POLYMER DISPERSION MADE FROM (METH)ACRYLATES HAVING LONG SIDE CHAINS

Abstract

An aqueous polymer dispersion is based on alkyl (meth)acrylates having long side chains. The aqueous polymer dispersion also contains at least one cosolvent and an emulsifier system containing at least two emulsifiers from the group of sulfosuccinates.

Claims

1: A polymer dispersion, containing: (a) 10 to 70 parts by weight of at least one copolymer, units of which are derived from (a1) 50% to 99.9% by weight of one or more alkyl (meth)acrylate monomers having the general formula (1): ##STR00017## wherein R=C.sub.nH.sub.2n+1 with n≥16 and R′=CH.sub.3 or H; (a2) 0.1% to 10% by weight of at least one of an ethylenically unsaturated monocarboxylic acid, a dicarboxylic acid, or a salt or acid anhydride thereof; (a3) 0% to 49.9% by weight of one or more alkyl (meth)acrylate monomers of the general formula (2): ##STR00018## wherein R′=C.sub.nH.sub.2n+1 with n=8 to 15 and R′=CH.sub.3 or H: (a4) 0% to 30% by weight of one or more monomers selected from the group consisting of (meth)acrylamide, N-alkyl(meth)acrylamide wherein alkyl=C.sub.nH.sub.2n+1 and wherein n is between 1 and 60, N,N-dialkyl(meth)acrylamide wherein alkyl=C.sub.nH.sub.2n+1 and wherein n is between 1 and 60, N-vinylpyrrolidone, 2-vinylpyridine, 4-vinylpyridine, styrene, vinyl acetate, isobornyl (meth)acrylate, tert-butyl (meth)acrylate, methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, i-butyl (meth)acrylate, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, cyclohexyl (meth)acrylate, isohexyl (meth)acrylate, n-hexyl (meth)acrylate, benzyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, 2-dimethylaminoethyl (meth)acrylate, 2-diethylaminopropyl methacrylate, 3-dimethylaminopropyl(meth)acrylamide, trimethylaminopropyl (meth)acrylate chloride, 3-trimethylammoniopropyl(meth)acrylamide chloride, hydroxyethylethylurea (meth)acrylate, N-methylol(meth)acrylamide, polyalkylene glycol ether (meth)acrylates of the general formula (3), hydroxyethyl (meth)acrylate phosphate, and an alkyl (meth)acrylate of the general formula (2) but with radical R″ with n<8; ##STR00019## wherein n=1 to 200; R′=CH.sub.3 or H; R′″=C.sub.mH.sub.2m+1 with m=1 to 30; and R″″=CH.sub.3 or H; (b) 0.5 to 20 parts by weight of an emulsifier system comprising at least two different sulfosuccinate emulsifiers; (c) 1 to 40 parts by weight of at least one water-miscible cosolvent; (d) 0 to 20 parts by weight of one or more further emulsifiers; (e) 0 to 20 parts by weight of further components; and (f) water to a total of 100 parts by weight of the polymer dispersion.

2: The polymer dispersion according to claim 1, wherein the emulsifier system contains a sulfosuccinate having at least one C.sub.10 to C.sub.15 alkyl radical and a further sulfosuccinate having at least one C.sub.<10 alkyl radical.

3: The polymer dispersion according to claim 1, wherein the at least two different sulfosuccinate emulsifiers are dialkyl sulfosuccinates in each case.

4: The polymer dispersion according to claim 1, wherein the at least two different sulfosuccinate emulsifiers are independently 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, and disodium N-octadecyl sulfosuccinate.

5: The polymer dispersion according to claim 1, wherein the emulsifier system contains sodium bis(2-ethylhexyl) sulfosuccinate and sodium bistridecyl sulfosuccinate.

6: The polymer dispersion according to claim 5, wherein sodium bis(2-ethylhexyl) sulfosuccinate and sodium bistridecyl sulfosuccinate are present in a ratio of 1:10 to 10:1.

7: The polymer dispersion according to claim 1, wherein the one or more alkyl (meth)acrylate monomers having the general formula (1) is behenyl (meth)acrylate, and/or wherein the at least one of the ethylenically unsaturated monocarboxylic acid, the dicarboxylic acid, or the salt or acid anhydride thereof is (meth)acrylic acid and/or a derivative thereof.

8: The polymer dispersion according to claim 1, wherein the at least one water-miscible cosolvent is/are selected from the group consisting of short-chain alcohols, dialcohols, trialcohols, glycols, glycol ethers, ketones, ethers, and mixtures thereof.

9: The polymer dispersion according to claim 1, wherein the one or more further emulsifiers is/are selected from the group consisting of water-in-oil emulsifiers and mixtures of water-in-oil emulsifiers.

10: A process for preparing the polymer dispersion according to claim 1, the process comprising: reacting monomers of the at least one copolymer in a free-radical emulsion polymerization in water in the presence of at least one cosolvent and in the presence of the emulsifier system.

11: The process according to claim 10, wherein at least one initiator selected from the group consisting of peroxides, organic hydroperoxides, peracids, and peroxodisulfates is used for the free-radical emulsion polymerization.

12: The process according to claim 10, wherein at least one alkyl mercaptan chain transfer agent is used for the free-radical emulsion polymerization.

13: The process according to claim 10, wherein the free-radical emulsion polymerization is carried out at a temperature of 20° C. to 100° C., and/or wherein a buffer substance is added.

14: The process according to claim 10, wherein an emulsifier selected from the group consisting of water-in-oil emulsifiers and mixtures of water-in-oil emulsifiers is added after completion of the free-radical emulsion polymerization.

15: A method for inhibiting deposition of paraffins in crude mineral oil and/or for reducing pour point of crude mineral oil, the method comprising: mixing the polymer dispersion according to claim 1 with the crude mineral oil.

16: The polymer dispersion according to claim 9, wherein the one or more further emulsifiers is/are selected from the group consisting of water-in-oil emulsifiers having a Griffin HLB value of less than 9 and mixtures of water-in-oil emulsifiers yielding together a Griffin HLB value of less than 9.

17: The process according to claim 14, wherein the emulsifier is selected from the group consisting of water-in-oil emulsifiers having a Griffin HLB value of less than 9 and mixtures of water-in-oil emulsifiers yielding together a Griffin HLB value of less than 9.

Description

[0106] FIG. 1 shows the flow behaviour of the polymer solutions in solvent naphtha S as solvent (examples 1a to 1d). What can be seen here from the sharp rise in viscosity is that the polyBEA solutions become solid at temperatures <20° C. owing to the side-chain crystallization of the polymers. In the case of the polyBEMA solutions, solidification does not take place until at <5° C.

[0107] FIG. 2 shows the flow behaviour of sodium bistridecyl sulfosuccinate-stabilized dispersions having different contents of GMAA as comonomer. The dispersion without and with a 1% GMMA content (examples 2c and 2d) show a sharp rise in viscosity at temperatures below 10° C. In the case of a GMAA content of 2%, this rise is somewhat flatter. Below about 0° C., the viscosities however also rise here to quite high values, and this has an adverse effect on applicability at low temperatures.

[0108] For comparison, the pure external phase (water/dipropylene glycol methyl ether mixture; 75:25 ratio) has a very flat rise in viscosity, which only increases suddenly at approx. −14° C.

[0109] An increase in the amount of sodium bistridecyl sulfosuccinate to over 3% (examples 2g and 2h) can achieve a distinctly flatter viscosity profile over a broad temperature range (see FIG. 3), but these dispersions have a moderate to poor filterability and a coagulate content of 0.5% or higher.

[0110] The use of sodium dicyclohexyl sulfosuccinate (example 2i) did not lead to a stable dispersion, and so flow behaviour was not tested here.

[0111] By using sodium bis(2-ethylhexyl) sulfosuccinate as emulsifier, it is possible to achieve a flat viscosity profile over a broad temperature range (FIG. 4). In this case, the viscosity increases only slowly with decreasing temperature. Only at very low temperatures does a steep rise in viscosity occur as a result of solidification of the continuous phase of the dispersion.

[0112] However, dispersions having a coagulate content of <0.6% cannot be achieved here. Moreover, even after filtration, the dispersions still have many specks, i.e. fine coagulates, that are not retained by the filter. These too can deposit on pipelines in end uses and lead to problems there.

[0113] The use of a mixture of sodium bistridecyl sulfosuccinate and sodium bis(2-ethylhexyl) sulfosuccinate achieves similarly flat viscosity profiles (FIG. 5) as in the case of use of sodium bis(2-ethylhexyl) sulfosuccinate alone, but the combination of two different emulsifiers can produce dispersions which additionally have a very low amount of coagulate (<0.3%, in some cases even <0.2%), can be easily filtered and have only a very low amount of specks after filtration. Only at temperatures of usually <−20° C. does a steep rise in viscosity occur as a result of the solidification of the continuous phase of the dispersion.

4. Pour point measurements of the Polymer solutions and dispersions

[0114] To ascertain below which temperature the polymer solutions or dispersions become solid without action of a shearing force (e.g. during storage at low temperatures), the pour point was ascertained in accordance with ASTM D5985.

[0115] As can be seen in Table 4, the solution polymers 1a to 1d have a pour point >0° C. Dispersion 2d, too, shows a pour point of >0° C. By contrast, the pour points of the dispersions 3b and 3f according to the invention are distinctly below 0° C.

[0116] In the case of use at even lower temperatures, an additional investigation was done to determine whether the pour point can be further reduced by subsequent addition of dipropylene glycol methyl ether (DPM). These results as well are compiled in Table 4. Whereas the dispersion 2d containing only tridecyl sulfosuccinate as emulsifier cannot be readily diluted because the dispersion becomes inhomogeneous, the dispersion according to the invention can be diluted with DPM up to a ratio of approx. 1:1 without the dispersion being destabilized. As a result, the pour point can be distinctly reduced to as far as <−45° C.

TABLE-US-00004 TABLE 4 Overview of pour points of different polymer solutions and dispersions Added amount Pour point Ex. of DPM*** [° C.] Note 1a /  6 1b /  6 1c / 21 1d / 21 2d /  3 2d 10% −9 Dispersion stable after addition of DPM 2d 20% Not determined Distinct increase in speck count due to addition of DPM 2d 50% Not determined Dispersion becomes inhomogeneous 3b / −6 3b 10% −18  Dispersion stable after addition of DPM 3b 20% −27  Dispersion stable after addition of DPM 3b 50%  <−45**** Dispersion stable after addition of DPM 3f / −9 ***DPM: dipropylene glycol methyl ether ****Lowest reachable temperature of the instrument is −45° C. Pour point not yet reached at this temperature.

5. Pour Point Depression of Crude Oils

[0117] To test the effect of the different polymer solutions and 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 D5985. Here, the amount of added polymer solution or dispersion was chosen such that the same amounts of polymer were added in each case (100 and 1000 ppm in each case, based on the crude oil). In the case of the test in Texas crude oil (from Texas Raw Crude), 5% of a paraffin wax were added in order to artificially increase the amount of wax in the crude oil. This system served as the reference for the comparison of the different polymer solutions and dispersions. Furthermore, tests in a Caspian crude oil were carried out.

[0118] As can be seen in Table 5 and Table 6, approximately the same pour point depressions are achieved both in Texas crude oil and in Caspian crude oil with the polymer dispersions as with the corresponding solution polymers. Thus, the alternative form of administration of the polymers does not have an adverse effect on the effect thereof as pour point depressant. In the case of low metering rates (100 ppm), the dispersions achieve even greater pour point depressions than with the corresponding solutions in organic solvent.

TABLE-US-00005 TABLE 5 Pour point measurements in Texas crude oil (WAT = 22° C.)***** Pour point Pour point depression Polymer added [° C.] [° C.] No addition of 12 / polymer 100 ppm 1a −15 27 1000 ppm 1a −36 48 100 ppm 1b −15 27 1000 ppm 1b −39 51 100 ppm 2d −15 27 1000 ppm 2d −39 51 100 ppm 2e −18 30 1000 ppm 2e −39 51 100 ppm 2k −21 33 1000 ppm 2k −39 51 100 ppm 2n −24 36 1000 ppm 2n −39 51 100 ppm 3b −24 36 1000 ppm 3b −39 51 100 ppm 3f −24 36 1000 ppm 3f −39 51 *****Crude oil from Texas Raw Crude + 5% paraffin wax (melting point 53-57° C. in accordance with ASTM D87; from Sigma Aldrich)

TABLE-US-00006 TABLE 6 Pour point measurements in a Caspian crude oil (WAT = 24° C., wax content ~2%) Pour point Pour point depression Polymer added [° C.] [° C.] No addition of 0 / polymer 100 ppm 1b −6 6 1000 ppm 1b −12 12 100 ppm 2d −3 3 1000 ppm 2d −12 12 100 ppm 2e −6 6 1000 ppm 2e −9 9 100 ppm 3b −6 6 1000 ppm 3b −9 9 100 ppm 3f −6 6 1000 ppm 3f −12 12

6. Wax Inhibition in Crude Oils

[0119] 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 polymers were added in the form of solutions or dispersions. The specified amount is also based here on the pure polymer in order to ensure better comparability. From the weighed wax deposits, wax inhibition was calculated via the following formula:

Wax inhibition(%)=(w.sub.0−w.sub.x)/w.sub.0*100

where w.sub.0 corresponds to the wax deposit in g without addition of polymer and w.sub.x corresponds to the wax deposit in g with addition of polymer.

[0120] Table 7 shows the results of the cold finger deposition tests for selected polymer dispersions in comparison with a corresponding solution polymer at a bath temperature of 37° C. and a finger temperature of 4° C. in Texas crude oil.

[0121] What can be seen is that both the polymer solutions and the dispersions lead to a distinct reduction in wax deposition and that they therefore act as wax inhibitors. Here, in the case of the same metered addition of polymer, the dispersion 3b even achieved a higher wax inhibition than the polymer solution 1a and dispersion 2j.

TABLE-US-00007 TABLE 7 Wax inhibition in Texas crude oil (WAT = 22° C.)***** (bath temperature 37° C., finger temperature 4° C.) After 3 h After 22 h Wax Wax Wax Wax deposition inhibition deposition inhibition after after after after Polymer added 3 h [g] 3 h [%] 22 h [g] 22 h [%] No addition of 3.53 / 4.04 / polymer 100 ppm 1a 1.45 59 2.24 45 100 ppm 2j 1.86 47 2.82 30 100 ppm 3b 1.32 62 2.00 51 No addition of 3.42 / 4.86 / polymer 500 ppm 1a 1.35 61 1.55 68 500 ppm 2j 1.54 55 2.03 58 500 ppm 3b 1.21 65 1.54 68 *****Crude on from Texas Raw Crude + 5% paraffin wax (melting point 53-57° C. in accordance with ASTM D87; from Sigma Aldrich)

7. Stability Tests of the Dispersions

[0122] To investigate whether the dispersions have a sufficient storage stability under different ambient conditions, freezing stability, warm-storage stability and storage stability at room temperature were tested.

Testing of Freezing Stability:

[0123] 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 pasty polymers were stirred using a propeller stirrer (500 rpm) for 30 min. Thereafter, an optical check for coagulate, specks and inhomogeneity was carried out, the polymers were filtered across a sieve fabric (Schnellsieb 125 μm) and the coagulate was weighed. After a further 2 hours of holding the temperature at 23° C., Brookfield viscosity and particle size were determined. This cycle of freezing and thawing was repeated 5 times.

[0124] The results are compiled in Table 8. What can be seen is that, in the case of the dispersion 2d, a distinct rise in Brookfield viscosity and in particle size already occurs after the first freeze-thaw cycle. Moreover, significant amounts of coagulate are formed in every cycle. In the case of the dispersions 3d and 3f according to the invention, no coagulate can be seen in the filter with the naked eye, and the weighed amounts of coagulate are very low. Viscosity and particle size, too, remain unchanged in said dispersions within the limit of measurement accuracy.

TABLE-US-00008 TABLE 8 Summary of the results of the freezing stability tests Dispersion as per example: 2d 3f 3d Start Viscosity 25 mPas 16 mPas 15 mPas Particle size 125 nm 211 nm 221 nm 1st Viscosity 123 mPas 16 mPas 15 mPas cycle Particle size 239 nm 218 nm 226 nm Coagulate wet/dry 1.1%/0.5% 0.3%/0.1% 0.3%/0.2% Filterability − + + (− = poor; + = good) Opt. assessment Highly viscous, Unchanged Unchanged some coagulate 2nd Viscosity 126 mPas 16 mPas 15 mPas cycle Particle size 233 nm 219 nm 223 nm Coagulate wet/dry 1.4%/0.6% 0.3%/0.1% 0.3%/0.1% Filterability − + + Opt. assessment Highly viscous, Unchanged Unchanged some coagulate 3rd Viscosity 139 mPas 16 mPas 15 mPas cycle Particle size 244 nm 210 nm 219 nm Coagulate wet/dry 1.4%/1.0% 0.3%/0.2% 0.4%/0.2% Filterability − + + Opt. assessment Highly viscous, Unchanged Unchanged some coagulate 4th Viscosity 142 mPas 16 mPas 15 mPas cycle Particle size 236 nm 215 nm 226 nm Coagulate wet/dry 1.1%/0.5% 0.4%/0.2% 0.3%/0.1% Filterability − + + Opt. assessment Highly viscous, Unchanged Unchanged some coagulate 5th Viscosity 160 mPas 16 mPas 15 mPas cycle Particle size 266 nm 219 nm 224 nm Coagulate wet/dry 1.2%/0.5% 0.4%/0.2% 0.4%/0.2% Filterability − + + Opt. assessment Highly viscous, Unchanged Unchanged some coagulate

Testing of Warm-Storage Stability:

[0125] Warm-storage stability was tested for the dispersions 3d and 3f according to the invention. Samples of 30 g each were weighed in 50 mL PE wide-neck bottles (glass) and stored at 80° C. in an air-circulation drying cabinet. A visual check for coagulate formation was made every two hours on the first two days and every 4 hours on the following days. After 7 days of storage, the polymers were filtered across a sieve fabric (Schnellsieb 125 μm), any coagulate present was weighed and particle size was determined. The polymers are considered to have warm-storage stability if no significant changes occurred after 7 days.

[0126] No optical changes could be observed here. Particle size, too, was unchanged and the amounts of coagulate formed were, at 0.3% (wet) in each case, relatively low.

[0127] Testing of room-temperature stability: Samples of 245 g each were weighed in 250 mL PE wide-neck bottles and stored at 23° C. in a climate-controlled room. After one week and after 1, 3, 6 and 8 months, the polymers 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 μm) and any coagulate present was weighed. After 2 hours of holding the temperature at 23° C. in a water bath, Brookfield viscosity and particle size were determined.

[0128] Here too, no optical changes, changes in viscosity or in particle size or significant amounts of coagulate could be observed for dispersions 3f and 3d. The dispersions are thus storage-stable at room temperature for at least 8 months.

Summary of the Results of the Examples

[0129] Although dispersions made from BEA or BEMA as monomer can be prepared in accordance with example 1 of U.S. Pat. No. 7,790,821 B2 (examples 2a and 2c), they contain large amounts of coagulate and are very difficult to filter, this being unfavourable for commercial use. In example 2a, there was even the occurrence of a complete coagulation of the dispersion.

[0130] By copolymerization with small amounts of methacrylic acid and by varying the amount of sodium bistridecyl sulfosuccinate as emulsifier (examples 2d to h), it is possible to prepare dispersions which have low amounts of coagulate (<0.5%), but they show an unfavourable flow behaviour at low temperatures, this ruling out use at low ambient temperatures.

[0131] By using sodium bis(2-ethylhexyl) sulfosuccinate, it is possible to obtain dispersions which show an improved flow behaviour at low temperatures and are also easily filterable, but it was not possible to obtain dispersions having less than 0.5% coagulate. Moreover, even after filtration, the dispersions still contain relatively large amounts of specks, i.e. relatively fine inhomogeneities in the dispersion, that are not retained by the filter. These too indicate a non-ideal stability of the system and can lead to unwanted deposits, for example in the supply lines, in the end use. Even an increase in the proportion of methacrylic acid (example 2m) cannot achieve any further improvement here.

[0132] By a combination of two emulsifiers (sodium bistridecyl sulfosuccinate and sodium bis(2-ethylhexyl) sulfosuccinate), it is possible to obtain dispersions which have a similar low-temperature flowability as the dispersions containing only sodium bis(2-ethylhexyl) sulfosuccinate, but moreover contain a distinctly lower amount of coagulate than dispersions containing only one emulsifier. Moreover, the dispersions can be easily filtered and have only a low amount of specks after filtration.

[0133] At the same metered addition, the dispersions can achieve comparable pour point depressions of crude oils as comparable solution polymers, but with the advantage that the dispersions can additionally be metered in at distinctly lower temperatures owing to their flow behaviour.

Analysis Methods:

Ascertainment of Solids Content:

[0134] 5 g of sample were dried to constant weight in an aluminium dish in a vacuum drying cabinet at 80° C. for approx. 3 days.

Brookfield Viscometry:

[0135] 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:

[0136] pH was measured using the pH meter Calimatic 761 from Knick, comprising a pH/Pt-100 glass combination electrode with ceramic diaphragm and 3 M KCl filling.

Determination of Particle Size:

[0137] Particle size was measured using the Delsa Nanosizer from Beckmann Coulter (rDNC). The sample was diluted with distilled water before measurement.

Molar Mass Distribution by Means of GPC:

[0138] The polymers (approx. 5 g) were dried in aluminium dishes in a vacuum drying cabinet at 80° C. for 3 days. Molar mass distribution was ascertained on the dried polymers by means of GPC (polymer standard for calibration: PMMA). The weight-average and the number-average molar mass (MW and Mn) of the polymers were determined therefrom.

Measurement of Pour Point:

[0139] The pour points of the polymer solutions and polymer dispersions and of the crude oils doped with the polymers were measured in accordance with ASTM D5985 using a pour point tester PPT 45150 from PSL Systemtechnik. The measurement yields the “no flow point” with a measurement accuracy of 0.1° C. The “no flow point” was determined as the mean of a triplicate determination. From the “no flow point”, the pour point was then calculated in accordance with ASTM D97.

Cold Finger Deposition Test (Reduction in Wax Deposition from Crude Oils on Cold Surfaces by Addition of Polymer):

[0140] The cold finger deposition test was carried out using a cold finger deposition tester from PSL Systemtechnik (model CF15120).

[0141] Here, 80 mL of the mixture of crude oil+polymer solution or dispersion are heated to the desired bath temperature (e.g. 37° 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 certain time intervals (e.g. after 3 and 22 h), this amount of wax is determined by weighing. The cold finger is kept at a desired finger temperature (e.g. 4° C.) here. The chosen bath and finger temperature simulates here the passage of a warm oil through a pipeline having a cold surface (e.g. in winter or in the deep sea).

Rheological Tests:

[0142] The change in viscosity as a function of temperature was measured using an Anton Paar rheometer MCR302 with cone-plate geometry CP50-1 (diameter 50 mm, cone angle 1°) with TrueGap. Measurement was carried out at a constant shear rate of 100 s.sup.−1 and a cooling rate of 1 K/min over a temperature range of +30 to −30° C. measurement range.

Determination of WAT (Wax Appearance Temperature) and of Wax Content:

[0143] Wax content and WAT were determined by means of DSC. Measurement was carried out here with a cooling rate of 2 K/min.