POLYMER DISPERSIONS FOR WAX INHIBITION

Abstract

The present invention relates to a process of a process for preparation of a polymer dispersion comprising a step (E) of free radical polymerization in an aqueous medium (M) in the presence of: at least a pre-polymer (pO) soluble in the medium (M), at least one free-radical polymerization initiator, and at least one ethylenically unsaturated hydrophobic monomer (m) which is chosen from an alkyl (meth)acrylate of at least C6, wherein the aqueous medium (M) includes water and at least one water miscible solvent.

Claims

1. A process for preparation of a polymer dispersion, the process comprising a step (E) of free radical polymerization in an aqueous medium (M) in the presence of: at least a pre-polymer (p0) soluble in the medium (M) of formula (I):
(R.sup.11)x-Z.sup.11C(S)Z.sup.12-[A]-R.sup.12(I) wherein: Z.sup.11 represents C, N, O, S or P, Z.sup.12 represents S or P, R.sup.11 and R.sup.12, which may be identical or different, represent: an optionally substituted alkyl, acyl, aryl, alkene or alkyne group (i), or a saturated or unsaturated, optionally substituted or aromatic carbon-based ring (ii), or a saturated or unsaturated, optionally substituted heterocycle (iii), these groups and rings (i), (ii) and (iii) possibly being substituted with substituted phenyl groups, substituted aromatic groups or groups: alkoxycarbonyl or aryloxycarbonyl (COOR), carboxyl (COOH), acyloxy (O.sub.2CR), carbamoyl (CONR.sub.2), cyano (CN), alkylcarbonyl, alkylarylcarbonyl, arylcarbonyl, arylalkylcarbonyl, phthalimido, maleimido, succinimido, amidino, guanidimo, hydroxyl (OH), amino (NR.sub.2), halogen, allyl, epoxy, alkoxy (OR), S-alkyl, S-aryl, groups of hydrophilic or ionic nature, the alkali metal salts of sulphonic acid, polyalkylene oxide chains or cationic substituents, R representing an alkyl or aryl group, x corresponds to the valency of Z.sup.11, or alternatively x is 0, in which case Z.sup.11 represents a phenyl, alkene or alkyne radical, optionally substituted with an optionally substituted alkyl; acyl; aryl; alkene or alkyne group; an optionally substituted, saturated, unsaturated, or aromatic, carbon-based ring; an optionally substituted, saturated or unsaturated heterocycle; alkoxycarbonyl or aryloxycarbonyl (COOR); carboxyl (COOH); acyloxy (O.sub.2CR); carbamoyl (CONR.sub.2); cyano (CN); alkylcarbonyl; alkylarylcarbonyl; arylcarbonyl; arylalkylcarbonyl; phthalimido; maleimido; succinimido; amidino; guanidimo; hydroxyl (OH); amino (NR.sub.2); halogen; allyl; epoxy; alkoxy (OR), S-alkyl; S-aryl groups; groups of hydrophilic or ionic nature, the alkali metal salts of sulphonic acid, polyalkylene oxide chains or cationic substituents; and [A] represents a polymer chain; at least one free-radical polymerization initiator, and at least one ethylenically unsaturated hydrophobic monomer (m) which is chosen from an alkyl (meth)acrylate of at least C6, wherein the aqueous medium (M) includes water and at least one water miscible solvent.

2. The process according to claim 1, wherein the polymer chain [A] is selected from the homo- and copolymers (random, gradient or block) resulting from the polymerization of at least one or more hydrophilic monomers (mA.sub.h) selected from the group consisting of: ethylenically unsaturated monocarboxylic and dicarboxylic acids, unsaturated carboxylic acid amides, and vinylamine amides.

3. The process according to claim 2, wherein the polymer chain [A] has a number-average molar mass of less than 50 000 g/mol.

4. The process according to claim 2, wherein the pre-polymer (p0) is obtained by a preparation step (E.sup.0) of controlled radical polymerization of a composition comprising: monomers containing identical or different hydrophilic monomers (mA.sub.h), optionally together with at least one hydrophobic monomer; a radical polymerization control agent; and a free-radical polymerization initiator.

5. The process according to claim 4, wherein the radical polymerization control agent is a xanthate, dithiocarbamate or dithiocarbazate.

6. The process according to claim 1, wherein the water miscible solvent is present in the medium (M) in an amount of at least 15% by weight of the total weight of the medium.

7. The process according to claim 1, wherein the water is present in an amount of at least 50% by weight of the total weight of the medium.

8. The process according to claim 1, wherein the water miscible solvent is a glycol.

9. The process according to claim 1, wherein at least one monomer (m) is chosen from an alkyl (meth)acrylate between C8 and C24.

10. The process according to claim 9, wherein the monomer (m) is selected from the group consisting of iso-octyl (meth)acrylate, iso-bornyl (meth)acrylate, lauryl (meth)acrylate, octadecyl (meth)acrylate, 2-ethyl hexyl (meth)acrylate, C22 alkyl acrylate and a mixture thereof.

11. A polymer dispersion obtained according to the process of claim 1.

12. A wax inhibitor composition including the polymer dispersion of claim 11 and an additive selected from the group consisting of amphoteric surfactants, anionic surfactants, wetting agent, phosphate esters, sulfosuccinates, olefin sulfonates, linear alkyl benzene sulfonates, alkyl polyglucosides, alkyl ether carboxylates, alcohol ethoxylates, fatty acid ethoxylates, alkyl amine ethoxylates, alkanolamides, quaternary ammonium salts, amidoamines, diamines, corrosion inhibitors, and asphaltene inhibitors.

13. A method for inhibiting wax formation in an oil, the method comprising adding to said oil a polymer dispersion of claim 11.

14. A method for improving the flow properties of an oil, the method comprising adding to said oil a polymer dispersion of claim 11.

15. The process according to claim 1, wherein the groups of hydrophilic or ionic nature are alkali metal salts of carboxylic acids.

16. The process according to claim 1, wherein the polyalkylene oxide chains are PEO or PPO chains.

17. The process according to claim 1, wherein the cationic substituents are quaternary ammonium salts.

18. The process according to claim 2, wherein the ethylenically unsaturated monocarboxylic and dicarboxylic acids comprise acrylic acid, methacrylic acid, itaconic acid, maleic acid or fumaric acid.

19. The process according to claim 2, wherein the unsaturated carboxylic acid amides comprise acrylamide, methacrylamide, N-methylolacrylamide or -methacrylamide, N-alkyl(meth)acrylamides, N,N-dimethyl(meth)acrylamide, N,N-dimethylaminomethyl(meth)acrylamide, 2-(N,N-dimethylamino)ethyl(meth)acrylamide, 3-(N,N-dimethylamino)propyl(meth)acrylamide, or 4-(N,N-dimethylamino)butyl(meth)acrylamide.

20. The process according to claim 2, wherein vinylamine amides comprise vinylformamide, vinylacetamide, N-vinylpyrrolidone and N-vinylcaprolactam.

Description

EXAMPLES

[0160] The following examples made use of an aqueous solution of pre-polymer called P-Xa prepared as follows:

[0161] In a 2 L double jacketed reactor, equipped with a condenser, a mechanical stirrer, a thermal probe and a nitrogen inlet, one introduced 140.68 g of deionized water, 78.15 g of ethanol, 18.74 g of Rhodixan A1, and 67.50 g of dimethylacrylamide. The mixture was deoxygenated by nitrogen bubbling for 30 minutes. Then the mixture was heated to 40 C. in 30 minutes. When the temperature into the reactor reached 40 C., 11.13 g of an aqueous solution of ammonium persulfate at 10 wt % and 3.12 g of an aqueous solution of sodium formaldehyde sulfoxilate at 0.65 wt % were added shotwise. Then 908 g of an aqueous solution of dimethylacrylamide at 42 wt % was added for 180 minutes, and 24.50 g of an aqueous solution of sodium formaldehyde sulfoxilate at 0.75 wt % was added for 300 minutes. After the end of the introduction of NaFS, the mixture was heated to 40 C. for 3 hours.

[0162] The poly(dimethylacrylamide)-Xa (P-Xa) was obtained at the end of the reaction.

Example 1

[0163] In a 2 L double jacketed reactor, equipped with a condenser, a mechanical stirrer, a thermal probe and a nitrogen inlet, one introduced 238 g of deionized water, 517 g of tripropylene glycol, 450 g of an aqueous solution of P-Xa at 38 wt %, and 570 g of octadecyl acrylate. The mixture was deoxygenated by nitrogen bubbling for 30 minutes. Then the mixture was heated to 70 C. When the temperature into the reactor reached 70 C., 4.88 g of sodium persulfate solubilized in a minimum amount of water was added shotwise. The mixture was then heated to 70 C. for 8 hours.

[0164] After filtration over 45 m, one obtained a stable dispersion D1 with a solid content of 40 wt % on average.

Example 2

[0165] In a 250 mL three neck round bottom flask, equipped with a condenser, a mechanical stirrer, a thermal probe and a nitrogen inlet, one introduced 16.23 g of deionized water, 47.24 g of tripropylene glycol, 50 g of an aqueous solution of P-Xa at 38 wt %, 22.83 g of 2-Ethyl hexyl acrylate (2-EHA) and 53.21 g of octadecyl acrylate. The mixture was deoxygenated by nitrogen bubbling for 30 minutes. Then the mixture was heated to 70 C. When the temperature into the reactor reached 70 C., 0.54 g of sodium persulfate solubilized in a minimum amount of water was added shotwise. The mixture was then heated to 70 C. for 8 hours.

[0166] After filtration over 45 m, one obtained a stable dispersion D2 with a solid content of 40 wt % on average.

Example 3

[0167] In a 250 mL three neck round bottom flask, equipped with a condenser, a mechanical stirrer, a thermal probe and a nitrogen inlet, one introduced 32.01 g of deionized water, 0.14 of sodium bicarbonate, 56.82 g of tripropylene glycol, 40 g of an aqueous solution of P-Xa at 38 wt %, and 42.58 g of iso-octyl acrylate. The mixture was deoxygenated by nitrogen bubbling for 30 minutes. Then, 18.22 g of vinyl acetate was introduced into the flask and homogenized with the reaction mixture. The mixture was then heated to 70 C. When the temperature into the reactor reached 70 C., 0.41 g of ammonium persulfate solubilized in a minimum amount of water was added shotwise. The mixture was then heated to 70 C. for 8 hours.

[0168] After filtration over 45 m, one obtained a stable dispersion D3 with a solid content of 40 wt % on average.

Example 4

[0169] In a 250 mL three neck round bottom flask, equipped with a condenser, a mechanical stirrer, a thermal probe and a nitrogen inlet, one introduced 16.23 g of deionized water, 47.24 g of tripropylene glycol, 50 g of an aqueous solution of P-Xa at 38 wt % and 53.21 g of octadecyl acrylate., The mixture was deoxygenated by nitrogen bubbling for 30 minutes. Then the mixture was heated to 70 C. When the temperature into the reactor reached 70 C., 0.54 g of sodium persulfate solubilized in a minimum amount of water was added shotwise. After one hour, 22.83 g of 2-Ethyl hexyl acrylate were added shotwise in the reactor. The mixture was then heated to 70 C. for 7 hours.

[0170] After filtration over 45 m, one obtained a stable dispersion D4 with a solid content of 40 wt % on average.

Example 5

[0171] In a 2 L double jacketed reactor, equipped with a condenser, a mechanical stirrer, a thermal probe and a nitrogen inlet, one introduced 238 g of deionized water, 517 g of tripropylene glycol, 450 g of an aqueous solution of P-Xa at 38 wt %, 5.7 g of dodecylbenzene sulfonate and 570 g of octadecyl acrylate. The mixture was deoxygenated by nitrogen bubbling for 30 minutes. Then the mixture was heated to 70 C. When the temperature into the reactor reached 70 C., 4.88 g of sodium persulfate solubilized in a minimum amount of water was added shotwise. The mixture was then heated to 70 C. for 8 hours.

[0172] After filtration over 45 m, one obtained a stable dispersion D5 with a solid content of 40 wt % on average.

Example 6

[0173] In a 2 L double jacketed reactor, equipped with a condenser, a mechanical stirrer, a thermal probe and a nitrogen inlet, one introduced 120 g of deionized water, 850 g of tripropylene glycol, 264 g of an aqueous solution of P-Xa at 38 wt %, and 400 g of octadecyl acrylate. The mixture was deoxygenated by nitrogen bubbling for 30 minutes. Then the mixture was heated to 70 C. When the temperature into the reactor reached 70 C., 6.58 g of sodium persulfate solubilized in a minimum amount of water was added shotwise. The mixture was then heated to 70 C. for 8 hours.

[0174] After filtration over 45 m, one obtained a stable dispersion D6 with a solid content of 30 wt % on average.

Example 7

[0175] In a 2 L double jacketed reactor, equipped with a condenser, a mechanical stirrer, a thermal probe and a nitrogen inlet, one introduced 120 g of deionized water, 850 g of tripropylene glycol, 264 g of an aqueous solution of P-Xa at 38 wt %, 4 g of dodecylbenzene sulfonate and 400 g of octadecyl acrylate. The mixture was deoxygenated by nitrogen bubbling for 30 minutes. Then the mixture was heated to 70 C. When the temperature into the reactor reached 70 C., 6.58 g of sodium persulfate solubilized in a minimum amount of water was added shotwise. The mixture was then heated to 70 C. for 8 hours.

[0176] After filtration over 45 m, one obtained a stable dispersion D7 with a solid content of 30 wt % on average.

Comparative Example

[0177] A dispersion (D0) has been prepared according to the example 1 of WO 03/014170.

Stability Test of Dispersion

[0178] Samples of the polymer dispersions were stored at 20 C. and 50 C. respectively to assess the stability of the dispersions. The appearance of the dispersions was assessed over a 4 week period.

TABLE-US-00001 TABLE 1 Stability of the dispersions at ambient (20 C.) and 50 C. respectively Stability (weeks) Dispersion Temperature ( C.) 1 4 D1 20 Yes Yes 50 Yes Yes D2 20 Yes Yes 50 Yes Yes D3 20 Yes Yes 50 Yes Yes D4 20 Yes Yes 50 Yes Yes D5 20 Yes Yes 50 Yes Yes D6 20 Yes Yes 50 Yes Yes D7 20 Yes Yes 50 Yes Yes D0 20 Yes No 50 Yes No

[0179] It has been found that the dispersions of invention (D1 to D7) are stable (with no signs of phase separation and no solidification) over at least 4 weeks.

[0180] In addition, the dispersions D5, D6 and D7 have also been tested at 80 C. for 48 hours, it has been found that these dispersions are stable (with no signs of phase separation and no solidification) at the end of testing time.

[0181] Also, it has been found that the dispersions of invention are stable at 20 C. over at least 24 h.

[0182] As a comparison, the dispersion of comparative example D0 shows instability (solidification of the dispersion) after 4 weeks at each temperature (20 C., 20 C. and 50 C.).

Application Tests

Model Crude Oil

[0183] The model crude oil was comprised of a mixture of paraffin waxes dispersed in a dodecane. The mixture of paraffins used for the crude oil is provided as followings:

TABLE-US-00002 Component Paraffin wax, melting point c.a. 53-57 C. (commercialized by Sigma Aldrich under ref. 327204) Paraffin wax, melting point c.a. 65 C. min (commercialized by Sigma Aldrich under ref. 411663)

[0184] The waxes were dissolved in the dodecane by heating the mixture to 70-80 C. until clear. The mixture is then stored at this temperature for several hours prior to use to remove the thermal history. The compositions of the crude oils used for the various tests are provided as followings:

TABLE-US-00003 Mixture 1 Mixture 2 Component Wax morphology study Rheology study Paraffin wax, melting point 2.75% w/v 5.50% w/v c.a. 53-57 C. Paraffin wax, melting point 2.25% w/v 4.50% w/v c.a. 65 C. min Dodecane Balance to Balance to 100% w/v 100% w/v

Formulation 1

[0185] The dispersion D1 was formulated with a wetting agent (AEROSOL OT-70/PG) and propylene glycol. The polymer concentration was reduced to 35% active (as solids) for the tests. Formulation 1 has the composition given in the table below:

TABLE-US-00004 Component % w/w dispersion D1 87.5 AEROSOL OT-70/PG 7.0 Propylene glycol 5.5

Methods

Polarized Light MicroscopyWax Morphology

[0186] The performance attributes of the Formulation 1 were screened by adding Formulation 1 (5000 ppm active) to sample of 10 g of Mixture 1. The sample was mixed thoroughly and stored at 85 C. (above the wax appearance temperature) for 1-2 hours to eliminate the thermal history of the sample before cooling overnight in a refrigerator at 0-5 C.

[0187] The appearance of the sample was noted after removal from the refrigerator and assessed using a polarized light microscope (model SP200 XP ex Brunel Microscopes Limited) with camera attachment. The microscope was set at 100 magnification and the textures observed were viewed either with crossed polarizers or crossed polarizers and mica filter ( test plate). Images of the textures were taken using a digital camera (Canon EOS1200D) and processed using image capture software (Canon EOS utility software).

Rheology Studies

[0188] A Brookfield DVI+ viscometer and small sample adapter was used to measure the viscosity of the oil. The small sample adapter was connected to a refrigerated bath that was programmed to reduce the temperature at a rate of 0.5-1.0 C./min. The adapter and spindle (SC-18 or No 31) were pre-heated at 85 C. before the oil was added. The samples containing Formulation 1 were stored in an oven at 85 C., above the wax appearance temperature, to remove any thermal history. The model crude oil was allowed to equilibrate in the sample cell at the designated temperature, i.e. 85 C., for 30 minutes before starting the test. The temperature of the samples was monitored using a thermocouple mounted in the cell and the viscosity was measured at regular intervals. The shear rate was fixed and could be calculated from the rotation rate and the conversion factor for the spindle. The onset of gelation was observed by the rapid increase in the apparent viscosity of the samples. The end point of the test was taken at the point where the maximum torque reading on the viscometer was exceeded.

[0189] Viscosity vs temperature profiles were determined for Mixture 2, without and with Formulation 1 of different concentration (50, 100 and 500 ppm active). The viscosity of selected samples was measured over 15 C. to 35 C. temperature range.

Cloud Point and Pour Point Studies

[0190] Pour points of Mixture 2 containing Formulation 1 at a concentration of 500 ppm active were determined using standard test methodologies (ASTM D97). Samples of the Mixture 2 without and with Formulation 1 were stored in clear glass vials and immersed in a programmable refrigerated circulator bath. The samples were stored at a temperature above the wax appearance temperature, c.a. 60-70 C. for several hours before reducing the temperature of the bath. The vials were removed from the bath at regular intervals and the appearance was assessed. The temperatures of the cloud point, and ceases to pour when the vials were tilted was recorded.

Results

Wax Morphology: Appearance of the Mixture 1 Containing Formulation 1 (5000 ppm Active)

[0191] Paraffin wax crystals exhibit characteristic textures when observed with polarized light. The waxes produced an elongated batonet or rod shape crystal. Formulation 1 changed the shape of the crystals and produced a dispersion of the crystals in the mixture.

TABLE-US-00005 Appearance at 0-5 C. Mixture 1 alone Thick gel. Sample does not move when the vial is tipped. Mixture 1 with Mobile, pourable dispersion. Wax crystals are Formulation 1 <5 m and appear to be fully dispersed when viewed with polarized light microscope.

Rheology Study: Viscosity vs Temperature Data for Mixture 2 Without and With Formulation 1

[0192]

TABLE-US-00006 Conc. of Formulation 1 added Viscosity (cps) at temperature of Sample (ppm) 10 C. 5 C. 0 C. 5 C. 10 C. 15 C. 20 C. 25 C. 30 C. 35 C. Mixture 2 0 557 369 232 131 56 1 alone Mixture 2 with 50 190 172 137 84 33 2 1 1 Formulation 1 100 133 128 102 50 7 1 1 1 500 135 115 103 94 83 39 3 1 1 1

Cloud Point and Pour Point Measurements: Pour Point Results for Formulation 1 (500 ppm Active) in Mixture 2

[0193]

TABLE-US-00007 Cloud Point ( C.) Pour Point ( C.) Mixture 2 alone 33 32 Mixture 2 with 33 0 Formulation 1