BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a dispersant for motor oil. In particular, an epoxyamine alkoxylate that serves as an effective dispersant in polyalkylene glycol oil.

Introduction

Motor oils provide lubrication in a demanding environment that includes proximity to combustion reactions that produce tremendous heat and combustion byproducts such as soot. Soot detrimentally increases the viscosity of motor oil, thereby reducing engine fuel efficiency, while also increasing engine wear. Build-up of soot is especially problematic in diesel engines because their design tends to introduce greater oil contamination in return for reduced emissions.

Dispersant and detergents are included in fully formulated motor oils to control soot and other deposits. A detergent functions to neutralize the precursors that lead to oil degradation whereas dispersants suspend soot and similar contaminants. The suspension of these particles prevents an increase in engine oil viscosity, soot induced wear, and filter blockage.

Polyalkylene glycol (PAG) motor oils are an attractive alternative to hydrocarbon motor oil. PAG-based motor oils offer desirable advantages over hydrocarbon -based motor oils such as higher viscosity index, improved film formation, non-varnishing, improved heat transfer, excellent shear performance and stability. These inherent properties of PAGs allow them to be used as motor oils without need for added viscosity modifiers typical in many motor oils. Viscosity modifiers can break down during use and contribute to motor oil contaminates and diminished performance.

A challenge with PAG-based motor oils is identifying a suitable dispersant. Many dispersants suitable for use in hydrocarbon-based motor oils are not effective in PAG-based motor oils. PAGs are generally more polar than hydrocarbon based motor oil and, as a result, dispersants suitable for use in hydrocarbon based motor oils tend to not be soluble in PAG-based motor oil. Therefore, there is a need in the art to identify dispersants that are soluble in PAG-based motor oil, and that are effective soot dispersants especially in diesel motor oil applications.

BRIEF SUMMARY OF THE INVENTION

The present invention provides a solution to the need for a dispersant that is soluble in PAG-based motor oil, even under the demanding application of diesel motor oil applications.

Surprisingly, an epoxy amine alkoxylate has been found to be soluble in PAG-based motor oil and successfully disperses soot in the PAG-based motor oil even under stringent diesel motor testing. The epoxy amine alkoxylate has the structure of Structure I:

Structure I where A is a homopolymer of propylene oxide or a random copolymer of ethylene oxide (EO) and propylene oxide (PO) and where the concentration of EO moieties in A is from zero to 30 weight percent (wt ) based on total weight of EO and PO moieties. The desirable molecular weight of the epoxy amine alkoxylate is in a range of 5,000 grams per mole (g/mol) to 7,500 g/mol, most preferably 6,000 g/mol to 7,000 g/mol.

In a first aspect, the present invention is a composition comprising a base oil and a dispersant wherein the base oil comprises a polyalkylene glycol and the dispersant has the following structure:

where A is homopolymer of propylene oxide or a random copolymer of ethylene oxide and propylene oxide and where the concentration of ethylene oxide moieties in A is from zero to 30 weight percent based on total weight of ethylene oxide and propylene oxide moieties and wherein the dispersant has a molecular weight in a range of 5,000 grams per mole and 7,500 grams per mole.

In a second aspect, the present invention is process comprising the steps of providing the composition of the first aspect into a mechanical device where parts move with respect to one another such that the composition contacts at least a portion of the area between the parts that move with respect to one another.

The composition of the present invention is useful as motor oil. The process of the present invention is useful for employing the composition as a lubricant.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows an exemplary schematic for a two-step synthesis process for preparing a dispersant for use in the present invention.

Figures 2a and 2b illustrate shear stress sweep and time sweep curves for indicating formulation viscosities for formulations containing 5 wt dispersant and 5 wt carbon black.

Figures 3a and 3b illustrate shear stress sweep and time sweep curves for indicating formulation viscosities for formulations containing 5 wt dispersant and 5, 6, 7 and 8 wt loadings of carbon black.

Figures 4a and 4b illustrate shear stress sweep and time sweep for indicating formulation viscosities for formulations containing 6 wt dispersant and 5, 6, 7 and 8 wt loadings of carbon black. Figures 5a and 5b illustrate shear stress sweep and time sweep curves for indicating formulation viscosities for formulations containing 7 wt dispersant and 5, 6, 7 and 8 wt loadings of carbon black. DETAILED DESCRIPTION OF THE INVENTION

Test methods refer to the most recent test method as of the priority date of this document unless a date is indicated with the test method number. References to test methods contain both a reference to the testing society and the test method number. Test method organizations are referenced by one of the following abbreviations: ASTM refers to ASTM International (formerly known as American Society for Testing and Materials); EN refers to European Norm; DIN refers to Deutsches Institute fiir Normung; and ISO refers to International Organization for Standards.

"And/or" means "and, or as an alternative". "Multiple" and "plurality" mean two or more. All ranges include endpoints unless otherwise indicated.

"Polymer" refers generally to both homopolymers and copolymers (that is, heteropolymers) without limitation unless otherwise indicated. "Copolymer" refers to a molecule containing multiple polymerized units of more than one monomeric species.

The composition of the present invention comprises a base oil that comprises a polyalkylene glycol (PAG). The base oil desirably is composed primarily of (that is, contains more than 50 weight-percent based on total base oil weight) and can consist of one or a combination of more than one PAG.

Suitable PAGs normally have a viscosity at 40 degrees Celsius (°C) that is within a range of from 18 centiStokes, preferably 20 centiStokes (cSt)( 20 square millimeters per second (mm ² /s)), to 10,000 cSt (10,000 mm ² /s) and a viscosity at 100°C that is within a range of from 3 to 2,000 cSt (3 to 2,000 mm ² /s).

Suitable PAGs include reaction products of a 1,2-oxide (vicinal epoxide) with one or more material selected from a group consisting of water, an alcohol, or an aliphatic polyhydric alcohol containing from 2 hydroxyl groups to 6 hydroxyl groups and two or more, preferably three or more, more preferably four or more while at the same time 22 or fewer, preferably 16 or fewer and more preferably 12 or fewer carbon atoms per molecule. Suitable 1,2-oxides (alkylene oxides) include lower alkylene oxides (that is, alkylene oxides containing from two to eight carbon atoms). Examples of suitable 1,2-oxides includes ethylene oxide, propylene oxide, butylene oxide, cyclohexene oxide and glycidol as well as any combination of more than one of these 1,2-oxides. The PAG can be formed by known techniques in which an aliphatic polyhydric alcohol or water or monohydric alcohol (often called an "initiator") is reacted with a single 1,2-oxide or a mixture of two or more 1,2- oxide. If desired, the initiator can be first oxyalkylated with one type of 1,2-oxide followed by oxyalkylation with a different 1,2-oxide or a mixture of 1,2-oxides. The oxyalkylated initiator can be further oxyalkylated with a still different 1,2-oxide.

For convenience, "mixture", when applied to a PAG containing a mixture of 1,2- oxides, includes both random and/or block polyethers such as those prepared by: (1) random addition obtained by simultaneously reacting two or more 1,2-oxides with the initiator; (2) block addition in which the initiator reacts first with one 1,2-oxide and then with a second 1,2-oxide, and (3) block addition in which the initiator first reacts with a first 1,2-oxide followed by random addition wherein the initiator reacts with a combination of the first 1,2- oxide and a second 1,2-oxide.

Any suitable ratio of different 1,2-oxides may be employed. When a mixture of ethylene oxide (EO) and propylene oxide (PO) is utilized to form polyethers by random and/or block addition, the proportion of EO is generally three weight percent (wt%) or more, preferably 5 wt or more and at the same time typically 60 wt or less, preferably 50 wt or less based on total mixture weight.

Aliphatic polyhydric alcohol reactants used in making the PAG include those containing from two hydroxyl (OH) groups to six OH groups and at the same time two or more, preferably three or more, more preferably four or more while at the same time 22 or fewer, preferably 16 or fewer and more preferably 12 or fewer carbon atoms carbon atoms per molecule. Examples of suitable aliphatic alcohol reactants include ethylene glycol, propylene glycol, 2,3-butylene glycol, 1,2-butylene glycol, 1,2-butanediol, 1,3-propanediol, 1,5-pentane diol, 1,6-hexene diol, glycerol, trimethylolpropanes, sorbitol, pentaerythritol, and mixtures thereof. Cyclic aliphatic polyhydric compounds such as starch, glucose, sucrose, and methyl glucoside may also be employed in PAG preparation. Each of the aforesaid polyhydric compounds and alcohols can be oxyalkylated with EO, PO, butylene oxide (BO), cyclohexene oxide, glycidol, or mixtures thereof. For example, glycerol can be first oxyalkylated with PO and the resulting PAG oxyalkylated with EO. Alternatively, glycerol can be reacted with EO and the resulting PAG reacted with PO and EO. Each of the above-mentioned polyhydric compounds can be reacted with mixtures of EO and PO or any two or more of the aforesaid 1,2-oxides, in the same manner. Techniques for preparing suitable polyethers from mixed 1,2-oxides are shown in U.S. Patents 2,674,619; 2,733,272; 2,831,034; 2,948,575; and 3.036,118.

Monohydric alcohols typically used as initiators include the lower acyclic alcohols such as methanol, propylene glycol methyl ether (for example DOWANOL™ PM,

DOWANOL is a trademark of The Dow Chemical Company), ethanol, propanol, butanol, pentanol, hexanol, neopentanol, isobutanol, and decanol as well as higher acyclic alcohols derived from both natural and petrochemical sources with 11 carbon atoms to 22 carbon atoms. As noted previously, water can also be used an initiator.

Preferably, the PAG for use in the present invention is selected from PAGs produced by the polymerization of PO or both EO and PO onto an initiator. One desirable PAG is an alcohol initiated water-insoluble PO polymer.

The base oil can contain up to less than 50 wt based on total base oil weight of other lubricating oils such as vegetable oil, mineral oil, synthetic lubricants such as polyolesters, alkylaromatics, polyethers, hydrogenated or non-hydrogenated poly-alpha- olefins and similar substances of lubricating viscosity. The base oil can also be free of any other lubricating oils.

PAGs are desirably selected from those having the following formula:

R-[X-(CH ₂ CH ₂ 0) _n (C _y H _2y O) _p -Z] where R is hydrogen or an alkyl or an alkyl-phenyl group having from one carbon atom to 30 carbon atoms; X is oxygen, sulfur, or nitrogen; y is a single or combined integer from three to 30; Z is hydrogen or a hydrocarbyl or hydrocarboxyl group containing from one carbon atom to 30 carbon atoms; n+p is from six to 60 and the distribution of n and p can be random or in any specific sequence; m is one to 8; and polyether molecular weight is from 350 Daltons to 3,500 Daltons.

A variety of suitable PAG products are currently available commercially, including but not limited to those products sold under the following brand names: PLURIOL™ A750E; PLURACOL™ WS55; WS100, WS170, B 11/25, B 11/50, B32/50; BREOX™ A299; BREOX™ 50A; PPG-33-series; UCON™ 50-HB series; SYNALOX™ 50-xxB series; SYNALOX™ 100-xxB series; D21/150; PLURONIC™ 450PR, PLURONIC™ 600PR; TERRALOX WA46; TERRALOX WA110; SYNALOX™ 40-D150; polygycol BO 1/20, BO 1/40, B01/50, B15, B35; UCON™ LB65, LB125, LB285, WI285, W1625, P41/200; PLURONIX GENAPOL™; WAKO T01/15, T01/35, T01/60; LUPRANOL™ 9209 and 330; AND SELEXOL™.

PLURIOL is a trademark of BASF SE Societas Europae. PLURACOL and

PLURONIC are a trademarks of BASF Corporation. BREOX is a trademark of BP p.l.c. UCON and SELEXOL are trademarks of Union Carbide Corporation. SYNALOX is a trademark of The Dow Chemical Company. GENAPOL is a trademark of Clariant Produkte GMBH. LUPRANOL is a trademark of BASF Aktiengesellschaft Corporation.

The composition further comprises a dispersant that has the following structure:

where A is propylene oxide or a random copolymer of ethylene oxide and propylene oxide and where the concentration of ethylene oxide moieties in A is from zero to 30 weight percent based on total weight of ethylene oxide and propylene oxide moieties and wherein the dispersant has a molecular weight in a range of 5,000 grams per mole and 7,500 grams per mole.

The dispersant is obtainable from a two-step synthesis process where an initial epoxy resin reacts with di-butyl- amine (DBA) in a first step and then the resulting product is alkoxylated in a second step, as shown schematically in Figure 1. Each step can comprise any number of sub-steps. For example, the alkoxylation step can comprise any number of feed steps and digestion steps. The final product shown in Figure 1 corresponds to Structure 1 where A of Structure 1 is indicated by the following structure:

where each occurrence of n is either a PO moiety or an EO moiety as is indicated by the option of a pendant methyl or hydrogen group.

The initial epoxy resin is a liquid reaction product of epichlorohydrin and bisphenol A such as that which is commercially available as DER™-331 Liquid Epoxy Resin (DER is a trademark of The Dow Chemical Company). The epoxy resin reacts with two mole equivalents of DBA, with the DBA fed over 1.5 hours at 140°C and then allowed to digest at 140°C for three hours.

The second reaction step is the alkoxylation of the reaction product of the first reaction step (intermediate product). Alkoxylation can be accomplished via multiple epoxide feeds. Alkoxylation includes reacting with PO or EO and PO to create an alkoxy chain from the pendant hydroxyl (OH) groups of the intermediate product. The alkoxy chain is either PO oxide or a random copolymer of EO and PO. Conduct the alkoxylation by adding a base catalyst (for example, potassium hydroxide) and removing water by means of a vacuum. Slowly add alkylene oxide to the reactor as 125°C. Once all of the alkylene oxide has been added, keep the reactor at 125°C for five hours to allow the alkylene oxide to react. Remove the catalyst remains by absorption on a filter agent and filtration.

The alkoxylation step in preparing the dispersant is sufficient to achieve a concentration of EO moieties that is from zero to 30 weight percent based on the total weight of EO and PO moieties. EO moieties correspond to the copolymerized components of ethylene oxide in the resulting polymer. Similarly, PO moieties correspond to the copolymerized components of propylene oxide in the resulting polymer. Desirably, the concentration of EO moieties is greater than zero, preferably three wt or more, more preferably five wt or more, and can be ten wt or more, 15 wt or more, 20 wt or more and even 25 wt or more but is 30 wt or less based on total weight of EO and PO moieties. If the concentration of EO exceeds 30 wt the material does not perform as a desirable soot dispersant.

The alkoxylation step in preparing the dispersant is further sufficient to achieve a dispersant molecule having a molecular weight that is in a range of 5,000 to 7,500 grams per mole. Desirably, the molecular weight of the dispersant is 5,500 g/mol or more, preferably 6,000 g/mol or more, still more preferably 6,500 g/mol or more and can be 7,000 g/mol or more while at the same time is 7,500 g/mol or less, preferably 7,000 g/mol or less.

Determine molecular weight of the dispersant by gel permeation chromatography (GPC).

Preferably, the dispersant is of the structure of Structure I where A is a random copolymer of EO and PO with a PO moiety concentration that is 90 wt or more, preferably 93 wt or more, still more preferably 95 wt or more and less than 100 wt based on total combined weight of EO and PO moieties and where the dispersant has a molecular weight of 6,000 g/mol or more, preferably 6,500 g/mol or more and at the same time 7,000 g/mol or less.

The concentration of dispersant in the base oil is desirably one wt or more, preferably three wt or more, still more preferably four wt or more, even more preferably five wt or more and can be six wt or more, seven wt or more, eight wt or more , nine wt or more, ten wt or more and even 11 wt or more while at the same time is desirably 12 wt or less, preferably 11 wt or less and can be ten wt or less, nine wt or less, eight wt or less and even seven wt or less. At concentrations below one wt the dispersant is generally too dilute to effectively disperse soot particulates at a high enough concentration to be valuable in a motor oil. At concentrations above 12 wt the dispersant can cause an increase in the composition viscosity and that requires base oil modifications to compensate.

The dispersant of the present invention surprisingly has the necessary properties to act as a soot dispersant in PAG-based oils. The dispersant is soluble in PAGs. The dispersant demonstrates an ability to disperse soot in PAGs, even under motor oil use temperatures. The dispersant is thermally stable in motor oil applications. By

concomitantly possessing all of these characteristics, the dispersant proves to be a surprisingly effective dispersant in PAG-based motor oil.

The composition of the present invention can further comprise other additives in addition to the dispersant and base oil. Examples of suitable additives include extreme pressure (EP) and anti-wear (AW) additives. Suitable additives include zinc

dialkyldithiophosphates, arylphosphate esters, molybdenumdithiocarbamate, aminic antioxidants, phenolic antioxidants, corrosion inhibitors, aminic phosphate esters, anti- foaming agents, silicon oil, and total base number (TBN) boosters. The process of the present invention provides a method for lubricating a mechanical device with the composition of the present invention. The process of the present invention comprises providing the composition of the present invention into a mechanic device where parts move with respect to one another such that the composition contacts at least a portion of the area between the parts that move with respect to one another. A particularly desirable mechanical device for this process is an engine where the parts that move with respect to one another are a piston and piston shaft of the engine. One particularly demanding application for which the process of the present invention is suitable is where the mechanical device is a diesel engine. Diesel engines produce more soot in the motor oil lubricant than most engines so the dispersant serves a particularly demanding role in diesel engine motor oil compositions. Yet, the composition of the present invention has proven to be successful in dispersing soot in diesel engine applications.

Examples

The following examples serve to illustrate aspects of the present invention including characteristics of the dispersant in PAG motor oil compositions.

Dispersant

The following examples use a dispersant having the structure of Structure I and are further characterized by "A" being a random copolymer of EO and PO where the EO moiety concentration is five weight percent of the combined weight of EO and PO moieties and the average molecular weight of the dispersant is between 6,000 and 7,000 g/mol. Prepare the dispersant using the two-step synthesis as described previously herein.

Base Oil

The base oils used are selected from those in Table 1.

Table 1

SPECTRASYN and SYNESSTIC are trademarks of Exxon Mobil Corporation.

YUBASE is a trademark of SK Lubricants Co. Dispersant Solubility in Base Oils

The solubility of the dispersant in the base oils was characterized at concentrations up to 6 wt based on composition weight at 5°C and at 80°C. Characterize the solubility using Phase Identification and Characterization Apparatus (PICA) Π in combination with Epoch software PICA II VI 0.0.5 -current version as of priority date of this document. To conduct the characterization, prepare compositions in one milliliter glass vials and place in a 96 well aluminum plate in an enclosed test space with a robotic gripper arm. An image of each vial is collected with both standard white light and plane polarized light using a Canon Rebel XTi camera. Determine the clarity of each formulation as a dimensionless measurement in a grayscale intensity of the pixels from 1-255. A formulation that is cloudy possesses a clarity measurement of 20 or greater. Cloudy formulations indicate lack of solubility. Therefore, clarity measurement values below 20 correspond to formulations of soluble components.

Tables 2 and 3 reveal clarity measurements for formulations of the dispersant with the various base oils at different concentrations. Table 2 is an evaluation at 5°C and Table 3 is an evaluation at 80°C. The results reveal that the dispersant is soluble in the full variety of base oils at both temperatures.

Table 2

Table 3

Solubility was further characterized using a formulation that includes common oil additives to confirm solubility in the presence of the additives. Table 4 contains the additive package used in the screening with concentration in wt% relative to total formulation weight. Tables 5 and 6 present the clarity values for the additive-containing formulations with the dispersant at different concentrations. Table 5 is at 5°C and Table 6 is at 80°C. Notably, results are only shown for the oils that the additive package itself was soluble in.

The data reveals that the dispersant is soluble in formulations where the additive package is soluble in the oil.

Table 4

IRGANOX is a trademark of CIBA Specialty Chemicals Corporation.

DESMOPHEN s a trademark of Bayer Aktiengesellschaft Corporation. Table 5

Table 6

Dispersing Efficiency

Dispersing efficiency of the dispersant in a base oil was characterized using carbon black in an oil formulation containing a full set of additives. Carbon black was used to simulate soot. The ability to disperse carbon black, which represents soot, was

characterized by measuring the viscosity of the formulations over time and at different shear stresses. Better dispersibility is represented by a more uniform viscosity over time and at various shear stresses.

Testing was done using 5 wt%, 6 wt%, 7 wt% and 8 wt% carbon black based on formulation weight. Formulations containing dispersant loadings of 5 wt% , 6 wt% and 7 wt% were tested. The general test formulation is shown in Table 7 with concentration in wt% relative to total formulation weight. Base oil is a mixture of UCON™ LB- 165 and UCON LB-285 in a 72.5/27.5 weight ratio. UCON is a trademark of Union Carbide Corporation

UCON LB- 165 is a PAG characterized as an alcohol-initiated base stock of oxypropylene groups with one terminal hydroxyl group. It is water insoluble and has an average molecular weight of 740 g/mole and a viscosity of 34 cSt at 40°C. UCON LB-285 is a PAG characterized as an alcohol-initiated base stock of oxypropylene groups with one terminal hydroxyl group. It is water insoluble and has an average molecular weight of 1020 g/mole and a viscosity of 61 cSt at 40°C.

Table 7

IRGAMET and IRGALUBE are trademarks of BASF SE Company.

Figures 2a and 2b illustrate shear stress sweep and time sweep curves for indicating formulation viscosities for formulations containing 5 wt dispersant and 5 wt carbon black. The "aged" sample was heat aged at 150°C for 100 hours to simulate aged motor oil. The figures reveal that a 5 wt loading of the dispersant effectively disperses a 5 wt loading of carbon black in the PAG formulation, even upon heat aging.

Figures 3a and 3b illustrate shear stress sweep and time sweep curves for indicating formulation viscosities for formulations containing 5 wt dispersant and 5, 6, 7 and 8 wt loadings of carbon black. The data reveals that 5 wt loading of the dispersant effectively dispersed up to 6 wt carbon black equally well but less well for 7 and 8 wt carbon black loadings.

Figures 4a and 4b illustrate shear stress sweep and time sweep for indicating formulation viscosities for formulations containing 6 wt dispersant and 5, 6, 7 and 8 wt loadings of carbon black. The data in these figures reveals that increasing dispersant concentration to 6 wt improves dispersability of the carbon black over 5 wt loading of dispersant.

Figures 5a and 5b illustrate shear stress sweep and time sweep curves for indicating formulation viscosities for formulations containing 7 wt dispersant and 5, 6, 7 and 8 wt loadings of carbon black. The data in these figures reveals that increasing dispersant concentration to 7 wt improves dispersability of the carbon black over 6 wt loading of dispersant. Peugeot DV-4 Engine Test

The Peugeot DV-4 Engine Test (ACEA European Oil Sequences, Dec. 2010, 2.6 Medium temperature dispersivity test CEC L-093-04 (DV4TD)) evaluates the ability of an engine lubricant to disperse the combustion soot accrued during severe diesel engine operation. The test consists of 240 thirty-minute cycles operated at 4000 revolutions per minute and 11.8 kilograms per hour of fuel flow and includes brief periods of operation at idle. The test is conducted at 120°C. Oil performance is evaluated by determining the viscosity increase of the oil at 100°C relative to the viscosity of fresh oil. Oil performance is evaluated once the oil achieves at least 6 wt soot as determined by thermogravimetric analysis (TGA). Piston merit is also assessed. The test is included in the ACEA European Oil Sequences for the A, B and C categories for both viscosity increase and piston merit. The Peugeot DV-4 Engine Test was performed by ISP, Grand-Couronne, France.

Table 8 indicates the formulation tested in the Peugeot DV-4 Engine Test. The base oil is the same as used in the carbon black dispersion evaluation as described above.

Table 8

Figure 6 reveals that the test results showing viscosity of the formulation as a function of soot concentration. A maximum viscosity of 18.13 cSt is allowable to pass the test. The data in Figure 6 reveals that the formulation of the present invention described in Table 8 passes the Peugeot DV-4 Engine Test with soot concentrations in excess of 6 wt .