CA1284489C - Lubricating oil - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

A lube oil composition and a method of manufacturing same are described. The lube oil comprises:
A. a basestock;

B. a metal phosphate;

C. a metal carbamate; and, D. an alkyl hydroxy-aryl sulfide.

Description

~ 2E~L~ 3;9 F~ACK(~R011~3D OF THE I~VEMTIO~

The present invention is directed at an improved lube oil formulation. ~ore specifically, the present invention is directed at a lube oil composition having a reduced phosphorus content while exhibiting satisfactory anti-wear and friction reducing properties.

In current lube oil formulations for internal combustion engines, phosphorus-containing compounds such as zinc dialkyldithiophosphate (ZDDP), are added to the lube oil formulation to provide im-proved anti-wear properties. ~owever, it has been foun~ that phosphorus from phosphoru~-containing compounds becomes deposited on the catalyst in cata-lytic converters, therehy decreasing the ef~iciency of catalytic converters over time. As a result, vehicle manufacturers have recommended that engine oil contain reduced phosphorus contents. At the present time automotive lube oils typically contain a maximum of about 0.10 to about 0.14 weight percent phosphorus. To reduce the rate at which catalytic converters become fouled by phosphorus, it would be advantageous to reduce the phosphorus content of the lube oils to about 0.08 wei~ht percent, or lower.

The use of dialkyldithiocarbamates in lube oils is known. U.S. Patent No. 4,178,258 discloses the use of zinc dia~kyldithiophos~hate (ZDDP) and a wear inhibiting amount molybdenum bis(dialkyldithiocarba-mate~. This Patent also discloses the ad~ition of sulfurized calcium phenates in the lube oil formula-tion. However, the addition of sulfurized calcium - ? -~henates to a lube oil is not desirable beca~se it mayreduce the fuel economy and anti-rust properties of the lube oil.

~ .S. Patent No. 3,513,094 also discloses the use of ~etal dithiocarbamates in lube oils. This patent discloses the use of the metal dithiocarbamates in combination with antimony dihydrocarbyldithioate.
This patent also discloses the use of sulfurized sper~
oil.

U.S. Patent ~o. 3,923,669 discloses the use of zinc dialkyldithio~hosphate and a neutral bariu~
salt of a petroleum sulfonate diaryldithiocarbamate.
The use of neutral barium salts of a petroleum sulfonate is not de~irable because o~ the toxicity of barium.

Japanese Patent Publication J54,113,604 dis-closes the combination of molybdenum sulfide-oxide, ~DDP and dialkyldithiocarbamate in a lubricant for internal combustion engines.

It is desirable to decrease the concentra-tion of phosphate-containing compounds, such as zinc dialkyldithiophosphate, present in lubricating oil to therehy decrease the r~te at which phosphates become deposited on the catalyst.

It also is desirable to provide a lube oil havin~ anti-wear and friction reducin~ properties comparable to presently available lube oils while also having a reduced phosphorus content.

The present invention is directed at a lube oil and method o~ manufacturinq same wherein the lube oil co~prises:

A. a basestock;

~ . a metal phosphate;

C. a metal carbamate; and, D. a para alkyl hydroxy-aryl sulfide.

SUMMARY O~ T~E I~VENTION

The present invention is directed at a lube oil having improved properties comprising:

A. a basestock;

B. a metal phosphate;

C. a metal carbamate; and, D. a para alkyl hydroxy-aryl sulfide.

The concentration of the metal phosphate, preferably a metal dithio~hosphate (MDTP), may be limited to a range of about 0.2 to about 1.0 weight percent of the lube oil so that the concentration of phosphorus is less than about 0.0~ weight percent, preferably 0.05 weight percent or less of the lube oil.

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`. 2~

The present invention also is directed at a method for im~roving the anti-wear ~roperties of a lube oil base-stock co~prisina the addition to the basestock of an effective amount of:

A. a metal phosphate;

. a metal carbamate; and, . a para alkyl hydroxy-aryl sulfide.

In a pre~erred embodiment the metal salt is a metal dialkyldithiophosphate salt including a Group I~, IIB, VI~ or VIIIB ~etal with zinc, nickel and copper heing particularly preferred. The alkyl groups preferably comprise C3-Clo alkyls. The concentration of the metal dialkylflithiophosphate salt relative to the hasestock ranges between about 0.1 and about 1.0 weight percent, pre~erably between about ~.3 and about 0.6 weight percent.

The metal carbamate preferably comprises a metal dithiocarbamate wherein the ~etal is selected from ~roups IB, IIB, VIB, VIIIB of the Periodic Table and mixtures thereof. Preferred metals include zinc, iron and nickel, with zinc being particularly prefer-red. The concentration of the metal dithiocarbamate ~ay range between about 0.1 and about 1.3 weight per-cent, based upon the hasestock content, preferably between about 0.2 and about 0.8 weiaht percent.

The para alkyl hydroxy-aryl sulfide preferably comprises a para alkyl phenol sulfide where the alkyl group preferably ranges between about C6 and about Clg with a para nonyl phenol sulfide being particularly prefer-3~

red. The concentration of the para alkyl hydroxy aryl sul-fide may range between about n.2 and ahout 2.0 weight percent, based upon the basestock content, preferably between about n.4 and about 0.8 weight percent.

RRIEF ~ESCRIPTIO~ OF T~ DRAWJN~S

The Figure represents a plot of average cam lobe wear as a function of time for varying lube oil additive combinations.

nETAILED DESCRIPTIO~ OF THE INV~NTIO~

The Present invention is directed at a lube oil composition and method of makinq same ~here the lubricant has a reduced phosphorus content yet exhibits satisfactory anti-wear and friction reducing Properties. The present invention is directed at a lube oil having improved properties comprising:

. a basestock;

~. a metal phosphate;

C. a metal carbamate; and, n . a para alkyl hydroxy-aryl sulfide.

The basestock utilized in the present invention is not critical and may be selected to achieve the desired final properties of the lube oil.
The basestock may be natural or synthetic.

The metal ~hosphate of the present invention preferably comprises a metal ~ialkyldithioPhosphate wherein the metal is selected from the group consisting ~r ~

f.39 ~ 6 --of ~roup I~ rIB, vr II8 and mixtures thereof, with nickel, copper and zinc being particularly preferred.
The alkyl groups oreferably comprise C3-Clo alkyls.
Particularly preferred compounds are zinc dialkyldi-thiophosphates. These compounds and the ~ethods ~or making same are well-known by those skilled in the art.
The concentration of the metal dialkyldithiophosphate may range between about ~.1 and about 1.0 weight per-cent based upon the basestock content, preferably be-tween about 0.~ and about 0.6 weight percent.

The metal carbamate preferably comprises a metal dithiocarbamate where the metal preferably is selected from the group consisting of Group IB, II~, VII~ and VIIIB Preferred metals include zinc, nickel and iron, with zinc dithiocarbamate being particularly preferred. The concentration of the metal carbamate may range between about 0.1 and about 1.3 weight percent, hased upon the ~asestock content, preferably between about 0.2 and a~out 0.8 weight percent. The zinc dithiocarba~ate (ZDTC) is readily available as an article of commerce.

The para alkyl hydroxy-aryl sulfide preferably comprises a para alkyl phenol sulfide in which the alkyl groups preferably range between about C6 and C18.
Para nonyl phenol sulfide is a particularly preferred com-pound. The concentration of the para alkyl hydroxy-aryl sulfide may range between about 0.2 and about 2.0 weig~t percent, based upon the basestock content, pref-erably between about 0.4 and about 0.8 weight percent.
Para nonyl phenol sulfide (NPS) is well-known by those skilled in the art and is readily obtainable as an article of commerce.

~l'2~

The following comparative examples and examples demonstrate the utility of the present invention. The tests comprised valve train wear tests utilizing a Ford 2.3 liter engine with the pistons and connecting rods removed. The engine was driven with an 11.2 KM (15 horsepower) DC drive motor through a 1.2 timing belt drive. The engine was equipped with Oldsmobile valve springs (146.5-148.3 KG) to increase the load between the cam lobes and the followers. Both oil and coolant circulation were accomplished by use of the engine mounted pumps. All test runs were made at 90C oil temperature, 90C coolant temperature, approximately 331 kPa oil pressure and an engine speed of 1,000 plus or minus 6 rpm.

During operation, wear is generated on the lobes of the cam shaft and followers due to the sliding contact. As in the sequence V-D test described in ASTM Test No. STP 315H-Part 3, wear is defined as the reduction of the head-to-toe measurement at the point of maximum lift on the cam shaft. A pre-measured cam shaft is measured at various time intervals during the test to establish the reduction in the head-to-toe distance, i.e. the degree of wear.
The tests were conducted with a commercially available lubricating oil from which the anti-wear additive had been removed and which were modified somewhat to simulate actual used oil conditions.

Comparative Example 1 In this test 0.41 weight percent of zinc dialkyldithiophosphate and 0.80 weight percent of zinc dithiocarbamate were added to the lube oil noted above.

The engine was run for only 40 hours to prevent engine seizure due to high wear which had been detected after 2n hours of operation. The average cam lohe wear was 29.5 micrometers ~m) and 95.4 ~m after 20 and 4n hours, respectively.

~omparative Example 2 A test similar to that described in Comparative ~xam~le 1 was run in which the lube oil contained 0.41 weiaht percent of ~n~P and 0.80 weight percent of nonyl phenol sulfide. Again, the test was run for 40 hours after which the cam lobe was measured.
The averaqe cam lobe wear was 36 ~m and 95.2 ~m after 20 and 40 hours of testing, respectively.

Comparative Example 3 This Comparative Example was conducted similar to that of Comparative Example 1, but in this test 0.80 weight percent of zinc dithiocarbamate and 0.41 weight percent nonyl phenol sulfide were added to the lube oil. The average cam lube wear was 39.9,um an~ 106 ~m after 2~ and 4n, resPectiVely~

Example 1 This test was conducted in a manner similar to that described hereinabove for the Comparative ÆxamPles. However, in this test the lube oil had added thereto all three of the above-noted additives, 0.41 weight percent zinc dialkyldithiophosohate, 0.30 weight percent zinc dithiocarba~ate and 0.50 weight percent para nonyl phenol sulfide. The a~erage cam lobe wear was only 9.2 ~m, ln~fi ~m, ll.fi ~m and 11.6 ~m after 20, 40, 60 and R0 hours o~ testing, respectively.

$~3 The data obtained in Comparative Examples 1-3 and in FxamPle l are Plotted on Figure 1. The average cam lobe wear in micrometers is plotted as a function of time. ~rom a review of the data presented in Figure 1 and in Table I it can be seen that the com~ination of zinc dialkYldithiophosphate, zinc dithiocarbamate and para nonyl phenol sulfide resulted in lower cam lobe wear than an equal weight of only two of the three additives.

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Claims (10)

1. A lube oil having improved properties comprising:

A. a basestock;

B. a metal phosphate;

C. a metal carbamate; and, D. a para alkyl hydroxy aryl sulfide.

2. The lube oil of claim 1 wherein the metal phosphate comprises a metal selected from the group consisting of Groups IB, IIB, VIB, VIIIB and mix-tures thereof.

3. The lube oil of claim 2 wherein the metal phosphate is selected from the group consisting of zinc, nickel, copper and mixtures thereof.

4. The lube oil of claim 3 wherein the metal phosphate comprises a metal alkylphosphate.

5. The lube oil of claim 1 wherein the metal carbamate comprises a metal dithiocarbamate.

6. The lube oil of claim 1 wherein the para alkyl hydroxy-aryl sulfide comprises a para alkyl phenol sulfide.

7. A lube oil comprising:

A. a basestock;

B. about 0.1 to about 1.0 wt.% metal dialkyldithiophosphate;

C. about 0.1 to about 1.3 wt.% metal dithiocarbamate; and, D. about 0.2 to about 2.0 wt. % para alkyl hydroxy-aryl sulfide, the concentration of components B, C and D being based on the basestock.

8. The lube oil of claim 7 comprising:

A. about 0.3 to about 0.6 wt.% metal dialkyldithiophosphate;

B. about 0.2 to about 0.8 wt.% metal dithiocarbamate; and, C. about 0.4 to about 0.8 wt. % para alkyl hydroxy-aryl sulfide, the concentrations of components A, B and C based on the basestock.

9. A method of improving the anti-wear properties of a lube oil basestock comprising the addition to the basestock of an effective amount of:

A. a metal phosphate;

B. a metal carbamate; and, C. a para alkyl hydroxy aryl sulfide.

10. The method of claim 9 comprising the addition to the basestock of an effective amount of:

A. zinc dialkyldithiophosphate;

B. zinc dithiocarbamate; and, C. para nonyl phenol sulfide.