JP3567334B2 - Epoxy varnish composition and method of use - Google Patents

Description

【０００５】
従来例１の配合によるエポキシワニスは低粘度であるため、どぶ漬け処理時にワニスがスロット４内コイル５及びコイルエンド３などの中に容易に浸透する。次にステ−タをどぶ漬け槽から取り出し加熱硬化処理を行うが、この時ワニスは温度が上昇されるため更に粘度が低下して、スロット４内コイル５及びコイルエンド３のエナメル電線間に保持されていたワニスの大部分は流れ落ちてしまう。この結果、エナメル電線の表面に形成される皮膜は極めて薄くなり、エナメル電線間及びエナメル電線と絶縁紙などの間に空隙を残して小さな接着力しか得られず、また十分な耐環境性及び熱放散性を得ることも出来ない。
従来例１の欠点を改良するため、従来例１の配合組成に更に揺変成剤、例えばコロイド状シリカ粉末（平均粒子径０．０１μｍ）を添加してエポキシワニスのチクソトロピ−を増大させる方法がある。この配合組成の例を従来例２に示す。
従来例２による配合組成のエポキシワニスは従来例１に比べて静的粘度が増大するが、どぶ漬け処理時にワニスをスロット４内コイル５及びコイルエンド３等の中に浸透させることに関しては特に問題が無い。また、加熱硬化時のワニス温度上昇による粘度低下に関しても、ワニスのチクソトロピ−が大きいためスロット４内コイル５及びコイルエンド３等の中に保持されていたワニスは容易に流れ落ちることはない。このため、エナメル電線上にワニス皮膜が厚く付着し、エナメル電線間及びエナメル電線と絶縁紙などとの間には強力な接着力が得られ、更に空隙が少ないため良好な耐環境性と熱放散性が得られる。
【０００６】
【発明が解決しようとする課題】
ところが、揺変成剤エアロジルの添加によりチクソトロピ−を増大した従来例２の配合によるエポキシワニスは、外部から撹拌や振動などのズリ応力が加わった時に粘度が低下し、また配合後経時的にチクソトロピ−が失われていく性質を有しているため、以下に示すような問題点を残していた。
従来例２では、エポキシワニスにチクソトロピ−を持たせ静的粘度を大きく保持しているため、ステ−タをエポキシワニス中にどぶ漬け処理した後の、取り出し作業中または加熱硬化中に、外部から振動などのズリ応力が加わると粘度が低下し一度含浸し付着したワニスが流れ落ちてしまう。
また、配合直後のエポキシワニスを使用してどぶ漬けし加熱硬化処理をすると、期待する効果が得られる場合でも、配合後数日経過すると時効によりチクソトロピ−が低下して、従来例１と同様に加熱硬化時の粘度が小さくなってしまう（静的粘度が小さいため）。
この状態のエポキシワニスで同じ処理を行うと、スロット４内コイル５及びコイルエンド３などの中に一度含浸されたワニスの大部分がどぶ漬け槽からの取り出し時や加熱硬化時に流れ落ちて、エナメル電線表面に付着するワニス皮膜が薄くなり、期待するほどの接着力、耐環境性及び熱放散性が得られなくなる。
上記のような処理中の振動など取扱上の制約や、配合後の経時的な粘度変化などの問題がなく、配合後長期間経過後に使用しても一定厚みのワニス被覆層を形成することが可能で、高い接着強度を有し耐振動性、耐環境性や熱放散性が優れた接着層を形成出来るエポキシワニス組成物を提供するとともに、この組成物を使用して電機機器のコイルおよび電線集合体などに含浸処理する方法を提供することが本発明に課せられた課題である。
【０００７】
【課題を解決するための手段】
本発明によるエポキシワニス組成物は、従来からの成分であるエポキシ樹脂、反応性希釈剤、酸無水物の硬化剤、硬化促進剤とに加え、コロイダルシリカの代わりに一定の粒度分布を有するシリカ微粉末を充填剤（フィラ−）として配合した無溶剤型エポキシ樹脂である。
本発明のエポキシワニス組成物を構成するエポキシ樹脂としては、ビスフェノ−ルＡ型やビスフェノ−ルＦ型のエポキシ樹脂などが好適に用いられ、そのようなエポキシ樹脂としては、エピコ−ト８２８、８２７、８０７（いずれも商品名：油化シェル社製）などがある。また、脂環式エポキシ樹脂、水添ビスフェノ−ルＡ型エポキシ樹脂などを用いることもできる。更に、フェノ−ルノボラックエポキシ樹脂やクレゾ−ルノボラックエポキシ樹脂等も用いることが出来、これらとビスフェノ−ルＡ型、ビスフェノ−ルＦ型、脂環式エポキシ樹脂、水添ビスフェノ−ルＡ型エポキシ樹脂を適当量混合したものも用いることが出来る。このような混合樹脂からなるワニスは更に耐熱性の高いものとなる。
また、必要に応じてモノグリシジルエ−テル、ジグリシジルエ−テル等の反応性希釈剤を添加することも出来る。
【０００８】
本発明のエポキシワニス組成物を構成する硬化剤としては、吸湿結晶化の恐れのないＭＮＡ（メチルナジックアンハイドライド）、ＭＨＡＣ−Ｐ（無水メチルハイミック酸）、メチルヘキサハイドロ無水フタル酸、メチルテトラハイドロ無水フタル酸、ポリアゼライン酸無水物等の酸無水物硬化剤がある。
また、硬化促進剤としては第３級アミン硬化促進剤（例えばＫ−６１Ｂジメチルアミノメチルフェノ−ル）やイミダゾ−ル化合物があるが、ポットライフや耐熱性の点からイミダゾ−ル化合物が特に好ましい。イミダゾ−ル化合物の中でも上記エポキシ樹脂との相溶性が良くポットライフが長い点で、２−エチル−４−メチルイミダゾ−ル、オクチル酸変成２−エチル−４−メチルイミダゾ−ル及びイミダゾ−ル環中の第２級アミン官能基を不活性のシアノエチル基で置換した１−シアノエチル−２−メチルイミダゾ−ル、１−シアノエチル−２−フェニル−４、５−ジ−（シアノエトルキシメチル）イミダゾ−ル、１−シアノエチル−２−フェニルイミダゾ−ルなどが好適に用いられるが、中でも１−シアノエチル−２−エチル−４−メチルイミダゾ−ルが最も好適に使用できる。
エポキシ樹脂系の成形体、ＩＣ封止樹脂やモ−ルド樹脂等に通常添加されている無機充填材としては、シリカ、タルク、炭酸カルシウム、アルミナなどが知られているが、本発明のエポキシワニス組成物を構成する無機充填材としては、特に絶縁性（誘電率、体積固有抵抗等）及び熱伝導率、線膨張係数や価格の面からシリカ（高純度結晶性石英）が最適である。
【０００９】
課題を解決するために適したシリカは、粒子径１０μｍ以上の粒子の含有率が１０重量％未満で、粒子径１０μｍ未満で１μｍ以上の粒子の含有率が９０％以上であるシリカ微粉末が特に好ましく、エポキシ樹脂組成物中の前記シリカ微粉末の含有率は２０〜４０％の範囲が好ましい。
さらに、配合された上記のエポキシワニス組成物を長期保存した場合に生じるシリカ微粉末の沈降による粘度の低下を一層遅らすため、また積極的に沈降を阻止するため、本発明の第２の組成ではドロマイト粘土微粉末を添加した。該ドロマイト粘土微粉末はシリカ微粉末より平均粒子径が小さい粒子からなり、エポキシワニス組成物に配合するシリカ微粉末の添加量の３〜１０重量％を添加する。これによって、配合したエポキシワニス組成物中でのシリカ微粉末の沈降を防止し長期間にわたって一定の粘度を保つことを可能にした。
【００１０】
【作用】
本発明で使用するシリカは粒子径１０μｍ以上の粒子が１０重量％未満で、粒子径１０μｍ未満で１μｍ以上の粒子が９０重量％以上で構成されるシリカ微粉末を、エポキシ樹脂、反応性希釈剤、酸無水物硬化剤、イミダゾ−ル化合物促進剤とともにエポキシワニス組成物中に２０〜４０重量％添加することにより、さらにドロマイト粘土をシリカ微粉末の添加量に対して外掛けで３〜１０重量％添加することにより、配合後の分散性と粘度の経時変化をなくし、硬化後のワニスに十分な接着強度、耐環境性、熱放散性を付与するとともに、振動の激しい使用環境においても十分な耐クラック性を保持することが可能になった。
前述したシリカ（高純度結晶性石英フィラ−）はその物性としての熱伝導率が８Ｗ／（ｍ・Ｋ）で、線膨張係数が０．４〜０．６×１０^−６であるため、前記エポキシワニスに前記重量％添加すると、熱伝導率はシリカを含まない時の０．２から２〜３Ｗ／（ｍ・Ｋ）に増大し、線膨張係数はシリカを含まない時の８０×１０^−６から５０〜６０×１０^−６に低下させる作用を有する。
ドロマイト粘土はシリカとほぼ等しい比重を有するため、シリカ微粒子より平均粒子径が小さいドロマイト粘土微粒子を添加することにより、これら粒子が沈降する際にシリカ微粒子間にドロマイト微粒子が浸入し、シリカ微粒子の凝集を妨げかつ長期保管後の再分散を容易にする。
【００１１】
【実施例】
以下本発明の実施例を従来例や比較例と比較しながら具体的に説明する。
表１に示すエポキシ樹脂、反応性希釈剤、酸無水物硬化剤と硬化促進剤からなるエポキシ樹脂分に、前記シリカ微粉末を内掛けで１０〜５０重量％添加したエポキシワニス組成物を配合し、それぞれ図３に示すＪＩＳ Ｃ ２１０３に規定された１−ＡＩＷφ１．６ストラッカ試験片にワニス処理し、最適条件である１３０℃で５時間加熱してゲル化させ、その後ポストキュアさせて試料を作成し、接着力を試験した。ワニス中のシリカ微粉末の含有率とストラッカ接着力の関係を図４に示す。
【表１】

この実験の結果によれば、前記シリカ微粉末の含有率が２０重量％未満では接着力が小さく２０重量％から５０重量％までの範囲では接着力が大きいことが解る。
表１に示すエポキシ樹脂、反応性希釈剤、酸無水物硬化剤と硬化促進剤からなるエポキシ樹脂分に表２に示す各種フィラ−を量を変えて添加させた種々のエポキシワニス組成物を配合し、それぞれを用いて図１に示した３相誘導電動機のステ−タをどぶ漬けして、その後１３０℃で５時間加熱してゲル化させ、その後ポストキュアさせて試料を作成した。これら各試料に付着したワニス硬化皮膜を外観的に観察しまた表面平滑性を調べるとともに、ステ−タ中央部とコイルエンドを切断しその断面を研磨してスロット内コイル及びコイルエンド中へのワニスの含浸性を調べた。また、前記各種エポキシワニス組成物について図３の試験片を用いてそれぞれ前記ストラッカ試験を行い接着力を試験した。
これらの結果をまとめて表２に示す。
【表２】

ここに示した実施例１と実施例２はそれぞれ前記従来例１と前記従来例２による配合組成と同じエポキシワニスを使用したものである。
また、３種の比較例は添加するシリカ粉末の粒径分布と添加量の適正範囲を決定するために作成した試料であり、比較例３は図３に示したシリカ微粒子を５０重量％添加した組成と同じエポキシワニスである。
【００１２】
充填剤を添加しない従来例１は接着力が小さく、揺変成剤を添加しかつ配合直後の従来例２はワニス付着厚みが３０μｍで接着力、含浸性そして表面平滑性ともに良好であったが、従来例２と同じ組成で配合後１週間経過した従来例３は、ワニス厚みが１０μｍに減少し接着強度も充分な値は得られなかった。
粒子径１０μｍ以上の粒子の含有率が３０重量％以上であるシリカ小粒粉末を３０重量％添加した比較例１は含浸性は良好であったが表面平滑性が不十分であった。
シリカ粒子径１μｍ以下の粒子の含有率が５０重量％以上である、シリカ極微粒粉末を３０重量％添加した比較例２は、形成されたエポキシワニスの粘度が高くなりすぎるためコイル内への含浸性が十分ではなかった。
本発明で使用したシリカ微粉末を本発明の含有率範囲を越えて５０重量％含有させた比較例３は、前記図３でも示したように十分大きな接着力を示したが、エポキシワニスの粘度が高くなりすぎるため含浸性が十分ではなかった。
これらに比較して、粒子径１０μｍ以上の粒子が１０重量％未満で、粒子径１０μｍ未満で１μｍ以上の粒子が９０重量％以上であるシリカ微粒粉末を３０重量％添加したエポキシワニス組成物は配合後１日の実施例１及び配合後３０日の実施例２ともにワニス付着厚み２０μｍを確保し、接着力、含浸性そして表面平滑性の全てに関して良好な結果を得た。
【００１３】
粒子径１０μｍ以上の粒子が１０重量％未満で、１０μｍ未満で１μｍ以上の粒子が９０重量％以上で構成されるシリカ微粉末を３０重量％添加した実施例１と実施例２はともに十分良好な特性を示したが、配合後３０日目ではシリカ微粉末の沈降が認められこれを再分散するためにかなりの撹拌処理を行った。
配合後３０日という経過日数は十分長いもので、実用的に使用できるという点で満足できるものではあるが、更に取扱を容易にするための分散性を増した実施例を以下に示す。
実施例１の配合に沈降防止剤即ち分散剤としてカルシウムとマグネシウムの複合炭酸塩であり平均粒子径が２〜１０μｍであるドロマイト粘土の微粉末（商品名マイクロド−ル：ヘキスト合成Ｋ．Ｋ．製）を添加して分散性を高めた。

【００１４】
実施例３及び実施例４のエポキシワニス組成物を配合し、その３０日後におけるシリカ微粉末の沈降の状態及び分散作業の難易度と、配合直後と配合後３０日目のエポキシワニス組成物の接着力、含浸性及び表面平滑性とを検討した。
その結果によれば、マイクロド−ルをシリカ微粉末の添加量に対して外掛けで５重量％添加した実施例３では、シリカ微粉末の沈降は生じたものの容易に再分散でき、またマイクロド−ルをシリカ微粉末の添加量に対し外掛けで１０重量％添加した実施例４ではシリカ微粉末の沈降は全く生じないことが認められた。
なお、実施例３、４ともに配合直後と配合後３０日目にワニス処理したものはそれぞれ良好な目的特性を得た。
本発明による機構的な効果を、隣接するエナメル電線Ｂ間に付着し硬化したエポキシワニス接着剤Ａの断面により比較した。
従来例３と実施例２について観察した結果を模式化して図５に示す。従来例３のエナメル電線Ｂの表面に付着したワニスＡ′の皮膜は比較的薄く、特に２本の電線の接触部Ｃ′表面でネッキング（くびれ）が生じている。一方、実施例２のエナメル電線Ｂの表面に付着したワニスＡの皮膜は比較的厚く、２本の電線の接触部Ｃの表面に於いてもなだらかな曲線を描きネッキングは生じてなく、空隙を生じにくい皮膜が形成されている。
【００１５】
【発明の効果】
粒子径１０μｍ以上の粒子が１０重量％未満で、粒子径１０μｍ未満で１μｍ以上の粒子が９０重量％以上で構成されるシリカ微粉末を、エポキシ樹脂、反応性希釈剤、酸無水物硬化剤、イミダゾ−ル化合物促進剤とともにエポキシワニス組成物中に２０〜４０重量％添加することにより、さらに前記エポキシワニス組成物にドロマイト粘土をシリカ微粉末の添加量に対して外掛けで３〜１０重量％添加することにより、エポキシワニスの粘度を高めまた配合後における該粘度の経時変化を無くし、どぶ漬け処理後加熱硬化した絶縁コイル等において、十分な接着強度、耐環境性や熱放散性を付与するとともに、振動の激しい使用環境においても十分な耐クラック性を保持することが可能になる。
更に、シリカを無機充填剤として選択したことにより、硬化したエポキシワニスの熱伝導率を高め線膨張係数を小さくする効果を得た。
【図面の簡単な説明】
【図１】３相誘導電動機用ステ−タの外観斜視図である。
【図２】図１の半径方向内側の斜視図である。
【図３】ＪＩＳ Ｃ ２１０３によるストラッカ試験片の平面図を示す。
【図４】エポキシ樹脂分にシリカ微粉末を種々の量添加させたワニスで処理して行ったストラッカ試験片の接着強度を示す。
【図５】エナメル電線の表面に接着させた従来のワニスと本発明のワニスの状態を示す断面図である。
【符号の説明】
１ ステ−タ鉄心
２ 絶縁板
３ コイルエンド
４ スロット
５ コイル
６ スロットライナ−
７ 相間絶縁
Ａ エポキシワニス
Ａ′エポキシワニス
Ｂ エナメル電線
Ｃ エナメル電線の接触部
Ｃ′エナメル電線の接触部[0001]
[Industrial applications]
The present invention relates to electric coils such as electric motors and generators used in vehicles such as railway vehicles, automobiles and forklifts, aircraft and various industrial machines, and insulating coils incorporated in electric motors mounted in vibrators and the like. The present invention also relates to a composition of an epoxy varnish for insulation mainly used as an impregnating agent. More specifically, in order to insulate, fix or shield from the external environment, such as coils and wire assemblies used in devices that receive mechanical force such as vibration, fill them with dip, brush or other methods Epoxy varnish compositions and methods of using the same.
[0002]
[Prior art]
Insulated coils such as electric motors are affected by moisture, dust, vibration, etc. from the operating environment during operation.In particular, the coil end has many connection parts and is a free end, so this part becomes a weak point and breaks due to vibration. The insulating property is apt to deteriorate due to the absorption of moisture in the use environment. In addition, dust accumulates in the space between the enameled electric wires and the insulating property is reduced, thereby causing a short circuit and easily impairing functions such as rotation stop. Therefore, in order to prevent the deterioration of the insulation property, fix the wire bundle, improve the vibration resistance, and further reduce the moisture absorption, a varnish is impregnated between the wires to insulate the coil.
An example in which a stator for a three-phase induction motor is insulated with a varnish according to the prior art will be described below as an example. FIG. 1 is an external perspective view of a stator coil assembly common to the present invention, FIG. 2 is a partial perspective view showing the inside of the stator coil assembly shown in FIG. 1, and a stator 1 is an iron core. 1a, an insulating plate 2 punched in the same shape as the horizontal cross section of the iron core 1a, a plurality of slots 4 provided in the iron core 1a, a slot liner 6 disposed along the inner peripheral surface of the slot, A bundle (coil 5) of enameled electric wires arranged inside the liner 6, an interphase insulation 7 inserted between coils of different phases, and a portion exposed outside the slot 4 of the coil 5, that is, a coil end 3. Have been.
[0003]
When the stator is soaked in an epoxy varnish (hereinafter referred to as varnish as required), the epoxy varnish penetrates into the coil 5 and the coil end 3 in the slot 4. When the stator is taken out of the dipping bath and heat-cured, the coil 5 in the slot 4 and the enamel wires in the coil end 3 are adhered to each other, and the enamel wire and the slot liner 6, the enamel wire and the interphase insulation 7. The slot liner 6 and the core 1a are bonded to each other, and the core 1a and the insulating plate 2 are bonded to each other.
It is generally well known that non-solvent varnishes are more effective and more effective in insulating such coils than solvent varnishes.
Epoxy resins and unsaturated polyester resins are mainly used as solventless varnishes.Epoxy resins are particularly useful because of their excellent heat resistance and mechanical properties, as well as excellent adhesiveness and low shrinkage. Often done. Among epoxy resins, epoxy resins using an acid anhydride (polyfunctional carboxylic anhydride) having excellent electric properties as a curing agent are widely used.
[0004]
Examples of such conventional epoxy varnish compounding compositions are shown below as Conventional Example 1 and Conventional Example 2.

[0005]
Since the epoxy varnish according to the formulation of Conventional Example 1 has a low viscosity, the varnish easily penetrates into the coil 5 in the slot 4, the coil end 3, and the like during the soaking process. Next, the stator is taken out of the soaking tank and subjected to heat curing. At this time, the temperature of the varnish rises and the viscosity further decreases, and the varnish is held between the coil 5 in the slot 4 and the enameled wire at the coil end 3. Most of the varnish that has been run off. As a result, the film formed on the surface of the enameled wire becomes extremely thin, leaving only a small adhesive force between the enameled wires and between the enameled wire and insulating paper, etc., and has sufficient environmental resistance and heat resistance. It is not possible to obtain radiation.
In order to improve the disadvantages of the conventional example 1, there is a method of increasing the thixotropy of the epoxy varnish by further adding a thixotropic agent, for example, a colloidal silica powder (average particle diameter 0.01 μm) to the composition of the conventional example 1. . An example of this composition is shown in Conventional Example 2.
Although the epoxy varnish of the composition according to Conventional Example 2 has a higher static viscosity than that of Conventional Example 1, there is a particular problem with penetrating the varnish into the coil 5 in the slot 4 and the coil end 3 during the soaking process. There is no. Regarding the decrease in viscosity due to the increase in varnish temperature during heat curing, the varnish held in the coil 5 in the slot 4, the coil end 3, and the like does not easily flow down due to the large thixotropy of the varnish. As a result, the varnish film adheres thickly on the enameled wires, and a strong adhesive force is obtained between the enameled wires and between the enameled wires and the insulating paper. Further, since there are few gaps, good environmental resistance and heat dissipation are obtained. Property is obtained.
[0006]
[Problems to be solved by the invention]
However, the epoxy varnish of the conventional example 2 in which the thixotropic property was increased by the addition of the thixotropic agent Aerosil, the viscosity was reduced when shearing stress such as stirring or vibration was applied from the outside, and the thixotropic property was gradually increased after the compounding. Has the property of being lost, leaving the following problems.
In the conventional example 2, since the epoxy varnish has thixotropy to maintain a large static viscosity, after the stator is soaked in the epoxy varnish, during the taking-out work or during the heat curing, it is externally provided. When shear stress such as vibration is applied, the viscosity decreases, and the varnish once impregnated and adhered flows down.
Also, when the epoxy varnish immediately after blending is soaked and heat-cured, even if the expected effect is obtained, the thixotropy decreases due to aging several days after blending, as in Conventional Example 1, even if the expected effect is obtained. The viscosity at the time of heat curing becomes small (because the static viscosity is small).
When the same treatment is performed with the epoxy varnish in this state, most of the varnish once impregnated in the coil 5 and the coil end 3 in the slot 4 flows down at the time of being taken out of the soaking bath or at the time of heat curing, and the enamel electric wire The varnish film attached to the surface becomes thin, and the expected adhesive strength, environmental resistance and heat dissipation cannot be obtained.
There is no restriction on handling such as vibration during processing as described above, and there is no problem such as change in viscosity over time after blending, and it is possible to form a varnish coating layer with a constant thickness even after long use after blending. The present invention provides an epoxy varnish composition capable of forming an adhesive layer which is capable of forming an adhesive layer having high adhesive strength and excellent vibration resistance, environmental resistance and heat dissipation, and using this composition, a coil and an electric wire of an electric appliance. It is an object of the present invention to provide a method for impregnating an aggregate or the like.
[0007]
[Means for Solving the Problems]
The epoxy varnish composition according to the present invention comprises, in addition to the conventional components, an epoxy resin, a reactive diluent, a curing agent for an acid anhydride, and a curing accelerator, a silica fine particle having a certain particle size distribution instead of colloidal silica. It is a solventless epoxy resin containing powder as a filler.
As the epoxy resin constituting the epoxy varnish composition of the present invention, bisphenol A type or bisphenol F type epoxy resin is preferably used, and as such epoxy resin, epicoats 828 and 827 are used. , 807 (both trade names: manufactured by Yuka Shell). Also, an alicyclic epoxy resin, a hydrogenated bisphenol A type epoxy resin, or the like can be used. Further, phenol novolak epoxy resin, cresol novolak epoxy resin and the like can also be used, and bisphenol A type, bisphenol F type, alicyclic epoxy resin and hydrogenated bisphenol A type epoxy resin can be used. Those obtained by mixing an appropriate amount of resin can also be used. The varnish made of such a mixed resin has higher heat resistance.
If necessary, a reactive diluent such as monoglycidyl ether or diglycidyl ether can be added.
[0008]
Examples of the curing agent constituting the epoxy varnish composition of the present invention include MNA (methylnadic anhydride), MHAC-P (methylhymic anhydride), methylhexahydrophthalic anhydride, and methyltetrahydrate, which are not likely to undergo moisture crystallization. There are acid anhydride curing agents such as hydrophthalic anhydride and polyazelain anhydride.
Examples of the curing accelerator include a tertiary amine curing accelerator (for example, K-61B dimethylaminomethylphenol) and an imidazole compound, and an imidazole compound is particularly preferable in view of pot life and heat resistance. . Among the imidazole compounds, 2-ethyl-4-methylimidazole, 2-ethyl-4-methylimidazole modified with octylic acid, and imidazole are preferred because of good compatibility with the epoxy resin and a long pot life. 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-phenyl-4,5-di- (cyanoethoxymethyl) imidazo in which the secondary amine function in the ring has been replaced by an inert cyanoethyl group Toluene, 1-cyanoethyl-2-phenylimidazole and the like are preferably used, and among them, 1-cyanoethyl-2-ethyl-4-methylimidazole is most preferably used.
As an inorganic filler usually added to an epoxy resin-based molded article, an IC sealing resin, a mold resin, and the like, silica, talc, calcium carbonate, alumina, and the like are known. As the inorganic filler constituting the composition, silica (high-purity crystalline quartz) is most suitable from the viewpoints of insulating properties (dielectric constant, volume resistivity, etc.), thermal conductivity, linear expansion coefficient and price.
[0009]
Silica suitable for solving the problem is, particularly, a fine silica powder having a content of particles having a particle size of 10 μm or more of less than 10% by weight and a content of particles having a particle size of less than 10 μm and 1 μm or more having a content of 90% or more. Preferably, the content of the silica fine powder in the epoxy resin composition is preferably in the range of 20 to 40%.
Further, in order to further delay the decrease in viscosity due to sedimentation of the silica fine powder generated when the compounded epoxy varnish composition is stored for a long period of time, and to positively prevent sedimentation, the second composition of the present invention Dolomite clay fine powder was added. The dolomite clay fine powder is composed of particles having an average particle diameter smaller than that of the silica fine powder, and 3 to 10% by weight of the added amount of the silica fine powder to be added to the epoxy varnish composition is added. As a result, sedimentation of the silica fine powder in the compounded epoxy varnish composition was prevented, and it became possible to maintain a constant viscosity for a long period of time.
[0010]
[Action]
The silica used in the present invention is a fine silica powder composed of less than 10% by weight of particles having a particle size of 10 μm or more and 90% by weight or more of particles having a particle size of less than 10 μm and 1 μm or more, epoxy resin and reactive diluent. , An acid anhydride curing agent and an imidazole compound accelerator together with 20 to 40% by weight of the epoxy varnish composition to further add dolomite clay to 3 to 10% by weight based on the amount of the silica fine powder added. %, Eliminates the time-dependent changes in dispersibility and viscosity after compounding, imparts sufficient adhesive strength, environmental resistance, and heat dissipation to the cured varnish, and is sufficient even in a severely vibrating use environment. Crack resistance can be maintained.
The above-mentioned silica (high-purity crystalline quartz filler) has a physical thermal conductivity of 8 W / (m · K) and a linear expansion coefficient of 0.4 to 0.6 × 10 ^−6. When the above-mentioned weight% is added to the epoxy varnish, the thermal conductivity increases from 0.2 when no silica is contained to 2-3 W / (m · K), and the linear expansion coefficient is 80 × 10 ⁻ when no silica is contained. It has the effect of lowering from ⁶ to 50 to 60 × 10 ⁻⁶ .
Dolomite clay has a specific gravity almost equal to that of silica, so by adding dolomite clay fine particles having an average particle diameter smaller than silica fine particles, when these particles settle, dolomite fine particles infiltrate between the silica fine particles and aggregate the silica fine particles. And facilitate redispersion after long-term storage.
[0011]
【Example】
Examples of the present invention will be specifically described below in comparison with conventional examples and comparative examples.
An epoxy varnish composition obtained by adding 10 to 50% by weight of the above-mentioned silica fine powder to the epoxy resin component comprising the epoxy resin, the reactive diluent, the acid anhydride curing agent and the curing accelerator shown in Table 1 was blended. A varnish treatment is applied to a 1-AIW φ1.6 strainer test piece specified in JIS C 2103 shown in FIG. 3 and heated at 130 ° C., which is the optimum condition, for 5 hours to gel, and then post-cured to prepare a sample. And tested for adhesion. FIG. 4 shows the relationship between the content of the fine silica powder in the varnish and the adhesive strength of the varnish.
[Table 1]

According to the results of this experiment, the adhesive strength is small when the content of the silica fine powder is less than 20% by weight, and the adhesive strength is large in the range from 20% by weight to 50% by weight.
Various epoxy varnish compositions were prepared by adding various fillers shown in Table 2 to the epoxy resin consisting of the epoxy resin, the reactive diluent, the acid anhydride curing agent and the curing accelerator shown in Table 1 in various amounts. Then, using each of them, the three-phase induction motor shown in FIG. 1 was immersed in the stator, heated at 130 ° C. for 5 hours to gel, and then post-cured to prepare a sample. The varnish cured film adhered to each of these samples was visually observed, and the surface smoothness was examined. The center of the stator and the coil end were cut and the cross section was polished to varnish the coil in the slot and into the coil end. Was examined for impregnation. Further, the above-mentioned various epoxy varnish compositions were subjected to the above-mentioned strainer test using the test pieces shown in FIG. 3 to test the adhesive strength.
Table 2 summarizes these results.
[Table 2]

Example 1 and Example 2 shown here use the same epoxy varnish as the composition according to Conventional Example 1 and Conventional Example 2, respectively.
The three comparative examples are samples prepared for determining the particle size distribution of the silica powder to be added and the appropriate range of the amount of addition. In Comparative Example 3, 50% by weight of the silica fine particles shown in FIG. 3 was added. Epoxy varnish with the same composition.
[0012]
Conventional Example 1 with no filler added had low adhesive strength, and Conventional Example 2 immediately after the addition of the thixotropic agent and compounding had a varnish adhesion thickness of 30 μm, and had good adhesive strength, impregnation and surface smoothness. In the case of Conventional Example 3 which had been mixed with the same composition as in Conventional Example 2 for one week after blending, the varnish thickness was reduced to 10 μm, and a sufficient value of the adhesive strength was not obtained.
Comparative Example 1, in which 30% by weight of a small silica powder having a content of particles having a particle diameter of 10 μm or more of 30% by weight or more was added, had good impregnation but insufficient surface smoothness.
In Comparative Example 2, in which the content of particles having a silica particle diameter of 1 μm or less was 50% by weight or more and 30% by weight of ultrafine silica powder was added, the viscosity of the epoxy varnish formed was too high, so that the impregnation into the coil was performed. Sex was not enough.
Comparative Example 3 containing 50% by weight of the silica fine powder used in the present invention exceeding the content range of the present invention showed a sufficiently large adhesive force as shown in FIG. Was too high, so that the impregnation was not sufficient.
In comparison with these, an epoxy varnish composition containing 30% by weight of silica fine powder containing less than 10% by weight of particles having a particle size of 10 μm or more and 90% by weight or more of particles having a particle size of less than 10 μm and 1 μm or more was formulated. In both Example 1 on the first day and Example 2 on the 30th day after blending, a varnish adhesion thickness of 20 μm was secured, and good results were obtained in all of the adhesive strength, impregnation property and surface smoothness.
[0013]
Example 1 and Example 2 in which 30% by weight of silica fine powder containing less than 10% by weight of particles having a particle diameter of 10 μm or more and 90% by weight or more of particles having a particle diameter of less than 10 μm and 1 μm or more were both satisfactory. Despite the characteristics, on the 30th day after the compounding, sedimentation of the silica fine powder was recognized, and considerable stirring was performed to redisperse the sedimentation.
Although the number of elapsed days of 30 days after compounding is sufficiently long, which is satisfactory in that it can be used practically, examples in which dispersibility is further increased for easier handling are shown below.
A fine powder of dolomite clay (commercial name: MicroDoll: Hoechst Synthetic KK) which is a composite carbonate of calcium and magnesium as an anti-settling agent, ie, a dispersant, and has an average particle size of 2 to 10 μm is added to the formulation of Example 1. Was added to increase dispersibility.

[0014]
The epoxy varnish compositions of Examples 3 and 4 were blended, the state of sedimentation of the silica fine powder 30 days later, the difficulty of dispersion work, and the adhesion of the epoxy varnish compositions immediately after blending and 30 days after blending. The force, impregnation and surface smoothness were studied.
According to the results, in Example 3 in which the microdole was added in an amount of 5% by weight based on the amount of the added silica fine powder, although the silica fine powder was precipitated, it could be easily redispersed. In Example 4 in which the dough was added in an amount of 10% by weight based on the amount of the silica fine powder added, it was recognized that no precipitation of the silica fine powder occurred.
In Examples 3 and 4, varnish treatment was performed immediately after compounding and 30 days after compounding, respectively, to obtain good target characteristics.
The mechanical effect according to the present invention was compared by the cross section of the cured epoxy varnish adhesive A attached between the adjacent enameled wires B.
FIG. 5 schematically shows the results of observation of Conventional Example 3 and Example 2. The coating of the varnish A 'adhered to the surface of the enameled electric wire B of the conventional example 3 was relatively thin, and necking (constriction) occurred particularly on the surface of the contact portion C' between the two electric wires. On the other hand, the coating of the varnish A adhered to the surface of the enameled electric wire B of Example 2 was relatively thick, drawn a gentle curve even on the surface of the contact portion C of the two electric wires, and did not cause necking. A film that hardly occurs is formed.
[0015]
【The invention's effect】
A silica fine powder composed of less than 10% by weight of particles having a particle diameter of 10 μm or more and 90% by weight or more of particles having a particle diameter of less than 10 μm and 1 μm or more is mixed with an epoxy resin, a reactive diluent, an acid anhydride curing agent, By adding 20 to 40% by weight to the epoxy varnish composition together with the imidazole compound accelerator, dolomite clay is further added to the epoxy varnish composition by 3 to 10% by weight based on the amount of the silica fine powder added. The addition increases the viscosity of the epoxy varnish and eliminates the time-dependent change in the viscosity after blending, and imparts sufficient adhesive strength, environmental resistance, and heat dissipation to an insulation coil or the like that has been heat-cured after being soaked. At the same time, it is possible to maintain sufficient crack resistance even in a use environment in which vibration is severe.
Furthermore, by selecting silica as the inorganic filler, the effect of increasing the thermal conductivity of the cured epoxy varnish and reducing the coefficient of linear expansion was obtained.
[Brief description of the drawings]
FIG. 1 is an external perspective view of a stator for a three-phase induction motor.
FIG. 2 is a perspective view of the radial inside of FIG. 1;
FIG. 3 shows a plan view of a JIS C 2103 strainer test piece.
FIG. 4 shows the adhesive strength of a test piece of a strainer obtained by treating with a varnish obtained by adding various amounts of silica fine powder to an epoxy resin.
FIG. 5 is a cross-sectional view showing the state of a conventional varnish adhered to the surface of an enameled electric wire and the varnish of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Stator core 2 Insulating plate 3 Coil end 4 Slot 5 Coil 6 Slot liner
7 Interphase insulation A Epoxy varnish A 'Epoxy varnish B Enamel wire C Contact portion of enamel wire C' Contact portion of enamel wire

Claims (2)

An epoxy resin, an acid anhydride curing agent, and an imidazole compound promoter, Ri formed by finely divided silica, the insulating coil incorporated in electrical equipment, electric machines, mainly an epoxy varnish composition for insulation treatment to be used as impregnating agent At
The varnish contains 20 to 40% by weight of a silica fine powder having a particle size distribution in which particles having a particle diameter of 10 μm or more are less than 10% by weight and particles having a particle diameter of less than 10 μm and 1 μm or more are 90% by weight or more. An epoxy varnish composition characterized in that the applied varnish has a uniform thickness, the coil has an increased adhesive strength, and the change with time is significantly reduced. 2. The epoxy varnish composition according to claim 1, wherein a fine powder of dolomite clay having an average particle diameter smaller than the fine silica powder is further added in an amount of 3 to 10% by weight based on the amount of the fine silica powder. An epoxy varnish composition characterized in that:

Images