【正文】 ced in a big cabin enclosing all the foaming devices, while the metering part is outside.After the squaring block is positioned inside the device, the main gate is closed and the pressure is adjusted to set value. Then the mix of the ponents is made inside the mixing cylinder, when positioned on the bottom of the box. After this last slowly rises (to avoid splashing), the squaring block is positioned under the top squaring station, where it stays for the necessary time to plete the reaction. When this process is finished, the pressure gradually returns to normal values, the produced foam is removed from the machine and the operations can restart.The formulation of the polyurethane as well as the foam properties change according to the pressure one wants to use for the process.The CPT bring with it more than one advantage: with extremely low density products, vacuum replaces blowing agents, and above all water, leading therefore to a saving in TDI 80/20.Another important aspect of this innovative technology is that the production plant is entirely environmentallyfriendly and dangerfree for both the environment and the workplace, being enclosed within an airtight tunnel and all gases developed are retained by activated carbon traps.At the end, a positive aspect is the possibility of introducing fillers in the foams, achieving easily a better hardness and a lower formulation cost.INTRODUCTIONIn the last years the use of ABA39。s are needed to produce the most widely used low density PU foams and their replacing cause problems to the foam manufacturers.To obviate this elimination of ABA39。Pa)/ DaWhere: Px is the controlled pressure value, Dx is the density at controlled pressure, Pa is the absolute atmospheric pressure, Da is the density at Pa.As a result of this formulation, we can foresee the working pressure without modifying the quantity of the chemical ponents to get the required density.The foam hardness can be calculated by applying the following formula:Hx ＝(Px2/Pa2) when the foam block has reached the desired length, the block is cut off (8) and then accelerated into the transferring and discharge area (second tunnel). The running speeds of both conveyors (foam block production and transferring conveyor) are synchronised (9/1+9/2).In phase 3, as soon as the Cut off machine has cut the foam block, the conveyor of the transferring area (9/2) accelerates its speed up to 15 times more and conveys the foam block to the block discharge conveyor (9/3). The speed of both conveyor 9/2 and 9/3 is synchronised.During this transfer, the production conveyor (9/1) conveys the foam block to the free turning roller conveyor (10). This system allows the production conveyor speed to remain unchanged.The length of the free roller conveyor is determined upon by the time allowable before the produced foam block reaches the discharge conveyor (9/3). This conveyor is back to synchronised speed with that of the production conveyor once the foam block is on the discharge conveyor.The degree of vacuum inside both sections of the tunnel is kept at a constant value set before the start of production. This is marked in yellow during phase 3.Phase 4/1 shows the foam block already transferred onto the third conveyor (9/3) named block discharge conveyor.As soon as this transfer is over, the foam block, in exit to the free rollers (10) reaches the transferring conveyor 9/2, which speed is already synchronised with that of conveyor 9/1. The intermediate air lock door closes (3/1) and the air inside the discharge area is returned –within a prefixed time to atmospheric pressure (marked in green).As highlighted by the yellow mark, the pressure in the first section of the tunnel has been kept constant despite the changes of pressure occur in the second tunnel. Phase 4/2 shows the discharge of the block onto the curing equipment not highlighted in the sketches.When the atmospheric pressure is reestablished inside the second section of the tunnel, the air lock exit door (3/2) opens and the conveyor (9/3) releases the foam block to the block curing system conveyor. In phase 5, when the foam block is out of the second section of the tunnel, the air lock exit door (3/2) closes. The intermediate air lock door (3/1) opens only when the CP pressure inside the second section of the tunnel is restored to the process tunnel pressure (marked in yellow).Each of the two sections of the tunnel is subjected to separate and independent vacuum and pressure control.The production cycle can now continue as shown previously in p