U.S. patent application number 10/811265 was filed with the patent office on 2004-10-07 for lubricating base stock for internal combustion engine oil and composition containing the same.
Invention is credited to Fukita, Susumu, Hirao, Keiji, Hoshikawa, Wataru, Memita, Michimasa, Tanaka, Hideki, Yamada, Munehiro.
Application Number | 20040198616 10/811265 |
Document ID | / |
Family ID | 33100402 |
Filed Date | 2004-10-07 |
United States Patent
Application |
20040198616 |
Kind Code |
A1 |
Hirao, Keiji ; et
al. |
October 7, 2004 |
Lubricating base stock for internal combustion engine oil and
composition containing the same
Abstract
The present invention provides a lubricating base stock for
internal combustion engine oil consisting essentially of an ester
(A) obtained from an ethylene oxide adduct of diol having a
neopentyl structure and a saturated aliphatic monocarboxylic acid
having 4 to 12 carbon atoms, wherein the ethylene oxide adduct is
obtained by adding ethylene oxide to a diol having a neopentyl
structure in a ratio of 1 to 4 moles with respect to 1 mol of the
diol, wherein the saturated aliphatic monocarboxylic acid is a
linear carboxylic acid or a mixture of saturated aliphatic
monocarboxylic acids comprising a linear aliphatic monocarboxylic
acid in a ratio of at least 50 mol %, and wherein a dynamic
viscosity of the ester (A) at 100.degree. C. is 1 to 5 mm.sup.2/s,
a viscosity index of the ester (A) is at least 140, and a total
acid value of the ester (A) is 0.5 mg KOH/g or less.
Inventors: |
Hirao, Keiji; (Hyogo,
JP) ; Memita, Michimasa; (Hyogo, JP) ; Fukita,
Susumu; (Hyogo, JP) ; Yamada, Munehiro;
(Hyogo, JP) ; Tanaka, Hideki; (Saitama, JP)
; Hoshikawa, Wataru; (Saitama, JP) |
Correspondence
Address: |
AMIN & TUROCY, LLP
1900 EAST 9TH STREET, NATIONAL CITY CENTER
24TH FLOOR,
CLEVELAND
OH
44114
US
|
Family ID: |
33100402 |
Appl. No.: |
10/811265 |
Filed: |
March 26, 2004 |
Current U.S.
Class: |
508/485 |
Current CPC
Class: |
C10M 105/38 20130101;
C10N 2040/25 20130101; C10N 2030/08 20130101; C10N 2020/02
20130101; C10N 2030/54 20200501; C10N 2030/02 20130101; C10N
2030/68 20200501; C10M 2207/026 20130101; C10M 145/38 20130101;
C10M 2209/1045 20130101; C10M 2207/026 20130101; C10M 2207/042
20130101; C10M 2207/2815 20130101; C10M 2207/2835 20130101; C10M
2209/084 20130101; C10M 2215/28 20130101; C10M 2223/045 20130101;
C10M 2209/1045 20130101; C10M 2209/1095 20130101 |
Class at
Publication: |
508/485 |
International
Class: |
C10M 15/38 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 27, 2003 |
JP |
2003-88696 |
Mar 27, 2003 |
JP |
2003-88697 |
Claims
1. A lubricating base stock for internal combustion engine oil
consisting essentially of an ester (A) obtained from an ethylene
oxide adduct of diol having a neopentyl structure and a saturated
aliphatic monocarboxylic acid having 4 to 12 carbon atoms, wherein
the ethylene oxide adduct is obtained by adding ethylene oxide to a
diol having a neopentyl structure in a ratio of 1 to 4 moles with
respect to 1 mol of the diol, the saturated aliphatic
monocarboxylic acid is a linear carboxylic acid or a mixture of
saturated aliphatic monocarboxylic acids comprising a linear
aliphatic monocarboxylic acid in a ratio of at least 50 mol %, and
a dynamic viscosity of the ester (A) at 100.degree. C. is 1 to 5
mm.sup.2/s, a viscosity index of the ester (A) is at least 140, and
a total acid value of the ester (A) is 0.5 mg KOH/g or less.
2. The lubricating base stock of claim 1, wherein the mixture of
saturated aliphatic monocarboxylic acids comprises a saturated
linear aliphatic monocarboxylic acid in a ratio of at least 80 mol
%.
3. A lubricating base stock for internal combustion engine oil
consisting essentially of the ester (A) according to claim 1 and an
ester (B) having an average molecular weight that is different from
that of the ester (A), wherein the ester (B) is obtained from a
neopentyl polyol alkylene oxide adduct and a saturated aliphatic
monocarboxylic acid, and a weight ratio of the ester (A) and the
ester (B) is 80:20 to 99.9:0.1.
4. An internal combustion engine lubricating oil composition
comprising the base stock according to claim 1 as a main component,
0.05 to 10 wt % of an antioxidant, 0.05 to 10 wt % of a
detergent-dispersant, and 0.01 to 30 wt % of a viscosity index
improver.
5. An internal combustion engine lubricating oil composition
comprising the base stock according to claim 3 as a main component,
0.05 to 10 wt % of an antioxidant, 0.05 to 10 wt % of an
detergent-dispersant, and 0.01 to 30 wt % of a viscosity index
improver.
6. A lubricating base stock for internal combustion engine oil
consisting essentially of the ester (A) according to claim 2 and an
ester (B) having an average molecular weight that is different from
that of the ester (A), wherein the ester (B) is obtained from a
neopentyl polyol alkylene oxide adduct and a saturated aliphatic
monocarboxylic acid, and a weight ratio of the ester (A) and the
ester (B) is 80:20 to 99.9:0.1.
7. An internal combustion engine lubricating oil composition
comprising the base stock according to claim 2 as a main component,
0.05 to 10 wt % of an antioxidant, 0.05 to 10 wt % of a
detergent-dispersant, and 0.01 to 30 wt % of a viscosity index
improver.
8. An internal combustion engine lubricating oil composition
comprising the base stock according to claim 6 as a main component,
0.05 to 10 wt % of an antioxidant, 0.05 to 10 wt % of an
detergent-dispersant, and 0.01 to 30 wt % of a viscosity index
improver.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a lubricating base stock
for internal combustion engine oil and a composition containing the
same.
[0003] 2. Description of the Related Art
[0004] In response to recent global environmental issues and the
exhaustion of oil resources, there is a great demand for reduction
of exhaust gas such as carbon dioxide and improvement of fuel
efficiency in the automobile industry.
[0005] The improvement of fuel efficiency depends on the
performance of lubricating oils. For example, it is known that when
a lubricating oil having a small difference (i.e., viscosity
change) between the dynamic viscosity in a low temperature state at
the time of engine start and the dynamic viscosity in a high
temperature state during driving is employed, that is, when a
lubricating oil having a high viscosity index is employed,
sufficient lubricity is maintained, and the power load on the
internal combustion engine and the drive system devices is reduced,
which leads to a reduction in fuel consumption.
[0006] Lubricating oils are generally made of a composition
comprising a lubricating base stock as the main component to which
an antioxidant or the like is added. As the lubricating base stock,
various mineral oils and synthetic oils have been developed.
[0007] As mineral oils, low viscosity index (LVI) base stocks
obtained by refinery of petroleum by distillation under reduced
pressure had been employed. Thereafter, high viscosity index (HVI)
base stocks in which aromatic components are removed by solvent
refining; high high viscosity index (HHVI) base stocks in which the
oxidation stability is improved by saturating aromatic components
by hydrogenation and removing other impurities as well; very high
viscosity index (VHVI) base stocks in which the heat stability at
high temperature is improved by hydrogenation of aromatic
components under a high temperature and a high pressure; and
extremely high viscosity index (XHVI) base stocks have been
developed.
[0008] However, the viscosity indexes of these mineral base stocks
are not sufficiently high, and the flowability and the lubricity at
low temperatures are not adequate, and the improvement of fuel
efficiency has not reached a satisfactory level either.
[0009] As synthetic oils, poly .alpha.-olefin (PAO), and various
ester oils have been proposed. Among these, PAO is not adequate in
terms of the viscosity index and the lubricity.
[0010] Japanese Laid-Open Patent Publication No. 7-305079 discloses
a lubricating oil comprising a polyether polyol fatty acid ester
obtained from a neopentyl polyol having 2 to 6 hydroxyl groups to
which 1 to 10 moles of alkylene oxide are added and a fatty acid
having 4 to 22 carbon atoms. Japanese Laid-Open Patent Publication
No. 2001-139978 discloses an alkylene oxide adduct of a partial
ester obtained by partial esterification of a polyhydric alcohol
with a fatty acid or an ester compound obtained by partial
esterification of polyethylene glycol with a fatty acid.
[0011] Furthermore, mixtures of synthetic oils and mineral oils
have been examined. For example, Japanese Laid-Open Patent
Publication No. 7-228642 discloses a lubricating oil obtained by
mixing a specific vinyl copolymer and a mineral oil.
[0012] All of these oils are developed to improve the lubricity and
the viscosity index, but have the following problems: the pour
point is high, the lubricity is poor; the viscosity index is
insufficient, and the susceptibility to deterioration is high, so
that the fuel efficiency is not sufficiently improved. When driving
a machine or an engine, shear is applied to the lubricating oils in
sliding portions of the machine or engine. Therefore, it is
important to improve the viscosity (i.e., shear viscosity)
characteristics of the lubricating oil in the state in which shear
load is applied in order to achieve high efficiency/high fuel
efficiency and maintain the lubricity at high temperature. However,
in the patent publications noted above, there is no consideration
on the shear viscosity characteristics of the lubricating oils.
[0013] As described above, various approaches have been followed to
improve fuel efficiency, but no lubricating base stock that can
improve fuel efficiency sufficiently can be obtained yet.
SUMMARY OF THE INVENTION
[0014] As a result of in-depth research to achieve the
above-described objects, the inventors of the present invention
found that a lubricating base stock for internal combustion engine
oil comprising an ester obtained from an ethylene oxide adduct of
diol having a neopentyl structure in which ethylene oxide is added
to a diol having a neopentyl structure in a specific ratio and a
specific saturated aliphatic monocarboxylic acid has a small change
of the shear viscosity, an excellent lubricity, and high viscosity
index, so that the high fuel efficiency of automobiles can be
achieved, and thus achieved the present invention.
[0015] A lubricating base stock for internal combustion engine oil
of the present invention consists essentially of an ester (A)
obtained from an ethylene oxide adduct of diol having a neopentyl
structure and a saturated aliphatic monocarboxylic acid having 4 to
12 carbon atoms, wherein the ethylene oxide adduct is obtained by
adding ethylene oxide to a diol having a neopentyl structure in a
ratio of 1 to 4 moles with respect to 1 mol of the diol, wherein
the saturated aliphatic monocarboxylic acid is a linear carboxylic
acid or a mixture of saturated aliphatic monocarboxylic acids
comprising a linear aliphatic monocarboxylic acid in a ratio of at
least 50 mol %, and wherein a dynamic viscosity of the ester (A) at
100.degree. C. is 1 to 5 mm.sup.2/s, a viscosity index of the ester
(A) is at least 140, and a total acid value of the ester (A) is 0.5
mg KOH/g or less.
[0016] In a preferred embodiment, the mixture of saturated
aliphatic monocarboxylic acids comprises a saturated linear
aliphatic monocarboxylic acid in a ratio of at least 80 mol %.
[0017] A lubricating base stock for internal combustion engine oil
of the present invention consists essentially of the ester (A) and
an ester (B) having an average molecular weight that is different
from that of the ester (A), wherein the ester (B) is obtained from
a neopentyl polyol alkylene oxide adduct and a saturated aliphatic
monocarboxylic acid, and a weight ratio of the ester (A) and the
ester (B) is 80:20 to 99.9 to 0.1.
[0018] An internal combustion engine lubricating oil composition of
the present invention comprises any one of the above-mentioned base
stock as a main component, 0.05 to 10 wt % of an antioxidant, 0.05
to 10 wt % of a detergent-dispersant, and 0.01 to 30 wt % of a
viscosity index improver.
[0019] Thus, the invention described herein makes possible the
advantages of: providing a lubricating base stock for internal
combustion engine oil consisting essentially of an ester (A) that
has low viscosity, excellent flowability at low temperature and a
high viscosity index and consequently has good lubricity over a
wide temperature range, has a small change of shear viscosity due
to temperature change, low volatility, good thermal oxidation
stability, and high fuel efficiency; providing a lubricating base
stock for internal combustion engine oil consisting essentially of
the ester (A) and an ester (B) having an average molecular weight
that is different from that of the ester (A) and having a
particularly small change of the shear viscosity due to temperature
change, in addition to the above-described excellent properties;
and providing internal combustion engine lubricating oil
composition containing the base stock.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0020] In this specification, "lubricating base stock for internal
combustion engine oil" refers to a base stock for a lubricating oil
used in internal combustion engines and the associated drive
systems. More specifically, it refers to a base stock for a
lubricating oil used in internal combustion engines such as 2-cycle
engines and 4-cycle engines; drive system devices such as manual
transmissions, automatic transmissions, and power steering; and
differential gears.
[0021] The lubricating base stock for internal combustion engine
oil of the present invention consists essentially of an ester
(i.e., ester (A)) obtained from an ethylene oxide adduct of diol
having a neopentyl structure and a saturated aliphatic
monocarboxylic acid having 4 to 12 carbon atoms, wherein the
ethylene oxide adduct is obtained by adding ethylene oxide to a
diol having a neopentyl structure in a ratio of 1 to 4 moles with
respect of 1 mol of the diol. Alternatively, the lubricating base
stock for internal combustion engine oil of the present invention
consists essentially of the ester (A) and an ester (B) having an
average molecular weight that is different from that of the ester
(A). The internal combustion engine lubricating oil composition of
the present invention comprises the lubricating base stock as the
main component. Hereinafter, the ester (A), the ester (B), the
lubricating base stock for internal combustion engine oil and the
internal combustion engine lubricating oil composition will be
described.
(1) Ester (A)
[0022] (1.1) Ethylene Oxide Adduct of Diol Having a Neopentyl
Structure
[0023] The ethylene oxide adduct of diol having a neopentyl
structure (in the following, "ethylene oxide adduct" or the
"alkylene oxide adduct" described later may be referred to simply
as "adduct"), which is a raw material of the ester (A) of the base
stock of the present invention, can be obtained by adding ethylene
oxide to a diol having a neopentyl structure in a ratio of 1 to 4
moles with respect to 1 mol of the diol, as described above. "Diol
having a neopentyl structure" refers to a diol having a neopentyl
structure as shown below. 1
[0024] Examples of the diol having a neopentyl structure include
the following compounds: neopentyl glycol
(2,2-dimethyl-1,3-propanediol), 2-ethyl-2-methyl-1,3-propanediol,
2,2-diethyl-1,3-propanediol, 2-propyl-2-methyl-1,3-propanediol,
2-propyl-2-ethyl-1,3-propanediol, 2,2-dipropyl-1,3-propanediol,
2-butyl-2-methyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol,
2-butyl-2-propyl-1,3-propanediol, and 2,2-dibutyl-1,3-propanediol.
By using these diols, the resultant ester can have a suitable
viscosity, so that suitable lubricity can be obtained, and high
fuel efficiency can be achieved. When an adduct derived from a
neopentyl polyol having 3 or more hydroxyl groups is used, the
resultant ester has high viscosity, so that high fuel efficiency
cannot be achieved. In order to obtain an ester having a low
viscosity from an adduct derived from a neopentyl polyol having 3
or more hydroxyl groups, it is necessary to employ a short chain
monocarboxylic acid, and such an ester has poor lubricity.
[0025] The ethylene oxide adduct of diol having a neopentyl
structure is a compound in which ethylene oxide is added to the
above-mentioned diol having a neopentyl structure.
[0026] The number of moles of the ethylene oxide added is 1 to 4,
preferably 1 to 3 and more preferably 1 to 2. When the number of
moles of the ethylene oxide added exceeds 4, the viscosity of the
resultant ester becomes high and the load torque at low temperature
is increased, which may lead to deterioration of the startability
at low temperature or deterioration of the thermal oxidation
stability. Therefore, the lubricating oil for internal combustion
engine comprising such an ester cannot withstand long term use. On
the other hand, when the number of moles of the ethylene oxide
added is 0, the resultant ester has problems in practical use. For
example, when a short or medium chain alkyl monocarboxylic acid is
used as a saturated aliphatic monocarboxylic acid as a raw
material, the resultant ester has a low viscosity index and the
viscosity is too low. Therefore, when the ester is used as a base
stock for lubricating oil, the oil film that is formed during
driving of an internal combustion engine would be ruptured.
Consequently, abrasion or seize-up may occur in the internal
combustion engine using the base stock made of such an ester. When
a long chain alkyl monocarboxylic acid is used, the resultant ester
may be crystallized at low temperature. When alkylene oxide other
than ethylene oxide, such as propylene oxide and butylene oxide, is
added instead of the ethylene oxide, the resultant ester may have
various problems due to the influence of its side chain alkyl.
Namely, the resistance and the interaction between molecules
increase at low temperature, which leads to a high viscosity. On
the other hand, the molecular motion becomes active at high
temperature, and the influence of the interaction of molecules is
almost eliminated, which leads to a low viscosity. In other words,
an ester base stock having a low viscosity index is obtained, so
that improvement of fuel efficiency cannot be achieved.
[0027] (1.2) Saturated Aliphatic Monocarboxylic Acid
[0028] The carboxylic acid that serves as a raw material of the
ester (A) is a saturated aliphatic monocarboxylic acid having 4 to
12 carbon atoms, as described above. The number of carbon atoms of
the saturated aliphatic monocarboxylic acid is preferably 5 to 12,
more preferably 6 to 12, and even more preferably 8 to 12. When a
saturated aliphatic monocarboxylic acid having 3 or less carbon
atoms is employed and the resultant ester is used for a lubricating
oil, the abrasion resistance effect is not adequate. On the other
hand, when a saturated aliphatic monocarboxylic acid having more
than 12 carbon atoms is used, the flowability at low temperature of
the resultant ester is poor. Furthermore, the viscosity is too
high, which may lead to poor fuel efficiency.
[0029] As the saturated aliphatic monocarboxylic acid used in the
present invention, it is necessary to include a saturated linear
aliphatic monocarboxylic acid in a ratio of at least 50 mol %.
Namely, the saturated aliphatic monocarboxylic acid is a linear
carboxylic acid or a mixture of saturated aliphatic monocarboxylic
acids comprising a linear aliphatic monocarboxylic acid in a ratio
of at least 50 mol %. The saturated linear aliphatic monocarboxylic
acid is contained preferably in a ratio of 80 mol % or more, more
preferably 90 mol % or more, and even more preferably 95 mol % or
more.
[0030] Saturated branched aliphatic monocarboxylic acids are
preferable in terms of the flowability at low temperature. In
particular, in terms of the hydrolysis resistance of the resultant
ester, it is preferable that saturated aliphatic monocarboxylic
acid having a branched chain at the carbon atom of the .beta.
position of the carboxylic acid is included. However, when the
ratio of branched fatty acid is too high, the viscosity index is
reduced. Therefore, the branched fatty acid is employed as
appropriate in a ratio of less than 50 mol % and in the range that
does not reduce the viscosity index. The ratio of the branched
fatty acid is preferably less than 20 mol %, more preferably less
than 10 mol %, and even more preferably less than 5 mol %.
[0031] Examples of saturated linear aliphatic monocarboxylic acids
include butanoic acid, pentanoic acid, caproic acid, heptanoic
acid, caprylic acid, nonanoic acid, capric acid, undecanoic acid,
and lauric acid.
[0032] Examples of saturated branched aliphatic monocarboxylic
acids include the following compounds: 2-methylpropanoic acid,
2-methylbutanoic acid, 3-methylbutanoic acid, 2,2-dimethylpropanoic
acid, 2-methylpentanoic acid, 3-methylpentanoic acid,
4-methylpentanoic acid, 2,2-dimethylbutanoic acid, 2-ethylbutanoic
acid, 3,3-dimethylbutanoic acid, 2,2-dimethylpentanoic acid,
2-methyl-2-ethylbutanoic acid, 2,2,3-trimethylbutanoic acid,
2-ethylpentanoic acid, 3-ethylpentanoic acid, 2-methylhexanoic
acid, 3-methylhexanoic acid, 4-methylhexanoic acid,
5-methylhexanoic acid, isoheptanoic acid, 2-ethylhexanoic acid,
3,5-dimethylhexanoic acid, 2,2-dimethylhexanoic acid,
2-methylheptanoic acid, 3-methylheptanoic acid, 4-methylheptanoic
acid, 2-propylpentanoic acid, isooctanoic acid,
2,2-dimethylheptanoic acid, 2,2,4,4-tetramethylpentanoic acid,
3,5,5-trimethylhexanoic acid, 2-methyloctanoic acid,
2-ethylheptanoic acid, 3-methtyloctanoic acid, isononanoic acid,
neononanoic acid, 2,2-dimethyloctanoic acid,
2-methyl-2-ethylheptanoic acid, 2-methyl-2-propylhexanoic acid,
isodecanoic acid, neodecanoic acid, and isododecanoic acid.
[0033] Other than the above, as saturated aliphatic monocarboxylic
acids, derivatives of the saturated aliphatic monocarboxylic acids
can be used. For example, acid chloride, methyl ester, acid
anhydride or the like of these carboxylic acids can be used. Among
these, it is preferable to use methyl ester or acid anhydride. Care
is necessary in handling acid chloride, because a corrosive
chlorine compound may be produced as a by-product when synthesizing
an ester.
[0034] By using such a saturated aliphatic monocarboxylic acid, the
resultant ester has excellent thermal oxidation stability.
Unsaturated aliphatic carboxylic acid cannot be used in the present
invention because the thermal oxidation stability of the resultant
ester is poor.
[0035] (1.3) Synthesis of Ester (A)
[0036] The ester (A), which is an essential component of the
lubricating base stock for internal combustion engine oil of the
present invention can be obtained by reacting the above-described
adduct with a saturated aliphatic monocarboxylic acid having 4 to
12 carbon atoms in any ratio. The ester can be obtained by reacting
a saturated aliphatic monocarboxylic acid in a ratio of preferably
about 2 to 5 moles, and more preferably about 2.1 to 4 moles, with
respect to one moles of the adduct.
[0037] The ester (A) can be produced by any ordinary method.
Examples of preparation of an adduct by the reaction of a diol
having a neopentyl structure with ethylene oxide and preparation of
an ester from the adduct will be described more specifically below.
First, a diol having a neopentyl structure and a catalyst (e.g., an
alkali catalyst such as alkali hydroxide, an alkali metal salt of
alcohol, and an alkanolamide or an acid catalyst such as tin
tetrachloride and boron trifluoride) are placed in an autoclave,
and the system is purged with inert gas such as nitrogen. If
necessary, moisture in the system is removed for the purpose of
suppressing generation of by-products by increasing the temperature
in the system to 80 to 120.degree. C. while stirring under reduced
pressure. Then, after the temperature in the system is increased to
100 to 150.degree. C., a predetermined amount of ethylene oxide is
injected gradually for reaction. After the reaction is completed,
if necessary, the pressure is reduced or inert gas is introduced so
as to remove unreacted ethylene oxide. The alkali component
contained in the obtained reaction mixture is removed with an
adsorbent or neutralized with an acid, and, if necessary, the
temperature in the system is kept at 80 to 120.degree. C. and under
reduced pressure so as to remove moisture in the system.
Furthermore, the adsorbent and a precipitated salt are removed, for
example, with a filter. Thus, an ethylene oxide adduct of diol
having a neopentyl structure can be obtained. Hydroxyl groups are
present at substantially all the ends of the molecule of this
compound.
[0038] Then, a predetermined amount of the saturated aliphatic
monocarboxylic acid is added to the adduct, and the mixture is
heated to 140 to 240.degree. C. and subjected to dehydration
condensation in the absence of a catalyst or the presence of an
acid catalyst such as Brensted acid or Lewis acid, if necessary,
together with an azeotropic solvent. After the reaction is
completed, for the purpose of removing unreacted monocarboxylic
acid and reaction by-products, stripping, distillation,
neutralization with alkaline water, and, if necessary, an
adsorption operation using alumina, magnesia, activated clay,
activated carbon, acid white clay, zeolite, ion-exchange resin or
the like is performed, and purification and separation of the ester
are performed by liquid chromatography or the like.
[0039] The thus obtained ester (A) has a specific dynamic
viscosity, viscosity index and total acid value as shown below.
[0040] The dynamic viscosity at 100.degree. C. of the ester (A) is
1 to 5 mm.sup.2/s, preferably 2 to 5 mm.sup.2/s, and more
preferably 3 to 5 mm.sup.2/s. When the dynamic viscosity of the
ester is less than 1 mm.sup.2/s and drive of an engine or a machine
is performed using a lubricating oil containing this ester as a
base stock, the oil film thickness at a lubricating portion is
reduced, which may cause rupture of the oil film and thus lead to
bearing abrasion, seize-up or the like. When the dynamic viscosity
is more than 5 mm.sup.2/s, the power loss due to the viscous
resistance is increased, so that the startability at low
temperature deteriorates and the high fuel efficiency effect cannot
be obtained.
[0041] The viscosity index of the ester (A) is 140 or more,
preferably 145 or more, and more preferably 150 or more.
[0042] In view of corrosion prevention, abrasion resistance and
stability, the total acid value of the ester (A) is 0.5 mg KOH/g or
less, preferably 0.3 mg KOH/g or less, more preferably 0.1 mg KOH/g
or less, and even more preferably 0.05 mg KOH/g or less.
[0043] The hydroxyl value of the ester (A) is preferably 5.0 mg
KOH/g or less, more preferably 3.0 mg KOH/g or less, and even more
preferably 1.0 mg KOH/g or less, in view of thermal oxidation
stability, hygroscopicity, low volatility, and durability.
(2) Ester (B)
[0044] The ester (B) is a polyether polyol ester compound obtained
from a neopentyl polyol alkylene oxide adduct and a saturated
aliphatic monocarboxylic acid, wherein the adduct is obtained by
adding alkylene oxide to a neopentyl polyol.
[0045] (2.1) Neopentyl Polyol Alkylene Oxide Adduct
[0046] "Neopentyl polyol" refers to a polyol having a neopentyl
structure as described above.
[0047] Examples of the neopentyl polyol include a diol having a
neopentyl structure described in section (1.1) (i.e., a neopentyl
polyol having two hydroxyl groups), and a neopentyl polyol having 3
or more hydroxyl groups such as trimethylolpropane,
pentaerythritol, and dipentaerythritol. Among these, neopentyl
polyols having two hydroxyl groups, in particular, neopentyl glycol
is preferable. When a neopentyl polyol having two hydroxyl groups
is employed, the resultant ester can have an appropriate viscosity,
so that appropriate lubricity can be obtained. When an adduct
derived from a neopentyl polyol having 3 or more hydroxyl groups is
employed, the viscosity of the resultant ester becomes high. In
order to obtain an ester having a low viscosity, a short chain
carboxylic acid has to be used. However, the lubricity of such an
ester may be poor. Therefore, an adduct derived from neopentyl
polyol having 3 or more hydroxyl groups can be used as appropriate,
depending on the purpose.
[0048] The neopentyl polyol alkylene oxide adduct is a compound in
which alkylene oxide is added to the above-mentioned neopentyl
polyol.
[0049] The number of carbon atoms of the alkylene oxide is
preferable 2 to 4. Examples of alkylene oxide having 2 to 4 carbon
atoms include ethylene oxide, propylene oxide, and butylene oxide.
Ethylene oxide is preferable. When propylene oxide or butylene
oxide is used, the resistance and the interaction between molecules
are increased at low temperature because of the influence of its
side chain alkyl, and therefore the viscosity is rather high. On
the other hand, the molecular motion becomes active at high
temperature, so that the influence of the interaction of molecules
is almost eliminated, and the viscosity becomes rather low.
Therefore, it is preferable to use propylene oxide adducts or
butylene oxide adducts as appropriate, depending on the properties
of a desired ester.
[0050] The number of moles of the alkylene oxide added is preferaby
2 to 10, and more preferably 2 to 6. When the number of moles of
the alkylene oxide added exceeds 10, the viscosity of the resultant
ester becomes high and the load torque at low temperature is
increased, which may lead to deterioration of the startability at
low temperature or deterioration of the thermal oxidation
stability. Therefore, a lubricating oil for internal combustion
engine containing of such an ester cannot withstand long term use.
When the number of moles of the alkylene oxide added is less than
2, and for example, a short or medium chain alkyl monocarboxylic
acid is used as a saturated aliphatic monocarboxylic acid to be
reacted, then the viscosity of the obtained ester is too low.
Therefore, when driving is performed using lubricating oil
containing such an ester as a base stock, the oil film formed
during driving is ruptured, and abrasion or seize-up may occur in
the drive portion. When a long chain alkyl monocarboxylic acid is
used, the resultant ester may be crystallized at low
temperature.
[0051] (2.2) Saturated Aliphatic Monocarboxylic Acid
[0052] There is no particular limitation regarding the number of
carbon atoms of the saturated aliphatic monocarboxylic acid, but 4
to 12 are preferable and 4 to 10 are more preferable. When a
saturated aliphatic monocarboxylic acid having 3 or less carbon
atoms is used and a lubricating oil is prepared with the resultant
ester, the abrasion resistance effect may not be adequate. On the
other hand, when a saturated aliphatic monocarboxylic acid having
more than 12 carbon atoms is used, the flowability at low
temperature of the base stock containing the resultant ester may be
poor. Furthermore, the viscosity of the resultant ester is too
high, which may lead to poor fuel efficiency.
[0053] The saturated aliphatic monocarboxylic acid may be linear or
branched, or a mixture of these. It is preferable that a small
amount of saturated branched aliphatic monocarboxylic acid is mixed
with saturated linear aliphatic monocarboxylic acid, because the
flowability at low temperature of the resultant ester is excellent.
In particular, in terms of the hydrolysis resistance, it is
preferable that saturated aliphatic monocarboxylic acid having a
branched chain at the carbon atom of the .beta. position of the
carboxylic acid is included. However, when the ratio of branched
fatty acid is too high, the viscosity index of the resultant ester
is reduced, and therefore branched fatty acid is used as
appropriate in a range that does not reduce the viscosity
index.
[0054] As the saturated linear aliphatic monocarboxylic acid and
the saturated branched aliphatic monocarboxylic acid, for example,
the saturated aliphatic monocarboxylic acids described in section
(1.2) of the ester (A) can be used.
[0055] (2.3) Synthesis of Ester (B)
[0056] The ester (B) used in the present invention can be obtained
by reacting the above-described neopentyl polyol alkylene oxide
adduct with a saturated aliphatic monocarboxylic acid in any ratio.
The ester can be obtained by reacting a saturated aliphatic
monocarboxylic acid in a ratio of, preferably about 2 to 5 moles,
and more preferably about 2.1 to 4 moles, with respect to one mol
of the adduct. Such an ester (B) can be obtained by the production
method described in the section of the ester (A) as above.
(3) Lubricating Base Stock for Internal Combustion Engine Oil
[0057] The lubricating base stock for internal combustion engine
oil of the present invention consists essentially of the ester (A)
obtained in the above-described manner, or consists essentially of
the ester (A) and the ester (B) having an average molecular weight
that is different from that of the ester (A). When the base stock
consists essentially of the ester (A) and the ester (B), the weight
ratio of the ester (A) and the ester (B) is 80:20 to 99.9:0.1,
preferably 90:10 to 98:2. Each of the esters (A) and (B) can be a
single compound or a mixture of two or more compounds. When the
ratio of the esters (A) and (B) is outside the above-described
ranges, it is difficult to provide sufficient temperature-shear
viscosity characteristics.
[0058] When the lubricating base stock for internal combustion
engine oil consists essentially of the ester (A) and the ester (B),
it is preferable that the base stock has a specific dynamic
viscosity (i.e., 1 to 5 mm.sup.2/s at 100.degree. C.), a specific
viscosity index (i.e., 140 or more) and a specific total acid value
(i.e., 0.5 mgKOH/g or less) that are in the same range as those
possessed by the ester (A).
[0059] The lubricating base stock for internal combustion engine
oil of the present invention, in particular, the base stock
consisting essentially of the ester (A) and the ester (B) has a
small change of the shear viscosity due to temperature change.
(4) Internal Combustion Engine Lubricating Oil Composition
[0060] The internal combustion engine lubricating oil composition
of the present invention comprises the base stock as described
above as the main component, and contains (i) an antioxidant, (ii)
a detergent-dispersant and (iii) an viscosity index improver. If
necessary, further additives can be contained. Examples of the
additives include (iv) mineral oil or non-ester synthetic oil such
as poly .alpha.-olefin (PAO) and polybutene, (v) basic metal
compounds, (vi) friction reducing agents, (vii) abrasion resistance
agents, (viii) extreme pressure agents, (ix) rust inhibitors, (x)
pour point depressants, (xi) anti-foaming agents, (xii) corrosion
inhibitors, (xiii) metal deactivators, and (xiv) coloring
agents.
[0061] Examples of antioxidants (i) include amine antioxidants such
as alkylated diphenylamine (e.g., dioctyldiphenylamine),
phenyl-.alpha.-naphthylamine, and alkylated
phenyl-.alpha.-naphthylamine; phenol antioxidants such as
2,6-di-tert-butylphenol, 2,6-di-tert-butyl-4-methylphenol,
2,2'-methylenebis(4-methyl-6-tert-butyl- phenol), 4,4'-butylidene
bis(6-t-butyl-3-methylphenol), and
4,4'-methylenebis(2,6-di-tert-butylphenol); sulfur antioxidants
such as dilauryl-3,3'-thiodipropionate, and diphenyl sulfide;
phosphorus antioxidants such as phosphite; dialkyl dithiophosphoric
acid metal salts of zinc, molybdenum or the like. Among these,
amine antioxidants, phenol antioxidants, and dialkyl
dithiophosphoric acid metal salts are preferable.
[0062] The antioxidant is contained in the internal combustion
engine lubricating oil composition in a ratio of 0.05 to 10 wt %,
preferably 0.1 to 5 wt %. When the content is too low, the
antioxidation effect cannot be obtained. When the content is too
high, it is not possible to attain an effect commensurate to the
addition amount, and furthermore, sludge may be generated, and
therefore too high a content is not preferable. These antioxidants
can be used in combination within the above-described range of the
content. The internal combustion engine lubricating oil composition
of the present invention comprises an antioxidant in combination
with the above-mentioned base stock having high oxidation
stability, so that the oxidation stability is very good.
[0063] The detergent-dispersant (ii) may be either a metal
detergent containing a metal salt or ashless dispersant that does
not contain a metal salt. Examples of metal detergents include
sulfonates, phenates, succinates, phosphonates, each of which
contains a metal such as calcium, magnesium, barium, or sodium.
Examples of ashless dispersants include copolymers of alkyl
methacrylate and each of the following compounds: alkenyl
succinimide compounds, alkenyl succinamide compounds, alkenyl
succinate compounds, alkenyl succinate-amide compounds, benzylamine
compounds, dialkylaminoethyl methacrylate, polyethylene glycol
methacrylate, and vinyl pyrrolidone.
[0064] The detergent-dispersant is contained in the internal
combustion engine lubricating oil composition in a ratio of 0.05 to
10 wt %, preferably 0.1 to 5 wt %. When the content is too low,
sludge generated in the lubricating oil may be deposited. When the
content is too high, an effect commensurate to the content cannot
be obtained.
[0065] Examples of viscosity index improvers (iii) include
polymethacrylate compounds, olefin copolymer compounds (e.g.,
polyisobutylene compounds, ethylene-propylene copolymer compounds),
polyalkylstyrene compounds, styrene-butadiene hydrogenated
copolymer compounds, styrene-maleic anhydride ester copolymer
compounds, and star-shaped isoprene compounds. Among these,
polymethacrylate compounds are preferable in terms of the
solubility in the ester base stock. The weight average molecular
weight of the polymethacrylate employed herein is particularly
preferably 100000 or more (in terms of polystyrene in GPC
analysis).
[0066] The viscosity index improver is contained in the internal
combustion engine lubricating oil composition in a ratio of 0.01 to
30 wt %, preferably 0.1 to 20 wt %. When the content is too low,
the viscosity index cannot be improved, and the fuel efficiency
cannot be improved. When the content is too high, it is not
possible to attain an effect commensurate to the content.
Furthermore, the polymer molecules of the viscosity index improver
are cut by mechanical shear, and the viscosity is reduced, so that
the viscosity index may not be improved.
[0067] The various additives (iv) to (xiv) can be contained, if
necessary, in order to ensure various performances as a lubricating
oil in driving internal combustion engines and the associated drive
systems.
[0068] The mineral oil and the non-ester synthetic oil (iv) are oil
components that are added to the lubricating base stock containing
the ester, and can be mixed as appropriate within the predetermined
ranges of the dynamic viscosity, viscosity index, and total acid
value of the lubricating base stock. Therefore, it is preferable
that the mineral oil and the non-ester synthetic oil have
predetermined dynamic viscosities and viscosity indexes as
below.
[0069] The dynamic viscosity at 100.degree. C. of the mineral oil
and the non-ester synthetic oil is 1 to 10 mm.sup.2/s, preferably 1
to 5 mm.sup.2/s, more preferably 2 to 5 mm.sup.2/s, and even more
preferably 3 to 5 mm.sup.2/s. When the dynamic viscosity is less
than 1 mm.sup.2/s, the lubricating performance of the lubricating
oil composition is insufficient, and the evaporation loss is large.
When the dynamic viscosity is more than 10 mm.sup.2/s, the
viscosity of the lubricating oil composition is increased, so that
the power loss due to viscous resistance is increased, during
driving of a machine or engine, and thus the fuel efficiency effect
is poor.
[0070] The viscosity index of the mineral oil and the non-ester
synthetic oil is preferably 90 or more, and more preferably 100 or
more. When it is less than 90, the viscosity index of the
lubricating oil composition is reduced, so that the fuel
consumption is increased.
[0071] As the mineral oils that can be used, HVI base stocks, HHVI
base stocks, VHVI base stocks, and XHVI base stocks are preferable,
VHVI base stocks and XHVI base stocks are more preferable, and XHVI
base stocks are even more preferable.
[0072] PAO can be obtained by polymerizing or copolymerizing one or
two or more .alpha.-olefins having 2 to 16 carbon atoms, preferably
6 to 12 carbon atoms. The average polymerization degree of the PAO
is preferably 2 to 10, and more preferably 2 to 7.
[0073] Specific examples of .alpha.-olefin include ethylene,
propylene, butene-1, pentene-1, hexene-1, heptene-1, octene-1,
nonene-1, decene-1, undecene-1, dodecene-1, tetradecene-1, and
hexadecene-1. Hexene-1, heptene-1, octene-1, nonene-1, decene-1,
undecene-1, and dodecene-1 are preferable.
[0074] The PAO can be produced by, for example, a method employing
a Ziegler-Natta catalyst, a radical catalyst, an aluminum chloride
catalyst or a catalyst comprising boron fluoride and alcohol.
[0075] The basic metal compounds (v) can be contained for the
purpose of neutralizing corrosive acid to prevent corrosion by the
acid. Examples of the basic metal compounds include overbase metal
compound such as sulfonate compounds and phenate compounds, each of
which contains calcium, magnesium or the like. It is preferable
that the basic metal compounds are contained in the composition in
a ratio of 0.05 to 5 wt %.
[0076] It is considered that the friction reducing agents (vi)
serve to prevent metal fusion in a sliding portion by forming a
strong adsorption film on the surface of the metal of the sliding
portion so as to reduce friction. For such friction reducing
agents, a compound having a long chain alkyl group and a polar
group in a molecule can be employed. For example, the following
compounds or materials can be used: higher carboxylic acids such as
oleic acid, stearic acid, and lauric acid; higher alcohols such as
oleyl alcohol, stearyl alcohol, and lauryl alcohol; oil and fat
such as castor oil and rape seed oil; carboxylates such as methyl
oleate and butyl stearate; amine carboxylates such as tallow amine;
and organic molybdenum compounds such as molybdenum dithiophosphate
and molybdenum dithiocarbamate. It is preferable that the friction
reducing agent is contained in the composition in a ratio of 0.05
to 3 wt %.
[0077] The abrasion resistance agents (vii) and the extreme
pressure agents (viii) form a protective film on the surface of a
metal on which friction is applied to reduce the abrasion of the
metal and prevent seize-up. Examples of the abrasion resistance
agents and the extreme pressure agents include zinc
dialkyldithiophosphates; molybdenum compounds such as molybdenum
dithiophosphates and molybdenum dithiocarbamates; phosphates such
as tricresyl phosphate and lauryl acid phosphate; phosphites such
as trioleyl phosphite and dilauryl hydrogen phosphite; amine salts
of phosphate; sulfur compounds such as dialkyl disulfide,
sulfurized oil and fat, dialkylpolysulfide, and sulfurized olefin;
and chlorine compounds such as chloroparaffin and chlorinated
carboxylic acid methyl esters. Among these, care is necessary for
compounds containing chlorine, because they generate toxic chlorine
compounds such as dioxin when being incinerated at the time of
disposal. It is preferable that the abrasion resistance agents and
the extreme pressure agents are contained in the composition in a
ratio of 0.05 to 10 wt %. In particular, when zinc
dialkyldithiophophate is used, it is preferable that it is
contained in the composition such that the zinc concentration is
0.02 to 1.2 wt %.
[0078] The rust inhibitors (ix) serve to prevent rust from
occurring by adsorbing onto the surface of a metal to form a
protective film or by neutralizing acids. Examples of the rust
inhibitors include the following compound or materials: amines such
as amine carboxylate, carboxylic acid amide, alkylimidazole, and
alkylimidazoline; esters such as sorbitan monooleate,
alkenylsuccinic acid half ester, and succinic acid tetrapropenyl
ester; carboxylates such as oleoyl sarcosine; sulfonates such as
alkali metal or alkaline earth metal salts of petroleum sulfonic
acid, alkaline-earth metal salts of alkylbenzenesulfonic acid, and
alkaline-earth metal salts of alkylnaphthalenesulfonic acid;
oxidized paraffin; and alkylpolyoxyethylene ether. It is preferable
that the rust inhibitor is contained in the composition in a ratio
of 0.01 to 3 wt %.
[0079] The pour point depressants (x) serve to prevent formation of
a three-dimensional network structure by adsorbing onto the surface
of crystals of a crystalline substance such as paraffin to form
eutectic crystals with the crystalline substance. It is considered,
as a result, aggregation is prevented, that is, the freezing point
is lowered. Examples of the pour point depressant include
polymethacrylate, a condensation product of chlorinated paraffin
and alkylnaphthalene, polybutene, polyalkylstyrene, and polyvinyl
acetate. Polymethacrylate is preferable, and polymethacrylate
having an weight average molecular weight of about 100000 is
particularly preferable. Care is necessary for the condensation
product of chlorinated paraffin and alkylnaphthalene, because it
generates toxic chlorine compounds such as dioxin when being
incinerated at the time of disposal. It is preferable that the pour
point depressant is contained in the composition in a ratio of 0.01
to 5 wt %.
[0080] The anti-foaming agents (xi) can reduce the surface tension
of foam films, or enter into foam films and rupture the foam films.
In particular, in the case of internal combustion engines, foaming
in a lubricating oil in a crankcase can be reduced. Examples of the
anti-foaming agents include dimethylsiloxane and polyacrylate. The
anti-foaming agent can be contained in the composition in a small
amount, for example, in a ratio of about 0.002 wt %.
[0081] The lubricating base stock for internal combustion engine
oil of the present invention has a low viscosity, excellent
flowability at low temperature, and a high viscosity index, and
thus has good lubricity over a wide range of temperatures, and has
a small change of the shear viscosity due to temperature change.
Furthermore, the base stock has low volatility, good thermal
oxidation stability, and high fuel efficiency. The lubricating base
stock for internal combustion engine oil of the present invention
and the composition containing the same can be used in internal
combustion engines and the associated drive systems. For example,
the base stock and the composition can be used preferably in
internal combustion engines such as 2-cycle engines and 4-cycle
engines; drive system devices such as manual transmissions,
automatic transmissions, and power steering; and differential
gears.
EXAMPLES
[0082] Hereinafter, the present invention will be described more
specifically by way of examples, but the present invention is not
limited by the examples. In the examples, % refers to wt %.
[0083] The test method of esters produced in the examples and the
comparative examples will be described below.
[0084] <Total acid value> The total acid value is measured
according to JIS K2283.
[0085] <Hydroxyl value> The hydroxyl value is measured
according to JIS K0070.
[0086] <Dynamic viscosity and viscosity index> The dynamic
viscosity is measured with a Cannon-Fenske viscometer at 40.degree.
C. and 100.degree. C. according to JIS K2283, and the viscosity
index is calculated from the resultant values.
[0087] <Pour point> The pour point is measured according to
JIS K2269.
[0088] <Shear viscosity> The shear viscosity is measured at
100.degree. C. and 150.degree. C. by the tapered bearing simulator
method (TBS method) according to Japan petroleum Institute
JPI-5S-36-91. The gap is adjusted such that the shear rate is
1.times.10.sup.6/sec.
[0089] <Hot tube test> The hot tube test is performed under
the following conditions according to Japan petroleum Institute
JPI-5S-55-99: test temperature, 300.degree. C.; test time, 24
hours; air flow rate, 10.+-.0.5 cc/min; and test oil flow rate,
0.30.+-.0.01 cc/min.
[0090] <SRV friction abrasion test> The friction coefficient
is measured under the following conditions using SRV Lubricant and
Material Test System (manufactured by OPTIMOL Corporation): test
temperature, 80.degree. C.; frequency, 50 Hz; amplitude, 1 mm; and
loading, 500N.
Example 1
[0091] First, 1185.2 g (8.0 moles of an ethylene oxide adduct of
neopentyl glycol (hereinafter, referred to as NPG-EO) (molar amount
of addition: 1) as the alkylene oxide adduct of polyol having a
neopentyl structure and 2764.8 g (19.2 moles) of caprylic acid as
the saturated aliphatic monocarboxylic acid were placed in a
four-necked flask provided with a thermometer, a nitrogen inlet
tube, a stirrer, and a condenser. The mixture was allowed to react
under a nitrogen stream at 220.degree. C. at an atmospheric
pressure for 15 hours while water generated by the reaction was
removed by distillation. After the reaction, stripping was
performed under a reduced pressure of 5 kPa so as to remove
excessive caprylic acid, and thus an esterified crude product was
obtained.
[0092] Then, 10% potassium hydroxide corresponding to 1.5
equivalent of the acid value of the esterified crude product was
added to this esterified crude product, and the mixture was stirred
at 70.degree. C. for 30 minutes. Furthermore, the resultant mixture
was allowed to stand for 30 minutes and the aqueous layer was
removed. Then, 1000 g of ion-exchanged water was added thereto and
the mixture was stirred at 70.degree. C. for 30 minutes, and
thereafter was allowed to stand for 30 minutes and the aqueous
layer was removed. The ester layer was washed with water four times
until the pH of the discharged water became neutral, and the ester
layer was dried at 100.degree. C. under a reduced pressure of 1
kPa.
[0093] To this, 30 g of Kyowaad 500 (manufactured by Kyowa Chemical
Industry Co., Ltd.) was added for adsorption treatment. The
adsorption temperature, the pressure and the adsorption time were
100.degree. C., 1 kPa, and three hours, respectively. The mixture
was filtered, and thus a carboxylic acid ester of NPG-EO (molar
amount of addition: 1) was obtained in an amount of 3001.2 g. The
product was referred to as ester a1. The yield with respect to the
initial raw materials was 76.0%.
[0094] Regarding the obtained ester a1, the dynamic viscosity, the
viscosity index, the total acid value, the hydroxyl value, and the
pour point were measured by the above-described method. Further, in
order to examine the thermal oxidation stability, a hot tube test
was performed. In this hot tube test, the higher the point is, the
better the thermal oxidation stability. It is considered that the
samples having at least 8 points in the hot tube test can be used
in practice as the lubricating base stock or lubricating oil. Table
1 shows the results. Table 1 also shows the results of Examples 2
to 10 and Comparative Examples 1 to 7.
[0095] Examples 2 to 10
[0096] Esters a2 to a10 were produced by performing a reaction in
the same manner as in Example 1, using 8.0 moles of alkylene oxide
adducts of polyol having a neopentyl structure and 19.2 moles of
saturated aliphatic monocarboxylic acids shown in Table 1. In
Examples 5 and 9, two compounds were used as the saturated
aliphatic monocarboxylic acid. The molar ratios thereof are
parenthesized in Table 1. Regarding the obtained esters, the same
tests as in Example 1 were performed.
Comparative Examples 1 to 7
[0097] Esters b1 to b7 were produced by performing a reaction in
the same manner as in Example 1, using 8.0 moles of alkylene oxide
adducts of polyol having a neopentyl structure and 19.2 moles of
saturated aliphatic monocarboxylic acids shown in Table 1. In
Comparative Example 6, two compounds were used as the saturated
aliphatic monocarboxylic acid. The molar ratio thereof is
parenthesized in Table 1. Regarding the obtained esters, the same
tests as in Example 1 were performed.
1 TABLE 1 Examples 1 2 3 4 5 6 7 8 9 10 Raw Alkylene oxide Polyol
having neopentyl NPG NPG NPG NPG NPG NPG NPG NPG DEPG BEPG
materials adduct.sup.a) structure Alkylene oxide (Molar EO EO EO EO
EO EO EO EO EO EO amount of addition) (1) (2) (2) (2) (3) (4) (4)
(4) (3) (1) Saturated aliphatic monocarboxylic acid C8 C5 C10 C12
C7/bC8 C8 C10 C5 C7/C10 C9 (mol %) (100) (100) (100) (100) (95/5)
(100) (100) (100) (80/20) (100) Ester a1 a2 a3 a4 a5 a6 a7 a8 a9
a10 Test Dynamic viscosity at 40.degree. C. (mm.sup.2/s) 8.286
6.505 13.68 18.23 11.39 13.78 17.54 9.813 12.99 15.46 results
Dynamic viscosity at 100.degree. C. (mm.sup.2/s) 2.568 2.151 3.761
4.669 3.240 3.809 4.560 2.943 3.585 3.785 Viscosity index 153 146
178 189 163 183 190 167 171 140 Total acid value (mgKOH/g) 0.05
0.02 0.01 0.05 0.02 0.01 0.05 0.10 0.20 0.02 Hydroxyl value
(mgKOH/g) 0.5 1.6 0.7 0.1 3.6 2.1 1.3 1.1 2.4 3.4 Pour point
(.degree. C.) <-50.0 <-50.0 -25.0 -25.0 <-50.0 <-50.0
-20.0 <-50.0 -35.0 -40.0 Hot tube test 9 9 9 9 8 8 9 8 8 8
Comparative Examples 1 2 3 4 5 6 7 Raw Alkylene oxide Polyol having
neopentyl TMP NPG NPG NPG DEPG TMP NPG materials adduct.sup.a)
structure Alkylene oxide EO PO EO EO EO EO BO (Molar amount of
addition) (0) (3) (8) (3) (2) (3) (2) Saturated aliphatic
monocarboxylic acid C10 C10 C10 C10 bC8 C8/bC8 C9 (mol %) (100)
(100) (100) (100) (100) (95/5) (100) Ester b1 b2 b3 b4 b5 b6 b7
Test Dynamic viscosity at 40.degree. C. (mm.sup.2/s) 25.12 20.88
24.28 14.71 11.06 26.52 15.26 results Dynamic viscosity at
100.degree. C. (mm.sup.2/s) 5.107 4.427 6.027 3.957 2.761 5.504
3.715 Viscosity index 136 124 212 179 88 124 135 Total acid value
(mgKOH/g) 0.05 0.10 0.20 2.20 0.02 0.03 0.02 Hydroxyl value
(mgKOH/g) 0.5 1.2 2.9 1.0 1.1 0.8 1.5 Pour point (.degree. C.)
-10.0 <-50.0 <-50.0 -40 <-50.0 -45.0 <-50.0 Hot tube
test 8 7 6 5 6 7 6 NPG: Neopentylglycol; DEPG:
2,2-diethyl-1,3-propanediol BEPG: 2-butyl-2-ethyl-1,3-propanediol;
TMP: Trimethylolpropane EO: Ethylene oxide; PO: propylene oxide;
BO: Butylene oxide C5: Pentanoic acid; C7: Heptanoic acid; C8:
Caprylic acid; bC8: 2-Ethylhexanoic acid; C9: Nonanoic acid; C10:
Capric acid; C12: lauric acid .sup.a)Alkylene oxide adduct of
polyol having neopentyl structure
[0098] As can be seen from the results of Table 1, all the esters
of Examples 1 to 10 have a dynamic viscosity at 100.degree. C. of
about 2 to 5 mm.sup.2/s, a viscosity index of 140 or more, and a
total acid value of 0.5 mg KOH/g or less. Furthermore, the values
of the hot tube test were so high that no problem would be caused.
These esters have low total acid values, and therefore the heat
stability is excellent, and the drive portion of an internal
combustion engine is not corroded or worn. The dynamic viscosity at
40.degree. C. is low and the flowability at low temperature is
excellent, and the viscosity index is high, which indicates that
these esters have good lubricity over a wide range of temperatures.
Therefore, it is evident that these esters are useful to obtain a
lubricating oil having high fuel efficiency. On the other hand, the
esters of Comparative Examples 1, 2, 5, 6, and 7 have a viscosity
index of less than 140, and the esters in Comparative Examples 3
and 6 have high dynamic viscosity at 100.degree. C. Therefore,
these esters cannot be used for an internal combustion engine
lubricating oil having satisfactory fuel efficiency. The ester of
Comparative Example 4 has a high total acid value. All the esters
of Comparative Examples 2 to 7 have a low point in the hot tube
test, and therefore cannot be used in practice.
[0099] Regarding the esters of Examples 2 to 4, 6 and 8, and
Comparative Example 7, the shear viscosity was measured, and the
shear viscosity ratio (shear viscosity at 100.degree. C./shear
viscosity at 150.degree. C.) was calculated from the obtained
values of the shear viscosity. Table 2 shows the results.
2 TABLE 2 Examples Com. Ex Base stock 2 3 4 6 8 7 Shear viscosity
100.degree. C. 2.01 3.26 4.03 3.46 2.82 3.22 (mPa .multidot. s)
150.degree. C. 1.05 1.68 2.03 1.76 1.46 1.58 Shear viscosity
ratio*.sup.1 1.91 1.94 1.98 1.97 1.93 2.04 *.sup.1Ratio of shear
viscosity at 100.degree. C./shear viscosity at 150.degree. C.
[0100] The results in Table 2 indicate that the ester (ester (A))
that is an essential component of the lubricating base stock of the
present invention has a small value of shear viscosity ratio (i.e.,
the ratio of the shear viscosity at 100.degree. C. and the shear
viscosity at 150.degree. C.).
Example 11
[0101] A lubricating base stock was obtained by mixing the ester a3
of Table 1 and the ester a8 of Table 1 in a ratio shown in Table 3.
The dynamic viscosity at 40.degree. C. and 100.degree. C. and the
shear viscosity at 100.degree. C. and 150.degree. C. of this
lubricating base stock were measured, and the shear viscosity ratio
was calculated. Table 3 shows the results.
Examples 12 to 15
[0102] A lubricating base stock was obtained by mixing the ester a3
of Table 1 and the ester a8 of Table 1 in a ratio shown in Table 3.
Regarding the obtained base stock, the same tests as in Example 11
were performed. Table 3 shows the results.
Comparative Example 8
[0103] A lubricating base stock was obtained by mixing the ester a3
of Table 1 and the ester a8 of Table 1 in a ratio by weight of
70:30. Regarding the obtained lubricating base stock, the same
tests as in Example 11 were performed. Table 3 shows the
results.
Examples 16 to 19 and Comparative Examples 9 to 10
[0104] A lubricating base stock was obtained by mixing the ester a3
of Table 1 and the ester b7 of Table 1 in a ratio shown in Table 4.
Regarding the obtained lubricating base stock, the same tests as in
Example 11 were performed. Table 4 shows the results.
3 TABLE 3 Examples Com. Ex 11 12 13 14 15 8 Ester A a3 a3 a3 a3 a3
a3 (wt %) (98) (90) (80) (0) (100) (70) Ester B a8 a8 a8 a8 a8 a8
(wt %) (2) (10) (20) (100) (0) (30) Dynamic 40.degree. C. 13.72
13.30 12.75 9.813 13.68 12.32 viscosity 100.degree. C. 3.725 3.650
3.560 2.943 3.761 3.470 (mm.sup.2/s) Shear viscosity 100.degree. C.
3.300 3.320 3.170 2.820 3.260 3.120 (mPa .multidot. s) 150.degree.
C. 1.780 1.750 1.650 1.460 1.680 1.580 Shear viscosity ratio*.sup.1
1.85 1.90 1.92 1.93 1.94 1.97 *.sup.1Ratio of shear viscosity at
100.degree. C./shear viscosity at 150.degree. C.
[0105]
4 TABLE 4 Com. Examples Examples 16 17 18 19 9 10 Ester A a3 a3 a3
a3 a3 a3 (wt %) (98) (90) (80) (100) (0) (70) Ester B b7 b7 b7 b7
b7 b7 (wt %) (2) (10) (20) (0) (100) (30) Dynamic viscosity
40.degree. C. 13.76 13.96 14.44 13.68 15.26 14.84 (mm.sup.2/s)
100.degree. C. 3.730 3.740 3.752 3.761 3.715 3.748 Shear viscosity
100.degree. C. 3.177 3.200 3.223 3.260 3.220 3.491 (mPa .multidot.
s) 150.degree. C. 1.751 1.720 1.680 1.680 1.580 1.786 Shear
viscosity ratio*.sup.1 1.81 1.86 1.92 1.94 2.04 1.95 *.sup.1Ratio
of shear viscosity at 100.degree. C./shear viscosity at 150.degree.
C.
[0106] The results in Tables 3 and 4 indicate that the lubricating
base stock for internal combustion engine oil containing the ester
(A) and the ester (B) of the present invention in a predetermined
ratio has a small value of shear viscosity ratio (i.e., the ratio
of shear viscosity at 100.degree. C. and the shear viscosity at
150.degree. C.).
Example 20
[0107] A lubricating oil was prepared by mixing the ester obtained
in Example 1 as the base stock,
4,4-methylenebis(2,6-di-t-butylphenol) and di(primary n-octyl) zinc
dithiophosphate as antioxidants, succinimide as an ashless
dispersant and polymethacrylate dispersion as the viscosity index
improver in a ratio shown in Table 5. The dynamic viscosity at
40.degree. C. and 100.degree. C., the viscosity index and the shear
viscosity at 100.degree. C. of the obtained lubricating oil were
measured. Furthermore, the hot tube test and the SRV friction and
abrasion test were performed. Table 5 shows the results. Table 5
also shows the results of Examples 21 and 22, and Comparative
Example 11.
Examples 21 and 22
[0108] Instead of the ester obtained in Example 1, the esters
obtained in Examples 2 and 3 were used, and the materials shown in
Table 5 were mixed in a ratio shown in Table 5 so that lubricating
oils were obtained. Regarding the obtained lubricating oils, the
same tests as in Example 20 were performed.
Comparative Example 11
[0109] Regarding a commercially available engine oil OW-20
(manufactured by Idemitsu Kosan Co., Ltd), the same tests as in
Example 20 were performed.
5 TABLE 5 Examples Com. Ex. 20 21 22 11 Materials Base stock a1 a2
a3 -- Amount of base stock (wt %) 87.0 85.0 88.0 --
4,4-Methylenebis(2,6-di-t-butylphe- nol) 0.5 0.5 0.5 -- C8
ZDTP*.sup.1 (wt %) 1.5 1.5 1.5 -- Succinimide (wt %) 5.0 5.0 5.0 --
Polymethacrylate (wt %) 6.0 8.0 5.0 -- OW - 2O*.sup.2 (wt %) -- --
-- 100 Test Dynamic viscosity at 40.degree. C. (mm.sup.2/s) 23.16
20.61 26.81 34.80 results Dynamic viscosity at 100.degree. C.
(mm.sup.2/s) 7.250 7.275 7.217 7.850 Viscosity index 312 365 255
207 Shear viscosity at 100.degree. C. (mPa .multidot. s) 5.00 4.84
5.22 5.46 Hot tube test 10 10 10 10 Friction coefficient at SRV:
500 N 0.11 0.12 0.11 0.12 *.sup.1Di-(primary-n-octyl) zinc
dithiophosphate *.sup.2Produced by Idemitsu Kosan Co., Ltd.
[0110] As can seen from the result of Table 5, the lubricating oils
of Examples 20 to 22 have low shear viscosities, and these
lubricating oils can contribute to fuel efficiency. Furthermore,
these oils have excellent values in the hot tube test and have good
thermal oxidation stability. On the other hand, the commercially
available lubricating oil of Comparative Example 11 has a lower
viscosity index and a higher shear viscosity at 100.degree. C. than
those of the lubricating oils of Examples 20 to 22, and thus the
fuel efficiency is lower than the lubricating oils of these
examples.
[0111] The invention may be embodied in other forms without
departing from the spirit or essential characteristics thereof. The
embodiments disclosed in this application are to be considered in
all respects as illustrative and not limiting. The scope of the
invention is indicated by the appended claims rather than by the
foregoing description, and all changes which come within the
meaning and range of equivalency of the claims are intended to be
embraced therein.
* * * * *