Polymer dispersions and their use as paraffin inhibitors in crude oil

Abstract

The invention relates to polymer dispersions made from (meth)acrylates having long side chains, as well as to the preparation process to prepare the same. The invention also relates to a crude oil composition comprising a crude oil and the polymer dispersion according to the invention. The invention also relates to the use of these polymer dispersions as paraffin inhibitors to improve the flow properties of crude oil, as well as their use to improve the transport and / or storage of a crude oil.

Description

[0001] Polymer dispersions and their use as paraffin inhibitors in crude oil

[0002] TECHNICAL FIELD OF THE INVENTION

[0003] The invention relates to polymer dispersions made from (meth)acrylates having long side chains, as well as to the preparation process to prepare the same. The invention also relates to a crude oil composition comprising a crude oil and the polymer dispersion according to the invention. The invention also relates to the use of these polymer dispersions as paraffin inhibitors to improve the flow properties of crude oil, as well as their use to improve the transport and / or storage of a crude oil.

[0004] BACKGROUND OF THE INVENTION

[0005] Flow improvers are often used to improve the flow properties of crude oil and / or crude oil fractions. This kind of additives are especially needed to secure flowability of the oils at low temperatures, where a neat crude oil would already have issues to flow.

[0006] Flow issues are related to the precipitation / crystallization of long alkyl chain paraffins and / or asphaltenes present in the oils. The precipitation / crystallization of these components can either lead to a significant increase of the viscosity of the oils, a complete solidification of the oil or can lead to the formation of solid deposits, which then lead to a constriction of the pipelines used in the transportation of the oil.

[0007] One measure to determine the flowability of an oil is the pour point (PP) of the oil. One measure to evaluate the efficiency of a flow improver is its ability to reduce the PP of the oil.

[0008] Polymers are often used as paraffin inhibitors and contain long alkyl side chains (>C16, preferably >C18), which act as crystallization inhibitor by co-crystallizing with long chain paraffins of the oil. This kind of polymers are often based on (meth)acrylates with long alkyl side chains (>C16, preferably >C18). As this kind of polymers are solids at the typical temperature of use, they are normally applied as solutions in organic solvents to be able to dose them into the oil. Apart from negative characteristics of the used organic solvents e.g., flammability and toxicity, this kind of solutions in organic solvent bring additional disadvantages. As the long alkyl side chains of the polymer tend to crystallize, the flow inhibitor formulation can become solid already at relatively moderate temperatures, which prevents a dosing of this kind of formulations at lower temperatures. To counter this issue, one option is to heat the storage tanks and dosing lines, which leads to high energy costs. Another possibility is to reduce the pour point of the product by further dilution of the formulation to an active polymer concentration of less than 10%. This leads to extra costs such as costs for diluent, transportation, storage capacity, additional safety measures due to flammability of the diluent.

[0009] To get around this issue, instead of using polymer solutions in organic solvents, polymer dispersions can be used. They bring the benefit, that the viscosity and the flow behavior of the formulation is almost independent on the properties and the amount of polymer in the dispersed phase. This enables the use of high concentrated formulations even at very low dosing temperatures, as they remain low viscous down to low temperatures. This makes it possible to achieve a good performance as flow improver at low treat rates of the additive. For example, WO 9833846 A1 , US 20100025290 A1 and WO 2019057396 A1 describe the manufacturing of this kind of dispersions as secondary dispersions. To produce a secondary dispersion, the formulation is derived from a multistep process. First, the polymer is synthesized via solution polymerization in an organic solvent and is subsequently dispersed in a continuous phase. To produce a dispersion with sufficient stability, the formed particles need to be small enough. For the manufacturing of the secondary dispersion with small particle sizes, high shear forces need to be applied (for example by using a high shear mixer, a high-pressure homogenizer or ultrasound). These processes are costly, especially in commercial scale. In addition, the organic solvent used in the polymerization steps, either needs to be removed afterwards by distillation, or stays in the final formulation, which reduces the active content of the formulation and can bring other disadvantages, such as a lower flash point.

[0010] Another method to manufacture this kind of dispersions is to synthesize the dispersion via emulsion polymerization. Here the dispersion is directly formed in one step from the corresponding monomers. While emulsion polymerization is widely used for different kind of monomers, the emulsion polymerization of (meth)acrylate monomers with long side chains (>C16) is a challenge due to the hydrophobicity of these monomers. Therefore, conventional recipes used for example to synthesize dispersion-based resin formulations used for coatings or adhesive applications, are not suitable to obtain stable dispersions of very nonpolar monomers. For a successful process, a special procedure and special additives are required.

[0011] DE 3830913 describes the preparation of such polymer dispersions by emulsion polymerization. To obtain a low-coagulate and storage-stable dispersion, a high amount of ethylenically unsaturated mono- and / or dicarboxylic acid or anhydrides thereof must be used as comonomer. These large amounts of comonomer that must be used for stability reasons lead to restrictions in the choice of copolymer composition with regard to the effect as flow improver. For instance, an amount of 20% to 40% by weight of ethylenically unsaturated monocarboxylic acid or 5% to 20% by weight of dicarboxylic acids is required in order to obtain a stable, low-coagulate dispersion.

[0012] However, the correct copolymer composition is critical in many cases for the end use as flow improver in different (crude) oils. A good prediction which polymer composition exhibits the optimal effect in which oil is not possible to date, since the exact mechanisms of action for pour point depression and paraffin inhibition, or improving the flow properties, have not been clarified. Therefore, the optimal polymer composition must generally be adapted empirically to the particular oil to be treated.

[0013] For example, the preparation of stable polymer dispersions, in which the polymers comprise a high proportion of (meth)acrylates having side chains of 16 or more carbon atoms (> C16) is not possible via the method described in DE 3830913. In addition, storage stability tests described therein were only done at room temperature and therefore, storability and / or dispersion viscosity at low temperatures were not shown, although this is critical for the end use.

[0014] US 7,790,821 B2 likewise describes the preparation of polymer dispersions made from acrylates having long side chains that are prepared via free-radical emulsion polymerization. In this case, the use of unsaturated mono- or dicarboxylic acids as stabilizing comonomers can be avoided, thereby achieving a higher flexibility with respect to the polymer composition. Besides the use of an emulsifier, the stabilization of the dispersion is achieved by a water-miscible cosolvent in the continuous phase of the dispersion. Nevertheless, it was found that dispersions synthesized as taught in this patent do show high amount of coagulate after synthesis and do not show a good storage stability, which makes them unsuitable for the use as flow improver and / or pour point depressant. This was also found by others, as described in WO 2018 / 224599 A1.

[0015] WO 2021 / 191348 A1 and WO 2021 / 191349 A1 also describe emulsion polymerization of long chain alkyl (meth)acrylates. Stable dispersions are obtained by the combination of mixtures of water and a water mixable co-solvent as continuous phase and one or more surfactants from the class of sulfosuccinates. It is taught to use methacrylate with long alkyl side chain as exemplified in the experimental part where the examples are focused on behenyl methacrylate as long alkyl side chain monomer. Indeed, the polymer dispersions made of acrylate with long side chains (behenyl acrylate) as described in examples 2a and 2b coagulated completely or showed high amount of coagulate and contained many specks.

[0016] Therefore, it would be desirable to develop improved polymer dispersions for use as paraffin inhibitors and / or pour point depressant that have high contents of polymers, that can be processed easily and that simultaneously have a high stability as well as a good flowability over a broad temperature range, and that especially remain applicable / pumpable even at low temperatures (< 0°C). This would enable to use the flow improver at low treat rate even in regions where the additive needs to be dosed at low temperature e.g. during winter season and / or in cold areas.

[0017] BRIEF SUMMARY OF THE INVENTION

[0018] After thorough investigation, the inventors of the present invention have surprisingly found that polymer dispersions comprising copolymers having long alkyl chain acrylates, instead of long alkyl chain methacrylates as taught in the prior art, perform significantly better as flow improver in crude oil. It has been observed that they stay liquid down to low temperatures, which makes it possible to apply them easily at low environmental temperatures without the need to inject them via heated injection lines or dilute them to very low active contents (low treat rates are sufficient).

[0019] In addition, while it was not possible to achieve polymer dispersions having long chain acrylates as main component by the methods as described in the state of the art, due to lack of process stability as well as stability of the resulting polymer dispersions, it has been surprisingly found, that the performance of the process can be significantly increased, when small portions of a long alkyl chain methacrylates are added as a minor component of the polymer. While this improves the robustness of the process which makes it possible to achieve stable dispersions of consistent quality at different batch sizes in different reactors, it has been also found that small amounts of the methacrylate comonomer do not negatively affect the good performance as flow improver in different crude oils. Therefore, in a first aspect, the present invention relates to water-based polymer dispersion useful to improve the flowability of crude oils, which can be easily applied even at low temperatures.

[0020] According to a second aspect, the invention relates to the preparation process of these water-based polymer dispersion according to the invention.

[0021] A third aspect of the invention is a crude oil composition comprising the polymer dispersions according to the invention and crude oil.

[0022] A fourth aspect of the present invention is the use of these polymer dispersions as a paraffin inhibitor additive for crude oils to improve the flowability of said crude oil even at low temperatures.

[0023] A fifth aspect of the present invention is a method of improving the transport or storage of a crude oil comprising the step of adding a polymer dispersion according to the invention to said crude oil.

[0024] BRIEF DESCRIPTION OF THE DRAWING

[0025] For the purpose of better illustrating the advantages and properties of the claimed polymer dispersions, object of the present invention, one graph is attached as a non-limiting example:

[0026] Figure 1 is a graph showing the evolution of the viscosity as a function of temperature for polymer dispersions according to examples 20 and 34.

[0027] DETAILED DESCRIPTION OF THE INVENTION

[0028] Polymer dispersions according to the invention

[0029] The present invention relates is a polymer dispersion comprising a) from 10 to 70 % by weight, based on the total weight of the polymer dispersion, of a copolymer (a) prepared by emulsion polymerization of a monomer composition comprising: a1) from 50 to 94 % by weight of alkyl acrylate of formula (I), based on the total weight of the monomer composition: wherein R1a linear, branched or cyclic alkyl residue with 15 to 40 carbon atoms, a2) from 1 to 8 % by weight of monomer selected from the group consisting of ethy lenically unsaturated monocarboxylic acid, dicarboxylic acid, salt thereof, acid anhydride thereof, or a mixture thereof, based on the total weight of the monomer composition, a3) from 5 to 10.5 % by weight of alkyl methacrylate of formula (II), based on the total weight of the monomer composition, where R2is a linear, branched or cyclic alkyl residue with 8 to 30 carbon atoms, b) from 0.5 to 20 % by weight of a sulfosuccinate emulsifier selected from a sulfosuccinate monoester of formula (II), a sulfosuccinate diester of formula (IV) or a mixture thereof, based on the total weight of the polymer dispersion,

[0030] Sulfosuccinate Sulfosuccinate

[0031] Monoester Diester wherein, in formula (III) or (IV), M+is H+or a metal ion, preferably an alkali metal ion, like Na+or an 1 / 2 alkaline earth metal ion like 1 Ca2+, in this case (M+= 1 / 2 M2+), R3and R4are independently alkyl, aryl, aralkyl or alkylaryl radicals or R5(O-CH2-CH2)n, wherein R5is an alkyl, aryl, aralkyl or alkylaryl radical, and n = 1 to 30, c) from 1 to 40 % by weight of a water-miscible cosolvent or a mixture of multiple water-miscible cosolvents, based on the total weight of the polymer dispersion, and d) water.

[0032] The polymer dispersions according to the invention are easy to filtrate, stay very stable over a long period of time without the formation of coagulates (aggregation of particle) or a thick film at the top of the polymer dispersion, even when stored for a long period of time.

[0033] The polymer dispersions according to the invention are less sensitive to changes in the process conditions during the manufacturing compared to corresponding polymer dispersions prepared with monomer composition not containing any monomer a3). This improvement in robustness is essential for upscaling of the process, as it is usually not possible to retain all process conditions exactly the same when transferring to a different batch size. Copolymer a)

[0034] According to the present invention, the component a) of the polymer dispersion corresponds to one copolymer a) or a mixture of one or more copolymers a).

[0035] Within the context of the present invention, the monomer composition of the copolymer a) corresponds to the total amount of monomers used to prepare the copolymer a).

[0036] As used herein, the term “(meth)acrylate” refers to esters of acrylic and methacrylic acid, and to mixtures thereof. The term “alkyl (meth)acrylate” refers to esters of (meth)acrylic acid and aliphatic alcohols. The alkyl (meth)acrylates described herein are characterized by the number of carbon atoms in the alkyl chain derived from the alcohol.

[0037] According to a preferred aspect of the invention, the weight-average molecular weight of the copolymer a) is from 10,000 to 250,000 g / mol, more preferably from 30,000 to 200,000 g / mol, even more preferably from 50,000 to 180,000 g / mol, most preferably from 80,000 to 170,000 g / mol, determined by gel permeation chromatography using poly(methyl-methacrylate) calibration standards according to DIN EN ISO 13885-1 (GPC method as described in more detail in the experimental section below).

[0038] Preferably the polymer dispersion comprises from 15 to 60 % by weight, more preferably from 20 to 50 % by weight based on the total weight of the polymer dispersion, of a copolymer a).

[0039] Monomers a1) in the monomer composition of copolymer (a)

[0040] According to the present invention, the monomer composition of copolymer a) comprises from 50 to 94 % by weight of alkyl methacrylate of formula (I), based on the total weight of the monomer composition, wherein R1in formula (I) of the alkyl acrylates a1) is a linear, branched or cyclic alkyl residue with 15 to 40 carbon atoms. Preferably, R1is a linear, branched or cyclic alkyl residue with 16 to 30 carbon atoms, more preferably with 16 to 22 carbon atoms. Most preferably, R1is a linear alkyl residue with 16 to 22 carbon atoms.

[0041] According to the present invention, the monomer composition to prepare the copolymer a) comprises from 50 to 94 % by weight, more preferably from 60 to 92 % by weight, even more preferably from 70 to 90 % by weight, most preferably from 80 to 89 % by weight of one or more alkyl acrylate monomer a1) of formula (I), based on the total weight of the monomer composition. Preferably, the alkyl acrylate a1) is selected from the group consisting of C16-C30 acrylate monomers or a mixture thereof. Preferred alkyl acrylates a1) are selected from the group consisting of hexadecyl acrylate, 2-methylhexadecyl acrylate, heptadecyl acrylate, 5-isopropylheptadecyl acrylate, 4-tert-butyloctadecyl acrylate, 5-ethyloctadecyl acrylate, 3-isopropyloctadecyl acrylate, octadecyl acrylate, nonadecyl acrylate, eicosyl acrylate, cetyl acrylate, stearyl acrylate, , docosyl acrylate, behenyl acrylate, tetratriacontyl acrylate; cycloalkyl acrylates such as 2,3,4,5-tetra-t-butylcyclohexyl acrylate, or a mixture thereof. Preferred alkyl acrylate (a1) is selected from the group consisting of stearyl acrylate, eicosyl acrylate, docosyl acrylate or a mixture thereof. Most preferred acrylate monomer a1) is behenyl acrylate (Cis to C22 acrylate).

[0042] Monomers a2) in the monomer composition of copolymer a)

[0043] According to the present invention, the monomer composition of copolymer a) comprises from 1 to 8 % by weight, preferably from 2 to 7 % by weight, most preferably 4 to 6% of monomer a2) selected from the group consisting of ethy lenically unsaturated monocarboxylic acid, dicarboxylic acid, salt thereof, acid anhydride thereof, or a mixture thereof, based on the total weight of the monomer composition.

[0044] Preferred monomer a2) is selected from maleic acid, maleic acid anhydride, maleic acid derivatives, fumaric acid, fumaric acid derivatives, acrylic acid, methacrylic acid, salts thereof, or a mixture thereof. More preferred monomer a2) is selected from acrylic acid, methacrylic acid, salts thereof or mixtures thereof. Most preferred monomer a2) is acrylic acid.

[0045] Monomers a3) in the monomer composition of copolymer a)

[0046] According to the present invention, the monomer composition of copolymer a) comprises from 5 to 10.5 % by weight of alkyl methacrylate of formula (II), based on the total weight of the monomer composition, wherein R2is a linear, branched or cyclic alkyl residue with 8 to 30 carbon atoms, preferably with 12 to 22 carbon atoms, more preferably with 15 to 20 carbon atoms, even more preferably, R2is a linear alkyl residue with 15 to 20 carbon atoms, most preferably R2is a linear alkyl residue with 16 to 18 carbon atoms.

[0047] Preferably, the monomer composition of the copolymer a) comprises from 6 to 10 % by weight, more preferably from 7 to 9.5 % by weight, of alkyl methacrylate a3) of formula (II), based on the total weight of the monomer composition.

[0048] According to the invention monomer a3) is a linear, branched or cyclic Cs-Cao methacrylate monomer, or a mixture thereof. Preferred monomer a3) is selected from the group consisting of 2-ethylhexyl methacrylate, n-octyl methacrylate, iso-octyl methacrylate, n-decyl methacrylate, iso-decyl methacrylate, undecyl methacrylate, n-dodecyl methacrylate, 2-methyldodecyl methacrylate, tridecyl methacrylate, 5-methyltridecyl methacrylate, n-tetradecyl methacrylate, pentadecyl methacrylate; oleyl methacrylate, bornyl methacrylate, isobornyl methacrylate, hexadecyl methacrylate, 2-methylhexadecyl methacrylate, heptadecyl methacrylate, 5-isopropylheptadecyl methacrylate, 4-tert-butyloctadecyl methacrylate, 5-ethyloctadecyl methacrylate, 3-isopropyloctadecyl methacrylate, octadecyl methacrylate, nonadecyl methacrylate, eicosyl methacrylate, cetyl methacrylate, stearyl methacrylate, docosyl methacrylate, behenyl methacrylate or a mixture thereof. More preferred monomer a3) is behenyl methacrylate (Cis to C22 methacrylate), stearyl methacrylate (C16 to C18 methacrylate) or a mixture thereof. Most preferred monomer a3) is stearyl methacrylate (C16 to C18 methacrylate).

[0049] Monomers a4) in the monomer composition of copolymer a)

[0050] As an optional component, the copolymer a) may contain further monomer units derived from one or more monomers a4) selected from C1-C14 acrylate monomers, C1-C7 methacrylate monomers, or a mixture thereof.

[0051] Preferred monomers a4) are methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, hexyl and cyclohexyl (meth)acrylate, cyclohexyl (meth)acrylate, octyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, decyl acrylate, isodecyl methacrylate, undecyl acrylate, 5-methylundecyl acrylate, n-dodecyl acrylate, 2-methyldodecyl acrylate, tridecyl acrylate, 5-methyltridecyl acrylate, n-tetradecyl acrylate, bornyl acrylate and isobornyl acrylate, or a mixture thereof.

[0052] Most preferred monomer a4) is selected from the group consisting of methyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl acrylate or a mixture thereof.

[0053] Preferably, the amount of monomer a4) in the monomer composition of the copolymer a) is from 0 to 10 % by weight, more preferably from 0.1 to 5 % by weight, based on the total weight of the monomer composition of the copolymer a).

[0054] Monomers a5) in the monomer composition of copolymer a)

[0055] As an optional component, the monomer composition of the copolymer (a) may further comprise monomer a5) selected from: hydroxyalkyl (meth)acrylates, preferably hydroxyalkyl (meth)acrylates selected from 2-hydroxypropyl (meth)acrylate and 2-hydroxyethyl (meth)acrylate; aminoalkyl (meth)acrylates and aminoalkyl (meth)acrylamides, preferably aminoalkyl (meth)acrylates and aminoalkyl (meth)acrylamides selected from 3-di methylaminopropyl (meth)acrylamide and 2-dimethyaminoethyl (metha)crylate;aminoalkyl (meth)acrylate chlorides and aminoalkyl (meth)acrylamide chlorides, preferably aminoalkyl (meth)acrylate chlorides and aminoalkyl (meth)acrylamide chlorides selected from 3-trimethlyaminopropyl (meth)acrylamide chloride and 2-trimethyaminoethyl (metha)crylate; aryl (meth)acrylates, preferably benzyl (meth)acrylate or phenyl (meth)acrylate, where the acryl residue in each case can be unsubstituted or substituted up to four times;

[0056] (meth)acrylates of ether alcohols, preferably (meth)acrylates of ether alcohols selected from tetrahydrofurfuryl (meth)acrylate and esters of (meth)acrylic acid and methoxy polyethylene glycols; vinyl esters, preferably vinyl acetate; vinyl monomers containing aromatic groups, preferably vinyl monomers containing aromatic groups selected from styrene, substituted styrenes with an alkyl substituent in the side chain, such as alpha-methylstyrene and alpha-ethylstyrene, substituted styrenes with an alkyl substituent on the ring such as vinyltoluene and p-methylstyrene, halogenated styrenes such as monochlorostyrenes, dichlorostyrenes, tribromostyrenes and tetrabromostyrenes; or a mixture thereof.

[0057] Most preferred monomer a5) is selected from the group consisting of hydroxyalkyl (meth)acrylates, aminoalkyl (meth)acrylates, aminoalkyl (meth)acrylamides, styrene, 4-vinyltoluene or a mixture thereof. Most preferred monomers (a6) are 2-hydroxyethyl (meth)acrylate, N-(3-dimethyl-aminopropyl)methacrylamide, 3- diethylaminopentyl (meth)acrylate, or a mixture thereof.

[0058] Preferably, the amount of monomer a5) in the monomer composition of the copolymer a) is from 0 to 5 % by weight, more preferably from 0.1 to 4 % by weight, even more preferably from 0.2 to 3 % by weight, based on the total weight of the monomer composition of the copolymer (a).

[0059] Sulfosuccinate emulsifier b) of the polymer dispersion according to the invention

[0060] According to the present invention, the component b) of the polymer dispersion corresponds to one sulfoccinate emulsifier b) or a mixture of one or more sulfoccinate emulsifiers b).

[0061] According to the present invention, the polymer dispersion comprises from 0.5 to 20 % by weight of a sulfosuccinate emulsifier b) selected from a sulfosuccinate monoester of formula (III), a sulfoccinate diester of formula (IV), or a mixture thereof, based on the total weight of the polymer dispersion,

[0062] Sulfosuccinate Sulfosuccinate

[0063] Monoester Diester

[0064] (HI) (IV) wherein, in formula (III) or (IV), M+is H+or a metal ion, preferably an alkali metal ion, like Na+or an 1 / 2 alkaline earth metal ion like 1 Ca2+, in this case (M+= 1 / 2 M2+), R3and R4are independently alkyl, aryl, aralkyl or alkylaryl radicals or R5(O-CH2-CH2)n, wherein R5is an alkyl, aryl, aralkyl or alkylaryl radical, and n = 1 to 30.

[0065] According to the present invention, the polymer dispersion comprises from 0.5 to 20 % by weight, preferably from 2 to 10 % by weight, more preferably from 3 to 5.5 % by weight, of one or more sulfosuccinate emulsifier b), based on the total weight of the polymer dispersion.

[0066] The sulfosuccinate emulsifier b) is preferably dialkyl sulfosuccinate emulsifier or mixture thereof. The alkyl group can be linear or branched or contain an aliphatic ring. Examples of suitable alkyl radicals (hydrophobic groups) are isobutyl, isohexyl, cyclohexyl, 2-ethylhexyl, isooctyl, isodecyl, and isotridecyl. In the case of diesters, the alkyl groups are preferably identical.

[0067] The sulfosuccinate emulsifier b) is preferably selected from the group consisting of sodium bis(2-ethylhexyl) sulfosuccinate, sodium bistridecyl sulfosuccinate, sodium bisisooctyl sulfosuccinate, sodium biscyclohexyl sulfosuccinate, sodium bisoctyl sulfosuccinate, sodium diamyl sulfosuccinate, sodium diisobutyl sulfosuccinate, sodium dihexyl sulfosuccinate, disodium lauryl sulfosuccinate, disodium salt of ethoxylated nonylphenol sulfosuccinate, disodium ethylhexyl sulfosuccinate or a mixture thereof. Instead of sodium, salts with other counterions such as Li+, K+, Mg2+, Ca2+, Sr2+, Ba2+can also be used.

[0068] Most preferred sulfosuccinate b) is sodium bis(2-ethylhexyl) sulfosuccinate, sodium bistridecyl sulfosuccinate or a mixture thereof; even more preferably is sodium bis(2-ethylhexyl) sulfosuccinate.

[0069] Water-miscible cosolvent c) of the polymer dispersion according to the invention

[0070] The polymer dispersion according to the invention comprises from 1 to 40 % by weight, preferably from 5 to 30 % by weight, more preferably from 10 to 20 % by weight, of a water-miscible cosolvent or a mixture of water-miscible cosolvents, based on the total weight of the polymer dispersion.

[0071] The water-miscible cosolvent c) is preferably selected from the group consisting of short-chain alcohols, dialcohols, trialcohols, glycols and glycol ethers, ketones, ethers, glycerol and a mixture thereof.

[0072] Preferably, the water-miscible cosolvent c) is preferably selected from the group consisting of methanol, ethanol, n-propanol or iso-propanol, 1 ,3-propanediol, 1 ,2-propanediol, neopentyl glycol, glycerol, ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, polyethylene glycol having an average molar mass of up to 600 g / mol, glycol ethers such methyl glycol, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monobenzyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, butyl diglycol, 1-methoxy-2-propanol, ethoxypropanol, propylene glycol monobutyl ether, dipropylene glycol methyl ether, polyalkylene glycol ether of the general formula CnH2n+i(OCH2-CH2)mOH with n = 0 to 5 and m = 0 to 20, ethylene glycol dimethyl ether, acetone, methyl ethyl ketone, 1 ,4-dioxane, or a mixture thereof. More preferred water-miscible cosolvent is selected from the group consisting of ethanol, ethylene glycol, dipropylene glycol methyl ether, or a mixture thereof. Most preferred water-miscible cosolvent c) is dipropylene glycol methyl ether.

[0073] Water: component d) of the polymer dispersion according to the invention

[0074] According to the present invention, the polymer dispersion comprises water.

[0075] Preferably, the amount of water is chosen to adjust the total amount of polymer dispersion to 100 % by weight of the total weight of the polymer dispersion, once the components a), b), c) and any other optional components are added to the polymer dispersion. Once the components a), b), c), as well as any optional components, preferably component e) and / or f), have been added to the polymer dispersion, the remaining amount to sum up to 100 % by weight of the total weight of the polymer dispersion is water.

[0076] Emulsifier e)

[0077] According to a preferred aspect of the present invention, the polymer dispersion may further comprise an emulsifier e) which does not belong to the group of the sulfosuccinates. The emulsifier e) is thus different from the emulsifier b). The emulsifier e) can be an ionic or a non-ionic emulsifier, or a mixture thereof.

[0078] Example for a non-ionic emulsifier e) is an alkoxylated alcohol or a mixture thereof. Preferably the non-ionic emulsifier e) is an ethoxylated or propoxylated fatty alcohol or a mixture thereof. The ionic emulsifier (e) is preferably an alkylcarboxylate, alkylbenzolsulfonate, alkylsulfonate, a fatty alcohol sulfate, an alkoxylated fatty alcohol sulfate, alkylethersulfate, or a mixture thereof.

[0079] Preferably, the polymer dispersion according to the present invention, comprises from 0 to 10 % by weight, preferably from 0.5 to 5 % by weight, of one or more sulfosuccinate emulsifier e), based on the total weight of the polymer dispersion.

[0080] Further additives f)

[0081] According to a preferred aspect of the present invention, the polymer dispersion may further comprise an additive f) selected from the group consisting of scale inhibitors, corrosion inhibitors, oxygen scavengers, biocides, emulsion breakers, antifoam agents, drag reducing agents, hydrate inhibitors, paraffin dispersants, asphaltene control agents, a pour point depressant other than copolymer a), or a mixture thereof.

[0082] Preferably, the polymer dispersion comprises from 0 to 20 % by weight of an additive f), preferably from 0.1 to 15 % by weight, more preferably from 1 to 10 % by weight, based on the total weight of the polymer dispersion. Process for preparing the polymer dispersion according to the invention

[0083] The present invention also relates to a process for preparing the polymer dispersions as defined herein.

[0084] The inventors have found, that when a small amount of monomer a3) as defined in claim 1 is used as part of the monomer composition to prepare the copolymer a), then the resulting dispersions show less variations in product quality, resulting from batch to batch variations as well as variations in the process conditions, which makes the process more robust. Examples for variations in the process conditions are variations of the stirring speed, reactor size and / or stirrer geometry. This is a huge advantage compared to the state of the art as described for example in US 7,790,821 or WO 2021 / 191349 A1 , especially when it comes to upscaling of the process to commercial scale. A robust process, which leads to a stable product in a wide range of process conditions is crucial, because it is usually not possible to mimic exactly the same conditions when the process is transferred from lab scale to intermediate scale-up and finally to commercial scale.

[0085] According to the present invention, the process for preparing the polymer dispersion as defined in the invention comprises the following steps: i) providing a mixture of water d) and cosolvent c) ii) adding a monomer composition comprising monomers a1), a2), a3) and any other optional monomers as defined above to the mixture i) iii) polymerizing the mixture of step ii) by free-radical emulsion polymerization to obtain the polymer dispersion according to the invention.

[0086] The polymer a) of the polymer dispersion according to the present invention can be obtained by free-radical emulsion polymerization. More preferably, the polymer a) of the polymer dispersion according to the present invention is prepared by free-radical emulsion polymerization. Most preferably, the free-radical emulsion polymerization is done in a mixture of water and a water-mixable cosolvent as external phase.

[0087] Initiators used for the radical polymerization are preferably selected from the group consisting of peroxides, organic hydroperoxides, peracids, peroxydisulfates, azo initiators or a mixture thereof.

[0088] Initiators ("radical initiators") are known from the prior art. The radical initiators in the context of the invention that can be used are all commercially available initiators, for example azo compounds such as N,N- azobisisobutyronitrile (AIBN) and peroxides or peroxide derivatives, it being possible to use them individually or in a mixture. Examples of suitable peroxides or peroxide derivatives are benzoyl peroxides, such as dibenzoyl peroxide (BPO), dicumyl peroxide, tert-butyl cumyl peroxide, lauroyl peroxide, tert-butyl perbenzoate, tert-butyl peroxy-2-ethylhexanate and / or tert-butylperoxy isopropyl carbonate, or peracids, organic hydroperoxides or peroxydisulfates.

[0089] Preference is given to using radical initiators which are soluble in water or in a mixture of water and cosolvent, such as, for example, potassium peroxydisulfate, sodium peroxydisulfate, ammonium peroxydisulfate, 2,2‘- azobis(2-methylpropionamidine) dihydrochloride, hydrogen peroxides or other hydroxy peroxides. Besides a thermal initiation of initiator decomposition, it is also possible to initiate initiator decomposition by a redox reaction (so-called redox polymerization) or by a UV initiator.

[0090] Most preferably, sodium peroxydisulfate (NaPS), potassium peroxydisulfate (KPS), ammonium peroxydisulfate (APS), or a mixture thereof, are used as free-radical initiator.

[0091] Preferably, the monomer mixture to prepare the copolymer a) of the present invention may comprise 0.05 to 7 % by weight, preferably 0.1 to 5 % by weight and more preferably 0.2 to 1 % by weight of initiator based on the total weight of the monomer composition.

[0092] Furthermore, a chain transfer agent can optionally be used and is preferably added with the mixture of step ii). It is well-known in the art that a good way to control the molecular weight of a polymer chain is to use chain transfer agents during the polymerization synthesis. Chain transfer agents are molecules with a weak chemical bond which facilitate the chain transfer reaction. During the chain transfer reaction, the radical of the polymer chain abstracts a hydrogen from the chain transfer agent, resulting in the formation of a new radical on the sulfur atom of the chain transfer agent capable of further propagation. Common chain transfer agents are organic compounds comprising SH groups such as n-butyl mercaptan, n-octyl mercaptan, n- dodecyl mercaptan, tert-dodecyl mercaptan, butylthiol glycolate, and octylthiol glycolate. A preferred chain transfer agent is selected from n-dodecyl mercaptan, tert-dodecyl mercaptan or a mixture thereof, most preferably n-dodecyl mercaptan.

[0093] The amount of chain transfer agents to prepare the copolymer (a) is preferably in the range of 0 to 5 % by weight, more preferably 0.01 to 5 % by weight, even more preferably 0.05 to 4 % by weight, most preferably 0.1 to 1 % by weight, based on the total weight of the monomer composition.

[0094] The polymerization may be carried out at standard pressure, reduced pressure, or elevated pressure. The polymerization can be carried out within a temperature range from 0°C to 100 °C, preferably from 30 °C to 100 °C, more preferably from 60 to 90 °C, most preferably at 80 °C. The reaction time is preferably from 0.5 to 5 hours.

[0095] Optionally, the pH of the monomer composition before the polymerization can be adjusted. For pH regulation, a buffer substance, such as, for example, sodium tetraborate, sodium carbonate or acetate buffer, or a base, for example sodium hydroxide solution, ammonia solution, or an organic base e.g. triethanolamine, can be added before the radical polymerization is started or when the polymerization is already running. Preferably sodium carbonate (water free or in hydrated form such as decahydrate) is used to adjust the pH of the mixture of step ii) before starting the radical polymerization. More preferably, the pH of the polymer dispersion according to the invention is within the range of 0 to 7, preferably within 2 to 5, most preferably 2.5 to 4.

[0096] The preparation of the dispersions can be carried out batchwise in a so-called batch process, in a feed process (so-called semi-batch process or fed-batch process), or via a continuous process. Preferably, the preparation is carried out via a batch or semi-batch process. Most preferably the preparation carried out via a batch process.

[0097] A radical initiator is either added before the polymerization of step iii) or during the polymerization of step iii). It is also possible to first add a portion of the initiator before the polymerization of step iii) and feed the remaining amount of initiator during the polymerization of step iii). Preferably the initiator is added from the beginning of the free radical polymerization of step iii) over a period of less than 30 minutes, more preferably less than 15 minutes, most preferably over a period of less than 5 minutes.

[0098] Optional post-modification(s) of the polymer dispersion:

[0099] After the preparation steps above to prepare the polymer dispersion according to the invention, some optional additional steps can be conducted, namely, a pH adjustment step and / or a dilution step as described hereinbelow:

[0100] Optional pH adjustment step:

[0101] After step iii), an optional additional step can be conducted, wherein the pH of the polymer dispersion according to the invention is adjusted to a pH according to the requirements of the final application. Adjustment of the pH can influence the stability of the polymer dispersion or reduce corrosion that might be caused by the acidic dispersion. Preferably, the pH value is adjusted to a pH value of 6 to 14, more preferably to a pH value of 6.8 to 7.2, even more preferably 7.

[0102] Neutralization can be done by different bases, e.g. sodium hydroxide solution, ammonia solution, or an organic base (e.g. triethanolamine or 2-amino-2-methyl-1 -propanol). pH adjustment using organic bases is preferred, as it was surprisingly found, that this kind of bases leads to polymer dispersions having similar viscosity as before the pH adjustment, while neutralization with e.g. sodium hydroxide or ammonia solution can lead to a significant increase of the viscosity of the polymer dispersion. Most preferred organic base is triethanolamine.

[0103] Optional dilution step:

[0104] The polymer dispersion according to the invention obtained after the emulsion polymerization process of step iii) has preferably a pour point (PP) value of less than 0 °C, more preferably less than minus 10 °C (-10 °C), which is an important property for the application in the winter season or cold climate areas. For very extreme temperature conditions, the PP can be further reduced by adding additional amounts of a cosolvent g), which is water miscible. This optional dilution step is conducted with or without a pH adjustment step as described above. As the dilution reduces the active polymer content of the final formulation, the amount of added solvent can be adjusted, to achieve the required PP value of the polymer dispersion, but keeping the polymer content as high as possible. The solvent g) used for the post-dilution can either be the same as used in the polymerization process as component c) or can be different. Most preferred solvent g) to be used for the post dilution is selected from dipropylene glycol ether, ethylene glycol, ethanol, methanol or a mixture thereof. Typically, the weight ratio of polymer dispersion obtained after of step iii) to the additional cosolvent g) is from 90:10 to 30:70, preferably the ratio is between 85:15 to 40:60, most preferably the weight ratio is from 80:20 to 50:50.

[0105] Crude oil composition

[0106] The present invention also relates to a crude oil composition comprising the polymer dispersion according to the present invention as defined above and a crude oil.

[0107] In the context of the present invention, the term “crude oil” or “waxy crude oils and condensates” is equally defined as the crude oil that contains high amount of long chain paraffin wax (alkanes) compounds, making the crude oil possess a high pour point and become viscous at lower temperatures than wax appearance temperatures.

[0108] Preferably, the amount of polymer dispersion in the crude oil composition is from 0.005 to 2 % by weight, more preferably 0.01 to 1 % by weight, even more preferably 0.01 to 0.2 % by weight, based on the total weight of the crude oil composition.

[0109] The crude oil composition according to the invention may also contain further additives used in crude oil production. Typical additives are scale inhibitors, corrosion inhibitors, oxygen scavengers, biocides, emulsion breakers, antifoam agents, drag reducing agents, hydrate inhibitors, paraffin dispersants, asphaltene control agents, a pour point depressant other than copolymer a), or a mixture thereof.

[0110] Use of the polymer dispersions according to the invention as paraffin inhibitor for crude oils

[0111] The invention also relates to the use of a polymer dispersion according to the present invention for inhibiting the deposition of paraffins in a crude mineral oil and / or reducing the pour point of a crude mineral oil and / or for reducing the viscosity of a crude mineral oil, by adding said polymer dispersion to said crude oil.

[0112] Method of improving the transport or storage of a crude oil

[0113] The invention also relates to a method of improving the transport or storage of a crude oil comprising the step of adding a polymer dispersion according to the invention to said crude oil.

[0114] Advantageously, as exemplified in the experimental part, the polymer dispersions according to the invention allow to lower the pour point, wax deposition and viscosity of a crude oil in comparison to the same untreated crude oil. Crude oils usually solidify making them difficult to transport. In contrast, crude oils treated with the polymer dispersions according to the invention reach a lower pour point and remain liquid at lower temperatures, thus making them easier to transport because heat does not need to be applied to the crude oil before transportation and storage. Another issue is that the long chain paraffins tend to deposit on cold surfaces, e.g. the surface of an oil pipeline, which over time reduces the effective inner diameter of the pipeline. The polymer dispersion according to the invention allows to reduce the amount of deposited solid wax from a crude oil in comparison to the same untreated crude oil, as exemplified in the experimental part below.

[0115] EXPERIMENTAL PART

[0116] The invention is further illustrated in detail hereinafter with reference to examples and comparative examples, without any intention to limit the scope of the present invention.

[0117] List of abbreviations:

[0118] AA: Acrylic Acid

[0119] BEA: Behenyl acrylate (mixture of acrylates with linear alkyl side chains, chain length mainly from Ci a to C22)

[0120] Comp.: Comparative example

[0121] CTA: Chain Transfer Agent

[0122] DPM: Dipropylene glycol methyl ether

[0123] Ex.: Example

[0124] GPC: Gel permeation chromatography

[0125] INTERMIG: Interference multi-stage counter-current stirrer

[0126] Inv.: Example according to invention

[0127] KPS: Potassium peroxydisulfate

[0128] MEG: Monoethylene glycol

[0129] MIG stirrer: Multi-stage pulse counter-current stirrer

[0130] Mn: Number average molecular weight

[0131] Mw: Weight average molecular weight

[0132] NaPS: Sodium peroxydisulfate n.d.: Not determined

[0133] PE: Polyethylene

[0134] PMMA: Poly methyl methacrylate

[0135] PP: Pour point

[0136] PPD: Pour point depressant rDNc: Mean particle radius of the polymer particles in the polymer dispersion measured by dynamic light scattering.

[0137] Rl: Refractive index

[0138] Rpm: Rounds per minute

[0139] SMA: Stearyl methacrylate (mixture of methacrylates with linear alkyl side chains, chain length mainly from C16 to Cis)

[0140] SMA ratio: SMA weight ratio in polymer (related to sum of all monomers)

[0141] TEA: Triethanolamine

[0142] THF: Tetra hydrofuran

[0143] WAT: Wax appearance temperature w / '. with w / o: without methods:

[0144] So / ids content determination:

[0145] 1-2 g of polymer dispersion was weighed in an aluminum petri dish and dried to constant weight in a vacuum drying oven at 70°C for 2 days. Afterwards the solid content was calculated:

[0146] Solid content (weight %) = (Net weight of the dried polymer / Net weight of the initial polymer dispersion) x 100

[0147] Filter residue:

[0148] The dispersion was filtered through a filter “E-D-Schnellsieb” (nylon fabric, super-fine, 125 pm) to remove small amounts of coagulate eventually formed during the process.

[0149] To quantitatively determine the amount of clot, the weight increase of the filter after filtration was analyzed and calculated as weight % filter residue relative to the total weight of filtered dispersion. In most cases where the filter residue was <0.5wt%, no significant amount of coagulate was present in the filter and the filter residue was mainly related to the weight increase by wetting of the filter material by small portions of dispersion.

[0150] Brookfield viscometry:

[0151] The polymers were adjusted in temperature to 23°C in a constant-temperature water bath, and dynamic viscosity was measured using a Brookfield rotary viscometer LVT DV II with guard leg at a rotational speed of 60 rpm with spindle I. pH value:

[0152] The pH value was measured using the pH meter Calimatic 761 from Knick, comprising a pH / Pt-100 glass combination electrode with ceramic diaphragm and 3 M KCI filling.

[0153] Determination of particle size:

[0154] Mean particle size of the particles in the polymer dispersion was measured using the Delsa Nanosizer from Beckmann Coulter. Mean particle size is provided as mean particle radius (rDNc). The sample was diluted with distilled water before measurement. Refractive index of water was used as the refractive index of the external phase.

[0155] Molar mass distribution by means of GPC:

[0156] The polymers (approx. 1-2 g) were dried in a vacuum drying oven at 70°C for 2 days. Molar mass distribution was ascertained on the dried polymers by means of GPC (polymer standard for calibration: polymethylmethacrylate (PMMA)). The weight-average and the number-average molar mass (Mwand Mn) of the polymers were determined therefrom. In the present invention, the weight-average molecular weights (Mw) and the number-average molecular weights (Mn) of the polyalkyl(meth)acrylates (copolymer (a)) were determined by gel permeation chromatography (GPC) using poly(methyl-methacrylate) calibration standards according to DIN EN ISO 13885-1 using the following measurement conditions:

[0157] Column set: the column set consists of a precolumn and 4 SDV columns as disclosed in Table 1 :

[0158] Table 1 :

[0159] Instruments: Agilent 1100 Series Pump; PSS SECcurity Inline-Degaser; Agilent 1100 Series Autosampler; Agilent 1260 Series Rl-Detector; Agilent 1260 Series System Pilot; PSS SECurity column oven;

[0160] Oven temperature: 35°C;

[0161] Standards: poly(methyl-methacrylate) (so called PMMA) calibration standards PSS (Mainz);

[0162] Eluent: tetrahydrofuran (THF) + 0.2 vol% trifluoroacetic acid;

[0163] Flow rate: 1 mL / min;

[0164] Injected volume: 100 pL;

[0165] Detection: Rl at a temperature of 35°C.

[0166] Concentration sample solution: 2 g / L

[0167] Concentration PMMA standard solutions: 1 g / L (for Mw >106: 0.5 g / L)

[0168] Internal Standard: 1 ,2-dichlorobenzene 0.2 pL to 99.8 pL sample solution

[0169] Skin formation rating after 4 weeks:

[0170] To evaluate the storage stability of the dispersion with respect to phase separation, the dispersions were stored in 250 mL- or 500 mL-bottles (wide necked, glass or PE) with a filling degree of approx. 90% at room temperature. During the period of investigation the bottles should not be moved. After 4 weeks the texture of the surface of the dispersion was controlled by inserting a glass rod and judged according to the following rating:

[0171] 0 = completely liquid no indication of any inhomogeneity on the surface of the dispersion.

[0172] 1 = slightly marbled or slimy surface

[0173] 2 = very thin skin formed on the surface

[0174] 3 = skin formed on the surface

[0175] 4 = thick skin (several mm) formed on the surface

[0176] 5 = very thick skin, large part of the dispersion is solid

[0177] Centrifuge Test:

[0178] In addition to the skin formation tests described above, a centrifuge test was performed to evaluate the accelerated phase separation tendency of the dispersion. This test leads to faster results (2 hours instead of several weeks) compared to the skin formation test and provides an indication for storage stability for storing periods of more than 4 weeks.

[0179] The dispersion sample is centrifuged in three runs under the following parameters:

[0180] Device: Centrifuge Universal 1200, from Hettich

[0181] Centrifuge tube: 50 mL, round bottomed, DURAN

[0182] Speed: 3900 rpm (g-force: approx. 2200 g)

[0183] Temperature: 30°C

[0184] Sample weight: approx. 20-25 g

[0185] 1st run: 20 min

[0186] 2nd run: 40 min

[0187] 3rd run: 60 min

[0188] (total centrifuge time = 120 min)

[0189] After every run the surface of the sample was optically judged after tilting the centrifuge tube by 90°.

[0190] Rating: Description:

[0191] 100 no change

[0192] 90 marbled surface, flows immediately

[0193] 80 thin film on surface, but sample flows directly by tilting

[0194] 60 sample flows after 1-2 s

[0195] 40 sample flows after 2-5 s

[0196] 20 sample flows after 5-10 s

[0197] 0 sample needs > 10 s to flow

[0198] After the judgement, the same sample is used for the next run. The points received in each run are summarized to the final centrifuge score (0 and 300 points).

[0199] In most cases the centrifuge test and the skin formation rating show a similar trend. To make sure, to have a good dispersion stability with respect to phase separation, it is desired, that both tests show good results (skin formation rating of 2 or lower and a centrifuge rating of 200 points or higher).

[0200] Synthesis of the polymer dispersions

[0201] Inventive examples 1 to 12 and comparative examples Comp. 1 to Comp. 4: (Reactor A)

[0202] 1 L double jacket reactor fitted with reflux condenser, propeller stirrer, stirrer motor, and circulating constanttemperature bath, Testo data logger with Pt100 digital thermometer for temperature measurement in the reactor and in the circulating constant-temperature bath. The reaction was carried out under a nitrogen atmosphere (nitrogen flow rate ~6 L / h), with the nitrogen being conducted below the liquid surface by means of a glass tube. Step 1 . Behenyl acrylate (BEA) was melted beforehand in a drying cabinet at 60°C.

[0203] Step 2. A mixture of water, sodium carbonate decahydrate, dipropylene glycol methyl ether (DPM) and emulsifier was added to the reactor adjusted in temperature to 50°C, and was heated to 50°C under stirring. Immediately after filling, the inertization with nitrogen was started.

[0204] Step 3. The other monomers (AA and SMA) and dodecyl mercaptan were dissolved in the melted BEA and filled into the reactor. The mixture was adjusted in temperature to 80°C, and the initiator solution consisting of the radical initiator (NaPS or KPS) in water was subsequently metered in within one minute. The mixture was stirred at 80°C for 2 h and then cooled to room temperature.

[0205] The dispersion was filtered through a filter “E-D-Schnellsieb” (nylon fabric, super-fine, 125 pm) to remove small amounts of coagulate eventually formed during the process.

[0206] The used amounts of raw materials, process conditions and analytical characteristics of the resulting polymer dispersions for the different examples are summarized in table 2 and 3.

[0207] Aerosol® OT75 (sodium bis(2-ethylhexyl) sulfosuccinate, 75% in ethanol / water mixture) was used as surfactant, BEA (behenyl acrylate; BASF BEA 1822F), SMA (stearyl methacrylate; Visiomer® C17.4MA) and AA (Acrylic Acid, Sigma Aldrich) have been used as monomers.

[0208] NaPS (Sodium peroxydisulfate) or KPS (potassium peroxydisulfate) have been used as radical initiators and n-dodecyl mercaptan was used as chain transfer agent (CTA).

[0209] Table 2: Raw materials and process conditions for inventive examples 1 to 12 and comparative examples Comp. 1 to Comp. 4.

[0210]

[0211] SMA weight ratio in polymer (related to sum of all monomers)

[0212] Table 3: Analytical results of inventive examples 1 to 12 and comparative examples Comp. 1 to Comp. 4.

[0213] Comparative examples Comp.5 to Comp.16: (Reactor A w / o SMA) Experiments have been performed like described for examples 1 to 12 and comparative examples Comp.1 to Comp.4, but no SMA was used in the monomer mixture. The used amounts of raw materials, process conditions and analytical characteristics of the resulting polymer dispersions for the different examples are summarized in table 4 and 5.

[0214] Table 4: Raw materials and process conditions for comparative examples Comp.5 to Comp.16 (w / o SMA)

[0215] Table 5: Analytical results of comparative examples Comp.5 to Comp.16 (w / o SMA) Inventive examples 13 to 19: (Reactor B):

[0216] Experiments have been performed like examples 1 to 12 and comparative examples Comp.1 to Comp. 4, but in a 3 L double jacket reactor with a INTERMIG - stirrer instead of a propeller stirrer. Stirring speed has been adjusted to have a similar stirring intensity like for the propeller stirrer in the 1 L reactor. The nitrogen flow rate has been adjusted to the larger reactor volume [~18 L / h]. The used amounts of raw materials, process conditions and analytical characteristics of the resulting polymer dispersions for the different examples are summarized in table 6 and 7 below.

[0217] Comparative examples Comp.17 to Comp.29: (Reactor B, w / o SMA)

[0218] Experiments have been performed like examples 13 to 19 but no SMA was used in the monomer mixture. The used amounts of raw materials, process conditions and analytical characteristics of the resulting polymer dispersions for the different examples are summarized in Tables 8 and 9 below.

[0219] Table 6: Raw materials and process conditions for inventive examples 13 to 19 Table 7: Analytical results of inventive examples 13 to 19

[0220] Table 8: Raw materials and process conditions for comparative examples Comp.17 to Comp.29

[0221] Table 9: Analytical results of comparative examples Comp.17 to Comp.29

[0222] Comparative examples 30 and 31 according to example 1 of US 7790821

[0223] Experiments were performed using the same equipment and nitrogen flow rate as described for examples 1 to 12 with a propeller stirring speed of 200rpm.

[0224] 220 g of demineralized water, 2 g of sodium tetraborate, 80 g of monomethyl ether dipropylene glycol (Dowanol™ DPM from Dow), and 10 g of sodium bistridecyl sulfosuccinate (Aerosol TR70 by Cytec) were added into the reactor.

[0225] Once the temperature of 50° C. was reached, a mixture of 169 g of behenyl acrylate (BEA) for comparative example 30 or behenyl methacrylate (BEMA) for comparative example 31 , and 0.5 g of n-dodecyl mercaptan, previously melted at 50° C., are added, and the mixture is brought to 80° C.

[0226] Then, within one minute, a solution of 1 g of potassium persulfate is introduced into 20 g of demineralized water. After the exothermic peak, the reaction is allowed to take place for 2 hours, then it is cooled to room temperature.

[0227] The dispersion was filtered through a filter “E-D-Schnellsieb” (nylon fabric, super-fine, 125 pm) to remove small amounts of coagulate eventually formed during the process.

[0228] Although dispersions made from BEA or BEMA as monomer can be prepared in accordance with example 1 of US 7,790,821 B2, they contain large amounts of coagulate leading to a high filter residue and are very difficult to filter, this being unfavourable for commercial use. In comparative example 30, there was even the occurrence of a complete coagulation of the dispersion after only a few days of storage at room temperature. Therefore, no solid content and particle sizes have been determined for example 30. The analytical characteristics of the resulting polymer dispersions are summarized in Table 9a below. Table 10a: Analytical results of comparative examples Comp.30 and 31

[0229] Inventive example 20 to 22: (Reactor A)

[0230] Experiments have been performed like examples 1 to 12, except that the single monomers and the CTA have been added to the reactor separately instead of doing a premix, and the initiator solution was added over a period of 5 instead of 1 min.

[0231] The used amounts of raw materials, process conditions and analytical characteristics of the resulting polymer dispersions for the different examples are summarized in table 10 and 1 1 . Inventive examples 23 to 24: (Reactor B)

[0232] Experiments have been performed like examples 20 to 22, but in a 3 L double jacket reactor with a INTERMIG - stirrer instead of a propeller stirrer. Stirring speed has been adjusted to have a similar stirring intensity like for the propeller stirrer in the 1 L reactor. The nitrogen flow rate has been adjusted to the larger reactor volume [~18 L / h]. The used amounts of raw materials, process conditions and analytical characteristics of the resulting polymer dispersions for the different examples are summarized in table 12 and 13.

[0233] Table 11 : Raw materials and process conditions for inventive examples 20 to 22

[0234] Table 12: Analytical results of inventive examples 20 to 22

[0235] 5 Table 13: Raw materials and process conditions for inventive examples 23 to 24.

[0236] Table 14: Analytical results of inventive examples 23 to 24

[0237] Inventive examples 25 to 33: (Reactor C)

[0238] Experiments have been performed like examples 23 to 24, but in a 10 L stainless steel reactor with a MIG - stirrer instead of a propeller stirrer. Nitrogen wa conducted above instead of below the liquid surface by means of a glass tube and counter cooling of the reaction was done, when the reaction reached it exothermic phase. Stirring speed has been adjusted to have similar stirring intensity like for the propeller stirrer in the 1 L reactor.

[0239] The used amounts of raw materials, process conditions and analytical characteristics of the resulting polymer dispersions for the different examples are summarize in table 14 and 15.

[0240] Table 15: Raw materials and process conditions for inventive examples 25 to 33

[0241] Table 16: Analytical results of inventive examples 25 to 33

[0242] ‘Examples 29 to 33 have been combined and mixture filtered using a pilot scale filter with a 450 mm diameter and a mesh size of 125 pm and filter residue was determined from this filtration. For evaluating other parameters of the single batches (pH, TONC etc.), a small portion of each example filtered through filter “E-D-Schnellsieb” (nylon fabric, super-fine, 125 pm).

[0243] Inventive example 34:

[0244] The dispersions according to examples 29 to 33 have been combined and filtered through a 450 mm diameter pilot scale filter with a mesh size of 125 pm. The resulting mixture is called inventive example 34. Analytical characteristics are summarized in Table 16 below.

[0245] Table 17: Analytical results of Inventive example 34

[0246] Result discussion related to the synthesis of the polymer dispersion (examples 1 to 34 and examples Comp. 1 to Comp.29):

[0247] Examples 1 to 12, which contain monomer a3) in the monomer composition of the polymer within the range of the present invention, show a good combination of low particles size (rDNc) of <220 nm, a low skin formation rating (<2) and a high centrifuge rating of >200. All 3 parameters are indicators for a good storage stability of the dispersion without a tendency of agglomeration or destabilization by phase separation. In addition, they show a very good performance as pour point depressant and paraffin inhibitor in crude oils, as can be seen in Tables 27 to 32. Even examples Comp. 1 to Comp. 4, which contain monomer a3) in the monomer composition of the polymer outside of the amounts according to the present invention, show acceptable performance with respect to particle size (rDNc), skin formation rating and centrifuge tests (as can be seen in Table 3), the performance of the polymer dispersion as pour point depressant or paraffin inhibitor in crude oils, is not as good as corresponding polymer dispersions containing monomer (a3) in the monomer composition of the copolymer in an amount according to the invention (see table 29 and 31).

[0248] Same like inventive examples 1 to 12, also inventive examples 13 to 34 using a different reactor size, stirrer geometry or different process conditions show a good combination of low particles size (rDNc) of <220 nm, a low skin formation rating (<2) and a high centrifuge rating of >200. This high consistency of polymer dispersion stability is an important aspect, especially for transferring to a large scale commercial process.

[0249] In contrast to the examples according to the invention, none of the comparative examples (Comp.5 to Comp.29) that do not contain a monomer (a3) in the monomer composition of the copolymer shown in table 4, 5, 8 and 9, is able to achieve a good combination of low particles size (rDNc) of <220 nm, a low skin formation rating (<2) and a high centrifuge rating of >200. All 3 parameters are indicators for a good storage stability of the dispersion without a tendency of agglomeration or destabilization by phase separation. In most cases, none of the 3 criteria can be met, in some cases the resulting dispersions achieved acceptable results in one criteria but failed in the other two and therefore do not fulfill the requirements with respect to product stability.

[0250] Another important aspect is, that the comparative examples, that do not contain a monomer a3) in the monomer composition of the copolymer, show an extremely wide variation of the stability measures (particle size, skin formation rating and centrifuge rating) of the formed polymer dispersion from batch to batch as well as when different reactors, stirrers or process conditions are used and therefore are not considered to be suitable for a transfer to a commercial scale process.

[0251] Pour point measurement of the polymer dispersions:

[0252] To ascertain below which temperature the polymer dispersions become solid without action of a shearing force (e.g. during storage at low temperatures), the pour point of the dispersions was analyzed according to ASTM D6892 and pour point values are reported in 3°C temperature intervals.

[0253] Table 18: Pour point of polymer dispersions

[0254] As can be seen in Table 17, the pour points of the polymer dispersions are significantly lower than corresponding formulations based on polymer solutions in organic solvents, which typically show PP > 0°C at similar polymer content. (PP of corresponding polymer solutions can be found in WO 2021 / 191348 A1). In addition, the dispersion according to the invention even shows a slightly lower pour point as the comparative polymer dispersion Comp.7.

[0255] In case an even lower pour point is needed, the dispersions can be diluted with a suitable water miscible solvent, as can be seen in Table 18 below.

[0256] Table 19: Pour point of mixtures polymer dispersion with different water mixable solvents.

[0257] DPM: dipropylene glycol methyl ether; MEG: Monoethylenglycol

[0258] * Dispersion was still liquid at the lowest temperature, that was reached by the device

[0259] Rheological tests:

[0260] To show the flow behavior during later application at different temperatures, rheological measurements were carried out as a function of temperature. To simulate the shearing strain on the polymer dispersions during application into a well, for example when metering in via a supply line. The change in viscosity as a function of temperature was measured using rheometer with plate-on-plate geometry. Measurements were carried out at a constant shear rate of 100 s-1and a cooling rate of 1 K / min.

[0261] As can be seen in Figure 1 , the viscosity of the dispersions remains relatively low down to temperatures of less than minus 10°C (-10°C). At a certain temperature around -15 to -18°C, there is a steep increase in the viscosity. At this temperature, the dispersion becomes solid. As can be seen, this temperature is in a similar temperature range, then the PP values of the corresponding dispersion shown in Table 17. The solidification temperature of the dispersion mainly is related to the freezing temperature of the solvent mixture used as external phase of the dispersion. If needed this freezing temperature can be shifted to lower temperatures by the addition of a water mixable cosolvent, as can be seen from the shift in the PP shown in Table 18. Storage tests of dispersion:

[0262] Storage stability during cold and warm cycling:

[0263] This test was used to determine if the dispersions can resist temperature changes without destabilization (coagulation) of the dispersions. This is important, e.g. if the dispersions are stored outside in cold environments, as especially freezing of a dispersion often leads to a full coagulation.

[0264] Samples of 245 g each were weighed in 250 ml PE wide-neck bottles and cooled to -20°C in a freezer. After 16 h at this temperature, thawing was carried out at 23°C for 4 h in a constant temperature bath and the dispersion were stirred using a propeller stirrer (500 rpm) for 30 min.

[0265] Thereafter, an optical check for coagulate, specks and inhomogeneity was carried out, the polymers were filtered across a sieve fabric (Schnellsieb 125 pm) and the coagulate was weighed, if present in the filter. After a further 2 h of holding the temperature at 23°C, Brookfield viscosity and particle size were determined. This cycle of freezing and thawing was repeated 5 times.

[0266] Some of the samples that have been solid / frozen after the cold storage, have been slightly viscous after the thawing, but simple stirring was sufficient, to fully recover the original dispersion consistency.

[0267] As can be seen in table 19 below, dispersion according to the invention in pure form as well as dilutions with water mixable solvents, can withstand several temperature cycles w / o indications of destabilization.

[0268] Cold and warm cycling tests have also been done for corresponding dispersions that have been neutralized with Triethanolamine (TEA) to a pH value of 7.0. Dispersions have been neutralized using a mixture of 50% by weight of TEA and 50% by weight of water.

[0269] As can be seen in table 20, also dispersions that have been neutralized to a pH of 7 can withstand several temperature cycles w / o indications of destabilization. The particle size slightly increased due to the change in pH value, but particle size did not change significantly during the test cycles and the slightly larger particle size of the neutralized dispersion did not negatively affect the stability. Same like for the dispersions shown in table 19, dilution with a water miscible cosolvent does not negatively affect the stability.

[0270] able 20: Summary of the results of the cold and warm cycling test

[0271]

[0272] Table 21 : Summary of the results of the cold and warm cycling test for dispersions neutralized with Triethanolamine (TEA)

[0273] Storage stability at 23 °C, 30 °C and 50 °C for 6 months:

[0274] Samples of 245 g each were weighed in 250 ml PE wide-neck bottles and stored at 23, 30 or 50°C. After one week and after 1 , 3 and 6 months, the polymer dispersions were stirred using a propeller stirrer (500 rpm) for 30 min and optically checked for coagulate, specks and inhomogeneity. Thereafter, the dispersions were filtered across a sieve fabric (Schnellsieb 125 pm) and in case coagulate present, it was weighed. After 2 hours of holding the temperature at 23°C in a water bath, Brookfield viscosity and particle size were determined.

[0275] Results are summarized in Tables 21 to 23. As can be seen, the pure dispersion as received from inventive example 34, as well as corresponding mixtures with different water mixable solvents show good storage stability at different temperatures over a period of several months. Filtration of the dispersions showed in most cases no coagulate in the filter, in few cases low amounts of remaining coagulate. In addition, within the error of the methods, product viscosity and particle size remain unchanged over the whole storage time, which is a good indication for a high dispersion stability.

[0276] Storage stability was also investigated for dispersions neutralized with TEA to a pH value of 7.0. Dispersions have been neutralized using a mixture of 50% by weight of TEA and 50% by weight of water. Results are summarized in tables 24 to 26. It can be seen that the neutralization of the dispersions does not negatively affect the storage stability. Filtration of the dispersions showed no coagulate in the filter. The particle size slightly increased due to the change in pH value. But within the error of the methods both product viscosity and particle size remain unchanged over the whole storage time, which is a good indication for a high dispersion stability.

[0277] Table 22: Summary of the results of the storage tests at 23 °C

[0278] Table 23: Summary of the results of the storage tests at 30°C

[0279] Table 24: Summary of the results of the storage tests at 50°C

[0280] Table 25: Summary of the results of the storage tests at 23°C for dispersions neutralized with

[0281] Triethanolamine (TEA)

[0282]

[0283] Table 26: Summary of the results of the storage tests at 30°C for dispersions neutralized with

[0284] Triethanolamine (TEA) Table 27: Summary of the results of the storage tests at 50°C for dispersions neutralized with

[0285] Triethanolamine (TEA)

[0286] Performance testing in crude oils:

[0287] 3 different crude oils, as well as a model oil (artificial system based on a mixture of wax in oil), have been used for performance testing.

[0288] Crude Oil A has a wax appearance temperature (WAT) of 23°C, a wax content of 5.6% by weight and a pour point of 15°C.

[0289] Crude Oil B has a WAT of 52°C, a wax content of 17.4% by weight and a pour point of 33°C. Crude Oil C has a WAT of 49°C, a wax content of 12.1% by weight and a pour point of 24°C.

[0290] The Model Oil was prepared by mixing 4 g of Sigma Aldrich >65°C paraffin wax and 96 g Holly 100N oil. The components were heated to 80°C and blended for 60 minutes using an overhead stirrer. The resulting blend had a pour point of 33°C and a WAT of 40°C.

[0291] Pour point depression of crude oils:

[0292] To test the effect of the different polymer dispersions as pour point depressant, the pour point of different crude oils with and without addition of the polymers was ascertained in accordance with ASTM D5853.

[0293] The amount of added polymer dispersion is given as ppm of active ingredient calculated based on the solid content of the dispersion (e.g. for 100 ppm polymer added, for a dispersion with 40.0% solid content 250 ppm dispersion are added to the crude oil).

[0294] Results are shown in table 27 to 30.

[0295] Table 28: PP reduction in crude oil Crude Oil A (wax content 5.9%; WAT 23°C)

[0296] ‘Concentration of added polymer was calculated based on the solid content of the corresponding polymer dispersion.

[0297] Table 29: PP reduction in Crude Oil B (wax content 17.4%; WAT 52°C)

[0298] ‘Concentration of added polymer was calculated based on the solid content of the corresponding polymer dispersion. Table 30: PP reduction in crude oil Crude Oil C (wax content 12.1 %; WAT 49°C)

[0299] ‘Concentration of added polymer was calculated based on the solid content of the corresponding polymer dispersion.

[0300] Table 31 : PP reduction in Model Oil (wax content 4%; WAT 40°C)

[0301] ‘Concentration of added polymer was calculated based on the solid content of the corresponding polymer dispersion.

[0302] As can be seen in Tables 27 to 30, the polymer dispersions according to the invention that contain small amounts of SMA as additional building block can achieve at least the same or even better performance as PPD in the tested crude oil compared to the polymer dispersion without any SMA tested in the same crude oil. As can be seen in table 29, if the SMA amount in the polymer is too high, then the performance as PPD is worse. Not only the polymer dispersions according to the invention achieve great stability performance over the time, but also show great result in PP depression. This combination of performance is not achieved by the comparative polymer dispersions. Wax / paraffin inhibition in crude oils:

[0303] To test the effect of the polymer dispersions and solutions as paraffin inhibitors, the so-called cold finger deposition test was carried out. Here, paraffin deposition from crude oil on a cold finger was tested, by comparing the amount of deposition with and without addition of polymer. The amount of added polymer dispersion is given as ppm of active ingredient calculated based on the solid content of the dispersion. From the weighed wax deposits, the wax inhibition was calculated via the following formula:

[0304] Wax inhibition (%) = (wo-Wx) / wo*1 OO where wo corresponds to the weight of wax deposit without addition of polymer and wxcorresponds to the weight of wax deposit with addition of polymer.

[0305] The cold finger deposition test was carried out using a cold finger deposition tester from PSL Systemtechnik (model CF15120).

[0306] Here, 80 mL of the mixture of crude oil + polymer dispersion are heated to the desired bath temperature (e.g. 59°C) and stirred continuously at the same time. The cold finger is immersed into the sample, with the result that the wax present deposits on the finger surface little by little. After a defined time interval of 24 hours, the amount of wax deposited on the cold finger is determined by weighing. The cold finger is kept at a desired finger temperature (e.g. 34°C).

[0307] Table 31 shows the results of the cold finger deposition tests for selected polymer dispersions at a bath temperature of 59°C and a finger temperature of 34°C in Crude Oil C. The wax inhibition was determined after 24 hours.

[0308] Table 32: Wax inhibition in Crude Oil C (wax content 12.1 %, WAT = 49°C) (bath temperature 59°C, finger temperature 34°C)

[0309] Table 32 below shows the results of the cold finger deposition tests for selected polymer dispersion at a bath temperature of 45°C and a finger temperature of 20°C in the Model Oil. The wax inhibition was determined after 24 hours. Table 33: Wax inhibition in Model Oil (wax content 4%, WAT = 40°C) (bath temperature 45°C, finger temperature 20°C)

[0310] As can be seen in table 31 and 32, the polymer dispersions according to the invention that contain small amounts of SMA as additional building block can reduce the wax deposition in different crude oils at least on the same or even better performance level compared to the corresponding dispersion that do not contain SMA. As can be also seen in table 31 , if the SMA amount in the polymer is too high, the wax inhibition performance is reduced. Not only the polymer dispersions according to the invention achieve great stability performance over the time, but also show great result in reducing the paraffin deposition. This combination of performance is not achieved by the comparative polymer dispersions.

[0311] Result discussion

[0312] As shown in the experimental part above, it has been found that water-based polymer dispersions prepared by incorporating a copolymer made out of a monomer combination of a high amount of alkyl acrylate with long side chains of more than 15 carbon atoms with a specific small amount alkyl methacrylate having 8 to 30 carbon atoms, and some acid or acid anhydride monomers, are very stable polymer dispersions. These stability improvements lead to better handling properties while maintaining great cold flow performance even at low temperatures.

[0313] It has been shown that the polymer dispersions according to the invention are easy to filtrate, stay very stable over a long period of time without the formation of coagulates (aggregation of particle) or a thick film at the top of the polymer dispersion, even when stored for a long period of time. The polymer dispersions according to the invention are less sensitive to changes in the process conditions (e.g. changing the batch size, the used reactor, stirrer geometry & stirring speed) during the manufacturing compared to comparative dispersions that do not contain monomer (a3) in the monomer composition. One important aspect is also, that the polymer dispersions according to the invention show much lower batch to batch variation under the same as well as slightly different process conditions compared to the comparative dispersions, that do not contain monomer a3) in the monomer composition. This improvement in robustness is essential for upscaling of the process, as it is usually not possible to retain all process conditions exactly the same when transferring to a different batch size. This is especially advantageous during upscaling of the process to commercial scale, as prediction of suitable process parameters is not trivial, when the process is transferred to a different batch size and reacts very sensitive to changes in the process. As also can be seen in the results, the dispersions according to the invention show at least the same, or even better performance as PPD and paraffin inhibitor when used as additive in different kinds of crude oils, while having great stability and handling properties, what is not observed by the polymer dispersions of the state of the art.

Claims

CLAIMS1 . A polymer dispersion comprising a) from 10 to 70 % by weight, based on the total weight of the polymer dispersion, of a copolymer (a) prepared by polymerizing by emulsion polymerization a monomer composition comprising: a1) from 50 to 94 % by weight of alkyl acrylate of formula (I), based on the total weight of the monomer composition:wherein R1a linear, branched or cyclic alkyl residue with 15 to 40 carbon atoms, a2) from 1 to 8 % by weight of monomer selected from the group consisting of ethy lenically unsaturated monocarboxylic acid, dicarboxylic acid, salt thereof, acid anhydride thereof, or a mixture thereof, based on the total weight of the monomer composition, a3) from 5 to 10.5 % by weight of alkyl methacrylate of formula (II), based on the total weight of the monomer composition,wherein R2is a linear, branched or cyclic alkyl residue with 8 to 30 carbon atoms, b) from 0.5 to 20 % by weight of a sulfosuccinate emulsifier selected from a sulfosuccinate monoester of formula (II), a sulfosuccinate diester of formula (IV) or a mixture thereof, based on the total weight of the polymer dispersion,Sulfosuccinate SulfosuccinateMonoester Diesterwherein, in formula (III) or (IV), M+is H+or a metal ion, R3and R4are independently alkyl, aryl, aralkyl or alkylaryl radicals or R5(O-CH2-CH2)n, wherein R5is an alkyl, aryl, aralkyl or alkylaryl radical, and n = 1 to 30,c) from 1 to 40 % by weight of a water-miscible cosolvent or a mixture of multiple water-miscible cosolvents, based on the total weight of the polymer dispersion, and d) water.

2. The polymer dispersion according to claim 1 , wherein in formula (I) of the alkyl acrylate a1), the residue R1is a linear, branched or cyclic alkyl residue with 16 to 30 carbon atoms, preferably with 18 to 22 carbon atoms.

3. The polymer dispersion according to claim 1 or 2, wherein in formula (II) of the alkyl methacrylate a3), the residue R2is a linear, branched or cyclic alkyl residue with 12 to 22 carbon atoms, preferably with 15 to 20 carbon atoms.

4. The polymer dispersion according to any one of the previous claims, wherein the monomer composition of the copolymer a) comprises from 6 to 10 % by weight, preferably from 7 to 9.5 % by weight, of alkyl methacrylate a3) of formula (II), based on the total weight of the monomer composition.

5. The polymer dispersion according to any one of the previous claims, wherein the monomer composition of the copolymer a) further comprises a monomer a4) selected from Ci to C5 acrylates, Ci to C7 methacrylates, or a mixture thereof.

6. The polymer dispersion according to any one of the previous claims, wherein the monomer composition of the copolymer a) further comprises a monomer a5) selected from 2-hydroxyethyl (meth)acrylate, N-(3-dimethyl-aminopropyl)methacrylamide, 3-diethylaminopentyl (meth)acrylate, or a mixture thereof.

7. The polymer dispersion according to any one of the previous claims, wherein the alkyl acrylate a1) of formula (I) is selected from the list consisting of stearyl acrylate, eicosyl acrylate, docosyl acrylate, or a mixture thereof.

8. The polymer dispersion according to any one of the previous claims, wherein the alkyl methacrylate a3) of formula (II) is selected from the list consisting of behenyl methacrylate, stearyl methacrylate, or a mixture thereof.

9. The polymer dispersion according to any one of the previous claims, wherein the weight-average molecular weight of the copolymer a) is from 10,000 to 250,000 g / mol, more preferably from 30,000 to 200,000 g / mol, even more preferably from 50,000 to 180,000 g / mol, most preferably from 80,000 to 170,000 g / mol, determined by gel permeation chromatography using poly(methyl-methacrylate) calibration standards according to DIN EN ISO 13885-1.

10. The polymer dispersion according to any one of the previous claims, wherein the polymer dispersion further comprises from 0 to 10 % by weight, preferably from 0.5 to 5 % by weight, of an emulsifier e) not belonging to the family of sulfosuccinate emulsifiers b), based on the total weight of the polymer dispersion.11 . The polymer dispersion according to any one of the previous claims, wherein the polymer dispersion further comprises from 0.1 to 20 % by weight, preferably from 0.1 to 15 % by weight, more preferably from 1 to 10 % by weight, of an additive f) selected from the group consisting of scale inhibitors, corrosion inhibitors, oxygen scavengers, biocides, emulsion breakers, antifoam agents, drag reducing agents, hydrate inhibitors, paraffin dispersants, asphaltene control agents, a pour point depressant other than copolymer a), or a mixture thereof.

12. A process for preparing a polymer dispersion as defined in any one of claims 1 to 11 , wherein the process comprises the following steps: i) providing a mixture of water d) and cosolvent c), ii) adding a monomer composition comprising monomers a1), a2), a3) and any other optional monomers to the mixture i) iii) polymerizing the mixture of step ii) by free-radical emulsion polymerization to obtain the polymer dispersion as defined in any one of claims 1 to 11 .

13. A crude oil composition comprising a polymer dispersion as defined in any one of claims 1 to 11 and a crude oil.

14. Use of a polymer dispersion as defined in any one of claims 1 to 11 to inhibit the deposition of paraffins in a crude mineral oil and / or to reduce the pour point of a crude oil and / or to reduce the viscosity of a crude oil, by adding said polymer dispersion to said crude oil.

15. A method of improving the transport and / or storage of a crude oil comprising the step of adding a polymer dispersion as defined in any one of claims 1 to 11 to said crude oil.

Images