The novel compounds of the invention are diethers of the formula where R; and R are olefinically unsaturated aliphatic radicals having at least 3 carbon atoms, advantageously olefinically unsaturated aliphatic hydrocarbons having at least 3 carbon atoms, and R is an acetylenically unsaturated aliphatic radical having at least 4 carbon atoms, advantageously an acetylenically unsaturated aliphatic h