THERMOPLASTIC ELASTOMER COMPOSITION, FORMED ARTICLE AND SEALING MATERIAL HAVING LOW HARDNESS

摘要

A first thermoplastic elastomer composition which comprises 100 parts by mass of the sum of 5 to 60 mass % of [A] an ethylene.alpha-olefin based copolymer having a limiting viscosity of 3.5 dl/g or more as measured in a decalin solvent at 135°C, 1 to 20 mass % of [B] a polyolefin based resin and 30 to 94 mass % of [C] a mineral oil based softening agent (provided that the sum of [A], [B] and [C] is 100 mass %), and 0.1 to 50 parts by mass of a hydrogenated diene based polymer, wherein at least the above [A] an ethylene.alpha-olefin based copolymer and [B] a polyolefin based resin have been subjected to a dynamic heat treatment in the presence of a cross-linking agent; or a second thermoplastic elastomer composition obtained by substituting [A] component of the first thermoplastic elastomer composition with an oil-extended rubber consisting of 20 to 80 mass % of [A1] an ethylene.alpha-olefin based copolymer having a limiting viscosity of 3.5 dl/g or more as measured in a decalin solvent at 135°C and 20 to 80 mass % of [C1] a mineral oil based softening agent (provided that the sum of [A1] and [C1] is 100 mass %). The above thermoplastic elastomer composition is excellent in processability, has a low hardness, is free from the bleeding of a softening agent such as a mineral oil, has softness, is excellent in rubbery elastic properties (rebound, compression set) and further can be recycled.