US20080125337A1

US20080125337A1 - Lubricant formulations and methods

Info

Publication number: US20080125337A1
Application number: US11/564,424
Authority: US
Inventors: Gregory H. Guinther; William Y. Lam
Original assignee: Afton Chemical Corp
Current assignee: Afton Chemical Corp
Priority date: 2006-11-29
Filing date: 2006-11-29
Publication date: 2008-05-29
Also published as: GB2444354A; FR2910023A1; DE102007044144A1; GB0718271D0; CN101191095A; JP2008138174A

Abstract

The embodiments described herein relate to particular formulations and methods that provide reduced exhaust catalyst deactivation and/or reduced oil consumption.

Description

TECHNICAL FIELD

BACKGROUND

For over fifty (50) years automotive engine oils have been formulated with zinc dialkyl dithio phosphate (ZDDP) resulting in low levels of wear, oxidation, and corrosion. The additive is truly ubiquitous and found in nearly every modern engine oil. It imparts multifunctional performance in the areas of anti-wear, anti-oxidation, and anti-corrosion and is undeniably one of the most cost-effective additives in general use by engine oil manufacturers and marketers. It is, however, known to cause a significant problem in the area of exhaust catalytic converters and oxygen sensors when the phosphorus from combusted oil forms an impermeable glaze and masking the precious metal catalytic sites. As a result there is pressure by the automakers to control and reduce the amount of ZDDP used in engine oils to facilitate longer converter and oxygen sensor life, and to reduce the manufacturer's initial costs of converters through lower precious metal content.

SUMMARY

In an embodiment a lubricant composition may comprise a base oil having a NOACK volatility of from about 5 to about 15: and a zinc dialkyl dithio phosphate having a primary alkoxy moiety. The lubricant composition may be essentially free of zinc dialkyl dithio phosphate having all-secondary alkoxy moieties.
In another embodiment a lubricant composition may comprise (a) a base oil having a NOACK volatility of from about 5 to about 15 and (b) the reaction product of: (i) about 50 to about 100 mol % of about C1 to about C18 primary alcohol, (ii) up to about 50 mol % of about C3 to about C18 secondary alcohol; (iii) a phosphorus-containing component: and (iv) a zinc-containing component.
In another embodiment, a method for providing a decrease in catalyst deactivation in an automotive exhaust catalytic converter may comprise lubricating an engine with a lubricant composition comprising (a) a base oil having a NOACK volatility of from about 5 to about 15; and (b) a zinc dialkyl dithio phosphate having a primary alkoxy moiety. The lubricant composition may be essentially free of zinc dialkyl dithio phosphate having all-secondary alkoxy moieties.
In another embodiment, a method for decreasing oil consumption in an engine may comprise lubricating an engine with a lubricant composition comprising (a) a base oil having a NOACK volatility of from about 5 to about 15; and (b) a zinc dialkyl dithio phosphate having a primary alkoxy moiety. The lubricant composition may be essentially free of zinc dialkyl dithio phosphate having all-secondary alkoxy moieties. The lubricant composition may decreases oil consumption compared to a lubricant composition containing zinc dialkyl dithio phosphate having all-secondary alkoxy moieties.
In another embodiment, a method for lubricating an engine may comprise contacting said engine with a lubricant composition wherein said lubricant composition comprises (a) a base oil having a NOACK volatility of from about 5 to about 15; and (b) a zinc dialkyl dithio phosphate having a primary alkoxy moiety. The lubricant composition may be essentially free of zinc dialkyl dithio phosphate having all-secondary alkoxy moieties. The lubricant composition may provide decreased oil consumption compared to a lubricant composition containing zinc dialkyl dithio phosphate having all-secondary alkoxy moieties. Further, the lubricant composition may provide a decrease in catalyst deactivation in an automotive exhaust catalytic converter compared to a lubricant composition containing zinc dialkyl dithio phosphate having all-secondary alkoxy moieties.
The compositions and methods described herein are particularly suitable for reducing exhaust catalyst deactivation and/or reducing oil consumption. Other features and advantages of the compositions and methods described herein may be evident by reference to the following detailed description which is intended to exemplify aspects of the embodiments without intending to limit the embodiments described herein.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are intended to provide further explanation of the embodiments disclosed and claimed.

DETAILED DESCRIPTION

Lubricant compositions according to embodiments described herein may comprise a base oil and a zinc dialkyl dithio phosphate having a primary alkyl moiety, wherein the lubricant composition is essentially free of zinc dialkyl dithio phosphate having a secondary alkyl moiety.
The lubricant compositions may be suitable for use in a variety of applications, including but not limited to engine oil applications and/or heavy duty engine oil applications. Examples may include the crankcase and/or the catalytic converter for a variety of applications including spark-ignited and compression-ignited internal combustion engines, automobile and truck engines, marine and railroad diesel engines, and the like.
The lubricant compositions may comprise a base oil and one or more suitable additive components. The additive components may be combined to form an additive package which is combined with the base oil. Or, alternatively, the additive components may be combined directly with the base oil.

Base Oil

Base oils suitable for use with present embodiments may comprise one ore more oils of lubricating viscosity such as mineral (or natural) oils, synthetic lubricating oils, vegetable oils, and mixtures thereof. Such base oils include those conventionally employed as crankcase lubricating oils for spark-ignited and compression-ignited internal combustion engines, such as automobile and truck engines, marine and railroad diesel engines, and the like. Suitable base oils may have a NOACK volatility of from about 5 to about 15. As another example, suitable base oils may have a NOACK volatility of from about 10 to about 15. As even further example suitable base oils may have a NOACK volatility of from about 9 to about 13. Base oils are typically classified as Group I, Group II, Group III, Group IV and Group V, as described in Table 1 below.

TABLE 1

Group I–V Base Oils

Base Oil	% Sulfur		% Saturates	Viscosity Index

Group I	>0.03	and/or	<90	80–120
Group II	≦0.03	and/or	≧90	80–120
Group III	≦0.03	and/or	≧90	≧120
Group IV	*
Group V	**

* Group IV base oils are defined as all polyalphaolefins
** Group V base oils are defined as all other base oils not included in Groups I, II, III and IV and may include gas to liquid base oils.

Non-limiting examples of synthetic base oils include alkyl esters of dicarboxylic acids, polyglycols and alcohols, poly-alpha-olefins, including polybutenes, alkyl benzenes, organic esters of phosphoric acids, polysilicone oils, and alkylene oxide polymers, interpolymers, copolymers and derivatives thereof where the terminal hydroxyl groups have been modified by esterification, etherification, and the like.
Mineral base oils include, but are not limited to, animal oils and vegetable oils (e.g., castor oil, lard oil), liquid petroleum oils and hydrorefined, solvent-treated or acid-treated mineral lubricating oils of the paraffinic, naphthenic and mixed paraffinic-naphthenic types. Oils of lubricating viscosity derived from coal or shale are also useful base oils.

ZDDP Component

Lubricant compositions disclosed herein may comprise a zinc dialkyl dithio phosphate (ZDDP) having a primary alkoxy moiety. The lubricant composition is essentially free of ZDDP having all-secondary alkoxy moieties. Further, the total amount of phosphorus in the lubricant composition may comprise less than about 20% phosphorus derived from zinc dialkyl dithio phosphate having all-secondary alkoxy moieties. As another example, the total amount of phosphorus in the lubricant composition may comprise less than about 15% phosphorus derived from zinc dialkyl dithio phosphate having all-secondary alkoxy moieties. As another example, the total amount of phosphorus in the lubricant composition may comprise less than about 10% phosphorus derived from zinc dialkyl dithio phosphate having all-secondary alkoxy moieties.
The lubricant composition may comprise ZDDP having a primary alkoxy moiety in an amount sufficient to contribute from about 0.03 wt % to about 0.15 wt % phosphorus in the lubricant composition. The lubricant composition may also further comprise a ZDDP having both primary and secondary alkoxy moieties. The ZDDP having both primary and secondary alkoxy moieties may be present in an amount sufficient to contribute from about 0.03 wt % to about 0.15 wt % phosphorus in the lubricant composition.
Suitable ZDDPs may be prepared from specific amounts of primary and secondary alcohols. For example, the alcohols may be combined in a ratio of from about 100:0 to about 50:50 primary-to-secondary alcohols. As an even further example, the alcohols may be combined in a ratio of about 60:40 primary-to-secondary alcohols. An example of a suitable ZDDP may comprise the reaction product obtained by combining: (i) about 50 to about 100 mol % of about C1 to about C18 primary alcohol; (ii) up to about 50 mol % of about C3 to C18 secondary alcohol; (iii) a phosphorus-containing component; and (iv) a zinc-containing component. As a further example, the primary alcohol may be a mixture of from about C1 to about C18 alcohols. As an even further example, the primary alcohol may be a mixture of a C4 and a C8 alcohol. The secondary alcohol may also be a mixture of alcohols. As an example, the secondary alcohol may comprise a C3 alcohol. The alcohols may contain any of branched, cyclic, or straight chains.
The ZDDP may comprise the combination of about 60 mol % primary alcohol and about 40 mol % secondary alcohol.
The phosphorus-containing component may comprise any suitable phosphorus-containing component such as, but not limited to a phosphorus sulfide. Suitable phosphorus sulfides may include phosphorus pentasulfide or tetraphosphorus trisulfide.
The zinc-containing component may comprise any suitable zinc-containing component such as, but not limited to zinc oxide, zinc hydroxide, zinc carbonate, zinc propylate, zinc chloride, zinc propionate, or zinc acetate.
The reaction product may comprise a resulting mixture, component, or mixture of components. The reaction product may or may not include unreacted reactants, chemically bonded components, products, or polar bonded components.

Optional Components

The lubricant compositions described herein may comprise one or more additional additive components. Suitable additive components may include, but are not limited to dispersants, oxidation inhibitors (i.e., antioxidants), friction modifiers, viscosity modifiers, rust inhibitors, demulsifiers, pour point depressants, antifoamants, and seal swell agents. Each of the foregoing additives, when used, is used at a functionally effective amount to impart the desired properties to the lubricant. Thus, for example, if an additive is a corrosion inhibitor, a functionally effective amount of this corrosion inhibitor would be an amount sufficient to impart the desired corrosion inhibition characteristics to the lubricant. Generally, the concentration of each of these additives, when used, ranges up to about 20% by weight based on the weight of the lubricant composition, and in one embodiment from about 0.001% to about 20% by weight, and in one embodiment about 0.01% to about 10% by weight based on the weight of the lubricant composition.
The use of all-primary alcohol ZDDP anti-wear chemistry has been shown to provide two benefits over oils formulated with all-secondary alcohol ZDDP's. It reduced the amount of exhaust catalyst deactivation related to chemical poisoning and it reduced the amount of oil consumption. These findings were unexpected because the phosphorus volatility of the oil containing the all-primary component has been characterized by the Phosphorus Emissions Index test (PEI at 250° C.) as being exceptionally high relative to formulations containing the all-secondary alcohol ZDDP. (As used herein, “PEI” is intended to be the same as “PEI at 250° C.”). The PEI test measuring phosphorus volatility has been proposed by the Savant Corporation, automakers, and others as a means to assess and control passenger car engine oil phosphorus volatility, thereby limiting the degradation of exhaust catalytic converters and extending their service life. The present embodiments show, surprisingly, that the opposite is true.

EXAMPLES

The following examples are given for the purpose of exemplifying aspects of the embodiments and are not intended to limit the embodiments in any way.
Inventive and comparative fluids were tested in a catalyst test designed by Afton Chemical Corporation (hereinafter the “Afton Catalyst Test”) to simulate a Ford vehicle cruising at approximately 70 mph. In the test, a new close-coupled catalytic converter was attached to an engine that was operated for 10 days. To exacerbate phosphorus volatility-related effects, the oil in the engine was changed every 24 hours, and the oil and coolant temperatures were elevated to 150 and 122° C., respectively. Oil consumption was accurately determined by weighing the mass removed and subtracting this value from the mass that was installed. The operating conditions of the Afton Catalyst Test are listed in Table 2.

TABLE 2

Operating Conditions of Afton Catalyst Test

Test Engine:	Ford SOHC 4.6L V8 operated on unleaded
	gasoline
Test Fuel:	EEE Emissions-grade gasoline
Test Catalyst:	Ford Part Number 3W1Z-5E212-GB
Test Duration:	240 hours
Oil Change Interval:	24 hours
Oil Charge:	4500 grams
Engine Speed:	2000 rpm
Oil Temperature:	150° C.
Coolant Temperature:	122° C.
Catalyst Inlet Temperature:	550° C.
Fuel Consumption:	10.7 kg/hr

Formulations were tested in the Afton Catalyst Test using formulations containing 15% NOACK volatility oils. The comparative formulation included a typical all-secondary alcohol ZDDP with low PEI. The inventive formulation included an all-primary alcohol ZDDP with high PEI. Table 3 shows the results of the testing. As shown in the results the inventive formulation retained more phosphorus in the used oil, gave less catalyst deactivation, and produced lower oil consumption than the comparative formulation.
Oil consumption is indicated by grams/hour. The amount of catalyst deactivation was measured by the loss in “T50” light-off time. T50 is used in emissions testing to describe the temperature at which 50% conversion efficiency takes place. Maintaining a lower T50 temperature is desirable because this leads to overall lower emissions.

	TABLE 3

	Inventive Formulation	Comparative Formulation

NOACK, %	15	15
PEI (at 250° C.), mg/L	90	11
ZDDP Type	Primary	Secondary
Phosphorus, wt %	0.10	0.10
Oil Consumption, g/h	30	33
Phosphorus Retention,	82.8	81.6
%
Catalyst T50 Increase
HC, ° C.	19	35
CO, ° C.	28	66
NO_x, ° C.	28	60

At numerous places throughout this specification, reference has been made to a number of U.S. patents and publications. All such cited documents are expressly incorporated in full into this disclosure as if fully set forth herein.
The foregoing embodiments are susceptible to considerable variation in its practice. Accordingly, the embodiments are not intended to be limited to the specific exemplifications set forth hereinabove. Rather, the foregoing embodiments are within the spirit and scope of the appended claims, including the equivalents thereof available as a matter of law.
The patentees do not intend to dedicate any disclosed embodiments to the public, and to the extent any disclosed modifications or alterations may not literally fall within the scope of the claims, they are considered to be part hereof under the doctrine of equivalents.

Claims

1. A lubricant composition comprising:

(a) a base oil having a NOACK volatility of from about 5 to about 15; and

(b) a zinc dialkyl dithio phosphate having a primary alkoxy moiety,

wherein the lubricant composition is essentially free of zinc dialkyl dithio phosphate having all-secondary alkoxy moieties.

2. The lubricant composition of claim 1, wherein the lubricant composition is an engine oil.

3. The lubricant composition of claim 1, wherein the lubricant composition is a heavy duty engine oil.

4. The lubricant composition of claim 1, wherein the base oil has a NOACK volatility of from about 10 to about 15.

5. The lubricant composition of claim 4, wherein the base oil has a NOACK volatility of from about 9 to about 13.

6. The lubricant composition of claim 1, wherein the base oil comprises a mineral oil, a synthetic oil, or a mixture thereof.

7. The lubricant composition of claim 1, wherein the base oil comprises on or more of a member selected from the group consisting of: a group I base oil, a group II base oil, a group III base oil, a group IV base oil, and a group V base oil.

8. The lubricant composition of claim 1, wherein the total amount of phosphorus in the lubricant composition comprises less than about 20% phosphorus derived from zinc dialkyl dithio phosphate having all-secondary alkoxy moieties.

9. The lubricant composition of claim 1, wherein the total amount of phosphorus in the lubricant composition comprises less than about 15% phosphorus derived from zinc dialkyl dithio phosphate having all-secondary alkoxy moieties.

10. The lubricant composition of claim 1, wherein the total amount of phosphorus in the lubricant composition comprises less than about 10% phosphorus derived from zinc dialkyl dithio phosphate having all-secondary alkoxy moieties.

11. The lubricant composition of claim 1, wherein the zinc dialkyl dithio phosphate having a primary alkoxy moiety is present in an amount sufficient to contribute from about 0.03 wt % to about 0.15 wt % phosphorus in the lubricant composition.

12. The lubricant composition of claim 1, wherein the lubricant composition further comprises a zinc dialkyl dithio phosphate having both primary and secondary alkoxy moieties.

13. The lubricant composition of claim 12, wherein the zinc dialkyl dithio phosphate having both primary and secondary alkoxy moieties is present in an amount sufficient to contribute from about 0.03 wt % to about 0.15 wt % of phosphorus in the lubricant composition.

14. A lubricant composition comprising

(a) a base oil having a NOACK volatility of from about 5 to about 15 and

(b) the reaction product of:

(i) about 50 to about 100 mol % of about C1 to about C18 primary alcohol;

(ii) up to about 50 mol % of about C3 to about C18 secondary alcohol;

(iii) a phosphorus-containing component; and

(iv) a zinc-containing component.

15. The lubricant composition of claim 14, wherein the phosphorus component comprises phosphorus pentasulfide.

16. The lubricant composition of claim 14, wherein the zinc component comprises zinc oxide.

17. A method for providing a decrease in catalyst deactivation in an automotive exhaust catalytic converter, comprising lubricating an engine with a lubricant composition comprising:

(a) a base oil having a NOACK volatility of from about 5 to about 15; and

(b) a zinc dialkyl dithio phosphate having a primary alkoxy moiety, wherein the lubricant composition is essentially free of zinc dialkyl dithio phosphate having all-secondary alkoxy moieties.

18. A method for decreasing oil consumption in an engine, comprising lubricating an engine with a lubricant composition comprising:

(a) a base oil having a NOACK volatility of from about 5 to about 15; and

19. The method of claim 18, wherein the lubricant composition decreases oil consumption compared to a lubricant composition containing zinc dialkyl dithio phosphate having all-secondary alkoxy moieties.

20. The method of claim 18, wherein the engine includes an internal combustion engine having a crankcase and wherein the lubricant composition comprises a crankcase oil present in the crankcase of the engine.

21. A method for lubricating an engine, comprising:

contacting said engine with a lubricant composition wherein said lubricant composition comprises:

(a) a base oil having a NOACK volatility of from about 5 to about 15; and

22. The method of claim 21, wherein the lubricant composition provides decreased oil consumption compared to a lubricant composition containing zinc dialkyl dithio phosphate having all-secondary alkoxy moieties.

23. The method of claim 21, wherein the lubricant composition provides a decrease in catalyst deactivation in an automotive exhaust catalytic converter compared to a lubricant composition containing zinc dialkyl dithio phosphate having all-secondary alkoxy moieties.