PROBLEM TO BE SOLVED: To provide a medical instrument which includes a housing made of a cyclic polyolefin resin and a gasket made of a thermoplastic elastomer composition and is free from problems such as whitening of the housing when the medical instrument is subjected to heating conditions in a sterilization treatment or the like and adhesion of the housing and the gasket.SOLUTION: A thermoplastic elastomer composition constituting a gasket includes a component (A): a block copolymer having at least two polymer blocks P which are mainly made of a vinyl aromatic compound and at least one polymer block Q which is mainly made of conjugated dienes and/or a hydrogenated block copolymer obtained by hydrogenation of the block copolymer, a component (B): a softening agent for a polybutene-based rubber, and a component (C): a polyolefin resin. The content of the component (A) relative to a total of the component (A) and the component (B) is 25- 90 wt.%. The content of the component (C), based on a total 100 pts.wt. of the component (A) and the component (B), is 1-45 pts.wt.SELECTED DRAWING: NoneCOPYRIGHT: (C)2016,JPO&INPIT【課題】環状ポリオレフィン系樹脂からなる筐体と、熱可塑性エラストマー組成物からなるガスケットとを有する医療用器具であって、滅菌処理等で加熱条件に晒された場合における筐体の白化や筐体とガスケットとの固着の問題のない医療用器具を提供する。【解決手段】ガスケットを構成する熱可塑性エラストマー組成物が、成分(A):ビニル芳香族化合物を主体とする少なくとも2個の重合体ブロックPと、共役ジエンを主体とする少なくとも1個の重合体ブロックQとを有するブロック共重合体及び/または該ブロック共重合体を水素添加して得られる水添ブロック共重合体と、成分(B):ポリブテン系ゴム用軟化剤と、成分(C):ポリオレフィン系樹脂を含む。成分(A)及び成分(B)の合計に対する成分(A)の含有量は25~90重量%、成分(A)及び成分(B)の合計100重量部に対して成分(C)を1~45重量部含有する。【選択図】なし
