Closure for a straw of thin-walled flexible packaging

A closure for a spout of a flexible thin-walled packaging, comprising:

• a cap comprising an annular cap wall having a central cap axis that extends between a cap lower end and a cap upper end, a main plane of symmetry being defined through the central cap axis for the annular cap wall, wherein the cap is internally threaded to be suitable for screwing onto a thread of the spout;
• a tamper-evident seal comprising a tamper-evident ring suitable for being applied to the spout, an annular tamper-evident band placed between the tamper-evident ring and the cap lower end, and a plurality of breakable bridges that join the annular tamper-evident band to the tamper-evident ring and the cap, wherein the annular tamper-evident band extends between a first end permanently joined to the cap and a second end permanently joined to the tamper-evident ring to form a tie between the cap and the tamper-evident ring;
• a grip surface for gripping the closure, comprising an annular grip surface wall coaxial to the central cap axis, surrounding the annular cap wall and radially arranged spaced apart therefrom, the annular grip surface wall axially extending from a lower end to an upper end, wherein the annular grip surface wall has, at the lower end, an undulated grip surface edge made up of a succession of low sections and high sections that are joined to each other to create bulges and windows of the grip surface, in circumferential sequence;
• wherein a first window of said windows is circumferentially delimited by a first limit section of the undulated grip surface edge belonging to a first bulge of said bulges, and by a second limit section of the undulated grip surface edge belonging to another bulge of said bulges;
• wherein a first window plane tangent to the first limit section and parallel to the main plane of symmetry and a second window plane tangent to the second limit section and parallel to the main plane of symmetry are defined for said first window;
• wherein the cap and the tamper-evident seal are contained in width between said first and second window planes;
• wherein an imaginary plane orthogonal to the central cap axis is tangent inferiorly to a low section of the undulated grip surface edge that axially delimits inferiorly at least one of said bulges;
• and
• wherein said imaginary plane is arranged axially below the cap lower end of the cap wall.