Additives for improving the cold properties of fuel oils

Abstract

The invention provides additive mixtures comprising A) at least one terpolymer of ethylene, propene and at least one ethylenically unsaturated ester, whichi) contains from 6.0 to 12.0 mol % of structural units derived from at least one ethylenically unsaturated ester having a C1- to C3-alkyl radical,ii) contains from 0.5 to 4.0 methyl groups derived from propene per 100 aliphatic carbon atoms,iii) has fewer than 8.0 methyl groups stemming from chain ends per 100 CH2 groups, andB) from 0.5 to 20 parts by weight, based on A), of at least one further component which is effective as a cold additive for mineral oils and is selected fromB1) copolymers of ethylene and ethylenically unsaturated compounds whose content of ethylenically unsaturated compounds is at least 2 mol % higher than the content of ethylenically unsaturated esters in the terpolymer defined under A),B2) comb polymers, andB3) mixtures of B1) and B2), and also their use as a cold additive for middle distillates.

Description

EXAMPLES

The following additives were used:

Preparation of ethylene copolymers A

Process A): in a continuous tubular reactor, ethylene, propene and vinyl acetate were copolymerized at 200 MPa and a peak temperature of 250° C. with addition of a mixture of various free-radical chain starters and of the molecular weight regulator specified in table 1. The polymer formed was removed from the reaction mixture and then freed of residual monomers.

Process B): in a continuous high-pressure autoclave, ethylene, vinyl acetate and propene were copolymerized with addition of a 10% by weight solution of bis(2-ethylhexyl)peroxodicarbonate as an initiator and the molecular weight regulator specified in table 1. The polymer formed was removed from the reaction mixture and then freed of residual monomers.

For comparison, a terpolymer of ethylene, vinyl acetate and propene according to EP 0 190 553, a terpolymer of ethylene, vinyl acetate and 4-methylpentene-1 according to EP 0 807 642, and a terpolymer of ethylene, vinyl acetate and isobutylene were employed.

The vinyl acetate content was determined by means of pyrolysis of the polymer which had been freed of residual monomers at 150° C./100 mbar. To this end, 100 mg of the polymer are dissociated thermally with 200 mg of pure polyethylene in a pyrolysis flask at 450° C. in a closed system under reduced pressure for 5 minutes, and the dissociation gases are collected in a 250 ml round-bottom flask. The acetic acid dissociation product is reacted with an Nal/KIO₃ solution, and the iodine released is titrated with Na₂S₂O₃ solution.

The total number of methyl groups in the polymer which do not stem from vinyl esters is determined by means of ¹H NMR spectroscopy at a measurement frequency of 500 MHz on 10 to 15% solutions in C₂D₂Cl₄ at 300 K. The integral of the methylprotons between 0.7 and 0.9 ppm is determined as a ratio relative to that of the methylene and methine protons between 0.9 and 1.9 ppm. A correction of the number of the methyl groups for the structural units which are derived from the moderator used and overlap with the signals of the main chain is effected on the basis of the methine proton of the moderator which appears separately (for example, methyl ethyl ketone exhibits multiplets at 2.4 and 2.5 ppm).

The content of methyl groups which derive from propene is determined by means of ¹³C NMR spectroscopy at a measurement frequency of 125 MHz on likewise 10 to 15% solutions in C₂D₂Cl₄ at 300 K. The integral of the methyl groups derived from propene between 19.3 and 20.2 ppm is determined as a ratio relative to that of the aliphatic hydrocarbons of the polymer backbone between 22 and 44 ppm. Advantageously, ¹H and ¹³C NMR measurement is performed on the same sample.

The number of chain ends is determined by subtracting the number of methyl groups derived from propene, determined by means of ¹³C NMR, from the total number of methyl groups, determined by means of ¹H NMR. The two values should be treated as dimensionless numbers.

TABLE 1
Characterization of the ethylene copolymers A used
		Vinyl acetate in the
	Polymerization	polymer	Propene-CH3	Number of chain ends		V140
Polymer	process/moderator	[mol %]	per 100 aliph. CH2	[CH3/100 CH2]	Total G	[mPas]
P1	A/PA	8.9	2.1	4.3	10.3	314
P2	A/PA	9.3	1.5	4.7	10.8	357
P3	B/MEK	9.7	1.4	3.2	11.1	346
P4	B/MEK	10.1	1.8	3.4	11.9	316
P5	A/PA	9.6	1.3	4.0	10.9	286
P6	A/MEK	9.8	1.2	3.9	11.0	288
P7	A/PA	11.4	0.8	4.9	12.2	371
P8	A/PA	7.8	2.7	5.1	10.5	302
P9 (comp.)	B/propene	9.4	6.4	6.2	15.8	347
P10 (comp.)	B/PA	9.7	2.1 mol % of 4-MP-1	n.a.	n.a.	325
P11 (comp.)	B/PA	9.5	2.5 mol % of DIB	n.a.	n.a.	297
PA = propionaldehyde;
MEK = methyl ethyl ketone;
4-MP-1 = 4-methylpentene-1;
DIB = diisobutylene;
n.a. = not applicable

Characterization of flow improver components (B) and further flow improver components (C):

• • B1-I) Terpolymer of ethylene, 14 mol % of vinyl acetate and 2 mol % of vinyl neodecanoate with a melt viscosity measured at 140° C. of 95 mPas.
  • B1-II) Copolymer of ethylene and 13.5 mol % of vinyl acetate with a melt viscosity measured at 140° C. of 150 mPas.
  • B2-I) Alternating copolymer of maleic anhydride and octadecene, fully esterified with a mixture of equal parts of tetradecanol and hexadecanol.
  • C-I) Mixture of a reaction product of a copolymer of C₁₆-α-olefin and maleic anhydride with 2 equivalents of di(hydrogenated tallow fat)amine and a nonylphenol-formaldehyde resin in a weight ratio of 2:1.

All additives A, B and C used were, unless stated otherwise, used as 50% by weight dilutions in relatively high-boiling, predominantly aliphatic solvents.

Table 2: Characterization of the Test Oils Used

The test oils used were current oils from European refineries. The CFPP value was determined to EN 116 and the cloud point to ISO 3015. The paraffin content was determined by gas chromatography separation of the oil with detection by an FID detector and calculation of the integral of the n-paraffins with a chain length of at least 20 carbon atoms in relation to the total integral.

	Test oil 1	Test oil 2	Test oil 3	Test oil 4	Test oil 5	Test oil 6
Distillation
IBP [° C.]	163	160	174	167	153	187
20% [° C.]	222	206	222	238	195	223
90% [° C.]	343	339	354	341	354	337
FBP [° C.]	366	363	371	359	375	360
Cloud Point [° C.]	−3.9	−2.5	0.0	−3.9	+0.7	−5.1
CFPP [° C.]	−6	−4	−3	−7	−3	−9
Sulfur [ppm]	19	25	8	5	66	8
Density @15° C.	0.835	0.829	0.858	0.845	0.858	0.834
Paraffin content ≧C20	5.7	5.9	7.6	5.2	7.0	7.9

Effectiveness of the Additives as Cold Flow Improvers

The superior effectiveness of the inventive additives for mineral oils and mineral oil distillates is described with reference to the CFPP test (Cold Filter Plugging Test to EN 116).

TABLE 3
Testing as a cold flow improver in test oil 1
	CFPP [° C.]
	Additive	200	400	600
Example	A	B	C	ppm	ppm	ppm
1	20% P1	55% B1-I	25% C-I	−19	−22	−25
2	20% P2	55% B1-I	25% C-I	−23	−28	−27
3	20% P3	55% B1-I	25% C-I	−24	−22	−26
4	20% P4	55% B1-I	25% C-I	−18	−22	−26
5	20% P5	55% B1-I	25% C-I	−23	−26	−27
6	20% P6	55% B1-I	25% C-I	−23	−29	−28
7	20% P7	55% B1-I	25% C-I	−18	−21	−24
8	20% P8	55% B1-I	25% C-I	−19	−22	−24
9 (comp.)	20% P9	55% B1-I	25% C-I	−14	−16	−18
10	20% P10	55% B1-I	25% C-I	−17	−20	−23
(comp.)
11	—	69% B1-I	31% C-I	−10	−12	−17
(comp.)

TABLE 4
Testing as a cold flow improver in test oil 2
	CFPP [° C.]
	Additive	200		600
Example	A	B	C	ppm	400 ppm	ppm
12	20% P1	55% B1-I	25% C-I	−15	−20	−20
13	20% P2	55% B1-I	25% C-I	−17	−23	−23
14	20% P3	55% B1-I	25% C-I	−18	−21	−22
15	20% P4	55% B1-I	25% C-I	−16	−20	−22
16	20% P5	55% B1-I	25% C-I	−16	−22	−25
17	20% P6	55% B1-I	25% C-I	−18	−19	−22
18	20% P7	55% B1-I	25% C-I	−14	−18	−19
19	20% P8	55% B1-I	25% C-I	−15	−19	−20
20	20% P9	55% BI-I	25% C-I	−9	−13	−14
(comp.)
21	20% P11	55% B1-I	25% C-I	−14	−17	−18
(comp.)
22	—	69% B1-I	31% C-I	−8	−12	−16
(comp.)

TABLE 5
Testing as a cold flow improver in test oil 3
	Additive	CFPP [° C.]
Example	A	B	50 ppm	100 ppm	150 ppm
23	85% P1	15% B1-II	−5	−10	−12
24	85% P2	15% B1-II	−4	−8	−13
25	85% P3	15% B1-II	−4	−7	−14
26	85% P4	15% B1-II	−4	−9	−11
27	85% P5	15% B1-II	−5	−12	−15
28	85% P6	15% B1-II	−4	−8	−14
29 (comp.)	85% P9	15% B1-II	−3	−5	−7
30 (comp.)	85% P10	15% B1-II	−4	−6	−11
31 (comp.)	—	100% B1-II	−4	−4	−5
32 (comp.)	100% P1	—	0	−2	−4

TABLE 6
Testing as a cold flow improver in test oil 4
	Additive	CFPP [° C.]
Example	A	B	50 ppm	100 ppm	200 ppm
33	35% P1	65% B1-I	−10	−16	−20
34	35% P2	65% B1-I	−10	−17	−20
35	35% P3	65% B1-I	−11	−17	−20
36	35% P5	65% B1-I	−11	−17	−19
37	35% P6	65% B1-I	−10	−16	−18
38 (comp.)	35% P9	65% B1-I	−10	−13	−15
39 (comp.)	35% P10	65% B1-I	−11	−15	−18
40 (comp.)	—	100% B1-I	−10	−9	−14
41 (comp.)	100% P1	—	−8	−13	−16

TABLE 7
Testing as a cold flow improver in test oil 5
	Additive	CFPP [° C.]
Example	A	B	300 ppm	400 ppm
42	65% P1	35% B2-I	−7	−11
43	65% P2	35% B2-I	−7	−12
44	65% P4	35% B2-I	−6	−11
45	65% P6	35% B2-I	−6	−10
46 (comp.)	65% P9	35% B2-I	−4	−8
47 (comp.)	65% P11	35% B2-I	−4	−9

Handling and Filter Blocking Tendency of the Polymers

To assess the cold flowability of concentrates of the inventive polymers, the polymers described in table 1 were dissolved at 35% strength by weight in a predominantly aliphatic solvent mixture with boiling range of 175-260° C. and a flashpoint of 66° C. To this end, polymer and solvent were heated to 80° C. with stirring and, after homogenization, cooled to room temperature.

Subsequently, the pour point of the concentrate was determined to DIN ISO 3016.

TABLE 8
Intrinsic pour point of the polymer concentrates
	Example	Specimen	Pour Point
	48	P1	+6° C.
	49	P2	+6° C.
	50	P3	0° C.
	51	P4	−6° C.
	52	P5	+3° C.
	53	P6	0° C.
	54 (comp.)	P9	−3° C.
	55 (comp.)	P10 (comp.)	+9° C.
	56 (comp.)	P11 (comp.)	+9° C.

In addition, the filter blocking tendency of a test oil treated with inventive additives was determined to IP 387/97. In this test, 300 ml of an additized diesel fuel are filtered through a 1.6 pm glass fiber filter at defined temperature and a pump output of 20 ml/min. The test is considered to have been passed when a volume of 300 ml passes through the filter without the pressure (P) having attained or exceeded 105 kPa (filter blocking tendency FBT=(1+(P/105)²)^0.5≦1.41). It is considered not to have been passed when the pressure reaches 105 kPa before the total volume (V) of 300 ml has passed through the filter (filter blocking tendency FBT=(1+(300/V)²)^0.5>1.41). For the assessment of the additives, it is also important that the filter blocking tendency of the unadditized fuel is increased as little as possible by adding the additive.

For the performance of the test, 350 ml of the test oil 6 of temperature 20-22° C. were admixed with 500 ppm of the additive of temperature 60° C. (50% solution). After manual shaking and storage at 60° C. for 30 minutes, the additized oil was stored at 20° C. for 16 hours. Subsequently, the additized oil was used for filtration without shaking again.

TABLE 9
Filter blocking tendency of the additized test oil 6 to IP 387/97
	Example	Specimen	Filter blocking tendency
	57	none	1.01
	58	P1	1.02
	59	P2	1.02
	60	P3	1.11
	61	P4	1.02
	62	P5	1.03
	63	P6	1.09
	64	P7	1.25
	65	P8	1.27
	66 (comp.)	P9	1.05
	67 (comp.)	P10	1.57
	68 (comp.)	P11	1.76

The experiments show that the inventive additives, with regard to the improvement in the cold flowability and especially the lowering of the CFPP of middle distillates are superior to the prior art additives. At the same time, they are usable at relatively low temperatures. In particular, they are also usable in applications in which particularly clean fuels with very low filter blocking tendency are required.

Claims

1. An additive mixture comprising A) at least one terpolymer of ethylene, propene and at least one ethylenically unsaturated ester, whichi) contains from 6.0 to 12.0 mol % of structural units derived from at least one ethylenically unsaturated ester having a C1- to C3-alkyl radical,ii) contains from 0.5 to 4.0 methyl groups derived from propene per 100 aliphatic carbon atoms,iii) has fewer than 8.0 methyl groups stemming from chain ends per 100 CH2 groups, andB) from 0.5 to 20 parts by weight, based on A), of at least one further component which is effective as a cold additive for mineral oils and is selected from the group consisting ofB1) a copolymer of ethylene and an ethylenically unsaturated compound whose content of ethylenically unsaturated compounds is at least 2 mol % higher than the content of ethylenically unsaturated ester in the terpolymer defined under A),B2) a comb polymer, andB3) mixtures of B1) and B2).

2. The additive mixture as claimed in claim 1, in which the ethylenically unsaturated ester of component A) is the vinyl ester of a carboxylic acid having from 1 to 4 carbon atoms.

3. The additive mixture as claimed in claim 1, in which the ethylenically unsaturated ester is vinyl acetate.

4. The additive mixture of claim 1, in which the sum G of molar content of unsaturated ester i) and the number of methyl groups derived from propene per 100 aliphatic carbon atoms of the polymer ii) G=[mol % of unsaturated ester]+[propene-CH3]

5. The additive mixture of claim 1, in which component A) further comprises from 0.3 to 5.0% by weight of at least one structural unit derived from a moderator comprising carbonyl groups.

6. The additive mixture of claim 1, in which the content of ethyleneicaly unsaturated compounds in copolymer B1) is at least three mol % higher than that of the ethylenically unsaturated ester in the terpolymer A).

7. A process for preparing the terpolymer A) by reacting a mixture of ethylene, propene and at least one vinyl ester under elevated pressure and elevated temperature in the presence of a free radical-forming initiator, and in which the molecular weight of the terpolymer A) is adjusted by a moderator comprising carbonyl groups.

8. (canceled)

9. A process for improving the flowability of a fuel oil by adding to the fuel oil the additive mixture of claim 1.

10. A composition comprising the additive mixture of claim 1 and at least one oil-soluble polar nitrogen compound.

11. A composition comprising the additive mixture of claim 1 and at least one alkylphenol-aldehyde resin.

12. A composition comprising the additive mixture of claim 1 and at least one olefin polymer.

13. A composition comprising the additive mixture of claim 1 and at least one polyoxyalkylene compound.

14. A fuel oil composition comprising a middle distillate and the additive mixture of claim 1.