New energy vehicle high-low voltage connector insulation protective agent and preparation method thereof

Abstract

The application discloses a new energy automobile high-low voltage connector insulation protective agent and a preparation method thereof, and belongs to the technical field of new energy automobile electrical safety. In order to solve the problems of insufficient interface stability of the existing protective material and inconvenient construction and maintenance, the application provides an aerosol type normal-temperature curing protection system. The protective agent comprises, in terms of weight fraction ratio, 8-20 parts of main film-forming resin, 0.5-3 parts of adhesion promoter, 0.5-2.5 parts of hydrophobic modifier, 0.2-1 part of stabilizer, 25-45 parts of a solvent system and 35-55 parts of a propellant, and the main film-forming resin is a modified organic polysiloxane film-forming resin containing a polyether flexible chain segment. Through the special flexible block modified resin structure, the synergistic effect of the adhesion promoter and the hydrophobic modifier is combined, an interface self-adaptive protective film with excellent dielectric properties, high resilience and strong adhesion is formed at the joint interface, and the long-term reliability of the new energy automobile electrical connection system in a complex environment is ensured.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of new energy vehicle electrical safety, and particularly relates to a new energy vehicle high-low voltage connector insulation protective agent and a preparation method thereof. BACKGROUND

[0002] With the continuous improvement of the power level and integration of the high-voltage (HV) and low-voltage (LV) electrical systems of new energy vehicles, the parts such as electrical connectors, busbars, battery poles and wire harness terminals are long-term subjected to vibration impact, frequent thermal expansion and contraction, and complex environments such as moisture and salt spray, and the insulation and protection reliability thereof becomes an important factor affecting the electrical safety and service life of the vehicle. The existing insulation and protection coatings or three-proofing paints for electrical components are mainly based on rigid or semi-rigid polymer systems, and are mainly designed for planar circuit board environments. When applied to the multi-material heterogeneous interfaces and non-planar structures of new energy vehicle high-low voltage connectors, the following problems are prone to occur:

[0003] (1) Microcracks or local debonding occur at the interface between the coating and the metal, plastic and other substrates under the action of vehicle vibration and thermal cycling;

[0004] (2) Water vapor and corrosive media penetrate along the interface microdefects, leading to accelerated electrochemical corrosion and increased risk of electric leakage;

[0005] (3) The construction process of some protective coatings is complex and requires heating or ultraviolet curing, which is not suitable for on-site construction or maintenance scenarios after assembly is completed.

[0006] The prior art CN119039859A discloses a full-solid light-cured coating for power / energy storage battery insulation, and a preparation method and application thereof. It mainly uses epoxy acrylate and polyurethane acrylate as film-forming substances. Although this technology improves coating uniformity by adjusting rheological additives, it must rely on specific light curing equipment in actual application due to the use of ultraviolet curing system, which cannot meet the in-situ maintenance or on-site recoating needs of vehicle parts in a small space. In addition, the crosslinking density of acrylate resin after curing is high, the internal stress is high, and the film layer is relatively rigid. In the high and low temperature impact and continuous vibration environment of new energy vehicles, it is difficult to effectively dissipate interface stress like flexible silicone materials, and brittle cracking or falling off is prone to occur, thereby affecting the durability of insulation and protection.

[0007] Therefore, there is an urgent need to provide an insulation protection technical solution that can adapt to the complex service environment of new energy vehicle high-low voltage connectors, has good interface stability, can be quickly constructed, and takes into account long-term protection. SUMMARY

[0008] The present application aims to provide a new energy vehicle high-low voltage connector insulation protective agent and a preparation method thereof, so as to overcome the shortcomings of the prior art and solve the problems of insufficient interface stability and inconvenient construction and maintenance of the existing protective materials.

[0009] The specific technical scheme is as follows:

[0010] The new energy vehicle high-low voltage connector insulation protective agent is an aerosol type normal temperature curing protective system, and a continuous insulation protective film layer is formed after normal temperature spraying.

[0011] Further, the insulation protective agent comprises the following components by weight fraction: 8-20 parts of main film-forming resin; 0.5-3 parts of adhesion promoter; 0.5-2.5 parts of hydrophobic modifier; 0.2-1 part of stabilizer; 25-45 parts of solvent system; and 35-55 parts of propellant.

[0012] Further, the adhesion promoter is an epoxy silane or a titanate; the hydrophobic modifier is a silicone oil type hydrophobic modifier; the stabilizer is a hindered phenol; the solvent system has a weight ratio of dimethylbenzene: butyl acetate: propylene glycol methyl ether acetate = 5:3:2; and the propellant is one or a combination of dimethyl ether, liquefied petroleum gas and hydrofluoroalkene.

[0013] Further, the preparation method of the new energy vehicle high-low voltage connector insulation protective agent comprises the following steps:

[0014] S1: preparation of a flexible block modifier, including the following specific steps: using allyl-terminated polypropylene glycol and dihydro-terminated polydimethylsiloxane to undergo a silicon-hydrogen addition reaction to obtain a flexible block modifier terminated at both ends by hydrogen-containing siloxane and having a flexible polypropylene glycol segment in the middle;

[0015] S2: preparation of a modified organopolysiloxane film-forming resin, including the following specific steps: first, synthesizing a hydroxyl-terminated polydimethylsiloxane main chain containing a vinyl group, then grafting the flexible block modifier to the main chain and introducing a micro-crosslinking agent, and finally, end-capping to obtain the modified organopolysiloxane film-forming resin;

[0016] S3: mixing the components of the insulation protective agent to obtain an aerosol type normal temperature curing insulation protective agent.

[0017] Further, the silicon-hydrogen addition reaction in step S1 is specifically as follows: the allyl-terminated polypropylene glycol is dissolved in toluene, heated to 80℃, and then platinum catalyst is added, followed by dropwise addition of the toluene solution of dihydrogen-terminated polydimethylsiloxane to carry out the reaction. After dropwise addition is completed, the reaction is continued at 80℃ until the viscosity of the system is stable. After removal of the solvent, the flexible block modifier is obtained. The molar ratio of the allyl-terminated polypropylene glycol to the dihydrogen-terminated polydimethylsiloxane is controlled to be Si-H: allyl = 2.1:2.

[0018] Further, the preparation process of the vinyl-containing hydroxyl-terminated polydimethylsiloxane main chain in step S2 is as follows: the vinylcyclosiloxane and dimethylcyclosiloxane are subjected to ring-opening polymerization reaction in the presence of water and an alkaline catalyst, the reaction temperature is controlled at 135±5℃, and when the viscosity of the system is 2500 mPa·s, acetic acid is added to terminate the reaction, and the unreacted cyclic monomers are removed under reduced pressure at 140℃ to obtain the vinyl-containing hydroxyl-terminated polydimethylsiloxane main chain.

[0019] Further, the process of grafting the flexible block modifier prepared in step S1 to the main chain and introducing a micro-crosslinking agent in step S2 is as follows: the flexible block modifier prepared in step S1 is dropwise added to the vinyl-containing polydimethylsiloxane prepolymer in the presence of a solvent and under the catalysis of platinum catalyst to carry out grafting reaction at 80±5℃. After the grafting reaction is stable, the hydrogen-containing polysiloxane is added as a micro-crosslinking agent to continue the reaction to form micro-crosslinking nodes between the molecular chains. The amount of the hydrogen-containing polysiloxane added is controlled within a range that does not cause the system to gel.

[0020] Further, the end-capping step in step S2 includes: after the micro-crosslinking reaction is completed, hexamethyldisilazane is added to the reaction system to react at 90℃ for 40 minutes to cap the residual hydroxyl groups. After the reaction is completed, distillation is carried out under reduced pressure at 120℃ to finally obtain the modified organopolysiloxane film-forming resin.

[0021] Further, the preparation process of the aerosol type room temperature curing insulation protective agent in step S3 includes: the solvent system is added to a reaction kettle, followed by addition of the modified organopolysiloxane film-forming resin, and the temperature is raised to 50±10℃ for stirring and dissolution. Then, the adhesion promoter, the hydrophobic modifier and the stabilizer are sequentially added, and stirring is carried out for more than 30 minutes until the mixture is uniformly mixed to obtain a stock solution. The stock solution is filtered through a 10μm pore size filter screen and is packaged together with the propellant.

[0022] Compared with the prior art, the present application has the following beneficial effects:

[0023] (1) Improve electrical safety and service life: the protective film layer formed by the modified organic polysiloxane film-forming resin has good dielectric properties, hydrophobicity and salt spray corrosion resistance, which helps to delay the aging failure process of the electrical connection part, and improves the safety and reliability of the electrical system of new energy vehicles.

[0024] (2) Improve the long-term stability of the interface: through the synergistic effect of the main film-forming resin, the adhesion promoter and the hydrophobic modifier, the interface microcracks and debonding phenomena generated by the high-low voltage connector under vibration and thermal expansion and contraction conditions are significantly inhibited, and the risk of water vapor and corrosion medium penetrating along the interface is reduced.

[0025] (3) Adapt to the complex structure and working conditions of new energy vehicles: use aerosol type system, which can form a continuous and uniform protective film layer on the special-shaped structure, gap and hidden part without disassembling the electrical connector, reducing the blind area caused by traditional brushing or spot coating. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 is the preparation process flow chart of the insulation protective agent of the present application;

[0027] Figure 2 is a preparation schematic diagram of the modified organic polysiloxane film-forming resin of the present application;

[0028] Figure 3 is a comparison chart of sample surface drying time and dielectric strength results of the present application and the comparative example;

[0029] Figure 4 is a comparison chart of single spraying film thickness results of the sample of the present application and the comparative example;

[0030] Figure 5 is the infrared spectrum of the modified organic polysiloxane film-forming resin obtained in Example 1 of the present application. DETAILED DESCRIPTION

[0031] The following examples further explain and illustrate the technical solutions of the present application. It is particularly pointed out that each specific embodiment is a specific embodiment and explanation of the technical solution, and should not be regarded as a limitation on the protection scope of the present application. Those skilled in the art still have the right to modify the technical solutions of these examples, to replace some or all of the technical features with equivalent ones, and these modifications or replacements do not change the essence of the corresponding technical solution, and do not make the essence of the corresponding technical solution deviate from the scope of the technical solution described in the present application.

[0032] The present application proposes a kind of insulation protective agent for high-low voltage connector of new energy vehicle and preparation method thereof, as shown in Figure 1 is the preparation process flow chart of the insulation protective agent of the present application, and the specific preparation steps are as follows:

[0033] S1. Preparation of flexible block modifier

[0034] The purpose of this step is to prepare a key modified intermediate which is terminated by hydrogen-containing siloxane (H-PDMS) at both ends and has a flexible polypropylene glycol (PPG) segment in the middle. The unique rigid-flexible-rigid structure of the modified intermediate can effectively introduce the flexibility and hydrophobicity of the PPG segment into the final silicone network, and is the basis for achieving the inhibition of interface micro-cracks and the improvement of electrical safety. As shown in FIG. 1, it is a schematic diagram for preparing the modified organopolysiloxane film-forming resin according to the present application. Figure 2

[0035] Raw materials: allyl-terminated polypropylene glycol (Diallyl-PPG), number average molecular weight Mn = 500 g / mol; dihydrogen-terminated polydimethylsiloxane (H-PDMS-H), Mn = 1000 g / mol; platinum catalyst (Pt-cat); toluene.

[0036] Preparation process: In a clean reaction kettle equipped with mechanical stirring, thermometer, condenser and dropping funnel, 100 parts of Diallyl-PPG and 200 parts of toluene were added, nitrogen protection was started, stirring was started and the temperature was raised to 80°C. At 80°C, 0.02 parts of Pt-cat were added, and stirring was continued at this temperature for 15 minutes to ensure uniform dispersion and activation of the catalyst. 210 parts of H-PDMS-H were dissolved in 500 parts of toluene to ensure that the molar ratio of Si-H to allyl was 2.1:2, i.e. Si-H was slightly excessive, and the solution was slowly added to the reaction kettle through the dropping funnel within 2 hours. The temperature in the kettle should be controlled to be no more than 90°C during the dropping process to prevent the reaction from being too violent. After the dropping was completed, the reaction was continued at 80°C for 4 hours. The system viscosity was monitored by an online viscometer, and the reaction was stopped when the online viscometer reading fluctuated by less than ± 2% within 30 minutes and reached a plateau. After the reaction was completed, the temperature was lowered to room temperature. The toluene solvent was removed under reduced pressure at 70°C to obtain a colorless to light yellow transparent viscous liquid, which was the flexible block modifier H-PDMS-PPG-PDMS-H, and was sealed for use.

[0037] In the H-PDMS-PPG-PDMS-H, Diallyl-PPG is the central flexible block, which provides low-temperature flexibility and stress absorption capacity; H-PDMS-H is the reactive block at the end, which provides silicone properties and Si-H reaction sites.

[0038] S2. Preparation of modified organopolysiloxane film-forming resin

[0039] (1) Preparation of a hydroxyl-terminated polydimethylsiloxane (PDMS-OH) main chain containing a vinyl group:

[0040] ​Raw materials: vinylcyclosiloxane (Vi-D4); dimethylcyclosiloxane (D4); water; basic catalyst KOH; acetic acid neutralizer.

[0041] Preparation process: 60 parts of Vi-D4 and 517 parts of D4 were added to the reaction kettle, with a molar ratio of Vi-D4:D4=1:10 and a vinyl content of 9.1 mol%, 2.5 parts of water and 0.03 parts of KOH were added at the same time, and the temperature was raised to 135±5°C under nitrogen protection, and ring-opening polymerization was started. The reaction was maintained at this temperature, and the system viscosity was monitored by an online viscometer. When the system viscosity was 2500 mPa·s, 0.04 parts of acetic acid neutralizer were added to terminate the reaction; under the condition of 140°C and reduced pressure, the unreacted cyclic monomers and other low-boiling-point substances were removed, and a vinyl-containing PDMS-OH main chain was obtained.

[0042] (2) Directional grafting chain extension of polyether blocks

[0043] Raw materials: the above-obtained block copolymer H-PDMS-PPG-PDMS-H; Pt-cat; dimethylbenzene.

[0044] Molar ratio: vinyl groups in vinyl-containing PDMS-OH main chain: Si-H from block copolymer = 1:0.25.

[0045] Preparation process: the vinyl-containing PDMS-OH main chain prepared in step (1) was added to the reaction kettle, 600 parts of dimethylbenzene were added, and the temperature was heated to 80±5°C under nitrogen protection and stirring; 0.01 parts of Pt-cat were slowly added; 218 parts of H-PDMS-PPG-PDMS-H were prepared into a H-PDMS-PPG-PDMS-H / dimethylbenzene solution with a concentration of 50% (w / w), and were slowly added through a dropwise pump to ensure stable system temperature; the temperature was maintained at 80±5°C, and the reaction was carried out for 2-4 h. The system viscosity was monitored by an online viscometer. When the online viscometer reading fluctuated less than ±2% within 30 minutes and reached a plateau, the reaction was stopped.

[0046] (3) Introduction of micro-crosslinking points

[0047] Raw materials: polymethylhydrosiloxane (PMHS), Mn=800 g / mol, Si-H content 1.6 wt%.

[0048] Preparation process: on the basis of the reaction liquid in step (2), without cooling, continue to keep the system temperature at 80±5℃; 1.5 parts of PMHS is prepared into a PMHS solution with a concentration of 10% (w / w) with xylene, and slowly added to the reaction liquid. Due to the multiple reaction sites, the reaction rate is fast, and it must be added slowly to control the heat of reaction and prevent local overheating from causing gelation. Continue to react for 1-2h, complete the micro-crosslinking process. At this time, the viscosity of the system will increase significantly, but it is controllable, and the final state is still a flowable viscous liquid, without forming a gel.

[0049] (4) End-capping and refining

[0050] Raw material: hexamethyldisilazane (HMDS)

[0051] Preparation process: after step (3) is completed, HMDS is added, and the temperature is raised to 90℃, and reacted for 40min to ensure that all residual -OH is completely capped. After the reaction is completed, the xylene solvent, excess capping agent and low molecular residue in the system are removed under the condition of 120℃ and reduced pressure, and finally the modified organopolysiloxane film-forming resin is obtained.

[0052] S3. Preparation of aerosol type room temperature curing insulation protective agent

[0053] The formula is as follows in terms of weight fraction: 8-20 parts of main film-forming resin; 0.5-3 parts of adhesion promoter; 0.5-2.5 parts of hydrophobic modifier; 0.2-1 part of stabilizer; 25-45 parts of solvent system; 35-55 parts of propellant.

[0054] The main film-forming resin is the self-made modified organopolysiloxane film-forming resin, which is the skeleton of the entire protective film, providing the core insulation, flexibility, weather resistance and hydrophobic properties.

[0055] The adhesion promoter is an epoxy silane or a titanate, which can form a chemical bond with the hydroxyl group on the surface of the metal or plastic substrate at one end of the molecule, and can be physically entangled or reacted with the silicone resin at the other end, like double-sided tape, greatly enhancing the bonding force of the film layer and the joint substrate.

[0056] The hydrophobic modifier is a silicone oil type hydrophobic modifier, which is used to further reduce the surface energy of the film layer, effectively repel liquid water, and prevent the formation of conductive water film.

[0057] The stabilizer is a hindered phenol. The solvent system is xylene: butyl acetate: propylene glycol methyl ether acetate = 5:3:2 in terms of weight ratio. The propellant is one or a combination of dimethyl ether (DME), liquefied petroleum gas (LPG) and hydrofluoroalkene (HFO).

[0058] Preparation step: solvent system was added into a mixing kettle, stirring was started, main film-forming resin was added, the jacket was heated to 50±10℃, the viscosity was reduced, and the fluidity was good; adhesion promoter, hydrophobic modifier and stabilizer were added in turn, stirring was continued for 30 minutes to ensure that all the additives were completely dissolved and uniformly dispersed in the resin; the obtained liquid was precisely filtered through a 10 μm filter to remove any small impurities. The obtained solution was filled into a pressure-resistant aerosol can, the aerosol valve was immediately buckled on the can opening and sealed. The can was filled with propellant through the valve, the packaging was completed, and an aerosol type room temperature curing insulation protective agent was obtained.

[0059] Reagents used in the following examples

[0060]

[0061] Example 1

[0062] 1. Preparation of flexible block modifier

[0063] In a reaction kettle, 100 parts of Diallyl-PPG and 200 parts of toluene were added, nitrogen protection, stirring and heating to 80℃, 0.02 parts of Pt-cat was added, and stirring was continued at this temperature for 15 minutes. Then, 210 parts of H-PDMS-H was dissolved in 500 parts of toluene, and was slowly dropped into the reaction kettle through a dropping funnel within 2 hours, and the temperature during dropping was controlled to be not more than 90℃. After dropping was completed, the reaction was continued for 4 hours, at this time, the online viscometer reading fluctuated less than ±2% within 30 minutes and reached a plateau, and the reaction was stopped. After the reaction was completed, the temperature was reduced to room temperature. The toluene solvent was removed under reduced pressure at 70℃, and a colorless to light yellow transparent viscous liquid was obtained, which was the flexible block modifier H-PDMS-PPG-PDMS-H, and was sealed for use.

[0064] 2. Preparation of modified organopolysiloxane film-forming resin

[0065] (1) Preparation of PDMS main chain containing vinyl group: 60 parts of Vi-D4 and 517 parts of D4 were added into a reaction kettle, 2.5 parts of water and 0.03 parts of KOH were added at the same time, and the temperature was increased to 135±5℃ under nitrogen protection, and the reaction was continued at this temperature for 5 hours, at this time, the online viscometer monitored the viscosity of the system to be 2500 mPa·s, 0.04 parts of acetic acid neutralizer was added to terminate the reaction; the unreacted cyclic monomer and other low boiling point substances were removed under reduced pressure at 140℃, and a PDMS-OH main chain containing vinyl group was obtained.

[0066] (2) Directional grafting and chain extension of polyether blocks: The vinyl PDMS-OH main chain obtained in step (1) was added to the reactor, 600 parts of xylene were added, and the mixture was heated to 80±5℃ under nitrogen protection and stirring; 0.01 parts of Pt-cat were slowly added; 218 parts of H-PDMS-PPG-PDMS-H were prepared into a 50% (w / w) H-PDMS-PPG-PDMS-H / xylene solution, which was slowly added to the reaction solution by a drop pump, and the temperature was maintained at 80±5℃. The reaction was carried out for 3 hours. When the online viscometer reading fluctuated less than ±2% within 30 minutes and reached the plateau period, the reaction was stopped.

[0067] (3) Introduction of micro-crosslinking points: Based on the reaction solution in step (2), continue to maintain the system temperature at 80±5℃, and slowly add 1.5 parts of PMHS to the reaction solution to prepare a 10% (w / w) PMHS solution with xylene. Continue the reaction for 2 hours to complete the micro-crosslinking process.

[0068] (4) End-capping and purification: After step (3) is completed, HMDS is added, the temperature is raised to 90℃, and the reaction is carried out for 40 min. After the reaction is completed, the xylene solvent, excess end-capping agent, and low molecular weight residues in the system are removed under reduced pressure at 120℃ to finally obtain the self-made modified organopolysiloxane film-forming resin, which is then cooled for later use. (See attached...) Figure 5 The image shows the infrared spectrum of the modified organopolysiloxane film-forming resin obtained in this embodiment: In the spectrum, 2914 cm⁻¹ -1 and 2847cm -1 A strong saturated CH stretching vibration peak appeared at 1047 cm⁻¹. -1 A very broad and deep composite absorption band exists at this point, attributed to the overlapping vibrations of Si-O-Si and COC bonds in the polyether segment, confirming the successful grafting of the flexible polyether segment; 1623 cm⁻¹ -1 The weak absorption peak at 1301 cm⁻¹ corresponds to a small amount of residual vinyl groups, confirming the occurrence and extent of the addition reaction; simultaneously, the absorption peak at 1301 cm⁻¹... -1 and 821cm -1 The typical absorption peak at 2160 cm⁻¹ reflects the characteristic structure of the organosilicon framework. Furthermore, the peak at 2160 cm⁻¹... -1 and 3400cm -1 There was no significant absorption in the area, and 682cm -1 The characteristic peak at that point corresponds to the trimethylsilyl group, indicating that the hydrosilylation reaction was complete and the end-capping was thorough.

[0069] 3. Preparation of aerosol-type room-temperature curing insulating protective agent

[0070] Formulation by weight ratio: 8 parts of modified organopolysiloxane film-forming resin; 0.5 parts of epoxy silane adhesion promoter Silquest A-187; 0.5 parts of silicone oil type hydrophobic modifier PMX-200; 0.2 parts of stabilizer Irganox 1010; 25 parts of solvent system: xylene: butyl acetate: propylene glycol methyl ether acetate = 5:3:2; 35 parts of DME.

[0071] Preparation method: add 25 parts of solvent system in the reaction kettle, start stirring. Slowly add 8 parts of modified organopolysiloxane film-forming resin, heat the jacket to 50±10°C, continue stirring until completely dissolved. Add 0.5 parts of Silquest A-187, 0.5 parts of PMX-200 and 0.2 parts of Irganox 1010 in turn, continue stirring for 30 minutes to obtain the stock solution. The stock solution is filtered through a 10 μm pore size filter screen, then filled with 35 parts of DME in an aerosol pressure tank to finally obtain an aerosol type insulation protective agent.

[0072] Example 2

[0073] Formulation by weight ratio: take 14 parts of modified organopolysiloxane film-forming resin of the same batch as in Example 1; 1.5 parts of epoxy silane adhesion promoter Silquest A-187; 1.5 parts of silicone oil type hydrophobic modifier AK-1000; 0.5 parts of stabilizer Irganox 1010; 34.5 parts of solvent system: xylene: butyl acetate: propylene glycol methyl ether acetate = 5:3:2 by weight ratio; 48 parts of propellant LPG. The preparation process is the same as in Example 1 to finally obtain an aerosol type insulation protective agent.

[0074] Example 3

[0075] Formulation by weight ratio: take 20 parts of modified organopolysiloxane film-forming resin of the same batch as in Example 1; 3 parts of titanium adhesion promoter Tyzor TPT; 2.5 parts of silicone oil type hydrophobic modifier KF-96L; 1 part of stabilizer Irganox 1010; 45 parts of solvent system: xylene: butyl acetate: propylene glycol methyl ether acetate = 5:3:2 by weight ratio; 55 parts of propellant HFO. The preparation process is the same as in Example 1 to finally obtain an aerosol type insulation protective agent.

[0076] Comparative Example 1

[0077] The same as in Example 1, except that the main film-forming resin is polyurethane three-proofing paint HumiSeal 1A33.

[0078] Comparative Example 2

[0079] Use commercially available aerosol type acrylic three-proofing paint MG Chemicals 419E.

[0080] Comparative Example 3

[0081] The same as Example 1, except that no adhesion promoter and hydrophobic modifier were added.

[0082] Performance test:

[0083] Sample preparation: The test substrate was selected as a purple copper bar with a size of 100 mm x 50 mm x 2 mm and a PBT-GF30 sample plate with a size of 100 mm x 50 mm x 2 mm. All substrates were wiped with absolute ethanol to remove oil and dried for standby. In an environment of 25 ± 2℃ and humidity of 50 ± 5%, the aerosol products of the examples and comparative examples were shaken well, sprayed at a distance of 15-20 cm from the substrate, and tested after standing for 24 hours.

[0084] 1. Tack-free time: measured according to the finger touch method in GB / T 1728-2020 "Paint film, putty film drying time determination method". Record the time when the finger touches the surface of the paint film without sticking hand and no fingerprint mark, unit min, keep one decimal place.

[0085] 2. Single spray film thickness: at room temperature, use a dry film thickness gauge to measure the cured film layer on the surface of the metal substrate at multiple points, unit μm, keep integer.

[0086] 3. Dielectric strength: tested according to GB / T 1408.1-2016 "Insulating materials - Electrical strength test methods". The protective agent was sprayed on the copper sheet, and the breakdown voltage was tested after curing to calculate the dielectric strength (kV / mm), and the result was kept to one decimal place.

[0087] 4. Adhesion evaluation: according to GB / T 9286-2021 "Paint and varnish cross-cut test". Use a cross-cut knife with a 1 mm spacing to draw a cross on the PBT-GF30 sample plate and the copper substrate, respectively, paste high-adhesion pressure-sensitive tape and quickly tear it open, observe the peeling condition, and evaluate the grade as 0-5, with 0 being the best.

[0088] 5. Neutral salt spray test: according to GB / T 10125-2021 "Artificial atmosphere corrosion test - Salt spray test" standard. Draw "X" marks on the surface of the copper bar sprayed with the protective agent to damage the coating to the substrate, place it in the salt spray chamber for continuous spraying for 240 h, and observe the corrosion expansion at the scratch and whether there is blistering and rusting in the non-scratch area.

[0089] 6. Thermal cycle test: simulate the high and low temperature environment of new energy vehicles. Set the temperature cycle range to -40℃ to +125℃, with a high and low temperature residence time of 30 min each, and a conversion time of <5 min. After 50 cycles, observe whether the film layer has cracking, peeling or peeling phenomenon.

[0090] 7. Vibration test: refer to ISO 16750-3 Road vehicles - Environmental conditions and testing for electrical and electronic equipment - Part 3: Mechanical loads. The sprayed sample was fixed on the vibration table, and the random vibration test was carried out with the frequency of 10-1000 Hz and the root mean square value of acceleration of 27.8 m / s2 for 8 hours. The film layer integrity was observed after the test. 2

[0091] Table 2: Test results of basic physical and electrical properties of each example and comparative example

[0092]

[0093] Table 3: Test results of reliability and environmental adaptability of each example and comparative example

[0094]

[0095] Analysis of the comparison results of Table 2 and Table 3:

[0096] (1) The aerosol type insulation protective agent prepared in Examples 1-3 is superior to Comparative Examples 1-3 in terms of surface drying time, single spraying film thickness and dielectric strength, and meets the industry application standards, as shown in Tables 1-3. Figure 3 4 The adhesion test, salt spray test, thermal cycle test and vibration test results show that the flexible chain segment introduced by the flexible block modifier in the present application gives the resin excellent stress dissipation ability, enabling it to adapt to the deformation of the high and low voltage connector of the new energy vehicle under extreme temperature difference and severe jolting, and maintaining the continuity and integrity of the film layer.

[0097] (2) The results of Comparative Example 1 show that although the polyurethane three-proofing paint has acceptable initial adhesion, micro-cracks appear at the interface after the thermal cycle test. This is because the polyurethane resin is rigidly enhanced at low temperature, and the stress in the film layer is large. Comparative Example 2 uses a commercially available acrylic three-proofing paint, which meets the requirements of conventional electronic protection applications in terms of dielectric strength and surface drying time, but the film layer integrity significantly decreases after salt spray, thermal cycle and vibration tests, with phenomena such as blistering, peeling and brittle fracture, indicating that this type of material lacks long-term reliability under complex vehicle conditions. The silicone modified system of the present application maintains excellent flexible and elastic properties and strain resistance in a wide temperature range, effectively avoiding cracking caused by stress concentration.

[0098] (3) Comparative Example 3 uses the same main film-forming resin as Example 1, but does not add adhesion promoters and hydrophobic modifiers. The test results show that the dielectric strength of Comparative Example 3 decreases significantly, the adhesion is poor, the single spraying film thickness is significantly reduced, and large area corrosion and peeling occur in the salt spray test. This strongly proves the necessity of the adhesion promoters and hydrophobic modifiers in the present application. ​​

[0099] In summary, the insulation protective agent provided by the present application effectively solves the problems of poor temperature resistance, insufficient interface bonding force and the like in the prior art through specific modification of the resin structure and synergistic compounding of functional additives, and significantly improves the safety and reliability of the electrical connection system of the new energy vehicle.

Claims

1. An insulating protective agent for high and low voltage joints in new energy vehicles, which is an aerosol-type room-temperature curing protective system that forms a continuous insulating protective film layer after being sprayed at room temperature, characterized in that... The insulating protective agent is composed of a main film-forming resin, an adhesion promoter, a hydrophobic modifier, a stabilizer, a solvent system, and a propellant. The main film-forming resin is a modified organopolysiloxane film-forming resin containing polyether flexible segments. It has a polydimethylsiloxane main chain, side chains containing polyether flexible segments, and micro-crosslinking nodes formed by hydrogen-containing polysiloxane. The residual hydroxyl groups at the ends of the polydimethylsiloxane main chain are end-capped with hexamethyldisilazane. The preparation method of the modified organopolysiloxane film-forming resin containing polyether flexible segments is as follows: first, allyl-terminated polypropylene glycol and dihydro-terminated polydimethylsiloxane undergo a hydrosilylation reaction to prepare a flexible block modifier; then, a vinyl-containing hydroxyl-terminated polydimethylsiloxane main chain is synthesized, the flexible block modifier is grafted onto the main chain, and a micro-crosslinking agent is introduced and the chain is end-capped.

2. The insulating protective agent for high and low voltage joints of new energy vehicles as described in claim 1, characterized in that, The insulating protective agent comprises the following components by weight: 8-20 parts of main film-forming resin; 0.5-3 parts of adhesion promoter; 0.5-2.5 parts of hydrophobic modifier; 0.2-1 parts of stabilizer; 25-45 parts of solvent system; and 35-55 parts of propellant.

3. The insulating protective agent for high and low voltage joints of new energy vehicles as described in claim 2, characterized in that, The adhesion promoter is an epoxy silane or titanate; the hydrophobic modifier is a silicone oil-type hydrophobic modifier; the stabilizer is a hindered phenol; the solvent system is xylene: butyl acetate: propylene glycol methyl ether acetate = 5:3:2 by weight; the propellant is one or a combination of dimethyl ether, liquefied petroleum gas, and hydrofluoroolefins.

4. A method for preparing an insulating protective agent for high and low voltage joints of new energy vehicles according to any one of claims 1-3, characterized in that, Includes the following steps: S1: The preparation of the flexible block modifier includes the following steps: using allyl-terminated polypropylene glycol and dihydro-terminated polydimethylsiloxane to undergo a hydrosilylation reaction to prepare a flexible block modifier with hydrogen-containing siloxane end caps at both ends and flexible polypropylene glycol segments in the middle. S2: Preparation of modified organopolysiloxane film-forming resin, the specific steps include: first synthesizing a vinyl-containing hydroxyl-terminated polydimethylsiloxane backbone, then grafting the flexible block modifier onto the backbone and introducing a micro-crosslinking agent, then capping, and finally obtaining the modified organopolysiloxane film-forming resin. S3: The components of the insulating protective agent are mixed to obtain an aerosol-type room temperature curing insulating protective agent.

5. The preparation method of the insulating protective agent for high and low voltage joints of new energy vehicles as described in claim 4, characterized in that, The specific steps of the hydrosilylation reaction in step S1 are as follows: allyl-terminated polypropylene glycol is dissolved in toluene, heated to 80°C, a platinum catalyst is added, and then a toluene solution of dihydro-terminated polydimethylsiloxane is added dropwise for reaction. After the addition is complete, the reaction continues at 80°C until the viscosity of the system stabilizes. After removing the solvent, a flexible block modifier is obtained. The molar ratio of allyl-terminated polypropylene glycol to dihydro-terminated polydimethylsiloxane is controlled at Si-H:allyl = 2.1:

2.

6. The preparation method of the insulating protective agent for high and low voltage joints of new energy vehicles as described in claim 4, characterized in that, The preparation process of the vinyl-containing hydroxyl-terminated polydimethylsiloxane backbone in step S2 is as follows: 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane and octamethylcyclotetrasiloxane are subjected to ring-opening polymerization reaction in the presence of water and an alkaline catalyst. The reaction temperature is controlled at 135±5℃. When the viscosity of the system reaches 2500 mPa·s, acetic acid is added as a neutralizing agent to terminate the reaction. Unreacted cyclic monomers are removed under reduced pressure at 140℃ to obtain the vinyl-containing hydroxyl-terminated polydimethylsiloxane backbone.

7. The preparation method of the insulating protective agent for high and low voltage joints of new energy vehicles as described in claim 4, characterized in that, The process of grafting onto the main chain and introducing a micro-crosslinking agent in step S2 is as follows: In the presence of a solvent and under the catalysis of a platinum catalyst, the flexible block modifier obtained in step S1 is added dropwise to the vinyl-containing hydroxyl-terminated polydimethylsiloxane main chain, and the grafting reaction is carried out at 80±5℃; after the grafting reaction is stable, hydrogen-containing polysiloxane is added dropwise as a micro-crosslinking agent, and the reaction continues to form micro-crosslinking nodes between molecular chains; wherein, the amount of hydrogen-containing polysiloxane added is controlled within a range that does not cause the system to gel.

8. The preparation method of the insulating protective agent for high and low voltage joints of new energy vehicles as described in claim 4, characterized in that, The end-capping step in step S2 includes: after the micro-crosslinking reaction is completed, adding hexamethyldisilazane to the reaction system and reacting at 90°C for 40 minutes to cap the residual hydroxyl groups; after the reaction is completed, distilling under reduced pressure at 120°C to finally obtain the modified organopolysiloxane film-forming resin.

9. The preparation method of the insulating protective agent for high and low voltage joints of new energy vehicles as described in claim 4, characterized in that, The specific preparation process of the aerosol-type room temperature curing insulating protective agent in step S3 includes: adding the solvent system to the reaction vessel, followed by adding the modified organopolysiloxane film-forming resin, heating to 50±10℃ and stirring to dissolve; then, sequentially adding the adhesion promoter, the hydrophobic modifier and the stabilizer, stirring for more than 30 minutes until uniformly mixed to obtain the stock solution; filtering the stock solution through a 10μm pore size filter and then encapsulating it together with the propellant.

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