A method for making a cap for a container that includes the steps of inserting in a mould a material in a solid state or a solid dispersed in a liquid, the material containing at least 70% cellulose by weight; pressing the material in the mould to obtain a cup-shaped component, the cup-shaped component having a skirt which extends around an axis and an end wall which closes the skirt at one end thereof; making on the skirt a breakable line which at least partly surrounds the axis to define on the cup-shaped component a closure body and an annular band; and folding a portion of the annular band inwards towards the inside of the cup-shaped component, to obtain at least one retaining element which projects inwards towards the inside of the annular band so as to keep the annular band joined to a neck of the container.

Described is a compression moulding device and method, wherein the device comprises: a female element (2) for housing a dose made of material suitable for compression moulding; a male punch (5) which can be at least partly inserted in the female element (2) to compress said dose and make a relative product; wherein said punch (5) has an outer surface (10) for moulding the dose, and wherein said punch (5) comprises a first portion (6) slidable relative to at least a second portion (7) between a moulding condition wherein the second portion (7) radially compresses the dose against the female element (2) and a collapsed condition wherein the second portion (7) is radially retracted away from the dose.