises the following components by mass percentage:

[0014]

[0015] In one preferred embodiment of the present application, the crosslinking agent is dicumyl peroxide; the latent curing agent is one of ketimine or diethylene triamine; and the modifier is glycidyl methacrylate.

[0016] In one preferred embodiment of the present application, in the step of S3, the reactive paint solution comprises the following components by mass percentage:

[0017]

[0018] In one preferred embodiment of the present application, the hydroxyl-containing polyurethane resin is a hydroxyl-terminated polyurethane resin; the amino nano-filler is one of amino-modified nano-silicon carbide or amino-modified fumed silica, with a particle size of 20-100 nm; the phosphorus-based flame retardant is one of DOPO or triphenyl phosphate; and the solvent is one of propylene glycol methyl ether acetate or butyl acetate.

[0019] In one preferred embodiment of the present application, in the step of S2, the process parameters of the atmospheric plasma treatment are: power 3-8 kW, treatment gas is a mixture of argon and oxygen, with a mixing volume ratio of 8-9:1-2, and treatment speed is 1-3 m / min.

[0020] In one preferred embodiment of the present application, in the step of S3, the coating process is one of electrostatic spraying or dip coating.

[0021] In one preferred embodiment of the present application, in the step of S3, the thickness of the paint film is 5-20 μm, and the surface roughness Ra of the cured paint film is ≤0.5 μm.

[0022] In one preferred embodiment of the present application, in the step of S4, in the segmented temperature control, the temperature gradient of the first stage and the second stage is achieved by an infrared catalytic oven or a catenary crosslinking pipe, and the second stage is carried out under a nitrogen protective atmosphere with an oxygen content <200 ppm.

[0023] The application provides a power cable prepared by the processing technology in any one of the above, wherein the interface peeling strength between the XLPE insulating layer on the side of the metal conductor and the paint film is greater than or equal to 13.5 MPa, and the power frequency breakdown field strength is greater than or equal to 36 kV / mm.

[0024] The application solves the defects in the background art and has the following beneficial effects:

[0025] (1) The application provides a processing technology for enameled wire, wherein the latent curing agent in the XLPE base material is combined with the molecular thermal response characteristics to keep inert in the XLPE high-temperature crosslinking stage, and to release active groups to trigger the paint film curing in the subsequent medium-temperature stage, and then the molecular-level staged triggering mechanism ensures that the paint film curing reaction is activated only after the XLPE crosslinking network is fully formed, avoids the energy competition or mutual interference of the two reactions, keeps the high crosslinking density of the XLPE, and guarantees the uniform curing of the paint film, so as to finally realize the overall compactness and thermal mechanical stability of the insulating structure.

[0026] (2) In the application, the epoxy groups provided by the glycidyl methacrylate are combined with the amine curing agent in the paint film curing stage through the modification agent in the XLPE base material, so that covalent bonding can occur to form a stable chemical interface, the adhesion between the paint film and the XLPE insulating layer is greatly enhanced through the covalent bond network, the corona resistance and breakdown strength of the insulating material are significantly improved through the microscopic propagation path of the covalent bond network, and then the free ends of the molecular chains are reduced, the local electric field distortion is inhibited, and the overall electrical stability of the cable is improved.

[0027] (3) In the application, the nano filler with modified amino active groups can form hydrogen bonds with the hydroxyl groups of the polyurethane resin, and the polyethylene segments are orderly arranged through the Van der Waals force, the interface coupling at the molecular scale enhances the interface compatibility between the XLPE and the paint film, effectively disperses the mechanical stress and inhibits crack propagation, the introduction of the nano filler optimizes the heat conduction path of the material, accelerates heat diffusion through phonon transmission, avoids polymer degradation caused by local overheating, and thus improves the long-term temperature resistance and environmental adaptability of the cable. BRIEF DESCRIPTION OF DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are only some embodiments described in the application, and other drawings can be obtained by those skilled in the art without creative labor;

[0029] Figure 1A process flow chart for processing the enameled wire according to a preferred embodiment of the present application;

[0030] Figure 2 A cable cross-sectional structure schematic diagram according to a preferred embodiment of the present application;

[0031] In the figure: 1, metal conductor; 2, XLPE insulation layer; 3, paint film. DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0033] In the following description, many specific details are set forth in order to provide a thorough understanding of the present application. However, the present application can be practiced in a variety of ways beyond the specific embodiments described herein, and the scope of the present application is not limited to the specific embodiments described herein.

[0034] SUMMARY

[0035] In order to improve the limitations of traditional XLPE cables, some studies attempt to introduce the enameled wire process into power cable manufacturing. The enameled wire technology has the characteristics of uniform thickness and strong chemical resistance by coating multiple layers of polymer paint film on the surface of the conductor and forming a dense insulation layer through baking and curing.

[0036] Applicants have found that in the traditional enameled wire process, the curing of the paint film requires high-temperature baking (usually at 200-300℃), and if XLPE is subjected to high temperature again after crosslinking, it is easy to cause the crosslinking network to break down (thermal aging), reduce the mechanical strength, and the traditional paint film is only combined with XLPE through physical adsorption, the interfacial bonding force is insufficient, and delamination phenomenon is easy to occur under thermal cycling or mechanical stress, affecting the insulation performance and reliability of the cable.

[0037] In view of the above problems, the present application proposes a new type of power cable manufacturing process, which realizes the synchronization / step-by-step cooperation of the two by designing the reaction path cooperation and energy matching of the chemical crosslinking of XLPE and the curing of the paint film, effectively solving the technical problems faced by traditional XLPE cables when introducing the enameled wire process, and improving the comprehensive performance of the cable.

[0038] It should be noted that: the raw materials, equipment and reagents used in the present application can be purchased from the market or prepared by the preparation method of the prior art.

[0039] For example, Figure 1As shown, a processing technology for enameled wire is applied to the manufacturing of XLPE insulated power cable, comprising the following steps:

[0040] S1, extruding an XLPE insulation layer on the surface of the metal conductor and performing chemical crosslinking treatment to form the XLPE insulation layer;

[0041] S2, performing atmospheric plasma surface pretreatment on the XLPE insulation layer;

[0042] S3, coating a reactive paint solution on the surface of the pretreated XLPE insulation layer to form a paint film;

[0043] S4, synchronously completing the chemical crosslinking of the XLPE insulation layer and the curing reaction of the paint film through segmented temperature control;

[0044] a. The first stage triggers the chemical crosslinking of XLPE at 160-200℃;

[0045] b. The second stage completes the curing of the paint film through a latent curing agent at 120-150℃.

[0046] In some specific embodiments, in the step of S1, the XLPE base material comprises the following components in mass percentage:

[0047]

[0048] In some specific embodiments, the crosslinking agent is dicumyl peroxide; the latent curing agent is one of ketimine or diethylenetriamine; and the modifier is glycidyl methacrylate.

[0049] In some specific embodiments, in the step of S3, the reactive paint solution comprises the following components in mass percentage:

[0050]

[0051] In some specific embodiments, the hydroxyl-containing polyurethane resin is a hydroxyl-terminated polyurethane resin; the amino nano-filler is one of amino-functionalized nano-silicon carbide or amino-functionalized fumed silica, with a particle size of 20-100nm; the phosphorus-based flame retardant is one of DOPO or triphenyl phosphate; and the solvent is one of propylene glycol methyl ether acetate or butyl acetate.

[0052] It should be noted that the amino-functionalization of the nano-filler specifically comprises the following steps:

[0053] a1, using a mixed solvent of ethanol and water in a volume ratio of 9:1, adjusting the pH to 4-5 through hydrochloric acid, adding an amino silane coupling agent (KH-550 or γ-aminopropyl triethoxysilane) at a concentration of 2-5wt% of the nano-filler, and magnetically stirring for 30min to obtain a silane coupling agent solution;

[0054] a2, the nanofiller is added into the silane coupling agent solution (solid-liquid ratio 1:20), ultrasonic dispersion for 30 min, and continuous stirring in 60℃ water bath for 4-8h, the solution gradually changes from turbidity to uniform dispersion, indicating that the modification is successful;

[0055] a3, the S32 product is washed by anhydrous ethanol by centrifugation for 2-3 times (centrifugal speed 3000-5000rpm, time 10min), and dried at 80℃ in a vacuum environment for 12h to obtain the amino nanofiller.

[0056] In some specific embodiments, in the step of S2, the process parameters of the atmospheric plasma treatment are: power 3-8kW, the treatment gas is a mixed gas of argon and oxygen, the mixing volume ratio is 8-9:1-2, and the treatment speed is 1-3m / min.

[0057] In some specific embodiments, in the step of S3, the coating process is one of electrostatic spraying or dip coating.

[0058] In some specific embodiments, in the step of S3, the thickness of the paint film is 5-20μm, and the surface roughness Ra of the paint film after curing is ≤0.5μm.

[0059] In some specific embodiments, in the step of S4, in the segmented temperature control, the temperature gradient of the first stage and the second stage is realized by an infrared catalytic oven or a catenary crosslinking pipe, and the second stage is carried out in a nitrogen protective atmosphere, and the oxygen content is <200ppm.

[0060] As shown in Figure 2 , the present application provides a power cable prepared by any one of the above processing techniques, the interface peeling strength between the XLPE insulating layer 2 on the side of the metal conductor 1 and the paint film 3 is ≥13.5MPa, and the power frequency breakdown field strength is ≥36kV / mm.

[0061] In order to further make the purpose and effect of the present application simple and easy to understand, the present application is further described in combination with examples and comparative examples. Among them, the raw materials in the examples and comparative examples are specifically: annealed copper conductor (cross-sectional area 240mm 2 , diameter 18mm), low density polyethylene (LDPE, brand: Dow Chemical 210GGN, density 0.921g / cm 3Dicumyl peroxide (DCP, purity 98%), ketimine (trade name: Evonik VESTAGON B1530), diethylenetriamine (DETA, trade name: Huntsman JEFFLINK 7150, purity ≥99%), glycidyl methacrylate (GMA, purity 99%), hydroxyl-terminated polyurethane resin (solid content 40%, trade name: Covestro Desmophen 670BA), nano-silicon carbide (SiC, trade name: Washington Mills NanoSiC-50, 30-50m 2 / g, particle size 50nm), fumed silica (trade name: Aerosil 200, specific surface area 200m 2 / g, particle size 50nm), DOPO (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide), triphenyl phosphate (TPP, trade name: Lanxess Disflamoll TP, phosphorus content: 9.5wt%), propylene glycol methyl ether acetate (PMA, purity 99%), butyl acetate (trade name: Eastman Eastman BA, purity: ≥99.5%).

[0062] The XLPE base material and the raw materials of the reactive lacquer solution of Examples 1-6 are different in raw material ratio, and the raw materials are measured in mass percentage.

[0063] Table 1: Preparation of raw materials and ratio of XLPE base material and reactive lacquer solution of Examples 1-6

[0064]

[0065] Example 1

[0066] A processing process of a power cable enameled wire, comprising the following steps:

[0067] S1, preheat the copper conductor to 80°C through an induction heating device to eliminate surface moisture and impurities;

[0068] S2, put the XLPE base material into a single screw extruder to extrude a 5.0mm thick XLPE insulation layer on the surface of the copper conductor, and the extrusion parameters are: barrel temperature: zone 1 150°C, zone 2 170°C, zone 3 180°C, die 190°C, extrusion pressure: 15MPa;

[0069] S3, send the coated cable into a catenary crosslinking pipe, and crosslink at a temperature of 180°C for 10min;

[0070] S4, surface pretreatment of the XLPE insulation layer by the atmospheric plasma treatment equipment using a mixed gas of argon and oxygen with a mixing volume ratio of 9:1 at a flow rate of 15 L / min, a treatment power of 5 kw, and a spray gun moving speed of 2 m / min;

[0071] S5, forming a paint film by coating the reactive paint liquid on the surface of the pretreated XLPE insulation layer by the electrostatic rotary cup spraying machine at a spraying voltage of 60 kV, a paint liquid viscosity of 200 cP, a spraying amount of 10 g / m, and a paint film thickness of 15 μm.

[0072] S6, drying the coated cable in the infrared catalytic oven at a temperature of 130℃ for 5 min, cooling the cable to below 50℃ by the water cooling device (water temperature 20℃), and winding the cable at a speed of 0.5 m / s to obtain the paint film XLPE cable-1.

[0073] The configuration of the XLPE base material specifically includes: dry mixing LDPE, ketimine and GMA at 60℃ for 8 min to obtain a premix, and melting the premix with DCP by a twin-screw extruder with the following process parameters: temperature zoning: zone 1 150℃, zone 2 170℃, zone 3 180℃, die 190℃; screw speed: 200 rpm, residence time 3 min.

[0074] The configuration of the reactive paint liquid specifically includes: stirring hydroxyl-terminated polyurethane resin, amino-SiC, DOPO and PMA for 40 min, standing for 24 h (to eliminate bubbles), and filtering through a 200-mesh screen.

[0075] The preparation of the amino-SiC includes the following steps:

[0076] a1, using a mixed solvent of ethanol and water with a volume ratio of 9:1, adjusting the pH to 4.5 by hydrochloric acid, adding KH-550 with a concentration of 4 wt% of SiC, and stirring magnetically for 30 min to obtain a silane coupling agent solution;

[0077] a2, adding SiC to the silane coupling agent solution (solid-liquid ratio 1:20), ultrasonic dispersion for 30 min, and continuous stirring in a 60℃ water bath for 6 h, the solution gradually changes from turbidity to uniform dispersion, indicating that the modification is successful;

[0078] a3, washing the S32 product with anhydrous ethanol by centrifugation for 3 times (centrifugal speed 3000 rpm, time 10 min), and drying at 80℃ in a vacuum environment for 12 h to obtain amino-SiC.

[0079] Example 2

[0080] This example is basically the same as example 1, the difference is that the raw materials and the raw material ratio are different, as shown in table 1; S6 step is: the coated cable is sent into the infrared catalytic oven, dried at 150℃ for 5min, forming a 15μm thick paint film, and using water cooling device (water temperature 20℃) to cool the cable to below 50℃, with a speed of 0.5m / s winding, get paint film @XLPE cable-2.

[0081] Example 3

[0082] This example is basically the same as example 1, the difference is that the raw materials and the raw material ratio are different, as shown in table 1; S6 step is: the coated cable is sent into the infrared catalytic oven, dried at 120℃ for 5min, forming a 15μm thick paint film, and using water cooling device (water temperature 20℃) to cool the cable to below 50℃, with a speed of 0.5m / s winding, get paint film @XLPE cable-3.

[0083] Example 4

[0084] This example is basically the same as example 1, the difference is that the raw materials and the raw material ratio are different, as shown in table 1; S3 step is: the coated cable is sent into the catenary crosslinking pipe, crosslinked at 160℃ for 10min; finally get paint film @XLPE cable-4.

[0085] Example 5

[0086] This example is basically the same as example 1, the difference is that the raw materials and the raw material ratio are different, as shown in table 1; S3 step is: the coated cable is sent into the catenary crosslinking pipe, crosslinked at 200℃ for 10min; finally get paint film @XLPE cable-5.

[0087] Example 6

[0088] This example is basically the same as example 1, the difference is that the raw materials and the raw material ratio are different, as shown in table 1; S4 step is: by atmospheric plasma treatment equipment, using the mixed gas of argon and oxygen with a mixed volume ratio of 9:1, with a flow rate of 15L / min, a treatment power of 5kw, a spray gun moving speed of 3m / min, the surface of XLPE insulation layer is pretreated; finally get paint film @XLPE cable-6.

[0089] Performance test: the paint film @XLPE cable obtained by the above examples 1-6 is respectively subjected to the performance test of paint film adhesion, power frequency breakdown field strength, heat extension and salt spray resistance, and the results are shown in table 2.

[0090] Paint film adhesion (peeling strength): according to GB / T 5210-2006 “Paint and varnish pull-off method adhesion test”, a metal test column with a diameter of 20 mm is fixed on the surface of the paint film by an adhesive (such as epoxy resin), and the adhesive needs to be completely cured; a tensile testing machine is used to apply tension at a constant speed in the vertical direction until the coating and the substrate or the interlayer are peeled off; the maximum tensile force value (unit: MPa) at the time of damage is recorded;

[0091] Power frequency breakdown field strength: according to GB / T 1408.1-2016 “Insulating materials - Determination of electrical strength in liquid - Part 1: Test at power frequency”, the cable sample is placed between the electrodes and immersed in insulating oil, and the power frequency voltage is applied at a rate of 1 kV / s until the insulating layer breaks down, and the breakdown field strength is calculated;

[0092] Thermal extension: according to GB / T 2951.21-2008 “Cables and optical cables - Insulation and sheath materials - General test methods - Part 21: Special test methods for elastomer compounds - Thermal extension test”, the dumbbell-shaped sample is hung in a 200℃ constant temperature oven, and a 20N / cm 2 weight is hung below, and the elongation of the sample is measured after 15 minutes, and the permanent deformation is measured after cooling;

[0093] Salt spray resistance: according to GB / T 10125-2012 “Salt spray test for artificial atmosphere corrosion test”, the sample is placed in a salt spray test chamber, the spraying medium is 5% NaCl solution, the test temperature is set to 35℃, the spraying amount is 1-2 mL / (h·80cm 2 ), and the sample is continuously sprayed for 500h, and the paint film condition is observed after the sample is taken out.

[0094] Table 2: Performance test results of paint film @ XLPE cable obtained by examples 1-6

[0095]

[0096]

[0097] As shown in Table 2:

[0098] Through the comparison of examples 1-6, it can be seen that the obtained paint film @ XLPE cable has excellent performance in paint film adhesion, power frequency breakdown field strength, thermal extension and salt spray resistance; the present application solves the problems of interface defects and environmental sensitivity of traditional XLPE cable through chemical bonding interface, segmented temperature control synergy and multi-scale material synergy. The data of examples show that the optimized process makes the paint film adhesion increase to 13.5-15.3 MPa, the breakdown field strength reaches 36-39.6 kV / mm, and has excellent thermal mechanical stability and environmental adaptability, thereby comprehensively improving the performance of the cable.

[0099] Comparative example 1

[0100] This comparative example is basically the same as Example 1, except that steps S4-S6 are omitted. Specifically, it includes the following steps:

[0101] S1. Preheat the copper conductor to 80°C using an induction heating device to remove surface moisture and impurities;

[0102] S2. Feed the XLPE base material into a single screw extruder and extrude a 5.0mm thick XLPE insulation layer onto the surface of the copper conductor. The extrusion parameters are: barrel temperature: zone 1 150℃, zone 2 170℃, zone 3 180℃, die 190℃, and extrusion pressure: 15MPa.

[0103] S3. The coated cable is fed into a catenary cross-linking tube and cross-linked at 180°C for 10 minutes to obtain an XLPE cable.

[0104] The specific configuration of the XLPE base material includes: melting LDPE and DCP through a twin-screw extruder, with the following process parameters: temperature zones: zone 1 150℃, zone 2 170℃, zone 3 180℃, and die head 190℃; screw speed: 200 rpm, residence time 3 min.

[0105] Comparative Example 2

[0106] This comparative example is basically the same as Example 1, except that the temperature of the second stage temperature control is different. Specifically, step S6 is as follows: the coated cable is sent into an infrared catalytic oven and dried at 110°C for 5 minutes to form a 15μm thick paint film. The cable is then cooled to below 50°C using a water cooling device (water temperature 20°C) and wound up at a speed of 0.5m / s to obtain the paint film@XLPE cable.

[0107] Comparative Example 3

[0108] This comparative example is basically the same as Example 1, except that the temperature of the second stage temperature control is different. Specifically, step S6 is as follows: the coated cable is sent into an infrared catalytic oven and dried at 160°C for 5 minutes to form a 15μm thick paint film. The cable is then cooled to below 50°C using a water cooling device (water temperature 20°C) and wound up at a speed of 0.5m / s to obtain the paint film@XLPE cable.

[0109] Comparative Example 4

[0110] This comparative example is basically the same as Example 1, except that the application location of the latent curing agent is different, and the specific dosage of XLPE base material and reactive paint is as follows:

[0111] The XLPE base material is configured as follows: LDPE and GMA are dry mixed at 60°C for 8 minutes to obtain a premix, and the premix and DCP are melted by a twin-screw extruder with the following process parameters: temperature zones: 150°C for the first zone, 170°C for the second zone, 180°C for the third zone, and 190°C for the die; screw rotation speed: 200 rpm; and residence time: 3 minutes.

[0112] The reactive paint is configured as follows: the hydroxyl-terminated polyurethane resin, the amino-modified SiC, the DOPO, the PMA, and the ketimine are stirred for 40 minutes, allowed to stand for 24 hours for curing (to eliminate bubbles), and filtered through a 200-mesh screen.

[0113] Comparative Example 5

[0114] This comparative example is basically the same as Example 1, except that the amount of the latent curing agent in the XLPE base material is different, and the raw material amounts of the XLPE base material are as follows: LDPE (91.5%), DCP (1%), ketimine (5.7%), and GMA (1.8%).

[0115] Comparative Example 6

[0116] This comparative example is basically the same as Example 1, except that the amount of the latent curing agent in the XLPE base material is different, and the raw material amounts of the XLPE base material are as follows: LDPE (96.5%), DCP (1%), ketimine (0.7%), and GMA (1.8%).

[0117] Comparative Example 7

[0118] This comparative example is basically the same as Example 1, except that there is no modifier in the XLPE base material, and the raw material amounts of the XLPE base material are as follows: LDPE (95.3%), DCP (1%), and ketimine (3.7%);

[0119] The XLPE base material is configured as follows: LDPE and ketimine are dry mixed at 60°C for 8 minutes to obtain a premix, and the premix and DCP are melted by a twin-screw extruder with the following process parameters: temperature zones: 150°C for the first zone, 170°C for the second zone, 180°C for the third zone, and 190°C for the die; screw rotation speed: 200 rpm; and residence time: 3 minutes.

[0120] Comparative Example 8

[0121] This comparative example is basically the same as Example 1, except that the amount of the modifier in the XLPE base material is different, and the raw material amounts of the XLPE base material are as follows: LDPE (92%), DCP (1%), ketimine (3.7%), and GMA (3.3%).

[0122] Comparative Example 9

[0123] The comparative example is basically the same as example 1, the difference is that the amount of modifier in the XLPE base material is different, the amount of raw materials in the XLPE base material is: LDPE (95%), DCP (1%), ketimine (3.7%), GMA (0.3%).

[0124] Comparative example 10

[0125] The comparative example is basically the same as example 1, the difference is that the reactive paint solution does not contain amino nano filler, the amount of raw materials in the reactive paint solution is: hydroxyl terminated polyurethane resin (40%), DOPO (3.4%), PMA (56.6%);

[0126] The preparation of the reactive paint solution specifically includes: stirring the hydroxyl terminated polyurethane resin, DOPO and PMA for 40 min, standing for 24 h (to eliminate bubbles), and passing through a 200 mesh filter.

[0127] Comparative example 11

[0128] The comparative example is basically the same as example 1, the difference is that the nano filler in the reactive paint solution is not aminated, the amount of raw materials in the reactive paint solution is: hydroxyl terminated polyurethane resin (40%), SiC (1.6%), DOPO (3.4%), PMA (55%);

[0129] The preparation of the reactive paint solution specifically includes: stirring the hydroxyl terminated polyurethane resin, SiC, DOPO and PMA for 40 min, standing for 24 h (to eliminate bubbles), and passing through a 200 mesh filter.

[0130] Performance test: the XLPE cable of comparative example 1 and the paint film @ XLPE cable obtained by comparative examples 2-11 are tested for paint film adhesion, power frequency breakdown field strength, heat extension and salt spray resistance by the same performance test method as the paint film @ XLPE cable obtained by examples 1-6, the results are shown in table 3.

[0131] Table 3: performance test results of XLPE cable obtained by comparative example 1 and paint film @ XLPE cable obtained by comparative examples 2-11

[0132]

[0133]

[0134] As shown in table 3:

[0135] By comparing Example 1-6 with Comparative Example 1, it can be seen that: the paint film blocks environmental erosion through chemical bonding interface, while the nano filler fills the surface pores of XLPE, inhibits crack propagation, when there is no paint film protection, XLPE surface defects are directly exposed to the environment, resulting in local electric field distortion, PDIV reduction (breakdown field strength is only 24.3 kV / mm), and no paint film barrier salt spray penetration, insulation layer corrosion, while the heat conduction path is not optimized, the thermal elongation is as high as 91.5%.

[0136] By comparing Example 1-3 with Comparative Example 2-3, it can be seen that: when the temperature of the second stage temperature control is too low, the latent curing agent (ketone imine) is not fully activated, and the primary amine group cannot be fully released, the paint film is not fully cured, and the peel strength is only 8.7 MPa, and when the temperature is too high, it causes the XLPE cross-linked network to partially decompose (thermal aging), and the interface micro-cracks increase due to the accumulation of internal stress caused by the too fast curing of the paint film, and the peel strength decreases to 9.2 MPa.

[0137] By comparing Example 1-6 with Comparative Example 4, it can be seen that: by protecting the latent curing agent (ketone imine) in the XLPE base material from heat, only the active amine group is released in the second stage, and it reacts synchronously with the epoxy group in the paint film to form a covalent bond interface, with an adhesion of 15.3 MPa. When the latent curing agent is directly added to the paint, it is prematurely exposed to trace amounts of moisture in the solvent (PMA), which releases the primary amine, causing the paint to pre-cure before spraying, resulting in poor coating uniformity, which prevents it from working according to the "staged trigger" mechanism, and the epoxy-amine reaction is disturbed, resulting in a decrease in covalent bond density.

[0138] By comparing Example 1 with Comparative Example 5-6, it can be seen that: due to the excess curing agent, the unreacted amine group is left in the XLPE base material, causing side reactions, resulting in increased brittleness of the paint film, with a thermal elongation elongation of 73.2% and a permanent deformation of 8.2%, and when the curing agent is insufficient, the paint film is not fully cured, resulting in weak interfacial bonding (peel strength of 9.6 MPa).

[0139] By comparing Example 1-6 with Comparative Example 7, it can be seen that: by covalently bonding the epoxy group of GMA with the amine group, the bond energy is much higher than physical adsorption, when the epoxy group provided by GMA is missing, it cannot form a covalent bond with the amine group in the paint film, and the interface only relies on physical adsorption, with a peel strength of only 7.4 MPa, and the interface is prone to brittle flaking in a salt spray environment.

[0140] By comparing Example 1 with Comparative Example 8-9, it can be seen that: when the density of the epoxy group matches the amine group, the interface has a high covalent bond coverage, which can achieve excellent performance, and excessive GMA causes the cross-linked network to be too dense, limiting molecular chain movement, resulting in an increase in thermal elongation permanent deformation to 7.5%, a decrease in temperature resistance, and insufficient GMA resulting in a low density of epoxy groups, insufficient covalent bonding, and a breakdown field strength of 30.2 kV / mm.

[0141] By comparing example 1-6 with comparative example 10-11, it can be seen that: by forming hydrogen bond between amino and resin hydroxyl, SiC crystal lattice induces the ordered arrangement of polyethylene chain, which further improves the thermal conductivity, and the adhesion reaches 15.3 MPa. When the paint film lacks nano filler reinforcement, the thermal conductivity is low, local heat accumulation leads to polymer degradation, thermal elongation permanent deformation reaches 16.7%, the paint film is easy to fail, and the general SiC surface has no amino group, no hydrogen bond with the resin, poor interface compatibility, filler agglomeration leads to interface stress concentration, and the adhesion decreases to 9.2 MPa.

[0142] The above is based on the ideal embodiment of the application, and for those skilled in the art, it is obvious that the application is not limited to the details of the above exemplary embodiments, and the application can be realized in other specific forms without departing from the spirit or basic characteristics of the application. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting, and the scope of the application is defined by the appended claims rather than the above description, and therefore all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the application. Any reference signs in the claims should not be regarded as limiting the claims involved.

[0143] In addition, it should be understood that although the present specification is described in terms of embodiments, not every embodiment contains only one independent technical solution, and the description of the specification is only for the sake of clarity, and those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can be properly combined to form other embodiments that those skilled in the art can understand.

Claims

1. A process for the processing of enameled wire, applied to the manufacture of XLPE insulated power cables, characterized in that, The method comprises the following steps: S1, extruding a XLPE insulation layer on the surface of a metal conductor, and performing chemical cross-linking treatment at 160-200 ℃ to form a XLPE insulation layer; the base material of the XLPE comprises the following components in mass percentage: low-density polyethylene 90.5-98 %; cross-linking agent 0.5-1.5 %; latent curing agent 1-5 %; modifier 0.5-3 %; S2, performing atmospheric plasma surface pretreatment on the XLPE insulation layer; S3, coating a reactive paint liquid on the surface of the pretreated XLPE insulation layer to form a paint film; the reactive paint liquid comprises the following components in mass percentage: hydroxyl-containing polyurethane resin 30-50 %; amino nano-filler 0.5-2 %; phosphorus-based flame retardant 2-5 %; solvent in the rest amount; S4, triggering a curing reaction by the latent curing agent at 120-150 ℃ to complete the curing of the paint film, and the curing process is performed cooperatively with the cross-linking structure of the XLPE insulation layer.

2. A process for the manufacture of an enameled wire as claimed in claim 1, characterized in that: The cross-linking agent is dicumyl peroxide; the latent curing agent is one of ketimine or diethylene triamine; and the modifier is glycidyl methacrylate.

3. A process for the manufacture of an enameled wire as claimed in claim 1, characterized in that: The hydroxyl-containing polyurethane resin is a hydroxyl-terminated polyurethane resin; the amino nano-filler is one of amino-modified nano-silicon carbide or amino-modified fumed silica, with a particle size of 20-100 nm; the phosphorus-based flame retardant is one of DOPO or triphenyl phosphate; and the solvent is one of propylene glycol methyl ether acetate or butyl acetate.

4. A process for the manufacture of an enameled wire as claimed in claim 1, characterized in that: In the step S2, the process parameters of the atmospheric plasma treatment are: power 3-8 kW, treatment gas is a mixed gas of argon and oxygen, with a mixing volume ratio of 8-9:1-2, and treatment speed is 1-3 m / min.

5. A process for the manufacture of an enameled wire as claimed in claim 1, wherein: In the step S3, the coating process of the reactive paint liquid is one of electrostatic spraying or dipping.

6. A process for the manufacture of an enameled wire as claimed in claim 1, wherein: In the step S3, the thickness of the paint film is 5-20 μm, and the surface roughness Ra of the cured paint film is ≤0.5 μm.

7. A process for the manufacture of an enameled wire as claimed in claim 1, wherein: In the steps S1 and S4, the chemical cross-linking treatment and the curing reaction are realized by an infrared catalytic oven or a catenary cross-linking pipe, and the curing reaction is performed in a nitrogen protection atmosphere with an oxygen content <200 ppm.

8. A power cable, characterized by The XLPE insulation layer on the side of the metal conductor in the cable prepared by the processing technology according to any one of claims 1-7 has an interface peeling strength of the XLPE insulation layer and the paint film ≥13.5 MPa, and a power frequency breakdown field strength ≥36 kV / mm.

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