【０００１】
【発明の属する技術分野】
本発明は、希土類系永久磁石などの成形体の表面に形成される付加型ポリイミド樹脂被膜の接着性を簡易かつ安価に向上させる方法に関する。
【０００２】
【従来の技術】
Ｎｄ−Ｆｅ−Ｂ系永久磁石に代表されるＲ−Ｆｅ−Ｂ系永久磁石やＳｍ−Ｆｅ−Ｎ系永久磁石に代表されるＲ−Ｆｅ−Ｎ系永久磁石などの希土類系永久磁石は、資源的に豊富で安価な材料が用いられ、かつ、高い磁気特性を有していることから、特にＲ−Ｆｅ−Ｂ系永久磁石は今日様々な分野で使用されている。
しかしながら、希土類系永久磁石は反応性の高い希土類元素：Ｒを含むため、大気中で酸化腐食されやすく、何の表面処理をも行わずに使用した場合には、わずかな酸やアルカリや水分などの存在によって表面から腐食が進行して錆が発生し、それに伴って、磁石特性の劣化やばらつきを招く。さらに、錆が発生した磁石を磁気回路などの装置に組み込んだ場合、錆が飛散して周辺部品を汚染する恐れがある。
上記の点に鑑み、希土類系永久磁石の表面に耐食性被膜として付加型ポリイミド樹脂被膜を形成する方法が提案されている。
付加型ポリイミド樹脂は、樹脂分子の末端に不飽和基を有し、付加反応やラジカル反応による三次元架橋により得られるものであるが、有機溶剤に可溶であるため溶液状で塗布でき、また、硬化に際して水が生成することがないので、希土類系永久磁石が酸化腐食されやすいことを考慮すれば非常に都合のよい樹脂である。また、付加型ポリイミド樹脂からなる被膜は、優れた耐食性に加え、電気絶縁性や耐熱性にも優れることから、特に自動車用モータや家電製品などに希土類系永久磁石を適用する際に非常に価値が高い。
【０００３】
【発明が解決しようとする課題】
しかしながら、付加型ポリイミド樹脂被膜を表面に有する希土類系永久磁石を自動車用モータや家電製品などの部品に組み込んだ場合には、当該被膜と部品との間には接着剤を介して強い接着性が要求されるにもかかわらず、当該被膜の接着性が十分でないことから、当該被膜の表面において接着剤の剥離が起こり、その結果、当該被膜を表面に有する希土類系永久磁石が部品から外れてしまうといったことが起こる恐れがあることが本発明者の検討結果により判明した。このような問題への対処法としては、付加型ポリイミド樹脂を主成分とする専用接着剤を使用する方法が考えられるが、このような接着剤は常温での粘性が非常に高くて取扱性に劣り、価格も高いといった問題がある。
そこで本発明は、希土類系永久磁石などの成形体の表面に形成される付加型ポリイミド樹脂被膜の接着性を簡易かつ安価に向上させる方法を提供することを目的とする。
【０００４】
【課題を解決するための手段】
本発明者は、上記の点に鑑みて鋭意検討を行った結果、付加型ポリイミド樹脂被膜中に無機質微粒子を分散させることで当該被膜の接着性を向上させることができることを知見した。特開２００１−１６０５０８号公報や特開２００２−６０６７４号公報には、付加型ポリイミド樹脂被膜を表面に有する希土類系永久磁石が開示され、当該被膜中に着色顔料や体質顔料を分散させてもよいこと、着色顔料として金属酸化物が使用できることなどが記載されているが、付加型ポリイミド樹脂被膜の接着性については何ら記載や示唆はなく、従って、付加型ポリイミド樹脂被膜中に無機質微粒子を分散させることで当該被膜の接着性を向上させることができるという本発明者が得た知見は、これらの先行特許から想到できるものではない。
【０００５】
上記の知見に基づいてなされた本発明の付加型ポリイミド樹脂被膜の接着性向上方法は、請求項１記載の通り、当該被膜中に平均粒子径が０．０１μｍ〜３０μｍの無機質微粒子を分散させることを特徴とする。
また、請求項２記載の接着性向上方法は、請求項１記載の接着性向上方法において、無機質微粒子が金属酸化物微粒子であることを特徴とする。
また、請求項３記載の接着性向上方法は、請求項２記載の接着性向上方法において、金属酸化物微粒子がＳｉＯ２微粒子および／またはＡｌ２Ｏ３微粒子であることを特徴とする。
また、請求項４記載の接着性向上方法は、請求項１乃至３のいずれかに記載の接着性向上方法において、付加型ポリイミド樹脂被膜中における無機質微粒子の分散量が５重量％〜７５重量％であることを特徴とする。
また、請求項５記載の接着性向上方法は、請求項１乃至４のいずれかに記載の接着性向上方法において、付加型ポリイミド樹脂被膜がビスアリルナジイミドから得られる樹脂被膜であることを特徴とする。
また、請求項６記載の接着性向上方法は、請求項１乃至５のいずれかに記載の接着性向上方法において、付加型ポリイミド樹脂被膜の膜厚が１μｍ〜５０μｍであることを特徴とする。
また、請求項７記載の接着性向上方法は、請求項１乃至６のいずれかに記載の接着性向上方法において、付加型ポリイミド樹脂被膜により表面被覆される成形体が希土類系永久磁石であることを特徴とする。
【０００６】
【発明の実施の形態】
本発明の付加型ポリイミド樹脂被膜の接着性向上方法は、当該被膜中に平均粒子径が０．０１μｍ〜３０μｍの無機質微粒子を分散させることを特徴とするものである。本発明によれば、アクリル系接着剤やエポキシ系接着剤などのような汎用的な有機系接着剤を使用した場合でも、付加型ポリイミド樹脂被膜と当該被膜を表面に有する希土類系永久磁石が組み込まれる部品との間で強い接着性を確保することができる。
【０００７】
本発明における付加型ポリイミド樹脂被膜としては、無水アリルナジック酸とジアミンから合成され、脱水閉環反応が完結した両末端にアリル基を有するイミドモノマーであるビスアリルナジイミド（ＢＡＮＩ：下記化学式参照）（必要ならば特開平５−９２２２号公報や特開平７−５３５１６号公報を参照）から得られる樹脂被膜の他、末端ナジック酸型ポリイミド樹脂（ＰＭＲ）、ビスマレイミド型ポリイミド樹脂、末端アセチレン型ポリイミド樹脂などからなる公知の被膜が挙げられる。
【０００８】
【化１】
【０００９】
付加型ポリイミド樹脂被膜中に分散させる無機質微粒子としては、例えば、ＳｉＯ２微粒子やＡｌ２Ｏ３微粒子などの金属酸化物微粒子が挙げられる。無機質微粒子の平均粒子径を０．０１μｍ〜３０μｍと規定するのは、平均粒子径が０．０１μｍ未満であると、その製造が困難であることに加え、付加型ポリイミド樹脂被膜中に無機質微粒子を均一分散させるためには、付加型ポリイミド樹脂自体やその原料モノマーやオリゴマーなどを含んだ溶液中に無機質微粒子が均一分散した処理液を調製することが肝要であるが、粒子径が小さすぎると処理液中で無機質微粒子の凝集や沈降が起こるので、その調製が困難であることなどの理由による。また、平均粒子径が３０μｍを超えると、無機質微粒子が分散した処理液をスプレー法にて希土類系永久磁石の表面に塗布する場合に無機質微粒子がノズルつまりを起こしたりすることや、付加型ポリイミド樹脂被膜の膜厚が大きくなることで希土類系永久磁石の有効体積に影響を及ぼすことなどの理由による。
【００１０】
付加型ポリイミド樹脂被膜中における無機質微粒子の分散量は５重量％〜７５重量％とすることが望ましく、５０重量％〜７０重量％とすることがより望ましい。分散量が５重量％未満であると、付加型ポリイミド樹脂被膜中に無機質微粒子を分散させることによる十分な接着性向上効果が得られない恐れがある一方、分散量が７５重量％を超えると、付加型ポリイミド樹脂被膜自体の優れた耐食性などの特性に影響を及ぼす恐れがある。
【００１１】
無機質微粒子を分散させた付加型ポリイミド樹脂被膜の希土類系永久磁石の表面への形成は、付加型ポリイミド樹脂自体やその原料モノマーやオリゴマーなどを含む溶液中に無機質微粒子が分散した処理液を希土類系永久磁石の表面に塗布した後、熱処理する方法（いわゆる溶液法）によって行う。付加型ポリイミド樹脂自体やその原料モノマーやオリゴマーなどを含む溶液は、これらを必要に応じて有機溶剤に溶解して調製すればよい。例えば、ビスアリルナジイミドは、かさ高い構造を有した低分子量のイミドモノマーであるので、脂肪族炭化水素、脂肪族アルコールを除くほとんどの有機溶剤に可溶である。
【００１２】
処理液中での無機質微粒子の凝集や沈降を抑制することなどを目的として、処理液中に有機分散媒を添加してもよい。有機分散媒としては、無機質微粒子に対する優れた単分散化能により凝集や沈降を効果的に抑制することができるくし型ブロックコポリマーを構成する、アニオン性分散媒（脂肪族系多価カルボン酸、ポリエーテルポリエステルカルボン酸塩、高分子ポリエステル酸ポリアミン塩、高分子量ポリカルボン酸長鎖アミン塩など）、非イオン性分散媒（ポリオキシエチレンアルキルエーテルやソルビタンエステルなどのカルボン酸塩やスルフォン酸塩やアンモニウム塩など）、高分子分散媒（水溶性エポキシのカルボン酸塩やスルフォン酸塩やアンモニウム塩など、スチレン−アクリル酸共重合物、ニカワなど）などが好適に使用できる。
【００１３】
処理液の希土類系永久磁石の表面への塗布方法としては、ディップコーティング法、スプレー法、スピンコート法など自体公知の方法を用いることができる。
【００１４】
処理液を希土類系永久磁石の表面に塗布した後の熱処理は、２００℃〜３００℃で行うことが望ましい。２００℃未満であると硬化反応が十分に進行しない恐れがある一方、３００℃を越えると付加型ポリイミド樹脂被膜の劣化を招く恐れがあるからである。熱処理時間は、通常、５分〜２４時間である。
なお、必要に応じて、熱処理を行う前に、希土類系永久磁石の表面に塗布された処理液中の有機溶剤を除去するための乾燥処理（例えば、６０℃〜９０℃の条件下、５分〜１時間）を行ってもよい。
【００１５】
上記の方法によって希土類系永久磁石の表面に形成された無機質微粒子を分散させた付加型ポリイミド樹脂被膜は、希土類系永久磁石の表面に強固に密着しているので、膜厚が１μｍ以上であれば当該被膜自体が優れた耐食性などの特性を発揮するとともに、その表面において優れた接着性を発揮する。当該被膜の膜厚の上限は限定されるものではないが、希土類系永久磁石の有効体積を確保する観点からは５０μｍが望ましい。なお、必要に応じて、希土類系永久磁石の表面への処理液の塗布、それに続く熱処理を複数回繰り返して行ってもよい。
【００１６】
なお、本発明において接着性向上の対象となる付加型ポリイミド樹脂被膜は、希土類系永久磁石の表面に直接形成されたものに限定されず、希土類系永久磁石の表面に金属めっき被膜などを介して形成されたものであってもよい。
【００１７】
また、本発明は、付加型ポリイミド樹脂被膜を表面に有する希土類系永久磁石を自動車用モータや家電製品などの部品に組み込む場合に限定されず、付加型ポリイミド樹脂被膜を表面に有する希土類系永久磁石同士を接着して一体化磁石体を作成する場合などにも有効である。
【００１８】
【実施例】
本発明を以下の実施例によってさらに詳細に説明するが、本発明はこれに限定して解釈されるものではない。
なお、以下の実験は、例えば、米国特許４７７０７２３号公報や米国特許４７９２３６８号公報に記載されているようにして、公知の鋳造インゴットを粉砕し、微粉砕後に成形、焼結、熱処理、表面加工を行うことによって得られた１４Ｎｄ−７９Ｆｅ−６Ｂ−１Ｃｏ組成（ａｔ％）の縦１０ｍｍ×横８ｍｍ×高さ３ｍｍ寸法の焼結磁石（以下、磁石体試験片と称する）および以下の基本処理液，処理液１〜６を用いて行った。
【００１９】
基本処理液：
ビスアリルナジイミド（ＢＡＮＩ−Ｍ：丸善石油化学社製）をキシレンを用いて希釈し、その濃度を５０重量％に調整して基本処理液とした。
【００２０】
処理液１：
無機質微粒子としてＳｉＯ２微粒子（平均粒子径４μｍ）８ｇと有機分散剤としてソルスパース２６０００（アビシア社製）２０ｍｇを添加したキシレン１６ｇを基本処理液１４４ｇに加え、１０分間の機械攪拌とそれに続く５分間の超音波分散を行い、処理液１とした。
【００２１】
処理液２：
無機質微粒子としてＳｉＯ２微粒子（平均粒子径４μｍ）３１ｇと有機分散剤としてソルスパース２６０００（アビシア社製）８５ｍｇを添加したキシレン６２ｇを基本処理液１４４ｇに加え、１０分間の機械攪拌とそれに続く５分間の超音波分散を行い、処理液２とした。
【００２２】
処理液３：
無機質微粒子としてＳｉＯ２微粒子（平均粒子径４μｍ）１０５ｇと有機分散剤としてソルスパース２６０００（アビシア社製）３００ｍｇを添加したキシレン２１０ｇを基本処理液１４４ｇに加え、１０分間の機械攪拌とそれに続く５分間の超音波分散を行い、処理液３とした。
【００２３】
処理液４：
無機質微粒子としてＳｉＯ２微粒子（平均粒子径４μｍ）の代わりにＡｌ２Ｏ３微粒子（平均粒子径２．５μｍ）を使用したこと以外は処理液１の調製と同様にして処理液４とした。
【００２４】
処理液５：
無機質微粒子としてＳｉＯ２微粒子（平均粒子径４μｍ）の代わりにＡｌ２Ｏ３微粒子（平均粒子径２．５μｍ）を使用したこと以外は処理液２の調製と同様にして処理液５とした。
【００２５】
処理液６：
無機質微粒子としてＳｉＯ２微粒子（平均粒子径４μｍ）の代わりにＡｌ２Ｏ３微粒子（平均粒子径２．５μｍ）を使用したこと以外は処理液３の調製と同様にして処理液６とした。
【００２６】
実験Ａ：
基本処理液および処理液１〜６の各処理液を磁石体試験片の表面にスプレー法により塗布した後、２２０℃×９０分間の熱処理をオーブンで行い、続いて４５分かけて室温まで冷却し、膜厚が１５μｍの各種の付加型ポリイミド樹脂被膜を磁石体試験片の表面に形成した。
処理液１を縦３０ｍｍ×横２０ｍｍ×高さ１０ｍｍの炭素鋼（Ｓ４５Ｃ）の表面にスプレー法により塗布した後、２２０℃×９０分間の熱処理をオーブンで行い、続いて４５分かけて室温まで冷却し、膜厚が１５μｍのＳｉＯ２微粒子を１０重量％分散させた付加型ポリイミド樹脂被膜を炭素鋼の表面に形成した。
縦１０ｍｍ×横８ｍｍ面にアクリル系接着剤としてＧ５５（電気化学工業社製）を塗布した付加型ポリイミド樹脂被膜を表面に有する磁石体試験片を、ＳｉＯ２微粒子を分散させた付加型ポリイミド樹脂被膜を表面に有する炭素鋼の縦３０ｍｍ×横２０ｍｍ面に４０Ｎの加重をかけて接着し、接着面からはみ出した接着剤を取り除いて接着面積を一定にし、室温に６０時間放置して接着剤を硬化させた。こうして得られた接着体に対し、せん断試験装置としてＡＧ−１０ＴＢ（島津製作所社製）を用い、せん断速度２ｍｍ／分（測定温度２３℃）で接着体から付加型ポリイミド樹脂被膜を表面に有する磁石体試験片が脱離する強度を接着強度として測定し、接着性を評価した。結果を表１および表２に示す。
【００２７】
実験Ｂ：
基本処理液および処理液１の各処理液を磁石体試験片の表面にスプレー法により塗布した後、２２０℃×９０分間の熱処理をオーブンで行い、続いて４５分かけて室温まで冷却し、膜厚が１５μｍの各種の付加型ポリイミド樹脂被膜を磁石体試験片の表面に形成した。
処理液１を縦３０ｍｍ×横２０ｍｍ×高さ１０ｍｍの炭素鋼（Ｓ４５Ｃ）の表面にスプレー法により塗布した後、２２０℃×９０分間の熱処理をオーブンで行い、続いて４５分かけて室温まで冷却し、膜厚が１５μｍのＳｉＯ２微粒子を１０重量％分散させた付加型ポリイミド樹脂被膜を炭素鋼の表面に形成した。
縦１０ｍｍ×横８ｍｍ面にエポキシ系接着剤としてＥＰ１３８（セメダイン社製）を塗布した付加型ポリイミド樹脂被膜を表面に有する磁石体試験片を、ＳｉＯ２微粒子を分散させた付加型ポリイミド樹脂被膜を表面に有する炭素鋼の縦３０ｍｍ×横２０ｍｍ面に４０Ｎの加重をかけて接着し、接着面からはみ出した接着剤を取り除いて接着面積を一定にし、１２０℃のオーブンに１時間収容して接着剤を硬化させた。こうして得られた接着体に対し、実験Ａと同様にして接着強度を測定し、接着性を評価した。結果を表１および表２に示す。
【００２８】
【表１】
【００２９】
【表２】
【００３０】
表１および表２から明らかなように、付加型ポリイミド樹脂被膜中に無機質微粒子を分散させなかった場合、接着強度が低く、磁石体試験片の表面に形成された付加型ポリイミド樹脂被膜の表面において接着剤の剥離が容易に起こったが、付加型ポリイミド樹脂被膜中に無機質微粒子を分散させたことで、接着強度の増加が認められ、その効果は無機質微粒子の分散量の増加に伴って増加した。実験Ａの処理液１，２，４，５では最終的には磁石体試験片の表面に形成された付加型ポリイミド樹脂被膜の表面において接着剤の剥離が起こったが、実験Ａの処理液３と６ではこのような現象は起こらずに接着剤の凝集破壊が起こったこと、実験Ｂの処理液１では磁石体試験片の表面に形成された付加型ポリイミド樹脂被膜の破壊と接着剤の凝集破壊が起こったことから、磁石体試験片の表面に形成された付加型ポリイミド樹脂被膜の接着性は当該被膜中に無機質微粒子を分散させたことで大幅に向上することが判明した。この効果には、磁石体試験片の表面に形成された付加型ポリイミド樹脂被膜の表面の濡れ性やアンカー効果、被膜自体の硬質化など様々な因子が寄与しているものと考えられた。
【００３１】
【発明の効果】
本発明によれば、希土類系永久磁石などの成形体の表面に形成される付加型ポリイミド樹脂被膜の接着性を簡易かつ安価に向上させる方法が提供される。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for easily and inexpensively improving the adhesiveness of an additional polyimide resin film formed on the surface of a molded article such as a rare earth permanent magnet.
[0002]
[Prior art]
Rare earth permanent magnets such as R-Fe-B permanent magnets represented by Nd-Fe-B permanent magnets and R-Fe-N permanent magnets represented by Sm-Fe-N permanent magnets are resources. In particular, R-Fe-B-based permanent magnets are used in various fields today because they are made of abundant and inexpensive materials and have high magnetic properties.
However, since rare-earth permanent magnets contain highly reactive rare-earth elements: R, they are easily oxidized and corroded in the air, and when used without any surface treatment, a slight amount of acid, alkali, moisture, etc. Corrosion progresses from the surface due to the presence of rust and rust is generated, which leads to deterioration and variation in magnet characteristics. Further, when the rusted magnet is incorporated into a device such as a magnetic circuit, the rust may scatter and contaminate peripheral components.
In view of the above, there has been proposed a method of forming an additional polyimide resin film as a corrosion-resistant film on the surface of a rare-earth permanent magnet.
The addition type polyimide resin has an unsaturated group at the terminal of the resin molecule and is obtained by three-dimensional crosslinking by an addition reaction or a radical reaction, but is soluble in an organic solvent and can be applied in a solution state. Since no water is generated during curing, it is a very convenient resin in consideration of the fact that the rare-earth permanent magnet is easily oxidized and corroded. In addition, coatings made of addition-type polyimide resin have excellent electrical insulation and heat resistance in addition to excellent corrosion resistance, making them extremely valuable especially when applying rare-earth permanent magnets to motors for automobiles and home appliances. Is high.
[0003]
[Problems to be solved by the invention]
However, when a rare-earth permanent magnet having an addition-type polyimide resin film on its surface is incorporated into components such as motors for automobiles and home appliances, strong adhesion between the film and the component via an adhesive is obtained. Despite the requirement, the adhesion of the coating is not sufficient, so that the adhesive is peeled off on the surface of the coating, and as a result, the rare-earth permanent magnet having the coating on the surface comes off the component. It has been found from the result of the study by the present inventor that there is a possibility that the above may occur. To cope with such a problem, a method using a special adhesive mainly composed of an addition-type polyimide resin can be considered, but such an adhesive has a very high viscosity at room temperature and is difficult to handle. Inferior and expensive.
Therefore, an object of the present invention is to provide a method for easily and inexpensively improving the adhesiveness of an additional polyimide resin film formed on the surface of a molded product such as a rare earth permanent magnet.
[0004]
[Means for Solving the Problems]
The present inventor has conducted intensive studies in view of the above points, and as a result, has found that by dispersing inorganic fine particles in an addition-type polyimide resin film, the adhesiveness of the film can be improved. JP-A-2001-160508 and JP-A-2002-60674 disclose a rare-earth permanent magnet having an addition-type polyimide resin film on its surface, and a color pigment or an extender may be dispersed in the film. Although it is described that metal oxides can be used as the coloring pigment, there is no description or suggestion about the adhesiveness of the addition type polyimide resin film, and therefore, the inorganic fine particles are dispersed in the addition type polyimide resin film. The findings obtained by the present inventor that the adhesiveness of the coating can be improved thereby cannot be imagined from these prior patents.
[0005]
According to the method for improving the adhesion of an addition-type polyimide resin film of the present invention based on the above findings, as described in claim 1, inorganic fine particles having an average particle diameter of 0.01 μm to 30 μm are dispersed in the film. It is characterized.
The method for improving adhesion according to claim 2 is characterized in that, in the method for improving adhesion, the inorganic fine particles are metal oxide fine particles.
A third aspect of the present invention is characterized in that the metal oxide fine particles are SiO 2 fine particles and / or Al 2 O 3 fine particles.
According to a fourth aspect of the present invention, in the method for improving the adhesion according to any one of the first to third aspects, the dispersion amount of the inorganic fine particles in the addition type polyimide resin coating is 5% by weight to 75% by weight. It is characterized by being.
According to a fifth aspect of the present invention, in the method for improving the adhesion according to any one of the first to fourth aspects, the additional polyimide resin film is a resin film obtained from bisallylnadiimide. And
According to a sixth aspect of the present invention, there is provided the method for improving the adhesion according to any one of the first to fifth aspects, wherein the thickness of the additional polyimide resin film is 1 μm to 50 μm.
According to a seventh aspect of the present invention, there is provided the adhesiveness improving method according to any one of the first to sixth aspects, wherein the molded body surface-coated with the additional polyimide resin film is a rare earth permanent magnet. It is characterized.
[0006]
BEST MODE FOR CARRYING OUT THE INVENTION
The method for improving the adhesion of an addition type polyimide resin film according to the present invention is characterized by dispersing inorganic fine particles having an average particle size of 0.01 μm to 30 μm in the coating. According to the present invention, even when a general-purpose organic adhesive such as an acrylic adhesive or an epoxy adhesive is used, an addition type polyimide resin film and a rare earth permanent magnet having the film on the surface are incorporated. Strong adhesion with the parts to be manufactured.
[0007]
As the addition-type polyimide resin film of the present invention, bisallylnadiimide (BANI: see the following chemical formula), which is an imide monomer having an allyl group at both ends where dehydration ring-closing reaction is completed and synthesized from allylnadic anhydride and diamine, If necessary, besides resin coatings obtained from JP-A-5-9222 and JP-A-7-53516), nadic acid type polyimide resin (PMR), bismaleimide type polyimide resin, terminal acetylene type polyimide resin And a known coating consisting of
[0008]
Embedded image
[0009]
Examples of the inorganic fine particles dispersed in the addition type polyimide resin film include fine metal oxide particles such as SiO 2 fine particles and Al 2 O 3 fine particles. When the average particle diameter of the inorganic fine particles is defined as 0.01 μm to 30 μm, when the average particle diameter is less than 0.01 μm, in addition to the difficulty in producing the inorganic fine particles, the inorganic fine particles are added to the addition type polyimide resin film. In order to perform uniform dispersion, it is important to prepare a treatment liquid in which inorganic fine particles are uniformly dispersed in a solution containing the addition-type polyimide resin itself or its raw material monomer or oligomer. This is because the aggregation and sedimentation of the inorganic fine particles occur in the liquid, which makes the preparation difficult. Further, when the average particle diameter exceeds 30 μm, the inorganic fine particles may cause nozzle clogging when the treatment liquid in which the inorganic fine particles are dispersed is applied to the surface of the rare-earth permanent magnet by spraying, or the addition type polyimide resin This is because an increase in the thickness of the coating affects the effective volume of the rare-earth permanent magnet.
[0010]
The dispersion amount of the inorganic fine particles in the addition type polyimide resin film is preferably 5% by weight to 75% by weight, and more preferably 50% by weight to 70% by weight. When the amount of dispersion is less than 5% by weight, a sufficient adhesiveness improving effect by dispersing the inorganic fine particles in the addition type polyimide resin coating may not be obtained. On the other hand, when the amount of dispersion exceeds 75% by weight, This may affect the properties such as excellent corrosion resistance of the addition type polyimide resin coating itself.
[0011]
The addition type polyimide resin coating in which the inorganic fine particles are dispersed is formed on the surface of the rare earth permanent magnet by adding a processing liquid in which the inorganic fine particles are dispersed in a solution containing the addition type polyimide resin itself or its raw material monomer or oligomer to the rare earth type permanent magnet. After applying to the surface of the permanent magnet, heat treatment (so-called solution method) is performed. A solution containing the addition-type polyimide resin itself, its raw material monomer, oligomer, or the like may be prepared by dissolving these in an organic solvent as needed. For example, bisallylnadiimide is a low molecular weight imide monomer having a bulky structure and is soluble in most organic solvents except aliphatic hydrocarbons and aliphatic alcohols.
[0012]
An organic dispersion medium may be added to the treatment liquid for the purpose of suppressing aggregation and sedimentation of the inorganic fine particles in the treatment liquid. As the organic dispersion medium, an anionic dispersion medium (such as an aliphatic polycarboxylic acid or polycarboxylic acid), which constitutes a comb-type block copolymer capable of effectively suppressing aggregation and sedimentation due to its excellent monodispersibility with respect to inorganic fine particles. Ether polyester carboxylate, high molecular weight polycarboxylic acid polyamine salt, high molecular weight polycarboxylic acid long chain amine salt, etc.), nonionic dispersion medium (carboxylate such as polyoxyethylene alkyl ether or sorbitan ester, sulfonate or ammonium) Salts and the like, and polymer dispersion media (such as water-soluble epoxy carboxylate, sulfonate and ammonium salt, styrene-acrylic acid copolymer, glue and the like) can be preferably used.
[0013]
As a method of applying the treatment liquid to the surface of the rare earth permanent magnet, a method known per se such as a dip coating method, a spray method, and a spin coating method can be used.
[0014]
The heat treatment after applying the treatment liquid to the surface of the rare earth permanent magnet is desirably performed at 200 ° C to 300 ° C. If the temperature is lower than 200 ° C., the curing reaction may not proceed sufficiently. On the other hand, if the temperature exceeds 300 ° C., the addition type polyimide resin film may be deteriorated. The heat treatment time is usually 5 minutes to 24 hours.
In addition, if necessary, before performing the heat treatment, a drying treatment for removing the organic solvent in the treatment liquid applied to the surface of the rare-earth permanent magnet (for example, for 5 minutes at 60 ° C. to 90 ° C.) １1 hour).
[0015]
The addition type polyimide resin coating in which the inorganic fine particles formed on the surface of the rare-earth permanent magnet are dispersed by the above method is firmly adhered to the surface of the rare-earth permanent magnet, so if the film thickness is 1 μm or more. The coating itself exhibits excellent properties such as corrosion resistance and also exhibits excellent adhesiveness on its surface. The upper limit of the thickness of the film is not limited, but is preferably 50 μm from the viewpoint of securing the effective volume of the rare earth permanent magnet. If necessary, the application of the treatment liquid to the surface of the rare-earth permanent magnet and the subsequent heat treatment may be repeated a plurality of times.
[0016]
Incidentally, the addition type polyimide resin film to be improved in the adhesive property in the present invention is not limited to those directly formed on the surface of the rare-earth permanent magnet, the metal plating film or the like on the surface of the rare-earth permanent magnet. It may be formed.
[0017]
Further, the present invention is not limited to the case where a rare-earth permanent magnet having an addition-type polyimide resin film on its surface is incorporated into parts such as motors for automobiles and home electric appliances. Rare-earth permanent magnets having an addition-type polyimide resin film on its surface It is also effective when an integrated magnet body is formed by bonding together.
[0018]
【Example】
The present invention will be described in more detail with reference to the following examples, but the present invention should not be construed as being limited thereto.
In the following experiments, for example, as described in U.S. Pat. No. 4,770,723 and U.S. Pat. No. 4,792,368, a known casting ingot was pulverized, and after fine pulverization, molding, sintering, heat treatment, and surface processing were performed. A sintered magnet (hereinafter, referred to as a magnet body test piece) of 14Nd-79Fe-6B-1Co composition (at%) obtained by performing the measurement, having a length of 10 mm, a width of 8 mm, and a height of 3 mm, and the following basic treatment liquid: This was performed using treatment solutions 1 to 6.
[0019]
Basic treatment liquid:
Bisallylnadiimide (BANI-M: manufactured by Maruzen Petrochemical Co.) was diluted with xylene, and the concentration was adjusted to 50% by weight to obtain a basic treatment liquid.
[0020]
Treatment liquid 1:
16 g of xylene to which 8 g of SiO 2 fine particles (average particle diameter: 4 μm) as inorganic fine particles and 20 mg of Solsperse 26000 (manufactured by Avicia) as an organic dispersant were added to 144 g of the basic treatment liquid, and mechanical stirring for 10 minutes followed by 5 minutes of mechanical stirring Ultrasonic dispersion was performed to obtain a treatment liquid 1.
[0021]
Treatment liquid 2:
62 g of xylene to which 31 g of SiO 2 fine particles (average particle size: 4 μm) as inorganic fine particles and 85 mg of Solsperse 26000 (manufactured by Avicia) as an organic dispersant were added to 144 g of the basic treatment liquid, and mechanical stirring for 10 minutes followed by 5 minutes of mechanical stirring Ultrasonic dispersion was performed to obtain a treatment liquid 2.
[0022]
Treatment liquid 3:
210 g of xylene to which 105 g of SiO 2 fine particles (average particle diameter: 4 μm) as inorganic fine particles and 300 mg of Solsperse 26000 (manufactured by Avicia) as an organic dispersant were added to 144 g of the basic treatment liquid, and mechanical stirring for 10 minutes followed by 5 minutes of mechanical stirring Ultrasonic dispersion was performed to obtain a treatment liquid 3.
[0023]
Treatment liquid 4:
Processing liquid 4 was prepared in the same manner as in the preparation of processing liquid 1, except that Al 2 O 3 fine particles (average particle diameter 2.5 μm) were used instead of SiO 2 fine particles (average particle diameter 4 μm) as inorganic fine particles.
[0024]
Treatment liquid 5:
Processing liquid 5 was prepared in the same manner as in the preparation of processing liquid 2, except that Al 2 O 3 fine particles (average particle diameter 2.5 μm) were used instead of SiO 2 fine particles (average particle diameter 4 μm) as inorganic fine particles.
[0025]
Treatment liquid 6:
Processing liquid 6 was prepared in the same manner as the preparation of processing liquid 3 except that Al 2 O 3 fine particles (average particle diameter 2.5 μm) were used instead of SiO 2 fine particles (average particle diameter 4 μm) as inorganic fine particles.
[0026]
Experiment A:
After applying the basic processing solution and each of the processing solutions 1 to 6 to the surface of the magnet test piece by a spray method, a heat treatment at 220 ° C. × 90 minutes is performed in an oven, and then cooled to room temperature over 45 minutes. Various additional polyimide resin coatings having a thickness of 15 μm were formed on the surface of the magnet test piece.
After the treatment liquid 1 is applied to the surface of carbon steel (S45C) having a length of 30 mm, a width of 20 mm and a height of 10 mm by a spray method, a heat treatment at 220 ° C. for 90 minutes is performed in an oven, and then cooled to room temperature over 45 minutes. Then, an addition type polyimide resin film in which SiO 2 fine particles having a thickness of 15 μm were dispersed at 10% by weight was formed on the surface of the carbon steel.
A magnet body test piece having an additional polyimide resin coating on the surface of 10 mm length × 8 mm width coated with G55 (manufactured by Denki Kagaku Kogyo Co., Ltd.) as an acrylic adhesive, was added to an additional polyimide resin coating in which SiO 2 fine particles were dispersed. Adhesion is applied to the surface of carbon steel with a surface of 30 mm length × 20 mm width by applying a load of 40 N, the adhesive that has protruded from the adhesion surface is removed, the adhesion area is constant, and the adhesive is left at room temperature for 60 hours to cure the adhesive I let it. A magnet having an additional polyimide resin coating on the surface of the adhesive obtained from the adhesive at a shear rate of 2 mm / min (measuring temperature 23 ° C.) using an AG-10TB (manufactured by Shimadzu Corporation) as a shear test device. The strength at which the body test piece detached was measured as the adhesive strength, and the adhesiveness was evaluated. The results are shown in Tables 1 and 2.
[0027]
Experiment B:
After applying each treatment liquid of the basic treatment liquid and the treatment liquid 1 to the surface of the magnet body test piece by a spray method, a heat treatment at 220 ° C. × 90 minutes is performed in an oven, and then cooled to room temperature over 45 minutes to form a film. Various additional polyimide resin coatings having a thickness of 15 μm were formed on the surface of the magnet test piece.
After the treatment liquid 1 is applied to the surface of carbon steel (S45C) having a length of 30 mm, a width of 20 mm and a height of 10 mm by a spray method, a heat treatment at 220 ° C. for 90 minutes is performed in an oven, and then cooled to room temperature over 45 minutes. Then, an addition type polyimide resin film in which SiO 2 fine particles having a thickness of 15 μm were dispersed at 10% by weight was formed on the surface of the carbon steel.
A magnet test piece having an additional polyimide resin coating on the surface of 10 mm long by 8 mm wide coated with EP138 (manufactured by Cemedine) as an epoxy-based adhesive was coated on the surface with an additional polyimide resin coating on which SiO 2 fine particles were dispersed. A carbon steel having a length of 30 mm and a width of 20 mm is bonded to a surface of the carbon steel by applying a load of 40 N, the adhesive protruding from the bonding surface is removed to make the bonding area constant, and the adhesive is placed in an oven at 120 ° C. for 1 hour to remove the adhesive. Cured. The adhesive strength of the thus obtained adhesive body was measured in the same manner as in Experiment A, and the adhesiveness was evaluated. The results are shown in Tables 1 and 2.
[0028]
[Table 1]
[0029]
[Table 2]
[0030]
As is clear from Tables 1 and 2, when the inorganic fine particles were not dispersed in the addition type polyimide resin film, the adhesive strength was low, and the surface of the addition type polyimide resin film formed on the surface of the magnet test piece was low. Although the peeling of the adhesive easily occurred, the dispersion of the inorganic fine particles in the addition type polyimide resin coating increased the adhesive strength, and the effect increased with the increase in the amount of the inorganic fine particles dispersed. . In the treatment liquids 1, 2, 4, and 5 of the experiment A, the adhesive was finally peeled off on the surface of the additional polyimide resin film formed on the surface of the magnet test piece. In Nos. 6 and 7, such a phenomenon did not occur and the cohesive failure of the adhesive occurred. In the treatment liquid 1 of Experiment B, the destruction of the additional polyimide resin film formed on the surface of the magnet test piece and the cohesion of the adhesive were observed. Since the fracture occurred, it was found that the adhesiveness of the additional type polyimide resin film formed on the surface of the magnet test piece was significantly improved by dispersing the inorganic fine particles in the film. It is thought that various factors contribute to this effect, such as wettability of the surface of the additional type polyimide resin film formed on the surface of the magnet test piece, an anchor effect, and hardening of the film itself.
[0031]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the method of simply and inexpensively improving the adhesiveness of the addition type polyimide resin film formed on the surface of a molded object such as a rare earth permanent magnet is provided.
