JPS6260428B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a highly heat-resistant electrically insulating powder coating composition that maintains film properties and electrically insulating properties even at temperatures up to about 700°C. In recent years, there has been a trend toward smaller and lighter rotating electrical equipment and other electrical equipment, and rotating electrical equipment is increasingly subject to high loads and generates high heat.
There is a strong desire to develop electrically insulating paints that can maintain film properties and electrically insulating properties even at high temperatures. Conventionally, epoxy resin powder coatings, molded films such as polyimide, etc. have been used for heat-resistant insulation treatment of rotating electric machines, but since these are organic materials, they have limited heat resistance. Paints that can maintain film properties and electrical insulation properties even at high temperatures of about 500℃ to 700℃ include glass frits or glass frits and inorganic substances suspended in organic solvents, colloidal silica, aluminum phosphate, etc. There are some that are suspended in water glass, but these require firing at high heat to form a coating film.
Furthermore, the coating film formed was brittle and caused problems in practical use. For example, Japanese Patent Application Laid-open No. 57-12073, JP-A No. 58-32665, and JP-A No.
As described in Japanese Patent No. 58-34870, heat-resistant paints made of silicone resins, epoxy resins, low melting point frits, and high melting point inorganic substances are known.
The coating film formed with this heat-resistant paint is produced in a temperature range of 250°C to 300°C or lower, where the resin does not decompose much, and in a temperature range of 400°C to 450°C, where the low melting point frit softens and melts and exhibits its strength as a binder. It exists as a strong insulating coating layer for a long time in the temperature range of Because it does not melt, it has almost no mechanical strength and is extremely incomplete as a heat-resistant paint. The inventors of the present invention have carried out intensive studies to overcome the drawbacks of these conventional techniques, and have found that a specific silicone-modified epoxy resin, a heat-resistant epoxy resin obtained from a specific isocyanate and an epoxy resin, a specific low-melting glass powder, A heat-resistant powder coating composition containing a high-melting-point inorganic filler in a specific proportion can be used in a high temperature range from room temperature to about 700℃, especially in the temperature range of 300℃ to 400℃, where conventional problems occurred. It was discovered that good film properties and electrical insulation properties can be continuously maintained, leading to the completion of the present invention. That is, the present invention provides (A) an organosilicone intermediate having a functional group capable of reacting with an epoxy resin containing a hydroxyl group;
Silicone-modified epoxy resin with a melting point of 50 to 90°C and an epoxy equivalent of 600 to 1500, obtained by modifying an epoxy resin in a range of 10 to 50% by weight; (B) an epoxy resin having two or more epoxy groups in the molecule; A compound containing an oxazolidone ring and an isocyanurate ring or an oxazolidone ring obtained by reacting at least one isocyanate selected from diisocyanate, diphenylmethane diisocyanate, or a trimer thereof, and has a melting point of 50 ~90
The main components are a heat-resistant epoxy resin with an epoxy equivalent of 200 to 1200 °C, (C) a low melting point glass powder with a melting point of 400 to 500 °C, and (D) a high melting point inorganic filler, the mixing ratio of which is the weight ratio. So (A):(B)=50:50~90:10, (C):(D)=10:90~50:50, (A)+(B):(C)+(D)=20 :80 to 50:50. The silicone-modified epoxy resin (A) used in the present invention is obtained by modifying an epoxy resin in a range of 10 to 50% by weight with an organic silicone intermediate having a functional group that can react with an epoxy resin containing a hydroxyl group. ~90°C and an epoxy equivalent of 600 to 1,500, preferably a melting point of 60 to 75°C, a number average molecular weight of 700 to 3,000, and an epoxy equivalent of 700 to 1,200. If the amount of modification by the organosilicone intermediate is less than 10% by weight, the heat resistance of the paint will be insufficient;
If it exceeds , the wettability with the painted body will be insufficient.
If the melting point of the silicone-modified epoxy resin (A) is below 50°C, it will flow too much when the powder coating composition is heated, melted, and cured, and the edge coverage of the formed insulating layer will be extremely low. Insulation failure is likely to occur, and blocking occurs within several hours even if the powder coating composition is left at room temperature. On the other hand, if the melting point exceeds 90°C, the fluidity when heating, melting, and curing the powder coating composition will be insufficient, and the smoothness of the formed insulating layer will deteriorate, resulting in a coated product with a good appearance. It becomes difficult to obtain. Furthermore, if the blending ratio of silicone-modified epoxy resin (A) is increased in order to improve the appearance, the heat resistance becomes insufficient. When the epoxy equivalent of the silicone-modified epoxy resin (A) is less than 600, the crosslinking density of the insulating layer formed by heating, melting, and curing the powder coating composition becomes too high, resulting in a decrease in impact resistance. If the epoxy equivalent exceeds 1500,
Since the crosslinking density of the insulating layer becomes too low, the hardness of the insulating layer decreases, which poses a practical problem. The organic silicone intermediate used to obtain the silicone-modified epoxy resin (A) of the present invention includes:
Those that have a functional group that can react with an epoxy resin containing a hydroxyl group, that is, those that have a hydroxyl group directly bonded to a silicon atom, a halogen group such as chlorine or bromine, an alkoxy group such as a methoxy group or an ethoxy group, an acetoxy group, etc. Among these, those having an alkoxy group are most preferred because they can easily react with the epoxy resin. For other substituents directly bonded to silicon,
For example, those having two or more types of groups having different decomposition temperatures, such as methyl group and phenyl group, are preferable because decomposition occurs in stages at high temperatures. Furthermore, the epoxy resin used to obtain the silicone-modified epoxy resin (A) of the present invention has two or more epoxy groups in the molecule, such as bisphenol type epoxy resin, halogenated bisphenol type epoxy resin, etc. , novolac type epoxy resin, resorcinol type epoxy resin, tetrahydroxydiphenylethane type epoxy resin, polyalcohol type epoxy resin, polyglycol type epoxy resin, glycerin triether type epoxy resin,
Polyolefin type epoxy resins, alicyclic type epoxy resins, etc. are not particularly limited, and these epoxy resins can be used alone or in combination. The heat-resistant epoxy resin (B) used in the present invention is
An epoxy resin containing an oxazolidone ring and an isocyanurate ring or an oxazolidone ring, which is obtained by reacting an epoxy resin having two or more epoxy groups in the molecule with a specific isocyanate, and has a melting point of 50 to 90°C. equivalent weight is 200
-1200, preferably a melting point of 60-80°C and an epoxy equivalent of 300-700. If the melting point of the heat-resistant epoxy resin (B) is below 50°C, the powder coating composition will flow too much when heated, melted, and cured, resulting in extremely low edge coverage of the formed insulating layer, resulting in poor insulation. Even if the powder coating composition is left at room temperature, blocking occurs within several hours. On the other hand, if the melting point exceeds 90°C, the fluidity when heating, melting, and curing the powder coating composition will be insufficient, and the smoothness of the formed insulating layer will deteriorate, resulting in a coated product with a good appearance. It becomes difficult to obtain. Furthermore, if the blending ratio of the heat-resistant epoxy resin (B) is increased in an attempt to improve the appearance, the heat resistance becomes insufficient. When the epoxy equivalent of the heat-resistant epoxy resin (B) is less than 200,
The crosslinking density of the insulating layer formed by heating, melting, and curing the powder coating composition becomes too high, resulting in a decrease in impact resistance and making it easy to crack.If the epoxy equivalent exceeds 1200, the insulating layer becomes Since the crosslinking density becomes too low, the hardness of the insulating layer decreases, which poses a practical problem. The epoxy resin used to obtain the heat-resistant epoxy resin (B) of the present invention has two or more epoxy groups in the molecule, such as bisphenol type epoxy resin, halogenated bisphenol type epoxy resin, novolac Particularly limited epoxy resins, resorcinol epoxy resins, tetrahydroxydiphenylethane epoxy resins, polyalcohol epoxy resins, polyglycol epoxy resins, glycerin triether epoxy resins, polyolefin epoxy resins, alicyclic epoxy resins, etc. These epoxy resins can be used alone or in combination. Also heat resistant epoxy resin
The isocyanates used to obtain (B) are tolylene diisocyanate, diphenylmethane diisocyanate, or their combinations with potassium acetate, sodium carbonate,
It is limited to at least one kind of isocyanate selected from polyisocyanates containing isocyanurate rings trimerized in the presence of a catalyst such as oxalic acid, and the reason is that the above isocyanates and epoxy resin The resin obtained by reacting the
This is because it has the best heat resistance in the temperature range of . The general formula for the trimerization reaction of isocyanate groups is shown in (). Trimerized polyisocyanate has an isocyanurate ring with good heat resistance, and its trifunctionality increases crosslinking density, so it is preferable to use as much as possible to improve mechanical strength and heat resistance, but if too much is used, epoxy Since there is a risk of gelation during reaction with groups, it is preferable to limit the amount of trimerized polyisocyanate to within 30% by weight of the isocyanates used. The heat-resistant epoxy resin (B) can be obtained by reacting the above-mentioned epoxy resin with an isocyanate in the presence of a catalyst such as an alkyldimorpholine, imidazole, or a boric acid ester. Its general formula is shown in (). The mixing ratio of the epoxy resin and isocyanate is preferably such that the amount of epoxy group is 1.5 equivalents or more and 5 equivalents or less per equivalent of isocyanate group. The resins used in the present invention include silicone-modified epoxy resin (A) and heat-resistant epoxy resin.
The mixing ratio with (B) is (A):(B)=50:50-90:
A range of 10 is used. If the blending ratio of heat-resistant epoxy resin (B) is less than 10% by weight, at high temperatures,
In particular, there is little improvement in mechanical strength and adhesive strength in the temperature range of 300°C to 400°C, and if it exceeds 50% by weight, the crosslinking density increases too much and impact resistance decreases. Low melting point glass powder (C) used in the present invention
has an average particle size of 1 to 60μ and a melting point of 400 to 500°C. Glass frit with a melting point lower than 400°C is advantageous for film formation at high temperatures, but it is not sanitary because it contains a large amount of lead in its composition, and it softens at temperatures between 400°C and 600°C. This is so severe that the coating film hardness at high temperatures becomes insufficient. Furthermore, if the glass frit has a melting point higher than 500°C, film formation at high temperatures will be insufficient. High melting point inorganic filler (D) used in the present invention
is an inorganic powder that softens and does not melt at about 500 to 700°C, for example, one or more of silica, clay, mica, calcium carbonate, alumina, aluminum hydroxide, high melting point glass, etc. are used, among which Most preferably, silica, alumina, and mica are used. Inorganic components used in the present invention include:
The blending ratio of the low melting point glass powder (C) and the high melting point inorganic substance (D) is in the range of (C):(D)=10:90 to 50:50 by weight. If the blending ratio of the low melting point glass powder (C) is less than 10% by weight, the mechanical strength and adhesion to the base body in the temperature range of 400 to 700°C will be insufficient, and the
If it exceeds this weight percent, the insulating layer tends to be thermally softened at 400°C to 700°C, resulting in insufficient hardness. The mixture containing silicone-modified epoxy resin (A), heat-resistant epoxy resin (B), low-melting point glass powder (C), and high-melting point inorganic filler (D) as main components used in the present invention has a compounding ratio of is the weight ratio (A)
+(B):(C)+(D)=20:80 to 50:50 is used. The blending ratio of resin components (A) + (B) is 20% by weight
If it is less than 50% by weight, good flowability cannot be obtained, and if the
If it exceeds this, the heat resistance will be insufficient. Silicone-modified epoxy resin (A) according to the present invention
As the curing agent for the heat-resistant epoxy resin (B), curing agents commonly used for epoxy resins can be used as they are. That is, carboxylic acid anhydride group, amino group, carboxyl group, carboxylic acid hydrazide group, hydroxy group, -SH group, CONH- group, -NCO group, -NCS
organic compounds containing groups, organic mineral acid esters, organometallic compounds Lewis acids, titanium containing organic groups,
Conventionally known hardening agents such as zinc boron or aluminum compounds and other acidic or basic compounds are used. For example, aliphatic polyamines such as ethylenediamine and triethylenetetramine, aliphatic hydroxylamines such as monoethanolamine and propanolamine, aromatic amines such as metaphenylenediamine and 4,4'-diaminodiphenylmethane, piperazine, triethylenediamine, etc. Aliphatic amines having a cyclic structure, imidazoles such as 2-ethyl 4-methylimidazole and 2-phenylimidazole, and other nitrogen-containing curing agents include dicyandiamide, carboxylic acid dihydraside, and the like. As acid curing agents, phthalic acid, maleic acid, tetrahydrophthalic acid, trimellitic acid,
Examples include polyhydric carboxylic acids such as azelaic acid, benzophenonetetracarboxylic acid, and adipic acid, and their anhydrides. Other examples include novolac type or resol type phenolic resins, -NCO group-containing prepolymers of polyurethane resins, titanium and zinc compounds containing organic groups such as tetrabutyl titanate and zinc octoate. In addition, some of these curing agents can achieve rapid curing by using a small amount of curing accelerator such as tertiary amine, imidazole, organic acid metal salt, Lewis acid, or amine complex salt. It is mixed as appropriate. Among these curing agents, imidazole,
Dicyandiamide and carboxylic acid dihydrazide are preferably used for reasons such as storage stability. The mixture containing silicone-modified epoxy resin (A), heat-resistant epoxy resin (B), low-melting point glass powder (C), and high-melting point inorganic powder (D) used in the present invention includes the above-mentioned resins, In addition to the inorganic filler, curing agent, and curing accelerator, various additives can be added as necessary. Examples of such additives include inorganic pigments,
Examples include organic additives, flame retardants, flame retardant aids, silane coupling agents, antifoaming agents, mold release agents, thixotropic improvers, surface smoothness improvers, fluidity improvers, and the like. Further, methods for forming an insulating coating layer on a coated body using the powder coating composition of the present invention include a fluidized dipping method,
Any general powder coating method such as a hot spray method, an electrostatic dynamic dipping method, or an electrostatic spray method can be used, and an insulating coating layer with good smoothness can be easily obtained. The insulating coating layer obtained by heating, melting, and curing the powder coating composition of the present invention has smoothness,
Good adhesion to the element and temperature range from room temperature to 700℃
It has good mechanical strength, adhesion to the base body, and electrical insulation properties for a long time even in a wide temperature range, especially in the temperature range of 300 to 400 degrees Celsius, which has not been overcome with conventional technology. This is due to the following reasons. That is, in the powder coating composition, a silicone-modified epoxy resin in which an epoxy resin is partially modified with an organic silicone intermediate having good heat resistance is used as the resin.
(A) and a heat-resistant epoxy resin (B) containing an oxazolidone ring and an isocyanurate ring or an oxazolidone ring obtained by partially modifying the epoxy resin with a specific isocyanate, so the powder coating composition is heated, The insulating coating layer obtained by melting and curing has good flowability when melted, which is a characteristic of epoxy resin, good smoothness due to adhesion,
It has adhesion to the element body. In addition, the insulating coating layer obtained by heating, melting, and curing the powder coating composition can be heated from room temperature to
It has good heat resistance and electrical insulation properties for a long time in the temperature range of around 300℃, and due to the action of the oxazolidone ring and isocyanurate ring or oxazolidone ring contained in the heat-resistant epoxy resin, it can be used from room temperature to around 400℃, especially at 300℃. It has good heat resistance and electrical insulation properties for a long time even in the temperature range of ~400℃, and in the temperature range of 400 to 700℃, the silicon-oxygen remaining after the organic silicone of the silicone-modified epoxy resin (A) is thermally decomposed. A substance having a bond, a skeleton having a partially remaining oxazolidone ring and an isocyanurate ring or an oxazolidone ring of the heat-resistant epoxy resin (B), a low melting point glass (C) that starts softening and melting, and a high melting point inorganic filler (D)
700°C from room temperature to become enameled.
It has continuous good heat resistance and electrical insulation properties over a wide temperature range of ℃. Heating a powder coating composition consisting of a silicone-modified epoxy resin (A) excluding the heat-resistant epoxy resin (B) of the present invention, a low melting point glass (C), and a high melting point inorganic filler (D),
Even for insulating coating layers obtained by melting and curing, the temperature is below 300℃ or 400℃ for the above reasons.
It has good heat resistance and electrical insulation properties for a long time in the above temperature range, but if kept in the temperature range of 300 to 400℃ for a long time, the silicone-modified epoxy resin (A) gradually decomposes, while the low melting point glass softens. , the mechanical strength of the insulating coating layer is weak because it does not melt, and there is a heat-resistant epoxy resin (B) containing an oxazolidone ring and an isocyanurate ring or an oxazolidone ring that is extremely difficult to thermally decompose even in the temperature range of 300 to 400°C. For the first time, it has consistently good heat resistance and electrical insulation properties over a wide temperature range from room temperature to 700°C. The present invention will be explained in more detail with reference to Examples below. Example 1 Bisphenol A diglycidyl ether type epoxy resin (Epicote 1001, manufactured by Yuka Ciel Co., Ltd.)
100 parts, tolylene diisocyanate 5 parts and 2-
1 part of ethyl 4-methylimidazole is reacted,
A heat-resistant epoxy resin _B1 having an oxazolidone ring with a melting point of 75°C and an epoxy equivalent of 720 was obtained. Next, silicone-modified epoxy resin [25% by weight of bisphenol A diglycidyl ether type epoxy resin modified with a methoxy group-containing silicone intermediate, melting point 70°C, epoxy equivalent 1300-1350] 30 parts heat-resistant epoxy resin B ₁ 10 A mixture consisting of 3 parts: low melting point glass powder (melting point 450-480°C), 20 parts silica powder, 34 parts inorganic pigment (red iron), 1 part dicyandiamide (Epicure 108FF, manufactured by Yuka Ciel Co., Ltd.) was kneaded with two rolls. This was made into a sheet, and this was crushed using a crusher to obtain a powder coating composition. The above powder coating composition was applied onto an iron piece preheated to 180°C using a fluidized dipping device, and further cured at 200°C for 10 minutes to obtain a coating film with good smoothness and adhesion.
The obtained iron pieces were placed in an electric furnace set at 300°C, 400°C, and 500°C, and after 500 hours, they were taken out and evaluated. The evaluation results are shown in Table 1. In accordance with JISK6850, shearing of iron-iron test pieces bonded by heating and curing the above powder coating composition was performed under normal conditions, after treatment at 300℃ for 500 hours, after treatment at 400℃ for 500 hours, and after treatment at 500℃ for 500 hours. Adhesive strength was measured. The results are shown in Table 2. Example 2 Bisphenol A diglycidyl ether type epoxy resin (Epicote 1001, manufactured by Yuka Ciel Co., Ltd.)
100 parts of diphenylmethane diisocyanate, 7 parts of 2-ethyl 4-methylimidazole, and 1 part of 2-ethyl 4-methylimidazole were reacted to obtain heat-resistant epoxy resin _B2 having an oxazolidone ring and having a melting point of 72°C and an epoxy equivalent of 710. In Example ₁ , heat-resistant epoxy resin _B2 was used instead of heat-resistant epoxy resin B1, and the melting point was 450.
Melting point 410~ instead of ~480℃ low melting point glass powder
A powder coating composition was obtained in the same manner except for using a low melting point glass powder of 430°C. In the same manner as in Example 1, the obtained powder coating composition was used to coat an iron piece and adhere a test piece for measuring adhesive strength, and evaluation was performed in the same manner as in Example 1. The evaluation results are shown in Tables 1 and 2. Example 3 Bisphenol A diglycidyl ether type epoxy resin (Epicote 1001, manufactured by Yuka Ciel Co., Ltd.)
100 parts, 4 parts of tolylene diisocyanate, 2 parts of trimer of diphenylmethane diisocyanate and 2 parts.
-Ethyl 4-methylimidazole (1 part) was reacted to obtain a heat-resistant epoxy resin _B3 containing an oxazolidone ring and an isocyanurate ring and having a melting point of 69°C and an epoxy equivalent of 680. A powder coating composition was obtained in the same manner as in Example ₁ except that heat-resistant epoxy resin _B3 was used instead of heat-resistant epoxy resin B1. In the same manner as in Example 1, the obtained powder coating composition was used to coat an iron piece and adhere a test piece for measuring adhesive strength, and evaluation was performed in the same manner as in Example 1. The evaluation results are shown in Tables 1 and 2. Example 4 100 parts of a cresol novolak type epoxy resin (EOCN102, manufactured by Nippon Kayaku Co., Ltd.), 8 parts of tolylene diisocyanate, 2 parts of a trimer of diphenylmethane diisocyanate, and 1 part of 2-ethyl 4-methylimidazole were reacted. A heat-resistant epoxy resin _B4 containing an oxazolidone ring and an isocyanurate ring and having a melting point of 68° C. and an epoxy equivalent of 300 was obtained. A powder coating composition was obtained in the same manner as in Example 1 except that heat-resistant epoxy resin _B4 was used instead of heat-resistant epoxy resin _B1 . The powder coating composition obtained in the same manner as in Example 1 was used to coat an iron piece and adhere a test piece for measuring adhesive strength, and evaluation was made in the same manner as in Example 1.
The evaluation results are shown in Tables 1 and 2. Comparative Example 1 In Example 1, except for heat-resistant epoxy resin B ₁ , 40 parts of silicone-modified epoxy resin was used,
A powder coating composition was obtained in the same manner as above. In the same manner as in Example 1, the obtained powder coating composition was used to coat an iron piece and adhere a test piece for measuring adhesive strength, and evaluation was performed in the same manner as in Example 1. The evaluation results are shown in Tables 1 and 2. Comparative example 2 Methyl phenyl silicone resin (TR3168, manufactured by Toshiba Silicon Co., Ltd.) 26 parts epoxy resin (GY-6084, manufactured by Ciba Geigy)
A mixture consisting of 14 parts low melting point glass (lead-based, melting point 450°C), 57 parts silica powder, and 3 parts was kneaded with two rolls to form a sheet, and this was crushed with a crusher to obtain a powder coating composition. . The above powder coating composition was applied using a fluidized dipping device onto a piece of iron preheated to 150°C, and was further cured at 200°C for 60 minutes, but the resulting coating film was striped and had poor smoothness, and it did not stick to the piece of iron. The adhesion was also extremely poor. The obtained iron pieces were placed in an electric furnace set at 300°C, 400°C, and 500°C, and after 500 hours, they were taken out and evaluated. The evaluation results are shown in Table 1. In accordance with JISK6850, shearing of iron-iron test pieces bonded by heating and curing the above powder coating composition was performed under normal conditions, after treatment at 300℃ for 500 hours, after treatment at 400℃ for 500 hours, and after treatment at 500℃ for 500 hours. Adhesive strength was measured. The results are shown in Table 2.

【table】

【table】

[Table] In Table 1, appearance was determined visually, and coating film hardness and adhesion were determined by allowing the treated test pieces to cool to room temperature and then impacting them with a hammer. As is clear from Tables 1 and 2, in the examples of the present invention, compared to the conventionally known comparative examples, the
Heat resistance in the temperature range around 400℃ has been significantly improved.

Claims (1)

[Scope of Claims] 1 (A) An epoxy resin having a melting point of 50 to 90°C, which is obtained by modifying an epoxy resin in a range of 10 to 50% with an organic silicone intermediate having a functional group that can react with an epoxy resin containing a hydroxyl group. a silicone-modified epoxy resin having an equivalent weight of 600 to 1,500; (B) an epoxy resin having F or more epoxy groups in the molecule; and at least one selected from tolylene diisocyanate, diphenylmethane diisocyanate, or a trimer thereof. Contains an oxazolidone ring and an isocyanurate ring or an oxazolidone ring obtained by reacting with more than one type of isocyanate, and has a melting point of 50 to 90.
The main components are a heat-resistant epoxy resin with an epoxy equivalent of 200 to 1200 °C, (C) a low melting point glass powder with a melting point of 400 to 500 °C, and (D) a high melting point inorganic filler, the mixing ratio of which is the weight ratio. So (A):(B)=50:50~90:10, (C):(D)=10:90~50:50, (A)+(B):(C)+(D)=20 :80-50:50 High heat-resistant electrically insulating powder coating composition.