U.S. patent application number 10/293710 was filed with the patent office on 2004-05-13 for high temperature stability lubricant composition containing short chain acids and method for making the same.
Invention is credited to Aldrich, Haven S., Godici, Patrick E., Kim, Jeenok T., Krevalis, Martin A., Pafford, Bernie J., Schlosberg, Richard H..
Application Number | 20040092411 10/293710 |
Document ID | / |
Family ID | 32176181 |
Filed Date | 2004-05-13 |
United States Patent
Application |
20040092411 |
Kind Code |
A1 |
Godici, Patrick E. ; et
al. |
May 13, 2004 |
High temperature stability lubricant composition containing short
chain acids and method for making the same
Abstract
This invention generally relates to a high temperature stable
polyol ester lubricant composition containing short chain
carboxylic esters and a process for making the same. The polyol
ester lubricant compositions are preferably formed from
pentaerythritol and a mixture of C.sub.2 to C.sub.10 carboxylic
acids in which (1) from 95 to 80 mole %, based on total acids, are
C.sub.5 to C.sub.10 carboxylic acid, and (2) from 5 to 20 mole %,
based on total acids, are at least one C.sub.2 to C.sub.4
carboxylic acid The polyol ester lubricant compositions of the
present invention, specifically those using at least one C.sub.2 to
C.sub.4 carboxylic acid, are useful as base stock for high
temperature application such as Aviation Turbine Oils and exhibit
enhanced anti-deposition and oxidation stability compared with the
base polyol ester compositions while maintaining a good viscosity
index.
Inventors: |
Godici, Patrick E.;
(Naperville, IL) ; Kim, Jeenok T.; (Fairfax,
VA) ; Krevalis, Martin A.; (Houston, TX) ;
Pafford, Bernie J.; (Berkeley Heights, NJ) ; Aldrich,
Haven S.; (Baton Rouge, LA) ; Schlosberg, Richard
H.; (Bridgewater, NJ) |
Correspondence
Address: |
CAROL WILSON
BP AMERICA INC.
MAIL CODE 5 EAST
4101 WINFIELD ROAD
WARRENVILLE
IL
60555
US
|
Family ID: |
32176181 |
Appl. No.: |
10/293710 |
Filed: |
November 13, 2002 |
Current U.S.
Class: |
508/486 |
Current CPC
Class: |
C10N 2020/02 20130101;
C10M 2207/301 20130101; C10M 105/38 20130101; C10N 2030/10
20130101; C10M 2207/2835 20130101; C10N 2030/08 20130101; C10N
2030/02 20130101; C10N 2040/12 20130101; C10M 105/42 20130101; C10N
2040/13 20130101 |
Class at
Publication: |
508/486 |
International
Class: |
C10M 15/38 |
Claims
We claim:
1. A lubricant composition, comprising: a mixed polyol ester,
wherein the carboxylic acid portion of the ester, comprises: (a)
5-20 mole % of short chain acids; and, (b) 80-95 mole % of a
C.sub.5-10 aliphatic carboxylic acid; and the alcohol portion of
the ester, comprises: an aliphatic polyol.
2. A lubricant composition according to claim 1, wherein the
carboxylic acid portion of the ester, comprises: (a) 5-20 mole % of
a C.sub.2-4 carboxylic acid; (b1) 30-70 mole % of a C.sub.5
carboxylic acid; (b2) 0-15 mole % of an i-C.sub.9 carboxylic acid;
and (b3) 10-60 mole % of C.sub.7-10 carboxylic acids.
3. A lubricant composition according to claim 2, wherein the
carboxylic acid portion of the ester, comprises: (a) 10-20 mole %
of a C.sub.2-4 carboxylic acid; (b1) 30-60 mole % of a C.sub.5
carboxylic acid; (b2) 0-10 mole % of an i-C.sub.9 carboxylic acid;
and (b3) 10-55 mole % of linear C.sub.7-10 carboxylic acids.
4. A lubricant composition according to claim 3, wherein the
carboxylic acid portion of the ester, comprises: (a) 10-15 mole %
of a C.sub.2-4 carboxylic acid; (b1) 30-60 mole % of valeric acid;
(b2) 0-10 mole % of 3,3,5-trimethylhexanoic acid; and (b3) 10-55
mole % of a mixture of n-heptanoic acid, n-octanoic acid, and
n-decanoic acid.
5. A lubricant composition according to claim 1, wherein the
aliphatic polyol, comprises: 4-7 carbon atoms and 2-4 esterifiable
hydroxyl groups.
6. A lubricant composition according to claim 5, wherein the
aliphatic polyol is selected from neopentyl glycol, 2,2-dimethylol
butane, trimethylol ethane, trimethylol propane, trimethylol
butane, mono-pentaerythritol, technical grade pentaerythritol,
dipentaerythritol, tri-pentaerythritol, ethylene glycol, propylene
glycol and polyalkylene glycols.
7. A lubricant composition according to claim 6, wherein the
aliphatic polyol is selected from trimethylolpropane, technical
grade pentaerythritol, monopentaerythritol, dipentaerythritol,
neopentyl glycol, and tripentaerythritol.
8. A lubricant composition according to claim 7, wherein the
aliphatic polyol is selected from technical grade pentaerythritol,
trimethylolpropane, and neopentyl glycol.
9. A lubricant composition according to claim 8, wherein the
aliphatic polyol is technical grade pentaerythritol.
10. A lubricant composition according to claim 1, wherein mixed
polyol ester is formed by esterifying a mixture of the short chain
C.sub.2-4 carboxylic acids and the C.sub.7-10 carboxylic acids.
11. A lubricant composition according to claim 1 having an inclined
panel rating at 580.degree. F. of less than 4.00.
12. A lubricant composition according to claim 1 having an inclined
panel rating at 590.degree. F. of less than 5.00.
13. A lubricant composition according to claim 1 further comprising
0.5 to 15 wt % of a lubricant additive package.
14. A process for preparing a mixed polyol ester, comprising: (i)
contacting 5-20 mole % of short chain C.sub.2-4 carboxylic acids
with 80-95 mole % of a C.sub.5-10 aliphatic carboxylic acid; and,
(ii) esterifying the resulting mixture with an aliphatic
polyol.
15. A process for preparing a mixed polyol ester, comprising: (i)
esterifying a short chain C.sub.2-4 carboxylic acid with an
aliphatic polyol; and, (ii) contacting the esterification mixture
with a C.sub.5-10 aliphatic carboxylic acid; wherein the resulting
ester is a mixed ester and the carboxylic acid portion of the
ester, comprises: (a) 5-20 mole % of short chain C.sub.2-4
carboxylic acids; and, (b) 8095 mole % of a C.sub.5-10 aliphatic
carboxylic acid.
16. A process for preparing a mixed polyol ester, comprising: (i)
esterifying a C.sub.5-10 aliphatic carboxylic acid with an
aliphatic polyol; and, (ii) contacting the esterification mixture
with short chain C.sub.2-4 carboxylic acids; wherein the resulting
ester is a mixed ester and the carboxylic acid portion of the
ester, comprises: (a) 5-20 mole % of short chain C.sub.2-4
carboxylic acids; and, (b) 8095 mole % of a C.sub.5-10 aliphatic
carboxylic acid.
17. A method of lubricating a turbine engine comprising operating
the engine and lubricating the engine with a lubricant composition
as claimed in claim 1.
18. The use of the lubricant composition as defined in claim 1 for
enhancing the thermal and oxidative stability of a lubricating oil.
Description
FIELD OF THE INVENTION
[0001] The present invention relates, generally, to a high
temperature stable lubricant polyol ester composition containing
short chain acids and a process of making the same. More
particularly, this invention relates to ester derivatives of
pentaerythritol and a mixture of aliphatic carboxylic acids
containing at least one C.sub.2 to C.sub.4 chain acids.
BACKGROUND OF THE INVENTION
[0002] Organic compositions, such as mineral oils and lubricating
compositions, are subject to deterioration by oxidation and in
particular are subject to such deterioration at high temperatures
in the presence of air. This deterioration often leads to buildup
of insoluble deposits that can foul engine parts, deteriorate
performance, and increase maintenance. This is particularly the
case for lubricating oils used in jet aircraft where wide
temperature ranges and extreme operating conditions are likely to
be encountered. Proper lubricating of aircraft gas turbines, for
example, requires ability to function at bulk oil temperatures from
as low as minus 60.degree. C. to as high as 230.degree.-280.degree.
C. Such an extreme temperature range places unique demands on the
characteristics of the lubricant. Aviation jet turbine lubricants
require superior thermal and oxidative stability, good
viscosity-temperature characteristics (high VI), low volatility and
a low pour point. Organic hydrocarbon-based oils are typically not
robust enough to satisfy these requirements. Thus, aviation
applications have relied on the superior performance
characteristics of synthetic ester lubricants.
[0003] Ester base lubricating oil compositions prepared from
polyols such as neopentyl glycol, trimethylolpropane or
pentaerythritol, and a mixture of fatty acids and containing
selected additive combinations are well known. These lubricants are
functional over a wide temperature range and exhibit good thermal
and oxidative stability. An ester base lubricant composition that
will operate under more severe conditions, however, is a major goal
of lubricant manufacturers. This invention addresses that
continuing need by providing a polyol ester basestock composition
containing short chain acids having higher temperature stability.
These polyol esters exhibit enhanced anti-deposition and oxidation
stability over polyol ester to which short chain acids were not
added.
[0004] Many prior art references generally discuss the use of short
chain acids to form synthetic ester base lubricants. However, none
of the references address the need for higher thermal and oxidative
stability in certain esters used in aviation turbo oils ("ATO"s)
and the benefits provided by the use of at least one C.sub.2 to
C.sub.4 chain acids.
[0005] U.S. Pat. No. 3,681,440 to Monsanto Company discloses the
use of C.sub.1 to C.sub.12 aromatic or aliphatic carboxylic acids
to provide new esters of tetrahydroxy dineoalkyl ethers and their
use as lubricant basestocks.
[0006] U.S. Pat. No. 3,756,952 to Texaco Inc. discloses a synthetic
lubricating oil composition comprising a major portion of aliphatic
ester base oil formed by the reaction of pentaerythritol or
trimethylolpropane and an organic monocarboxylic acid having 2 to
18 carbon atoms per molecule containing a certain weight percent of
ammonium thiocyanate.
[0007] U.K. Patent No. 1,180,388 to The British Petroleum Company
discloses an ester basestock consisting of a synthetic lubricant
for aero gas turbines prepared by reacting together under
esterification conditions an aliphatic mono- and/or polyhydric
alcohol having 5-15 carbon atoms per molecule and an aliphatic
mono- and/or polycarboxylic acid having 2-14 carbon atoms per
molecule.
[0008] U.K. Patent No. 1,402,697 to Texaco Development Corporation
discloses a synthetic lubricating oil composition comprising a
major portion of an aliphatic ester base oil having lubricating
properties formed from the reaction of pentaerythritol, a
polypentaerythritol or trimethylolpropane and an organic
monocarboxylic acid having from 2 to 18 carbon atoms and a
critically balanced blend of additives.
[0009] U.S. Pat. No. 5,503,761 is directed to a synthetic ester
base stock having reduced deposit formation. The base stock is the
esterified product of technical pentaerythritol and a mixture of
C.sub.5 to C.sub.10 carboxylic acids. Notwithstanding the benefits
of such base stock, there remains a need for synthetic ester base
stocks that have even further reduced tendencies to form deposits
under conditions of use.
SUMMARY OF THE INVENTION
[0010] It has now been discovered that polyol ester lubricant
compositions formed from polyols and a mixture of C.sub.2 to
C.sub.10 aliphatic carboxylic acids in which the mixture comprises
(1) 95 to 80 mole %, based on total acids of C.sub.5 to C.sub.10
carboxylic acid, and (2) from 5 to 20 mole %, based on total acids,
of at least one C.sub.2 to C.sub.4 carboxylic acid exhibit enhanced
thermal and oxidative stability compared to polyol ester lubricant
compositions that do not contain at least one C.sub.2 to C.sub.4
carboxylic acid.
[0011] The polyol ester lubricant compositions of the present
invention, specifically those using least one C.sub.2 to C.sub.4
carboxylic acid, are useful as base stock for high temperature
application such as ATOS and exhibit enhanced anti-deposition and
oxidation stability compared with the base polyol ester
compositions while maintaining a good viscosity index.
[0012] The polyol ester base stock of the present invention may be
blended with additive packages to provide a turbo oil composition
with improved cleanliness.
DETAILED DESCRIPTION OF THE INVENTION
[0013] In the following description, for purposes of explanation
and not limitation, specific details are set forth, such as
particular acids, esterification processes, testing procedures,
etc. in order to provide a thorough understanding of the present
invention. However, it will be apparent to one skilled in the art
that the present invention may be practiced in other embodiments
that depart from these specific details. Detailed descriptions of
well-known processes, acids, and methods for manufacturing the same
are omitted so as not to obscure the description of the present
invention.
[0014] The polyol ester lubricant compositions of the present
invention, comprise: a polyol ester, wherein the carboxylic acid
portion of the ester, comprises: (a) short chain carboxylic acids
and (b) conventional acids, and the alcohol portion of the ester,
comprises: an aliphatic polyol. Polyol esters from a mixture of
acids ester, as used herein, is intended to mean a polyol ester
having at least two different carboxylic acids (e.g., C.sub.2 to
C.sub.4 short chain carboxylic acid and C.sub.5 to C.sub.10
conventional carboxylic acid) attached to the same polyol molecule.
The amount of each individual carboxylic acid present during
esterification will determine how many of the polyol molecules
present in the esterification process will form esters having short
chain acids. One of ordinary skill in the art will recognize that
during an esterification process to form polyol esters having short
chain acids, a portion of polyol esters without short chain acids
will likely be formed. Thus, the present polyol ester compositions
are intended to cover compositions comprising a mixture of short
chain acids and conventional C.sub.5 to C.sub.10 acids mixed polyol
esters having the defined mole percentages of short chain
carboxylic acids.
[0015] Preferably, the carboxylic acid portion of the ester
comprises: 5, 10, 15, to 20 mole % of the short chain carboxylic
acid and the remaining portion being the conventional acids.
Preferably, the ester comprises 10 to 15 mole % of the short chain
acids. One of ordinary skill in the art would recognize that the
amount of short chain carboxylic acid used would depend on the
viscometric specifications required for the desired
application.
[0016] Conventional acids, as used herein, are carboxylic acids
typically used in lubricating compositions. Preferably, these are
C.sub.5 to C.sub.10 aliphatic acids. The C.sub.5 to C.sub.10
carboxylic acids which are used to prepare the synthetic ester
lubricant base stock are aliphatic carboxylic acids having minimal
number of reactive hydrogens while meeting MIL-L-23699
specifications on the low temperature flow and elastomer
compatability. The aliphatic acids are monocarboxylic acids or a
mixture of mono- and di-carboxylic acids and are linear or
branched. Preferably, the aliphatic acids are monocarboxylic acids.
Even more preferably, the acids are a mixture of C.sub.5,
i-C.sub.9, and linear C.sub.7-10 acids. It is noted that C.sub.7-10
is intended to represent a mixture of C.sub.7, C.sub.8, C.sub.9,
and C.sub.10 acids. Preferably, this mixture comprises only linear
acids. Even more preferably, this mixture comprises linear C.sub.7,
linear C.sub.8, and linear C.sub.10. Still more preferably, the
acids are a mixture of a C.sub.5, i-C.sub.9, and linear C.sub.7
(e.g., n-heptanoic acid), C.sub.8 (e.g., n-octanoic acid), and
C.sub.10 (e.g., n-decanoic acid) acids. A preferred C.sub.5 acid is
valeric acid. A preferred i-C.sub.9 acid is 3,5,5-trimethylhexanoic
acid.
[0017] The carboxylic acid portion of the polyol ester preferably,
comprises: 5-20 mole % of the short chain acid, 30-70 mole %
C.sub.5, 0-15 mole % i-C.sub.9, and 10-60 mole % C.sub.7-10. More
preferably, the carboxylic acid portion of the polyol ester,
comprises: 10-20 mole % of the short chain acid, 30-60% C.sub.5,
0-10 mole % i-C.sub.9, and 10-55 mole % of linear C.sub.7-10. Even
more preferably, the carboxylic acid portion of the mixed polyol
ester, comprises: 10-15 mole % of the short chain acid, 30-60 mole
% C.sub.5, 0-10 mole % i-C.sub.9, and 10-55 mole % of a mixture of
n-heptanoic acid, n-octanoic acid, and n-decanoic acid. Still more
preferably, the carboxylic acid portion of the polyol ester,
comprises: 10-15 mole % of the short chain acid, 30-60 mole % of
valeric acid, 0-10 mole % of 3,5,5-trimethylhexanoic acid, and
10-55 mole % of a mixture of n-heptanoic acid, n-octanoic acid, and
n-decanoic acid. The preferred distribution of C.sub.5 to C.sub.10
carboxylic acids is described in U.S. Pat. No. 5,503,761.
[0018] The alcohol used to form the ester portion of the polyol
ester lubricant composition of the present invention may be any one
or more of neopentyl glycol, trimethylolpropane, pentaerythritol,
dipentaerythritol, tripentaerythritol or tetrapentaerythritol. The
preferred polyol is pentaerythritol or Technical pentaerythritol
(TechPE). Technical pentaerythritol is a mixture that includes
about 85 to 92 wt % monopentaerythritol and 8 to 15 wt %
dipentaerythritol. A typical commercial technical pentaerythritol
contains about 88 wt % monopentaerythritol and about 12 wt % of
dipentaerythritol. The technical pentaerythritol may also contain
some tri and tetra pentaerythritol which are typically formed as
by-products during the production of technical pentaerythritol.
[0019] The polyol ester of the present invention can be prepared by
esterifying the short chain acid(s) and conventional acid(s) with
the aliphatic polyol. Thus, a process of making the present
composition, comprises: (a) contacting 5-20 mole % of a short chain
carboxylic acid and 95-80 mole % of a C.sub.5-20 aliphatic
carboxylic acid; and, (b) esterifying the resulting mixture with an
aliphatic polyol. Alternatively, a process of making the present
composition, comprises: (a) esterifying a short chain carboxylic
acid with an aliphatic polyol; and, (b) contacting the
esterification mixture with a C.sub.5-20 aliphatic carboxylic acid.
Alternatively, a process of making the present composition
comprises: (a) esterifying a C.sub.5-20 aliphatic carboxylic acid
with an aliphatic polyol; and, (b) contacting the esterification
mixture with a short chain carboxylic acid. In both of the
alternative processes, the second component can be added during
esterification of the first component or after esterification of
the first component. As one of ordinary skill in the art
recognizes, different acids esterify at different rates. Thus, the
selection of the method of esterification may depend on the
activity of the chosen short chain carboxylic acid(s), conventional
acid(s) and the aliphatic polyol. In addition, the choice of when
to add the second component will also be based on the reactivity of
the first component. Thus, one could choose to completely form an
ester from either short chain acid(s) or conventional acid(s) with
the polyol, and then the mixed polyol ester could be formed.
Alternatively, an ester of short chains acid(s) could be partially
formed at the time the second component is introduced. Preferably,
the addition of the acids to the polyol is staged with the lower
boiling point acid being added first. Regardless of the chosen
route, the desired outcome is a polyol ester, wherein the
carboxylic acid portion of the ester, comprises: (a) 5-20 mole % of
a short chain carboxylic acid and (b) 95-80 mole % of conventional
acids, and the alcohol portion of the ester, comprises: an
aliphatic polyol.
[0020] The esterification reaction can be run using conventional
methods and techniques known to those skilled in the art. For
example, technical pentaerythritol can be heated with the desired
short chain and conventional acid mixture, optionally in the
presence of a catalyst. Generally, a slight excess of the acids is
employed to force the reaction to completion. Water is removed
during the reaction and any excess acid is then stripped from the
reaction mixture. The esters of technical pentaerythritol may be
used without further purification or may be further purified using
conventional techniques such as distillation. The process may be
carried out continuously or discontinuously.
[0021] The lubricant composition of the present invention
preferably has at least one of the following uses: crankcase engine
oils, two-cycle engine oils, catapult oils, hydraulic fluids,
drilling fluids, turbine oils (e.g., aircraft turbine oils),
greases, compressor oils, gear oils and functional fluids.
Preferably, the lubricant composition of the present invention is
used in an aero-derived, gas turbine engines (e.g., jet turbine
engines, marine engines, and power generating applications).
[0022] The lubricant compositions of the present invention may also
comprise other conventional lubricant additives. Lubricating oil
additives are described generally in "Lubricants and Related
Products" by Dieter Klamann, Verlag Chemie, Deerfield, Fla., 1984,
and also in "Lubricant Additives" by C. V. Smalheer and R. Kennedy
Smith, 1967, pp. 1-11, the contents of which are incorporated
herein by reference.
[0023] Lubricating oil additives are also described in U.S. Pat.
Nos. 6,043,199, 5,856,280, and 5,698,502, the contents of which are
incorporated herein by reference. The lubricant composition
according to the present invention preferably comprises about 0 to
15%, preferably 2 to 10 wt %, most preferably 3 to 8% by weight of
a lubricant additive package. Thus, the lubricant composition
according to the present invention would comprise about 85 to 99.5
wt % polyol ester base stock and about 0.5 to 15 wt % conventional
additive package.
[0024] Thus, fully formulated turbine oils may contain one or more
of the following classes of additives: antioxidants, antiwear
agents, extreme pressure additives, antifoamants, detergents,
hydrolytic stabilizers, metal deactivators, other rust inhibitors,
etc. in addition to the dispersant of the present invention. Total
amounts of such other additives can be in the range 0.5 to 15 wt %
preferably 2 to 10 wt %, most preferably 3 to 8 wt % of the fully
formulated lubricant.
[0025] Antioxidants, which can be used, include aryl amines, e.g.
phenylnaphthylamines and dialkyl diphenylamines and mixtures
thereof, hindered phenols, phenothiazines, and their derivatives.
The antioxidants are typically used in an amount in the range 1 to
5 wt % of the fully formulated lubricant.
[0026] Antiwear/extreme pressure additives include hydrocarbyl
phosphate esters, particularly trihydrocarbyl phosphate esters in
which the hydrocarbyl radical is an aryl or alkaryl radical or
mixture thereof. Particular antiwear/extreme pressure additives
include tricresyl phosphate, triaryl phosphate and mixtures
thereof. Other or additional anti wear/extreme pressure additives
may also be used. The antiwear/extreme pressure additives are
typically used in an amount in the range 0 to 4 wt %, preferably 1
to 3 wt % of the fully formulated lubricant.
[0027] Industry standard corrosive inhibitors may also be included
in the turbo oil. Such known corrosion inhibitors include the
various triazols, for example, tolyltriazol, 1,2,4 benzotriazol,
1,2,3 benzotriazol, carboxy benzotriazole, allylated benzotriazol.
The standard corrosion inhibitor additive can be used in an amount
in the range 0.02 to 0.5 wt %, preferably 0.05 to 0.25 wt % of the
fully formulated lubricant. Other rust inhibitors common to the
industry include the various hydrocarbyl amine phosphates and/or
amine phosphates.
[0028] Foam control can be provided by many compounds including an
antifoamant of the polysiloxane type, e.g., silicone oil or
polydimethyl siloxane.
[0029] Another additive that can be used is an anti-deposition and
oxidative additive. A typical anti-deposition and oxidation
additive is a sulfur containing carboxylic acid (SCCA) as described
in U.S. Pat. No. 5,856,280. The SCCA derivative is used in an
amount in the range 100 to 2000 ppm, preferably 200 to 1000 ppm,
most preferably 300 to 600 ppm.
[0030] As previously indicated, other additives can also be
employed including hydrolytic stabilizers, pour point depressants,
anti foaming agents, viscosity and viscosity index improver, as
well as other additives useful in lubricating oil compositions.
[0031] The individual additives may be incorporated into the
present lubricant composition in any convenient way. Thus, each of
the components can be added directly to the base stock by
dispersing or dissolving it in the base stock at the desired level
of concentration. Such blending may occur at ambient temperature or
at an elevated temperature. Preferably, all the additives except
for the viscosity modifier and the pour point depressant are
blended into a concentrate or additive package, which is
subsequently blended into base stock to make finished lubricant.
Use of such concentrates in this manner is conventional. The
concentrate will typically be formulated to contain the additive(s)
in proper amounts to provide the desired concentration in the final
formulation when the concentrate is combined with a predetermined
amount of base lubricant. The concentrate is preferably made in
accordance with the method described in U.S. Pat. No. 4,938,880,
the contents of which are incorporated herein by reference. That
patent describes making a pre-mix of ashless dispersant and metal
detergents that is pre-blended at a temperature of at least about
100.degree. C. Thereafter, the pre-mix is cooled to at least
85.degree. C. and the additional components are added.
[0032] The present invention is further described by reference to
the following non-limiting examples. These examples are provided
for purposes of explanation and not limitation. Specific polyols,
carboxylic acids and esterification processes are used in order to
provide a thorough understanding of the present invention. However,
it will be apparent to one skilled in the art that the present
invention may be practiced in other embodiments that depart from
these specific examples.
EXAMPLE 1
[0033] Synthesis of Novel Ester Containing C.sub.2 to C.sub.4
Carboxylic Acid
[0034] The procedure for preparing the polyol esters of the present
invention was generally as follows:
[0035] A multi-necked round bottom flask was used for the reaction
vessel. This reactor was fitted with a means of stirring, an inlet
for nitrogen (reactor is purged with N.sub.2 prior to the run and
an N.sub.2 flow is maintained during the run), and a connection to
a Dean-Stark apparatus and a condenser. The polyol (technical grade
pentaerythritol) plus the C.sub.5 to C.sub.10 acids were charged to
the reactor. In at least two of the runs, a small amount of
entrainer (xylene) was also added. The reaction mixture was heated
to 220.degree. C. and the mixture refluxed to remove the water of
reaction (oil/water are separated in the Dean-Stark apparatus and
the oil returned to the reactor). Vacuum is pulled as needed to
maintain the reflux. The reaction was continued under these
conditions until approximately the stoichiometric amount of water
was removed from the reactor.
[0036] At this stage, the reaction mixture was cooled to a
temperature below the boiling point of the acid anhydride to be
added (acetic anhydride, proprionic anhydride or butyric
anhydride.) The anhydride was slowly added dropwise using an
additional funnel. Once addition was complete, the reaction mixture
was heated until reflux began, then maintained at reflux for
approximately three hours.
[0037] At the end of the reaction period, unreacted acids were
removed at 220.degree. C. under vacuum. The reaction mixture was
then neutralized with an Na.sub.2CO.sub.3 solution (only if acid
number is above target of 0.05 mg KOH/g), and de-colored using
"admix," a blend of activated carbon and filter aid. The
neutralization/de-coloring step was carried out at 90.degree. C.
for 2-3 hours. At the end of this time, a vacuum was pulled on the
reactor and the temperature was raised to 100.degree. C. to remove
water. The mixture was then filtered, giving the desired
product.
[0038] Details of the runs, along with the results from the
analytical tests carried out, are provided in Tables I-IV
below.
[0039] Based on the weight of acids charged to the reactor, the
distribution of acids for each run is as follows. The actual acid
content of each ester is likely to be somewhat different than that
based on the feed to the reactor, as the acids do have different
reactivities.
1TABLE I Acid Feed Content (Mole %) Run Acid Content, Mole % (based
on feed to reaction) Number n-C.sub.5 N-C.sub.7 n-C.sub.8/10
i-C.sub.9 C.sub.2 C.sub.3 C.sub.4 1038-88 41.6 19.2 12.4 6.8 20.0 0
0 1038-90 41.6 19.2 12.4 6.8 0 0 20.0 1038-94 46.8 21.6 14.0 7.6
10.0 0 0 1038-97 46.8 21.6 14.0 7.6 0 0 10.0 1038-138 41.6 19.2
12.4 6.8 0 20.0 0 1038-140 46.8 21.6 14.0 7.6 0 10.0 0 Control 54.0
22.8 15.0 8.2 0 0 0 Base Ester
[0040]
2TABLE II Acid Feed Content (grams) Feed Amount, g Short Run Chain
Number Tech PE n-C.sub.5 n-C.sub.7 n-C.sub.8/10 i-C.sub.9 Acid
Amount 1038-88 335.5 390.4 229.6 176.8 98.9 C.sub.2 224.4 1038-90
333.5 390.4 229.6 176.8 98.9 C.sub.4 349.6 1038-94 319.0 420.0
247.1 190.3 106.3 C.sub.2 107.8 1038-97 304.5 400.9 235.8 181.7
101.4 C.sub.4 159.4 1038-138 333.5 390.4 229.6 176.8 98.9 C.sub.3
287.0 1038-140 319.0 420.0 247.1 190.3 106.3 C.sub.3 137.4
[0041]
3TABLE III Analytical Tests Stage 1 Anhydride Kinematic Theoretical
Actual Addition Viscosity eSt HPDSC, OH# by H.sub.2O, g H.sub.2O, g
Temp, .degree. C. 40.degree. C. 100.degree. C. VI min FTIR 1038-88
133 128 133 25.77 4.81 107 41.85 10.07 1038-90 133 130 188 22.88
4.66 123 NA 0.15 1038-94 143 142 130 24.74 4.78 114 42.99 5.56
1038-97 136.5 130+ 188 23.38 4.73 124 47.05 6.07 1038-138 133 135
160 22.06 4.51 118 27.82 2.94 1038-140 149 148+ 160 23.23 4.69 121
43.23 9.55 Control 26.01 4.98 118 Base Ester
[0042] Table III demonstrates that a polyol ester base oil of
approximately 5 centistokes was produced in accordance with
industry standard.
EXAMPLE II
Performance Testing
[0043] Inclined Panel Deposit Test (IPDT)
[0044] The IPDT is generally used to predict field performance in
the oil-washed areas 10 of the engine, and successfully correlates
with more expensive bearing rig tests. The IPDT is typically
employed as a screener test for additives in base stocks and fully
formulated lubricants.
[0045] Test Procedure
[0046] During the IPDT, the test oil flows at a rate of 60 mL/h
over a heated panel (stainless steel 304) that is inclined at an
angle of 4 degrees with respect to the horizontal. Moist air flows
through the system continuously during the test at a rate of 12
L/h. The panel is heated to a specified temperature (up to
600.degree. F.) and is held constant for the entire test duration
of 24 hours. Oil flowing off the panel is collected in a sump and
is continuously recirculated by a positive displacement pump.
[0047] When the test is complete, the deposit formed on the panel
during the test is rated using a demerit rating scale. The IPDT
uses the same deposit demerit system as the High Temperature
Bearing Test. (FED. Test Method STD. No. 791C, Method 3410.1).
During the rating process, the total deposit is portioned into
different deposit types, depending on the severity of the deposit.
Each type of deposit is assigned a demerit factor related to the
deposit severity. The demerit factor is multiplied by the area of
the deposit type to obtain the demerits for that particular deposit
type. The total number of demerits is then obtained by adding
together the demerits for each deposit type. Dividing the total
number of demerits by the total area of the deposits gives the
final deposit demerit panel rating. Only the oil wetted areas of
the panel are rated. Varnish deposits rate from 0 (clean metal) to
5 (heavy varnish). Sludge deposits rate from 6 (light) to 8
(heavy). Carbon deposits rate from 9 (light carbon) to 11
(heavy/thick carbon). Higher ratings (12 to 20) are given to carbon
deposits that crinkle or flake away from the metal surface during
the test. The total weight of the deposit formed in 24 hours is
also measured.
[0048] Table 1 shows IPDT rating and deposit weight of short chain
acid esters made in Example 2 and compares their performance with
that of the base ester without the short chain acids. The additive
system was held constant in all of these compositions. The deposit
control capability of each experimental formulation was tested by
IPDT at two separate temperatures: 580.degree. F. and 590.degree.
F.
[0049] In the IPDT runs at 580.degree. F. and 590.degree. F., the
incorporation of 10 or 20% C.sub.2, C.sub.3 or C.sub.4 acids gave
noticeable improvement in the panel rating. In addition, increasing
the short chain acid concentration to 20% resulted in better
anti-deposition performance for the C.sub.4 acid at both
580.degree. F. and 590.degree. F. and for the C.sub.2 acid at
590.degree. F.
4TABLE IV IPDT Performance of Esters With or Without Short Chain
Acids Molar % of IPDT @ 590.degree. F. Run Short Chain IPDT @
580.degree. F. Panel Deposit Number Acid Panel Rating Deposit (g)
Rating (g) Control None.sup.1 4.07 0.30 5.23 0.39 1038-94 10%
C.sub.2 2.82 0 21 4.73 0.34 1038-140 10% C.sub.3 2.49 0.11 3.62
0.29 1038-97 10% C.sub.4 3.03 0.24 3.85 0.36 1038-88 20% C.sub.2
Not available Not available 4.19 0.34 1038-138 20% C.sub.3 3.81
0.33 4.34 0.39 1038-90 20% C.sub.4 2.69 0.14 3.46 0.15 .sup.1median
value of 33 samples
* * * * *