WO2023072893A1 - Use of high molecular weight narrow polydispersity polymers as flocculants or viscosifiers - Google Patents

Abstract

Use of high molecular weight narrow polydispersity polymers as flocculants or viscosifiers Use of a polymer as a flocculant to aid in the dewatering of an aqueous solids suspension wherein the polymer is formed from one or more ethylenically unsaturated monomers and which polymer has a weight average molecular weight Mw of greater than 500,000 g/mol and a polydispersity index (Mw/Mn) of less than 2.5. Specifically, the aqueous solids suspension may be derived from a mineral processing or mining operation. A further aspect relates to the same polymer used for increasing the viscosity of an aqueous composition. The aqueous composition may be a personal care product, oilfield chemicals all for use in the oil industry.

Description

Use of high molecular weight narrow polydispersity polymers as flocculants or viscosifiers

Field of the Invention

The present invention relates to the utilisation of high molecular weight polymers exhibiting narrow polydispersity index as either flocculants performing solid liquid separation of aqueous suspensions or agents for thickening or viscosifying aqueous liquids. The use as a flocculant according to the present invention is applicable to a variety of industries and particularly to the mining and minerals industries where flocculants are employed in the alumina industry, oil sands industry, mineral sands industry etc. The use as a viscosifier according to the present invention is applicable to a variety of industries and particularly to the oil industry for the viscosifying of injection fluids or to the personal care industries for viscosifying aqueous personal care products, such as shampoos.

Background of the Invention

The use of high molecular weight polymers as flocculants or viscosifiers is known and well documented in the literature and patents over several decades.

Typically, such high molecular weight polymers are formed from water-soluble ethylenically unsaturated monomers. A monomer which is frequently used in the formation of such high molecular weight polymers is acrylamide and may be polymerised alone or in conjunction with other water-soluble ethylenically unsaturated monomers. Such comonomers may include water-soluble anionic monomers such as acrylic acid, or methacrylic acid maleic acid, itaconic acid, 2- acrylamido-2-methyl propane sulfonic acid or salts, usually alkali metal or ammonium salts. Acrylamide may also be copolymerised with cationic ethylenically unsaturated monomers such as acrylroyloxyethyl trimethylammonium chloride, methacrylroyloxyethyl trimethylammonium chloride, acrylamidopropyl trimethylammonium chloride, methacrylamidopropyltrimethylammonium chloride or diallyldimethyl ammonium chloride. Examples of polyacrylamides employed as flocculants include GB 1314431 , which describes a method of flocculated particulate materials dispersed in in an aqueous medium, for instance colliery tailings involving the addition of water-soluble starch phosphate and a water-soluble synthetic flocculant, preferably polyacrylamide polyacrylate; and US 3837482 describing a method of purifying kaolin clay employing anionic polymeric flocculants, such as partially hydrolysed polyacrylamide.

US 5653946 describes a process for fluidifying flocculated aqueous suspensions of red muds employed a flocculant consisting of a polyacrylamide of molecular weight greater than 10 million and a dispersing agent.

US 4478786 describes a method of preparing a composition for dewatering clay slimes involving the treatment of the slimes with a fly ash coated with a silane coupling reagent to which is bonded a polyacrylamide flocculant.

US 4478599 describes controlling the formation of crystal fines in a continuous crystallising process by adding a flocculant which may be an anionic polyacrylate and/or polyacrylamide polymers.

RU 2132239 relates to a high clay potassium or treatment employing a flocculant and a collector. Polyacrylamide is said to be used as a flocculant.

The treatment of aqueous slurries such as tailings through the use of polymer flocculants has been described in several other references, including EP 388108, WO 96/05146, WO 01/92167, WO 04/060819, WO 01/05712 and WO 97/06111 .

The formation of high molecular weight polymers suitable as flocculants may be achieved by polymerising water-soluble ethylenically unsaturated monomers using any one of a variety of polymerisation techniques. Typically, this would involve subjecting an aqueous solution of the water-soluble ethylenically unsaturated monomer or monomers to polymerisation conditions often involving the inclusion of polymerisation initiators. Various polymerisation techniques are known, usually employing free radical polymerisation, typically by redox initiation, photo initiation or thermal initiation. Redox initiation would involve employing a redox couple, comprising of a reducing agent and an oxidising agent. Photo polymerisation normally employs photo initiators which generate polymerisation initiating radicals once subjected to light energy at a particular frequency, for instance UV light. Thermal initiation typically employs thermal initiators which decompose to generate radicals predominantly at or above a particular temperature. Such polymerisation techniques may also include other additives such as chain transfer agents. Typically, chain transfer agents may be added to help regulate the chain length. High molecular weight flocculants, particularly polyacrylamide flocculants, are frequently produced by a combination of redox initiation and thermal initiation.

Other polymerisation techniques are known for producing polymers in general. One such technique includes reversible addition fragmentation chain transfer (RAFT). RAFT is a type of living polymerisation involving a conventional radical polymerisation which is mediated by a RAFT agent.

Carmean et al., Chem 2, 93-101 January 12, 2017 Elsevier Inc.

(http://dx.doi. orq/10.1016/i.chempr.2O16.12.007) describes a technique involving UV irradiation of thiocarbonylthio compounds in the presence of final monomers producing what are described as ultra high molecular weight polymers. The photo mediated polymerisation is said to reach number average molecular weights in excess of 8.00 x 10⁶ g/mol with degrees of polymerisation above 85,000. The polymerisation of acrylamide and N, N-dimethyl acrylamide in water at temperatures around 35°C in the presence of a tri-thio carbonate - 2-(2-carboxy ethyl sulfanyl thio carbonyl)-2-methyl propionic acid. Molecular weights of homopolymers prepared by this route were said to range from 1.10 x 10⁶ g/mol to 4.82 x 10⁶ g/mol. The article suggests that it is believed that the thiocarbonylthio undergoes carbon sulphur bond photolysis under UV and visible light irradiation and that upon absorption, reversible photolytic cleavage of the carbon sulphur bond results in carbon and sulphur centred radicals, the former of which initiate polymerisation and the latter of which allow reversible termination with the propagating chain end. The article goes on to suggest that as polymerisation proceeds, activation of the dormant thiocarbonylthio terminated chain ends continues to occur by photodissociation of the terminal carbon sulphur bond and as such the thiocarbonylthio group can operate as a chain transfer agent or as an in iferter, and control is most likely achieved through a combination of degenerative chain transfer and reversible termination. This is said to be in contrast to traditional RAFT polymerisation procedures, which require both a thiocarbonylthio compound and an exogenous initiating source, photo iniferter polymerisation operate without the addition of an external initiator.

Lewis et al., Polym. Chem., 2018, 9, 60 describes ultrafast aqueous polymerisation of acrylamides by high power visible light direct photo activation RAFT polymerisation. The investigation of the effects of visible LED power on kinetics and control of direct photo activation RAFT polymerisation is of acrylamide and dimethyl acrylamide were revealed. Minimal reduction in polymerisation control is said to have been observed at high irradiation intensity for acrylamide, while an increased production of low molecular weight dead chains was said to be observed for dimethyl acrylamide. The synthesis of ultrahigh molecular weight acrylamide polymers with a number average molecular weight greater than 1 million g/mol was said to have been produced.

Over the years, polymerisation techniques have developed and polymers of increased molecular weight with other significant improvements in properties have been possible. However, despite the various improvements in polymerisation techniques there is a need to provide flocculants exhibiting more efficient flocculation capability.

Flocculants normally work by a bridging mechanism in which the high molecular weight polymer molecules absorb simultaneously on one or more particle. In this way a high molecular weight polymer flocculant can more easily produce flocs by bridging many suspended particles.

The inventors of the present invention realised that frequently polymers used as flocculants contain a range of different molecular weights. Thus, while the weight average molecular weight may be high the distribution of polymer chain lengths may tend to be relatively large. The inventors realised that the presence of shorter chain length, lower molecular weight components of polymers produced by conventional polymerisation techniques e.g. by conventional free radical polymerisation may have a deleterious effect on the performance of flocculation.

The inventors addressed and solved the problem of improving the effectiveness as flocculants polymers of a particular weight average molecular weight by producing high molecular weight polymers having a much narrower molecular weight spread than previously understood to have been employed when producing flocculants. The inventors also realised that the new polymers were also very effective as viscosifiers.

Summary of the Invention

The present invention provides the use of a polymer as a flocculant to aid in the dewatering of an aqueous solids suspension wherein the polymer is formed from one or more ethylenically unsaturated monomers and which polymer has a weight average molecular weight Mw of greater than 500,000 g/mol and a polydispersity index (Mw/Mn) of less than 2.5.

Description of Drawings

Figure 1 compares the mechanism for a “standard” RAFT process compared to the mechanism for the photoiniferter process.

Figure 2 illustrates (a) chemical structures of various monomers used in the examples; and (b) chemical schematic showing the typical synthesis process to generate a PAM-stat-PDMA3q statistical copolymer using UV-light driven photoiniferter polymerisation process.

Figure 3 is the post purification NMR spectra of CTA 1 (a) 1 H NMR (b) 13C NMR.

Figure 4 is the NMR spectra of CTA 2 after purification (a) 1 H NMR (b) 13C NMR.

Figure 5 is the NMR spectra of CTA 3 after purification (a) 1 H NMR (b) 13C NMR.

Figure 6 is the NMR spectra of CTA 4 after purification (a) 1 H NMR (b) 13C NMR. Figure 7 is the NMR spectra of CTA 9 after purification (a) 1 H NMR (b) 13C NMR.

Figure 8 is the NMR spectra of CTA 10 after purification (a) 1 H NMR (b) 13C NMR.

Figure 9 is the emission spectra from the various polymerisation reactors: (a) Nail Lamp (365 nm) (b) UV/Black Light LED (420 nm) (c) Blue LED (470 nm) (d) Green LED (520 nm).

Figure 10 is the normalised UV-Vis absorption spectra for CTA 3 and CTA 8 showing the Amax values for the (a) TT-TT* transitions and (b) n-n* transitions.

Figure 11 illustrates the aqueous FFF traces of PAM homopolymers synthesised using either CTA 8 or CTA 9 under either Blue LED (470 nm) or UV Nail Lamp (365 nm) irradiation.

Figure 12 illustrates the molecular weight traces from PAM homopolymers (target DP = 1 ,000, 10,000 and 100,000) synthesised using the water-cooled reactor at 15°C with CTA 8 under Blue LED (470 nm) irradiation (a) Aqueous GPC calibrated with Dextran standards (b) FFF coupled with a light scattering detector

Figure 13 illustrates aqueous acidic GPC chromatograms obtained for PDMA3qx homopolymers synthesised using CTA 8 under 470 nm blue LED UV irradiation with a target DP of either 1 ,000 or 10,000. Polyvinylpyridine standards were used as calibrants for GPC molecular weight determination.

Figure 14 shows aqueous acidic GPC chromatograms obtained for PAPTACx homopolymers synthesised using CTA 8 under 470 nm blue LED UV irradiation with a target DP of either 1 ,000 or 10,000. Polyvinylpyridine standards were used as calibrants for GPC molecular weight determination.

Figure 15 shows the basic (pH 11 , 0.1 M NaCI) aqueous FFF chromatograms obtained for PNaATBSx homopolymers synthesised using CTA 8 under 470 nm blue LED UV irradiation with a target DP of either 1 ,000 or 10,000. Figure 16 illustrates molecular weight chromatgraphs obtained for various P(AM-

DMA3q) copolymers using Triple-detector acidic aqueous FFF

Figure 17 reveals (a) Phosphate-buffered (pH 7.4) aqueous GPC chromatograms obtained for P(AM-stat-NaAA)x statistical copolymers synthesised using CTA 8 under 405 nm LED UV irradiation with a target DP of either 1 ,000 or 10,000 with poly(sodium acrylate) used as calibration standards for GPC molecular weight determination (b) Aqueous FFF chromatograms (0.1 M NaCI) obtained for P(AM- stat-NaAA)80,000 synthesised using CTA 8 under 365 nm UV Nail Lamp irradiation.

Figure 18 shows Aqueous FFF chromatograms (0.1 M NaCI) obtained for P(AM-stat- NaATBS) with various target degrees of polymerisation (1 ,000, 10,000 and 100,000) synthesised using CTA 8 under either 470 nm Blue LED or 365 nm UV Nail Lamp irradiation.

Figure 19 illustrates Kaolin flocculation test results for the commercial product Product A and the narrow-polydispersity, lab-synthesised “P156” material at various dose-rates: (a) Relative turbidity of a kaolin solution as measured by UV- spectroscopy (b, c) Digital photographs showing each kaolin solution directly prior to the U V-turbidity measurement. Each experiment is the conducted in triplicate.

Detailed Description of the Invention

The inventors have found that the polymers defined according to the present invention are more effective in flocculating aqueous suspensions of solids than conventional polymer flocculants.

The inventors believe that this may be as a result of employing high molecular weight polymer flocculants which have a narrow molecular weight distribution (polydispersity index) and without being limited to theory the absence of a lower molecular weight component may be responsible for the enhancement in the effectiveness of the polymer flocculants. Suitably the polymer employed in the inventive use according to the present invention has a weight average molecular weight of greater than 500,000 g/mol and preferably at least 1 million g/mol. The weight average molecular weight may be for instance from greater than 500,000 to 12 million g/mol and preferably froml to 12 million g/mol or higher. Suitably this may be in the range of from 2 to 10 million g/mol, for instance from 3 to 9 million g/mol, such as from 4 to 8 million g/mol. The number average molecular weight desirably will be at least 1 million g/mol and typically is in the range of from 400,000 to 10 million g/mol or higher. Suitably this may be in the range of from 1 to 10 million g/mol or from 2 to 10 million g/mol, for instance from 3 to 9 million g/mol, such as from 4 to 8 million g/mol.

The polymer employed in the inventive use according to the present invention has a polydispersity index (Mw/Mn) of less than 2.5. Suitably, the polydispersity index is less than 2.3, preferably below 2.0, more preferably below 1.7 and especially preferably below 1 .5.

The one or more ethylenically unsaturated monomers desirably are water-soluble. By water-soluble we mean that the solubility in water is at least 5 g monomer per 100 mL of water at 25°C. When more than one ethylenically unsaturated monomer is employed it is possible that one of the ethylenically unsaturated monomers is not water-soluble or of limited water solubility (i.e. having a water solubility less than 5 g monomer per 100 mL water at 25°C) provided that the mixture of monomers is water-soluble. Thus, it may be possible to incorporate small amounts of ethylenically unsaturated monomer with no or limited water solubility provided that this monomer is compatible with the water-soluble monomer and the overall solubility in water meets the above criteria. Preferably, however, the one or more ethylenically unsaturated monomers should all be water-soluble.

Desirably the one or more ethylenically unsaturated monomers are selected from one or more of the compounds of formula (I) and/or formula (II) BASF SE 191112

wherein R is selected from at least one of H, methyl; X is selected from at least one of NH₂, NH(CH₃), N(CH₃)₂, OH, O- M⁺, O(CH2)2N⁺(CH3)3 Y-, NH(CH2)3N⁺(CH3)3 Y-, NHC(CH3)2CH2SO3- M⁺; M is selected from at least one of H, alkali metal ion, alkaline earth metal ion or ammonium; Y is an anion selected from at least one of halide or methosulfate; R¹ is H; R² is H or CH3; or R1 and R2 together are C3 or C4 alkylene and form a ring. Typical ethylenically unsaturated monomers according to formula (I) include acrylamide; methacrylamide; N-methyl acrylamide; N-methyl methacrylamide; N, N- dimethyl acrylamide; N, N-dimethyl methacrylamide; acrylic acid; methacrylic acid; metal or ammonium salts of acrylic acid, for instance alkali metal salts of acrylic acid, preferably sodium acrylate, or alkaline earth metal salts of acrylic acid, preferably calcium acrylate; metal or ammonium salt of methacrylic acid, for instance alkali metal salts of methacrylic acid, preferably sodium methacrylate, or alkaline earth metal salts of methacrylic acid, preferably calcium methacrylate; acrylroyloxy ethyl trimethyl ammonium halide or methosulfate, for instance acrylroyloxy ethyl trimethyl ammonium chloride; methacryloyloxy ethyl trimethyl ammonium halide or methosulfate, for instance methacryloyloxy ethyl trimethylammonium chloride; acrylamido propyl trimethyl ammonium halide or methosulfate, for instance acrylamido propyl trimethylammonium chloride; methacrylamido propyl trimethylammonium halide or methosulfate, for instance methacrylamido propyl chloride; 2-acrylamido-2-methyl propane sulfonic acid, alkali metal salts, alkaline earth metal salts or ammonium salts of 2-acrylamido-2-methyl propane sulfonic acid, for instance sodium 2-acrylamido-2-methyl propane sulfonate or calcium 2- acrylamido-2 methyl propane sulfonate; 2-methacrylamido-2-methyl propane sulfonic acid, alkali metal salts, alkaline earth metal salts or ammonium salts of 2- methacrylamido-2-methyl propane sulfonic acid, for instance sodium 2 methacrylamido-2 methyl propane sulfonate or calcium 2-methacrylamido-2 methyl propane sulfonate.

Typical ethylenically unsaturated monomers according to formula (II) include N-vinyl formamide, N-vinyl acetamide, N-vinyl pyrrolidone.

The polymer according to the present invention may be a copolymer or a homopolymer desirably of at least one water-soluble monomer, and more desirably of at least one of the monomers selected from compounds of formula (I) and/or formula (II). When the polymer is a copolymer it may be a random copolymer of two or more of the monomers randomly distributed along the polymer chains. Nevertheless, preferably the copolymer is a block copolymer.

In one desirable form the polymer is a copolymer of acrylamide and/or methacrylamide with an ethylenically unsaturated comonomer, which is preferably ionic or ionisable. By ionic we mean that the monomer carries a permanent ionic charge and by ionisable we mean that the monomer is capable of developing and ionic charge, for instance by adjustment of pH. Examples of ionic monomers include cationic monomers which carry a positive charge, for instance monomers which carry a quaternary ammonium group and examples of ionisable monomers include monomers where a cationic charge can be generated, for instance monomers carrying a primary, secondary or tertiary amine group where reducing the pH will protonate the nitrogen atom thereby generating a cationic charge. Examples of anionic monomers also include anionic monomers which carry a positive charge, for instance monomers which carry an acid radical ion, such as a carboxylate group or a sulfonate group, and ionisable monomers which can generate an anionic charge may include an undissociated acid which on raising the pH will enable the positive anionic charge all the monomer to be generated.

Preferably, the polymer is a copolymer of acrylamide and/or methacrylamide with an ethylenically unsaturated monomer selected from the group consisting of acrylic acid (or salts thereof), 2-acrylamido-2-methyl propane sulfonic acid (or salts thereof), 2- (acrylroyloxy)ethyl trimethylammonium chloride, 2-(methacrylroyloxy)ethyl trimethylammonium chloride, 3-(methacrylamido)propyl trimethylammonium chloride and 3-(acrylamido)propyl trimethylammonium chloride.

In another desirable form of the invention, the polymer is a homopolymer.

Suitably such a homopolymer may be formed from an ethylenically unsaturated monomer selected from the group consisting of acrylic acid (or salts thereof), 2- acrylamido-2-methyl propane sulfonic acid (or salts thereof), 2-(acryloyloxy ethyl) trimethylammonium chloride, 2-(meth acryloyloxy ethyl) trimethylammonium chloride, 3-(meth acrylamido propyl) trimethylammonium chloride and 3-(acrylamido propyl) trimethylammonium chloride.

Preferably the polymer according to the present invention is obtainable by a photoiniferter polymerisation mechanism. Polymers produced by this polymerisation mechanism have been found to provide especially improved performance characteristics in regard to flocculation performance. It is believed that this may be as a result of the particular polymer structure and that this polymer structure leads to an improved flocculation performance.

The photoiniferter polymerisation may be carried out using any suitable compound that can function as a photoiniferter. Suitable iniferters include xanthates and trithiocarbonate based compounds. Suitable iniferters include ethyl 2- (ethoxycarbonothioyl)thiopropionate, 2-(ethoxycarbonothioyl)thiopropionic acid, 2- (ethoxycarbonothioyl)thio-2-methylpropionic acid, ethyl 2-(ethoxycarbonothioyl)thio- 2-methylpropionate, 2-(2-carboxyethylsulfanylthiocarbonylsulfanyl)-2-methylpropionic acid, 3-((((1-carboxyethyl)thio)carbonothioyl)thio)-propionic acid, 4-((((2- carboxyethyl)thio)carbonothioyl)thio)-4-cyano-pentatonic acid and S, S’-bis (a,a’- dimethyl-a”-acetic acid)-trithio-carbonate. The photoiniferter may be provided in a suitable solvent. Suitably the solvent should be inert with respect to the photoiniferter. In one desirable form the solvent may be an aprotic solvent, for instance dimethyl sulfoxide (DMSO).

The photoiniferter polymerisation process is suitably carried out using electromagnetic radiation, which we refer to as light in this specification, and is typically visible light or UV light. Typically, this would be generated from a suitable light source, for instance an LED lamp. A suitable light source may have a power penetration ranging from 2 to 20 W rrr¹. Desirably the light would have a wavelength in the range from 200 nm to 650 nm, more desirably between 250 nm to 600 nm, preferably from 300 nm to 550 nm. The power of the light employed may range from 10 W to 50 W, for instance from 20 W to 40 W. The power chosen may depend to some extent on the wavelength of the specific light used.

Based on spectral analysis xanthate based photoiniferters have been found to exhibit intense TT-TT* transitions in the region of about 280 nm and weak n-rr* transitions in the region of about 355 nm. It has also been found that trithiocarbonate based photoiniferters exhibit transitions shifted towards longer wavelengths, with the TT-TT* transitions in the region of about 310 nm and the n-rr* transitions in the region of from 430 to 455 nm.

It may be desirable to employ light at a wavelength (Amax) from 325 nm to 405 nm, more desirably from 335 nm to 395 nm, more desirably still from 345 nm to 385 nm, especially from 355 nm to 375 nm when using a xanthate based photoiniferter for the polymerisation. Typically, this may be provided by a suitable UV lamp.

It may be desirable to employ light at a wavelength (Amax) from 375 nm to 500 nm, more desirably from 385 nm to 490 nm, for instance from 395 nm to 480 nm when using a trithiocarbonate based iniferter for the polymerisation. Suitably, this may be achieved by using a suitable LED setup. For instance, this may be an LED setup using with Amax uv/Biack LED of about 405 nm or LED setup using Amax Blue LED of about 470 nm.

A generalised representation of the photoiniferter polymerisation mechanism is shown in Figure 1 described as “Photoiniferter Process” and contrasts the mechanism employed in a conventional or standard RAFT process. A more detailed reaction scheme is provided in Figure 2 (b) using the monomer pair acrylamide and acrylroyloxy trimethylammonium chloride as representative monomers and 4-((((2- carboxyethyl)thio)carbonothioyl)thio)-4-cyano-pentatonic acid (CTA 8) as a representative photoiniferter.

The polymerisation is preferably carried out in a suitable solvent, preferably an aqueous medium. It may be possible to include small amounts of non-aqueous solvents in to set an aqueous medium. This may include the solvent, for instance aprotic solvent, used to carry the photoiniferter. The polymerisation is typically carried out by providing the ethylenically unsaturated monomer or monomers monomers as an aqueous solution and then combining photoiniferter, for instance carried in an aprotic solvent, into the aqueous solution of ethylenically unsaturated monomer or monomers. It is generally desirable to remove oxygen that may be present in the aqueous monomer solution, for instance by bubbling an inert gas through it, preferably the inert gas being nitrogen. This is generally referred to as degassing. This degassing may be continued for a sufficient period of time to ensure that the monomer solution is completely degassed. Typically, this may be for a period of from 10 minutes to 50 minutes, suitably from 15 minutes to 40 minutes, and perhaps from 20 minutes to 40 minutes. Polymerisation is then initiated by irradiating the aqueous monomer solution using light at the desired wavelength generated from a suitable light source. The so formed polymer may be provided as an aqueous solution or alternatively as a polymer gel. In the case of a polymer gel this may be broken into smaller pieces, dried and then ground to a powder. In one form of the invention, it may be desirable that the polymer is in the form of a powder.

Suitably the polymer according to the inventive use is water-soluble or potentially water-soluble. This would be typically measured at 25°C. By water-soluble we mean that most of the polymer will dissolve in water form an aqueous solution. Desirably the polymer may be entirely soluble in water such that it all dissolves. Suitably the solubility of the polymer may be at least 90% by weight. Typically, the solubility of the polymer in water may be determined as having a gel content measurement of less than 50% by weight gel, preferably less than 40% by weight gel, more preferably less than 30% by weight gel, more preferably still less than 20% by weight gel and yet more preferably no more than 10% by weight gel, for instance less than 5% by weight gel.

The gel content may be determined by filtering an aqueous stock solution of the polymer through a sieve with a 190 pm mesh size. The residue which stays in the filter is washed, recovered, dried (110°C) and weighed and the percentage of undissolved polymer is calculated (weight of dry residue from the filter [g] I weight of dry polymer before filtration [g]). The aqueous stock solution may be prepared by dissolving 1.0 g of polymer by weight in a bottle into 199 mL of deionised water. The mixture would be mixed for 4 hours on a tumble wheel at 25°C.

By potentially water-soluble we mean that the polymer will become soluble having undergone some form of post polymerisation modification. This may, for instance, be a change in pH or this could be for instance a post polymerisation reaction that changes the functional groups on the polymer.

In one preferred aspect of the present invention the inventive use as a flocculant relates to a flocculation process employed in a mining or mineral processing operation. Typically, the use concerns the dewatering of an aqueous solids suspension in which the suspension is a suspension in resulting from a mining and mineral processing operation. This may, for instance, be the dewatering of solids suspended in a thickener vessel or other stirred sedimentation vessel. For example, the use may relate to applying the polymer as a flocculant in the thickener vessel or washer vessels employed in a Bayer alumina process. Alternatively, the use may relate to the treatment of a tailings stream from a mineral processing operation in order to remove as much liquor from the tailings stream before disposal of the tailings solids. Such tailings may, for example, be coal fines tailings, iron ore tailings, mineral sands tailings, oil sands tailings or red mud. Alternatively, the use may relate to removal or separation of solids from an aqueous mineral suspension low solids content, for instance as an additive for removing suspended solids from a liquor containing the mineral values, for instance a sodium aluminate liquor of a Bayer alumina process.

In a further aspect of the present invention, we provide the use of a polymer as an agent for increasing the viscosity of an aqueous composition, wherein the polymer is formed from one or more ethylenically unsaturated monomers and which copolymer has a weight average molecular weight Mw of greater than 500,000 g/mol and preferably at least 1 million g/mol and a polydispersity index (Mw/Mn) of less than 2.5. The polymer may incorporate any of the characteristics recited above.

Desirably the aqueous composition may be selected from the group consisting of oilfield chemicals, additives for use in the oil industry and personal care products. Applications for use in the oil industry include viscosifiers for increasing the viscosity of injection fluids used in enhanced oil recovery (EOR). Applications for use in personal care products include viscosifiers for use in shampoos and personal care products employed to cleanse the skin, for instance shower gels or body washes.

Examples

Materials Used

Dimethylformamide (DMF), acetone, ethanol, dichloromethane, cyclohexane, ethyl acetate, isopropanol, acrylamide (AM) (50 wt% aqueous solution), 3- (acryloyloxyethyl)trimethylammonium chloride (DMA3q) (80 wt% aqueous solution)and acrylic acid (each from BASF). 3-(acrylamidopropyl)trimethylammonium chloride (APTAC) (74-76 wt% aqueous solution) (supplied by Tokyo Chemical Industries). N,N-Dimethylacrylamide 99 %, 2-bromo-2-methylpropionic acid 98 %, 2- bromopropionic acid 99 %, ethyl 2-bromopropionate 99 %, ethyl a-bromoisobutyrate 98 %, 3-mercaptopropionic acid > 99 %, 2,2'-Azobis(2-methylpropionamidine) dihydrochloride, silicon dioxide washed and calcinated, kaolin, and tetrabutylammonium bisulfate > 99 % (each obtained from Sigma Aldrich). 3-((((1- Carboxyethyl)thio)carbonothioyl)thio)-propionic acid > 97 % (CTA 7) and 4-((((2- carboxy-ethyl)thio)carbonothioyl)thio)-4-cyano-pentanoic acid > 95 % (CTA 8) (each obtained from Boron Molecular). Basic aluminium oxide (Brockmann), 50-200 pm, 60 A and silica gel, 50-200 pm, 60 A (each obtained from Machery-Nagel).

Dimethylsulfoxide 99.9 % (obtained from Riedel de Haen). Hydrochloric acid 32 % and anhydrous sodium sulfate were purchased from Bernd Kraft. Anhydrous magnesium sulfate (obtained from Fischer Scientific). Trifluoroacetic acid 99.5 % (obtained from Apollo Chemical). Potassium O-ethyldithiocarbonate 97 %, carbon disulfide and 2-acrylamido-2-methylpropane sulfonic acid (ATBS) > 99 % (each obtained from Merck). ATBS was neutralized with NaOH to pH 6.5 to obtain a 34.4 wt% sodium 2-acrylamido-2-methylpropane sulfonate solution prior to use. NORIT™ GAC 1240 (obtained from CABOT Corporation). Solarox® 520 nm, 470 nm and 420 nm LED strips (5 m, 4.8 W/m), SOLAROX® Mini LED Dimmer Remote and a 12 V, 5 A Power supply. A Sina 36 W halogen Nail lamp with Amax at 365 nm and broad emission spectrum. A 5 m, 470 nm LED strip with 9.6 W rrr¹.

All monomers were used as received up to a target degree of polymerisation (DP) = 10,000. For iniferter polymerisations with target DP > 10,000, the uncharged monomers (acrylamide, dimethylacrylamide, acrylic acid) were destabilized through an activated basic aluminum oxide column to minimise polymerisation inhibition. For iniferter polymerisations with target DP > 10,000, the charged monomers (APTAC, DMA3q, NaATBS) were destabilized by stirring in the presence of activated carbon (25 wt %) in the dark at 0°C for 16 h, followed by filtration before use.

Photoiniferter Synthesis

Xanthate Syntheses

Ethyl 2-(ethoxycarbonothioyl)thiopropionate (CTA 1 )

CTA 1 was synthesised using the methodology outlined by Destarac et al. (see Scheme 1 ) [6], Ethyl 2-bromopropionate (27.8 g, 0.15 mol) was dissolved in ethanol (250 mL), cooled in an ice bath to 0 °C for 1 h before adding potassium O-ethyl xanthate (24.6 g, 0.15 mol) at a rate of 2 g min-1 and stirred overnight. The solvent was evaporated under reduced pressure and the crude product dissolved in dichloromethane (250 mL). After extraction with demineralized water (3 x 250 mL) the product was dried over magnesium sulfate (30 g), filtered, and the solvent evaporated to obtain of a clear yellow oil. The extraction process was repeated to yield the pure product (16.8g, 49 % yield) (see Figure 3).

Scheme 1 . Synthetic procedure for the synthesis of CTA1

1 H-NMR (500 MHz, DMSO-d6, δ in ppm): 1.21 (t, -C=OOCH2CH3, 3H), 1.35 (t, CH3CH2O-C=SS-, 3H), 1.48 (d, -SCHCH3C(=O)O-, 3H), 4.14 (q, -C=OOCH2CH3, 2H), 4.36 (q, -SCH-CH3C=OO-, 1 H), 4.61 (q, CH3CH2OC(=S)S-, 2H). 13C-NMR (75 MHz, CDCI3, 5 in ppm): 13.69 (CH3CH2-O-), 14.13 (CH3CH2-O-C(=O)-), 16.93 (CH3CH-), 47.22 (-O(O=)C-CH(CH3)-S-), 61.76 (CH3CH2-O-C(=O)-), 70.72 (CH3CH2-O-), 171.39 (-O(O=)C-), 212.16 (-S-C(=S)-O-). 2-(Ethoxycarbonothioyl)thiopropionic acid (CTA 2)

CTA 2 was synthesised using and similar procedure to CTA 1 , but ethanol was substituted for acetone to prevent esterification (see Scheme 2). 2-Bromopropionic acid (44.7 g, 0.29 mol) was dissolved in acetone (400 mL), cooled in an ice bath to 0 °C for 1 h before adding potassium O-ethyl xanthate (45.4 g, 0.29 mol) at a rate of 2 g min-1 and stirred overnight. The solvent was evaporated under reduced pressure and the crude product dissolved in dichloromethane (400 mL). After extraction with 1 M aqueous hydrochloric acid (3 x 400 mL) the product was dried over magnesium sulfate (30 g). The extraction process was repeated to yield a clear yellow oil (31 .1 g, 55 % yield) (See Figure 4).

Scheme 2. Synthetic procedure for the synthesis of CTA 2

1 H-NMR (500 MHz, DMSO-d6, δ in ppm): 1.35 (t, CH3CH2OC=SS- 3H), 1.48 (d, - SCH-CH3C(=O)O-, 3H), 4.28 (q, -SCHCH3C(=O)O-, 1 H), 4.61 (q, CH3CH2OC(=S)S-, 2H), 13.05 (s (broad), -C(=O)OH, 1 H). 13C-NMR (75 MHz, CDCI3, 5 in ppm): 13.65 (CH3CH2-O-), 16.51 (CH3C-), 46.78 (HO(O=)C-C(CH3)-S- ), 70.59 (CH3CH2-O-), 177.40 (HO(O=)C-), 211.68 (-S-C(=S)-O-).

2-(Ethoxycarbonothioyl)thio-2-methylpropionic acid (CTA3)

CTA 3 was synthesised using the methodology outlined by Lai et al. [7], with some minor modifications (see Scheme 3). Potassium O-ethyl xanthate (16.3 g, 0.1 mol), chloroform (17.9 g, 0.15 mol), acetone (58.1 g, 1.0 mol), tetrabutylammonium hydrogensulfate (1.36 g, 4.0 mmol) and toluene (150 mL) were mixed and cooled in an ice bath. Potassium hydroxide pellets (28.05 g, 0.5 mol) were added portion-wise while maintaining the temperature below 25 °C and stirred overnight. Water (250 mL) was added, the aqueous layer separated and then acidified with concentrated hydrochloric acid (32 wt%, 30 mL, 0.26 mol) and a beige solid was obtained by filtration. The solid was dried under vacuum and recrystallized from cyclohexane to obtain the pure product (8.3 g, 41 % yield) (see Figure 5).

Scheme 3. Synthetic procedure for the synthesis of CTA 3

1 H-NMR (500 MHz, DMSO-d6, δ in ppm): 1.26 (t, CH3CH2OC(=S)S-, 3H), 1.57 (s, - SC-(CH3)2C=OOH, 6H), 4.65 (t, CH3CH2OC(=S)S-, 2H), 12.32 (s (broad), C(=O)OH, 1 H). 13C-NMR (75 MHz, CDCI3, 5 in ppm): 13.24 (CH3CH2O), 25.64 ((CH3)2C-), 54.0 (HO(O=)C-C(CH3)2-S-), 70.01 (CH3CH2-O-), 179.47 (HO(O=)C-), 210.53 (-S-C(=S)-O-).

Ethyl 2-(ethoxycarbonothioyl)thio-2-methyl-propionate (CTA 4)

CTA 4 was synthesised using and similar procedure to CTA 1 , but ethyl a- bromoisobutyrate was substituted for ethyl 2-bromopropionate (see Scheme 4). Ethyl a-bromoisobutyrate (48.76 g, 0.29 mol) was dissolved in ethanol (500 mL), cooled in an ice bath to 0 °C for 1 h before adding potassium O-ethyl xanthate (48.09 g, 0.29 mol) at a rate of 2 g min-1 and stirred overnight. Ethanol was removed under reduced pressure and the crude product dissolved in dichloromethane (250 mL). After extraction with demineralized water (3 x 250 mL) the product was dried over magnesium sulfate (30 g), filtered and the solvent evaporated. Due to low purity, the material was further purified via column chromatography (cyclohexane: ethyl acetate 30:1 as eluent) to obtain the final product (7.45 g, 13 % yield) (see Figure 6).

Scheme 4. Synthetic procedure for the synthesis of CTA 4.

1 H-NMR (500 MHz, DMSO-d6, δ in ppm): 1.20 (t, -C(=O)OCH2CH3, 3H), 1.32 (t, CH3CH2O-C(=S)S- 3H), 1.55 (s, -SC(CH3)2C-(=O)O- 6H), 4.13 (q, - C(=O)OCH2CH3, 2H), 4.56 (q, CH3CH2OC(=S)S-, 2H). 13C-NMR (75 MHz, CDCI3, 5 in ppm): 13.39 (CH3CH2-O-), 14.14 (CH3CH2-O-C(=O)-), 25.80 ((CH3)2C-), 54.23 (-O(O=)C-C(CH3)2-S-), 61.76 (CH3CH2-O(=O)C-), 70.72 (CH3CH2-O-), 171.39 (- O(O=)C-), 212.16 (-S-C(=S)-O-).

Trithiocarbonate Syntheses

2-(2-Carboxyethylsulfanylthiocarbonylsulfanyl)-2-methylpropionic Acid (CTA 9) CTA 9 was synthesised using the methodology outlined by Skey and O’Reilly [8], with some minor modifications (see Scheme 5). 3-Mercaptopropionic acid (13.25 g, 0.125 mol) was added dropwise to an ice-cooled slurry of K3PO4 (53 g, 0.25 mol) in acetone (550 mL). After 15 min of stirring, CS2 (21 .0 g, 0.275 mol) was added dropwise. The resulting yellow solution was stirred for 30 min and 2-bromo-2- methylpropionic acid (21 g, 0.125 mol) was added. The mixture was stirred overnight, and the solvent was removed under reduced pressure. The obtained solid was dissolved demineralized water (300 mL) and concentrated hydrochloric acid (200 mL) was added. The mixture was stirred vigorously for 15 min and filtered to obtain a yellow solid. The filtrate was dried for 48 h at 30 °C under vacuum, dissolved in acetone (500 mL) and stirred overnight in the presence of anhydrous sodium sulfate. The suspension was filtered, acetone removed under reduced pressure, and the final CTA 9 product was obtained after two-fold recrystallisation from ethyl acetate (10.98 g, 33 % yield) (see Figure 7). BASF SE 191112

Scheme 5. Synthetic procedure for the synthesis of CTA 9

1 H-NMR (500 MHz, DMS0-d6, δ in ppm): 1.62 (s, -SC(CH3)2C(=O)OH, 6H), 2.65 (t, -CH2C(=0)0H, 2H), 3.46 (t, -CH2CH2C(=O)OH, 2H), 12.72 (s, -C(=O)OH, 2H). 13C-NMR (75 MHz, DMS0-d6, δ in ppm): 25.5 (-C(CH3)2, 31.9 (-CH2-S), 32.8 (H0(0=)C-CH2-), 56.8 (-S-C(CH3)2C(=O)OH), 172.9 (CH2C(=0)0H), 173.6 (C(CH3)2-C(=O)OH)

S,S'-Bis(a,a'-dimethyl-a"-acetic acid)-trithio-carbonate (CTA 10)

CTA 10 was synthesised using the methodology outlined by Lai et al. [9] (see Scheme 6). Carbon disulfide (27.4 g, 0.36 mol), chloroform (107.5 g, 0.90 mol), acetone (52.3 g, 0.90 mol), tetrabutylammonium hydrogen sulfate (2.41 g, 7.1 mmol) and n-heptane (120 mL) were mixed under cooling in an ice bath and placed under nitrogen atmosphere. Sodium hydroxide (50 wt%, 201.6 g, 2.52 mol) was added dropwise over 90 min to maintain the temperature below 25 °C, and the mixture was stirred overnight. DI Water (900 mL) was added to dissolve the generated precipitate, followed by concentrated hydrochloric acid (32 wt%, 120 mL, 1 ,05 mol) to acidify the aqueous layer. The mixture was stirred for 30 min under a nitrogen purge, filtered and the resulting filtrate thoroughly rinsed with water. After dissolving the precipitate in acetone and drying with sodium sulfate overnight, removal of acetone yielded a red/yellow colored solid. The product was purified by washing three-fold in a mixture of toluene and acetone (4:1 , 250 mL), followed by a two-fold recrystallization from ethyl acetate to obtain the pure yellow solid product (13.46 g, 26 % yield) (see Figure 8).

BASF SE 191112

Polymerisation Reactor Set up

The LED reactors were constructed by wrapping a glass beaker (d = 13.4 cm) with LED strips (5 m, 4.8 W m-1 , Aspecified = 420, 470 or 520 nm) with electric power sources (12 V, 5 A) and covered in aluminum foil for high reflectivity. The resulting distance from the LEDs to the surface of the reaction vials (vials = 80 mm x 33 mm) was measured to be 48 mm. A water-cooled LED reactor was constructed by wrapping the LED strip (5 m, 9.6 W m-1 , Aspecified = 470 nm) around a one-liter double jacketed reactor. In this case a Voltacraft DPS-4005PFC power source was used to power the reactor at 100 W.

The emission spectra of the LED strips and UV nail lamp were measured using a Quest 4 CCD array spectrometer by bwtek. The measurement distance from the light source was set at 48 mm. The specified wavelength differed slightly to the measured for some LED reactors: A = 520 nm (measured: 519 nm), A = 470 nm (measured: 473 nm) and A = 420 nm (measured: 405 nm) (see Figure 9).

Light Driven Photoiniferter Polymerisation

Monomers were all used as received up to a target degree of polymerisation (DP) of 10,000.

For iniferter polymerisations with target DP > 10,000, non-ionic monomers (acrylamide, dimethylacrylamide, acrylic acid) were destabilized through an activated basic aluminum oxide column to minimise polymerisation inhibition.

For iniferter polymerisations with target DP > 10,000, the charged monomers (APTAC, DMA3q, NaATBS) were destabilized by stirring in the presence of activated carbon (25 wt %) in the dark at 0°C for 16 h, followed by filtration before use.

Homopolymerisation of acrylamide

Polyacrylamide with a target degree of polymerisation (DP) = 1 ,000 was synthesised using the following procedure. CTA 8 in DMSO stock solution (4.325 mL @ 10 mg mL^-1), aqueous acrylamide solution (20 g @ 50 wt %), DI Water (15.28 mL) and DMF (400 pL as 1 H NMR standard) were mixed in a reactor vial (50 mL) to reach a target acrylamide monomer concentration (25 wt %). The vial was sealed with a rubber septum and degassed for 30 min via the bubbling of N2 through the monomer solution with a needle. The vial was left under a slight N2 overpressure, placed in the reactor and irradiated. For the ultra-high molecular weight PAM syntheses, the N2 needle was left in the vial to maintain an inert atmosphere. The final monomer conversion was measured via 1 H NMR and molecular weight determined via GPC (and FFF for UHMW) measurements.

Statistical copolymerisation of acrylamide with DMA3q

A statistical copolymer of AM and DMA3q (90:10 mol %) with a target degree of polymerisation (DP) = 1 ,000 was synthesised using the following procedure. CTA 8 in DMSO stock solution (3.628 mL @ 10 mg mL^-1), aqueous acrylamide solution (15.98 g @ 50 wt %), aqueous DMA3q solution (3.063 g @ 80 wt %), adipic acid (0.8 g - added to lower the monomer solution pH and reduce DMA3q hydrolysis), DI Water (17.81 mL) and DMF (400 pL as 1 H NMR standard) were mixed in a reactor vial (50 mL) to reach a target 25 wt % monomer concentration. The vial was sealed with a rubber septum and degassed for 30 min via the bubbling of N2 through the monomer solution with a needle. The vial was left under a slight N2 overpressure, placed in the reactor and irradiated. For the ultra-high molecular weight PAM syntheses, the N2 needle was left in the reactor vial to maintain an inert atmosphere. The final monomer conversion was measured via 1 H NMR and molecular weight determined via GPC (and FFF for LIHMW) measurements.

Analytical Measurements

UV-Vis Absorption Spectra

The absorption spectra of the various CTAs (iniferters) were measured in DMSO at 10 mg mL-1 in 10 mm quartz cuvettes using a Shimadzu LIV1800 Photospectrometer. To measure the higher intensity TT-TT transitions, the CTA solutions were diluted with DMSO accordingly.

Size Exclusion Chromatography

Four separate GPC set ups were used, depending on the (co)polymer composition and targeted molecular weight range.

The molecular weight distributions of low molecular weight PAM and PDMA homopolymers were assessed using aqueous acidic GPC. The set-up comprised three HEMA bio columns (average column pore sizes 2000 A, 1000 A and 100 A respectively) and a HEMA bio 10 p-8x50 mm pre-column connected in series to an Agilent 1200 GPC system equipped with a refractive index detector. The GPC eluent was acidic deionised water with a flow rate of 1 .0 mL min^-1. Tert-butanol was used as a flow-rate marker. Calibration was achieved using a series of DIN-Dextran standards (ranging in M_P from 200 to 280 000 g mol^-1) from PSS.

The molecular weight distributions of PNVP homopolymers were assessed using DMAc GPC. The set-up comprised three two polyester copolymer columns with elution limits 1 ,000 - 1 ,000,000 g mol^-1 (GRAM 1000A) and a polyester copolymer column with an elution limit 100 - 10,000 g mol’¹ (GRAM 1000A) connected in series to an Agilent 1100 GPC system equipped with a refractive index detector at 85°C. The GPC eluent was DMAc with LiBr (0.5 wt %) with a flow rate of 1.0 mL min^-1.

Calibration was achieved using a series of PMMA standards (ranging in M_P from 800 to 2,200,000 g mol^-1) from PSS.

The molecular weight distributions of PAA, PVFA, PAM macro-iniferters and anionic block copolymers (e.g. PAM-b-PNaAA, PAM-b-PNaATBS) were assessed using aqueous GPC. The set-up comprised two Hydroxylated PMMA TSKgel GMPWXL columns with elution limits of 1 ,000 - 8,000,000 connected in series to an Agilent 1200 GPC system equipped with both refractive index and UV detectors at 35°C. The GPC eluent was phosphate buffered saline (0.01 mol^-1) with NaNs (0.01 mol I^-1) at pH 7.4 and a flow rate of 1 .0 mL min^-1. Tert-butanol was used as a flow-rate marker. Calibration was achieved using a series of poly(sodium acrylate) standards (ranging in M_P from 1 ,250 to 1 ,100,00 g mol^-1) from PSS.

The molecular weight distributions of PDMA3q, PAPTAC, cationic statistical copolymers (e.g. P(AM-stat-DMA3q), PAM macroiniferters and cationic block copolymers (e.g. PAM-b-PDMA3q) were assessed using aqueous GPC. The set-up comprised three NOVEMA Max Ultrahigh acrylate copolymer columns with elution limits of 100 - 30,000,000 g mol^-1 connected in series to an Agilent 1200 GPC system equipped with both refractive index and UV GAT-LCD 503 detectors at 35 °C. The GPC eluent was DI water with trifluoracetic acid (0.1 wt %) with NaCI (0.1 mol I^-1) and a flow rate of 1.0 mL min^-1. Calibration was achieved using a series of poly(vinylpyridine) standards (ranging in Mp from 620 to 2,890,00 g mol^-1) from PSS.

Field Flow Fractionation

Field flow fractionation of the various (co)polymers were measured on an Eclipse Asymmetric field flow fractionation by Wyatt Technology equipped with a Dawn Heleos II multi-angle light scattering detector and an Optilab T-Rex Rl-detector by Wyatt Technology. For the measurement of neutral and cationic polymers, the samples were diluted in demineralized water and mixed with NaCI solution (0.2 mol L’¹) solution at pH of 3 at a ratio of 1 :1 . The samples were then further diluted to a concentration of 75 ppm for the measurements. Anionic polymers were measured at pH values of 10-11 instead of 3. Static Light Scattering

The radius of gyration (Rg) and size dispersity of the various (co)polymers were assessed via static light scattering (SLS) using an ALV CGS3 goniometer system eguipped with a He-Ne Laser (633 nm). The measurements were conducted in the angular range 15 - 150° with a 1 ° resolution averaging of two measurements. Samples were dissolved in NaCI solution (1 mol 1-1 ) at a concentration of 50 ppm prior to measurement. The Rg values were evaluated using the Debye method for a gaussian coil.

Copolymer viscosity (K-value and Standard Viscosity (SV))

The K-value was determined using a Ubbelodhe viscometer in a Lauda Eco Silver water bath at 25°C. Herein, the (co)polymer solutions were prepared via the dispersion of polymer (0.5 g) in acetone (5 mL), followed by dissolution in a 1 mol L’¹ NaCI solution (95 ml). The resulting solution was stirred for 48 h to enable full dissolution. The (co)polymer solution (10 g) was then diluted to 100ml with 1 mol L^-1 NaCI solution. The relative viscosity was then determined using the Ubbelohde viscometer and the K-value determined using the following formula from Fikentscher:

The standard viscosity (SV) of a (co)polymer solution was determined using the following protocol. Dry polymer powder (0.5 g) was added to DI water (100 mL) in a glass beaker (600 mL) under stirring at 200 rpm. After achieving full polymer dissolution (ca. 1 - 2 h stirring), the solution was diluted with DI water (390 mL) and NaCI (29.25 g) was added to generate a 0.1 wt % solution. After full NaCI dissolution (ca. 5 min), the solution was filtered through a sieve (0.1 mm mesh size, d = 5 cm). The SV of the resulting solution was then determined using a Brookfield Viscometer equipped with a UL-Adapter, with a spindle speed of 60 rpm at 25°C.

Nuclear Magnetic Resonance Spectroscopy (NMR)

¹H-NMR spectra for all homopolymers, copolymers and CTAs (iniferters) were measured in D2O or DMSO-c/6 using a A500a Agilent (Varian) DD2 500 MHz NMR spectrometer. 13C-NMR spectra of CTAs (iniferters) were measured in CDCI3 or DMSO-d6 using a Bruker ARX 300 MHz spectrometer. Conversions and theoretical molecular weights were determined from the integrated intensities according to (1 ):

heoretical number average molecular weight olecular weight of the monomer umber average degree of polymerization ntegrated intensity of the vinyl protons ntegrated intensity of the DMF protons Integrated intensity of the vinyl protons of the to sample. Integrated intensity of the DMF protons of the to sample.

Photoiniferter (CTA) Synthesis and Absorption Spectra

The adsorption spectra of the in iferter CTAs used in this work were measured in DMSO via UV-Vis spectroscopy. The xanthate-based iniferters (CTA 1 to CTA 4) were found to exhibit intense TT-TT* transitions « 280 nm and weak n-rr* transitions « 355 nm. The trithiocarbonate-based iniferter (CTA 7 to 10) transitions were shifted towards longer wavelengths, with the TT-TT* transitions « 310 nm and the n-ir* « 430 - 455 nm (see Table 2 and Figure 10). As shown in Table 2, the effect of either the ester/acid- or methyl/dimethyl-substituents within the xanthate-based CTAs did not significantly alter the Amax of either the TT-TT* transitions (Amax = 274 to 287 nm) or n-rr* transitions (Amax = 356 to 359 nm). The trithiocarbonate-based CTAs also showed negligible differences for TT -TT* transitions (Amax = 308 to 314 nm). However, the triothiocarbonate n-rr* transitions were found to be somewhat structure-dependent with Amax values measured from 432 to 454 nm (AA = 22 nm).

Several literature reports claim that the n-n* transition results in a faster rate of homolytic cleavage with high quantum yields. Therefore, polymerisations conducted using xanthate-based iniferters should be most suited to the Nail Lamp UV-lamp set up (4 max Nail Lamp = 365 nm) and those conducted using trithiocarbonate-based iniferters using the LED set up (Amax uv/Biack LED = 405 nm and Amax Blue LED = 470 nm).

Table 2 illustrates the UV-Visible light Amax of the TT-TT* and n-rr* transitions and corresponding chemical structures of the xanthate and trithiocarbonate-based photoiniferter (CTA) based on the test work of the inventors.

BASF SE 191112

Table 2

BASF SE 191112

Table 2 continued

Photoiniferter based homopolymerisation of various water-soluble monomers

Under Blue LED (470 nm) irradiation, CTA 8 was successfully used to synthesise PAM with a DP range from 1 ,000 to 100,000 (e.g. see P10 and P71 in Table 6), although the GPC-measured polydispersity increased from Mw/Mn = 1.27 to 1.64 upon increasing the target molecular weight up ca. 5 million g mol’¹. However, the wide GPC polydispersity indexes may be a measurement artefact, as FFF- measurements of P71 indicated narrow a polydispersity Mw/Mn = 1 .09 at Mn = 3.5 million g mol’¹. Nevertheless, increasing the target DP did result in lower monomer conversions in the allotted time (ca. 8 h), with P71 only achieving ca. 40 % conversion. Therefore, CTA 8 was tested to excellent effect under UV nail lamp (365 nm) irradiation, producing PAM with high monomer conversion (90 % in 5 h), high molecular weights and low polydispersity (see P82 in Table 3 and Figure 11 ; Mn GPC = 2.3 million g mol’¹, Mw/Mn GPC = 1.16; Mn FFF = 4.1 million Da, Mn/Mw FFF = 1.16).

Both CTA 9 and CTA 10 were successfully used to synthesise narrow polydispersity, high molecular weight PAM under Blue LED (470 nm) irradiation (see P122 and P165 in Table 6, Mn « 3 million g mol’¹, Mw/Mn < 1.2). However, higher monomer conversions were only observed when using CTA 10 in comparison to CTA 9 (e.g. DP = 100,000; conversion = 73% vs. 41 % respectively).

Table 3 provides a summary of the monomer conversions, molecular weights and molecular weight distributions for the polymerisation of AM using either CTA 7, 8, 9 or 10 under irradiation at either 365 nm, 405 nm or 470 nm with target DPs up to 100,000 (Mn « 10 million g mol’¹). Monomer concentration = 3.5 M (25 wt %)

Due to the high temperatures (« 55°C) inside the self-built LED reactors, the influence of polymerisation temperature upon the final polymer molecular properties were investigated using a temperature-controlled reactor. Reducing the reactor temperature to 15°C had a significant influence on the GPC-measured molecular weight properties of the resulting PAM homopolymers, as shown in Table 4 and Figure 12. These findings are supported by literature work studying the effect of temperature on side-reactions during acrylamide polymerisation

Table 4 provides a summary of the monomer conversions, molecular weights and molecular weight distributions for the polymerisation of AM using CTA 8 under irradiation at 470 nm with target DPs up to 100,000 (Mn « 10 x 10⁶ g mol^-1) in a temperature-controlled reactor at 15°C. Monomer concentration = 3.5 M (25 wt %).

Narrow polydispersity polyacrylamide homopolymers (Mn «1 - 5 million g mol’¹, Mw/Mn < 1.3) were readily synthesised using trithiocarbonate-based iniferters. UV Nail Lamp irradiation (365 nm) enabled higher monomer conversions (ca. 90 %) in comparison to blue LED irradiation (470 nm, ca. 40 - 60 % conversion) when targeting high molecular weight PAM. The use of a water-cooled blue LED reactor reduced the polymerisation temperature from ca. 55°C to 15 °C, resulting in a further narrowing of the polydispersity index values due to the minimization of side reactions during polymerisation.

2-(acrylroyloxy)ethyltrimethylammonium chloride [DMA3q]

The water-soluble, cationic acrylate monomer DMA3q was readily polymerized to high conversion (> 80 %) using the trithiocarbonate-based CTA 8 under blue LED irradiation (470 nm) when targeting a DP up to 10,000. Acidic aqueous GPC measurements using polyvinylpyridine standards indicated reasonable molecular weight control (Mw/Mn « 1.5). The results are illustrated in Table 8 and Figure 13.

Table 5 provides a summary of the monomer conversions, molecular weights and molecular weight distributions for the polymerisation of DMA3q using CTA 8 under irradiation at 470 nm with target DPs up to 10,000 (Mn « 1 .9 million g mol’¹).

Monomer concentration = 1 .2 M (25 wt %)

3-(acrylamido)propyltrimethylammonium chloride [APTAC1

The cationic acrylamide-based monomer APTAC could be readily polymerized (up to 80 % conversion) to generate homopolymers with high molecular weights (ca. 0.5 - 1 million g mol’¹) and narrow polydispersity indexes (Mw/Mn « 1.3). The GPC measured molecular weights were somewhat below the theoretical values, but this could again be due to the use of non-optimal polyvinylpyridine calibration standards. Improved molecular weight control was observed for PAPTAC materials in comparison to PDMA3q, which can be attributed to the higher control obtained when using acrylamides vs. acrylate monomers. The results are illustrated in Table 9 and Figure 14.

Table 6 provides a summary of the monomer conversions, molecular weights and molecular weight distributions for the polymerisation of APTAC using CTA 8 under irradiation at 470 nm with target DPs up to 10,000 (Mn « 2.1 million g mol’¹). Monomer concentration = 1 .2 M (25 wt %).

Sodium 2-acrylamido-2-methylpropylsulfonate [Na ATBS1

Na ATBS was successfully polymerised using CTA 8 under blue-light LED (470 nm) irradiation to high monomer conversion (> 95 %) in less than 8 h at target a DP up to 10,000 (Mn « 2.3 million g mol’¹). Aqueous field-flow fractionation (FFF) measurements at pH 11 indicated the synthesised acrylamide-based P(Na ATBS) homopolymers have narrow molecular weight distributions (Mw/Mn < 1.4).

Furthermore, as the FFF measurements are not based on calibration standards (FFF with triple detection molecular weight determination), the measured molecular weights correlate well with the theoretical molecular weights, again indicating excellent polymerisation control under such reaction conditions. The results are shown in Figure 15 and Table 7.

Table 7 provides a summary of the monomer conversions, molecular weights and molecular weight distributions for the polymerisation of NaATBS using CTA 8 under irradiation at 470 nm with target DPs up to 10,000 (Mn « 2.3 million g mol’¹).

Monomer concentration = 25 wt %

Photoiniferter statistical copolymerisations with acrylamide

Acrylamide-stat-2-(acrylroyloxy)ethyltrimethylammonium chloride [AM-stat-DMA3q]

Product A is a low cationic (10 mol % DMA3q 190 mole % acrylamide) commercial polyacrylamide panda product, synthesised via standard free radical gel polymerisation, with high FFF-measured molecular weight (Mw = 5.5 million g mol-1) and relatively wide polydispersity (Mw/Mn = 5.5) (see Table 14).

Experiments with target molecular weights up to Mn « 20 million g mol-1 (DP = 300,000) were conducted using CTA 8 as the iniferter under nail lamp irradiation (365 nm). The sample P156 with a target DP = 200,000 reached high monomer conversion of 81 % within 7 h, achieving a similar molecular weight, K-value and SV as the standard Product A (see Table 8). However, the FFF-measured P156 polydispersity of Mw/Mn = 1 .04 is significantly below the benchmark Product A product (Mw/Mn = 5.5), showing the excellent polymerisation control afforded by the light-driven iniferter synthetic method. The experiments P218, P219 and P220 illustrate high molecular weights, narrow polydispersities and good monomer conversion are still possible when targeting high degrees of polymerisation. Samples were purified via isopropyl alcohol (IPA) extraction to remove residual monomer prior to analytical measurements and performance testing. The results are shown in Table 8 and Figure 16.

Table 8 provides a summary of the monomer conversions, molecular weights and molecular weight distributions for the polymerisation of a ACM:DMA3q 90:10 mol % mixture using CTA 8 under either blue LED at 470 nm or UV Nail Lamp irradiation at 365 nm with target DP up to 300,000 (Mn ca. 10 - 20 million g mol-1 ). Monomer concentration = 23 wt % (2 M).

Acrylamide-stat-(Sodium-Acrylate) [AM-stat-NaAAl

Copolymerisation of sodium acrylate with acrylamide using photoiniferter technology enabled the synthesis of high molecular weight, low polydispersity anionic polymers to be produced. The experimental results when targeting an ACM-NaAA 90:10 mol % copolymer composition using iniferter technology are summarized in Table 15.

Copolymers with narrow polydispersity indexes (Mw/Mn < 1 .3) were synthesised using CTA 8 under either UV LED (405 nm) or UV nail lamp (365 nm) irradiation when targeting a degree of polymerisation up to 100,000 (Mw « 8 million g mol’¹) (see Figure 17 and Table 9). UV nail lamp irradiation resulted in both higher monomer conversion and increased rates of polymerisation.

Table 9 provides a summary of the monomer conversions, molecular weights and molecular weight distributions for the polymerisation of a ACM:NaAA 90:10 mol % mixture using CTA 8 under either UV LED at 405 nm or UV Nail Lamp irradiation at 365 nm with target DP up to 100,000 (Mn « 8 million g mol’¹). Monomer concentration = 25 wt % (3.2 M).

Acrylamide-stat-Sodium 2-Acrylamido-2-methv propanesulfonate [AM-stat-Na ATBS1 Acrylamide and Na ATBS was successfully polymerised at a molar ratio of 90:10 mol %, generating highly monodisperse statistical copolymers up to measured molecular weights of ca. 7 million g mol’¹. FFF measurements indicated good correlation between the theoretical and measured molecular weights, with Mw/Mn values < 1.1 observed up to Mn « 3 million g mol’¹. For target degrees of polymerisation > 100,000, higher monomer conversions were again observed when using CTA 8 under UV nail lamp irradiation at 365 nm (ca. 99 %) in comparison to blue LED light at 470 nm (ca. 40 %). Furthermore, static light scattering (SLS) measurements confirmed both the high molecular weight and narrow polydispersity of the generated copolymers (Rg/Rh values are close to the theoretical monodisperse Debye coil model of 1.78, indicating narrow polydispersity). The Results are shown in Table 10 and Figure 18.

Table 10 provides a summary of the monomer conversions, molecular weights and molecular weight distributions for the polymerisation of a ACM:NaATBS 90:10 mol % mixture using CTA 8 under either blue LED at 470 nm or UV Nail Lamp irradiation at 365 nm with target DP up to 200,000 (Mn ca. 10 - 20 million g mol-1 ). Monomer concentration = 25 wt %.

Copolymer Flocculation Performance Testing

Kaolin Flocculation Test

A Kaolin dispersion (0.1 wt %) at pH 7 was stirred at 200 rpm in an Erlenmeyer flask for 2 h prior to use. Stock solutions of the various copolymers for testing were generated (0.0002 wt %) and left to stir overnight to enable full dissolution. Small volumes (0.25 mL, 0.5 mL, 1 .0 mL, 2.5 mL and 5.0 mL, which equates to dosage levels of 0.5, 1 .0, 2.0, 5.0 and 9 ppm respectively) of the stock copolymer solution were diluted to maximum volume of 5 ml with water and added to the Kaolin dispersion (100 mL) under constant stirring at 160 rpm. After stirring for 120 s at 160 rpm, the dispersion is left to settle for 60 s and a small volume of solution (3 mL) is removed from the top layer of the Kaolin dispersion (ca. 1 cm below the surface) and the turbidity assessed using a Shimadzu UV1800 Photospectrometer.

The flocculation performance of the narrow polydispersity cationic polyacrylamide (10 mol % DMA3q) was compared with commercial product Product A in a Kaolin flocculation test.

Kaolin Flocculation Test

Herein, a simple Kaolin flocculation test was used to assess the flocculation performance of the commercial product Product A and the lab-synthesised “P156”. The test is described in detail in the experimental section, but fundamentally measures the rate of sedimentation and time-dependent water clarity of aqueous Kaolin solutions after dosing with known amounts of copolymer flocculant. As shown in Table 11 , both Product A and P156 have similar SV and Mw values, but P156 has a significantly narrower polydispersity index in comparison to Product A (Mw/Mn = 1.04 vs. 5.5 respectively). As shown in Figure 19 the copolymer molecular weight distribution has a considerable influence on the flocculation efficiency, with significantly improved performance observed for the sample “P156”.

A copolymer dose-rate of 2 ppm results in relative turbidity of ca 80 % when using Product A, whereas a relative turbidity of ca. 50 % was measured when using P156. Furthermore, increasing the dose-rate to 10 ppm results in relative turbidities of ca. 50 % and 0 % when using Product A and P156 respectively. The photographic images in Figure 19 (b) further demonstrate the effect of polydispersity, with the sample at 10 ppm dose-rate with P156 showing optical clarity, whereas Product A at 10 ppm shows significant turbidity. These results indicate that the reduction in the lower molecular weight components significantly improves flocculation performance, as anticipated based on a “bridging” flocculation mechanism.

Table 11 provides FFF-measured molecular weights and the corresponding standard viscosities (SV) for the benchmark Product A and “P156” materials. The copolymers contain 10 mol % DMA3q comonomer.

Claims

Claims

1 . Use of a polymer as a flocculant to aid in the dewatering of an aqueous solids suspension wherein the polymer is formed from one or more ethylenically unsaturated monomers and which polymer has a weight average molecular weight Mw of greater than 500,000 g/mol and a polydispersity index (Mw/Mn) of less than 2.5.

2. Use according to claim 1 , wherein the polymer has a weight average molecular weight Mw is at least 1 million g/mol.

3. The use according to claim 1 or claim 2, wherein the polymer exhibits a number average molecular weight (Mn) in the range of from 1-10 million g/mol.

4. The use according to any preceding claim, wherein the one or more ethylenically unsaturated monomers are selected from one or more of the compounds of formula (I) and/or formula (II)

wherein

R is selected from at least one of H, methyl; X is selected from at least one of NH2, NH(CHs), N(CHs)2, OH, O’ M⁺, O(CH₂)2N⁺(CH₃)3 Y’, NH(CH₂)3N⁺(CH₃)3 Y’, NHC(CH3)2CH₂SO3’ M⁺;

M is selected from at least one of H, alkali metal ion, alkaline earth metal ion or ammonium;

Y is an anion selected from at least one of halide or methosulfate;

R¹ is H; R² is H or CH3; or R1 and R2 together are C3 or C4 alkylene and form a ring.

5. The use according to any preceding claim, wherein the polymer is a block copolymer.

6. The use according to any preceding claim, wherein the polymer is a copolymer of acrylamide and/or methacrylamide with an ethylenically unsaturated comonomer, which is preferably ionic or ionisable.

7. The use according to any preceding claim, wherein the polymer is a copolymer of acrylamide and/or methacrylamide with an ethylenically unsaturated comonomer selected from the group consisting of acrylic acid (or salts thereof), 2- acrylamido-2-methyl propane sulfonic acid (or salts thereof), N-vinyl formamide (VFA), N-vinyl pyrrolidone (NVP), 2-(acryloyloxy)ethyl trimethylammonium chloride, 2-(methacryloyloxy)ethyl trimethylammonium chloride, 3-(methacrylamido)propyl trimethylammonium chloride and 3-(acrylamido)propyl trimethylammonium chloride.

8. The use according to any of claims 1 to 4, wherein the polymer is a homopolymer.

9. The use according to claim 8 in which the ethylenically unsaturated monomer is selected from the group consisting of acrylic acid (or salts thereof), 2-acrylamido- 2-methyl propane sulfonic acid (or salts thereof), N-vinyl formamide (VFA), N-vinyl pyrrolidone (NPV), 2-(acryloyloxy ethyl) trimethylammonium chloride, 2-(meth acryloyloxy ethyl) trimethylammonium chloride, 3-(meth acrylamido propyl) trimethylammonium chloride and 3-(acrylamido propyl) trimethylammonium chloride.

10. The use according to any preceding claim, wherein the polymer is obtainable by a photoiniferter polymerisation mechanism.

11 . The use according to any preceding claim, wherein the polymer is water- soluble or potentially water-soluble.

12. The use according to any preceding claim, wherein the aqueous solids suspension is a suspension in or resulting from a mining or mineral processing operation.

13. Use of a polymer as an agent for increasing the viscosity of an aqueous composition, wherein the polymer is formed from one or more ethylenically unsaturated monomers and which copolymer has a weight average molecular weight Mw of greater than 500,000 g/mol and preferably at least 1 million g/mol and a polydispersity index (Mw/Mn) of less than 2.5.

14. The use according to claim 13, wherein the polymer contains any one or combination of the features of any of claims 2 to 11 .

15. The use according to claim 13 or claim 14, wherein the aqueous composition is selected from the group consisting of oilfield chemicals, additives for use in the oil industry and personal care products.