Patent Application
20090036338
The invention relates generally to metalworking compositions exhibiting improved anti-mist properties, having a low foaming tendency and excellent air release properties.
Industrial metal cutting operations, such as the cutting of silicon wafers by the semiconductor industry, utilize machining or metalworking fluids to aid in or enhance the cutting process. Metalworking fluids can be used as cutting oils, rolling oils, drawing oils, pressing oils, forging oils, abrasive working oils for aluminium disks, abrasive oils for silicon wafers and coolants. In high-speed machining operations involving require rapid fluid application and recirculation, foam and air entrainment are sometimes experienced with undesirable results. Foaming is undesirable because it may reduce cooling at the workpiece-tool or chip-tool contact zones and cause containment transport and control problems. Various methods or strategies have been implemented to eliminate or reduce foaming, including the addition of foam control agent(s) when manufacturing the product or while the fluid is in-service. The use of certain foam control agent(s), such as such as silicon-based foam inhibitors, could leave a residue on machined parts and make subsequent painting of the parts difficult. Additionally, some foam control agent(s)may worsen a metalworking fluid's air release properties.
A fluid's air release properties can also be critical to its in-service performance, especially for high-speed operations. In some cases, using a fluid with poor air release properties can lead to air entrainment issues and cavitation of machine parts.
Besides foaming and air release, another common in-service problem associated with metalworking fluids is fog or mist generation. During the cutting process, small amounts of cutting oil tend to escape into the surrounding air as micro-sized droplets known as mist. Workers in the vicinity are exposed to the mist and, unless a protective breathing apparatus is worn, a portion of the mist may be drawn into the workers' lungs. Although metal cutting fluids in the prior art are essential for machining, they are currently being examined with increased scrutiny because of possible hazards associated with worker exposure.
Various additives have been tried in the prior art to reduce the formation of mist, including the use of minor amounts of at least one of polyisobutene, poly-n-butene and mixtures thereof, having a viscosity average molecular weight ranging from 0.3 to 10 million. Rhamsan gum, hydrophobic and hydrophilic monomers, styrene or hydrocarbyl-substituted styrene hydrophobic monomers and hydrophilic monomers are amongst other additives suggested for use to reduce the mist formation. Some metal cutting fluids in the prior art with the use of various additives pose environmental problems associated with their disposal. There is now universal agreement on the need for safer more environmentally friendly metalworking fluids.
Recent reforming processes have formed a new class of oil, e,g, Fischer Tropsch base oil (FTBO), wherein the oil, fraction, or feed originates from or is produced at some stage by a Fischer-Tropsch process. The feedstock for a Fischer-Tropsch process may come from a wide variety of hydrocarbonaceous resources, including biomass, natural gas, coal, shale oil, petroleum, municipal waste, derivatives of these, and combinations thereof. Crude product prepared from the Fischer-Tropsch process can be refined into products such as diesel oil, naphtha, wax, and other liquid petroleum or specialty products. In a number of patent publications and applications, i.e., US 2006/0289337, US2006/0201851, US2006/0016721, US2006/0016724, US2006/0076267, US2006/020185, US2006/013210, US2005/0241990, US2005/0077208, US2005/0139513, US2005/0139514, US2005/0133409, US2005/0133407, US2005/0261147, US2005/0261146, US2005/0261145, US2004/0159582, US7018525, US7083713, U.S. application Ser. Nos. 11/400570, 11/535165 and 11/613936, which are incorporated herein by reference, an isomerized base oil is produced from a process in which the feed is a waxy feed recovered from a Fischer-Tropsch synthesis. The process comprises a complete or partial hydroisomerization dewaxing step, using a dual-functional catalyst or a catalyst that can isomerize paraffins selectively. Hydroisomerization dewaxing is achieved by contacting the waxy feed with a hydroisomerization catalyst in an isomerization zone under hydroisomerizing conditions.
There is a need for an improved metalworking fluid with reduced mist and foam formation and excellent air release properties as compared to the compositions of the prior art. Additionally, there is a need for an environmentally friendly metalworking fluid.
In one embodiment, there is provided a metalworking fluid comprising a lubricant base oil having consecutive numbers of carbon atoms and less than 10 wt % naphthenic carbon by n-d-M; and 0.10 to 10 wt. %. of at least an additive selected from the group of a metalworking fluid additive package; metal deactivators; corrosion inhibitors; antimicrobial; anticorrosion; extreme pressure agents; antifriction; antirust agents; polymeric substances; anti inflammatory agents; bactericides; antiseptics; antioxidants; chelating agents such as edetic acid salts, and the like; pH regulators; antiwear agents; and mixtures thereof, and wherein the metalworking fluid has an air release by ASTM D 3427-03 of less than 0.6 minutes at 50° C., and a sequence II foam tendency by ASTM D 892-03 of less than 50 mL.
In another aspect, there is provided a method to improve the foam formation and air release properties of a metalworking fluid, the method comprising blending a composition comprising a lubricant base oil having consecutive numbers of carbon atoms and less than 10 wt % naphthenic carbon by n-d-M; and 0.10 to 10 wt. %. of at least an additive selected from the group of a metalworking fluid additive package; metal deactivators; corrosion inhibitors; antimicrobial; anticorrosion; extreme pressure agents; antifriction; antirust agents; polymeric substances; anti inflammatory agents; bactericides; antiseptics; antioxidants; chelating agents such as edetic acid salts, and the like; pH regulators; antiwear agents; and mixtures thereof.
The following terms will be used throughout the specification and will have the following meanings unless otherwise indicated.
As used herein, the term “metalworking fluid” may be used interchangeably with “metalworking composition,” “metal removal fluid,” “cutting fluid,” “machining fluid,” referring to a composition that can be used in industrial metal cutting, metal grinding operations or in the semiconductor industry wherein the shape of the final object, e.g., silicon wafer or machine part, is obtained by with or without the progressive removal of metal or silicon. Metalworking fluids amongst other functions, are used to cool and to lubricate.
“Fischer-Tropsch derived” means that the product, fraction, or feed originates from or is produced at some stage by a Fischer-Tropsch process. As used herein, “Fischer-Tropsch base oil” may be used interchangeably with “FT base oil,” “FTBO,” “GTL base oil” (GTL: gas-to-liquid), or “Fischer-Tropsch derived base oil.”
As used herein, “isomerized base oil” refers to a base oil made by isomerization of a waxy feed.
As used herein, a “waxy feed” comprises at least 40 wt % n-paraffins. In one embodiment, the waxy feed comprises greater than 50 wt % n-paraffins. In another embodiment, greater than 75 wt % n-paraffins. In one embodiment, the waxy feed also has very low levels of nitrogen and sulphur, e.g., less than 25 ppm total combined nitrogen and sulfur, or in other embodiments less than 20 ppm. Examples of waxy feeds include slack waxes, deoiled slack waxes, refined foots oils, waxy lubricant raffinates, n-paraffin waxes, NAO waxes, waxes produced in chemical plant processes, deoiled petroleum derived waxes, microcrystalline waxes, Fischer-Tropsch waxes, and mixtures thereof In one embodiment, the waxy feeds have a pour point of greater than 50° C. In another embodiment, greater than 60° C.
“Kinematic viscosity” is a measurement in mm2/s of the resistance to flow of a fluid under gravity, determined by ASTM D445-06.
“Viscosity index” (VI) is an empirical, unit-less number indicating the effect of temperature change on the kinematic viscosity of the oil. The higher the VI of an oil, the lower its tendency to change viscosity with temperature. Viscosity index is measured according to ASTM D 2270-04.
Cold-cranking simulator apparent viscosity (CCS VIS) is a measurement in millipascal seconds, mPa·s to measure the viscometric properties of lubricating base oils under low temperature and high shear. CCS VIS is determined by ASTM D 5293-04.
The boiling range distribution of base oil, by wt %, is determined by simulated distillation (SIMDIS) according to ASTM D 6352-04, “Boiling Range Distribution of Petroleum Distillates in Boiling Range from 174 to 700° C. by Gas Chromatography.”
“Noack volatility” is defined as the mass of oil, expressed in weight %, which is lost when the oil is heated at 250° C. with a constant flow of air drawn through it for 60 min., measured according to ASTM D5800-05, Procedure B.
Brookfield viscosity is used to determine the internal fluid-friction of a lubricant during cold temperature operation, which can be measured by ASTM D 2983-04.
“Pour point” is a measurement of the temperature at which a sample of base oil will begin to flow under certain carefully controlled conditions, which can be determined as described in ASTM D 5950-02.
“Auto ignition temperature” is the temperature at which a fluid will ignite spontaneously in contact with air, which can be determined according to ASTM 659-78.
“Ln” refers to natural logarithm with base “e.”
“Traction coefficient” is an indicator of intrinsic lubricant properties, expressed as the dimensionless ratio of the friction force F and the normal force N, where friction is the mechanical force which resists movement or hinders movement between sliding or rolling surfaces. Traction coefficient can be measured with an MTM Traction Measurement System from PCS Instruments, Ltd. , configured with a polished 19 mm diameter ball (SAE AISI 52100 steel) angled at 220 to a flat 46 mm diameter polished disk (SAE AISI 52100 steel). The steel ball and disk are independently measured at an average rolling speed of 3 meters per second, a slide to roll ratio of 40 percent, and a load of 20 Newtons. The roll ratio is defined as the difference in sliding speed between the ball and disk divided by the mean speed of the ball and disk, i.e. roll ratio=(Speed1−-Speed2)/((Speed1+Speed2)−/2).
As used herein, “consecutive numbers of carbon atoms” means that the base oil has a distribution of hydrocarbon molecules over a range of carbon numbers, with every number of carbon numbers in-between. For example, the base oil may have hydrocarbon molecules ranging from C22 to C36 or from C30 to C60 with every carbon number in-between. The hydrocarbon molecules of the base oil differ from each other by consecutive numbers of carbon atoms, as a consequence of the waxy feed also having consecutive numbers of carbon atoms. For example, in the Fischer-Tropsch hydrocarbon synthesis reaction, the source of carbon atoms is CO and the hydrocarbon molecules are built up one carbon atom at a time. Petroleum-derived waxy feeds have consecutive numbers of carbon atoms. In contrast to an oil based on poly-alpha-olefin (“PAO”), the molecules of an isomerized base oil have a more linear structure, comprising a relatively long backbone with short branches. The classic textbook description of a PAO is a star-shaped molecule, and in particular tridecane, which is illustrated as three decane molecules attached at a central point. While a star-shaped molecule is theoretical, nevertheless PAO molecules have fewer and longer branches that the hydrocarbon molecules that make up the isomerized base oil disclosed herein.
“Molecules with cycloparaffinic functionality” mean any molecule that is, or contains as one or more substituents, a monocyclic or a fused multicyclic saturated hydrocarbon group.
“Molecules with monocycloparaffinic functionality” mean any molecule that is a monocyclic saturated hydrocarbon group of three to seven ring carbons or any molecule that is substituted with a single monocyclic saturated hydrocarbon group of three to seven ring carbons.
“Molecules with multicycloparaffinic functionality” mean any molecule that is a fused multicyclic saturated hydrocarbon ring group of two or more fused rings, any molecule that is substituted with one or more fused multicyclic saturated hydrocarbon ring groups of two or more fused rings, or any molecule that is substituted with more than one monocyclic saturated hydrocarbon group of three to seven ring carbons.
Molecules with cycloparaffinic functionality, molecules with monocycloparaffinic functionality, and molecules with multicycloparaffinic functionality are reported as weight percent and are determined by a combination of Field Ionization Mass Spectroscopy (FIMS), HPLC-UV for aromatics, and Proton NMR for olefins, further fully described herein.
Oxidator BN measures the response of a lubricating oil in a simulated application. High values, or long times to adsorb one liter of oxygen, indicate good stability. Oxidator BN can be measured via a Dornte-type oxygen absorption apparatus (R. W. Dornte “Oxidation of White Oils,” Industrial and Engineering Chemistry, Vol. 28, page 26, 1936), under 1 atmosphere of pure oxygen at 340° F., time to absorb 1000 mL of O2 by 100 g. of oil is reported. In the Oxidator BN test, 0.8 mL of catalyst is used per 100 grams of oil. The catalyst is a mixture of soluble metal-naphthenates simulating the average metal analysis of used crankcase oil. The additive package is 80 millimoles of zinc bispolypropylenephenyldithiophosphate per 100 grams of oil.
Molecular characterizations can be performed by methods known in the art, including Field Ionization Mass Spectroscopy (FIMS) and n-d-M analysis (ASTM D 3238-95 (Re-approved 2005)). In FIMS, the base oil is characterized as alkanes and molecules with different numbers of unsaturations. The molecules with different numbers of unsaturations may be comprised of cycloparaffins, olefins, and aromatics. If aromatics are present in significant amount, they would be identified as 4-unsaturations. When olefins are present in significant amounts, they would be identified as 1-unsaturations. The total of the 1-unsaturations, 2-unsaturations, 3-unsaturations, 4-unsaturations, 5-unsaturations, and 6-unsaturations from the FIMS analysis, minus the wt % olefins by proton NMR, and minus the wt % aromatics by HPLC-UV is the total weight percent of molecules with cycloparaffinic functionality. If the aromatics content was not measured, it was assumed to be less than 0.1 wt % and not included in the calculation for total weight percent of molecules with cycloparaffinic functionality. The total weight percent of molecules with cycloparaffinic functionality is the sum of the weight percent of molecules with monocyclopraffinic functionality and the weight percent of molecules with multicycloparaffinic functionality.
Molecular weights are determined by ASTM D2503-92(Reapproved 2002). The method uses thermoelectric measurement of vapour pressure (VPO). In circumstances where there is insufficient sample volume, an alternative method of ASTM D2502-04 may be used; and where this has been used it is indicated.
Density is determined by ASTM D4052-96 (Reapproved 2002). The sample is introduced into an oscillating sample tube and the change in oscillating frequency caused by the change in the mass of the tube is used in conjunction with calibration data to determine the density of the sample.
Weight percent olefins can be determined by proton-NMR according to the steps specified herein. In most tests, the olefins are conventional olefins, i.e. a distributed mixture of those olefin types having hydrogens attached to the double bond carbons such as: alpha, vinylidene, cis, trans, and tri-substituted, with a detectable allylic to olefin integral ratio between 1 and 2.5. When this ratio exceeds 3, it indicates a higher percentage of tri or tetra substituted olefins being present, thus other assumptions known in the analytical art can be made to calculate the number of double bonds in the sample. The steps are as follows: A) Prepare a solution of 5-10% of the test hydrocarbon in deuterochloroform. B) Acquire a normal proton spectrum of at least 12 ppm spectral width and accurately reference the chemical shift (ppm) axis, with the instrument having sufficient gain range to acquire a signal without overloading the receiver/ADC, e.g., when a 30 degree pulse is applied, the instrument having a minimum signal digitization dynamic range of 65,000. In one embodiment, the instrument has a dynamic range of at least 260,000. C) Measure the integral intensities between: 6.0-4.5 ppm (olefin); 2.2-1.9 ppm (allylic); and 1.9-0.5 ppm (saturate). D) Using the molecular weight of the test substance determined by ASTM D 2503-92 (Reapproved 2002), calculate: 1. The average molecular formula of the saturated hydrocarbons; 2. The average molecular formula of the olefins; 3. The total integral intensity (=sum of all integral intensities); 4. The integral intensity per sample hydrogen (=total integral/number of hydrogens in formula); 5. The number of olefin hydrogens (=olefin integral/integral per hydrogen); 6. The number of double bonds (=olefin hydrogen times hydrogens in olefin formula/2); and 7. The wt % olefins by proton NMR=100 times the number of double bonds times the number of hydrogens in a typical olefin molecule divided by the number of hydrogens in a typical test substance molecule. In this test, the wt % olefins by proton NMR calculation procedure, D, works particularly well when the percent olefins result is low, less than 15 wt %.
Weight percent aromatics in one embodiment can be measured by HPLC-UV. In one embodiment, the test is conducted using a Hewlett Packard 1050 Series Quaternary Gradient High Performance Liquid Chromatography (HPLC) system, coupled with a HP 1050 Diode-Array UV-Vis detector interfaced to an HP Chem-station. Identification of the individual aromatic classes in the highly saturated base oil can be made on the basis of the UV spectral pattern and the elution time. The amino column used for this analysis differentiates aromatic molecules largely on the basis of their ring-number (or double-bond number). Thus, the single ring aromatic containing molecules elute first, followed by the polycyclic aromatics in order of increasing double bond number per molecule. For aromatics with similar double bond character, those with only alkyl substitution on the ring elute sooner than those with naphthenic substitution. Unequivocal identification of the various base oil aromatic hydrocarbons from their UV absorbance spectra can be accomplished recognizing that their peak electronic transitions are all red-shifted relative to the pure model compound analogs to a degree dependent on the amount of alkyl and naphthenic substitution on the ring system. Quantification of the eluting aromatic compounds can be made by integrating chromatograms made from wavelengths optimized for each general class of compounds over the appropriate retention time window for that aromatic. Retention time window limits for each aromatic class can be determined by manually evaluating the individual absorbance spectra of eluting compounds at different times and assigning them to the appropriate aromatic class based on their qualitative similarity to model compound absorption spectra.
HPLC-UV Calibration. In one embodiment, HPLC-UV can be used for identifying classes of aromatic compounds even at very low levels, e.g., multi-ring aromatics typically absorb 10 to 200 times more strongly than single-ring aromatics. Alkyl-substitution affects absorption by 20%. Integration limits for the co-eluting 1-ring and 2-ring aromatics at 272 nm can be made by the perpendicular drop method. Wavelength dependent response factors for each general aromatic class can be first determined by constructing Beer's Law plots from pure model compound mixtures based on the nearest spectral peak absorbances to the substituted aromatic analogs. Weight percent concentrations of aromatics can be calculated by assuming that the average molecular weight for each aromatic class was approximately equal to the average molecular weight for the whole base oil sample.
NMR analysis. In one embodiment, the weight percent of all molecules with at least one aromatic function in the purified mono-aromatic standard can be confirmed via long-duration carbon 13 NMR analysis. The NMR results can be translated from % aromatic carbon to % aromatic molecules (to be consistent with HPLC-UV and D 2007) knowing that 95-99% of the aromatics in highly saturated base oils are single-ring aromatics. In another test to accurately measure low levels of all molecules with at least one aromatic function by NMR, the standard D 5292-99 (Reapproved 2004) method can be modified to give a minimum carbon sensitivity of 500:1 (by ASTM standard practice E 386) with a 15-hour duration run on a 400-500 MHz NMR with a 10-12 mm Nalorac probe. Acorn PC integration software can be used to define the shape of the baseline and consistently integrate.
Extent of branching refers to the number of alkyl branches in hydrocarbons. Branching and branching position can be determined using carbon-13 (13C) NMR according to the following nine-step process: 1) Identify the CH branch centers and the CH3 branch termination points using the DEPT Pulse sequence (Doddrell, D. T.; D. T. Pegg; M. R. Bendall, Journal of Magnetic Resonance 1982, 48, 323ff.). 2) Verify the absence of carbons initiating multiple branches (quaternary carbons) using the APT pulse sequence (Patt, S. L.; J. N. Shoolery, Journal of Magnetic Resonance 1982, 46, 535ff.). 3) Assign the various branch carbon resonances to specific branch positions and lengths using tabulated and calculated values known in the art (Lindeman, L. P., Journal of Qualitative Analytical Chemistry 43, 1971 1245ff; Netzel, D. A., et. al., Fuel, 60, 1981, 307ff). 4) Estimate relative branching density at different carbon positions by comparing the integrated intensity of the specific carbon of the methyl/alkyl group to the intensity of a single carbon (which is equal to total integral/number of carbons per molecule in the mixture). For the 2-methyl branch, where both the terminal and the branch methyl occur at the same resonance position, the intensity is divided by two before estimating the branching density. If the 4-methyl branch fraction is calculated and tabulated, its contribution to the 4+methyls is subtracted to avoid double counting. 5) Calculate the average carbon number. The average carbon number is determined by dividing the molecular weight of the sample by 14 (the formula weight of CH2). 6) The number of branches per molecule is the sum of the branches found in step 4. 7) The number of alkyl branches per 100 carbon atoms is calculated from the number of branches per molecule (step 6) times 100/average carbon number. 8) Estimate Branching Index (BI) by 1H NMR Analysis, which is presented as percentage of methyl hydrogen (chemical shift range 0.6-1.05 ppm) among total hydrogen as estimated by NMR in the liquid hydrocarbon composition. 9) Estimate Branching proximity (BP) by 13C NMR, which is presented as percentage of recurring methylene carbons—which are four or more carbons away from the end group or a branch (represented by a NMR signal at 29.9 ppm) among total carbons as estimated by NMR in the liquid hydrocarbon composition. The measurements can be performed using any Fourier Transform NMR spectrometer, e.g., one having a magnet of 7.0 T or greater. After verification by Mass Spectrometry, UV or an NMR survey that aromatic carbons are absent, the spectral width for the 13C NMR studies can be limited to the saturated carbon region, 0-80 ppm vs. TMS (tetramethylsilane). Solutions of 25-50 wt. % in chloroform-d1 are excited by 30° pulses followed by a 1.3 seconds (sec.) acquisition time. In order to minimize non-uniform intensity data, the broadband proton inverse-gated decoupling is used during a 6 sec. delay prior to the excitation pulse and on during acquisition. Samples are doped with 0.03 to 0.05 M Cr (acac)3 (tris (acetylacetonato)-chromium (III)) as a relaxation agent to ensure full intensities are observed. The DEPT and APT sequences can be carried out according to literature descriptions with minor deviations described in the Varian or Bruker operating manuals. DEPT is Distortionless Enhancement by Polarization Transfer. The DEPT 45 sequence gives a signal all carbons bonded to protons. DEPT 90 shows CH carbons only. DEPT 135 shows CH and CH3 up and CH2180 degrees out of phase (down). APT is attached proton test, known in the art. It allows all carbons to be seen, but if CH and CH3 are up, then quaternaries and CH2 are down. The branching properties of the sample can be determined by 13C NMR using the assumption in the calculations that the entire sample was iso-paraffinic. The content of unsaturates may be measured using Field Ionization Mass Spectroscopy (FIMS).
In one embodiment, the metalworking fluid comprises a number of components, including optional additives, in a matrix of base oil.
Base Oil Matrix Component: In one embodiment, the base oil or blends thereof forming the matrix comprises at least an isomerized base oil which the product itself, its fraction, or feed originates from or is produced at some stage by isomerization of a waxy feed from a Fischer-Tropsch process (“Fischer-Tropsch derived base oils”). In another embodiment, the base oil comprises at least an isomerized base oil made from a substantially paraffinic wax feed (“waxy feed”). In a third embodiment, the base oil consists essentially of at least an isomerized base oil.
Fischer-Tropsch derived base oils are disclosed in a number of patent publications, including for example U.S. Pat. Nos. 6,080,301, 6,090,989, and 6,165,949, and US Patent Publication No. US2004/0079678A1, US20050133409, US20060289337. The Fischer-Tropsch process is a catalyzed chemical reaction in which carbon monoxide and hydrogen are converted into liquid hydrocarbons of various forms including a light reaction product and a waxy reaction product, with both being substantially paraffinic.
In one embodiment the isomerized base oil has consecutive numbers of carbon atoms and has less than 10 wt % naphthenic carbon by n-d-M. In yet another embodiment the isomerized base oil made from a waxy feed has a kinematic viscosity at 100° C. between 1.5 and 3.5 mm2/s.
In one embodiment, the isomerized base oil is made by a process in which the hydroisomerization dewaxing is performed at conditions sufficient for the base oil to have: a) a weight percent of all molecules with at least one aromatic functionality less than 0.30; b) a weight percent of all molecules with at least one cycloparaffinic functionality greater than 10; c) a ratio of weight percent molecules with monocycloparaffinic functionality to weight percent molecules with multicycloparaffinic functionality greater than 20 and d) a viscosity index greater than 28×Ln (Kinematic viscosity at 100° C.)+80.
In another embodiment, the isomerized base oil is made from a process in which the highly paraffinic wax is hydroisomerized using a shape selective intermediate pore size molecular sieve comprising a noble metal hydrogenation component, and under conditions of 600-750° F. (315-399° C.) In the process, the conditions for hydroisomerization are controlled such that the conversion of the compounds boiling above 700° F. (371° C.) in the wax feed to compounds boiling below 700° F. (371° C.) is maintained between 10 wt % and 50 wt %. A resulting isomerized base oil has a kinematic viscosity of between 1.0 and 3.5 mm2/s at 100° C. and aNoack volatility of less than 50 weight %. The base oil comprises greater than 3 weight % molecules with cycloparaffinic functionality and less than 0.30 weight percent aromatics.
In one embodiment the isomerized base oil has a Noack volatility less than an amount calculated by the following equation: 1000×(Kinematic Viscosity at 100° C.)−2.7. In another embodiment, the isomerized base oil has a Noack volatility less than an amount calculated by the following equation: 900×(Kinematic Vicosity at 100° C.)−2.8. In a third embodiment, the isomerized base oil has a Kinematic Vicosity at 100° C. of >1.808 mm2/s and a Noack volatility less than an amount calculated by the following equation: 1.286+20 (kv100)−1.5+551.8 e−kv100, where kv100 is the kinematic viscosity at 100° C. In a fourth embodiment, the isomerized base oil has a kinematic viscosity at 100° C. of less than 4.0 mm2/s, and a wt % Noack volatility between 0 and 100. In a fifth embodiment, the isomerized base oil has a kinematic viscosity between 1.5 and 4.0 mm2/s and a Noack volatility less than the Noack volatility calculated by the following equation: 160−40 (Kinematic Viscosity at 100° C.).
In one embodiment, the isomerized base oil has a kinematic viscosity at 100° C. in the range of 2.4 and 3.8 mm2/s and a Noack volatility less than an amount defined by the equation: 900×(Kinematic Viscosity at 100° C.)−2.8−15). For kinematic viscosities in the range of 2.4 and 3.8 mm2/s, the equation: 900×(Kinematic Viscosity at 100° C.)−2.8−15) provides a lower Noack volatility than the equation: 160−40 (Kinematic Viscosity at 100° C.)
In one embodiment, the isomerized base oil is made from a process in which the highly paraffinic wax is hydroisomerized under conditions for the base oil to have a kinematic viscosity at 100° C. of 3.6 to 4.2 mm2/s, a viscosity index of greater than 130, a wt % Noack volatility less than 12, a pour point of less than −9° C.
In one embodiment, the isomerized base oil has an auto-ignition temperature (AIT) greater than the AIT defined by the equation: AIT in ° C.=1.6×(Kinematic Viscosity at 40° C., in mm2/s)+300. In a second embodiment, the base oil as an AIT of greater than 329° C. and a viscosity index greater than 28×Ln (Kinematic Viscosity at 100° C., in mm2/s)+100.
In one embodiment, the isomerized base oil has a relatively low traction coefficient, specifically, its traction coefficient is less than an amount calculated by the equation: traction coefficient=0.009×Ln (kinematic viscosity in mm2/s)−0.001, wherein the kinematic viscosity in the equation is the kinematic viscosity during the traction coefficient measurement and is between 2 and 50 mm2/s. In one embodiment, the isomerized base oil has a traction coefficient of less than 0.023 (or less than 0.021) when measured at a kinematic viscosity of 15 mm2/s and at a slide to roll ratio of 40%. In another embodiment the isomerized base oil has a traction coefficient of less than 0.017 when measured at a kinematic viscosity of 15 mm2/s and at a slide to roll ratio of 40%. In another embodiment the isomerized base oil has a viscosity index greater than 150 and a traction coefficient less than 0.015 when measured at a kinematic viscosity of 15 mm2/s and at a slide to roll ratio of 40 percent.
In some embodiments, the isomerized base oil having low traction coefficients also displays a higher kinematic viscosity and higher boiling points. In one embodiment, the base oil has a traction coefficient less than 0.015, and a 50 wt % boiling point greater than 565° C. (1050° F.). In another embodiment, the base oil has a traction coefficient less than 0.011 and a 50 wt % boiling point by ASTM D 6352-04 greater than 582° C. (1080° F.).
In some embodiments, the isomerized base oil having low traction coefficients also displays unique branching properties by NMR, including a branching index less than or equal to 23.4, a branching proximity greater than or equal to 22.0, and a Free Carbon Index between 9 and 30. In one embodiment, the base oil has at least 4 wt % naphthenic carbon, in another embodiment, at least 5 wt % naphthenic carbon by n-d-M analysis by ASTM D 3238-95 (Reapproved 2005).
In one embodiment, the isomerized base oil is produced in a process wherein the intermediate oil isomerate comprises paraffinic hydrocarbon components, and in which the extent of branching is less than 7 alkyl branches per 100 carbons, and wherein the base oil comprises paraffinic hydrocarbon components in which the extent of branching is less than 8 alkyl branches per 100 carbons and less than 20 wt % of the alkyl branches are at the 2 position. In one embodiment, the FT base oil has a pour point of less than −8° C.; a kinematic viscosity at 100° C. of at least 3.2 mm2/s; and a viscosity index greater than a viscosity index calculated by the equation of=22×Ln (kinematic viscosity at 100° C.)+132.
In one embodiment, the base oil comprises greater than 10 wt. % and less than 70 wt. % total molecules with cycloparaffinic functionality, and a ratio of weight percent molecules with monocycloparaffinic functionality to weight percent molecules with multicycloparaffinic functionality greater than 15.
In one embodiment, the isomerized base oil has an average molecular weight between 600 and 1100, and an average degree of branching in the molecules between 6.5 and 10 alkyl branches per 100 carbon atoms. In another embodiment, the isomerized base oil has a kinematic viscosity between about 8 and about 25 mm2/s and an average degree of branching in the molecules between 6.5 and 10 alkyl branches per 100 carbon atoms.
In one embodiment, the isomerized base oil is obtained from a process in which the highly paraffinic wax is hydroisomerized at a hydrogen to feed ratio from 712.4 to 3562 liter H2/liter oil, for the base oil to have a total weight percent of molecules with cycloparaffinic functionality of greater than 10, and a ratio of weight percent molecules with monocycloparaffinic functionality to weight percent molecules with multicycloparaffinic functionality of greater than 15. In another embodiment, the base oil has a viscosity index greater than an amount defined by the equation: 28×Ln (Kinematic viscosity at 100° C.)+95. In a third embodiment, the base oil comprises a weight percent aromatics less than 0.30; a weight percent of molecules with cycloparaffinic functionality greater than 10; a ratio of weight percent of molecules with monocycloparaffinic functionality to weight percent of molecules with multicycloparaffinic functionality greater than 20; and a viscosity index greater than 28×Ln (Kinematic Viscosity at 100° C.)+110. In a fourth embodiment, the base oil further has a kinematic viscosity at 100° C. greater than 6 mm2/s. In a fifth embodiment, the base oil has a weight percent aromatics less than 0.05 and a viscosity index greater than 28×Ln (Kinematic Viscosity at 100° C.)+95. In a sixth embodiment, the base oil has a weight percent aromatics less than 0.30, a weight percent molecules with cycloparaffinic functionality greater than the kinematic viscosity at 100° C., in mm2/s, multiplied by three, and a ratio of molecules with monocycloparaffinic functionality to molecules with multicycloparaffinic functionality greater than 15.
In one embodiment, the isomerized base oil contains between 2 and 10% naphthenic carbon as measured by n-d-M. In one embodiment, the base oil has a kinematic viscosity of 1.5-3.0 mm2/s at 100° C. and 2-3% naphthenic carbon. In another embodiment, a kinematic viscosity of 1.8-3.5 mm2/s at 100° C. and 2.5-4% naphthenic carbon. In a third embodiment, a kinematic viscosity of 3-6 mm2/s at 100° C. and 2.7-5% naphthenic carbon. In a fourth embodiment, a kinematic viscosity of 10-30 mm2/s at 100° C. and greater than 5.2% naphthenic carbon.
In one embodiment, the isomerized base oil has an average molecular weight greater than 475; a viscosity index greater than 140, and a weight percent olefins less than 10. The base oil improves the air release and low foaming characteristics of the mixture when incorporated into the metalworking fluid.
In one embodiment, the isomerized base oil is a FT base oil having a kinematic viscosity at 100° C. between 2 mm2/s and 6 mm2/s; a kinematic viscosity at 40° C. between 7 mm2/s and 20 mm2/s; CCS viscosity of less than 2300 mPa·s at −35° C.; pour point in the range of −20 and −40° C.; molecular weight of 300-500; density in the range of 0.800 to 0.820; paraffinic carbon in the range of 93-97%; naphthenic carbon in the range of 3-7%; Oxidator BN of 30 to 60 hours; and Noack volatility in wt. % of 8 to 20 as measured by ASTM D5800-05 Procedure B.
In another embodiment for an anti-mist performance, the isomerized base oil is a FT base oil of “light” range viscosity having a kinematic viscosity at 100° C. between 2 mm2/s and 3 mm2/s; a kinematic viscosity at 40° C. between 7 mm2/s and 25 mm2/s; a viscosity index of 120-150; pour point in the range of −20 and −50° C.; molecular weight of 300-500; density in the range of 0.800 to 0.820; paraffinic carbon in the range of 92-97%; naphthenic carbon in the range of 3-7%; Oxidator BN of 30 to 60 hours; and Noack volatility in wt. % of 8 to 60 as measured by ASTM D5800-05 Procedure B. In another embodiment, the isomerized base oil is a FT base oil of “medium” range viscosity, having a kinematic viscosity at 100° C. between 5 mm2/s and 7 mm2/s; a kinematic viscosity at 40° C. between 25 mm2/s and 50 mm2/s; a viscosity index of 140-160; pour point in the range of −15 and −25° C.; molecular weight of 450-550; density in the range of 0.820 to 0.830; paraffinic carbon in the range of 90-95%. In a third embodiment, the base oil comprises a mixture of “light” and “medium” range viscosity FT base oils.
In one embodiment, the metalworking fluid employs at least one of the isomerized base oils described above. In another embodiment, the composition consists essentially of at least a Fischer-Tropsch base oil. In yet another embodiment, the metalworking fluid employs at least an isomerized based oil as the base oil matrix and optionally 5 to 95 wt. % of at least another type of oil, e.g., lubricant base oils selected from Group I, II, III, IV, V, and VI lubricant base oils as defined in the API Interchange Guidelines, and mixtures thereof. In a fourth embodiment, the metalworking fluid employs an isomerized based oil and 5 to 20 wt. % of at least another type of oil. Examples include conventionally used mineral oils, synthetic hydrocarbon oils or synthetic ester oils, or mixtures thereof depending on the application. Mineral lubricating oil base stocks can be any conventionally refined base stocks derived from paraffinic, naphthenic and mixed base crudes. Synthetic lubricating oils that can be used include esters of glycols and complex esters. Other synthetic oils that can be used include synthetic hydrocarbons such as polyalphaolefins; alkyl benzenes, e.g., alkylate bottoms from the alkylation of benzene with tetrapropylene, or the copolymers of ethylene and propylene; silicone oils, e.g., ethyl phenyl polysiloxanes, methyl polysiloxanes, etc., polyglycol oils, e.g., those obtained by condensing butyl alcohol with propylene oxide; etc. Other suitable synthetic oils include the polyphenyl ethers, e.g., those having from 3 to 7 ether linkages and 4 to 8 phenyl groups. Other suitable synthetic oils include polyisobutenes, and alkylated aromatics such as alkylated naphthalenes.
Additional Components: The metalworking fluid in one embodiment is characterized as having reduced mist formation, lower foaming tendency, and better air release properties compared to compositions of the prior art. Depending on the applications, e.g., straight oils (neat oils) or soluble oils, the metalworking fluid may contain applicable additives known in the art to improve the properties of the composition in amounts ranging from 0.10 to 40 wt. %. These additives include metal deactivators; corrosion inhibitors; antimicrobial; anticorrosion; emulsifying agents; couplers; extreme pressure agents; antifriction; antirust agents; polymeric substances; anti inflammatory agents; bactericides; antiseptics; antioxidants; chelating agents such as edetic acid salts, and the like; pH regulators; antiwear agents including active sulphur anti-wear additive packages and the like; a metalworking fluid additive package containing at least one of the aforementioned additives.
In different embodiments, there is no need to add any of the anti-mist additives (mist control agents or anti-misting agents) nor the foam inhibitors in the prior art, for a metalworking fluid that consists essentially of the base oil matrix comprising the isomerized base oil and at least an additive other than an anti-misting agent/foam inhibitor. However, in other embodiments and depending on the end-use applications, small quantities of additives such as anti-misting agents may be optionally added in an amount ranging from 0.05 to 5.0% by vol. in one embodiment and less than 1 wt. % in other embodiments. Non-limiting examples include rhamsan gum, hydrophobic and hydrophilic monomers, styrene or hydrocarbyl-substituted styrene hydrophobic monomers and hydrophilic monomers, oil soluble organic polymers ranging in molecular weight (viscosity average molecular weight) from about 0.3 to over 4 million such as isobutylene, styrene, alkyl methacrylate, ethylene, propylene, n-butylene vinyl acetate, etc. In one embodiment, polymethylmethacrylate or poly(ethylene, propylene, butylene or isobutylene) in the molecular weight range 1 to 3 million is used.
In some embodiments and for certain applications, a small amount of foam inhibitors in the prior art can also be added to the composition in an amount ranging from 0.05 to 15.0 wt. %. Non-limiting examples include polydimethylsiloxanes, often trimethylsilyl terminated, alkyl polymethacrylates, polymethylsiloxanes, an N-acylamino acid having a long chain acyl group and/or a salt thereof, an N-alkylamino acid having a long chain alkyl group and/or a salt thereof used concurrently with an alkylalkylene oxide and/or an acylalkylene oxide, acetylene diols and ethoxylated acetylene diols, silicones, hydrophobic materials (e.g. silica), fatty amides, fatty acids, fatty acid esters, and/or organic polymers, modified siloxanes, polyglycols, esterified or modified polyglycols, polyacrylates, fatty acids, fatty acid esters, fatty alcohols, fatty alcohol esters, oxo-alcohols, fluorosurfactants, waxes such as ethylenebistereamide wax, polyethylene wax, polypropylene wax, ethylenebisstereamide wax, and paraffinic wax, ureum. The foam control agents can be used with suitable dispersants and emulsifiers. Additional active foam control agents are described in “Foam Control Agents”, by Henry T. Kemer (Noyes Data Corporation, 1976), pages 125-162.
In various embodiments, the metalworking fluid further comprises anti-friction agents include overbased sulfonates, sulfurized olefins, chlorinated paraffins and olefins, sulfurized ester olefins, amine terminated polyglycols, and sodium dioctyl phosphate salts. In yet other embodiment, the composition further comprises corrosion inhibitors including carboxylic/boric acid diamine salts, carboxylic acid amine salts, alkanol amines, alkanol amine borates and the like.
In various embodiments, the metalworking fluid further comprise oil soluble metal deactivators in an amount of 0.01 to 0.5 vol % (based on the final oil volume). Non-limiting examples include triazoles or thiadiazoles, specifically aryl triazoles such as benzotriazole and tolyltriazole, alkyl derivatives of such triazoles, and benzothiadiazoles such as R(C6H3)N2S where R is H or C1 to C10 alkyl. Suitable materials are available from Ciba Geigy under the tradenames Irgamet and Reomet or from Vanderbilt Chemical Corporation under the Vanlube tradename.
In one embodiment, such as when the composition serves the dual purpose of cutting fluid and machine lube oil, a small amount of at least an antioxidant in the range 0.01 to 1.0 weight % can be added. Non-limiting examples include antioxidants of the aminic or phenolic type or mixtures thereof, e.g., butylated hydroxy toluene (BHT), bis-2,6-di-t-butylphenol derivatives, sulfur containing hindered phenols, and sulfur containing hindered bisphenol.
In some embodiments, the metalworking fluid further comprises 0.1 to 20 wt. % of at least an extreme-pressure agent. Non-limiting examples of extreme pressure agents include zinc dithiophosphate, molybdenum oxysulfide dithiophosphate, molybdenum oxysulfide thithiocarbamate, molybdenum amine compounds, sulfurized oils and fats, sulfurized fatty acids, sulfurized esters, sulfurized olefins, dihydrocarbyl polysulfides, thiocarbamates, thioterpenes, dialkyl thiodipropionates, and the like.
In addition to the above additives, various other conventional additives can be added to such extent that they do not inhibit the effects of the metalworking fluid. Examples include fatty acids and salts thereof, polyhydric alcohols such as propylene glycol, glycerin, butylene glycerol, and the like; surfactants such as anionic surfactants, amphoteric surfactants, nonionic surfactants, and the like; and boron nitride dispersed in a dispersant such as a surfactant.
Method for Making: The optional additives used in formulating the metalworking fluid composition can be blended into the base oil matrix individually or in various sub-combinations. In one embodiment, all of the components are blended concurrently using an additive concentrate (i.e., additives plus a diluent, such as a hydrocarbon solvent). The use of an additive concentrate takes advantage of the mutual compatibility afforded by the combination of ingredients when in the form of an additive concentrate.
In another embodiment, the metalworking fluid is prepared by mixing the base oil matrix with the optional additives and/or additive package(s) at an appropriate temperature, such as approximately 60° C., until homogeneous, for use as a straight oil cutting fluid. In yet another embodiment, the emulsifying agents may be added to the metalworking fluid to form an oil-in-water emulsion.
Properties: In one embodiment, the metalworking fluid composition is characterized as having reduced mist formation, low foaming tendency and excellent air release properties. The foaming tendency of the metalworking fluids can be measured using the ASTM D892-95 foam test. In one embodiment, the metalworking fluid when evaluated under ASTM D892-06 method shows a sequence II foam tendency foam height of less than 50 mL. In yet another embodiment, the metalworking fluid shows a sequence II foam height of less than 40 mL. In a third embodiment, a sequence II foam height of less than 30 mL. In a fifth embodiment, the sequence II foam height is less than 20 mL. In a six embodiment, none can be measured (0 mL).
In one embodiment, the metalworking fluid shows a sequence I foam tendency by ASTM D 892-03 of less than 100 mL. In another embodiment, the fluid has a sequence I foam tendency of less than 50 mL. In a third embodiment, a sequence I foam tendency of less than 30 mL.
In one embodiment, the metalworking fluid has a number of minutes to 3 mL emulsion at 54° C. by ASTM D 1401-02 of equal or less than 30. In yet another embodiment, the fluid has a number of minutes to 3 mL emulsion at 82° C. by ASTM D 1401-02 equal to or less than 60.
Air release properties can be measured using the ASTM D 3427 (2003) method for gas bubble separation time of petroleum oil to measure the ability of a fluid to separate entrained gas. In one embodiment, the metalworking fluid has an air release time at 50° C. of less than 0.60 minutes as measured according to ASTM D 3427 (2003). In a second embodiment, an air release time of less than ½ minutes.
In one embodiment, the metalworking fluid exhibits reduced mist formation property and imparts aerosol control or particulate control to the fluid, e.g., having 5 to 50% mist reduction compared to metalworking fluids comprising base oil Group I in the prior art. Mist reduction experiments can be measured according to similar to the aerosol (mist) formation test as described in “Polymer Additives as Mist Suppressants in Metal Cutting Fluids,” by Marano et al., Journal of the Society of Tribologists and Lubrication Engineers, October 1995, pp. 25-35. In one embodiment, the metalworking fluid without any addition of anti-mist additives has an average mist accumulation rate of less than 300 mg/mm3 in the first 30 seconds (after start) of the aerosol mist formation test. In another embodiment, the metalworking fluid without any mist additive has an average mist accumulation rate of less than 250 mg/mm3 in the first 30 seconds of the aerosol mist formation test. In a third embodiment, the average mist accumulation rate is less than 200 mg/mm3 in the first 30 seconds of the test. In a fourth embodiment, the average mist accumulation rate is less than 150 mg/mm3 in the first 60 seconds of the test.
In one embodiment, the metalworking fluid composition is readily biodegradable, with the base oil having an OECD 301D level ranging from 30 to 95%. In one embodiment, the metalworking fluid has a kinematic viscosity at 40° C. of 10-14 mm2/s and an OECD 301D biodegrability of >=60%. In a second embodiment, the composition has a kinematic viscosity at 40° C. of less than 10 mm2/s and an OECD 301D biodegrability of >=80%. In a third embodiment, the composition has a kinematic viscosity at 40° C. of less than 8 mm2/s and an OECD 301D biodegrability of >=90%. In a fifth embodiment, the metalworking fluid has a biodegradability of at least 30% as measured according to OECD 301D.
Metalworking fluids can be characterized as suitable or unsuitable for extreme pressure applications. A fluid that is considered as suitable for extreme pressure is one that prevents sliding metal surfaces from seizing under extreme pressure conditions. The seizing of metal surfaces result from friction between opposing asperities. Asperities are microscopic projections on metal surfaces resulting from metalworking operations. One technique for measuring extreme pressure properties of a fluid is to measure a load force between sliding surfaces which can be sustained by lubricant without seizing of the sliding surfaces. Such a technique is described as a Falex load test, which is an ASTM standard test for fluid lubricants (ASTM D-3233 (2003)). In one embodiment, the metalworking fluid is characterized has having a Falex reference wear of less than ten teeth. In another embodiment, the metalworking fluid is characterized as having a Falex reference load of greater than about 4,500 pounds force.
In one embodiment, the metalworking fluid is characterized as having excellent lubricating property, specifically lubricating surfaces in sliding contacts, as measured in a Four-Ball Wear Test per ASTM D4172-94(2004)e1. In one embodiment, the metalworking fluid has a Four-Ball wear scar diameter of less than about 0.07 mm.
In some applications and with the use of isomerized base oils having a low kinematic viscosity, the metalworking fluid is characterized has having a smooth liquid flow for excellent circulation in a pump. Moreover, the metalworking fluid has an excellent which can prevent frictional heat from being produced between a tool and a workpiece, so that the effective tool life can be increased.
Applications: In one embodiment, the metalworking fluid is used in the production of semiconductors, plant equipment, and auto parts, etc. wherein the shape of the final object, e.g., silicon wafer or machine part, is obtained by with or without the progressive removal of metal or silicon. Non-limiting examples of the operations include cutting, drilling, boring, honing, broaching, grinding, forming, stamping, casting, forging, rolling, piercing, coining, drawing, press forming, deburring, milling, grooving, tapping, chamfering, broaching, reaming, honing, lapping, straightening, and drawing.
In one embodiment of a metalworking operation, the metalworking fluid is applied to the contact zone between tool and workpiece. The fluid may be applied by a variety of methods, including immersing the contact zone in the fluid, spraying the fluid into the contact zone, flooding the contact zone with fluid, pumping a stream of fluid into the contact zone, periodically wetting the tool or the workpiece with lubricating fluid, or any means of constantly or intermittently applying the lubricant to the contact zone between the tool and the workpiece.
Unless specified otherwise, the compositions are prepared by mixing the components in the amounts indicated in the Examples/Tables. The components used in the Examples are listed below.
EP agent is a commercially available sulfurized polymerized ester, 10% inactive sulphur extreme-pressure agent.
HYNAP™ N100HTS hydrotreated, naphthenic oil (Group V) is from San Joaquin Refining Oil, Inc. of Bakersfield, Calif.
Ashland™ 100SN Group 1 oil is from Ashland Inc.
Chevron™ 100R group 2 oil, Chevron™ 100R group 3 oil, and Chevron Synfluid 4 cSt PAO oil are all from Chevron Corporation of San Ramon, Calif.
Additive 2 is a sulfurized vegetable fatty acid ester. Defoamer is an acrylate oligomer antifoam/defoamer. Additive CAS is a commercially available overbased calcium sulphonate PEP metalworking additive containing carbonated alkylbenzene sulfonate. Additive SO is a sulfurized olefin.
Mineral seal oil (MSO) having a visocisty of 3.39 mm2/sec at 40° C., and basestock oils SN 100 (density of 0.864 and viscosity of 20.6 mm2/sec at 40° C.), SN 150 and SN 600 (API Group 1) are commercially available from a number of sources.
GTL Fischer-Tropsch derived base oils GST0449, FTBO L, FTBO XL, FTBO XXL, and FTBO M are from Chevron Corp. Properties of the Fischer-Tropsch derived base oils used in the Examples are shown in Table 3.
Anti-mist agent 1 is a methacrylate copolymer. Anti-mist agent 2 is a commercially available high molecular weight oil soluble polymer tackifier.
A number of metalworking fluid compositions having components as listed in Table 1 were formulated and their properties were measured using various standard test methods: ASTM D1401-02 for Water Separability of Petroleum Oils and Synthetic Fluids; ASTM D 3427 (2003) Standard Test Method for Air Release Properties of Petroleum Oils; and ASTM D892-95 Foam Stability Sequence Test. As shown in the table, the example incorporating the isomerized base oil shows low foaming tendency (foam height of nil) and air release property that is comparable if not better than the prior art oil (in view of the test repeatability of 1 min.).
A number of metalworking fluid compositions having components as listed in Table 2 were formulated and their properties were measured/recorded. Examples 11-13 compare the compositions each with 0.25 wt. % of an anti-mist agent added (a high molecular weight oil soluble polymer tackifier).
The samples were subject to an aerosol (mist) formation experiment similar to the one described in “Polymer Additives as Mist Suppressants in Metal Cutting Fluids,” by Marano et al., Journal of the Society of Tribologists and Lubrication Engineers, October 1995, pp. 25-35. Basically in the test, metalworking fluid (in 100 mL sample) was supplied to a coaxial atomizer's tip through a tube (e.g., ID of 0.0011 m) by a syringe pump at constant flow rates up to 0.0084 litre/min. Compressed air was supplied through the annulus between the outer and inner tubes (ID 0.0021 m and OD 0.0013 m, respectively) at flow rates up to 35 litres/min. Mist generated by the atomizer was directed to a long wide plexiglass duct of square cross section or chamber (e.g., a 12″ by 12″ by 18″ chamber). The amount of mist generated as a function of time (as mg/mm3 over a duration of 5 minutes) was captured by a datalogger and recorded. In the experiments, a portable, real time aerosol monitor DataRAM® [MIE Instruments Inc., Bedford Mass.] was used as the datalogger to continuously quantify the mist levels generated. The DataRAM is a nephelometric monitor used to measure airborne particle concentration by sensing the amount of light scattered by the population of particles passing through a sampling volume.
For all of the samples, most of the mist was generated at the beginning of the test. After atomizing, the mist tended to drop to the bottom of the container and thereby showing a drop in the amount of mist collected.
Measurements from the aerosol (mist) formation experiments were plotted in
For the purposes of this specification and appended claims, unless otherwise indicated, all numbers expressing quantities, percentages or proportions, and other numerical values used in the specification and claims, are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the present invention. It is noted that, as used in this specification and the appended claims, the singular forms “a,” “an,” and “the,” include plural referents unless expressly and unequivocally limited to one referent. As used herein, the term “include” and its grammatical variants are intended to be non-limiting, such that recitation of items in a list is not to the exclusion of other like items that can be substituted or added to the listed items.
This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to make and use the invention. The patentable scope is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.
All citations referred herein are expressly incorporated herein by reference.
