Method for manufacturing a closure for a product-retaining container

A method for manufacturing a closure for a product-retaining container constructed for being inserted and securely retained in a portal-forming neck of said container, said method comprising at least the following method steps:

• i. forming a plurality of coated particles, said coated particles each comprising (1) a core comprising cork material and (2) at least one outer shell comprising a first plastic material that comprises one or more thermoplastic polymers, the forming comprising blending the cork material and the first plastic material, and causing the first plastic material to be heated to at least a substantially molten form;
• ii. intimately combining the following components, to form a composition:
• (a) 51 to 80 wt. % as dry weight or 51 to 85 wt. % as dry weight of the plurality of coated particles;
• (b) 12 to 49 wt. % of a second plastic material comprising one or more thermoplastic polymers;
• (c) optionally 0 to 10 wt. % of one or more blowing agents;
• (d) optionally, 0 to 15 wt. % of one or more lubricants;
• (e) optionally, 0 to 2 wt. % of one or more pigments;
• and
• (f) optionally, 0 to 10 wt. % of one or more additives and/or fillers;
• iii. heating the composition obtained in step ii to form a melt;
• iv. forming, by means of extrusion or molding, a closure precursor from the melt obtained in step iii,
• v. optionally cutting and/or finishing the closure precursor to form the closure.