Method for producing a moulded body that encloses a cavity by welding two partial bodies, and die for welding two partial bodies

A process for producing a molded body which encloses a cavity, by welding of two partial bodies (1a, 1b), comprising the steps a), b), c), d) and e):

• a) providing a first partial body (1a), wherein the first partial body (1a) comprises a continuous first welding web (2a) with a course,
• b) providing a die (5) which comprises a continuous first channel (7a) with a course, wherein the course of the first channel (7a) corresponds to the course of the first welding web (2a), wherein the first channel (7a) comprises first means (11a) for introducing hot gas, and wherein the die (5) comprises a first means (30a) for an active regulation of pressure,
• c) positioning the first welding web (2a) of the first partial body (1a) in a region of the first channel (7a) of the die (5), whereupon a first internal space (20a) is formed between the first partial body (1a) of the two partial bodies and the die (5),
• d) introducing hot gas through the first channel (7a), with resultant melting of the first welding web (2a) of the first partial body (1a), and active regulation of a pressure in the first internal space (20a) by the first means (30a) and
• e) bringing the molten first welding web (2a) of the first partial body (1a) into contact with a second welding web (2b) with a course of a second partial body (1b), wherein the course of the second welding web (2b) corresponds to the course of the first welding web (2a),
• wherein gas is discharged from the first internal space (20a) and/or a second internal space (20b) by the first means (30a) and/or a second means (30b) for an active regulation of pressure.