A BASE OIL ADDITIVE

Abstract

There is provided a base oil additive comprising an ester of a palmitic acid, a method of forming the base oil additive, a lubricating oil composition comprising the base oil additive and a method of modifying a property of a base oil.

Claims

1. A lubricating oil composition comprising: a. a base oil; and b. a base oil additive comprising an ester of a palmitic acid of the formula
R.sub.2(OOCC.sub.15H.sub.31).sub.m, wherein R.sub.2 is an alkyl, an alkenyl or an alkynyl; and m is 2, 3, 4, 5 or 6, and wherein said base oil additive is at a concentration of 1 wt % to 50.0 wt % based on the weight of the base oil.

2. The lubricating oil composition of claim 1, wherein said ester is a reaction product of said palmitic acid and an alcohol.

3. The lubricating oil composition of claim 2, wherein said alcohol is of the formula R.sub.2(OH)m, wherein R.sub.2 is an alkyl, an alkenyl or an alkynyl; and m is 2, 3, 4, 5 or 6.

4. The lubricating oil composition of claim 3, wherein m is 2 and said alcohol is selected from the group consisting of ethylene glycol, propane-1,2-diol, propane-1,3-diol, butanediol, cyclohexanediol, cyclohexanedimethanol, dianhydrohexitol, diethylene glycol, dihydroxyacetone, dipropylene glycol, ethambutol, ethylhexylglycerin, etohexadiol, 1,6-hexanediol, neopentyl glycol, octane-1,8-diol, 1,5-pentanediol, pinacol, propylene glycol, tartaric acid and triethylene glycol.

5. The lubricating oil composition of claim 3, wherein m is 3, 4, 5 or 6 and said alcohol is selected from the group consisting of trimethylolpropane, trimethylolethane, 1,2,4-butanetriol, glycerol, miglitol, natural oil polyols, pentaerythritol, triethanolamine, maltitol, sorbital, xylitol, erythritol, isomalt, volemitol, threitol, arabitol, ribitol, mannitol, galactitol, iditol, fucitol, inositol, lactitol, isomalt, phloroglucinol, dipentaerythritol, 1,1,1-tris(hydroxymethyl)ethane, 2-hydromethyl-1,3-propanediol, 2,2-bis(hydroxymethyl)propane-1,3-diol, fragmented cellulose, fragmented chitosan, and fragmented lignin.

6. The lubricating oil composition of claim 5, wherein said alcohol is 2,2-bis(hydroxymethyl)propane-1,3-diol and said palmitic acid ester is 2,2-Bis((palmitoyloxy)methyl)propane-1,3-diyl dipalmitate, having ##STR00006##

7. A method of forming a base oil additive comprising an ester of a palmitic acid of the formula
R.sub.2(OOCC.sub.15H.sub.31).sub.m, wherein R.sub.2 is an alkyl, an alkenyl or an alkynyl; and m is 2, 3, 4, 5 or 6, and wherein said base oil additive is at a concentration of 1 wt % to 50.0 wt % based on the weight of a base oil, comprising esterifying the palmitic acid in the presence of an acid catalyst selected from methanesulfonic acid and an alcohol to form an ester of said palmitic acid.

8. The method of claim 7, comprising the step of selecting the concentration of said acid catalyst from the range of 0.1 wt % to 10.0 wt %.

9. A method of modifying a property of lubricating oil composition comprising a base oil, said method comprising adding an ester of a palmitic acid as an additive to said base oil, wherein said ester of palmitic acid is of the formula
R.sub.2(OOCC.sub.15H.sub.31).sub.m, wherein R.sub.2 is an alkyl, an alkenyl or an alkynyl; and m is 2, 3, 4, 5 or 6, and wherein said base oil additive is at a concentration of 1 wt % to 50.0 wt % based on the weight of the base oil.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0054] The accompanying drawings illustrate a disclosed embodiment and serves to explain the principles of the disclosed embodiment. It is to be understood, however, that the drawings are designed for purposes of illustration only, and not as a definition of the limits of the invention.

[0055] FIG. 1 is a graph showing the viscosity change of polypropylene glycol after addition of different ratios of palmitic acid based thickeners.

[0056] FIG. 2 is a photograph showing a number of bottled samples based on base oil (polyethylene glycol) having different amounts of additives added therein at different temperatures. FIG. 2(a) from left to right shows base oil (PEG) with 0 wt %, 5 wt %, 10 wt % and 20 wt % of base oil additives on microscopic plate (at a temperature of around 20 C.). FIG. 2(b) from left to right shows base oil (PEG) with 0 wt %, 5 wt %, 10 wt % and 20 wt % of base oil additives at room temperature.

[0057] FIG. 3 is a graph showing the thermal gravity analysis of polypropylene glycol blended with different ratios of the palmitic acid based additives.

[0058] FIG. 4 is a graph showing the differential scanning calorimetry data of polypropylene glycol blended with different ratios of palmitic acid based thickeners.

[0059] FIG. 5 is a series of scanning electron microscopy images showing polypropylene glycol blended with different ratios of palmitic acid based thickeners, where (a) the top row is obtained at 10000 magnification and (b) the bottom row is obtained at 35000 magnification.

[0060] FIG. 6 is a series of photographs showing the thermo-reversibility test of the formed grease lubricants where (a) is the first cycle, (b) is at the tenth cycle, (c) is at the 20.sup.th cycle and (d) is at the 30.sup.th cycle. The four bottled samples at the left of each figure shows the state of the grease lubricants when in the cool state and the four bottled samples at the right of each figure shows the state of the grease lubricants when in the heat state (at 80 C.).

EXAMPLES

[0061] Non-limiting examples of the invention and a comparative example will be further described in greater detail by reference to specific Examples, which should not be construed as in any way limiting the scope of the invention.

Example 1

[0062] A palmitic acid ester was produced in this example from palmitic acid, 2,2-bis(hydroxymethyl)propane-1,3-diol in the presence of toluene and methanesulfonic acid (MSA). The reaction scheme is that depicted in Scheme 1 above and reproduced below.

##STR00005##

2,2-Bis((palmitoyloxy)methyl)propane-1,3-diyl dipalmitate

[0063] To a dry round bottom flask, palmitic acid (50 grams, 0.195 mol, 4 equiv.), 2,2-bis(hydroxymethyl)propane-1,3-diol (6.64 grams, 0.0475 mol, 1 equiv.), methane sulfonic acid (0.187 gram, 1%) and toluene (300 mL) were added. The round bottom flask was equipped with a Dean-Stark apparatus to remove the generated water during the reaction. The reaction flask was heated to 120 C. for 2 hours. After cooling to room temperature, the solution was extracted with sodium carbonate and the organic layer was dried by rotary evaporation. The obtained product was obtained as the neat desired product. (51 grams, 99% yield).

Example 2

[0064] The palmitic acid ester obtained from Example 1 was blended with base oil at varying concentrations. Base oil (10 grams) and palmitic acid ester (1 gram, varying weight percents) were added to a beaker. The mixture was heated to 100 C. with stirring. After the whole mixture became homogeneous and transparent, the mixture was cooled to room temperature. The mixture was then used directly for physical property measurement.

[0065] After addition of the palmitic acid based esters to commercial lubricant base oils, grease formation phenomenon and significant viscosity increase were observed, as can be seen in FIG. 1. As the prepared esters were simply blended with commercial engine oils with a low feed ratio (up to 1.5 wt. %), the viscosity of the generated mixture increased significantly and the final mixtures appeared greasy-like instead of oily (as observed in FIG. 2). This is a very interesting phenomenon and can be used for developing grease based formulation of lubricant. Other than commercial engine oil, a number of commercially available base oils, such as PEG, PPG, mineral oil, and synthetic esters have been tried and the ester additive can behave as a thickener and greater in a similar way. The additive behaves in a similar manner for most of the oils except for difference in the viscosity of the generated blends. For this example, PPG oil was used here.

Thermal Properties of Blend

[0066] The thermal properties of the blend were analysed using a thermal gravimetric analysis (TGA) analyzer and differential scanning calorimetric (DSC) analyzer. The typical operation procedure of the TGA analyzer and DSC analyzer applies for the measurement of this sample. After addition of different ratios of thickeners into the polypropylene glycol (PPG) base oil at 5 wt %, 10 wt % and 20 wt %, there was no significant variation of the degradation temperature, which was steady around 210 C. (see FIG. 3). Polypropylene base oil without any addition of the thickener was used as a control.

[0067] Differential scanning calorimetry data (see FIG. 4) showed that before addition of any thickeners, there was no phase transition of the PPG polymer up to 140 C. After addition of 5 wt % of the thickener, a clear transition at about 50 C. was clearly observed, which was mainly due to the melting of the additive. Upon further addition of the additive, the enthalpy of the melting peak became larger and larger. This indicates that the thickener is able to function up to 50 C. and can stabilize the grease at a temperature below this temperature.

Morphology Analysis

[0068] The detailed morphology of the PPG/thickener blend was investigated by scanning electron microscopy to further understand why addition of the thickener will make the whole system creamy. At 5 wt % addition, it was found that very clear formation of interconnecting network type morphology was generated after the thickener was added into the PPG base oils. The diameter of each thread was about 500 nm. After introducing more thickeners, there was no significant variation of the network morphology. The observed interconnecting network-type morphology explained why the added thickener behaved as a gelling agent. As the network was formed, the PPG molecules were trapped within the network and the randomness of the oil was therefore reduced. As a result, the mixture became more viscious and creamy and after addition of more than 1.5 wt % of the thickener, the whole mixture became a gel (data not shown for 1.5 wt %).

Thermo-Reversibility Analysis

[0069] The thermo-reversibility of the formed grease was also tested under heating-cooling cycles. As revealed by DSC measurements, after heating the grease sample to 80 C., a transparent solution was obtained for all three samples with different ratios of thickener (at 5 wt %, 10 wt % and 20 wt %). This indicated the melting of the thickener compounds in the PPG solution. After cooling to room temperature, the grease state was formed again, indicating the thermo-reversibility of the formed grease. After 30 heating-cooling cycles, there was no obvious morphological change of the grease compared with the initial state. This results indicated that the formed grease had very good thermo-reversibility. For all samples, PPG solution with no thickener added was used as control.

[0070] A summary of the thermal properties of the palmitic acid ester and base oil composite measured in this example is shown in Table 1 below.

TABLE-US-00001 TABLE 1 Summary of the thermal properties of the palmitic acid ester and base oil composite. DSC transition Composite (weight % of temperature additive) T.sub.g (@5% mass loss) ( C.) ( C.) 0% 191 5% 202 63.9, 47.6 10% 196 65.2, 52.1 20% 204 64.9, 71.1, 51.3

[0071] Hence, the palmitic acid ester can be used to modify the rheological properties and lead to grease formation when added to a base oil.

INDUSTRIAL APPLICABILITY

[0072] The palmitic acid ester can be used as an additive in natural and synthetic base oils. The palmitic acid ester can be blended with a variety of natural and synthetic base oils to prepare grease lubricant. The natural base oils can include mineral oils (light, heavy, paraffinic, naphthenic, aromatic, etc) and the synthetic base oils can include polyalphaolefins, synthetic esters, polyalkylene glycols, phosphate esters, alkylated naphthalenes, silicon oils, silicate esters, ionic fluids, etc. The grease lubricant can be used as potential water resistant grease formulation, food grade lubricant grease, railroad grease, sewing machine grease, gear lubrication, bearing lubrication and glassware joint lubrication.

[0073] The palmitic acid ester compounds can serve as an efficient grease formation agent to easily convert oil-type lubricant into grease and gel type lubricant. As the palmitic acid based esters are non-ionic, the use of the palmitic acid ester compound would widen the potential use of such lubricant in watery environment, such as underwater grease and marine grease.

[0074] The palmitic acid ester can be used as a viscosity modifier. Hence, the palmitic acid ester may be used for modifying the viscosity of a base oil as well as for forming grease.

[0075] As palmitic acid can be obtained from palm oil, the use of palmitic acid ester as a base oil additive is much cheaper and environmentally friendlier as compared to other base oil additives.

[0076] It will be apparent that various other modifications and adaptations of the invention will be apparent to the person skilled in the art after reading the foregoing disclosure without departing from the spirit and scope of the invention and it is intended that all such modifications and adaptations come within the scope of the appended claims.