A flexible storage device (1) for packaging of particulate solids or liquids, having a bottom and side walls defining a substantially parallelepiped storage volume with four corners at four longitudinal edges of the parallelepiped storage volume, said flexible storage device comprising:
- a flexible container (2), including a bottom (20), an upper part, at least two side walls (21, 22, 23, 24), and suspension loops (25) in the upper part for lifting, said suspension loops (25) secured to the upper part of said flexible container (2), the flexible container formed of a web of raw, coated or laminated polymeric fibers;
- and
- a unit (3) configured as an insert between the bottom (20) and said at least two side walls (21, 22, 23, 24) of said flexible container, said unit (3) comprising:
- a flexible outer envelope (30), comprising at least four side walls (31, 32, 33, 34) and a bottom wall, the bottom wall forming the bottom of the storage volume and the at least four side walls forming the side walls of the storage volume, said outer envelope having, at the four corners of the storage volume, substantially vertical flaps (B1, B2, B3, B4) along a height of the storage volume, said vertical flaps (B1, B2, B3, B4) being configured as a bonding edge or seam edge for securing said unit (3) to said flexible container, and
- a tubular, flexible inner envelope (40) secured by vertical attachment lines (41, 42, 43, 44) to the at least four side walls (31, 32, 33, 34) of the outer envelope (30), the inner envelope comprising sidewalls defined between the vertical attachment lines, and the inner envelope and the vertical attachment lines dividing the storage volume into five vertical compartments (C1, C2, C3, C4, C5), including a central compartment (C1) defined by an interior volume of the inner envelope, and four peripheral compartments (C2, C3, C4, C5), respectively defined between the at least four side walls of the outer envelope (30) and the side walls of the inner envelope (40),
- wherein the inner envelope (40) has an upper edge (50) defining an upper mouth of said central compartment (C1) and a lower edge (51) defining a lower mouth of said central compartment (C), the upper edge (50) of the inner envelope (40) being located at the same height or below an upper edge of the side walls of the storage volume, so that the upper edge (50) of the inner envelope constitutes an overflow allowing the discharge of material from the central compartment (C1) to the four peripheral compartments (C2 to C5), said inner envelope (40) having no opening greater than 200 microns in diameter between the upper edge (50) of the inner envelope (40) and the lower edge (51) of the inner envelope (40),
- wherein the outer envelope (30) is constituted by a first polymer film and the inner envelope (40) is constituted by a second polymer film, the first polymer film forming a first sheath and each vertical flap of the outer envelope obtained by welding together two thicknesses of the first polymer film, and the second polymer film forming a second bellows sheath that is extruded as one piece and deprived of a weld, said vertical attachment lines being weld lines between the first polymer film and the second polymer film, each weld line directly joining the outer envelope (30), to the inner envelope (40),
- wherein the second polymer film and the first polymer film are between 50 microns and 250 microns thick,
- wherein the bottom (38) of the storage volume is provided with a discharge chute (36) formed by the outer envelope (30) that extends through an opening (26) in the bottom (20) of the flexible container (2), and
- wherein the outer envelope (30) defines a cover (35) provided with a filling chute (37).