CA1097905A - Composition and method for suppressing vapor loss of volatile hydrocarbons - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

An evaporation retarding composition for hydrocarbons comprises a fluorosurfactant, a silicone surfactant, a polyglycol and a glycol ether.

Description

~7~
1 ~AC~ OUNI GF Tl~ lNVENTION

2. l. Fle.ld of the Invention .. ,_ ..., .. _

3 This in~en~ion relates to ~echniques for minlmiz-

4 ~ng ~he evaporative losses of stored hydroc~rbons. In part~cul.ar, the presen~ inventlon is concerned with suppres-6 sing the volatilization of hydrocarbons oontained ln petro~
7 leum produots suoh as crude oil.
8 20 ~_ 9 . In the pas~ petroleum products, par~icu~arly crude oil9 have been rela~i~ely inexpens lve com~od~ ties O In 11 very recent years, ho~ever9 increased world demand for all 12 natural resources has signl~i¢ant~y altered tlle prior supply/
13 demand relationships so that losses of hydrocarbons from 14 evapora~ion is deemed ~ui~e seriou~ from an economic point of ~iew~ Moreo~er3 there is a concern for pxeserving not 16 only pekroleum hydrocarbons bu~ all vola~ile llquids.
17 ~portant also i~ ~he ne~d to protect the en~lron-18 ment from contamination by ~ola~ e hy~rocarbons~ ~ndeed, 19 ln~reased world use of petroleum products has increased the ~ neëds or improvemenes in s~ppress~ng the loss of hydro~
21 carbons in~c the a~mosphere, e~c~
22 In ~he description ~o foLlow, reference will be 23 made primariLy tG suppressing the loss o hydrocarbons by 24 vaporization from crude oils; however, it ls to be under-stood tha~c crude oil is merely one example of a hydrocarbon 26 which contains suficient amounts of volatile components 27 which wil~ undergc~ vaporlæation in suhstanl:ial amounts 28 du:ring s~vrage O
29 As will be apprecîa~ed~ crude oil con~ains a very wid~ spectrum of hydrooarbon~ ranging i~rom 'chose which have 31 ~ery high boiling poi.nts to those which would exist in the 32 v~por stat^ if thf~y w3re isolated~ Indeed, it is ~h~
~ .

3~S
. .:
1 presence of these latter ~aterials that contribu~es to the 2 ~ignificant vapor pressure o~ crude oil.
3 There have been a numher of technique~ sugges~ed 4 in the pas~ ~or inhi~iting the vaporiza~ion o~ hydrocarbons.

S For example~ ~n U.SO Patent L,98S,491, it is suggested that 6 a fat y acid soap be mixed with wa~er and then beat into a 7 froth wi~h a vigorous air blastO The froth, thereafter, i5 spread on the s~lrface of oil, SO aS t:o mlnimize evaporation 9 and oxidatlon of the oil.

In UOS. Patent 2,8~292389 evaporation of volatile 11 nonaqueous liquid product$ is re~arded by floating small 12 hollow ~articles9 wet by water, on ~he surface of the vola-13 tile liquldO.

14 In U.SO Patent 2~9079627; a technique is disclosed for inhibiting ~apor loss by spreadin~ a syntheti~ ~esin 16 plastio such as a poly71re~hane on the surace of the crude 17 petroleum. In con~rast thereto, UOS ~ Patent 3,42l~838 dis~

18 close~ ~he u~e of ru~ber cement as a ~apor barrier for 19 volatile ~e~roleum produots.

~ Other teehniques suggested for inhibit~ng ~apori-21 za~ion ~f hydroearbon materials inelude the use of a gelling 22 material ~o crea~e an integral roof on an oil tank. In 23 this regard9 see UOS. 3,6399258. Mention should be made 24 also o~ the technique of preventing hydrocarbon losses during ~he loading o vesseLsby use o~ an aqueous foam 26 which is stabl.e during the period corresponding to that 27 required or loading. For ~his technique, see U~S. P~tent 28 3~850~206O The last two techniques for inhibiting vapori-z~tion of hydrocarbons have more limited ~pplicability than ~ ~he ~bove-men~ioned techI1lques.

31 Xn Canadlan Application 281,989 there q~y~L~r :~rr ~ ? ~ ?~7~? ~? ,.~ ~,r~ rl~: 6/~ rl, ~ ,, .1,'. ?? ~ r~ t~ rr c ~7?~ ? .~,~

is disclosed a very e:Efe~ re composition for inhibi.~ing 2 vapor loss~s o stored hydrocarbons whlch comprise.s a mlx-3 ~ure o a surfactant and a polyglycol. Thls composition, 4 when applied to che surface o~ a body of hydrocarhon liquid,

5 forms an effective film t~rpe barrier thereby reducing vapor

6 lossO No~withstanding the signi~icant u~ cy of such com~

7 positlon in reducing vapor 105s of hydrocarbons, ~he searrh

8 or even more efective and more economic ~echniques for

9 conserving natural resources and pro~ecting the environment continue.
11 SUMMAR~ OF T~E INVENTIO~
_, _ . . . . .. . .
12 According to ~he presen~ inven~ion, ~here is pro-1~ vided an i~proved evapcra~i~n retarding mix~ure capable of 14 forming a continuous s~able ilm over th~ surace of a body o~ liquid hydrocarbon ma~eriaL comprlsing a fluorosurfac-16 tant, a silicone sura~tan~p a polyglycol a~d a ~y~ol ether.
17 In general~ ~he fluoro~urfactant employed in the 18 composition of the present lnven~ion is a fluorinated sur~
19 factant wh:ich ls subs~antially hydrooarbon insoluble~, It ~ must be a material which has the ability ~o pack tigh~ly 21 and ~o orlent itself perperldicularly to ~che ~ur~ace of the 22 liquid hydrocarbon material being treatedO Finally, the ?3 ~luo~osurfactant is one havirlg a fluorocarbon moiety con~
24 ta~ning from ~bout 7 to about 16 carbon atomsA Preferably 25 the flu~rocarbon moiety will be linear~
26 The slllcone sur~actant is an organo substltuted 27 sili~one fluid selec~ed fr~m the group consisting of alkyl, 28 aryl and aralk.yl polyslloxanes and copolymers OLC such .^
2~ organo polysiloxanes with polycthers such as polyethylene 30 oxide, polyethylene o~ide~pc~lypropylenrJ oxlde copolymers, 31 and ~che l~lceO Preerably the silicone surfactant is a 32 copoiymer of a pol-ysllo~t~ne wlth1 a polyalkyleYe oxir1e .~ . _ ~ 7 ¦ 1 copolymer, .
2 - The polyglycol is selected from a wide range of 3 liquid polyhydro~y alkanes including polyethylene glycols, 4 polypropylene glycols, and ~he like. Pre~er~bly the poly-glycol is polyethylene glycol ha~ing a gram molécular ~Jeight 6 o about 400.
.
7 T&e glycol e~her employed is selected from a wide 8 range o~ primary alcohols of linear alkoxy alkanes~ Pre-9 ferred is l~hydroxy~2-bu~xy ethane.
In ge~eral~ the cGmbined fluorosurfac~ant and ll silicone surfaet~nt wlll represent ~rom about 10% to about 12 40%, and preferably 30%, of the composition. Indeed, ~he 13 amounts of the.constituents of the composition of the in-14 ~ention, with pereen~ages by weight are as ~ollows:
. (a) about 5 to ~b~ut 20% fluorosurfactant 16 . (b) about 5 to about 10% silicone surfactant 17 (s) abo~t 5 to ~b~u~ 35% polyglycol 18 ~d~ abou~ 5 to abou~ 35% glyeol ether 19 BRIEF D~SO~IPTION QF T~ DRhWINGS
Fjgure 1 i~ a graphic representation comparing the 21 evaporat~on loss of an untrea~ed Southern Loui.siana erude 2~ oi~ with ~amples of the same crude treated ln accordance 23 with the inven~ionD the 1uarosurfac~an~ being varied in 24 each ~es~ run.
~gure 2 ~s a graphlc representa~ion comp~ring 26 ~he resul~s of tes~s similar to ~hat shown in Figure 1 bu~
27 using a light Arabian crucle o-ll.
28 Figure 3 ls a g~aphic representation comparing results o ~es~s similar to ~ha~ shown in Figllre 1, but:
~ using unleaded gasoline.
31 Figure 4 is a graphlc representation comparing 32 ~he evaporation L~s~ of an untre~lt.ed Sout-hern Lo~lisi.ana 7s~

~rude oil wiEh a sample c?f 'che s~me crtade trea~ed in accor-2 dance with this invention, both samples being subjected ~o 3 pexlodic tilting.
4 Figure 5 ls a schematic diagram of a port:l on of a corrnnerciaLl tanker showing the rela~cive position o two 6 tanks used ln the field tes~c of an evaporation retarding 7 mixture ac~rding to this invelltion4 8 Figure 6 is a gr~phic representation o~ the pro-9 file o vap~sr $pat~e ~sf an untreated t~nk of a cormrlercial tanker durlng disc:harge alld a tank ~created in acc~ordance 11 wlth this i~en~ionO
12 I)~TAILE~ D~S~RIPTIO~ INVENTION
~_~
13 As ~ndic~te~ hereina~re,, ~he present inven~ion 14 is concerned generally wi~h suppressing hydrocarbon vapor 15 loss from ~ be~dy of the hydrQearbon liquid by forming a 16 con~cinuous stabLe i~m o a b~rrier ~ayer s)ver to the sur-17 face of the body ~f liquid hydr~arbon. In the detailed ~8 de~crip~on whi¢h follows~ llowever9 speci~ic reference will 19 be made ~o preve~ng lo~s of v~la~ile hy~rocar~on compounds rom crude oil a~though t~e pre~ent invention is applicable 21 to a wide range of volatil~. ~rganic materials in addition 22 to crude oilsO Indeed~ among the numerous hydro~arbon 23 materi~ls, ~he vap~rization ~f which can be suppressed iII
24 a~cordance with the presen~ ln~ention, are llqu~d aliphatic hydrocarb~ns, llquid alicycli~ hydrocarbons, liquid a~omat~c 26 hydro~arbons and mix~ures of these~ ~peciic examples o~
27 volatile hydrocarbons, the var3Grization of which can be 28 substantially suppressed in a~c~rdan~e with the presen~
~nvention, include gasolines, heptanes~ cyclohexanes, ben-~ zene, pyridene and the like. The foregoing recitatlon of 31 these hydroear~cn ma~erla~s that can be effectively treated 3~ in ~ecordance wi~h ~he pre~ent lnventiGn i~ not -lntended ~o ~ 6 ~

U979~5 1 be limi~lng, but rn~ely exe~oplary of the w~de applicab:Llity 2 of ~he present ln~ention.
3 Generally speaking, hydrocarbon losses by vaporl-~ zation are substantially reduced in accordance with the prac 5 t.ice o~ the present invention by forrning a continuous s~cable 6 f~lm over the surface of a body of liquid hydrocarbon which 7 operates as a barrier ~o ~apor lossO It has now been found 8 ~ha~ excellen~ evaporatic~n xetardir~g compositiorls :Eor such purposes comprise a fluairosurfactan~,, a silicone surfactant9 a polyglycol and a glycol e~her. In general, the surfac-11 tants, i.e~ the fluoro~ur~ac~an~ and silicone suractan~g 12 will represen~ rom ab~ lO wt. % ~o about 40 wt~ %~ and-.
13 pre~era~ly about 30%, of the composi.tion. The amounts o.
14 t~e components of the evaporation ret~rding compositlon will be discussed hereinafter in greater detail.
16 Concerning the nature o~ ~he components, the 17 fluorosuractant of ~he re~arding mix~ures according to ~l~e 18 presen~ i~vention are charac~erized by the following cri~
19 teria~ F~rst, the fLuorosuract~nt m~st be lnsolubLe ln ~ the part~cu~ar liquid hydrocarb~n body being treated.
21 ~eco~d9 the f~uorosur4actant m~s~ have the ability to pack 22 tightly and ~o orient i~sel~ perpendi~ularly to the surface 23 of the liquid hydrocarbon body~ Third~ the ~uorosur~actarl~5 24 to have suf~icient resistance ~o hydrocarbon transfer from the sur~ace of the li~uid hydrocarbon body, must have fluoro-26 c.arbon chain or moiety greater than about 7 carbon atoms, 27 and more typlcally w~l have fluorocarbon moieties conta:Lning ~8 about 8 to about 16 carbon a~oms. P~eferably ~he ~luorocar~
bon ~o~eties will be linear chains o~ from about B to about ~ 16 carbon at~ms~
31 I~: wi~ 1 be appreciated by 'chose skilled ln the art 3~ tha~ surfactants ~re generally classed as organic rnolec1llet;

.,.' !

1 containil1g both hydrophobic and hydrophilic groups in an 2 organic molecule. Surfactants are urther classified as 3 being strong wett:ing agents or as s~cron~ detergents. In 4 the case of strong wettlng agents, the hydrophilic group ~ends to be in the middle o~ the molecule. In ~on~rast 6 thereto, in strong de~ergents ~he hydrophi.lic group is at 7 the end a a hydrophobic gr~upO Indeed, the hydrophobic 8 group ~ends to be a linear hydrocarbon. In accordance with 9 the practiee o~ the present. invention, the fluorosurfactants that are satisa¢tory ha~e flu~r~alkanes as a hydrophobic 1t groupO These fluorosurfa tants ca~ be anionic9 cat~onic, 12 nonionic.and ~mpho~.ericO
13 Many of ~he foregoing fluorosurfaetants are avail~
14 able commercially. Consequen~ly9 it is one of ~h~ advantages of the present inventi~n that commercially available fluoro-16 suractants f~an be usedO Such fluorosurfac~an~s include the 17 ~luor~surfactant$ ~old under the trademark l~onlor" by ICI
18 United S~a~es, Inc 4 ~ wi~ming~on9 Del~ware and that sold 19 ~nder the trademaLk 1'Zony~'t b~ duPont, Wilmington, Delaware.
~ The silicone surf~c~n~ employed in this in~ention 21 is an organo subst~tuted s~llcone fluid or liquid polysilox~
22 alleO ~ile not wishing ~o be bound by any theory, ~t ls 23 belie~ed that the po1y$iloxane contributes to khe spreading 24 of the compcsltion on the hydrocarbon surface4 Additionally, it ls believed that the polysiloxane enhances molecular 26 ~acking. In any event, th2 polysiloxane is selecte~ from 27 allcyl, a~yl and arallcyl polysiloxanes and cGpolymers of al~
28 kyl, aryl and ar~lk~l polysiloxanes w~.th polyethers having 29 linear all.phàtic groups o fr~m 4 ~o 6 carbon atoms, and 30 copolymers o such polyethers O Particularly preferred are 31 the block copoly~ncrs of lcw~r dialhyl polysiloxanes, iOe.
32 h~vl.ng from l to 4 carh~n at~m~ l.n a linear aliphatJ.c P,ro11p~
33 and copolymer~ of ethylenc and pr~pylene oxide. Especi.ally 1 preferred ls a copolymer of dime thyl polysilsxane and 2 polyethylene oxlde-polypropylene oxide copol~mer3 3 ~ust as with the 1uorosurfactants, these slli-4 cone ~luids are commercially ~ail~ble and men~ion, by way 5 o example~ is made herein to the sllîcone fluids designated 6 SF~969 SF~1075C SF~L066 and the like sold by General Elec~ric 7 Company, New York, NY~
8 The polyols su1t~ble in the practlce o ~he present 9 invention inelude liquid etl~ylene glycol.s such as tri.ethy~ene ! glycol~ polypropylene glyc~l and polyethylene glycol. ~ener-11 ally) the glycol is one which has a molecular weight in the l2 range of ab~ut ~00 to ~200 and preferably about 400. The l3 pre~erred polyg~y~ol is polyethylene glycol having a mole~
l4 cular weight of abou~40~
The glycol ethers suitable in the practice of the 16 subject in~en~ion inol~de a w~de range o~ primary alcoho~s 17 of l~nea~ al~oxy alka~esO Indeedg ~he alkoxy alkanes may l8 be symme~ri~al or asymme~ al compounds having generally 19 from about 6 to 10 carbon atoms O P~rticularly preferred are the lohyd~o~y~2o~agkoæy e~chanes and espeeially l hydroxy-21 2-butoxy ethaneO
22 In order to efeetively inhibit ~:he vaporization 23 o~ hydrocarbons from a body o~ liquid hydrc3carbon materials, 24 i~ is necessary that the evaporation retarding mixture form a continu~us stable film over the surface of the body of 26 l~qllid hydrocarbon m~erial. While not wishing to be bound 27 by~ any theory~, the polye~hylene glyc~l and glycol ether ~8 components o the evaporative retarding ml~ures o~ ~he present invention app~rently associa~e wlth the hy~rophillc 30 port:ion of th~ sur~actant t.hrough weak vall der Waal ~orces 31 thereby improv~ng the impermeability o~ the ilm~ A limited 32 lamella of the gl~ol ls supported by sur~ace orce~;0 By ~ ~ ~f~ 9 1 assoclation with the hydrophlllc moiety of the suractant 2 package, a sandwich-like moleoul~r configuration results~
In any event, i~ has been discovered tha~c the add~.-4 tion o~ ~oth the polyethylene glycol and the glycol ether to 5 the fvregoing above~mentioned suractants provides an effec-6 ti~re evapora~ion re~ardir.g mix~ure which is capable of form~
7 ~ng a continuous s~able film over the surace of a body o~
8 liquld hydrocarbon material~
The amounts of the constituents of the composition of the in~entlo~a3 wlth per¢en'cages by weight, are as follows:
11 ~a) 5 to 20% flluoresselrfae~an~
12 (b) 5 to ~Oa/~ sili¢on sur~actant 13 (c) 5 ~:o 35% polygly~ol 14 ~d) 5 to 3S% glycol et:her !5 Preerred co~ap~itions comprise:
16 (a) S ~:o 20% of ~n amph~eric luorosurf~c~an~c 17 represented by ~he general formula 18 NH4 ~F3CcF2c~3coo lq and having a gram rnolecu~r weigh~ of abou~ 550;
(b) ~ to 10% Gf a slllcone fluld~ especially a 21 copolymer of d~ethyl polys ilo~ane and pol~e~hylene polypro-22 pylene oxide copoiymer ~nd ha~ing a gram average molecular ~3 weight of about 7000;
24 (c) 5 teD 35% polyethylene glycol having a mole~
2~ cular weight of about 40b; and 26 (d) 5 ~o 35% o a gly~ol ether having ~rom about 27 6 to ~0 carbon ~toms in the eompo~nd.
28 In applying ~he evapora~ion re~arding mix~ure ~o ~ ~he surface of a liquid hydrocarbon body, ~he mixture may ~ be spread over the surfa~e o~ ~he liquid hydr~carbon body 31 by a eonveni2n~ means. In ~he practice o~ the pre.sent lnven~
3~ tion9 it ~s partlcularly preferred9 however, ~hat the - -1 evaporation retarding mixture be applied to the hydrocarbon 2 body as a flne aerosol spray~ Application in the form o~ a 3 ine aerosol spray tends to more effect~vely u~ilize the 4 material in ilm forming and minimizes the amount which may ~ink through the liquid hydrocarbon~
6 The amount of evapora~icn retarding material ap-7 plied to the surace of the liquid hydrocarbon bodies is not 8 criticalO It can be app7ied in almost ~ny manner suficient 9 to form a con~inuous ~hin ~1m of ~he e~aporation retarding

10 mixture cn the surface of the liquld hydrocarbon body. For

11 most ef~ect~,Te retardatie~n of ev~.p~bration, however, the mix~

12 ture will be applled in amounts sufficient to provide a film l3 thickness greater ~han 70 mon~l~yers and preferably in an 14 ~mount ranging from abou~ 2~0 ~o 350 monolayers. Thus, it will be readily appreciated by persons skilled in the art 16 ~chat ~he amounl: of materlal needed to orm an efective 17 barrier is ~elati~eiy ver~ s~a~l~ Indeed~ to ~orm a fllm 18 thick~ess o~ approx~mately 350 monolayers on the cargo of a l9 909 000 t~:Dn tanker, only about 3~ gallons of the evapora'cive retard~ng mix~ure wou~d be requlredu 21 The unique e~ures o~ certa~n aspects o ~he pre-22 sent invention are br~ught cu~ in the following examples 23 which are strlc~ly illustrative and no~ to be cons~rued as 24 limiting in scope.

.
2~ A series of tests was conducted using an op~n 27 beaker that had a diame~:er o~ 3-1/8 inches~ Some be~kers 28 were char~ed solely with ~ Southerrl Louisiana crude oil.
29 Other be~kers were charged wit.h 'chf~ Southern Louislana crude 3~ oil and were sprayed by means of ~n aerosol spray for abo~t 31 S seconds each ~ith an evaporatIon retarding mixture. The 32 amount o~ spray was su~lcient to apply an estimated 350 to ~7~l~5 1 1000 monolayers of evaporation re~ardant mixture on the 2 crude oil, The amount of hydrocarbon loss was deter~ined 3 over a period o timeO The results from the tes~s are set 4 ~orth graphi.cally in Figure lo In each of the tes~s the c~mposition was maintained at 3S wto % polyethylene glycol 6 having a molecular weight of about 400, 35% of 1-hydroxy-2-7 butoxy ethane and 10% c a fluid silicone surfactant sold by 8 General Electric Company under the trademark SF~1066 and 20%
9 of a fluorosurfac~an~ In each o~ the tes~s, a di~feren~
type ~luorosur~actant was employed~ The type o fluorosur-11 fac~ant is descr~bed generally in Table I~

- 12.

u ~o h h ~ O ~
c.~ a. o h ~_ O ra~ 0 ' ~ O t~
,~1 0 n 00tO ,~
o ~ C~ ~ U t~
~~ J ~O E3 5~ ta ~ ~. ~ h t~ C.) O C~ ~ O~
~n t`lo o C`J-rl ~ O 00 0 W
~ c~
a ~ ta ~ ~rr~ ~ t~ ~ ~) N ^
:~ h ~ h.s: tl) cor~ 3 U~ ~ ~ u~ ~ ~ ~ .C: h a Z
C~ ~
H ~ ~ 3 E~ ~: o o ~ ~ o ~ o H ~ ca ~ 1rl ~
o . o :ao ~: o ,~ c P~ ~ u a~ u o :~ 1o o :~ ~ O O
o~ o ~ o ~r~ o o~
~1 - O ~ 1~ ~ 4 r~ ~ V H
P~ ~
~1 E-~ ~ ~ ~rl .
t~ E~ 51 t . . 4~ ~
C~ ~ ~ ~ ~ O S:\
P~ t~ 1:~ ~ ~
~ O O ~ O
-- P O H ~ Z V
.~ ~
''. ~ . ~C .. . ...
;~3 E-l O 51 .
~ ~ ~1 i~E~ ~ U
~ ~ ~ ~ ~ c~ rt .
c~ ~ ~ a ~ P a~
H ~ I cd H U~ ~ U) ~ ~ .
' Pq v ~4 c~
t-~ ~ V) U~
F~ ~ ; ~
,~ ~ O O O
o s-~ ~ o ~ o :~ E~ X
E-~

~1 ' ~-1 ~ ~ . ~ u~ ~
E~
C~ .
c~ ~ ~ ~c~ a~ o ~ c~ tS~ C~

~ 13 -^
~ ' .

2 The procedure of ~xample 1 was followed excep~
3 that the hydrocarbon treated was a light Arabian crude oilO
4 The results of such tests are shown graphically in Flgure 2.
Also, the fluorosurfactants9 identified by number in Figure 6 2, are described generally in Table Io 8 The procedure of E~ample 1 was followed except 9 that the beakers were charged wi~h a commercially available iO unleaded gasoline. ~he results of ~hese tests are set forth 11 ~n Figure 39 ~he 1uor~s~rfactant numbers of Figure 3 being 12 keyed to ~he generaL descrip~ions in Table I~ As can be

13 seen in the oregoing tests~ linear ~luorosurfactants are

14 more ef~ecti~e components of evapbratlon re~arding mix~ures tha~ their branched ¢ounterpar~s and conseq~en~ly fluoro 16 sur~actants are particularly pre~errcd.

18 ` In this example9 a nwmber o samples of Sou~hern 19 Louisiana crude oil were pla~ed in open 100 ml beakers~ In some of ~hese beakers~ the crude oil was coated with a 35%
1~ 21 polyethylene glycol9 35% l~hydrox~2~butoxy ethane, 10% GE
22 s~licone SF~1066 and 20% Zcnyl FSB fluorocarbon~ Un~reated 23 crude oil served as a control~ The beakers were arranged 24 on a platform whieh could be inclined a~ 30~ After so arranging the beakers and coating all but the controls with 26 the vapor retardant mixture, the platorm was tllted in one 27 direction. Thereafter, ~chree times in every 24 hour period 28 the platform was til~ed in the opposite d1rection~ This impar~ed ~n increase and decrease, or flexing, o ~he sur-~ a~e coa~1ng. The resu~ts of ~hls tes~ are deplcted ~n 31 F~gure 4O

~ 14 2 A field tes~ was conducted during the unloading 3 of light Arabian crude oll from a co~mercial tanker. The 4 arrangement of ~he cargo compartment selected for the pur-pose o~ the test is show~ in Figure 5~ Before dlscharge 6 commenced, two liters o:~ an evaporation retarding mixture 7 having the composi~i0n set for~h ~n Example 4 were sprayed 8 onto the sur~ace of the crude oil in the #1 port wing tan~
In order to assure op~imum distribu~ion of ~he vapor retard~
1~ ant compositionJ al~ the tank oovers were removed one at a 11 time for a peri~d not exceeding 60 secondsO The ullage at 12 ~he time o dis~r~bution w~s only 2 ~ee~, making it dlffl~
13 cult, h~wever5 to del~ver the chemical~composition to the 14 low surace at some locations because of the inter~erence

15 o stnlctural members ~n the ~ankO The #l staxboard wing

16 tank was u~ili.zed as a control for a c:omparative purpose

17 and hence ~he crude oil therein was no~ ~reated with any

18 evaporation re~arding c~mposi~ionO A~er applica~ioIl o~

19 the ~apor re~rdant ~ompositlon in the #l pDr~ wing tank9 ~ ~le vapor $pace o ~he ~an~ was pro~iled and compared ~o ~1 the untrea~ed ~l starboard wing tank~ When the ullage in 22 the tank was 16 feetD a s~c~nd application of two liters of 23 ~he vapor retardant mixture was appliPd to ~he crude in the ~4 ~l por~ wing tank. In thls appli¢a~ion the oil surface w~s more accessible ~o ~he vapor ret~rdan~ compositiorl and was 26 applied ~rGm the de~k through th2 tank openings by means o 27 a garden type spray ¢an. A m~erately coar~e spray was 28 utilized to obtain maxlmum traject0r~ The tanks were 30 fee~ by lO0 feet by 59 fee~ deepO
~ As the dl~charge of bo~h tanlcs continued, add~-31 tLonal vapor space proflle~ were obtalned. The mon.Ltoring 32 of the hydroearbo~ concentrntiorl in ~he tanlc ~ co~in-led ~ ~5 ~

s 1 or two hours a~ter the ccrnpartments were completely empty 2 and ready to rece-ive ballast. The profile o:E the tar.k com-3 pared with ~he appropriate control is dep~cted ln Figure 6.
4 It is interesting ~o no~e tha~ the suppress~on o~ hydro-5 carbon vapor loss from the oil clingage on tank bulkheads 6 and bottoms was ~till eviden~ two hours a~ter the compart 7 ment was empti~d as shown in Figure 60 This .~lgure Lllus~
8 trates that there was a redue~isn o~ 450 pounds of hydrocar-9 bon in the tank treated wl~h ~he composition of this in~en-tion. This represen~s a significant reduction in the total 11 hydrocarbGn vented to the atmo~phere when the tank was ~al-12 lasted.

. . .

.

Claims (12)

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

1. An evaporation retarding composition capable of forming a continuous stable film over the surface of a liquid hydrocarbon body, said composition comprising:
a fluorosurfactant which is insoluble in the liquid hydrocarbon body and which has a linear fluorocarbon moiety containing from about 7 to about 16 carbon atoms;
a silicone surfactant selected from the group consisting of alkyl, aryl and aralkyl polysiloxanes and copolymers of alkyl, aryl and aralkyl poly-siloxanes with polyethers having linear aliphatic groups of from 4 to 6 carbon atoms;
a polyglycol and a glycol ether, said polyglycol being selected from dihydroxy derivatives of linear aliphatic hydrocarbons having a molecular weight of from about 100 to about 1200 and said glycol ether being selected from alkoxy alkanes having from 6 to 10 carbon atoms;
said fluorosurfactant and said silicone surfactant representing between about 10 wt. % and about 40 wt. % of said mixture.

2. The composition of claim 1, wherein said silicone surfactant is a copolymer of a polysiloxane having from 1 to 4 carbon atoms in a linear aliphatic group with a copolymer of ethylene and propylene oxide.

3. The composition of claim 1, wherein the polyglycol is polyethylene glycol having a molecular weight of 400.

4. The composition of claim 3, wherein the glycol ether is selected from alkoxy alkanes having from 6 to 10 carbon atoms.

5. The composition of claim 4, wherein said fluorosurfactant is present in the range of from about 5 wt. % to about 20 wt. %, said silicone surfactant is present in the range of from about 5 wt. % to about 10 wt. %, said polyglycol is present in the range of from about 5 wt. % to about 35 wt. %, and said glycol ether is present in the range of from about 5 wt. % to about 35 wt. 96.

6. The composition of claim 5, wherein said fluorosurfactant has the general formula NH4+?F3CCF2CF2?3COO-and has a gram molecular weight of 550; wherein said silicone surfactant is a copolymer of dimethyl polysiloxane and polyethylene oxide-polypropylene oxide copolymer; wherein said polyglycol is polyethylene glycol having a molecular weight of about 400; wherein said glycol ether is a 1-hydroxy-2-alkoxy ethane.

7. A hydrocarbon evaporation retarding composition comprising:
from about 5 wt. % to about 20 wt. % fluorosurfactant which is insoluble in the liquid hydrocarbon body and which has a linear fluorocarbon moiety containing from about 7 to about 16 carbon atoms;
from about 5 wt. 96 to about 10 wt. 96 silicone surfactant, said silicone surfactant being selected from the group consisting of alkyl, aryl and aralkyl polysiloxanes and copolymers of alkyl, aryl and aralkyl polysilox-anes with polyethers having linear aliphatic groups of from 4 to 6 carbon atoms;
from about 5 wt. % to about 35 wt. % polyglycol, said polyglycol being selected from dihydroxy derivatives of linear aliphatic hydrocarbons having a molecular weight of from about 100 to about 1200; and from about 5 wt. % to about 35 wt. % polyether, said polyether being selected from alkoxy alkanes having from 6 to 10 carbon atoms.

8. The composition of claim 7, wherein the fluorosurfactant has linear fluorocarbon moieties of from 8 to 16 carbon atoms.

9. The composition of claim 8, wherein the fluorosurfactant has the general formula NH4+?F3CCF2CF2?3COO-and has a gram molecular weight of about 550.

10. The composition of claim 9, wherein said silicone surfactant is a copolymer of a polysiloxane having from 1 to 4 carbon atoms in a linear aliphatic group with a copolymer of ethylene and propylene oxide.

11. The composition of claim 10, wherein the polyglycol is poly-ethylene glycol having a molecular weight of 400.

12. In the method of suppressing evaporation from a body of liquid hydrocarbons by applying a vapor retarding mixture in an amount sufficient to provide a continuous thin film, the improvement wherein said vapor retardant mixture applied to said hydrocarbon comprises:
from about 5 wt. % to about 20 wt. % fluorosurfactant which is insoluble in the liquid hydrocarbon body and which has a linear fluorocarbon moiety containing from about 7 to about 16 carbon atoms;
from about 5 wt. % to about 10 wt. % silicone surfactant, said silicone surfactant being selected from the group consisting of alkyl, aryl and aralkyl polysiloxanes and copolymers of alkyl, aryl and aralkyl polysiloxanes with polyethers having linear aliphatic groups of from 4 to 6 carbon atoms;
from about 5 wt. % to about 35 wt. % polyglycol, said polyglycol being selected from dihydroxy derivatives of linear aliphatic hydrocarbons having a molecular weight of from about 100 to about 1200; and from about 5 wt. % to about 35 wt. % polyether, said polyether being selected from alkoxy alkanes having from 6 to 10 carbon atoms.