TWI703186B - Coating composition, coating and varistor containing the coating - Google Patents

Abstract

The coating composition provided by the present invention includes a silicone resin, a filler, a fiber and a solvent, and the length of the fiber is 100 micrometers to 500 micrometers. Wherein, based on the total weight of the coating composition, the content of the silicone resin is 5% to 20% by weight, and the total weight of the filler and the fiber is 75% to 90% by weight; based on the filler and the fiber Based on the total weight, the fiber content is 4% to 8% by weight; the coating composition of the present invention is cured to form a coating; the varistor of the present invention includes a varistor coated on a varistor element The coating can still have the explosion-proof characteristics of no spark, no combustion or no explosion and dispersion of the coating when subjected to excessive instantaneous voltage, and has the advantages of time-saving and low-cost preparation.

Description

Coating composition, coating and varistor containing the coating

The present invention relates to a coating composition, especially a coating composition with fibers. The present invention also relates to a coating formed by curing the aforementioned coating composition, and a varistor comprising the aforementioned coating.

Varistor, also known as rheostat, its current-voltage characteristic curve shows a non-linear change, so it can adjust its own resistance according to the magnitude of the applied voltage; when an instantaneous surge voltage occurs, the resistance of the varistor will change The current is quickly reduced to shunt the current, thereby preventing the instantaneous surge voltage from harming other electronic components, so it has the function of protecting electronic components.

However, the energy or power that the varistor can withstand is limited. Under the repeated action of the instantaneous surge voltage, the leakage current of the varistor becomes larger and larger, and the temperature of the varistor increases, the leakage current becomes greater As a result, the temperature of the varistor is as high as the ignition point of the packaging material, and the packaging material melts to form a short-circuit point; when the next larger current is poured into the short-circuit point, it will form high heat and generate sparks, and even the ceramic body will burst and The phenomenon of flying fragments, and the exploded fragments may affect peripheral circuits or other electronic components, resulting in equipment damage.

In order to prevent the occurrence of sparks, combustion, explosion and other phenomena caused by instantaneous surge voltage, there are two main processing methods for improving the explosion-proof function of the existing varistor. One is to coat the exterior of the varistor with epoxy resin. The coating has the characteristics of moisture resistance, insulation, and flame retardancy, which can inhibit the generation of sparks, thereby reducing the occurrence of bursts; but the coating is not incombustible. Once the instantaneous surge voltage is too large, it exceeds the power that the varistor can withstand , The epoxy resin coating on the outside of the varistor will still be ignited and may even burst and cause harm.

Another processing method to make the varistor device explosion-proof, such as the explosion-proof varistor of China New Patent No. 203218048, the varistor is sealed with an insulating shell, and the insulating shell is filled with a polymer material. The polymer material has the characteristics of temperature resistance and fire resistance; the cured polymer material covers the varistor to prevent the varistor from sparking, burning and bursting when the varistor is impacted by a transient surge voltage, thereby improving Safety during use. However, although the insulating shell can effectively prevent sparks and bursts, its manufacturing is time-consuming and costly, so that its application is limited.

In view of the technical defects of the above-mentioned existing varistors, the object of the present invention is to provide a coating composition, when the varistor contains a coating formed by curing the coating composition, the varistor Even if it is broken down by an excessively large instantaneous voltage, it will not produce sparks, burns, or explosions.

In order to achieve the foregoing objective, the present invention provides a coating composition comprising: a silicone resin, a filler, a fiber and a solvent, the length of the fiber is 100 micrometers (μm) to 500 μm; wherein the coating composition Based on the total weight, the content of the silicone resin is 5 wt% (wt%) to 20 wt%, and the total weight of the filler and the fiber is 75 wt% to 90 wt%; based on the total weight of the filler and the fiber As a benchmark, the content of the fiber is 4 wt% to 8 wt%.

In the present invention, a specific content range of fibers with a specific length are added to the coating composition. With the high insulation of the fibers, the fiber can form a network structure to enhance the strength of the coating after curing of the coating composition. The coated varistor after curing of the coating composition can have good explosion-proof performance, and even if it is broken down by being subjected to excessive instantaneous voltage, it will not produce sparks, combustion or coating bursting and dispersing.

According to the present invention, the coating composition is based on the silicone resin, and the silicone resin includes methyl silicone resin, methyl phenyl silicone resin, vinyl silicone resin, methyl vinyl silicone resin, amino silicone resin, and epoxy resin. Silicone resin or its combination, but not limited to this.

According to the present invention, the material of the filler includes metal oxide, talc, quartz, mica, calcium carbonate or a combination thereof, but is not limited to this. The filler has insulating properties and can be used to reduce the coefficient of thermal expansion of the coating composition. Furthermore, the filler can be in powder form, such as talc powder, quartz powder, and mica powder. For example, the coating composition may include one of the foregoing fillers, or two or more of the foregoing fillers at the same time; for example, the coating composition may be a combination of mica and calcium carbonate, or a combination of talc and quartz , Or a combination of quartz and mica, but not limited to this.

According to the present invention, the fiber includes glass fiber, quartz glass fiber, alumina fiber or a combination thereof, but is not limited to this. For example, the coating composition may include one of the foregoing fibers, or may include two or more of the foregoing fibers at the same time; for example, the coating composition may include fibers such as glass fibers and quartz glass fibers, but is not limited to this.

Preferably, the diameter of the fiber is 5 μm to 15 μm.

According to the present invention, based on the total weight of the coating composition, the content of the solvent is 2 wt% to 15 wt%; the solvent includes toluene, xylene or a combination thereof, but is not limited to this.

According to the present invention, the coating composition is cured to form a coating, and the cured coating has no residual solvent; the curing method includes thermal curing, but is not limited to this.

The present invention also provides a coating which is formed by curing the aforementioned coating composition.

The present invention also provides a varistor comprising the aforementioned coating. The varistor has good anti-explosion performance. Even if it is broken down by being subjected to excessive instantaneous voltage, it will not produce sparks, combustion or coating bursting and dispersion, and It has the advantages of time saving and low cost in preparation; it includes: a varistor element; a first coating layer covering the varistor element; and a second coating layer covering the varistor element On the first coating; wherein, the varistor element includes: a ceramic body with a first end and a second end opposite to the first end; a plurality of internal electrodes, the internal electrodes are arranged on the ceramic Outside the body, two adjacent inner electrodes are respectively connected to the first end and the second end; a first outer electrode disposed on the first end of the ceramic body and in contact with the corresponding inner electrode; and A second external electrode is arranged on the second end of the ceramic body and is in contact with the corresponding internal electrode; wherein, the first coating is the aforementioned coating.

According to the present invention, the first coating is the aforementioned coating, and the coating is formed by curing the aforementioned coating composition; because the coating composition contains fibers with a specific content range and a specific length, it can form a network Shaped structure to enhance the strength of the coating after curing of the coating composition, so the varistor containing the coating can have good explosion-proof performance, even if it is broken down by excessive instantaneous voltage, it will not generate sparks , Burning or coating bursting and dispersing.

Preferably, the thickness of the first coating is between 1.1 millimeters (mm) and 2 mm; the thickness of the second coating is between 1.1 mm and 2 mm.

According to the present invention, the second coating is cured by a second coating composition, the second coating composition includes a silicone resin, a filler, a flame retardant, and a solvent; wherein the second coating composition Based on the total weight of the coating composition, the content of the silicone resin is 10 wt% to 20 wt%, and the total weight of the filler and the flame retardant is 75 wt% to 90 wt%; based on the filler and the flame retardant Based on the total weight, the content of the flame retardant is 30 wt% to 50 wt%.

In some embodiments, the second coating composition may further include a fiber. Preferably, the fibers contained in the second coating composition may be the same as the fibers contained in the first coating composition.

According to the present invention, the second coating composition uses the silicone resin as a matrix, and the silicone resin includes methyl silicone resin, methyl phenyl silicone resin, vinyl silicone resin, methyl vinyl silicone resin, amino silicone resin, and ring Oxygen silicone resin or its combination, but not limited to this.

According to the present invention, the filler includes metal oxide, talc, quartz, mica, calcium carbonate or a combination thereof, but is not limited to this. The filler has insulating properties and can be used to reduce the thermal expansion coefficient of the second coating composition. Furthermore, the filler can be in powder form, such as talc powder, quartz powder, and mica powder. For example, the second coating composition may include one of the foregoing fillers, or two or more of the foregoing fillers at the same time; for example, the second coating composition may include fillers such as quartz and mica at the same time, but not Limited to this.

According to the present invention, the flame retardant is an inorganic flame retardant, which includes aluminum hydroxide, magnesium hydroxide, antimony trioxide, borate, calcium molybdate or a combination thereof, but is not limited to this. For example, the second coating composition may include one of the foregoing flame retardants, or may include two or more of the foregoing flame retardants at the same time; for example, the second coating composition may include both aluminum hydroxide and aluminum hydroxide. Flame retardants such as magnesium hydroxide, but not limited to this.

According to the present invention, based on the total weight of the second coating composition, the content of the solvent is 2 wt% to 10 wt%; the solvent includes toluene, xylene or a combination thereof, but is not limited thereto.

The varistor of the present invention has the first coating as the aforementioned coating, so the varistor can have good explosion-proof performance. Even if it is broken down by an excessive instant voltage, it will not produce sparks, combustion or The coating bursts and disperses, and has the advantages of time saving and low cost in the preparation process.

Hereinafter, examples will be used to illustrate the implementation of the present invention. Those skilled in the art can easily understand the advantages and effects of the present invention through the content of this specification, and make various modifications without departing from the spirit of the present invention. And changes to implement or apply the content of the present invention.

Example 1 to 6 And comparative example 1 to 7 ：Coating composition

According to the content of each component and the length of the fiber shown in Table 1 below, the silicone resin, filler, fiber and solvent were sequentially added into a container, and the coatings of Examples 1 to 6 and Comparative Examples 1 to 7 were obtained after stirring. combination. Taking Example 1 as an example, based on the total weight of the coating composition, 5 wt% methyl silicone resin, 80 wt% filler (68 wt% quartz powder, 4 wt% talc powder, and 8 wt% Mica powder) and 3.4 wt% glass fiber (the fiber length is 100 μm to 500 μm, and the fiber diameter is 5 μm to 15 μm), and 11.6 wt% solvent (5.8 wt% toluene and 5.8 wt% xylene) ) Mix and place in a container, stir for 30 minutes to obtain a coating composition. In addition, the diameters of the fibers of Examples 2 to 6 and Comparative Examples 1 to 7 are all 5 μm to 15 μm.

Table 1: The content of each component of the coating composition of Examples 1 to 6 and Comparative Examples 1 to 7 (unit: wt%):

Example 7 : Varistor

Example 7 contains a varistor with the coating formed by curing the coating composition of Example 1 as the first coating, which was prepared according to the content of each component shown in Table 2.

As shown in Figures 1 and 2, the varistor 10 of the present invention includes a varistor element 11 (model: TVR10511), a first coating 20, which is coated on the varistor element 11, and a second The coating 30 is coated on the first coating 20; wherein the varistor element 11 includes a ceramic body 12 having a first end 121 and a second end 122 opposite to the first end; a plurality of internal electrodes 13, The inner electrodes 13 are arranged outside the ceramic body 12, and two adjacent inner electrodes are respectively connected to the first end 121 and the second end 122; the first outer electrode 14 is arranged on the first end 121 of the ceramic body And are in contact with the corresponding internal electrodes 13; the second external electrode 15 is arranged on the second end 122 of the ceramic body and is in contact with the corresponding internal electrodes 13; wherein, the first coating 20 is formed by For the coating formed by curing the coating composition of Example 1, the coating thickness of the first coating layer 20 is 1.1 mm to 1.5 mm.

The aforementioned varistor element 11 is immersed in the coating composition of Example 1 and heated and cured to form the first coating layer 20, and then immersed in the second coating composition and heated and cured to form the second coating layer 30, thereby obtaining a varistor 10. The preparation containing the varistor 10 is as follows:

First, immerse the chip portion of the varistor element 11 in the coating composition of Example 1, take it out, and let it stand for 2 minutes until the varistor element 11 coated with the coating composition of Example 1 is dried. The varistor element 11 was immersed in the coating composition of Example 1 and taken out and allowed to stand for 2 minutes to be dried. The immersion and drying steps were repeated 4 times in total. Then put the aforementioned varistor element 11 for 6 hours and put it in an oven for heating and curing, and bake at 80˚C for 1 hour, then increase to 145˚C and bake for 2 hours to obtain a first coating The varistor element 11 of the layer 20, wherein the thickness of the first coating layer 20 is between 1.1 mm and 1.5 mm.

Next, the varistor element 11 with the first coating layer 20 is immersed in the second coating composition, which is formulated according to the content of each component of the second coating composition shown in Table 2 below. The second coating composition includes 10 wt% methyl silicone resin, 55 wt% filler (45 wt% quartz powder and 10 wt% mica powder), 25 wt% aluminum hydroxide, and 10 wt% solvent ( 5 wt% toluene and 5 wt% xylene) were mixed and placed in a container and stirred for 30 minutes to obtain a second coating composition; then the chip portion of the varistor element 11 with the first coating 20 was immersed in the second coating In the composition, after taking it out, let it stand for 2 minutes until the aforementioned varistor element 11 covered by the second coating composition is dried, and then immerse the aforementioned varistor element 11 in the second coating composition again and take it out and let it stand for 2 minutes After drying, repeat the immersion and drying steps a total of 4 times. Then put the aforementioned varistor element 11 to stand for 6 hours and put it in an oven for heating and curing, bake at 80˚C for 1 hour, and then increase to 145˚C for 2 hours to obtain a varistor 10. The thickness of the second coating layer 30 is between 1.1 mm and 1.5 mm. Examples 8 to 12 : Varistor

The preparation of the varistor of Examples 8 to 12 is approximately the same as that of the varistor of Example 7, except that the content of each component of the second coating composition of Examples 8 to 12 is shown in Table 2, and the first The coatings are the coatings formed by curing the coating compositions of Examples 2 to 6, wherein the thickness of the first coating is between 1.1 mm and 1.5 mm, and the thickness of the second coating is both medium At 1.1 mm to 1.5 mm. Comparative Examples 8 to 14 : Varistor

The preparation of the varistor of Comparative Examples 8 to 14 is approximately the same as that of the varistor of Example 7, except that the content of each component of the second coating composition of Comparative Examples 8 to 14 is shown in Table 2, and the first The coatings are the coatings formed by curing the coating compositions of Comparative Examples 1 to 7, wherein the thickness of the first coating of Comparative Examples 8 to 11, 13 and 14 are all between 1.1 mm and 1.5 mm , But Comparative Example 12 was unable to form the first coating due to the poor fluidity of the coating composition; Moreover, the coating thickness of the second coating of Comparative Examples 8 to 11, 13 and 14 were all between 1.1 mm and 1.5 mm , And Comparative Example 12 did not prepare the second coating. Comparative Example 15 : Insulating shell sealed varistor

The insulating shell-sealed varistor of Comparative Example 15 was prepared as follows: the varistor element (model: TVR10511) was placed inside the insulating shell, and the first and second outer electrodes of the varistor element were outwardly Extend the insulating shell, then pour the viscous phenolic resin into the accommodating space of the insulating shell to completely cover the varistor element, and then cure the phenolic resin to obtain an insulating shell to seal the varistor Device.

Table 2: The content of each component (unit: wt) of the second coating composition of Examples 7 to 12 and Comparative Examples 8 to 14:

Test example: Test of overvoltage

In this test example, the explosion-proof characteristics of the varistors of Examples 7 to 12, the varistors of Comparative Examples 8 to 14, and the insulating case sealed varistor of Comparative Example 15 were analyzed by the same test method as follows.

Test method: Start with AC 220 volts (V) and maintain for 1 minute, quickly increase to the starting voltage and the center voltage of 270V, which is the maximum allowable AC voltage of 320V, within 2 seconds, and maintain for 1 minute, then quickly increase to the maximum within 2 seconds Allow the AC voltage to be 320V and maintain it for 2 minutes, then increase the voltage at a rate of 10V every 30 seconds until the varistor fails the test, and observe the spark, burning or bursting of the varistor. Among them, the specification of the fuse is 5A slow type. If the varistor has sparking, burning, or bursting conditions, it is judged that the overvoltage test has failed, which is indicated as "X" in Table 3 below; if the varistor has no sparking, burning, or bursting conditions, it is judged as The overvoltage test passed, which is indicated as "O" in Table 3 below.

Table 3: Overvoltage test results of Examples 7 to 12 and Comparative Examples 8 to 15:

As shown in the overvoltage test results shown in Table 3 above, the varistors of Examples 7 to 12 contain the first coating formed by curing the coating composition of Examples 1 to 6, respectively, and therefore are resistant to sparking, burning, and coating. The results of the layer burst condition all passed the overvoltage test; while the varistors of Comparative Examples 8 to 14 (that is, the coating composition without the coating composition of the present invention) failed the test results of the spark and burst conditions; this proves that the varistor The varistor of the coating composition of the invention has good anti-explosion characteristics, and can not produce sparks, combustion and coating burst when subjected to instantaneous voltage. In addition, although the test result of the insulating case-sealed varistor of Comparative Example 15 was passed, the outer shell of the insulating case showed a bulging bulge, so there are still safety concerns in use.

Compare the overvoltage test results of the varistors of Examples 7 and 9 and Comparative Example 10, and compare the overvoltage test results of the varistors of Examples 8, 11 and Comparative Example 11. It can be found that silicon When the resin content exceeds the range of 5 wt% to 20 wt% of the present invention, the overvoltage test results of Comparative Example 10 (ie the silicone resin content is 4 wt%) and Comparative Example 11 (ie the silicone resin content is 25 wt%) Both sparks and explosions failed, that is to say, Examples 7 to 9 and 11 have the varistor of the present invention, and the specific content range of the silicone resin can make the varistor have a good explosion-proof effect.

Compare the overvoltage test results of the varistors of Example 7 with Comparative Example 8 and Comparative Example 9. When the same coating composition and the content of each component of the second coating composition are used to cure to form the first coating and the second coating composition In the case of two coatings, the overvoltage test results of the varistors of Comparative Example 8 (that is, the length of the fiber is between 10 μm to 100 μm) and Comparative Example 9 (that is, the length of the fiber is between 500 μm and 1000 μm) Neither of them passed nor burst, that is to say, the varistor with fiber length of 100 μm to 500 μm in Example 7 can achieve anti-sparking, non-combustion and non-blasting characteristics when subjected to excessive instantaneous voltage. This is because the fibers in the coating composition of Example 7 can effectively form a network structure, thereby enhancing the strength of the coating, thereby reducing the occurrence of coating bursts, and achieving anti-explosion effects without sparks, combustion, and bursts.

Compare the overvoltage test results of the varistors of Example 7 and Comparative Examples 13 and 14, and compare the varistors of Examples 9, 10, 12 and Comparative Example 12; it can be found that Comparative Examples 13 and 14 (Fiber content accounts for less than 4 wt% of the total weight of fiber and filler content) The overvoltage test results of the varistor failed in sparks and bursts. Among them, Comparative Example 12 (Fiber content is higher than 8 wt% ) Because of the poor fluidity of the coating composition, the first coating cannot be formed, so that the second coating cannot be continued and the overvoltage test can be performed. It can be seen that the varistor of Examples 7, 9, 10, and 12 through the process of the present invention contains fiber content that can enhance the strength of the coating, reduce the occurrence of bursting, and achieve no spark, combustion and burst Explosion-proof effect.

The overvoltage test results of the insulating case-sealed varistors of Examples 7 to 12 and Comparative Example 15 are compared. Although the test results of the insulating case-sealed varistors of Comparative Example 15 all pass, the insulating case The outer shell of the body presents a bulging bulge, which has safety concerns in use; and the varistors of Examples 7 to 12 can achieve explosion-proof effects without sparks, combustion, and explosions except for being subjected to excessive instantaneous voltage. The bulging of the coating expansion.

Based on the above analysis results, it can be seen that the technical means of the present invention can make the varistor have good anti-explosion performance, even if it is broken down by excessive instantaneous voltage, it will not produce sparks, combustion or coating bursting and dispersion. In addition, the present invention The invented varistor also has the effects of saving time and reducing cost in preparation, thereby enhancing the application value of the present invention.

10: Varistor 13: Inner electrode 11: Varistor element 14: First outer electrode 12: Ceramic body 15: Second outer electrode 121: First end of ceramic body 20: First coating 122: Ceramic body The second end 30: second coating

Figure 1 is a schematic front view of the varistor of the present invention. Fig. 2 is a schematic side sectional view of the varistor of the present invention.

10: Varistor

11: Varistor element

12: Ceramic body

121: The first end of the ceramic body

122: The second end of the ceramic body

13: inner electrode

14: The first outer electrode

15: second outer electrode

20: First coat

30: second coating

Claims (12)

A coating composition comprising: a silicone resin, a filler, a fiber, and a solvent; wherein the length of the fiber is 100 micrometers to 500 micrometers; the content of the silicone resin is based on the total weight of the coating composition 5 wt% to 20 wt%, the total weight of the filler and the fiber is 75 wt% to 90 wt%; based on the total weight of the filler and the fiber, the content of the fiber is 4 wt% to 8 wt% . The coating composition according to claim 1, wherein the diameter of the fiber is 5 μm to 15 μm. The coating composition according to claim 1 or 2, wherein the fiber comprises glass fiber, quartz glass fiber, alumina fiber or a combination thereof. The coating composition according to claim 1, wherein the silicone resin comprises methyl silicone resin, methyl phenyl silicone resin, vinyl silicone resin, methyl vinyl silicone resin, amino silicone resin, epoxy silicone resin or Its combination. The coating composition according to claim 1, wherein the filler comprises metal oxide, talc, quartz, mica, calcium carbonate or a combination thereof. The coating composition according to claim 1, wherein, based on the total weight of the coating composition, the content of the solvent is 2% to 15% by weight. The coating composition according to claim 1, wherein the solvent includes toluene, xylene or a combination thereof. A coating formed by curing the coating composition according to any one of claims 1 to 7. A varistor comprising: a varistor element; a first coating layer coated on the varistor element; and a second coating layer coated on the first coating layer; Wherein, the varistor element includes: a ceramic body, which has a first end and a second end opposite to the first end; a plurality of internal electrodes, the internal electrodes are arranged outside the ceramic body and adjacent Two inner electrodes are respectively connected to the first end and the second end; a first outer electrode arranged on the first end of the ceramic body and in contact with the corresponding inner electrode; and a second outer electrode, It is arranged on the second end of the ceramic body and is in contact with the corresponding internal electrode; wherein, the first coating is the coating described in claim 8. The varistor according to claim 9, wherein the second coating is cured by a second coating composition, the second coating composition comprising: a silicone resin; a filler; a flame retardant; And a solvent; wherein, based on the total weight of the second coating composition, the content of the silicone resin is 10% to 20% by weight, and the total weight of the filler and the flame retardant is 75% to 90% by weight %; Based on the total weight of the filler and the flame retardant, the content of the flame retardant is 30% to 50% by weight. The varistor according to claim 10, wherein the silicone resin includes methyl silicone resin, methyl phenyl silicone resin, vinyl silicone resin, methyl vinyl silicone resin, amino silicone resin, epoxy silicone resin Or a combination. The varistor according to claim 9, wherein the thickness of the first coating is between 1.1 mm and 2.0 mm; the thickness of the second coating is between 1.1 mm and 2.0 mm.

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