WO2020216433A1

WO2020216433A1 - A process and apparatus for producing aqueous compositions of water-soluble polymers

Info

Publication number: WO2020216433A1
Application number: PCT/EP2019/060349
Authority: WO
Inventors: Daniel Barrera-Medrano; Dennis Loesch; Faissal-Ali El-Toufaili; Anna-Corina SCHMIDT; Tobias Joachim Zimmermann; Jack Tinsley; Brent Busby; Markus OSTERMAYR
Original assignee: Basf Se
Priority date: 2019-04-23
Filing date: 2019-04-23
Publication date: 2020-10-29

Abstract

Process for producing aqueous compositions of water-soluble polymers from aqueous polymer gels by comminuting and mixing the aqueous polymer gels with an aqueous liquid using a comminution unit comprising a hollow cylinder comprising perforations, a flow chamber enclosing circumferentially the lateral area of the hollow cylinder comprising perforations and cutting means arranged within the flow chamber which rotate around the outside of the lateral area of the hollow cylinder comprising perforations, wherein the aqueous polymer gel is introduced into the hollow cylinder, a continuous stream of an aqueous liquid is introduced into the flow chamber through an inlet, the polymer gel is pressed through the perforations, cut by the rotating cutting means and dispersed in water thereby obtaining an aqueous liquid comprising dissolved aqueous polymer and undissolved aqueous polymer gel pieces which is homogenized in a further step thereby obtaining a aqueous compositions of water- soluble polymers. Apparatus for carrying out the process.

Description

A process and apparatus for producing aqueous compositions of water-soluble polymers

The invention relates to a process for producing aqueous compositions of water- soluble polymers from aqueous polymer gels by comminuting and mixing the aqueous polymer gels with an aqueous liquid using a comminution unit comprising a hollow cylinder comprising perforations, a flow chamber enclosing circumferentially the lateral area of the hollow cylinder comprising perforations and cutting means arranged within the flow chamber which rotate around the outside of the lateral area of the hollow cylinder comprising perforations, wherein the aqueous polymer gel is introduced into the hollow cylinder, a continuous stream of an aqueous liquid is introduced into the flow chamber through an inlet, the polymer gel is pressed through the perforations, cut by the rotating cutting means and dispersed in water thereby obtaining an aqueous liquid comprising dissolved aqueous polymer and undissolved aqueous polymer gel pieces which is homogenized in a further step thereby obtaining a aqueous compositions of water-soluble polymers. The invention furthermore relates to a suitable apparatus for carrying out the process.

Water-soluble, high molecular weight homo- and copolymers of water-soluble, monoethylenically unsaturated monomers such as for example acrylamide, acrylic acid, or ATBS are known in the art and may be used for various applications.

A common polymerization technology for manufacturing such high molecular weight polymers is the so called“gel polymerization”. In gel polymerization, an aqueous monomer solution having a relatively high concentration of monomers, for example from 20 % by weight to 35 % by weight is polymerized by means of suitable

polymerization initiators under essentially adiabatic conditions in an unstirred reactor thereby forming a polymer gel.

Such polymer gels formed often are converted to polymer powders by comminuting the gel into smaller pieces by one or more size reduction steps, drying such gel pieces for example in a fluid bed dryer followed by sieving, grinding and packaging. The obtained polymer powders, for example polyacrylamide powders are packaged and shipped to customers for use, for example in mining and oilfield applications, water treatment, sewage treatment, papermaking, and agriculture.

The polymer gel obtained from gel polymerization typically comprises from 65 wt. % to 80 wt. % of water. The residual amount of water in polyacrylamide powders typically is from about 4 to 12 wt. %. So,“drying” such polyacrylamide gels does not mean to remove only some residual moisture but rather about 0.55 kg to 0.75 kg of water need to be removed per kg of polymer gel, or -with other words- per kg of polymer powder produced also 1.5 to 2.5 kg of water are“produced”. It goes without saying that removing such a high amount of water from the polymer gel in course of drying is energy extensive and consequently the operational costs for drying are high. Furthermore, high-performance dryers are necessary as well as equipment for size reduction, sieving and grinding. Consequently, the capital expenditure for the entire post-processing equipment including size reduction, drying, sieving, grinding is significant in relation to the total capital expenditure for the entire plant.

It has therefore been suggested not to dry aqueous polymer gels after manufacture but directly dissolving said aqueous polymer gels in water thereby obtaining diluted aqueous solutions of water-soluble polymers such as polyacrylamides without drying and re-dissolving the dry powder. Advantageously, dissolving aqueous polymer gels in water may be performed on-site, i.e. at the side at which the solutions of water-soluble polymers are used.

Several technologies have been suggested for dissolving aqueous polymer gels in water.

DE 21 08 703 discloses a method of dissolving polymer gels by rubbing the gel against a rough surface in the presence of water.

GB 1 441 340 discloses a method of dissolving polymer gels by extruding the aqueous polymer gel through an orifice in an orifice sheet having an inside surface and an outside surface, periodically cutting the gel at the inside of the orifice sheet and continuing extruding, impinging solvent for the gel on the exiting segmented gel strand exiting from the outside of the orifice sheet, mixing the gel particles and solvent to dissolve the gel particles in the solvent.

US 3,255,142 discloses a method of dissolving polymer gels by extruding said polymer gels into a transversely flowing stream of liquid solvent.

US 4,1 13,688 discloses a method of dissolving polymer gels which comprises two size reduction steps. The method comprises extruding said polymer gels into flowing water through die perforations in an extrusion die sheet, said perforations having a diameter of ~ 0.15 mm to ~ 12.7 mm, forming polymer gel strands, and cutting such polymer gel strands to a length of less than ~ 19.05 mm, thereby obtaining a slurry of the cut gel particles in the flowing water. In the second size reduction step, the slurry of gel particles is subjected to high shear forces immediately after formation of such slurry, i.e. before any substantial dissolution of the polymer gel occurs, thereby reducing the average maximum dimension of the gel particles to less than 0.76 mm. In a final step, the resultant slurry of fine gel particles and additional water are mixed under low shear conditions thereby forming a dilute aqueous solution of the polymer. US 4,845,192 discloses a method of rapidly dissolving particles of gels of water-soluble polymers comprising forming a suspension of such gel particles in water and subjecting said suspension to instantaneous and momentary conditions of high shearing effective to finely slice said particles.

US 4,605,689 discloses a method for on-site production of aqueous polyacrylamide solutions for enhanced oil recovery. In a first step an aqueous polyacrylamide gel is provided by polymerizing acrylamide and preferably acrylic acid as comonomer. The aqueous polyacrylamide gel obtained is conveyed together with a minor amount of aqueous solvent through at least one static cutting device thereby obtaining a slurry of small gel particles in water, the gel particles are dissolved in the aqueous solvent which forms a homogeneous solution concentrate which is then readily diluted with aqueous solvent thereby obtaining a diluted aqueous polyacrylamide solution.

WO 2017/186567 A1 relates to a process for producing an aqueous polymer solution comprising the steps of providing an aqueous polymer gel comprising at least 10 % by weight of active polymer, cutting the aqueous polyacrylamide gel by means of a water- jet at a pressure of at least 150 bar to reduce the size of the aqueous polymer gel, and dissolving the aqueous polymer gel in an aqueous liquid.

WO 2017/186697 A1 relates to a method of preparing an aqueous polyacrylamide solution, comprising hydrolyzing acrylonitrile in water in presence of a biocatalyst thereby obtaining an acrylamide solution, directly polymerizing the acrylamide solution thereby obtaining a polyacrylamide gel, and directly dissolving the polyacrylamide gel by addition of water, preferably by means of a static mixer, thereby obtaining an aqueous polyacrylamide solution. The method may be carried out on-site.

WO 2017/186685 A1 relates to a method of preparing an aqueous polyacrylamide solution, comprising hydrolyzing acrylonitrile in water in presence of a biocatalyst thereby obtaining an acrylamide solution, directly polymerizing the acrylamide solution thereby obtaining a polyacrylamide gel, and directly dissolving the polyacrylamide gel by addition of water by means of a mixer comprising a rotatable impeller thereby obtaining an aqueous polyacrylamide solution. Such a mixer is also known in the art as Urschel-mixer and applies high shearing forces. The method may be carried out on site.

WO 2017/186698 A1 relates to a method of preparing an aqueous polyacrylamide solution, comprising hydrolyzing acrylonitrile in water in presence of a biocatalyst thereby obtaining an acrylamide solution, directly polymerizing the acrylamide solution thereby obtaining a polyacrylamide gel, and directly dissolving the polyacrylamide gel by addition of water by means of water jet cutting, thereby obtaining an aqueous polyacrylamide solution. The method may be carried out on-site. Our older applications PCT/EP2018/078489, PCT/EP2018/07851 1 ,

PCT/EP2018/078498, PCT/EP2018/078493, PCT/EP2018/078502,

PCT/EP2018/078492, PCT/EP2018/078485 disclose the manufacture of aqueous polyacrylamide solutions on-site in modular plants by adiabatic gel polymerization of aqueous solutions comprising acrylamide and optionally further monoethylenically unsaturated comonomers followed by comminuting and dissolving the aqueous gel obtained in water thereby yielding an aqueous polyacrylamide solution. The

applications suggest several comminution technologies. Examples of suitable means for comminuting aqueous polyacrylamide gels include cutting devices such as knives or perforated plates, crushers, kneaders, static mixers or water-jets or combinations thereof.

Our older application PCT/EP2018/078499 discloses a method of preparing an aqueous polyacrylamide solution comprising conveying an aqueous polymer gel through a comminution unit comprising at least a perforated sheet and moveable cutting means and adding at least a portion of the aqueous liquid into the comminution unit, wherein the relative velocity between the cutting means and the aqueous polymer gel does not exceed 3 m/s, thereby obtaining an aqueous mixture comprising an aqueous liquid comprising dissolved aqueous polymer and undissolved pieces of aqueous polymer gel, adding the remainder of the aqueous liquid to the mixture and dissolving the aqueous polymer gel pieces in the aqueous liquid. The document furthermore discloses a suitable apparatus for carrying out the process.

Our older application PCT/EP2018/078488 discloses a method of making aqueous polyacrylamide concentrates having a concentration of 1 to 14.9 % by wt, preferably 3.1 % by wt. to 7 % by wt. of polyacrylamides by adiabatic gel polymerization of aqueous solutions comprising acrylamide and optionally further monoethylenically unsaturated comonomers followed by comminuting and mixing the aqueous gel with water thereby yielding the abovementioned aqueous polyacrylamide concentrate. The concentrate may thereafter be transported to another location for use. The application suggests several technologies for comminution and mixing with water. Examples comprise static cutting devices, perforated plates, optionally in combination with a rotating knife, static mixers, water-jet cutters or combinations thereof such as a combination of water-jet cutting with static cutting members or with static mixers.

The application of high shearing forces in course of dissolving high molecular weight polyacrylamides may cause polymer degradation. There is still a need for improved processes and apparatuses for comminuting aqueous polymer gels gently. It was an object of the present invention to provide such a process and such an apparatus.

Accordingly, in one embodiment of the present invention, a process for providing aqueous polymer compositions has been found, which comprises at least the steps of [1 ] providing an aqueous polymer gel comprising 15 % to 45 % by weight of a water-soluble polymer obtainable by polymerization of an aqueous solution comprising water-soluble, monoethylenically unsaturated monomers,

[2] comminuting and mixing the aqueous polymer gel with an aqueous liquid, wherein step [2] comprises conveying the aqueous polymer gel through a comminution unit, comprising at least

• a hollow cylinder comprising two base areas and a lateral area, wherein one of the base areas comprises an opening for aqueous polymer gel, the opposite base area is closed and at least a part of the lateral area of the cylinder comprises perforations,

• a flow chamber enclosing circumferentially the lateral area of the hollow cylinder comprising perforations and the closed based area of the hollow cylinder, wherein the chamber comprises an inlet and an outlet for an aqueous liquid,

• cutting means arranged within the flow chamber which rotate around the outside of the lateral area of the hollow cylinder comprising perforations, wherein the rotating cutting means comprise at least a rotating support and at least one knife fixed to the rotating support,

• a drive for rotating the cutting means,

• means for pressing aqueous polymer gel through the opening into the hollow cylinder,

wherein

> the aqueous polymer gel is introduced into the hollow cylinder at a

pressure sufficient to pass from the inside of the hollow cylinder through the perforations to the outside of the lateral area of the hollow cylinder, thereby forming polymer gel strands,

> a continuous stream of an aqueous liquid is introduced into the flow

chamber through the inlet,

> the polymer gel strands are cut by the rotating cutting means into gel pieces and the pieces are dispersed in the aqueous, thereby obtaining an aqueous mixture comprising an aqueous liquid comprising dissolved aqueous polymer and undissolved aqueous polymer gel pieces, and

> a continuous stream of an aqueous mixture comprising an aqueous liquid comprising dissolved aqueous polymer and undissolved aqueous polymer gel pieces is removed from the flow chamber through the outlet, and

[3] homogenizing the aqueous mixture obtained in course of step [2], thereby obtaining an aqueous polymer composition comprising at least an aqueous liquid and water-soluble polymer, wherein the concentration of the polymer is less than 15 % by weight, relating to the total of all components of the aqueous polymer composition.

The invention furthermore relates to an apparatus for comminuting aqueous polymer gels, comprising at least

• a flow chamber enclosing circumferentially the lateral area of the hollow

cylinder comprising perforations and the closed based area of the hollow cylinder, wherein the chamber comprises an inlet and an outlet for aqueous liquid,

• a drive for rotating the cutting means,

• means for pressing aqueous polymer gel through the opening into the hollow cylinder.

List of figures:

List of figures (cont):

With regard to the invention, the following can be stated specifically:

By means of the process according to the present invention, it is possible to prepare aqueous compositions of water-soluble polymers, wherein the concentration of the polymer is less than 15 % by weight, relating to the total of all components of the aqueous polymer composition, using as starting material an aqueous polymer gel comprising 15 to 45 % by weight of water-soluble polymers, wherein the aqueous polymer gel is obtainable by polymerization of an aqueous solution comprising water- soluble, monoethylenically unsaturated monomers.

Such an aqueous polymer gel may be regarded as a polymer-water system in which there is a three-dimensional network structure composed of macromolecules or their associates and which is capable of retaining significant amounts of water. Such a system keeps its shape under the action of its own weight and differs in this feature from a polymer solution. Suitable definition of a polymer gel is given in the article by LZ Rogovina et al, Polymer Science, Ser. C, 2008, Vol. 50, No. 1 , pp. 85-92.

The aqueous polymer gel comprises 15 % by weight to 45 % by weight of a water- soluble polymer, wherein the percentages relate to the total of all components of the aqueous polymer gel. Suitably the contents of water-soluble polymer in the aqueous polymer gel may be from 20 % to 45 % by weight, desirably from 20 % to 40 % by weight, preferably from 20 to 35 % by weight and for example from 20 to 25 % by weight.

Aqueous polymer gel

The aqueous polymer gel to be used as starting material is obtainable by

polymerization of an aqueous solution comprising water-soluble, monoethylenically unsaturated monomers. Preferably, polymerization is conducted by radical polymerization. The term“water-soluble monomers” in the context of this invention means that the monomers are to be soluble in the aqueous monomer solution to be used for polymerization in the desired use concentration. It is thus not absolutely necessary that the monomers to be used are miscible with water without any gap; instead, it is sufficient if they meet the minimum requirement mentioned. It is to be noted that the presence of one monoethylenically unsaturated monomer in the monomer solution, for example acrylamide or acrylic acid, might enhance the solubility of other monomers as compared to water only. In general, the solubility of the water-soluble monomers in water at room temperature should be at least 50 g/l, preferably at least 100 g/l.

In a preferred embodiment of the invention the aqueous polymer gels are aqueous polyacrylamide gels. The term“polyacrylamide” as used herein means water-soluble polymers comprising at least 10 %, preferably at least 20 %, and more preferably at least 30 % by weight of acrylamide, wherein the amounts relate to the total amount of all monomers relating to the polymer. Polyacrylamides include homopolymers and copolymers of acrylamide and other monoethylenically unsaturated comonomers. Polyacrylamide copolymers are preferred.

Basically, the kind and amount of water-soluble, monoethylenically unsaturated comonomers to be used is not limited and depends on the desired properties and the desired use of the aqueous solutions of polymers to be manufactured.

Neutral monomers

Examples of suitable monomers comprise uncharged water-soluble, monoethylenically unsaturated monomers. Examples comprise acrylamide, methacrylamide, N- methyl(meth)acrylamide, N,N’-dimethyl(meth)acrylamide, N-methylol(meth)acrylamide or N-vinylpyrrolidone. Further examples have been mentioned in WO 2015/158517 A1 page 7, lines 9 to 14. In one embodiment of the invention, at least one of the water- soluble, monoethylenically unsaturated monomers in the aqueous monomer solution is acrylamide.

Anionic monomers

Further examples of suitable monomers comprise water-soluble, monoethylenically unsaturated monomers comprising at least one acid group, or salts thereof. The acidic groups are preferably selected from the group of -COOH, -SO3H and -PO3H2 or salts thereof. Preference is given to monomers comprising COOH groups and/or -SO3H groups or salts thereof. Suitable counterions include especially alkali metal ions such as Li⁺, Na⁺ or K⁺, and also ammonium ions such as NH₄ ⁺ or ammonium ions having organic radicals. Examples of ammonium ions having organic radicals include

[NH(CH₃)₃]⁺, [NH₂(CH₃)₂]⁺, [NH₃(CH₃)]⁺, [NH(C₂H₅ )₃]⁺, [NH₂(C₂H₅ )₂]⁺, [NH₃(C₂H₅ )]⁺, [NH₃(CH₂CH₂OH)]⁺, [H₃N-CH₂CH₂-NH₃]²⁺ or [H(H₃C)₂N-CH₂CH₂CH₂NH₃]²⁺. Examples of monomers comprising -COOH groups include acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid or fumaric acid or salts thereof.

Preference is given to acrylic acid or salts thereof.

Examples of monomers comprising -SO₃H groups or salts thereof include vinylsulfonic acid, allylsulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid (ATBS), 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 2-acrylamido-2-methylpropanesulfonic acid (ATBS) or salts thereof.

Examples of monomers comprising -PO₃H₂ groups or salts thereof include

vinylphosphonic acid, allylphosphonic acid, N-(meth)acrylamidoalkylphosphonic acids or (meth)acryloyloxyalkylphosphonic acids, preferably vinylphosphonic acid.

Preferred monomers comprising acidic groups comprise acrylic acid and/or ATBS or salts thereof.

Cationic monomers

Further examples of monomers comprise water-soluble, monoethylenically unsaturated monomers comprising cationic groups. Suitable cationic monomers include especially monomers having ammonium groups, especially ammonium derivatives of N-(w- aminoalkyl)(meth)acrylamides or w-aminoalkyl (meth)acrylates such as

2-trimethylammoniooethyl acrylate chloride H C=CH-CO-CH CH N⁺(CH ) CI- (DMA3Q). Further examples have been mentioned in WO 2015/158517 A1 page 8, lines 15 to 37. Preference is given to DMA3Q.

Associative monomers

In one embodiment, the monomers comprise at least one associative monomer.

Associative monomers typically may only be used as comonomers besides other monoethylenically unsaturated monomers, in particular besides acrylamide.

Associative monomers impart hydrophobically associating properties to polymers, in particular to polyacrylamides. Associative monomers to be used in the context of this invention are water-soluble, monoethylenically unsaturated monomers having at least one hydrophilic group and at least one, preferably terminal, hydrophobic group.

Examples of associative monomers have been described for example in WO

2010/133527, WO 2012/069478, WO 2015/086468 or WO 2015/158517.

“Hydrophobically associating copolymers” are understood by a 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.

Examples of suitable associative monomers comprise monomers having the general formula H2C=C(R¹)-R²-R³ (I) wherein R¹ is H or methyl, R² is a linking hydrophilic group and R³ is a terminal hydrophobic group. Further examples comprise having the general formula H2C=C(R¹)-R²-R³-R⁴ (II) wherein R¹, R² and R³ are each as defined above, and R⁴ is a hydrophilic group.

The linking hydrophilic R² group may be a group comprising ethylene oxide units, for example a group comprising 5 to 80 ethylene oxide units, which is joined to the

H2C=C(R¹)- group in a suitable manner, for example by means of a single bond or of a suitable linking group. In another embodiment, the hydrophilic linking group R² may be a group comprising quaternary ammonium groups.

In one embodiment, the associative monomers are monomers of the general formula H₂C=C(R¹)-0-(CH₂CH₂0)_k-R^3a (III) or H₂C=C(R⁵)-(C=0)-0-(CH₂CH₂0)_k-R^3a (IV), wherein R¹ has the meaning defined above and k is a number from 10 to 80, for example, 20 to 40. R^3a is an aliphatic and/or aromatic, straight-chain or branched hydrocarbyl radical having 8 to 40 carbon atoms, preferably 12 to 32 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.

In another embodiment, the associative monomers are monomers of the general formula H2C=C(R¹)-0-(CH2)n-0-(CH2CH20)x-(CH2-CH(R⁵)0)y-(CH2CH₂0)zH (V), wherein R¹ is defined as above and the R⁵ radicals are each independently selected from hydrocarbyl radicals comprising at least 2 carbon atoms, preferably from ethyl or propyl groups. In formula (V) n is a natural number from 2 to 6, for example 4, x is a number from 10 to 50, preferably from 12 to 40, and for example, from 20 to 30 and y is a number from 5 to 30, preferably 8 to 25. In formula (V), 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 an embodiment of the invention, it is possible to use at least two monomers (V), wherein the R¹ and R⁶ radicals and indices n, 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.

In another embodiment, the associative monomers are cationic monomers. Examples of cationic associative monomers have been disclosed in WO 2015/158517 A1 , page 1 1 , line 20 to page 12, lines 14 to 42. In one embodiment, the cationic monomers having the general formula H₂C=C(R¹)-C(=0)0-(CH₂)k-N⁺(CH3)(CH₃)(R⁶) X- (VI) or H₂C=C(R¹)-C(=0)N(R¹)-(CH2)k-N⁺(CH3)(CH₃)(R⁶) X- (VII) may be used, wherein R¹ has the meaning as defined above, k is 2 or 3, R⁶ is a hydrocarbyl group, preferably an aliphatic hydrocarbyl group, having 8 to 18 carbon atoms, and X- is a negatively charged counterion, preferably Ch and/or Br.

Further monomers

Besides water-soluble monoethylenically unsaturated monomers, also water-soluble, ethylenically unsaturated monomers having more than one ethylenic group may be used. Monomers of this kind can be used in special cases in order to achieve easy crosslinking of the 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 to be used in the present invention are only monoethylenically unsaturated monomers.

Composition of polymers

The specific composition of the polymers may be selected according to the desired use of the polymers.

Preferred polymers comprise, besides at least 10 % by weight, preferably at least 20 % by weight and for example at least 30 % by weight of polyacrylamide, one further water-soluble, monoethylenically unsaturated monomer, preferably at least one further monomer selected from the group of acrylic acid or salts thereof, ATBS or salts thereof, associative monomers, in particular those of formula (V) or DMA3Q, more preferably at least further one monomer selected from acrylic acid or salts thereof, ATBS or salts thereof, associative monomers, in particular those of formula (V).

In one embodiment, polyacrylamides comprise 20 % to 90 % by weight of acrylamide and 10 % to 80 % by weight of acrylic acid and/or salts thereof, wherein the amounts of the monomers relate to the total of all monomers in the polymer.

In one embodiment, polyacrylamides comprise 20 % to 40 % by weight of acrylamide and 60 % to 80 % by weight of acrylic acid and/or salts thereof.

In one embodiment, polyacrylamides comprise 55 % to 75 % by weight of acrylamide and 25 % to 45 % by weight of acrylic acid and/or salts thereof.

In one embodiment, polyacrylamides comprise 45 % to 75 % by weight of acrylamide and 25 % to 55 % by weight of ATBS and/or salts thereof. In one embodiment, polyacrylamides comprise 30 % to 80 % by weight of acrylamide, 10 % to 40 % by weight of acrylic acid and/or salts thereof, and 10 % to 40 % by weight of ATBS and/or salts thereof.

In one embodiment, polyacrylamides comprise 45 % to 75 % by weight of acrylamide, 0.1 to 5 %, preferably 0.1 to 2 % by weight of at least one associative monomer of the general formulas (I) or (II) mentioned above and 10 to 54.9 % by weight of acrylic acid and/or ATBS and/or salts thereof. Preferably, the associative monomer(s) have the general formula (V) including the preferred embodiments mentioned above.

In one embodiment, polyacrylamides comprise 60 % to 75 % by weight of acrylamide, 0.1 to 5 %, preferably 0.1 to 2 % by weight of at least one associative monomer of the general formula (V) mentioned above, including the preferred embodiments, and 20 to

39.9 % by weight of acrylic acid or salts thereof.

In one embodiment, polyacrylamides comprise 45 % to 55 % by weight of acrylamide, 0.1 to 5 %, preferably 0.1 to 2 % by weight of at least one associative monomer of the general formula (V) mentioned above, including the preferred embodiments, and 40 to

54.9 % by weight of acrylic acid or salts thereof.

In one embodiment, the polyacrylamides comprise 60 % to 99 % by weight of acrylamide and 1 % to 40 % by weight of DMA3Q.

In one embodiment, the polyacrylamides comprise 10 % to 50 % by weight of acrylamide and 50 % to 90 % by weight of DMA3Q.

In one embodiment, the polyacrylamides comprise 90 to 99.5 % by weight of acrylamide, 0.5 to 2 % by weight of at least one associative monomer, and 0 % to 9.5 % by weight of and anionic monomer, for example ATBS or a cationic monomer, for example DM3AQ. Preferably, the associative monomer(s) have the general formula (V) including the preferred embodiments mentioned above.

In all embodiments mentioned above, the amount of the monomers relates to the total of all monomers in the polymer. Further water-soluble, monoethylenically unsaturated monomers may be present besides those specifically mentioned, however, the embodiments each include also one embodiment in which besides the monomers specifically mentioned no further monomers are present, i.e. the total amount of the monomers specifically mentioned is 100 % by weight.

The weight average molecular weight M_w of the polymers to be manufactured may be selected by the skilled artisan according to the intended use of the polymers.

Preferably, the weight average molecular weight M_w of the polymers to be

manufactured, in particular polyacrylamides to be manufactured usually ranges from 1 ^*10⁶ g/mol to 50^*10⁶ g/mol, preferably from 1.5^*10⁶ g/mol to 40^*10⁶ g/mol, more preferably from 2^*10⁶ g/mol to 30^*10⁶ g/mol, and for example from 5^*10⁶ g/mol to 25^*10⁶ g/mol.

Step [1 ] - Providing an aqueous polymer gel

In course of step [1], an aqueous polymer gel comprising 15 % to 45 % by weight of a water-soluble polymer is provided, wherein the aqueous polymer gel is obtainable by polymerization of an aqueous solution comprising water-soluble, monoethylenically unsaturated monomers.

The concentration of the monomers in the aqueous monomer solution more or less corresponds to the polymer concentration in the aqueous polymer gel. In particular, the concentration of the monomers in the aqueous monomer solution is from

15 % by weight to 45% by weight, wherein the percentages relate to the total of all components of all components of the aqueous monomer solution. Suitably the contents of monomer in the aqueous monomer solution may be from 20 % to 45 % by weight, desirably from 20 % to 40 % by weight, preferably from 20 to 35 % by weight and for example from 20 to 25 % by weight.

“Providing an aqueous polymer gel” shall mean that the aqueous polymer gel is available at the site at which the process according to the present invention is conducted. In one embodiment of the invention, the polymerization of the aqueous solution comprising monoethylenically unsaturated monomers may be conducted at the same site. In another embodiment of the invention, the polymerization may be conducted at another site and the aqueous polymer gel transported to the site the process according to the present invention is conducted. In this embodiment, suitably the polymerization may be carried out in a transportable polymerization unit. After polymerization, the polymerization unit filled with the aqueous polymer gel may be transported to another site at which the process according to the present invention is carried out.

Preferably, the aqueous monomer solution is polymerized under adiabatic conditions. Such a polymerization technique is also briefly denominated by the skilled artisan as “adiabatic gel polymerization”. Reactors for adiabatic gel polymerization are unstirred. Due to the relatively high monomer concentration the aqueous monomer solution used solidifies in course of polymerization thereby yielding an aqueous polymer gel.

“Adiabatic” is understood by the person skilled in the art to mean that there is no exchange of heat with the environment. This ideal is naturally difficult to achieve in practical chemical engineering. In the context of this invention,“adiabatic” shall consequently be understood to mean“essentially adiabatic”, meaning that the reactor is not supplied with any heat from the outside during the polymerization, i.e. is not heated, and the reactor is not cooled during the polymerization. However, it will be clear to the person skilled in the art that - according to the internal temperature of the reactor and the ambient temperature - certain amounts of heat can be released or absorbed via the reactor wall because of temperature gradients, but this effect naturally plays an ever lesser role with increasing reactor size. The polymerization of the aqueous monomer solution generates polymerization heat. Due to the adiabatic reaction conditions the temperature of the polymerization mixture increases in course of polymerization.

The polymerization of the aqueous monomer solution comprising monoethylenically unsaturated monomers is performed in the presence of suitable initiators for radical polymerization. Suitable initiators for radical polymerization, in particular adiabatic gel polymerization, are known to the skilled artisan. Before polymerization the aqueous monomer solution should be inerted in basically known manner.

In a preferred embodiment, redox initiators are used for initiating. Redox initiators can initiate a free-radical polymerization even at temperatures of less than +5°C. Examples of redox initiators are known to the skilled artisan and include systems based on Fe²⁺/Fe³⁺ - H2O2, Fe²⁺/Fe³⁺ - alkyl hydroperoxides, alkyl hydroperoxides - sulfite, for example t-butyl hydroperoxide - sodium sulfite, peroxides - thiosulfate or alkyl hydroperoxides - sulfinates, for example alkyl hydroperoxides/ hydroxymethane- sulfinates, for example t-butyl hydroperoxide - sodium hydroxymethanesulfinate.

Furthermore, water-soluble azo initiators may be used. The azo initiators are preferably fully water-soluble, but it is sufficient that they are soluble in the monomer solution in the desired amount. Examples of suitable azo initiators include 2,2'-azobis[2-(2- imidazolin-2-yl)propane] dihydrochloride, 2,2'-azobis(2-methylpropionamidine) dihydrochloride, 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine hydrate, 2,2'- azobis{2-[1 -(2-hydroxyethyl)-2-imidazolin-2-yl]propane} dihydrochloride, 2,2'-azobis(1 - imino-1-pyrrolidino-2-ethylpropane) dihydrochloride or azobis(isobutyronitrile).

In one embodiment of the invention a combination of at least one redox initiator and at least one azo initiator is used. The redox initiator efficiently starts polymerization already at temperatures below +5°C. When the reaction mixture heats up, also the azo initiators decompose and start polymerization.

Besides monomers and initiators, also additives and auxiliaries may be added to the aqueous monomer solution. Examples of such further additives and auxiliaries comprise bases or acids, complexing agents, defoamers, surfactants, or stabilizers.

Radical polymerization starts after adding the initiator solutions to the aqueous monomer solution thereby forming an aqueous polyacrylamide gel. Due to the polymerization heat generated in course of polymerization and the adiabatic reaction conditions, the temperature in the polymerization unit increases. The temperature of the aqueous monomer solution before the onset of polymerization should not exceed 30°C and preferably may be from -5°C to +5°C. The temperature may rise to 50°C to 95°C in course of polymerization, for example to 55°C to 70°C. The polymerization may be performed in a polymerization unit having a volume of 1 m³ to 40 m³, preferably from 5 m³ to 40 m³, and for example 20 m³ to 30 m³. The polymerization unit may be a transportable polymerization unit which may be transported for instance by trucks or railcars. The polymerization unit may be of cylindrical or conical shape. In one embodiment, the polymerization unit comprises a cylindrical upper part and a conical part at its lower end. At the lower end, there is a bottom opening which may be opened and closed. Besides the opening at its lower end the polymerization unit comprises one or more feeds for the aqueous monomer solution, initiator solutions, gases such as nitrogen or other additives. After polymerization, the polyacrylamide gel formed is removed through the opening, for example by means of gas pressure. Transportable polymerization units furthermore may comprise means such as legs or similar elements allowing to deploy the polymerization unit in a vertical manner. They may be transported in a horizontal manner.

Step [2] Comminuting and mixing the aqueous polymer gel with an aqueous liquid

In course of step [2] the aqueous polymer gel is comminuted and mixed with an aqueous liquid, thereby obtaining an aqueous mixture comprising an aqueous liquid comprising dissolved aqueous polymer and undissolved pieces of aqueous polymer gel.

The aqueous liquid comprises water. The term“water” includes any kind of water such as desalinated water, fresh water or water comprising salts, such as brines, sea water, formation water, or mixtures thereof. Besides water, the aqueous liquid may comprise organic solvents miscible with water, however the amount of water relating to the total of the aqueous liquid should be at least 70 % by weight, preferably at least 90 % by weight, more preferably at least 95 % by weight. In one preferred embodiment, the aqueous liquid comprises only water as solvent. The aqueous liquid may optionally also comprise additives such as for example surfactants, complexing agents, bases, acids of the like. Kind and amount of such additives may be selected according to the intended use of the aqueous mixture.

Comminution unit to be used

The comminution unit comprises at least

a hollow cylinder comprising two base areas and a lateral area, wherein one of the base areas comprises an opening for aqueous polymer gel, the opposite base area is closed and at least a part of the lateral area of the cylinder comprises

perforations,

• a flow chamber enclosing circumferentially the lateral area of the hollow cylinder comprising perforations and the closed based area of the hollow cylinder, wherein the chamber comprises an inlet and an outlet for aqueous liquid,

• a drive for rotating the cutting means,

• means for pressing aqueous polymer gel through the opening into the hollow

cylinder.

Embodiments of the comminution unit and its function are shown in figures 1 to 6.

Figure 1 shows a schematic drawing of one embodiment of the comminution unit. The comminution unit comprises a hollow cylinder (1). The hollow cylinder preferably is made of metals, in particular steel. One of the base areas (8) is closed and the opposite base area (9) comprises an opening for introducing aqueous polymer gel into the hollow cylinder. The opening may only extend over a part of the base area of the cylinder or it may extend (as shown in figure 1 ) over the entire area of the base. At least a part of the lateral area of the hollow cylinder (1 ) comprises perforations (1 1).

The shape of the perforations is not specifically limited. Examples comprise

perforations of circular, ellipsoidal, triangular or quadrangular shape such as quadratic, rectangular, or rhombic perforations, perforations of pentagonal, hexagonal or star-like shape but also longitudinal perforations such as slots. The perforations may be cylindrical, but they may also be conical.

The dimensions of the perforations are not specifically limited. However, preferably at least one dimension of the perforations should be from 1 to 10 mm. In one embodiment of the invention, the hollow cylinder comprises circular perforations having a diameter from 1 to 10 mm, for example from 2 mm to 6 mm.

It is not necessary, that the entire lateral area of the hollow cylinder comprises perforations, but it is sufficient, if at least a part of the lateral area comprises perforations. Preferably, at least a section of the cylinder comprises perforations which are distributed over the entire circumference of the cylinder. Preferably, the section comprising perforations is a middle section accompanied by two sections towards the end which comprise no perforations. A flow chamber (4) encloses the lateral area of the hollow cylinder comprising perforations circumferentially and in furthermore encloses the closed based area of the hollow cylinder (8). The chamber furthermore comprises an inlet (5) and an outlet (6) for aqueous liquid, thereby allowing aqueous liquid to flow through the flow chamber. The hollow cylinder is the inner boundary of the flow chamber.

The cutting means (2) are arranged within the flow chamber and rotate around the outside of the lateral area of the hollow cylinder comprising perforations (1 ). The rotating cutting means comprise at least a rotating support and at least one knife fixed to the rotating support. Preferably, a plurality of knives is fixed to the rotating support.

The comminution unit furthermore comprises a drive (3) for rotating the cutting means. The drive may be mounted coaxial to the axis of the hollow cylinder. In such an embodiment, the flow chamber (4) comprises a water-tight lead-through for the axis connecting the drive (3) with the rotating cutting means (2). Of course, other methods of driving the rotating cutting means may also be used.

In one embodiment, the rotating support is cylindrical having a radius larger than that of the hollow cylinder comprising perforations.

Preferably, the cylindrical support comprises a circular base (10) connected to the drive and a lateral area which comprises a plurality of rips (12) in longitudinal direction, wherein the knives (13) are connected to the side walls of the rips. Such an

embodiment is schematically shown in figure (3). The circular base (10) may be a circular metal sheet but of course other constructions are possible. For example, the circular base may be a ring which is connected to the rotating axis by radius arms, preferably by at least three radius arms.

In one embodiment, the rips (12) may be parallel to the axis of the cylinder (as shown in figure 3) and consequently also the knives are parallel to the axis of the cylinder, but of course also other constructions are possible.

The knives may be perpendicular to the cylinder but preferably, they are tiled, so that the cutting edge shows in the direction of rotation. The tilt angle may be from 0° to 90° relating to the circumference of the cylinder (0° is parallel to the circumference, 90°C is perpendicular to the circumference), in particular from 5° to 85°, preferably from 40° to 70° and for example about 60°.

The distance between the cutting edge of the knives and the outer surface of the hollow cylinder preferably is £ 1 mm, for example £ 0.4 mm.

In order to further illustrate the invention, figure 2 shows a sectional view in longitudinal direction of the comminution showing the hollow cylinder comprising perforations (1), surrounded by the cutting means (2) comprising knives which are enclosed by a flow chamber (4) comprising an inlet (5) and an outlet (6).

The dimensions of the cutting device depend in known manner on the desired output per time. In embodiments of the invention, the diameter of the hollow cylinder comprising perforations may be from 0.2 m to 0.5 m and the length may be from 0.4 m to 1 m.

The rotational speed to the cutting means may be selected by the skilled artisan. In one embodiment of the invention, the effective velocity of the cylinder (i.e. the track speed of the knives rotating around the cylinder comprising perforations) should not exceed 3 m/s.

The comminution unit furthermore comprises means for pressing the aqueous polymer gel through the opening into the hollow cylinder. In one embodiment, the aqueous polymer gel is introduced into the hollow cylinder by means of a pump, for example a pump comprising a twin screw, a progressive cavity pump, a gear pump or an extruder.

In one embodiment of the invention, the comminution unit may be connected directly with the polymerization unit. For that purpose, an opening, preferably a bottom opening in the polymerization unit may be connected with the pump and the aqueous polymer gel may the transferred directly through the opening in the polymerization unit into the comminution unit. Removing the aqueous polymer gel from the reactor may be supported in known manner by means of pressure onto the gel, in particular by means of gas pressure.

Operation of the comminution unit

The comminution unit as described above is used for comminuting and mixing the aqueous polymer gel with an aqueous liquid.

Embodiment of the operation of the comminution unit are schematically shown in figures 4 to 6.

For carrying out the process according to the present invention, the aqueous polymer gel is introduced the opening of the hollow cylinder into the hollow cylinder at a pressure sufficient to pass from the inside of the hollow cylinder through the

perforations to the outside of the lateral area of the hollow cylinder, thereby forming polymer gel strands. This is shown in detail in figure 4. The pressure to be applied may be selected by the skilled artisan and may be for example up to 25^*10⁵ Pa.

Furthermore, a continuous stream of an aqueous liquid is introduced into the flow chamber through the inlet. The stream may be a constant stream, i.e. the amount of aqueous liquid per time is not varied. In other embodiments of the invention, the amount per time may be varied.

The polymer gel strands formed as mentioned above are cut by the rotating cutting means into gel pieces and the pieces are dispersed in the aqueous liquid flowing through the flow chamber. The process of dispersing is supported by the cutting means rotating in the flow chamber. While the product obtained mainly is a dispersion of gel pieces in the aqueous liquid, inevitably already a small amount of the water-soluble polymer dissolves in the aqueous liquid already in the flow chamber. So, the product obtained is an aqueous mixture comprising an aqueous liquid comprising dissolved aqueous polymer and undissolved aqueous polymer gel pieces. The gel pieces may have dimensions in one direction from 1 mm to several cm without wishing to limit the invention to said numbers. In general, finer pieces are advantageous because they dissolve better, for example less than 1 cm in at least one dimension, preferably less than 1 cm in three dimensions.

Said aqueous mixture comprising an aqueous liquid comprising dissolved aqueous polymer and undissolved aqueous polymer gel pieces is removed from the flow chamber through the outlet as a continuous stream.

Figure 5 shows the operational mode of the comminution unit as sectional view in longitudinal direction.

Figure 6 shows a preferred embodiment of the process in the comminution unit comprises additionally a displacement device (7) mounted in the inside of the hollow cylinder at its closed end. The displacement device preferably is a rotationally symmetric body comprising a base area and a top. Examples of such bodies comprise cones, in particular cones with a rounded down top. As indicated in figure 6, such displacement devices divert the stream of aqueous polymer gel introduced into the hollow cylinder towards its lateral area so that the aqueous polymer gel can pass through the perforations in the lateral area, thereby avoiding that aqueous polymer gel remains in dead ends of the hollow cylinder.

The total amount of aqueous liquid used in course of step [2] may be adjusted by the skilled artisan. Naturally, there is an upper limit for the amount of water used which depends on the desired concentration of the final product, which has a polymer concentration of less than 15 % by weight, relating to the total of all components.

In one embodiment of the invention, already in course of step of step [2] the entire amount of aqueous liquid necessary to achieve the desired final concentration is added. In other embodiments, only a part the aqueous liquid necessary to achieve the desired final concentration is added and the remainder in course of step [3]. However, as a rule, at least 30 % by wt. of the total amount of water necessary should be added already in course of step [2], for example from 30 % by wt. to 99 % by wt., from 50 % by wt. to 99 % by wt., or from 80 % to 99 % by wt..

Step [3] Homogenization

In course of step [3], the aqueous mixture obtained in course of step [2] is

homogenized, thereby obtaining an aqueous polymer composition comprising at least an aqueous liquid and water-soluble polymer, wherein the concentration of the polymer is less than 15 % by weight, relating to the total of all components of the aqueous polymer composition.

Depending on parameters such as the chemical composition, the molecular weight and the concentration, the aqueous polymer composition may be a solution or a (soft) solid. In general, the concentrate is pumpable. In general, the concentration of the aqueous polymer composition may be from 0.01 % to less than 15 % by wt., preferably from 0.01 % to less than 10 % by wt..

In one embodiment of the invention, the aqueous polymer composition is an aqueous polymer solution comprising 0.01 % to 2 % by wt. of polymers, relating to the total of all components of the aqueous polymer solution. Preferably, the amount is from 0.1 % to 1 % by wt..

In another embodiment of the invention, the aqueous polymer composition is an aqueous polymer concentrate comprising 2.1 % to 14.9 % by wt. of polymers, relating to the total of all components of the aqueous polymer concentrate, for example from 3.1 % to 14.9 % by weight, in particular from 3.1 % by weight to 10 % by weight, preferably 3.1 % by weight to 7 % by weight, for example from 4 % by weight to 6 % by weight.

In course of the homogenization step [3] ideally, a homogeneous mixture of

polyacrylamides and aqueous liquid should be obtained, i.e. a (solid) solution.

However, the invention shall not be limited to such an embodiment and shall encompass also aqueous polymer composition which are not absolutely

homogeneous.

If not already done, any remaining amount of aqueous liquid to achieve the desired concentration of the aqueous polyacrylamide concentrate -if any- is added in course of step [3]. In one embodiment of the invention, the step [3] may be carried out by simply allowing the mixture obtained in course of step [2] to stand in a suitable vessel in order to homogenize without mixing. The time, the mixture is allowed to stand may be from minutes to several hours, for example from 5 min to 1 day, in particular from 1 h to 12 h. Of course, also longer times may be chosen.

Step [3] may be carried out as separate step, but it may also be combined with other process steps.

In one embodiment of the invention, the process comprises an additional step [4] of transporting the aqueous polymer composition from the production site to another site in a suitable transport unit. If such a transport step [4] follows, step [3] advantageously may be carried out by filling the mixture obtained in course of step [2] into the transport unit used for step [4] Advantageously, in this embodiment, the transport time may be used for homogenization.

In other embodiments, the mixture obtained in course of step [2] may be further mixed using suitable means. If the aqueous polyacrylamide composition has a viscosity which is not too high so that stirring is possible, a stirred vessel may be used for

homogenization. Naturally, such an embodiment is suitable in particular for more dilute compositions, such as the aqueous polymer solutions comprising 0.01 % to 2 % by wt. of polymers as mentioned above.

Other embodiments include the use of static mixers. In one embodiment, the mixture may be circulated using circulation pumps. Optionally, the loop may comprise one or more static mixers. Further examples include tumbling, shaking or any mixing method known to skilled in the art for highly viscous liquids, for example using progressive cavity pumps. In one embodiment, the mixture obtained in course of step [2] in homogenized by filling it into a vessel which is equipped with a mixing loop which may comprise one to more than one static mixers. The loop rate may be from 10 to 100 % of the storage tank volume per hour, for example from more 20 to 40 %.

In case a transport step [4] follows, in one embodiment the transport unit, for example a truck may comprise a rotating drum. Trucks comprising rotating drums are known on the art for transporting concrete. Homogenization may be effected in course of transport by rotating the drum.

Optional further steps

The process according to the present invention may optionally comprise further process step. In one embodiment of the invention, the process comprises an additional step [4] of transporting the aqueous polymer composition from a location A to a location B.

Location A is a location, at which the aqueous polymer compositions are manufactured. The plant for carrying out the process may be a fixed plant, but is also may be a relocatable, modular plant which may be erected at a location close to the users of the aqueous polymer composition, i.e. on an oilfield or close to an oilfield.

Locations B are the site-of-use for the aqueous polymer composition, for example at an oil well.

Transport may be effected by pumping the aqueous polymer composition through a pipeline from location A to location B. The pipeline may comprise a series of pumps for maintaining the pressure. Pipeline transport is in particular suitable, if the aqueous polymer composition is an aqueous polymer solution comprising 0.01 % to 2 % by wt. of polymers. Preferred embodiments have already been disclosed above.

In another embodiment, the transport is carried out, by filling the aqueous polymer composition into a suitable transport unit and transporting the transport unit from location A to location B. T ransport in a transport unit is in particular suitable, if the aqueous polymer composition is an aqueous polymer concentrate comprising 2.1 % to 14.9 % by wt. of polymers. Preferred embodiments have already been disclosed above.

The transport unit may have a volume from 1 m³ to 40 m³, in particular 5 m³ to 40 m³, for example 20 m³ to 30 m³. Examples of suitable transport units comprise vessels comprising at least one opening, tank containers, or tipping vessels.

The transport may be carried out by any transport means suitable for transporting the transport unit, for example by trucks, railcars or ships. In one embodiment, the transport is carried out by trucks. The transport unit may also be fixed on a truck.

In one embodiment, the transport unit may be an ISO tank container. Typical dimensions of ISO containers have already been mentioned above.

In another embodiment, tanks fixed on a truck may be used. In one embodiment, the tank comprises an outlet opening at the rear end of the truck and for supporting removal of the contents the tank may be tilted. In another embodiment, the tank comprises an outlet opening at the bottom side of the tank. Additionally, the tank may comprise a conus at the bottom side of the tank and the outlet opening in located at the lower end of the conus. The tank may also be rotatable, so that the concentrate may become homogenized in course of transport. For example, a concrete mixer may be used for transporting the concentrate. Filling the transport unit with the aqueous polyacrylamide concentrate may be carried out by pumping the concentrate into the transport unit.

The transport time, i.e. the time for transporting the transport unit filled with aqueous polyacrylamide concentrate may be very different, depending on the distance between the locations A and B. It may range from minutes to several days, for example from 1 h to 28 days, in particular from 2 hours to 14 days, in particular 5 hours to 7 days.

Use of the aqueous polymer solutions

The aqueous polymer solutions manufactured according to the present invention, preferably the aqueous polyacrylamide solutions, may be used for various purposes, for example for mining applications, oilfield applications, water treatment, waste water cleanup, paper making or agricultural applications.

For the application, the aqueous polymer solutions, preferably the aqueous

polyacrylamide solutions may be used as such or they may be formulated with further components. The specific composition of aqueous polymer solutions is selected by the skilled artisan according to the intended use of the polymer solution.

Advantages of the process according to the invention The present invention provides an advantageous process for providing aqueous polymer compositions.

As compared to other technologies, there are only little shear forces which is important for dissolving aqueous polymer gels of high-molecular weight polymers without damaging the polymer. In particular, in other cutting devices comprising blades rotating perpendicular around the axis of rotation (such a meat-grinder like cutting devices) naturally the effective velocity of the blades is smaller at a low radius and is larger at a large radius. Consequently, also the shear forces acting upon the gels may become large in such devices. In the present device, the rotating knives are parallel to the axis of rotation and therefore the effective velocity of the blades is equal at all positions. It can be selected to be small.

The apparatus may be constructed very compact. Furthermore, it is an easy construction principle (in contrast to the construction principle of an impact mill for example) thereby enabling the construction of a cheap apparatus. Finally, the apparatus comprises no dead space in which aqueous polymers gels may dry and stick the apparatus.

Claims

Claims:

1. A process for providing aqueous polymer compositions comprising at least the steps of

[1] providing an aqueous polymer gel comprising 15 % to 45 % by weight of a water-soluble polymer obtainable by polymerization of an aqueous solution comprising water-soluble, monoethylenically unsaturated monomers,

• a drive for rotating the cutting means,

wherein

> the aqueous polymer gel is introduced into the hollow cylinder at a

> a continuous stream of an aqueous liquid is introduced into the flow

chamber through the inlet,

2. Process according to claim 1 , wherein the cutting means comprise plurality of knives fixed to the rotating support.

3. Process according to claims 1 or 2, wherein the rotating support is cylindrical having a radius larger than that of the hollow cylinder comprising perforations.

4. Process according to claim 3, wherein the cylindrical support comprises a circular base connected to the drive and a lateral area which comprises a plurality of rips in longitudinal direction, wherein the knives are connected to the side walls of the rips.

5. Process according to any of claims 1 to 4, wherein the distance between the knives and the outer surface of the hollow cylinder is £ 1 mm.

6. Process according to any of claims 1 to 5, wherein the aqueous polymer gel is introduced into the hollow cylinder by means of a pump.

7. Process according to claim 6, wherein the pump comprises a twin screw.

8. Process according to any of claims 1 to 7, wherein comminution unit comprises additionally a displacement device mounted in the inside of the hollow cylinder at its closed end.

9. Process according to any of claims 1 to 7, wherein the entire amount of aqueous liquid necessary to achieve the final concentration is added in course of step [2]

10. Process according to any of claims 1 to 7, wherein only a part of the amount of aqueous liquid necessary to achieve the final concentration is added in course of step [2] and the remainder in course of step [3].

1 1. Process according to any of claims 1 to 10, wherein the homogenization step [3] is carried out by allowing the mixture obtained in course of step [2] to stand in a vessel.

12. Process according to any of claims 1 to 10, wherein the homogenization step [3] is carried out by stirring the mixture obtained in course of step [2] in a vessel.

13. Process according to any of claims 1 to 10, wherein the homogenization step [3] is carried out by pumping the mixture obtained in course of step [2] through a static mixer.

14. Process according to any of claims 1 to 13, wherein the aqueous polymer

composition is an aqueous polymer solution comprising 0.01 % to 2 % by wt. of polymers, relating to the total of all components of the aqueous polymer solution.

15. Process according to any of claims 1 to 13, wherein the aqueous polymer

composition is an aqueous polymer concentrate comprising 3.1 % to 14.9 % by wt. of polymers, relating to the total of all components of the aqueous polymer concentrate.

16. Process according to any of claims 1 to 15, wherein the aqueous polymer gel comprises from 20 % by wt. to 45 % by wt. of water-soluble polymers.

17. Process according to any of claims 1 to 13, wherein the process comprises a further process step [4] of transporting the aqueous polymer composition from location A to a different location B.

18. Process according to claim 17, wherein the transport is carried out by means of a pipeline.

19. Process according to claim 17, wherein the aqueous polymer composition is filled into a suitable transport unit and the transport unit is transported from location A to location B.

20. Process according to claim 19, wherein process step [3] is carried out in course of step transporting the aqueous polymer composition in the transport unit.

21. An apparatus for comminuting aqueous polymer gels, comprising at least

a hollow cylinder comprising two base areas and a lateral area, wherein one of the base areas comprises an opening for aqueous polymer gel, the opposite base area is closed and at least a part of the lateral area of the cylinder comprises perforations,

a flow chamber enclosing circumferentially the lateral area of the hollow cylinder comprising perforations and the closed based area of the hollow cylinder, wherein the chamber comprises an inlet and an outlet for aqueous liquid, • cutting means arranged within the flow chamber which rotate around the outside of the lateral area of the hollow cylinder comprising perforations, wherein the rotating cutting means comprise at least a rotating support and at least one knife fixed to the rotating support,

• a drive for rotating the cutting means,

22. Apparatus according to claim 21 , wherein the cutting means comprise plurality of knives fixed to the rotating support.

23. Apparatus according to claims 21 or 22, wherein the rotating support is cylindrical having a radius larger than that of the hollow cylinder comprising perforations.

24. Apparatus according to claim 23, wherein the cylindrical support comprises a circular base connected to the drive and a lateral area which comprises a plurality of rips in longitudinal direction, wherein the knives are connected to the side walls of the rips.

25. Apparatus according to any of claims 21 to 24, wherein the distance between the knives and the outer surface of the hollow cylinder is £ 1 mm.

26. Apparatus according to any of claims 21 to 25, wherein the means for pressing aqueous polymer gel through the opening into the hollow cylinder is a pump.

27. Apparatus according to claim 26, wherein the pump comprises a twin screw.

28. Apparatus according to any of claims 21 to 27, wherein comminution unit

comprises additionally a displacement device mounted in the inside of the hollow cylinder at its closed end.