Double-sided coating of porous webs with paint using web positioning elements

In a first aspect, the invention relates to a coating apparatus (41, 42) for double-sided coating of a porous web (10) with a coating material (30), comprising (i) a slot die coating head (50) comprising an upper lip (51), a lower lip (52) and a slot (53) between the upper lip (51) and the lower lip (52), (ii) a counter element (60) arranged opposite the lower lip (52) across a reference plane (15), (iii) a slit (70) defined between the lower lip (52) and the counter element (60), and (iv) a slot (70) for passing the porous web (10) therethrough, the slot (53) opening towards the slot (70), and (iv) a web positioning element (51, 61); wherein the web positioning element (51, 61) is either an upper lip (51) of the slot die coating head (50) or a spacer structure (61) on an opposing element (60), the upper lip (51) protruding to the reference plane (15) such that there is an offset (d) between the upper lip (51) and the lower lip (52), the spacer structure (61) protruding to the reference plane (15) such that t