JPH0565045B2 - - Google Patents

Description

[Detailed description of the invention]

(a) Object of the Invention The present invention relates to a resin composition for coating a film capacitor. (Industrial Application Field) The film capacitor coating resin composition of the present invention coats a film capacitor, and after a short period of ultraviolet irradiation, the coating film is completely cured by heating at a relatively low temperature for a short period of time, and the performance is improved. Advantageously used to produce superior film capacitors. (Prior Art) Conventionally, thermosetting resins such as epoxy resins and polybutadiene resins have been mainly used for coating film capacitors. These resins can provide film capacitors with excellent moisture resistance, mechanical properties, electrical insulation properties, and the like. However, these resins require curing conditions of at least 2 hours at a temperature of 100 to 130°C. In addition, the viscosity decreases due to the temperature rise during heat curing, causing sag in the coating even if a thixotropic agent is added.
Thick coating is not possible, and it is necessary to apply multiple coats, resulting in poor coating productivity. For this reason, in recent years, research has been conducted on coatings using ultraviolet curable resins that have a short curing time and are less likely to cause dripping, and various resins have been proposed as coating resins. For example, radically polymerizable coating resins that can be completely cured by ultraviolet rays (Japanese Patent Publication No. 1989-892), and radically polymerizable coating resins that can completely cure resin that has entered the inside of the element by using both ultraviolet curing and thermosetting. A coating composition (Japanese Patent Publication No. 58-49582), a film capacitor coating resin (Japanese Patent Publication No. 1987-49582), which is a combination of ultraviolet curing and thermosetting radically polymerizable resin compositions containing an epoxy resin and an acid anhydride curing agent. 56-76517), and a mixture of an ultraviolet curable radical polymerizable resin and a linear polymer compound having an etrahydrofurfuryl group and an N-alkoxymethylcarbamoyl group in the side chain, various types such as imidazole type etc. A coating resin composition containing an epoxy resin containing an epoxy resin curing agent (Japanese Unexamined Patent Publication No. 144430/1982) has been proposed. However, when the UV-curable radical polymerizable coating resin described above is used to coat a film capacitor element, the resin that has penetrated into the element cannot be completely cured, so deterioration in capacitor performance cannot be avoided. do not have. Since the radically polymerizable coating resin is a combination of ultraviolet curing and thermosetting, the resin that has entered the inside of the element can be cured by heating. However, the cured resin of this resin does not have sufficient moisture resistance and insulation properties, and does not have sufficient capacitor performance. The coating resin improves the moisture resistance and insulation properties of the cured coating by blending an epoxy resin with an acid anhydride curing agent into a radically polymerizable resin that can be cured by both ultraviolet rays and heat. It is. However, since urethane prepolymer or polyester acrylate is used as the prepolymer of the radically polymerizable resin, this resin alone does not have sufficient moisture resistance, and the publication recommends that it be further layered with other ultraviolet curable radical resins. Painting is in progress. The coating resin is a combination of a radically polymerizable resin and an epoxy resin containing a curing agent, but this radically polymerizable resin does not contain a thermal polymerization initiator (organic peroxide). When a capacitor is coated with a resin, the radically polymerizable resin in the resin that has entered the inside of the element cannot be completely cured. Additionally, this resin can be used as an epoxy resin curing agent such as an imidazole curing agent (for example, 2-ethyl-
Even if 4-methyl-imidazole) is used,
The pot life of the resin is relatively short, and a special polymer compound called a linear polymer compound having a tetrahydrofurfuryl group and an N-alkoxymethylcarbamoyl group in the side chain is required. There are drawbacks. (Problems to be Solved by the Invention) The present invention improves the drawbacks of conventional coating resin compositions of this type, has a long pot life, and can be completely cured by heating at a relatively low temperature for a short time. It is an object of the present invention to provide a resin composition for coating a film capacitor, which can easily produce a film capacitor with extremely excellent performance such as moisture resistance without the need for overcoating. (b) Structure of the Invention (Means for Solving the Problems) As a result of various studies in order to solve the above problems, the present inventors have developed a radical containing a photosensitizer and a thermal polymerization initiator. In a coating composition in which a polymerizable resin is blended with an epoxy resin containing a curing agent, if epoxy (meth)acrylate is used as a prepolymer of the radically polymerizable resin, other prepolymers such as urethane (meth)acrylate or polyester can be used. It is possible to obtain a film capacitor with better performance such as moisture resistance than when using (meth)acrylate, and even when using epoxy (meth)acrylate, imidazole having a specific chemical structure can be used as the curing agent. It was discovered that the usable life can be extended by using such compounds, and the present invention was achieved. That is, the resin composition for coating a film capacitor of the present invention is a radically polymerizable resin composition containing (A) epoxy (meth)acrylate, a monomer having an ethylenic double bond, a photosensitizer, and a thermal polymerization initiator. and (B) an epoxy resin composition containing a 1-cyanoethyl-2-ethyl-4-methyl-imidazole curing agent in a weight ratio of 1:9 to 9:1. It is. In this specification, "acrylic acid" and "methacrylic acid" are collectively referred to as "(meth)acrylic acid".
``acrylate'' and ``methacrylate''
These are collectively called "(meth)acrylates." If another epoxy resin curing agent is used instead of the 1-cyanoethyl-2-ethyl-4-methyl-4-imidazole curing agent used in the present invention, the usable life of the resin composition will be shortened. For example, when an acid anhydride curing agent is used, the pot life is significantly shortened because the curing agent reacts with the hydroxyl groups of the epoxy (meth)acrylate. Furthermore, even if an imidazole-based hardening agent is used, if a hardening agent other than 1-cyanoethyl-2-ethyl-4-methyl-imidazole is used, such as a 2-ethyl-4-methyl-imidazole hardening agent, the pot life will be shortened. (See Comparative Example 4). Various epoxy (meth)acrylates can be used in the present invention. Examples include epoxy (meth)acrylates obtained by reacting bisphenol (eg, bisphenol A) type epoxy resins, novolac type epoxy resins, or alicyclic epoxy resins with (meth)acrylic acid. Epoxy (meth)acrylate has a large effect on the curing speed and physical properties of the coating film, and when epoxy (meth)acrylate is used,
Improved film capacitor and moisture resistance than with other prepolymers. In addition to participating in the polymerization curing reaction as a crosslinking agent, the monomer having an ethylenic double bond in the present invention acts as a diluent for epoxy (meth)acrylate, and further acts as an agent for imparting flexibility to the coating film. There is also. Examples of monomers having an ethylene double bond include styrene compounds such as styrene, divinylbenzene, and methylstyrene; esters of (meth)acrylic acid and alcohols, such as 2-hydroxyethyl (meth)
Examples include acrylate, carbitol (meth)acrylate, trimethylolpropane tri(meth)acrylate, 1,6-hexanediol di(meth)acrylate, and compounds having an allyl group such as diallyl phthalate and triallyl isocyanurate. These compounds may be used alone or in combination of two or more. Examples of the photosensitizer in the present invention include benzoin, benzoin ether, benzophenone, benzyl dimethyl ketal, hydroxycyclohexyl phenyl ketone, 2-ethylanthraquinone, and the like.
Or two or more types can be used in combination. The proportion of the photosensitizer used is about 0.5 to 5% by weight based on the total amount of epoxy (meth)acrylate and ethylenically unsaturated compound. Examples of the thermal polymerization initiator in the present invention include methyl ethyl ketone peroxide, benzoyl peroxide, t-butyl peroxybenzoate, 1,1-di-t-butyl peroxy-
Examples include 3,3,5-trimethylcyclohexane, and these can be used alone or in combination of two or more. The ratio of thermal polymerization initiator used is 0.5 to the total amount of epoxy (meth)acrylate and ethylenically unsaturated compound.
It is about 3% by weight. The epoxy resin used in the present invention contributes to improving the moisture resistance and insulation properties of the cured coating film, and various epoxy resins can be used, but typical examples include bisphenol A epoxy resin and Examples include novolak type epoxy resins. In addition, in the present invention, as a curing agent for epoxy resin, chemical structural formula: 1-cyanoethyl-2-ethyl-4 represented by
-Methyl-imidazole curing agent is selected and used. The reason is that this curing agent has the longest pot life among imidazole curing agents and can be cured at low temperatures. The amount of this curing agent used is preferably in the range of 2 to 10% by weight based on the epoxy resin. The coating resin composition of the present invention contains the radically polymerizable resin composition (A) and the curing agent-containing epoxy resin composition (B) in a ratio of 1:9 to 9:1, preferably 2:1.
It is prepared by blending at a weight ratio of 8:8 to 8:2 and mixing uniformly. If the proportion of epoxy resin (B) is too high, the ultraviolet curing speed will be slow and sag will occur during heat curing, making it impossible to obtain a uniform cured film. If the proportion is too small, radical polymerization will occur due to oxygen in the air. Even after heating and curing, the surface does not harden, and the surface of the cured coating film remains sticky, and the moisture resistance of the cured coating film deteriorates. The coating composition of the present invention may further contain fillers such as talc, silica powder, and calcium carbonate; thixotropes such as organic bentonite, finely divided silica powder, and asbestos powder; other pigments, flame retardants, etc. be able to. (Examples etc.) Below, Examples and Comparative Examples will be given and further explained in detail. Examples 1 to 5 A radically polymerizable resin composition (A ₁ ) and an epoxy resin composition (B ₁ ) having the following compositions were prepared. Radical polymerizable resin composition (A ₁ ) Kayalad R-011 ^* 100 parts by weight Styrene 50 〃 2-ethylanthraquinone 1 〃 t-butyl peroxybenzoate 2 〃 *...Product name of epoxy acrylate from Nippon Kayaku Co., Ltd. Epoxy resin Resuscitator (B ₁ ) Epicote 828 ^* 100 parts by weight 1-cyanoethyl-2-ethyl-4-methyl-imidazole 4 *...Product name of Yuka Ciel Epoxy Co., Ltd. The above resin composition (A ₁ ) and resin composition Thing (B ₁ )
and mixed at various weight ratios shown in Table 1,
Add 1.0% by weight of asbestos powder to this and stir.
A coating resin composition was prepared. Each resin composition obtained was stored at 25° C., and the time required for the viscosity to become twice the initial viscosity was measured to determine the pot life. The results were as shown in Table 1. Further, each resin composition was applied to a non-inductive film capacitor (50 nF) made of polyethylene terephthalate by a dip method. The thickness of each coating film was approximately 0.3 mm as a cured coating film. Each of the coated elements was first cured by ultraviolet irradiation and then by heating. The ultraviolet irradiation conditions are
The device was placed on a conveyor moving at a speed of 1 cm per second, and irradiated while the device was moving using a 1 kW metal halide lamp installed at a position where the shortest distance from the moving device was 10 cm. Further, the heating conditions were such that the element was heated in an oven with hot air at each temperature listed in Table 1 for a predetermined period of time. As a humidity test, each element was tested at a temperature of 40°C.
The rate of change in capacity was investigated when the sample was left in a desiccator at a relative humidity of 95% for 1000 hours. The results were as shown in Table 1. Comparative Example 1 Radical polymerizable resin composition (A') with the following composition
and an epoxy resin composition (B') was prepared. Radical polymerizable resin composition (A'): Kayalad R-011 ^* 100 parts by weight Styrene 80 〃 Benzyl dimethyl ketal 2 〃 t-Butyl peroxybenzoate 2 〃 *...Product name of epoxy acrylate from Nippon Kayaku Co., Ltd. Epoxy resin Resuscitator (B'): Epicote 828 ^* 100 parts by weight Methylhexahydrophthalic anhydride 85 〃 2-ethyl-4-methyl-4-imidazole (accelerator) 0.5 〃 *...Product name of Yuka Ciel Epoxy Co., Ltd. The resin composition (A') and the resin composition (B') are mixed at a weight ratio of 5:5, and asbestos powder is added.
A coating resin composition was prepared by adding 1.0% by weight.
The pot life of the obtained resin composition is shown in Examples 1-
The results measured in the same manner as in Example 5 are shown in Table 1. The resin compositions were also applied to film capacitors in the same manner as in Examples 1 to 5, and then cured in the same manner as in Examples 1 to 5, but under two different curing conditions shown in Table 1. The results were as shown in Table 1. Comparative Example 2 A composition in which 1.0% by weight of asbestos powder was added to the radically polymerizable resin composition (A ₁ ) described in Examples 1 to 5 (its pot life was as shown in Table 1).
It took over 500 hours. ) was applied to film capacitors in the same manner as in Examples 1-5 using only the coating resin. The coating thickness was approximately 0.3 mm as a cured coating. This coating film was irradiated with ultraviolet rays in the same manner as in Examples 1 to 5, and then heated and cured in the same manner. The obtained elements were subjected to a moisture resistance test in the same manner as in Examples 1 to 5, and the results were as shown in Table 1. Comparative Example 3 Only a composition in which 1.0% by weight of asbestos powder was added to the epoxy resin composition (B ₁ ) described in Examples 1 to 5 (its usable life was 80 hours as shown in Table 1) was applied as a coating resin to the same film capacitors as in Examples 1 to 5 so that the average thickness of the cured coating was about 0.3 mm. The obtained elements were cured by heating in an oven at 100° C. for 2 hours, and then subjected to a moisture resistance test in the same manner as in Examples 1-5. The results were as shown in Table 1. Comparative Example 4 A radically polymerizable resin composition having the same composition as the radically polymerizable resin composition (A ₁ ) in Examples 1 to 5 was prepared without blending t-butyl peroxybenzoate at all. In addition, 4 parts of 2-ethyl-4-methylimidazole was used instead of 1-cyanoethyl-2-ethyl-4-methyl-imidazole, and the rest was the same as the epoxy resin composition (B ₁ ) in Examples 1 to 5. An epoxy resin composition of the following composition was prepared. Both of the obtained resin compositions were mixed at a weight ratio of 5:5, and 1.0% by weight of asbestos powder was added to prepare a coating resin composition. The pot life of the resin composition was as shown in Table 1. Furthermore, the results of a moisture resistance test performed on elements obtained by coating and curing the resin composition in the same manner as in Examples 1 to 5 were as shown in Table 1. Example 6 Radical polymerizable resin composition (A ₂ ) having the following composition
and an epoxy resin composition (B ₂ ) was prepared. Radical polymerizable resin composition (A ₂ ) Kayalad R-130 ^* 100 parts by weight Styrene 40 〃 Hydroxycyclohexylphenyl ketone 2 〃 1,1-di-t-butylperoxy-3,3,5
-Trimethylcyclohexane 1 〃 *...Nippon Kayaku Co., Ltd.'s epoxy acrylate trade name Epoxy resin composition ( _B2 ) PE-10 ^* 100 parts by weight 1-cyanoethyl-2-ethyl-4-methylimidazole 4 〃 *...Large Product name of epoxy acrylate manufactured by Nippon Shikizai Kogyo Co., Ltd. This resin composition (A ₂ ) and (B ₂ ) are combined into A ₂ :B ₂ =
A coating resin composition was prepared by blending at a ratio of 5:5 (weight ratio) and adding 1.0% by weight of asbestos powder. ) and cured. The pot life of the coating resin composition and the physical properties of the resulting coating film were as shown in Table 1.

[Table] As is clear from Table 1, the resin composition of Comparative Example 1 has an extremely short pot life, and when cured at low temperatures, the moisture resistance of the capacitor is extremely poor. Although the resin composition of Comparative Example 2 has a long pot life, its moisture resistance is extremely poor. The resin composition of Comparative Example 3 has a relatively short pot life and has relatively poor moisture resistance even though it is coated with an epoxy resin.
This is thought to be because the cured coating film at the corner portions of the element becomes thinner due to sagging during heat curing. The resin composition of Comparative Example 4 has a relatively shorter pot life than the composition of Example 3. (c) Effects of the Invention The coating resin composition of the present invention has a long pot life, and the coating film can be formed by heating at a low temperature of around 100°C for about 2 hours after irradiation with ultraviolet light for a short time. Even the resin that has penetrated into the capacitor can be completely cured, and the resulting capacitor has excellent performance such as moisture resistance.

Claims (1)

[Claims] 1. (B) 1-cyanoethyl-2-ethyl- 1. A resin composition for coating a film capacitor, comprising an epoxy resin composition containing a 4-methyl-imidazole curing agent at a weight ratio of 1:9 to 9:1.