JP4256134B2 - Method for producing iron-containing acicular titanium dioxide fine particles - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明は鉄化合物を含有する針状二酸化チタン微粒子及びその製造方法に関し、特に、透明性の紫外線遮蔽剤として有用な鉄含有針状二酸化チタン微粒子及びそれを製造する方法に関する。また、その鉄含有針状二酸化チタン微粒子を配合した日焼け止め化粧料、紫外線遮蔽用塗料に関する。
【０００２】
【従来の技術】
針状二酸化チタン微粒子は、平均長軸径が平均短軸径より大きいものであり、一般的に紡錘状、棒状などとも呼ばれているものである。このような針状二酸化チタン微粒子は、球状などの非針状形状を有する通常の二酸化チタン微粒子と同じ用途に用いられる以外に、その粒子形状特性を利用して、紫外線遮蔽剤、充填剤、添加剤、磁気記録媒体の下層材、触媒担体や、導電性材料、抗菌性材料などの機能性材料を表面に付着する基体粒子などとしても有用である。特に、針状二酸化チタン微粒子は透明性が高く、紫外線遮蔽能が非常に優れており、紫外線遮蔽剤として日焼け止め化粧料等への利用が進んでいる。
【０００３】
紫外線はその波長の長い順にＡ、Ｂ、Ｃの３領域に大別され、波長が２００〜２９０ｎｍのＣ領域の紫外線はオゾン層に遮蔽されるので、一般に日焼けや炎症等の皮膚への障害を引き起こすのは、波長が３２０〜３８０ｎｍのＡ領域と２９０〜３２０ｎｍのＢ領域であると言われている。Ｂ領域の紫外線（ＵＶＢ）は皮膚への影響が最も大きいと言われており、一方、Ａ領域の紫外線（ＵＶＡ）は、Ｂ領域の紫外線（ＵＶＢ）と比較して皮膚への影響は穏やかであるが、太陽光中に多量に含まれており、透過性が高く皮膚の深部で障害を引き起こし易く、近年はＵＶＡの遮蔽能も重視されるようになってきた。
【０００４】
針状酸化チタン微粒子の製造方法としては、特開平５−１８６２２１号公報、特公平６−１０２５４５号公報等に、含水二酸化チタンを水酸化ナトリウムで処理した後、加熱・塩酸処理する方法が開示されている。しかし、この方法では透明性、ＵＶＢ遮蔽能、ＵＶＡ遮蔽能のいずれの特性も十分に満足する針状二酸化チタン微粒子は得られなかった。更に、このものは微粒子の白色粉末であるが故に、短波長の可視光を強く散乱させ青味の色調を呈し、このためこれを用いた日焼け止め化粧料は透明感を有するものの、皮膚本来の自然な色調を損うという問題もあった。
【０００５】
【発明が解決しようとする課題】
本発明は以上に述べた従来技術の問題点を解決し、透明性、ＵＶＢ遮蔽能、ＵＶＡ遮蔽能のいずれもが高い針状二酸化チタン微粒子及びその製造方法を提供するものである。更に、本発明は、高い透明性、ＵＶＢ遮蔽能、ＵＶＡ遮蔽能を有する日焼け止め化粧料、紫外線遮蔽用塗料を提供するものである。
【０００６】
【課題を解決するための手段】
本発明者は鋭意研究を重ねた結果、（１）結晶子径が十分に小さい、即ち非常に微細で、長軸径がある程度大きい針状二酸化チタン微粒子は、透明性、ＵＶＢ遮蔽能、ＵＶＡ遮蔽能のいずれの特性にも優れていること、（２）このものに鉄化合物を含有させれば、微細な粒子であっても青味を呈さないばかりでなく、ＵＶＡ遮蔽能が更に向上すること、（３）含水酸化チタンと塩基性ナトリウム化合物で処理した後、加熱・塩酸処理する針状酸化チタン微粒子の製造方法において、前記塩酸処理を塩化鉄の存在下で行えば、鉄化合物を含有させられると同時に、前記のような特定の大きさのものが得られることを見出し、本発明を完成した。
【０００７】
すなわち、本発明は、
（１）塩化鉄の存在下、含水酸化チタンと塩基性ナトリウム化合物との反応生成物を塩酸と反応させることを特徴とする鉄含有針状二酸化チタン微粒子の製造方法、である。
【０００８】
【発明の実施の形態】
二酸化チタン微粒子を構成する結晶子を小さく、即ち微細化すると、理論上透明性とＵＶＢ遮蔽能は向上するが、同時に表面エネルギーが大きくなり分散性が低下するので、実際に化粧料や塗料等に配合して用いると、高い透明性やＵＶＢ遮蔽能が得られなかった。また、微細化に伴い、ＵＶＡ遮蔽能は却って低下してしまった。しかし、二酸化チタン微粒子を構成する結晶子を十分に微細にし、しかも、その結晶子が集合して形成された二酸化チタン微粒子を針状形状にすることによって、表面エネルギーを低下させることができ、二酸化チタン微粒子が本来持っている透明性やＵＶＢ遮蔽能を引き出すことができると考えられる。しかも、針状形状とすることによって、大きい長軸径を確保でき、ＵＶＡ遮蔽能の低下を抑制することができる。また、鉄化合物を含有することにより粒子が淡い肌色〜茶色を呈しており、白色微粒子であることに起因する青味色調を抑制でき、同時にＵＶＡの可視光に近接した領域に吸収が生じるので、ＵＶＡ遮蔽能が更に向上する。すなわち、本発明の二酸化チタン微粒子は、鉄成分を鉄化合物として、粒子内部または粒子表面の少なくともどちらかに含有し、０．００５〜０．１５μｍの範囲の平均長軸径を有する針状二酸化チタン微粒子であり、その結晶子の平均径は４０〜１７５Åの範囲である。ここでは、平均長軸径が平均短軸径より大きい粒子を針状と言い、一般的に紡錘状、棒状などと呼ばれているものも包含する。
【０００９】
本発明における平均長軸径は電子顕微鏡法により求めた一次粒子の累積５０％粒子径で、平均結晶子径は二酸化チタンの（１１０）面のＸ線回折ピークより、後記のＳｃｈｅｒｒｅｒの公式（式１）を用いて算出したものである。平均長軸径が０．００５μｍより小さいと、所望のＵＶＡ遮蔽能や分散性が得られず、０．１５μｍより大きいと、平均結晶子径が前記範囲にあっても透明性やＵＶＢ遮蔽能が低下してしまう。また、平均結晶子径が１７５Åより大きいと、所望の透明性やＵＶＢ遮蔽能が得られず、４０Åより小さいと、平均長軸径が前記範囲にあっても、表面エネルギーが大きくなり過ぎ分散性が低くなる。平均長軸径の好ましい範囲は０．０１〜０．１５μｍであり、平均結晶子径の好ましい範囲は４０〜１５０Åであり、更に好ましい範囲は５０〜１３０Åである。
【００１０】
比表面積は表面被覆を行うと、被覆種や被覆量によって大きく異なってくるが、例えば後述の表面被覆を行っていない鉄含有針状二酸化チタン自体では、１５０〜２５０ｍ２／ｇの範囲にあるのが好ましい。本発明の鉄含有針状二酸化チタン微粒子は、本発明の目的を損なわない範囲で一部に非晶質のものを含んでいても良いが、実質的に結晶構造を有している。結晶構造には制限は無いが、特に後述の製造法で得られるものは、ルチル型を主体としている。
【００１１】
本発明では鉄化合物は、例えば酸化鉄や水和酸化鉄として針状二酸化チタン微粒子の表面に被覆されたり、粒子内部に取り込まれたり、酸化鉄として二酸化チタンの結晶中に固溶されたり、あるいはこれらが複合した状態等、二酸化チタンと強固に結合しており、単なる鉄化合物と針状二酸化チタン微粒子との混合物は含まない。鉄化合物の含有量は、Ｆｅ２Ｏ３換算でＴｉＯ２に対し０．１〜５０重量％の範囲が好ましく、０．１〜２０重量％の範囲がより好ましい。鉄化合物の含有量が前記の０．１〜５０重量％の範囲にあると、最も効果的に青味感を抑制し易いため好ましく、この範囲より少ないと所望する色調やＵＶＡ遮蔽能が得られ難く、この範囲より多くしても経済的に不利になり易いばかりでなく、粒子が著しく濃色に着色し易いので好ましくない。
【００１２】
本発明の鉄含有針状二酸化チタン微粒子には、無機化合物及び有機化合物から選ばれる少なくとも１種で粒子表面が被覆されていても良い。被覆量は目的に応じて適宜設定することができ、例えば鉄含有針状二酸化チタン微粒子のＴｉＯ２換算に対してそれぞれ０．１〜５０重量％の範囲の量を被覆するのが好ましく、０．１〜３０重量％の範囲がより好ましい。
【００１３】
分散性や耐候性等を向上させるためには、無機化合物を被覆するのが好ましく、アルミニウム、ケイ素、ジルコニウム、亜鉛、チタニウム、スズ、アンチモン等から選ばれる少なくとも１種の化合物、例えば、それらの元素の酸化物または含水酸化物を被覆するのがより好ましい。また、有機系バインダーとの親和性を高めたり、流動性を高めたりする等の目的で粒子の表面、または前記の無機化合物被覆を行った粒子の表面に、少なくとも１種の有機化合物により被覆しても良い。
【００１４】
有機化合物としては例えばステアリン酸、カルボン酸等の高級脂肪酸、ジメチルポリシロキサン、メチルハイドロジェンポリシロキサン等のシリコーン系化合物、トリメチロールエタン、トリメチロールプロパン等の多価アルコール類、トリエチルアミン等のアルカノールアミン類、シランカップリング剤、チタネートカップリング剤等のカップリング剤などが挙げられる。
【００１５】
次に、本発明は鉄含有針状二酸化チタン微粒子の製造方法であって、塩化鉄の存在下、含水酸化チタンと塩基性ナトリウム化合物との反応生成物を塩酸と反応させる方法である。
【００１６】
本方法における反応機構は必ずしも明確ではないが、含水酸化チタンと塩基性ナトリウムとの反応によりチタン酸ナトリウムが生成し、そして、チタン酸ナトリウムと塩酸との反応によりチタン酸ナトリウムからナトリウムが脱離すると考えられ、その過程で、針状二酸化チタン微粒子が、特にルチル型のものが生成すると推測される。塩化鉄には、針状二酸化チタン微粒子に含有する鉄化合物の原料になると同時に、その際に針状二酸化チタン微粒子の結晶子の成長を抑制する作用があるのではないかと考えられる。
【００１７】
本発明で用いる含水酸化チタンは四塩化チタン、硫酸チタニル等の加水分解等、公知の方法により得られたものを用いることができる。塩基性ナトリウム化合物としては水酸化ナトリウム、炭酸ナトリウム、シュウ酸ナトリウム等を用いることができる。
【００１８】
含水酸化チタンと塩基性ナトリウム化合物との反応は、含水酸化チタンと塩基性ナトリウム化合物とを混合することにより行われる。含水酸化チタンを予め有機溶媒等の分散媒に、好ましくは水に分散させた懸濁液に、塩基性ナトリウム化合物またはその溶液を添加するか、あるいは、塩基性ナトリウム化合物の溶液に、含水酸化チタンまたはその分散液を添加すると、均一に反応し易いので好ましい。この反応は、好ましくは８０〜１００℃の範囲で、更に好ましくは９０〜１００℃の範囲で行う。反応温度が８０〜１００℃の範囲であれば、含水酸化チタンと塩基性ナトリウム化合物との反応が短時間で進行しやすく、オートクレーブ等の耐圧反応器を必要としないため、工業的に有利である。含水酸化チタン中に含まれるチタン分のＴｉＯ２換算量１モルに対し、１モル以上の塩基性ナトリウム化合物と反応させると、微細な結晶子を有する反応生成物が得られ易く、好ましくは５モル以上、更に好ましくは５〜８モルで反応させる。反応生成物が得られた後、連続的に塩酸と反応する工程に供しても良いが、反応生成物を一旦濾過・洗浄してから、前記工程に供すると、粒子径や粒子形状の均一な鉄含有針状二酸化チタン微粒子が得られ易いので好ましい。
【００１９】
次いで、塩化鉄の存在下、反応生成物を塩酸と反応させるには、反応生成物を予め有機溶媒等の分散媒に、好ましくは水に分散させた懸濁液に、塩化鉄を添加した後塩酸を添加するか、両者を同時に添加するか、あるいは、両者を混合して添加すると、均一に反応し易いので好ましい。反応温度は６０〜１００℃の範囲が好ましく、８５〜１００℃の範囲が更に好ましい。温度が６０〜１００℃の範囲であれば、微細な結晶子を有する針状二酸化チタン微粒子が得られ易く、また、オートクレーブ等の耐圧反応器を必要としないため、工業的に有利である。反応温度の調整は塩化鉄及び塩酸を添加する前に行っても、添加した後に行っても、添加しながら行っても良い。
【００２０】
塩化鉄は、反応生成物に含まれるチタンのＴｉＯ２換算量に対し、Ｆｅ２Ｏ３換算で０．１〜５０重量％に相当する量を用いるのが好ましく、０．１〜２０重量％に相当する量を用いるのがより好ましい。用いる塩化鉄の量が０．１重量％より少ないと、粒子が十分に着色し難いだけでなく、前記の平均長軸径０．００５〜０．１５μｍの範囲で、平均結晶子径が４０〜１７５Åの範囲のものが得られ難く、５０重量％より多くしてもそれに伴う顕著な効果は認められ難い。
【００２１】
塩化鉄としては三塩化鉄、二塩化鉄等を用いることができるが、特に三塩化鉄が効果が高く好ましい。用いた塩化鉄は、得られた針状二酸化チタン微粒子を濾過・洗浄、乾燥する過程で、最終的に酸化鉄、水酸化鉄または含水酸化鉄として、おそらくは一部が粒子の内部で、且つ結晶格子の外部に存在し、一部が粒子の表面に被覆層として被着されるものと推測される。
【００２２】
用いる塩酸の量は、反応生成物中に含まれるチタン分のＴｉＯ２換算量で１モルに対し、０．１〜２モルの範囲にするのが好ましく、０．４〜１．５モルの範囲が更に好ましい。反応時のｐＨが３以下であると、非針状粒子が生成し難いので好ましく、１以下が更に好ましい。ｐＨが２〜３になるまで塩酸を添加した後、更に塩酸を添加すると、粒度分布や粒子形状の整ったものが、より得られ易くなるので好ましい。本発明では塩化鉄も酸性化合物であるので、塩化鉄及び塩酸を前記範囲で用いた場合、特にｐＨを調整する必要は無い。
【００２３】
なお、例えば、前記範囲の平均長軸径と平均結晶子径とを有する針状二酸化チタン微粒子を予め生成することができれば、公知の方法により、酸化鉄等の鉄化合物を粒子表面に被着させることでも、目的のものが得られる。しかし、この方法では被着工程で粒子が凝集して分散性が低下するので、以上に述べた方法を用いるのが好ましい。
【００２４】
前記のように鉄含有針状二酸化チタン微粒子を合成した後、必要に応じて公知の方法により無機化合物や有機化合物を被覆することができる。アルミニウム、ケイ素、ジルコニウム、亜鉛、チタニウム、スズ、アンチモン等の酸化物または含水酸化物などの無機化合物を表面に被覆する場合は、例えば得られた鉄含有針状二酸化チタン微粒子の水性懸濁液中に、これらの成分を含む水溶性化合物を所定量添加し、塩基性あるいは酸性化合物を用いて中和する。
【００２５】
有機化合物の被覆を行う場合は、例えば粉砕工程で粉砕機中に有機物を添加し、粉砕させながら被覆処理したり、あるいは乾燥後または粉砕後に高速ミキサー等を用いて有機化合物と混合しながら被覆処理する等、いわゆる乾式処理により行うことができる。また被覆する有機化合物が、水性懸濁液中で二酸化チタンと強固に結合するものであれば、湿式処理を用いることができる。そのような有機化合物としてステアリン酸ソーダ等の高級脂肪酸塩や、シランカップリング剤の加水分解物等が挙げられ、鉄含有針状二酸化チタン微粒子の懸濁液にこれらを添加、中和して、被覆させることができる。
【００２６】
以上の方法により得られた鉄含有針状二酸化チタン微粒子あるいは被覆処理した針状二酸化チタン微粒子は、通常行われる手法で濾別、洗浄、乾燥しても良く、必要に応じて、得られた乾燥物をジェットミル等の流体エネルギーミルや、ハンマーミル等の衝撃粉砕機等の粉砕機で粉砕しても良い。また乾燥後、加熱焼成すれば、鉄成分を針状二酸化チタン微粒子の結晶構造中に固溶させることもできる。
【００２７】
本発明の日焼け止め化粧料は、以上に述べた鉄含有針状二酸化チタン微粒子を配合したもので、その他に通常化粧料に用いられるバインダー、溶剤、着色剤、界面活性剤、香料、保湿剤等の添加剤を含んでいても良い。この日焼け止め化粧料は透明性が高く、ＵＶＢ、ＵＶＡのいずれに対しても高い遮蔽能を有するので、従来の球状や針状の二酸化チタン微粒子を紫外線遮蔽剤として用いたものと比較して、皮膚を紫外線から保護する効果が優れている。また、このものは透明感のある淡い肌色〜茶色を呈しており、皮膚本来の自然な色調を損なわないという機能も有する。
【００２８】
更に、本発明は以上に述べた鉄含有針状二酸化チタン微粒子を配合した紫外線遮蔽塗料である。この塗料は例えばアクリル、アルキド、メラミン、ポリエステル、ウレタン等の樹脂に、本発明の鉄含有針状二酸化チタン微粒子をディスパー、サンドミルを用いる等の公知の方法で分散したもので、分散剤、レベリング剤、硬化剤等の添加剤を適宜配合できる。本発明の塗料は表面コート剤として用いるもので、これらをプラスチックス、紙等の有機系基材の表面に塗布して塗膜化すると、紫外線劣化を効果的に防ぐことができる。特に基剤が木材のように茶系の色を呈するものに適しており、本発明の透明感のある肌色〜茶色の色調により、基材本来の外観が損なわれない。
【００２９】
本発明の鉄含有針状二酸化チタン微粒子は、前記の日焼け止め化粧料や紫外線遮蔽塗料以外にも様々な用途に用いることができる。例えば、透明なプラスチックス・フィルムに配合し、基材に貼付すれば、紫外線遮蔽塗料と同様の効果が得られる。プラスチックス、圧縮ボード、紙等の基材を成形する際に、紫外線遮蔽フィラーとして直接配合しても良い。更には、トナー、シリコーンゴム等の添加剤、磁気記録材料の下層材、触媒担体、導電材料の基体粒子などとして用いることができる。
【００３０】
【実施例】
以下に実施例を挙げて本発明を更に詳細に説明するが、これらは本発明を限定するものではない。
【００３１】
実施例１
１．反応生成物の合成
ＴｉＯ２として１００ｇ／リットルの含水酸化チタンの水性懸濁液２０００ミリリットルに、４８％水酸化ナトリウム水溶液１４００ｇを撹拌しながら添加し、９５℃で１２０分間加熱処理した後、濾過・洗浄し、反応生成物の洗浄ケーキを得た。含水酸化チタンに含まれるチタン分のＴｉＯ２換算量１モルに対し、６．７２モルの塩基性ナトリウム化合物を用いた。
【００３２】
２．鉄含有針状二酸化チタン微粒子の合成
洗浄ケーキを水に再分散させ、反応生成物をＴｉＯ２として７０ｇ／リットルの水性懸濁液とした。この懸濁液１４００ミリリットルに、反応生成物中のＴｉＯ２に対し、Ｆｅ２Ｏ３として５重量％に相当する三塩化鉄の水溶液と、３５％塩酸４０ミリリットルとを同時に２０分で添加し撹拌したところ、懸濁液のｐＨは３であった。引き続き、懸濁液を６０℃に昇温して３０分間撹拌し、更に３５％塩酸６１ミリリットルを添加したところ、ｐＨは１以下になった。塩酸の合計使用量は、反応生成物中に含まれるチタンのＴｉＯ２換算で１モルに対し、０．８モルであった。その後、温度を９５℃に保ちながら６０分間熟成し、ルチル型の鉄含有針状二酸化チタン微粒子のスラリーを得た。スラリーを一部分取し、洗浄、濾別、乾燥後、サンプルミルで粉砕して、本発明の鉄含有針状二酸化チタン微粒子（試料ａ）を得た。
【００３３】
３．表面被覆処理
前記のスラリーを８０℃に加温して、２００ｇ／リットルの水酸化ナトリウム水溶液でｐＨが８になるように中和した。次に、Ａｌ２Ｏ３として３００ｇ／リットルのアルミン酸ナトリウムを５３．３ミリリットルと２０％硫酸とを、スラリーのｐＨが８〜９に保持しながら同時に２０分間で添加し、１０分間撹拌した後、２０％硫酸でｐＨを５．５になるように３０分間かけて中和した。次いで、ステアリン酸ナトリウムをＴｉＯ２に対して２０重量％添加し、３０分間撹拌した後、２０％硫酸でｐＨが６になるように４０分間かけて中和し、６０分間熟成した。その後、洗浄、濾別、乾燥し、ハンマーミルを用いて粉砕して、ＴｉＯ２に対してアルミニウム含水酸化物１０重量％とステアリン酸１５重量％とで被覆された本発明の鉄含有針状二酸化チタン微粒子（試料Ａ）を得た。
【００３４】
比較例１
三塩化鉄を用いなかったこと以外は、実施例１と同様にしてルチル型針状二酸化チタン微粒子（試料ｂ）、及び、そのアルミニウム含水酸化物とステアリン酸との表面処理品（試料Ｂ）を得た。
【００３５】
評価１
実施例１及び比較例１で得られた鉄含有針状二酸化チタン微粒子及び針状二酸化チタン微粒子（試料ａ、ｂ、Ａ、Ｂ）の長軸及び短軸の平均一次粒子径を、電子顕微鏡写真法により測定した。また、比表面積を、比表面積測定装置（島津製作所製、フローソーブII ２３００型）を用いてＢＥＴ法により測定した。
【００３６】
評価２
実施例１及び比較例１で得られた鉄含有針状二酸化チタン微粒子及び針状二酸化チタン微粒子（試料ａ、ｂ、Ａ、Ｂ）の平均結晶子径を（１１０）面のＸ線回折ピークから下式を用いて算出した。
式１：ＤＨＫＬ＝Ｋ＊λ／βｃｏｓθ
ＤＨＫＬ：平均結晶子径（Å）
λ ：Ｘ線の波長
β ：回折ピークの半価幅
θ ：Ｂｒａｇｇ'ｓ角
Ｋ ：定数
【００３７】
平均長軸径及び短軸径、平均結晶子径、比表面積の測定結果を表１に示す。この結果から、本発明の鉄含有針状二酸化チタン微粒子は、０．００５〜０．１５μｍの平均長軸径と４０〜１７５Åの平均結晶子径とを有することが分かった。また、電子顕微鏡観察の結果、凝集粒子がほとんど無いこと、Ｘ線回折の結果、実質的にルチル型結晶が得られることが分かった。
【００３８】
【表１】
評価３
実施例１及び比較例１で得られた鉄含有針状二酸化チタン微粒子及び針状二酸化チタン微粒子（試料Ａ、Ｂ）の粉体色を測定した。アルミリング（内径３３ｍｍΦ、外径３８ｍｍΦ、厚さ５ｍｍ）に試料２ｇを充填し、これをステンレス版に挟んだ後、プレス機にて１９．６ＭＰａの圧力で１０秒間プレスして成形した。この成形体の色調（ｂ）を色差計を用いて測定した。ｂ値が小さい程青白さが強くなる。
【００４０】
粉体色の測定結果を表２に示す。本発明の鉄含有針状二酸化チタン微粒子は、鉄化合物を含有していない二酸化チタン微粒子（比較例１の試料Ｂ）に比べて、青味感が無いことが分かる。
【００４１】
【表２】
評価４
実施例１及び比較例１で得られた鉄含有針状二酸化チタン微粒子及び針状二酸化チタン微粒子（試料Ａ、Ｂ）を以下に示す方法で、化粧料を想定したペーストとした。このペーストをドクターブレードを用いて透明なトリアセテート・フィルム上に、膜厚が約２５μｍになるように塗布した後、３０分間風乾した。この塗膜の波長が５５０ｎｍにおける光の透過率Ｔ５５０、３５０ｎｍにおける光（ＵＶＡ）の透過率Ｔ３５０及び３００ｎｍの光（ＵＶＢ）の透過率Ｔ３００を、積分球を装着した分光光度計（島津製作所製、ＵＶ−ＶＩＳ ＵＶ−２２００Ａ型）を用いて測定し、下式に従ってＡ３５０／Ａ５５０を算出した。また、それと同じように、Ａ３００／Ａ５５０値を算出した。
式：Ａ350／Ａ550＝ｌｏｇ（１００／Ｔ350）／ｌｏｇ（１００／Ｔ550）
【００４３】
（ペースト化処方）
試料 １．２ｇ
バインダー（流動パラフィン／ワセリン／ステアリン酸
＝４０／２６．７／１（重量比）） ４０．０ｇ
ガラスビーズ ５０．０ｇ
【００４４】
（ペーストの調製方法）
前記処方を２２５ｃｃの蓋付ガラス瓶に仕込み、密閉してからペイントコンディショナー（レッドデビル社（米）製、クイックミル）を用いて分散させた。
【００４５】
ペーストを用いた透過率の測定結果を表３に示す。可視光の透過率が高くなれば、当然の結果としてＵＶＡの透過率も高くなる。このため、二酸化チタン微粒子の透明性、ＵＶＡ遮蔽能の優劣は、透過率の絶対値よりも、吸光度の比：Ａ３５０／Ａ５５０値で比較するのが適当である。Ａ３５０／Ａ５５０値が高いもの程、透明性とＵＶＡ遮蔽能とが高いレベルでバランスしたものである。本発明の鉄含有針状二酸化チタン微粒子はＡ３５０／Ａ５５０値が高く、Ａ３００／Ａ５５０値も高い。従って、本発明の鉄含有針状二酸化チタン微粒子を化粧料に用いると、透明性、ＵＶＢ遮蔽能、ＵＶＡ遮蔽能のいずれの特性も優れていることが分かる。
【００４６】
【表３】
評価５
実施例１及び比較例１で得られた鉄含有針状二酸化チタン微粒子及び針状二酸化チタン微粒子（試料Ａ、Ｂ）を以下に記す方法で塗料とした。この塗料を２ミル・アプリケーターを用いて透明のトリアセテート・フィルム上に塗布し、３０分間放置後、１４０℃で２分間焼付けた。焼付後の塗膜の厚さは約９μｍであった。この塗膜のＴ５５０、Ｔ３５０、Ｔ３００を評価４と同様の方法により測定し、Ａ３５０／Ａ５５０値、Ａ３００／Ａ５５０値をそれぞれ算出した。
【００４８】
（塗料化処方）
［処方Ａ］
試料 ５．４ｇ
アクリル樹脂
（大日本インキ化学製、アクリディック４７−７１２） ６．４ｇ
混合溶剤（トルエン／酢酸ブチル＝１／１） １４．７ｇ
ガラスビーズ ４５．０ｇ
［処方Ｂ］
処方Ａにより調製した成分 ２６．５ｇ
アクリル樹脂
（大日本インキ化学製、アクリディック４７−７１２） ４１．６ｇ
メラミン樹脂
（大日本インキ化学製、スーパーべッカミンＬ−１１７） １０．０ｇ
混合溶剤（トルエン／酢酸ブチル＝１／１） ５．０ｇ
【００４９】
（塗料の調製方法）
処方Ａを２２５ｃｃの蓋付ガラス瓶に仕込み、密閉してからペイントコンディショナー（レッドデビル社（米）製、クイックミル）を用いて分散させた後、得られた成分を抜き出し、処方Ｂにて残りの成分と混合した。
【００５０】
この結果を表４に示す。本発明の鉄含有針状二酸化チタン微粒子は、塗料に用いても、Ａ３５０／Ａ５５０値、Ａ３００／Ａ５５０値が高いことが分かる。
【００５１】
【表４】
【発明の効果】
本発明は、鉄化合物を含有し、０．００５〜０．１５μｍの範囲の平均長軸径と４０〜１７５Åの範囲の平均結晶子径とを有することを特徴とする鉄含有針状二酸化チタン微粒子である。この鉄含有針状二酸化チタン微粒子は、従来の球状や針状の二酸化チタン微粒子と比較して透明性、ＵＶＢ遮蔽能、ＵＶＡ遮蔽能のいずれの性能も優れ、日焼け止め化粧料や塗料に配合すると、紫外線からの皮膚や基材の保護効果が高いばかりでなく、透明感のある淡い肌色〜茶色を呈するので、皮膚に独特の素肌感を与える。また、トナー、シリコーンゴム等の添加剤、磁気記録媒体の下層材、触媒担体、導電性材料等の基体粒子などとしても用いることもできる。更に本発明は、塩化鉄の存在下で、含水酸化チタンと塩基性ナトリウム化合物との反応生成物を塩酸と反応することにより、微細な結晶子を有する鉄含有針状二酸化チタン微粒子を製造することができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to acicular titanium dioxide fine particles containing an iron compound and a method for producing the same, and more particularly to iron-containing acicular titanium dioxide fine particles useful as a transparent ultraviolet shielding agent and a method for producing the same. The present invention also relates to sunscreen cosmetics and ultraviolet shielding paints containing the iron-containing acicular titanium dioxide fine particles.
[0002]
[Prior art]
The acicular titanium dioxide fine particles have an average major axis diameter larger than the average minor axis diameter, and are generally called spindle-shaped or rod-shaped. Such acicular titanium dioxide fine particles are used in the same applications as ordinary titanium dioxide fine particles having a non-acicular shape such as a spherical shape. It is also useful as an agent, a lower layer material of a magnetic recording medium, a catalyst carrier, and base particles for attaching a functional material such as a conductive material or an antibacterial material to the surface. In particular, acicular titanium dioxide fine particles have high transparency and are extremely excellent in ultraviolet shielding ability, and are being used as sunscreen cosmetics as ultraviolet shielding agents.
[0003]
Ultraviolet rays are broadly divided into three areas, A, B, and C, in the order of their wavelengths, and ultraviolet rays in the C area with a wavelength of 200 to 290 nm are shielded by the ozone layer, so there are generally problems with skin damage such as sunburn and inflammation. It is said that the cause is an A region having a wavelength of 320 to 380 nm and a B region having a wavelength of 290 to 320 nm. It is said that the ultraviolet ray (UVB) in the B region has the largest effect on the skin, while the ultraviolet ray (UVA) in the A region has a milder effect on the skin than the ultraviolet ray (UVB) in the B region. However, it is contained in a large amount in sunlight, is highly permeable and easily causes damage in the deep part of the skin, and in recent years, the shielding ability of UVA has also been emphasized.
[0004]
As a method for producing acicular titanium oxide fine particles, JP-A-5-186221, JP-B-6-102545 and the like disclose a method of treating hydrous titanium dioxide with sodium hydroxide, followed by heating and hydrochloric acid treatment. ing. However, in this method, acicular titanium dioxide fine particles that sufficiently satisfy all the characteristics of transparency, UVB shielding ability, and UVA shielding ability were not obtained. In addition, since this is a fine white powder, it strongly scatters short-wavelength visible light and exhibits a bluish color tone. There was also the problem of damaging the natural color.
[0005]
[Problems to be solved by the invention]
The present invention solves the above-mentioned problems of the prior art, and provides acicular titanium dioxide fine particles having high transparency, UVB shielding ability, and UVA shielding ability, and a method for producing the same. Furthermore, the present invention provides sunscreen cosmetics and UV shielding paints having high transparency, UVB shielding ability, and UVA shielding ability.
[0006]
[Means for Solving the Problems]
As a result of extensive research, the present inventor has (1) acicular titanium dioxide fine particles having a sufficiently small crystallite diameter, that is, very fine and having a long axis diameter to some extent, transparency, UVB shielding ability, UVA shielding. (2) If this compound contains an iron compound, it will not only exhibit a bluish color even if it is a fine particle, but will further improve the UVA shielding ability. (3) In the method for producing acicular titanium oxide fine particles, which is treated with hydrous titanium oxide and a basic sodium compound and then heated and treated with hydrochloric acid, if the hydrochloric acid treatment is performed in the presence of iron chloride, the iron compound is contained. At the same time, the inventors have found that a product having a specific size as described above can be obtained, thereby completing the present invention.
[0007]
That is, the present invention
(1) the presence of a salt of iron, is a manufacturing method, the iron-containing acicular titanium dioxide particles characterized by reacting the reaction product of hydrous titanium oxide and a basic sodium compound with hydrochloric acid.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
When the crystallites constituting the titanium dioxide fine particles are made small, that is, finer, the transparency and UVB shielding ability are theoretically improved, but at the same time the surface energy is increased and the dispersibility is lowered. When blended and used, high transparency and UVB shielding ability were not obtained. Moreover, the UVA shielding ability has decreased with the miniaturization. However, by making the crystallites constituting the titanium dioxide fine particles sufficiently fine and making the titanium dioxide fine particles formed by the aggregation of the crystallites into a needle shape, the surface energy can be reduced, It is considered that the transparency and UVB shielding ability inherent to titanium fine particles can be brought out. In addition, by adopting a needle shape, a large major axis diameter can be secured, and a decrease in UVA shielding ability can be suppressed. In addition, by containing an iron compound, the particles have a light skin color to brown color, and can suppress the bluish color tone caused by being white fine particles, and at the same time, absorption occurs in a region close to UVA visible light, The UVA shielding ability is further improved. That is, the titanium dioxide fine particles of the present invention contain an iron component as an iron compound and are contained in at least either the inside of the particle or the surface of the particle, and acicular titanium dioxide having an average major axis in the range of 0.005 to 0.15 μm. The average diameter of the crystallites is in the range of 40 to 175 mm. Here, particles having an average major axis diameter larger than the average minor axis diameter are referred to as needles, and those generally called spindles, rods and the like are also included.
[0009]
In the present invention, the average major axis diameter is the cumulative primary particle diameter of 50% obtained by electron microscopy, and the average crystallite diameter is the Scherrer formula (formula below) from the X-ray diffraction peak of the (110) plane of titanium dioxide. 1). If the average major axis diameter is less than 0.005 μm, the desired UVA shielding ability and dispersibility cannot be obtained. If the average major axis diameter is more than 0.15 μm, transparency and UVB shielding ability are obtained even if the average crystallite diameter is within the above range. It will decline. If the average crystallite diameter is larger than 175 mm, the desired transparency and UVB shielding ability cannot be obtained. If the average crystallite diameter is smaller than 40 mm, the surface energy becomes too large even if the average major axis diameter is in the above range. Becomes lower. A preferable range of the average major axis diameter is 0.01 to 0.15 μm, a preferable range of the average crystallite diameter is 40 to 150 mm, and a more preferable range is 50 to 130 mm.
[0010]
When the surface coating is performed, the specific surface area varies greatly depending on the coating type and the coating amount. For example, in the case of iron-containing acicular titanium dioxide which is not subjected to the surface coating described later, it is in the range of 150 to 250 m 2 / g. Is preferred. The iron-containing acicular titanium dioxide fine particles of the present invention may partially contain an amorphous material as long as the object of the present invention is not impaired, but has a substantially crystalline structure. Although there is no restriction | limiting in crystal structure, The thing obtained by the below-mentioned manufacturing method is mainly a rutile type.
[0011]
In the present invention, the iron compound is coated on the surface of acicular titanium dioxide fine particles, for example, as iron oxide or hydrated iron oxide, is taken into the inside of the particles, is dissolved in titanium dioxide crystals as iron oxide, or These are combined with titanium dioxide in a composite state and the like, and do not include a simple mixture of iron compound and acicular titanium dioxide fine particles. The content of the iron compound is preferably 0.1 to 50% by weight and more preferably 0.1 to 20% by weight with respect to TiO 2 in terms of Fe 2 O 3 . When the content of the iron compound is in the range of 0.1 to 50% by weight, it is preferable because the blueness is most effectively suppressed, and when it is less than this range, the desired color tone and UVA shielding ability can be obtained. It is difficult, and if it exceeds this range, it is not preferable because it is not only economically disadvantageous, but also particles are remarkably easily colored in dark colors.
[0012]
The iron-containing acicular titanium dioxide fine particles of the present invention may have a particle surface coated with at least one selected from inorganic compounds and organic compounds. The coating amount can be appropriately set according to the purpose. For example, it is preferable to coat an amount in the range of 0.1 to 50% by weight with respect to TiO 2 of the iron-containing acicular titanium dioxide fine particles. A range of 1 to 30% by weight is more preferable.
[0013]
In order to improve dispersibility, weather resistance, etc., it is preferable to coat an inorganic compound, and at least one compound selected from aluminum, silicon, zirconium, zinc, titanium, tin, antimony, etc., for example, those elements More preferably, the oxide or hydrated oxide is coated. In addition, the surface of the particle or the surface of the particle coated with the inorganic compound is coated with at least one organic compound for the purpose of increasing the affinity with the organic binder or increasing the fluidity. May be.
[0014]
Examples of organic compounds include higher fatty acids such as stearic acid and carboxylic acid, silicone compounds such as dimethylpolysiloxane and methylhydrogenpolysiloxane, polyhydric alcohols such as trimethylolethane and trimethylolpropane, and alkanolamines such as triethylamine. , Coupling agents such as silane coupling agents and titanate coupling agents.
[0015]
Next, the present invention is a method for producing iron-containing acicular titanium dioxide fine particles, in which a reaction product of hydrous titanium oxide and a basic sodium compound is reacted with hydrochloric acid in the presence of iron chloride.
[0016]
Although the reaction mechanism in this method is not necessarily clear, sodium titanate is produced by the reaction between hydrous titanium oxide and basic sodium, and sodium is released from sodium titanate by the reaction between sodium titanate and hydrochloric acid. It is conceivable that, in the process, acicular titanium dioxide fine particles, in particular, rutile-type particles are generated. It is considered that iron chloride serves as a raw material for the iron compound contained in the acicular titanium dioxide fine particles and at the same time has an action of suppressing the growth of crystallites of the acicular titanium dioxide fine particles.
[0017]
As the hydrous titanium oxide used in the present invention, those obtained by a known method such as hydrolysis of titanium tetrachloride, titanyl sulfate and the like can be used. As the basic sodium compound, sodium hydroxide, sodium carbonate, sodium oxalate and the like can be used.
[0018]
The reaction between the hydrous titanium oxide and the basic sodium compound is carried out by mixing the hydrous titanium oxide and the basic sodium compound. A basic sodium compound or a solution thereof is added to a suspension in which a hydrous titanium oxide is previously dispersed in a dispersion medium such as an organic solvent, preferably in water, or a hydrous titanium oxide is added to a basic sodium compound solution. Alternatively, it is preferable to add the dispersion because it easily reacts uniformly. This reaction is preferably performed in the range of 80 to 100 ° C, more preferably in the range of 90 to 100 ° C. If the reaction temperature is in the range of 80 to 100 ° C., the reaction between the hydrous titanium oxide and the basic sodium compound is likely to proceed in a short time, and a pressure resistant reactor such as an autoclave is not required, which is industrially advantageous. . When 1 mol or more of basic sodium compound is reacted with respect to 1 mol of TiO 2 equivalent of titanium contained in hydrous titanium oxide, a reaction product having fine crystallites can be easily obtained, preferably 5 mol. More preferably, the reaction is carried out at 5 to 8 mol. After the reaction product is obtained, it may be subjected to a step of continuously reacting with hydrochloric acid, but once the reaction product is filtered and washed, it is subjected to the above step to obtain a uniform particle diameter and particle shape. It is preferable because iron-containing acicular titanium dioxide fine particles are easily obtained.
[0019]
Next, to react the reaction product with hydrochloric acid in the presence of iron chloride, after adding the iron chloride to a suspension in which the reaction product is previously dispersed in a dispersion medium such as an organic solvent, preferably in water. It is preferable to add hydrochloric acid, to add both at the same time, or to add both in a mixed manner because they can easily react uniformly. The reaction temperature is preferably in the range of 60 to 100 ° C, more preferably in the range of 85 to 100 ° C. If the temperature is in the range of 60 to 100 ° C., acicular titanium dioxide fine particles having fine crystallites are easily obtained, and a pressure resistant reactor such as an autoclave is not required, which is industrially advantageous. The reaction temperature may be adjusted before adding iron chloride and hydrochloric acid, after adding, or while adding.
[0020]
Iron chloride is preferably used in an amount corresponding to 0.1 to 50% by weight in terms of Fe 2 O 3 with respect to the TiO 2 equivalent of titanium contained in the reaction product. More preferably, the corresponding amount is used. When the amount of iron chloride used is less than 0.1% by weight, not only the particles are not easily colored, but in the range of the average major axis diameter of 0.005 to 0.15 μm, the average crystallite diameter is 40 to It is difficult to obtain a product in the range of 175%, and even if it exceeds 50% by weight, a significant effect associated therewith is hardly recognized.
[0021]
As iron chloride, iron trichloride, iron dichloride and the like can be used, and iron trichloride is particularly preferable because of its high effect. The iron chloride used is a process of filtering, washing and drying the obtained acicular titanium dioxide fine particles, and finally, as iron oxide, iron hydroxide or hydrous iron oxide, possibly partly inside the particles and crystallized. It is presumed that it exists outside the lattice and a part thereof is deposited as a coating layer on the surface of the particle.
[0022]
The amount of hydrochloric acid to be used is preferably in the range of 0.1 to 2 mol, and in the range of 0.4 to 1.5 mol, with respect to 1 mol in terms of TiO 2 equivalent of titanium contained in the reaction product. Is more preferable. When the pH during the reaction is 3 or less, non-needle particles are less likely to be produced, and preferably 1 or less. It is preferable to add hydrochloric acid after the addition of hydrochloric acid until the pH is 2 to 3, and then to further improve the particle size distribution and particle shape. In the present invention, iron chloride is also an acidic compound. Therefore, when iron chloride and hydrochloric acid are used in the above ranges, it is not necessary to adjust the pH.
[0023]
For example, if acicular titanium dioxide fine particles having an average major axis diameter and an average crystallite diameter in the above range can be generated in advance, an iron compound such as iron oxide is deposited on the particle surface by a known method. Even the target can be obtained. However, in this method, since the particles are aggregated in the deposition step and the dispersibility is lowered, it is preferable to use the method described above.
[0024]
After synthesizing the iron-containing acicular titanium dioxide fine particles as described above, an inorganic compound or an organic compound can be coated by a known method as necessary. When the surface is coated with an inorganic compound such as an oxide such as aluminum, silicon, zirconium, zinc, titanium, tin, antimony or a hydrated oxide, for example, in an aqueous suspension of the obtained iron-containing acicular titanium dioxide fine particles A predetermined amount of a water-soluble compound containing these components is added, and neutralized with a basic or acidic compound.
[0025]
When coating with an organic compound, for example, an organic substance is added to the pulverizer in the pulverization step, and coating is performed while pulverizing, or after drying or pulverization, the organic compound is mixed with the organic compound using a high-speed mixer or the like. It can carry out by what is called dry processing. Moreover, if the organic compound to coat | cover is a thing couple | bonded firmly with titanium dioxide in aqueous suspension, a wet process can be used. Examples of such organic compounds include higher fatty acid salts such as sodium stearate, hydrolysates of silane coupling agents, etc., and these are added to a suspension of iron-containing acicular titanium dioxide fine particles, neutralized, Can be coated.
[0026]
The iron-containing acicular titanium dioxide fine particles obtained by the above method or the coated acicular titanium dioxide fine particles may be filtered, washed and dried by a usual method. The product may be pulverized by a pulverizer such as a fluid energy mill such as a jet mill or an impact pulverizer such as a hammer mill. Moreover, if it heat-fires after drying, an iron component can also be made into solid solution in the crystal structure of acicular titanium dioxide microparticles | fine-particles.
[0027]
The sunscreen cosmetics of the present invention are those containing the iron-containing acicular titanium dioxide fine particles described above, and other binders, solvents, colorants, surfactants, fragrances, moisturizers, etc. that are usually used in cosmetics. The additive may be included. This sunscreen cosmetics is highly transparent and has a high shielding ability against both UVB and UVA, so compared with those using conventional spherical or acicular titanium dioxide fine particles as an ultraviolet shielding agent, The effect of protecting the skin from ultraviolet rays is excellent. Moreover, this thing exhibits the pale skin color-brown with a transparent feeling, and also has the function of not impairing the natural natural tone of skin.
[0028]
Furthermore, the present invention is an ultraviolet shielding coating containing the iron-containing acicular titanium dioxide fine particles described above. This paint is obtained by dispersing the iron-containing acicular titanium dioxide fine particles of the present invention in a resin such as acrylic, alkyd, melamine, polyester, and urethane by a known method such as using a disper or a sand mill. Additives such as curing agents can be blended as appropriate. The coating material of the present invention is used as a surface coating agent. When these are applied to the surface of an organic base material such as plastics and paper to form a coating film, ultraviolet deterioration can be effectively prevented. In particular, the base is suitable for a wood-like color such as wood, and the original appearance of the base material is not impaired by the transparent skin tone to brown color tone of the present invention.
[0029]
The iron-containing acicular titanium dioxide fine particles of the present invention can be used for various applications other than the sunscreen cosmetics and ultraviolet shielding paints. For example, if blended into a transparent plastic film and affixed to a substrate, the same effect as an ultraviolet shielding paint can be obtained. When molding a substrate such as plastics, compression board, paper, etc., it may be blended directly as an ultraviolet shielding filler. Further, it can be used as an additive such as toner and silicone rubber, a lower layer material of a magnetic recording material, a catalyst carrier, and a base particle of a conductive material.
[0030]
【Example】
EXAMPLES The present invention will be described in more detail with reference to examples below, but these do not limit the present invention.
[0031]
Example 1
1. Synthesis of reaction product As an aqueous suspension of hydrous titanium oxide of 100 g / liter as TiO 2 , 1400 g of a 48% aqueous sodium hydroxide solution was added with stirring, heat-treated at 95 ° C. for 120 minutes, filtered, Washing gave a reaction product washed cake. 6.72 mol of basic sodium compound was used for 1 mol of TiO 2 equivalent of titanium contained in hydrous titanium oxide.
[0032]
2. The synthetic washed cake of iron-containing acicular titanium dioxide fine particles was redispersed in water, and the reaction product was made into TiO 2 to form an aqueous suspension of 70 g / liter. An aqueous solution of iron trichloride corresponding to 5% by weight as Fe 2 O 3 and 40 ml of 35% hydrochloric acid were simultaneously added to 1400 ml of this suspension in 20 minutes with respect to TiO 2 in the reaction product and stirred. As a result, the pH of the suspension was 3. Subsequently, the suspension was heated to 60 ° C. and stirred for 30 minutes, and when 61 ml of 35% hydrochloric acid was further added, the pH became 1 or less. The total amount of hydrochloric acid used was 0.8 mol with respect to 1 mol in terms of TiO 2 of titanium contained in the reaction product. Thereafter, the mixture was aged for 60 minutes while maintaining the temperature at 95 ° C. to obtain a slurry of rutile iron-containing acicular titanium dioxide fine particles. A part of the slurry was taken, washed, filtered, dried, and then pulverized by a sample mill to obtain iron-containing acicular titanium dioxide fine particles (sample a) of the present invention.
[0033]
3. Surface coating treatment The slurry was heated to 80 ° C., and neutralized with a 200 g / liter sodium hydroxide aqueous solution to a pH of 8. Next, as Al 2 O 3 , 53.3 milliliters of 300 g / liter sodium aluminate and 20% sulfuric acid were added simultaneously for 20 minutes while maintaining the pH of the slurry at 8 to 9, and stirred for 10 minutes. The solution was neutralized with 20% sulfuric acid over 30 minutes so that the pH was 5.5. Next, 20% by weight of sodium stearate was added to TiO 2 , stirred for 30 minutes, neutralized with 20% sulfuric acid so that the pH became 6 and aged for 60 minutes. Thereafter, the iron-containing acicular dioxide of the present invention coated with 10% by weight of aluminum hydroxide and 15% by weight of stearic acid with respect to TiO 2 after washing, filtration, drying, pulverization using a hammer mill. Titanium fine particles (sample A) were obtained.
[0034]
Comparative Example 1
A rutile needle-like titanium dioxide fine particle (sample b) and a surface-treated product of the aluminum hydrous oxide and stearic acid (sample B) were prepared in the same manner as in Example 1 except that iron trichloride was not used. Obtained.
[0035]
Evaluation 1
The average primary particle diameters of the major axis and minor axis of the iron-containing acicular titanium dioxide fine particles and acicular titanium dioxide fine particles (samples a, b, A, and B) obtained in Example 1 and Comparative Example 1 were measured with an electron micrograph. Measured by the method. Moreover, the specific surface area was measured by the BET method using a specific surface area measuring apparatus (manufactured by Shimadzu Corporation, Flowsorb II 2300 type).
[0036]
Evaluation 2
The average crystallite diameter of the iron-containing acicular titanium dioxide fine particles and acicular titanium dioxide fine particles (samples a, b, A, and B) obtained in Example 1 and Comparative Example 1 was determined from the X-ray diffraction peak of the (110) plane. Calculation was made using the following formula.
Formula 1: D HKL = K * λ / βcos θ
D HKL : Average crystallite diameter (Å)
λ: wavelength of X-ray β: half width of diffraction peak θ: Bragg's angle K: constant
Table 1 shows the measurement results of the average major axis diameter and minor axis diameter, average crystallite diameter, and specific surface area. From this result, it was found that the iron-containing acicular titanium dioxide fine particles of the present invention had an average major axis diameter of 0.005 to 0.15 μm and an average crystallite diameter of 40 to 175 mm. Further, as a result of observation with an electron microscope, it was found that there were almost no aggregated particles, and as a result of X-ray diffraction, a rutile crystal was substantially obtained.
[0038]
[Table 1]
Evaluation 3
The powder colors of the iron-containing acicular titanium dioxide fine particles and acicular titanium dioxide fine particles (samples A and B) obtained in Example 1 and Comparative Example 1 were measured. An aluminum ring (inner diameter: 33 mmΦ, outer diameter: 38 mmΦ, thickness: 5 mm) was filled with 2 g of sample, sandwiched between stainless plates, and then pressed and molded with a press at a pressure of 19.6 MPa for 10 seconds. The color tone (b) of this molded body was measured using a color difference meter. The smaller the b value, the stronger the bluish white.
[0040]
Table 2 shows the measurement results of the powder color. It can be seen that the iron-containing acicular titanium dioxide fine particles of the present invention do not have a bluish sensation as compared with the titanium dioxide fine particles not containing the iron compound (sample B of Comparative Example 1).
[0041]
[Table 2]
Evaluation 4
The iron-containing acicular titanium dioxide fine particles and acicular titanium dioxide fine particles (samples A and B) obtained in Example 1 and Comparative Example 1 were prepared as pastes assuming cosmetics by the following method. This paste was applied onto a transparent triacetate film using a doctor blade so that the film thickness was about 25 μm, and then air-dried for 30 minutes. A spectrophotometer (Shimadzu) equipped with an integrating sphere was used to determine the light transmittance T 550 at a wavelength of 550 nm, the light transmittance T 350 at 350 nm and the light transmittance T 300 at 300 nm (UVB). A 350 / A 550 was calculated according to the following formula. Similarly, the A 300 / A 550 value was calculated.
Formula: A 350 / A 550 = log (100 / T 350 ) / log (100 / T 550 )
[0043]
(Paste formulation)
Sample 1.2g
Binder (liquid paraffin / petroleum / stearic acid = 40 / 26.7 / 1 (weight ratio)) 40.0 g
Glass beads 50.0g
[0044]
(Paste preparation method)
The formulation was charged into a 225 cc glass bottle with a lid, sealed, and then dispersed using a paint conditioner (manufactured by Red Devil (USA), Quick Mill).
[0045]
Table 3 shows the measurement results of the transmittance using the paste. As the visible light transmittance increases, the UVA transmittance naturally increases as a result. Therefore, it is appropriate to compare the transparency of the titanium dioxide fine particles and the superiority or inferiority of the UVA shielding ability with the ratio of absorbance: A 350 / A 550 rather than the absolute value of the transmittance. The higher the A 350 / A 550 value, the higher the balance between transparency and UVA shielding ability. The iron-containing acicular titanium dioxide fine particles of the present invention have a high A 350 / A 550 value and a high A 300 / A 550 value. Therefore, it can be seen that when the iron-containing acicular titanium dioxide fine particles of the present invention are used in cosmetics, all the properties of transparency, UVB shielding ability, and UVA shielding ability are excellent.
[0046]
[Table 3]
Evaluation 5
The iron-containing acicular titanium dioxide fine particles and acicular titanium dioxide fine particles (samples A and B) obtained in Example 1 and Comparative Example 1 were used as paints by the method described below. This paint was applied onto a transparent triacetate film using a 2 mil applicator, allowed to stand for 30 minutes, and baked at 140 ° C. for 2 minutes. The thickness of the coating film after baking was about 9 μm. T 550 , T 350 , and T 300 of this coating film were measured by the same method as in Evaluation 4, and A 350 / A 550 value and A 300 / A 550 value were calculated, respectively.
[0048]
(Paint formulation)
[Prescription A]
5.4 g of sample
Acrylic resin (manufactured by Dainippon Ink & Chemicals, Acrydic 47-712) 6.4g
Mixed solvent (toluene / butyl acetate = 1/1) 14.7g
Glass beads 45.0g
[Prescription B]
Ingredient 26.5 g prepared according to formulation A
Acrylic resin (Dainippon Ink Chemical Co., Ltd., Acrydic 47-712) 41.6g
Melamine resin (Dainippon Ink Chemical Co., Ltd., Super Becamine L-117) 10.0g
Mixed solvent (toluene / butyl acetate = 1/1) 5.0 g
[0049]
(Paint preparation method)
Formula A was charged into a glass bottle with a lid of 225 cc, sealed, and dispersed using a paint conditioner (manufactured by Red Devil (USA), Quick Mill). Mixed with ingredients.
[0050]
The results are shown in Table 4. It can be seen that the iron-containing acicular titanium dioxide fine particles of the present invention have high A 350 / A 550 values and A 300 / A 550 values even when used in paints.
[0051]
[Table 4]
【The invention's effect】
The present invention provides iron-containing acicular titanium dioxide fine particles containing an iron compound and having an average major axis diameter in the range of 0.005 to 0.15 μm and an average crystallite diameter in the range of 40 to 175 mm. It is. These iron-containing acicular titanium dioxide fine particles are superior in transparency, UVB shielding ability, and UVA shielding ability compared to conventional spherical or acicular titanium dioxide fine particles, and are incorporated into sunscreen cosmetics and paints. The skin and base material are not only highly protected from ultraviolet rays, but also have a light skin color to brown color with transparency, giving the skin a unique feeling of bare skin. Further, it can also be used as additives such as toner and silicone rubber, base material of magnetic recording medium, catalyst carrier, conductive material and other base particles. Furthermore, the present invention produces iron-containing acicular titanium dioxide fine particles having fine crystallites by reacting a reaction product of hydrous titanium oxide with a basic sodium compound with hydrochloric acid in the presence of iron chloride. Can do.
Claims (9)
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| JP4562492B2 (en) * | 2004-10-28 | 2010-10-13 | 石原産業株式会社 | Rod-like titanium dioxide, near-infrared shielding agent containing the same, and resin composition containing the near-infrared shielding agent |
| CN101330898A (en) * | 2005-12-14 | 2008-12-24 | 株式会社资生堂 | Dispersion of fine titanium oxide particles and cosmetic preparation containing the same |
| EP2140854A1 (en) * | 2008-07-01 | 2010-01-06 | The Procter & Gamble | Cosmetic Composition |
| EP2140855A1 (en) * | 2008-07-01 | 2010-01-06 | The Procter and Gamble Company | Cosmetic Composition |
| JP6068927B2 (en) * | 2012-10-24 | 2017-01-25 | チタン工業株式会社 | Rutile titanium oxide and cosmetics using the same |
| GB201806041D0 (en) * | 2018-04-12 | 2018-05-30 | Croda Int Plc | Titanium dioxide particles |
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