Sleeve valve for flexible bags

A flexible bag comprising side walls, a top wall and a bottom wall, an open mouth in the corner of said top wall comprising an end flap, a sleeve valve mounted in said open mouth, said sleeve valve comprising a tubular sleeve and a backing panel, the upper front portion of the tubular sleeve being adhered to the backing panel by an adhesive area and the lower front portion of the sleeve adhered to the end flap of said open mouth of the bag, the upper and lower rear portions of said sleeve being unattached to the backing panel and to said end flap and being adapted to hang within the bag, and a longitudinal slit located exclusively in the upper rear portion of said sleeve, said slit terminating short of said adhesive area to form an unslit area of said upper rear portion unadhered to said backing panel whereby the said unslit area together with the lower rear portion of said sleeve folds over the open mouth to seal the open mouth in the two-ply region of the sleeve.