US2447551A - Clearing water surfaces of oil - Google Patents

Description

Patented Aug. 24, 1948 CLEARINGIWATER SURFACES OFOIL William-A. Zisman, Washington,- D*."C., and-Lamar Pickett, Arlington, Va.

No Drawing. Application-.June22, 15143,, Serial No. 491,838!

(Granted under the. act of..March.3, 1883, as amended April 30, 1928.; .370 0.;Gfl'757) 4 Claims.

Thisinvention relatestoa method of clea n water surfaces of oil. and to compositions used therewith. In particular the invention is concerned with theprotection oi the crews of torpedoed or sinking ships where fuel oil or gasoline from,the ship has spread over the water.

Thefuel oils,,lubricating oils and the gasoline escaping from a bombed ..or torpedoed ship or storage -.tankoften spread out over the water forming ..a.layer or blanket which may be anywhere fromless than a thousandth. of. an inchto many inchesdeep, depending on the viscosity of theoiLthe amount of escapingoil and the efiects of the wind. If the oil film .is of .the orderof a thousandth of an inch thick it is not a serious menace.since. it-is. kept cool by the water underneath, although it may cause discomfort to swimmers. Onthe other hand, films or blankets only one-fourth of an inch thick are a fire hazard and 'evenwhen not burning they tend to blind and suffocate swimmers.

This inventionxprovides a method of clearing limitedareas of water surfaces of oil where the original-oil film or layer is not greater thanabout one-fourth-to one-half inch thick, and it is especially adapted "to the protection of swimmers .and

survivors in life boats or on rails by holding the oil film 'at a distance. The lengthier time which-the oil -film"may be held at bay depends largely on the weather prevailing at the time, as. rough weather tends tocounteract the effects of the method. However, moderate winds tend to blow the oil film away from the vessel so that there is a better chance of escape by leaving from the windward side, whereas in calm weather the oil tends to form a blanket or pool equally extensive in all directions about the ship. It is under the latter circumstances that the method of this invention is most efficacious. The invention also includes certain compositions of matter used in repelling the oil film.

The principle of the invention resides in the use of certain agents to repel the oil when they are applied to the water. Those agents are certain polar organic compounds which are insoluble or slightly soluble in water and which therefore spread out over the water surface in an invisible layer one molecule thick. In addition the compounds are insoluble or nearly so in fuel oils, gasoline and the like, they are not harmful to human beings and they have unusually high spreading pressures, the latter enabling them to repel oil layers of thicknesses of the order of onefourth to one-half inch. Another essential characteristic of these compounds is the fact that the 2;. are liquid. (1. e., notsolid). andalsomaintain high spreading-pressures \attemperatures ashlow as 40 F., thusenabling them to operateefiectively -in.co1d .waters.

The compounds used in this .inventionare liquid esters of. higher .fatty acidsand .hydroxy compounds selected-from. the group; consisting. of sugars and sugar derivatives. In partic'ularesters ofoleiciand ricinoleic acidsare most, suitable-because they remainliquidat low temperatures,

andthe esters of-these acidswhich show the greatest oil. and water. insolubilityland highest spreading pressures are .those vof .sorbitol and mannitoland derivatives. of sorbitol .andmannitol. Particularly desirable compounds include scrbitan monooleate, sorbitan monoricinoleate, sorbitan trioleate, modified. sorbitan. I. diricinoleate, monolaurate .andhexaricinoleate, modified mannitan .monooleate and mannidemonooleate... The

spreading pressures .of -.these.compounds. invdynes per centimeter,measuredat. the boundary line of the oilIfilm,is given. in thefo'llowing table.

Tl'ible Spreading.

pressure Compound sorbitan monooleate 40. 6 46. 5 modified sorbitan diricinoleate 34. 3 37:4 modified sorbitmmouolaunate 3t 8 37. 3 sorbitan monoricinoleate 34.3 36:8 modifiedmannitan monooleate' 39:0 37. '5 sorbitan trioleate 36. 8 35. 6 modified sorbitan hexariciuoleate. 33. 8 37. 6 mannide monooleate 37. 0 39. 0

The esters shown above are all derivatives of sorbitol and mannitol. The sorbitans and mannitans are the products obtained by removing one molecule of water from sorbitol and mannitol, forming an internal ether linkage or lactone ring in the molecule, and the sorbides and mannides are the products resulting from the removal of two molecules of water from sorbitol and mannitol, respectively. Since sorbitol and mannitol are hexahydroxy compounds, it is obvious that the sorbitans and mannitans have four hydroxy groups available for esterification or other reaction, and the sorbides and mannides have two available hydroxyls. The modified esters listed in the table were those in which one or more hydroxyls of the sorbitan or mannitan not used in ester linkage were reacted with polyalkylene oxides to give polyoxyalkylene side chains to the ester. This side chain renders the ester less oil soluble and more water soluble.

It is obvious that mixtures of the above have almost any desired characteristics of oil and/or water solubility (or insolubility), to yield spreading agents of maximum efiiciency. In fact the compounds employed in the above tests contained small amounts of other similar esters inasmuch as they were of commercial grade when used, rather than chemically pure.

the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

I claim:

1. A method of opening an oil-free area in a water surface oil blanket not exceeding one-half inch in thickness comprising impelling the oil from the area into the surrounding region by In use the ester is applied to the water either life jacket, as only a relatively small amount is.

needed.

Tests with the esters listed in the table showed them capable of holding back a one-fourth inch wall of fuel oil on a water surface for over twentyfour hours without apparent diminution of strength. These tests were made under ideal conditions, so that further tests were undertaken at sea. With a Wind velocity of a few miles per hour and calm sea at a temperature of about 48 F., a puddle of oil amounting to between 800 and 900 gallons spreading over a circular area about 300 yards in diameter was forced back from a spot in its center to a distance of about 35 feet from the ship by dumping about two gallons of a 25% solution of the ester in hexanol into the water. Where the oil layer was churned by the propeller the effect of the ester was quite evident in assisting breaking the oil up into small discs which floated on the water rather than emulsified with it.

For individual use in swimming in the sea the ester is better applied in concentrated form to the water surface by means of a sponge or other absorbent material soaked in the ester, or it may be applied from a collapsible tube, as only a few ounces per person are necessary. However, prolonged contact of the ester with the filling in life jackets should be avoided because the buoyancy of the latter is adversely affected in time. Of course the esters have no such effect on inflatable types of life rafts and preservers.

Many variations will be apparent to those skilled in the art, and the invention should not be limited other than as defined by the appended claims.

The invention described herein may be manufactured and used by or for the Government of introducing to the water surface at a positio within said blanket a solution of a compound selected from the group consisting of sorbitan monooleate, sorbitan monoricinoleate and mannide monooleate, the said solution consisting of about twenty-five percent by weight of said compound dissolved in a solvent selected from the group consisting of hexanol and octanol.

2. The method as defined in claim 1 in which the solution introduced to the water surface within said blanket consists of about twenty-five percent by weight of sorbitan monooleate dissolved in ,a solvent selected from the group consisting of hexanol and octanol.

3. The method as defined in claim 1 in which the solution introduced to the water surface within said blanket consists of about twenty-five percent by weight of mannide monooleate dissolved in a solvent selected from the group consisting of hexanol and octanol.

4. The method as defined in claim 1 in which the solution introduced to the water surface within said blanket consists of about twenty-five percent by weight of sorbitan monoricinoleate dissolved in a solvent selected from the group consisting of hexanol and octanol.

WILLIAM A. ZISMAN. LAMAR PICKETT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,950,937 Brown Mar. 13, 1934 2,017,868 Nolan Oct. 22, 1935 2,285,422 Epstein et a1. June 9, 1942 2,322,820 Brown June 29, 1943 2,322,822 Brown June 29, 1943 OTHER REFERENCES Spans and Tweens, Booklet of Atlas Powder Co. (1942), pages 7, 8, 11 and 16.