Abstract:
The present invention relates to a washing machine in which a composition is used comprising at least one liquid-liquid interface, with an interfacial tension of at least 5 mN/m. The washing machine comprises a heatable wash drum, means for storing dispensing and mixing the liquids, means for introducing the liquids into the drum, and means for filtering, separating, distilling and condensing the wash liquor and vapours and recovering the solvents. Use of the machine enables discharge of waste water with only low levels of solvent, and facilities recovering of the solvents.

Description:
TECHNICAL FIELD  
         [0001]    The present invention relates to a tumbling action washing machine. More particularly, the invention relates to a tumbling action washing machine for an immiscible, high interfacial tension system comprising two or more solvents, wherein one of the solvents is water, wherein the solvents can be conveniently recycled or the waste water treated to contain acceptable levels of the other solvent or solvents prior to disposal and to an improved process of washing using such tumbling action washing machine.  
         BACKGROUND AND PRIOR ART  
         [0002]    Conventionally fabric is cleaned using water and a detergent composition which is known as wet washing. Surfactants in the detergent composition adsorb on both fabric and soil and thereby reduce the respective interfacial energies and this facilitates removal of soil from the fabric.  
           [0003]    Alternatively cleaning can be carried out by dry cleaning wherein organic solvents are used for cleaning. Dry cleaning is traditionally an industrial laundering process carried out in a washing machine. The organic solvent helps in removal of oily soil. The particulate soil is largely removed by providing agitation.  
           [0004]    While it is desirable to add surfactants to enhance dry cleaning, surfactants are insoluble in the organic solvent. A small amount of water is therefore added to the organic solvent in a dry cleaning process to facilitate surfactant dissolution.  
           [0005]    Soil removal is achieved by a small reduction in interfacial tension.  
           [0006]    Our earlier-filed co-pending application WO-A-01/90474 published Nov. 29, 2001 discloses a process of cleaning fabric using the liquid-liquid interface of at least two immiscible liquid phases with an interfacial tension greater than 5 mN/m, under agitation. The process uses no or very much reduced levels of conventional detergent surfactants. The system is especially suitable for removing particulate soil.  
           [0007]    The process as disclosed in WO-A-01/90474 requires agitation, which may be provided by any suitable means, provided for domestic laundering or industrial laundering. The invention is especially suitable for industrial laundering.  
           [0008]    Washing machines, which provide cleaning through a tumbling action, are known to be used for dry cleaning. In such machines one or more tanks for holding the solvent are provided. The solvent is pumped into a drum where the cleaning of fabrics takes place by tumbling action. Once the cleaning is over, the solvent is drained and taken to a distillation column where the solvent is recovered and can be reused for dry cleaning.  
           [0009]    The washed fabrics in the drum are then dried by raising the temperature of the drum and thus removing the solvent from the fabrics. The solvent that is removed during drying is taken to a condenser and is then taken to the distillation column.  
           [0010]    Recovery of the solvent is essential during dry cleaning processes as most employ organic solvents that cannot be discharged into the drain.  
           [0011]    Washing machines as described above, while suitable for dry cleaning, cannot be employed for the systems as described in WO-A-01/90474, in particular for cleaning systems containing water. For systems containing 5-95% water and a less polar liquid, the ratio of the two liquids and their mixing is important and conventional pumping systems known in the art that transfer the liquid to the drum cannot be suitably employed. Such cleaning systems cannot also be directly taken to the distillation column for recovery of the solvent. Further, for solvent mixtures comprising water, it is a requirement that organic solvent should be present only at low levels in water before discharging the waste water, hence the water needs to be suitably treated before discharge.  
           [0012]    It is thus the basic object of the present invention to provide a washing machine for cleaning/washing employing a composition comprising at least two liquids and having at least one liquid-liquid interface with an interfacial tension of at least 5 mN/m (as measured by the Wilhelmy plate method, using a Kruss Processor Tensiometer K12, at 25° C.), wherein one of the liquids is a polar solvent, preferably water, and the other liquid is an organic solvent which would avoid problems of washing using such compositions in conventional washing or dry cleaning machines as discussed above. It is understood that although the terms polar and organic solvent are used in the singular, the invention also encompasses embodiments wherein mixtures of polar solvents and mixtures of organic solvents are used, respectively.  
           [0013]    Another object of the invention is directed to provide a washing machine which would enable washing/cleaning using a composition containing 5-95% a polar solvent, preferably water, and a less polar liquid, preferably an organic solvent, having means for suitable mixing of the liquids in desired proportions and allowing for separate recovery of the liquids with possible discharge of the polar solvent, preferably water, containing acceptable levels of the organic solvent.  
           [0014]    A further object is directed to an improvement in the process of laundering using a composition containing 5-95% water or other polar solvents and a less polar solvent using a washing machine thereby avoiding the problems of aqueous washing or dry cleaning as experienced in the known art.  
         SUMMARY OF THE INVENTION  
         [0015]    Thus according to one aspect, the present invention relates to a washing machine especially adapted for cleaning/washing using a composition comprising at least two liquids and having at least one liquid-liquid interface with an interfacial tension of at least 5 mN/m, wherein one of the liquids a polar solvent, preferably water, and the other liquid is an organic solvent, said washing machine comprising means to pump the liquids in the required proportions individually and/or as a mixture into a wash drum, said wash drum operatively connected to means for separation of said liquids from the wash liquor and recovery of the solvent therefrom.  
           [0016]    In accordance with a preferred aspect of the present invention, the washing machine comprises at least two holding tanks for at least two liquids, comprising at least one polar solvent and at least one organic solvent, wherefrom said liquids are pumped in said required proportions individually and/or as a mixture into the wash drum, the wash drum being provided with a drainage means which is operatively connected to a) separation means where said liquids get separated and further to a filter means for recovery of the organic solvent from the polar solvent stream, b) a distillation column for the organic solvent, and c) a condenser for recovery of organic solvent during the cleaning cycle.  
           [0017]    According to another aspect, the present invention provides an improved process for laundering fabrics in a washing machine using a composition comprising at least two liquids with at least one liquid-liquid interface with an interfacial tension of at least 5 mN/m, wherein one of the liquids is a polar solvent, preferably water, pumping the liquids, separately and/or as a mix in desired proportions into a wash drum adapted to provide agitation, the agitation taking the form of, but not limited to tumbling, reciprocating, stirring, ultrasonics and combinations thereof, washing the fabrics with said cleaning composition, the agitation being provided by the tumbling action, and drying the fabrics by raising the temperature of the drum.  
           [0018]    According to one embodiment of the invention, there is provided a washing machine for washing/cleaning of fabrics comprising:  
           [0019]    a. one or more tanks for holding liquids, the liquids being such that when mixed there is at least one liquid-liquid interface with an interfacial tension of at least 5 mN/m, wherein one of the liquids is a polar solvent, preferably water;  
           [0020]    b. means for pumping the liquids from the tank into a drum, said liquids being pumped separately or as a mixture, wherein the polar solvent is present in an amount from 5 to 95% of the total liquid composition;  
           [0021]    c. optionally providing one or more filters for the pumped liquids before introducing the said liquids into the drum;  
           [0022]    d. a drum providing for agitation for cleaning, said drum being capable of being heated and said drum being provided with an outlet for the removal of liquids and optionally an inlet for introducing a polar solvent, preferably water, from a tap;  
           [0023]    e. said drum being connected to 1) one or more filters for removal of insoluble material after the cleaning/washing process, 2) optionally a holding tank for storing the wash liquor obtained after filtering, 3) a separator for separation of the immiscible liquids provided with two outlets for removal of the liquids, one outlet being connected to one or more distillation columns; and the outlet for the polar solvent being connected to one or more filters, and 4) a means for displacing liquid vapour during drying and a condenser for recovery of said liquid vapour.  
           [0024]    According to an embodiment the improved process for laundering of fabrics of the invention comprises using a composition comprising at least two liquids with at least one liquid interface with an interfacial tension of at least 5 mN/m and wherein at least one of the liquids is a polar solvent, preferably water, and at least one of the other liquids is an organic solvent and maintaining a selective ratio of said liquids during washing and wherein after the washing process the solvents, are separated and recovered. Preferably, the selective weight/weight ratio of polar solvent to organic solvent is at least 5:95, more preferably at least 10.1:89.9, more preferably at least 25:75 most preferably at least 40:60 but preferably at most 95:5 and more preferably at most 90:10.  
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0025]    The present invention is illustrated in greater detail in relation to non-limiting exemplary illustration of the washing machine of the invention using water as the polar solvent as shown in accompanying FIG. 1.  
         [0026]    As illustrated in FIG. 1, the washing machine comprises one or more tanks for holding the liquids of the cleaning composition. Preferably three tanks (T 1 , T 2  and T 3 ) are provided, one tank holding water, the second tank holding one or more liquids immiscible with water and the third tank for optionally storing the liquid recovered after washing and distillation. Depending upon the liquids, the tanks are constructed of any suitable material like stainless steel, plastic, glass and can be of any suitable capacity.  
         [0027]    The liquid from the tanks is pumped into the wash drum (D) of the washing machine. The liquids can be pumped separately and then mixed in the drum or may be first mixed and the mixture pumped into the drum. It is preferred that the liquids be pumped separately and mixed in the drum. This can be suitably achieved by providing for two pumps (P 1 , P 2 ). Further two valves, V 1  and V 2  can be used to regulate the amount of the liquid that is being pumped. Optionally, the organic liquid is filtered by passing through a filter F 1 , for example a nylon mesh, carbon filter etc. The drum D comprises two co-axial cylindrical vessels, the outer vessel D 1  having an inlet I 1  for the liquids and an outlet O 1  for the wash liquor, an inlet I 2  and an outlet O 2  for air. The inner vessel D 2  is preferably perforated so as to allow only the passage of the liquids and to retain the fabrics in the drum. The preferred material of construction for drum D is stainless steel.  
         [0028]    It is preferred to have a dispenser on D 1  for adding benefit agents like blueing agents, bleaches, perfumes, fabric conditioners, fluorescers, anti-redeposition agents, dye transfer inhibitors etc.  
         [0029]    The outlet O 1  is connected to a filter F 2  to remove insoluble material from the wash liquor. Optionally a holding tank (HT) is provided for temporary storage of the liquids. The filter F 2  (or the Holding Tank HT) is connected to a separator (S 1 ) where the polar solvent, preferably water, and the organic solvent are separated. The separator is a vessel provided with separate outlets (O 3  and O 4 ) for the organic solvent and water. The organic solvent is removed from O 3  and taken to a distillation column (DC). The solvent recovered by distillation can be condensed in condenser C 1  and then stored in T 3 . It is possible to provide a connection between T 3  and T 1  to replenish the organic solvent in T 1 . A valve V 3  can be provided between T 3  and T 1  to regulate the amount of organic solvent entering T 1 .  
         [0030]    The outlet O 4  is connected to one or more filters, preferably carbon cartridge filters (F 3  and F 4 ). During filtering, the organic solvent is removed from the water to ensure that the water contains an acceptably low level of the organic solvent. Alternatively, the polar solvent, preferably water, can be aerated and the air can be compressed and organic solvent trapped in the air can be condensed and recycled to minimise organic solvent losses. This process of aeration can be carried out before or after passing organic through carbon filters. The polar solvent, preferably water, thus obtained can be discharged. Alternatively the polar solvent, preferably water, can be re-cycled.  
         [0031]    It is possible to periodically clean the filters F 3  and F 4  by heating said filters to remove the organic solvent or replacing said filters periodically.  
         [0032]    Optionally, the organic solvent that is recovered is sent to a condenser C 1  and then to tank T 3 .  
         [0033]    The outer vessel D 1  has a heating element to heat the washed fabrics and dry the same. Heating is done by use of known means of heating like a hot water jacket, steam heating or by electrical heating. Vapour is generated during the heating of washed fabrics. The vapour is displaced by passing air through the drum D. A suitable means like a fan (FA) can be used for circulating air. The displaced vapour and air are taken to a condenser C 2  and a filter F 5  that removes lint. The condensed liquid can be taken to holding tank HT or to the separator S 2 .  
         [0034]    The air from the condenser C 2  is typically at a low temperature. The air is passed through a heater H 1  and filters F 5  and F 6  before entering the drum. The system of FA, C 2 , H 1  and the filters forms a closed loop so that organic liquid vapours do not escape into the environment.  
         [0035]    Optionally, the condensed liquid from C 2  is taken to a separator S 2  which is provided with two outlets O 5  and O 6 . The organic liquid from outlet O 5  is taken either to the tank T 3  or to DC from where it can be returned to T 3 . The water from outlet O 6  can be suitably discharged after passing through filters F 3  and F 4 .  
         [0036]    While the washing process of the invention is especially suitable for cleaning with compositions as described in WO-A-01/90474, it can also be used for conventional wet cleaning and dry cleaning. In both processes, it is not essential to use the separators S 1  and S 2  and the filters F 3  and F 4 . The organic solvent in a dry cleaning process is taken to the distillation column DC and sent to T 3  after distillation. Similarly in the dry cleaning process, the organic solvent from condenser C 1  is sent to tank T 3 . Recovery of the solvent is not required during wet cleaning where water may be discharged as with conventional washing machines meant for wet cleaning.  
         [0037]    Process of Cleaning  
         [0038]    In the improved process for cleaning according to the invention using the above washing system, a mixture of a polar solvent, preferably water, and a less polar liquid, preferably an organic solvent, is taken such that the amount of polar solvent is from 5 to 95%, more preferably from 10.1 to 90%, more preferably from 25 to 90% and most preferably from 40 to 90% by weight of the total composition. The organic solvent can be chosen from alcohols, esters, ethers, ketones, hydrocarbons, paraffins, aromatic solvents, halogenated solvents, heterocyclics etc.  
         [0039]    Preferably, the less polar liquid is an organic solvent having a carbon chain length of at least 4, preferably more than 6 selected from branched and linear alkanes (chemical formula C n H 2n+2  where n is greater than 6), including but not limited to hexane, heptane, octane, nonane, decane, dodecane, tridecane, tetradecane, pentadecane etc. and mixtures thereof. Commercially available mixtures of this type include Isopar L (C 11 -C 15  alkanes—ex-Exxon) and DF2000 (C 11 -C 15  iso-alkanes ex-Exxon). Branched and linear alkenes with more than 6 carbon atoms including but not limited to octenes, nonenes, decenes, undecenes, dodecenes etc, with one or more double bonds and mixtures may also be used.  
         [0040]    Halogenated solvents include hydrofluorocarbons, chlorocarbons or chlorofluorocarbons. Examples thereof include perchloroethylene, tetrachloromethane (carbon tetrachloride) or trichloroethylene (chloroform).  
         [0041]    Ethers including fluoroethers such as methoxy nonafluorobutane HFE-7100™ (i.e. C 4 F 9 —OCH 3 ) and ethoxy nonafluorobutane HFE-7200™ (i.e. C 4 F 9 -OC 2 H 5 ), esters, such as dibutyl phthalate, dioctyl phthalate and terpenes, such as limonene or mixtures thereof may be used. Particularly fatty acid methyl esters are suitable, such as C 8 -C 24  saturated and/or unsaturated fatty acid methyl esters, particularly C 12 -C 18  fatty acid methyl esters like methyl laurate, methyl myristate methyl stearate, methyl linoleate, methyl linolenate and mixtures thereof.  
         [0042]    Silicones with more than 3 SiO units can also be used as the less polar liquid. They may be selected from polydimethyl siloxane oils. Linear and cyclic siloxanes known as Lx and Dx where x is greater than three are suitable for this technology. Specific examples include octamethylcyclotetrasiloxane(D4) (ex-Dow Corning), decamethylcyclopentasiloxane (D5), dodecamethylcyclohexasiloxane (D6), decamethyltetrasiloxane (L4) and do decamethyl pentasiloxane (L5).  
         [0043]    The polar liquid is preferably selected from the group comprising alcohols, (including diols, triols) alkanolamines, sulphoxides, sulphoxamine, water and mixtures thereof. Especially preferred are short chained alcohols, C1-C10, more preferably C1-C4, especially monohydric alcohols, water and mixtures thereof. Preferable liquids include ethanol, methanol, monoethanol amine, water and mixtures thereof.  
         [0044]    Benefit agents (I) can be added either to the solvents or through the dispenser.  
         [0045]    The polar liquid and the other liquid generally form a system of two immiscible liquids and are preferably separately pumped into the drum D and then mixed by a tumbling action. Soiled fabrics ( 2 ) maybe present in the drum before pumping the liquids or may be introduced into the pumped liquids. The cloth:liquor ratio (w/w) is suitably maintained at 1:10 to 1:20.  
         [0046]    The fabrics are agitated for a suitable period by means of the tumbling action for a suitable amount of time. Preferably the agitation time is at least 5 minutes, more preferably 15 minutes and most preferably 60 minutes.  
         [0047]    The liquids are then drained through the outlet O 1 . The fabrics are then dried by heating the drum D. The evaporated solvents are taken to a condenser and recovered.  
         [0048]    The process of the invention provides for enhanced detergency, in particular for detergency of particulate soil.