A Process And A Device For Removing A Stain From A Fabric

Abstract

The invention is to provide a process for removing a stain from a fabric comprising a step of passing an electric current of from 0.01 A to 10 A using a voltage/current source across at least two electrodes through an aqueous solution of a substance capable of generating an oxidative or reductive bleaching species, whilst keeping the stained area of the fabric in contact with the aqueous solution and positioned at a distance not greater than 3 cm from one of the electrodes.

Information

Applicants

Inventors

Specification

FORM-2
THE PATENTS ACT, 1970
(39 of 1970)
&
The Patents Rules, 2006
PROVISIONAL SPECIFICATION
(See Section 10 and Rule 13)
A PROCESS AND A DEVICE FOR REMOVING A STAIN FROM A FABRIC
HINDUSTAN UNILEVER LIMITED, a company incorporated under
the Indian Companies Act, 1913 and having its registered office
at 165/166, Backbay Reclamation, Mumbai -400 020, Maharashtra, India
The following specification describes the invention

Technical Field
The invention relates to a process, a device, and a kit for removing a stain from a fabric.
Background and Prior Art
Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of the common general knowledge in the field.
Use of bleaching agents, particularly of oxidative bleaches is well known for removing stains. The cleaning compositions comprising bleaching agents are however prone to the problem of storage stability and loss of bleaching species with time. Other problem associated with bleaching compositions, particularly those with high concentration of bleaching agents, is potential damage to fabric as well as skin/eyes of the user. Further, the bleaching agents may not be compatible with commonly used packaging materials.
Electrochemical generation of oxidative or reductive bleaching species near the point of use avoids certain problems associated with storage, stability and safety of bleaching compositions.
Electrochemical generation of bleaching compounds in washing machines is also known. For example, CN1370879 (Wu Hao, 2002) describes a process for washing clothes by installing electrodes in washing machine and electrolyzing sodium chloride added into water to produce hypochlorous acid ion for eliminating dirt. EP0146184 (Whirlpool, 1989) describes an automatic laundry washing machine comprising a container for the salt (NaCl), a water reservoir connectable to a water source, and a cell for the electrochemical production of sodium hypochlorite (NaOCl) and hydraulically connected to the reservoir by way of the salt container. The water reservoir is also hydraulically connected to the cell by a further path which enables the cell to be filled with water


to a predetermined height by using the water which exceeds a given level in the reservoir.
The electrolytic cleaning methods in washing machines described in the prior art suffer from certain disadvantages. Firstly, the washing machines typically operate at a ratio by weight of water to fabric of 10 or more. At such ratios, the generation of effective amount of bleach concentration required to remove stains would require relatively long electrolysis time and/or relatively high voltage/current, resulting into relatively high energy consumption. Further, in washing machines, it is common practice to clean a washload comprising several other garments and clothing articles along with the stained garment. Contact of effective concentration of bleach with unstained portion of the stained garment and delicate and/or coloured garments in the rest of the washload and garment accessories like lace and buttons can cause damage and/or discolouration. In addition, using washing machine for cleaning localized stains from a fabric is not convenient, particularly when the user wants to quickly clean stain on a single fabric.
Some of the problems associated with electrolytic generation of bleaching agents in washing machines can be mitigated by electrolytically generating the bleaching agents and dispensing them on the stained area of a fabric.
US2003062267 (Nakamura et al, 2003) teaches a method and an apparatus for generating a portable sterilizing water that can be easily used at, for example, hospitals, cafeterias of nursing facilities, restaurants, hair salons or homes. The electrolyzer is structured such that a tubular-shaped ferrite anode and a cathode are arranged alternately in a concentric manner with an inter-electrode distance, and integrated with a pressurizable solution container containing halogen ions and a power control apparatus so that it can be carried and operated by one hand.


US20020023847 (Natsume et al, 2002) describes a cleansing system comprising an electrolysis chamber wherein the alkaline solution is formed from an electrolyte, such as salt and water. At least one pump outputs the alkaline solution onto an object to be cleansed. Further, a second pump may output an acidic solution formed in the electrolysis onto the object to disinfect or sterilize the object.
US20030098244 (Ruhr et al, 2003) describes generation of chlorinated alkaline cleaning solutions by electrolysis by providing electrolytic cell for producing and dispensing chlorine and sodium hydroxide for use in various cleaning and/or sanitizing formulations as and when needed.
The methods described above involve generating and dispensing or spraying of electrochemically generated bleaching agents. One of the problems associated with these methods is that the amount of free chlorine available in the water decreases upon storage. The process of dispensing or spraying the solution is accompanied by further reduction in free chlorine available for bleaching. Another problem associated with dispensing of electrochemically generated pre-prepared bleaching compositions is the possibility of spillage or contact with unwanted area of fabric or hands. The containers used to carry out electrolysis, if left open to atmosphere, lead to reduction in available chlorine with time. On the other hand, if electrolysis is carried out in closed and/or pressurized containers, the accumulation of gaseous hydrogen released during electrolytic process in a confined space can be potentially hazardous.
In view of the above disadvantages of the prior art, there is a need for an effective and efficient process for removing localized stains from a fabric.


Therefore, one of the objects of the present invention is to overcome or ameliorate at least some of the disadvantages of the prior art, or to provide a useful alternative.
Another object of the present invention is to provide a process for removing a stain from a fabric that provides relatively faster and/or better cleaning.
Yet another object of the present invention is to provide a process for removing a stain from a fabric that is relatively more energy-efficient.
Yet another object of the present invention is to provide a
process for removing a stain from a fabric that reduces or
eliminates the requirement of contact of user with the
bleaching compositions.
The present inventors have found that the stain can be removed from a fabric by passing a current of from 0.01 A to 10 A using a voltage/current source across at least two electrodes through an aqueous solution of specific substances whilst keeping the stained area of the fabric within specific distance from the electrodes.


Summary of the invention
According to the present invention there is provided a process for removing a stain from a fabric comprising a step of passing an electric current of from 0.01 A to 10 A using a voltage/current source across at least two electrodes through an aqueous solution of a substance capable of generating an oxidative or reductive bleaching species, whilst keeping the stained area of the fabric in contact with the aqueous solution and positioned at a distance not greater than 3 cm from one of the electrodes.
According to another aspect of the present invention, there is provided a device for removing a stain from a fabric comprising a body attached to and electrically insulated from at least two electrodes, wherein:
a. the electrodes are electrically contactable with
a voltage/current source;
b. the body comprises a container for holding an
aqueous solution of a substance capable of
generating an oxidative or reductive bleaching
species, and;
c. said container is connected to a handle, which in
turn is hingedly connected with a lid such that
the lid can be manipulated to position the
stained area within a distance not greater than 3
cm from one of the electrodes.
According to another aspect of the present invention, there is provided a kit for removing a stain from a fabric; said kit comprises (i) a device, (ii) a substance capable of generating an oxidative or reductive bleaching species during dissolution or electrolysis, and (iii) a set of instructions for use, wherein;
the device comprises a body attached to and electrically insulated from at least two electrodes, the electrodes being electrically contactable with a voltage/current source, and the device being capable of passing an electric current of 0.01 to 10 A across the electrodes, and;


the set of instructions for use instructs the user to dissolve said substance in water to form an aqueous solution, to contact the stained area of the fabric with the aqueous solution of said substance and to hold the device such that the stained area of the fabric is positioned within a distance not greater than 3 cm from one of the electrodes, and to electrically contact the electrodes with a voltage/current source.
Brief Description of the drawings:
Figure 1 - Process of removing a stain from a fabric.
Figure 2 - Container-type device for removing a stain from a
fabric.
(a) lid open
(b) lid closed
Figure 3 - Device for removing a stain from a fabric, with delivery system, during use.
The numerals used in the drawings represent the following.
1 - Device
2 - Body
3 - Anode
4 - Cathode
5 - Current/voltage source
6 - Aqueous medium
7 - Stained area of the fabric
8 - Handle
9 - Container

10 - Lid
11 - Hinge
12 - Aperture
13 - In-built power supply
14 - Delivery means
15 - Refillable container made of a resilient material
16 - Tube
17 - Pressure-actuated valve
18 - Filling port


Detailed description of the invention
According to the present invention there is provided a process for removing a stain from a fabric comprising a step of passing an electric current of from 0.01 A to 10 A using a voltage/current source across at least two electrodes through an aqueous solution of a substance capable of generating an oxidative or reductive bleaching species during dissolution or electrolysis, whilst keeping the stained area of the fabric in contact with the aqueous solution and positioned at a distance not greater than 3 cm from one of the electrodes.
Aqueous solution of the substance
In the process, an aqueous solution of a substance is used. The substance that can be used according to the process of the present invention is capable of generating a bleaching species during dissolution or electrolysis.
Ay substance that is capable of generating a bleaching species during dissolution, i.e., a bleaching agent, can be used according to the present invention. The substance can be an elelctrolyte or a non-electrolyte. However, it is preferred that the substance is an electrolyte capable of generating a bleaching species during electrolysis. The electrolyte need not be a bleaching agent itself.
Bleaching species may be oxidative or reductive. Preferably, the substance is capable of generating an oxidative or reductive bleaching species during electrolysis. The applied electric current can also activate/ accelerate the bleaching process.
There are several types of bleaching species. For example, sodium hypochlorite or calcium hypochlorite, which generate hypochlorous bleaching species upon dissolution, hydrogen peroxide, sodium perborate or sodium percarbonate, which generate peroxide bleaching species. Other bleaching agents include sodium persulfate, sodium perphosphate, sodium


persilicate, their ammonium, potassium and lithium analogs, calcium peroxide, zinc peroxide, sodium peroxide, carbamide peroxide, chlorine dioxide, bromate, and organic peroxides (e.g., benzoyl peroxide).
Oxidative bleaching species include chlorine, chlorine dioxide, nascent oxygen, and hypochlorite. It is also envisaged that when oxidative bleaching species, in particular hypochlorite, is generated during electrolysis, there is additional biocidal effect besides the removal of stains. Some examples of electrolytes capable of generating an oxidative bleaching species during electrolysis include chloride or chlorate salt of alkali metal or alkaline earth metal. Some examples of substances capable of generating oxidative bleaching species upon dissolution include phthalimido perhexonic acid and hydrogen peroxide.
While most bleaches are oxidizing agents, other processes can be used to remove colour. For example, sodium dithionite is a powerful reducing agent that can be used as a bleach. Some examples of electrolytes capable of generating a reductive bleaching species during dissolution or electrolysis include sulphite, dithionite, sulphate and bisulphite of alkali metal. Other substance that can be preferably used according to the present invention includes reducing sugars. Reducing sugars may be selected from dextrose, lactose, sucrose or mixtures thereof.
According to a preferred aspect, the substance capable of of generating a bleaching species during dissolution or electrolysis is selected from (a) hypochlorite, hypochlorite, perborate, percarbonate, persulfate, perphosphate, persilicate, bromate, chloride, or chlorate salt of ammonium, alkali metal, or alkaline earth metal, or (b) sulphite, dithionite, sulphate or bisulphite of alkali metal, or (c) peroxide of alkali metal, hydrogen, or alkaline earth metal, carbamide peroxide or benzoyl


peroxide, or (d) phthalimido perhexonic acid, or (e) dextrose, lactose, or sucrose.
The concentration of the substance is at least 0.1 g/L of the aqueous solution. The upper limit of concentration of substance is the maximum concentration of the substance beyond which it is insoluble. The concentration of the substance is preferably from 0.1 to 400, more preferably from 1 to 300, and most preferably from 10 to 300 g/L of the aqueous solution.
Aqueous solution may further comprise an additional electrolyte that is not capable of producing an oxidative or reductive bleaching species upon dissolution or electrolysis, particularly when the substance itself is not an electrolyte. The aqueous solution may further comprise a surfactant. The surfactant may be anionic, cationic or non-ionic. It is envisaged that the aqueous solution may further comprise of fluoroscer, optical brightner, perfume, and other benefit agents.
The conductivity of the aqueous solution is preferably from 0.1 to 1000, more preferably from 1 to 1000 and most preferably from 1 to 500 mS/cm.
The stained area of fabric is preferably completely wetted by the aqueous solution. The stained area of the fabric may be wetted by spraying or pouring the aqueous solution on the stained area or by pre-soaking the stained area of the fabric in the aqueous solution. It is preferred that the stained area of the fabric is immersed in a pool of the aqueous solution. The amount of aqueous solution in contact with the fabric is preferably enough to completely wet the stained area. The passage of current is preferably started after ensuring that the stained area of the fabric is sufficiently wetted. If stained area of the fabric is not completely wetted, or if the amount of aqueous solution used is not enough, the local temperature increase can cause


damage to fabrics. The amount of aqueous solution is preferably from 0.1 to 30, more preferably from 1 to 20, most preferably from 2 to 10 g/cm2 area of fabric. The term area of the fabric as used herein means the apparent surface area of one side of the fabric that is in contact with the aqueous solution of electrolyte. For example, a 10 cm x 10 cm square swatch of fabric has an area of 100 cm2.
Typically, the stained area of fabric is a small fraction of the entire surface area of the fabric. It is preferred that the aqueous solution is contacted with the stained area. It is envisaged that some unstained area surrounding the stain is inevitably wetted by the aqueous solution. However, it is preferred that the unstained area of fabric in contact with the aqueous solution is minimal. It is particularly preferred that the entire fabric is not contacted with the aqueous solution. The liquor to cloth ratio, i.e. the ratio of mass of the aqueous solution to the mass of the fabric is preferably less than 15, more preferably less than 10, and most preferably less than 5. The liquor to cloth ratio in washing machines is normally above 20. Therefore, the wastage of aqueous solution, and that of the bleaching species generated in the aqueous solution, is thus avoided in the process of the present invention. If the bleaching species is generated by electrolysis, the required high power consumption would render the process economically unviable. Further, only the area that is contacted with the aqueous solution needs to be dried. Therefore, the process of present invention offers relatively more convenient and fast removal of a stain as compared to washing machines capable of generating bleaching species in which entire fabric needs to be wetted. Other advantage of the process of the present invention over washing machines capable of generating bleaching species is that entire fabric and rest of the washload is not contacted with the aqueous solution and/or bleaching species thereby avoiding potential damage to other garments in the washload and/or delicate garment accessories like lace, buttons and elastic.


Preferably, the aqueous medium is open to atmosphere so that gaseous products generated during the process are not accumulated in a confined space. Preferably, the aqueous medium is not enclosed in a confined space. Alternatively, if the aqueous medium is enclosed in a confined space, an opening or an aperture is provided for discharging the gaseous products generated during the process to prevent or reduce accumulation thereof in a confined space.
Aqueous solution is at a temperature preferably from 1 to 95°C, more preferably from 10 to 70 °C and most preferably from 20 to 60 °C. The aqueous solution may be preheated prior to the process or heated at the point-of-use by heating means such as electrical resistive heaters. It is also envisaged that the heat is generated in-situ by electrical dissipation due to passage of current through the aqueous solution.
Voltage/current source, current, period of current The voltage/current is periodic or aperiodic with respect to time. The voltage/current is preferably ac or dc or pulsed. More preferably, the voltage/current is ac or dc. It is particularly preferred that the current/voltage is dc. In case of ac, any waveform such as rectangular, triangular, sinusoidal can be used. If the voltage/current is sinusoidal ac, the frequency is preferably less than or equal to 60 Hz.
The current that is passed through the aqueous medium is preferable from 0.01 A to 10 A, more preferably from 0.5 A to 5 A, and most preferably from 1 to 3 A. In case the voltage/current is ac, the current refers to root mean square value.
The current is passed through the aqueous solution of the substance for a period of preferably from 10 to 600 s, more preferably from 10 to 400 s, and most preferably from 20 to 180 s.


The voltage/current source may be battery powered. More preferably, the voltage/current source is powered by household electricity mains (110 V, 60 Hz or 230 V, 50 Hz) . Preferably, a step-down transformer is used to lower the voltage, and a voltage rectifier circuit is used to convert the ac voltage into dc. Other power supplies that can be used include constant voltage/ current supplies; switch mode power supply (SMPS), pulsed power supplies, charge injectors and the like.
Electrodes
In the process of the present invention, an electric current of from 0.01 to 10 A is passed across at least two electrodes through the aqueous solution of a substance capable of generating bleaching species. It is possible to use a plurality of electrodes in various configurations with at least two electrodes electrically connected to a voltage/current source. Additional electrodes may be active electrodes connected to voltage/current source. Alternatively, additional electrodes may be passive electrodes interspersed between active electrodes.
The electrodes are spatially separated by a distance of preferably 0.01 to 10 cm, more preferably from 0.1 to 5 cm, and most preferably from 0.1 to 2 cm.
Electrodes are made of conducting or semiconducting material, i.e. metals, conducting polymers, metalloids, semimetals, alloys, carbon, graphite, or combinations thereof. Preferably, electrode material is graphite, metal, or alloy.
It is preferred that the electrode surface is coated with metallic oxides. It is particularly preferred that the electrode surface is coated with titanium oxide, molybdenum oxide, ruthenium oxide or mixtures thereof. Other commercial surface coating referred to as dimensionally stable anode or DSA can also be used. Coated electrodes are


particularly preferred if the electrode material is aluminium, copper, iron or steel.
During the process of the present invention, the stained area of the fabric is positioned at a distance not greater than 3 cm, preferably 2 cm, more preferably 1 cm from one of the electrodes. At least one of the electrodes is positioned at a distance of less than 3 cm from the stained area of the fabric. It is particularly preferred that the stained area of the fabric is in contact with at least one electrode.
Without wishing to be limited by theory, it is believed that the bleaching species generated during electrolysis is highly unstable, and hence, positioning the stained area of the fabric closer to the electrode where the bleaching species is generated provides more effective stain removal. It is particularly preferred that the distance of at least one of the electrodes from the stained area of the fabric is maintained at a distance of less than 3 cm, throughout the duration of passage of current.
It is preferred that the electrode nearest to the stained area of the fabric is anode when the electrolyte is capable of producing an oxidative bleaching species upon electrolysis or dissolution. It is preferred that the electrode nearest to the stained area of the fabric is cathode when the electrolyte is capable of producing a reductive bleaching species upon electrolysis or dissolution.
The electrodes may be positioned on the same side of the stained area of the fabric. The electrodes may be below the fabric or above the fabric. Alternatively and preferably, the stained area of the fabric is interspersed between the electrodes.


Some additional preferred features of the process According to a preferred aspect, agitation is provided to promote the contact of the stained area of the fabric with the solution. The agitation may be provided by motion of the aqueous solution, motion of electrode, motion of the fabric or by providing an external agitation means such as a mechanical agitator/stirrer.
The aqueous solution may be recirculated or replenished at a suitable flow rate to the stained area of the fabric. The aqueous solution may be preferably stored in a container and supplied to the stained area.
A delivery means is preferably used to deliver the aqueous solution to the stained area of the fabric. The aqueous solution is delivered to the stained area of the fabric preferably prior to or during the passage of current.
A suction means is preferably used to transport the aqueous solution away from the stained area of the fabric. Suction means is used preferably during or after the passage of current.
The stained area of the fabric is preferably contacted with a stain-absorbent pad made of material capable of absorbing water. The stain-absorbent pad reduces or prevents the spreading of stain to unstained area of fabric and/or restaining.
It is envisaged that the process of the present invention may by used along with the process of cleaning of a fabric using electric field as described in patent applications by Unilever (WO2004/105970 and WO2006/056367) which are incorporated herein by reference. The step of cleaning using an electric field can be prior to, after, or concurrent with the process of the present invention.


Device for removing a stain from a fabric
According to one aspect of the present invention, there is provided a device for removing a stain from a fabric comprising a body attached to and electrically insulated from at least two electrodes, the electrodes being electrically contactable with a voltage/current source, and the device being capable of passing an electric current of 0.01 to 10 A across the the electrodes through an aqueous solution of a substance capable of generating an oxidative or reductive bleaching species during dissolution or electrolysis, whilst keeping the stained area of the fabric in contact with the aqueous solution and positioned within a distance not greater than 3 cm from one of the electrodes.
Preferably, the device comprises a handle attached to the body. The handle provides convenience for maintaining the electrodes in position during cleaning.
In one of the preferred embodiment of the device, the body comprises a container capable of holding the aqueous solution in contact with the stained area of the fabric.
According to a particularly preferred embodiment, there is provided a device for removing a stain from a fabric comprising a body attached to and electrically insulated from at least two electrodes, wherein:
a. the electrodes are electrically contactable with
a voltage/current source;
b. the body comprises a container for holding an
aqueous solution of a substance, capable of
generating an oxidative or reductive bleaching
species, in electrical contact with the
electrodes, and;
c. said device comprises a handle attached to the
container, said handle is hingedly connected with
a lid such that the lid can be manipulated to
position the stained area within a distance not
greater than 3 cm from one of the electrodes.


It will be appreciated that the device is capable of passing an electric current of from 0.01 A to 10 A across the electrodes through the aqueous solution whilst keeping the stained area of the fabric in contact with the aqueous solution and positioned within a distance not greater than 3 cm from one of the electrodes.
Preferably, the lid has an aperture for discharging gaseous products generated during the process to prevent or reduce accumulation thereof in a confined space.
Preferably, the body comprises a delivery means capable of delivering the aqueous solution to the stained area of the fabric.
Preferably, the body comprises a suction means capable of transporting the aqueous solution away from the stained area of the fabric.
Preferably, the device comprises a stain-absorbent pad made of water-absorbable material is removably attachable to an electrode such that the pad can be contacted with the stained area of the fabric.
Preferably, the device comprises of a fabric holding means for holding the fabric within said distance.
Preferably, the device comprises an agitation means to promote the contact of the fabric with the solution. The agitation means may be an agitator in rotary or reciprocal motion of electrodes. The agitation means may be a jet of liquid or gas directed towards stained area. The agitation means can be in form of a scrubbing means that is capable of rotary or reciprocating movement. The scrubbing means is provided with preferably at least one bristle head, and more preferably a plurality of bristles.


According to another particularly preferred embodiment, there is provided a device for removing a stain from a fabric comprising a body attached to and electrically insulated from at least two electrodes, wherein:
a. the electrodes are electrically contactable with
a voltage/current source located within the body;
b. the electrodes are positioned in the body such
that the device is capable of being placed on
the fabric with the stained area of the fabric
within a distance not greater than 3 cm from one
of the electrodes;
c. the body comprises a refillable container for
holding an aqueous solution of a substance,
capable of generating an oxidative or reductive
bleaching species, in electrical contact with the
electrodes and;
d. the container is connected to a delivery means
capable of delivering the aqueous solution to the
stained area of the fabric.
It will be appreciated the device is capable of passing an electric current of from 0.01 A to 10 A across the electrodes through the aqueous solution whilst keeping the stained area of the fabric in contact with the aqueous solution and positioned within a distance not greater than 3 cm from one of the electrodes.
Detailed Description of the drawings:
Referring to Figure 1, the process for removal of a stain is carried out using a device (1) which comprises a body (2) attached to and electrically insulated from electrodes (anode(3) and cathode(4)), which are connected to an external current/voltage source (5). The device is positioned such that the electrodes are immersed in the aqueous medium (6) comprising a substance capable of generating an oxidative or reductive bleaching species during dissolution or electrolysis, and the stained area of the fabric (7) is positioned at a distance of not greater


than 3 cm from one of the electrodes. It will be appreciated that when a current is passed across the electrodes through the aqueous medium, the bleaching agent is generated in-situ that effectively cleans the stain. The device further comprises a handle (8) attached to the body. It can be appreciated that the device can be conveniently placed on the stained area of the fabric by manipulating the device using the handle.
Now referring to Figure 2, the body of the device (1) comprises a container (9) capable of holding the aqueous medium (6) in contact with the stained area of the fabric (7). The container is attached to a handle (8) which in turn is attached to a lid (10) by means of a hinge (11) . The anode (3) is attached to and electrically insulated from the bottom of the container (9) whilst the cathode (4) is attached to and electrically insulated from the lid (10). The lid is provided with an aperture (12) for discharging the gaseous products of electrolysis thereby preventing accumulation thereof in a confined space. The current/voltage source is an in-built power supply (13) to which the electrodes are connected. Figure 3(a) shows the device with lid open, for easy insertion of the stained area of the fabric (7) in the aqueous medium (6). It will be appreciated that the lid (10) can be easily manipulated in closed position as shown in Figure 3(b) by using hinge (11) such that the stained area of the fabric is positioned at a distance of not greater than 3 cm from one of the electrodes. When a current is passed across the electrodes through the aqueous medium, the bleaching species is generated in-situ that effectively cleans the stain.
Now referring to Figure 3, the body comprises an in-built power supply (13) and a delivery means (14). The delivery means (14) comprises a refillable container made of a resilient material (15) to store the aqueous solution and a tube (16) connected to the said container through a pressure-actuated valve (17). The container can be


replenished with the aqueous solution through the filling port (18). During use, the device is placed on the stained area of the fabric (7) with the electrodes touching the fabric and pressure is applied to the container (15) manually to actuate the valve (17) such that the aqueous solution is delivered to the stained area of the fabric (7) through the tube (16).
Kit for removing a stain from a fabric
According to another aspect of the present invention, there is provided a kit for removing a stain from a fabric; said kit comprises (i) a device, (ii) a substance capable of generating an oxidative or reductive bleaching species during dissolution or electrolysis, and (iii) a set of instructions for use, wherein;
the device comprises a body attached to and electrically insulated from at least two electrodes, the electrodes being electrically contactable with a voltage/current source, and the device being capable of passing an electric current of 0.01 to 10 A across the electrodes, and;
the set of instructions for use instructs the user to mix said substance with water to form an aqueous solution, to contact the stained area of the fabric with the aqueous solution of said substance and to hold the device such that the stained area of the fabric is positioned within a distance not greater than 3 cm from one of the electrodes, and to electrically contact the electrodes with a voltage/current source.
Although the above kit comprises a specific embodiment of a device, it is envisaged that the kit may comprise any other embodiments of the device according to the present invention.
Preferably, the instructions to user instruct the user to form an aqueous solution wherein the concentration of the substance is from 0.1 to 400 g/L.


Examples
The invention will now be demonstrated with examples. The examples are by way of illustration only and do not limit the scope of the invention in any manner.
Materials and Methods
Following materials/equipment was used in the examples.
Table 1: Materials/equipment

Material/equipment Source
Deionized water Scientific Distillery Works, Bangalore
Sodium Chloride Merck
Sodium sulphite (anhydrous) Qualigens fine chemicals
Sodium carbonate Merck
Graphite electrode Graphite India
Power supply (DC 0-300 V) DOT Technologies, Bangalore
Spectrophotometer - Colour Eye 7000 A Gretag Macbeth
Dimmerstat step down transformer (0-260 V rms AC, 50 Hz) AE
Test fabric with black tea stain, RAGU® sauce stain, lipstick stain, black shoe polish stain, mud stain Warwick Equest, UK
Chlorine estimation protocol
Aqueous solutions, for which free chlorine was to be measured, were stored in a stoppered conical flask and covered with aluminium foil to minimize interaction with light and/or air. Free chlorine was measured by iodometric titration method; the details are given in Vogel's Text Book of Quantitative Chemical Analysis (Fifth Edition, 1989, Longman Publishers).
Fabric cleaning protocol
Fabric was placed in aqueous solution of a substance. Substances used include electrolytes (sodium chloride, magnesium chloride, potassium chloride, sodium carbonate, sodium sulphite, sodium dithionite, sodium bisulphite, and


sodium sulphate). Non-electrolyte substances include dextrose and pthalamido perhexonic acid. All the aqueous solutions were made using deionized water. The concentration of the substance used was in the range of 0 to 300 g/L. The conductivity of the solutions was in the range of 0.05 mS/cm to 500 mS/cm. A stained fabric swatch was dipped in the aqueous solution. Two electrodes were also immersed in the aqueous solution. Various types of electrodes were used including graphite, titanium.
The electrodes were connected to the power supply, which was also equipped with an ammeter for measurement the current passing through the aqueous solution and a voltmeter for measurement of potential difference across the electrodes. Most of the experiments were carried out using dc voltage/current source. Some experiments were carried out with ac voltage/current source at frequency of 50 Hz (sinusoidal waveform). When ac voltage/current source was used, the measured value was root mean square value of current/voltage.
The electrodes were positioned such that the distance between the stained area of the fabric and one of the electrodes was varied from 0 to 5 cm. The distance of 0 cm meant that the electrode was in contact with the fabric. The details of the electrode used and the distance between the stained area of the fabric and one of the electrodes are given separately.
Rectangular flat plate electrodes (2 cm x 3 cm) were used in the experiments. The electrodes were placed adjacent to each other in same plane with the nearest distance between the electrodes being 0.5 cm.
The current was passed through the aqueous solution for a duration varying from 0 to 180 seconds, and was measured using a stopwatch.


No agitation of the aqueous solution was provided unless mentioned otherwise. In some experiments, a magnetic stirrer was used at rpm of approximately 50 for promoting agitation of the aqueous solution. In some experiments, the electrodes were manually moved over the stained area to provide agitation of the aqueous solution.
Control experiment was carried out using sodium carbonate as a substance that does not generate a bleaching species during electrolysis or dissolution. Another control experiment was carried out using known amount of bleaching agent sodium hypochlorite at a concentration of 0.66 g/L.
Measurement of degree of stain removal
Spectrophotometer was used for measurement of AE. AE was calculated from the difference in L, a and b values after and before cleaning, from the equation given below.

Effect of distance between stained area of the fabric and one of the electrodes
30 V dc was applied across graphite electrodes, and the current of 1.4 A was passed through 30 mL of aqueous solution of 13.2 g/L sodium chloride (conductivity 12 mS/cm) whilst the fabric swatch stained with black tea was positioned at a distance varied from 0 cm (fabric touching the electrode) and 2 cm from one of the electrodes (anode) , corresponding to Example 1 and Example 2 respectively. The passage of current was for 180 seconds. Examples 3 and 4 were similar to Examples 1 and 2, respectively, except that the stirring was provided by means of a magnetic stirrer. Example 5 was similar to example 3 except that AC current was passed instead of DC.
Process of comparative example 1-A was carried out with the stained area of the fabric positioned at a distance of 6 cm


from one of the electrodes. Comparative example 1-B was similar to comparative example 1-A except that the stirring was provided by a magnetic stirrer.
The process of comparative example 1-C was similar to the process of example 1, except that the stained fabric was not contacted with the aqueous solution during passage of current. Instead, the stained fabric was contacted with the aqueous solution immediately after the passage of current. In comparative example 1-D, fabric swatch was immersed in 30 mL of sodium hypochlorite solution in which free chlorine was approximately equivalent to the amount electrolytically generated. Comparative example 1-E was similar to example 1-D in all respects expect that stirring was provided by using a magnetic stirrer. The cleaning efficacy was evaluated by measurement of AE. Free chlorine was measured in all the cases. The results are tabulated below.
Table 2: Effect of distance between fabric and nearest electrode

Example Distancebetweenfabric andnearestelectrode(cm) Stirring Electrolysis Freechlorine(ppm) AE
1 0 No Yes 710 31.8
2 2 No Yes 710 20.4
3 0 Yes Yes 852 31.1
4 2 Yes Yes 852 24.2
5 0 Yes Yes* 78.1 16.8
1-A 6 No Yes 710 13.8
1-B 6 Yes Yes 852 13.4
1-C 0 No Yes** 852 11.6
1-D - No No*** 887.5 11.4
1-E - Yes No*** 887.5 10.6
* AC current
** Fabric contacted with the solution after electrolysis
*** Fabric contacted with the solution of sodium
hypochlorite


Comparison of cleaning efficacy of processes of examples 1 and 2, to that of example 1-A and 1-B, clearly shows the importance of positioning the electrode such that the distance between the fabric and nearest electrode is not greater than 3 cm. It is also seen that cleaning efficacy is the best when the stained area of the fabric is in contact with electrode. Superior cleaning efficacy of processes of examples 1 and 2 over that of comparative examples 1-C and 1-D, shows that contacting fabric with the electrolyte solution during electrolysis whilst chlorine is generated in-situ, is better as compared to contacting the fabric with aqueous solution comprising equivalent amount of free chlorine. Processes of example 3 and 4 indicate the role of stirring. Stirring is seen to improve cleaning efficacy when the fabric is not in contact with the fabric. Cleaning result for example 4 and example 5 shows that dc is preferable over ac. The process is seen to be suitable for removing local stains in relatively short time and consequently is more energy-efficient.
Effect of current, voltage, duration of electrolysis, and concentration of substance
Following experiments were carried out under similar conditions to those of example 3. However, the concentration of substance, voltage/current and duration of electrolysis was varied, and the details along with cleaning efficacy are tabulated below.


Table 3: Effect of current, voltage, duration of electrolysis and electrolyte concentration

Example No Concentration of sodium chloride (g/L) Voltage (V) Current (A) Duration of electrolysis (s) AE
6 300 20 3.6 15 14.0
7 300 20 3.6 30 26.7
8 300 20 3.6 60 33.4
9 300 20 3.6 120 36.2
10 300 9 1.0 120 25.6
11 300 15 2.0 120 32.6
12 300 25 4.0 120 36.8
13 0.05 310 0.15 180 14.6
Examples 6-9 show that the cleaning efficacy increases with the duration of electrolysis. Examples 9-13 indicate that cleaning efficacy increase with amount of current passed. It can be also seen that the amount of current is very low even when the voltage is relatively high when the concentration of electrolyte is low (Example 13).
Type of substance
Examples 14-17 and corresponding comparative examples 14-A-16-A demonstrate the various types of substances that are capable of generating a bleaching species, and also various types of stains that can be cleaned. Examples 14 and 15 are with electrolytes capable of generating bleaching species during dissolution. Example 16 is for a substance capable of generating oxidative bleaching species during dissolution. Example 17 is for a substance capable of generating reducing bleaching species during dissolution. Comparative Examples 14-A to 17-A correspond to Examples 14-17, respectively, except that no electrical current was passed. The cleaning efficacy was evaluated using various stains. The duration of each experiment was 180 s. The experimental details and the cleaning efficacy are tabulated below.


Table 4: Effect of type of substance

ExNo Stain Substance and its cone. (g/L) Voltage (V) Current (A) AE
14 Lipstick Sodium sulphite, 10 g/L 50 1.05 47.4
15 Lipstick Sodium dithionite, 13.8 g/L 50 1.05 45.5
16 Black tea Phthalimido perhexonic acid 8 g/L 200 0.1 22.7
17 Lipstick Dextrose 14.2 g/L 317 0.04 12.9
14-A Lipstick Sodium sulphite, 10 g/L — _ 3.5
15-A Lipstick Sodium dithionite, 13.8 g/L — __ 4.4
16-A Black tea Phthalimido perhexonic acid 8 g/L 12.8
17-A Lipstick Dextrose 14.2 g/L - - 5.6
By comparing the AE values, it is clear that cleaning efficacy is better when electric current is passed through an aqueous solution of a substance capable of generating a bleaching species.
It will be appreciated that the example above describe the manner in which the process of the present invention can be performed, and go on demonstrate that the process of the present invention provides relatively faster and/or better cleaning and is relatively more energy-efficient. As the entire fabric need not be contacted with the aqueous solution, the process of the present invention is more convenient and can reduce damage by avoiding contact of delicate and/or unstained area of the fabric with the bleaching species.

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