HYDRAULIC FLUID COMPOSITION

PROBLEM TO BE SOLVED: To provide a hydraulic fluid composition which has excellent characteristics as a hydraulic fluid, no leakage problem when using a nitrile-based rubber sealing material and a flash point of 200°C or more and satisfies regulations in the Fire Defense Law.SOLUTION: There is provided a hydraulic fluid composition which comprises a base oil obtained by mixing (A) 20 to 70 mass% of a paraffin oil, (B) 15 to 50 mass% of a naphthene oil and (C) 15 to 50 mass% of an ester oil obtained by synthesis of an alcohol and a fatty acid having 10 or more carbon atoms and has a flash point of 200°C or more. 【課題】作動油としての特性に優れ、ニトリル系ゴムシール材を用いたときの漏洩問題も無く、かつ、引火点が２００℃以上で消防法上の規定を満足する油圧作動油を提供する。【解決手段】（Ａ）パラフィン油を２０〜７０質量％、（Ｂ）ナフテン油を１５〜５０質量％及び（Ｃ）アルコールと、炭素数１０以上の脂肪酸とを合成してなるエステル油を含むエステル油を１５〜５０質量％の割合で混合してなる基油を含み。引火点が２００℃以上である油圧作動油組成物。【選択図】なし