Mercaptide Microemulsion

Abstract

The present invention provides mercaptide microemulsions and methods for forming mercaptide microemulsions.

Description

[Technical Field]

[0001] The present invention relates to novel mercaptide microemulsions. [Background technology]

[0002] The present invention generally relates to novel compositions comprising mercaptide microemulsions. Summary of the Invention [Problem to be solved by the invention]

[0003] Heavy mercaptans have unique chemical properties that make them particularly useful in applications such as mineral recovery, metal protection, surface modification, polymer functionalization, etc. However, heavy mercaptans also exhibit a strong odor and miscibility with water, limiting their use in many applications. [Means for solving the problem]

[0004] In accordance with the present invention, we have discovered that mercaptide microemulsions can be used in place of mercaptans in many applications while minimizing the odor exhibited by mercaptans. The objective of this invention is to reduce the perceived odor of heavy mercaptans (liquids) by converting thiol groups to ionic thiolates. The resulting heavy mercaptide salts (solids) also have improved compatibility with water, allowing for the preparation of aqueous formulations with unique microstructures (microemulsions). Mercaptide microemulsions are formed in a single container by combining ingredients such as thiolates, water, alcohols, surfactants, and dispersants. These aqueous mercaptide microemulsions are a new product form of heavy mercaptans that exhibits a lower perceived odor and enhances the activity of these molecules due to the increased interfacial area typical of the microstructure. [Brief explanation of the drawings]

[0005] [Figure 1]FIG. 1 shows a mercaptide microemulsion according to an embodiment of the present invention (sample 5 on the left) and a conventional mercaptan emulsion (sample 8 on the right). DETAILED DESCRIPTION OF THE INVENTION

[0006] Detailed Description of Specific Embodiments of the Invention "Microemulsion" means a dispersion of a continuous phase material having substantially uniformly dispersed droplets of a dispersed phase material therein, the droplets having a size in the range of about 1 to 100 nm, typically 10 to 50 nm.

[0007] In at least one embodiment, a microemulsion is provided that includes a continuous phase material and has dispersed therein droplets of a dispersed phase material. The droplet size ranges from approximately 1 to 100 nm, typically from about 10 to 50 nm. Due to the very small droplet size, the microemulsion is optically clear, isotropic, and thermodynamically stable. In at least one embodiment, the continuous phase material includes water. In at least one embodiment, the dispersed phase material and / or the continuous phase material includes one or more hydrophobic materials. In at least one embodiment, the dispersed phase material and / or the continuous phase material includes an amphiphilic material and / or an ionic material.

[0008] Mercaptans (also known as thiols) are composed of hydrocarbon chains of 8 to 12 carbon atoms and can be in a liquid state at standard ambient temperature and pressure. Such liquid mercaptans are not miscible with water. Furthermore, the high volatility of these liquids raises concerns related to noxious odors, limiting their use in many applications, especially those performed in open containers. In the present invention, liquid thiols are treated with a strong organic or inorganic base to produce mercaptides (ionic salts of mercaptans). In one embodiment, the mercaptides are produced as pure products, solid powders, which have improved compatibility with water and do not present odor concerns related to the volatility of thiols. In further embodiments according to the present invention, mercaptide formation can be achieved in the presence of other components, such as water, alcohols, hydrocarbons, surfactants, and / or dispersants. Preparing mercaptides in such multi-component liquid systems can result in formulations characterized by unique microstructures. The present invention's preparation of mercaptide microemulsions can be a one-pot process.

[0009] The alcohol may be selected from the following group including ethanol, propanol, butanol, pentanol, hexanol, heptanol, octanol, cresylic acid, and any isomers and combinations thereof.

[0010] The hydrocarbon may be selected from the group of pentane, hexane, heptane, octane, nonane, decane, dodecane, propylene tetramer, kerosene, diesel fuel, biodiesel (methyl ester fatty acids), and any combination thereof.

[0011] The surfactant may be selected from the group of ethoxylated mercaptans, alkylphenol ethoxylates, alkylbenzene sulfonates, poloxamers (pluronics), polysorbates, and any combination thereof.

[0012] The dispersing agent may be selected from the group of polyethylene glycols, polypropylene glycols, polyglycol ethers and / or other polyols.

[0013] Although the formation of the mercaptide microemulsion by the one-pot method is preferred, the mercaptide salt derived from the mercaptan may be in solid form after reaction with the base alone. The solid mercaptide salt can be used to prepare the microemulsion by mixing with the liquid components. The mercaptide can also be commercially available in solid form and mixed with the liquid components to form the mercaptide microemulsion of the present invention.

[0014] During extensive manipulation, it was discovered that solids precipitated from the microemulsion liquid. By subjecting duplicate samples to different post-reaction treatments, it was discovered that mercaptides in the microemulsion could be oxidized to disulfides in the presence of oxygen. Therefore, for stability, it is desirable to minimize or avoid the oxidation of mercaptide ions to disulfides.

[0015] Heavy mercaptans are thiols ( - The hydrocarbon chain may be linear, branched, or cyclic. Mercaptides may be formed from mercaptans (containing only one thiol group per molecule) or dithiols or polythiols (containing two or more thiol groups per molecule). Mercaptans used to form the mercaptides of the present invention may be primary, secondary, or tertiary mercaptans having 8 to 15 carbon atoms. Exemplary dithiols and polythiols include 1,8-dimercaptan-3,6-dioxaoctane and pentaerythritol tetra(3-mercaptopropionate), respectively. When these molecules are exposed to pH values of about 11 or greater, conjugate base mercaptides are formed, - The SH group is ionic. - M + where M +is an organic or inorganic cation from a strong base. For example, alkali metal or alkaline earth metal hydroxide bases such as sodium hydroxide, potassium hydroxide, rubidium hydroxide, magnesium hydroxide, calcium hydroxide, lithium hydroxide, barium hydroxide, magnesium hydroxide, etc., or organic bases such as ammonium hydroxide, tetramethylguanidine (which forms a guanidinium cation), guanidine, tetramethylammonium hydroxide, etc., form conjugated mercaptides when contacted with mercaptans.

[0016] Heavy mercaptide salts are free-flowing solids in their pure state. In accordance with one embodiment of the present invention, a one-pot method has been discovered in which mercaptides are not only produced but also serve as a major component in the formulation of aqueous microemulsions. The microemulsion formulation can include mercaptides, water, and optionally alcohols, hydrocarbons, glycols, polyglycols, surfactants, and / or excess amounts of mercaptans and bases from the mercaptide conversion.

[0017] The mercaptide-based microemulsions of the present invention can be formed by combining the components in a single vessel, followed by stirring (with a stir bar, overhead stirrer, vortex mixer, static mixer, or high-shear mixer) until a homogeneous liquid composition is achieved. These formulations may be cloudy initially, but upon standing for several minutes, a clear microemulsion forms. The components can be added to the vessel sequentially or all at once. Alternatively, although stirring is a known method for rapidly obtaining a homogeneous liquid formulation, the components of the present invention can be added to the vessel (in any order) and allowed to react without stirring, resulting in a thermodynamically stable microemulsion as a result of Brownian motion and entropy.

[0018] Certain mercaptide powders alone have a moderate affinity for water, producing homogeneous liquid products without the need for other ingredients. For example, mercaptide salts of N-dodecyl mercaptan can form homogeneous mixtures in water at concentrations up to about 2% by weight (0.00001 to 2% by weight). When liquid components are added, microemulsions containing as much as 60% by weight of mercaptide are formed. A preferred range is about 0.01 to about 40% by weight of mercaptide. Water content can range from about 20 to about 98.0% by weight (as a diluent for pure mercaptide powder), with a preferred range of about 40 to about 98% by weight for multi-component microemulsions. Alcohol can be added at about 2 to about 30% by weight. A preferred range for alcohol is about 5 to about 20% by weight. Surfactants can be added at 0 to about 10% by weight. Dispersants can be added at 0 to about 20% by weight, more preferably 5 to 15% by weight. Mercaptide formation can be achieved by reacting the thiol with an equimolar amount of base, although an excess of about 1 to about 5% by weight of base can also be used.

[0019] The mercaptide microemulsions of the present invention can be used in applications such as collectors in the flotation of mineral ores, the formation of self-assembled monolayers (SAMs) for surface modification and protection of metals and lignocellulosic materials, antioxidants in the processing and end use of polyolefin polymers, the formation of larger sulfide and / or polysulfide structures, and the stabilization of nanoscale inorganic structures such as nanoparticles and quantum dots. [Example]

[0020] Example 1 Table 1 shows the compositions used to form mercaptide microemulsions in accordance with the present invention. The ingredients in the table are N-dodecyl mercaptan (NDDM), N-decyl mercaptan (NDM), N-octyl mercaptan (NOM), sodium hydroxide (NaOH), potassium hydroxide (KOH), methyl isobutyl carbinol (MIBC), polypropylene glycol (PPG), and polyethylene glycol (PEG). The mercaptide microemulsions were formed by simply mixing the specified ingredients in any order at room temperature with stirring. The same mercaptide microemulsions can also be produced by mixing the ingredients in a high-shear mixer.

[0021] [Table 1]

[0022] For the samples listed in Table 1, the conversion of mercaptans to mercaptides was confirmed by pH measurements (mercaptides are strong bases, and the pH of microemulsions containing mercaptides was measured to be above 13), UV-Vis spectroscopy (detecting the typical mercaptide anion absorption between 240 and 260 nm), and 1 H - and 13 C - This was confirmed by NMR, which detected different chemical shifts for mercaptide and mercaptan molecules.

[0023] The submicron structure of these samples was determined by droplet size measurements by dynamic light scattering (DLS), which showed the formation of droplets less than 100 nm. The Z-average diameters of samples 1, 2, and 6 are shown in Table 2.

[0024] [Table 2]

[0025] The one-pot method produced mercaptide microemulsions, which formed quantifiably finely divided and well-dispersed microstructures, as evidenced by the presence of mercaptides instead of mercaptans in the final product.

[0026] Table 3 shows the compositions used to form mercaptan O / W emulsions obtained by high shear mixing with the indicated ingredients. Sample 8 did not form a microemulsion. The droplet size of Sample 8 could not be measured using DLS because the air bubbles were too large for the instrument. Observation of Sample 8 under an optical microscope showed that the average particle size of Sample 8 was approximately 20 microns, far above the microemulsion level. Observation of Sample 5 under an optical microscope showed visible droplets.

[0027] Example 2 (comparison)

[0028] [Table 3]

Claims

1. A mercaptide microemulsion comprising an aqueous continuous phase and a dispersed phase of mercaptide having a droplet size of about 1 to about 100 nm.

2. 14. The mercaptide microemulsion of claim 13, wherein the droplet size is from about 10 to about 50 nm.

3. 2. The mercaptide microemulsion of claim 1, wherein the continuous phase is water.

4. 2. The mercaptide microemulsion of claim 1, wherein the mercaptide is selected from the group consisting of a mercaptide, a dimercaptide, a polymer captide, and any combination thereof.

5. 2. The mercaptide microemulsion of claim 1, wherein the mercaptide is selected from the group consisting of linear, branched, or cyclic primary C8 to C15 mercaptides, linear, branched, or cyclic secondary C8 to C15 mercaptides, linear, branched, or cyclic tertiary C8 to C15 mercaptides, and any combination thereof.

6. 10. The mercaptide microemulsion of claim 1, further comprising at least one item selected from the group consisting of surfactants, alcohols, hydrocarbons, dispersants, and any combination thereof.

7. 10. The mercaptide microemulsion of claim 1, wherein the microemulsion further comprises a surfactant with at least one co-surfactant.

8. 7. The mercaptide microemulsion of claim 6, wherein the surfactant is selected from the group of ethoxylated mercaptans, alkylphenol ethoxylates, alkylbenzene sulfonates, poloxamers, polysorbates, and any combination thereof.

9. 7. The mercaptide microemulsion of claim 6, wherein the alcohol is selected from the group of ethanol, propanol, butanol, pentanol, hexanol, heptanol, octanol, cresylic acid, and any isomers and combinations thereof.

10. 7. The mercaptide microemulsion of claim 6, wherein the hydrocarbon is selected from the group consisting of pentane, hexane, heptane, octane, decane, dodecane, propylene tetramer, kerosene, diesel fuel, biodiesel (methylated fatty acids), and any combination thereof.

11. 7. The mercaptide microemulsion of claim 6, wherein the dispersing agent is selected from the group consisting of polyethylene glycol, polypropylene glycol, polyglycol ether, polyol, and any combination thereof.

12. 10. The mercaptide microemulsion of claim 1 formed by contacting a mercaptan with a base in an aqueous carrier fluid, followed by optional mixing.

13. 13. The mercaptide microemulsion of claim 12, wherein the base is an alkali metal or alkaline earth metal base.

14. 14. The mercaptide microemulsion of claim 13, wherein the alkali metal or alkaline earth metal base is selected from the group consisting of sodium hydroxide, potassium hydroxide, rubidium hydroxide, magnesium hydroxide, calcium hydroxide, lithium hydroxide, barium hydroxide, magnesium hydroxide, and any combination thereof.

15. 13. The mercaptide microemulsion of claim 12, wherein the base is an organic base.

16. 16. The mercaptide microemulsion of claim 15, wherein the organometallic base is selected from the group consisting of ammonium hydroxide, tetramethylguanidine, guanidine or tetramethylammonium hydroxide, and any combination thereof.

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