Open mouth sack

Cement used to be packed in wooden casks or steel drums. Nowadays jute or paper sacks are used, especially the latter. The paper valve sack is the type most extensively employed. In contrast with the ordinary open mouth sack the valve sack is closed on all sides except for a small opening at one corner through which the cement is introduced into the sack. As a result of the excess pressure that develops inside the sack, this opening automatically closes (in the manner of a non-return valve) on completion of the filling operation. 

These may be used for bulk excipients where there is no risk to or from the environment, e.g. chalk. They comprise two to six plies of sack Kraft types of paper, with possibly LDPE coated or metallised paper or one ply of LDPE in the case of composite sacks. The sacks may or may not have a gusset. They will all be either stitched or glued at the base and usually stitched to close the open mouth. 

The disposable packaging consists of a large square-bottom sack made of a plastic ribbon fabric, lined with plastic sheet. During the filling operation the mouth of the sack is held wide open. On completion of this operation the sack is closed by... 

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