B - Operations – Transporting – 29 – C
Patent
B - Operations, Transporting
29
C
18/657
B29C 44/28 (2006.01)
Patent
CA 1130523
ABSTRACT OF THE DISCLOSURE The disclosure describes a process for eliminating den- sification of the bottom area during the manufacture of blocks of polyurethane foam. It is characterized in that: (1) the end- less conveyor belt of the foaming tunnel of the foam-producing installation is made to function for a period of time of between 15 and 90 minutes, at the same time as the endless belt is heated, so that the surface temperature of the upper portion of the belt, which constitutes the floor of the tunnel, passes from room temp- erature to a temperature Tp of between 60 and 80°C; (2) the move- ment of the endless belt is stopped, a web of material, prefer- ably paper, is placed on the belt to be interposed between the foam and the plates of the belt, and immediately feeding is begun from the mixer-feeder head of the mixture of the reactants consti- tuting the foam upstream of the endless belt, the temperature during this stopped period decreasing from the value Tp to a value TR; (3) at the moment the value TR is attained the endless belt is again put into motion, operation is started of the devices for supplying and taking up the web of material, preferably paper, which covers the surface of the endless belt, controlling at the same time the temperature of the surface of the upper portion of the belt forming the floor of the tunnel so that in a first reac- tion area situated upstream of the endless belt it acquires a constant value TR, and in a second consolidation area another constant value TC, the temperature values being constant for each type of foam, and in that the time the temperature is maintained for each type of foam is determined by the ratio tT = tR + tC, tT being the total time of permanence of the foam in the reaction tunnel, tR being the time it takes a foam element to traverse the reaction area, a fixed value for each type of foam and tC being the time it takes a foam element to traverse the consolida- tion area; and (4) after leaving the foaming tunnel the block in formation undergoes, in at least one area located either before the drawing conveyors, between them or after the last of the conveyors which constitute the drawing means, drying in the lower part of the block in a so-called drying area which is held at a constant temperature TS notably higher than TR and TC, after the passing of which removal is made of the web of material, prefer- ably paper, to which is adhered a thin film of foam, thus obtain- ing a block of polyurethane foam having no densified bottom and a uniform surface which does not require final trimming.
319766
Swabey Ogilvy Renault
Tecfoam S.a.
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