JP2011246676A

JP2011246676A - Fired pencil lead

Info

Publication number: JP2011246676A
Application number: JP2010124022A
Authority: JP
Inventors: Jun Yoshimori; 潤吉森
Original assignee: Pentel Co Ltd
Current assignee: Pentel Co Ltd
Priority date: 2010-05-31
Filing date: 2010-05-31
Publication date: 2011-12-08

Abstract

PROBLEM TO BE SOLVED: To provide a fired pencil lead which is obtained by subjecting at least an inorganic extender and/or an inorganic additive and an organic binder to kneading, extrusion molding in a thin line shape and heat treatment to a firing temperature, although when inorganic particles are used, uniform dispersion of the particles in an organic binder is difficult and the particles are liable to segregate in the material.SOLUTION: The fired pencil lead which ensures more uniform dispersion and smaller variation of bending strength for each lead is provided while suppressing production costs low by using inorganic particles hydrophobized preliminarily with one or more selected from alcohols, aldehydes, ethers, ketones, carboxylic acids and esters each capable of forming a hydrogen bond with a hydroxyl group.

Description

本発明は、少なくとも無機体質材及び又は無機添加剤と有機結合材とを、混練、細線状に押出成形後、焼成温度まで熱処理を施し得られる焼成鉛筆芯に関する。 The present invention relates to a fired pencil lead which can be subjected to heat treatment up to a firing temperature after kneading and extrusion molding at least an inorganic extender and / or an inorganic additive and an organic binder into a fine line.

一般的に鉛筆芯は、黒鉛や窒化ホウ素、タルク、マイカ、カーボンブラックなどの無機体質材及び又は無機添加剤と、粘土、界面活性剤及び可塑剤としての水などを混合及び混練し、細線状に成形した後、高温で焼成し、得られた焼結体に必要に応じて油状物を含浸させてなる粘土タイプの芯と、前記無機体質材及び又は無機添加剤と、有機結合材としての合成又は天然樹脂、可塑剤、無機添加剤などを混合及び混練し、細線状に成形した後、非酸化雰囲気中にて高温で焼成し樹脂を炭素化し、得られた焼成体に必要に応じて油状物を含浸させてなる樹脂タイプの芯に大別される。
後者の樹脂タイプの鉛筆芯は、大きな強度が得られることから主としてシャープペンシル用に使われており、黒鉛、窒化ホウ素、タルクなどの無機体質材と、ポリ塩化ビニル、ポリ塩化ビニリデン、塩素化ポリエチレン、尿素樹脂、メラミン樹脂、フラン樹脂、ポリビニルアルコール、ポリアクリルアミド、ブチルゴムといった有機結合材とを主材として使用し、必要に応じてフタル酸エステルなどの可塑剤、メチルエチルケトン、水などの溶剤、ステアリン酸塩などの安定剤、ステアリン酸などの滑材、カーボンブラック、無定形シリカといった充填効果のある無機微粉末を添加剤として併用している。
押出成形時の芯径を種々選択することにより目的の芯径の芯体を得ることができ、また配合や焼成温度を変えることなどにより、目的の硬度（濃度）の芯体を得ることもできるが、基本的に濃い筆跡と、筆記時に加わる力や落下した際の衝撃などで折れない強さ、すなわち曲げ強さとの両立が求められる。
鉛筆芯の体質材には前述したように、黒鉛、窒化ホウ素、タルクなどが一般的に使用されているが、中でも扁平状黒鉛は、細線状に芯体を成形する際に押出方向に配向することで芯体の強度を向上させ、また、その高い劈開性により紙面への摩耗筆記を可能にさせる。ところが、黒鉛粒子のベーサル面は不活性で光の反射が大きいため、筆記線が黒色ではなく鉛色に見える。
光の反射を軽減させて筆記線をより黒く見せる為に、窒化ホウ素やタルク、天然雲母、板状アルミナなど、黒鉛以外の結晶質板状粒子を体質材として併用する方法が知られている。これら黒鉛以外の体質材には、焼成のために炭化した有機結合材が付着し黒色化し、黒鉛表面を覆うことで黒鉛の光の反射を軽減し黒く見える効果がある。
しかしこのような結晶質板状粒子は、結晶表面の活性が低く、有機結合材の炭化物の付着量が十分ではないため、筆記線の黒さを上げるには限界があった。また、鉛筆芯は黒鉛の配向構造が芯体の曲げ強さを向上させているが、結晶質板状粒子のように配向可能な黒鉛以外の材料と、黒鉛との複合配向構造は、黒鉛が単独で形成する構造よりも強度が低く、黒鉛単独使用の場合よりも鉛筆芯の曲げ強さが低下するのが一般的であった。
これに対し本願発明者らは、体質材として少なくとも無機非晶質板状粒子を使用すると、黒鉛以外の結晶質板状粒子を用いることで生じる問題を回避し、曲げ強さと筆記線の黒さと濃度とのバランスに優れた鉛筆芯が得られることを見出した（特許文献１参照）。 In general, the pencil lead is a fine line-shaped material that is made by mixing and kneading inorganic constituents such as graphite, boron nitride, talc, mica, carbon black and / or inorganic additives with water as clay, surfactant and plasticizer. After molding into a clay-type core obtained by firing at a high temperature and impregnating the obtained sintered body with an oil as necessary, the inorganic extender and / or the inorganic additive, and the organic binder Synthetic or natural resins, plasticizers, inorganic additives, etc. are mixed and kneaded, formed into fine wires, and then fired at high temperature in a non-oxidizing atmosphere to carbonize the resin. Roughly divided into resin-type cores impregnated with oil.
The latter resin-type pencil lead is mainly used for mechanical pencils because of its high strength, and is composed of inorganic materials such as graphite, boron nitride, and talc, polyvinyl chloride, polyvinylidene chloride, and chlorinated polyethylene. Organic binders such as urea resin, melamine resin, furan resin, polyvinyl alcohol, polyacrylamide, and butyl rubber are used as main materials, and plasticizers such as phthalate esters, solvents such as methyl ethyl ketone and water, stearic acid as necessary Stabilizers such as salts, lubricants such as stearic acid, inorganic fine powders having a filling effect such as carbon black and amorphous silica are used as additives.
A core body having a target core diameter can be obtained by variously selecting a core diameter at the time of extrusion molding, and a core body having a target hardness (concentration) can also be obtained by changing the blending or firing temperature. However, it is basically required to have both a strong handwriting and a strength that does not break due to a force applied at the time of writing or an impact when dropped, that is, a bending strength.
As described above, graphite, boron nitride, talc and the like are generally used as the material for the pencil core, but flat graphite is oriented in the extrusion direction when the core is formed into a thin wire. As a result, the strength of the core is improved, and the high cleaving property enables wear writing on the paper surface. However, since the basal surface of the graphite particles is inactive and the reflection of light is large, the writing lines appear to be lead color instead of black.
In order to reduce the reflection of light and make the writing line appear blacker, a method is known in which crystalline plate-like particles other than graphite, such as boron nitride, talc, natural mica, and plate-like alumina, are used in combination. These extender materials other than graphite have an effect that the organic binder carbonized for firing adheres and becomes black, and covers the surface of the graphite to reduce the reflection of light of the graphite so that it looks black.
However, such crystalline plate-like particles have a low crystal surface activity and an insufficient amount of carbide adhering to the organic binder, so there is a limit to increasing the blackness of the writing lines. In addition, the pencil core has a graphite orientation structure that improves the bending strength of the core, but the composite orientation structure of graphite and a material other than graphite that can be oriented, such as crystalline plate-like particles, In general, the strength is lower than the structure formed alone, and the bending strength of the pencil core is generally lower than when graphite is used alone.
On the other hand, the inventors of the present application avoid the problems caused by using crystalline plate-like particles other than graphite when at least inorganic amorphous plate-like particles are used as the extender, and the bending strength and blackness of the writing line. It has been found that a pencil lead excellent in balance with density can be obtained (see Patent Document 1).

しかしながら、単に無機非晶質板状粒子を体質材として使用しただけでは、粒子が自身の表面水酸基により疎水性の有機結合材と親和性が乏しく、凝集し易い。すなわち有機結合材中への分散性が悪く材料中に偏析してしまうことがあり、得られた芯体の曲げ強さが芯毎にばらつくこともあった。 However, simply using inorganic amorphous plate-like particles as a constitutional material causes the particles to have a poor affinity with a hydrophobic organic binder due to their surface hydroxyl groups and easily aggregate. That is, the dispersibility in the organic binder is poor and segregation may occur in the material, and the bending strength of the obtained core may vary from core to core.

一方、特許文献２には、充填材として一般的には親水性の無定形シリカを使用する際に発生する分散不均一性を解決するために、無定形シリカの表面を化学反応により疎水化して使用することが開示されている。 On the other hand, in Patent Document 2, in order to solve the dispersion non-uniformity generally generated when hydrophilic amorphous silica is used as a filler, the surface of amorphous silica is hydrophobized by a chemical reaction. It is disclosed to use.

（特許文献１）特開２００９−２２８００２号公報
（特許文献２）特開２００４−１７５９００号公報 (Patent Document 1) JP 2009-228002 A (Patent Document 2) JP 2004-175900 A

しかし、特許文献２に記載の疎水化方法は、窒素等の不活性ガスで満たされた４００℃前後の反応器内で、ガス状の疎水化剤と水蒸気と共に被疎水化粒子を攪拌するものである。この疎水化反応では非疎水化粒子と疎水化剤との結合反応の際に分離ガスが発生するため、ガス回収装置が欠かせない。さらにメチルクロロシランなど疎水化剤の種類によっては、強酸性の塩化水素ガス発生により機器劣化が促進される。したがって、無定形シリカに限らず種々の無機体質材及び又は無機添加剤の疎水化処理に用いようとした場合、反応ラインやガス回収ラインの設置、メンテナンスなどのコストがかかる点で問題があり、この問題を回避しながらも、有機結合材中への分散不均一性を改善し、曲げ強さのばらつきがより小さい鉛筆芯を得ることが望まれていた。 However, the hydrophobization method described in Patent Document 2 stirs the particles to be hydrophobized with a gaseous hydrophobizing agent and water vapor in a reactor at about 400 ° C. filled with an inert gas such as nitrogen. is there. In this hydrophobization reaction, a separation gas is generated during the binding reaction between the non-hydrophobized particles and the hydrophobizing agent, so that a gas recovery device is indispensable. Furthermore, depending on the type of hydrophobizing agent such as methylchlorosilane, deterioration of equipment is promoted by the generation of strongly acidic hydrogen chloride gas. Therefore, not only amorphous silica but also various inorganic extenders and / or inorganic additives are used for hydrophobizing treatment, there is a problem in terms of cost of installation and maintenance of reaction lines and gas recovery lines, While avoiding this problem, it has been desired to improve the non-uniformity of dispersion in the organic binder and to obtain a pencil lead with less variation in bending strength.

本発明は、少なくとも無機体質材及び又は無機添加剤と有機結合材とを、混練、細線状に押出成形後、焼成温度まで熱処理を施し得られる鉛筆芯において、予め、水酸基と水素結合可能な、アルコール類、エーテル類、アルデヒド類、ケトン類、カルボン酸類、エステル類から選ばれる１種又は２種以上とにより疎水化処理を施した無機粒子を含有することを特徴とする鉛筆芯を要旨とする。 The present invention is capable of hydrogen bonding with a hydroxyl group in advance in a pencil core obtained by kneading at least an inorganic extender material and / or an inorganic additive and an organic binder, extruding into a fine wire shape, and then subjecting to a firing temperature. A gist is a pencil lead characterized by containing inorganic particles that have been subjected to a hydrophobic treatment with one or more selected from alcohols, ethers, aldehydes, ketones, carboxylic acids, and esters. .

予め、水酸基と水素結合可能な、アルコール類、アルデヒド類、エーテル類、ケトン類、カルボン酸類、エステル類から選ばれる１種又は２種以上の溶液中に浸漬して攪拌後、乾燥処理を施すことで疎水化した無機粒子を鉛筆芯の無機体質材及び又は無機添加剤として使用することが出来る。水素結合による疎水化は分離ガスの発生が無い為、製造コストを大幅に軽減させながら、疎水性の無機粒子を得ることが出来る。得られた疎水性の無機粒子は芯体中で、疎水性の有機結合材や黒鉛などと馴染み易くなる。また、表面水酸基の極性が水素結合により抑えられていることで無機粒子には電気的な作用反作用が働き難く、電荷の偏りを持つ材料を核に凝集することも無い。よって、材料中の分散性がよくなって芯体の曲げ強さのばらつきが小さい芯が得られるものと推察する。
特に、無機体質材及び又は無機添加剤として上記疎水化処理を施した非晶質板状粒子を使用することにより、曲げ強さと筆記線の黒さと濃度とのバランスに優れた鉛筆芯が得られる。 Preliminarily dipping in one or more solutions selected from alcohols, aldehydes, ethers, ketones, carboxylic acids, and esters capable of hydrogen bonding with hydroxyl groups, stirring, and then drying. The inorganic particles hydrophobized with can be used as a pencil core inorganic extender and / or an inorganic additive. Hydrophobing by hydrogen bonding does not generate a separation gas, so that hydrophobic inorganic particles can be obtained while greatly reducing the manufacturing cost. The obtained hydrophobic inorganic particles are easily compatible with the hydrophobic organic binder, graphite and the like in the core. In addition, since the polarity of the surface hydroxyl group is suppressed by hydrogen bonding, the electrical action and reaction of the inorganic particles are difficult to work, and a material having a charge bias does not aggregate into the nucleus. Therefore, it is presumed that a dispersibility in the material is improved and a core with a small variation in the bending strength of the core is obtained.
In particular, by using the amorphous plate-like particles subjected to the above-described hydrophobization treatment as an inorganic extender and / or an inorganic additive, a pencil core having an excellent balance between bending strength, writing line blackness and density can be obtained. .

以下、本発明を詳細に説明する。
無機粒子の疎水化処理に用いる、アルコール類、エーテル類、アルデヒド類、ケトン類、カルボン酸類、エステル類は、水酸基と水素結合でき、水素結合後に無機粒子へ疎水性を与えるものであれば特に限定されない。
具体的には、アルコール類として、メタノール、エタノール、プロパノール、プロパノール、ブタノール、エーテル類として、ジエチルエーテル、ジエチレングリコールジメチルエーテル、ジエチレングリコールエチルメチルエーテル、テトラヒドロフラン、アルデヒド類として、アセトアルデヒド、プロピオンアルデヒド、ビニルアルデヒド、ベンズアルデヒド、ケトン類として、アセトン、メチルエチルケトン、ジエチルケトン、メチルイソブチルケトン、カルボン酸類として、エタン酸、プロパン酸、エステル類として酪酸メチル、サリチル酸メチル等が挙げられる。これらの溶剤は単独で用いても良いし、また、これらの中から２種以上を混合した溶剤を用いても良い。 Hereinafter, the present invention will be described in detail.
Alcohols, ethers, aldehydes, ketones, carboxylic acids, and esters used for the hydrophobic treatment of inorganic particles are particularly limited as long as they can hydrogen bond with hydroxyl groups and give hydrophobic properties to inorganic particles after hydrogen bonding. Not.
Specifically, as alcohols, methanol, ethanol, propanol, propanol, butanol, ethers, diethyl ether, diethylene glycol dimethyl ether, diethylene glycol ethyl methyl ether, tetrahydrofuran, aldehydes, acetaldehyde, propionaldehyde, vinyl aldehyde, benzaldehyde, Examples of ketones include acetone, methyl ethyl ketone, diethyl ketone, methyl isobutyl ketone, carboxylic acids such as ethanoic acid, propanoic acid, and esters such as methyl butyrate and methyl salicylate. These solvents may be used alone, or a solvent in which two or more of these solvents are mixed may be used.

予め、水酸基と水素結合可能な、アルコール類、アルデヒド類、エーテル類、ケトン類、カルボン酸類、エステル類から選ばれる１種又は２種以上とにより無機粒子を疎水化させる方法は、前述の通り、化合物の溶液中に無機粒子を浸漬して攪拌後、乾燥処理をすればよい。攪拌時には、用いる化合物に応じて加熱をして反応を促進させても良い。
また、疎水化処理を施す無機粒子は、非晶質シリカ、合成雲母、アルミナ、酸化チタンなど焼成鉛筆芯の体質材及び又は無機添加剤として一般に用いられる無機粒子の中において、親水性を有するものであれば特に限定することなく使用することができるが、中でも無機非晶質板状粒子として劈開性のある非晶質劈開性板状シリカが特に好ましく用いられる。非晶質劈開性板状シリカは、バーミキュライトを酸処理して、シロキサンと結合していた金属元素など大量に含まれる不純物を除去することで得られるが、不純物除去の際にシロキサンと金属元素の結合が切れる為、電荷の偏りが生じる。そこに周囲の水分が反応して水酸基を作る。したがって他の無機粒子に比べて水酸基が多く存在することから、疎水化後の表面には水素結合した化合物が多く存在して有機結合材中への馴染みがより良くなるので、分散の効果がより得やすい。
疎水化処理を施す無機粒子の市販品の具体例としては、非晶質シリカとして、アエロジル９０、同１３０、同１５０、同２００、同３００、同３８０、同ＯＸ５０、同ＥＧ５０、同ＴＴ６００、同２００ＳＰ、同３００ＳＰ（以上、日本アエロジル（株）製）、レオロシールＱＳ−１０２（（株）トクヤマ製）、合成雲母として、ソマシフＭＥ−１００（コープケミカル（株）製）、アルミナとして、セラフ００６１０、同０２０２５、同０２０５０、同０５０２５、同０５０７０、同０７０７０、同１００３０（以上、キンセイマテック（株）製）、酸化チタンとして、ＴＴＯ−５１（Ａ）、ＴＴＯ−５５（Ａ），ＴＴＯ−５５（Ｂ）、ＴＴＯ−５５（Ｄ）、ＴＴＯ−Ｓ−１、ＴＴＯ−Ｓ−３、ＴＴＯ−Ｖ−３（以上、石原産業（株）製）などが挙げられ、また非晶質劈開性板状シリカとして、シルリーフ（水澤化学（株）製）が挙げられる。 The method for hydrophobizing inorganic particles with one or more selected from alcohols, aldehydes, ethers, ketones, carboxylic acids, and esters that can be hydrogen-bonded to a hydroxyl group in advance is as described above. What is necessary is just to dry-process, after immersing an inorganic particle in the solution of a compound and stirring. During stirring, the reaction may be promoted by heating according to the compound used.
The inorganic particles to be subjected to the hydrophobizing treatment are hydrophilic among the inorganic particles generally used as a build material and / or inorganic additive of a baked pencil core such as amorphous silica, synthetic mica, alumina, and titanium oxide. Can be used without any particular limitation, but among them, amorphous cleaved plate-like silica having a cleavage property as inorganic amorphous plate-like particles is particularly preferably used. Amorphous cleaved plate-like silica is obtained by acid-treating vermiculite to remove impurities contained in large quantities such as metal elements bonded to siloxane. Since the bond is broken, the charge is biased. The surrounding moisture reacts to form hydroxyl groups. Therefore, since there are more hydroxyl groups than other inorganic particles, there are many hydrogen-bonded compounds on the surface after hydrophobization, and the familiarity into the organic binder becomes better, so the dispersion effect is more effective. Easy to get.
Specific examples of commercially available inorganic particles subjected to hydrophobizing treatment include amorphous silica, Aerosil 90, 130, 150, 200, 300, 380, OX50, EG50, TT600, 200SP, 300SP (manufactured by Nippon Aerosil Co., Ltd.), Leorosil QS-102 (manufactured by Tokuyama Co., Ltd.), synthetic mica, Somasif ME-100 (manufactured by Coop Chemical Co., Ltd.), alumina as Seraph 0700, 02025, 02050, 05025, 05070, 07070, 10070 (above, manufactured by Kinsei Matec Co., Ltd.), titanium oxide, TTO-51 (A), TTO-55 (A), TTO-55 ( B), TTO-55 (D), TTO-S-1, TTO-S-3, TTO-V-3 (above, manufactured by Ishihara Sangyo Co., Ltd.) Etc. can be mentioned, and as amorphous cleavage plate-like silica, Shirurifu (Mizusawa Kagaku Co.) and the like.

上記以外の使用原材料としては、従来用いられている構成材料を限定なく用いることができる。また、従来公知の製造方法を限定なく用いて製造することができる。 As the raw materials other than those described above, conventionally used constituent materials can be used without limitation. Moreover, it can manufacture using a conventionally well-known manufacturing method without limitation.

黒鉛や窒化硼素等の各種無機体質材及び又は無機添加剤と、各種合成樹脂などを結合材として使用し、必要に応じて使用される着色材、気孔形成材、可塑剤、溶剤などと共にニーダー、ヘンシェルミキサー、３本ロールなどで均一分散させ、押し出し成形後、８００℃〜１３００℃で高温焼成して得られる。 Various inorganic extenders and / or inorganic additives such as graphite and boron nitride, various synthetic resins, etc. are used as binders, kneaders together with coloring materials, pore forming materials, plasticizers, solvents, etc. It is obtained by uniform dispersion with a Henschel mixer, three rolls, etc., extrusion molding, and high-temperature firing at 800 ° C. to 1300 ° C.

具体的には、ポリ塩化ビニル、ポリ塩化ビニリデン、ポリ酢酸ビニル、塩素化ポリエチレン、フラン樹脂、ポリアクリルアミド、塩素化パラフィン、尿素樹脂、などの有機結合材を結合材として使用し、黒鉛、窒化硼素、タルク、雲母などの無機体質材及び又は無機添加剤、必要に応じて使用される有機顔料や無機顔料などの着色材、フタル酸ジオクチル（ＤＯＰ）、フタル酸ジブチル（ＤＢＰ）などの可塑剤、ケトン、芳香族炭化水素などの溶剤と共にニーダー、ヘンシェルミキサー、３本ロールなどで均一分散させた後に細線状に成形し、空気中で室温から３００℃前後までの熱処理を施し、その後不活性雰囲気中で８００℃〜１３００℃の焼成処理を施して黒色の焼成鉛筆芯を得る。さらにシリコーン油、流動パラフィン、スピンドル油といった油状物や、パラフィンワックス、マイクロクリスタリンワックス、ポリエチレンワックス、モンタンワックス、カルナバワックスといったワックス類を含浸させて製造する。 Specifically, organic binders such as polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, chlorinated polyethylene, furan resin, polyacrylamide, chlorinated paraffin, and urea resin are used as the binder, graphite, boron nitride Inorganic materials such as talc and mica and / or inorganic additives, colorants such as organic pigments and inorganic pigments used as necessary, plasticizers such as dioctyl phthalate (DOP) and dibutyl phthalate (DBP), After being uniformly dispersed with a kneader, Henschel mixer, 3 rolls, etc. together with solvents such as ketones and aromatic hydrocarbons, it is formed into a thin wire, heat treated from room temperature to around 300 ° C. in air, and then in an inert atmosphere A baking treatment at 800 ° C. to 1300 ° C. is performed to obtain a black fired pencil lead. Furthermore, it is produced by impregnating oils such as silicone oil, liquid paraffin and spindle oil, and waxes such as paraffin wax, microcrystalline wax, polyethylene wax, montan wax and carnauba wax.

以下、実施例を挙げて本発明を更に説明するが、本発明はこれら実施例に限定されるものではない。
（実施例１）
＜無機粒子の疎水化処理＞
メタノール（関東化学（株）製）に、無機非晶質板状粒子のシルリーフ（水澤化学工業（株）製）の非晶質劈開性板状シリカ（平均粒子径：６μｍ（レーザ回折散乱法における測定値））を浸漬、攪拌後に濾過して１２０℃のオーブンで乾燥し、疎水化したシルリーフを得た。処理前後のシルリーフの重量測定の結果、シルリーフに付着したメタノールは、シルリーフに対して０．５重量％であった。
＜焼成鉛筆芯の作製＞
ポリ塩化ビニル樹脂５５重量部
上記疎水化処理したシルリーフ３重量部
黒鉛７０重量部
フタル酸ジオクチル２５重量部
ステアリン酸塩２重量部
ステアリン酸１重量部
メチルエチルケトン２０重量部
上記材料をヘンシェルミキサーによる分散混合処理、３本ロールによる混練処理をした後、細線状に押出成形し、空気中で室温から３００℃まで約１０時間かけて昇温し、３００℃で約１時間保持する加熱処理をし、更に、密閉容器中で１１００℃を最高とする焼成処理を施し、冷却後、流動パラフィンを含浸させて、呼び径０．５の鉛筆芯を得た。
（実施例２）
実施例１において、メタノールをジエチレングリコールエチルメチルエーテル（東邦化学工業（株）製）として疎水化処理した以外は、実施例１と同様にして、呼び径０．５の鉛筆芯を得た。
（実施例３）
実施例１において、メタノールをベンズアルデヒド（昭和化学（株）製）として疎水化処理した以外は、実施例１と同様にして、呼び径０．５の鉛筆芯を得た。
（実施例４）
実施例１において、メタノールをメチルイソブチルケトン（三協化学（株）製）として疎水化処理した以外は、実施例１と同様にして、呼び径０．５の鉛筆芯を得た。
（実施例５）
実施例１において、メタノールをエタン酸（和光純薬工業（株）製）として疎水化処理した以外は、実施例１と同様にして、呼び径０．５の鉛筆芯を得た。
（実施例６）
実施例１において、メタノールをサリチル酸メチル（昭和化学（株）製）として疎水化処理した以外は、実施例１と同様にして、呼び径０．５の鉛筆芯を得た。
（実施例７）
実施例１において、シルリーフをアエロジル２００（非晶質球状シリカ、平均粒子径：１２ｎｍ、日本アエロジル（株）製）に変えて疎水化処理した以外は、実施例１と同様にして、呼び径０．５の鉛筆芯を得た。
（実施例８）
実施例１において、シルリーフをセラフ０５０２５（結晶質板状アルミナ、平均粒子径：５μｍ、キンセイマテック（株）製）に変えて疎水化処理した以外は、実施例１と同様にして、呼び径０．５の鉛筆芯を得た。
（実施例９）
実施例１において、シルリーフをＴＴＯ−５５（Ａ）（結晶質柱状酸化チタン、粒子径：０．０３〜０．０５μｍ、石原産業（株）製）に変えて疎水化処理した以外は、実施例１と同様にして、呼び径０．５の鉛筆芯を得た。
（実施例１０）
実施例１において、焼成鉛筆芯の作製時に用いる、疎水化処理したシルリーフの使用量を１重量部に変え、黒鉛の使用量を７２重量部に変えた以外、すべて実施例１と同様にして、呼び径０．５の鉛筆芯を得た。
（実施例１１）
実施例１において、焼成鉛筆芯の作製時に用いる、疎水化処理したシルリーフの使用量を１０重量部に変え、黒鉛の使用量を６３重量部に変えた以外、すべて実施例１と同様にして、呼び径０．５の鉛筆芯を得た。
（実施例１２）
実施例１において、焼成鉛筆芯の作製時に用いる、疎水化処理したシルリーフの使用量を３０重量部に変え、黒鉛の使用量を４３重量部に変えた以外、すべて実施例１と同様にして、呼び径０．５の鉛筆芯を得た。
（実施例１３）
実施例１において、メタノールをメタノールとベンズアルデヒドとの混合溶液（混合比＝１：１）として疎水化処理した以外は、実施例１と同様にして、呼び径０．５の鉛筆芯を得た。
（実施例１４）
実施例１において、メタノールをエタン酸とサリチル酸メチルとの混合溶液（混合比＝２：３）として疎水化処理した以外は、実施例１と同様にして、呼び径０．５の鉛筆芯を得た。
（比較例１）
実施例１において、メタノールにより疎水化したシルリーフに変えて、疎水化処理を施していないシルリーフを焼成鉛筆芯の作製時に用いた以外、すべて実施例１と同様にして、呼び径０．５の鉛筆芯を得た。
（比較例２）
実施例１において、メタノールに変えてメチルシクロヘキサン（三協化学（株）製）を用いて疎水化処理した以外、すべて実施例１と同様にして、呼び径０．５の鉛筆芯を得た。
（比較例３）
実施例１において、メタノールに変えてエチルベンゼン（和光純薬工業（株）製）を用いて疎水化処理した以外、すべて実施例１と同様にして、呼び径０．５の鉛筆芯を得た。
（比較例４）
実施例１において、メタノールにより疎水化したシルリーフに変えて、疎水化処理を施していないアエロジル２００を焼成鉛筆芯の作製時に用いた以外は、実施例１と同様にして、呼び径０．５の鉛筆芯を得た。
（比較例５）
実施例１において、メタノールにより疎水化したシルリーフに変えて、疎水化処理を施していないセラフ０５０２５を焼成鉛筆芯の作製時に用いた以外は、実施例１と同様にして、呼び径０．５の鉛筆芯を得た。
（比較例６）
実施例１において、メタノールにより疎水化したシルリーフに変えて、疎水化処理を施していないＴＴＯ−５５（Ａ）を焼成鉛筆芯の作製時に用いた以外は、実施例１と同様にして、呼び径０．５の鉛筆芯を得た。
（比較例７）
実施例１０において、疎水化処理したシルリーフに変え、疎水化処理を施していないシルリーフを焼成鉛筆芯の作製時に用いた以外は、実施例１０と同様にして、呼び径０．５の鉛筆芯を得た。
（比較例８）
実施例１１において、疎水化処理したシルリーフに変え、疎水化処理を施していないシルリーフを焼成鉛筆芯の作製時に用いた以外は、実施例１１と同様にして、呼び径０．５の鉛筆芯を得た。
（比較例９）
実施例１２において、疎水化処理したシルリーフに変え、疎水化処理を施していないシルリーフを焼成鉛筆芯の作製時に用いた以外は、実施例１２と同様にして、呼び径０．５の鉛筆芯を得た。
以上、各実施例及び比較例で得た鉛筆芯各々１００本ずつについて、ＪＩＳＳ６００５に準じて曲げ強さと筆跡濃度を測定し、曲げ強さについては、ばらつきの評価として標準偏差σを算出した。黒さの評価としてＹ値も測定した。その結果を表１に示す。
Ｙ値は、荷重５００ｇで上質紙に均一に面塗りしたものを、ＳＰＥＣＴＲＯＰＨＯＴＯＭＥＴＥＲ「ＣＭ−３７００ｄ」（コニカミノルタホールディングス（株）製）で測定した。Ｙ値は小さいほど黒さのあること示す。 EXAMPLES Hereinafter, although an Example is given and this invention is further demonstrated, this invention is not limited to these Examples.
Example 1
<Hydrophobic treatment of inorganic particles>
Methanol (manufactured by Kanto Chemical Co., Inc.), amorphous cleaved plate silica (average particle size: 6 μm (in the laser diffraction scattering method) of silaleaf (produced by Mizusawa Chemical Co., Ltd.) of inorganic amorphous plate-like particles Measurement value)) was soaked and stirred and then filtered and dried in an oven at 120 ° C. to obtain a hydrophobized sylleaf. As a result of measuring the weight of the sill leaf before and after the treatment, the amount of methanol adhering to the sill leaf was 0.5% by weight with respect to the sill leaf.
<Production of fired pencil lead>
Polyvinyl chloride resin 55 parts by weight Hydrophobized silleaf 3 parts by weight Graphite 70 parts by weight Dioctyl phthalate 25 parts by weight Stearic acid salt 2 parts by weight Stearic acid 1 part by weight Methyl ethyl ketone 20 parts by weight Dispersing and mixing the above materials with a Henschel mixer After kneading with three rolls, it was extruded into a thin line, heated from room temperature to 300 ° C. in air over about 10 hours, and heated at 300 ° C. for about 1 hour, A baking treatment at a maximum of 1100 ° C. was performed in a sealed container, and after cooling, liquid paraffin was impregnated to obtain a pencil lead having a nominal diameter of 0.5.
(Example 2)
In Example 1, a pencil lead having a nominal diameter of 0.5 was obtained in the same manner as in Example 1 except that methanol was subjected to a hydrophobization treatment using diethylene glycol ethyl methyl ether (manufactured by Toho Chemical Industry Co., Ltd.).
(Example 3)
In Example 1, a pencil lead having a nominal diameter of 0.5 was obtained in the same manner as in Example 1 except that the hydrophobization treatment was performed using methanol as benzaldehyde (manufactured by Showa Chemical Co., Ltd.).
Example 4
In Example 1, a pencil lead having a nominal diameter of 0.5 was obtained in the same manner as in Example 1 except that methanol was hydrophobized with methyl isobutyl ketone (manufactured by Sankyo Chemical Co., Ltd.).
(Example 5)
In Example 1, a pencil lead having a nominal diameter of 0.5 was obtained in the same manner as in Example 1 except that methanol was treated with ethanoic acid (manufactured by Wako Pure Chemical Industries, Ltd.) as a hydrophobic treatment.
(Example 6)
In Example 1, a pencil lead having a nominal diameter of 0.5 was obtained in the same manner as in Example 1 except that methanol was hydrophobized as methyl salicylate (manufactured by Showa Chemical Co., Ltd.).
(Example 7)
In Example 1, the nominal diameter was 0 in the same manner as in Example 1, except that the silleaf was changed to Aerosil 200 (amorphous spherical silica, average particle size: 12 nm, manufactured by Nippon Aerosil Co., Ltd.) and subjected to hydrophobic treatment. A pencil lead of .5 was obtained.
(Example 8)
In Example 1, the nominal diameter was 0 in the same manner as in Example 1 except that the sill leaf was changed to Seraph 05025 (crystalline plate-like alumina, average particle size: 5 μm, manufactured by Kinsei Matec Co., Ltd.) and subjected to hydrophobic treatment. A pencil lead of .5 was obtained.
Example 9
In Example 1, except that the sill leaf was changed to TTO-55 (A) (crystalline columnar titanium oxide, particle diameter: 0.03 to 0.05 μm, manufactured by Ishihara Sangyo Co., Ltd.) and subjected to a hydrophobic treatment. In the same manner as in Example 1, a pencil lead having a nominal diameter of 0.5 was obtained.
(Example 10)
In Example 1, except that the amount of hydrophobized sylleaf used at the time of preparation of the fired pencil lead was changed to 1 part by weight and the amount of graphite used was changed to 72 parts by weight, all in the same manner as in Example 1, A pencil lead with a nominal diameter of 0.5 was obtained.
(Example 11)
In Example 1, except that the amount of hydrophobized sylleaf used in the preparation of the fired pencil lead was changed to 10 parts by weight and the amount of graphite used was changed to 63 parts by weight, all in the same manner as in Example 1, A pencil lead with a nominal diameter of 0.5 was obtained.
(Example 12)
In Example 1, except that the amount of hydrophobized sylleaf used at the time of preparation of the fired pencil lead was changed to 30 parts by weight and the amount of graphite used was changed to 43 parts by weight, all in the same manner as in Example 1, A pencil lead with a nominal diameter of 0.5 was obtained.
(Example 13)
In Example 1, a pencil lead having a nominal diameter of 0.5 was obtained in the same manner as in Example 1 except that methanol was hydrophobized as a mixed solution of methanol and benzaldehyde (mixing ratio = 1: 1).
(Example 14)
In Example 1, a pencil lead having a nominal diameter of 0.5 was obtained in the same manner as in Example 1 except that methanol was hydrophobized as a mixed solution of ethanoic acid and methyl salicylate (mixing ratio = 2: 3). It was.
(Comparative Example 1)
In Example 1, a pencil having a nominal diameter of 0.5 was used in the same manner as in Example 1 except that a silleaf that had not been hydrophobized was used in the preparation of the fired pencil lead in place of the silleaf that had been hydrophobized with methanol. I got a wick.
(Comparative Example 2)
In Example 1, a pencil lead having a nominal diameter of 0.5 was obtained in the same manner as in Example 1 except that the hydrophobization treatment was performed using methylcyclohexane (manufactured by Sankyo Chemical Co., Ltd.) instead of methanol.
(Comparative Example 3)
In Example 1, a pencil lead having a nominal diameter of 0.5 was obtained in the same manner as in Example 1 except that it was hydrophobized using ethylbenzene (manufactured by Wako Pure Chemical Industries, Ltd.) instead of methanol.
(Comparative Example 4)
In Example 1, it changed into the sill leaf hydrophobized with methanol, and it used the same as Example 1 except having used the Aerosil 200 which has not been hydrophobized at the time of preparation of a baked pencil lead. I got a pencil lead.
(Comparative Example 5)
In Example 1, except that Seraph 05025 not subjected to hydrophobization treatment was used in the preparation of the fired pencil lead in place of the sylleaf hydrophobized with methanol, the same as in Example 1, the nominal diameter of 0.5 I got a pencil lead.
(Comparative Example 6)
In Example 1, the nominal diameter was changed in the same manner as in Example 1, except that TTO-55 (A) that had not been hydrophobized was used in the preparation of the fired pencil lead in place of the sylleaf hydrophobized with methanol. A pencil lead of 0.5 was obtained.
(Comparative Example 7)
In Example 10, a pencil lead with a nominal diameter of 0.5 was used in the same manner as in Example 10 except that the sill leaf that was hydrophobized was replaced with a sill leaf that was not hydrophobized. Obtained.
(Comparative Example 8)
In Example 11, a pencil lead having a nominal diameter of 0.5 was used in the same manner as in Example 11 except that a sill leaf that was not hydrophobized was used in the preparation of the fired pencil lead in place of the hydrophobized sill leaf. Obtained.
(Comparative Example 9)
In Example 12, a pencil lead with a nominal diameter of 0.5 was used in the same manner as in Example 12 except that a sill leaf that was not hydrophobized was used in the preparation of the baked pencil lead, instead of the hydrophobized sill leaf. Obtained.
As described above, the bending strength and the handwriting density were measured according to JIS S 6005 for each of the 100 pencil cores obtained in each of the examples and comparative examples, and the standard deviation σ was calculated as an evaluation of variation for the bending strength. . The Y value was also measured as an evaluation of blackness. The results are shown in Table 1.
The Y value was measured with SPECTROTOPOMETER “CM-3700d” (manufactured by Konica Minolta Holdings Co., Ltd.) on a fine paper evenly coated with a load of 500 g. It shows that there is blackness, so that Y value is small.

この結果から、水酸基と水素結合可能な、アルコール類、アルデヒド類、エーテル類、ケトン類、カルボン酸類、エステル類から選ばれる１種又は２種以上とにより疎水化処理を施した無機粒子を、無機体質材及び又は無機添加剤として使用することにより、曲げ強さのばらつきが小さい鉛筆芯を得られることが確認できた。また、特に、無機体質材及び又は無機添加剤として上記疎水化処理を施した非晶質板状粒子を使用することにより、曲げ強さと筆記線の黒さと濃度とのバランスに優れた鉛筆芯が得られることが確認できた。

From this result, inorganic particles that have been subjected to a hydrophobization treatment with one or more selected from alcohols, aldehydes, ethers, ketones, carboxylic acids, and esters that are capable of hydrogen bonding with hydroxyl groups are obtained. It has been confirmed that a pencil lead having a small variation in bending strength can be obtained by using as an extender and / or an inorganic additive. In particular, by using the amorphous plate-like particles subjected to the hydrophobic treatment as an inorganic extender and / or an inorganic additive, a pencil lead having an excellent balance between bending strength, writing line blackness and density can be obtained. It was confirmed that it was obtained.

Claims

Alcohols, aldehydes, ethers that can be hydrogen-bonded to hydroxyl groups in advance in a pencil core that is made up of an extender and an organic binder, kneaded, extruded into a thin wire, and then heat treated up to the firing temperature A fired pencil lead comprising inorganic particles that have been subjected to a hydrophobization treatment with one or more selected from ketones, carboxylic acids, and esters.

The fired pencil lead according to claim 1, wherein the inorganic particles are amorphous plate-like particles.