PROBLEM TO BE SOLVED: To provide an acoustic medium for an ultrasonic diagnosis which has flexibility, transparency, heat resistance against steam sterilization, and acoustic impedance almost equal to a human organism.SOLUTION: An acoustic medium comprises: at least two polymer blocks [A] having as main components repeating units originated in an aromatic vinyl compound and at least one polymer block [B] having as a main component a repeating unit originated in a chain conjugated diene compound. When weight fractions of the polymer block [A] and the polymer block [B] in the whole polymer are wA and wB, an elastic body formed by blending a block copolymer hydride [2] where 90% or more of an entire unsaturated bond of a block copolymer [1] in which a ratio (wA:wB) between wA and wB ranges from 30:70 to 65:35 and a specific low-molecular-weight hydrocarbon polymer when necessary is molded into the acoustic medium.COPYRIGHT: (C)2014,JPO&INPIT【課題】柔軟性、透明性、蒸気滅菌に耐える耐熱性および人体にほぼ等しい音響インピーダンスを有する超音波診断用音響媒体の提供。【解決手段】芳香族ビニル化合物由来の繰り返し単位を主成分とする重合体ブロック[A]の少なくとも2つと、鎖状共役ジエン化合物由来の繰り返し単位を主成分とする重合体ブロック[B]の少なくとも1つとからなり、重合体全体に占める重合体ブロック[A]および重合体ブロック[B]の重量分率をwAおよびwBとしたときに、wAとwBとの比(wA:wB)が30:70~65:35であるブロック共重合体[1]の、全不飽和結合の90%以上が水素化されたブロック共重合体水素化物[2]、および、必要に応じ特定の低分子量炭化水素系重合体を配合してなる弾性体を成形して音響媒体とする。【選択図】なし
