Pipes used in offshore oil fields include risers (pipes for pumping up crude oil), umbilicals (integration of pipes for supplying chemicals for crude oil viscosity reduction for the purpose of controlling the pumping, power cables, and others), flow lines (pipes for transporting pumped crude oil which extend on the sea floor), and the like. They have various structures, and known pipes include metal-made pipes and metal/resin hybrid pipes. In order to achieve weight reduction, use of metal-made pipes tends to be reduced and metal/resin hybrid pipes are becoming the mainstream. Since oil drilling sites become much deeper and the temperature of crude oil pumped therefrom rises, resins used for these pipes need to have better mechanical strength and chemical resistance at high temperatures (resistance to high-temperature crude oil, resistance to acidic gas, such as hydrogen sulfide, contained in crude oil at high temperatures, resistance to chemicals such as methanol, CO2, and hydrogen chloride injected so as to reduce the crude oil viscosity at high temperatures), and lower permeability at high temperatures. Thus, there is a demand for materials which can take the place of polyamide (the operating temperature range is up to 90° C.) and polyvinylidene fluoride (the operating temperature range is up to 130° C.) which have been used for the pipes.
Patent Literature 1 discloses as a material suitable for flexible pipes a fluororesin which is a copolymer containing copolymerized units of tetrafluoroethylene, vinylidene fluoride, and an ethylenic unsaturated monomer excluding tetrafluoroethylene and vinylidene fluoride, and has a specific storage elastic modulus.