Extreme pressure additive

There is disclosed a lubricant additive ingredient that imparts extreme pressure anti-wear properties to lubricant additive compositions. Specifically, there is disclosed a derivative of a vegetable oil triglyceride, a wax ester or a telomerized oil reacted with phosphorous pentasulfide to produce a phosphorous-sulfur (PS) extreme pressure additive.

TECHNICAL FIELD OF THE INVENTION 
The present invention provides a lubricant additive ingredient that imparts 
extreme pressure anti-wear properties to lubricant additive compositions. 
Specifically, the present invention provides a derivative of a base oil 
reacted with phosphorous and sulfur-containing material to produce a 
phosphorous-sulfur (PS) extreme pressure additive. 
BACKGROUND OF THE INVENTION 
The field of lubricant additives has seen a wide variety of materials used 
to reduce friction and wear between moving parts. Lubricants are composed 
principally of a base stock and lubricant additives. The lubricant 
additive provides the anti-friction and anti-wear characteristics to the 
lubricant. The base stock imparts improved viscosity and thermal oxidative 
stability, which can also be improved by the addition of various 
additives. One significant advance in the field was the invention of a 
material called a "telomer". The telomer invention is described in 
WO92/07051 and in U.S. Pat. No. 5,229,023, the disclosures of which are 
incorporated by reference herein. 
Briefly, a telomer is a polymerized triglyceride oil, principally derived 
from a seed oil, that has thermal oxidative stability and viscosity 
improvement characteristics that makes the telomer an essential component 
of a large variety of lubricant compositions. The process to synthesize 
telomers begins with a triglyceride and heats the oil in a non-oxidizing 
atmosphere with a trace water catalyst to lower the iodine number such 
that no more than 4% of the fatty acid chains of the telomerized vegetable 
oil are polyunsaturated. The triglyceride vegetable oils are characterized 
as having from about 10% to about 75% polyunsaturated fatty acid chains of 
from about 16 to about 26 carbon atoms in length. 
The present invention was made in an effort to improve the telomer product 
and other appropriate base oils by discovering a phosphorous sulfur "PS" 
derivative having the desirable viscosity and oxidative stability 
properties as a telomer and the anti-wear properties of an 
extreme-pressure additive. 
SUMMARY OF THE INVENTION 
The present invention provides an extreme pressure additive composition 
comprising the reaction product of a base oil with from about 0.01% to 
about 10.0% by weight of a phosphorus/sulfur compound under anaerobic 
conditions at temperatures from about 150.degree. C. to about 250.degree. 
C. for at least two hours but no longer than 48 hours, wherein the base 
oil is selected from the group consisting of triglyceride oils having at 
least a monounsaturated alkyl chain (branched or straight), wax esters 
having from about 6 to about 22 carbon atom chains (branched or straight) 
on either side of the ester group and containing at least one 
carbon-carbon double bond, and telomer oils having at least one 
carbon-carbon double bond in each triglyceride monomer in an aliphatic 
ring structure, and wherein the phosphorus/sulfur compound is selected 
from the group consisting of phosphorous pentasulfide (P.sub.2 S.sub.5) 
and its dimer P.sub.4 S.sub.10, P.sub.4 S.sub.3, P.sub.4 S.sub.5 and 
P.sub.4 S.sub.7. Preferably, the reaction product of the phosphorous 
pentasulfide reaction contains an amount of sulfur equal to about 2.5 
times the weight percent of phosphorous. Preferably, a second reaction 
step adds from about 0.1% to about 20.0% by weight of a dialkyl hydrogen 
phosphite or a monoalkyl hydrogen phosphite to increase the phosphorous 
content of the resulting reaction product to improve anti-friction 
characteristics, wherein the alkyl moiety of dialkyl hydrogen phosphite or 
monoalkyl hydrogen phosphite is independently selected from a saturated 
straight chain alkyl group having from two to 20 carbon atoms in length. 
The present invention further provides a process for synthesizing an 
extreme pressure PS additive composition, comprising reacting a base oil 
with from about 0.01% to about 10.0% by weight of a phosphorous/sulfur 
compound under anaerobic conditions at temperatures from about 150.degree. 
C. to about 250.degree. C. for at least two hours but no longer than 48 
hours, wherein the base oil is selected from the group consisting of 
triglyceride oils having at least a monounsaturated alkyl chain (branched 
or straight), wax esters having from about 6 to about 22 carbon atom 
chains (branched or straight) on either side of the ester group and 
containing at least one carbon-carbon double bond, and telomer oils having 
at least one carbon-carbon double bond in each triglyceride monomer in an 
aliphatic ring structure, and wherein the phosphorus/sulfur compound is 
selected from the group consisting of phosphorous pentasulfide (P.sub.2 
S.sub.5) and its dimer P.sub.4 S.sub.10, P.sub.4 S.sub.3, P.sub.4 S.sub.5 
and P.sub.4 S.sub.7. Preferably, the reaction product of the phosphorous 
pentasulfide reaction contains an amount of sulfur equal to about 2.5 
times the weight percent of phosphorous. Preferably, a second reaction 
step adds from about 0.1% to about 20.0% by weight of a dialkyl hydrogen 
phosphite or a monoalkyl hydrogen phosphite to increase the phosphorous 
content of the resulting reaction product to improve anti-friction 
characteristics, wherein the alkyl moiety of dialkyl hydrogen phosphite or 
monoalkyl hydrogen phosphite is independently selected from a saturated 
straight or branched chain alkyl group having from two to 20 carbon atoms.

DETAILED DESCRIPTION OF THE INVENTION 
The present invention provides an extreme pressure additive composition 
comprising the reaction product of a base oil with from about 0.01% to 
about 10.0% by weight phosphorous pentasulfide (P.sub.2 S.sub.5) under 
anaerobic conditions at temperatures from about 150.degree. C. to about 
250.degree. C. for at least two hours but no longer than 48 hours, wherein 
the base oil is selected from the group consisting of triglyceride oils 
having at least a monounsaturated alkyl chain (branched or straight), wax 
esters having from about 6 to about 22 carbon atom chains (branched or 
straight) on either side of the ester group and containing at least one 
carbon-carbon double bond, and telomer oils having at least one 
carbon-carbon double bond in each triglyceride monomer in an aliphatic 
ring structure. Preferably, the reaction product of the phosphorous 
pentasulfide reaction contains an amount of sulfur equal to about 2.5 
times the amount of phosphorous by weight. 
P.sub.2 S.sub.5 reacts with remaining unsaturated (carbon-carbon double 
bonds) on the telomer oil, triglyceride or wax ester, linking a 
phosphorous group with the site of unsaturation and allowing sulfur to 
cross link with other chains or with other P.sub.2 S.sub.5 molecules. When 
analyzed for elemental phosphorous, the final product of this reaction 
contains between 0.1% and 20.0% phosphorous by weight. When P.sub.2 
S.sub.5 is used, the amount of sulfur on the final product is in 
stoichiometric proportion to the amount of phosphorous. Specifically, for 
P.sub.2 S.sub.5 addition, the weight percent of sulfur is equal to 2.58 
times the weight percent of phosphorous. 
From a structural standpoint, the initial P.sub.2 S.sub.5 reaction will be 
P.sub.4 S.sub.10 (dimer of P.sub.2 S.sub.5) reacting with a carbon-carbon 
double bond of the base oil, shown structurally as: 
EQU R(CH.sub.2).sub.x --CH.dbd.CH--(CH.sub.2).sub.y --COOR 
wherein x and y are integers denoting the alkyl chain length (straight or 
branched) and R denotes the rest of the base oil molecule. This forms an 
initial reaction product with the addition of phosphorous and sulfur as 
follows: 
##STR1## 
This product can also be made into its phosphite adduct derivative by the 
second step addition of an alkyl (straight or branched) phosphorous 
derivative, such as 
##STR2## 
wherein R1 is a straight or branched alkyl group having from 2 to 20 
carbon atoms. The phosphite adduct gets added across the carbon-carbon 
double bond to form a product as follows: 
##STR3## 
wherein x, y, R and R.sub.1 are defined as above. 
The EP product is formed by a reaction of a base oil with a compound 
containing phosphorous and sulfur exclusively or phosphorous, sulfur and 
oxygen exclusively in stoichiometric ratios of 1%-50%, 3%-75%, and 0%-50% 
by weight respectively under anaerobic conditions at temperatures within 
the range of 150.degree. C. to 250.degree. C. for at least four hours. 
Preferably, the base oil is an unsaturated triglyceride, such as rapeseed 
oil (HEAR) or linseed oil or combinations thereof, and the preferred 
reactant is phosphorous pentasulfide. 
Preferably, a second reaction step adds from about 0.1% to about 20.0% by 
weight of a dialkyl hydrogen phosphite or a monoalkyl hydrogen phosphite 
to increase the phosphorous content of the resulting reaction product to 
improve anti-friction characteristics, wherein the alkyl moiety of dialkyl 
hydrogen phosphite or monoalkyl hydrogen phosphite is independently 
selected from a saturated straight or branched chain alkyl group having 
from two to 20 carbon atoms. 
The present invention further provides a process for synthesizing an 
extreme pressure additive composition comprising reacting a base oil with 
from about 0.01% to about 10.0% by weight phosphorous pentasulfide 
(P.sub.2 S.sub.5) under anaerobic conditions at temperatures from about 
150.degree. C. to about 250.degree. C. for at least two hours but no 
longer than 48 hours, wherein the base oil is selected from the group 
consisting of triglyceride oils having at least a monounsaturated alkyl 
chain, wax esters having from about 6 to about 22 carbon atom chains on 
either side of the ester group and containing at least one carbon-carbon 
double bond, and telomer oils having at least one carbon-carbon double 
bond in each triglyceride monomer in an aliphatic ring structure. 
Preferably, the reaction product of the phosphorous pentasulfide reaction 
contains an amount of sulfur equal to about 2.5 times the amount of 
phosphorous by weight. Preferably, a second reaction step adds from about 
0.1% to about 20.0% by weight of a dialkyl hydrogen phosphite or a 
monoalkyl hydrogen phosphite to increase the phosphorous content of the 
resulting reaction product to improve anti-friction characteristics, 
wherein the alkyl moiety of dialkyl hydrogen phosphite or monoalkyl 
hydrogen phosphite is independently selected from a saturated straight or 
branched chain alkyl group having from two to 20 carbon atoms. 
EXAMPLE 1 
This example illustrates the synthesis of an inventive EP additive using a 
mixture of rapeseed oil (HEAR) and linseed oil, both unsaturated 
triglyceride oils, as the base oil and phosphorous pentasulfide as the PS 
reactant. Approximately 500 g of a mixture of HEAR and linseed oil in a 
ratio of 60% HEAR oil to 40% linseed oil by weight into a reactor that was 
heated to 150.degree. C. Phosphorous pentasulfide (17.9 g) was slowly fed 
into the reactor over four hours of time. This was the equivalent of a 1% 
by weight on a phosphorous basis of P.sub.2 S.sub.5. It was important not 
to raise the temperature much above 150.degree. C. as this will cause the 
formation of poly-sulfide chains causing the product to increase viscosity 
and degrade thermal stability of the product. Phosphorous pentasulfide was 
fed continuously as the solids were observed to dissolve. After the 
reactants are added, the temperature of the reaction mixture was raised to 
200.degree. C. over a minimum time of 30 minutes and the reaction 
continued for 2 hours. The product was cooled under nitrogen gas at about 
100.degree. C., after which air exposure was allowed and the product was 
evaluated and analyzed. 
The products were subject to IR scans to determine the presence of new bond 
formations. FIG. 1 (Scan D) is a control IR scan of a 6000 sus telomer 
product formed by the same ratio of HEAR oil and linseed oil as provided 
in this example. FIG. 2 (scan A) shows the product of this example and 
should be compared with the control FIG. 1. FIG. 2 shows high absorption 
in the 900-1100 cm.sup.-1 range, showing the presence of 
phosphorous-sulfur bonds. The absorption at 1050 cm.sup.-1 indicates 
carbon-sulfur-phosphorous bonds and confirming the chemical reaction 
between the telomer and P.sub.2 S.sub.5 or P.sub.4 S.sub.10. 
EXAMPLE 2 
This example illustrates a synthesis of a preferred EP additive. The 
product from example 1 is further reacted with a dialkyl (butyl) hydrogen 
phosphite. Specifically, The product of example 1 is cooled down to only 
150.degree. C. and a charge of 2.7% (by weight) dibutyl hydrogen phosphite 
and 1% (by weight) di-tertiary butyl peroxide catalyst was added to the 
reactor over a five minute period. The product was maintained over heat 
and a nitrogen gas blanket for 3-5 hours, or until completion of the 
phosphite reaction had consumed the phosphite (as evidenced by 
condensation of butyl alcohol overhead. When the reaction was completed, 
nitrogen is discontinued and the product was cooled to about 100.degree. 
C. under a vacuum for discharge from the reaction vessel. 
FIG. 3 (scan B) shows an IR scan of the product of example 2. When compared 
with FIG. 2, the scan for the product of example 2 (FIG. 3) shows a larger 
1050 cm.sup.-1 absorption, indicating dibutyl ester 
carbon-oxygen-phosphorous bonds and a lack of double bonds at 3005 
cm.sup.-1, which indicates that the dibutyl hydrogen phosphite adducted to 
the remaining double bonds of the telomer base oil. 
EXAMPLE 3 
This example illustrates a comparison of various inventive EP additives 
with current commercial EP additives in various predictive test for 
anti-wear and anti-friction characteristics. A lubricity test using a 4 
Ball apparatus tested compared anti-wear properties of four EP products 
added as 2.5% by weight into 97.5% MVI Neutral Base Oil. Product A is a 
commercial chlorinated paraffin EP product (Mayfree 133, Mayco Oil and 
Chemical, Warminster, Pa.), product B is a commercial chlorine-free EP 
product (Idachlor SS, Ideos, Inc., Chicago, Ill.) product C is the product 
of example 1 herein and product D is the product of example 2 herein. The 
following table 1 shows that the inventive EP additives are superior to 
current commercial EP additives. 
TABLE 1 
______________________________________ 
Product 
Product 
Product 
Product 
Test Units Control A B C D 
______________________________________ 
4 Ball wear scar 
0.70 0.84 0.58 0.40 0.43 
ear dia mm 
4 Ball EP 
weld load 
&lt;100 160 200 250 250 
kg 
______________________________________ 
Tables 2 and 3 show a Falex pin and Vee block test comparison of products 
A-D and MVI vehicle control at various clamp forces. The MVI vehicle 
control tests failed at a load of 500 units?!. Table 2 shows the torque 
measurements and table 3 shows the temperature (.degree. C.) measurement. 
TABLE 2 
______________________________________ 
clamp force 
Control Product A 
Product B 
Product C 
Product D 
______________________________________ 
0 0 0 0 0 0 
250 13 12 9 9 12 
500 fail 27 13 16 18 
750 49 19 20 25 
1000 50 22 27 31 
1250 48 26 31 37 
1500 49 29 34 41 
1750 48 36 36 46 
2000 48 50 38 48 
2250 48 90 42 49 
2500 50 95 47 52 
2750 52 90 63 56 
3000 56 82 65 61 
______________________________________ 
TABLE 3 
______________________________________ 
clamp force 
Control Product A 
Product B 
Product C 
Product D 
______________________________________ 
0 120 120 120 120 120 
250 120 138 123 125 155 
500 fail 185 162 160 156 
750 185 164 160 157 
1000 185 168 162 158 
1250 191 175 164 159 
1500 198 180 167 162 
1750 205 179 171 166 
2000 212 178 176 170 
2250 217 185 182 176 
2500 223 218 188 182 
2750 230 246 200 191 
3000 236 262 218 200 
______________________________________ 
These data (tables 2 and 3) show reduced friction, as manifest by lower 
temperature readings, for the inventive EP additive over existing EP 
additives when added at the same concentration in MVI base oil. Moreover, 
the lower torque numbers (Table 2) provide evidence that the inventive EP 
additive provides superior results over existing EP additives. 
EXAMPLE 4 
This example illustrates a comparison of the inventive EP additive of 
example 1 in gear fluid compared with a commercial EP additive in gear 
fluid versus control gear fluids without additives in a pin and vee block 
test, which is a measure of friction and wear. Table 4 shows the torque 
readings (in pounds) over different run times for each of the four 
(additive or no additive) gear fluid formulas called Products A-D. Product 
A is the product of example 2 as 6% by weight in an 80W90 gear fluid (low 
pass). Product B is a high pass gear fluid which is an ASTM standard 
reference oil. Product C is the low pass gear fluid. Product D is a 
commercial GL5 approved gear oil (Valvoline). 
TABLE 4 
______________________________________ 
Falex pin and 
Product A Product B Product C 
Product D 
vee wear 
testing 
______________________________________ 
pin wear 126.2 mg 101.4 mg 219.9 mg 
193.4 mg 
(mg) 
max temp. 
200.2 245.8 230.1 255 
(.degree.C.) 
______________________________________ 
2 hr at 1250 
torque (lb.) 
torque (lb.) 
torque (lb.) 
torque (lb.) 
lb applied 
load 
______________________________________ 
250 9 9 11 9 
500 14 40 43 46 
750 22 39 45 58 
1000 21 40 49 57 
1250 24 46 56 43 
1250 30 38 44 36 
1250 33 34 42 32 
1250 32 41 42 32 
1250 34 39 46 31 
1250 33 34 43 29 
1250 32 33 42 30 
1250 35 32 43 37 
1250 39 34 41 39 
1250 41 36 43 36 
1250 40 38 41 38 
1250 40 53 40 30 
1250 42 58 40 29 
______________________________________