CA1043048A

CA1043048A - Copolymers of ethylene and ethylenically unsaturated monomers, process for their preparation and distillate oil containing said copolymers

Info

Publication number: CA1043048A
Application number: CA223,853A
Authority: CA
Inventors: Stephan Ilnyckyj
Original assignee: Exxon Research and Engineering Co
Current assignee: ExxonMobil Technology and Engineering Co
Priority date: 1974-04-17
Filing date: 1975-04-04
Publication date: 1978-11-21
Also published as: FR2268028A1; DE2515805A1; GB1499568A; FR2268028B1

Abstract

ABSTRACT OF THE DISCLOSURE

Polymers of 1,000 to 50,000 number average molecular weight, comprising 3 to 40 proportions of ethylene per molar proportion of an ehtylenically unsaturated monomer, are prepared using an ester peroxide as the free radical initiator, in a solvent, for use as wax crystal modifying agents, e.g., pour depressants and flow improvers for middle distillate fuel oil.

Description

0 ~ 3 1 The present invention relates to ethylene back~

2 bone copolymers, distillate oil compo~itions cQntaining

3 the copolymers, and an ~mproved method o~ preparing these

4 copolymers for use as pour depressants and flow improvers for distillate oil, which method involves free radical po ~ 6 lymerization using an ester peroxide~ These copolymers.com--; 7 prise about 3 to 40 molar proportions of ethylene per one 8 molar proportion of an unsaturated monomer other than ethy-9 lene and have number average molecular weights in t~e range of about 1,000 to 50,000~
11 The commercially most important ethylene~contain-: - 12 ing pour depressant and flow improvers for distillate oil : 13 are copolym~rs of ethylene and ethylenically unsaturated 14 ester monomers, such as the copolymers of ethylene`and v~-nyl alcohol esters, particularly vinyl acetateS which copo~
16 lymers are well known ln the prior artl For example, U~S~
17 Patent 39048,479 teaches copolymers of ethylene and C3 ~o .~ 18 Cs vinyl esters, e~gO, vinyl acetate9 having molecular 19 weights of about 19000 to 3,000 according to K~ Rast's .
method of determining molO wto (BerO 55~ 1051~ 3727 (1922?)~
21 as pour deprèssants for fuels, specifically heating oils, .
22 diesel and jet fuelsO The copolymers of the examples of 23 said patent were prepared by free radical catalyeis, using 24 ditertiary~butyl peroxide as the catalyst (although the 25 patent teaches any~peroxide catalyst), at temperatures of 26 280 t~340F., in a solvent~ U~S~ Patent 3,131,168 teach-27 es a free radical process for making ethylene~vlnyl acetate 28 copolymers as pour depre~san~cs ~or middle distillate using 29 temperatures up to 440Fo ~ a solvent such as toluene or . 30 he~ane, a~y peroxy compound as catalyst, ~.ut preferably :

: ~ 2 ~ ~ 3~ 4 ~
1 ditertiary butyl peroxide, and adding additional ethylene 2 to the reaction during the polymerization. UOS..Patent 3 3,093,623 teaches still an~t~er method for makin~ ~hese 4 ethylene-vinyl acetate pour depressants for middle distil-lates by con~inuously adding vinyl acetate and Pthylene 6 during the course of the reaction.- U~SO Pa~ten~..3,250~714 7 teaches ethylene~vinyl acetate copolymers having molecular 8 weights of 3500 to 7000 às V.I. improvers ~or lubricat~ng 9 oils.
More recently~ British Patents 1,263,151 and 11 1,263,152 teach an improvement over the aforesa~d U.SO
12 patents by u~-ing a polymerization temperature below about 13 130C. and acyl peroxide as the initiator, as opposed to 14 the alkyl peroxide, tert. butyl peroxide, and higher tem~
peratures used by the aforesaid U.S. pa~entsO By the tech-16 .nique of said British patents9 it was found that the amount ~17 of ethylene branching was considerably reduced and copoly-18 mers produced by this method were generally superior pour 19 point depressant and fl~w improvers to prior art copolymers prepared at higher temperatures with alkyl peroxidesO Spe-21 cifically, copolymers prepared with alkyl peroxides and 22 high temperatures, while very effective in treating ~istil;
23 iate fuel oil to lower the pour point, frequently result - 24 in wax crystals having large particle sizes ranging from 25~ one millimeter up to an inch in their largest dimension, 26 depending upon the exact nature of the distillate oil, e.g.
27 crude source9 narrowness of the boiling range, etcO While 28 the treated distil~ate oil containing these large wa~ cry 29 stals exhibits ~ pour point significantly under the origi-nal pour point of the untreated oil, in many cases, the -- 3 ~

,:

~ ~043Q4~
1 large wax~ crystals will tend to plug filter equipment and 2 lines norm~lly used on del-ivery trucks and fuel oil storag~
~ 3 systems when the oil is cooled below its cloud point, even - 4 though above its pour point. Thus, as the oil containing the pour point depressant is cooled, the cloud point (the point a~ which the oiI becomes- cloudy due to crys~alliza~
7 tion of w~) will generally be reached at a tempera~ure sig-8 nificantly above the pour po~nt (the point at which the oil 9 can no longer conveniently be poured). As a result, oils below their cloud point and above their pour point will be 11 pourabLe, but at the-same time the wa~ crystals that have.
;12 formed, if too large, can result in plugging the a~oresaid 13 filter eq~ipment. Copolymerizing ethylene and vinyl ace-14 tate at a low temperature with the acyl peroxides of said British Patents was able to give the good pour point redu~-. 16 tion and in addition form smaller wa~ crystals during cool-17 ing of the treated oil.
18 The present invention represents a further im : 19 provement over the two prior art processes noted above, i.e.
: 20 (1) using alkyl peroxide and high temperatures, or (2) acyl 21 peroxides and low temperatures. Thus, the present invention 22 uses an ester peroxide, which in general gi~es a higher 23 yield of pounds of polymer fonmed per pound of peroxide - 24 ~han either prior art processes (1) and (2). This is im-25 portant since the cos~ of initiator consumed is a rela~ive~
26 ly large expense in the commercial preparation of these ~27 polymers. In addition, the ester peroxide process of the ; 28 i~vention can give a polymer whlch appears to have better 29 solubility characterist~cs in oil concentrates at low tem-peratures than similar polymers produced with the acyl per-~ ~ 3~ 4 ~
1 oxide pr~cess~ i.e., (2) aboveO This characteristic ~s 2 important in handling or storage of the polymer conce~-3 trates so that separation9 or sediment f~rmation, is avo~d-4 ed. The effectiveness of the polymers prepared by the pro-cess of the invention in improving the flow characteristics 6 of distillate fuel oil9 appears generally superior to the 7 polymers prepared by alkyl peroxide and abou~ equal to 8 those prepared with acyl peroxide~
9 In brief, the ester peroxides can significantly.
reduce the initiator cost, as compared to aIkyl or acyl 11 perox-ides, in the polymerizat;on, and can give polymers as 12 effec~ive in flow improvement as those prepared with acyl 13 pero~ides, but with good solubility in concentrates; and 14 can give polymers better in flow improvement than the poly-mers prepared wi h alkyl peroxidesO
16 The polymers of the lnvention will consist essen-17 tially of aboùt 3 to 40, and preferably 3 to 20 molar pro~
18 portions of ethylene per molar proport~on of ethylenieally 19 unsaturated monomer, which latter monomer can be a single monomer or a mixture of such monomers in any proportion, 21 said polymer being oil~soluble and having a number average 22 molecular weight in the range of about 1,000 to 50,000, 23 preferably about 1,000 to about 5,000, as measured by Vapor 24 Phase Osmo~etry, ~or example by using a Mechrolab Vapor Phase Osmometer Model 310Ao 26 The unsaturated monomers, ~opolymerizable with 27 ethylene, incLude unsaturated mono and diesters of the gen-28 eral ~ormula: Rl H
.~ ~
29 C ~ C

304~
1 wherein Rl is hydrogen or methyl; R2 is a ~OOCR4 or ~COOR~, 2 group wherein R4 is hydrogen or a Cl to C16, pre~erably a 3 Cl to C4, straight or branched chain alkyl group; and R3 is 4 hydro~n or ~COOR4O The monomer, when R~ and R3 are hydro~
gen and R2 is ~OOCR4 includes vinyl alcohol esters of C2 to 6 C17 monocarboxylic acids, preerably C2 to C5 monocarboxy-7 lic acids. Examples of such esters include vinyl acetate, 8 vinyl isobu~yrat , vinyl laurate, vinyl myristate, vinyl 9 palmitate, eto. When R2 is -COOR4, such e~ters include 10 method acrylate, methyl metacrylate, lauryl acryl ate, pal~
11 mityl alcohol ester of alpha~methyl acryl~ c acid, C13 ~o 12 alcohol esters of methacrylic acld, etc. Examples of mono-13 mers where Rl is hydrogen and R2 and R3 are ~COOR4 groups, 14 include mono and di esters of unsaturated dlcarboxylic 15 acids such as mono C13 Oxo fumarate, di C13 Oxo fumarate, 16 di-isopropyl maleate, di~lauryl fumarate, ethyl methyl 17 fumarates, etc.
18 As previously mentioned, about 3 to 40 moles of :: 19 ethylene will be used per mole of other monomer, wh~ch other monomer is preferably an ester as hereinbefore de~
21 fined, or a mixture of about 30 to 99 mole % ester and 70 22 to 1 mole % of a C3 to C16~ preferably C4 to C14, b~anched 23 or straight chain alpha monoolefin. Examples of such ole~
24 fins include propylene~ n~octene-l, n decene-l, étc.
Xn general, the polymerizations can be carried 26 out as follows: Solvent and a portion of the unsaturated 27 ester, e.g., 0~50~ preferably 10 to 30 wto %~ of ~he total 28 amoun~ of unsaturated ester used in the batch, are charged 29 to a stainless qteel pressure vessel which is equipped with a stirrer. The temperature of the pressure vessel is then : - 6 --1~43~8 1 brought to the desired reacti~n temperature and pressured.
2 to the desired pressure with ethylene. Then ini~iator and 3 additional amounts of unsaturated ester are added t~ ~he 4 vessel continuously, or at least periodically, during the reaction time, which continuous addi~ion gives a more homo-6 geneous copolymer product as compared to adding all ~he un-7 saturated ester at the beginning of the reaction~ Also 8 during this reaction time, as ethylene is consumed in the 9 polymerization reaction, additional ethylene is supplied through a pressure controlling regulator so as to maintain 11 the des~red reaction pressure fairly constant at all timesO
12 Following the completion of the reaction, the liquid phase 13 o~ the pressure vessel is dlstilled to remove the solvent 14 an~ other volatile constituents of the reacted mixture3 leaving the polymer as residueO
16 ~ Usually, based upon 100 parts by weight of copoly-17 mer to be produced, then about 100 to 600 parts by weight of 18 solvent9 and about 0.1 to 5~ eOg., about .5 to 3 parts by 19 weight of initiator~ will be used.
The solvent can be any substantially non~reactive 21 organic solvent for furnishing a liquid phase reaction 22 which will not poison the ini~ia~or or otherwise interfere 23 with the reaction. Exa~ples of solvents which may be used 24 include Cs to C10 ~ydrocarbons, whioh can be aromatic such as benzenep toluene, etc~; aliphatic such as n~eptane, n-26 hexane, n-oc~ane, isooç~a~e~ etc.; eyeloaliphatic such as 27 cyclohexane, cyclopentane, etcO Varlous polar solvents may 28 also be used such as hydro~arbyl esters, ethers and ketones 29 of 4 to 10 carbon atoms such as ethyl acetate, methyl bu-tyra~e, acetone, dloxane, etc. may also be used. A parti-.

~ - 7 -1~)4304~
1 cularly preferred sol~ent is cyclohexane which i~ easily 2 handled-an~ ~h-ich gave very good utilization of the initi-3 ator.
4 The temperature usecl during the reaction will generally be in the range of 150 to 350F., e.g. 200-270F., 6 pre~era~ly about 200 to 250Fo 7 Preferred free radical ini~lators are those which 8 have a half life of less than about s~x hours at 1~0G.
9 These initiators are hyddocarbon soluble, ester peroxides o the general formula:

12 R~C~O~O~R' 13 where R and R' are each hydrocarbon group~5 such as alkyl, 14 aryl, alkaryl, cycloalkyl, etcO, preferably alkyl groups, either straight chain or branched chain, of 2 to 20, eOgO, 16 4 to 12 csrbon~atoms each. Usually the ester peroxide ~ill 17 contain a total of 4 to 24, preferably 6 to 18 carbon atomsO
18 Some specific examples of such ester peroxides ~nclude: t~
19 butyl peroxypivalate, t-butyl peroctoate (iOeO,~t~butyl ~20 pero~y~2~-ethylhexanoate)~ t~butyl peroxyisobutyrate5 t-21 ~butyl peraceta~e, t-bu~yl perbenzoate, etc~
22 The pressures e~ployed can range between 500 to 23 30,000 psig. However7 relatively moderate pre~sures of 700 24 to about 3000 p5ig will generally suffice with vinyl esters such as vinyl acetate~ In the case of esters having a high-:
~- 26 ~er relative reactivi~y to ethylene, such as methyl me~tha-27 crylate, than somewhat higher pressures~ ~uch as 3,000 to : 28 10~000 psi have been found to give more optimum results 29 than lower pressures. In general, the pressure should be at least suf~ieient to main~ain a liquid phase medium under .;~ .

1~)431~48 1 the reaction conditions, and to maintain the desired con~
2 centration ~f eth~Lene in solution in-thé solvent.
3 The time of reaction will depend upon, and is in~
4 terrelated to, the temperature of the reaction, the choic.e of catalyst~ and the pressure employed. In general, how-6 ever, 1/2 to 109 usually 2 ~o 5 hours will complete the 7 desired réac t ion.
8 ; The polymers of the invention will generally be 9 added to distilla~e hydrocarbon oils in amounts of .001 to 2 wt. %, generally .005 to about 0.5 wt. %, said wt. J/O be-11 ing based upon the weight of the oil to be treated.
. . .
12 The distillate hydrocarbo~ oils, which are treat-13 ed f~r pour depression with the polymers of ~his invention, 14 inc~ude craeked and virgin distillate oils boil~ng in the range oP 250 to 750F., such as heating oil and diesel 16 fuel oil.
17 The polymers of the invention may be used alone 18 as the sole oil additive, or in co~b~nation with o~her oil 19 additi~es such a~ other pour depressants or dewaxin~ aids;
corrosion inhlbitors; antioxidants; sludge inhibitors;- etc.
21 ~XAM~LE I
22 A stirred autoclave was charged with 4500 ml. of 23 cyclohexane as solvent and 500 ml. of vinyl acetate. The 24 autocIave was then purged with nitrogen and then with ethy-lene. The autoclave was then heated to 105C. (about 220F.) 26 while et~ylene was pressured into the autoclave until the 27 pressure was raised ~o 1050 psigo Then, while maintaining 28 a temperature of 105C. and said 1050 psig pressure~ 1249 29 ml. of vinyl acetate was injected a~ a constan~ rate over a two hour 2criod. At the same time3 30 grams of t~butyl -- g _ . .

~0 4 ~V ~
1 peroctoate diluted with 757 ml. of cyclohexane was al50 2 slowly pumped into the reactor over the two hour period 3 a~ a constant rate. At the end of said two hour period, 4 and after the last o~ said vinyl acetate and peroxide was injected, the batch was maintained a~ 105C. for an addi-6 tional 10 minutes. Then, the temperature of the reac~or 7 contents was lowered to about 60Co~ the reactor was de-8 pressurized, and the con~ents were discharged ~rom the-9 autoclave. The product was then stripped o~ the solvent and unreacted monomers. The f~nal stripped product C0~8-iS-11 ted-of about 1577 grams of copolymer of ethylene and vinyl 12 ace~ate.
13 ~XANPLES II T0 VII
14 Examples II to VII were carried out following the general procedure of E~ample I, except ~hat changes in 16 pres~ure, temperature, or amount of peroxide wçre made.
17 COMPARISON EXAMPLES A A~D B
18 These comparison examples were carried out using 19 the same general technique as in Example I, except that 54.5 grams of dilauroyl peroxide, usually designated as 21 lauroyl peroxide (an acyl peroxide)~ was used in place of 22 the 30 gra~s o~ tert~ butyl peroctoate. Al~o, the lauroyl .
23 peroxide (as it is a solid) was added as a solution dissol-24 ved in 757 ml. of cyclohe~ane so it sould be pumped.
Concentrates of all the above polymers were made 26 by dissolving 45 wt. % of ~he polymer in 55 wt. % of a 27 heavy aromatic naph~ha (HAN) for ease in further handling.
28 The polymers were tested for flow imprQving abil~
29 ity at temperatures below the cloud point in a "Cold ~ilter Plugging Point Test" (CFPPT) which i~ described in detail ~6~4;~ 8 1 in Journal of the Institute of Petrol~um, Volume 52, Nu~ber 2 510, June 1966, pp. 173;18S. In brief, the Cold Filter 3 Plugging Point Test is carried out with a 45 ml.-sample of 4 the oil to be tested which is cooled in a bath maintained at-ab~u~ -30F. Every ~wo degrees drop in ~emperature~
6 starting from 4F~ a~ove the cloud point, the oil is tested 7 with a test device consisting of a pipette to whose lower 8 end is attached an inverted funnel. Stretched across the 9 mouth of the funnel is a 350 mesh screen having an-area.of about 0.45 square inch. A ~acuum of abou~ 7" of water ls 11 applied to the upper end of the pipette by means o a va~
12 cuum line while the screen is immersed in the oil sampLe~
13 Due ~o th~ vacuum, oil is drawn across ~he screen up into 14 the pipette to a mark indicating 20 ml. of oil. The tes~
is repeated with each ~wo degrees drop in tempera~ure un~
16 ~il the v~cuum fa~ls to fill the pipette to the aforesaid 17 mark due to clogging of the screen with wax crystals. The 18 results of the test are reported as the "operability limit"
19 or cold filter plugging point (CFPP), which is the tempera~
ture at which the oil no longer flows.
21 Test Fuel A was a diesel fuel boiling in the 22 range of about 17Z to 353C., having a cloud point of -3C.,' 23 an aniline point of 73C., a specific gravity o 0.8193 24 and a viscos~ty of 2.64 cs. at 100F. This fuel in the CFPPT ga~ a plugging poin~ of about +28F.
26 A series of blends of 0.02 wt. % of the afore-27 ~aid polymer concentrates in Fuel A were made up and then 28 tested in duplicate using the CFPPT procedure. The f.ollow-29 ing Table summarizes the preparation details of the afore-said Example~, and Compari~ons A and B, along with the 16~43~4B
1 yLelds and eiiectiveness in Test Fuel A.
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~1 ~ O O _1 0rl ~ U $1 ~ ~ r l E3 tq ~ ~ ~ U ~ ~î ~., ~, ~ ~ ~

5 O C t~ ~ ~1 ~a~ P~ ~ -rl ~ 1-1 O P.l PC ~ 1~ ~) p1~ p H ~ . ~ ~i _ ~04304~ 1 1 As seen from the Table, the use of the t~butyl 2 peroctOate (i.e., t-butyl peroxy 2-ethyl-hexanoate) ga~e 3 higher yields of polymer per amount of ini~iator than the 4 dilauroyl peroxide. Specifically, ~xamples I to VII gave yields r~nging from 50.9 to 145 grams of polymer per gram

6 of initiator, as compared to the dilauroyl peroxide which

7 in Comparisons A and B gave 36.5 and 36~1 grams of polymer

8 per gram of initiator, respectivelyO Since the molecular

9 weight of the peroctoate peroxide is about 54% that of t~e dilauroyl peroxide, one could have expected ab~utan 85%
11 lncrease in yieldO Yet, Examples V to VII show a much 12 greater yield using the peroctoate than would have been 13 expected from mere molecular weight differences. At the 14 same time, the se~s of duplicate runs in the CFPPT show that about comparable flow improvement could be obtained 16 with the polymer prepared by the peroctoate as opposed to 17 the dilauroyl peroxide.

.

~ - 14 -

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A method of preparing a copolymer of ethylene and a vinyl alcohol ester, useful as a middle distillate fuel oil flow improver, by free radical initiation wherein said copolymer has a number average mole-cular weight by Vapor Phase Osmometry in the range of 1,000 to 50,000 and comprises essentially about 3 to 40 molar proportions of ethylene per molar proporiton of vinyl alcohol ester of a C2 to C5 monocarboxylic acid, which method comprises copolymerizing said monomers in an ethylen pressur temperature in the range of about 150 to 350°F. under an ethylene pressure of about 700 to 3,000 psig using a hydrocarbon-soluble free-radical initiator having a hlaf life at 110°c. of under 6 hours, said initiator being defined by the formula:
wherein R and R' are alkyl groups of 2 to 20 carbon atoms each and said initiator contains a total of about 4 to 24 carbon atoms.

2. A method according to claim 1, wherein said ester is vinyl acetate and said solvent is a hydrocarbon solvent.

3. A method according to claim 1 or 2 wherein said ethylene and ester are copolymerized at a temperature of about 200 to 250°F, R andR' are alkyl groups of about 4 to 12 carbon atoms and said initiator con-tains a total of about 6 to 18 carbon atoms.

4. A metod according to claim 1 or 2 wherein said solvent is cyclohexane and said initiator is t-butyl peroctose.

5. A method according to claim 1 or 2 wherein the number average molecular weight is in the range of 1,000 to 5,000

6. A method according to claim 1 or 2 which comprises utilizing essentially about 3 to 20 molar proportions of ethylene per molar proportion of said ester.