Insulating varnish composition, cured insulating varnish product, and method for producing cured insulating varnish product

Abstract

The present invention provides an insulating varnish composition, an insulating varnish cured product, and a method for manufacturing an insulating varnish cured product, which can improve the dielectric constant (PDIV) by uniformly incorporating air bubbles and increasing the creepage distance in an insulating varnish cured product used in the gaps between wires such as coils that have been treated with insulating varnish. [Solution] A thermosetting insulating varnish composition comprising (A) a base polymer, (B) a reactive diluent, (C) a microencapsulated foaming agent, and (D) a curing agent, characterized in that the foaming start temperature of (C) the microencapsulated foaming agent is lower than the curing start temperature of the insulating varnish composition, and the atmospheric pressure boiling point of (B) the reactive diluent is higher than the maximum exothermic temperature of the insulating varnish composition, is provided as an insulating varnish composition, an insulating varnish cured product, and a method for producing an insulating varnish cured product.

Description

Technical Field

[0001] The present invention relates to an insulating varnish composition containing a microcapsule-type foaming material, a cured product, and a method for producing the cured product.

Background Art

[0002] Wires wound in a coil shape, such as generators and transformers of electric and electronic devices, are used.

[0003] In such wires, in order to prevent electromagnetic vibration, PDIV (partial discharge inception voltage) between coils, and vibration, a liquid thermosetting resin is applied and heat-cured.

[0004] In the future, in order to meet the need for higher voltage, it is essential to improve PDIV. As a method, it is known that by forming bubbles in the cured insulating varnish and reducing the relative permittivity, PDIV can be improved.

[0005] As a prior art document regarding such an insulating varnish composition, for example, Patent Document 1 discloses a thermosetting resin containing at least one resin selected from an unsaturated polyester resin, an epoxy resin, and a vinyl ester resin, which contains a high molecular weight polymer having a weight average molecular weight of 2000 or more, and a bubble-forming component in a liquid state having a vapor pressure of 1 mmHg or more and less than 80 mmHg in the standard state of the gas.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

[0008] On the other hand, as shown in Figure 3, in an insulating varnish cured product in which air bubbles 7 are formed inside the insulating varnish cured product layer 8, the relative permittivity is reduced and the PDIV is improved.

[0009] Thus, when air bubbles are present in a cured product obtained by heat-curing an insulating varnish composition, the relative permittivity decreases and the creepage distance C increases, resulting in improved PDIV (Permitted Dielectric Vinyl Inspection).

[0010] However, if there is variation in the size of the bubbles, or if the maximum diameter of the bubbles is too large, the bubbles will connect with each other, forming giant bubbles or connecting holes, which prevents the desired PDIV improvement effect from being fully achieved. In this regard, the cured product described in Patent Document 1 suppressed the formation of large bubbles and connecting holes by miniaturizing the bubbles.

[0011] Furthermore, the insulating varnish composition used in varnish impregnation insulation treatment is required to have high impregnation properties into the gaps between wires in the coil and low viscosity. However, if the viscosity is low, the amount of insulating varnish composition adhering to areas with wide gaps between wires, such as the coil ends, will be insufficient to form a sufficiently cured insulating varnish, which can lead to a decrease in PDIV (Performance-Dependent Insulation).

[0012] In addition, while extending the insulation distance is an effective means of improving insulation between coils, in addition to reducing the dielectric constant by forming bubbles as described above, the average diameter of the bubbles contained in the cured product in Patent Document 1 is very fine, ranging from 0.1 μm to 10 μm. Therefore, it is not only difficult to obtain a sufficient creepage distance, but the volume expansion rate of the cured product is low, and there is a possibility that the curing that enhances the insulation effect of the insulating varnish cured product, i.e., the PDIV, is insufficient in the wide gaps between the wires of the coil. Therefore, the present invention aims to provide an insulating varnish composition that can form a cured insulating varnish in the wide gaps between electric wires, thereby increasing PDIV, even if the insulating varnish composition has low viscosity and high penetration.

[0013] In other words, the present invention aims to provide an insulating varnish composition, an insulating varnish cured product, and a method for manufacturing an insulating varnish cured product that can improve PDIV by reducing the dielectric constant and increasing the creepage distance, preferably by uniformly incorporating air bubbles of 50 μm or less in size, in an insulating varnish cured product used in the gaps between electric wires such as coils that have been treated with insulating varnish. [Means for solving the problem]

[0014] The inventors conducted diligent research and found that in a thermosetting insulating varnish composition comprising a base polymer, a reactive diluent, a microencapsulated foaming agent, and a curing agent, the foaming initiation temperature of the microencapsulated foaming agent is lower than the curing initiation temperature of the insulating varnish composition, and the atmospheric pressure boiling point of the reactive diluent is higher than the maximum exothermic temperature of the insulating varnish composition. By uniformly incorporating bubbles, the dielectric constant is reduced, and the creepage distance is increased, thereby improving the PDIV (Permeable Discharge Isolation). This led to the completion of the present invention. In other words, the present invention provides the following:

[0015] (1) A first aspect of the present invention is a thermosetting insulating varnish composition comprising (A) a base polymer, (B) a reactive diluent, (C) a microencapsulated foaming agent, and (D) a curing agent, characterized in that the foaming start temperature of (C) the microencapsulated foaming agent is lower than the curing start temperature of the insulating varnish composition, and the atmospheric pressure boiling point of (B) the reactive diluent is higher than the maximum exothermic temperature of the insulating varnish composition.

[0016] (2) A second aspect of the present invention is an insulating varnish composition as described in (1), characterized in that (A) the base polymer is an epoxy acrylate resin which is a thermosetting resin having one or more radical polymerizable groups in one molecule, (B) the reactive diluent is a reactive diluent which has one or more radical polymerizable groups in one molecule, and (D) the curing agent is an organic peroxide curing agent whose half-life temperature at one hour is lower than the curing furnace setting temperature.

[0017] (3) A third aspect of the present invention is an insulating varnish cured product formed by curing an insulating varnish composition described in (1) or (2), characterized in that the average diameter of bubbles contained in the insulating varnish cured product is 1 to 50 μm, and the maximum diameter of bubbles is 50 μm or less.

[0018] (4) A fourth aspect of the present invention is a method for producing an insulating varnish cured product, characterized by comprising the steps of: producing an insulating varnish composition as described in (1) or (2); impregnating an object to be insulated with the insulating varnish composition; and heating and curing the insulating varnish composition that has coated the object to be insulated. [Effects of the Invention]

[0019] According to the present invention, it is possible to provide an insulating varnish composition, an insulating varnish cured product, and a method for manufacturing an insulating varnish cured product that can improve PDIV by reducing the relative permittivity by uniformly incorporating air bubbles and increasing the creepage distance in an insulating varnish cured product used in the gaps between electric wires such as coils that have been treated with insulating varnish. [Brief explanation of the drawing]

[0020] [Figure 1] This is the curing temperature profile image of the insulating varnish composition of the present invention. [Figure 2] This is a cross-sectional view of a conventional cured insulating varnish between flat copper wires and round copper wires. [Figure 3] This is a cross-sectional view of a cured insulating varnish that forms bubbles in the cured product between flat copper wires and round copper wires.

Mode for Carrying Out the Invention

[0021] Hereinafter, a mode for carrying out the present invention (hereinafter simply referred to as "this embodiment") will be described in detail. The following embodiments are examples for explaining the present invention, and are not intended to limit the present invention to the following contents. The present invention can be appropriately modified and implemented within the scope of its gist.

[0022] In the present invention, the normal boiling point is a measured value by atmospheric distillation. For compounds whose normal boiling point cannot be observed, the normal boiling point converted from the reduced boiling point, which is a measured value by reduced pressure distillation, using a boiling point conversion table (Science of Petroleum, Vol. II. p. 1281 (1938)) is used.

[0023] <Insulating Varnish Composition> The insulating varnish composition in the present invention is a thermosetting composition containing (A) a base polymer, (B) a reactive diluent, (C) a microcapsule type foaming agent, and (D) a curing agent. Hereinafter, each component will be described in detail.

[0024] ((A) Base Polymer) The (A) base polymer used in the present invention (hereinafter also simply referred to as component (A)) is preferably one whose terminal structure is a radical polymerizable group, which is commonly used in thermosetting resins, but it may also have epoxy groups or isocyanate groups. Furthermore, from the viewpoint of volatility, it is preferable that the weight-average molecular weight is 500 or more. For example, among those in the (A) base polymer with a radical polymerizable group, examples include bisphenol A diglycidyl ether dimethacrylate, bisphenol A diglycidyl ether dimethacrylate, bisphenol F diglycidyl ether dimethacrylate, and among those with an epoxy group, examples include bisphenol A type liquid epoxy resin, diaminodiphenylmethane type epoxy resin, phenol novolac type liquid epoxy resin, etc., and one or more of these can be used in combination.

[0025] ((B) Reactive diluent) The reactive diluent (B) used in the present invention (hereinafter also simply referred to as component (B)) is a compound having radical polymerizable groups such as vinyl groups or (meth)acrylic groups, or epoxy groups, and from the viewpoint of variations in heating temperature in the curing furnace, its boiling point at atmospheric pressure is higher than the maximum exothermic temperature, preferably 10°C or more higher (the detailed reasons will be described later). For example, if the maximum exothermic temperature is 260°C, examples include neopentyl glycol dimethacrylate (boiling point at atmospheric pressure: 273°C), dicyclopentenyloxyethyl methacrylate (boiling point at atmospheric pressure: 315°C), and trimethylolpropane trimethacrylate (boiling point at atmospheric pressure: 354°C), and one or more of these can be used in combination.

[0026] ((C) Microencapsulated foam material) The (C) microencapsulated foam material used in the present invention (hereinafter also simply referred to as component (C)) has a hydrocarbon compound as the foaming component and a thermoplastic resin as the shell portion. In the heat curing process described later, in order to ensure that the foaming start temperature is lower than the curing start temperature, and that the average bubble diameter in the cured insulating varnish is 1 to 50 μm, and the maximum bubble diameter is 50 μm or less, it is preferable to select a microcapsule-type foaming material from the catalog in which the average bubble diameter calculated using the particle size before foaming and the expansion coefficient at the curing start temperature is 1 to 50 μm.

[0027] Examples of such microencapsulated foaming materials include FN-80GSD (foaming start temperature: 100-110°C, average bubble diameter: approximately 28 μm) and FN-65 (foaming start temperature: 105-115°C, average bubble diameter: approximately 45 μm) (both manufactured by Matsumoto Oil & Fat Pharmaceutical Co., Ltd.) when the curing start temperature is 130°C, and one or more types can be used in combination. In this invention, the foaming start temperature of (C) microcapsule-type foam material is the value listed in the catalog of a commercially available product.

[0028] ((D) hardening material) The curing agent (D) used in the present invention (hereinafter also simply referred to as component (D)) is selected to be suitable for the above-mentioned components (A) and (B). (A) If the base polymer has radical polymerizable groups, it is necessary to select an organic peroxide. Preferably, the organic peroxide has a 1-hour half-life temperature lower than the curing furnace setting temperature. For example, when the curing furnace setting temperature is 150°C, examples include 1,1-di(t-hexylperoxy)cyclohexane (1-hour half-life temperature: 107°C), 1,1-di(t-butylperoxy)cyclohexane (1-hour half-life temperature: 111°C), t-hexylperoxy-isopropyl-monocarbonate (1-hour half-life temperature: 115°C), etc., and one or more of these can be used in combination.

[0029] Furthermore, if the (A) base polymer has epoxy groups, it is necessary to select an acid anhydride or amine as the (D) curing agent. In this case, similar to component (B), it is preferable that the boiling point at atmospheric pressure is 10°C or more higher than the maximum exothermic temperature. Examples include 1,2,3,6-tetrahydrophthalic anhydride (boiling point at atmospheric pressure: 297°C) and triethylenetetramine (boiling point at atmospheric pressure: 266°C), and one or more of these can be used in combination.

[0030] ((E) Polymerization inhibitors) Furthermore, the insulating varnish composition in the present invention may contain (E) a polymerization inhibitor from the viewpoint of storage stability. Examples of (E) polymerization inhibitors include hydroquinone, methoquinone, 1,4-benzoquinone, phenothiazine, etc., and one or more of these can be used in combination.

[0031] ((F) Metal hair dryer) Furthermore, in the insulating varnish composition of the present invention, a (F) metal dryer such as an organic acid metal salt may be used from the viewpoint of drying properties of the coating surface and interior. Organic acid metal salts are salts of organic acids such as octic acid and naphthenic acid with metals such as Co, Mn, Sn, Ni, Zn, Pb, Cr, and Fe. Examples include cobalt naphthenate, manganese naphthenate, tin naphthenate, nickel naphthenate, zinc naphthenate, lead naphthenate, chromium naphthenate, and iron naphthenate, and one or more of these can be used in combination.

[0032] ((G) Other ingredients) (G) Other components may be added within any range that does not impair the properties of the insulating varnish composition and cured product in the present invention.

[0033] (Method for manufacturing insulating varnish composition) The insulating varnish composition of the present invention is manufactured by uniformly stirring and mixing (A) a base polymer, (B) a reactive diluent, (C) a microencapsulated foaming agent, (D) a curing agent, and other components.

[0034] (Containing amount) The amount of the insulating varnish composition in the present invention is preferably 10 to 300 parts by mass, and more preferably 50 to 200 parts by mass, per 100 parts by mass of the (A) base polymer. Furthermore, when an organic peroxide is added as a curing agent (D) to a total of 100 parts by mass of (A) base polymer and (B) reactive diluent, the amount added is preferably 0.5 to 2.0 parts by mass, and when an acid anhydride or amine is added, the amount added is preferably 50 to 100 parts by mass. In addition, the amount of (C) microencapsulated foaming agent added is preferably 5 to 55 parts by mass.

[0035] <Insulating varnish cured product and method for manufacturing the same> The insulating varnish composition of the present invention is used for varnish impregnation insulating treatment of objects to be insulated. In this process, an insulating varnish cured product is obtained by going through the steps of manufacturing an insulating varnish composition, impregnating the object to be insulated with the insulating varnish composition, and heating and curing the insulating varnish composition that has coated the object to be insulated. The method of applying the insulating varnish composition to the object to be insulated is not limited to impregnation; for example, it may be a coating process using a coating device.

[0036] The heating conditions for curing in the heat curing process are preferably 100-200°C for 10-180 minutes, and more preferably 130-180°C for 30-120 minutes. In this case, the number of heating cycles may be modified as appropriate. Furthermore, the definition of temperature in this case may be the temperature set in the furnace settings when heating using a furnace such as a curing furnace, or it may be the temperature of the varnish composition itself, measured separately with a measuring device during heating.

[0037] Figure 1 shows an image of the curing temperature profile of the insulating varnish composition of the present invention. In the insulating varnish composition of the present invention, the change in the bubble diameter of the heated and expanded (C) microcapsule-type foam material is fixed by the thickening that occurs as the insulating varnish composition begins to harden. Therefore, as shown in Figure 1, the foaming start temperature of (C) microcapsule-type foam material must be lower than the hardening start temperature of the insulating varnish composition. The specific difference between the hardening start temperature of the insulating varnish composition and the foaming start temperature of (C) microcapsule-type foam material is as described in the detailed explanation of component (C).

[0038] Furthermore, in order to suppress the formation of large bubbles and connecting pores originating from the reactive diluent (B) that occur in the hardened insulating varnish due to heat curing, the atmospheric pressure boiling point of the reactive diluent (B) must be higher than the maximum exothermic temperature of the insulating varnish composition, as shown in Figure 1. The specific difference between the maximum exothermic temperature of the insulating varnish composition and the atmospheric pressure boiling point of the reactive diluent (B) is as described in the detailed explanation of component (B).

[0039] Furthermore, if (D) the curing agent is an organic peroxide, it is preferable that the 1-hour half-life temperature of (D) the curing agent is lower than the curing furnace setting temperature (not shown). If (D) the curing agent is an organic peroxide and the 1-hour half-life temperature of (D) the curing agent is higher than the curing furnace setting temperature, there is a possibility that (C) the microcapsule-type foam material will reach the curing start temperature before it expands to a sufficient size. The difference between the maximum exothermic temperature of the specific insulating varnish composition and the atmospheric pressure boiling point of (B) the reactive diluent is as described in the detailed explanation of component (B). The difference between the specific curing furnace setting temperature and the 1-hour half-life temperature of the organic peroxide curing agent is as described in the detailed explanation of component (D).

[0040] The curing start temperature and maximum heat generation temperature of the insulating varnish composition of the present invention shall be the values ​​obtained from the following test method, which is based on Section 5.8 of JIS K 6901:2008. The specific test method involves placing 3.0 g of an insulating varnish composition in a φ60 aluminum petri dish with a thermocouple at the center of the bottom surface, and measuring the temperature change when heating and curing at an arbitrary curing temperature and time. The temperature at which heat generation begins due to the curing reaction is defined as the curing start temperature, and the highest temperature reached due to heat generation is defined as the maximum heat generation temperature.

[0041] Furthermore, the insulating varnish cured product obtained through the heat curing process has an average bubble diameter of 1 to 50 μm and a maximum bubble diameter of 50 μm or less. Since both the average bubble diameter and the maximum bubble diameter are within the above numerical range, the bubbles are uniformly contained within the insulating varnish cured product. This reduces the relative permittivity and increases the creepage distance, resulting in an insulating varnish composition with improved PDIV.

[0042] (Examples of applications for insulating varnish compositions and cured products) The insulating varnish composition and cured product of the present invention can be applied to insulating components of electrical and electronic equipment, automobiles, semiconductor devices, and the like. The components are not particularly limited as long as they are materials that require insulation, such as coils, wires, and circuit boards, but it is especially preferable to apply it to coils.

[0043] Although the present invention has been described above using embodiments, it goes without saying that the technical scope of the present invention is not limited to the scope described in the above embodiments. It will be obvious to those skilled in the art that various modifications or improvements can be made to the above embodiments. Furthermore, it is clear from the claims that such modified or improved forms may also be included in the technical scope of the present invention. [Examples]

[0044] The present invention will be described in detail below with reference to examples. However, the present invention is not limited in any way to the examples shown below.

[0045] [Example 1] As Example 1, (A) Bisphenol A diglycidyl ether diacrylate: 50 parts by mass, (B) Dicyclopentenyloxyethyl methacrylate: 50 parts by mass, (C)FN-80GSD:30 Mass part, (D) 1,1-di(t-butylperoxy)cyclohexane: 1.0 part by mass was stirred and mixed to obtain an insulating varnish composition.

[0046] The curing start temperature and the maximum heat generation temperature were measured using the test method described above with a φ60 aluminum petri dish.

[0047] The test specimens were prepared by impregnating the upper and lower surfaces of an arrow pair (0.3 mm coil distance) of polyimide flat copper wire with the above-mentioned insulating varnish composition, and then heating and curing it using an ESPEC Safety Oven SPHH-201 at a curing oven setting of 150°C / 60 min.

[0048] For PDIV measurement, the above test specimens were measured in n=3, and the average value was taken as the PDIV value. The ratio of the PDIV values ​​in each example was calculated, with the PDIV value of Comparative Example 1 (described later) set to 1.

[0049] For bubble diameter measurement, the above-mentioned test specimen was cut, the cross-section was observed using a scanning electron microscope (SEM), and the diameters of 10 randomly selected bubbles were measured. A "○" (○) was given if the average bubble diameter was 50 μm or less, and a "×" (×) was given if it was larger than 50 μm. Similarly, a "○" (○) was given if the maximum bubble diameter was 50 μm or less, and a "×" (×) was given if it was larger than 50 μm.

[0050] [Example 2] In Example 2, the same composition as in Example 1 was prepared and evaluated in the same manner, except that neopentyl glycol dimethacrylate (boiling point at atmospheric pressure: 273°C) was selected as component (B) in the experiment of Example 1.

[0051] [Comparative Example 1] In Comparative Example 1, the same composition as in Example 1 was prepared and evaluated in the same way, except that component (C) was not added.

[0052] [Comparative Example 2] In Comparative Example 2, the same composition as in Example 1 was prepared and evaluated in the same manner, except that 2-hydroxyethyl methacrylate (boiling point at atmospheric pressure: 205°C) was selected as component (B) in the experiment of Example 1.

[0053] [Comparative Example 3] In Comparative Example 3, the same composition as in Example 1 was prepared and evaluated in the same manner, except that FN-36D (foaming start temperature: 70-80°C, average bubble diameter: approximately 128 μm) was selected as component (C) in the experiment of Example 1.

[0054] The experimental results for each of the above examples and comparative examples are shown in Table 1. [Table 1]

[0055] As shown in Table 1, in Examples 1 and 2, by setting the foaming start temperature of the (C) microcapsule-type foam material lower than the curing start temperature, and setting the atmospheric pressure boiling point of the reactive diluent higher than the maximum exothermic temperature, bubbles generated by the volatilization of the reactive diluent are suppressed, resulting in a PDIV greater than 1 and a score of ○ for the average bubble diameter and maximum bubble diameter.

[0056] On the other hand, in Comparative Examples 1 to 3, Comparative Example 1, which did not contain (C) microencapsulated foaming agent, was unable to increase the creepage distance and did not sufficiently improve the PDIV effect. Furthermore, in Comparative Example 2, where (B) the boiling point of the reactive diluent at atmospheric pressure was lower than the maximum exothermic temperature, and in Comparative Example 3, where (C) a microcapsule-type foam material was selected with an average bubble diameter greater than 50 μm at the curing start temperature, the PDIV improvement effect was not sufficiently obtained due to the formation of large bubbles and connecting pores.

[0057] From the above, it has been shown that the present invention provides an insulating varnish composition that can improve PDIV by reducing the dielectric constant through the uniform incorporation of air bubbles and increasing the creepage distance. [Explanation of symbols]

[0058] 1. Insulating coating 2 flat conductor 3 Flat copper wire 4 Round wire 5 Round enameled wire 6. Insulating varnish cured product 7 bubbles 8. Insulating varnish cured layer C Creepage distance

Claims

1. A thermosetting insulating varnish composition comprising (A) a base polymer, (B) a reactive diluent, (C) a microencapsulated foaming agent, and (D) a curing agent, (C) The foaming start temperature of the microencapsulated foam material is lower than the curing start temperature of the insulating varnish composition, (B) An insulating varnish composition characterized in that the boiling point of the reactive diluent at atmospheric pressure is higher than the maximum exothermic temperature of the insulating varnish composition.

2. (A) The base polymer is an epoxy acrylate resin, which is a thermosetting resin having one or more radical polymerizable groups in one molecule. (B) The reactive diluent is a reactive diluent having one or more radical polymerizable groups in one molecule, (D) The insulating varnish composition according to claim 1, characterized in that the curing agent is an organic peroxide curing agent whose 1-hour half-life temperature is lower than the curing furnace setting temperature.

3. An insulating varnish cured product formed by curing the insulating varnish composition according to claim 1 or 2, An insulating varnish cured product characterized in that the average diameter of bubbles contained in the insulating varnish cured product is 1 to 50 μm, and the maximum diameter of bubbles is 50 μm or less.

4. A method for manufacturing an insulating varnish cured product, A step of manufacturing the insulating varnish composition according to claim 1 or 2, A step of impregnating the object to be insulated with an insulating varnish composition, A method for producing a cured insulating varnish, comprising the step of heating and curing an insulating varnish composition that has been applied to an object to be insulated.

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