Process for the production of products of light cellular plastic with closed cells

A process for the production of products of light cellular plastic with closed cells from a plastic composition containing chemical blowing agent and, optionally, other process-regulative substances and additives, where the plastic composition is processed mechanically in a plastic processing machine to a well homogenized, melted plastic compound, and transferred directly to a form cavity, the process comprising the steps of:

• transferring the plastic compound to the form cavity at a temperature above the decomposition temperature of the blowing agent in combination with optional decomposition regulative additives and at a time when the compound has reached a temperature sufficient for the blowing agent in the plastic compound to decompose, and before a time when decomposition starts,
• filling the form cavity fully with plastic compound and holding the temperature in the plastic compound in the form cavity higher than the decomposition temperature for the blowing agent in the plastic compound until a desired degree of decomposition of the blowing agent has been reached, holding the pressure in the form cavity sufficiently high to prevent the plastic compound from expanding when the blowing agent decomposes, and
• reducing the pressure in the form cavity after the desired degree of decomposition has been obtained in order to allow the plastic compound to expand.