JP4146963B2

JP4146963B2 - Powder containing granular iron oxide aggregate particles

Info

Publication number: JP4146963B2
Application number: JP12504199A
Authority: JP
Inventors: 陽史萩野; 昌宏三輪
Original assignee: Mitsui Mining and Smelting Co Ltd
Current assignee: Mitsui Mining and Smelting Co Ltd
Priority date: 1999-04-30
Filing date: 1999-04-30
Publication date: 2008-09-10
Anticipated expiration: 2019-04-30
Also published as: JP2000319020A

Description

【０００１】
【発明の属する技術分野】
本発明は、粒状酸化鉄凝集粒子及び該凝集粒子を含む粉末に関し、詳しくは酸化鉄一次粒子が凝集している特定の酸化鉄凝集粒子とすることにより、ハンドリング性、流動性、分散性に優れた、特に静電複写磁性トナー用材料粉、静電潜像現像用キャリア用材料粉、塗料用黒色顔料粉等の用途に用いられる粒状酸化鉄凝集粒子及び該凝集粒子を含む粉末に関する。
【０００２】
【従来の技術及び発明が解決しようとする課題】
一般に、静電複写磁性トナーや静電潜像現像用キャリア等は、アクリル樹脂やポリエステル樹脂等の熱可塑性樹脂を基材として、マグネタイト粒子に代表されるような磁性と黒色顔料の性能を併せ持つ酸化鉄粒子が添加されて製造される。この際、酸化鉄粒子に要求される特性として、樹脂中へのより高い分散性が挙げられる。磁性トナー製造において、この分散性が不良だとトナー中の酸化鉄粒子の存在がばらつき、磁気特性を始めとする諸特性に悪影響を与える。
【０００３】
一方、磁性トナー製造においては、酸化鉄粒子のハンドリング性、流動性も重要な特性である。例えば、樹脂との混合、粉砕等の製造工程において、酸化鉄粒子のハンドリング性や流動性が不良で供給が安定しない場合、より具体的には、ホッパー内や供給口での棚つりや居付き、閉塞等が発生すると酸化鉄粒子と樹脂等の混合品や粉砕品中において既に酸化鉄粒子の重量的な分布不良が発生してしまうからである。
【０００４】
このような不都合を抑制するためには、使用する酸化鉄粒子自体のハンドリング性、流動性、分散性を改良する必要があり、これまでにも種々の提案がなされている。例えば特開平６−１３０７１８号公報には粒子表面にシリカ微粒子を付着させたものが提案されている。特開平６−２３０６０３号公報には粒子表面にＳｉ及び／又はＴｉ化合物及びカップリング剤層を有することがことが開示されている。また、特開平７−２４０３０６号公報にはケイ素含有マグネタイト粒子表面にシリカ及びアルミナ微粒子その他を付着させることが示されている。特開平９−５９０２４号公報にはケイ素その他の金属元素含有マグネタイト粒子の各稜線を曲面状とすることが記載されている。さらに特開平９−２４１０２５号公報にはケイ素含有マグネタイト粒子の形状を角の丸い金平糖状とすることが開示されている。しかし、これらの従来技術を始めとして乾式、湿式を問わず公知の製造工程により得られた酸化鉄粒子を用いたのでは、粉体そのものの凝集性に加え、磁気凝集の影響も相俟って酸化鉄粒子自体のハンドリング性、流動性、分散性の改良効果には限界があった。
【０００５】
また、特開平８−２５９２３８号公報には、個数平均粒子径が０．０５〜１μｍの酸化鉄粒状粒子が凝集した粒子径２０μｍ以下の凝集粒子からなる着色用顔料粉末が開示されており、該粉末は剪断作用が大きい容器固定の水平複軸型の混練機を使用することにより得られるとしている。そして、同公報には、大きな凝集粒子を粉砕して凝集粒子の粒子径を数十μｍ以下とする手段、例えば衝撃式粉砕機、ボールミル、振動ミル、ロール圧縮成形機、ホイール型混練機を使用する手段についても触れ、これらにより得られた凝集粒子に対する上記粒子径２０μｍ以下の凝集粒子の優位性について記載されている。
【０００６】
同公報に開示の技術によれば、確かに樹脂成形物製造の際の分散性には優れているものの、凝集粒子の大きいものは分散性が悪いという観点に立っており、さらにハンドリング性、流動性の面で充分な性能を有していない。
【０００７】
以上のように、工程内での流動性に優れ、かつ樹脂等との混練時の分散性に優れた酸化鉄凝集粒子については未だ提案されていない。
【０００８】
従って、本発明の目的は、搬送性に優れ、またハンドリング性、流動性が良好で、凝集粒子でありながら適度な強度を有することで樹脂との混練時の分散性に優れた酸化鉄凝集粒子及び該凝集粒子を含む粉末を提供することにある。
【０００９】
【課題を解決するための手段】
本発明者らは、鋭意検討の結果、従来の製造方法で製造された酸化鉄粒子を用いて意図的な凝集操作を加え、凝集粒子の形状、大きさ、強度等を制御することによって、出発原料の酸化鉄粒子に比べ、分散性、ハンドリング性、流動性が格段に優れた酸化鉄凝集粒子が得られ、このことにより本発明の目的が達成し得ることを知見した。
【００１０】
本発明は、上記知見に基づきなされたもので、製造に際して、水分や有機物をバインダーとして添加することなく得られ、個数平均粒子径が０．０５〜１μｍの酸化鉄一次粒子が凝集しており、個数平均粒子径が３０〜３０００μｍであり、かつ加熱減量が０．０５〜２重量％であり、圧縮度が４０％以下である粒状酸化鉄凝集粒子を含み、
風力分級により得られた粒径３０μｍ以上の凝集粒子の重量比率が８０重量％以上であることを特徴とする粒状酸化鉄凝集粉末を提供するものである。
【００１２】
【発明の実施の形態】
以下、本発明の実施の形態を説明する。
一般的に、意図的な凝集操作の中には造粒という手段があり、この手段により得られるものを造粒物と呼んだりして、固有の粉体特性等に起因する凝集、並びにそれによる凝集物と区別されることが多いが、本発明でいう「意図的な凝集」は意図的に行う造粒、凝集手段の双方を指す。
【００１３】
また、粒状凝集粒子とは、光学顕微鏡８０倍にて観察した際に、凝集粒子中に空隙が認められず、かつ一次粒子が稠密に凝集しているものを指し、粒状酸化鉄凝集粒子とは、粒状凝集粒子が酸化鉄粒子からなるものを指す。さらに、粒状凝集粉末とは粒状凝集粒子を含む粉末を指し、粒状酸化鉄凝集粉末とは粒状酸化鉄凝集粒子を含む粉末を指す。
【００１４】
また、一次粒子又は凝集粒子という場合には、その内容によって個々の粒子又はその集合のいずれも意味する。
【００１５】
本発明の出発原料である酸化鉄一次粒子の形態は、マグネタイト（Ｆｅ₃Ｏ₄）を始めとして、マグヘマイト（γ−Ｆｅ₂Ｏ₃）やその中間組成のベルトライド化合物（ＦｅＯｘ・Ｆｅ₂Ｏ₃、０＜Ｘ＜１）、及びこれらの単独又は複合化合物にＦｅ以外のＳｉ、Ａｌ、Ｍｎ、Ｎｉ、Ｚｎ、Ｃｕ、Ｍｇ、Ｔｉ、Ｃｏ、Ｚｒ、Ｗ、Ｍｏ、Ｐ等を少なくとも１種以上含むスピネルフェライト粒子等を必要な特性に応じて選択すればよく、その形状はトナー用に適した特性を付与できるものなら特に限定されないが、トナー用材料粉として一般的な粒状品（球状、八面体状、六面体状）が好ましい。
【００１６】
さらに、分散性を向上させるために、ＳｉやＡｌ、あるいは有機処理剤等による表面処理を施した酸化鉄一次粒子を用いてもよい。
【００１７】
一般に静電複写磁性トナーや静電潜像現像用キャリアに用いられる酸化鉄粒子の一次粒子の個数平均粒子径は０．０５〜１μｍ程度のものが汎用されているが、本発明においては意図的な凝集操作を加えることにより、この一次粒子や一次粒子の微細な凝集粒子が凝集してなる粒状酸化鉄凝集粒子であり、その個数平均粒子径は３０〜３０００μｍであることが重要である。また、本発明の酸化鉄凝集粒子の形状は、粒状であれば特に限定されないが、流動性の面からすると好ましくは球状である。
【００１８】
上述した従来技術に示されるような、乾式、湿式を問わず公知の製造工程により得られる凝集した酸化鉄粒子や、該凝集した酸化鉄粒子を粉砕して凝集粒子の粒子径を数十μｍ以下とすることにより得られる凝集粒子は、粉体自体の凝集や磁気凝集の影響が強かったり、元の凝集粒子の形状に起因して不定形であるばかりか、一次粒子が枝状に絡み合ったり、粒子中に空隙が多く存在したりするため、分散性、ハンドリング性、流動性に劣るものである。
【００１９】
これに対し、本発明の粒状酸化鉄凝集粒子は、基本的に水分や有機物等をバインダーとして意図的に添加することなく、かつ強制的に粉体同士を圧着するような製造方法も用いず、粉体同士の凝集力を利用して遊離粒子の発生を抑制しているため、ハンドリング性、流動性に優れているのはもちろん、樹脂中での分散性にも優れている。
【００２０】
また、上記特開平８−２５９２３８号公報に記載の粒子径２０μｍ以下の凝集粒子は、凝集粒子が大きいと分散性が不良になるという観点から提案されているのに対し、本発明では樹脂中で粒状酸化鉄凝集粒子が均一な分散性を示した上で、凝集粒子を構成する一次粒子や微細な凝集粒子がさらに分散してゆくという二段分散が達成できることを前提として、凝集粒子を大きくしてハンドリング性、流動性をも向上させているのである。
【００２１】
つまり、本発明の粒状酸化鉄凝集粒子を用いることにより、まず樹脂中で凝集粒子は速い分散速度で、かつ均一に分散していく。次いで、混練の際、凝集粒子が適度にバランスされた強度で凝集されているので個々の凝集粒子に均等な応力がかかり、二次分散が完結するのである。
【００２２】
上述した従来技術による酸化鉄粒子においては、流動性に劣るため、一次分散が進みにくく、その結果一次分散と二次分散が同時に進行せざるを得ず、結果として均等な混練応力が粒子にかからず一次粒子の分散に不具合が生じるものと推測される。
【００２３】
従って、凝集粒子を適度な大きさの粒径に整えると共に、その強度を加熱減量でバランスよく制御した凝集粒子とすることは本発明において重要な点である。
【００２４】
特に、凝集粒子径の大きさと凝集粒子の強度のバランスは重要で、本発明の粒状酸化鉄凝集粒子の個数平均粒子径が３０μｍ未満の場合には、分散性の面では良好であっても、ハンドリング性、流動性の面で劣ったものとなる。この個数平均粒子径が３０００μｍを超える場合には、凝集粒子が大きすぎてバインダーを用いない場合には強度が全く不足し、バインダーを使用すると強度が上がりすぎ、凝集粒子から一次粒子レベルへの分散性の不良を免れない。
【００２５】
また、本発明の粒状酸化鉄凝集粒子は、加熱減量が０．０５〜２重量％である。加熱減量が０．０５重量％未満の場合には、凝集粒子中の一次粒子同士の凝集力が弱すぎ、一次粒子の一部が凝集粒子から分離してしまい、特にハンドリング性、流動性が不良となる。また、凝集粒子の加熱減量が２重量％を超える場合には、水分過多により一次粒子同士の凝集力が強すぎ、分散性が不良となる。
【００２６】
本発明の粒状酸化鉄凝集粒子は、圧縮度が好ましくは４０％以下であり、さらに好ましくは３５％以下である。圧縮度が４０％を超える場合には、凝集強度が不足を起こしやすく、衝撃による凝集粒子の破壊や粒子の遊離が生じ、ひいてはハンドリング性や流動性の悪化による設備内での付着、棚つり、閉塞の原因となる。また、凝集強度が強すぎても樹脂中での分散性、特に混練時の一次粒子の分散性に影響がでやすいので、好ましくは圧縮度は２０％以上である。
【００２７】
本発明の酸化鉄凝集粒子は、安息角が好ましくは４０°以下であり、さらに好ましくは３８°以下である。安息角が４０°を超える場合には、ハンドリング性、流動性が不良となる。
【００２８】
本発明の粒状酸化鉄凝集粒子は、見掛嵩密度が好ましくは１ｇ／ｃｍ³以上であり、さらに好ましくは１．１ｇ／ｃｍ³以上である。見掛嵩密度が１ｇ／ｃｍ³未満の場合には、樹脂中での粒状酸化鉄凝集粒子の分散性が不良となる。
【００２９】
本発明の粒状酸化鉄凝集粒子は、衝撃を加えた後のスパチュラ角が好ましくは４５°以下であり、さらに好ましくは４０°以下である。このスパチュラ角が４５°を超える場合には、ハンドリング性、流動性が不良となる。
【００３０】
本発明の粒状酸化鉄凝集粒子は、４５°傾斜金属板上での重量付着率が１０重量％以下であることが望ましい。この重量付着率が１０重量％を超える場合には、流動性、特に設備内での粒子付着が多くなり好ましくない。
【００３１】
次に、本発明の粒状酸化鉄凝集粉末は、上記特性、性状を有する粒状酸化鉄凝集粒子のみで構成されていることが好ましいが、実用面から考えて、風力分級により得られた粒径３０μｍ以上の凝集粒子の重量比率が８０重量％以上となるように、上記粒状酸化鉄凝集粒子を含有していればよく、好ましくは９０重量％以上、より好ましくは９５重量％以上が望ましい。この重量比率が８０重量％未満の場合には、凝集粉末のハンドリング性、流動性、搬送性は著しく劣るものとなる。
【００３２】
次に、本発明の粒状酸化鉄凝集粒子及び粒状酸化鉄凝集粉末の具体的な製造方法について述べる。
本発明の粒状酸化鉄凝集粒子の出発原料としては、乾式、湿式を問わず公知の製造工程により得られる酸化鉄粒子であればよく、乾燥工程を経たものであれば成形物でもよいが、一次粒子や一次粒子の微細な凝集粒子レベルまでジェットミルやハンマーミル等の粉砕機による常法の粉砕を加えて、大きな凝集粒子を少なくしておく方が好ましい。
【００３３】
本発明における粒状酸化鉄凝集粒子及び粒状酸化鉄凝集粉末は、一次粒子の面接触に基づく固い凝集を避け、点接触に基づく柔らかでほぐれやすい凝集を実現し、かつ強度を加熱減量で調整しながら凝集操作を加えられる方法としてナウターミキサーのように粒子同士の接触機会の多い密閉式構造で、かつ二種類の混練動作（公転混練と自転混練）を有する装置を使用して製造できる。
【００３４】
この製造の際には、水分や有機物等をバインダーとして意図的に添加する必要はなく、出発原料の加熱減量に応じて、装置のおかれた温湿度環境を調整した上で運転時間等の条件を調整することが好ましい。
【００３５】
なお、個々の粒子を強力に相互圧縮、又は圧密させるような装置、詳しくは打錠機やブリケッティングマシン等に代表される圧縮成形装置、スクリュー押出し機やペレットミル等に代表される押出し成形装置、又はシンプソンミックスマーラーや圧縮ロールに代表される圧密処理装置を単独で用いたのでは、凝集粒子の流動性は改善されるものの、凝集粒子を構成する一次粒子や一次粒子の微細な凝集粒子同士の凝集力が強すぎて分散性に劣るものとなる。
【００３６】
本発明では、凝集物をある程度の大きさにすることにより、工程での二次粒子の均一な供給が行え、かつ、その凝集粒子の硬さを柔らかくすることで、一次粒子まで分散させることができる。
【００３７】
この凝集粒子の粒径や強度が維持できない場合には、工程内での搬送中の衝撃や応力等により凝集粒子がこわれ、その結果ハンドリング性や流動性に劣る粒子が発生するので、装置内での付着や閉塞を起こすこととなり、安定した供給が困難になる。
【００３８】
また、本発明の粒状酸化鉄凝集粒子及び粒状酸化鉄凝集粉末は、工程で粉体を供給するときに、安定して、かつ容易に投入のコントロールができる。特に、連続式で投入され、全体の再混合、再混練が行われないときは、供給時の複数物質のバランスが重要となり、いかに一定して物質を供給し続けるかが重要になる。そういう観点から、本発明の酸化鉄凝集粒子及び粒状酸化鉄凝集粉末は優れている。
【００３９】
【実施例】
以下、実施例等に基づき本発明を具体的に説明する。
【００４０】
［試験例］
表１に出発原料となる酸化鉄粒子Ａ〜Ｅについて、下記の方法によって測定した諸特性を示す。この酸化鉄粒子は通常の湿式酸化法によって製造され、通常の方法で洗浄、乾燥、粉砕されたものである。
【００４１】
（１）一次粒子の個数平均粒子径；透過型電子顕微鏡写真（倍率３０，０００倍）により、写真上の粒径を計測し、その個数平均粒子径を求めた。
（２）安息角；ホソカワミクロン社製パウダーテスターを用い、本体付属のマニュアルに従って測定した。
（３）見掛嵩密度；試料をふるい等を使用せず、そのまま内容量１００ｃｍ³の容器に投入し、重量を測定し単位体積当たりの重量を求めた。
（４）加熱減量；窒素雰囲気下で、試料を９０℃、１時間加熱し、変化した重量の元重量に対する割合を求めた。
（５）衝撃後のスパチュラ角；ホソカワミクロン社製パウダーテスターを用い、本体付属のマニュアルに従って測定した。
（６）圧縮度；見掛嵩密度と、ホソカワミクロン社製パウダーテスターを用い、本体付属のマニュアルに従って測定したタップ密度に基づき、次式で計算して求めた。
圧縮度＝｛（タップ密度−見掛嵩密度）／（タップ密度）｝×１００
（７）鏡面反射率；ＪＩＳＫ５１０１のフーバーマーラー法に準じて調製した分散ペーストと硝化綿クリヤーラッカーとの混練物を１ｍｉｌのフィルムアプリケーターを用いて白紙に展色した塗布膜面における２０°の反射率を測定した。
（８）傾斜板上に付着する割合；厚さ０．５ｍｍ、縦３０ｃｍ、横２０ｃｍの金属製板（材質ＳＵＳ３０４）を４５°に傾け、試料１０ｇを高さ１０ｃｍのところから一度に落下させ、金属板上を転がし、又は滑らせる。その操作を１０回、計１００ｇの試料を落下させ、金属板上に付着した重量を求め、投入した１００ｇに対する割合で示した。
【００４２】
【表１】

【００４３】
［実施例１］
上記酸化鉄粒子Ａ３０ｋｇを、温度２３℃、湿度３５％の環境を維持しながら、ナウターミキサー（ホソカワミクロン（株）社製、ＮＸ−１）を用い、スクリューの自転９０ｒｐｍ、公転３ｒｐｍの回転で、６０分間処理することにより粒状酸化鉄凝集粉末を得た。
【００４４】
この粒状酸化鉄凝集粉末について、上記試験例の酸化鉄粒子の測定に準拠して諸特性を評価した。また、風力分級による３０μｍ以上の凝集粒子の重量比率、凝集粒子の個数平均粒子径、粒状酸化鉄凝集粉末と樹脂との混練物中のムラ、粒状酸化鉄凝集粉末と樹脂との混練物中の分散については下記の方法によって測定した。結果を表２に示す。
【００４５】
（９）風力分級による３０μｍ以上の凝集粒子の重量比率；風力分級機（日清エンジニアリング社製、ターボクラシファイアＴＣ−１５Ｍ型）を用いて３０μｍ以上の凝集粒子を分級し、その重量と分級に供した粒状酸化鉄凝集粉末重量により３０μｍ以上の凝集粒子重量比率を求めた。
（１０）凝集粒子の個数平均粒子径；光学顕微鏡（倍率８０倍）により、写真上の粒径を計測し、その個数平均粒子径を求めた。
（１１）粒状酸化鉄凝集粉末と樹脂との混練物中のムラ；試料と樹脂（三洋化成社製ＴＢ−１０００Ｆ）を用いて重量比１：１でヘンシェルミキサーを用いて混合し、２軸のニーダーで１８０℃、１分間溶融混練した後、混練物をローラーを用いて板状に成型、冷却した。この板状の成型物を切断し、切断面を走査型電子顕微鏡を用いて観察し（倍率５，０００倍）、切断面中の酸化鉄粒子が均一に分布しているものを○、少し分布に偏りがあるものを△、分布の偏りが著しいものを×として評価した。
（１２）粒状酸化鉄凝集粉末と樹脂との混練物中の分散；上記（１１）の観察において、切断面中の酸化鉄一次粒子が凝集していないものを○、やや凝集しているものを△、著しく凝集しているもの×として評価した。
【００４６】
［実施例２］
上記酸化鉄粒子Ｂ３０ｋｇを、温度２３℃、湿度５５％の環境を維持しながら、ナウターミキサー（ホソカワミクロン（株）社製、ＮＸ−１）を用い、スクリューの自転４５ｒｐｍ、公転３ｒｐｍの回転で、１２０分間処理することにより粒状酸化鉄凝集粉末を得た。この粒状酸化鉄凝集粉末について、実施例１に準拠して諸特性を評価した。結果を表２に示す。また、この酸化鉄凝集粉末の光学顕微鏡写真（８０倍）を図１に示す。
【００４７】
［実施例３］
上記酸化鉄粒子Ｃ３０ｋｇを、温度３５℃、湿度８５％の環境を維持しながら、ナウターミキサー（ホソカワミクロン（株）社製、ＮＸ−１）を用い、スクリューの自転９０ｒｐｍ、公転３ｒｐｍの回転で、１２０分間処理することにより粒状酸化鉄凝集粉末を得た。この粒状酸化鉄凝集粉末について、実施例１に準拠して諸特性を評価した。結果を表２に示す。
【００４８】
［実施例４］
上記酸化鉄粒子Ｄ３０ｋｇを、温度２３℃、湿度３５％の環境を維持しながら、ナウターミキサー（ホソカワミクロン（株）社製、ＮＸ−１）を用い、スクリューの自転９０ｒｐｍ、公転３ｒｐｍの回転で、６０分間処理することにより粒状酸化鉄凝集粉末を得た。この粒状酸化鉄凝集粉末について、実施例１に準拠して諸特性を評価した。結果を表２に示す。
【００４９】
［実施例５］
上記酸化鉄粒子Ｅ３０ｋｇを、温度２３℃、湿度３５％の環境を維持しながら、ナウターミキサー（ホソカワミクロン（株）社製、ＮＸ−１）を用い、スクリューの自転９０ｒｐｍ、公転が３ｒｐｍの回転で、６０分間処理することにより粒状酸化鉄凝集粉末を得た。この粒状酸化鉄凝集粉末について、実施例１に準拠して諸特性を評価した。結果を表２に示す。
【００５０】
［比較例１］
上記酸化鉄粒子Ａについて何ら処理を施さなかった。この酸化鉄粒子について、実施例１に準拠して諸特性を評価した。結果を表２に示す。また、この酸化鉄凝集粉末の光学顕微鏡写真（８０倍及び８００倍）を図２及び図３にそれぞれ示す。
【００５１】
［比較例２］
上記酸化鉄粒子Ａ３０ｋｇを、温度２３℃、湿度３５％の環境を維持しながら、ナウターミキサー（ホソカワミクロン（株）社製、ＮＸ−１）を用い、スクリューの自転９０ｒｐｍ、公転３ｒｐｍの回転で、２０分間処理することにより酸化鉄凝集粉末を得た。この酸化鉄凝集粉末について、実施例１に準拠して諸特性を評価した。結果を表２に示す。
【００５２】
［比較例３］
上記酸化鉄粒子Ａ３０ｋｇを、温度３５℃、湿度８５％の環境を維持しながら、ナウターミキサー（ホソカワミクロン（株）社製、ＮＸ−１）を用い、スクリューの自転９０ｒｐｍ、公転３ｒｐｍの回転で、４０分間処理することにより得た酸化鉄凝集粉末を、さらに温度３５℃、湿度８５％の環境下で２週間放置した後のものを酸化鉄凝集粉末とした。この酸化鉄凝集粉末について、実施例１に準拠して諸特性を評価した。結果を表２に示す。
【００５３】
［比較例４］
上記酸化鉄粒子Ａ３０ｋｇを、温度１０℃、湿度１０％の環境を維持しながら、ナウターミキサー（ホソカワミクロン（株）社製、ＮＸ−１）を用い、スクリューの自転９０ｒｐｍ、公転３ｒｐｍの回転で、１２０分間処理することにより酸化鉄凝集粉末を得た。この酸化鉄凝集粉末について、実施例１に準拠して諸特性を評価した。結果を表２に示す。
【００５４】
［比較例５］
上記酸化鉄粒子Ａ３０ｋｇを、温度２３℃、湿度３５％の環境を維持しながら、ナウターミキサー（ホソカワミクロン（株）社製、ＮＸ−１）を用い、スクリューの自転９０ｒｐｍ、公転３ｒｐｍの回転で、６０分間かけて定量的に酸化鉄粒子Ａを供給し、引き続き１０分間処理することにより酸化鉄凝集粉末を得た。この酸化鉄凝集粉末について、実施例１に準拠して諸特性を評価した。結果を表２に示す。
【００５５】
［比較例６］
上記酸化鉄粒子Ｄ３０ｋｇを、温度２３℃、湿度３５％の環境を維持しながら、ナウターミキサー（ホソカワミクロン（株）社製、ＮＸ−１）を用い、スクリューの自転９０ｒｐｍ、公転３ｒｐｍの回転で、２０分間処理することにより酸化鉄凝集粉末を得た。この酸化鉄凝集粉末について、実施例１に準拠して諸特性を評価した。結果を表２に示す。
【００５６】
［比較例７］
上記酸化鉄粒子Ｅ３０ｋｇを、温度２３℃、湿度３５％の環境を維持しながら、ナウターミキサー（ホソカワミクロン（株）社製、ＮＸ−１）を用い、スクリューの自転９０ｒｐｍ、公転３ｒｐｍの回転で、２０分間処理することにより酸化鉄凝集粉末を得た。この酸化鉄凝集粉末について、実施例１に準拠して諸特性を評価した。結果を表２に示す。
【００５７】
【表２】

【００５８】
表２から明らかな通り、実施例１〜５で得られた粒状酸化鉄凝集粉末は、いずれも安息角が４０°以下、見掛嵩密度が１ｇ／ｃｍ³以上、加熱減量が０．０５〜２重量％、衝撃を加えた後のスパチュラ角が４５°以下、圧縮度が４０％以下、傾斜板上に付着する割合が１０重量％以下であり、かつ鏡面反射率が出発原料と比較しても良好な結果が得られ、樹脂との混練の製造工程において、二次粒子の均一な供給と一次粒子の良好な分散とを兼ね備えていた。また、混練物中のムラや一次粒子の分散性の評価においても良好な結果が得られた。なお、樹脂との混合粉末を混練する際の供給も安定していた。
【００５９】
一方、比較例１、２、６及び７の酸化鉄粒子や粒状酸化鉄凝集粉末は、見掛嵩密度が低く、かつ衝撃を加えた後のスパチュラ角、安息角、圧縮度が実施例１〜５に比べて大きく、流動性や凝集強度において劣るものであった。また、傾斜板上に付着する粒子も多く、混練物中のムラや一次粒子の分散性の評価においても劣るものであった。なお、樹脂との混合粉末を粉体供給フィーダーやホッパーに供給する際、付着や閉塞を度々起こし、強制的に粉体を押し込む操作が必要であった。
【００６０】
また、比較例３の粒状酸化鉄凝集粉末は、見掛嵩密度、安息角、及び衝撃を加えた後のスパチュラ角は良好なため、流動性に優れ安定して粉体を供給できるが、加熱減量（水分）が多いため粒子同士の凝集力が強すぎ、圧縮度が低めで、混練物中のムラはないものの、一次粒子の分散性に劣るものであった。
【００６１】
比較例４の粒状酸化鉄凝集粉末は、加熱減量（水分）が少ないため、圧縮度が大きいことからも明らかなように、粒子同士の凝集力が弱かった。また、見掛嵩密度が低く、かつ衝撃を加えた後のスパチュラ角、安息角がいずれも大きく、流動性に劣るものであった。また、傾斜板上に付着する粒子も多く、混練物中のムラや一次粒子の分散性の評価においても劣るものであった。なお、樹脂との混合粉末を粉体供給フィーダーやホッパーに供給する際、付着や閉塞を度々起こし、強制的に粉体を押し込む操作が必要だった。
【００６２】
比較例５の粒状酸化鉄凝集粉末は、凝集操作の不足により、小粒径の微粒凝集粒子もしくは凝集されていない粒子が多いため、見掛嵩密度が低く、かつ衝撃を加えた後のスパチュラ角、安息角がいずれも大きく、流動性に劣るものであった。また、傾斜板上に付着する粒子も多く、混練物中のムラや一次粒子の分散性の評価においても劣るものであった。なお、樹脂との混合粉末を粉体供給フィーダーやホッパに供給する際、付着や閉塞を度々起こし、強制的に粉体を押し込む操作が必要だった。
【００６３】
【発明の効果】
以上説明したように、本発明の粒状酸化鉄凝集粒子及び該凝集粒子を含む粉末は、凝集粒子でありながら適度な強度を有することで樹脂との混合時の分散性に優れ、かつハンドリング性、流動性にも優れるので、静電複写磁性トナー用材料粉、静電潜像現像用キャリア用材料粉、塗料用黒色顔料粉等の用途に好適である。
【図面の簡単な説明】
【図１】図１は、実施例２の酸化鉄凝集粉末の光学顕微鏡写真（８０倍）である。
【図２】図２は、比較例１の酸化鉄粒子の光学顕微鏡写真（８０倍）である。
【図３】図３は、比較例１の酸化鉄粒子の光学顕微鏡写真（８００倍）である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to granular iron oxide agglomerated particles and powder containing the agglomerated particles, and more specifically, by handling specific iron oxide agglomerated particles in which iron oxide primary particles are agglomerated, the handling properties, fluidity, and dispersibility are excellent. In particular, the present invention relates to granular iron oxide agglomerated particles used for applications such as electrostatic copying magnetic toner material powder, electrostatic latent image developing carrier material powder, and black pigment powder for paint, and a powder containing the agglomerated particles.
[0002]
[Prior art and problems to be solved by the invention]
In general, electrostatic copying magnetic toner, electrostatic latent image developing carrier, and the like are based on a thermoplastic resin such as an acrylic resin or a polyester resin, and have an oxidation property having both magnetic properties, typically magnetite particles, and black pigments. Manufactured with iron particles added. At this time, the properties required for the iron oxide particles include higher dispersibility in the resin. In the production of magnetic toner, if this dispersibility is poor, the presence of iron oxide particles in the toner varies, which adversely affects various characteristics including magnetic characteristics.
[0003]
On the other hand, in the production of magnetic toner, the handling property and fluidity of iron oxide particles are also important characteristics. For example, in the manufacturing process such as mixing with resin and pulverization, when the handling and fluidity of iron oxide particles are poor and the supply is not stable, more specifically, shelves and shelters in the hopper and at the supply port This is because, when clogging or the like occurs, a poor distribution of the weight of iron oxide particles already occurs in a mixture or pulverized product of iron oxide particles and resin.
[0004]
In order to suppress such an inconvenience, it is necessary to improve the handling property, fluidity, and dispersibility of the iron oxide particles used, and various proposals have been made so far. For example, Japanese Patent Laid-Open No. 6-130718 proposes a method in which silica fine particles are adhered to the particle surface. JP-A-6-230603 discloses that a particle surface has a Si and / or Ti compound and a coupling agent layer. Japanese Patent Application Laid-Open No. 7-240306 discloses that silica and alumina fine particles are adhered to the surface of silicon-containing magnetite particles. Japanese Patent Application Laid-Open No. 9-59024 describes that each ridge line of silicon or other metal element-containing magnetite particles is curved. Furthermore, Japanese Patent Application Laid-Open No. 9-241025 discloses that the shape of silicon-containing magnetite particles is made into a confetti shape with rounded corners. However, using iron oxide particles obtained by known manufacturing processes, both dry and wet, starting with these conventional technologies, in addition to the cohesiveness of the powder itself, the influence of magnetic coagulation is combined. There was a limit to the effect of improving the handling, fluidity, and dispersibility of the iron oxide particles themselves.
[0005]
JP-A-8-259238 discloses a coloring pigment powder comprising aggregated particles having a particle diameter of 20 μm or less in which iron oxide granular particles having a number average particle diameter of 0.05 to 1 μm are aggregated. It is said that the powder can be obtained by using a container-fixed horizontal double-shaft kneader having a large shearing action. The same publication uses means for pulverizing large agglomerated particles to reduce the particle size of the agglomerated particles to several tens of μm or less, such as an impact pulverizer, a ball mill, a vibration mill, a roll compression molding machine, and a wheel type kneader. The advantages of the agglomerated particles having a particle diameter of 20 μm or less over the agglomerated particles thus obtained are also described.
[0006]
According to the technology disclosed in the publication, although the dispersibility during the production of the resin molded product is certainly excellent, the one with a large aggregated particle is from the viewpoint that the dispersibility is poor, and further handling property, fluidity It does not have sufficient performance in terms of safety.
[0007]
As described above, iron oxide agglomerated particles having excellent fluidity in the process and excellent dispersibility when kneaded with a resin or the like have not been proposed yet.
[0008]
Accordingly, the object of the present invention is to provide iron oxide aggregated particles having excellent transportability, handling properties and fluidity, and being excellent in dispersibility during kneading with a resin by having an appropriate strength while being aggregated particles. And providing a powder containing the aggregated particles.
[0009]
[Means for Solving the Problems]
As a result of intensive studies, the inventors added a deliberate agglomeration operation using iron oxide particles produced by a conventional production method, and controlled the shape, size, strength, etc. of the agglomerated particles to start It was found that iron oxide agglomerated particles having significantly superior dispersibility, handling properties and fluidity were obtained compared to the raw material iron oxide particles, and that the object of the present invention could be achieved.
[0010]
The present invention has been made on the basis of the above findings, and in the production, moisture and organic matter are removed.As a binderObtained without addition, iron oxide primary particles having a number average particle diameter of 0.05 to 1 μm are aggregated, the number average particle diameter is 30 to 3000 μm, and the loss on heating is 0.05 to 2% by weight. InIncluding granular iron oxide aggregated particles having a compressibility of 40% or less,
Granular iron oxide agglomerated powder characterized in that the weight ratio of agglomerated particles having a particle size of 30 μm or more obtained by air classification is 80% by weight or moreIs to provide.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below.
Generally, there is a means of granulation in the intentional agglomeration operation, and what is obtained by this means is called a granulated product, and agglomeration caused by inherent powder characteristics etc. Although often distinguished from aggregates, “intentional aggregation” in the present invention refers to both intentional granulation and aggregation means.
[0013]
Further, the granular aggregated particles refer to those in which voids are not recognized in the aggregated particles and the primary particles are densely aggregated when observed with an optical microscope 80 times. The granular agglomerated particles are composed of iron oxide particles. Furthermore, the granular aggregated powder refers to a powder containing granular aggregated particles, and the granular iron oxide aggregated powder refers to powder containing granular iron oxide aggregated particles.
[0014]
In addition, the term “primary particle” or “aggregated particle” means any individual particle or aggregate thereof depending on the content.
[0015]
The form of the iron oxide primary particles that are the starting material of the present invention is magnetite (Fe_ThreeO_Four), Maghemite (γ-Fe₂O_Three) And intermediate composition beltride compounds (FeOx · Fe₂O_Three, 0 <X <1), and at least one or more of Si, Al, Mn, Ni, Zn, Cu, Mg, Ti, Co, Zr, W, Mo, P, etc. The spinel ferrite particles to be contained may be selected according to the required characteristics, and the shape is not particularly limited as long as it can provide the characteristics suitable for the toner. A plane shape and a hexahedron shape) are preferable.
[0016]
Furthermore, in order to improve dispersibility, iron oxide primary particles that have been surface-treated with Si, Al, or an organic treatment agent may be used.
[0017]
In general, the number average particle diameter of primary particles of iron oxide particles used for electrostatic copying magnetic toners and electrostatic latent image developing carriers is generally about 0.05 to 1 μm. It is important that the primary particles and the fine aggregated particles of the primary particles are aggregated by adding an aggregating operation, and that the number average particle diameter is 30 to 3000 μm. Further, the shape of the iron oxide aggregated particles of the present invention is not particularly limited as long as it is granular, but is preferably spherical from the viewpoint of fluidity.
[0018]
Agglomerated iron oxide particles obtained by a known manufacturing process, whether dry or wet, as shown in the above-mentioned prior art, or pulverizing the agglomerated iron oxide particles to reduce the particle diameter of the agglomerated particles to several tens of μm or less Aggregated particles obtained by the above are strongly affected by the aggregation of the powder itself and magnetic aggregation, are not only irregular due to the shape of the original aggregated particles, but the primary particles are entangled in branches, Since there are many voids in the particles, it is inferior in dispersibility, handling properties and fluidity.
[0019]
On the other hand, the granular iron oxide agglomerated particles of the present invention basically do not intentionally add moisture or organic matter as a binder, and without using a manufacturing method for forcibly pressing powders together, Since the generation of free particles is suppressed by utilizing the cohesive force between the powders, it has excellent handling properties and fluidity, as well as excellent dispersibility in the resin.
[0020]
Further, the agglomerated particles having a particle diameter of 20 μm or less described in JP-A-8-259238 are proposed from the viewpoint that if the agglomerated particles are large, the dispersibility becomes poor. Assuming that the granular iron oxide agglomerated particles exhibit a uniform dispersibility and that a two-stage dispersion in which the primary particles and fine agglomerated particles constituting the agglomerated particles are further dispersed can be achieved, the agglomerated particles are enlarged. This improves handling and fluidity.
[0021]
That is, by using the granular iron oxide aggregated particles of the present invention, first, the aggregated particles are uniformly dispersed at a high dispersion rate in the resin. Next, since the aggregated particles are aggregated with a moderately balanced strength during kneading, an even stress is applied to each aggregated particle, and the secondary dispersion is completed.
[0022]
In the above-described iron oxide particles according to the prior art, the primary dispersion is difficult to proceed because of poor fluidity, and as a result, the primary dispersion and the secondary dispersion have to proceed simultaneously, and as a result, uniform kneading stress is applied to the particles. Therefore, it is assumed that there is a problem in the dispersion of primary particles.
[0023]
Therefore, it is an important point in the present invention that the aggregated particles are adjusted to a moderately sized particle size, and the strength of the aggregated particles is controlled in a balanced manner by heat loss.
[0024]
In particular, the balance between the size of the aggregated particle size and the strength of the aggregated particles is important. When the number average particle size of the granular iron oxide aggregated particles of the present invention is less than 30 μm, even in terms of dispersibility, Inferior handling and fluidity. When the number average particle diameter exceeds 3000 μm, the aggregated particles are too large and the strength is not sufficient when the binder is not used. When the binder is used, the strength is excessively increased, and the dispersion from the aggregated particles to the primary particle level is achieved. Inevitable sexual defects.
[0025]
The granular iron oxide aggregated particles of the present invention have a loss on heating of 0.05 to 2% by weight. When the loss on heating is less than 0.05% by weight, the agglomeration force between the primary particles in the aggregated particles is too weak, and part of the primary particles separate from the aggregated particles, and in particular, handling properties and fluidity are poor. It becomes. When the weight loss of the aggregated particles exceeds 2% by weight, the cohesive force between the primary particles is too strong due to excessive water, resulting in poor dispersibility.
[0026]
The granular iron oxide aggregated particles of the present invention preferably have a compressibility of 40% or less, and more preferably 35% or less. If the degree of compression exceeds 40%, the agglomeration strength tends to be insufficient, and the agglomerated particles are broken and the particles are released due to the impact. Causes blockage. Further, even if the cohesive strength is too strong, the dispersibility in the resin, particularly the dispersibility of the primary particles at the time of kneading is likely to be affected, so the degree of compression is preferably 20% or more.
[0027]
The iron oxide aggregated particles of the present invention have an angle of repose of preferably 40 ° or less, and more preferably 38 ° or less. When the angle of repose exceeds 40 °, handling properties and fluidity are poor.
[0028]
The granular iron oxide aggregated particles of the present invention preferably have an apparent bulk density of 1 g / cm.^ThreeOr more, more preferably 1.1 g / cm^ThreeThat's it. Apparent bulk density of 1 g / cm^ThreeIf it is less than 1, the dispersibility of the granular iron oxide aggregated particles in the resin becomes poor.
[0029]
The granular iron oxide aggregated particles of the present invention preferably have a spatula angle of 45 ° or less, more preferably 40 ° or less after impact. When this spatula angle exceeds 45 °, handling and fluidity are poor.
[0030]
The granular iron oxide aggregated particles of the present invention desirably have a weight adhesion rate on a 45 ° inclined metal plate of 10% by weight or less. When the weight adhesion rate exceeds 10% by weight, the fluidity, particularly the particle adhesion in the facility increases, which is not preferable.
[0031]
Next, the granular iron oxide aggregated powder of the present invention is preferably composed only of the granular iron oxide aggregated particles having the above characteristics and properties. However, in terms of practical use, the particle size obtained by air classification is 30 μm. The granular iron oxide aggregated particles may be contained so that the weight ratio of the aggregated particles is 80% by weight or more, preferably 90% by weight or more, and more preferably 95% by weight or more. When this weight ratio is less than 80% by weight, the handling property, fluidity and transportability of the agglomerated powder are remarkably inferior.
[0032]
Next, the specific manufacturing method of the granular iron oxide aggregated particle and granular iron oxide aggregated powder of this invention is described.
The starting material of the granular iron oxide aggregated particles of the present invention may be iron oxide particles obtained by a known production process regardless of whether it is dry or wet, and may be a molded product as long as it has undergone a drying process. It is preferable that large agglomerated particles are reduced by adding conventional pulverization to a fine agglomerated particle level of particles and primary particles by a pulverizer such as a jet mill or a hammer mill.
[0033]
The granular iron oxide agglomerated particles and the granular iron oxide agglomerated powder in the present invention avoid the hard agglomeration based on the surface contact of the primary particles, realize the soft and easy agglomeration based on the point contact, and adjust the strength by heating loss. As a method for adding the agglomeration operation, it can be produced using an apparatus having a closed structure with many opportunities for contact between particles, such as a Nauter mixer, and two kinds of kneading operations (revolving kneading and rotation kneading).
[0034]
In this production, it is not necessary to intentionally add moisture or organic matter as a binder, and adjust the temperature and humidity environment where the equipment is placed according to the heating loss of the starting material, and conditions such as operating time Is preferably adjusted.
[0035]
Equipment that strongly compresses or compacts individual particles, specifically, compression molding equipment represented by tableting machines and briquetting machines, extrusion molding represented by screw extruders and pellet mills. The use of an apparatus or a compaction processing device represented by a Simpson mix muller or a compression roll alone improves the fluidity of the agglomerated particles, but the primary particles constituting the agglomerated particles and the fine agglomerated particles of the primary particles The cohesive force between them is too strong and the dispersibility is poor.
[0036]
In the present invention, by making the aggregates to a certain size, the secondary particles can be uniformly supplied in the process, and the hardness of the aggregated particles can be softened to disperse the primary particles. it can.
[0037]
If the particle size and strength of the agglomerated particles cannot be maintained, the agglomerated particles are broken due to impact or stress during conveyance in the process, and as a result, particles with poor handling and fluidity are generated. Adhesion and blockage of the water will occur, and stable supply will be difficult.
[0038]
In addition, the granular iron oxide aggregated particles and the granular iron oxide aggregated powder of the present invention can be controlled stably and easily when supplying the powder in the process. In particular, when continuously charged and the entire remixing and re-kneading are not performed, the balance of a plurality of substances at the time of supply is important, and how to keep supplying the substances constant is important. From such a viewpoint, the iron oxide aggregated particles and the granular iron oxide aggregated powder of the present invention are excellent.
[0039]
【Example】
Hereinafter, the present invention will be specifically described based on examples and the like.
[0040]
[Test example]
Table 1 shows various properties of iron oxide particles A to E, which are starting materials, measured by the following methods. The iron oxide particles are produced by a usual wet oxidation method, and are washed, dried and pulverized by a usual method.
[0041]
(1) Number average particle diameter of primary particles: The particle diameter on the photograph was measured by a transmission electron micrograph (magnification of 30,000), and the number average particle diameter was determined.
(2) Angle of repose: Measured according to a manual attached to the main body using a powder tester manufactured by Hosokawa Micron.
(3) Apparent bulk density: without using a sieve or the like, the inner volume is 100 cm.^ThreeThe weight was measured and the weight per unit volume was determined.
(4) Loss on heating: The sample was heated at 90 ° C. for 1 hour under a nitrogen atmosphere, and the ratio of the changed weight to the original weight was determined.
(5) Spatula angle after impact: Measured according to a manual attached to the main body using a powder tester manufactured by Hosokawa Micron.
(6) Compressibility: Using an apparent bulk density and a tap density measured in accordance with a manual attached to the main body using a powder tester manufactured by Hosokawa Micron Co., calculated by the following equation.
Compressibility = {(tap density−apparent bulk density) / (tap density)} × 100
(7) Specular reflectivity: 20 ° on the coated film surface, in which a kneaded mixture of a dispersion paste prepared in accordance with the Hoovermarer method of JIS K 5101 and a nitrified cotton clear lacquer is spread on white paper using a 1 mil film applicator The reflectance was measured.
(8) The rate of adhesion on the inclined plate; a metal plate (material SUS304) having a thickness of 0.5 mm, a length of 30 cm, and a width of 20 cm is inclined at 45 °, and 10 g of the sample is dropped at once from a height of 10 cm, Roll or slide on a metal plate. The operation was repeated 10 times, a total of 100 g of the sample was dropped, the weight adhering to the metal plate was determined, and the ratio was shown as a percentage of the charged 100 g.
[0042]
[Table 1]

[0043]
[Example 1]
While maintaining the environment of the above-mentioned iron oxide particles A30 kg at a temperature of 23 ° C. and a humidity of 35%, using a Nauter mixer (manufactured by Hosokawa Micron Co., Ltd., NX-1) By treating for 60 minutes, granular iron oxide aggregated powder was obtained.
[0044]
About this granular iron oxide aggregated powder, various characteristics were evaluated based on the measurement of the iron oxide particle of the said test example. Moreover, the weight ratio of aggregated particles of 30 μm or more by wind classification, the number average particle diameter of aggregated particles, unevenness in the kneaded product of granular iron oxide aggregated powder and resin, in the kneaded product of granular iron oxide aggregated powder and resin The dispersion was measured by the following method. The results are shown in Table 2.
[0045]
(9) Weight ratio of aggregated particles of 30 μm or more by air classification: Aggregated particles of 30 μm or more are classified using an air classifier (Nisshin Engineering Co., Ltd., turbo classifier TC-15M type), and used for weight and classification The weight ratio of aggregated particles of 30 μm or more was determined from the weight of the granular iron oxide aggregated powder.
(10) Number average particle diameter of aggregated particles: The particle diameter on the photograph was measured with an optical microscope (magnification 80 times), and the number average particle diameter was determined.
(11) Unevenness in the kneaded product of granular iron oxide agglomerated powder and resin; using sample and resin (TB-1000F manufactured by Sanyo Chemical Co., Ltd.) at a weight ratio of 1: 1 using a Henschel mixer, After melt-kneading at 180 ° C. for 1 minute with a kneader, the kneaded product was molded into a plate shape using a roller and cooled. This plate-shaped molded product is cut, and the cut surface is observed with a scanning electron microscope (magnification: 5,000 times). The iron oxide particles in the cut surface are uniformly distributed. The case where the bias was biased was evaluated as Δ, and the case where the distribution was significantly biased was evaluated as ×.
(12) Dispersion of granular iron oxide aggregated powder and resin in a kneaded product; in the observation of (11) above, the iron oxide primary particles in the cut surface are not aggregated. Δ, markedly agglomerated ×.
[0046]
[Example 2]
While maintaining the environment of the above iron oxide particles B30 kg at a temperature of 23 ° C. and a humidity of 55%, using a Nauter mixer (manufactured by Hosokawa Micron Co., Ltd., NX-1) By processing for 120 minutes, a granular iron oxide aggregated powder was obtained. Various characteristics of this granular iron oxide aggregated powder were evaluated according to Example 1. The results are shown in Table 2. Moreover, the optical microscope photograph (80 time) of this iron oxide aggregation powder is shown in FIG.
[0047]
[Example 3]
While maintaining the temperature of 35 ° C. and humidity of 85% with the above iron oxide particles C30 kg, using a Nauter mixer (manufactured by Hosokawa Micron Co., Ltd., NX-1), the rotation of the screw is 90 rpm, the revolution is 3 rpm, By processing for 120 minutes, a granular iron oxide aggregated powder was obtained. Various characteristics of this granular iron oxide aggregated powder were evaluated according to Example 1. The results are shown in Table 2.
[0048]
[Example 4]
While maintaining the environment of the above-mentioned iron oxide particles D30 kg at a temperature of 23 ° C. and a humidity of 35%, using a Nauter mixer (manufactured by Hosokawa Micron Corporation, NX-1), the rotation of the screw is 90 rpm, the rotation is 3 rpm, By treating for 60 minutes, granular iron oxide aggregated powder was obtained. Various characteristics of this granular iron oxide aggregated powder were evaluated according to Example 1. The results are shown in Table 2.
[0049]
[Example 5]
While maintaining the environment of the above-described iron oxide particles E30 kg at a temperature of 23 ° C. and a humidity of 35%, using a Nauter mixer (NX-1 manufactured by Hosokawa Micron Corporation), the rotation of the screw is 90 rpm and the revolution is 3 rpm. The granular iron oxide aggregated powder was obtained by processing for 60 minutes. Various characteristics of this granular iron oxide aggregated powder were evaluated according to Example 1. The results are shown in Table 2.
[0050]
[Comparative Example 1]
The iron oxide particles A were not treated at all. Various characteristics of the iron oxide particles were evaluated according to Example 1. The results are shown in Table 2. Moreover, the optical microscope photograph (80 time and 800 time) of this iron oxide aggregation powder is shown in FIG.2 and FIG.3, respectively.
[0051]
[Comparative Example 2]
While maintaining the environment of the above iron oxide particles A30 kg at a temperature of 23 ° C. and a humidity of 35%, using a Nauter mixer (manufactured by Hosokawa Micron Corporation, NX-1), the rotation of the screw is 90 rpm, the revolution is 3 rpm, The iron oxide aggregated powder was obtained by processing for 20 minutes. Various characteristics of this iron oxide aggregated powder were evaluated according to Example 1. The results are shown in Table 2.
[0052]
[Comparative Example 3]
While maintaining the temperature of 35 ° C. and humidity of 85% with the above iron oxide particles A30 kg, using a Nauter mixer (manufactured by Hosokawa Micron Corporation, NX-1), the rotation of the screw is 90 rpm, the rotation is 3 rpm, The iron oxide aggregated powder obtained by treating for 40 minutes was further allowed to stand for 2 weeks in an environment of a temperature of 35 ° C. and a humidity of 85% to obtain an iron oxide aggregated powder. Various characteristics of this iron oxide aggregated powder were evaluated according to Example 1. The results are shown in Table 2.
[0053]
[Comparative Example 4]
While maintaining the environment of the iron oxide particles A30 kg at a temperature of 10 ° C. and a humidity of 10%, using a Nauter mixer (manufactured by Hosokawa Micron Corporation, NX-1), the rotation of the screw is 90 rpm, the revolution is 3 rpm, The iron oxide aggregated powder was obtained by processing for 120 minutes. Various characteristics of this iron oxide aggregated powder were evaluated according to Example 1. The results are shown in Table 2.
[0054]
[Comparative Example 5]
While maintaining the environment of the above-mentioned iron oxide particles A30 kg at a temperature of 23 ° C. and a humidity of 35%, using a Nauter mixer (manufactured by Hosokawa Micron Co., Ltd., NX-1), the rotation of the screw is 90 rpm, the revolution is 3 rpm, Iron oxide particles A were quantitatively supplied over 60 minutes, and subsequently treated for 10 minutes to obtain an iron oxide aggregated powder. Various characteristics of this iron oxide aggregated powder were evaluated according to Example 1. The results are shown in Table 2.
[0055]
[Comparative Example 6]
While maintaining the environment of the above-mentioned iron oxide particles D30 kg at a temperature of 23 ° C. and a humidity of 35%, using a Nauter mixer (manufactured by Hosokawa Micron Corporation, NX-1), the rotation of the screw is 90 rpm, the rotation is 3 rpm, The iron oxide aggregated powder was obtained by processing for 20 minutes. Various characteristics of this iron oxide aggregated powder were evaluated according to Example 1. The results are shown in Table 2.
[0056]
[Comparative Example 7]
While maintaining the environment of the iron oxide particles E30 kg at a temperature of 23 ° C. and a humidity of 35%, using a Nauter mixer (manufactured by Hosokawa Micron Co., Ltd., NX-1), the rotation of the screw is 90 rpm, the revolution is 3 rpm, The iron oxide aggregated powder was obtained by processing for 20 minutes. Various characteristics of this iron oxide aggregated powder were evaluated according to Example 1. The results are shown in Table 2.
[0057]
[Table 2]

[0058]
As is apparent from Table 2, the granular iron oxide aggregated powders obtained in Examples 1 to 5 all have an angle of repose of 40 ° or less and an apparent bulk density of 1 g / cm.^ThreeAs described above, the loss on heating is 0.05 to 2% by weight, the spatula angle after impact is 45 ° or less, the degree of compression is 40% or less, the rate of adhesion on the inclined plate is 10% by weight or less, and the mirror surface Good results were obtained even when the reflectance was higher than that of the starting material, and in the production process of kneading with the resin, both uniform supply of secondary particles and good dispersion of primary particles were combined. Also, good results were obtained in the evaluation of unevenness in the kneaded product and the dispersibility of the primary particles. The supply when kneading the mixed powder with the resin was also stable.
[0059]
On the other hand, the iron oxide particles and granular iron oxide agglomerated powders of Comparative Examples 1, 2, 6 and 7 have low apparent bulk density and have a spatula angle, repose angle and compression degree after application of the examples 1 to 3. It was larger than 5, and was inferior in fluidity and cohesive strength. Moreover, there are many particles adhering on the inclined plate, and the evaluation of the unevenness in the kneaded material and the dispersibility of the primary particles was also inferior. In addition, when supplying mixed powder with resin to a powder supply feeder or a hopper, adhesion and blockage frequently occurred, and an operation of forcibly pushing in the powder was necessary.
[0060]
In addition, the granular iron oxide aggregated powder of Comparative Example 3 has an apparent bulk density, an angle of repose, and a spatula angle after applying an impact, so that the powder can be stably supplied with excellent fluidity. Since the weight loss (moisture) was large, the cohesive force between the particles was too strong, the degree of compression was low, and there was no unevenness in the kneaded product, but the dispersibility of the primary particles was poor.
[0061]
The granular iron oxide agglomerated powder of Comparative Example 4 had a small amount of heat loss (moisture), so that the agglomeration force between the particles was weak as apparent from the high degree of compression. In addition, the apparent bulk density was low, and the spatula angle and repose angle after impact were both large and the fluidity was poor. Moreover, there are many particles adhering on the inclined plate, and the evaluation of the unevenness in the kneaded material and the dispersibility of the primary particles was also inferior. In addition, when the mixed powder with the resin was supplied to the powder supply feeder or the hopper, it often required adhesion and blockage, and forced operation to push the powder.
[0062]
The granular iron oxide agglomerated powder of Comparative Example 5 has a small apparent particle density due to a lack of agglomeration operation and a small agglomerated particle or non-agglomerated particles. The angle of repose was large and the fluidity was inferior. Moreover, there are many particles adhering on the inclined plate, and the evaluation of the unevenness in the kneaded material and the dispersibility of the primary particles was also inferior. In addition, when the mixed powder with the resin was supplied to the powder supply feeder or the hopper, an operation of forcibly pushing in the powder was required due to frequent adhesion and blockage.
[0063]
【The invention's effect】
As described above, the granular iron oxide agglomerated particles of the present invention and the powder containing the agglomerated particles are excellent in dispersibility at the time of mixing with the resin by having an appropriate strength while being agglomerated particles, and handling properties, Since it is excellent in fluidity, it is suitable for uses such as electrostatic copying magnetic toner material powder, electrostatic latent image developing carrier material powder, and black pigment powder for paint.
[Brief description of the drawings]
1 is an optical micrograph (magnification 80 times) of the iron oxide aggregated powder of Example 2. FIG.
FIG. 2 is an optical micrograph (magnification 80 times) of the iron oxide particles of Comparative Example 1.
FIG. 3 is an optical micrograph (800 magnifications) of the iron oxide particles of Comparative Example 1.

Claims

In the production, iron oxide primary particles having a number average particle diameter of 0.05 to 1 μm are aggregated, the number average particle diameter is 30 to 3000 μm, and obtained without adding moisture or organic matter as a binder. weight loss Ri 0.05-2 wt% der includes granular iron oxide agglomerated particles compressibility is 40% or less,
A granular iron oxide agglomerated powder characterized in that the weight ratio of agglomerated particles having a particle size of 30 μm or more obtained by air classification is 80% by weight or more .

Particulate iron oxide agglomerated powder of claim 1 angle of repose of the particulate iron oxide agglomerated particles is 40 ° or less.

The granular iron oxide aggregated powder according to claim 1 or 2 , wherein the apparent bulk density of the granular iron oxide aggregated particles is 1 g / cm ³ or more.

The granular iron oxide aggregated powder according to any one of claims 1 to 3 , wherein a spatula angle after the impact of the granular iron oxide aggregated particles is 45 ° or less.