AU3705999A - Dispersions containing homopolymers or copolymers of hydroxy carboxylic acids as a rheological additive - Google Patents

Description

WO 99/52623 1 PCT/EP99/02323 Dispersions Containing Homopolymers or Copolymers of Hydroxycarboxylic Acids as a Rheological Additive This invention relates to dispersions containing certain homo- or copolymers as rheological additives, to the use of such polymers as rheological additives and to a process for reducing the viscosity of aqueous solids-containing dispersions. 5 Many technical liquids, for example paints and pharmaceutical, cosmetic or food preparations, are present in the form of dispersions with considerable solids contents. Liquids such as these generally show thixotropic behavior when subjected to shearing, i.e. the viscosity of these liquids - which are also known as non-newtonian liquids - decreases under 10 the effect of increasing shear forces or shear rates. This behavior can give rise to problems in practice when the liquids are to be transported or pumped and are exposed to different mechanical loads in the process. These problems apply in particular to working fluids in the field of geological exploration, so-called drilling fluids. Drilling fluids are used for 15 drilling holes in rock and bringing up the cuttings. Drilling fluids are also required to have a certain density (generally above 1.5 g/cm 3 ) in order to be able to prevent the formation from being penetrated. To this end, solids are added to weight the drilling fluid. Barium sulfate is generally used. In addition, so-called thickeners are used to increase the viscosity of the 20 drilling fluid which makes the cuttings easier to carry away. At the same time, however, the viscosity of the fluid should not become so high that its flowability and pumpability are adversely affected. In practical application, however, the rheological properties of a drilling fluid change continuously, for example through the nature and quantity of the cuttings or through 25 inrushes of liquid. or. gas from the formation surrounding the borehole. Accordingly, the flowability of the drilling fluid in operation is in constant . ,n4 WO 99/52623 2 PCT/EP99/02323 danger of being reduced to such an extent that progress is no longer possible. It is therefore standard practice to influence the viscosity of a drilling fluid through chemical additives in order to prevent uncontrolled thickening of the system. 5 The effect of these additives is explained by the fact that they reduce the electrostatic interactions of the dispersed particles with one another, thereby reducing the viscosity of the system as a whole. Various substances are known for this purpose. EP 549 958 B1, for example, discloses hydrogenated castor oil as a suitable rheological additive for 10 solids-containing dispersions, especially paints. GB 1,514,586 describes reaction products of oligomers of hydroxycarboxylic acids with acrylate based copolymers which are suitable as dispersion aids for solids containing liquid media. Suitable additives, especially for drilling fluids, above all for water-based systems, are phosphates or lignites as described, 15 for example, by G. Gray and H.C.H. Darley in "Composition and Properties of Oil Well Drilling Fluids", Gulf Publishing Company, Houston 1988, pages 564 et seq. Where such additives are used in drilling fluids, however, they have to meet more stringent requirements. They have to be liquid over a broad 20 temperature range, additives which can still be used at temperatures well below 0*C being particularly sought-after. In addition, the additives are expected to withstand high pressures and intensive shearing and to meet the biodegradability requirements which such systems are increasingly having to satisfy. In addition, the use of these additives should not affect 25 the stability of the drilling fluid. Accordingly, the present invention starts out from the observation that the additives currently available on the market do not yet fully satisfy the requirement profile described above. However, it has been found that certain polymers based on ricinoleic 30 acid are eminently suitable as a rheological additive for aqueous solids 0~ 12 WO 99/52623 3 PCT/EP99/02323 containing systems. Accordingly, in a first embodiment, the present invention relates to dispersions which contain an oil phase and a water phase, at least one dispersed solid and optionally other auxiliaries and, as a rheological 5 additive, homopolymers or copolymers obtainable by condensation of ricinoleic acid on its own or in the presence of hydroxycarboxylic acids corresponding to formula (1) or ring-closed derivatives thereof: HO-X-CO-OH (I) 10 where X is a linear or branched, saturated alkylene group containing 1 to 23 carbon atoms. The solids-containing dispersions according to the invention may be used in various branches of industry. In a preferred embodiment, however, 15 the dispersions according to the invention are used as drilling fluids. Drilling fluids are flowable systems thickened to a limited extent which, in principle, may be assigned to one of the following three classes: purely water-based drilling fluids, oil-based drilling muds which are generally used as so-called invert emulsion muds and water-based o/w emulsions which 20 contain a heterogeneous finely dispersed oil phase in the continuous aqueous phase. Drilling muds based on a continuous oil phase are generally made up of three phases, namely: oil, water and fine-particle solids. The aqueous phase is heterogeneously and finely dispersed in the continuous 25 oil phase. Various additives may be present, including in particular emulsifiers, weighting agents, fluid loss additives, alkali reserves, viscosity adjusters and the like. Relevant particulars can be found, for example, in the articles. by P.A.. Boyd et al. entitled: "New Base Oil Used in Low Toxicity Oil Muds" in Journal of Petroleum Technology, 1985, 137 to' 30 142 and by R.B. Bennett entitled "New Drilling Fluid Technology IR WO 99/52623 4 PCT/EP99/02323 Mineral Oil Mud" in Journal of Petroleum Technology, 1984, 975 to 981 and the literature cited therein. Drilling fluids based on aqueous o/w emulsion systems occupy an intermediate position between purely water-based systems and oil-based 5 invert muds in terms of their performance properties. Detailed information can be found in the relevant specialist literature, cf. for example the book by George R. Gray and H.C.H. Darley entitled "Composition and Properties of Oil Well Drilling Fluids", 4th Edition, 1980/81, Gulf Publishing Company, Houston, and the extensive literature cited therein 10 and the manual entitled "Applied Drilling Engineering" by Adam T. Borgoyne, Jr. et al., First Printing, Society of Petroleum Engineers, Richardson, Texas (USA). Even today, however, oil-based w/o invert systems are still without question the safest working media, particularly in the drilling of water-sensitive clay layers. 15 The homopolymers and copolymers serving as rheological additives in accordance with the present invention are prepared by condensation of ricinoleic acid on its own or in the presence of the described hydroxycarboxylic acids corresponding to formula (1) at temperatures of 180 to 2000C, the reaction being accompanied by the elimination of water. 20 The condensation is preferably carried out over a period of 2 to 6 hours. The details of such reactions are described, for example, by S.N. Modak and J.G. Kane in JAOCS, Vol. 42, 1965, pages 428 to 432. The condensation is generally carried out in the absence of a catalyst. In certain cases, however, it can be of advantage to add suitable catalysts, for 25 example propylene glycol, titanium tetrabutylate or zinc acetate, in quantities of 0.5 to 3% by weight during the reaction. In the condensation of ricinoleic acid with hydroxycarboxylic acids, it can be of advantage to use the two educts in a ratio by weight of 1:2 to 2:1 and preferably in a ratio by weight of 1:1. 30 The ricinoleic acid is used in standard commercially available form. SRAZ, 13 WO 99/52623 5 PCT/EP99/02323 It is obtained by saponification of castor oil. The hydroxycarboxylic acids of formula (I) used are compounds in which X is an alkylene group containing 1 to 23, preferably 1 to 12 and more preferably 1 to 6 carbon atoms. Examples of such acids are hydroxystearic acid, glycolic acid, lactic acid or 5 hydroxybutyric acid or ring-closed derivatives thereof. Ring-closed derivatives are understood to be compounds which are formed from the corresponding acids by intramolecular esterification. y-Butyrolactone and s-caprolactone, for example, are suitable. The dispersions according to the invention preferably contain 10 homopolymers of ricinoleic acid as rheology additives, homopolymers with an acid value - as measured by DGF method C-V 2 - below 45 and more particularly below 40 preferably being used. If, by contrast, copolymers of ricinoleic acid and hydroxycarboxylic acid are used as the rheology additive, dispersions containing copolymers of ricinoleic acid and 12 15 hydroxystearic acid are preferred. The polymers have a low pour point (as measured to DIN ISO 3016) of at most 00C and preferably in the range from -5 to -350C. The dispersions according to the invention contain the additives in quantities of normally 0.1 to 1.0% by weight and preferably 0.2 to 0.8% by weight, based on the dispersion as a whole. 20 The dispersions according to the invention are three-phase systems of an oil phase, a water phase and a solids phase. Dispersions in which the ratio by volume of water phase to oil phase is 90-10 parts water to 10 90 parts oil are preferred. Dispersions containing 70-90 parts by volume oil phase and 30-10 parts by volume water phase are particularly preferred. 25 Dispersions in the form of a w/o emulsion of the type described above are preferred. Such systems are known as invert systems in the field of drilling fluids. The solids content of the dispersions is in the range from 1 to 70% by weight and preferably in the range from 10 to 55% by weight, based on the dispersion. The density of the dispersions is preferably in the range 30 from 1.5 g/cm 3 to 2.5 g/cm 3 . U j y7 WO 99/52623 6 PCT/EP99/02323 The oil phase of the dispersions may contain basically any water immiscible or substantially water-immiscible compounds liquid at room temperature. If the dispersions are used as a drilling fluid or other similar well servicing fluid, the oil phases are limited to the substances known to 5 the expert in this technical field. Originally, mineral oil fractions were used as the oil phase in drilling fluids. However, this resulted in considerable environmental pollution, for example when the drilling muds entered the environment either directly or via the drilled rock. Mineral oils are not readily biodegradable and, anaerobically, are virtually nondegradable and 10 so may be regarded as long-term pollutants. Over the last decade in particular, various proposals have been put forward with a view to replacing the mineral oil fractions by ecologically safer and more readily degradable oil phases. Applicants describe possible alternatives for the oil phase in a relatively large number of patents; mixtures of such replacement oils may 15 also be used. In particular, selected oleophilic monocarboxylic acid esters, polycarboxylic acid esters, at least substantially water-insoluble alcohols which flow under working conditions, corresponding ethers and selected carbonic acid esters have been described, cf. the following patents: EP 0 374 671, EP 0 374 672, EP 0 386 638, EP 0 386 636, EP 0 382 070, EP 0 20 382 071, EP 0 391 252, EP 0 391 251, EP 0 532 570, EP 0 535 074. However, proposals for alternative oil phases for the field in question have also been put forward by other parties. For example, the following classes of compounds have been proposed as replacements for the mineral oil phase in w/o invert muds: acetals, a-olefins (LAO), poly-a-olefins (PAO), 25 internal olefins (10), (oligo)amides, (oligo)imides and (oligo)ketones, cf.: EP 0 512 501, EP 0 627 481, GB 2,258,258, US 5,068,041, US 5,189,012 and WO 95/30643 and WO 95/32260. Preferred dispersions are those of which the oil phase consists partly or completely of carboxylic acid esters of saturated and unsaturated, 30 linear or branched Cl-22 alcohols and saturated and unsaturated, linear or \5CAj WW 0A~ WO 99/52623 7 PCT/EP99/02323 branched C1.22 carboxylic acids. According to the present invention, oil phases of which more than 50% by volume contains the above-mentioned esters are preferred. These esters and invert drilling muds containing them are described in detail in applicants' EP 374 671 B1, EP 374 672 B1, EP 5 386 638 B1 and EP 386 636 B1. The disclosures of these documents is hereby made part of the present invention. The esters of saturated C12-16 monocarboxylic acids and monohydric C2-12 alcohols are particularly preferred. In addition, esters of polyhydric alcohols with monocarboxylic acids and, in particular, glycerol esters of natural and/or synthetic origin 10 may effectively be used as the oil phase or as part of the oil phase. For example, triglycerides of vegetable and/or animal origin, for example of the rapeseed oil or fish oil type, which could be of advantage both ecologically and from the cost/effectiveness ratio perspective, may be used. Another factor to be taken into consideration on safety grounds in 15 the choice of suitable constituents of the oil phase is their flash point. Compounds with flash points (to DIN 51 376) above 800C, preferably above 100*C and more preferably above 160*C are particularly suitable. In addition, it has been found to be of advantage to use compounds with a Brookfield viscosity at 0 to 5*C of no more than 55 mPa s and preferably no 20 more than 45 mPa s in the oil phase. Other suitable solids are substances which are insoluble or incompletely soluble in -water or the oil phase. Solids selected from the group consisting of barium sulfate (barite) and/or calcium carbonate, which serve as weighting agents, are preferably used in the case of drilling fluids. 25 Organophilic clay minerals, such as bentonites and montmorillonites, are particularly suitable as viscosity generators or "thickeners". Another important constituent of drilling fluids are basic compounds for adjusting the pH value because the inrush of acidic gases, such as C02 or H 2 S, from the formation can lead to serious corrosion problems. 30 Accordingly, the pH of the water phase of the drilling fluid Is preferably WO 99/52623 8 PCT/EP99/02323 adjusted to a value in the weakly alkaline range, preferably to a value of pH 8.5 to 9.0. Accordingly, Ca(OH) 2 or CaO (lime or quicklime) is normally added to the drilling fluid as alkali reserve. However, it has been found, particularly in the case of invert drilling muds based on ester oils, that 5 excessive levels of lime can lead to unwanted hydrolysis of the esters. The fatty acids formed as reaction products of the hydrolysis then preferentially react with Ca ions to form the corresponding soaps which can lead to uncontrolled thickening of the drilling fluids. Accordingly, the quantity of free lime present as alkali reserve in the drilling fluid is preferably limited to 10 at most about 2 lb/bbl drilling fluid. Besides the constituents described above, the dispersions may contain other auxiliaries and additives known to the expert. These include in particular emulsifiers, fluid loss additives, corrosion inhibitors and wetting agents. Preferred emulsifiers are the compounds (or mixtures thereof) 15 described in applicants' German patent application DE 196 43 840.3. In addition, water-soluble salts, preferably calcium chloride or potassium chloride, may be present, preferably being used in such quantities that the aqueous phase is saturated. The dispersions according to the invention are distinguished by a 20 low viscosity which they largely retain even when exposed to shearing. The dispersions according to the invention preferably have a plastic viscosity (PV) of 10 to 60 mPa s and a yield point (YP) of 5 to 50 lb/I 00 ft 2 , both as measured at 50*C. These values relate to freshly prepared systems free from any thermal stressing. The rheological parameters in 25 question are measured by standard methods as described, for example, in "Manual of Drilling Fluids Technology" published by Baroid/NL Industries, Inc., 1979. By virtue of the low pour point of the polymers present in them, the rheology additives retain their effect, even at low temperatures, and may be used, for example, in drilling operations in Arctic 30 and Antarctic regions.

WO 99/52623 9 PCT/EP99/02323 In another embodiment, the present invention relates to the use of homopolymers or copolymers obtainable by condensation of ricinoleic acid on its own or in the presence of hydroxycarboxylic acids corresponding to formula (1) as described above or ring-closed derivatives thereof as a 5 rheological additive for solids-containing aqueous dispersions. The addition of the additives according to the invention leads to a distinct reduction in viscosity without any reduction, for example, in emulsion stability. The present invention also relates to a process for reducing the 10 viscosity of thixotropic, solids-containing aqueous dispersions, preferably drilling fluids, by adding homopolymers or copolymers obtainable by condensation of ricinoleic acid on its own or in the presence of hydroxy carboxylic acids corresponding to formula (1) as described above or ring closed derivatives thereof to the dispersion in quantities of 0.1 to 1.0% by 15 weight, based on the dispersion. Examples A drilling fluid was prepared from the following ingredients: 20 Ester oil') 1617.0 g Emulsifier) 212.3 g Water 659.8 g CaCl 2 -2H 2 0 212.3 g Organophilic bentonite 91.0 g 25 Orangophilic lignite 10.1 g Ca(OH) 2 20.2 g BaSO 4 2756.0 g Clay 3 ) 99.8 g 30 0OMC 586: ester mixture of substantially saturated fatty acids based on Rj), WO 99/52623 10 PCT/EP99/02323 palm kernel oil, which consists largely of C114 fatty acids, and 2-ethyl hexanol. 2) EZ Mul, a Baroid product 3) Hymond Prima Clay, a Baroid product 5 The following conversion factors may be used for converting the units typically used in the technical field in question into SI-conforming units: 1 lb = 0.454 kg; 1 bbl = 159 1 10 1 lb/bbl = 2.85 kg/m 3 1 lb/100 ft 2 = 0.4788 Pa The ratio by volume of the fluids was 25 parts water phase to 75 parts oil phase. Their density was 1.52 g/cm 3 . A diluent was then added to the fluids in a concentration of 2 lb/bbl. The rheological properties were 15 them determined. Viscosity was measured at 50*C in a Fann 35 viscosimeter (Baroid Drilling Fluids Inc.). Plastic viscosity (PV), yield point (YP) and gel strength (lb/100 ft 2 ) after 10 seconds and 10 minutes are determined in known manner. The measurements were then repeated after ageing of the fluids for 16 hours in a roller oven at 300*F (ca. 150*C). 20 The results are set out in Tables .1a and 1b. The acid value was determined by DGF Method C-V 2, the OH value by DGF Method C-V 17a and the iodine value by DGF Method C-V 11d. Products A to D according to the invention were measured as rheological additives by comparison with a commercially available product 25 C2 based on polyhydroxystearic acid (pour point: + 1 C). A drilling fluid with no diluent was also investigated (Cl). The diluents according to the invention were prepared as follows: ricinoleic acid is heated under nitrogen to 2200C in an autoclave. After the end of the reaction, the product is left to cool and is used without any 30 further working up. c

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WO 99/52623 11 PCT/EP99/02323 Additive A: Condensation of ricinoleic acid (acid value 174, OH value 152, iodine value 87) for 8 hours at 2200C. End product: acid value 38.6, pour point - 29*C. 5 Additive B: Condensation of ricinoleic acid (acid value 174, OH value 152, iodine value 88) for 7.5 hours at 220 0 C in the presence of 2% by weight propylene glycol as catalyst. End product: acid value 25, pour point -10*C. 10 Additive C: Condensation of ricinoleic acid (acid value 171, OH value 152, iodine value 88) for 5 hours at 220*C in the presence of 0.9% by weight zinc acetate as catalyst. End product: acid value 43, pour point -10*C. 15 Additive D: Condensation of 325 g ricinoleic acid (acid value 171, OH value 152, iodine value 88) with 325 g hydroxystearic acid (acid value 181) for 5.5 hours at 2200C. End product: acid value 42, pour point 00C. Table 1a: Measurements before ageing A B C D C1 C2 PV (mPas) 42 44 40 43 65 43 YP (lb/100ft 2 ) 9 42 14 7 91 4 Gel strength after 10 secs./10 mins. 7/13 22/28 6/12 7/10 45/49 5/7 (lb/1 00 ft 2

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WO 99/52623 12 PCT/EP99/02323 Table 1b: Measurement after ageing A B C D C1 C2 PV (mPa s) 45 48 45 45 44 48 YP (lb/1 00ft 2 ) 51 58 41 39 70 49 Gel strength after 10 secs.I1 0 mins. 23/27 26/29 20/24 17/21 34/38 22/27 (lb/1 00 ft 2 ) It can be seen that the additives according to the invention are comparable with or better than the commercially available product in their effect on the rheology of the drilling fluid. RTFq<

Claims (4)

1. Dispersions containing an oil phase and a water phase, at least one dispersed solid and optionally other auxiliaries, characterized in that the dispersion contains homopolymers or copolymers obtainable by 5 condensation of ricinoleic acid on its own or in the presence of hydroxycarboxylic acids corresponding to formula (I) or ring-closed derivatives thereof: HO-X-CO-OH (i) 10 where X is a linear or branched, saturated alkylene group containing 1 to 23 carbon atoms, as a rheological additive.

2. A dispersion as claimed in claim 1, characterized in that it contains 15 homopolymers of ricinoleic acid.

3. A dispersion as claimed in claim 1 or 2, characterized in that it contains homopolymers with an acid value below 45 and preferably below

40. 4. A dispersion as claimed in claims 1 to 3, characterized in that it 20 contains copolymers of ricinoleic acid with hydrogycarboxylic acids corre sponding to formula (1) selected from the group consisting of hydroxystearic acid, glycolic acid, lactic acid and hydroxybutyric acid or ring-closed derivatives thereof. 5. A dispersion as claimed in any of claims 1 to 4, characterized in that 25 it contains copolymers of ricinoleic acid and 12-hydroxystearic acid. 6. A dispersion as claimed in any of claims 1 to 5, characterized in that it contains the homopolymers of copolymers in quantities of 0.1 to 1.0% by weight and preferably in quantities of 0.2 to 0.8% by weight, based on the total weight of the dispersion. 30 7. A dispersion as claimed in any of claims I to 6, characterized in that WO 99/52623 14 PCT/EP99/02323 the ratio by volume of the water phase to the oil phase is 90-10 parts water to 10-90 parts oil. 8. A dispersion as claimed in any of claims 1 to 7, characterized in that it contains from 1 to 70% by weight and preferably from 10 to 55% by 5 weight of dispersed solids. 9. A dispersion as claimed in any of claims 1 to 8, characterized in that the solid is selected from the group consisting of barium sulfate and/or calcium carbonate. 10. A dispersion as claimed in any of claims 1 to 9, characterized in that 10 it contains emulsifiers, weighting agents, thickeners, wetting agents, corrosion inhibitors or fluid loss additives as auxiliaries. 11. A dispersion as claimed in any of claims 1 to 10, characterized in that it contains esters of saturated and unsaturated, linear or branched alcohols containing 1 to 22 carbon atoms with saturated and unsaturated, 15 linear or branched carboxylic acids containing 1 to 22 carbon atoms in the oil phase. 12. A dispersion as claimed in any of claims 1 to 11, characterized in that it contains the water phase dispersed in a continuous oil phase. 13. A dispersion as claimed in any of claims 1 to 12, characterized in 20 that it has a plastic viscosity (PV) of 10 to 60 mPa s and a yield point (YP) of 5 to 50 lb/1 00 ft 2 , both as measured at 50 0 C. 14. The use of the dispersion claimed in any of claims 1 to 13 as a drilling fluid. 15. The use of homopolymers or copolymers obtainable by condensa 25 tion of ricinoleic acid on its own or in the presence of hydroxycarboxylic acids corresponding to formula (1) in claim 1 or ring-closed derivatives thereof as a rheological additive for solids-containing aqueous dispersions. 16. A process for reducing the viscosity of thixotropic, solids-containing aqueous dispersions, characterized in that homopolymers or copolymers 30 obtainable by condensation of ricinoleic acid on its own or in the presence \'o R WO 99/52623 15 PCT/EP99/02323 of hydroxycarboxylic acids corresponding to formula (1) in claim 1 or ring closed derivatives thereof are added to the dispersion in quantities of 0.1 to 1.0% by weight, based on the dispersion. \~R,q<,