US3241908A - Monomolecular film formers for water surfaces - Google Patents

Description

United States Patent Ofi 3,241,908 Patented Mar. 22, 1966 ice 3,241,908 MONOMOLECULAR FiLM FORMERS FOR WATER SURFAfiES Paul A. Mazur, 22 Conlrlin Place, Burnout, Ni, and Curtis Michel, 148 E. 48th St, New York, NY. N Drawing. Filed P421". 5, 1962, See. No. 177,233 12 Claims. (Cl. 21-4565) This invention relates to the formtaion of monomolecular films of polar compounds on water surfaces. More specifically, it deals with the efficient formation of insoluble monomolecular layers of solid fatty alcohols and similar polar compounds on water surfaces to reduce evaporation loss of water from reservoirs, and the like.

Although, in the past, water has been a cheap commodity, the conservation of which has not been of any consequence, the picture thereof has changed considerably in recent years, so that now, even the loss from evaporation is taken quite seriously. Then, of course, there is the forced problem of conservation imposed in areas of ambient high temperature, low humidity and high aerodynamic turbulence, wherein water losses created through surface evaporation and evapo-transpiration are great enough not to be ignored.

Within the last thirty years it has been definitely established that the evaporation of water from open reservoirs can be reduced considerably by deposition, on the water surface, of a monomolecular film of a polar compound, such as, for example, a solid fatty alcohol, e.g., cetyl alcohol, stearyl alcohol, and the like.

Various efforts have been made in the past to contol or reduce such losses on a commercial scale. For example, slabs or blocks of the film-forming compounds, sometimes with an anchor line cast in them, have been floated on the water. While such a method appears to be quite simple, it possesses the great disadvantage in that, on relatively short exposure, the compounds (e.g., fatty alcohols) lose their ability to disperse into a monomolecular film because of coating of their surfaces with algae, suspended solid matter, silt, and the like. Another meth- 'od involved placing the fatty alcohol, in flake form, in a wire or plastic mesh raft attached to anchored floats. Besides wire and plastic mesh, gauze bags have been used. Unfortunately, the results achieved have been similar to those heretofore described with solid blocks, resulting in random and discontinuous release of monomolecular film.

Attempts have been made also to employ solid alcohols in bead form for generation of more continuous films, but it was found that the beads tended to float too low in the water, so that the area of contact at the interface was even less than that achieved with the flake form. The same disadvantages were observed when the fatty alcohol was employed in the form of cast elongated rods.

Since the distribution energy for spreading a compound into a monomolecular film must be derived mainly from difference in surface tension, it is highly important that the film former be distributed on top of the water surface as much as possible. In order to achieve this condition, the film formers have been applied in solution form, dissolved in liquid solvents, using the drip, spray, or subsurface release techniques. While the solvent does leave a monomolecular film on evaporation, this method entails .the disadvantage of solvent retention by the alcohol film unless highly volatile (and thus, less practical) solvents, such as petroleum ether, are employed. Unfortunately, use of solvents involves many concomitant evils, including toxicity, taste and odor effects on the water, fire hazards, etc., so that they have not been considered seriously for commercial installations. It might be mentioned, also, that such additives, including surface-active agents, possess the disadvantage of molecular interference so as to impair the proper orientation of the alcohols on the water surface into continuous compressed monolayers.

A further prior art method resorted to the casting of the solid alcohol on strings or cords which were distributed on the water surface and merely floated on it. While this procedure was somewhat less wasteful of alcohol than the other methods described, the film-forming tendency of the alcohol was hardly better than with blocks or flakes.

Attempts have been made to spray from airplanes the surface of bodies of water with film-forming compounds, but results have not proved satisfactory because of the inability to maintain a complete cover due to blowing away of the charge by the wind. Similarly, agricultural dusting equipment, akin to that used for dusting dry insecticides on crops, was found unsuitable for intermittent depositions of small additions of film-formers necessary to sustain adequate film cover during normally-windy field conditions.

One prior art technique used a machine mounted on a motor-driven boat and employing a rapidly-revolving brush to which was applied a solid block of alcohol. Small particles thus chipped off were blown out of the machine through a motor-driven fan. The trouble here was that the particle size obtained was coarse and of random size, resulting in eificient monomolecular layer formation.

When powdered fatty alcohol, for example, is suspended in water in the form of a dispersion, with or without the aid of a dispersing agent, and is then dripped, sprayed or otherwise applied to the water surface, the prewetting has been found to be objectionable because less surface is made available at the air/ water interface, whereby formation of the monomolecular film is delayed. Extended wetting makes the formation of a properly oriented and compressed mono-layer still less likely, while added dispersing agents further interfere with the uniformity and evaporation-suppression effectiveness of the film.

Incidentally, another procedure of the prior art involved melting the fatty alcohol which then was sprayed at some distance above the water surface, whereupon the alcohol solidified and settled upon the water surface. A particular disadvantage of this method was that the melting equipment required considerable care in operation, and was of limited use in inaccessible areas. Furthermore, sustained storage of fatty alcohols and similar film formers in melted form may increase the formation of degradation products which interfere with the formation of the desired film. Also, there are indications that the interior of the sprayed particles does not cool sufficiently to form the preferred sub-alpha crystal phase which spreads spon taneously to form the desired m-onolayer. The orientation of these film formers, during aging, proceeds from the alpha phase to the sub-alpha phase and then to the eta phase. The desired orientation is in the two latter crystalline phases.

Finally, powdered fatty alcohols have been packaged in polyvinyl alcohol packets for use on small water storages. Their disadvantage lies in the fact that, as the polyvinyl alcohol dissolves it coats the individual film former particles and thus interferes with desired film formation. And, besides, there is no residual fatty alcohol available for replenishment of the film when it is blown off by the wind.

All of the aforesaid prior art methods have been mentioned to point out the fact that considerable work has been done in this field. Yet, in spite of this, there has not been developed a commercially-applicable and efiicient film former, or process of producing such a material.

According to the present invention, the aforesaid disadvantages and limitations have been overcome and the uniform dispersion of the film former has been accomplished so as to achieve unbroken continuity of compressed film and thus effect maximum evaporation-retard ing efficiency. Furthermore, film former losses have been reduced to a minimum and spreading efficiency has been extended so that an attenuated rate of deposition will produce maximum reduction in water evaporation loss. Also, use of the present invention enables utilization of materials which heretofore have been considered as having poor spreading ability when applied in large particle size.

According to the present invention, the waxy compounds ordinarly preferred as film-forming agents, are produced in a foamed form. Specifically, the material is first heated to its melting point and melted. Then, air or other gas, such as carbon dioxide, nitrogen, etc., is whipped or beaten into it, and this mixing is continued while the material is cooled. The foam thus created is retained in the compound as it cools and hardens, resulting in a solid foamed mass of thin-walled cells, and having a density of about 75% to about 50% or even 30% or less of the original solid material in the unfoamed state at normal or room temperature. In this foamed condition, the film former may be stored and transported without undesirable deterioration. Also, due to the fact that it is self-insulating, ambient heat can melt the outer surface of a cake of the material, but the main inner bulk thereof is still in foamed condition, ready for use.

When it is to be used, the foamed film-forming composition is easily abraded, e.g., by scraping or grating, or it is comminuted, pulverized, crushed, or the like, to produce a fine powder of very small particle size. This abraded powder, in abraded form, is very light and it has a very low density, so that it rides high on the surface of the water. Thus, particle surface is increased at the air/Water interface for monolayer generation. Inasmuch as the object of using a film former is to produce an oriented monomolecular film on the Water surface as rapidly as possible for optimum evaporation-suppression, the smaller the particle size from which such film is formed, the more desirable it is. By applying the film former in this manner without the use of solvents, there is no danger of fire or toxicity. Since no pre-wetting is necessary, there is no loss of efiiciency or increase in cost due to use of extraneous chemicals. Reversion to an unstable crystalline phase is eliminated, and sintering (as is encountered with pres-powdered materials) is not encountered to any appreciable extent.

Although a mixture of n-hexadecanol and n-octadecanol (e.g., a 50%50% mixture of cetyl-stearyl alcohols) is preferred as the film forming material, other compounds may be similarly prepared and used, including other solid straight chain aliphatic alcohols (e.g., C to C or even C alcohols), acids and esters having from ten to 40 carbon atoms. Similar use also can be made of resins, such as polyvinyl acetate, styrene-maleic acid copolymers, synthetic ester waxes, and other similar solid materials.

The foam may be produced by whipping or beating the molten film former in a vessel equipped with stirring blades, preferably at high speed, the whipping action being continued while the foam is cooling. Other methods for producing the foamed product include bubbling the air or other suitable gas through the molten material while it is vibrated, aerating the material by blowing it through a jet with air or other gas, etc. Another method for producing the foam is to dissolve a normally-gaseous liquid compound (such as butane, propane, nitrous oxide, chloro-fluorohydrocarbons, etc.) under pressure, and then release the pressure. The resulting cooling effect immediately produces a solid foamed mass of film former. The foamed material may be extruded in rods or sheets, or it may be cut into blocks, fragments, or the like, or it may be formed into balls, pellets (which could be crushed by light pressure), and the like.

4 The following examples will illustrate some of the many phases of the present invention:

EXAMPLE 1 Experiments on ponds of 1 to 2 acres in surface area demonstrated the improvements of this means of applying a substance capable of generating a monomolecular layer. A number of simple floating rafts served as dispensers, in which a block of foamed cetyl-stearyl alcohol, a mixture of approximately 60-70% normal hexadecanol and 3040% normal octadecanol, foamed by melting the alcohols and beating in air with a high speed stirrer until the solidified alcohol mixture gravity was only 25% of its normal gravity, was abraded by the action of an abrading screen rubbing against its surface by Wind and wave motion. The raft dispensers were anchored in the pond in such a manner and location as to secure adequate film coverage over the ponds surface for the prevailing meteorological conditions. The movement of the abrading screen against the foamed block caused small particles of the film-generating agent to fall to the surface of the water. The presence of a compressed monomolecular surface film was detected by the use of standard indicating piston oils. The rate of application of the foamed mixture was in the order of 0.5 to 2.0 ounces per acre per day, which was found sufficient to replenish film losses and maintain an evaporation-retarding monolayer on the pond during periods of winds of between 2 to 18 miles per hour. Comparisons conducted over a six-week period showed a reduction in evaporation of water of beetween 2535%, for treated ponds, as opposed to untreated ponds under substantially similar conditions, with due allowance for the effects of rain and seepage.

EXAMPLE 2 Experiments on a lake of about 80-100 acres demonstrated the ability of a foamed substance to generate a rapidly-spreading monomolecular layer. A dispenser consisting of a shredder and a rotary exhaust fan was attached to the side of a boat. Blocks of foamed cetylstearyl alcohol, a mixture of approximately 60-70% normal hexadecanol and 3040% normal octadecanol (foamed to 30% of normal density) fed into the hopper of the dispenser, were comminuted by the action of the shredder, and the resultant fine particles were blown out by the exhaust fan. The stream of fine particles was directed toward the surface of the water while the boat was driven on a transverse course across the lake of number of times, creating a pattern of parallel layers of discrete particles perpendicular to the prevailing breeze. Within about 20-30 minutes, the particles generated a monomolecular film which had joined to form a continuous layer over the surface of the lake. The following comparisons with conventional solid block and flake applications of cetylstearyl alcohol of the same composition demonstrated greater effective film-forming abilities of the instant comminuted foamed product in terms of time or continuity of film coverage:

Time in minutes to form detectable compressed Dist-nice in feet from monolayer single source Ahraded foam Flake Solid block 3-5 2030 60. 7-10 -70. 120-180. 16-25 120-180. Exceeding 360. 30%50 Excee ling 3fi0 Do.

We claim:

1. A monomolecular film former for controlling water evaporation from water surfaces comprising a solid compound forming an insoluble monomolecular film on a water surface, present in solid foamed condition and having a density of less than about of the density of the compound in the unfoamed state.

2. A monomolecular film former for controlling Water evaporation from water surfaces comprising a solid normal aliphatic alcohol having at least carbon atoms and not over 40 carbon atoms, in the foamed condition, and having a density of less than about 50% of the density of the alcohol in the unfoamed state.

3. A monomolecular film former for controlling water evaporation from water surfaces comprising a solid normal aliphatic acid having at least 10 carbon atoms and not over 40 carbon atoms, in the foamed condition, and having a density of less than about 50% of the density of the acid in the unfoamed state.

4. A monomolecular film former for controlling water evaporation from water surfaces comprising a solid normal aliphatic ester having at least 10 carbon atoms and not over 40 carbon atoms, in the foamed condition, and having a density of less than about 50% of the density of the ester in the unfoamed state.

5. A monomolecular film former for controlling water evaporation from Water surfaces comprising an aliphatic alcohol in the C to C range, in the foamed condition, and having a density of less than about 50% of the density of the alcohol in the unfoamed state,

6. A monomolecular film former for controlling water evaporation from water surfaces comprising a mixture of cetyl-stearyl alcohols in the foamed condition and having a density of less than about 50% of the density of the mixture in the unfoamed state.

7. The method of producing a film former for control ling water evaporation from Water surfaces comprising heating a solid insoluble monomolecular film-forming compound at least to its melting point, incorporating gas into the melted compound until it is in the foamed condition, and cooling the foamed compound to the solid foamed state. v

8. The method of producing a film former for controlling water evaporation from water surfaces comprising heating a solid insoluble monomolecular film-forming compound at least to its melting point, incorporating gas into the melted compound until the latter reaches a foamed state, and cooling said compound while the incorporating operation is continued and until the compound reaches the solid foamed state. i

9. The method of producing a film former for controlling Water evaporation from water surfaces comprising heating a solid aliphatic alcohol at least to its melting point, incorporating gas into the melted alcohol until it is in the foamed condition with a normal density of not over about of that of the unfoamed alcohol, and cooling the foamed alcohol to the solid foamed state.

10. The method of forming an efiicient monomolecular evaporation-reducing film over a water surface for controlling water evaporation from said surface comprising forming a foamed mass of solid insoluble monomolecular film former, abrading said mass to form a fine powder, and scattering said powder over a water surface.

11. The method of forming an efiicient monomolecular evaporation-reducing film over a water surface for controlling water evaporation from said surface comprising abrading a foamed solid alcohol mass into a powder and strewing said powder over a water surface.

12. The method of forming an eflicient monomolecular evaporation-reducing film over a water surface for con trolling water evaporation from said surface comprising heating a solid aliphatic alcohol to at least its melting temperature, incorporating gas into the melted alcohol until it acquires a foamed state having a normal density of not over about 50% of that of the unfoamed alcohol, cooling said foamed mass to the solid state, abrading said solid foamed mass into a powder, and strewing said powder over a water surface.

References Cited by the Examiner UNITED STATES PATENTS 1,414,015 4/1922 Godfrey 252-368 1,571,625 2/1926 Dawes 252-368 2,200,298 4/ 1939 Robinson 260632 2,903,330 9/1959 Dressler 2160.5

OTHER REFERENCES RosanoJournal of Physical Chemistry, volume 60, No. 3, March 1596, pp. 348353.

MORRIS O. WOLK, Primary Examiner.

JOSEPH SCOVRONEK, Examiner.

S. ROSEN, F. W. BROWN, Assistant Examiners.

Claims (1)

1. 7. THE METHOD OF PRODUCING A FILM FORMER FOR CONTROLLING WATER EVAPORATION FROM WATER SURFACES COMPRISING HEATING A SOLID INSOLUBLE MONOMOLECULAR FILM-FORMING COMPOUND AT LEAST TO ITS MELTING POINT, INCORPORATING GAS INTO THE MELTED COMPOUND UNTIL IT IS IN THE FOAMED CONDITION, AND COOLING THE FOAMED COMPOUND TO THE SOLID FOAMED STATE.