The invention relates to a process for preventing or restricting oil spills from oil tankers. The process comprises application of block copolymer particles having a high active surface in the form of fine particles or a fluffy structure. The block copolymer has at least one predominantly poly(vinyl aromatic compound) block and at least one predominantly poly(conjugated diene) block. The process may comprise introduction of the block copolymer into damaged compartments of the ship and permanent placement of the block copolymer in the double hull space of the ship. The process may further comprise automatic introduction of the block copolymer upon detection of a hard shock or high temperatures.