METHOD FOR PREPARING AN AQUEOUS POLYACRYLAMIDE SOLUTION

Abstract

A method for preparing an aqueous polyacrylamide solution is disclosed. The method comprises:hydrating acrylonitrile in water in presence of a biocatalyst capable of converting acrylonitrile to acrylamide so as to obtain an acrylamide solution,directly polymerizing the acrylamide solution so as to obtain a polyacrylamide gel, anddirectly dissolving the polyacrylamide gel by addition of water so as to obtain an aqueous polyacrylamide solution.

Claims

1-21. (canceled)

22. A method for preparing an aqueous polyacrylamide solution, the method comprising: hydrating acrylonitrile in water in the presence of a biocatalyst, to obtain an acrylamide solution, wherein the biocatalyst is capable of converting acrylonitrile to acrylamide, directly polymerizing the acrylamide solution, to obtain a polyacrylamide gel, wherein the polyacrylamide gel comprises 16 to 50% by weight of polyacrylamide solids, and directly dissolving the polyacrylamide gel by adding water, to obtain an aqueous polyacrylamide solution, wherein the method is carried out on site.

23. The method of claim 22, wherein the polyacrylamide gel is dissolved with at least one static mixer.

24. The method of claim 22, wherein the aqueous polyacrylamide solution comprises 0.03 to 5.0% by weight of polyacrylamide.

25. The method of claim 23, wherein the polyacrylamide gel is dissolved with a resting time within the at least one static mixer of 0.05 to 10 s.

26. The method of claim 22, wherein the biocatalyst encodes the enzyme nitrile hydratase.

27. The method of claim 22, wherein the biocatalyst is a nitrile hydratase producing microorganism.

28. The method of claim 22, further comprising: adding at least one monoethylenically unsaturated, water-soluble comonomer to the acrylamide solution.

29. The method of claim 28, wherein the at least one monoethylenically unsaturated, water-soluble comonomer is selected from the group consisting of acrylic acid, 2-acrylamido-2-methylpropane sulfonic acid and a salt thereof.

30. The method of claim 29, wherein an amount of the at least one monoethylenically unsaturated, water-soluble comonomer is 25 to 40% by weight relative to a total amount of all monomers.

31. The method of claim 22, wherein the biocatalyst is removed before directly polymerizing the acrylamide solution.

32. The method of claim 22, wherein a conversion of acrylonitrile to acrylamide is carried out at a starting temperature of 15 to 30 C.

33. The method of claim 22, wherein the polymerization of the acrylamide is initiated by adding an initiator for radical polymerization.

34. The method of claim 33, wherein the initiator is selected from the group consisting of a peroxide, a persulfate, an azo compound, a redox couple and a mixture thereof.

35. The method of claim 22, wherein the method is monitored on line.

36. The method of claim 22, wherein the method is carried out at an oilfield or a mining area.

37. The method of claim 22, wherein the method is carried out in at least one mobile reactor.

38. The method of claim 22, wherein the method is carried out for 12 to 72 h.

39. A process for producing mineral oil from an underground mineral oil deposit, the process comprising: a) preparing an aqueous polyacrylamide solution, b) injecting an aqueous fluid comprising the aqueous polyacrylamide solution into the underground mineral oil deposit through at least one injection well, and c) withdrawing crude oil from the underground mineral oil deposit through at least one production well, wherein a) comprises: hydrating acrylonitrile in water in the presence of a biocatalyst, to obtain an acrylamide solution, wherein the biocatalyst is capable of converting acrylonitrile to acrylamide, directly polymerizing the acrylamide solution, to obtain a polyacrylamide gel, wherein the polyacrylamide gel comprises 16 to 50% by weight of polyacrylamide solids, and directly dissolving the polyacrylamide gel by adding water, to obtain an aqueous polyacrylamide solution, wherein the aqueous polyacrylamide solution is prepared on an oil field.

40. A process for mining, mineral processing and/or metallurgy, the process comprising: a) preparing an aqueous polyacrylamide solution, and b) separating a solid and a liquid, disposing of tailings, depositing polymer modified tailings, managing tailings, modifying a density or a rheological property, aiding an agglomeration, binding, and/or handling a material with the aqueous polyacrylamide solution, wherein a) comprises: hydrating acrylonitrile in water in the presence of a biocatalyst, to obtain an acrylamide solution, wherein the biocatalyst is capable of converting acrylonitrile to acrylamide, directly polymerizing the acrylamide solution, to obtain a polyacrylamide gel, wherein the polyacrylamide gel comprises 16 to 50% by weight of polyacrylamide solids, and directly dissolving the polyacrylamide gel by adding water, to obtain an aqueous polyacrylamide solution, wherein the aqueous polyacrylamide solution is prepared in a mining area.

Description

SHORT DESCRIPTION OF THE FIGURES

[0087] Further features and embodiments of the invention will be disclosed in more detail in the subsequent description of embodiments, particularly in conjunction with the dependent claims. Therein, the respective features may be realized in an isolated fashion as well as in any arbitrary feasible combination, as the skilled person will realize. The scope of the invention is not restricted by the embodiments. The embodiments are schematically depicted in the figures. Therein, identical reference numbers in these figures refer to identical or functionally comparable elements.

[0088] In the figures:

[0089] FIG. 1 shows a block diagram of an installation for the preparation of a polyacrylamide solution.

[0090] FIG. 2 schematically shows a polymerization reactor having a tubular part and a conical taper at its lower end.

[0091] FIG. 3 schematically shows a polymerization reactor having a conical part and a second conical taper at its lower end.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0092] FIG. 1 shows a block diagram of an installation 10 for preparing of a polyacrylamide solution. The installation 10 basically comprises at least one reactor for preparing acrylamide from acrylonitrile, one reactor for polymerizing the aqueous monomer solution comprising acrylamide and optionally further monoethylenically unsaturated, water-soluble monomers and a device for dissolving the polyacrylamide gel to an aqueous polyacrylamide solution as will be explained in further detail hereinafter.

[0093] According to the exemplary embodiment shown in FIG. 1, the installation 10 comprises a first reactor 12, a second reactor 14 and a static mixer 16. The first reactor 12 is connected to the second reactor 14 by means of a pipe 18. The second reactor 14 is connected to the static mixer 16 by means of a pipe 20. The installation 10 is configured to be used with a method for preparing of an aqueous polyacrylamide solution as will be explained in further detail hereinafter.

[0094] The first reactor 12 comprises at least one feed 22. By means of the feed 22, water and acrylonitrile are supplied to the first reactor 12. Further, a biocatalyst is supplied to the first reactor 12. The acrylonitrile is hydrated in the water in presence of the biocatalyst. The biocatalyst is capable of converting acrylonitrile to acrylamide so as to obtain an acrylamide solution. The biocatalyst encodes the enzyme nitrile hydratase. For this purpose, the biocatalyst is a nitrile hydratase producing microorganism. For example, the nitrile hydratase producing microorganism is a species belonging to a genus selected from the group consisting of Rhodococcus, Aspergillus, Acidovorax, Agrobacterium, Bacillus, Bradyrhizobium, Burkholderia, Escherichia, Geobacillus, Klebsiella, Mesorhizobium, Moraxella, Pantoea, Pseudomonas, Rhizobium, Rhodopseudomonas, Serratia, Amycolatopsis, Arthrobacter, Brevibacterium, Corynebacterium, Microbacterium, Micrococcus, Nocardia, Pseudonocardia, Trichoderma, Myrothecium, Aureobasidium, Candida, Cryptococcus, Debaryomyces, Geotrichum, Hanseniaspora, Kluyveromyces, Pichia, Rhodotorula, Comomonas, and Pyrococcus. In preferred embodiments of the invention the biocatalyst is selected from bacteria of the genus Rhodococcus, Pseudomonas, Escherichia and Geobacillus. Preferred biocatalysts to be employed in context with the method of the present invention comprise representatives of the genus Rhodococcus. Species suitable as biocatalyst to be employed in context with any one of the method of the present invention may comprise, e.g., Rhodococcus rhodochrous. In order to increase the contact of the acrylonitrile and the biocatalyst, a stirrer (not shown in detail) may be present within the first reactor 12. As a biocatalyst is used for converting acrylonitrile to acrylamide, the conversion is carried out at a temperature of 15 C. to 30 and preferably of 20 C. to 25 C. Thus, a heating for initiating the conversion is not necessary. Rather, the conversion may be carried out at ambient temperature. For example, the conversion is carried out at a temperature of 22 C. The amount of biocatalyst used for the conversion process depends on the concentration of the acrylamide solution to be produced within a target time. Thus, the higher the target concentration of the acrylamide solution is the more biocatalyst is used in order to produce this acrylamide amount in the same time as with a lower concentration.

[0095] The thus formed acrylamide solution is directly supplied to the second reactor 14. For example, the acrylamide solution may be discharged from the first reactor 12 through an outlet 24 thereof and is supplied to the second reactor 14 through the pipe 18 and a feed 26 of the second reactor 14. It is to be noted that a buffer tank (not shown in detail) may be disposed between the first reactor 12 and the second reactor 14 fur buffering the acrylamide solution before being supplied to the second reactor 14 if technically required. For example, a buffer tank, which is configured to contain an amount or volume corresponding to at least the target amount or target volume of the acrylamide solution supplied to the second reactor 14, may be disposed between the first reactor 12 and the second reactor 14. Thus, the buffer tank may buffer one filling amount or volume of the second reactor 14. The biocatalyst may be removed from the acrylamide solution. For example, a filter (not shown in detail) may be present within the pipe 18 configured to hold back the biocatalyst. Within the second reactor 14, the acrylamide solution is directly polymerized so as to obtain a polyacrylamide gel. The polymerization of the acrylamide is initiated by addition of a radical polymerization initiator. The radical polymerization initiator may be added with a concentration of 0.01% to 5.0% by weight and preferably of 0.02% to 2.0% by weight relating to the total weight of its solution such as 0.1%. The radical polymerization initiator may be selected from the group of peroxides, persulfates, azo compounds, redox couples and mixtures thereof. Suitable examples have already been provided above.

[0096] The polymerization of the acrylamide solution to polyacrylamide gel preferably may be carried out under adiabatic conditions. Details have already been mentioned above.

[0097] The polymerization may be performed in any kind of reactor suitable for gel polymerization. Such reactors are basically known to the skilled artisan. Particularly advantageously, it is possible to use conical reactors for this purpose, as described, for example, by U.S. Pat. No. 5,633,329 or U.S. Pat. No. 7,619,046 B2.

[0098] FIG. 2 schematically shows vertical tubular reactor (1) which narrows conically (2) at the lower end. The capacity of the reactors is chosen by the person skilled in the art according to the desired production capacity and may be 1 to 100 m.sup.3, for example 5 to 50 m.sup.3, without any intention that the invention be restricted thereto. The inner surface of the reactor has preferably been provided with a coating to reduce the adhesion of the reaction mixture to the reactor wall, for example with a Teflon coating. At the lower end, the reactor has a shut-off device (3). The reactor further comprises at least one feed (4). Through this feed (4), the aqueous monomer solution and/or gases and/or further components can be passed into the reactor. Gases may especially be inert gases such as nitrogen, argon or CO.sub.2. Inert gases can be used to purge the reactor for inertization. Of course, it is also possible for different feeds to be present for different components, for example separate feeds for the aqueous reaction solution and gases. The at least one feed (4) may preferably be mounted at the top of the reactor or at the side in the upper region of the reactor, but other arrangements are of course also possible.

[0099] The shut-off device (3) is closed during polymerization. To withdraw the polymer gel from the reactor, the shut-off device (3) is opened. In general, the polymer gel obtained is such viscous that it does not flow out of the reactor without additional measures. For removing the polyacrylamide gel (5) a gas such as nitrogen, pressurized air or carbon dioxide or a liquid, in particular water is injected at the top of the tubular reactor via the feed (4) or another feed, thereby pressing the polyacrylamide gel out of the reactor. The shut-off device may be connected with a screw conveyor or some other conveyor which transfers the polyacrylamide gel to the device for dissolving. Such a screw conveyor may also support removing the gel from the polymerization reactor. Furthermore, it already causes some comminution of the polyacrylamide gel.

[0100] FIG. 3 shows another embodiment of a conical reactor. In this embodiment, the upper part is not tubular but also slightly conical, i.e. the reactor comprises two different conical sections. Besides that, the function of the reactor is the same.

[0101] In the exemplary embodiment according to FIG. 1, the thus formed polyacrylamide gel is directly supplied to the static mixer 16. For example, the polyacrylamide gel may be discharged from the second reactor 14 through an outlet 28 (for example the bottom outlet as indicated in FIG. 1 or 2) thereof and is supplied to the static mixer 16 through the pipe 20 and a feed 30 of the static mixer 16. The polyacrylamide gel is directly dissolved by addition of water so as to obtain an aqueous polyacrylamide solution by means of the static mixer. The water may be added through a separate feed 32 of the static mixer 16. The polyacrylamide gel is dissolved with a resting time within the mixer of 0.05 s to 10 s and preferably 0.1 s to 2 s such as 1.0 s. The aqueous polyacrylamide solution may be discharged from the static mixer 16 through an outlet 34. The polyacrylamide gel is dissolved such that the aqueous polyacrylamide solution comprises 0.03% to 5.0% and preferably 0.05% to 2.0% by weight polyacrylamide such as 1.0%. Thus, the aqueous polyacrylamide solution is suitable in mining and/or oil recovery.

[0102] In another embodiment, the static mixer may comminute the gel and partly dissolve it, thereby obtaining a mixture of water, polyacrylamide already dissolved therein and particles of polyacrylamide gel not yet dissolved. The process of dissolving may be finalized in a vessel, for example a stirred vessel or by passing the mixture through a second static mixer.

[0103] The method is carried out in a time of 12 h to 72 h and preferably of 15 h to 60 h such as 20 h. For example, the step of converting acrylonitrile to acrylamide may be carried out such that it takes 4 h to 8 h and preferably 6 h to 7 h so as to provide an acrylamide solution comprising 50% acrylamide. In order to produce 1 t acrylamide solution with a concentration of 50% by weight acrylamide, 0.1 kg to 1.0 kg, preferably 0.16 kg to 0.75 kg and more preferably 0.2 kg to 0.6 kg biocatalyst is used. The biocatalyst may be used as a dried powder such as dried by means of spray drying. If the target concentration within the same time is lower, the amount of biocatalyst may be linearly reduced. For example, if the target concentration of the acrylamide solution is 30% by weight acrylamide, 0.06 kg to 0.6 kg, preferably 0.10 kg to 0.45 kg and more preferably 0.13 kg to 0.36 kg biocatalyst is used per ton acrylamide solution. If the target concentration of the acrylamide solution is 35% by weight acrylamide, 0.07 kg to 0.7 kg, preferably 0.11 kg to 0.53 kg and more preferably 0.15 kg to 0.42 kg biocatalyst is used per ton acrylamide solution. If the target concentration of the acrylamide solution is 40% by weight acrylamide, 0.08 kg to 0.8 kg, preferably 0.13 kg to 0.60 kg and more preferably 0.17 kg to 0.48 kg biocatalyst is used per ton acrylamide solution.

[0104] Needless to say, the step of the conversion of acrylonitrile to acrylamide is carried out with a speed that is adapted to the speed of the polymerizing step. Thus, it is ensured that the polymerization step is entered with exactly the amount of acrylamide that is formable by the conversion of acrylonitrile to acrylamide. This avoids the provision of storage tanks for storing acrylamide and the method may be continuously carried out. For example, the step of polymerizing acrylamide to polyacrylamide may be carried out such that it takes 4 h to 8 h and preferably 6 h to 7 h so as to provide a polyacrylamide gel with a concentration of 25% to 40% by weight, preferably of 26% to 39% by weight and more preferably 27% to 38% by weight acrylamide within the polyacrylamide gel in water such as 30%.

[0105] The method may be monitored on line. Further, may be carried out on site. Thus, the installation 10 may be disposed at a site where the polyacrylamide solution is actually used, for example at an oilfield or at a mining area. The at least one reactor may be mobile. For example, the above described first and second reactors 12, 14 may be mobile and disposed on a vehicle. Needless to say, the static mixer 16 may be mobile as well such that the complete installation 10 may be mobile.

[0106] Basically, by means of the disclosed method, water-soluble homo- or copolymers of (meth)acrylamide by free-radical polymerization are provided as an aqueous solution. In this process, acrylamide or methacrylamide is obtained from acrylonitrile or methacrylonitrile and includes monomers in aqueous solution in a comparatively high concentration, namely 25 to 45% by weight. Because of the high concentration, the mixture does not remain liquid in the course of the polymerization; instead, a solid, water-containing polymer gel is obtained.

Homo- and Copolymers of Acryl Amide to be Manufactured

[0107] Accordingly, by means of the process according to the invention, it is possible to prepare water-soluble homo- or copolymers of (meth)acrylamide. They comprise monoethylenically unsaturated, hydrophilic monomers (A1), where at least one of the monomers is (meth)acrylamide. Optionally, monoethylenically unsaturated, amphiphilic monomers (A2) other than the hydrophilic monomers (A1) and further ethylenically unsaturated monomers (A3) may be present.

[0108] The monoethylenic monomers (A1) are hydrophilic. The term hydrophilic in the context of this invention means that the monomers (A) are to be soluble in the aqueous acrylamide solution to be used for polymerization, i.e. a solution comprising 25 to 45% by weight of monomers (A1), in the desired use concentration. It is thus not absolutely necessary that monomers (A) to be used are miscible with water without any gap; instead, it is sufficient if they meet the minimum requirement mentioned. In general, the solubility of the hydrophilic monomers (A) in water at room temperature should be at least 50 g/l, preferably at least 100 g/l and more preferably at least 150 g/l.

[0109] The hydrophilic, monoethylenically unsaturated monomers (A1) may be uncharged monomers (A1a). The monomers (A1a) comprise hydrophilic groups which impart at least a certain water solubility to the monomers. (Meth)acrylamide is a monomer (A1a). Examples of further monomers (A1a) include derivatives of (meth)acrylamide such as N-methyl(meth)acrylamide, N,N-dimethyl(meth)acrylamide or N-methylol(meth)acrylamide.

[0110] Further examples include monomers comprising hydroxyl and/or ether groups, for example hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, allyl alcohol, hydroxyvinyl ethyl ether, hydroxyvinyl propyl ether, hydroxyvinyl butyl ether, polyethylene glycol (meth)acrylate, N-vinylformamide, N-vinylacetamide, N-vinylpyrrolidone or N-vinylcaprolactam, and vinyl esters, for example vinyl formate or vinyl acetate. N-Vinyl derivatives can be hydrolyzed after polymerization to give vinylamine units, and vinyl esters to give vinyl alcohol units.

[0111] Hydrophilic, monoethylenically unsaturated monomers (A1) may be hydrophilic, anionic monomers (A1b) comprising at least one acidic group, or salts thereof.

[0112] The acidic groups are preferably acidic groups selected from the group of COOH, SO.sub.3H and PO.sub.3H.sub.2 or salts thereof. Preference is given to monomers comprising COOH groups and/or SO.sub.3H groups, particular preference to monomers comprising SO.sub.3H groups. The salts of the acidic monomers may of course also be involved. Suitable counterions include especially alkali metal ions such as Li.sup.+, Na.sup.+ or K.sup.+, and also ammonium ions such as NH.sub.4.sup.+ or ammonium ions having organic radicals. Examples of ammonium ions having organic radicals include [NH(CH.sub.3).sub.3].sup.+, [NH.sub.2(CH.sub.3).sub.2].sup.+, [NH.sub.3(CH.sub.3)].sup.+, [NH(C.sub.2H.sub.5).sub.3].sup.+, [NH.sub.2(C.sub.2H.sub.5).sub.2].sup.+, [NH.sub.3(C.sub.2H.sub.5)].sup.+, [NH.sub.3(CH.sub.2CH.sub.2OH)].sup.+, [H.sub.3NCH.sub.2CH.sub.2NH.sub.3].sup.2+ or [H(H.sub.3C).sub.2NCH.sub.2CH.sub.2CH.sub.2NH.sub.3].sup.2+.

[0113] Examples of monomers (A1b) comprising COOH groups include acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid or fumaric acid. Preference is given to acrylic acid.

[0114] Examples of monomers (A1b) comprising sulfo groups include vinylsulfonic acid, allylsulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, 2-methacrylamido-2-methylpropanesulfonic acid, 2-acrylamidobutanesulfonic acid, 3-acrylamido-3-methylbutanesulfonic acid or 2-acrylamido-2,4,4-trimethylpentanesulfonic acid. Preference is given to vinylsulfonic acid, allylsulfonic acid or 2-acrylamido-2-methylpropanesulfonic acid and particular preference to 2-acrylamido-2-methylpropanesulfonic acid (APMS) or salts thereof.

[0115] Examples of monomers (A1b) comprising phosphonic acid groups include vinylphosphonic acid, allylphosphonic acid, N-(meth)acrylamidoalkylphosphonic acids or (meth)acryloyloxyalkyl-phosphonic acids, preferably vinylphosphonic acid.

[0116] Preferably, monomer (A1b) may be selected from the group consisting of acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, vinylsulfonic acid, allylsulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid (AMPS), 2-methacrylamido-2-methylpropane-sulfonic acid, 2-acrylamidobutanesulfonic acid, 3-acrylamido-3-methylbutane-sulfonic acid, 2-acrylamido-2,4,4-trimethylpentanesulfonic acid, vinylphosphonic acid, allylphosphonic acid, N-(meth)acrylamidoalkylphosphonic acids and (meth)acryloyloxyalkyl-phosphonic acids, more preferably from acrylic acid and/or APMS or salts thereof.

[0117] Further, monoethylenically unsaturated, hydrophilic monomers may be hydrophilic, cationic monomers (A1c). Suitable cationic monomers (A1c) include especially monomers having ammonium groups, especially ammonium derivatives of N-(-aminoalkyl)(meth)acrylamides or -aminoalkyl (meth)acrylates.

[0118] More particularly, monomers (A1c) having ammonium groups may be compounds of the general formulae H.sub.2CC(R.sup.1)CONR.sup.2R.sup.3N(R.sup.4).sub.3+ X.sup. (Ia) and/or H.sub.2CC(R.sup.1)COOR.sup.3N(R.sup.4).sub.3+ X.sup. (Ib). In these formulae, R.sup.1 is H or methyl, R.sup.2 is H or a C.sub.1 to C.sub.4-alkyl group, preferably H or methyl, and R.sup.4 is a preferably linear C.sub.1 to C.sub.4-alkylene group, for example a 1,2-ethylene group CH.sub.2CH.sub.2 or a 1,3-propylene group CH.sub.2CH.sub.2CH.sub.2. The R.sup.4 radicals are each independently C.sub.1- to C.sub.4-alkyl radicals, preferably methyl or a group of the general formula R.sup.5SO.sub.3H where R.sup.5 is a preferably linear C.sub.1 to C.sub.4-alkylene group or a phenyl group, with the proviso that generally not more than one of the R.sup.4 substituents is a substituent having sulfo groups. More preferably, the three R.sup.4 substituents are methyl groups, meaning that the monomer has an N(CH.sub.3).sub.3+ group. X.sup. in the above formula is a monovalent anion, for example Cl.sup.. X.sup. may of course also be a corresponding fraction of a polyvalent anion, although this is not preferred. Examples of preferred monomers (A1c) of the general formula (Ia) or (Ib) include salts of 3-trimethylammoniopropyl(meth)acrylamides or 2-trimethylammonioethyl (meth)acrylates, for example the corresponding chlorides such as 3-trimethylammoniopropylacrylamide chloride (DIMAPAQUAT) and 2-trimethylammonioethyl methacrylate chloride (MADAME-QUAT).

[0119] The amphiphilic monomers (A2) are monoethylenically unsaturated monomers having at least one hydrophilic group and at least one, preferably terminal, hydrophobic group. Monomers of this kind serve to impart hydrophobically associating properties to copolymers comprising (meth)acrylamide.

[0120] Hydrophobically associating copolymers are understood by the person skilled in the art to mean water-soluble copolymers which, as well as hydrophilic units (in a sufficient amount to assure water solubility), have hydrophobic groups in lateral or terminal positions. In aqueous solution, the hydrophobic groups can associate with one another. Because of this associative interaction, there is an increase in the viscosity of the aqueous polymer solution compared to a polymer of the same kind that merely does not have any associative groups.

[0121] Suitable monomers (A2) especially have the general formula H.sub.2CC(R.sup.5)R.sup.6R.sup.7 (IIa) where R.sup.5 is H or methyl, R.sup.6 is a linking hydrophilic group and R.sup.7 is a terminal hydrophobic group. In a further embodiment, the monomer (A2) may have general formula H.sub.2CC(R.sup.5)R.sup.6R.sup.7R.sup.8 (IIb) where R.sup.5,

[0122] R.sup.6 and R.sup.7 are each as defined above, and R.sup.8 is a hydrophilic group.

[0123] The linking hydrophilic R.sup.6 group may be a group comprising alkylene oxide units, for example a group comprising 5 to 50 alkylene oxide units, which is joined to the H.sub.2CC(R.sup.5) group in a suitable manner, for example by means of a single bond or of a suitable linking group, where at least 70 mol %, preferably at least 90 mol %, of the alkylene oxide units are ethylene oxide units. In addition, the group may be a group comprising quaternary ammonium groups.

[0124] In one embodiment of the invention, the hydrophobic R.sup.7 group comprises aliphatic and/or aromatic, straight-chain or branched C.sub.8-40-hydrocarbyl radicals R.sup.7a, preferably C.sub.12-32-hydrocarbyl radicals. In a further embodiment, the hydrophobic R.sup.7 group may be an R.sup.7b group comprising alkylene oxide units having at least 3 carbon atoms, preferably at least 4 carbon atoms.

[0125] In one embodiment of the invention, the monomers (A2) are monomers of the general formula

H.sub.2CC(R.sup.5)O(CH.sub.2CH(R.sup.8)O).sub.k (IIc) or H.sub.2CC(R.sup.5)(CO)O(CH.sub.2CH(R.sup.8)O).sub.kR.sup.7a(IIId).

[0126] In the formulae (IIc) and (IId), R.sup.5 is as defined above, and the O(CH.sub.2CH(R.sup.8)O).sub.k and (CO)O(CH.sub.2CH(R.sup.8)O).sub.k groups are each specific linking R.sup.6 groups, meaning that (IIc) is a vinyl ether and (IId) is an acrylic ester.

[0127] The number of alkylene oxide units k is a number from 10 to 80, preferably 12 to 60, more preferably 15 to 50 and, for example, 20 to 40. It will be apparent to the person skilled in the art in the field of alkylene oxides that the values stated are mean values.

[0128] The R.sup.8 radicals are each independently H, methyl or ethyl, preferably H or methyl, with the proviso that at least 70 mol % of the R.sup.8 radicals are H. Preferably at least 80 mol % of the R.sup.8 radicals are H, more preferably at least 90 mol %, and they are most preferably exclusively H. The block mentioned is thus a polyoxyethylene block which may optionally also have certain proportions of propylene oxide and/or butylene oxide units, preferably a pure polyoxyethylene block.

[0129] R.sup.7a is an aliphatic and/or aromatic, straight-chain or branched hydrocarbyl radical having 8 to 40 carbon atoms, preferably 12 to 32 carbon atoms. In one embodiment, the aliphatic hydrocarbyl groups have 8 to 22, preferably 12 to 18 carbon atoms. Examples of such groups include n-octyl, n-decyl, n-dodecyl, n-tetradecyl, n-hexadecyl or n-octadecyl groups. In a further embodiment, the groups are aromatic groups, especially substituted phenyl radicals, especially distyrylphenyl groups and/or tristyrylphenyl groups.

[0130] In a further embodiment of the invention, the monomers (A2) are monomers of the general formula

H.sub.2CC(R.sup.5)R.sup.9O(CH.sub.2CH(R.sup.10)O).sub.x(CH.sub.2CH(R.sup.11)O).sub.y(CH.sub.2CH.sub.2O).sub.zR.sup.12(IIe).

[0131] In the monomers (A2) of the formula (IIe), an ethylenic group H.sub.2CC(R.sup.5) is bonded via a divalent, linking group R.sup.9O to a polyoxyalkylene radical having block structure, where the CH.sub.2CH(R.sup.10)O).sub.x, (CH.sub.2CH(R.sup.11)O).sup.l and optionally CH.sub.2CH.sub.2O).sub.zR.sup.12 blocks are arranged in the order shown in formula (IIe). The transition between the two blocks may be abrupt or else continuous.

[0132] In formula (IIe), R.sup.5 is as already defined, i.e. R.sup.5 is H or a methyl group.

[0133] R.sup.9 is a single bond or a divalent linking group selected from the group consisting of (C.sub.nH.sub.2n)[R.sup.9a group], O(C.sub.nH.sub.2n) [R.sup.9b group] and C(O)O(C.sub.nH.sub.2n) [R.sup.9c group]. In the formulae stated, each n is a natural number from 1 to 6, n and n are each a natural number from 2 to 6. In other words, the linking group comprises straight-chain or branched aliphatic hydrocarbyl groups having 1 to 6 hydrocarbon atoms, which are bonded to the ethylenic group H.sub.2CC(R.sup.5) directly, via an ether group O or via an ester group C(O)O. Preferably, the (C.sub.nH.sub.2n), (C.sub.nH.sub.2n) and (C.sub.nH.sub.2n) groups are linear aliphatic hydrocarbyl groups.

[0134] Preferably, the R.sup.9a group is a group selected from 1'CH.sub.2, CH.sub.2CH.sub.2 and CH.sub.2CH.sub.2CH.sub.2, particular preference being given to a methylene group CH.sub.2.

[0135] Preferably, the R.sup.9b group is a group selected from OCH.sub.2CH.sub.2, OCH.sub.2CH.sub.2CH.sub.2 and OCH.sub.2CH.sub.2CH.sub.2CH.sub.2, more preferably OCH.sub.2CH.sub.2CH.sub.2CH.sub.2.

[0136] Preferably, the R.sup.9c group is a group selected from C(O)OCH.sub.2CH.sub.2, C(O)OCH(CH.sub.3)CH.sub.2, C(O)OCH.sub.2CH(CH.sub.3), C(O)OCH.sub.2CH.sub.2CH.sub.2CH.sub.2 and C(O)OCH.sub.2CH.sub.2CH.sub.2CH.sub.2CH.sub.2CH.sub.2, more preferably C(O)OCH.sub.2CH.sub.2 and C(O)OCH.sub.2CH.sub.2CH.sub.2CH.sub.2 and most preferably C(O)OCH.sub.2CH.sub.2.

[0137] More preferably, the R.sup.9 group is an R.sup.9b group, most preferably OCH.sub.2CH.sub.2CH.sub.2CH.sub.2.

[0138] In the (CH.sub.2CH(R.sup.10)O).sub.x block, the R.sup.10 radicals are each independently H, methyl or ethyl, preferably H or methyl, with the proviso that at least 70 mol % of the R.sup.10 radicals are H. Preferably at least 80 mol % of the R.sup.10 radicals are H, more preferably at least 90 mol %, and they are most preferably exclusively H. The block mentioned is thus a polyoxyethylene block which may optionally have certain proportions of propylene oxide and/or butylene oxide units, preferably a pure polyoxyethylene block.

[0139] The number of alkylene oxide units x is a number from 10 to 50, preferably 12 to 40, more preferably 15 to 35, even more preferably 20 to 30 and is, for example, about 22 to 25. It will be apparent to the person skilled in the art in the field of polyalkylene oxides that the numbers stated are mean values of distributions.

[0140] In the second (CH.sub.2CH(R.sup.11)O).sub.y block, the R.sup.11 radicals are each independently hydrocarbyl radicals of at least 2 carbon atoms, for example 2 to 10 carbon atoms, preferably 2 or 3 carbon atoms. This radical may be an aliphatic and/or aromatic, linear or branched carbon radical. Preference is given to aliphatic radicals.

[0141] Examples of suitable R.sup.11 radicals include ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl or n-decyl, and phenyl. Examples of preferred radicals include ethyl, n-propyl, n-butyl, n-pentyl, and particular preference is given to ethyl and/or n-propyl radicals. The (CH.sub.2CH(R.sup.11)O).sub.y block is thus a block consisting of alkylene oxide units having at least 4 carbon atoms.

[0142] The number of alkylene oxide units y is a number from 5 to 30, preferably 8 to 25.

[0143] In formula (IIe), z is a number from 0 to 5, for example 1 to 4, i.e. the terminal block of ethylene oxide units is thus merely optionally present. In a preferred embodiment of the invention, it is possible to use a mixture of at least two monomers (A2) of the formula (IIe), where the R.sup.5, R.sup.9,

[0144] R.sup.10, R.sup.11, R.sup.12 radicals and indices x and y are each the same, but in one of the monomers z=0 while z>0 in the other, preferably 1 to 4.

[0145] The R.sup.12 radical is H or a preferably aliphatic hydrocarbyl radical having 1 to 30 carbon atoms, preferably 1 to 10 and more preferably 1 to 5 carbon atoms. Preferably, R.sup.12 is H, methyl or ethyl, more preferably H or methyl and most preferably H.

[0146] The hydrophobically associating monomers (A2) of the formulae (IIc), (IId) and (IIe), acrylamide copolymers comprising these monomers and the preparation thereof are known in principle to those skilled in the art, for example from WO 2010/133527 and WO 2012/069478.

[0147] In a further embodiment, the associative monomer (A2) is a cationic monomer of the general formula H.sub.2CC(R.sup.5)C(O)OR.sup.13N.sup.+(R.sup.14)(R.sup.15)(R.sup.16) X.sup. (IIf) or H.sub.2CC(R.sup.5)C(O)N(R.sup.17)R.sup.13N.sup.+(R.sup.14)(R.sup.15)(R.sup.16) X.sup. (IIg).

[0148] In the formulae (IIf) and (IIg), R.sup.5 is as defined above.

[0149] R.sup.13 is an alkylene radical, especially a -alkylene radical having 1 to 8 carbon atoms, preferably 2 to 4 carbon atoms and especially 2 or 3 carbon atoms. Examples include CH.sub.2, CH.sub.2CH.sub.2, CH.sub.2CH.sub.2CH.sub.2 and CH.sub.2CH.sub.2CH.sub.2CH.sub.2. Particular preference is given to CH.sub.2CH.sub.2 and CH.sub.2CH.sub.2CH.sub.2.

[0150] R.sup.13, R.sup.14 and R.sup.15 are each independently H or an alkyl group having 1 to 4 carbon atoms, preferably H or methyl. R.sup.13 is preferably H, and R.sup.14 and R.sup.15 are preferably each methyl. X.sup. is a negatively charged counterion, especially a halide ion selected from F.sup., Cl.sup., Br and I.sup., preferably Cl.sup. and/or Br.

[0151] R.sup.16 is an aliphatic and/or aromatic, linear or branched hydrocarbyl group having 8 to 30 carbon atoms, preferably 12 to 18 carbon atoms. R.sup.16 may especially comprise aliphatic hydrocarbyl radicals having 8 to 18, preferably 12 to 18 carbon atoms. Examples of such groups include n-octyl, n-decyl, n-dodecyl, n-tetradecyl, n-hexadecyl or n-octadecyl groups, preference being given to n-dodecyl, n-tetradecyl, n-hexadecyl or n-octadecyl groups.

[0152] Preference is given to a monomer of the general formula (IIg). Examples of such monomers include N-(meth)acrylamidopropyl-N,N-dimethyl-N-dodecylammonium chloride, N-(meth)acrylamidopropyl-N,N-dimethyl-N-tetradecylammonium chloride, N-(meth)acrylamidopropyl-N,N-dimethyl-N-hexadecylammonium chloride or N-(meth)acrylamidopropyl-N,N-dimethyl-N-octadecylammonium chloride or the corresponding bromides. Monomers of this kind, and acrylamide copolymers having monomers of this kind, are known and described, for example, in U.S. Pat. No. 7,700,702 B2.

[0153] As well as the hydrophilic monomers (A1) and/or associative monomers (A2), acrylamide copolymers may optionally comprise ethylenically unsaturated monomers other than the monomers (A1) and (A2), preferably monoethylenically unsaturated monomers (A3). It is of course also possible to use mixtures of various monomers (A3). Monomers of this kind can be used for fine control of the properties of acrylamide copolymers.

[0154] The monomers (A3) may, for example, be monoethylenically unsaturated monomers which have a more hydrophobic character than the hydrophilic monomers (A1) and which are correspondingly water-soluble only to a small degree. In general, the solubility of the monomers (A3) in water at room temperature is less than 50 g/l, especially less than 30 g/l. Examples of monomers of this kind include N-alkyl- and N,N-dialkyl(meth)acrylamides, where the number of carbon atoms in the alkyl radicals together is at least 3, preferably at least 4. Examples of monomers of this kind include N-butyl(meth)acrylamide, N-cyclohexyl(meth)acrylamide and N-benzyl(meth)acrylamide.

[0155] In addition, monomers (A3) may also be ethylenically unsaturated monomers having more than one ethylenic group. Monomers of this kind can be used in special cases in order to achieve easy crosslinking of the acrylamide polymers. The amount thereof should generally not exceed 2% by weight, preferably 1% by weight and especially 0.5% by weight, based on the sum total of all the monomers. More preferably, the monomers (A3) are exclusively monoethylenically unsaturated monomers.

[0156] One embodiment of the invention involves a homopolymer of methacrylamide or of acrylamide, preferably a homopolymer of acrylamide. The term homopolymer shall also include copolymers of acrylamide and methacrylamide

[0157] (Meth)acrylamide copolymers comprise, as well as (meth)acrylamide, preferably acrylamide, at least one further, monoethylenically unsaturated monomer other than (meth)acrylamide. This is at least one monomer selected from the group of non-(meth)acrylamide hydrophilic monomers (A1), amphiphilic monomers (A2) or further monomers (A3). Preferred (meth)acrylamide copolymers comprise, as well as (meth)acrylamide, at least one further, different hydrophilic monomer (A1). Other preferred (meth)acrylamide copolymers comprise, as well as (meth)acrylamide, at least one further, different hydrophilic monomer (A1) and at least one hydrophilic monomer (A2).

[0158] The amount of all the hydrophilic monomers (A1) together, i.e. including (meth)acrylamide, is at least 70% by weight based on the amount of all the monomers, preferably at least 80% by weight and more preferably at least 90% by weight.

[0159] In (meth)acrylamide copolymers, generally at least 20% by weight, especially at least 30% by weight, preferably at least 50% by weight, more preferably at least 60% by weight and, for example, at least 70% by weight of the monoethylenically unsaturated monomers (A) are (meth)acrylamide, where the stated amount is based on the sum total of all the monomers.

[0160] If present, the amount of amphiphilic monomers (A2) may be up to 15% by weight, based on the total amount of all the monomers in acrylamide copolymers, for example 0.1 to 15% by weight, especially 0.2 to 10% by weight, preferably 0.5 to 5% by weight and, for example, 0.5 to 2% by weight.

[0161] If they are present at all, the amount of optionally present monomers (A3) may be up to 15% by weight, preferably up to 10% by weight, more preferably up to 5% by weight, based in each case on the total amount of all the monomers. An upper limit for ethylenically unsaturated monomers having more than one ethylenic group has already been given. Most preferably, no monomers (A3) are present.

[0162] Apart from the monomers (A1), (A2) and (A3), it is generally the case that no further monomers are present, i.e. the sum total of the monomers (A1), (A2) and (A3) is generally 100%.

[0163] In one embodiment of the invention, the copolymer is a copolymer comprising 85% by weight to 99.9% by weight of hydrophilic monomers (A1) including at least (meth)acrylamide, preferably 90% by weight to 99.8% by weight, more preferably 95% by weight to 99.5, and 0.1% by weight to 15% by weight of amphiphilic monomers (A2), preferably 0.2% by weight to 10% by weight, more preferably 0.5% by weight to 5% by weight, where the sum of all the monomers (A1) and (A2) is 100% by weight.

[0164] In a preferred embodiment, the (meth)acrylamide polymer is a copolymer comprising (meth)acrylamide and at least one anionic, monoethylenically unsaturated, hydrophilic monomer (A1b). More particularly, the monomer (A1b) is a monomer comprising at least one acidic group selected from the group of COOH, SO.sub.3H or PO.sub.3H.sub.2 or salts thereof, preferably COOH and/or SO.sub.3H or salts thereof.

[0165] In a preferred embodiment, the acrylamide polymer is a copolymer comprising (meth)acrylamide and acrylic acid or salts thereof. This may especially be a copolymer comprising 60 to 80% by weight of (meth)acrylamide and 20 to 40% by weight of acrylic acid. Optionally, the copolymer may comprise at least one amphiphilic copolymer (A2) in an amount of up to 15% by weight, preferably 0.2 to 10% by weight. More preferably, this is an amphiphilic monomer of the general formula (IIe) H.sub.2CC(R.sup.5)R.sup.9O(CH.sub.2CH(R.sup.10)O).sub.x(CH.sub.2CH(R.sup.11)O).sub.y(CH.sub.2CH.sub.2O).sub.zR.sup.12. The radicals and indices and the preferred ranges thereof have already been defined above.

[0166] In a further preferred embodiment, the acrylamide polymer is a copolymer comprising (meth)acrylamide and ATBS (2-acrylamido-2-methylpropane-1-sulfonic acid, H.sub.2CCHCONHC(CH.sub.3).sub.2CH.sub.2SO.sub.3H or salts thereof. This may especially be a copolymer comprising 40 to 60% by weight of (meth)acrylamide and 40 to 60% by weight of AMPS. Optionally, the copolymer may comprise at least one amphiphilic comonomer (A2) in an amount of up to 15% by weight, preferably 0.2 to 10% by weight. More preferably, this is an amphiphilic monomer of the general formula (IIe) H.sub.2CC(R.sup.5)R.sup.9O(CH.sub.2CH(R.sub.10)O).sub.x(CH.sub.2CH(R.sup.11)O).sub.y(CH.sub.2CH.sub.2O).sub.zR.sup.12. The radicals and indices and the preferred ranges thereof have already been defined above.

[0167] In a further preferred embodiment, the (meth)acrylamide polymer is a copolymer comprising (meth)acrylamide and at least two anionic, monoethylenically unsaturated, hydrophilic monomers (A1b).

[0168] More particularly, the monomers (A1b) are monomers comprising at least one acidic group selected from the group of COOH, SO.sub.3H or PO.sub.3H.sub.2 or salts thereof, preferably COOH and/or SO.sub.3H or salts thereof. An acrylamide polymer of this kind is preferably a copolymer comprising (meth)acrylamide, 2-acrylamido-2-methylpropanesulfonic acid (AMPS) and acrylic acid. This may especially be a copolymer comprising 40 to 60% by weight of (meth)acrylamide and 20 to 30% by weight of acrylic acid and 20 to 30% by weight of AMPS. Optionally, the copolymer may comprise at least one amphiphilic comonomer (A2) in an amount of up to 15% by weight, preferably 0.2 to 10% by weight. More preferably, this is an amphiphilic monomer of the general formula (IIe) H.sub.2CC(R.sup.5)R.sup.9O(CH.sub.2CH(R.sup.10)O).sub.x(CH.sub.2CH(R.sup.11)O).sub.y(CH.sub.2CH.sub.2O).sub.zR.sup.12. The radicals and indices and the preferred ranges thereof have already been defined.

[0169] In a further preferred embodiment, the (meth)acrylamide polymer is a copolymer comprising (meth)acrylamide and at least one cationic, monoethylenically unsaturated, hydrophilic monomer (A1c). The monomers (A1c) may especially be monomers H.sub.2CC(R.sup.1)CONR.sup.2R.sup.3N(R.sup.4).sub.3+X.sup. (Ia) and/or H.sub.2CC(R.sup.1)COOR.sup.3N(R.sup.4).sub.3.sup.+ X.sup. (Ib). The radicals and indices and the preferred ranges thereof have already been defined above. This may especially be a copolymer comprising 60 to 80% by weight of (meth)acrylamide and 20 to 40% by weight of cationic monomers (A1c). Optionally, the copolymer may comprise at least one amphiphilic comonomer (A2) in an amount of up to 15% by weight, preferably 0.2 to 10% by weight.

[0170] In a further preferred embodiment, the (meth)acrylamide polymer is a copolymer comprising (meth)acrylamide, at least one anionic, monoethylenically unsaturated, hydrophilic monomer (A1b) and at least one amphiphilic monomer (A2) of the general formula H.sub.2CC(R.sup.5)C(O)OR.sup.13N.sup.+(R.sup.14)(R.sup.15)(R.sup.16) X.sup. (IIf) or H.sub.2CC(R.sup.5)C(O)N(R.sup.17)R.sup.13N.sup.+ (R.sup.14)(R.sup.15)(R.sup.16) X.sup. (IIg). It is preferably a monomer of the general formula (IIg). The radicals and indices and the preferred ranges thereof have already been defined above. This may especially be a copolymer comprising 60 to 80% by weight of (meth)acrylamide and 10 to 40% by weight of anionic monomers (A1b) and 0.1 to 10% by weight of said monomer (A2) of the formula (IIf) and/or (IIg), preferably (IIg).

Use of the Aqueous Poly Acrylamide Solutions

[0171] The aqueous polyacrylamide solutions manufactured according to the present invention may be used for various purposes, for example for mining applications, oilfield applications, including but not limited to the application in enhanced oil recovery, oil well drilling or as friction reducer, or waste water cleanup, water treatment, paper making or agricultural applications. The composition of the polyacrylamide solutions is selected by the skilled artisan according to the intended use of the polyacrylamide solution.

Enhanced Oil Recovery

[0172] In one embodiment of the invention, the method for manufacturing aqueous polyacrylamide solutions according to the present invention is carried out on an oilfield and the polyacrylamide solution thus manufactured is used for enhanced oil recovery.

[0173] Accordingly, the present invention also relates the use of aqueous polyacrylamide solutions for producing mineral oil from underground mineral oil deposits by injecting an aqueous fluid comprising at least an aqueous poly acrylamide solution into a mineral oil deposit through at least one injection well and withdrawing crude oil from the deposit through at least one production well, wherein the aqueous polyacrylamide solution is prepared on the oilfield using a process comprising the following steps, particularly in the given order: [0174] hydrating acrylonitrile in water in presence of a biocatalyst capable of converting acrylonitrile to acrylamide so as to obtain an acrylamide solution, [0175] directly polymerizing the acrylamide solution so as to obtain a polyacrylamide gel, and [0176] directly dissolving the polyacrylamide gel by addition of water so as to obtain an aqueous polyacrylamide solution.

[0177] For the inventive use, at least one production well and at least one injection well are sunk into the mineral oil deposit. In general, a deposit will be provided with a plurality of injection wells and with a plurality of production wells. An aqueous fluid is injected into the mineral oil deposit through the at least one injection well, and mineral oil is withdrawn from the deposit through at least one production well. By virtue of the pressure generated by the aqueous fluid injected, called the polymer flood, the mineral oil flows in the direction of the production well and is produced through the production well. In this context, the term mineral oil does not of course just mean a single-phase oil; instead, the term also encompasses the customary crude oil-water emulsions.

[0178] The aqueous fluid for injection comprises the aqueous poly acrylamide solution prepared according to the process according to the present invention. Details of the process have been disclosed above. The aqueous acryl amide solution obtained may be used as such or it may be mixed with further components. Further components for enhanced oil recovery fluids may be selected by the skilled artisan according to his/her needs.

[0179] For enhanced oil recovery, a homopolymer of acryl amide may be used, however preferably copolymers of acryl amide and one or more additional monoethylenically unsaturated, hydrophilic monomers are used.

[0180] In one embodiment, the acryl amide copolymers comprise at least one hydrophilic, anionic monomer (A1b) comprising at least one acidic group, or salts thereof. Examples of such monomers (A1b) have been disclosed above.

[0181] Preferably, monomer (A1b) may be selected from the group consisting of acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, vinylsulfonic acid, allylsulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid (AMPS), 2-methacrylamido-2-methylpropane-sulfonic acid, 2-acrylamidobutanesulfonic acid, 3-acrylamido-3-methylbutane-sulfonic acid, 2-acrylamido-2,4,4-trimethylpentanesulfonic acid, vinylphosphonic acid, allylphosphonic acid, N-(meth)acrylamidoalkylphosphonic acids and (meth)acryloyloxyalkyl-phosphonic acids, more preferably from acrylic acid and/or APMS or salts thereof.

[0182] In such copolymers comprising acryl amide and monomers (A1b), preferably acrylic acid and/or APMS or salts thereof, the amount of acryl amide usually is from 40% by wt. to 90% by wt. and the amount of monomers (A1b) is from 10% by wt. to 60% by wt., relating to the amount of all monomers in the copolymer. Preferably, the amount of acryl amide is from 60% by wt. to 80% by wt. and the amount of monomers (A1b) is from 20% by wt. to 40% by wt.,

[0183] In another embodiment, the acryl amide copolymers comprise at least one hydrophilic, anionic monomer (A1b) comprising at least one acidic group, or salts thereof, preferably acrylic acid and/or APMS or salts thereof, and at least one amphiphilic monomer (A2). Examples of amphiphilic monomers (A2) have been disclosed above.

[0184] Preferably, the monomers (A2) are monomers of the general formula H.sub.2CC(R.sup.5)R.sup.9O(CH.sub.2CH(R.sup.10)O).sub.x(CH.sub.2CH(R.sup.11)O).sub.y(CH.sub.2CH.sub.2).sub.zR.sup.12 (IIe). The definitions of R.sup.5, R.sup.9, R.sup.10, R.sup.11, R.sup.12 and x, y, z in (IIe) have been disclosed above and we refer to said definitions, including the preferred embodiments.

[0185] The amount of amphiphilic monomers (A2), in particular those of formula (IIe) may be up to 15% by weight, based on the total amount of all the monomers in acrylamide copolymers, for example 0.1 to 15% by weight, especially 0.2 to 10% by weight, preferably 0.5 to 5% by weight and, for example, 0.5 to 2% by weight.

[0186] In such copolymers comprising acryl amide, monomers (A1b), preferably acrylic acid and/or APMS or salts thereof, and monomers (A2), preferably of formula (IIe), usually the amount of acryl amide is from 40% by wt. to 89.9% by wt., the amount of monomers (A1b) is from 10% by wt. to 59.9% by wt., and the amount of amphiphilic monomers (A2) is from 0.1 to 15% by wt. relating to the amount of all monomers in the copolymer. Preferably, the amount of acryl amide is from 40% by wt. to 59.5% by wt., the amount of monomers (A1b) is from 40% by wt. to 59.5% by wt., and the amount of amphiphilic monomers (A2) is from 0.5 to 2% by wt.

[0187] The aqueous fluid for injection can be made up in freshwater or else in water comprising salts, such as seawater or formation water. Water comprising salts may already be used for dissolving the polyacrylamide gel. Alternatively, the polyacrylamide gel may be dissolved in fresh water, and the solution obtained can be diluted to the desired use concentration with water comprising salts.

[0188] The aqueous injection fluid may of course optionally comprise further components. Examples of further components include biocides, stabilizers, free-radical scavengers, initiators, surfactants, cosolvents, bases and complexing agents.

[0189] The concentration of the copolymer in the injection fluid is fixed such that the aqueous formulation has the desired viscosity for the end use. The viscosity of the formulation should generally be at least 5 mPas (measured at 25 C. and a shear rate of 7 s.sup.1), preferably at least 10 mPas.

[0190] In general, the concentration of the polyacrylamide in the injection fluid is 0.02 to 2% by weight based on the sum total of all the components in the aqueous formulation. The amount is preferably 0.05 to 0.5% by weight, more preferably 0.1 to 0.3% by weight and, for example, 0.1 to 0.2% by weight.

Mining Applications

[0191] In one embodiment, the method for preparing an aqueous polyacrylamide solution according to the present invention is carried out in areas where mining, mineral processing and/or metallurgy activities takes place. Consequently, the aqueous polyacrylamide solution as product obtained by the method of the present invention is preferably used for applications in the field of mining, mineral processing and/or metallurgy and the method for preparing the aqueous polyacrylamide solution is preferably used at the plant of the respective industry.

[0192] Preferably, mining activities comprises extraction of valuable minerals or other geological materials from certain deposits. Such deposits can contain ores, for example metal containing ores, sulfidic ores and/or non-sulfidic ores. The ores may comprise metals, coal, gemstones, limestone or other mineral material. Mining is generally required to obtain any material in particular mineral material that cannot be grown through agricultural processes, or created artificially in a laboratory or factory. The aqueous polyacrylamide solution according to the present invention is preferably used to facilitate the recovery of mineral material, for beneficiation of ores and for further processing of ores to obtain the desired minerals or metals.

[0193] Typically, mining industries, mineral processing industries and/or metallurgy industries are active in the processing of ores and in the production of for example alumina, coal, iron, steel, base metals, precious metals, diamonds, non-metallic minerals and/or areas where aggregates play an important role. In such industries, the method of the present invention and the obtained homo- or copolymer of acrylamide can be used for example [0194] at plants for alumina production, where alumina is extracted from the mineral bauxite using the Bayer caustic leach process, [0195] at plants where the coal washing process demands a closed water circuit and efficient tailings disposal to satisfy both economic and environmental demands, [0196] at plants for iron and steel production, where the agglomeration of fine iron concentrates to produce pellets of high quality is a major challenge for the iron ore industry, [0197] at plants for base metal production, where flocculants find several uses in base metal production, [0198] at plants for precious metals production, where reagents are used to enhance the tailings clarification process allowing the reuse of clean water, [0199] at diamond plants, where efficient water recovery is paramount in the arid areas where diamonds are often found, [0200] at plants for non-metallic mineral production where reagents enhance water recovery or aid the filtration processes to maximize process efficiency, [0201] at plants where aggregates have to be produced and flocculants and filter aids are needed to enhance solid/liquid separation.

[0202] Accordingly, the present invention relates to the use of an aqueous polyacrylamide solution for mining, mineral processing and/or metallurgy activities comprising the use for solid liquid separation, for tailings disposal, for polymer modified tailings deposition, for tailings management, as density and/or rheology modifier, as agglomeration aid, as binder and/or for material handling, wherein the aqueous polyacrylamide solution is prepared at the plant of the respective industry, comprising the following steps in the given order: [0203] hydrating acrylonitrile in water in presence of a biocatalyst capable of converting acrylonitrile to acrylamide so as to obtain an acrylamide solution, [0204] directly polymerizing the acrylamide solution so as to obtain a polyacrylamide gel, and [0205] directly dissolving the polyacrylamide gel by addition of water so as to obtain an aqueous polyacrylamide solution.

[0206] For the mining, mineral processing and/or metallurgy activities a homopolymer of acrylamide for example can be used. Further preferred are also copolymers of acrylamide. Such copolymers of acrylamide can be anionic, cationic or non-ionic. Anionic copolymers are for example copolymers of acrylamide with increasing proportions of acrylate groups, which give the polymers negative charges, and thus anionic active character, in aqueous solution. Anionic copolymers of acrylamide can in particular be used for waste water treatment in metallurgy like iron ore plants, steel plants, plants for electroplating, for coal washing or as flocculants. Non-ionic polymers and/or copolymers of acrylamide can be used for example as nonionic flocculants suitable as settlement aids in many different mineral processing applications and are particularly effective under very low pH conditions, as encountered for example in acidic leach operations. Cationic copolymers of acrylamide have in particular an increasing proportion of cationic monomers. The cationic groups, which are thus introduced into the polymer, have positive charges in aqueous solution.

[0207] It is preferred, that the polymer obtained from the method of the present invention is used as flocculant in a process in which individual particles of a suspension form aggregates. The polymeric materials of the present invention forms for example bridges between individual particles in the way that segments of the polymer chain adsorb on different particles and help particles to aggregate. Consequently, the polymers of the present invention act as agglomeration aid, which may be a flocculant that carries active groups with a charge and which may counterbalance the charge of the individual particles of a suspension. The polymeric flocculant may also adsorb on particles and may cause destabilization either by bridging or by charge neutralization. In case the polymer is an anionic flocculant, it may react against a positively charged suspension (positive zeta potential) in presence of salts and metallic hydroxides as suspension particles, for example. In case the polymer of the present invention is for example a cationic flocculant, it may react against a negatively charged suspension (negative zeta potential) like in presence of for example silica or organic substances as suspension particles. For example, the polymer obtained from the method of the present invention may be an anionic flocculant that agglomerates clays which are electronegative.

[0208] Preferably, the method of the present invention and the obtained polymer and/or copolymer of acrylamide (polyacrylamide) is used for example in the Bayer process for alumina production. In particular, the polyacrylamide can be used as flocculant in the first step of the Bayer-Process, where the aluminum ore (bauxite) is washed with NaOH and soluble sodium aluminate as well as red mud is obtained. Advantageously, the flocculation of red mud is enhanced and a faster settling rate is achieved when acrylamide polymers and/or co-polymers are added. As red mud setting flocculants, polyacrylamide may be used for settling aluminum red mud slurries in alumina plants, provides high settling rates, offers better separation performance and reduces suspended solids significantly. Also the liquor filtration operations are improved and with that the processing is made economically more efficient. It is further preferred that the polyacrylamides are used in decanters, in washers, for hydrate thickening, for green liquor filtration, as crystal growth modifiers, as thickener and/or as rheology modifier.

[0209] It is further preferred that the method of the present invention and the polymers of acrylamide are used in processes for solid liquid separation as for example flocculant or dewatering aid, which facilitate thickening, clarifying, filtration and centrifugation in order to enhance settling rates, to improve clarities and to reduce underflow volumes. In particular, in filtration processes the polyacrylamide homo- or co-polymer of the present invention increase filtration rates and yields, as well as reducing cake moisture contents.

[0210] Further preferred is the use of the method and the obtained polyacrylamide of the present invention in particular for material handling and as binder. In the mining industry, the movement of large volumes of material is required for processing the rock and/or ores which have been extracted from the deposits. The typical rock and/or ore processing for example starts with ore extraction, followed by crushing and grinding the ore, subsequent mineral processing (processing or the desired/valuable mineral material), then for example metal production and finally the disposal of waste material or tailings. It was a surprise that with the method of the present invention and in particular the obtained polyacrylamide the handling of the mineral material can be enhanced by increasing efficiency and yield, by improving product quality and by minimizing operating costs. Particularly, the present invention can be used for a safer working environment at the mine site and for reduction of environmental discharges.

[0211] Preferably, the method and the obtained polyacrylamide of the present invention can for example be used as thickener, as density and/or rheology modifier, for tailings management. The obtained polyacrylamide polymer can modify the behavior of the tailings for example by rheological adjustment. The obtained polyacrylamide polymers are able to rigidify tailings at the point of disposal by initiating instantaneous water release from the treated slurry. This accelerates the drying time of the tailings, results in a smaller tailings footprint and allows the released water to be returned to the process faster. This treatment is effective in improving tailings properties in industries producing alumina, nickel, gold, iron ore, mineral sands, oil sands or copper for example. Further benefits of the polymers obtained according to the present invention are for example maximized life of disposal area, slurry placement control, no re-working of deposit required, co-disposal of coarse and fine material, faster trafficable surface, reduced evaporative losses, increased volume for recycling, removed fines contamination, reduced fresh water requirement, lower land management cost, less mobile equipment, lower rehabilitation costs, quicker rehabilitation time, lower energy consumption, accelerated and increased overall water release, improved rate of consolidation, reduced rate of rise, reduced amount of post depositional settlement.

[0212] Preferably, the obtained product from the method of the present invention is used for agglomeration of fine particulate matter and for the suppression of dust. Particularly, polyacrylamide polymers or copolymers are used as organic binders to agglomerate a wide variety of mineral substrates. For example, the polyacrylamide polymers or copolymers are used for iron ore pelletization as a full or partial replacement for bentonite. The product from the method of the present invention can be used as binder, in particular as solid and liquid organic binders in briquetting, extrusion, pelletization, spheronization and/or granulation applications and gives for example excellent lubrication, molding and/or binding properties for processes such as coal-fines briquetting, carbon extrusion, graphite extrusion and/or nickel briquetting.

[0213] It is preferred that the method of the present invention and in particular the aqueous polyacrylamide solution obtained by the method is used for the beneficiation of ores which comprise for example coal, copper, alumina, gold, silver, lead, zinc, phosphate, potassium, nickel, iron, manganese, or other minerals.

[0214] The method according to the present invention will be described in further detail based on the following example.

EXAMPLE 1

[0215] The method is carried out on site. Particularly, the method is carried out in at least one mobile reactor. For example, the installation 10 is provided on a vehicle. The first reactor 12 is supplied with 1,554.18 g acrylonitrile, 2,609.24 g water and 1.67 g biocatalyst capable of converting acrylonitrile to acrylamide. The biocatalyst is rhodococcus rhodochrous. The biocatalyst is provided as a powder. Within the first reactor 12, the acrylonitrile is hydrated in water in presence of the biocatalyst so as to obtain an acrylamide solution. The hydrating is carried out at ambient temperature, i.e. 25 C., and atmospheric pressure. The hydrating takes 7 h. Thereby, the acrylamide solution comprises a concentration of 50% by weight acrylamide monomers. The thus obtained acrylamide solution is directly and immediately after its preparation supplied to the second reactor 14, wherein the biocatalyst is removed, e.g. by means of the filter within the pipe 18.

[0216] The acrylamide solution is cooled to a temperature of 4 C. before entering the second reactor 14. For this purpose, a heat exchanger is present within the pipe 18. The second reactor 14 is not only supplied with the acrylamide solution but also with 2,622.9 g of sodium acrylate solution (35% in water), 2,966 g of water, 50 g of a suspension of azobisisobutyronitrile (AlBN) in water (4% active content) and 75 g of a solution 4,4-Azobis(4-cyanovaleric acid) (ACVA) in 1N NaOH solution (4% active content of ACVA) and a redox initiator system comprising tBHP and sodium sulfite, which is added to the acrylamide solution for initiating a polymerization process. The redox initiator is added with a concentration of 1% by weight in water and a final concentration of the redox initiators is set to 2.4 ppm for sodium sulfite and 4.8 ppm for tBHP (on the whole reaction mixture). Thus, the acrylamide solution is directly polymerized so as to obtain a polyacrylamide gel. The polymerization is carried out at atmospheric pressure. The polyacrylamide gel comprises 30% polyacrylamide solids (by means of a copolymer comprising approx. 75 mol % of acrylamide). The polymerization takes 7 h.

[0217] Thus, approx. 10 kg polyacrylamide gel is obtained. The thus obtained polyacrylamide gel is directly and immediately after its preparation supplied to the static mixer 16. The static mixers 16 are from Fluitec mixing+reaction solutions AG, Seuzachstrasse 40, 8413 Neftenbach, Switzerland. Particularly, a first sub tube having an inner diameter of 36 mm, a length of 1,000 mm and equipped with a static mixer of the type CSE-W was used. A second sub tube having an inner diameter of 36 mm, a length 270 mm and equipped with a static mixer of the type CSE-W was used. Further, a third sub tube having an inner diameter 36 mm, a length of 1,000 mm and equipped with a static mixer of the type CSE-X was used. The sub tubes were connected in series to form a U-Shape, wherein the first sub tube and the third sub tube are parallel to each other and are perpendicular to the second sub tube. The polyacrylamide gel is supplied with kg/h. Water is added to the polyacrylamide gel with 25 kg/h for dissolving the same by means of the static mixer 16 so as to obtain an aqueous polyacrylamide solution. The polyacrylamide gel is dissolved with a resting time within the mixers 16 of 0.05 s to 10 s and preferably 0.1 s to 2 s. The resulting suspension of gel particles with a size of 1-2 mm was subsequently diluted with 272 kg water to obtain an active content of 1% by weight of polyacrylamide. This suspension turned into a discrete solution within 1 h under slow stirring. The intrinsic viscosity of the solution was 24 dl/g.

[0218] Thereby, the aqueous polyacrylamide solution is prepared so as to be suitable in oil recovery and /or mining. According to the times described before, the complete method is carried out in a time of 15 h. The method is monitored on line by means of a plurality of sensors provided within the pipes 18, 20 and the reactors 12, 14.