Anti-aging insulating paint and preparation method thereof

Abstract

The invention relates to the technical field of coatings, in particular to an anti-aging insulating coating and a preparation method thereof.The insulating coating is prepared from, by weight, 15-25 parts of hydroxyl-terminated polysiloxane, 2-5 parts of diluent, 0.5-3 parts of cross-linking agent, 30-35 parts of filler, 0.01-0.03 part of catalyst and 42-47 parts of solvent. The insulating paint prepared by the invention has the advantages of higher mechanical strength, favorable aging resistance and favorable insulating property.

Description

Technical Field

[0001] This invention relates to the field of coating technology, specifically to an aging-resistant insulating coating and its preparation method. Background Technology

[0002] Insulating coatings, also known as insulating varnishes, are functional coatings with excellent electrical insulation properties. Belonging to the category of dielectric materials, their core function is to isolate conductive parts at different potentials, ensuring the safe and stable operation of electrical equipment. Often referred to as the "heart of the motor," their performance directly determines the economic and technical indicators and service life of electrical equipment. Since the successful trial production of phenolic resin in 1907, marking the birth of insulating materials, insulating coatings have gradually evolved from early simple resin systems to diversified products covering various substrates such as epoxy resin, silicone resin, and polyimide, adapting to different application scenarios. They are widely used in core sectors of the national economy, including power systems, new energy equipment, rail transportation, and electronic components.

[0003] Patent CN104212345B discloses an insulating coating specifically for plasma equipment, comprising the following components by weight: 25-40 parts methyl ethylene silicone rubber, 5-15 parts polyester-modified silicone resin, 5-15 parts nano-attapulgite, 5-15 parts mica powder, 15-30 parts butanol, 10-15 parts butyl acetate, 1-5 parts curing agent, 0.5-2 parts stabilizer, and 0.1-0.5 parts silane coupling agent. This invention not only possesses excellent insulation properties but also meets the requirements of plasma equipment for pressure resistance, flame retardancy, flashover prevention, corrosion resistance, and ozone resistance.

[0004] Patent CN115058192B discloses an anti-arc insulating coating for electric locomotives, comprising component A and component B in a mass ratio of 100:(5-10). Component A comprises the following raw materials in parts by weight: 100 parts of hydroxyl-terminated polydimethylsiloxane, 30-100 parts of dimethyl silicone oil, 10-40 parts of silica, 5-15 parts of diatomaceous earth, 20-40 parts of aluminum hydroxide, 3-5 parts of color paste, and 100-300 parts of mixed solvent. Component B comprises the following raw materials in parts by weight: 1-10 parts of crosslinking agent, 1-10 parts of silane coupling agent, 1-5 parts of catalyst, and 20-50 parts of mixed solvent. The anti-arc insulating coating provided by this invention, by using a mixed solvent and combining diatomaceous earth with a specific crosslinking system, ensures uniform dispersion of all raw materials in the coating. When the coating thickness reaches 10 mm, it significantly shortens the surface drying and deep curing times while maintaining excellent mechanical strength and electrical properties.

[0005] As described in the aforementioned patent, current insulating coatings have optimized their insulation performance, corrosion resistance, and mechanical properties. However, insulating coatings are widely used in various electrical equipment such as generators, transformers, switch cabinets, and power transmission lines. They are exposed to complex outdoor environments or high-temperature conditions inside the equipment for a long time. The performance requirements for insulating coatings are becoming increasingly stringent, especially their aging resistance. There is an urgent need to develop an aging-resistant insulating coating on the market. Summary of the Invention

[0006] In view of the problems existing in the prior art, the purpose of this invention is to obtain an aging-resistant insulating coating that not only has high mechanical strength, but also excellent insulation, high aging resistance, and long service life.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The first aspect of the present invention provides an aging-resistant insulating coating, comprising, by weight, the following raw materials: 15-25 parts of hydroxyl-terminated polysiloxane, 2-5 parts of diluent, 0.5-3 parts of crosslinking agent, 30-35 parts of filler, 0.01-0.03 parts of catalyst, and 42-47 parts of solvent.

[0008] In some embodiments, the diluent is epoxy-modified silicone oil.

[0009] In some embodiments, the crosslinking agent is methyltributanone oxime silane.

[0010] In some embodiments, the method for preparing the filler includes the following steps: (1) Add titanate coupling agent, 3-aminopropyltrimethylsilane and titanium dioxide to ethanol and stir at 35-45℃ for 1-2h. Filter and dry to obtain pretreated titanium dioxide. (2) Dissolve 3-(2,3-epoxypropoxy)propyltrimethoxysilane in ethanol, then add aluminum hydroxide and stir at 35-40℃ for 1-2 hours. Filter and dry to obtain pretreated aluminum hydroxide. (3) Under nitrogen protection, the pretreated titanium dioxide obtained in step (1) and the pretreated aluminum hydroxide obtained in step (2) are added to anhydrous ethanol, heated to 60-65℃, reacted for 45-55h, filtered, dried, and ground to obtain the filler.

[0011] In the current field of insulating coating fillers, conventional methods to improve the compatibility between fillers and organic resins mainly involve surface modification of single inorganic particles using a single coupling agent. While this approach can improve dispersibility to some extent, it lacks effective bridging between different inorganic particles, leading to particle agglomeration and ultimately limited improvement in coating insulation performance and aging resistance. In contrast, this application uses a differentiated coupling agent system for titanium dioxide and aluminum hydroxide: titanium dioxide is treated with a combination of titanate coupling agent and aminopropyltrimethylsilane. The titanate coupling agent forms coordination bonds with the hydroxyl groups on the titanium dioxide surface, while the amino groups introduced by the aminopropyltrimethoxysilane provide active sites for subsequent reactions. Aluminum hydroxide is treated with epoxy silane, allowing the epoxy groups to undergo ring-opening reactions with the hydroxyl groups on the aluminum hydroxide surface, thus connecting titanium dioxide and aluminum hydroxide through chemical bonds. This specific reaction-constructed "organic-inorganic-organic" cross-linked structure significantly enhances the interfacial compatibility between the filler and the terminal hydroxyl polysiloxane, resulting in improved mechanical properties, aging resistance, and insulation stability of the coating.

[0012] In some embodiments, the mass ratio of the titanate coupling agent, 3-aminopropyltrimethylsilane and titanium dioxide in step (1) is (0.05-0.07):(0.01-0.05):1.

[0013] In some embodiments, the mass ratio of 3-(2,3-epoxypropoxy)propyltrimethoxysilane to aluminum hydroxide in step (2) is (0.01-0.04):1.

[0014] In some embodiments, the mass ratio of pretreated titanium dioxide to pretreated aluminum hydroxide in step (3) is 1:(2-3).

[0015] This invention avoids the problem of insufficient reaction sites for chemical bonding with epoxy-silane-treated aluminum hydroxide due to competitive adsorption of the two coupling agents on the titanium dioxide surface, which reduces the compatibility between the filler and the silicone rubber matrix, by limiting the ratio of titanate coupling agent, 3-aminopropyltrimethylsilane, and titanium dioxide. This ensures that the titanium dioxide surface simultaneously retains sufficient titanate bonding sites and an appropriate amount of amino reactive groups, achieving a dual balance between dispersibility and reactivity. Furthermore, this invention limits the ratio of 3-(2,3-epoxypropoxy)propyltrimethoxysilane to aluminum hydroxide to avoid excessive use of silane coupling agent. This invention avoids the problem of insufficient epoxy group modification density on the aluminum hydroxide surface, leading to low reaction efficiency with aminated titanium dioxide. It also prevents excessive silane from undergoing self-condensation, forming a loose oligomer layer on the aluminum hydroxide surface, which weakens the bonding strength between the filler and the polysiloxane matrix, resulting in decreased mechanical properties and material waste. Furthermore, this invention limits the ratio of pretreated titanium dioxide to pretreated aluminum hydroxide to form an aluminum hydroxide-based structure with titanium dioxide as the dispersed reinforcing phase. This ensures moderate overall filler density and stable dispersion, achieving efficient UV shielding and improving aging resistance of the coating.

[0016] In some embodiments, the catalyst is an organotin catalyst.

[0017] In some embodiments, the solvent is tetrachloroethylene.

[0018] A second aspect of this invention provides a method for preparing an aging-resistant insulating coating, comprising the following steps: Under inert gas protection, hydroxyl-terminated polysiloxane, diluent, and filler are stirred at room temperature for 1-2 hours, then solvent is added and stirred for 20-30 minutes, and then crosslinking agent and catalyst are added and stirred for 5-10 minutes to obtain an aging-resistant insulating coating.

[0019] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention prepares an aging-resistant insulating coating by using hydroxyl-terminated polysiloxane, filler, crosslinking agent and other additives, which has the advantages of high mechanical strength, good aging resistance and good insulation.

[0020] (2) In this invention, titanium dioxide and aluminum hydroxide are treated with epoxy silane. The epoxy group can undergo a ring-opening reaction with the hydroxyl groups on the surface of aluminum hydroxide. A differentiated coupling agent system is used to connect titanium dioxide and aluminum hydroxide through chemical bonds, which enhances the interfacial compatibility between the filler and the terminal hydroxyl polysiloxane body, thereby improving the mechanical properties, aging resistance and insulation stability of the coating.

[0021] (3) By limiting the ratio of titanate coupling agent, 3-aminopropyltrimethylsilane and titanium dioxide, and the ratio of 3-(2,3-epoxypropoxy)propyltrimethoxysilane and aluminum hydroxide, the present invention solves the compatibility problem between filler and silicone rubber matrix and achieves a dual balance of dispersibility and reactivity. In addition, by limiting the ratio of pretreated titanium dioxide and pretreated aluminum hydroxide, the coating achieves high-efficiency UV shielding and improves aging resistance while ensuring that the overall density of the filler is moderate and the dispersion is stable. Detailed Implementation

[0022] The present invention will be described below with reference to specific embodiments. It should be noted that the following embodiments are examples of the present invention and are used only to illustrate the invention, not to limit it. Other combinations and various modifications within the scope of the present invention can be made without departing from its spirit or scope.

[0023] In the following examples and comparative examples, the compounds and related reagents used were all commercially available. The hydroxyl-terminated polysiloxane was silicone rubber 107, purchased from Shandong Dayi Chemical Co., Ltd., with a viscosity of 20,000 mPa·s at 25°C. The epoxy-modified silicone oil was model DY-E701, purchased from Shandong Dayi Chemical Co., Ltd. The titanium dioxide was purchased from Lingshou County Qianhao Mineral Products Processing Plant, with an average particle size of 10,000 mesh. The aluminum hydroxide was nano-aluminum hydroxide, purchased from Shanghai Qiaowei Chemical Technology Co., Ltd.

[0024] Unless otherwise specified, the post-processing steps such as "washing", "drying", "filtration", "rotary evaporation", and "reduced pressure distillation" used below are routine operations for those skilled in the art, and can be selected according to actual operation.

[0025] Preparation Example 1 The preparation method of filler-1 includes the following steps: (1) Add 0.6g titanate coupling agent PN-130, 0.3g 3-aminopropyltrimethylsilane and 10g titanium dioxide to 100ml 95wt% ethanol solution and stir at 40℃ for 1.5h. Filter and dry to obtain pretreated titanium dioxide. (2) Dissolve 0.9g of 3-(2,3-epoxypropoxy)propyltrimethoxysilane in 200ml of 95wt% ethanol solution, then add 30g of aluminum hydroxide and stir at 40℃ for 1.5h. Filter and dry to obtain pretreated aluminum hydroxide. (3) Under nitrogen protection, 10g of pretreated titanium dioxide obtained in step (1) and 25g of pretreated aluminum hydroxide obtained in step (2) were added to 500ml of anhydrous ethanol, heated to 63℃, reacted for 50h, filtered, dried, and ground for 2h at a grinding speed of 200rpm and a ball-to-material ratio of 8:1 to obtain filler-1.

[0026] Preparation Example 2 The preparation method of filler-2 is the same as that of preparation example 1, except that the amount of titanate coupling agent PN-130 added is 0.9g.

[0027] Preparation Example 3 The preparation method of filler-3 is the same as that of preparation example 1, except that the amount of 3-aminopropyltrimethylsilane added is 0.8g.

[0028] Preparation Example 4 The preparation method of filler-4 is the same as that of preparation example 1, except that the amount of 3-(2,3-epoxypropoxy)propyltrimethoxysilane added is 1.2g.

[0029] Preparation Example 5 The preparation method of filler-5 is the same as that of preparation example 1, except that the amount of pretreated aluminum hydroxide added is 35g.

[0030] Preparation Example 6 The preparation method of filler-6 includes the following steps: (1) Add 0.6g titanate coupling agent PN-130, 0.3g 3-aminopropyltrimethylsilane and 10g titanium dioxide to 100ml 95wt% ethanol solution and stir at 40℃ for 1.5h. Filter and dry to obtain pretreated titanium dioxide. (2) Dissolve 0.9g of γ-methacryloxypropyltrimethoxysilane in 200ml of 95wt% ethanol solution, then add 30g of aluminum hydroxide and stir at 40℃ for 1.5h. Filter and dry to obtain pretreated aluminum hydroxide. (3) Under nitrogen protection, 10g of pretreated titanium dioxide obtained in step (1) and 25g of pretreated aluminum hydroxide obtained in step (2) were added to 500ml of anhydrous toluene, and then 0.35g of triethylamine was added. The temperature was raised to 63℃ and reacted for 12h. The mixture was filtered, dried, and ground for 2h at a grinding speed of 200rpm and a ball-to-material ratio of 8:1 to obtain filler-6.

[0031] Preparation Example 7 The preparation method of filler-7 includes the following steps: (1) Add 0.6g titanate coupling agent PN-130, 0.3g 3-aminopropyltrimethylsilane and 10g titanium dioxide to 100ml 95wt% ethanol solution and stir at 40℃ for 1.5h. Filter and dry to obtain pretreated titanium dioxide. (2) Dissolve 0.9g of 3-(2,3-epoxypropoxy)propyltrimethoxysilane in 200ml of 95wt% ethanol solution, then add 30g of aluminum hydroxide and stir at 40℃ for 1.5h. Filter and dry to obtain pretreated aluminum hydroxide. (3) Under nitrogen protection, 10g of pretreated titanium dioxide obtained in step (1) and 25g of pretreated aluminum hydroxide obtained in step (2) were ground for 2 hours at a grinding speed of 200 rpm and a ball-to-material ratio of 8:1 to obtain filler-7.

[0032] Example 1 An aging-resistant insulating coating comprises, by weight, the following raw materials: 107 20 parts silicone rubber, 4 parts epoxy modified silicone oil, 1.8 parts methyl tributanone oxime silane, 1 33 parts filler-1, 0.02 parts dibutyltin dilaurate, and 45 parts tetrachloroethylene.

[0033] The preparation method of the aging-resistant insulating coating in this embodiment includes the following steps: Under nitrogen protection, silicone rubber 107, epoxy modified silicone oil, and filler-1 were stirred at 300 rpm for 1.5 h at room temperature. Tetrachloroethylene was then added and stirred for 25 min. Methyl tributanone oxime silane and dibutyltin dilaurate were then added and stirred for 8 min to obtain an aging-resistant insulating coating.

[0034] Example 2 An aging-resistant insulating coating comprises, by weight, the following raw materials: 15 parts silicone rubber, 2 parts epoxy modified silicone oil, 0.5 parts methyl tributanone oxime silane, 30 parts filler-1, 0.01 parts dibutyltin dilaurate, and 42 parts tetrachloroethylene.

[0035] The preparation method of the aging-resistant insulating coating in this embodiment includes the following steps: Under nitrogen protection, silicone rubber, epoxy modified silicone oil, and filler-1 were stirred at 300 rpm for 1 hour at room temperature. Tetrachloroethylene was then added and stirred for 20 minutes. Methyl tributanone oxime silane and dibutyltin dilaurate were then added and stirred for 5 minutes to obtain an aging-resistant insulating coating.

[0036] Example 3 An aging-resistant insulating coating comprises, by weight, the following raw materials: 107 25 parts silicone rubber, 5 parts epoxy modified silicone oil, 3 parts methyl tributanone oxime silane, 1 35 parts filler, 0.03 parts dibutyltin dilaurate, and 47 parts tetrachloroethylene.

[0037] The preparation method of the aging-resistant insulating coating in this embodiment includes the following steps: Under nitrogen protection, silicone rubber, epoxy modified silicone oil, and filler-1 were stirred at 300 rpm for 2 hours at room temperature. Tetrachloroethylene was then added and stirred for 30 minutes. Methyl tributanone oxime silane and dibutyltin dilaurate were then added and stirred for 10 minutes to obtain an aging-resistant insulating coating.

[0038] Example 4 An aging-resistant insulating coating and its preparation method are described. The specific implementation method is the same as that in Example 1, except that filler-1 is replaced with filler-2 in equal amounts.

[0039] Example 5 An aging-resistant insulating coating and its preparation method are described. The specific implementation method is the same as that in Example 1, except that filler-1 is replaced with filler-3 in equal amounts.

[0040] Example 6 An aging-resistant insulating coating and its preparation method are described. The specific implementation method is the same as in Example 1, except that filler-1 is replaced with filler-4 in equal amounts.

[0041] Example 7 An aging-resistant insulating coating and its preparation method are described. The specific implementation method is the same as that in Example 1, except that filler-1 is replaced with filler-5 in equal amounts.

[0042] Example 8 An aging-resistant insulating coating and its preparation method are described. The specific implementation method is the same as in Example 1, except that filler-1 is replaced with filler-6 in equal amounts.

[0043] Example 9 An aging-resistant insulating coating and its preparation method are described. The specific implementation method is the same as that in Example 1, except that filler-1 is replaced with filler-7 in equal amounts.

[0044] Example 10 An aging-resistant insulating coating and its preparation method are disclosed. The specific implementation method is the same as that in Example 1, except that filler-1 is replaced in equal amounts with a mixture of titanium dioxide and aluminum hydroxide, with a mass ratio of 1:2.5.

[0045] Performance testing The coatings obtained from each embodiment and comparative example were added to molds and cured for 4 hours according to the method in "DL / T 627-2018 Room Temperature Curing Silicone Rubber Anti-Pollution Flashover Coating for Insulators" to prepare 6mm thick samples, which were then subjected to the following tests: 1. Mechanical tensile strength: Tested according to DL / T 627-2018, the standard requirement is ≥3MPa; 2. Volume resistivity: Tested according to DL / T 627-2018, the standard requirement is ≥1.0×10⁻⁶. 12 Ω·m; 3. Aging resistance: A xenon lamp aging test chamber was used, with an irradiance of 0.51 W / m²@340nm, a black standard temperature of 65±3℃, a relative humidity of 50±5%, and a spray cycle of 102 min light exposure / 18 min spraying. After continuous aging for 1000 h, the coating was observed to check for cracking, peeling, or flaking. The test results are shown in Table 1: Table 1 As shown in Table 1, the coatings of Examples 1-3 exhibit good mechanical strength, insulation, and aging resistance. A comparison of the data from Examples 4 and 5 with Example 1 reveals that changes in the ratio of titanate coupling agent, 3-aminopropyltrimethylsilane, and titanium dioxide can lead to multilayer physical adsorption on the filler surface, compatibility with the silicone rubber matrix, and a decrease in tensile strength. Furthermore, the titanate coupling agent itself contains Ti-O bonds and possesses certain ionic conductivity; excessive PN-130 may undergo polarization or ion migration under an electric field. The amino group, being a polar group, also exhibits certain hydrophilicity and ionic conductivity, reducing the volume resistivity of the coating. The presence of a large number of polar groups may catalyze the hydrolysis or thermal degradation of the silicone rubber backbone, resulting in a decrease in aging resistance. A comparison of the data from Example 6 with Example 1 shows that changes in the ratio of 3-(2,3-epoxypropoxy)propyltrimethoxysilane and aluminum hydroxide may lead to excessive epoxy ring-opening self-polymerization and the generation of a large amount of... The presence of hydroxyl groups leads to a decrease in crosslinking density and an increase in hydrophilicity, resulting in a decline in all properties of the coating. A comparison of data from Examples 1 and 7 shows that changing the ratio of pretreated titanium dioxide to pretreated aluminum hydroxide may disrupt the original filler network structure, reducing compatibility with silicone rubber and making it easier for cracks to form at these weak interfaces during stretching, thus reducing the mechanical tensile strength of the coating. Data from Examples 8 and 1 shows that replacing 3-(2,3-epoxypropoxy)propyltrimethoxysilane with an equal amount of γ-methacryloyloxypropyltrimethoxysilane alters the bonding mode between the pretreated titanium dioxide and pretreated aluminum hydroxide, causing local double bond polymerization to form tiny gel particles that act as stress concentration points or conductive impurities in the coating, resulting in a decrease in mechanical strength and insulation properties. Data from Examples 9 and 10 and Example 1 show that directly mixing pretreated titanium dioxide and pretreated aluminum hydroxide physically or using titanium dioxide and aluminum hydroxide directly results in a decline in all properties of the coating.

[0046] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it. They should not be used to limit the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. An aging-resistant insulating coating, characterized in that, By weight, it includes the following raw materials: 15-25 parts of hydroxyl-terminated polysiloxane, 2-5 parts of diluent, 0.5-3 parts of crosslinking agent, 30-35 parts of filler, 0.01-0.03 parts of catalyst, and 42-47 parts of solvent.

2. The aging-resistant insulating coating according to claim 1, characterized in that, The diluent is epoxy-modified silicone oil.

3. The aging-resistant insulating coating according to claim 1, characterized in that, The crosslinking agent is methyltributanone oxime silane.

4. The aging-resistant insulating coating according to claim 1, characterized in that, The method for preparing the filler includes the following steps: (1) Add titanate coupling agent, 3-aminopropyltrimethylsilane and titanium dioxide to ethanol and stir at 35-45℃ for 1-2h. Filter and dry to obtain pretreated titanium dioxide. (2) Dissolve 3-(2,3-epoxypropoxy)propyltrimethoxysilane in ethanol, then add aluminum hydroxide, stir for 1-2 hours, filter, and dry to obtain pretreated aluminum hydroxide. (3) Under nitrogen protection, the pretreated titanium dioxide obtained in step (1) and the pretreated aluminum hydroxide obtained in step (2) are added to anhydrous ethanol, heated to 60-65℃, reacted for 45-55h, filtered, dried, and ground to obtain the filler.

5. The aging-resistant insulating coating according to claim 4, characterized in that, The mass ratio of the titanate coupling agent, 3-aminopropyltrimethylsilane and titanium dioxide in step (1) is (0.05-0.07):(0.01-0.05):

1.

6. The aging-resistant insulating coating according to claim 4, characterized in that, The mass ratio of 3-(2,3-epoxypropoxy)propyltrimethoxysilane to aluminum hydroxide in step (2) is (0.01-0.04):

1.

7. The aging-resistant insulating coating according to claim 4, characterized in that, The mass ratio of pretreated titanium dioxide to pretreated aluminum hydroxide in step (3) is 1:(2-3).

8. The aging-resistant insulating coating according to claim 1, characterized in that, The catalyst is an organotin catalyst.

9. The aging-resistant insulating coating according to claim 1, characterized in that, The solvent is tetrachloroethylene.

10. A method for preparing an aging-resistant insulating coating according to any one of claims 1-9, characterized in that, Includes the following steps: Under inert gas protection, hydroxyl-terminated polysiloxane, diluent, and filler are stirred at room temperature for 1-2 hours, then solvent is added and stirred for 20-30 minutes, and then crosslinking agent and catalyst are added and stirred for 5-10 minutes to obtain an aging-resistant insulating coating.

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