【発明の詳細な説明】[Detailed description of the invention]
（産業上の利用分野）
本発明はシヤープペンシル用の芯に関するもの
である。
（従来の技術）
従来、シヤープペンシル用の芯は、黒鉛、カー
ボンブラツク等の着色材に、粘土、天然高分子化
合物、合成高分子化合物、ピツチ、アスフアルト
等の結合材を加え、さらに必要に応じて所要な溶
剤及び可塑剤を添加してこれらを混練し、この混
練物を芯状に押出成形した後900〜1200℃の温度
で焼成し、得られた焼結体の気孔中に油脂類を含
浸させて完成されている。そして焼結体に含浸さ
せる油脂類としては、鯨油、ラード、なたね油、
大豆油等の動植物油、又はスピンドル油、流動パ
ラフイン等の鉱油、さらにシリコーン油やワツク
ス類があり、これらが単独で又は組み合わされて
適宜選択されながら使用されている。
（発明が解決しようとする問題点）
ところで上記したように芯の焼結体（以下焼成
芯という。）に油脂類を含浸させるのは、筆跡濃
度を高めると共に運筆を滑らかにするためである
が、上記従来例の油脂類には夫々欠点がある。先
ず動植物油及びワツクス類は、焼成芯に含浸され
ても筆跡濃度をそれ程高めることができず、又シ
ヤープペンシルのチヤツクによる芯保持性が鉱油
類に比べてかなり劣つている。次に鉱油類は、シ
ヤープペンシルのチヤツクによる芯保持性には優
れているが筆跡濃度の増加がそれ程望めない。さ
らにシリコーン油は、上記の油脂類の中では最も
筆跡濃度を高められるが、逆にシヤープペンシル
による芯保持性は最も劣つており、その上価格が
非常に高価である。尚、油脂類を含浸させる以外
にも筆跡濃度を高めるためには種々の手段が提案
されており、例えば染料を含浸させる方法や、着
色物を形成させる物質を含浸させる方法等がある
が、いずれも初期の目的を達成するとは言い難
く、また消去性に問題が生ずるという弊がある。
本発明は以上のような欠点や問題がなく、筆跡濃
度の増加効果が大きく、運筆が滑らかで、シヤー
プペンシルの芯保持性も良好なるシヤープペンシ
ル用芯の提供を目的とする。
（問題点を解決するための手段）
本発明は、芯の焼結体にアルフアーオレフイン
オリゴマーが含浸させたことを特徴とするもの
で、シヤープペンシル用芯の含浸物として衛生性
が優れていること及び経時変化性が極めて少ない
ことを前提条件とし、さらに上記目的の達成に必
要な以下の条件、即ち、焼成芯中の開気孔に容
易に隈無く充填されること、焼成芯に含浸され
たときに筆跡の濃度増加程度がなるべく大きいこ
と、シヤープペンシルから芯を繰り出して垂直
に荷重を加えたときに少なくとも焼成芯と同等か
それ以上の芯保持力を有すること、運筆時に筆
圧により芯が崩壊するとき均一で円滑な崩壊を助
け運筆を滑らかにする効果が大きいこと、等の条
件を具備する物質を鋭意研究した結果アルフアー
オレフインオリゴマーを発見したことに基づきな
されたものである。ここでアルフアーオレフイン
オリゴマーとは、低級アルフアーオレフインを原
料として重合度を制御して得られる合成炭化水素
油であり、次の化学式で示される。
アルフアーオレフインオリゴマーは潤滑剤とし
ての用途もあるが、本発明の如くシヤープペンシ
ル用芯の含浸物として使用するときは一般の油脂
類と同様に常圧含浸、又は減圧・加圧含浸法を用
いて、温度を80〜120℃に保ち、動粘度を下げて
含浸を行なうと、短時間に芯内部に隈無く充填で
きる。尚、アルフアーオレフインオリゴマーを含
浸させると焼成芯の組成材料及び焼成条件等は任
意で良い。焼成芯にアルフアーオレフインオリゴ
マーを充分に含浸させた後に表面に付着した余分
のアルフアーオレフインオリゴマーは遠心分離、
又は蒸気吹き付け洗浄等により除去されて芯は完
成される。
（作用）
焼成芯にアルフアーオレフインオリゴマーを含
浸させると、紙面に付着した黒鉛粒子表面をア
ルフアーオレフインオリゴマーが良く濡らしてい
て黒鉛の灰色光沢を打ち消し反射光を減少させ
る、筆圧による摩耗量が焼成芯より増加して着
色材である黒鉛粒子の紙面への付着量が増大する
という２つの理由により筆跡濃度が増加する。こ
こで上記の理由をより詳しく説明する。芯の主
要成分である黒鉛粒子は元来固体潤滑剤として知
られており筆記時の紙面との摩擦抵抗は比較的小
さい。従つて摩擦による芯の摩耗量を増大させる
には黒鉛より潤滑性の劣る物質を含ませれば良
く、一般的な油脂類に比べて潤滑性に於てかなり
劣るアルフアーオレフインオリゴマーを含有させ
れば芯の摩耗量もそれだけ増えることになる。因
に鉱油系油脂の摩擦係数が0.15〜0.20であるのに
対し、アルフアーオレフインオリゴマーのそれは
0.40以上であり潤滑性能はかなり低い。
次に、シヤープペンシルの芯保持力に影響を及
ぼす要因には、三つ割チヤツクの芯に接する面
の粗さ、締め具の作動性、チヤツバネの強さ等の
チヤツク機構に関するもの、芯表面の硬さ又は
粗さ等の芯自体に関するもの、及び、含浸した
油脂の芯表面に於ける作用等の含浸油脂に関する
もの、等が存在するが、この中でも含浸油脂の影
響はかなり大きい。そして含浸油脂がチヤツクの
芯保持力に及ぼす影響は、含浸油脂の芯表面に於
ける乾燥性と、芯内部から芯表面への浸出性によ
つて異なる。即ち芯表面での乾燥性が劣り且つ芯
表面への浸出性が大きいものは、チヤツクの芯保
持部分と芯との間に潤滑油膜が形成されるような
ことになつて芯保持力が低下するが、逆に芯表面
での乾燥性が良く且つ芯内部から芯表面への浸出
性が悪いと芯保持力は増大する。そして芯表面で
の乾燥性が良いということは含浸油の揮発性が大
きいということであり、又芯表面への浸出性が悪
いということは含浸油の表面張力が大きいという
ことであり、本願のアルフアーオレフインオリゴ
マーはこの２条件を具備しているのでチヤツクの
芯保持力を増大せしめるのに最適ということにな
る。本願のアルフアーオレフインオリゴマーは以
上のように、黒鉛粒子表面を良く濡らせること、
潤滑性が低いこと、含浸後の芯表面に於ける揮発
性が高くて乾燥性が良いこと、及び芯表面に於け
る表面張力が大きくて芯表面への浸出性が悪いこ
と、等の性質及び運筆時に筆圧による芯の崩壊時
に均一で円滑な崩壊を助けるという特性を有する
ことにより、筆跡の濃度を増大させると共に運筆
を滑らかにし且つシヤープペンシルの芯保持力を
増大させる作用がある。
（実施例）
以下に本発明の実施例と、比較例及びそれらの
試験結果を記す。
実施例 １
外径が0.5mmで硬度Ｈの焼成芯にアルフアーオ
レフインオリゴマー（ライオン(株)製、リボループ
20、平均分子量370）を120℃３時間の常圧下で含
浸させ、含浸後直ちに遠心分離機にて表面の付着
物を振り切り、完成されたシヤープペンシル用
芯。
実施例 ２
外径が0.5mmで硬度HBの焼成芯に実施例１と同
様にアルフアーオレフインオリゴマーを含浸させ
て完成されたシヤープペンシル用芯。
比較例 １〜８
外径が0.5mmで硬度Ｈ及びHBの焼成芯に夫々ラ
ード油、スピンドル油又はシリコーン油を所定の
含浸条件の下で含浸させて、又は何ものも含浸さ
せないで完成されたシヤープペンシル用芯。
試験結果
(Industrial Application Field) The present invention relates to a lead for a sharp pencil. (Prior art) Conventionally, the lead for a sharp pencil is made by adding a coloring agent such as graphite or carbon black, a binder such as clay, a natural polymer compound, a synthetic polymer compound, pitch, or asphalt, and then adding it as needed. The necessary solvent and plasticizer are added and kneaded, and this kneaded product is extruded into a core shape and then fired at a temperature of 900 to 1200°C, and oils and fats are injected into the pores of the resulting sintered body. Completed by impregnation. The oils and fats to be impregnated into the sintered body include whale oil, lard, rapeseed oil,
There are animal and vegetable oils such as soybean oil, mineral oils such as spindle oil and liquid paraffin, as well as silicone oils and waxes, and these are used alone or in combination as appropriate. (Problems to be Solved by the Invention) As mentioned above, the purpose of impregnating the sintered body of the lead (hereinafter referred to as the sintered lead) with oils and fats is to increase the density of the handwriting and to make the stroke smoother. The above-mentioned conventional oils and fats each have their own drawbacks. First, animal and vegetable oils and waxes cannot significantly increase the density of handwriting even when impregnated into a fired lead, and their ability to retain the lead in the chuck of a sharp pencil is considerably inferior to that of mineral oils. Next, mineral oils have excellent lead retention properties due to the chuck of a pencil pencil, but cannot be expected to significantly increase the density of handwriting. Furthermore, silicone oil can improve the density of handwriting the most among the above-mentioned oils and fats, but on the other hand, it has the poorest lead retention ability with sharp pencils, and is also very expensive. In addition to impregnating with oils and fats, various methods have been proposed to increase the density of handwriting, such as impregnating with dyes and impregnating with substances that form colored objects. However, it is difficult to say that the initial purpose was achieved, and there is also a problem in erasability.
The object of the present invention is to provide a lead for a sharp pencil that does not have the above-mentioned drawbacks and problems, has a large effect of increasing handwriting density, provides smooth strokes, and has good lead retention properties. (Means for Solving the Problems) The present invention is characterized in that the sintered body of the lead is impregnated with alpha olefin oligomer, which has excellent hygiene as an impregnated material for the lead of a sharp pencil. In addition, the following conditions are necessary to achieve the above objectives: that the open pores in the fired core are easily and thoroughly filled, and that the fired core is impregnated with In some cases, the degree of increase in density of handwriting is as large as possible, the lead retention force is at least equal to or greater than that of a fired lead when the lead is taken out from the sharp pencil and a load is applied vertically, and the lead is held in place by the pressure of the pen when writing. This was based on the discovery of alpha-olefin oligomers as a result of intensive research into substances that help disintegrate uniformly and smoothly and have a great effect on smoothing the strokes of the brush. Here, alpha olefin oligomer is a synthetic hydrocarbon oil obtained by controlling the degree of polymerization using lower alpha olefin as a raw material, and is represented by the following chemical formula. Alpha olefin oligomers are also used as lubricants, but when used as an impregnating material for sharp pencil leads as in the present invention, normal pressure impregnation or reduced pressure/pressure impregnation methods are used in the same way as with general oils and fats. By maintaining the temperature between 80 and 120°C and lowering the kinematic viscosity during impregnation, the inside of the core can be thoroughly filled in a short time. Note that when the alpha olefin oligomer is impregnated, the composition of the firing core, the firing conditions, etc. may be arbitrary. After the firing core is sufficiently impregnated with alpha-olefin oligomer, excess alpha-olefin oligomer adhering to the surface is removed by centrifugation.
Alternatively, the core is completed by removing it by steam spray cleaning or the like. (Function) When the fired core is impregnated with alpha-olefin oligomer, the alpha-olefin oligomer wets the surface of the graphite particles adhering to the paper well, canceling out the gray luster of graphite and reducing reflected light, reducing the amount of wear due to pen pressure. The density of handwriting increases for two reasons: the amount of graphite particles, which are colorants, attached to the paper surface increases compared to the fired core. Here, the above reason will be explained in more detail. Graphite particles, which are the main component of the core, are originally known as solid lubricants, and their frictional resistance with the paper surface when writing is relatively small. Therefore, in order to increase the amount of wear on the core due to friction, it is sufficient to include a substance that is less lubricating than graphite, and it is sufficient to contain alpha olefin oligomers, which have considerably inferior lubricating properties compared to general oils and fats. The amount of wear on the core will also increase accordingly. Incidentally, while the friction coefficient of mineral oil-based fats and oils is 0.15 to 0.20, that of alpha olefin oligomers is
It is over 0.40 and the lubrication performance is quite low. Next, factors that affect the lead retention force of a sharp pencil include those related to the chuck mechanism such as the roughness of the surface of the three-split chuck that contacts the lead, the operability of the fastener, and the strength of the chuck spring; There are factors related to the core itself such as hardness or roughness, and factors related to the impregnated fat and oil such as the effect of the impregnated fat and oil on the core surface, but among these, the influence of the impregnated fat and oil is quite large. The influence of the impregnating oil on the core holding power of the chuck varies depending on the dryness of the impregnating oil on the core surface and the permeability of the impregnating oil from the inside of the core to the core surface. In other words, if the drying property on the core surface is poor and the lubricating oil film is large in leaching to the core surface, a lubricating oil film will be formed between the core holding part of the chuck and the core, resulting in a decrease in core holding power. However, on the contrary, if the drying property on the core surface is good and the permeability from the inside of the core to the core surface is poor, the core retention strength will increase. Good drying properties on the core surface means that the impregnating oil has high volatility, and poor leaching properties on the core surface means that the impregnating oil has a high surface tension. Since alpha olefin oligomers meet these two conditions, they are ideal for increasing the core retention of chucks. As described above, the alpha olefin oligomer of the present application can wet the graphite particle surface well,
Properties such as low lubricity, high volatility and good drying properties on the core surface after impregnation, and high surface tension on the core surface and poor leaching to the core surface. It has the property of helping the lead to collapse uniformly and smoothly due to writing pressure during writing, thereby increasing the density of the handwriting, making the writing smoother, and increasing the lead retention force of the sharp pencil. (Example) Examples of the present invention, comparative examples, and test results thereof are described below. Example 1 A fired core with an outer diameter of 0.5 mm and a hardness of H was coated with alpha olefin oligomer (manufactured by Lion Corporation, Rivolup)
20, average molecular weight 370) at 120°C for 3 hours under normal pressure. Immediately after impregnation, the surface deposits are shaken off using a centrifuge to create a completed sharp pencil lead. Example 2 A sharp pencil lead was completed by impregnating a fired lead with an outer diameter of 0.5 mm and a hardness of HB with alpha olefin oligomer in the same manner as in Example 1. Comparative Examples 1 to 8 Fired cores with an outer diameter of 0.5 mm and hardness H and HB were impregnated with lard oil, spindle oil, or silicone oil under predetermined impregnation conditions, or were completed without impregnation with anything. Lead for sharp pencil. Test results
【表】
尚、試験に於ける濃度はJIS S6005に準じ、又
芯保持性はJIS S6013の試験法に基づき同一種類
のシヤープペンシルを使用して垂直荷重値を測定
したものである。さらに含浸率は次の式により算
出した。
含浸率〔（含浸後芯荷重／含浸前芯荷重）−１〕
×（１／含浸物比重）×100（％）
（発明の効果）
本発明のシヤープペンシル用芯は、上記実施例
の試験結果からも明らかなとおり、筆跡の濃度増
加効果が大きく、又芯保持性も充分で、さらに運
筆が滑らかで良好であるという諸効果を有する。
又、同じく試験結果からも明らかなとおり、例え
ば硬度Ｈの焼成芯から硬度HBの完成芯が得られ
る如く2B・Ｂ・HB等の柔らかめの硬度の芯の製
造に好適である。又、一般に芯の硬度と強度は反
比例するので高強度の芯の製造にも好適となる。[Table] The concentration in the test was in accordance with JIS S6005, and the lead retention was determined by measuring the vertical load value using the same type of sharpening pencil based on the test method of JIS S6013. Further, the impregnation rate was calculated using the following formula. Impregnation rate [(core load after impregnation/core load before impregnation) -1] × (1/specific gravity of impregnated material) × 100 (%) (Effects of the invention) The lead for sharpening pencils of the present invention meets the test results of the above examples. As is clear from the above, it has various effects such as a large effect of increasing the density of handwriting, sufficient lead retention, and smooth and good brushstrokes.
Further, as is also clear from the test results, for example, a finished core with a hardness of HB can be obtained from a fired core with a hardness of H, so it is suitable for manufacturing cores with softer hardness such as 2B, B, and HB. Furthermore, since the hardness and strength of the core are generally inversely proportional, it is also suitable for producing a high-strength core.