NZ206666A

NZ206666A - Flow improvement of distillate fuel using an ethylene/vinyl ester copolymer

Info

Publication number: NZ206666A
Application number: NZ206666A
Authority: NZ
Inventors: F Rossi; Greef J J P De; N A Richardson
Original assignee: Exxon Research Engineering Co
Priority date: 1983-01-04
Filing date: 1983-12-21
Publication date: 1987-06-30
Also published as: JPH05186782A; DK164792B; GB8300016D0; DD236940A5; IN159929B; JPS59136391A; ATE80651T1; NO834889L; JP2534818B2; DK3184D0; DK164792C; EP0113581B2; DE3382624T3; NO172650C; NO172650B; FI834887A; KR840007434A; EP0113581A1; FI834887A0; JPH0330637B2

Abstract

The flow properties of a distillate petroleum fuel oil whose 20% and 90% distillation points differ within the range of from 65 to 100 DEG C, and/or whose 90% to final boiling point is 10 to 20 DEG C is improved by the inclusion of a copolymer of ethylene and a vinyl ester of a carboxylic acid containing 1 to 4 carbon atoms containing 32 to 35 wt % of the vinyl ester and having a number average molecular weight of 1000 to 6000.

Description

<div class="application article clearfix" id="description"> New Zealand Paient Spedficaiion for Paient Number £06666 2066 66 No.: Date: COMPLETE SPECIFICATION "MIDDLE DISTILLATE COMPOSITIONS WITH IMPROVED LOW TEMPERATURE PLOW PROPERTIES" Si/We, EXXON RESEARCH AND ENGINEERING COMPANY, of Florham Park, New Jersey 07932, United States of America, a corporation organized and existing under the laws of the State of Delaware, United States of America, hereby declare' the invention for whiciggi / we pray that a patent may be granted tojQfg/us, and the method by which it is to be performed, to be particularly described in and by the following statement: - - 1 - (followed by page la) 2 086 66^ -lov - WV Middle Distillate Compositions with Improved Low Temperature Flow Properties 1 Mineral oils containing paraffin wax have the characteristic of becoming less fluid as the temperature of the oil decreases. This loss of fluidity is due to the crystallization of the wax into plate-like 5 crystals which eventually form a spongy mass entrapping the oil therein. It has long been known that various compositions act as wax crystal modifiers when blended with waxy mineral oils. These compositions modify the size and 10 shape of wax crystals and reduce the adhesive forces between the wax and oil in such a manner as to permit the oil to remain fluid at a lower temperature. Various pour point depressants have been described in the literature and several of these are in commercial 15 use. For example, U.S. Pat. No. 3,048,479 teaches the use of copolymers of ethylene and C^-Cg vinyl esters, e.g. vinyl acetate, as pour depressants for fuels, specifically heating oils, diesel and jet fuels. Hydrocarbon polymeric pour depressants based 20 on ethylene and higher alpha-olefins, e.g. propylene, are also known. U.S. Patent 3,961,916 teaches the use of a mixture of copolymers, one of which is a wax crystal nucleator and the other a growth arrestor to control the size of the wax crystals. Similarly United Kingdom Patent 1263152 suggests that the size of the wax crystals may be controlled by using a copolymer having a lower degree of side chain branching. With the increasing diversity in distillate fuels, types of fuel have emerged which cannot be treated by the existing additives or which require an uneconomi-cally high level of additive. One particular group of fuels that present such problems are those which have a relatively narrow boiling range. Fuels are frequently characterised by their Initial Boiling Point, Pinal Boiling Point and the interim temperatures at which certain volume percentages of the initial fuel have distilled. Fuels whose 20% to 90% distillation point differ withip the range of from 65 to 100"C especially 70 to 100* C (ASTM D86) and 90% boiling temperature is generally from 10 to 30*C especially 10 to 25'C of the final boiling point have been found particularly difficult to treat sometimes being virtually unaffected by additives or otherwise requiring very high levels of additive. All distillations referred to herein are according to ASTM D86 Furthermore with the increase in the cost of crude oil it has also become important for a refiner to increase his production of distillate fuels and to optimise - 3 - his operations using what is known as sharp fractionation again resulting in distillate fuels that are difficult to treat with conventional additives or that require a treat level than is unacceptably high for the economic standpoint. Typical sharply fractionated fuels have a 90% to final boiling point of 10 to 20*C usually with a 20 to 90% boiling range of 90 to 110'C. Both types of fuel have final boiling points above 350°C generally a final boiling point in the range 350°C to 375"C especially 350°C to 370'C. The copolymers of ethylene and vinyl acetate which have found widespread use for improving the flow of the previously widely available distillate fuels generally contained up to about 30 wt % vinyl acetate where the additive was used to control the size of wax crystals forming in the fuel or they contained around 36 wt % or more vinyl acetate where their prime function was to lower the pour point of the distillate fuel. We have not found either of these types of additive to be effective in the treatment of the narrow boiling and/or sharply fractionated fuels described above. We have, however, found that copolymers of ethylene and vinyl esters of carboxylic acids containing from 1 to 4 carbon atoms containing from 32 to 35 wt % of the - 4 - 2066 1 vinyl ester and having a number average molecular weight of from 1000 to 6000 are particularly effective in the treatment of these of fuels. The present invention therefore provides the use as an 5 additive for improving the flow properties of a distillate petroleum fuel oil whose 20% and 90% distillation points differ within the range of from 65 to 100#C, and/or for improving the flow properties of a distillate fuel whose 90% to final boiling point is 10 10 to 20°C of an additive comprising a copolymer of ethylene and a vinyl ester of a carboxylic acid containing 1 to 4 carbon atoms containing 32 to 35 wt % of the vinyl ester and having a number average molecular weight of 1000 to 6000. 15 The present invention further provides a distillate fuel whose 20% and 90% distillation point differ by 65 to 100"C and whose 90% boiling temperature is from 10 to 30'C of the final boiling point and/or whose 90% to final boiling point is 10 to 20°C and 20 containing from 50 to 500 ppm (parts per million) of a copolymer of ethylene and a vinyl ester of a carboxylic acid containing 1 to 4 carbon atoms containing 32 to 35 wt % of the vinyl ester and having a number average molecular weight of 1000 to 6000. 2066 6& - 5 - The copolymer of the ethylene and vinyl ester of the carboxylic acid may be a mixture of two copolymers such as those generally described in United States Patent 3,961,916 which may or may not contain the same vinyl ester. In particular we find that an additive combination containing at least 10 parts by weight of the growth arrestor for each part by weight of the wax crystal nucleator is suitable for treating this type of fuel. The mixture being particularly useful since it allows added flexibility. A preferred embodiment of the present invention therefore provides the use as an additive for improving the flow properties of a distillate petroleum fuel oil whose 20% to 90% distillation points differ within the range of from 65 to 100*C, and/or of a distillate fuel whose 90% boiling temperature is from 10 to 30*C preferably 10 to 20°C of the final boiling point an additive comprising from 10 to 15 parts by weight of a synthetic polymeric material having the property of a wax growth arrestor in said fuel for each part of a synthetic polymeric material having the properties of a wax growth stimulator, said wax growth arrestor and growth stimulator being copolymers of ethylene and vinyl esters of carboxylic acids containing from 1 to 4 carbon atoms the average ester content of said copolymers being in the range 32 to 35 wt.% and the number average molecular weight thereof being in the range 1000 to 6000. In a further embodiment the present invention provides a distillate fuel whose 20% to 90% boiling fraction differ in their boiling point by from 65 to 100°C and/or a distillate fuel whose 90% to final boiling point is 10 to 20*C containing from 50 to 500 ppm parts per million of an additive mixture of 10 to 15 parts by weight of a synthetic polymeric material having the property of a wax growth arrestor in said fuel for each part of a synthetic polymeric material having the properties of a wax growth stimulator said growth arrestor and growth stimulator being copolymers of ethylene and vinyl esters of carboxylic acids containing from 1 to 4 carbon atoms, the average ester content of said copolymers being in the range 32 to 35 wt.% and the number average molecular weight thereof being in the range 1000 to 6000. 2 066 66 The fuels whose 20% to 90% distillation points differ within the range 65 to 100°C their 90% boiling temperature generally is from 10 to 30"C of the final boiling points generally have a final boiling point above 350®C usually between 350®C and 375#C more usually between 350*C and 370°C. The fuels whose 90% to final boiling point is 10" to 20*C usually have a 20 to 90% distillation range of from 90* to 110"C and also generally have -final boiling points above 350*C usually between 350"C and 375°C more usually between 350*C and 370#C. Where the additive is a mixture the wax growth stimulator or nucleator is a synthetic polymeric material which is soluble in the distillate at temperatures substantially above the saturation temperature but on cooling of the distillate progressively separates out in the form of small particles as the temperature of the distillate approaches the saturation point, e.g. is cooled from a point slightly above (e.g. 10"C above; preferably about 5#C above) said saturation temperature. The term "saturation temperature" is defined as the lowest temperature at which solute, e.g. wax, cannot be crystallized out of the solution even if known crystallization inducement methods are used. Whilst not known certainly it is believed that as cooling continues, additional nucleator particles separate out in a more or less continuous manner. These additional particles act as nucleators for continued wax crystallization, which in effect, would prevent substantial supercooling of the distillate. The advantages of having fresh nucleator particles formed continuously is that the supersaturation of the distillate with n-paraffins is kept at the lowest possible level thus facilitating a molecule of growth arrestor to build itself into the growth center of growing crystals and by so doing to stop the further growth. The inhibitory effect of a growth arrester is believed to result from the presence of bulky groups in its molecule. Additional nucleator should separate out to replace the deactivated growth centers. The wax growth arrester is more soluble in said distiliate than said nucleator and it acts as a growth arrester as the wax crystal forms. The nucleator should not be insoluble in the distillate at elevated temperatures nor should it start to separate out at a temperature substantially above that at which wax crystallization can occur. If nucleators separate out at a temperature substantially above the temperature at which crystallization can occur, then they tend to settle at the bottom of the vessel holding the distillate, instead of remaining dispersed within the distillate. This factor is especially important when the distillate is subjected to repeated 2 066 66 - 9 - warming and cooling as during the warm and cool parts of a day since it does not result in adequate redisper-sion of the nucleant particles in the distillate. The synthetic polymeric materials used as wax growth stimulators and wax growth arresters may contain the same or different vinyl esters. For the purpose of this invention, wax crystal growth stimulators, wax nucleators and nucleants for wax are all considered equivalent terms and are used interchangeably. Wax growth arresters (hereinafter sometimes referred to as wax arresters), generally include in their molecular structure wax-like polymethylene segments which are capable of building themselves into the lattice of the wax crystals at the point of lattice dislocation, and also contain bulky groups which prevent incorporation of further molecules of n-paraffins at the point of lattice dislocation and by so doing stop further growth of crystal. A good synthetic polymeric wax nucleator, can be chosen by visually comparing a transparent container containing a 0.1 to 3.0 wt.% solution of the potential nucleator in a distillate to an identical container with the same distillate having no additive, as the temperature of the two materials is lowered. The onset - 10 - 1 of the wax crystallization from the distillate containing a polymeric material which has nucleator characteristics will occur at a higher temperature than that at which the crystallization will start in 5 the absence of said nucleator. Similarly, a wax arrester usually is characterized by the ability to delay onset of crystallization. The synthetic polymers used as nucleating agents arid as wax growth arresters are copolymers of ethylene 10 and vinyl ester and may contain the same or different ester monomer. With the preferred additive that is a mixture of polymers as described above the vinyl ester content and molecular weight are the average over the mixture. 15 The additive may however also be single polymer by which is meant material produced in a single polymerisation. In this instance the materials may be obtained by the well known high pressure or solution polymerisation techniques that have previously been 20 suggested for the production of ethylene vinyl ester, especially vinyl acetate copolymers for fuel additives Typical vinyl esters for both mixtures and single polymers include vinyl acetate, vinyl propionate, and vinyl butyrate. 2 066 66 -11- The flow improvers when incorporated into the distillate fuels preferably are effective in: 1. maintaining these fuels fluid at the operating temperatures, 2. arresting the growth of separating wax crystals when the oils are submitted to slow cooling, i.e. 0.2°F to 2*F./hr, which are typical of the rates encountered when "oil in bulk" is exposed to atmospheric cooling. 3. arresting the growth of separating wax crystals when the oils are submitted to fast cooling, i.e. 10*F. to TOO'F./hr/. which are typical of the rates encountered when relatively warm oil enters transfer lines and is there suddenly exposed to low temperatures. All three above-quoted criteria are desired in order to assure that a fuel is pumpable and filterable under the conditions of its distribution and it use. As mentioned where mixtures of polymers are used the molecular weight is the average of the two polymers and in general, the preferred number average molecular weight (VPO) for the nucleator will be within the range of 500-6000, more preferably 1200-6000. Specifically for example, a relatively low molecular weight ethylene- ^ vinyl ester copolymer with a relatively high vinyl ester content has been found to act as a wax growth 2 066 66s arrester. On the other hand, a relatively high molecular weight copolymer of ethylene with a vinyl ester which copolymer has a relatively low content of vinyl ester acts as a nucleating agent. Even more specifically, blends containing ethylene/vinyl acetate copolymers of number average molecular weights from 1200-6000 (VPO) with vinyl acetate contents of about 32-50 wt.% (e.g. about 11 to 25 mole % ester) as the wax arresters and ethylene/vinyl acetate copolymers of about 500-10,000 (VPO) number average molecular weight with vinyl acetate comonomer proportions by weight of 1-30 wt.% (e.g. about 0.3 to 12 mole % ester) as the wax growth stimulators have been found to be highly effective. Where the nucleant is an ethylene/vinyl acetate copolymer its number average molecular weight is preferably at least 500, preferably 1000, higher and/or the ester content at least 5% lower than the corresponding property of the wax growth arrester. All molecular weights specified herein are "number average molecular weights", which are molecular weights as measured by Vapor Phase Osmometry (VPO), e.g. using Mechrolab Vapor Phase Osmometer 301A. The vinyl acetate contents are determined by saponification. - 13 - 2 066 66 Thus, relative to the growth arrester, the nucleator can comprise an ethylene-vinyl acetate copolymer of a higher molecular weight if the vinyl acetate content of both polymeric materials is about equal. Where two synthetic polymers are used they may be made separately or they can be made consecutively in one batch by varying the reaction conditions. Thus, the reaction conditions can be selected so that the initial polymerization reaction produces a polymer having primarily nucleator characteristics and the reaction conditions can be changed to produce a polymer having primarily wax growth arresting properties or vice versa. In this manner, a mixture of polymers can be produced having both types of functions. In the specific embodiment of the invention which employs two different copolymers of ethylene and vinyl acetate the relationships between the concentration of vinyl acetate in the copolymer and molecular weight of the copolymers are important since they are factors which determines the role of the particular copolymer in the fuel. That is, they determine, given the other polymer properties are similar whether or not the copolymer as a whole will be performing within the composition as a wax arrester or as a wax nucleating agent. Thus, very generally as a rule of thumb, the nucleating agents should have relatively long poly- - 14 - dm U D O <5 ^ 1 methylene segments, and so as these synthetic polymers approach low molecular weight ranges, the proportion of vinyl acetate should also decrease. On the other hand, as the molecular weight increases, the 5 proportion of vinyl acetate should also increase. Thus, the specific wax nucleating agents will comprise a copolymer of ethylene and a relatively low proportion of vinyl acetate with a relatively high molecular weight. 10 The wax arrester on the other hand wall; in general, be a relatively low molecular weight copolymer of a relatively high vinyl acetate content since the function of wax arresting depends more on the presence of bulky groups, such as ester groups, attached to the 15 backbone of the molecule of the copolymer. Although the separate copolymers may be blended directly in the fuel, it will normally be found desirable to prepare a concentrate. This may be effected by first associating each with a separate 20 solvent, but most preferably by dissolving each in a common solvent. Thus, both the preferred relatively lower molecular weight high vinyl acetate (second) copolymer and the preferred first , the relatively high molecular weight low vinyl acetate copolymer, may 25 be dissolved in a kerosene or heavy aromatic naphtha. Preferred concentrates will contain 5-60%, preferably 2 066 66 10-50% total copolymer with the balance being a hydrocarbon oil solvent. The arrester copolymers may be prepared by known procedures employing free-radical initiators, preferably organic peroxide compounds. Suitable procedures are high temperature and high pressure processes or the solution processes U.S. specifications, such as U.S. Pat. Nos.3,048,479 or 3,093,623 and United Kingdom Patent Specification 1263152. In one aspect the fuels to which the present invention relates are difficult to treat with conventional additives because of the relatively narrow boiling range of the 20% to 90% degree fraction of the fuel, the 90% fraction boiling from 65 to 100*C above that of the 20% fraction and/or because of the relatively small gap between the 90% boiling point and the final boiling point of less than 25*C and even, in some instances less than 20"C. Suitably, there is present a total of 0.001% to 0.5% by weight of additive, based on the weight of fuel; preferably 0.005 to 0.1%, most preferably 0.01 to 0.04%, all percents being weight percents. Where a mixture is used the polymeric materials are used in 206666 ratios of 10 to 15 parts by weight of growth arrester, per part of the nucleator. The present invention is illustrated by the following Examples in which an additive of the present invention (additive A) was an oil solution containing 63 wt.% of a combination of polymers comprising 13 parts by weight of a wax crystal growth arrestor comprising an ethylene vinyl acetate copolymer of number average molecular weight 2500 and vinyl acetate content of 36 wt.% and 1 part by weight of wax crystal simulator of number average molecular weight 3500 and a vinyl acetate content of about 13 wt.% Additive B was an oil solution containing 45 wt.% of an additive combination of 3 parts by weight of the abovementioned wax crystal growth arrestor and 1 part of the wax crystal simulator according to United States Patent 3961916. Additive C is 50 wt.% solution in oil of an ethylene acetate copolymer of number average molecular weight 2000 and vinyl acetate content 30 wt.%. - 17 - 2 066 1 The fuels used in the Examples were as follows: Initial 20% 90% Pinal B.P. B.P. B.P. B.P. 1C °C "C *C Fuel 1 200 248 334 360 5 Fuel 2 228 280 351 374 Fuel 3 220 266 346 367 Fuel 4 224 268 341 359 Fuel 5 221 259 331 361 Fuel 6 244 264 336 360 10 Fuel 7 163 240 344 362 Fuel 8 160 234 344 358 Fuel 9 200 257 336 362 Fuel 10 213 264 338 360 In the Examples the Wax Crystal Size at Fast Cooling 15 Rates is measured by the Cold Filter Plugging Point test (CFPP). This test is carried out by the procedure described in "Journal of the Institute of Petroleum", Volume 52/ No. 510, June 1966, pp. 173-185. In brief, the CPPP test is carried out with a 45 ml sample of 20 the oil to be tested. The oil placed in the ASTM cloud point jar is cooled in a bath maintained at about —30*F. Every two degrees drop in temperature, starting from 4*F. above the cloud point, the oil is forced at a suction of 8 inches of water through a 25 filter element provided with a 350 mesh screen into a pipette to a mark indicating a volume of 20 ml., at 2 06 ft _ -J g _ .1 which time the oil is allowed to return by gravity flow to the cooling chamber. The test is repeated with each 2*C drop in oil temperature until the oil fails to fill the pipette in a period of 60 seconds to 5 the aforesaid mark. The results of the test are reported as the Cold Filter Plugging Point which is the highest temperature at which the oil fails to fill the pipette. The amounts of Additive A, Additive B and Additive C 10 required to achieve a 6"C, 8°C and 10#C reduction in the.temperature at which these fuels would pass the CFPP test were determined to be as follows: Fuel 6°C 8"C 10*C Additive Additive Additive Reduction Reduction A B C A B C A B C 1 410 760 700 560 1050 not 700 1360 not possible possible 2 130 400 440 190 540 620 250 650 " .3 420 700 500 850 - 520 820 4 • 700- not-- 800 not 900 not possible possible possible 5 780 - " 840 " not " 6 250 - 1000 330 1000 410 - 1000 7 570 - 900 620 - 950 710 1100 8 500 - 900 600 - 1000 700 - 1100 9 260 - not 370 - not 450 - not possible possible possible 10 530 - " 570 - 600 - 19 - 2066 66 1 In- a further series of experiments the amount of additive required to give a reduction of 6, 8 and 10'C in the CFPP value of various fuels was tested and compared with the amounts required for additives 5 outside of the present invention. The fuels used were: Fuel No. IBP 20% 90% FBP 11 107 244 351 381 12 113 242 355 375 13 200 248 334 360 14 220 263 350 : ; 373 ■■ ■ 15 : 220 266 346 ■ 367 16 221 259 331 361 17 222 260 328 354 18 228 280 351 374 and the additives used were A, B and C as used in the previous example together with Additives D to H as follows: .. .. Wt. % Vinyl Molecular Additives Acetate Weight 20 D 34.8 2650 E 27.1 3170 r) F 28.9 2590 G 28.2 2940 H 29.9 2300 The results are given in the following table. </div>

Claims

<div class="application article clearfix printTableText" id="claims">



CFPP Depression 

Amount of Additive Required p.p.m. 

Fuel No. 

"C 

A 

B 

C 

D 

E 

F 

G 

H 

11 

6 

45 

90 

35 

50 

100 

26 

40 

80 

8 

70 

110 

40 

75 

220 

35 

75 

105 

10 

90 

140 

70 

90 

>500 

85 

120 

135 

12 

6 

100 

250 

195 

155 

>500 

130 

145 

210 

a 

160 

320 

200 

195 

>500 

200 

210 

270 

10 

180 

380 

350 

270 

>500 

275 

30.0 

350 

13 

6 

500 

750 

550 

650 

>2000 

650 

200 

1050 

8 

650 

800 

1000 

1000 

>2000 

800 

300 

1020 

10 

730 

900 

1080 

1090 

>2000 

1000 

500 

1300 

14 

6 

280 

340 

300 

300 

>800 

320 

440 

420 

8 

350 

380 

400 

350 

>800 

420 

460 

450 

10 

370 

440 

470 

380 

>800 

500 

480 

480 

15 

6 

370 

460 

600 

500 

>1500 

550 

600 

650 

8 

450 

560 

710 

600 

>1500 

750 

650 

700 

10 

470 

760 

860 

1060 

>1500 

800 

750 

800 

16 

6 

580 

550 

750 

500 

1850 

600 

1100 

1000 

8 

800 

750 

110 

680 

>2000 

700 

1350 

1150 

10 

880 

880 

1330 

870 

>2000 

850 

1400 

1200 

17 

6 

600 

850 

1000 

580 

>2000 

1350 

1500 

1600 

8 

790 

980 

1300 

750 

>2000 

1850 

2000 

2000 

10 

890 

1160 

1500 

920 

>2000 

2200 

>2000 

>2000 

18 

6 

140 

400 

370 

140 

>750 

700 

>750 

>750 

8 

160 

470 

500 

160 

>750 

>750 

>750 

>750 

10 

180 

540 

650 

175 

>750 

>750 

>750 

>750 

N> O 

6 8 10 

327 429 474 

461 546 650 

474 656 789 

359 476 607 

High High High 

541 >688 >848 

>596 >718 >788 

>720 >828 >874 

-21- 

206666 

WHAT WE CLAIM IS 

© 

10 

1 The use as an additive for improving the flow properties of a distillate petroleum fuel oil whose 20% and 90% distillation points differ within the range of from 65 to 100°C, and/or for improving the flow properties of a distillate fuel whose 90% to final boiling point is 10 to 20"C of an additive comprising a copolymer of ethylene and a vinyl ester of a carboxylic acid containing 1 to 4 carbon atoms containing 32 to 35 wt % of the vinyl ester and having a number average molecular weight of 1000 to 6000.
2 The use according to claim 1 wherein the fuel has a final boiling point in the range 350 to 375"C. . 

15
3 The use according to claim 1 or claim 2 in which the fuel whose 20% and 90% distillation points differ within the range 65 to 100°C has a 90% boiling point from 10 to 30°C of the final boiling point.
4 The use according to any one of the preceding claims of an additive which is a mixture of two copolymers , both being copolymers of ethylene and .vinyl[acetate, oneof - 

which acts as a nucleator for the wax and the other of which acts as a growth arrestor for the wax crystals.
5 The use according to claim'4.of a mixture containing at least 10 parts by weight of the growth arrestor for each part by weight of the nucleator. 

-22- 

206666
6 The use according to any one of the preceding' claims: wherein the vinyl ester is vinyl acetate.
7 The use according to any one of the preceding claims wherein the 20% to 90% distillation range of the fuel oil is 70* to 100'C and the 90% to final boiling point is from 10* to 25 "C.
8 A distillate fuel whose 20% and 90% distillation point differ by 65 to 100'C and/or whose 90% to final boiling point is 10 to 20°C containing from 50 to 500 ppm of a copolymer of ethylene and a vinyl ester of a carboxylic acid containing 1 to 4 carbon atoms containing 32 to 35 wt % of the vinyl ester and having a number average molecular weight of 1000 to 6000.
9 A distillate fuel according to claim 8 whose final boiling point is in the range 350 to 375"C.
10 A distillate fuel according to claim 8 or claim 

9 whose 20%.and 90% distillation points differ within the range 65 to 100'C and whose 90% boiling point is from 

10 to 30°C of the final boiling point. 

206666 

-23-
11 A distillate fuel according to any one of -claims 8 to 10 in which the copolymer of ethylene and vinyl ester is a mixture of two copolymers one of which acts as a nucleator for the wax and the other of which acts as a growth arrestor for the wax crystals whose average vinyl ester content is in the range 32 •to 35 wt.% and whose average molecular weight number is in the range 1000-6000.
12 A fuel according to claim 11 in which the mixture, contains at least 10 parts by weight of the growth arrestor for each part by weight of the nucleator.
13 A distillate fuel according to any one of claims 8 to 12 wherein the vinyl ester is vinyl acetate.
14 A distillate fuel according to any one of claims 8 to 1 1 wherein the 20% to 90% distillation range of the fuel oil is 70* to 100"C and the 90% to final boiling point is from 10* to 25*C.
15 An additive concentrate suitable for incorporation into distillate fuels comprising a solution in a hydrocarbon solvent of from 5 to 60 wt.% of a copolymer of ethylene and a vinyl ester containing from 1 to,. 4 

i carbon atoms containing from 32 to 35 wt.% of the vinyl ester and having a number average molecular; 

weight of 1000 to 6000. ft-f?MAv 

4 

206666 

-24-
16 An additive concentrate according to claim 

15 in which the copolymer of ethylene and the vinyl ester is a mixture of two copolymers one of which acts as a nucleator for the wax crystals and the other as a growth arrestor the number average vinyl acetate content of the copolymers being in the range 32 to 35 wt.% and the number average molecular weight of the two copolymers being in the range 1000 to 6000 

17. The use as claimed in any one of claims 1 to 7 substantially as hereinbefore described with reference to any example thereof. 

18. A distillate fuel as claimed in any one of claims 8 to 14 substantially as hereinbefore described with reference to any example.thereof. 

19. An additive concentrate as claimed in either of claims 15 and 16 substantially as hereinbefore described with reference to any example, thereof. 

UAlED THIS n DAY OF nnRV ttlf 

A. i. PARK & SON 

PER 

AGENTS FOR THE APPLICANT! 

12 May 198?' 



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