A modified epoxy resin insulating coating for ZnO varistor and a preparation method thereof, a ZnO varistor and a preparation method thereof

Abstract

This invention provides a modified epoxy resin insulating coating for ZnO resistor sheets and its preparation method, as well as the ZnO resistor sheet and its preparation method. The preparation method of the modified epoxy resin insulating coating for ZnO resistor sheets provided by this invention involves first dissolving an epoxy-containing cage-like polysilsesquioxane EP-POSS in a solvent to obtain an EP-POSS solution; then mixing and dissolving the EP-POSS solution with epoxy resin to obtain mixture 1; then mixing mixture 1 with filler to obtain mixture 2; finally, mixing mixture 2 with a curing agent and adding solvent to adjust the viscosity to obtain the modified epoxy resin insulating coating; wherein the cage-like polysilsesquioxane EP-POSS used is 8EP-POSS and / or 1EP-POSS. The modified epoxy resin insulating coating for ZnO resistor sheets provided by this invention can effectively improve the electrical performance of the resistor sheet and improve the heat resistance of the material.

Description

Technical Field

[0001] This invention relates to the field of resistor sheet materials, and particularly to a modified epoxy resin insulating coating for ZnO resistor sheets and its preparation method, as well as ZnO resistor sheets and their preparation method. Background Technology

[0002] A resistive element is an electronically sensitive device with nonlinear current-voltage characteristics, made by firing ZnO as the base material and doping it with metal oxides such as Bi2O3, MnO2, Co2O3, and Sb2O3 at high temperatures. Currently, the side insulating coating of common ZnO resistive elements is based on epoxy resin with added inorganic fillers to improve the insulation strength of the coating.

[0003] In recent years, the development trend of surge arresters has gradually moved towards high current, high voltage, and miniaturization. Miniaturized surge arresters experience internal thermal stress concentration and generate a large amount of heat when struck by lightning. This places higher demands on the dielectric properties and high-temperature resistance of the resistor element's insulation layer. Therefore, a single epoxy resin-based resistor element insulation coating is insufficient to meet these requirements. Summary of the Invention

[0004] In view of this, the present invention provides a modified epoxy resin insulating coating for ZnO resistor sheets and a method for preparing the same, as well as a ZnO resistor sheet and a method for preparing the same. The modified epoxy resin insulating coating for ZnO resistor sheets provided by the present invention can effectively improve the electrical performance of the resistor sheet and improve the heat resistance of the material.

[0005] This invention provides a method for preparing a modified epoxy resin insulating coating for ZnO resistor sheets, comprising the following steps:

[0006] A) Dissolve the epoxy-containing cage-shaped polysilsesquioxane EP-POSS in a solvent to obtain an EP-POSS solution;

[0007] B) The EP-POSS solution is mixed and dissolved with epoxy resin to obtain mixture 1;

[0008] C) Mix the mixture 1 with the filler to obtain mixture 2;

[0009] D) Mix the mixture 2 with the curing agent and add solvent to adjust the viscosity to obtain a modified epoxy resin insulating coating;

[0010] in,

[0011] The cage-like polysilsesquioxane EP-POSS is an epoxycyclohexyl-cage-like polysilsesquioxane 8EP-POSS containing 8 epoxy groups and / or a cyclohexyl-cage-like polysilsesquioxane 1EP-POSS containing 1 epoxy group, with the following structure:

[0012]

[0013] Preferably, in step A), the amount of epoxy-containing cage-shaped polysilsesquioxane EP-POSS is 0.5% to 8% of the mass of epoxy resin in step B).

[0014] In step A), the amount of solvent used is 2 to 50 times the mass of the epoxy-containing cage-shaped polysilsesquioxane EP-POSS.

[0015] Preferably, in step A), the solvent is a dicarboxylic acid ester.

[0016] Preferably, in step B), the epoxy resin is an epoxy resin with an epoxy value of 0.25 to 0.54.

[0017] Preferably, in step C), the filler is boron nitride and / or a thin layer of mica;

[0018] The amount of filler used is 10% to 40% of the mass of epoxy resin in step B).

[0019] Preferably, in step D):

[0020] The curing agent is H-256 and / or triethylenetetramine;

[0021] The amount of curing agent used is 10% to 40% of the mass of epoxy resin in step B);

[0022] The temperature for mixing mixture 2 with the curing agent is 50–80°C;

[0023] The solvent is a dicarboxylic acid ester;

[0024] The amount of solvent used is such that the viscosity of the system mixture reaches 20–40,000 mPa·s.

[0025] The present invention also provides a modified epoxy resin insulating coating for ZnO resistor sheets prepared by the preparation method described in the above technical solution.

[0026] This invention also provides a method for preparing a ZnO resistive sheet, comprising the following steps:

[0027] S1. Preheat the ZnO resistance sheet;

[0028] S2. Spray an insulating coating onto the surface of the preheated resistor obtained in step S1 and dry it; then spray the insulating coating again and dry it; the above spraying-drying process is performed 4 to 6 times in total.

[0029] S3. The resistor sheet obtained in step S2 is cured at 80℃, 100℃, 120℃, 140℃ and 160℃ for 2 hours each to obtain a ZnO resistor sheet with an insulating coating.

[0030] The insulating coating is the modified epoxy resin insulating coating for ZnO resistor sheets described in the above technical solution.

[0031] Preferably, in step S1:

[0032] The preheating temperature is 40–100°C, and the time is 20–80 min;

[0033] In step S2:

[0034] The spraying process is as follows: the insulating coating is transferred to the storage tank of the spray gun and sprayed through the spray gun; the pressure of the spray gun is 0.1 to 0.3 MPa.

[0035] The drying conditions are: temperature 40–160℃, time 1–2 hours.

[0036] The present invention also provides a ZnO resistor sheet prepared by the preparation method described in the above technical solution.

[0037] This invention provides a method for preparing a modified epoxy resin insulating coating for ZnO resistor sheets. First, epoxy-containing cage-shaped polysilsesquioxane EP-POSS is dissolved in a solvent to obtain an EP-POSS solution. Then, the EP-POSS solution is mixed and dissolved with epoxy resin to obtain mixture 1. Next, mixture 1 is mixed with filler to obtain mixture 2. Finally, mixture 2 is mixed with a curing agent, and a solvent is added to adjust the viscosity to obtain the modified epoxy resin insulating coating. The cage-shaped polysilsesquioxane EP-POSS used is 8EP-POSS and / or 1EP-POSS. This invention uses the aforementioned specific cage-shaped polysilsesquioxane EP-POSS, and processes it with solvent, filler, and curing agent in a certain proportion and order to obtain the modified insulating coating. Using this insulating coating to treat resistor sheets can improve the electrical properties of the material and enhance its heat resistance.

[0038] Experimental results show that the modified epoxy resin insulating coating obtained in this invention can achieve a voltage gradient of over 234V / mm and a voltage ratio of less than 1.687 for the resistive element, exhibiting excellent electrical performance; simultaneously, its T... 5％ It exhibits high heat resistance at temperatures above 366℃. Detailed Implementation

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0040] In this article, the technical features described in an open-ended manner include both closed technical solutions composed of the listed features and open technical solutions that include the listed features.

[0041] The term “and / or” as used herein includes any and all combinations of one or more of the related listed items.

[0042] In this document, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when a range refers to an integer, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0043] In this article, when referring to units of data ranges, if the unit is only followed by the right endpoint, it indicates that the units of the left and right endpoints are the same. For example, 4~12h means that the units of the left endpoint "4" and the right endpoint "12" are both h (hours).

[0044] This document only specifically discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, just as any upper limit can be combined with any other upper limit to form an unspecified range. Furthermore, each individually disclosed point or single value can itself serve as a lower or upper limit and be combined with any other point or single value or with other lower or upper limits to form an unspecified range.

[0045] This invention provides a method for preparing a modified epoxy resin insulating coating for ZnO resistor sheets, comprising the following steps:

[0046] A) Dissolve the epoxy-containing cage-shaped polysilsesquioxane EP-POSS in a solvent to obtain an EP-POSS solution;

[0047] B) The EP-POSS solution is mixed and dissolved with epoxy resin to obtain mixture 1;

[0048] C) Mix the mixture 1 with the filler to obtain mixture 2;

[0049] D) Mix the mixture 2 with the curing agent and add solvent to adjust the viscosity to obtain a modified epoxy resin insulating coating;

[0050] in,

[0051] The cage-like polysilsesquioxane EP-POSS is an epoxycyclohexyl-cage-like polysilsesquioxane 8EP-POSS containing 8 epoxy groups and / or a cyclohexyl-cage-like polysilsesquioxane 1EP-POSS containing 1 epoxy group, with the following structure:

[0052]

[0053] Regarding step A) :

[0054] A) Dissolve the epoxy-containing cage-shaped polysilsesquioxane EP-POSS in a solvent to obtain an EP-POSS solution.

[0055] In this invention, the cage-like polysilsesquioxane EP-POSS is an epoxycyclohexyl-cage-like polysilsesquioxane 8EP-POSS containing 8 epoxy groups and / or a cyclohexyl-cage-like polysilsesquioxane 1EP-POSS containing 1 epoxy group, with the following structure:

[0056]

[0057] This invention does not impose any special restrictions on the source of the aforementioned 8EP-POSS and 1EP-POSS; they can be commercially available products, specifically provided by Forsmann Technology (Beijing) Co., Ltd. In the prior art, there are many types of cage-like polyhedral oligomeric silsesquioxane POSSes, such as various amino POSSes, various epoxy POSSes, etc. However, this invention uses the aforementioned specific 8EP-POSS and 1EP-POSS, which can better match and be compatible with epoxy resin and other components of this invention, improving the insulation strength of the material, as well as its dielectric properties and high-temperature resistance.

[0058] In this invention, the amount of the epoxy-containing cage-shaped polysilsesquioxane EP-POSS is preferably 0.5% to 8% of the mass of the epoxy resin in step B), specifically 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, or 8%. The amount of epoxy resin in the formula is determined in advance during weighing, and then EP-POSS is weighed according to the above-mentioned addition ratio.

[0059] In this invention, the solvent is preferably a dicarboxylic acid ester (DBE). The amount of solvent used is preferably 2 to 50 times the mass of the epoxy-containing cage-like polysilsesquioxane EP-POSS, specifically 2, 5, 10, 15, 20, 25, 30, 35, 40, 45, or 50 times.

[0060] In this invention, an epoxy-containing cage-shaped polysilsesquioxane EP-POSS is mixed and dissolved with a solvent to obtain an EP-POSS solution.

[0061] Regarding step B) :

[0062] B) The EP-POSS solution is mixed and dissolved with epoxy resin to obtain mixture 1.

[0063] In this invention, the epoxy resin is preferably an epoxy resin with an epoxy value of 0.25 to 0.54, and more preferably includes epoxy resin E-51 or epoxy resin E-44.

[0064] In this invention, the preferred method for mixing the EP-POSS solution and epoxy resin is ultrasonic dispersion. The preferred conditions for ultrasonic dispersion are: temperature 20–80°C, power 500–2000W, and time 5–60 min. Ultrasonic dispersion completely dissolves the materials, yielding mixture 1.

[0065] Regarding step C) :

[0066] C) Mix the mixture 1 with the filler to obtain mixture 2.

[0067] In this invention, the filler is preferably boron nitride (BN) and / or thin-layer mica. The amount of filler used is preferably 10% to 40% of the mass of the epoxy resin in step B), specifically 10%, 15%, 20%, 25%, 30%, 35%, or 40%.

[0068] In this invention, the mixing is preferably carried out in a high-speed disperser. The mixing speed is preferably 200 r / min. The mixing time is preferably 4 to 12 hours, specifically 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, or 12 hours. After uniform mixing, a mixture 2 is obtained.

[0069] Regarding step D) :

[0070] D) Mix the mixture 2 with the curing agent and add solvent to adjust the viscosity to obtain a modified epoxy resin insulating coating.

[0071] In this invention, the curing agent is preferably H-256 and / or triethylenetetramine. The amount of the curing agent is preferably 10% to 40% of the mass of the epoxy resin in step B), specifically 10%, 15%, 20%, 25%, 30%, 35%, or 40%.

[0072] In this invention, the preferred temperature for mixing the mixture 2 with the curing agent is 50-80°C, specifically 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, or 80°C; that is, the mixture 2 and the curing agent are mixed evenly under the above temperature conditions.

[0073] In this invention, after the mixture 2 and the curing agent are mixed evenly, a solvent is added to adjust the viscosity of the mixture. The solvent is preferably a dicarboxylic acid ester (DBE). The amount of solvent used in this step is preferably such that the viscosity of the mixture reaches 20–40000 mPa·s. After the above treatment, a modified epoxy resin insulating coating is obtained.

[0074] The present invention also provides a modified epoxy resin insulating coating for ZnO resistor sheets prepared by the preparation method described in the above technical solution.

[0075] This invention also provides a method for preparing a ZnO resistive sheet, comprising the following steps:

[0076] S1. Preheat the ZnO resistance sheet;

[0077] S2. Spray an insulating coating onto the surface of the preheated resistor obtained in step S1 and dry it; then spray the insulating coating again and dry it; the above spraying-drying process is performed 4 to 6 times in total.

[0078] S3. The resistor sheet obtained in step S2 is cured at 80℃, 100℃, 120℃, 140℃ and 160℃ for 2 hours each to obtain a ZnO resistor sheet with an insulating coating.

[0079] The insulating coating is the modified epoxy resin insulating coating for ZnO resistor sheets described in the above technical solution.

[0080] Regarding step S1 :

[0081] In this invention, the preheating temperature is preferably 40–100°C, specifically 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, or 100°C. The preheating time is preferably 20–80 min, specifically 20 min, 30 min, 40 min, 50 min, 60 min, 70 min, or 80 min.

[0082] Regarding step S2 :

[0083] In this invention, the specific operation for spraying insulating coating is as follows: the insulating coating is transferred to the storage tank of the spray gun and then sprayed through the spray gun. Preferably, the pressure of the spray gun is controlled at 0.1–0.3 MPa, specifically 0.1 MPa, 0.2 MPa, or 0.3 MPa.

[0084] In this invention, an insulating coating is first sprayed onto the surface of a preheated resistor sheet and then dried. The drying process involves placing the sheet in an oven. The preferred drying temperature is 40–160°C, and the preferred drying time is 1–2 hours. This drying process evaporates the solvent. After this treatment, the insulating coating is sprayed again and dried, thus repeating the process to increase the coating thickness. The drying conditions are the same as described above and will not be repeated here. The spraying-drying process is performed 4–6 times in total; that is, after spraying and drying the first layer of insulating coating to form the first coating layer, the process is repeated 3–5 times, for a total of 4–6 times.

[0085] Regarding step S3 :

[0086] In this invention, after step S2, the obtained resistor sheet is cured by being treated at 80℃, 100℃, 120℃, 140℃, and 160℃ for 2 hours each. After the above curing, an insulating coating is formed on the surface of the ZnO resistor sheet, thereby obtaining a ZnO resistor sheet with an insulating coating.

[0087] This invention, through the aforementioned specific gradient temperature curing procedure, can shorten curing time (reaching the required temperature in a shorter time, thereby reducing curing time and improving production efficiency), control internal stress distribution (the curing process of materials is accompanied by thermal expansion and contraction, which can easily cause uneven internal stress distribution; the aforementioned specific gradient temperature can control the curing speed, slow down the process of thermal expansion and contraction, thereby reducing the internal stress distribution of the material), improve heat transfer uniformity (the aforementioned gradient temperature system can make the internal temperature distribution of the material more uniform, thereby improving the uniformity of heat transfer and avoiding overheated or undercooled areas), and reduce the risk of bubble formation (the aforementioned gradient temperature system can control the heat transfer speed and avoid bubble formation).

[0088] The present invention also provides a ZnO resistor sheet prepared by the preparation method described in the above technical solution.

[0089] This invention provides a method for preparing a modified epoxy resin insulating coating for ZnO resistor sheets. First, epoxy-containing cage-like polysilsesquioxane EP-POSS is dissolved in a solvent to obtain an EP-POSS solution. Then, the EP-POSS solution is mixed and dissolved with epoxy resin to obtain mixture 1. Next, mixture 1 is mixed with filler to obtain mixture 2. Finally, mixture 2 is mixed with a curing agent, and a solvent is added to adjust the viscosity to obtain the modified epoxy resin insulating coating. The cage-like polysilsesquioxane EP-POSS used is 8EP-POSS and / or 1EP-POSS. This invention uses the aforementioned specific cage-like polysilsesquioxane EP-POSS, and processes it with solvent, filler, and curing agent in a certain proportion and order to obtain the modified insulating coating. Using this insulating coating to treat resistor sheets can improve the electrical properties (such as insulation properties) and enhance their heat resistance.

[0090] The modified epoxy resin insulating coating obtained by this invention is not only suitable for the insulation protection of resistor sheets, but also for the packaging of electronic devices and other fields.

[0091] Experimental results show that the modified epoxy resin insulating coating obtained in this invention can achieve a voltage gradient of over 234V / mm and a voltage ratio of less than 1.687 for the resistive element, exhibiting excellent electrical performance; simultaneously, its T... 5％ It exhibits high heat resistance at temperatures above 366℃.

[0092] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims of the present invention.

[0093] Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods. All instruments are conventionally selected in the art.

[0094] Example 1

[0095] 1. Preparation of insulating coating:

[0096] A) Weigh 8 EP-POSS and dissolve it in dicarboxylic acid ester to obtain an EP-POSS solution.

[0097] The amount of 8EP-POSS is 0.5% of the mass of epoxy resin E-51, and the amount of dicarboxylic acid ester is 30 times the mass of 8EP-POSS.

[0098] B) Add the EP-POSS solution to epoxy resin E-51 and ultrasonically disperse until completely dissolved to obtain mixture 1.

[0099] C) Add BN filler (filler amount is 10% of the mass of epoxy resin E-51) to mixture 1, and disperse it at 200 r / min for 4 h using a high-speed disperser to obtain mixture 2.

[0100] D) Add curing agent H-256 (the amount of curing agent is 33% of the mass of epoxy resin E-51) to mixture 2, mix evenly at 60°C, and then add dicarboxylic acid ester to adjust the viscosity of the mixture to 1000 mPa·s to obtain modified epoxy resin insulating coating.

[0101] 2. Preparation of ZnO resistor sheets:

[0102] S1. Preheat the ZnO resistance sheet at 60℃ for 60 minutes.

[0103] S2. Transfer the obtained insulating coating to the storage tank of the spray gun, control the spray gun pressure to 0.1MPa, spray a layer of insulating coating on the surface of the preheated resistor obtained in step S1, and treat it in an 80℃ oven for 1 hour; then repeat the above spraying-drying procedure 3 times.

[0104] S3. The resistor sheet obtained in step S2 is cured by treating it at 80℃, 100℃, 120℃, 140℃ and 160℃ for 2 hours each to obtain a ZnO resistor sheet with an insulating coating.

[0105] Example 2

[0106] 1. Preparation of insulating coating:

[0107] A) Weigh 1 EP-POSS and dissolve it in a dicarboxylic acid ester to obtain an EP-POSS solution.

[0108] The amount of 1EP-POSS is 4% of the mass of epoxy resin E-51, and the amount of dicarboxylic acid ester is 20 times the mass of 1EP-POSS.

[0109] B) Add the EP-POSS solution to epoxy resin E-51 and ultrasonically disperse until completely dissolved to obtain mixture 1.

[0110] C) Add BN filler (filler amount is 20% of the mass of epoxy resin E-51) to mixture 1, and disperse it at 200 r / min for 6 h using a high-speed disperser to obtain mixture 2.

[0111] D) Add curing agent H-256 (the amount of curing agent is 35% of the mass of epoxy resin E-51) to mixture 2, mix evenly at 70°C, and then add dicarboxylic acid ester to adjust the viscosity of the mixture to 1500 mPa.s to obtain modified epoxy resin insulating coating.

[0112] 2. Preparation of ZnO resistor sheets:

[0113] S1. Preheat the ZnO resistance sheet at 60℃ for 60 minutes.

[0114] S2. Transfer the obtained insulating coating to the storage tank of the spray gun, control the spray gun pressure to 0.1MPa, spray a layer of insulating coating on the surface of the preheated resistor obtained in step S1, and treat it in an 80℃ oven for 1 hour; then repeat the above spraying-drying procedure 4 times.

[0115] S3. The resistor sheet obtained in step S2 is cured by treating it at 80℃, 100℃, 120℃, 140℃ and 160℃ for 2 hours each to obtain a ZnO resistor sheet with an insulating coating.

[0116] Example 3

[0117] 1. Preparation of insulating coating:

[0118] A) Weigh 1 EP-POSS and dissolve it in a dicarboxylic acid ester to obtain an EP-POSS solution.

[0119] The amount of 1EP-POSS is 3% of the mass of epoxy resin E-51, and the amount of dicarboxylic acid ester is 30 times the mass of 1EP-POSS.

[0120] B) Add the EP-POSS solution to epoxy resin E-51 and ultrasonically disperse until completely dissolved to obtain mixture 1.

[0121] C) Add a thin layer of mica filler (the filler amount is 10% of the mass of epoxy resin E-51) to mixture 1, and disperse it at 200 r / min for 4 h using a high-speed disperser to obtain mixture 2.

[0122] D) Add curing agent H-256 (the amount of curing agent is 33% of the mass of epoxy resin E-51) to mixture 2, mix evenly at 80°C, and then add dicarboxylic acid ester to adjust the viscosity of the mixture to 1500 mPa.s to obtain modified epoxy resin insulating coating.

[0123] 2. Preparation of ZnO resistor sheets:

[0124] S1. Preheat the ZnO resistance sheet at 60℃ for 30 minutes.

[0125] S2. Transfer the obtained insulating coating to the storage tank of the spray gun, control the spray gun pressure to 0.1MPa, spray a layer of insulating coating on the surface of the preheated resistor obtained in step S1, and treat it in an 80℃ oven for 1 hour; then repeat the above spraying-drying procedure 4 times.

[0126] S3. The resistor sheet obtained in step S2 is cured by treating it at 80℃, 100℃, 120℃, 140℃ and 160℃ for 2 hours each to obtain a ZnO resistor sheet with an insulating coating.

[0127] Example 4

[0128] 1. Preparation of insulating coating:

[0129] A) Weigh 1 EP-POSS and dissolve it in a dicarboxylic acid ester to obtain an EP-POSS solution.

[0130] The amount of 1EP-POSS is 2% of the mass of epoxy resin E-51, and the amount of dicarboxylic acid ester is 20 times the mass of 1EP-POSS.

[0131] B) Add the EP-POSS solution to epoxy resin E-51 and ultrasonically disperse until completely dissolved to obtain mixture 1.

[0132] C) Add a thin layer of mica filler (the filler amount is 20% of the mass of epoxy resin E-51) to the mixture 1, and disperse it at 200 r / min for 5 h using a high-speed disperser to obtain mixture 2.

[0133] D) Add curing agent H-256 (the amount of curing agent is 35% of the mass of epoxy resin E-51) to mixture 2, mix evenly at 70°C, and then add dicarboxylic acid ester to adjust the viscosity of the mixture to 1000 mPa·s to obtain modified epoxy resin insulating coating.

[0134] 2. Preparation of ZnO resistor sheets:

[0135] S1. Preheat the ZnO resistance sheet at 60℃ for 60 minutes.

[0136] S2. Transfer the obtained insulating coating to the storage tank of the spray gun, control the spray gun pressure to 0.2MPa, spray a layer of insulating coating on the surface of the preheated resistor obtained in step S1, and treat it in an oven at 100℃ for 1 hour; then repeat the above spraying-drying procedure 4 times.

[0137] S3. The resistor sheet obtained in step S2 is cured by treating it at 80℃, 100℃, 120℃, 140℃ and 160℃ for 2 hours each to obtain a ZnO resistor sheet with an insulating coating.

[0138] Example 5

[0139] 1. Preparation of insulating coating:

[0140] A) Weigh 1 EP-POSS and dissolve it in a dicarboxylic acid ester to obtain an EP-POSS solution.

[0141] The amount of 1EP-POSS is 2% of the mass of epoxy resin E-51, and the amount of dicarboxylic acid ester is 30 times the mass of 1EP-POSS.

[0142] B) Add the EP-POSS solution to epoxy resin E-51 and ultrasonically disperse until completely dissolved to obtain mixture 1.

[0143] C) Add BN filler (the amount of filler is 40% of the mass of epoxy resin E-51) to mixture 1, and disperse it at 200 r / min for 4 h using a high-speed disperser to obtain mixture 2.

[0144] D) Add curing agent H-256 (the amount of curing agent is 34% of the mass of epoxy resin E-51) to mixture 2, mix evenly at 80°C, and then add dicarboxylic acid ester to adjust the viscosity of the mixture to 1500 mPa·s to obtain modified epoxy resin insulating coating.

[0145] 2. Preparation of ZnO resistor sheets:

[0146] S1. Preheat the ZnO resistance sheet at 60℃ for 40 minutes.

[0147] S2. Transfer the obtained insulating coating to the storage tank of the spray gun, control the spray gun pressure to 0.2MPa, spray a layer of insulating coating on the surface of the preheated resistor obtained in step S1, and treat it in an 80℃ oven for 1 hour; then repeat the above spraying-drying procedure 5 times.

[0148] S3. The resistor sheet obtained in step S2 is cured by treating it at 80℃, 100℃, 120℃, 140℃ and 160℃ for 2 hours each to obtain a ZnO resistor sheet with an insulating coating.

[0149] Comparative Example 1

[0150] The implementation follows Example 1, except that the insulating coating used is unmodified epoxy resin, specifically epoxy resin E-51.

[0151] Product Testing :

[0152] 1. Electrical performance testing

[0153] The electrical performance of the resistors obtained in each embodiment and comparative example was tested. Specifically, the test results were performed using U... 1mA (Varistor voltage), I (leakage current), 8 / 20μs (8 / 20μs surge current), gradient (potential gradient), and voltage ratio (residual voltage ratio). Test results are shown in Table 1.

[0154] Table 1: Electrical properties of resistors

[0155]

[0156]

[0157] As shown in Table 1, the gradient distribution of the insulating coating using the unmodified resin (i.e., Comparative Example 1) is 231 V / mm, and the voltage ratio is 1.701. However, when using the modified insulating coating of this invention (i.e., Examples 1-5), the gradient is above 234 V / mm, showing an increase, while the voltage ratio is below 1.687, showing a decrease. This demonstrates that using the modified insulating coating of this invention is beneficial for improving the electrical performance of the resistor sheet.

[0158] 2. Heat resistance test

[0159] The insulating coatings obtained in each example and comparative example were cured (curing conditions: 80℃, 100℃, 120℃, 140℃, and 160℃ for 2 hours each), and their TG (thermogravimetric analysis) values ​​were tested and recorded. 5％ (T 5％ (The thermal initiation temperature is commonly used to characterize material decomposition). See Table 2 for the results.

[0160] Table 2: Results of Heat Resistance Test

[0161] Comparative Example 1 Example 1 Example 2 Example 3 Example 4 Example 5 <![CDATA[T 5％ (℃)]]> 353 366 371 375 367 373

[0162] As can be seen from the test results in Table 2, the T of the insulating coating before modification (i.e., Comparative Example 1) 5％ At 353°C, the T of the modified insulating coating of the present invention (i.e., corresponding to Examples 1-5) 5％ The temperature above 366℃ shows a significant increase, proving that the modified insulating coating of this invention improves the heat resistance of the resin.

[0163] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of these embodiments are merely to aid in understanding the method and core ideas of the present invention, including the best mode, and to enable any person skilled in the art to practice the present invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that those skilled in the art can make various improvements and modifications to the present invention without departing from its principles, and these improvements and modifications also fall within the scope of protection of the claims. The scope of protection of this patent is defined by the claims and may include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements similar to those expressed in the claims, or if they include equivalent structural elements that are not substantially different from those expressed in the claims, then these other embodiments should also be included within the scope of the claims.

Claims

1. A method for preparing a ZnO resistive sheet, characterized in that, Includes the following steps: S1. Preheat the ZnO resistance sheet; S2. Spray an insulating coating onto the surface of the preheated resistor obtained in step S1 and dry it. Then, the insulating coating is sprayed again and dried; the above spraying-drying process is repeated 4 to 6 times. S3. The resistor sheet obtained in step S2 is cured at 80℃, 100℃, 120℃, 140℃ and 160℃ for 2 hours each to obtain a ZnO resistor sheet with an insulating coating. The insulating coating is prepared by the following method: A) Dissolve the epoxy-containing cage-shaped polysilsesquioxane EP-POSS in a solvent to obtain an EP-POSS solution; B) The EP-POSS solution is mixed and dissolved with epoxy resin to obtain mixture 1; C) Mix the mixture 1 with the filler to obtain mixture 2; D) Mix the mixture 2 with the curing agent and add solvent to adjust the viscosity to obtain a modified epoxy resin insulating coating; in, The cage-like polysilsesquioxane EP-POSS is an epoxycyclohexyl-cage-like polysilsesquioxane 8EP-POSS containing 8 epoxy groups and / or a cyclohexyl-cage-like polysilsesquioxane 1EP-POSS containing 1 epoxy group, with the following structure: 8EP-POSS 1EP-POSS; The epoxy resin is epoxy resin E-51 or epoxy resin E-44.

2. The preparation method according to claim 1, characterized in that, In step S1: The preheating temperature is 40~100℃, and the time is 20~80min; In step S2: The spraying process is as follows: the insulating coating is transferred to the storage tank of the spray gun and sprayed through the spray gun; the pressure of the spray gun is 0.1~0.3MPa; The drying conditions are: temperature 40~160℃, time 1~2h.

3. The preparation method according to claim 1, characterized in that, In step A), the amount of epoxy-containing cage-like polysilsesquioxane EP-POSS used is 0.5% to 8% of the mass of epoxy resin in step B). In step A), the amount of solvent used is 2 to 50 times the mass of the epoxy-containing cage-shaped polysilsesquioxane EP-POSS.

4. The preparation method according to claim 1, characterized in that, In step A), the solvent is a dicarboxylic acid ester.

5. The preparation method according to claim 1, characterized in that, In step C), the filler is boron nitride and / or a thin layer of mica; The amount of filler used is 10% to 40% of the mass of epoxy resin in step B).

6. The preparation method according to claim 1, characterized in that, In step D): The curing agent is H-256 and / or triethylenetetramine; The amount of curing agent used is 10% to 40% of the mass of epoxy resin in step B); The temperature for mixing mixture 2 with the curing agent is 50~80℃; The solvent is a dicarboxylic acid ester; The amount of solvent used is such that the viscosity of the system mixture reaches 20~40000 mPa·s.

7. A ZnO resistor sheet prepared by any one of claims 1 to 6.

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