The invention relates to containers for storage, transport and use of liquid chemicals including acids, solvents, bases, photo-resists, dopants, inorganics, organics, biological solutions, pharmaceuticals, and radio-active chemicals. In particular, the invention relates to a container which uses a dip tube, and to dispensing systems used in conjunction with this container.
A dip tube allows for safe dispensing of a liquid chemical from larger sized containers having capacities greater than one gallon. The use of a dip tube permits the container to be kept upright while the liquid chemical is dispensed from the container. Dip tubes have been commonly used to insure that the complete contents of the container have been emptied. However, in order to assure that the contamination is kept to a minimum, it would be desirable to install the dip tube immediately after the container is filled with the liquid chemical. Because dangerous drips and spills occur when the dip tube is removed, it is not practical to extract a long dip tube from one container to insert it in another container. Consequently, once the dip tube is installed, it should not be removed until all the liquid is dispensed.
If the dip tube is in place from immediately after filling the container, problems may arise when the liquid chemical is dispensed. During shipping and handling, vapor pressure is generated inside the container. If the container is not properly vented, the chemical vapor pressure will force the liquid chemical up the dip tube upon removal of the cap or seal used during shipment to cover the upper end of the dip tube. As a result, a vapor pressure build up can cause dangerous liquid chemical spills. To prevent these spills, chemical vapor pressure buildup must be vented before liquid chemical is dispersed. Consequently, liquid chemical containers using dip tubes are required to have an additional mouth or port to permit the venting of vapor pressure buildup before dispensing liquid chemical through the dip tube.
Before the employment of double containment containers for liquid chemicals, liquid chemicals were dispensed from containers by either pumping the liquid chemicals out or by placing the container in a pressure vessel to force liquid chemicals out to a dispense point.
To allow for direct pressurization of the shipping containers and to enable complete reuse of the containers, the containers were usually constructed of more substantial materials. The containers consisted of formed and welded metallic vessels, typically stainless steel, certified to specified transportation regulations. However, this system had several drawbacks. With certain chemicals, contact with a metallic container caused ionic contamination. In addition, removal of submicron particulate inside the container was extremely difficult. These particulates ended up in the liquid chemical and affected the purity of the liquid chemical. In addition, the handling logistics of returning the empty container to the chemical supplier for refilling was problematic. To avoid the possibility of cross-contamination, a specific container had to be dedicated to a specific chemical and to a specific user.
An additional feature which presently solves these problems is the use of a double containment container having a pre-cleaned, flexible film bag, constructed of inert materials and placed within an outer container. After the liquid chemicals have been dispensed from the film bag, the film bag can be easily disposed of. By inserting a fresh, pre-cleaned bag in the existing outer container, contamination, logistics, reuse and environmental issues are addressed. See U.S. Pat. No. 5,102,010 to Osgar et al. issued on Apr. 7, 1992, which is assigned to NOW Technologies, Inc.