Technological field of the invention

The present invention relates to high-molecular weight non-ionic surfactants comprising nitrogen or phosphorus end groups or a salt thereof. The present invention also relates to a process for the preparation of high-molecular weight non-ionic surfactants comprising nitrogen or phosphorus containing end groups or a salt thereof, and the use of these high-molecular weight non- ionic surfactants comprising nitrogen or phosphorus containing end groups as surfactants. In particular, the high molecular weight non-ionic surfactants according to the present invention can be used for coordination or binding anions, in particular multivalent anions, and can find application in the purification of aqueous effluent streams. More in particular, the present invention relates to high-molecular ethylene oxide propylene oxide block copolymers comprising nitrogen or phosphorus containing end groups or a salt thereof.

Background of the invention

Generally, compounds containing sulphur and phosphorous are substances that accelerate the growth of plants and thereby become a main element accelerating eutrophication of surface water, e.g. rivers, lakes and seas, waste water and the like. Therefore, research is devoted to find ways of selectively removing phosphates and sulphates in surface water or waste water since 1960's. Other anions of interest within this technical field comprise arsenate and chromate anions which are desirably removed from waste water streams to reduce pollution.

Materials that have been employed in the art for selective removal of anions are known as Polymeric Ligand Exchangers (PLE's). These polymers are for example based on styrene-divinyl benzene or polymethacrylate matrixes having neutral or cationic chelating groups.

US 6.136.199 discloses a process for removing phosphate and chromate anions from waste water wherein a styrene-divinylbenzene or polymethacrylate polymer is

employed, said polymer comprising neutral chelating functional groups and Lewis acid type metal cations bonded to said neutral chelating groups ion such a manner that the positive charge is not neutralised. However, the use of such PLE 's has the disadvantage that they must be regenerated by consecutive washing steps thereby leading to the production of substantial amounts of waste salts. A further disadvantage of these PLE's is that they lack thermo-reversible properties and do not show a critical micellisation temperature (CMT) in a temperature range of practical interest (e.g. below about -40°C or above about 200°C).

US 5.575.924 discloses a method for reducing the turbidity of an aqueous system wherein to the aqueous system an effective amount of a graft polymer comprising ammonium cations is added.

US 6.702.943 discloses a method for removing negatively charged substances from an aqueous liquid wherein polymers comprising ammonium groups are employed.

US 2004/0138331 discloses polymers prepared from acrylate monomers comprising amine or phosphine end-groups and their cationic equivalents. These polymers are used in anti- fouling coating compositions.

Summary of the invention

It is an object of the invention to provide high molecular weight non-ionic surfactants comprising nitrogen or phosphorus containing groups or salts thereof, preferably amine, quaternary ammonium, phosphine or quaternary phosphonium groups.

It is a further object of the invention to provide high molecular weight non- ionic surfactants comprising nitrogen or phosphorus containing end groups or salts thereof that are capable of displaying a critical micellisation temperature (CMT) of about 0° to about 200°C.

It is another object of the invention to provide high molecular weight non- ionic surfactants comprising nitrogen or phosphorus containing end groups or salts thereof that above the CMT are capable of substantial co-ordination of multivalent, in particular divalent anions whereas below the CMT such co-ordination is substantially absent.

It is a further object of the invention to provide a process for the removal of multivalent anions from an aqueous system, wherein said multivalent anions are thermo-reversibly bonded to a high molecular weight non-ionic surfactant comprising nitrogen or phosphorus containing terminal end groups. According to the invention, there is provided a block polymer comprising moieties selected from the group consisting of amino, ammonium, phosphino, phosphonium and mixtures thereof, wherein the polymer comprises at least an ethylene oxide block and a propylene oxide block and wherein the polymer has a number average molecular weight of 1 - 100 kD. The present invention further provides a surfactant composition comprising said block copolymer. The present invention also provides a process for the removal of multivalent anions from an aqueous system, wherein said aqueous system is treated with said block polymer.

Detailed description of the invention

The block polymer according to the present invention comprises the moieties selected from the group consisting of amino, ammonium, phosphino, phosphonium and mixtures thereof preferably as terminal groups. The block polymer according to the present invention is therefore either a non-ionic polymer when the moieties are amino or phosphino and a "cationic" polymer if these moieties are ammonium or phosphonium.

Amino groups have the general formula -NR" '2, ammonium groups have the general formula -N ⁺ R ⁵⁵ ^X ^" , phosphino groups have the general formula -PR" '2 and phosphonium groups have the general formula -P ⁺ R'" ₃ X ^" , wherein R'" is a substituent such as alkyl and X ^" is a counter ion such as halide as is well known to the person skilled in the art.

More in particular, the block polymer according to the present invention is preferably a high molecular weight non-ionic polymer comprising nitrogen or phosphorus containing end groups or salts thereof, preferably terminal nitrogen or phosphorus containing groups and salts thereof, according to formula A or B:

[R _o-p H _p ] - P - [A] _n - [B] _m - [A] _n - P - [R _o-P H _P ] (A)

[R _o-p H _p ] - P - [A] _n - [B] _m - P - [R _o-P H _P ] (B)

wherein: P is a nitrogen or phosphorus atom;

H is a hydrogen atom;

R is a linear or branched C ₁ -C ₁₂ alkyl group, a C ₆ -C ₁₂ aryl group, a C ₇ -C ₁₂ alkaryl or arylalkyl group or a -[CH ₂ CH ₂ -P ⁵⁵ Jq-Qr group wherein P ⁵⁵ is a nitrogen atom or an oxygen atom and wherein the - [CH ₂ CH ₂ -P ⁵⁵ ] _q -Q _r group may be in the form of a salt if P ⁵⁵ is a nitrogen atom;

A is ethylene oxide;

B is propylene oxide; n is in the range of 5 to 1000; m is in the rage of 5 to 1000; o is in the range of O to 2; p is in the range of 0 to 2 when P is a nitrogen atom and p is 0 when P is a phosphorus atom; q is in the range of 1 to 5;

Q is a hydrogen atom, a linear or branched C ₁ -C ₁₂ alkyl group a C ₆ -C ₁₂ aryl group, or a C ₇ -C ₁₂ alkaryl or arylalkyl group; when P ⁵⁵ is a nitrogen atom, then r is 2; and when P ⁵⁵ is an oxygen atom, then r is 1.

Although in formula (A) and (B) the nitrogen and phosphorus containing groups are indicated as end groups, they may also or exclusively be present within the high molecular weight non-ionic polymers as internal groups, wherein the nitrogen and phosphorus groups are either directly bonded to the backbone of the polymer or bonded to the backbone via e.g. a spacer. However, it is preferred that the nitrogen and phosphorus containing groups are present as terminal end groups. In addition, the polymers according to formulas (A) and (B) may have a star or hyperbranched type of structure depending on the starting materials used.

If the block polymer according to the present invention comprises ammonium and/or phosphonium groups, it is preferred that the counter ion is an anion derived from

an inorganic acid. Preferably, the counter ion is a halide, e.g. fluoride, chloride, bromide or iodide.

According to the invention, it is further preferred that n and m are independently in the range of 10 to 500, more preferably 10 to 100. The present invention also relates to a process for the preparation of a high molecular weight non- ionic polymer comprising nitrogen or phosphorus containing end groups or salts thereof, wherein a polymer comprising at least an ethylene oxide block, a propylene oxide block and a free or masked hydroxy group is reacted with a compound comprising a nitrogen or phosphorus containing end group and a substituent that is complementary reactive to hydroxy groups, so that the nitrogen or phosphorus containing end group can covalently be bonded to the polymer.

According to the invention, the complementary reactive groups are preferably selected from the group consisting of hydrogen, halide, hydroxy and epoxide.

Preferably, in the process a hydroxy terminated ethylene oxide propylene oxide diblock or triblock copolymer according to formula (I) or formula (II), respectively:

HO-[A] _n -[B] _1n -[A] _n -OH (I)

HO-[A] _n -[B] _1n -OH (II)

is reacted with a compound according to formula (III) or (IV):

H - P - (R _o-p H _p ) (III)

S-R'-P - (R _o - _P H _P ) (IV)

wherein A, B, P, R, H, n, m, o and p are defined as above;

R' is a linear or branched C ₁ -C ₁₂ alkylene group, optionally substituted with one or more hydroxy groups; and S is a halogen atom, a hydroxy group, or an epoxide group.

Although in formula (I) and (II) the hydroxy groups are indicated as end groups, they may also or exclusively be present within the high molecular weight non-ionic polymers as internal groups, wherein the hydroxy groups are either directly bonded to

the backbone of the polymer or bonded to the backbone via e.g. a spacer. In particular compounds wherein one or more hydroxy groups are bonded to the propylene oxide moiety B are believed to be suitable starting materials as well. However, it is preferred that the hydroxy groups are present as terminal end groups. Moreover, the starting materials (I) and (II) may have a star or hyperbranched type of structure. For example, three arm to six arm polyethoxylates are known in the art wherein trimethylolpropane, pentaerythritolor trimethylol propane ethoxylate are used as the core.

The hydroxy groups of the polymer comprising at least an ethylene oxide block, a propylene oxide block and free hydroxy groups, preferably a hydroxy terminated ethylene oxide propylene oxide diblock or triblock copolymer according to formula (I) or formula (II), respectively, are preferably in an activated form, e.g. as a tosylate or mesylate.

Whereas in formula (I) and (II) the diblock and triblock polymers are shown as having terminal hydroxy end groups, they can be replaced by amino groups -NH ₂ , carboxyl groups -COOH or carboxylate groups -COO ^" . Complementary reactive substituents for the compound comprising the a nitrogen or phosphorus containing end group can conveniently be selected by the person skilled in the art of synthetic organic and polymeric chemistry. A suitable example of a hydroxy terminated ethylene oxide propylene oxide block copolymer is Pluronic P85 (CAS number 9003-11-6) that is available from BASF. For other suitable examples, reference is made to the following web site of BASF showing the basic Pluronic grid:

www.basf.com/static/OpenMarket/Xcelerate/Preview cid-8293119993 l_pubid- 974236729499_c-Article.html

The high molecular weight non-ionic polymer comprising terminal nitrogen or phosphorus containing end groups or salts thereof has a CMT of about 0° to about 200°C, preferably about 25°C to about 100°C. The CMT can be adjusted by selecting a suitable block ratio of ethylene oxide and propylene oxide in the high molecular weight non-ionic polymer. In general, less propylene oxide in the polymer results in higher CMT values. If the CMT is about 0°C, the high molecular weight non-ionic polymer

according to the present invention can be used in a surfactant composition that may be employed under low temperature conditions, e.g. in groundwater or (sub)soil water. If the CMT is for example above 100°C, the polymer according to the invention can be used in a surfactant composition that can be employed under high temperature conditions, e.g. in industrial steam generators.

The high molecular weight non-ionic polymer comprising terminal nitrogen or phosphorus containing end groups or salts thereof is capable of quantitative binding of multivalent anions such as sulphate, phosphate, chromate, arsenate anions, preferably divalent anions, more preferably SO ₄ ^2" , CO ₃ ^2" , HPO ₄ ^2" , PO ₄ ^3" . The high molecular weight non- ionic polymers according to the present invention can also be used to bind anionic moieties derived from amino acids like glutamic acid, organic acids like citric acid, peptides, and proteins. All these substances are bonded above the CMT with high affinity, whereas essentially no binding occurs below the CMT. Decreasing the temperature to values below the CMT completely liberates the bonded multivalent anions, preferably divalent anions. Essentially no binding to free or individual surfactant molecules occur. The selective binding of multivalent anions, preferably divalent anions, is important to avoid unwanted salt depositions in many processes. Consequently, the present invention also relates to a process for the removal of a multivalent anion from an aqueous system, wherein the said aqueous system is treated with the block polymer according to the invention.

In the present patent application, the term "aqueous system" is to be understood as to include any system comprising water, including but not limited to surface water like lakes, underground water, cooling water, boiler water, desalination, house hold apparatus such as dish washers and laundry washing machines, gas scrubbers, blast furnaces, sewage sludge thermal conditioning equipment, membrane processes, paper processing, mining circuits and the like, as will be apparent to the person skilled in the art. The temperature of the aqueous system may be from 0° to 200°C.

According to the invention, it is preferred that the high molecular weight non- ionic polymer comprising terminal nitrogen or phosphorus end groups are neutral so that weakly coordinating or binding anions can be reversibly bonded.

The high molecular weight non-ionic polymer comprising terminal nitrogen or phosphorus containing end groups or salts thereof according to the invention are in particular suitable for the removal of PO ₄ ^3" , SO ₄ ^2" and CO ₃ ^2" from aqueous systems

contaminated with such anions and in industrial and domestic wash processes and products used for such processes.

According to the present invention, a multivalent anion is any anion that has an oxidation state of at least 2 or higher. The present invention also relates to a process for the removal of multivalent anions from an aqueous system, wherein said multivalent anions are contacted with and thermo-reversibly bonded to a high molecular weight non-ionic polymer comprising nitrogen or phosphorus containing terminal end groups or salts thereof. That is, that at higher temperatures the multivalent anions are bonded to the high molecular weight non- ionic polymer comprising nitrogen or phosphorus containing end groups or salts thereof, and that the multivalent anions are released from said high molecular weight non-ionic polymer comprising terminal nitrogen or phosphorus containing end groups or salts thereof at lower temperatures. The present invention relates therefore in particular to a process for the removal of a multivalent anion from an aqueous system, wherein said multivalent anion is contacted at a first temperature with and thermo- reversibly bonded to a high molecular weight non-ionic polymer comprising nitrogen or phosphorus containing end groups or salts thereof to form a anion-polymer complex, wherein the first temperature is higher than the critical micellisation temperature of the high molecular weight non-ionic polymer, and wherein said anion-polymer complex is subjected to a second temperature, the second temperature being lower than the first temperature and lower than the critical micellisation temperature of the high molecular weight non-ionic polymer, to release said multivalent anion from said high molecular weight non- ionic polymer comprising nitrogen or phosphorus containing end groups or salts thereof. Although the description and formulas generally refer to terminal end groups, the invention is not limited to the compounds of the invention comprising nitrogen or phosphorus containing groups or salts thereof as terminal end groups as described in preferred embodiments having formula's A or B. The invention is also directed to polymers according to the invention comprising non-terminal end groups, or polymers according to the invention comprising both non-terminal and terminal end groups, as will be clear to the person skilled in the art.

Examples

Example 1

Pluronic P85 (50 g) was dissolved in diethyl ether (200 mL) giving a cloudy solution. The mixture was centrifuged and the clear supernatant was added drop wise to pentane (200 mL) that was cooled in an ice bath. The formed suspension was stirred for a few hours, while being cooled. Filtration and drying of the residue gave purified Pluronic P85. The purified material (15 g) in dry pyridine (50 mL) was cooled in an ice bath, and to this solution tosyl chloride (20 g) was added. The whole solution was stirred at 4 °C for 7 days, after which period some ice water was added to eliminate the excess tosyl chloride. The mixture was stirred in an ice bath for about half an hour for this purpose. Then, more ice water was added and the aqueous mixture was extracted with several portions of chloroform. The collected organic layers were washed with a 2M HCl-solution and with a NaCl-solution. Drying with MgSO ₄ , filtration and evaporation of the chloroform gave the tosylated product. ¹ H NMR solution spectroscopy in CDCl ₃ showed signals at 7.6 and 7.2 ppm indicative for tosylate end groups.

The tosylated polymer (14 g) was dissolved in acetonitril (250 mL) and diethyl amine (25 g). The mixture was kept under an argon atmosphere and was heated in an oil bath (95 °C) for 16 hours. The solvents were evaporated under reduced pressure, and co-evaporation under reduced pressure with portions of chloroform got rid of the acetonitril and diethyl amine. The product (N3E-85) was then dissolved in chloroform and the organic solution was washed with a NaCl-solution, where a clear phase separation was achieved using centrifugation. The chloroform layer was collected and dried with MgSO ₄ , the suspension was filtered and the filtrate was reduced by vacuum evaporation of the solvent. ¹³ C NMR solution spectroscopy in CDCl ₃ showed resonances at ca. 52, 47 and 10 ppm indicative for the tertiary diethyl amine end groups. MALDI-TOF-MS showed a broad peak at about 3-6 kD. Finally, the aminated product (N3E-85) was dissolved in acetonitril (100 mL) and

MeI (25 mL), and this mixture was kept under an argon atmosphere. Heating at reflux was maintained for 16 hours and then the mixture was evaporated down, and co-

evaporated with chloroform to eliminate traces of MeI. ¹³ C NMR solution spectroscopy in CDCl ₃ of the product (N4E-85) showed signals at around 60 ppm and below 10 ppm indicative for diethyl methyl ammonium end groups. MALDI-TOF-MS shows a broad peak at about 3-6 kD.

Example 2

In this example, the temperature-induced aggregation behaviour to create thermo- reversible ion binding in the aqueous shell of the polymers according to Example 1 (N4E-85) is demonstrated.

Conductivity experiments (0.5 % by weight solution in water) demonstrated that N4E-85 according to Example 1 (N4E-85) had a critical micelle formation temperature (CMT) of around 33°C at low ionic strength (i.e. no salt added) (Figure 1). The presence of the diethylmethyl ammonium end groups lowers the CMT by approximately 1°C, since Pluronic P85 displays a CMT of 34°C at low ionic strength. The conductivity experiments were performed using a QiS M320 conductometer with a QiS QC203T epoxy/graphite conductivity cell. The cell constant was periodically checked and calibrated by a 0.01 M KCl solution. The solution temperature was kept constant (+/- 0.1 °C) with a Lauda C6 CP thermostat.

Temperature [ ⁰ Q

Figure 1: Conductivity of a 0.5% solution of N4E-85 as a function of temperature.

Example 3

To establish the selective multivalent anion-binding capacity of the tertiary amine-modified Pluronic P85 (N3E-85) of Example 1 Isothermal Titration Calorimetry (ITC) measurements have been made. The calorimetry titration experiments were performed by using a MicroCal VP-ITC apparatus with a cell volume of 1.4431 mL, adding 70 injections of 4 μL of a KCl (20.3 *10 ^"3 mol/L) or Na ₂ SO ₄ solution (10.1*10 ^~3 mol/L) to a 1 wt% solution of the polymer N3E-85 according to Example 1 at 20° and 50°C; concentrations were chosen such that both solutions contained an equal number of tertiary amine groups.

ITC has proven to be an effective method to evaluate the heat effects occurring upon aggregation and ion binding and release [T. Christensen et al., J. Am. Chem. Soc. 125, 7357 - 7366 (2003)].

ITC experiments at pH = 3.5 with SO ₄ ^2" or Cl ^" and the polymer according to Example 1 (N3E-85) yielded the results shown in Figure 2 for temperatures below the CMT (21°C) and above the CMT (50°C). No significant binding of Cl ^" to Pluronic P85 occurs at either temperature (results not shown). No significant binding of SO ₄ ^2" occurs to the polymer according to Example 1 (N3E-85) at 21°C. Binding of SO ₄ ^2" only occurs to the polymer according to Example 1 (N3E-85) at 50°C. Binding of Cl ^" is hardly observed at 50°C. The molar ratio, r, is defined as the concentration of added sulfate ions divided by the concentration of functional end groups. It has to be noted that because no exact concentration of end groups could be measured, this concentration was set to 5.0*10 ^"3 mol/L, which is the concentration of total end groups.

Molar ratb r [-]

Figure 2: N3E-85, pH 3.5, sulfate and chloride at 21° and 50°Celsius

Example 4

To establish the selective multivalent anion-binding capacity of the quaternary ammonium-modified Pluronic P85 (N4E-85) of Example 1, ITC measurements have been made. The calorimetry titration experiments were performed by using a MicroCal VP-ITC apparatus with a cell volume of 1.4431 mL, adding 70 injections of 4 μL of a NaCl (20.3*10 ^~3 ) or Na ₂ SO ₄ solution (10.0*10 ^~3 mol/L) to a 1 wt% solution of the polymer according to Example 1 at 20 and 50 °C; concentrations were chosen such that both solutions contained an equal number of quaternary ammonium groups.

ITC experiments at pH = 4.6 with SO ₄ ^2" or Cl ^" , the polymer according to Example 1 (N4E-85) yielded the results shown in Figure 3 for temperatures below CMT (20°C) and above CMT (50°C). From Figure 3, it can be seen that no significant binding of SO ₄ ^2" occurs to the polymer according to Example 1 (N4E-85) at 20°C. Binding of SO ₄ ^2" only occurs to the polymer according to Example 1 (N4E-85) at 50°C. Binding of Cl ^" is hardly observed at any of the experimental conditions applied.

Without being bound by theory, the binding of SO ₄ ^2" to aggregates of the polymer according to Example 1 (N4E-85) is caused by a charge compensation mechanism, rather than direct 1 :2 binding, similar to the behaviour of common ionic surfactants. The molar ratio, r, is defined as the concentration of added sulfate ions divided by the concentration of iunctional end groups. It has to be noted that because no exact concentration of end groups could be measured, this concentration was set to 5.0*10 ,-3 mol/L, which is the concentration of total end groups.

Mdar ratio [-]

Figure 3: N4E-85, pH 4.6, sulfate and chloride at 21 and 50 degrees Celsius

Example 5

To establish the pH-effect on the selective multivalent anion-binding capacity of the tertiary amine-modified Pluronic P85 (N3E-85) of Example 1, ITC measurements have been made at pH 3.5 and pH 9. The calorimetry titration experiments were performed by using a MicroCal VP-ITC apparatus with a cell volume of 1.4431 mL, adding 70 injections of 4 μL of a Na ₂ SO ₄ solution (10.1*10 ^~3 mol/L) to a 1 wt% solution of the polymer according to Example 1 at 50 °C; concentrations were chosen such that both solutions contained an equal number of tertiary amine groups. ITC experiments at pH = 3.5 and pH = 9 with SO ₄ ^2" and the polymer according to

Example 1 (N3E-85) yielded the results shown in Figure 4 for temperatures above the CMT (50°C). Binding of SO ₄ ^2" occurs to the polymer according to Example 1 (N3E- 85) at 50°C at both pH-values.

Molar ratio r [-]

Figure 4: N3E-85 at different pH's at 50°Celsius