FRICTION BODY COMPOSITION, FRICTION BODY AND WRITING INSTRUMENT

SOLUTION: There is provided a friction body resin composition (X) in which the mass ratio [(A)/(B)] of a 4-methyl-1-pentene/α-olefin copolymer (A) to a thermoplastic elastomer (B) is 10/90 to 67/33. Requirement (a); a melting point (Tm) of the copolymer (A) is not observed in the calorimeter measurement by a differential scanning calorimeter (DSC). Requirement (b); the copolymer (A) includes a structural unit (i) derived from 4-methyl-1-pentene and a structural unit (ii) derived from an α-olefin, and includes 60 to 78 mol% of the structural unit (i) and 22 to 40 mol% of the structural unit (ii) with the total of the structural unit (i) and the structural unit (ii) 100 mol%.EFFECT: Even when it is a handwriting with a novel metallic-like composition ink in which a metallic luster pigment is added to graphite, non-color-changing ink, or heat-discoloring ink, graphite can be erased, the heat-discoloring material can be decolorized or discolored, and the metallic luster pigment can be peeled off at the same time by rubbing the handwriting.SELECTED DRAWING: None 【解決手段】４−メチル−１−ペンテン・α−オレフィン共重合体（Ａ）と熱可塑性エラストマー（Ｂ）との質量の比率［（Ａ）／（Ｂ）］が１０／９０〜６７／３３である摩擦体用樹脂組成物（Ｘ）。要件（ａ）；示差走査型熱量計（ＤＳＣ）による熱量測定において共重合体（Ａ）の融点（Ｔｍ）が観測されない。要件（ｂ）；共重合体（Ａ）は、４−メチル−１−ペンテンから導かれる構成単位（ｉ）と、α−オレフィンから導かれる構成単位（ｉｉ）とを含み、構成単位（ｉ）と構成単位（ｉｉ）との合計を１００モル％として、構成単位（ｉ）６０〜７８モル％と、当該構成単位（ｉｉ）２２〜４０モル％とを含む。【効果】黒鉛や非変色性インキ、熱変色性インキ中に金属光沢顔料が添加されているメタリック調の新規構成インキによる筆跡であっても、筆跡を摩擦することで黒鉛の消去や、熱変色性材料の消色や変色、金属光沢顔料の剥離を同時に行うことができる。【選択図】なし