Apparatus and method for the production of expanded foam embryos

A product obtained by preparing an embryo having a volume Vfinal and exposing said embryo to expansion and cross-linking said embryo using heat and water or steam, wherein preparing the product from said embryo comprises the steps of:

• providing a plastisol;
• providing an injector unit for injection moulding comprising a barrel with a nozzle and a control unit adapted to control back pressure Pback inside the barrel and to maintain said back pressure Pback above a critical foaming pressure;
• providing a mould comprising an injector port, a force exerting means, a first mould half and a second mould half together forming a mould cavity with a cavity volume, wherein the first and second mould halves are moveable in relation to each other to vary the cavity volume, wherein the mould is provided in a cold state having a cavity volume of Vmin and wherein the force exerting means exerts a controlled maintained clamping force Fset on the mould cavity creating a clamping pressure P4 inside the mould;
• connecting the injector port of the mould to the nozzle of the injector unit;
• adding the plastisol to the injector unit;
• preparing a shot volume Vshot of hot melt of the plastisol in the injector unit;
• injecting the hot melt into the cold mould cavity of volume Vmin;
• continuing injecting the hot melt into the cold mould cavity creating a cavity pressure Pcavity equal to or higher than the clamping pressure P4 forcing the mould to expand so that it can receive the shot volume Vshot;
• allowing the injected hot melt to cool forming the embryo, wherein the volume of the formed embryo contracts when the force exerting means of the mould exerts the controlled maintained clamping force Fset thereby allowing the mould cavity to contract reducing a risk of a pressure drop in the mould cavity and causing foaming in the formed embryo;
• and
• opening the mould and removing the formed embryo;
• and
• exposing said embryo to expansion and cross-linking using heat and water or steam to form said product, said product being an expanded foam having an average a cell size of 350 μm or less.