Abstract: Process for recovering soda values from first and second soda deposits situated respectively in first and second underground cavities containing respectively first and second soda solutions, the second soda solution containing a higher concentration in sodium chloride and/or sodium sulfate than the first soda solution, the process comprising: extracting a stream of first soda solution from the first cavity; introducing the stream of first soda solution in a first process which produces first soda crystals and a first waste purge stream containing a higher concentration in sodium chloride and/or in sodium sulfate than the first soda solution; introducing at least part of the first waste purge stream in the second cavity; extracting a stream of second soda solution from the second cavity; and introducing the stream of second soda solution in a second process which produces second soda crystals which have a higher concentration in sodium chloride and/or sodium sulfate than the first soda crystals.

Abstract: Process for recovering soda values from first and second soda deposits situated respectively in first and second underground cavities containing respectively first and second soda solutions, the second soda solution containing a higher concentration in sodium chloride and/or sodium sulfate than the first soda solution, the process comprising: extracting a stream of first soda solution from the first cavity; introducing the stream of first soda solution in a first process which produces first soda crystals and a first waste purge stream containing a higher concentration in sodium chloride and/or in sodium sulfate than the first soda solution; introducing at least part of the first waste purge stream in the second cavity; extracting a stream of second soda solution from the second cavity; and introducing the stream of second soda solution in a second process which produces second soda crystals which have a higher concentration in sodium chloride and/or sodium sulfate than the first soda crystals.

Abstract: Multilayer hollow body made of plastic, especially a fuel tank, having at least two molded multilayer parts welded together to form a multilayer hollow body having a hollow portion formed by a multilayer wall, each of the multilayer parts comprising at least one thermoplastic non-barrier layer and at least one barrier layer which may be comprised of a liquid-crystal polymer (LCP).

Abstract: A process for processing a thermoplastic, which includes, in succession, the following steps: (1) a molten semicrystalline thermoplastic extrudate is cooled to a temperature T1 which is greater than the crystallization temperature (Tc) of the thermoplastic and is less than Tf+5° C., Tf denoting the melting point of the thermoplastic; (2) next, the extrudate is drawn in the molten state; (3) next, the extrudate is relaxed, at a temperature T3 which is between Tc and Tf, for a duration at least equal to the average relaxation time (&tgr;3) of the thermoplastic at the relaxation temperature, and after the drawing; (4) next, the extrudate is quenched to a temperature T4 which is less than Tc.

Abstract: Machine for welding hollow articles and process for welding these articles, for example half-shells of a plastic fuel tank, using the technique of hot-plate welding, in which the mirror is in the form of separate elements which can be moved independently. Particular processes in which the articles to be welded together are preshaped by pressing against cold-plate elements, which might not be plane, by stretching or compressing the side walls of the articles or by pressing against the walls of a mould. Process applied to the manufacturer of injection-moulded/welded fuel tanks. Use of the machine for manufacturing such tanks.

Abstract: Machine for welding hollow articles and process for welding these articles, for example half-shells of a plastic fuel tank, using the technique of hot-plate welding. A particular process in which the articles to be welded together are preshaped by pressing against a cold plate, which might not be plane, by stretching or compressing the side walls of the articles or by pressing against the walls of a mold. Process applied to the manufacturer of injection-molded/welded fuel tanks. Use of the machine for manufacturing such tanks.

Abstract: A process for preparing thermoplastics comprising the steps of cooling an extrudate to a temperature T1, drawing the molten extrudate, relaxing the extrudate at a temperature T3 for a duration of at least the average relaxation time of the thermoplastic at the relaxation temperature, and quenching the extrudate to a temperature T4. The process enables the manufacture of films consisting of at least one propylene homopolymer with a thickness of 100 to 250 &mgr;m and having a hot shrinkage of at most 20%, a haze of less than or equal to 3% and a total transparency with respect to air of greater than 70%.

Abstract: An oriented crystalline polymer includes a crystalline polymer which is oriented, preferably above its melting temperature, which is pliable in the absence of any plasticizing adjuvant, and which exhibits a tensile modulus E, measured in the drawing direction, of between 0.3 and 0.8 E.sub.0, E.sub.0 being the tensile modulus of the same polymer, unoriented.

Abstract: An oriented crystalline polymer, which is composed of a crystalline polymer which is oriented, which is pliable in the absence of any plasticizing adjuvant, and which exhibits a tensile modulus E, measured in the drawing direction, of between 0.3 and 0.8 E.sub.0, E.sub.0 being the tensile modulus of the same crystalline polymer, unoriented.