EP2655263A1

EP2655263A1 - Water clarification composition and process

Info

Publication number: EP2655263A1
Application number: EP11796699.4A
Authority: EP
Inventors: Sarmistha BISWAS; Sujitkumar Suresh Hibare; Bijal Dharmvirbhai SHAH; Rudra Saurabh SHRESTH; Dhanalakshmi THIRUMENI
Original assignee: Unilever PLC; Unilever NV
Current assignee: Unilever PLC; Unilever NV
Priority date: 2010-12-24
Filing date: 2011-12-14
Publication date: 2013-10-30
Also published as: AU2011347796A1; WO2012084623A1; ZA201304275B; AU2011347796B2; BR112013015919A2; MX2013007184A; BR112013015919B1; CN103282314A; CN103282314B

Abstract

The present invention is in the field of water purification compositions and processes. In particular the invention relates to the clarification of laundry wash and/or rinse liquor for water saving by re-use. It is therefore an object of the present invention to provide water saving in household process, especially laundry processes, especially hand washin a short time. We have found that a paste comprising an electrolyte flocculant and a polymer coagulant dispersed in a continuous phase of the solution of a quaternary ammonium compounds, provides a stable and effective water purification and clarification composition.

Description

WATER CLARIFICATION COMPOSITION AND PROCESS Field of the invention

The present invention is in the field of water purification compositions and processes. In particular the invention relates to the clarification of laundry wash and/or rinse liquor for water saving by re-use.

Background of the invention

Water is becoming a more and more scarcely available commodity, especially in developing countries, where it is not unusual that people have to walk many kilometres to arrive at a water source.

Washing processes, including laundry, dishwashing and other household cleaning processes, require large amounts of water throughout the world. The discarded water is a burden to waste water treatment facilities, or to the surface water supply in developing countries.

One way of saving water is to reuse the water. To be able to reuse household water, especially laundry wash water, for the next household washing or cleaning purpose, especially the next laundry wash or laundry rinse, it is required to remove at the very least undissolved materials, remove surfactant remains, alkalinity and discolouration of the water.

Several water purification processes have been disclosed in the art.

Drinking water purification processes are for instance disclosed in Indian application 918/MUM/2000, or WO2008/092724, both of Unilever. Such systems typically make use of flocculant material to flocculate material out of the solution and a coagulant material to coagulate particles into bigger agglomerates that are easier to separate. Further more, such compositions comprise some inorganic insoluble compound to act as a seed for flocculation on the one hand and as weight to make the floes settle faster on the other hand. Drinking water purification is highly complicated as it requires a product that is suitable for human consumption and should therefore contain very low amounts of bacteria, virus and cyst. It is therefore quite expensive, and the consumer accepts that it takes time to process.

For the simple use of water for washing Laundry in developing countries, or the cleaning of other household substrates, the requirement of removal of bacteria, virus and cyst can be less stringent while the removal of surfactant is required as the recycled water will be used in subsequent wash processes and surfactant build up is not preferred. Moreover consumers would want to re-use the water of a laundry wash liquor, for the subsequent rinse, or more typically to re-use the water of the first laundry rinse for the second laundry rinse, or even to reuse the final laundry rinse water for another household purpose they do not want to wait for an hour or half an hour to process the water. Therefore to avoid the long waiting period in between each wash stage, it is desirable to treat the water in much shorter time period.

Other applications of water purification methods are typically found in the area of industrial waste water purification. Various industries, including chemical

manufacturing waste, waste from dairies and canneries, distillery waste, fermentation waste, waste from paper manufacturing plants, waste from dyeing plants and waste water from sewage and sludge treatment. US2006016761 , Ciba, discloses a method of dewatering suspensions in which a high molecular weight, water soluble, cationic polymer flocculant and an encapsulated low molecular weight water soluble, coagulant are mixed with the suspension. According to US2006016761 , the coagulant is not released into the suspension until flocculation has taken place.

These processes typically required large water treatment plants and like for drinking water purification, it may take time to process.

A fast water purification and clarification process for the treatment of household water, especially laundry wash and more typically laundry rinse water remains to be desired. It is therefore an object of the present invention to provide water saving in household process, especially laundry processes, especially hand wash.

It is a further object of the invention to provide a simple water purification composition that can be added straight into a bucket containing the dirty water.

It is yet another object of the invention that the clarification is achieved in less than 15 minutes, more preferably less than 10 minutes, still more preferably less than 5 minutes, and ideally in 2 to 3 minutes.

It is yet another object of the invention that the composition not only clarifies the water, but also removes surfactants in the same time.

It is yet another object of the invention that the composition further reduces the alkalinity of the composition.

It is yet another object of the invention that the composition is a single composition and does not require the consumer to dose different compositions and/or dose different components in a specific order.

Surprisingly we have found that a paste comprising an electrolyte flocculant and a polymer coagulant dispersed in a continuous phase of the solution of a quaternary ammonium compounds, provides a stable and effective water purification and clarification composition.

Summary of the invention

Accordingly, the present invention provides a water purification composition comprising: 30-80% by weight of an electrolyte flocculant selected from aluminium and ferric salts; 0.5-5% by weight of a neutral and/or anionically modified polymer coagulant (MW > 100 kD); and 10-40% by weight of a solution of a quaternary ammonium cationic surfactant and/or polymers of quaternary ammonium compounds; wherein the composition is in the form of a paste, wherein the flocculant and the coagulant are dispersed in a continuous phase of the solution of the quaternary ammonium cationic surfactant and/or polymers of quaternary ammonium compounds.

In another aspect the invention provides a process for water purification of wash water comprising the steps of dosing 0.3 - 2 g of the composition according to claim 1 per litre of wash water, stirring for at least 10 sec, leaving the particle to settle, and separate the particles from the water.

In the context of the present invention by the term "floe" is meant materials

aggregated in to a flocculent mass.

In the context of the present invention by the term "wash water" is meant any household cleaning water, typically laundry wash water (also referred to as wash liquor), more specifically laundry rinse water (also referred to as rinse liquor).

These and other aspects, features and advantages will become apparent to those of ordinary skill in the art from a reading of the following detailed description and the appended claims. For the avoidance of doubt, any feature of one aspect of the present invention may be utilised in any other aspect of the invention. The word "comprising" is intended to mean "including" but not necessarily "consisting of" or "composed of." In other words, the listed steps or options need not be exhaustive. It is noted that the examples given in the description below are intended to clarify the invention and are not intended to limit the invention to those examples per se.

Similarly, all percentages are weight/weight percentages unless otherwise indicated. Except in the operating and comparative examples, or where otherwise explicitly indicated, all numbers in this description indicating amounts of material or conditions of reaction, physical properties of materials and/or use are to be understood as modified by the word "about". Numerical ranges expressed in the format "from x to y" are understood to include x and y. When for a specific feature multiple preferred ranges are described in the format "from x to y", it is understood that all ranges combining the different endpoints are also contemplated. Detailed description of the invention

The present invention provides a water purification composition and a process for the purification of wash water.

Water purification composition

The water purification composition according to the invention comprises an electrolyte, a polymer, a solution of a quaternary ammonium cationic surfactant and/or polymers of quaternary ammonium compounds.

Electrolyte flocculant

The electrolyte may be any Al or/and Fe salt. They may be in pre-hydrolyzed form of bacisity (B). It is preferred that the basicity (B = AI/OH) is from 10 to 90, more preferably the basicity is in the range of 40-80.

For Al-salts the minimum solubility of Al-hydroxide is typically in the pH range of 6.8- 7.5 whereas minimum solubility of Fe-hydroxide typically ranges from pH 4-8. Furthermore, the amount of solid precipitate generated in case of the system treated with Fe-salts is high as the solubility of Fe-hydroxide is lower than Al-hydroxide in the above stated respective pH ranges. This may be used to tune the precipitation kinetics, for instance by means of using combinations of the Al and Fe electrolyte salts. Thus system treated with Fe-salts would also require the pH to be controlled less minutely and hence is more robust. However the residual dissolved Fe-salts impart colour to the water which may have a negative impact on laundry fabrics and hence is less preferred.

Without wishing to be bound by a theory, it is though that the electrolyte flocculants cause particle aggregation by mainly two well-known mechanisms which include charge neutralization and sweep flocculation. The concentration of electrolyte employed in the system regulates the mechanism involved in the process. If the electrolyte is added at a very low concentration which is lower than the solubility limit of the electrolyte, charge neutralization mechanism takes place, in which the surface charge of particles get neutralized by the oppositely charged ions of electrolyte added in the system and thereby reduces the electrostatic repulsion in between particles and promotes the particle aggregation. When electrolyte is added in excess, it undergoes hydrolysis reaction and as a result AI(OH)₃ or Fe(OH)₃ precipitates out and releases a proton. The released proton helps in reducing the alkalinity of laundry liquor and brings the pH close to neutral. Furthermore, this AI(OH)₃ or Fe(OH)₃ particles form a porous network structure into which particles get entrapped, and as this matrix settles down the particles are swept away from the system. In presence of surfactant the charge neutralization is less likely to occur, as an adsorbed surfactant layer on AI(OH)₃ or Fe(OH)₃ particles inhibits aggregation of particles by imparting steric stabilization. This is found that in case of sweep flocculation the in-situ generated AI(OH)₃ or Fe(OH)₃ is thought to deplete surfactant from the wash or rinse liquor. It is understood that the surfactant gets depleted by adsorbing on the surface of positively charged AI(OH)₃ or Fe(OH)₃ particles. Therefore Sweep flocculation is the preferred route for the particle aggregation, for laundry liquor containing both surfactants and alkalinity.

The electrolyte flocculant is present in the composition in a concentration of 30 to 80% by weight. The electrolyte flocculant is preferably present in a concentration of at least 35% by weight, more preferably at least 40% by weight and still more preferably at least 45% by weight of the composition. The electrolyte flocculant is preferably present in a concentration of not more than 70% by weight, more preferably not more than 60% by weight and still more preferably not more than 55% by weight of the composition.

The electrolyte composition may be a solid composition, a liquid composition, or anything in between, including pastes and gels.

Polymer coagulant

By polymer coagulant is meant high molecular weight adsorbing neutral or ionically modified polymers e.g. polyacrylamide.

The process of sweep flocculation destabilizes and sweeps away the particles from a dispersion as it settles, however the kinetics of settling is very slow. Furthermore, the settled mass of the floe is loose in nature, i.e. it holds lot of water within its structure, and hence it may hamper the water recovery efficiency. This problem may be solved by addition of a long chain polymer. The long chain polymers are thought to adsorb on particle surfaces and thereby bring them together to form bigger and stronger floes. This phenomenon is known as bridging flocculation. This bridging mechanism helps in increasing the settling velocity of the floes, helps in faster clarification of water and also increases water recovery efficiency.

The polymer coagulant is present in the composition in a concentration of 0.5 to 5% by weight. The polymer coagulant is preferably present in a concentration of at least 1 % by weight, more preferably at least 1.5% by weight and still more preferably at least 2% by weight of the composition. The polymer coagulant is preferably present in a concentration of not more than 4.5% by weight, more preferably not more than 4% by weight and still more preferably not more than 3% by weight of the composition.

The polymer coagulant is preferably selected from neutral and/or anionically modified adsorbing polymers. The most preferred polymers are poly acrylamides.

The polymer preferably has a high molecular weight of MW >100 kD. The molecular weight (MW) is typically less than 5000 kD, more preferably less than 2000 kD, still more preferably less than 1000 kD. The polymer is preferably water soluble.

For the avoidance of doubt by D (Dalton) is meant atomic mass unit (amu, the less commonly used SI unit).

The most preferred polymer is a neutral and/or anionically modified polyacrylamide polymer having molecular weight > 100kD.

Solution of a quaternary ammonium cationic surfactant

By solution of a quaternary ammonium cationic surfactant is meant of a solution of a quaternary ammonium cationic surfactant and/or polymers of the quaternary ammonium compounds. Although it is thought that the surfactant gets depleted by adsorbing on AI(OH)₃ or Fe(OH)₃ precipitate, it does not get completely removed as the extent of removal depends on the starting concentration in the wash liquor and/or the kinetics of removal. Therefore the treated water containing left over surfactant can not be considered to be re-usable "fresh" water in the context of the present invention.

Furthermore a very low level of residual surfactant generates foam which may give an indication of a 'not clean water' to the consumers and does not meet the standard of fresh water and therefore that water may not be acceptable by them for further use in laundry process or any other household process. Therefore it is essential to remove the maximum surfactant to a level at which it does not visibly generate foam.

To meet this requirement, the cationic surfactant is added to the system to remove the remaining anionic surfactant by precipitation, which is having much faster kinetics compared to the adsorption.

The solution of the quaternary ammonium compound is present in the composition in a concentration of 10 to 40% by weight, more preferably 20 to 40% by weight. The cationic surfactant solution is preferably present in a concentration of at least 24% by weight and more preferably at least 26% by weight of the composition. The cationic surfactant is preferably present in a concentration of not more than 35% by weight, more preferably not more than 33% by weight of the composition.

The quaternary ammonium surfactants are preferably halides of Benzalkonium, Cetyl- trimethyl-ammonium, Tetradecyl-trimethyl-ammonium, Dodecyl-trimethyl-ammonium, Stearyl-trimethyl-ammonium, Octadecyl-trimethyl-ammonium, Dodecylpyridinium, Cetylpyridinium, Tetrabutyl-ammonium, Tetraheptyl-ammonium, 1 ,3-Decyl-2-methyl- imidazolium, 1-Hexadecyl-3-methyl-imidazolium, Didecyl-dimethyl-ammonium, Didecyl-dimethyl-ammonium.

Polymers of quaternary ammonium compounds are also suitable for use in the composition. Especially the class of diallyldimethylammonium halides are preferred in the context of the present invention. It is preferred that the polymers are selected from polydiallyldimethylammonium halides, having an allyl group, defined as H2C=CH-CH₂R, wherein the carbon chain (R) is between 8 and 22 carbon atoms.

The most preferred compounds of this class are Polydiallyldimethylammonium chlorides (also known as PolyDADMAC). The allyl group, defined as H₂C=CH-CH₂R, in the PolyDADMAC polymers preferably has a carbon chain (R) of between 8 and 22 carbon atoms, more preferably less than 20, still more preferably less than 18 carbon atoms, or not more than 16 carbon atoms.

Polymers of quaternary ammonium compounds typically have a molecular weight of between 10 and 1000 kD, preferably between 40 and 400 kD.

The most preferred halide is chloride. Fluorides and iodides are contemplated in the context of the invention for their biocidal activity. Bromides are typically not preferred due to their toxicity.

The most preferred cationic surfactants for use in the present invention are benzalkonium chloride (BAC) and the class of PolyDADMACs .

Many commercially available quaternary ammonium cationic surfactants and polymers of the quaternary ammonium compounds, are commercially available in solid lump form, often giving toxic and irritating fumes. Additionally it is difficult to mix them when added to a laundry liquor and it is difficult to process when paste is made using such compounds.

Therefore the cationic surfactant is typically dosed in the form of a solution of the cationic in water, wherein the ratio of cationic surfactant to water is preferably in the range of 4: 1 to 1 :2, more preferably 2: 1 to 1 : 1 , which is found to be easier to mix and process. Buffer

A buffer may be incorporated in the formulation in cases where a wide pH variation in the wash liquor is found. The pH variability is observed due to various reasons like the source water quality, the variable dosage of detergent formulations, detergent formulation with different compositions and different wash habit of consumers.

Therefore it is important to ensure the final pH to be maintained at a level where the soluble al remains at its minimum solubility limit and also the end ph which is similar to the source water or close to neutral.

The buffer may be carbonate or phosphate system. It may be present in a range of between 5 to 20 % of total composition.

Inorganic filler

The composition may optionally comprise a filler selected from inorganic material which is non reactive to any other ingredients present in the system. This is preferably solid with a very high density.

The inorganic filler is preferably selected from natural or synthetic clays and water insoluble inorganic salts. Preferred fillers include feldspar (KAISi₃0₈), kaoline, bentonite and Attapulgite, as well as alumina (including silica alumina compositions) and MgO

The inorganic filler is thought to increase the number of particles. The increased particle number density results in faster floe formation. The floes formed are also heavier due to the extra mass of the filler and therefore settle faster. Furthermore it is thought that the presence of fillers helps nucleate the AI(OH)₃ or Fe(OH)₃ network formation thereby improves the sweep flocculation kinetics. Additionally due to its higher density, it is thought to increase the settling velocity of the floe and improve the overall flocculation kinetics. Furthermore the fillers are found to play a role as a carrier of functional ingredient like cationic surfactant and/or cationic polymer which is found to aid in the removal of the residual surfactant present in the system by precipitation or complexation. The inorganic filler is present in the composition in a concentration of 5 to 35% by weight. The inorganic filler is preferably present in a concentration of at least 10% by weight and more preferably at least 15% by weight of the composition. The inorganic filler is preferably present in a concentration of not more than 30% by weight, more preferably not more than 25% by weight of the composition.

The most preferred filler would be the 1 : 1 clays e.g. Kaolin or Feldspar.

Composition format

The composition is in the form of a paste or gel.

Due to the nature of the electrolyte flocculant and the polymer coagulants of the invention, the rate of dissolution of the electrolyte is typically somewhat higher than for the coagulant. This is beneficial to the invention. This effect may be further enhanced, by making the electrolyte particles smaller and/or less dense than the coagulant particles.

When the polymer coagulant is in particulate form it typically dissolves slowly.

Therefore excellent results are obtained when the product format is a gel or paste, wherein the flocculant and the coagulant are dispersed in a continuous phase of the solution of the quaternary ammonium cationic surfactant and/or polymers of quaternary ammonium compounds.

An alternative way of solving the dissolution issue, that separated the flocculant electrolyte and the polymer coagulant is to physically separate the two in the packaging, e.g. by providing 2 dual compositions, or a single unit-dose sachet comprising 2 chambers or pouches. Such physical separation brings about more cost for the packaging and more work for the consumer and is not the most ideal solution for those perspectives, and therefore not preferred by the consumer. Water purification process

The invention further provides a process for the purification of water comprising the steps of dosing the composition according to the invention to the wash water, stirring for at least 10 sec, leaving the particle to settle, and separate the particles from the water.

For getting good results, about 0.3 - 2 g of the composition according to the invention should be dosed per litre of wash water.

It is preferred that at least 0.4 g/L is dosed, more preferably even at least 0.5 g/L. Dosing more than 1 g/L is not providing much more improvement of the purification effect, while dosing more than 2 g/L may even be detrimental to the effect obtained.

After dosing the wash water, comprising the composition must be stirred for at least 10 second, preferably at least 20 seconds, but typically not more than 1 minute. Stirring may be done with any kind of device, such as a spoon, stick or any other stirring device.

After stirring the particles are left to settle at the bottom of the container, after which the clear and purified water can be separated, e.g. decanted from the settled floes at bottom of the container.

Settling device

In general a bucket is used for doing laundry by hand wash, mostly in the developing countries.

In a preferred embodiment the invention provides a configuration where a

configuration of settling plates is for standard size buckets is provided.

The settling plate configuration includes a means for keeping the settling plates together, e.g. a central rod, to which the plates are connected. The settling plate configuration is preferably easily removable from the bucket. Since the settling time is linearly dependent on the distance that the particles need to travel, the time required for settling with the plate configuration can be reduced by approximately a factor equal to the number of plates: ithout plates = t_With plates * n_pi_ates-

The settling plate configuration typically comprises between 3 and 10 plates, preferably between 4 and 8 plates. The plates are at a distance relative to each other of between 2 and 15 cm, preferably between 4 and 10 cm.

In a further embodiment a kit is provided, comprising a bucket and the settling plate configuration, as well as at least one dose of the composition according to the invention and a set of instructions.

The bucket may further comprise a water discharge means, e.g. a stop cock or a valve or tap arrangement, at the bottom. For the avoidance of doubt, the water discharge means in the context of the invention has at least 2 states, one open, and one closed. This will enable water to be drained from the bucket into another container when the bucket is placed at elevated height over another container.

Examples

The invention will now be illustrated by means of the following non-limiting examples. Example 1 : paste composition

In example 1 , a paste is prepared of PAC and polymer dispersed in a continuous phase of the BAC solution (1 : 1 BAC and water), compared to a dual chamber sachet comprising BAC solution in one chamber and the other ingredients in another chamber, wherein the either the first or the second sachet is dosed first.

An artificial consumer rinse liquor was prepared, containing soil, surfactant, soda, electrolyte and hardness ions.

Rinse liquor soil is a mixture of: (A) 0.25 g/L model soil which is a mixture of 90% Clay, 5% Silica, 2.5 % Carbon soot, 1.25% Fe₂0₃ and 1.25% Fe₂0₄.

(B) 1 g/L Wheel Lemon and Jasmine detergent powder, commercially available in India sourced in July'2010. (-10% surfactant, -25% Soda, -50% electrolyte and rest -15 % is minor ingredients) and

(C) water of 6 fH (2: 1)=(Ca:Mg); fH is French hardness.

The rinse liquor was characterised as follows:

The following formulations were compared

The neutral polymer was polyacrylamide (PAM, Mw = 1000-2000 kD) and the anionic polymer was anionically modified PAM (Mw = 1000-2000 kD), PAC was polyaluminium chloride (B=60) and BAC was benzalkonium chloride.

The turbidity of the resultant rinse liquor was measured

The table shows that paste give good results, while when using the 2 chamber sachet the result is dependent on whether the contents of the right chamber was dosed first.

The single composition paste thus provides a consumer benefit over a dual chamber composition, without hampering the efficacy.

Claims

1 Water purification composition comprising:

a. 30-80% by weight of an electrolyte flocculant selected from aluminium and ferric salts

b. 0.5-5% by weight of a neutral and/or anionically modified polymer coagulant (MW > 100 kD); and

c. 10-40% by weight of a solution of a quaternary ammonium cationic surfactant and/or polymers of quaternary ammonium compounds in water, where in the ratio of cationic surfactant and/or polymers is between 4: 1 to 1 :2;

d. 5-35% of an inorganic filler;

wherein the composition is in the form of a paste, wherein the flocculant and the coagulant are dispersed in a continuous phase of the solution of the quaternary ammonium cationic surfactant and/or polymers of quaternary ammonium compounds.

2 Composition according to claim 1 , wherein the quaternary ammonium

surfactants are halides of Benzalkonium, Cetyl-trimethyl-ammonium, Tetradecyl-trimethyl-ammonium, Dodecyl-trimethyl-ammonium, Stearyl- trimethyl-ammonium, Octadecyl-trimethyl-ammonium, Dodecylpyridinium, Cetylpyridinium, Tetrabutyl-ammonium, Tetraheptyl-ammonium, 1 ,3-Decyl-2- methyl-imidazolium, 1-Hexadecyl-3-methyl-imidazolium, Didecyl-dimethyl- ammonium, Didecyl-dimethyl-ammonium.

3 Composition according to claim 1 , wherein the polymers of quaternary

ammonium compounds are selected from the class of polymers of diallyldimethylammonium halides Composition according to claim 3, wherein the polymers are selected from polydiallyldimethylammonium halides, having an allyl group, defined as H2C=CH-CH₂R, wherein the carbon chain (R) is between 8 and 22 carbon atoms Composition according to anyone of claims 3 or 4, wherein the polymers of quaternary ammonium compounds have a molecular weight of between 10 and 1000 kD. Process for water purification of wash water comprising the steps of a. dosing 0.3 - 2 g of the composition according to anyone of claims 1 to 5 per litre of wash water;

b. stirring for at least 10 sec;

c. leaving the particle to settle; and

d. separate the particles from the water.