U.S. patent application number 10/703951 was filed with the patent office on 2004-10-21 for synthetic lubricant base stock formed from high content branched chain acid mixtures.
Invention is credited to Carr, Dale D., Schaefer, Thomas G..
Application Number | 20040209788 10/703951 |
Document ID | / |
Family ID | 22882533 |
Filed Date | 2004-10-21 |
United States Patent
Application |
20040209788 |
Kind Code |
A1 |
Schaefer, Thomas G. ; et
al. |
October 21, 2004 |
Synthetic lubricant base stock formed from high content branched
chain acid mixtures
Abstract
An improved synthetic ester lubricant base stock formed by
reacting a neopentyl glycol with a mixture of aliphatic
monocarboxylic acids is provided. The mixture of acids includes
straight-chain acids having from 5 to 10 carbon atoms and an
iso-acid having from 7 to 10 carbon atoms, preferably iso-nonanoic
acid, wherein the iso-acid is present in about 60-90 weight percent
of the acid charge. The base stock is mixed with a conventional
ester lubricant additive package to form a lubricant having a
viscosity at 210.degree. F. of at least 7.0 with the resulting
lubricants having a decreased tendency to form deposits in high
temperature chain oil applications.
Inventors: |
Schaefer, Thomas G.;
(Parlin, NJ) ; Carr, Dale D.; (Morristown,
NJ) |
Correspondence
Address: |
REED SMITH, LLP
ATTN: PATENT RECORDS DEPARTMENT
599 LEXINGTON AVENUE, 29TH FLOOR
NEW YORK
NY
10022-7650
US
|
Family ID: |
22882533 |
Appl. No.: |
10/703951 |
Filed: |
November 7, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10703951 |
Nov 7, 2003 |
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10260190 |
Sep 30, 2002 |
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10260190 |
Sep 30, 2002 |
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08234722 |
Apr 28, 1994 |
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08234722 |
Apr 28, 1994 |
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07712190 |
Jun 7, 1991 |
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Current U.S.
Class: |
508/485 |
Current CPC
Class: |
C10N 2040/255 20200501;
C10N 2040/40 20200501; C10N 2040/50 20200501; C10N 2040/34
20130101; C10M 2215/223 20130101; C10N 2040/00 20130101; C10N
2040/44 20200501; C10M 2207/282 20130101; C10N 2040/13 20130101;
C10N 2040/38 20200501; C10M 2215/065 20130101; C10N 2040/30
20130101; C10M 2207/281 20130101; C10N 2030/08 20130101; C10M
2215/064 20130101; C10N 2030/04 20130101; C10N 2040/06 20130101;
C10N 2040/135 20200501; C10M 2223/041 20130101; C10N 2040/251
20200501; C10M 169/04 20130101; C10M 2207/283 20130101; C10M
2207/2835 20130101; C10N 2070/00 20130101; C10M 2207/286 20130101;
C10N 2040/28 20130101; C10N 2030/02 20130101; C10N 2040/42
20200501; C10M 105/38 20130101; C10N 2040/25 20130101; C10N 2040/32
20130101; C10N 2040/36 20130101 |
Class at
Publication: |
508/485 |
International
Class: |
C10M 15/38 |
Claims
What is claimed is:
1. A synthetic ester lubricant base stock, comprising the reaction
product of: a neopentyl polyol; and an acid mixture including (1)
at least one straight-chain acid having between about 5 and 10
carbon atoms and (2) an iso-acid selected from the group consisting
of iso-C.sub.7 acid, iso-C.sub.8 acid, iso-C.sub.9 acid,
iso-C.sub.10 acid and mixtures thereof; the iso-acid present in an
amount of from about 60 to 90 percent by weight of the acid
mixture; and the resulting mixture of ester when admixed with a
synthetic ester lubricant additive package has a viscosity at
210.degree. F. of at least about 7.0 centistokes.
2. The synthetic ester lubricant base stock of claim 1, wherein the
iso-acid is iso-nonanoic acid.
3. The synthetic ester lubricant base stock of claim 1, wherein the
iso-C.sub.9 acid is 3,5,5-trimethylhexanoic acid.
4. The synthetic ester lubricant base stock of claim 1, wherein the
neopentyl polyol is selected from the group consisting of
monopentaerythritol, dipentaerythritol, mixtures of
trimethylolpropane and/or neopentyl glycol with a higher viscosity
neopentyl polyol and mixtures thereof.
5. The synthetic ester lubricant base stock of claim 1, wherein the
polyol is a mixture of monopentaerythritol and
dipentaerythritol.
6. The synthetic ester lubricant base stock of claim 1, wherein the
polyol is technical grade pentaerythritol.
7. The synthetic ester lubricant base stock of claim 2, wherein the
straight chain acid is a mixture of heptanoic acid (C.sub.7 and
caprylic-capric acid (C.sub.8-C.sub.10).
8. The synthetic ester lubricant base stock of claim 7, wherein the
C.sub.7 and C.sub.8-C.sub.10 straight-chain acids are present in
about equal amounts by weight.
9. The synthetic ester lubricant base stock of claim 8, wherein the
iso-nonanoic acid is present from about 65 to 75% by weight of the
acid mixture.
10. The synthetic ester lubricant base stock of claim 2, wherein
the normal acid is valeric acid.
11. The synthetic ester lubricant base stock of claim 1, admixed
with an effective amont of a synthetic ester lubricant additive
package for improving the high temperature properties and the load
factor of the lubricant.
12. A synthetic ester lubricant base stock consisting essentially
of the reaction product of: a polyol selected from the group
consisting of monopentaerythritol, dipentaerythritol and mixtures
thereof; and a mixture of monocarboxylic acids including (1)
straight-chain acids having from 5 to 10 carbon atoms and (2)
iso-nonanoic acid; the iso-nonanoic acid is present from about 60
to 90% by weight of the acid mixture; and the resulting ester when
admixed with a synthetic ester lubricant additive package has a
viscosity at 210.degree. F. of at least about 7.0 centistokes.
13. The synthetic ester lubricant base stock of claim 12, wherein
the iso-nonanoic acid is 3,5,5-trimethylhexanoic acid.
14. The synthetic ester lubricant base stock of claim 12, wherein
the straight chain acids are heptanoic acid and capric-caprylic
acid.
15. The synthetic ester lubricant base stock of claim 12, wherein
the mixture of straight chain acids of heptanoic acid and
caprylic-capric acid include about equal weights of each.
16. The synthetic ester lubricant base stock of claim 12, admixed
with an effective amount of a synthetic ester lubricant additive
package for improving the high temperature properties and load
factor of the lubricant.
Description
BACKGROUND OF THE INVENTION
[0001] This invention relates to a synthetic ester base stock and,
in particular, to a synthetic ester base stock formed from an acid
mixture having a high content of branched chain acid, and a
lubricant from the base stock having increased viscosity at
elevated temperatures and a decreased tendency to form deposits in
high temperature uses.
[0002] Synthetic ester base stocks for use as chain oils and
lubricants for gas turbine engines are well known. The base stocks
are combined with standard lubricant additive packages to form the
lubricant. In order for the lubricant to have properties suitable
for such high temperature use, the base stock must have certain
physical properties. For example, it is a requirement that the
lubricant for turbine oils meet the specifications set forth in
military specification MIL-L-23699D. Chain oils should have low
deposition properties at high temperatures, a viscosity of at least
about 7.0 centistokes (cSt) and a reasonably low pour point below
its ambient storage temperature.
[0003] In general, synthetic high temperature lubricants use esters
as a base stock. The esters are formed by reacting a polyol, such
as pentaerythritol, either monopentaerythritol (MPE) and/or
dipentaerythritol (DPE) or trimethylolpropane (TMP) with various
acids, both straight chain and branched. Japanese patent
applications No. JP 55-105644 and No. 55-157537 disclose a
neopentyl polyol ester of iso-C.sub.9 acid and a straight chain
saturated acid having from 4 to 18 and 2-24 carbon atoms,
respectively, preferably 6 to 14 carbon atoms for air compressor
oils. U.S. Pat. No. 4,826,633, issued on May 2, 1989 and owned by
the assignee herein, is directed to an ester base stock for a
turbine oil formed by reacting MPE and/or TMP with an acid mixture
of straight chain C.sub.5-C.sub.10 acids and 5 to 40 weight percent
branched chain C.sub.7-C.sub.10 acids. Lubricants formed from these
esters have a decreased tendency to form deposits and have
acceptably low pour points without use of DPE.
[0004] Several other United States patents disclose additional
types of esters. For example, U.S. Pat. No. 3,694,382, issued to
Kleiman, et al. on Sep. 26, 1972, discloses an ester blend for use
as a synthetic lubricant. The ester blend includes esters of
trimethylolpropane and dipentaerythritol formed from a mixture of
aliphatic monocarboxylic acids.
[0005] U.S. Pat. No. 4,049,563, issued to Burrous on Sep. 20, 1977,
discloses a jet engine oil consisting of an ester of a
C.sub.4-C.sub.12 monocarboxylic acid, a polyol selected from
pentaerythritol, dipentaerythritol, tripentaerythritol,
trimethylolpropane, trimethylolmethane, trimethylolbutane,
neopentylglycol and mixtures thereof and a soluble methyl phenyl
polysiloxane.
[0006] U.S. Pat. No. 4,064,058, issued to Walker on Dec. 20, 1977,
discloses a grease base stock including a blend of a normally
liquid pentaerythritol ester product and a neopentyl glycol ester
product.
[0007] U.S. Pat. No. 3,360,465, issued to Warman on Dec. 26, 1967,
discloses synthetic ester lubricant compositions of pentaerythritol
mixed esters. The pentaerythritol utilized includes at least 1.5
weight percent dipentaerythritol. The acid includes a mixture of
from two to six monocarboxylic alkanoic acids having from five to
nine carbon atoms with some of the lower acids being branched
chain.
[0008] Every lubricant has a characteristic tendency to form
deposits when used in high temperature applications such as an
engine or on industrial oven chains. If the deposits are excessive
they will detract from the operating efficiency of the device and
create other problems such as filter plugging in engines or track
jumping of chains.
[0009] Accordingly, it is desirable to provide a synthetic
lubricant base stock which provides lubricants having acceptable
high temperature viscosity properties with improved resistance to
formation of carbon deposits when used in high temperature
applications.
SUMMARY OP THE INVENTION
[0010] Generally speaking, in accordance with the invention, an
improved synthetic ester base stock is prepared by reacting at
least one neopentyl polyol, with a monocarboxylic acid mixture
including at least one C.sub.5-C.sub.10 normal alkanoic acid and
between about 60 and 90 weight percent of C.sub.7-C.sub.10 branched
chain acid, based on the total weight of the acid charged. The
polyol may be a commercially available mono- or di-
pentaerythritol, trimethylolpropane or neopentyl glycol. The
straight chain monocarboxylic acids include those having between 5
and 10 carbon atoms, such as valeric acid (pentanoic acid), caproic
acid (hexanoic acid), oenanthic acid (heptanoic acid), caprylic
acid (octanoic acid), pelargonic acid (nonanoic acid), capric acid
(decanoic acid) and mixtures thereof. The branched chain acid is
preferably iso-C.sub.9 acid, iso-nonanoic acid. When mixed with a
standard lubricant additive package the synthetic ester base stock
prepared in accordance with the invention provides a lubricant
having a viscosity at 210.degree. F. of at least about 7.0
centistokes and remains cleaner at high chain oil operating
temperatures than conventional chain oils.
[0011] Accordingly, it is an object of the invention to provide an
improved synthetic ester base stock.
[0012] Another object of the invention is to provide an improved
synthetic ester base stock having a decreased tendency to form
deposits when used in a high temperature environment.
[0013] A further object of the invention is to provide an improved
synthetic ester base stock for high temperature applications and
with a suitably higher viscosity.
[0014] Yet another object is to provide a synthetic ester base
stock with higher oxidative stability.
[0015] Still another object of the invention is to provide al
synthetic ester base stock which when combined with a standard
lubricant additive package provides a lubricant with a viscosity at
210.degree. F. of at least about 7.0 centistokes and a pour point
of less than at least about -10.degree. F. still other objects and
advantages of the invention will in part be obvious and will in
part be apparent from the specification.
[0016] The invention accordingly comprises a composition of matter
possessing the characteristics, properties and the relation of
components which will be exemplified in the composition hereinafter
described, and the scope of the invention will be indicated in the
claims.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0017] The synthetic lubricant base stock prepared in accordance
with the invention is to be used with standard lubricant additive
packages. The lubricant base stock is the reaction product of a
neopentyl polyol and a monocarboxylic acid mixture having a high
branched chain acid content, preferably between about 60-90 weight
percent of a branched chain acid, based on the total acid charge.
When the base stock is mixed with a standard lubricant additive
package, the lubricant has a viscosity at 210.degree. F. of at
least about 7.0 centistokes and a pour point of less than about
-10.degree. F.
[0018] The neopentyl polyol may be monopentaerythritol,
C.sub.5H.sub.12O.sub.4 (MPE, CAS #=115-77-5) which is a colorless
solid with a melting point of 255.degree.-259.degree. C.;
dipentaerythritol, C.sub.10H.sub.22O.sub.7 (DPE, CAS #=126-58-9)
which is a colorless solid having a melting point of
215.degree.-218.degree. C.; commercially available technical grade
pentaerythritol which includes monopentaerythritol and typically
between about 6 to 15 weight percent dipentaerythritol;
commercially available dipentaerythritol which typically includes
about 85-weight % DPE, about 5% MPE and about 10%
tripentaerythritol and heavier stock; trimethylolpropane,
C.sub.6H.sub.14O.sub.3 (TMP, CAS #=77-99-6) a colorless solid with
a melting point of 60.degree.-62.degree. C. and/or neopentyl
glycol, C.sub.5H.sub.12O.sub.2 (NPG, CAS #=126-30-7) a colorless
solid with a melting point of 123.degree.-127.degree. C., mixed
with at least one other neopentyl polyol of heavier stock to yield
a base stock which will provide a lubricant with the desired
viscosity. In the preferred embodiments of the invention, the
polyol is technical grade PE which includes about 12 weight percent
DPE or a mixture of MPE and DPE, including from about 5 to about 90
weight percent DPE.
[0019] The acid component is monocarboxylic and includes at least
one straight chain acid having 5 to 10 carbon atoms and a branched
chain acid having from 7 to 10 carbon atoms. The branched chain
acid preferably has nine carbon atoms, namely, iso-nonanoic acid.
Suitable straight chain acids include, but are not limited to,
valeric acid, oenanthic acid, caprylic acid, pelargonic acid and
capric acid. Preferably, the straight chain acid component is
valeric (C.sub.5) or is a mixture of heptanoic (C.sub.7) and
caprylic-capric (C.sub.8-C.sub.10). The caprylic-capric acid is
identified as having between 8 and 10 carbon atoms, but actually
includes C.sub.6 to C.sub.12 acids and is substantially free of
C.sub.12 acid (less than 1%).
[0020] The amount of the preferred heptanoic and caprylic-capric
mixture straight chain acid component suitable for use in preparing
esters in accordance with the invention may vary widely. For
example, the mixture may be from about 30 to 70 weight percent
heptanoic acid and the balance the caprylic-capric mixture. In a
preferred embodiment, the normal acid mixture is about 40-60 parts
by weight of heptanoic acid and the balance caprylic-capric
acids.
[0021] The branched chain acid may be iso-C.sub.7 acid, iso-C.sub.8
acid, iso-C.sub.9 acid or iso-C.sub.10 acid. Preferably, the
branched chain acid used is the iso-C.sub.9 acid or iso-nonanoic
acid, specifically known as 3,5,5-trimethylhexanoic acid
(3,5,5-trimethylhexanoic acid CAS #=[03302-10-1]). As used herein,
iso-C.sub.9 or iso-nonanoic acid is 3,5,5-trimethylhexanoic acid
and has the formula: 1
[0022] Addition of the iso-nonanoic acid provides the necessary
viscosity characteristics and improves the pour point
characteristics of the base stock and improves the oxidative
stability and deposition tendency.
[0023] The iso-acids other than iso-nonanoic can be used to provide
base stocks which are suitable for turbine engine or chain
lubricant applications. For example, iso-C.sub.7, iso-C.sub.8 and
iso-C.sub.10 acids are available, but these acids contain a complex
mixture of isomers, unlike iso-C.sub.9 acid which is mainly
3,5,5-trimethylhexanoic acid. The physical properties of an acid
that is a complex mixture of isomers can change if the relative
ratios of the isomeric components change and this affects the
properties of an ester produced from the acid. Therefore, to
produce a consistent ester product, it is preferable to use raw
materials that consist of a single, high purity component, namely,
iso-C.sub.9 or iso-nonanoic acid.
[0024] The acid mixture is present in the reaction in an excess of
about 5 to 10 weight percent for the amount of the polyol mixture
used. The excess acid is used to force the reaction to completion.
The excess acid is not critical to carrying out the reaction except
that the smaller the excess, the longer the reaction time. After
the reaction is complete, the excess acid is removed by stripping
and refining. Generally, the esterification reaction is carried out
in the presence of conventional catalysts. For example, a tin or
titanium based catalyst of such a catalyst may be used. Tin oxalate
is an example.
[0025] Lubricants including ester base stocks prepared in
accordance with the invention are prepared by mixing a conventional
additive package to the base stocks in conventional concentrations.
Typical additive packages are described in U.S. Pat. Nos.
4,124,513, 4,141,845 and 4,440,657. The two former patents describe
additive packages based on an alkylphenyl or alkarylphenyl
naphthylamine, a dialkyldiphenylamine, a polyhydroxy anthraquinone,
a hydrocarbyl phosphate ester with an
S-alkyl-2-mercaptobenzo-triazole or an
N-(alkyl)-benzothiazole-2-thione. The third patent describes
additives of a selected tertiarybutylphenyl substituted phosphate
and a selected alkyl amine.
[0026] The invention will be better understood with reference to
the following examples. All percentages are set forth in percent by
weight. These examples are presented for purposes of illustration
only and are not intended to be construed in a limiting sense.
EXAMPLES 1-12
[0027] A variety of ester base stocks were prepared. In each of the
following runs the raw materials identified in the Table and a tin
oxalate catalyst were charged to a stirred reactor capable of
attaining 460.degree.-490.degree. F. and a vacuum of at least 29
inches of mercury. The reactor was provided with a nitrogen sparge
or blanket. The charge was heated to a reaction temperature between
about 440.degree. and 450.degree. F. and the water of reaction was
collected in a trap while the acids were returned to the reactor.
As reflux slowed, vacuum was applied in order to maintain a
reasonable reflux rate. When the hydroxyl value was reduced to a
sufficiently low level (a maximum of 5.0 mg KOH/gm), the bulk of
the excess acid was removed by distillation at the reaction
temperature and maximum vacuum. The residual acidity was removed by
treatment with lime and water. The resulting ester base stock was
dried and filtered.
[0028] The viscosity at 210.degree. F. was determined in accordance
with ASTM D-445 for each sample base stock together with the pour
point in accordance with ASTM D-97.
1TABLE I Table Run 1 2 3 4 5 6 7 RAW MATERIAL Tech PE 17.1 17.8 --
-- 14.8 -- 15.3 Mono PE -- -- -- -- -- 14.4 -- Di PE -- -- 20.1
21.3 -- -- -- Valeric -- 12.2 -- 15.7 -- -- -- Heptanoic 12.4 --
12.0 -- -- -- -- Caprylic-Capric 12.4 -- 12.0 -- -- -- --
Isononanoic 58.1 70.0 55.9 63 42.6 42.8 59.3 Dodecanoic -- -- -- --
42.6 42.8 25.4 PHYSICAL PROPERTIES Viscosity @ 8.91 9.9 17.5 19.7
10.1 9.51 10.6 210.degree. F., cst Viscosity Index 114 97 111 98
129 128 110 Pour Point, .degree. F. -45 -30 -20 -15 * * -35 Freeze
Point, .degree. F. +30 +60 *Product Crystallizes at Room
Temperature; Freeze point data are approximate since some liquid
remains
[0029] Lubricants prepared in accordance with the invention have
decreased tendency to form deposits when used in high temperature
applications. This reduced tendency was demonstrated by mixing base
stock with an additive package as follows:
Additive Package For Panel Test Work
[0030]
2 Additive Package For Panel Test Work Component Parts by Weight
Base Stock 100 Tricresyl Phosphate 2.0 p,p'-Dioctyl-diphenylamine
1.0 Octylphenyl-.alpha.-naphthylamine 1.0 Benzotriazole 0.05
[0031] This additive package was selected as the standard package
for comparing base stocks in the panel test.
[0032] In this bench panel test, a stainless steel panel is
electrically heated by means of two heaters which are inserted into
holes in the panel. The temperature is monitored by means of a
thermocouple. The panel is placed on a slight incline and heated to
540.degree. F. The lubricant to be tested is dropped onto the
heated panel and the characteristics are observed. The lubricant
contacts the panel near the top of the incline and is observed as a
central dark band. The lubricant then tends to thin out as it
travels towards the lower end of the heated panel. It is along the
oil-air-metal interface that the degradation of the lubricant is
best observed.
[0033] The results of the panel test for compositions prepared in
accordance with the composition of Run 1-4 of the Example showed
little degradation along the oil-air-metal interface. These
lubricants are an ester mixture formed by reacting technical grade
pentaerythritol or dipentaerythritol with an acid mixture including
valeric or heptanoic and capric-caprylic as the normal acid and
iso-I nonanoic acids.
[0034] Runs 5-7 were lubricants formed from base stocks prepared by
reacting technical grade PE or MPE and dodecanoic acid consistent
with Runs 5 and 6 of Example 1 in JP 55-105644. The panel test
results for a lubricant made from these esters formed from
dodecanoic acid showed significantly increased carbonization along
the oil-air-metal interface compared to Runs 1-4.
[0035] By preparing an ester from neopentyl polyols and an acid
mixture of a C.sub.-C.sub.10 straight chain acid and a high iso-
C.sub.7 to C.sub.10 acid content, synthetic ester lubricants having
improved properties may be obtained. The lubricants have improved
oxidation stability with lower depositing tendency at high
temperatures, a viscosity at 210.degree. F. of at least about 7.0
cSt and improved pour points. Preferably, the iso-acid is
iso-C.sub.9 acid and is present from 60 to 90 weight percent of the
total acid charge. Thus, the straight chain acid will be present
from 10 to 40 weight percent of the acid charge which maintains
good pour point characteristics and an improved viscosity index.
When linear acids above C.sub.10 are used, the resulting esters
tend to crystallize at ambient temperatures. When linear acids
having less than five carbon atoms are used, odor and corrosion
problems arise.
[0036] It will thus be seen that the objects set forth above, among
those made apparent from the preceding description, are efficiently
attained and, since certain changes may be made in the above
composition of matter without departing from the spirit and scope
of the invention, it is intended that all matter contained in the
above description shall be interpreted as illustrative and not in a
limiting sense.
[0037] It is also to be understood that the following claims are
intended to cover all of the generic and specific features of the
invention herein described and all statements of the scope of the
invention which, as a matter of language, might be said to fall
therebetween.
[0038] Particularly, it is to be understood that in said claims,
ingredients or compounds recited in the singular are intended to
include compatible mixtures of such ingredients wherever the sense
permits.
* * * * *