Carbon Dioxide Dry Cleaning

Abstract

A method for cleaning objects in a cleaning fluid is disclosed. The cleaning fluid initially includes a dense phase gas and water and in a subsequent cleaning step at least part of the water is filtered out of the cleaning fluid.

Description

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

According to the invention the objects are at least temporarily cleaned in a cleaning fluid comprising a dense phase gas and water. Preferably towards the end of the cleaning procedure, at least a fraction of the water is filtered out of the cleaning fluid. It is advantageous to remove essentially all water by filtration. Thus, after the cleaning procedure is finished it is no more necessary to dry the objects. At least, the time needed for drying the objects is minimized.

According to a preferred embodiment the objects are placed in a cleaning chamber and washed with a cleaning fluid comprising a dense phase gas and water. At least a fraction of the cleaning fluid is withdrawn from the cleaning chamber and water is filtered out of the fraction of the cleaning fluid. After the filtration step the filtered cleaning fluid is transferred back to the cleaning chamber.

In one preferred embodiment, the filtration device is placed in a pipe, and the cleaning fluid is pumped through the pipe continuously during the cleaning process whereby water is removed from the cleaning fluid. The pipe may be the pipe which is used for emptying the cleaning fluid into the recovery and distillation vessel. Optionally, the flow through the pipe is supported by pumping. The complete cleaning fluid is pumped through the pipe during the cycle at least once, optionally two, five, fifty or more times.

Preferably the cleaning method comprises at least a step of cleaning the objects in a dense phase gas and water and a step of cleaning the objects in dense phase gas only. Between these two steps the water is filtered out of the cleaning fluid according to the invention.

The filtration of water out of the cleaning fluid is preferably carried out by passing the cleaning fluid through a filtration device which comprises a hygroscopic material, especially a silica gel or a molecular sieve. In particular it is preferred to use a molecular sieve with a pore size between 3 Å and 4 Å.

According to a preferred embodiment the objects are cleaned in a cleaning chamber in a cleaning fluid comprising a dense phase gas and water. At least part of the water is filtered out of the cleaning fluid inside the cleaning chamber. This is preferably achieved by placing a filtration device inside the cleaning chamber.

According to a preferred embodiment the cleaning procedure is started with a cleaning fluid comprising a mixture of a dense phase gas, such as carbon dioxide, with a relative high content of water. The cleaning fluid is continuously passed through the filtration device and thus the water fraction continuously decreases. Towards the end of the cleaning procedure the objects are cleaned essentially in dense phase gas only.

Preferably the filtration device comprises a mechanical filter. The mechanical filter removes fibers, dirt, and other particulate material from the cleaning fluid and protects the hygroscopic material, such as a molecular sieve or a silica gel. In one embodiment, the cleaning chamber comprises a rotating drum. Simple net filters, for example made of steel wire, are arranged on the rotating drum to collect loose fibers during a garment cleaning cycle. The hygroscopic material may be provided on the exterior surface of the rotating drum or in a pipe connected to the cleaning chamber.

The filtration device is ideally constructed in such a manner that it can be easily be changed or replaced.

The cleaning fluid preferably comprises dense phase carbon dioxide in liquid or super-critical state. The cleaning result may be further improved by adding additives, in particular water-soluble additives, to the cleaning fluid.

The invention allows carbon dioxide-dry cleaning in the presence of water, but solves the problem caused by water which is present on carbon dioxide-dry-cleaned garments after the cleaning process. Equally, passing the cleaning fluid many times during the treatment process through a mechanical filter, effectively removes all solid particles, such as loose fibers, mites, and other particulate material, as it were, from the distribution equilibrium. In addition, certain surfactants used for detaching particulates from the substrate to be cleaned, e.g. of cationic type, are removed as well as they are strongly bound to the particulate material.

Claims

1-8. (canceled)

9. A method for cleaning objects in a cleaning fluid wherein in a beginning of a cleaning procedure the cleaning fluid comprises a dense phase gas and water, and wherein the water is filtered out of the cleaning fluid, and further wherein towards an end of the cleaning procedure the objects are cleaned essentially in the dense phase gas only.

10. The method according to claim 9, wherein carbon dioxide is used as the dense phase gas.

11. The method according to claim 9, wherein the objects are cleaned in a cleaning chamber and wherein the method further comprises the steps of: withdrawing part of the cleaning fluid from the cleaning chamber;filtering water out of the part of the cleaning fluid; andtransferring the filtered cleaning fluid back to the cleaning chamber.

12. The method according to claim 9, wherein the objects are cleaned in a cleaning chamber and wherein at least part of the water is filtered out of the cleaning fluid inside the cleaning chamber.

13. The method according to claim 9, wherein the cleaning fluid is passed through a filtration device wherein the filtration device comprises a hygroscopic material.

14. The method according to claim 13, wherein the hygroscopic material is a silica gel.

15. The method according to claim 13, wherein the hygroscopic material is a molecular sieve.

16. The method according to claim 15, wherein the molecular sieve has a pore size between 3 Å and 4 Å.

17. The method according to claim 13, wherein the filtration device includes a mechanical filter.

18. The method according to claim 9, wherein the cleaning fluid includes additives.

19. The method according to claim 18, wherein the additives are water-soluble additives.

20. A method of cleaning an object in a cleaning fluid, comprising the steps of: cleaning the object in a first phase of a cleaning procedure in a cleaning fluid including a dense phase gas and an amount of water;filtering at least a portion of the amount of water out of the cleaning fluid in a second phase of the cleaning procedure to result in a cleaning fluid with the dense phase gas and a reduced amount of water; andcleaning the object in a third phase of the cleaning procedure in a cleaning fluid including the dense phase gas and the reduced amount of water.

21. The method according to claim 20, wherein the step of filtering at least a portion of the amount of water out of the cleaning fluid removes essentially all of the amount of water from the cleaning fluid.

22. The method according to claim 20, wherein the step of filtering at least a portion of the amount of water out of the cleaning fluid includes the step of passing the cleaning fluid through a filtration device a plurality of times.

23. The method according to claim 22, wherein a remaining amount of water in the cleaning fluid decreases after each pass of the cleaning fluid through the filtration device.

24. The method according to claim 20, wherein the dense phase gas is carbon dioxide.

25. A method of cleaning an object in a cleaning fluid, comprising the steps of: cleaning the object in a cleaning fluid including a dense phase gas and water;filtering the water out of the cleaning fluid; andcleaning the object in the cleaning fluid after the water is filtered out of the cleaning fluid.

26. The method according to claim 25, wherein the step of filtering the water out of the cleaning fluid includes the steps of: withdrawing the cleaning fluid from a cleaning chamber;filtering the water out of the withdrawn cleaning fluid; andreturning the withdrawn cleaning fluid back to the cleaning chamber after the water is filtered out of the withdrawn cleaning fluid.

27. The method according to claim 26, wherein the cleaning fluid is withdrawn from the cleaning chamber and returned to the cleaning chamber through a pipe.

28. The method according to claim 27, wherein the step of filtering the water out of the withdrawn cleaning fluid includes pumping the cleaning fluid through a filtration device included in the pipe.