Field of the invention

The present application relates to a water clarification composition, and more particularly, to a metal-free polymeric water clarification composition for purification of dirty source water that is effective in clarifying both hard and soft water.

Background of the invention

There is an increasing need to provide efficient and cost-effective means to improve the quality of water at the point of use. For example, groundwater is a major source of water for both drinking and domestic use, especially in developing countries. However, groundwater is often contaminated with sediments and other particulates, which makes the water turbid. Not only is turbid water less appetizing to drink, in some cases it can harbour harmful bacteria. Additionally, the suspended solids may also change the appearance and colour of clothes washed in such water and, also damage appliances which use such water.

One way of removing turbidity in water is by precipitating suspended matter in water using a flocculent like alum (potassium aluminum sulfate dodecahydrate or aluminum sulphate). When turbid water is treated with a flocculent such as alum, the electrostatic repellent forces keeping the solids suspended is neutralized and the solids

agglomerate to form larger particles known as‘floes’ which settle down slowly to the bottom. Disadvantage of using alum as flocculant is that the performance is

substantially affected at lower temperatures and there is a poorer efficiency towards attracting organic suspended solids. A relatively large dose becomes necessary.

Adding excess coagulant beyond charge-neutralization results in the formation of metal coagulant precipitates and is termed sweep flocculation. Metal coagulants are for example metal hydroxides (e.g., AI(OH)3 or Fe(OH)3 (ferric chloride). Al-based salts or Fe-based salts, are added in sufficient amount so that they form amorphous AI(OH)3 or Fe(OH)3 particles. These amorphous particles entrap suspended solids leading to clarification of water. AI(OH)3 or Fe(OH)3 particles with entrapped suspended solids called sweep floes, have a size in the range of 100 pm or below. At this size the sweep floes are still difficult to separate from the water by, e.g. filtration or decantation. Moreover, the kinetics of settling of the sweep floes is very slow. Although ferric chloride is good at attracting inorganic solids, a lower efficiency for organic solids is observed.

It is known that in order to improve the kinetics of flocculation for achieving clarification of water a polymer flocculant, such as polyacrylamides (including acrylamide-acrylate copolymers), may be added. This type of flocculation encompasses the addition of a polymer flocculant with a molecular weight of at least 100 kDa. These polymers are believed to adsorb on to the sweep floes and thereby bring the sweep floes 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 and contributes therefore to faster clarification of water.

There are numerous issues with using metal-based flocculants. High levels of residual aluminium, especially high levels of polyaluminium chloride, in clarified water, are associated with potential health issues. One of the possible way of having lower levels of aluminium is to have iron in the formulation. However, residual iron in water causes yellowing of fabrics, which is a problem for laundry related applications.

US 2014/158633 AA (PSMG LLC) describes a flocculant composition comprising a blend of a particulate polyethylene oxide and a particulate polyacrylamide.

The order of these processes is regulated by the differences in dissolution kinetics; the electrolyte flocculants are readily soluble, in contrast to the polymer flocculants.

Betaine-based amphoteric polymers have been applied in detergent compositions. US 8,883,262 BB (RHODIA RECHERCHES AND TECH, 2014) describes a hard surface cleaning composition comprising a combination of (a) a sulphobetaine or

carboxybetaine zwitterionic polymer and (b) at least one cationic polymer. The US patent further describes hard surface cleaning compositions containing a combination of (a) a phosphobetaine zwitterionic polymer and (b) at least one anionic polymer.

Metal-free flocculation/coagulation compositions are not widely known/used for clarification/purification of dirty turbid water. Use of cationic polymers along with anionic polymers for flocculation is well known in prior art. However, the disadvantage of using cationic polymer based flocculants are two-fold: 1 ) they work in a specific range of cationic:anionic polymer and Any small change in the ratio leads to restabilization of particles (i.e. increase in turbidity) and; 2) they show aquatic toxicity)

WO2018062510 (Unilever,) discloses a composition comprising an anionic polymeric flocculent (polyacrylamide), an amphoteric polymer having carbo/sulpho betaine units The application is particularly effective against turbid water. The advantage of this polymer is that it is commercially available.

GB 211205 discloses water-soluble high molecular weight quaternary ammonium graft copolymers comprising a substrate portion and a graft portion. The substrate portion is derived from a water-soluble quaternary ammonium composition having a plurality of hydroxypropylene groups having the structure -A-CH2CH(OH)CH2-A-, wherein A is a tertiary or quaternary nitrogen and in which the number of quaternary nitrogen exceeds the number of tertiary nitrogen atoms. The graft portion is derived from a polymeric composition comprising polymerized water-soluble nonionic, anionic or cational vinyl addition monomers.

However, there is still an unmet need for coagulating compositions that are equally or almost equally effective against hard as well as soft water. While turbidity of impure water is a concern for those who need to use it for consumption and other household chores, the hardness, or alternatively the softness of the water may become a factor which limits or restricts the applicability of commercially available compositions/kits for purifying such water.

Summary of the invention

The present invention provides a metal-free water clarification composition comprising:

(i) 0.1 to 50% by weight of dry matter of anionic polymeric flocculant, preferably a polyacrylamide;

(ii) 0.4 to 90% by weight of dry matter of an amphoteric -copolymer having a weight-average molar mass from 2000 g/mol to 5,000,000 g/mol, said amphoteric copolymer comprising:

(a) at least one anionic monomer selected from the group of ethylenically

unsaturated acids, preferably (meth)acrylic acid; and (b) at least one cationic, amphoteric or zwitterionic monomer selected from the group of [N-substituted] (meth)acrylamide compounds comprising at least two quaternary nitrogen atoms; and

(iii) 0 to 95 % by weight of dry matter of inert filler, wherein the combination of the anionic polymer flocculant, the amphoteric copolymer and the inert filler constitutes from 50 % by weight to 70 % by weight of the water clarification composition.

The present invention also relates to a use of the water clarification composition for clarifying source water. The present invention further relates to a process for clarifying water. The process comprising the steps of: dosing the water clarification composition in a dose of 0.2 to 3 grams per liter of water to be clarified; dispersing the water clarification composition throughout the water to be clarified to induce the formation of floes; and, separating the floes from the water to obtain clarified water.

The water clarification composition of the present invention is effective in clarification of both hard and soft water with enhanced kinetics.

Detailed description of the invention As used herein the term“comprising” encompasses the terms“consisting essentially of and“consisting of”. Where the term“comprising” is used, the listed steps or options need not be exhaustive.

Unless otherwise specified, numerical ranges expressed in the format "from x to y" are understood to include x and y. In specifying any range of values or amounts, any particular upper value or amount can be associated with any particular lower value or amount.

Except in the examples and comparative experiments, or where otherwise explicitly indicated, all numbers are to be understood as modified by the word“about”. All percentages and ratios contained herein are calculated by weight unless otherwise indicated.

As used herein, the indefinite article“a” or“an” and its corresponding definite article “the” means at least one, or one or more, unless specified otherwise.

The various features of the present invention referred to in individual sections above apply, as appropriate, to other sections mutatis mutandis. Consequently, features specified in one section may be combined with features specified in other sections as appropriate. Any section headings are added for convenience only, and are not intended to limit the disclosure in any way.

The term‘flocculation’ as used herein refers to a process of contact and adhesion whereby the particles of a dispersion form larger-size clusters.

The term“turbidity” as used herein refers to the cloudiness or haziness of a fluid caused by a large number of individual particles.

The unit“NTU” as used herein refers to Nephelometric Turbidity Units (NTU), as measured by the nephelometer, Turbiquant 2100T, manufactured by Merck. The nephelometer is preferably calibrated by using the standard formazin solutions as recommended by the instrument manufacturer. The nephelometer measures the propensity of particles to scatter a light beam focused on them.

The term“inert filler” as used herein refers to particulate component(s) in the composition that do not significantly contribute to the clarification of turbid water.

The term hardness of water is the French hardness and indicated as FH.

The term“polyacrylamide” as used herein, unless indicated otherwise, refers to a polymer derived from acrylamide, and derivatives thereof (such as N,N- dimethacrylamide and N-isopropylacrlyamide) and/or methacrylamide and derivatives thereof.

For a given amount of soil present in a litre of water, if the turbidity of such water is measured, then there will be significant difference between the values depending on the hardness of the water. It is observed, in such cases, the turbidity of the soft(er) water is higher than the hard(er) water. It is known that particles of soil have a negative Zeta potential and in soft water there are no counterions to screen these charges. Therefore, the negative potentials keep the particles separated from each other and prevent, or at least significantly reduce, the coalescence of the particles. This leads to more stable colloids which appear more turbid. However, in hard(er) water, the cations eg, (Ca ²⁺ , Mg ²⁺ ) present in water screen the charges. This reduces the stability of the colloidal particles which manifests itself as lower turbidity.

The present invention provides a water clarification composition comprising:

(i) 0.1 to 50% by weight of dry matter of anionic polymeric flocculant;

(ii) 0.4 to 90% by weight of dry matter of an amphoteric copolymer having a weight-average molar mass ranging from 2000 g/mol to -5,000,000 g/mol, said amphoteric copolymer comprising:

(a) at least one anionic monomer selected from the group of

ethylenically unsaturated acids; and

(b) at least one cationic, amphoteric or zwitterionic monomer selected from the group of [N-substituted] (meth)acrylamide compounds comprising at least two quaternary nitrogen atoms; and

(iii) 0 to 95% by weight of dry matter of inert filler; wherein the combination of the anionic polymer flocculant, the amphoteric copolymer and the inert filler constitutes at least 50% by weight, to at least 70% by weight of the water clarification composition.

Preferably, the combination of the anionic polymer flocculant, the amphoteric copolymer and the inert filler constitutes at least 70% by weight of the water clarification composition, more preferably at least 80%, even more preferably at least 90% by weight of the water clarification composition.

The water clarification composition of the present invention comprises, calculated by weight of dry matter: • 0.2 to 10 % by weight, more preferably 0.5 to 5 % by weight of the anionic polymeric flocculant;

• 0.6 to 50 % by weight, more preferably 1 to 10 % by weight of the

amphoteric copolymer; · 45 to 99 % by weight, more preferably 70 to 97 % by weight filler.

The water clarification composition according to the present invention may be provided, for instance, in the form of a solid (e.g. a powder or tablet), a paste or a gel.

Preferably the water clarification composition of the present invention is a dry powder.

More preferably, the water clarification composition of the present invention is a powder having a mass weighted mean particle size in the range of 10 to 100 micrometers, more preferably in the range of 50 to 90 micrometers.

The inventors of the present invention have found that the aforementioned combination of an anionic polymer and an amphoteric copolymer provides excellent settling kinetics for clarification of turbid water, even in the absence of metal flocculants and metal coagulants. The experiments involve measuring the turbidity after two minutes of flocculation with the aforementioned combination of an anionic polymer and an amphoteric polymer. Typical metal-free flocculants show much higher turbidity after two minutes of flocculation.

Anionic Polymeric Flocculant The anionic polymeric flocculant employed in accordance with the present invention is preferably selected from anionic polyacrylamide, anionic polyacrylate and combinations thereof. Most preferably, the polymeric flocculant is anionic polyacrylamide.

The anionic polymeric flocculant is preferably a copolymer of acrylamide and one or more anionic monomers selected from acrylic acid, methacrylic acid, 2-acrylamido-2- methylpropane sulphonic acid and salts thereof.

At least 5%, more preferably 10 to 50% of the monomeric units in the anionic polyacrylamide are anionic monomers selected from acrylic acid, methacrylic acid, 2- acrylamido-2-methylpropane sulphonic acid and salts thereof. Preferably at least 5% of the monomeric units in the anionic polyacrylamide are selected from methacrylic acid, acrylic acid and salts thereof. More preferably 10 to 50% of the monomeric units in the anionic polyacrylamide are selected from

methacrylic acid, acrylic acid and salts thereof.

The anionic polymeric flocculant of the present invention has molecular weight of at least 100,000 Da. More preferably, the molecular weight of the anionic flocculant is at least 250,000 Da.

Even more preferably, the molecular weight of the anionic flocculant is at least 500,000 Da and most preferably at least 1 ,000,000 Da.

It is preferred that the molecular weight of the anionic flocculant does not exceed 20 million Da.

For avoidance of doubt, the unit Da (Dalton) as used herein refers to atomic mass unit (amu, the less commonly used SI unit).

Amphoteric Copolymer

The amphoteric copolymer employed in accordance with the present invention comprises at least one anionic monomer. The at least one anionic monomer is selected from a group of ethylenically unsaturated acids. Preferably, the ethylenically unsaturated acid is (meth)acrylic acid.

The amphoteric copolymer employed in accordance with the present invention comprises at least one cationic, amphoteric or zwitterionic monomer. The at least one cationic, amphoteric or zwitterionic monomer is selected from a group of [N-substituted] (meth)acrylamide compounds comprising at least two quaternary nitrogen atoms. The at least two quaternary nitrogen atoms are optionally modified with a sulfo or phospho end group. Preferably the end group is selected from sulfonate, sulfate, phosphonate, or phosphate. Preferably, the [N-substituted] (meth)acrylamide compound is N-[ 3- (Dimethylamino)propyl]methacrylamide

In general, the amphoteric copolymer of the present invention has a molar mass of at least 2000 g/mol.

Preferably, the amphoteric copolymer of the present invention has a molar mass from 10,000 to 10,000,000 g/mol. More preferably, the amphoteric copolymer of the present invention has a molar mass from 1 ,000,000 to 5,000,000 g/mol.

In general, the amphoteric copolymer of the present invention is represented by the general formula (I):

(Formula 1 )

Where in R1 , R2, R3, R4, R5, R6 are alkyl groups, V is either -NFh, -COOH or COCH ₃ , and Z is -SO3’ COO or PO4 ³ groups.

The amphoteric copolymer of the present invention is preferably a sodium sulfonate end-group modified copolymer of: Acrylic acid; and Methacrylamido propoyl pentamethyl hydroxypropane diammonium chloride.

Preferably, the amphoteric copolymer of the present invention is selected from the group consisting of polyquaternium -74, poly(hexamethylammonium) chloride (Q6/6 or its isomers Q12/6 and Q4/6), poly [oxyethylene (dimethylimino) ethylene- (dimethylimino) ethylene] dichloride (PDED), poly[dodecamethylene-dimethylimino chloride (Q6/12), and alkyldimethylammonium chloride].

One amphoteric copolymer that is particularly preferred is represented by the following formula II:

(Formula II) where, x having a number-average value of from 0 to 50% and preferably from 0 to 30%, preferably equal to 0, y having a number-average value of from 10% to 95% and preferably from 50% to 70%, z having a number-average value of from 0.1 % to 50% and preferably from 10% to 50%, the ratio y/z preferably being from about 4/1 to 1/2 and preferably between 4/1 and 1/1 , x+y is from 50% to 99.9%.

The ion X is advantageously chosen from halide, for example chloride, sulfate, methyl sulfate, hydrosulfate, phosphate, citrate, formate and acetate.

Most preferably, the amphoteric copolymer is Polyquaternium -74. Polyquaternium-74 is apolymeric quaternary ammonium salt consisting of dimethylaminopropyl methacrylamide, acrylic acid.

Inert Filler

The filler preferably comprises a coating that contains the anionic polymeric flocculant and/or the amphoteric polymer. Most preferably, the filler comprises a coating that contains the amphoteric polymer, optionally in combination with the anionic polymeric flocculant. By applying these polymers as part of a coating onto particulate filler rapid dissolution of the polymers can be achieved when the clarification composition is dispersed into water. Furthermore, homogeneous distribution of these polymers throughout the water clarification composition can be realised in this way. The inert filler preferably contains at least 80 % by weight more preferably at least 90 % by weight and most preferably 100 % by weight of one or more water soluble components. Here the term“water soluble components” refers to components that have a solubility in demineralized water at a temperature of 20 °C of at least 1 g/l, preferably of at least 5 g/l and most preferably of at least 10 g/l.

The one or more water-soluble components are preferably selected from

carbohydrates, polymers, electrolytes and combinations thereof. More preferably, the one or more water soluble components are selected from carbohydrates, electrolytes and combinations thereof. Most preferably, carbohydrate is used as a filler. Examples of suitable carbohydrates include monosaccharides, disaccharides, oligosaccharides and combinations thereof. Examples of electrolytes include salts such as sodium chloride, calcium chloride, magnesium chloride, potassium chloride and combinations thereof.

The inert filler preferably has a mass weighted mean particle size in the range of 5 to 500 micrometer, more preferably in the range of 10 to 150 micrometer, most preferably in the range of 50 to 90 micrometer.

The inert filler preferably has a surface area of at least 1 m ² /g and a porosity of less than 30 vol.%. Surface area measurements can be done using the BET method (Brunauer et al. "Adsorption of Gases in Multimolecular Layers". Journal of the American Chemical Society (1938) 60(2): 309-319.). Porosity can be measured by methods known in the art, for e.g., using mercury porosimetry.

The clarification composition of the present invention does not require metal salt coagulants to effectively remove turbidity from water. Accordingly, the composition preferably contains less than 0.5 % by weight dry matter of a metal salt coagulant selected from aluminum sulfate, aluminum chloride, polyaluminum chloride, aluminum chlorohydrate, ferric sulfate, ferrous sulfate, ferric chloride and combinations thereof.

Preferably, the ratio of the amphoteric copolymer to the anionic polymer, in the water clarification composition of the present invention, is selected from 3:1 , 4:1 or 5:1. The ratio of amphoteric copolymer to the anionic polymer, is preferably 3:1 , more preferably 4:1 and even more preferably at least 5:1.

In general, the ratio of the amphoteric copolymer to the anionic polymer, in the water clarification composition of the present invention, is 3:1. Preferably, the ratio of the amphoteric copolymer to the anionic polymer, in the water clarification composition of the present invention, is 4:1.

More preferably, the ratio of the amphoteric copolymer to the anionic polymer, in the water clarification composition of the present invention, is, 5:1. In a second aspect, the present invention relates to the use of an amphoteric copolymer as defined herein for clarifying turbid water.

In a third aspect, the present invention relates to a pprocess for clarifying water comprising suspended solids, said process comprising the steps of: a. dosing the water clarification composition according to the first aspect, in a dose of 0.2 to 3 grams per liter of water to be clarified; b. dispersing the water clarification composition throughout the water to be clarified to induce the formation of floes; and, c. separating the floes from the water to obtain clarified water.

In the process of the present invention the clarification composition is preferably dosed in a dose of 0.1 to 10 grams per litre water. More preferably the clarification

composition is dosed in a dose of 0.5 to 5 grams per litre water and most preferably in a dose of 0.5 to 2 grams per litre water.

Dispersing of the water clarification composition throughout the water to be clarified can be achieve, for instance, by stirring. Stirring in the process of the present invention is preferably performed for at least 10 seconds, more preferably performed for 15 to 60 seconds and most preferably the stirring of the mixture is performed for 15 to 50 seconds. Different patterns of stirring may be followed applied, e.g. stirring-pause- stirring or stirring-pause or variations thereof.

The separation of the precipitate from the water is preferably performed by filtration, decantation and combinations thereof. More preferably the separation of the precipitate from the water is performed by filtration.

Preferably, the turbidity of the water to be clarified is reduced to less than 20 NTU, more preferably to less than 10 NTU by the present process. Typically, the water to be clarified in the present process has an initial turbidity of 400 NTU or more.

The invention is further illustrated by the following non-limiting examples.

Example 1

Formulation development and Optimization

Formulation details: varying levels of amphoteric copolymer, Polyquaternium -74 (Mirapol PQ 74), and anionic polyacrylamide (MW 6 Ma, 70% acrylamide, 30% acrylic acid)

Procedure: To 1 litre of dirty source water (60 FH) containing 0.2 g/l of soil, a mixture of Mirapol PQ 74 and anionic polyacrylamide (for levels see examples below) were added. The water was stirred for 10 seconds, followed by a 10 seconds gap and a further 10 second stirring when floes start forming. The water is allowed to stand for a further two minutes by which time all floes settle at the bottom. An aliquot of the water from the top is taken and turbidity measured using a turbidity meter.

Effect of Water Hardness on flocculation

A turbidity value < 10 is acceptable to consumers and lower values are preferred. As can be seen, only polyquaternium 74 or only anionic polyacrylamide do not give optimal flocculation. When both the polymers are present in appropriate levels, water with very low turbidity results.