JPS6225185B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an electrically insulating coating paint for capacitors such as magnetic capacitors, plastic film capacitors, and mica capacitors. Capacitors are coated with an insulating coating to protect them from external moisture, insulate them from other parts, and mechanically protect the capacitor body. The characteristics of this insulating coating paint greatly affect not only the moisture resistance and mechanical properties of capacitors, but also the productivity of capacitors, and an insulating coating that satisfies all of these is desired. These coating methods for capacitors include a solvent dip coating method, a solvent-free dip coating method, a casting method, a powder coating method, a molding method, etc., but the solvent dip coating method accounts for the majority. This solvent-based dip coating method involves using a coating consisting of a thermosetting resin, filler, additives, and solvent either as is or by adding a solvent to adjust the viscosity to a level that makes it easy to dip coat, and then immersing the capacitors in the coating solution. In this method, the thermosetting resin is coated, air-dried to volatilize the solvent, and then heat is applied to harden the thermosetting resin to coat the capacitors. Furthermore, if moisture resistance is important, these coated capacitors may be impregnated with wax or epoxy resin. The resin for solvent-based dip coating used to carry out the solvent-based dip coating method is resin supplied in powder form (add solvent when using).
There are two types of resins: resins that are supplied in a solution state with a solvent already added thereto, and each has its own advantages and disadvantages. The former resin, which is supplied in powder form, is
Phenol resin is usually used as the thermosetting resin component, and although the resin has good storage stability, it has the disadvantage that the coated capacitor has poor moisture resistance and mechanical strength. On the other hand, the latter resin, which is supplied in a solution state, uses epoxy resin, epoxy resin and novolac type phenol resin, urethane resin, polyester resin, silicone resin, etc. as the thermosetting resin component, and is coated with The capacitor has good moisture resistance and mechanical strength, but the resin has poor storage stability and a long drying time. As a result of research to improve these needs and problems, the present inventors have developed a powder resin composition for electrical insulation coating for solvent-based dip coatings, which contains a thermosetting resin, a filler, and an additive. By using solid resol type phenolic resin and solid epoxy resin as thermosetting resin components,
It has been found that all the properties of the resin composition can be improved, such as good storage stability, fast drying, good moisture resistance as a capacitor property, and high mechanical strength. Furthermore, in the present invention, it has been found that the above-mentioned properties can be preferably improved by blending 40 to 70% by weight of solid resol type phenolic resin and 60 to 30% by weight of solid epoxy resin as thermosetting resin components. . The purpose of the present invention is to make a paint that can be stored in a powdered state (has good storage stability) by adding a solvent during use, and by coating capacitors with this paint by dip coating, the paint film dries quickly.
Another object of the present invention is to provide an insulating coating paint that has excellent coating film strength and moisture resistance in terms of capacitor properties. However, the present invention provides a powder resin composition for electrical insulation coating for solvent-based dip coatings containing a thermosetting resin, a filler, and an additive, in which the thermosetting resin component is 40 to 70% by weight of a solid resol type phenolic resin.
and a solid epoxy resin of 60 to 30% by weight, and the blending ratio of the thermosetting resin component in the entire composition is 5 to 30% by weight.
This is a powder resin composition characterized in that the content is 20% by weight. The solid resol type phenolic resin used in the present invention contains 1 mol or more of formaldehyde per 1 mol of phenols (preferably 1.2 to 2.0 in view of reactivity with the epoxy resin), and a nitrogen-containing compound catalyst as a catalyst. Alternatively, it is a resin that is condensed and dehydrated by a conventional method using an alkaline earth metal catalyst alone or in combination, and preferably has a melting point of 50° C. or higher. The phenols mentioned here include phenol, cresol, xylenol, resorcinol, and alkylphenols such as paratertiary butylphenol, paraoctylphenol, paranonylphenol, and paraphenylphenol. Formaldehyde is usually treated as an aqueous formalin solution, but may also be a solid such as parformaldehyde, and its concentration is not particularly limited. The nitrogen-containing compound catalyst includes ammonia, triethylamine, triethanolamine, diethyleneamine, dimethylamine, aniline, hexamethylenetetramine, and the like. Alkaline earth metals are oxides and hydroxides of alkaline earth metals such as calcium, magnesium, and barium. Note that alkali metal catalysts such as sodium hydroxide are not used in the present invention because they deteriorate electrical insulation. Although these nitrogen-containing compound catalysts and alkaline earth metal catalysts can be used alone for the condensation reaction between phenols and formaldehyde, it is preferable to use a combined catalyst of a nitrogen-containing compound catalyst and an alkaline earth metal catalyst. , strength and heat resistance properties can be further improved. Further, the melting point of the produced resin is preferably 50°C or higher; if a resin with a melting point of 50°C or lower is used, the powdered resin composition may solidify. The solid epoxy resin used in the present invention is
They are bisphenol type epoxy resin and novolak type epoxy resin. The bisphenol type epoxy resin is a condensation resin composed of bisphenol A and epichlorohydrin, and is preferably a solid resin having an epoxy equivalent of 400 to 3000. When the epoxy equivalent is 3000 or more, the reactivity decreases and the crosslinking density upon curing decreases, so that the moisture resistance and strength also tend to decrease. Furthermore, if the epoxy equivalent is less than 400, the epoxy resin cannot become solid and is not suitable for practical use. The novolak type epoxy resin is a condensation resin composed of phenols and epichlorohydrin, and is preferably a solid resin with a melting point of 50°C or higher. Incidentally, these bisphenol type epoxy resins and novolac type epoxy resins can also be used in combination. Next, the composition of the powder resin composition of the present invention will be described. Among the thermosetting resin components, the blending ratio of epoxy resin and phenol resin is particularly important and has a large influence on various properties. In other words, epoxy resin has superior moisture resistance and impact strength compared to phenolic resin, so generally speaking, the higher the proportion of epoxy resin blended, the better the moisture resistance and strength. If it exceeds this, drying properties will be poor, dip workability will also be reduced, and the resin composition will not be able to exhibit sufficient strength and moisture resistance. Also, the amount of
If the amount is less than 30% by weight, the blending ratio is small, resulting in poor effects and is not sufficient. Therefore, the blending ratio is 60 to 30% by weight of epoxy resin and 40 to 70% by weight of phenolic resin. The higher the proportion of the thermosetting resin component in the resin composition consisting of the thermosetting resin component, filler, and additives, the higher the strength will be, but if the proportion exceeds 20% by weight, the drying properties will be significantly slowed down. Practical problems tend to occur, such as hindering the impregnation of impregnating agents such as wax.On the other hand, if it is less than 5% by weight, the resin component is too small and will interfere with uniform bonding to the filler, resulting in weak strength and is not suitable. Not. Therefore, the proportion of the thermosetting resin component in the resin composition consisting of the thermosetting resin component, filler, and additives is 5 to 20% by weight. The filler used in the powder resin composition of the present invention is
Inorganic powders such as quartz powder, calcium carbonate powder, hydrated alumina powder, kaolin powder, alumina powder, clay, talc, and mica powder are used, but are not limited thereto. The additives used in the powder resin composition of the present invention are:
Additives include curing accelerators such as imidazole and aromatic amines, anti-sagging agents such as finely powdered silica, thickeners such as bentonite, antifoaming agents, pigments, and dyes. The present invention will be explained in detail below using examples. However, the present invention is not limited to the examples. Also, the “departments” listed here
All "%" refers to "parts by weight" and "% by weight" unless otherwise specified. Production example 1 94 parts of phenol, 130 parts of 37% formalin, 10 parts of 28% aqueous ammonia and calcium hydroxide as a catalyst
A reflux reaction was carried out at a temperature of 100°C for 20 minutes, followed by dehydration under vacuum to obtain a solid resol type phenolic resin having a contact point of 65°C (hereinafter referred to as solid resol A). Production example 2 94 parts of phenol, 146 parts of 37% formalin, and 15 parts of 28% ammonia water as a catalyst were mixed at a temperature of 100°C.
A reflux reaction was carried out for 40 minutes, and then dehydration was carried out under vacuum to obtain a solid resol type phenolic resin (hereinafter referred to as solid resol B) having a melting point of 70°C. Examples 1 to 5, Comparative Examples 1 to 3 Powdered resin compositions were obtained by pulverizing and mixing at the blending ratios shown in Table 1.

【table】

[Table] Paste preparation Examples 1 to 5 Powder resin compositions of Comparative Examples 1 to 3
Acetone to methanol = 3 to 1 for 100 parts
A paste having a viscosity of 2000 to 3000 centipoise at 25°C was prepared by blending and mixing 25 parts of a mixed solvent (weight ratio), and was further diluted with the above mixed solvent to adjust the viscosity to 1500 centipoise at 25°C. Evaluation Results The paste prepared as above was dip coated onto a ceramic capacitor, and its air drying properties, electrical properties such as moisture resistance, and bending strength were measured. Table 2 shows the evaluation results.

【table】

Claims (1)

[Scope of Claims] 1. In a solvent-based electric insulation coating powder resin composition for dip coating containing a thermosetting resin, a filler, and an additive, the thermosetting resin component is 40 to 70% by weight of a solid resol type phenolic resin. solid epoxy resin
1. A powder resin composition comprising 60 to 30% by weight and characterized in that the proportion of the thermosetting resin component in the entire composition is 5 to 20% by weight. 2. The solid resol type phenolic resin uses 1 mole or more of formaldehyde per mole of phenols, and the reaction catalyst is a nitrogen-containing compound alone catalyst or a combination catalyst of a nitrogen-containing compound and an alkaline earth metal catalyst, and this The powder resin composition according to claim 1, which is a solid resol type phenolic resin condensed in the presence of a catalyst. 3. The powder resin composition according to claim 1, wherein the solid epoxy resin is a bisphenol type epoxy resin that is solid at room temperature or a novolak type epoxy resin that is solid at room temperature.