Microemulsion of thiolate

Abstract

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

Description

Technical Field

[0001] The present invention relates to novel thiolate microemulsions. Background Art

[0002] The present invention generally relates to a novel composition comprising a thiolate microemulsion.

[0003] Heavy mercaptans have unique chemical properties that make them particularly suitable for applications such as mineral recovery, metal protection, surface modification, polymer functionalization, etc. However, heavy mercaptans also exhibit a strong odor and are immiscible with water, which limits their use in many applications. Summary of the invention

[0004] According to the present invention, it has been found that thiolate microemulsions can be used to replace mercaptans in many applications while minimizing the odor exhibited by the mercaptans. An object of the present invention is to reduce the perceived odor of heavy mercaptans (liquids) by converting the thiol groups into ionic thiolates. The resulting heavy mercaptans (solids) also have improved compatibility with water, allowing the preparation of water-based formulations with unique microstructures (microemulsions). The formation of the thiolate microemulsions can be carried out in one container by mixing components that may include thiolates, water, alcohol, surfactants and dispersants. These water-based thiolate microemulsions are new product forms for heavy mercaptans, wherein the perceived odor is lower and the activity of these molecules is enhanced due to the increased interfacial area typical of the microstructure. BRIEF DESCRIPTION OF THE DRAWINGS

[0005] Figure 1 Shown are a thiolate microemulsion according to one embodiment of the present invention (sample 5 on the left) and a prior art thiol emulsion (sample 8 on the right).

[0006] Specific embodiments of the present invention

[0007] "Microemulsion" refers to a dispersion comprising a continuous phase material having substantially uniformly dispersed droplets of dispersed phase material, the droplets ranging in size from about 1 to 100 nm, typically from 10 to 50 nm.

[0008] In at least one embodiment, a microemulsion is provided, which comprises a continuous phase material in which droplets of dispersed phase material are dispersed. The size of the droplets ranges from about 1 to about 100 nm, typically from about 10 to about 50 nm. Due to the extremely small droplet size, the microemulsion is optically transparent, isotropic, and thermodynamically stable. In at least one embodiment, the continuous phase material comprises water. In at least one embodiment, the dispersed phase material and / or the continuous phase material comprises one or more hydrophobic materials. In at least one embodiment, the dispersed phase material and / or the continuous phase material comprises an amphiphilic and / or ionic material.

[0009] Mercaptan [also known as thioalcohol (thiol)] can be in liquid form at standard ambient temperature and pressure, and it comprises a hydrocarbon chain consisting of eight to twelve carbon atoms. Such liquid mercaptans are immiscible with water. In addition, the volatility of these liquids is sufficient to cause concerns associated with toxic odors, which limits the use of these substances in many applications, particularly in applications carried out in open containers. In the present invention, liquid mercaptans are treated with (one or more) organic or inorganic strong bases to produce mercaptides (ionic salts of mercaptans). In one embodiment, mercaptides are produced as pure products, solid powders, and their compatibility with water is improved and there is no odor problem associated with mercaptan volatility. In another embodiment according to the present invention, the formation of mercaptides can be completed in the presence of other components (e.g., water, alcohol, hydrocarbons, surfactants and / or dispersants). Preparing mercaptides in this multi-component liquid system can produce formulations with unique microstructures. The preparation embodiment of the mercaptide microemulsion of the present invention can be a one-pot process.

[0010] The alcohol may be selected from the group consisting of ethanol, propanol, butanol, pentanol, hexanol, heptanol, octanol, cresol acid and any combination thereof, including isomers thereof.

[0011] The hydrocarbon may be selected from the group consisting of pentane, hexane, heptane, octane, nonane, decane, dodecane, propylene tetramer, kerosene, diesel, biodiesel (fatty acid methyl esters), and any combination thereof.

[0012] The surfactant may be selected from the group consisting of ethoxylated mercaptans, alkylphenol ethoxylates, alkylbenzene sulfonates, pluronics, polysorbates, and any combination thereof.

[0013] The dispersant may be selected from the group consisting of polyethylene glycol, polypropylene glycol, polyethylene glycol ethers and / or other polyols.

[0014] Although it is preferred to form the thiolate microemulsion by a one-pot process, the thiolates derived from thiols can also be in solid form after reacting only with a base. Solid thiolates can be used to prepare microemulsions by mixing them with liquid components. Thiolates can also be commercialized in solid form to be combined with liquid components to form the thiolate microemulsions of the present invention.

[0015] The study found that solids precipitate from the liquid microemulsion during a large number of operations. By performing different post-reaction treatments on repeated samples, it was found that the thiolates in the microemulsion can oxidize to disulfides in the presence of oxygen. Therefore, for stability, it is necessary to minimize or avoid the oxidation of thiolate ions to disulfides.

[0016] Heavy mercaptans are mercaptans (-SH) having a hydrocarbon chain of 4 to 18 carbon atoms, typically about 8 to 15 carbon atoms. The hydrocarbon chain may be linear, branched or cyclic. Mercaptide salts may be derived from mercaptans (molecules containing only one mercaptan group) or from dithiols or polythiols (each molecule containing two or more mercaptan groups). Mercaptans used to form mercaptides of the present invention may be primary, secondary or tertiary mercaptans having 8-15 carbon atoms. Exemplary dithiols and polythiols include 1,8-dithiol-3,6-dioxaoctane and pentaerythritol tetrakis (3-mercaptopropionate), respectively. When these molecules are at a pH of greater than or equal to about 11, a conjugate base mercaptide salt form is formed, converting the -SH group into an ionic SM. + , where M+ is an organic or inorganic cation from a strong base. For example, alkali metal or alkaline earth metal hydroxide bases (e.g., sodium hydroxide, potassium hydroxide, rubidium hydroxide, magnesium hydroxide, calcium hydroxide, lithium hydroxide, barium hydroxide, and magnesium hydroxide), or organic bases such as ammonium hydroxide, tetramethylguanidine (forming a guanidine cation), guanidine, or tetramethylammonium hydroxide, when contacted with a thiol, will form a conjugated thiolate.

[0017] Heavy mercaptides are free-flowing solids in pure form. According to one embodiment of the present invention, a one-pot process has been discovered in which mercaptides are not only produced but also used as a major component in a water-based microemulsion formulation. The microemulsion formulation may comprise mercaptides, water and optionally alcohols, hydrocarbons, glycols, polyethylene glycols, surfactants and / or excess mercaptans from mercaptide conversion and base.

[0018] The thiolate-based microemulsions of the present invention can be formed by mixing the components in a single container and then stirring (stir bar, overhead stirrer, vortex mixer, static mixer or high shear mixer) until a homogenous liquid composition is achieved. These formulations may be turbid initially, but will produce a clear microemulsion after settling for a few minutes. The components may be added to the container sequentially or all at once. Alternatively, although stirring is a known method for quickly obtaining a homogenous liquid formulation, the components of the present invention may also be added (in any order) to a container and allowed to react without stirring, thereby obtaining a thermodynamically stable microemulsion due to Brownian motion and entropy.

[0019] Certain thiolate powders have a moderate affinity for water by themselves and do not require additional components to produce a homogeneous liquid product. For example, the thiolate salt of N-dodecyl mercaptan can form a homogeneous mixture in water at concentrations up to about 2% by weight (from 0.00001 to 2% by weight). With the addition of the liquid component, the resulting microemulsion may contain up to 60% by weight of the thiolate salt. The preferred range is from about 0.01 to about 40% by weight of the thiolate salt. For multi-component microemulsions, the water content may range from about 20 to about 98.0% by weight (as a diluent for the pure thiolate powder), preferably from about 40 to about 98% by weight. About 2 to about 30% by weight of alcohol can be added. The preferred range of alcohol is about 5 to about 20% by weight. 0 to about 10% by weight of a surfactant can be added. 0 to about 20% by weight, more preferably 5 to 15% by weight of a dispersant can be added. The formation of the thiolate salt can be achieved by reacting the thiol with an equimolar amount of a base, but an excess of up to about 1 to about 5% by weight of the base can also be used.

[0020] The thiolate microemulsions of the present invention are useful in a variety of applications including collectors in ore flotation, formation of self-assembled monolayers (SAMs) for surface modification and protection of metals and lignocellulosic materials, antioxidants in polyolefin polymer processing and end-uses, formation of larger sulfide and / or polysulfide structures, and stabilization of nanoscale inorganic structures such as nanoparticles and quantum dots.

[0021] Example 1

[0022] Table 1 lists the composition for forming the thiolate microemulsion according to the present invention. The components 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 thiolate microemulsion is formed by mixing the specified components in any order at room temperature and under simple stirring. The same thiolate microemulsion can be produced by mixing the components with a high shear mixer.

[0023] Table 1

[0024]

[0025]

[0026] For the samples listed in Table 1, the conversion of thiols to thiolates was determined by pH measurement (thiolates are strong bases and the pH of the microemulsions containing thiolates was measured to be above 13), UV-visible spectroscopy (the absorption of typical thiolate anions was detected between 240 and 260 nm), and 1 H and 13The results were confirmed by C-NMR (different chemical shifts of thiolate and thiol molecules were detected).

[0027] The submicron structure of these samples was determined by measuring the droplet size by dynamic light scattering (DLC), indicating the formation of droplets smaller than 100 nm. The Z-average diameters of samples 1, 2 and 6 are shown in Table 2.

[0028] Table 2

[0029] Z average diameter (nm) Sample 1 24 Sample 2 13 Sample 6 25

[0030] The presence of thiolate instead of thiol in the final product and the formation of a quantifiable, finely divided, and well-dispersed microstructure demonstrated the one-pot production of thiolate microemulsions.

[0031] Table 3 lists the compositions for forming mercaptan oil-in-water emulsions obtained by high shear mixing with the components indicated. Sample 8 did not form a microemulsion. The droplet size of Sample 8 could not be measured using DLS because the bubbles were too large for the instrument. Observation of Sample 8 by optical microscopy showed that the average particle size of Sample 8 was about 20 microns, which is well above the microemulsion level. Observation of Sample 5 by optical microscopy showed visible droplets.

[0032] Example 2 Comparative Example

[0033] Table 3

[0034]

Claims

1. A thiolate microemulsion comprising an aqueous continuous phase and a thiolate dispersed phase, wherein the droplet size of the thiolate dispersed phase is from about 1 nm to about 100 nm.

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

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

4. The thiolate microemulsion of claim 1, wherein the thiolate is selected from the group consisting of thiolate, dithiolate, polythiolate, and any combination thereof.

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

6. The thiolate microemulsion of claim 1, further comprising at least one item selected from the group consisting of a surfactant, an alcohol, a hydrocarbon, a dispersant, and any combination thereof.

7. The thiolate microemulsion of claim 1, wherein the microemulsion further comprises a surfactant and at least one co-surfactant.

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

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

10. The mercaptan salt microemulsion of claim 6, wherein the hydrocarbon is selected from the group consisting of pentane, hexane, heptane, octane, nonane, decane, dodecane, propylene tetramer, kerosene, diesel, biodiesel (fatty acid methyl ester) and any combination thereof.

11. The thiolate microemulsion of claim 6, wherein the dispersant is selected from the group consisting of polyethylene glycol, polypropylene glycol, polyethylene glycol ether, polyol, and any combination thereof.

12. The thiolate microemulsion of claim 1 formed by contacting a thiol with a base in an aqueous carrier fluid, optionally followed by mixing.

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

14. The thiolate microemulsion of claim 13, wherein the alkali metal base 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 and magnesium hydroxide, and any combination thereof.

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

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

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