Aryl-PAG Monoesters as Lubricant Base Stocks

Abstract

The present invention discloses aryl-polyalkylene glycol monoester compound compositions suitable for use as base oils, particularly for use as base oils for use as automotive lubricants. The compositions can generally be characterized as having low kinematic viscosity at 100° C., high viscosity index, and low Noack volatility. The present invention also discloses lubricant formulations that include such aryl polyalkylene glycol monoester compounds along with other materials such as API Group I-V base oils and / or additives.

Description

[Technical field]

[0001] The present disclosure is directed to modified oil-soluble polyalkylene glycols having low kinematic viscosity at 100° C. with low volatility and high viscosity index, and their use as base oils.

[0002] Introduction Most lubricants used in modern equipment are manufactured using hydrocarbon base oils, which are typically mineral oils or synthetic hydrocarbon oils (such as polyalphaolefins). The American Petroleum Institute (API) has classified hydrocarbon base oils into Groups I, II, III, and IV based on their viscosity index (VI), saturate level, and sulfur level.

[0003] The move towards lower viscosity lubricants is a macro trend in the development of modern automotive lubricants, especially passenger car motor oils. Lower viscosity lubricants are known to provide better fuel economy, but still have some technical difficulties. Lower viscosity lubricants are known to be more volatile, resulting in evaporation of the lubricant during use. Furthermore, lower viscosity lubricants often have lower viscosity index (VI) values, which are a measure of how the viscosity of a lubricant changes with temperature. A lower VI value means a greater decrease in its viscosity at higher temperatures. A higher viscosity index value is generally preferred so that the lubricant maintains a small change in viscosity with increasing temperature from low to high temperatures that may occur during the operation of the equipment.

[0004] Base oil manufacturers are trying to develop new ultra-low viscosity lubricant base oils with lower Noack volatility (measured according to ASTM D6375) and higher viscosity index values ​​than previous ones. Base oils with kinematic viscosity (KV100) at 100°C of less than 5 mm2 / s (cSt), preferably less than 4 cSt, are desired. Base oils with KV100 of 4 cSt or less, preferably 3.5 cSt or less, or even 3 cSt or less, and VIs of more than 130, 140, or even 150 are particularly desired. Current hydrocarbon base oils used with KV100 of 3 cSt typically have VI values ​​of less than 120.

[0005] Recently, a new range of oil-soluble polyalkylene glycols (OSPs) has been developed called UCON® (which aids TM fluid life). Unfortunately, OSPs in the low viscosity range above typically have low VI values ​​(i.e., less than 130) and are therefore less interesting as primary base oils in lubricant formulations.

[0006] A recent publication, WO 2019 / 126923, discloses a new class of lubricants that are esterified OSPs (E-OSPs). These materials have significantly higher viscosity indexes and lower volatility than their respective parent (i.e., non-esterified) OSP base oils. This is especially true at lower viscosities, such as those with KV 100s of 4 cSt and 3 cSt, but even greater improvements in volatility performance are still desired.

[0007] There is a need for better additive and base stock technology for lubricant compositions that meet the ever more demanding demands of lubricant users, particularly advanced additive technology and synthetic base stocks that have improved fuel economy, solubility and dispersancy for polar additives or sludge generated during use of the lubricant, and oxidation stability. Summary of the Invention

[0008] The present invention discloses a composition suitable for use as a base oil, particularly for use as a base oil for use as an automotive lubricant. The composition can generally be characterized as having a low kinematic viscosity at 100° C., a high viscosity index, and a low Noack volatility. The compound includes an aryl-polyalkylene glycol monoester compound represented by the formula: RO-(AO)n-(C=O)-R x -R2 (wherein R1 is a straight or branched chain alkyl or aryl having 1 to 18 carbon atoms; AO refers to 1,2-alkylene oxide or mixtures thereof in a random or block feed sequence; n is an integer from 1 to 10; R x is a straight or branched chain alkyl group having 0 to 18 carbon atoms; R2 is an aryl group, a heteroaryl group, or an arylalkyl group having 4 to 18 carbon atoms, any of which may optionally contain oxygen, nitrogen, or sulfur atoms. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] The present invention discloses a composition comprising an aryl-polyalkylene glycol ("PAG") monoester compound represented by the following formula: RO-(AO)n-(C=O)-R x -R2 (wherein R1 is a straight or branched chain alkyl or aryl having 1 to 18 carbon atoms; AO refers to 1,2-alkylene oxide or mixtures thereof in a random or block feed sequence; n is an integer from 1 to 10; R x is a straight or branched chain alkyl group having 0 to 18 carbon atoms; R2 is an aryl group, a heteroaryl group, or an arylalkyl group having 4 to 18 carbon atoms, any of which may optionally contain oxygen, nitrogen, or sulfur atoms.

[0010] R1 may be a straight or branched chain alkyl or aryl having 1 to 18 carbon atoms, while R1 preferably has 1 to 12 carbon atoms. In general, it has been observed that the selection of the aryl moiety tends to increase the KV100 viscosity of the molecule, while the selection of a branched chain alkyl group tends to reduce the viscosity and improve low temperature performance (i.e., tends to reduce the pour point).

[0011] The AO group may be any 1,2-alkylene oxide, but is preferably ethylene oxide, 1,2-propylene oxide, or 1,2-butylene oxide. In general, it has been observed that the larger the alkyl group in the selected AO, the more compatible the molecule is in oil. It is also contemplated that mixtures of different AO groups may be used, and that they may be added in block or random order. Observations show that random structures tend to provide better oil compatibility, while block structures tend to improve properties such as reduced foaming, improved demulsibility, VI, etc.

[0012] The number of AO units, designated "n" in the formula, can be from 1 to 10, more preferably from 1 to 8, and most preferably from 2 to 6. Generally, the number of n is selected to provide the desired target kinematic viscosity at 100°C, with higher numbers resulting in higher viscosities. As will be appreciated by those skilled in the art, the exact value of n to achieve the desired viscosity will also depend on the AO (or AOs) selected, as well as the selection of R1, R x , and depends on the choice of R2.

[0013] R x R is a straight or branched chain alkyl having 0 to 18 carbon atoms. In general, the longer the chain, the higher the KV100 viscosity, the lower the Noack volatility, and the higher the viscosity index. x Branching on the group tends to result in better low temperature performance (eg, lower pour point and low temperature viscosity).

[0014] R2 is a substituted or unsubstituted aryl, heteroaryl, or arylalkyl group having 4 to 18 carbon atoms. If substituted, the substitution is preferably an oxygen or nitrogen or sulfur atom. The presence of an oxygen atom tends to increase the polarity of the molecule, providing potential benefits such as deposit control, compatibility with polar additives, and better friction profile. It has been observed that the presence of a nitrogen or sulfur atom in the R2 group can provide the molecule with potential benefits such as oxidation stability, antiwear, and extreme pressure performance. R2 preferably contains 1 to 3 aryl rings, more preferably 1 to 2 aryl rings.

[0015] The composition of the present invention can be prepared by coupling polyalkylene glycol to aryl acid moiety by general esterification reaction as known in the art.Polyalkylene glycol can be obtained from commercial sources or can be prepared from alcohol having desired configuration for R1 and desired alkylene oxide unit according to methods well known in the art.Aryl acid moiety can also be obtained from commercial sources or can be prepared according to methods well known in the art, such as cyanobenzyl hydrolysis, phenylacetamide hydrolysis, etc.

[0016] The compounds of the present invention preferably have a kinematic viscosity at 100° C. (KV100) of from 2 cSt, 2.5 cSt, or 3 cSt to 6 cSt, 5 cSt, 4 cSt, or 3 cSt, as determined according to ASTM D445.

[0017] The compounds of the present invention preferably have a Noack volatility, determined according to ASTM D6375, of less than 45%, preferably less than 40%, 30%, 20%, or even 15%.

[0018] The compounds of the present invention preferably have a pour point of less than -30°C, preferably less than -40°C, as determined according to ASTM D97.

[0019] The aryl-PAG ester compounds of the present invention can be used as the sole base oil or in blends with other base oils. If an additional base oil is used, it can advantageously be selected from API Groups I-V base oils, with Groups III and IV generally being preferred. If such a second base oil is present, it preferably has a kinematic viscosity at 100°C in the range of 2-8 cSt, more preferably 2-6 cSt.

[0020] Formulations containing the aryl-PAG ester compounds of the present invention, whether used as the sole base oil or in a blend with one or more other base oils, can also contain one or more additives as generally known in the art, including antiwear agents, rust inhibitors, metal deactivators, hydrolysis inhibitors, antistatic agents, antifoam agents, antioxidants, dispersants, detergents, extreme pressure additives, friction modifiers, viscosity index improvers, pour point depressants, tackifiers, metal detergents, ashless dispersants, and corrosion inhibitors.

[0021] The aryl-PAG ester compounds of the present invention, when used in a formulation with other materials such as other base oils or additives, should preferably comprise about 5-99.5% by weight of the formulation.

[0022] The aryl-PAG ester compounds of the present invention are suitable for use as base oils, particularly for use as base oils for use as automotive lubricants. EXAMPLES

[0023] The following examples can be used to demonstrate the effectiveness of the invention. The following test methods may be used to characterize the invention.

[0024] Kinematic viscosity is measured according to ASTM D7042 and D445.

[0025] Viscosity index is measured according to ASTM D2270.

[0026] Pour point is measured according to ASTM D97.

[0027] NOACK volatility is measured according to ASTM D6375.

[0028] Table I contains a description of the materials used in these examples. [Table 1]

[0029] The synthesis of the aryl-PAG monoester set is carried out as follows.

[0030] Example 1: PAA-TPnB TPnB (181.7 g, 0.732 mol) and phenylacetic acid (150 g, 1.1 mol) in toluene (300 mL) are stirred at room temperature. PTSA (5.6 g, 0.03 mol) is added with stirring, and the mixture is refluxed using a Dean-Stark distillation trap to remove water from the system at 165° C. for 21 hours. Most of the toluene is removed by evaporation using a vacuum rotary evaporator.

[0031] 437 g of 3.65% aqueous sodium hydroxide is added to the reaction solution with stirring. After stirring at 50° C. for 1 hour, the pH of the lower aqueous phase is 6. An additional 9.7 g of 20% aqueous sodium hydroxide is added and stirring is continued for an additional hour at 50° C. The pH of the lower aqueous phase is 10. The mixture is transferred to a 2 L separatory funnel and the aqueous phase is removed. The upper organic phase is mixed with 35 g of anhydrous magnesium silicate (MagSil) and the mixture is filtered under vacuum. The toluene is removed under vacuum at 50° C. to give a clear liquid weighing 189 g.

[0032] Example 2: PAA-50HB55 experiment: 50HB55 (174.4 g, 0.490 mol) and phenylacetic acid (100 g, 0.735 mol) in toluene (300 mL) are stirred at room temperature. PTSA (1.863 g, 0.0098 mol) is added with stirring and the mixture is refluxed with a Dean-Stark distillation trap to remove water from the system at 130° C. overnight.

[0033] Saturated aqueous sodium carbonate solution (400 g) is added to the reaction solution and stirred at room temperature for 2 hours. The mixture is transferred to a 1 L separatory funnel and the aqueous phase is removed. The organic layer is dried over anhydrous magnesium sulfate. After filtration, the organic solution is dried under vacuum to give the product (200 g) as a light yellow, clear oil.

[0034] Example 3: PAA-LB65 experiment: LB65 (333 g, 0.98 mol) and phenylacetic acid (200 g, 1.47 mol) in toluene (300 mL) are stirred at room temperature. PTSA (7.48 g, 0.04 mol) is added with stirring and the mixture is refluxed using a Dean-Stark distillation trap to remove water from the system at 165° C. for 21 hours. Most of the toluene is removed by evaporation.

[0035] 589 g of 3.65% aqueous sodium hydroxide is added with stirring. After stirring at 50° C. for 1 hour, the pH of the lower aqueous phase is 6. An additional 15.6 g of 20% aqueous sodium hydroxide is added and stirring is continued for an additional hour at 50° C. The pH of the lower aqueous phase is 10. The mixture is transferred to a 2 L separatory funnel and the aqueous phase is removed. The upper organic phase is mixed with 35 g of anhydrous magnesium silicate (MagSil) and the mixture is filtered under vacuum. The toluene is removed under vacuum at 50° C. to give a clear liquid weighing 405 g.

[0036] Example 4: PAA-OSP12 experiment: UCON OSP-12 (200 g, 0.535 mol) and phenylacetic acid (100 g, 0.734 mol) in toluene (300 mL) are stirred at room temperature. PTSA (2.2 g, 0.02 mol) is added with stirring, and the mixture is refluxed using a Dean-Stark distillation trap to remove water from the system at 165° C. for 21 hours. Most of the toluene is removed by evaporation.

[0037] 242 g of 3.65% aqueous sodium hydroxide is added with stirring. After stirring at 50° C. for 1 hour, the pH of the lower aqueous phase is 6. An additional 10 g of 20% aqueous sodium hydroxide is added and stirring is continued for an additional hour at 50° C. The pH of the lower aqueous phase is 10. The mixture is transferred to a 1 L separatory funnel and the aqueous phase is removed. The upper organic phase is mixed with 10 g of anhydrous magnesium silicate (MagSil) and the mixture is filtered under vacuum. The toluene is removed under vacuum at 50° C. to give a liquid weighing 190 g.

[0038] Example 5: BA-OSP12 experiment: UCON OSP-12 (400 g, 1.07 mol) and benzoic acid (144 g, 1.18 mol) in toluene (300 mL) are stirred at room temperature. PTSA (2.24 g, 0.012 mol) is added with stirring and the mixture is refluxed using a Dean-Stark distillation trap to remove water from the system at 165° C. for 20 hours. Additional benzoic acid (30 g total, 0.24 mol) is added and stirred at 165° C. until the reaction is observed to be greater than 90% of theoretical completion as calculated by OH number and is determined to be complete. Most of the toluene is removed by evaporation.

[0039] 403 g of 3.65% aqueous sodium hydroxide is added with stirring. After stirring at 50° C. for 1 hour, the pH of the lower aqueous phase is 6. An additional 17 g of 20% aqueous sodium hydroxide is added and stirring is continued for an additional hour at 50° C. The pH of the lower aqueous phase is 10. The mixture is transferred to a 2 L separatory funnel and the aqueous phase is removed. The upper organic phase is mixed with 20 g of anhydrous magnesium silicate (MagSil) and the mixture is filtered under vacuum. The toluene is removed under vacuum at 50° C. to give a liquid weighing 390 g.

[0040] These materials were analyzed to determine KV (at 40° C. and 100° C.), VI, pour point, and Noack volatility, and the results are shown in Table 2 (for materials with relatively high KV100) and Table 3.

[0041] Comparative examples are indicated as Comp Ex. and examples are indicated as Ex. [Table 2] KV-40, kinematic viscosity at 40℃ KV-100, kinematic viscosity at 100℃ [Table 3] KV-40, kinematic viscosity at 40℃ KV-100, kinematic viscosity at 100℃

[0042] Comparative Examples A and D are YUBASE 4 and YUBASE 3, which are commercially available hydrocarbon base oils commonly used in formulating commercial lubricants. Yubase 4 has a KV100 value of about 4.2 cSt and Yubase 3 has a KV100 value of about 3.1 cSt.

[0043] Comparative Examples B and E are OSP-18 and OSP-12. OSP-18 is a dodecanol-initiated random PO / BO (50 / 50 w / w) copolymer with a typical kinematic viscosity of 18 cSt at 40° C. OSP-12 is a dodecanol-initiated random PO / BO (50 / 50 w / w) copolymer with a typical kinematic viscosity of 12 cSt at 40° C.

[0044] Comparative Examples C and F are OSP18-C5 and OSP12-C5. OSP18-C5 is OSP18 esterified with valeric acid. OSP12-C5 is OSP12 esterified with valeric acid.

[0045] Comparative Examples A, B, and C have KV100 values ​​of about 4.0 cSt, as shown in Table 2, and are the benchmark samples for Examples 3-5 (these materials have KV100 values ​​of about 3.5-4.0 cSt).

[0046] Compared to Comparative Example A, Examples 3, 4, and 5 show significantly better low temperature performance (lower pour point). Examples 4 and 3 show significantly higher VI at lower viscosity grades. Example 4 shows significantly lower Noack volatility at lower viscosity grades.

[0047] Compared to Comparative Example B, Examples 4 and 3 show significantly higher VI at similar or lower viscosity grades. Examples 5 and 3 show significantly lower pour points. Examples 5, 4, and 3 all show significantly lower Noack volatility at similar or lower viscosity grades.

[0048] Compared to Comparative Example C, Examples 5, 4, and 3 all show significantly lower Noack volatility at similar or lower viscosity grades.

[0049] Comparative Examples D, E, and F have KV100 values ​​of about 3.0 cSt, as shown in Table 3, and are the benchmark samples of Examples 1-2 (these materials have KV100 values ​​of about 2.0-3.5 cSt).

[0050] Compared to Comparative Example D, Example 2 exhibits a significantly higher VI, as well as lower pour point and Noack volatility at similar viscosity grades.

[0051] Compared to Comparative Example E, Example 1 exhibits a significantly higher VI, as well as lower pour point and Noack volatility at a lower viscosity grade, and Example 2 exhibits a significantly higher VI, as well as lower pour point and Noack volatility at a similar viscosity grade.

[0052] Compared to Comparative Example F, Example 2 exhibits a similar VI at a similar viscosity grade, but significantly lower Noack volatility.

Claims

1. A composition comprising an aryl-PAG monoester compound represented by the formula: R １ --(AO).-(C=O)-R ｘ -R ２ (In the formula, R １ is a straight or branched chain alkyl or aryl having 1 to 18 carbon atoms; AO refers to 1,2-alkylene oxide or mixtures thereof in random or block feed sequence; n is an integer from 1 to 10; R ｘ is a straight or branched chain alkyl having 0 to 18 carbon atoms; R ２ is an aryl, heteroaryl, or arylalkyl group having 4 to 18 carbon atoms, any of which may optionally contain oxygen, nitrogen, or sulfur atoms.

2. 2. The composition of claim 1, wherein n is selected to provide a target kinematic viscosity at 100° C. of less than 6 cSt.

3. R １ The composition of claim 1, wherein is a straight or branched chain alkyl having 1 to 12 carbon atoms.

4. The composition of claim 1, wherein the 1,2-alkylene oxide is selected from the group consisting of ethylene oxide, 1,2-propylene oxide, 1,2-butylene oxide, and mixtures thereof.

5. R ｘ The composition of claim 1, wherein is a straight chain alkyl having 0 to 6 carbon atoms.

6. R ２ The composition of claim 1, wherein is an aryl or arylalkyl group having 6 to 12 carbon atoms.

7. R ２ The composition of claim 1, wherein has 1 to 3, preferably 1 to 2, aryl rings.

8. 10. The composition of claim 1 having a kinematic viscosity at 100°C, determined according to ASTM D445, of from 2 cSt to 6 cSt.

9. 10. The composition of claim 1, characterized in that it has a Noack volatility of less than 45%, determined according to ASTM D6375.

10. 10. The composition of claim 1, characterized in that it has a pour point of less than -40°C as determined by ASTM D97.

11. 10. The composition of claim 1, characterized by having a kinematic viscosity at 100°C of 2 to 6 cSt, as determined according to ASTM D445, a Noack volatility of less than 45%, as determined according to ASTM D6375, and a pour point of less than -40°C, as determined by ASTM D97.

12. A lubricant formulation comprising a base oil which is an aryl-PAG monoester compound represented by the formula: R １ --(AO).-(C=O)-R ｘ -R ２ (In the formula, R １ is a straight or branched chain alkyl or aryl having 1 to 18 carbon atoms; AO refers to 1,2-alkylene oxide or mixtures thereof in random or block feed sequence; n is an integer from 1 to 10; R ｘ is a straight or branched chain alkyl having 0 to 18 carbon atoms; R ２ is an aryl, heteroaryl, or arylalkyl group having 4 to 18 carbon atoms, any of which may optionally contain oxygen, nitrogen, or sulfur atoms.

13. 13. The lubricant formulation of claim 12, further comprising one or more additional base oils which are API Group I-V base oils.

14. 14. The lubricant formulation of claim 13, wherein the additional base oil has a kinematic viscosity at 100°C, determined according to ASTM D445, of from 2 cSt to 6 cSt.

15. 13. The lubricant formulation of claim 12, further comprising an antiwear agent, a rust inhibitor, a metal deactivator, an antihydrolysis agent, an antistatic agent, an antifoam agent, an antioxidant, a dispersant, a detergent, an extreme pressure additive, a friction modifier, a viscosity index improver, a pour point depressant, a tackifier, a metal detergent, an ashless dispersant, and a corrosion inhibitor.

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