Cleaning and liquid contact with solids – Processes – Using sequentially applied treating agents
Patent
1993-07-07
1995-06-13
Andrews, Melvyn J.
Cleaning and liquid contact with solids
Processes
Using sequentially applied treating agents
134 10, 134 254, 134 42, 68 18C, 68209, B08B 304, B08B 700, D06F 4300
Patent
active
054239214
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a method for cleaning textiles in FCHC-free manner by means of solvents on a benzine basis.
The invention also relates to the use of such a method.
2. Description of the Prior Art
Finally, the invention also relates to an apparatus for cleaning textiles by means of FCHC-free solvents on a benzine basis comprising a cleaning machine, distillation section, recovery section and drier.
Generally, in such a cleaning plant the drying takes place (after transferring the material from the cleaning machine) by means of hot air; the textile material in particular predried by spinning in a drum in the cleaning machine (for example down to 11% residual moisture content) is further dried and the cleaning agent is recovered from the solvent-charged air by distillation and condensation.
However, particular safety precautions are necessary here because the solvent on a benzine basis involves a considerable danger of explosion, at the least from the flashpoint of the solvent (71.degree. C.) used upwards. Also, the operations under vacuum necessary because of this are very complicated. FCHCs are however allowed for only a short period and the use of PER involves increasingly high demands on the apparatus quality, and consequently both the FCHC-operated and the PER-operated machines must be replaced or at least considerably modified. In addition, with all existing machines and the cleaning agents used therein a practically 100% distillation was necessary due to the considerable contamination of the cleaning agent.
Also known is a method for dry cleaning with a hydrocarbon having a low flashpoint (41.degree. C.) and high vapour pressure (EP 90 119 398.7). A so-called dry-to-dry cleaning machine is described, i.e. a machine in which both washing and drying is carried out. With this type of solvent, for safety, technical, humane-ecological and ecological reasons reloading in the moist state is not compatible with European standards, in particular German standards. In this case hot air is forced in between the washing bath and the dry conduit and the evaporated solvent condensed for recovery. Before this solvent recovery step a partial vacuum is generated and an inert gas introduced. The inert gas is however introduced into the washing bath until the oxygen density of a mixture containing a solvent assumes a value beneath a predetermined limit value. After the introduction of the inert gas into the washing bath (reduction of the oxygen density) washing, centrifuging and finally drying are carried out.
SUMMARY OF THE INVENTION
To be more exact, the rendering inert therein takes place as follows: residual oxygen content of 5 vol. %. This means however that the operations must be carried out with a gas-tight machine. to set the residual oxygen content to 5%. The method is technically complicated and involves the aforementioned problems such as the technically involved vacuum method with gas-tight machine.
Compared therewith, the invention is based on the problem of providing a method and an apparatus which operate not only PER-free and FCHC-free but in addition reduce the expenditure considerably and with which the drying operation can be carried out practically free of any danger even when individual apparatus parts should fail in their function.
This is achieved in surprisingly simple manner with a method of the type set forth at the beginning in that the drying is carried out under a protective gas.
Preferably, the drying is carried out under nitrogen.
It is particularly expedient to carry out the drying with nitrogen obtained from the air, oxygen being filtered out of the air in a manner known per se.
Pressure bottles, separate connections, and the replacement of such pressure bottles or tanks can be dispensed with if nitrogen obtained in situ is used for the drying.
Preferably, N2 is injected into the drier itself.
Preferably, the operation is carried out with an aroma-free solvent known per se and having a low evaporation value, in particular N
REFERENCES:
patent: 4572723 (1986-02-01), Ward
Saal Hans-Udo
Saal Ralf M.
Andrews Melvyn J.
Dishong George W.
El-Arini Zeinab
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