Emulsion

Abstract

It is an object of the present invention to provide an emulsion which shows sufficient rust preventive effect, in spite of water it contains as a constituent of the composition, on a metallic material which is otherwise corroded when coming into contact with water and oxygen.

Description

BACKGROUND OF THE INVENTION

[0001] (1) Field of the Invention

[0002] This invention relates to an emulsion produced by emulsifying water and oil by the aid of a surfactant, more particularly such an emulsion having a sufficient rust preventive effect.

[0003] (2) Background

[0004] One of the embodiments for use of an emulsion of two types of immiscible liquids, e.g., water and oil, mixed by the aid of a surfactant is an emulsion fuel, which comprises water and fuel oil emulsified by the aid of a surfactant. This type of emulsion fuel has been used as a fuel for diesel engines and boilers. When used for diesel engines, it is known to greatly reduce nitrogen oxide (NOx) and hydrocarbon (soot) emissions.

[0005] More concretely, it has been demonstrated that a diesel engine discharges 30 to 40% less NOx emissions on the emulsion fuel than on the normal fuel. Increasing proportion of water in the emulsion fuel tends to reduce NOx emissions. For example, a 50-50 mixture almost halves the emissions from the level associated with the normal fuel.

[0006] The above-described emulsion fuel, produced by emulsifying water and fuel oil, naturally contains a high proportion of water in the composition. As a result, it causes a problem of corrosion; a section in a diesel engine, boiler or the like coming directly into contact with the emulsion fuel, more particularly a metallic section which may be corroded when coming into contact with water and oxygen, may be corroded when coming into contact with water in the fuel. More concretely, a fuel injection nozzle as a member of diesel engine is generally made of an iron-based alloy and will be corroded when coming into contact with water in the emulsion fuel, causing problems that greatly exert adverse effects on operating performance of the diesel engine.

SUMMARY OF THE INVENTION

[0007] It is an object of the present invention to provide an emulsion which shows sufficient rust preventive effect, in spite of water it contains as a constituent of the composition, on a metallic material which is otherwise corroded when coming into contact with water and oxygen, to solve the above problems.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] FIG. 1 conceptually illustrates one embodiment for producing the emulsion of the present invention,

[0009] FIG. 2 conceptually illustrates another embodiment for producing the emulsion of the present invention,

[0010] FIG. 3 shows the relationship between redox potential of Fe (pure iron) and pH,

[0011] FIG. 4A, 4B and 4C conceptually illustrate situations of the emulsion of the present invention coming into contact with a metallic material, and

[0012] FIG. 5A and 5B conceptually illustrate types of the emulsion of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0013] One of the embodiments of the emulsion of the present invention (Emulsion 1) comprises water and oil emulsified by the aid of a surfactant, which is characterized in that it forms a passivation film on a metallic material which may be otherwise corroded when coming into contact with water and oxygen, and also forms a water-repellant layer of the surfactant molecules on the passivation film.

[0014] The above constitution prevents the metallic material from directly coming into contact with water and oxygen by the actions of the passivation film and water-repellant layer formed thereon. As a result, Emulsion 1 shows sufficient rust preventive effect on a metallic material which maybe otherwise corroded when coming into contact with water and oxygen, in spite of the fact that it contains water as a constituent of the composition.

[0015] Another embodiment of the emulsion of the present invention (Emulsion 2) is Emulsion 1, wherein the oil to be mixed with water is fuel oil as constituents of the emulsion fuel. This constitution prevents the metallic material from directly coming into contact with water and oxygen by the actions of the passivation film and the water-repellant layer formed thereon. As a result, Emulsion 2 shows sufficient rust preventive effect, in spite of water it contains as a constituent of the composition, on a metallic material that maybe otherwise corroded when coming into contact with water and oxygen. Emulsion 2 with the emulsified fuel oil as a constituent shows a sufficient rust preventive effect on the metallic material, and is useable as an emulsion fuel for, e.g., diesel engines and boilers.

[0016] Still another embodiment of the emulsion of the present invention (Emulsion 3 ) is Emulsion 1 or 2, wherein the surfactant has a neutral pH and a base is incorporated to make the emulsion alkaline. This constitution forms a passivation film and water-repellant layer of the surfactant molecules thereon by the alkaline emulsion, to prevent the metallic material from directly coming into contact with water and oxygen by the actions of the passivation film and water-repellant layer. As a result, Emulsion 3 shows sufficient rust preventive effect on a metallic material which may be otherwise corroded when coming into contact with water and oxygen, even though it contains water as a constituent of the composition.

[0017] Still another embodiment of the emulsion of the present invention (Emulsion 4) is Emulsion 1 or 2, wherein the surfactant has an alkaline pH to make the emulsion alkaline. This constitution forms a passivation film and water-repellant layer of the surfactant molecules thereon by the alkaline emulsion, to prevent the metallic material from directly coming into contact with water and oxygen by the actions of the passivation film and water-repellant layer. As a result, Emulsion 4 shows sufficient rust preventive effect, in spite of water it contains as a constituent of the composition, on a metallic material which may be otherwise corroded when coming into contact with water and oxygen.

[0018] The present invention is described more concretely by referring to the drawings for the embodiments. FIG. 1 illustrates an embodiment of the emulsion of the present invention for emulsion fuel, wherein the emulsion fuel 1 (hereinafter occasionally referred to simply as the “emulsion”) is composed of water 2, a fuel oil 3, neutral surfactant (nonionic) 4 and base 5, mixed with each other to be emulsified by an emulsifier (not shown). The fuel oil 3 can be diesel fuel, heating fuel, gas turbine fuel, jet fuel, boiler fuel, etc.

[0019] Water 2, the fuel oil 3 and surfactant 4 as constituents of the emulsion fuel 1 can be mixed in a volumetric ratio of approximately 100:100:1 (water:fuel oil:surfactant). The base 5 as a constituent of the emulsion fuel 1 is incorporated at approximately 0.5% by weight based on the surfactant 4. The emulsion fuel 1 can be made alkaline by the base 5. The alkalinity of the emulsion fuel 1 can vary in a pH range of 9 to 12 depending on types of the surfactant 4 and base 5 used.

[0020] The surfactant 4 as a constituent of the emulsion fuel 1 is not limited so long as it helps emulsify water and oil, and various types described later (refer to FIG. 5) may be used. As an example of the nonionic surfactant, there are polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, polyoxyethylene alkyl esters, sorbitan alkyl esters, polyoxyethylene sorbitan alkyl esters, glycerol esters, their derivatives and the like. More specifically examples of polyoxyethylene alkyl ethers are polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene behenyl ether and the like; examples of polyoxyethylene alkyl phenyl ethers are polyoxyethylene nonyl phenyl ether, polyoxyethylene octyl phenyl ether and the like; examples of polyoxyethylene alkyl esters are polyethylene glycol monolaurylate, polyethylene glycol monooleate, polyethylene glycol monostearate and the like; examples of sorbitan alkyl esters are polyoxyethylene sorbitan monolaurylate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan monooleate and the like; examples of polyoxyethylene sorbitan alkyl esters are polyoxyethylene sorbitan monolaurylate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate and the like; and examples of glycerol esters are glycerol monomyristate, glycerol monostearate, glycerol monooleate and the like. Also examples of their derivatives are polyoxyethylene alkyl amine, polyoxyethylene alkyl phenyl-formaldehyde condensate, polyoxyethylene alkyl ether phosphate and the like. Particularly preferable are nonionic surfactants that have an HLB value of 4 to 20.

[0021] The base 5, as a constituent of the emulsion fuel 1, can be selected from various bases, e.g., sodium or potassium compounds, so long as it is soluble in water and alkaline. One type of base or two or more types may be used, so long as the emulsion fuel 1 is kept alkaline at pH 9 to 12.

[0022] FIG. 2 illustrates another embodiment of the emulsion of the present invention for emulsion fuel, wherein the emulsion fuel (emulsion) 1′ is composed of water 2′, a fuel oil 3′ and alkaline surfactant (ionic) 4′, mixed with each other to be emulsified by an emulsifier (not shown). The emulsion fuel 1′ was made alkaline by the alkaline surfactant 4′, its alkalinity varied in a pH range of 9 to 12 depending on types of the surfactant 4′ used. The surfactant 4′ as a constituent of the emulsion fuel 1′ is not limited and may be selected from various types, so long as it helps emulsify water and oil, and, at the same time, keep the emulsion fuel 1′ at a given alkalinity (pH level). The surfactant can include those listed above.

[0023] The emulsion fuel 1 or 1′ was found to greatly reduce NOx emissions, almost to half of those associated with the usual fuel, when used as the fuel for a diesel engine. No rust was observed on any member of the diesel engine, e.g., fuel injection nozzle, in spite of use of the emulsion fuel 1 or 1′ for extended periods. Therefore, the emulsion fuels land 1′ show sufficient rust preventive effect, in spite of water it contains as a constituent of the composition, on a metallic material, which is otherwise corroded when coming into contact with water and oxygen.

[0024] The mechanisms involved in the rust preventive effect of the emulsion of the present invention on a metallic material that is otherwise corroded when coming into contact with water and oxygen were verified. It is known that rusting of iron-based alloys is controlled in an alkaline atmosphere. As shown in FIG. 3, which shows the relationship between redox potential of Fe (pure iron) and pH, an iron material in contact with water is in the corrosion region when water is neutral or acidic at pH 6 (marked with a solid circle &Circlesolid;), and in the passivation region when water is alkaline at pH 10 (marked with an open circle 0).

[0025] An iron material is coated with a passivation film, several &mgr;m to tens of &mgr;m in thickness, when its surface is exposed to an alkaline atmosphere, and the passivation film retards permeation of oxygen to protect the material from corrosion.

[0026] A test piece of carbon steel is “rusted” when immersed in water in a neutral to slightly acidic condition (pH: 6 to 7), whereas it is rusted but to a smaller extent, or controlled to an extent of “slightly rusted” when immersed in water doped with a base (e.g., sodium carbonate) to be alkaline (pH>10), as shown by the rusting test results with water and water/oil emulsion (Table 1). 1 TABLE 1 Rusting tests with water and water/oil emulsion Neutral (pH: 6 to 7) Alkaline (pH > 10) Water Rusted Slightly rusted Emulsion Slightly rusted Not rusted (Water + Oil + Alkaline Surfactant)

[0027] It is apparent, also as shown in the rusting test results given in Table 1, a test piece of carbon steel is not rusted when immersed in the alkaline (pH>10) emulsion of the present invention, but the emulsion decreases in rust preventive effect when doped with an acid (e.g., nitric acid) to be neutral (pH: 6 to 7), so that the test piece is slightly rusted. It is apparent, therefore, that the emulsion of the present invention exhibits, on the premise that it contains a surfactant in the composition, sufficient rust preventive effect when kept alkaline. The sufficient rust preventive effect of the emulsion of the present invention comes from formation of the passivation and water-repellant layers on a metallic material surface with which it comes into contact, as discussed below.

[0028] As shown in FIG. 4A, 4B, the emulsion fuel 1 of the present invention forms, when coming into contact with a metallic material 10 (e.g., fuel injection nozzle of carbon steel), a passivation film 10P thereon as discussed earlier, because it is alkaline. The surfactant as a constituent of the emulsion fuel 1 has a hydrophilic group 4h and hydrophobic (lipophilic) group 4o in its molecule 4M, and is dispersed in the emulsion fuel 1, as shown in FIG. 4A, 4B. The passivation film 10P, when formed on the metallic material 10, partly adsorbs the surfactant molecules 4M on the hydrophilic group 4h side, as shown in FIG. 4C. The passivation film 10P can also include the metallic material 10 surface, which is slightly oxidized and has hydrophilicity, so that it can adsorb the hydrophilic group 4h in the surfactant molecule 4M.

[0029] The passivation film 10P adsorbs the hydrophilic group 4h in the surfactant molecule 4M more strongly than the hydrophilic groups 4h adsorb each other. As a result, the water-repellant layer 4R of the surfactant molecules 4M is formed on the passivation film 10P, wherein each surfactant molecule 4M is arranged, as schematically illustrated in FIG. 4C, with its hydrophobic group 4o orienting outward (or upward in the figure).

[0030] As described above, the emulsion fuel 1 of the present invention forms a passivation film 10P on the metallic material 10 with which it comes into contact, and a water-repellent layer 4R of the surfactant molecules 4M on the film 10P. The emulsion fuel 1 of the present invention prevents corrosion of the metallic material 10 as far as possible, because the passivation film 10P and water-repellent layer 4R prevent the metallic material 10 surface from coming into contact with dissolved oxygen and water present in the emulsion fuel 1. It is needless to say that the emulsion fuel 1′ of the present invention (comprising water, an oil and alkaline surfactant) also prevents corrosion of the metallic material 10 as far as possible in a similar manner by forming a passivation film 10P on the metallic material 10 and water-repellent layer 4R of the surfactant molecules on the passivation film 10P.

[0031] Table 2 shows results of the rusting tests with emulsion fuels incorporated with a varying neutral surfactant. “HLB” in Table 2 quantitatively indicates the hydrophilic/lipophilic balance. 2 TABLE 2 Results of the rusting tests with emulsion fuels incorporated with a varying neutral surfactant (nonionic) Rusting Rusting pH of conditions conditions the in the in the aqueous aqueous alkaline Surfactants, (HLB) solutions solutions solutions Aromatic-based 5.73 6 +++ − ″ 10.2 6/7 ++ − ″ 11.0 6/7 +++ − Branched aliphatic, nonionic 8.0 6/7 ″ 10.5 6/7 ++ − ″ 12.2 6/7 +++ − Saturated, straight-chain 4 6 +++ − type nonionic ″ 8 6 ++ − ″ 10 6 +++ − ″ 12 6 +++ − Unsaturated, straight-chain 4 6 +++ − type nonionic ″ 7 6 +++ − ″ 11 6 +++ − ″ 12 6 +++ − Short-chain type nonionic 6 6 +++ − ″ 10 6 +++ − ″ 12 6 +++ − Long-chain type nonionic 5 6 +++ − ″ 10 6 +++ − ″ 20 6 ++ − Long-chain, branched 5 6 +++ − type nonionic ″ 9 6 +++ − ″ 12 6 ++ − − No rust observed + Rust observed slightly ++ Rust observed +++ Rust observed significantly

[0032] Rust was observed on each iron piece immersed in an aqueous solution with approximately 1 g of the surfactant dissolved in 100 mL of distilled water, because the solution is neutral. On the other hand, no rust was observed on each iron piece immersed in the emulsion fuel (alkaline solution) which was the above aqueous solution incorporated with an adequate quantity of sodium carbonate to keep the solution at pH 10 to 12, irrespective of type of the surfactant used.

[0033] The surfactant as a constituent of the emulsion fuel of the present invention may be alkaline ionic type or neutral nonionic type. In other words, it may be used for the emulsion of the present invention by adjusting the emulsion fuel at an alkaline pH level. The water/oil emulsion may be an O/W type with oil (oil droplets) 3 dispersed in water 2 (FIG. 5A) or W/O type with water (water droplets) 2 dispersed in oil 3 (FIG. 5B) The various types of surfactants shown in Table 2 include those forming each of the above types of the emulsion, and type of the emulsion of the present invention varies depending on the type of surfactant used. However, it is needless to say that the emulsion of the present invention exhibits sufficient rust preventive effect, whether it is an O/W or W/O type.

[0034] In the above embodiments, iron-based metals (e.g., pure iron and carbon steel) were used as the metallic materials which might be corroded on contacting water and oxygen. However, it is also needless to say that the emulsion of the present invention exhibits sufficient rust preventive effect on other metallic materials, e.g., copper-based and aluminum-based ones.

[0035] The above embodiments exemplify the emulsion fuels to which the emulsion of the present invention is applied. However, it is also needless to say that the emulsion of the present invention is effectively applicable to various other industrial areas, e.g., cutting oils and coolants for various machines, and rust preventives for protecting metallic surfaces as the special emulsion having sufficient rust preventive effect.

Claims

1. An emulsion comprising water and oil emulsified by the aid of a surfactant, characterized in that it forms a passivation film on a metallic material which may be otherwise corroded when coming into contact with water and oxygen, and also forms a water-repellant layer of the surfactant molecules on said passivation film.

2. The emulsion according to claim 1, wherein said oil to be mixed with said water is fuel oil as constituents of an emulsion fuel.

3. The emulsion according to claim 1, wherein said surfactant is neutral and a base is incorporated to make said emulsion alkaline.

4. The emulsion according to claim 2, wherein said surfactant is neutral and a base is incorporated to make said emulsion alkaline.

5. The emulsion according to claim 1, wherein said surfactant is alkaline to make said emulsion alkaline.

6. The emulsion according to claim 2, wherein said surfactant is alkaline to make said emulsion alkaline.