WO1995027098A1

WO1995027098A1 - Method and apparatus for dry cleaning garments

Info

Publication number: WO1995027098A1
Application number: PCT/IT1995/000035
Authority: WO
Inventors: Gabrio Renzacci
Original assignee: Renzacci S.P.A. Industria Lavatrici
Priority date: 1994-03-31
Filing date: 1995-03-09
Publication date: 1995-10-12
Also published as: IT1269091B; AU1959395A; EP0753092A1; ITFI940061A0; ITFI940061A1

Abstract

A method for the dry-cleaning of garments and linens which provides for the use as a washing solvent of a mixture of linear and branched haliphatic non-halogenated hydrocarbons substantially free of aromatics, with flash point between 40 and 100 °C. The method also provides for that drying and distilling operations for the solvent recovery be carried out under vacuum conditions. The relevant apparatus comprises means for creating vacuum conditions in the washing drum (pump 12), the ventilation circuit (2) and in the still (10) and its related equipment.

Description


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   DESCRIPTION
METHOD AND APPARATUS FOR DRY CLEANING GARMENTS. 



   Field of the Invention
The present invention relates to a method for the dry cleaning of garments and linens of the type using organic solvents. The invention also relates to a machine for dry cleaning garments and linens operating according to the above-mentioned method. 



   Description of the prior art
As is known in systems for dry cleaning garments and linens (these terms intended to also comprise any other item that can be dry cleaned), the most commonly used solvents are of a chlorinated type and in particular employ perchloroethylene and Freon 113 (cfc). In the traditional systems used in the great majority of cases, the cleaning of the garments is carried out by bringing them in contact with the solvent and maintaining this contact for a preestablished period. Subsequently the garments are separated from the solvent, by emptying the washing vessel, and dried by means of circulation of hot air which causes the evaporation of the solvent. The hot air containing the solvent is then cooled so that the latter condenses and can thus be recovered.

   Small amounts of solvent still remaining in the air used for drying can be removed in various ways, for example by absorption before discharging the air into the atmosphere. The cleaning solvent, used in a closed cycle, is periodically freed of impurities through distillation. 



   Dry cleaning machines of known types comprise, therefore, a washing vessel containing a rotating basket for garments and linens, a tank for the solvent and the relative means of circulation, a heating unit for the drying air, a condenser¯for the solvent entrained with said 

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 air and, finally, a distillation and recovery unit for the solvent. 



   One of the problems most felt by users of the systems described above is the one relative to the emissions of chlorinated solvents in the air which, because of their harmful characteristics, are regulated by very strict laws. 



  With the coming into force of new international regulations for the safeguard of the environment and ecosystem, the use of chlorinated solvents employed up to now will almost certainly be prohibited. 



   The main object of the present invention is, therefore, to provide a new dry cleaning method for garments and linens which does not provide for the use of chlorinated organic solvents. 



   A further object of the present invention is to provide a method of the above-mentioned type in which the steps of the cleaning cycle are optimized in relation to the type of solvent used without increasing, and possibly decreasing, the costs of operation with respect to traditional methods. 



   An additional object of the present invention is to provide a machine for dry cleaning garments and linens able to operate according to the above-mentioned method. 



     Summary   of the Invention
According to the present invention, as the washing solvent, there is used a solvent having a base of linear and branched non-halogenated aliphatic hydrocarbons that are essentially free of aromatic groups and having a flash point comprised between 40 and   100 C.   



   A further characteristic of the method according to the present invention consists in the fact that the drying steps for the garments and the steps for distillation of the solvent are carried out under a vacuum in order to reduce the operating temperature and therefore decrease the 

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 risks of inflammation of the air-solvent mixture during these steps. 



   According to the invention, a machine for dry cleaning garments is also provided comprising means for creating a vacuum in the washing vessel and in the ventilation circuit, as well as in the unit for distillation and recovery of the solvent. 



   The characteristics and advantages of the dry cleaning method for garments and linens and the relative dry cleaning machine will become more apparent in the following description of one of its embodiments, given as an example, but not limitative, with reference to the attached drawing in which a simplified scheme of the machine according to the invention is provided. 



     Besto   mode of carrying out the Invention
With reference to the above-mentioned figure, 1 indicates the barrel of a dry cleaning machine in which a basket (not shown) for garments is rotatingly mounted, whereas 2 indicates the ventilation circuit for the drying air for the garments comprising a condenser with its relative refrigerator group 3a for the removal of the solvent from the circulating air as well as a heater for the air 4 which uses the heat produced by the refrigerator group (heat pump), and finally a secondary heater such as a steam battery 5 with relative ventilator 3.

   The machine also comprises a tank for the solvent 6 and a distillation and recovery unit for the solvent generically indicated by 7 and comprising 8, a condenser 9, and a still collection tank 10 for the solvent-water mixture, a phase separator 11 and a vessel 27 for decantation of the solvent-water mixture before distillation to limit the water load in the still. The machine also comprises a power supply circuit as well as a solvent recovery circuit with the relative pump (not shown). The components indicated above are all 

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 of a conventional type and are functionally connected to one another in a known way. The blocks indicated with 25 and 26 indicate the conventional filters installed respectively downstream and upstream from the cleaning solvent circulation pump both for the solvent returning from and supplying the barrel 1. 



   According to the invention; the machine comprises means for producing a pre-established vacuum pressure inside the barrel and inside the ventilation circuit 2, as well as inside the distillation unit 7. These means comprise a vacuum pump 12 of the liquid ring type which aspirates the solvent from the auxiliary tank 13 through an aspiration duct 14. The pump 12 is connected to the barrel 1, the ventilation circuit 2 and the distillation unit 7 by means of the respective conduits 15,16 and 17 intercepted by electrovalves 18,19 and 20. By means of these conduits, to accomplish the desired vacuum pressure, the pump 12 aspirates air mixed with solvent which is sent by, means of the conduit 21 to the collection tank 10, and from the tank 10 into the solvent-water separator 11 from which the solvent is returned to the tank 13 through conduit 22. 



  The air, which is continuously aspirated by various components of the machine, is collected in the solvent tank 13 from which, through a conduit 23, it is conveyed to an absorber 24 through which it is passed before its definitive discharge into the atmosphere. 



   During the washing step in the barrel 1, the interception valves 18,19 and 20 remain closed and the vacuum pump 12 is inactive. At the termination of the washing cycle, before beginning the circulation of drying air through the circuit 2, the liquid ring pump 12 is put in operation and the opening of the valves 18,19 and 20 is commanded until the desired vacuum pressure is created in 

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 the barrel 1, the circuit 2 and, if in operation, in the distillation unit 7. 



   The solvent used is a linear and branched aliphatic hydrocarbon solvent having a flash point comprised between 40 and 100 C and preferably between 50 and 60 C. A product such as that commercially known as ACTREL 56, produced by EXXON, could be advantageously used for the purposes of the present invention. Its main physical characteristics are the following: - flash point: 56 C - lower explosive limit in air at 25 C 0.6% vol. 



   - upper explosive limit in air at 25 C 7% vol. 



   - density: 0.76 g/cm3 - commencement of distillation at atmospheric pressure: 180 C - end of distillation at atmospheric pressure: 195 C - inflammability class: A3 
The vacuum pressure necessary with this type of solvent is 150-350 millibars in the ventilation circuit 2 where, during drying, the temperature is on the order of 40-80 C, while it must be maintained at 50-150 millibars in the distillation unit 7 where the operating temperature is slightly higher. 

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   A typical cleaning cycle of the machine according to the present invention comprises the following steps: - a first washing step lasting about 5-15 minutes at room temperature and atmospheric pressure, with a solvent taken from the first tank, and a subsequent centrifuging of 2-6 minutes possibly sending the dirty solvent to the distillation unit 7; - a second wash step lasting about 4-5 minutes, at room temperature and atmospheric pressure, with the solvent taken from the second tank and passage through a filter, followed by a final centrifuging; - drying under vacuum for 30-60 minutes at a temperature of 40-80 C and at a pressure of 150-350 millibars; - cooling for 5-15 minutes at atmospheric pressure in order to bring the garments back to a temperature close to room temperature. 



   There are various types of hydrocarbon solvents available on the market equivalent to the one given as an example above which can obviously be used as an alternative. 



   It should be noted that the use of the vacuum in the drying step, besides avoiding the risks of inflammation of the solvent-air mixture, allows for a considerable saving in energy because of the lower temperatures used and the reduced drying time with respect to those required in traditional methods. Furthermore the drying step is faster. Similarly, operating under vacuum, the distillation and recovery of the solvent can be conducted more quickly and at a lower temperature with a consequent saving of energy.

Claims

CLAIMS 1. Method for dry cleaning garments and linens, of the type wherein the organic liquid solvent is kept in contact with the garments and linens for a defined time and is subsequently separated from them in order to proceed to their drying by means of circulation of hot air from which the solvent is subsequently removed by cooling and/or absorption, the solvent furthermore being subjected to cyclic distillations to eliminate the impurities accumulated in it, said method being characterized by the fact that said solvent is a linear and/or branched nonhalogenated aliphatic hydrocarbon fraction substantially free of aromatic groups and having a flash point comprised between 40 and 100 C and by the fact that the drying and distillation operations are carried out under vacuum conditions.

2. Method according to claim 1, wherein the flash point of the solvent is comprised between 50 and 60 C.

3. Method according to claim 1, wherein the vacuum pressure in the drying step is comprised between 150 and 350 millibars.

4. Method according to claim 1, wherein the vacuum pressure in the distillation step is comprised between 50 and 150 millibars.

5. Method according to claims 1 and 3, wherein the operative temperature in the drying step is comprisedbetween 40 and 80 C.

6. Apparatus for the dry cleaning of garments and linens comprising a barrel for bringing the garments or linens contained in a basket rotating within the barrel into contact with an organic cleaning solvent, means for supplying the solvent to said barrel from a collection tank, a ventilation circuit communicating with said barrel for bringing hot air in contact with the garments and <Desc/Clms Page number 8> providing for their drying by removing the solvent, said circuit comprising a condenser for recovering the solvent entrained with the air and a heater for heating the air before re-admitting it into the barrel, said apparatus being characterized in that it comprises means for creating a pre-established vacuum pressure inside said barrel and said ventilation circuit during the drying step of the garments, as well as inside said solvent distillation unit.

7. Apparatus according to claim 6, wherein said means for creating the vacuum comprises a vacuum pump communicating with a tank for the solvent, conduits intercepted by electrovalves returning from said barrel, as well as from said wentilation circuit and said distillation unit toward said pump and a unit for the treatment of the solvent containing air coming from said tank for removing the solvent before discharging the air into the atmosphere.

8. Apparatus according to claims 6 and 7, wherein said pump is of the liquid ring type.

9. Apparatus according to claim 7, wherein said airtreatment unit comprises a solvent-absorption column.