JP4318070B2 - Surface-modified silica fine powder - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明は、電子写真用トナーおよび粉体塗料等において、それらの粉体の流動性改善、固結防止、帯電調整等の目的で添加される経時安定性に優れた表面改質シリカ微粉末とこのシリカ粉末を含有するトナー組成物に関する。
【０００２】
【従来の技術】
電子写真用トナーや粉体塗料等では、一般にその流動性を高めるために疎水性無機酸化物微粉末を少量添加している。通常、この添加剤として用いるシリカ微粉末は気相法または液相法で合成したものをアルキルシランまたはオルガノポリシロキサン等で表面を疎水化処理したものを用いている。例えば、シリカ微粉末をアルキルハロゲン化シランで表面処理したもの（特開昭６１―１８８５４７号記載）、あるいはシリカ、チタニア、アルミナをオルガノポリシロキサンで表面処理したもの（特開平１１−１２４４６４号記載）、シリカ微粉末をヘキサメチルジシラザンで表面処理したもの（特開２００１−３５６５１６号記載）などが知られている。
【０００３】
このように、複写機、レーザープリンター、普通紙ファクシミリなどの電子写真において、微細なシリカ、チタニアやアルミナなどの無機酸化物微粉末を有機物によって表面処理したものをトナーに添加し、その流動性改善剤として広く用いられている。
【０００４】
【発明が解決しようとする課題】
近年、トナーの粒子径が１０μmから５μmに小粒化するのに伴い、トナーの流動性が低下する問題があり、これを改善するためにトナー外添剤の添加量が従来より増えており、さらに、この外添剤には従来より高い流動性が求められるようになっている。例えば、シリカ微粉末を用いた従来の外添剤を小粒径のトナーに用いるとトナー組成物の耐久性が低下する問題がある。一方、耐久性を改善するために表面処理剤を変えたものを用いると、トナーの流動性は改善されるものの感光体表面にトナーフィルミングを生じたり、かぶりを発生させるなどの問題が生じる場合がある。
【０００５】
本発明は、従来の表面処理シリカ微粉末について上記問題を解消したものであり、摩擦帯電量やトナー耐久性について経時安定性に優れた表面処理シリカ微粉末を提供するものである。
【０００６】
本発明によれば以下の構成からなる表面処理シリカ微粉末およびそのトナー組成物が提供される。
〔１〕 ＢＥＴ比表面積５０〜９０ｍ 2 /ｇのシリカ微粉末を、ヘキシル基以下のアルキルアルコキシシランを用い、アミン系触媒の存在下で表面処理したシリカ微粉末であって、安息角２０〜４２度およびＢＥＴ比表面積３３〜９０ｍ2/ｇであり、トナーに分散して５分経過後の初期摩擦帯電量（Ａ）に対する３０分後の経時摩擦帯電量（Ｂ）の変化率（Ａ／Ｂ）が１.０〜２.０であることを特徴とする表面改質シリカ微粉末。
〔２〕 トナーに分散して５分経過後の初期摩擦帯電量（Ａ）と３０分経過後の経時摩擦帯電量（Ｂ）の比（Ａ／Ｂ）が１.０〜１.７である上記[１]記載する表面改質シリカ微粉末。
〔３〕 ＢＥＴ比表面積５０〜９０ｍ2/ｇのシリカ微粉末をアルキルアルコキシシランによって表面処理したシリカ微粉末であって、ヘキシル基以下のアルキルアルコキシシランを用い、アミン系触媒の存在下で、シリカ微粉末に対するアルキルアルコキシシランの量、水分量、反応温度および時間を、表面処理後の摩擦帯電量の経時変化率（Ａ／Ｂ）が１.０〜２.０になるように調整して表面処理した上記[１]に記載する表面改質シリカ微粉末。
〔４〕 上記[１]、上記[２]または上記[３]に記載する表面改質シリカ微粉末をトナー材料に混合したトナー組成物であって、このトナー組成物の初期平均凝集粒子径（Ｘ）に対する９０分経時後の経時平均凝集粒子径（Ｙ）の変化率（Ｘ／Ｙ）が２.０以下であることを特徴とするトナー組成物。
【０００７】
【発明の実施の形態】
以下、本発明を実施例および比較例と共に詳細に説明する。
本発明の表面改質シリカ微粉末は、ＢＥＴ比表面積５０〜９０ｍ 2 /ｇのシリカ微粉末を、ヘキシル基以下のアルキルアルコキシシランを用い、アミン系触媒の存在下で表面処理したシリカ微粉末であって、安息角２０〜４２度およびＢＥＴ比表面積３３〜９０ｍ2/ｇであり、トナーに分散して５分経過後の初期摩擦帯電量（Ａ）に対する３０分経過後の経時摩擦帯電量（Ｂ）の変化率（Ａ／Ｂ）が１.０〜２.０であることを特徴とする。ここで、初期摩擦帯電量（Ａ）とは表面処理シリカ微粉末をトナーに分散させて一定時間振盪して摩擦帯電を与えたときに保持している摩擦帯電量であり、経時摩擦帯電量（Ｂ）はさらに振盪して一定時間経過後に保持している摩擦帯電量である。具体的には、例えば、表面処理シリカ微粉末をトナーに混合分散して振盪し、振盪５分経過後の摩擦帯電量を（Ａ）とし、一方、振盪３０分経過後の摩擦帯電量を（Ｂ）とする。なお、初期摩擦帯電量（Ａ）と経時摩擦帯電量（Ｂ）の経過時間はこの時間に限らない。例えば、振盪後２０分経過したものを初期摩擦帯電量（Ａ）とし、これよりさらに所定時間経過（例えば、さらに１０〜４０分）したものを経時摩擦帯電量（Ｂ）としてもよい。
【０００８】
上記摩擦帯電量の経時変化率(Ａ／Ｂ)の小さいものはトナーに添加した場合に耐久性に優れる。本発明の表面改質シリカ微粉末は、初期摩擦帯電量(Ａ)に対する３０分経過後の経時摩擦帯電量(Ｂ)の変化率(Ａ／Ｂ)が１.０〜２.０であり、好ましくは５分経過後の初期摩擦帯電量(Ａ)と３０分経過後の経時摩擦帯電量(Ｂ)の比(Ａ／Ｂ)が１.０〜１.７のものである。この経時変化率が上記範囲内のものはトナー組成物の耐久性に優れ、良好な画像を得ることができる。一方、この経時変化率が１.０より小さいものは次第に摩擦帯電量が大きくなり、分散不良などを招き、この経時変化率が２.０より大きいものは次第に帯電量が低下し、凝集やかぶりを生じる傾向がある。
【０００９】
また、本発明の表面改質シリカ微粉末は安息角２０〜４２度、ＢＥＴ比表面積３３〜９０ｍ2/ｇのものが好ましい。上記比表面積が３３ｍ2/ｇより小さいものを用いると安息角が４２度を上回って流動性が大幅に低下する傾向があり、またトナーに添加したときにトナーから分離しやすく、かぶりやフィルミングの原因となる。一方、上記比表面積が９０ｍ2/ｇより大きいと耐久性が大幅に低下する。また、安息角が２０度より小さいと流動性が過剰になり取り扱い難くなる。
【００１０】
本発明の上記表面改質シリカ微粉末をトナー材料、例えばトナーおよびキャリアーに混合分散したトナー組成物について、初期平均凝集粒子径(Ｘ)に対する経時平均凝集粒子径(Ｙ)の変化率(Ｘ／Ｙ)の小さいトナー組成物を得ることができる。ここで、初期平均凝集粒子径(Ｘ)はトナー組成物を調製した初期の平均凝集粒子径であり、経時平均凝集粒子径(Ｙ)は一定時間経過後の平均凝集粒子径である。具体的には、例えば、トナー組成物調製から５分経過後の平均凝集粒子径を(Ｘ)とし、９０分経過後の平均凝集粒子径を(Ｙ)とするとき、平均凝集粒子径の経時変化率(Ｘ／Ｙ)が２.０以下のトナー組成物を得ることができる。
【００１１】
平均凝集粒子径の上記経時変化率(Ｘ／Ｙ)が２.０以下のトナー組成物は耐久性が優れる。経時変化率(Ｘ／Ｙ)が２.０より大きくなるものは凝集粒子径が半減するので長時間運転後のトナー流動性に問題を生じ、トナーの耐久性が低下する。
【００１２】
本発明の表面改質シリカ微粉末は、ヘキシル基以下のアルキルアルコキシシランを用い、アミン系触媒の存在下で、シリカ微粉末に対するアルキルアルコキシシランの量、水分量、反応温度および時間を、表面処理後の摩擦帯電量の経時変化率(Ａ／Ｂ)が１.０〜２.０、好ましくは５分経過後の初期摩擦帯電量(Ａ)と３０分経過後の経時摩擦帯電量(Ｂ)の比(Ａ／Ｂ)が１.０〜１.７になるように調整して表面処理することによって得ることができる。
【００１３】
原料のシリカ微粉末は、実施例１〜２、実施例４〜５に示すように、ＢＥＴ比表面積５０〜９０ｍ2/ｇのものを用いるとよい。シリカ微粉末は表面処理によって多少とも粒子表面の微細構造が平坦化されて、表１に示すように、ＢＥＴ比表面積３３〜６４ｍ2/ｇの表面処理粉末を得ることができる。また、シリカ微粉末は気相法で合成されたものが好ましい。
【００１４】
アルキルアルコキシシランはモノメチルトリメトキシシラン、ジメチルジメトキシシラン、トリメチルメトキシシラン、モノエチルトリメトキシシラン、ジエチルジメトキシシラン、トリエチルメトキシシラン、プロピルトリメトキシシラン、イソプロピルトリメトキシシラン、ブチルトリメトキシシラン、イソブチルトリメトキシシランが好ましい。アルキル基がヘキシル基以上になると流動性に不具合が生じる。また、アルコキシ基が存在しないと流動性、耐久性、トナーフィルミング、かぶり、クリーニング性を全て満足するものを得られない。
【００１５】
シリカ微粉末１００重量部に対するアルキルアルコキシシランの量は概ね５〜３０重量部が適当である。これより少ないと十分な耐久性が得られない。これより多いと過剰の処理剤が不均一に分散して凝集塊発生の原因となる。
【００１６】
シリカ微粉末は調湿したものが好ましい。調湿方法および調湿の程度は特に限定されないが、水分量によって摩擦帯電量の経時変化率(Ａ/Ｂ)が異なるので、この経時変化率が１.０〜２.０、好ましくは１.０〜１.７の範囲になるように調整する。具体的には、基本的にアルコキシ基の加水分解を進める水分量が必要であり、また、シリカ微粒子表面に付着するアルコキシ基を増すには水分量の少ない方が好ましく、一方、アルコキシ基を減らすには水分量の多いほうがよい。一般には概ねアルコキシ基の当量に対して０.５〜３.０倍の水分量が目安になる。また、調湿方法は特に限定されず、製造後に長時間自然に調湿したものを使用しても良いし、意図的にスチームを導入したりスプレーしたものを用いてもよい。調湿の程度は、乾燥減量やカールフィッシャー法を用いて調べることができる。
【００１７】
表面処理は不活性ガス雰囲気下で行うのが好ましい。例えば、窒素ガス等で系内を置換した後に、アルキルアルコキシシランをシリカ微粉末にスプレーする。スプレー後、エージングを十分行った後に、アルキルアルコキシシランの沸点以上に加熱して一定時間保持する。その後、未反応物、副生成分を除去して冷却する。アルコキシ基の残存量(付着量)は表面処理によって発生するアルコール量で検出することができる。アルコール検知に関しては、回収ガスラインにアルコール濃度計を導入して測定すれば良い。あるいは、例えば表面改質シリカ微粉末をバイアル瓶に入れ、Head-Spaceガスクロマトグラフを用いて定量することによってアルコキシ基の残存量を直接的に測定してもよい。アルコキシ基の残存量(付着量)は摩擦帯電量の経時変化率(Ａ/Ｂ)に影響を与えるので、この経時変化率が上記範囲になるように調整する。
【００１８】
概ね反応温度は１２０〜１７０℃、反応時間は４０〜１２０分が適当である。反応温度および反応時間は経時変化率が上記範囲になるように調整すればよい。
【００１９】
また、トナーはキャリアを用いた２成分系に限定されず、トナー単独の１成分系でもよい。また、トナーはカラーでもモノクロでも良い。トナーの粒子径は平均粒径１０μm程度のものでも良く、効果が認められているが、特に平均粒径８μm程度以下のものがより効果が顕著に現れる。キャリアは特に限定されず一般のものを用いると良い。例えばフェライトキャリア、鉄粉キャリアが用いられ、これらはシリコーンやフッ素樹脂等でコーティングされていても、いなくても良い。
【００２０】
【発明の効果】
本発明の表面改質シリカ微粉末は高い耐久性、高流動性、安定した帯電性を同時に満たし、従って電子写真用トナー、粉体塗料等に用いたとき、それらの粉体の流動性を改善して固結を防止し、さらにトナーフィルミングやかぶり、クリーニング性に優れたものを得ることができる。
【００２１】
【実施例および比較例】
以下、本発明を実施例および比較例によって具体的に示す。なお、表面処理するシリカ微粉末はハロゲン化ケイ素化合物の火炎加水分解により生成された微粉末であって、窒素吸着法(BET法)によって測定された比表面積４０〜１００m2/gのいわゆるヒュームドシリカを用いた。また、安息角、平均凝集粒子径、帯電量は以下の方法で測定した。
(イ) 安息角の測定方法：市販の測定器（ホソカワミクロン社製パウダテスタPT-N型）を用い、規定の測定方法に従って測定した。
(ロ) 平均凝集粒子径の測定方法：市販の測定器（JEOL JSM-5300LV）を用いて倍率５万倍で観察し、凝集粒子径を測定した。
(ハ) 帯電量の測定方法：ガラス容器(75mL)に鉄粉キャリア５０ｇとシリカ微粉末０.１ｇを入れて蓋をし、ターブラミキサーで５分間、もしくは３０分間振盪した後、該シリカ微粉末が混在した鉄粉キャリアを０.１ｇ採取し、ブローオフ帯電量測定装置（東芝ケミカル社製TB-200型）で１分間窒素ブローした後の値を帯電量とした。
(ニ) 画像特性の評価方法：表面処理シリカ系微粒子をマゼンタトナー(粒子径6μm)に１重量％添加し、市販の複写機を用い５００００枚以上印刷したところで、画像特性（トナーフィルミング、かぶりの発生の有無）、クリーニング性を観察した。
【００２２】
〔実施例１〕
気相法によって製造されたBET比表面積５０m2/gのシリカ微粉末１００gを反応槽に入れ、窒素雰囲気下、撹拌しながら、水１.５ｇを噴霧した。これにジメチルジメトキシシラン１０ｇ、ジエチルアミン１.０ｇを噴霧し、１５０℃で１時間加熱撹拌し、その後冷却した。得られた表面改質シリカ微粉末の評価結果を表１に示す。
【００２３】
〔実施例２〕
気相法によって製造されたBET比表面積９０m2/gのシリカ微粉末１００gを反応槽に入れ、窒素雰囲気下、撹拌しながら水２.０ｇを噴霧した。これにイソブチルトリメトキシシラン２０ｇ、ジエチルアミン１.０ｇを噴霧した後に１５０℃で１時間加熱撹拌し、その後冷却した。得られた表面改質シリカ微粉末の評価結果を表１に示す。
【００２４】
〔参考例３〕
気相法によって製造されたＢＥＴ比表面積３０ｍ2/ｇのシリカ微粉末１００ｇを反応槽に入れ、窒素雰囲気下、撹拌しながら水０.５ｇを噴霧した。これにメチルトリメトキシシラン１０ｇ、ジエチルアミン１.０ｇを噴霧し、１５０℃で１時間加熱撹拌し、その後冷却した。得られた表面改質シリカ微粉末の評価結果を表１に示す。
【００２５】
〔実施例４〕
気相法によって製造されたBET比表面積５０m2/gのシリカ微粉末１００gを反応槽に入れ、窒素雰囲気下、撹拌しながら水２.５ｇを噴霧した。これにヘキシルトリメトキシシラン１０ｇ、ジエチルアミン１.０ｇを噴霧し、１５０℃で１時間加熱撹拌し、その後冷却した。得られた表面改質シリカ微粉末の評価結果を表１に示す。
【００２６】
〔実施例５〕
気相法によって製造されたＢＥＴ比表面積９０ｍ2/ｇのシリカ微粉末１００ｇを反応槽に入れ、窒素雰囲気下、撹拌しながら水２.０ｇを噴霧した。これにイソブチルトリエトキシシラン２０ｇ、ジエチルアミン１.０ｇを噴霧し、１５０℃で１時間加熱撹拌し、その後冷却した。得られた表面改質シリカ微粉末の評価結果を表１に示す。
【００２７】
〔比較例１〕
気相法によって製造されたBET比表面積１３０m2/gのシリカ微粉末１００gを反応槽に入れ、窒素雰囲気下、撹拌しながらジメチルジクロロシラン１０ｇを噴霧し、１５０℃で１時間加熱撹拌し、その後冷却した。得られた表面改質シリカ微粉末の評価結果を表１に示す。
【００２８】
〔比較例２〕
気相法によって製造されたBET比表面積５０m2/gのシリカ微粉末１００gを反応槽に入れ、窒素雰囲気下、撹拌しながら水２.０ｇを噴霧した。これにヘキサメチルジシラザン１０ｇを噴霧し、１５０℃で１時間加熱撹拌し、その後冷却した。得られた表面改質シリカ微粉末の評価結果を表１に示す。
【００２９】
〔比較例３〕
気相法によって製造されたBET比表面積５０m2/gのシリカ微粉末１００gを反応槽に入れ、窒素雰囲気下、撹拌しながら水２.０ｇを噴霧した。これにオクチルトリメトキシシラン１０ｇ、ジエチルアミン１.０ｇを噴霧し、１５０℃で１時間加熱撹拌し、その後冷却した。得られた表面改質シリカ微粉末の評価結果を表１に示す。
【００３０】
〔比較例４〕
気相法によって製造されたBET比表面積５０m2/gのシリカ微粉末１００gを反応槽に入れ、窒素雰囲気下、撹拌しながら水２.０ｇを噴霧した。これにデシルトリメトキシシラン１０ｇ、ジエチルアミン１.０ｇを噴霧し、１５０℃で１時間加熱撹拌し、その後冷却した。得られた表面改質シリカ微粉末の評価結果を表１に示す。
【００３１】
〔比較例５〕
気相法によって製造されたBET比表面積１５０m2/gのシリカ微粉末１００gを反応槽に入れ、窒素雰囲気下、撹拌しながら、水１.５ｇを噴霧した。これにジメチルジメトキシシラン１０ｇ、ジエチルアミン１.０ｇを噴霧し、１５０℃で１時間加熱撹拌し、その後冷却した。得られた表面改質シリカ微粉末の評価結果を表１に示す。
【００３２】
〔比較例６〕
気相法によって製造されたBET比表面積５０m2/gのシリカ微粉末１００gを反応槽に入れ、窒素雰囲気下、撹拌しながらジメチルジメトキシシラン１０ｇ、ジエチルアミン１.０ｇを噴霧し、１５０℃で１時間加熱撹拌し、その後冷却した。得られた表面改質シリカ微粉末の評価結果を表１に示す。
【００３３】
〔比較例７〕
気相法によって製造されたBET比表面積５０m2/gのシリカ微粉末１００gを反応槽に入れ、窒素雰囲気下、撹拌しながら、水１０ｇを噴霧した。これにジメチルジメトキシシラン１０ｇ、ジエチルアミン１.０ｇを噴霧し、１５０℃で１時間加熱撹拌し、その後冷却した。得られた表面改質シリカ微粉末の評価結果を表１に示す。
【００３４】
〔比較例８〕
気相法によって製造されたBET比表面積５０m2/gのシリカ微粉末１００gを反応槽に入れ、窒素雰囲気下、撹拌しながら、水１.５ｇを噴霧した。これにジメチルジメトキシシラン１０ｇ、ジエチルアミン１.０ｇを噴霧し、１５０℃で３時間加熱撹拌し、その後冷却した。得られた表面改質シリカ微粉末の評価結果を表１に示す。
【００３５】
【発明の効果】
本発明の表面改質シリカ微粉末はトナー外添剤として用いたときに、その流動性および耐久性が顕著に向上し、さらにフィルミングやかぶり、クリーニング性に優れた表面改質シリカ微粉末である。
【００３６】
【表１】
BACKGROUND OF THE INVENTION
The present invention relates to a surface-modified silica fine powder having excellent temporal stability, which is added for the purpose of improving the fluidity of the powder, preventing caking, and adjusting the charge in electrophotographic toners and powder coatings. The present invention relates to a toner composition containing the silica powder.
[0002]
[Prior art]
In electrophotographic toners, powder coatings, and the like, a small amount of hydrophobic inorganic oxide fine powder is generally added in order to improve the fluidity. Usually, the silica fine powder used as the additive is one synthesized by a gas phase method or a liquid phase method and having a surface hydrophobized with alkylsilane or organopolysiloxane. For example, a silica fine powder surface-treated with an alkyl halogenated silane (described in JP-A No. 61-188547), or a silica, titania, alumina surface-treated with an organopolysiloxane (described in JP-A No. 11-124464) In addition, a surface-treated silica fine powder with hexamethyldisilazane (described in JP-A-2001-356516) is known.
[0003]
In this way, in electrophotography such as copying machines, laser printers, plain paper facsimiles, etc., fine silica, fine powders of inorganic oxides such as titania and alumina that have been surface-treated with organic matter are added to the toner to improve their fluidity. Widely used as an agent.
[0004]
[Problems to be solved by the invention]
In recent years, as the particle size of the toner is reduced from 10 μm to 5 μm, there is a problem that the fluidity of the toner is lowered, and in order to improve this, the additive amount of the toner external additive has increased from the conventional level. The external additive is required to have higher fluidity than before. For example, when a conventional external additive using fine silica powder is used for a toner having a small particle diameter, there is a problem that the durability of the toner composition is lowered. On the other hand, if the surface treatment agent is changed to improve the durability, the fluidity of the toner will be improved, but there will be problems such as toner filming and fogging on the surface of the photoreceptor. There is.
[0005]
The present invention solves the above-mentioned problems with conventional surface-treated silica fine powder, and provides a surface-treated silica fine powder having excellent temporal stability in terms of triboelectric charge amount and toner durability.
[0006]
According to the present invention, a surface-treated silica fine powder having the following constitution and a toner composition thereof are provided.
[1] A silica fine powder obtained by surface-treating a silica fine powder having a BET specific surface area of 50 to 90 m 2 / g in the presence of an amine catalyst using an alkylalkoxysilane having a hexyl group or less, and an angle of repose of 20 to 42 And the BET specific surface area of 33 to 90 m 2 / g, and the change rate of the triboelectric charge amount (B) after 30 minutes with respect to the initial triboelectric charge amount (A) after 5 minutes of dispersion in the toner (A / B ) Is 1.0 to 2.0, surface-modified silica fine powder.
[2] The ratio (A / B) of the initial triboelectric charge amount (A) after 5 minutes after being dispersed in the toner and the triboelectric charge amount (B) with time after 30 minutes is 1.0 to 1.7. The surface-modified silica fine powder described in [1] above.
[3] A silica fine powder obtained by surface-treating a silica fine powder having a BET specific surface area of 50 to 90 m 2 / g with an alkylalkoxysilane, using an alkylalkoxysilane having a hexyl group or less, and in the presence of an amine catalyst, Adjust the amount of alkylalkoxysilane, the amount of moisture, the reaction temperature and the time with respect to the silica fine powder so that the rate of change with time (A / B) of the triboelectric charge after the surface treatment is 1.0 to 2.0. The surface-modified silica fine powder according to [1], which has been surface-treated.
[4] A toner composition obtained by mixing the surface-modified silica fine powder described in [1], [2] or [3] above with a toner material, wherein the initial average aggregate particle diameter ( A toner composition having a change rate (X / Y) of an average agglomerated particle diameter (Y) after 90 minutes with respect to X) of 2.0 or less.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail together with examples and comparative examples.
The surface-modified silica fine powder of the present invention is a silica fine powder obtained by subjecting a silica fine powder having a BET specific surface area of 50 to 90 m 2 / g to a surface treatment in the presence of an amine catalyst using an alkylalkoxysilane having a hexyl group or less. The angle of repose is 20 to 42 degrees and the BET specific surface area is 33 to 90 m 2 / g. The triboelectric charge amount with time after 30 minutes with respect to the initial triboelectric charge amount (A) after 5 minutes after being dispersed in the toner ( The change rate (A / B) of B) is 1.0 to 2.0. Here, the initial triboelectric charge amount (A) is the triboelectric charge amount held when the surface-treated silica fine powder is dispersed in the toner and shaken for a predetermined time to give the triboelectric charge. B) is the amount of triboelectric charge held after shaking for a certain period of time. Specifically, for example, the surface-treated silica fine powder is mixed and dispersed in the toner and shaken, and the triboelectric charge after 5 minutes of shaking is (A), while the triboelectric charge after 30 minutes of shaking is ( B). The elapsed time of the initial triboelectric charge amount (A) and the time-dependent triboelectric charge amount (B) is not limited to this time. For example, the initial triboelectric charge amount (A) after 20 minutes after shaking may be used as the initial triboelectric charge amount (A), and the triboelectric charge amount over time (for example, 10 to 40 minutes) may be used as the triboelectric charge amount (B).
[0008]
The frictional charge having a small rate of change with time (A / B) is excellent in durability when added to the toner. The surface-modified silica fine powder of the present invention has a rate of change (A / B) in the triboelectric charge amount (B) after 30 minutes with respect to the initial triboelectric charge amount (A) of 1.0 to 2.0, Preferably, the ratio (A / B) of the initial triboelectric charge amount (A) after 5 minutes and the time-dependent triboelectric charge amount (B) after 30 minutes is 1.0 to 1.7. When the rate of change with time is within the above range, the toner composition is excellent in durability and a good image can be obtained. On the other hand, when the rate of change with time is smaller than 1.0, the triboelectric charge amount gradually increases, leading to poor dispersion, and when the rate of change with time is greater than 2.0, the amount of charge gradually decreases, causing aggregation and fogging. Tend to produce.
[0009]
Further, the surface-modified silica fine powder of the present invention preferably has an angle of repose of 20 to 42 degrees and a BET specific surface area of 33 to 90 m 2 / g. If the specific surface area is less than 33 m 2 / g, the angle of repose exceeds 42 degrees and the fluidity tends to be greatly reduced, and when it is added to the toner, it is easily separated from the toner. Cause ming. On the other hand, if the specific surface area is greater than 90 m 2 / g, the durability is significantly reduced. On the other hand, if the angle of repose is smaller than 20 degrees, the fluidity becomes excessive and the handling becomes difficult.
[0010]
For a toner composition in which the above surface-modified silica fine powder of the present invention is mixed and dispersed in a toner material, for example, a toner and a carrier, the rate of change of the average average aggregate particle diameter (Y) with respect to the initial average aggregate particle diameter (X) (X / A toner composition having a small Y) can be obtained. Here, the initial average aggregated particle size (X) is the initial average aggregated particle size of the toner composition, and the time-averaged average aggregated particle size (Y) is the average aggregated particle size after a predetermined time. Specifically, for example, when the average aggregate particle diameter after 5 minutes from the preparation of the toner composition is (X) and the average aggregate particle diameter after 90 minutes is (Y), the average aggregate particle diameter over time A toner composition having a change rate (X / Y) of 2.0 or less can be obtained.
[0011]
A toner composition having an average aggregate particle size change rate with time (X / Y) of 2.0 or less is excellent in durability. When the rate of change with time (X / Y) is greater than 2.0, the aggregated particle size is halved, causing a problem in toner fluidity after long-time operation, and lowering the durability of the toner.
[0012]
The surface-modified silica fine powder of the present invention uses an alkylalkoxysilane having a hexyl group or less, and in the presence of an amine catalyst, the amount of alkylalkoxysilane, the amount of water, the reaction temperature and the time with respect to the silica fine powder are subjected to surface treatment. The rate of change with time (A / B) of the subsequent triboelectric charge is 1.0 to 2.0, preferably the initial triboelectric charge (A) after 5 minutes and the triboelectric charge with time (B) after 30 minutes. The ratio (A / B) can be adjusted to 1.0 to 1.7 and surface treatment can be performed.
[0013]
As the raw material silica fine powder , a BET specific surface area of 50 to 90 m 2 / g may be used as shown in Examples 1 and 2 and Examples 4 to 5 . The fine particle structure of the silica fine powder is flattened slightly by the surface treatment, and as shown in Table 1, a surface-treated powder having a BET specific surface area of 33 to 64 m 2 / g can be obtained. The silica fine powder is preferably synthesized by a gas phase method.
[0014]
Alkylalkoxysilane is monomethyltrimethoxysilane, dimethyldimethoxysilane, trimethylmethoxysilane, monoethyltrimethoxysilane, diethyldimethoxysilane, triethylmethoxysilane, propyltrimethoxysilane, isopropyltrimethoxysilane, butyltrimethoxysilane, isobutyltrimethoxysilane Is preferred. If the alkyl group is greater than or equal to the hexyl group, there will be a problem with fluidity. Further, if there is no alkoxy group, it is impossible to obtain a material that satisfies all of fluidity, durability, toner filming, fogging, and cleaning properties.
[0015]
The amount of alkylalkoxysilane with respect to 100 parts by weight of silica fine powder is generally 5 to 30 parts by weight. If it is less than this, sufficient durability cannot be obtained. If it is more than this, the excess treating agent will be dispersed non-uniformly and cause agglomerates.
[0016]
Silica fine powder is preferably conditioned. The humidity control method and the level of humidity control are not particularly limited, but the rate of change with time (A / B) of the triboelectric charge amount varies depending on the amount of water, so the rate of change with time is 1.0 to 2.0, preferably 1. Adjust so that it is in the range of 0-1.7. Specifically, the amount of water that promotes hydrolysis of the alkoxy group is basically required, and in order to increase the number of alkoxy groups adhering to the surface of the silica fine particles, a smaller amount of water is preferable, while the number of alkoxy groups is reduced. It is better to have more water. In general, a water content of about 0.5 to 3.0 times the equivalent of an alkoxy group is a standard. Moreover, the humidity control method is not particularly limited, and a product that has been naturally conditioned for a long time after production may be used, or a product that has been intentionally introduced or sprayed may be used. The degree of humidity control can be examined using loss on drying or the Karl Fischer method.
[0017]
The surface treatment is preferably performed in an inert gas atmosphere. For example, after substituting the inside of the system with nitrogen gas or the like, alkylalkoxysilane is sprayed on silica fine powder. After spraying, after sufficient aging, it is heated above the boiling point of the alkylalkoxysilane and held for a certain period of time. Thereafter, unreacted substances and by-products are removed and cooled. The remaining amount (deposition amount) of the alkoxy group can be detected by the amount of alcohol generated by the surface treatment. For alcohol detection, an alcohol concentration meter may be introduced into the recovery gas line. Alternatively, for example, the residual amount of alkoxy groups may be directly measured by placing fine powder of surface-modified silica in a vial and quantitatively using a Head-Space gas chromatograph. Since the remaining amount (adhesion amount) of alkoxy groups affects the rate of change with time (A / B) of the triboelectric charge amount, the rate of change with time is adjusted to be in the above range.
[0018]
In general, the reaction temperature is suitably 120 to 170 ° C., and the reaction time is suitably 40 to 120 minutes. The reaction temperature and reaction time may be adjusted so that the rate of change with time is in the above range.
[0019]
The toner is not limited to a two-component system using a carrier, and may be a one-component system using a toner alone. The toner may be color or monochrome. The toner may have an average particle diameter of about 10 μm, and the effect is recognized. However, the effect is particularly remarkable when the average particle diameter is about 8 μm or less. The carrier is not particularly limited and a general carrier may be used. For example, a ferrite carrier or an iron powder carrier is used, and these may or may not be coated with silicone, fluorine resin, or the like.
[0020]
【The invention's effect】
The surface-modified silica fine powder of the present invention satisfies high durability, high fluidity, and stable chargeability at the same time, and therefore improves the fluidity of these powders when used in electrophotographic toners, powder coatings, etc. Thus, caking can be prevented, and further, toner filming, fogging and excellent cleaning properties can be obtained.
[0021]
Examples and Comparative Examples
Hereinafter, the present invention will be specifically described by Examples and Comparative Examples. The silica fine powder to be surface-treated is a fine powder produced by flame hydrolysis of a silicon halide compound, and is a so-called fumed powder having a specific surface area of 40 to 100 m 2 / g measured by a nitrogen adsorption method (BET method). Silica was used. Moreover, the angle of repose, the average aggregate particle diameter, and the charge amount were measured by the following methods.
(A) Measuring method of angle of repose: Using a commercially available measuring instrument (Powder Tester PT-N type manufactured by Hosokawa Micron Corporation), the angle of repose was measured according to a prescribed measuring method.
(B) Measuring method of average agglomerated particle size: The agglomerated particle size was measured by observing at a magnification of 50,000 times using a commercially available measuring instrument (JEOL JSM-5300LV).
(C) Method for measuring the amount of charge: Put 50 g of iron powder carrier and 0.1 g of silica fine powder in a glass container (75 mL), cover it, shake with a tumbler mixer for 5 minutes or 30 minutes, 0.1 g of an iron powder carrier mixed with powder was sampled, and the value after blowing nitrogen with a blow-off charge measuring device (TB-200 type manufactured by Toshiba Chemical Corporation) for 1 minute was taken as the charge amount.
(D) Image characteristic evaluation method: 1% by weight of surface-treated silica-based fine particles are added to magenta toner (particle diameter 6 μm), and image characteristics (toner filming, fogging) are printed on 50000 sheets or more using a commercially available copying machine. The presence or absence of occurrence) was observed for cleaning properties.
[0022]
[Example 1]
100 g of fine silica powder having a BET specific surface area of 50 m 2 / g produced by the vapor phase method was placed in a reaction vessel and sprayed with 1.5 g of water while stirring under a nitrogen atmosphere. To this, 10 g of dimethyldimethoxysilane and 1.0 g of diethylamine were sprayed, heated and stirred at 150 ° C. for 1 hour, and then cooled. The evaluation results of the obtained surface-modified silica fine powder are shown in Table 1.
[0023]
[Example 2]
100 g of fine silica powder having a BET specific surface area of 90 m 2 / g produced by the vapor phase method was placed in a reaction vessel and sprayed with 2.0 g of water with stirring in a nitrogen atmosphere. After spraying 20 g of isobutyltrimethoxysilane and 1.0 g of diethylamine, the mixture was heated and stirred at 150 ° C. for 1 hour, and then cooled. The evaluation results of the obtained surface-modified silica fine powder are shown in Table 1.
[0024]
[Reference Example 3]
100 g of fine silica powder having a BET specific surface area of 30 m 2 / g produced by the vapor phase method was put in a reaction vessel, and 0.5 g of water was sprayed with stirring in a nitrogen atmosphere. To this, 10 g of methyltrimethoxysilane and 1.0 g of diethylamine were sprayed, heated and stirred at 150 ° C. for 1 hour, and then cooled. The evaluation results of the obtained surface-modified silica fine powder are shown in Table 1.
[0025]
Example 4
100 g of fine silica powder having a BET specific surface area of 50 m 2 / g produced by the vapor phase method was placed in a reaction vessel and sprayed with 2.5 g of water with stirring in a nitrogen atmosphere. This was sprayed with 10 g of hexyltrimethoxysilane and 1.0 g of diethylamine, heated and stirred at 150 ° C. for 1 hour, and then cooled. The evaluation results of the obtained surface-modified silica fine powder are shown in Table 1.
[0026]
Example 5
100 g of fine silica powder having a BET specific surface area of 90 m 2 / g produced by a gas phase method was put in a reaction vessel, and 2.0 g of water was sprayed with stirring in a nitrogen atmosphere. This was sprayed with 20 g of isobutyltriethoxysilane and 1.0 g of diethylamine, heated and stirred at 150 ° C. for 1 hour, and then cooled. The evaluation results of the obtained surface-modified silica fine powder are shown in Table 1.
[0027]
[Comparative Example 1]
100 g of silica fine powder having a BET specific surface area of 130 m 2 / g produced by the vapor phase method is put in a reaction vessel, sprayed with 10 g of dimethyldichlorosilane with stirring in a nitrogen atmosphere, heated and stirred at 150 ° C. for 1 hour, and then Cooled down. The evaluation results of the obtained surface-modified silica fine powder are shown in Table 1.
[0028]
[Comparative Example 2]
100 g of silica fine powder having a BET specific surface area of 50 m 2 / g produced by the vapor phase method was put into a reaction vessel, and 2.0 g of water was sprayed with stirring in a nitrogen atmosphere. This was sprayed with 10 g of hexamethyldisilazane, heated and stirred at 150 ° C. for 1 hour, and then cooled. The evaluation results of the obtained surface-modified silica fine powder are shown in Table 1.
[0029]
[Comparative Example 3]
100 g of silica fine powder having a BET specific surface area of 50 m 2 / g produced by the vapor phase method was put into a reaction vessel, and 2.0 g of water was sprayed with stirring in a nitrogen atmosphere. This was sprayed with 10 g of octyltrimethoxysilane and 1.0 g of diethylamine, heated and stirred at 150 ° C. for 1 hour, and then cooled. The evaluation results of the obtained surface-modified silica fine powder are shown in Table 1.
[0030]
[Comparative Example 4]
100 g of silica fine powder having a BET specific surface area of 50 m 2 / g produced by the vapor phase method was put in a reaction vessel, and 2.0 g of water was sprayed with stirring in a nitrogen atmosphere. This was sprayed with 10 g of decyltrimethoxysilane and 1.0 g of diethylamine, heated and stirred at 150 ° C. for 1 hour, and then cooled. The evaluation results of the obtained surface-modified silica fine powder are shown in Table 1.
[0031]
[Comparative Example 5]
100 g of fine silica powder having a BET specific surface area of 150 m 2 / g produced by the vapor phase method was placed in a reaction vessel and sprayed with 1.5 g of water while stirring in a nitrogen atmosphere. To this, 10 g of dimethyldimethoxysilane and 1.0 g of diethylamine were sprayed, heated and stirred at 150 ° C. for 1 hour, and then cooled. The evaluation results of the obtained surface-modified silica fine powder are shown in Table 1.
[0032]
[Comparative Example 6]
100 g of silica fine powder with a BET specific surface area of 50 m 2 / g produced by the vapor phase method is put in a reaction vessel, and 10 g of dimethyldimethoxysilane and 1.0 g of diethylamine are sprayed with stirring in a nitrogen atmosphere at 150 ° C. for 1 hour. The mixture was heated and stirred, and then cooled. The evaluation results of the obtained surface-modified silica fine powder are shown in Table 1.
[0033]
[Comparative Example 7]
100 g of silica fine powder having a BET specific surface area of 50 m 2 / g produced by the vapor phase method was placed in a reaction vessel, and 10 g of water was sprayed with stirring in a nitrogen atmosphere. To this, 10 g of dimethyldimethoxysilane and 1.0 g of diethylamine were sprayed, heated and stirred at 150 ° C. for 1 hour, and then cooled. The evaluation results of the obtained surface-modified silica fine powder are shown in Table 1.
[0034]
[Comparative Example 8]
100 g of fine silica powder having a BET specific surface area of 50 m 2 / g produced by the vapor phase method was placed in a reaction vessel and sprayed with 1.5 g of water while stirring under a nitrogen atmosphere. To this, 10 g of dimethyldimethoxysilane and 1.0 g of diethylamine were sprayed, heated and stirred at 150 ° C. for 3 hours, and then cooled. The evaluation results of the obtained surface-modified silica fine powder are shown in Table 1.
[0035]
【The invention's effect】
When the surface modified silica fine powder of the present invention is used as a toner external additive, the fluidity and durability are remarkably improved, and the surface modified silica fine powder is excellent in filming, fogging and cleaning properties. is there.
[0036]
[Table 1]
Claims (4)
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| US9098001B2 (en) | 2009-07-14 | 2015-08-04 | Nippon Aerosil Co., Ltd. | Surface-modified metal oxide powder and process for producing same |
| JP5675507B2 (en) * | 2011-06-14 | 2015-02-25 | 旭化成ケミカルズ株式会社 | Powder, molded body, enveloping body, and method for producing powder |
| JP2014196215A (en) * | 2013-03-29 | 2014-10-16 | 日揮触媒化成株式会社 | Modified metal oxide particulate powder and method for producing the same |
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