Process for moulding polymeric foam core sandwich articles

A process for producing a polymeric article comprising:

• (a) providing a female mould comprising a female mould cavity and providing heating and cooling means for heating and cooling the female mould cavity,
• (b) providing first, second, and third polymeric materials each independently being thermoplastic polymers, and providing a blowing agent, wherein the blowing agent is a substance which is capable of producing a cellular structure in the second polymeric material upon heating above an activation temperature,
• (c) filling the female mould cavity with the first, second, and third polymeric materials (1p-3p) and blowing agent (2 b) in the following sequence:
• a first batch of the first polymeric material is laid into the female mould cavity,
• a second batch comprising a mixture of the second polymeric material and 5 a blowing agent is placed over the first batch of the first polymeric material, and
• a third batch of the third polymeric material is laid over the second batch, and
• (d) closing the thus filled cavity with a lid (12) to form a mould (10) defining a closed cavity of constant volume in time,
• (e) heating the mould to a processing temperature, which is above the melting temperature of all of the first, second, and third polymeric materials and is above the activation temperature,
• (f) after a process time at the processing temperature, cooling the mould to or below a demoulding temperature, and
• (g) removing the lid to open the cavity and extracting the polymeric article thus produced,
• characterized in that,
• (h) the second polymeric material is at least 50 wt. % of recycled polymer in the form of shredded flakes comprising first and second main surfaces separated from one another by a thickness, wherein the mean thickness of the shredded flakes is between 0.1 and 10 mm, and the mean hydraulic diameter, Dh=4 A/P, of the first and second main surfaces is comprised between 5 and 150 mm, wherein A is an area and P a perimeter of each of the first and second main surfaces of the shredded flakes.