JP3957404B2

JP3957404B2 - Firing colored pencil lead

Info

Publication number: JP3957404B2
Application number: JP19039398A
Authority: JP
Inventors: 正昭干場; 昇神庭; 勝徳北澤
Original assignee: Mitsubishi Pencil Co Ltd
Current assignee: Mitsubishi Pencil Co Ltd
Priority date: 1998-07-06
Filing date: 1998-07-06
Publication date: 2007-08-15
Anticipated expiration: 2018-07-06
Also published as: JP2000017219A

Description

【０００１】
【発明の属する技術分野】
本発明は、十分な発色性、描線濃度をもちながら、機械的強度、即ち、曲げ強度、引張強度、衝撃強度等に優れた、焼成芯体にインクを含浸した焼成色鉛筆芯に関する。
【０００２】
【従来の技術】
従来の焼成色鉛筆芯は、結合材として一種及び／又は二種以上の粘土等が用いられ、これに窒化硼素等の体質材、更に必要に応じて耐熱性の顔料、反応促進材を添加、配合した配合組成物を混練し、この混練物を押出成形した後、熱処理を経て多孔質焼成芯体とし、この芯体の気孔中に染料および顔料から成るインク等を充填させて色鉛筆芯としていた。
この時、色鉛筆芯の重要特性としては、機械的強度が強く、発色性が良く、筆記描線の濃度が濃いものが要求されている。
【０００３】
ところが、従来の焼成色鉛筆芯は機械的強度が充分でなく、濃度および発色性においても充分なものが得られていないのが現状である。そこで、上記の要求を達成するためには、充分な機械的強度を保持しつつ、気孔率を増加させることにより芯体に充填されるインク量を多くする必要がある。
また、従来結合材として用いられている粘土等による焼成芯体は、窒化硼素等の体質材と粘土等の結合材の焼結力が弱く、粘土等自身の強度も低いため、得られる焼成色鉛筆芯は実用強度に達していないのが現状である。更に、粘土は不純物を含んでいるため、得られる焼成芯体は一般に有色となり、描線の発色性に悪影響を与えることとなる。特に、淡色系の描線のくすんだ色の原因となっている。
【０００４】
本発明者らは、上記の課題等を解決する方法として、少なくとも体質材からなる第２焼成芯体の気孔内に、ペルヒドロポリシラザン含有液を含浸し、窒素雰囲気等の不活性雰囲気中又はアンモニアガス雰囲気中での熱処理により結合材として窒化珪素を生成させた第３焼成芯体の気孔内にインクを充填させてなる焼成色鉛筆芯及びその製造方法を提案している（特開平８−４８９３１号）。この製造方法等は、十分な発色性、描線濃度をもちながら、機械的強度等に優れた焼成色鉛筆芯が得られるものである。
【０００５】
しかしながら、上記製造方法等による、少なくとも体質材からなる第２焼成芯体の気孔内に、ペルヒドロポリシラザン含有液を含浸し、窒素雰囲気等の不活性雰囲気中又はアンモニアガス雰囲気中での熱処理により結合材として窒化珪素を生成させた第３焼成芯体は、曲げ強度等の品質のバラツキが大きくなる場合があり若干の課題を有している。
【０００６】
【発明が解決しようとする課題】
本発明の目的は、上記従来技術の課題を解決すると共に、上記発明者らの先行技術を更に改良することであり、機械的強度と滑らかな書き味を保持しつつ、更に優れた発色性を有する焼成色鉛筆芯を提供することにある。
【０００７】
【課題を解決するための手段】
本発明者らは、前記課題を解決するために鋭意研究を行った結果、少なくとも体質材からなる第２焼成芯体の気孔内に、特定の分子量を有するペルヒドロポリシラザン含有液を含浸し、窒素雰囲気等の不活性雰囲気中又はアンモニアガス雰囲気中で熱処理し、結合材として窒化珪素を生成させることによって、上記目的の焼成色鉛筆芯が得られることを見い出し、本発明を完成するに至ったのである。
すなわち、本発明の焼成色鉛筆芯は、少なくとも体質材と有機質の賦形材を含む配合組成物を混練、押出成形、非酸化性雰囲気で焼成することにより、該有機質の賦形材が炭化された炭素をバインダーとする第１焼成芯体を形成し、該第１焼成芯体を酸化雰囲気中で加熱して炭素のバインダーを酸化除去させた少なくとも体質材からなる第２焼成芯体を形成し、該第２焼成芯体の気孔内に数平均分子量Ｍｎが５００〜２５００のペルヒドロポリシラザン含有液を含浸し、窒素雰囲気等の不活性雰囲気中又はアンモニアガス雰囲気中で熱処理することにより、第２焼成芯体の気孔内に窒化珪素を生成させた第３焼成芯体を形成し、該第３焼成芯体の気孔内にインクを充填させてなることを特徴とする。
前記有機質の賦形材等を炭素化する際に行う熱処理、前記炭素のバインダーを酸化除去する際に行う熱処理、前記窒化珪素を生成時の熱処理は、共に含有された体質材が分解あるいは脱水等を起こす温度より、低い熱処理温度で処理することが好ましい。
なお、本発明で規定する「窒素雰囲気等の不活性雰囲気中」とは、窒素ガス雰囲気中、または、アルゴンガス雰囲気中等の不活性ガス雰囲気中をいう。
【０００８】
【発明の実施の形態】
以下に、本発明の実施形態を詳しく説明する。
本発明の焼成色鉛筆芯は、少なくとも体質材と有機質の賦形材を含む配合組成物を混練、押出成形、非酸化性雰囲気で焼成することにより、該有機質の賦形材が炭化された炭素をバインダーとする第１焼成芯体を形成し、該第１焼成芯体を酸化雰囲気中で加熱して炭素のバインダーを酸化除去させた少なくとも体質材からなる第２焼成芯体を形成し、該第２焼成芯体の気孔内に数平均分子量Ｍｎが５００〜２５００のペルヒドロポリシラザン含有液を含浸し、窒素雰囲気等の不活性雰囲気中又はアンモニアガス雰囲気中で熱処理することにより、第２焼成芯体の気孔内に窒化珪素を生成させた第３焼成芯体を形成し、該第３焼成芯体の気孔内にインクを充填させてなることを特徴とするものである。
【０００９】
本発明で用いるペルヒドロポリシラザンは、主として（−ＳｉＨ₂ＮＨ−）なる骨格を有し、窒素雰囲気等の不活性雰囲気中又はアンモニアガス雰囲気中での熱分解で脱水素反応に伴う熱硬化収縮の後、非晶質の窒化珪素となるものである。また、ペルヒドロポリシラザンは、水酸基をもつ物質に対して加水分解性が非常に高い特性を有するものである。
第２焼成芯体の気孔内に含浸するペルヒドロポリシラザンの数平均分子量Ｍｎは、５００〜２５００、好ましくは、５５０〜２０００であることが望ましい。ペルヒドロポリシラザンの数平均分子量Ｍｎが５００未満であると、ペルヒドロポリシラザンは窒素雰囲気等の不活性雰囲気中又はアンモニアガス雰囲気中での熱処理途中で揮発してしまい、第２焼成芯体の気孔内に結合材として生成する窒化珪素の量は少なくなり、得られる第３焼成芯体の強度は弱くなり、好ましくない。また、ペルヒドロポリシラザンの数平均分子量Ｍｎが２５００を越えると、ペルヒドロポリシラザンの加水分解性が促進され、品質安定性が悪くなる。更に、数平均分子量Ｍｎが２５００を越えるペルヒドロポリシラザン含有液では、第２焼成芯体の気孔内への含浸がしづらくなり、しかも、得られる第３焼成芯体の曲げ強度等の品質のバラツキが大きくなる原因となる。
【００１０】
本発明で用いるペルヒドロポリシラザン含有液は、上記ペルヒドロポリシラザンを有機溶剤で溶解したものであり、該ペルヒドロポリシラザン含有液が第２焼成芯体に充填可能なものであれば、使用する有機溶剤は特に限定されず、いずれも使用可能である。使用する有機溶剤としては、例えば、ベンゼン、トルエン、キシレン、エーテル、ＴＨＦ、塩化メチレン、四塩化炭素等、芳香族炭化水素系等の有機溶剤が挙げられる。
【００１１】
本発明においては、第１焼成芯体は、少なくとも体質材と有機質の賦形材を含む配合組成物を原料とする。
本発明で用いる体質材としては、従来の焼成型の色鉛筆芯に使用されているものであれば、いずれも使用可能である。例えば、酸化チタン、雲母、タルク、窒化硼素、シリカ、アルミナ、炭酸カルシウム等白色系のものや、充填するインクの色相によっては二硫化モリブデン、二硫化タングステン等有色系のものも使用することができ、当然これら数種類の混合物も使用できる。また、必要に応じて耐熱性顔料を配合してもよい。
【００１２】
また、有機質の賦形材としては、例えば、ポリ塩化ビニル樹脂、塩素化ポリ塩化ビニル樹脂、ポリビニルアルコールなどの熱可塑性樹脂、フラン樹脂、フェノール樹脂、エポキシ樹脂などの熱硬化性樹脂、リグニン、セルロース、トラガントガムなどの天然高分子物質、石油アスファルト、コールタールピッチ、ナフサ分解ピッチ、合成樹脂の乾留ピッチなどのピッチ類等いずれも使用可能で、当然これら数種類の混合物も使用できる。
更に、高せん断力を加えて行う混練時の特性向上及び押出成形の特性向上の目的で、水、ジオクチルフタレート（ＤＯＰ）、ジブチルフタレート（ＤＢＰ）、リン酸トリクレジル（ＴＣＰ）、アジピン酸ジオクチル（ＤＯＡ）、プロピレンカーボナート、アルコール類、ケトン類、エステル類など有機質の賦形材の可塑剤又は溶剤の一種又は二種以上を、必要に応じて上記配合組成物に添加しても良い。
【００１３】
これら配合組成物をヘンシェルミキサー、加圧ニーダー、二本ロール等で十分混練した後、押出成形機により細線状等に押出成形し、次いで、窒素雰囲気中又はアルゴンガスなどの不活性ガス中等の非酸化性雰囲気中で焼成することにより、有機質の賦形材が炭化され炭素をバインダーとする第１焼成芯体が形成される。
なお、第２焼成芯体の強度及び取り扱い性を向上させるために、必要に応じて、第１焼成芯体を得る配合組成物中に粘土、例えば、ベントナイト、カオリナイト等の無機質の結合材を配合することもでき、その配合量は上記配合組成物中に２５重量％未満に抑えたほうが後述する窒化珪素による強度を発現しやすいものとなる。
また、必要に応じて、上記で得られた第１焼成芯体に数平均分子量Ｍｎが５００〜２５００のペルヒドロポリシラザン含有液を含浸せしめ、窒素雰囲気等の不活性雰囲気中又はアンモニアガス雰囲気中での熱処理により窒化珪素を生成させた焼成芯体であってもよい。
【００１４】
上記で形成した第１焼成芯体を酸化雰囲気中で加熱して、炭素のバインダーを酸化除去させることにより、多数の気孔を備えた多孔質芯体からなる第２焼成芯体が形成される。
ここで、第２焼成芯体の気孔は、体質材と有機質の賦形材等とからなる混練物を、非酸化性雰囲気で焼成することによって形成される気孔と、前記炭素のバインダーを除去することにより形成される気孔の両者から構成されている。
第２焼成芯体の気孔率の調整は、主に有機質の賦形材の配合割合を調整することにより行われるものであるが、他に炭素粒状物質等の気孔形成材を適宜添加してもかまわない。なお、全気孔に対する炭素のバインダーの除去による気孔の量は全く任意である。
【００１５】
本発明において、第３焼成芯体は、上記で形成した多孔質芯体からなる第２焼成芯体に数平均分子量Ｍｎが５００〜２５００のペルヒドロポリシラザン含有液に含浸せしめた後、窒素雰囲気等の不活性雰囲気中又はアンモニアガス雰囲気中で４００℃以上、好ましくは６００℃以上で、かつ、体質材の熱分解又は脱水等を起こす温度より低い温度での熱処理により、第２焼成芯体に結合材として窒化珪素を生成させることにより形成される。
本発明では、前記第１焼成芯体、第２焼成芯体、第３焼成芯体を形成する際に行う熱処理は、使用する体質材によって、熱処理温度を留意しなければならないものとなる。すなわち、前記有機質の賦形材等を炭素化する際に行う熱処理、前記炭素のバインダーを酸化除去する際に行う熱処理、上記窒化珪素の生成する際に行う熱処理において、夫々含有された体質材が分解又は脱水等の化学変化等を生じると、書き味を損ねたり、強度の劣化等を生じる場合があるので、使用する体質材の熱的性質と熱処理温度を考慮等して適宜熱処理温度等を選択する必要がある。
【００１６】
ペルヒドロポリシラザン含有液を第２焼成芯体に含浸させる方法としては、第２焼成芯体をペルヒドロポリシラザン含有液中に浸漬し、必要に応じて加熱、減圧、加圧等の条件下で含浸させることにより行うことができる。
得られた第３焼成芯体は、結合材としての窒化珪素が芯体中に微細で均一に分散して生成するものとなり、さらに、体質材が高配向しているため少量の窒化珪素の生成で芯体の強度を発現しやすく、筆記時の芯体の崩れも均一となる。なお、高強度の第３焼成芯体を得るために、必要に応じてペルヒドロポリシラザン含有液の含浸、焼成工程を繰り返し行ってもよい。
【００１７】
本発明において、焼成色鉛筆芯は、上記で形成した第３焼成芯体の気孔内に、インクを充填させることにより形成される。
第３焼成芯体に含浸させるインクとしては、従来公知の色鉛筆芯用のものであればいずれも使用することができる。例えば、染料、顔料等の着色剤を、動植物油、合成油、アルコール類、炭化水素油、水等に溶解、分散させ、あるいは必要に応じて樹脂、界面活性剤等を更に添加し製造された一般的に用いられている印刷用インク、スタンプインク、ボールペンインク、水性筆記用インク等が用いられる。
また、第３焼成芯体にインクを含浸させる方法としては、第３焼成芯体をインク中に浸漬し、加熱、減圧、加圧等の条件下で気孔内に充填させる。さらに、繰り返し含浸を行ってもよい。
【００１８】
このように構成される焼成色鉛筆芯は、第２焼成芯体の気孔内に数平均分子量Ｍｎが５００〜２５００に特定したペルヒドロポリシラザン含有液を含浸し、窒素雰囲気等の不活性雰囲気中又はアンモニアガス雰囲気中で熱処理することにより、品質のバラツキの小さい、結合材として窒化珪素を生成させた第３焼成芯体の気孔内にインクを充填させた構造となるので、気孔率が大きくても機械的強度に優れ、実用上折れ難く、更にインク充填量が多くなることにより、きわめて優れた発色が得られ、それと同時に、良好な書き味を有するものとなる。
【００１９】
【実施例】
次に、本発明を実施例により、更に具体的に説明するが、本発明はこの実施例によって何等限定されるものではない。
【００２０】
（実施例１）
窒化硼素５０重量部
塩化ビニル樹脂５０重量部
ジオクチルフタレート（ＤＯＰ）２０重量部
ステアリン酸亜鉛１重量部
上記配合組成物をヘンシェルミキサーで混合分散し、加圧ニーダー、二本ロールで混練した後、細線状に押出成形し、これから残留する可塑剤を除去すべく空気中で１８０℃にて加熱処理して、しかるのち窒素雰囲気中にて１０００℃まで昇温させた後、１０００℃にて焼成して第１焼成芯体を得た。
【００２１】
次いで、この第１焼成芯体を酸化雰囲気で約７００℃で加熱焼成して残留している炭素化した樹脂分を除去して白色の第２焼成芯体を得た。
この第２焼成芯体に、数平均分子量Ｍｎが１０２４のペルヒドロポリシラザン含有液（２０％キシレン溶液）を室温下で１日含浸後、空気中で６００℃まで昇温させて、６００℃にて焼成して焼成芯体を得た。更に、この焼成芯体に数平均分子量Ｍｎが１０２４のペルヒドロポリシラザン含有液（２０％キシレン溶液）を含浸し、焼成する工程を２回繰り返し、直径０．５７ｍｍの白色の第３焼成芯体を得た。
次に、赤色インクに上記第３焼成芯体を浸し、７０℃で２４時間放置した。この赤色インクが充填された第３焼成芯体表面をアルコールで洗浄し、直径０．５７ｍｍの赤色の焼成色鉛筆芯を得た。
【００２２】
（比較例１）
実施例１において、焼成芯体に含浸するペルヒドロポリシラザン含有液（２０％キシレン溶液）の数平均分子量Ｍｎが３１２である以外、すべて実施例１と同様にして直径０．５７ｍｍの赤色の焼成色鉛筆芯を得た。
【００２３】
（比較例２）
実施例１において、焼成芯体に含浸するペルヒドロポリシラザン含有液（２０％キシレン溶液）の数平均分子量Ｍｎが３６１３である以外、すべて実施例１と同様にして直径０．５７ｍｍの赤色の焼成色鉛筆芯を得た。
【００２４】
上記実施例１及び比較例１、２で得られた焼成色鉛筆芯について、ＪＩＳ−Ｓ−６００５−１９８９に準拠して曲げ強度（ＭＰａ）、曲げ強度標準偏差（ＭＰａ）、官能評価による書き味について評価した。
これらの結果を下記表１に示す。
【００２５】
【表１】

【００２６】
上記表１の結果から明らかなように、本発明範囲の実施例１の焼成色鉛筆芯は、本発明の範囲外となる比較例１、２に較べて、同じ繰り返し含浸、焼成回数に対して、曲げ強度が強く、また、曲げ強度の標準偏差から曲げ強度のバラツキは少なく、しかも、極めて良好な書き味の焼成色鉛筆芯が得られることが判明した。
【００２７】
【発明の効果】
本発明の焼成色鉛筆芯は、結合材として品質のバラツキの小さい窒化珪素を生成させた焼成芯体の気孔内にインクを充填させた構造となるので、気孔率が大きくても機械的強度に優れ、実用上折れ難く、更にインク充填量が多くなることにより、きわめて優れた発色が得られ、それと同時に、良好な書き味を有するものとなる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fired colored pencil lead having an excellent color strength and drawn line density and excellent mechanical strength, that is, bending strength, tensile strength, impact strength and the like, and a fired core body impregnated with ink.
[0002]
[Prior art]
A conventional fired colored pencil lead uses one and / or two or more types of clay as a binder, and is added to a constitution material such as boron nitride, and further, a heat-resistant pigment and a reaction accelerator as necessary. After the kneaded composition was kneaded and the kneaded product was extrusion-molded, it was heat-treated to form a porous fired core, and the core was filled with inks composed of a dye and a pigment to form a colored pencil core.
At this time, the important characteristics of the colored pencil lead are required to have high mechanical strength, good color development, and a high writing line density.
[0003]
However, the conventional fired colored pencil lead does not have sufficient mechanical strength, and the density and color developability have not been obtained. Therefore, in order to achieve the above requirements, it is necessary to increase the amount of ink filled in the core body by increasing the porosity while maintaining sufficient mechanical strength.
In addition, the fired core made of clay or the like conventionally used as a binding material has a weak sintering power between a material such as boron nitride and a binding material such as clay, and the strength of the clay and the like itself is low. At present, the core does not reach the practical strength. Furthermore, since clay contains impurities, the resulting fired core is generally colored, which adversely affects the color development of the drawn lines. In particular, it is the cause of the dull color of light-colored lines.
[0004]
As a method for solving the above-described problems and the like, the present inventors impregnate at least pores of the second fired core made of the extender with a perhydropolysilazane-containing liquid, and in an inert atmosphere such as a nitrogen atmosphere or ammonia Proposed is a calcined colored pencil lead in which ink is filled in the pores of a third calcined core in which silicon nitride is produced as a binder by a heat treatment in a gas atmosphere, and a method for manufacturing the same (Japanese Patent Laid-Open No. 8-48931). ). This production method and the like can provide a fired colored pencil lead having sufficient color developability and drawn line density and excellent mechanical strength.
[0005]
However, the pores of at least the second fired core made of the extender material are impregnated with the perhydropolysilazane-containing liquid and bonded by heat treatment in an inert atmosphere such as a nitrogen atmosphere or an ammonia gas atmosphere by the above manufacturing method or the like. The third fired core in which silicon nitride is produced as a material has some problems in that the quality of the bending strength and the like may vary greatly.
[0006]
[Problems to be solved by the invention]
The object of the present invention is to solve the above-mentioned problems of the prior art and to further improve the prior art of the above-mentioned inventors, and to further improve color development while maintaining mechanical strength and smooth writing quality. It is in providing the baking color pencil lead which has.
[0007]
[Means for Solving the Problems]
As a result of intensive studies to solve the above problems, the present inventors have impregnated a perhydropolysilazane-containing liquid having a specific molecular weight into the pores of at least the second fired core made of the extender, and nitrogen. It was found that the above-mentioned fired colored pencil lead was obtained by heat treatment in an inert atmosphere such as an atmosphere or in an ammonia gas atmosphere to generate silicon nitride as a binder, and the present invention was completed. .
That is, the fired colored pencil lead of the present invention is carbonized by kneading, extruding, and firing in a non-oxidizing atmosphere a blended composition containing at least an extender and an organic excipient. Forming a first fired core body using carbon as a binder, and heating the first fired core body in an oxidizing atmosphere to form a second fired core body made of at least a constitutional material obtained by oxidizing and removing the carbon binder; The second firing core is impregnated with a perhydropolysilazane-containing liquid having a number average molecular weight Mn of 500 to 2500 in the pores of the second firing core, and heat-treated in an inert atmosphere such as a nitrogen atmosphere or in an ammonia gas atmosphere. A third fired core body in which silicon nitride is generated is formed in the pores of the core body, and ink is filled into the pores of the third fired core body.
The heat treatment performed when carbonizing the organic shaped material, etc., the heat treatment performed when oxidizing and removing the carbon binder, and the heat treatment when forming the silicon nitride include decomposition or dehydration of the contained material. It is preferable to perform the treatment at a heat treatment temperature lower than the temperature at which heat treatment occurs.
Note that “in an inert atmosphere such as a nitrogen atmosphere” as defined in the present invention refers to a nitrogen gas atmosphere or an inert gas atmosphere such as an argon gas atmosphere.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail.
The calcined colored pencil lead of the present invention is obtained by kneading, extruding, and firing in a non-oxidizing atmosphere a compounded composition containing at least a constitutional material and an organic shaping material, thereby carbonizing the carbonized organic shaping material. Forming a first fired core body as a binder, heating the first fired core body in an oxidizing atmosphere to form a second fired core body made of at least a constitutional material obtained by oxidizing and removing the carbon binder; 2 The second fired core is obtained by impregnating the pores of the fired core with a perhydropolysilazane-containing liquid having a number average molecular weight Mn of 500 to 2500 and heat-treating it in an inert atmosphere such as a nitrogen atmosphere or in an ammonia gas atmosphere. A third fired core body in which silicon nitride is generated is formed in the pores, and the pores of the third fired core body are filled with ink.
[0009]
The perhydropolysilazane used in the present invention mainly has a skeleton of (—SiH ₂ NH—), and exhibits thermosetting shrinkage associated with the dehydrogenation reaction due to thermal decomposition in an inert atmosphere such as a nitrogen atmosphere or an ammonia gas atmosphere. Later, amorphous silicon nitride is formed. In addition, perhydropolysilazane has a property of being extremely hydrolyzable with respect to a substance having a hydroxyl group.
The number average molecular weight Mn of the perhydropolysilazane impregnated in the pores of the second fired core is 500-2500, preferably 550-2000. If the number average molecular weight Mn of the perhydropolysilazane is less than 500, the perhydropolysilazane volatilizes during the heat treatment in an inert atmosphere such as a nitrogen atmosphere or in an ammonia gas atmosphere, and the pores of the second fired core The amount of silicon nitride produced as a binder is reduced, and the strength of the obtained third fired core is weak, which is not preferable. On the other hand, when the number average molecular weight Mn of perhydropolysilazane exceeds 2500, the hydrolyzability of perhydropolysilazane is promoted and the quality stability is deteriorated. Furthermore, in a perhydropolysilazane-containing liquid having a number average molecular weight Mn exceeding 2500, it is difficult to impregnate the pores of the second fired core, and the quality of the third fired core obtained varies, such as bending strength. Will become larger.
[0010]
The perhydropolysilazane-containing liquid used in the present invention is a solution obtained by dissolving the perhydropolysilazane with an organic solvent, and the perhydropolysilazane-containing liquid can be filled into the second fired core, and the organic solvent to be used is used. Is not particularly limited, and any of them can be used. Examples of the organic solvent to be used include aromatic solvents such as benzene, toluene, xylene, ether, THF, methylene chloride, carbon tetrachloride and the like.
[0011]
In the present invention, the first fired core is made from a blended composition containing at least a body material and an organic shaping material.
Any extender used in the present invention can be used as long as it is used in a conventional fired-type colored pencil lead. For example, white materials such as titanium oxide, mica, talc, boron nitride, silica, alumina, calcium carbonate, and colored materials such as molybdenum disulfide and tungsten disulfide can be used depending on the color of the ink to be filled. Of course, a mixture of several of these can also be used. Moreover, you may mix | blend a heat resistant pigment as needed.
[0012]
Examples of the organic shaping material include thermoplastic resins such as polyvinyl chloride resin, chlorinated polyvinyl chloride resin, and polyvinyl alcohol, thermosetting resins such as furan resin, phenol resin, and epoxy resin, lignin, and cellulose. In addition, natural polymer substances such as tragacanth gum, petroleum asphalt, coal tar pitch, naphtha cracked pitch, pitches such as dry distillation pitch of synthetic resin, etc. can be used, and naturally these several kinds of mixtures can also be used.
Furthermore, water, dioctyl phthalate (DOP), dibutyl phthalate (DBP), tricresyl phosphate (TCP), dioctyl adipate (DOA) for the purpose of improving the characteristics during kneading performed by applying a high shear force and the characteristics of extrusion molding. ), Or one or more of plasticizers or solvents of organic shaping materials such as propylene carbonate, alcohols, ketones, esters, etc., may be added to the above blended composition as necessary.
[0013]
These blended compositions are sufficiently kneaded with a Henschel mixer, a pressure kneader, two rolls, etc., and then extruded into a thin line shape by an extruder, and then non-exhaust in a nitrogen atmosphere or an inert gas such as argon gas. By firing in an oxidizing atmosphere, the organic shaped material is carbonized to form a first fired core with carbon as a binder.
In addition, in order to improve the strength and handleability of the second fired core, an inorganic binder such as clay, for example, bentonite, kaolinite, or the like is added to the composition for obtaining the first fired core as necessary. It can also mix | blend and it will become easy to express the intensity | strength by the silicon nitride mentioned later that the compounding quantity shall be less than 25 weight% in the said compounding composition.
Further, if necessary, the first fired core obtained above is impregnated with a perhydropolysilazane-containing liquid having a number average molecular weight Mn of 500 to 2500, and in an inert atmosphere such as a nitrogen atmosphere or in an ammonia gas atmosphere. It may be a fired core in which silicon nitride is generated by the heat treatment.
[0014]
The first fired core body formed above is heated in an oxidizing atmosphere to oxidize and remove the carbon binder, thereby forming a second fired core body made of a porous core body having a large number of pores.
Here, the pores of the second fired core body remove pores formed by firing a kneaded material composed of an extender and an organic shaping material in a non-oxidizing atmosphere, and the carbon binder. It is comprised from both the pores formed by this.
The adjustment of the porosity of the second fired core is mainly performed by adjusting the blending ratio of the organic shaping material. It doesn't matter. The amount of pores obtained by removing the carbon binder with respect to all pores is completely arbitrary.
[0015]
In the present invention, the third fired core is impregnated with a perhydropolysilazane-containing liquid having a number average molecular weight Mn of 500 to 2500 on the second fired core made of the porous core formed above, and then a nitrogen atmosphere or the like. Bonded to the second fired core by heat treatment at 400 ° C. or higher, preferably 600 ° C. or higher in an inert gas atmosphere or ammonia gas atmosphere, and at a temperature lower than the temperature causing thermal decomposition or dehydration of the extender. It is formed by generating silicon nitride as a material.
In the present invention, the heat treatment performed when forming the first fired core body, the second fired core body, and the third fired core body requires attention to the heat treatment temperature depending on the build material used. That is, in the heat treatment performed when carbonizing the organic shaping material and the like, the heat treatment performed when the carbon binder is oxidized and removed, and the heat treatment performed when the silicon nitride is formed, the contained constitutional materials are respectively included. If chemical changes such as decomposition or dehydration occur, the writing quality may be impaired or the strength may be deteriorated. Must be selected.
[0016]
As a method of impregnating the second calcined core with the perhydropolysilazane-containing liquid, the second calcined core is immersed in the perhydropolysilazane-containing liquid, and impregnated under conditions such as heating, reduced pressure, and pressure as necessary. Can be performed.
The obtained third fired core body is produced by finely and uniformly dispersing silicon nitride as a binder in the core body. Further, since the build material is highly oriented, a small amount of silicon nitride is produced. It is easy to express the strength of the core, and the collapse of the core during writing is uniform. In order to obtain a high-strength third fired core, impregnation with a perhydropolysilazane-containing liquid and firing may be repeated as necessary.
[0017]
In the present invention, the fired colored pencil lead is formed by filling ink into the pores of the third fired core formed as described above.
As the ink to be impregnated into the third fired core body, any conventionally known ink for color pencil cores can be used. For example, colorants such as dyes and pigments were dissolved and dispersed in animal and vegetable oils, synthetic oils, alcohols, hydrocarbon oils, water, etc., or further added with resins, surfactants, etc. as necessary. Commonly used printing ink, stamp ink, ballpoint pen ink, water-based writing ink, and the like are used.
As a method for impregnating the third fired core with ink, the third fired core is immersed in the ink and filled in the pores under conditions such as heating, decompression, and pressurization. Furthermore, repeated impregnation may be performed.
[0018]
The fired colored pencil lead thus configured is impregnated with a perhydropolysilazane-containing liquid having a number average molecular weight Mn of 500 to 2500 in the pores of the second fired core, and in an inert atmosphere such as a nitrogen atmosphere or ammonia Heat treatment in a gas atmosphere results in a structure in which ink is filled in the pores of the third fired core body in which silicon nitride is generated as a binder with little variation in quality. Excellent in strength, practically difficult to break, and an increased amount of ink filling results in a very good color development and at the same time a good writing quality.
[0019]
【Example】
EXAMPLES Next, although an Example demonstrates this invention further more concretely, this invention is not limited at all by this Example.
[0020]
Example 1
Boron nitride 50 parts by weight Vinyl chloride resin 50 parts by weight Dioctyl phthalate (DOP) 20 parts by weight Zinc stearate 1 part by weight The above composition was mixed and dispersed with a Henschel mixer, kneaded with a pressure kneader and two rolls, and then fine wire In order to remove the remaining plasticizer, heat treatment was performed at 180 ° C. in air, and then the temperature was raised to 1000 ° C. in a nitrogen atmosphere, followed by firing at 1000 ° C. A first fired core was obtained.
[0021]
Next, this first fired core was heated and fired at about 700 ° C. in an oxidizing atmosphere to remove the remaining carbonized resin, thereby obtaining a white second fired core.
This second fired core was impregnated with a perhydropolysilazane-containing liquid (20% xylene solution) having a number average molecular weight Mn of 1024 at room temperature for 1 day, and then heated to 600 ° C. in air, at 600 ° C. Firing was performed to obtain a fired core. Further, this fired core was impregnated with a perhydropolysilazane-containing liquid (20% xylene solution) having a number average molecular weight Mn of 1024 and fired twice to obtain a white third fired core having a diameter of 0.57 mm. Obtained.
Next, the third fired core was dipped in red ink and left at 70 ° C. for 24 hours. The surface of the third fired core body filled with the red ink was washed with alcohol to obtain a red fired colored pencil lead having a diameter of 0.57 mm.
[0022]
(Comparative Example 1)
In Example 1, a red fired colored pencil having a diameter of 0.57 mm was used in the same manner as in Example 1 except that the number average molecular weight Mn of the perhydropolysilazane-containing liquid (20% xylene solution) impregnated in the fired core was 312. I got a wick.
[0023]
(Comparative Example 2)
In Example 1, a red calcined colored pencil having a diameter of 0.57 mm was used in the same manner as in Example 1 except that the number average molecular weight Mn of the perhydropolysilazane-containing liquid (20% xylene solution) impregnated in the calcined core was 3613. I got a wick.
[0024]
About the baked colored pencil lead obtained in Example 1 and Comparative Examples 1 and 2, bending strength (MPa), bending strength standard deviation (MPa), and sensory evaluation based on JIS-S-6005-1989 evaluated.
These results are shown in Table 1 below.
[0025]
[Table 1]

[0026]
As apparent from the results of Table 1 above, the fired colored pencil lead of Example 1 within the scope of the present invention has the same repeated impregnation and firing times compared to Comparative Examples 1 and 2, which are outside the scope of the present invention. It has been found that the bending strength is strong, and there is little variation in the bending strength from the standard deviation of the bending strength, and a fired colored pencil lead with very good writing quality can be obtained.
[0027]
【The invention's effect】
The fired colored pencil core of the present invention has a structure in which ink is filled in the pores of the fired core body in which silicon nitride having a small variation in quality is produced as a binder, so that it has excellent mechanical strength even if the porosity is large. In practice, it is difficult to break, and the ink filling amount increases, so that an extremely excellent color can be obtained, and at the same time, a good writing quality can be obtained.

Claims

A first fired core comprising carbon as a binder obtained by carbonizing the organic shaped material by kneading, extruding, and firing in a non-oxidizing atmosphere a blended composition containing at least a body material and an organic shaped material. And forming a second fired core made of at least a build material obtained by heating the first fired core in an oxidizing atmosphere to oxidize and remove the carbon binder, and in the pores of the second fired core Silicon nitride is generated in the pores of the second fired core by impregnating a perhydropolysilazane-containing liquid having a number average molecular weight Mn of 500 to 2500 and heat-treating it in an inert atmosphere such as a nitrogen atmosphere or in an ammonia gas atmosphere. A fired colored pencil lead formed by forming a third fired fired core and filling the pores of the third fired core with ink.