FREMGANGSM}TE TIL P} EN OVERLAPPENDE M}TE } SAMMENF¦YE TERMOPLASTISKE SKUMARK ELLER FILMER

摘要

1,265,923. Seaming non-metallic sheet material. STICHTING ONTWIKKELING VERPAKKINGSMETHODEN IN DE ZUIVELINDUSTRIE. 18 June, 1970 [18 June, 1969], No. 29592/70. Heading B5K. One or more thermoplastic foam films or foam sheets with a density below 250 kg. per cubic meter, preferably below 100 kg. per cubic meter, are sealed by overlapping the films or sheets without a bonding agent therebetween, enclosing the films or sheets at least substantially on all sides in dies 1, 2, 7, 8 adapted to compress them at a temperature above the softening point of the plastics material, foaming again the compressed product at the same temperature by decreasing the pressure, and sealing at a predetermined foam thickness by cooling at least one side. Preferably, the pressure is decreased by increasing the distance between the die sections until a predetermined foam thickness is reached. The pressure applied to the films or sheets enclosed in the dies is at least 2 kg. per square cm. If the films or sheets consist of polystyrene foam having a density of 40 kg. per cubic m., they are sealed at a pressure of 4 kg. per sq. cm. and a temperature of 120-130‹ C., e.g. 128‹ C. In another example, two cross-linked polypropylene foam sheets having a density of 70 kg. per cubic m. are sealed in 4 seconds at a pressure of 20 kg. per sq. cm. at a die temperature of 185‹ C. Other specified foam plastics compositions are polystyrene-rubber compositions, polyvinyl chloride, copolymers of vinyl derivatives, polyethylene and polypropylene and their copolymers and acrylonitrile-butadiene-styrene compositions. A container, Figs. 1 and 2, is made by folding a foam plastics blank 9 about a heated mandrel 1 with the upper flaps 11, 12, 13, 14 folded as shown in Fig. 2. The external planes of the blank are enclosed and compressed by heated die halves 7, 8 and a heated plunger 2. The pressure is reduced and the distance between the parts 2, 7, 8 and the mandrel 1 is increased to allow foaming. Cooling is then effected either by cooling the parts 2, 7, 8 or by removing these parts and shifting the mandrel 1 to another position in which cold or cooled parts 2, 7, 8 are applied to the blank.