LUBRICANT COMPOSITIONS FOR AUTOTRACTION

COMPOSITIONS DE LUBRIFIANTS POUR AUTO-TRACTION

English Abstract

A lubricant composition comprises: a) a mineral base oil; b)
a synthetic base oil; c) a dialkyl carbonate; d) conventional
additives; and e) viscosity index and pour point improvers.
Component c) is the product of transesterification of a
dialkyl carbonate with an alcoholic mixture consisting of at
least 98% by weight of branched alcohols having the general
formula
(see formula I)
where m is an integer and n is zero or a whole number, with
the condition that the total number of carbon atoms in the
molecule (I) is between 10 and 18.

Claims

13
CLAIMS
1. A lubricant additive composition comprising:
a) from 0 to 90% by weight of a mineral base oil;
b) from 0 to 90% by weight of a synthetic base oil;
c) from 5 to 50% by weight of a dialkyl carbonate;
d) from 6 to 12% by weight of conventional additives; and
e) from 0 to 15% by weight of viscosity index and pour
point improvers;
characterised in that component c) is the product of
transesterification of a dialkyl carbonate with an alcoholic
mixture consisting of at least 98% by weight of branched
alcohols having the general formula:
<IMG>
where m is an integer and n is zero or a whole number, with
the condition that the total number of carbon atoms in the
molecule (I) is between 10 and 18.
2. A composition according to claim 1, wherein said
alcoholic mixture used to prepare component c) is the
branched fraction of oxo alcohols that are obtained by
hydroformylating with hydrogen and carbon monoxide
predominantly linear olefins having a statistic internal or
terminal double bond by the agency of a Co-based or an Rh-
based catalyst, said branched fraction being separated from
the linear fraction by fractional crystallization in the
presence of a hydrocarbonaceous or an ethereal solvent.

14
3. A composition as claimed in claim 1 or in claim 2,
characterised in that the total number of carbon atoms in (I)
is from 13 to 16.
4. Composition according to claim 1, wherein the component
c) has the following properties:
Average molecular weight 340-560
Kinematic viscosity at 100°C:
(ASTM D 455) 3.10-6m2/s- 12.10-6m2/s (3 cSt-12 cSt)
Dynamic viscosity at -30°C:
(ASTM D2602) 0,8 Ns/m2-5 Ns/m2 (800 cP-5000 cP)
Viscosity Index V.I. (ASTM D2270) 120-140
Pour Point (ASTM D97) -60°C to -30°C
Flash Point (COC) (ASTM D92) 220°C-350°C
Noack evaporation loss (DIN 51581) 12% to 2%
Copper Corrosion (ASTM D130) Classif. 1 slight tarmish
TAN (mg KOH/g) (ASTN D974) 0,01-0,05.
5. Composition according to claim 1, wherein:
Component a) is present in an amount of from 0% by
weight to 60% by weight
Component b) is present in an amount of from 20% by
weight to 60% by weight;
Component c) is present in an amount of from 15% by
weight to 30% by weight;
Component d) is present in an amount of from 8% by
weight to 10% by weight, and
Component e) is present in an amount of from 5% by
weight to 10% by weight.
6. Composition according to claim 1, wherein the component
a) is a lubricating oil obtained by distilling and refining

15
petroleum and has a Viscosity index V.I. of from 102 to 108,
a pour point of from -12°C to -6°C and a Noack evaporation
loss of from 12% to 420.
7. Composition according to claim 1, wherein the component
b) is the product of the polymerization of terminal or
internal olefins, or of the isomerization and/or alkylation
of petroleum fractions.
8. Composition according to claim 1, wherein the component
d) comprises dispersants, antiwear additives, metal
passivators and copper deactivators, superbasic and neutral
detergents, and antioxidants.
9. Composition according to claim 1, wherein the component
e) comprises viscosity-index-raising additives and pour point
depressants.
10. Composition according to claim 4, wherein the component
c) has an average molecular weight of from 420 to 510 and a
kinematic viscosity at 100°C (ASTM D455) of from 4.10-6m2/s
to 8.10-6m2/s (4 cST-8 cSt).

Description

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CASE 3329
LUBRICANT COMPOSITIONS FOR AUTOTRACTION
This invention relates to an improved lubricant composition for
use in internal combustion engines.
It is known in the art to use synthetic bases in formulating
lubricant compositions both of single grade and of multigrade
type. In this respect, synthetic bases are able to eliminate or
at least alleviate the drawbacks often encountered when using only
;:
mineral bases, these requiring 1) the presence of extremely fluid
fractions to obtain the desired viscosity at low temperature and
to limit volatility, 2) the presence of a high percentage of
viscosity index improvers to improve the initial VI, and 3) other
additives for satisfying all the other lubricant performance
requirements.
For use in internal combustion engines, lubricant compositions
must possess certain characteristics, namely thermal stability,
oxidation resistance, low volatility and such viscosity-
temperature characteristics as to allow both cold starting and
goad lubrication at maximum operating temperature.
Lubricant compositions which have been proposed for this purpose
include those containing higher dialkyl carbonates in combination
with a mineral oil and usual additives. These compositions, which

CA 02053691 1999-O1-26
2
are described for example in U.S. 2,387,999, U.S. 2,758,975,
U.S. 3,642,858 and European patent application 89, 709,
result in various improvements compared with compositions
based on carboxylic esters, in particular in relation to
increased thermal, hydrolytic and oxidative stability.
A particular class of higher alkyl carbonates has now been
found which results in a general rheological and engine
performance improvement in the lubricant compositions in
which they are incorporated, and thus make them desirable for
use as high-performance lubricant compositions for four-
stroke gasoline and diesel engines.
In accordance with the invention, a first object of the
present invention is a lubricant composition comprising:
a) from 0 to 90% by weight of a mineral base oil;
b) from 0 to 90~ by weight of a synthetic base oil;
c) from 5 to 50~ by weight of a dialkyl carbonate;
d) from 6 to 12~ by weight of conventional additives; and
e) from 0 to 15~ by weight of viscosity index and pour
point improvers;
characterised in that component c) is the product of
transesterification of a dialkyl carbonate with an alcoholic
mixture consisting of at least 98g by weight of branched
alcohols having the general formula:
CH3- ( CH2 ) m- i H- ( CH2 ) n-CH3 ( I )
CH2
where m is an integer and n is zero or a whole number, with
the condition that the total number of carbon atoms in the
molecule (I) is between 10 and 18.

CA 02053691 1999-O1-26
2a
Inaccordance
therewith
the
present
invention
provides
a
lubricant composition comprising:
a)from 0 to 90o by weight of mineral base oil;
a
b)from 0 to 90~ by weight of synthetic base oil;
a
c)from 5 to 50$ by weight of long-chain dialkyl
a
carbonate;
d)from 6 to 12~ by weight of parcel of usual additives;
a
and
e) from 0 to 15~ by weight of viscosity index and pour
point improvement additives;
said composition being characterised in that the component c)
is the product of transesterification of a lower dialkyl
carbonate with an alcoholic mixture consisting of at least
98% by weight of aliphatic alcohols with a linear or
essentially linear hydrocarbon chain carrying a -CH2-OH group
on a non-terminal carbon atom, the total number of carbon
atoms in the alcohol varying from 10 to 18 and preferably
from 13 to 16.
In the preferred embodiment, component a) is present in a
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of between 0 and 60% by weight, component b) from 20 to 60% by
weight, component c) from 15 to 30% by Weight, component d) from 8
to 10% by weight and component e) from 5 to 10% by weight.
. Lubricant oils which can be used as component a) of the
composition of the present invention are oils of mineral origin
obtained by petroleum distillation followed by solvent and/or
hydrogen refining generally having a viscosity index of 102-108, a
pour point of between -12°C and -6°C and a Noack evaporation
loss
of 12-42%.
Synthetic base oils which can be used as component b) of the
composition of the present invention are oils of synthetic origin
and can be obtained by the polymerization of terminal or internal
olefins followed by purification, or by isomerization and/or
alkylation of petroleum fractions followed by purification.
Alcohols which can be used for preparing component a) of the
composition of the present invention are mixtures containing at
least 98% and preferably at least 99% of aliphatic alcohols with a
linear or essentially linear hydrocarbon chain carrying a -CHz-OH
group on a non-termin~.l carbon atom, the total number of carbon
atoms in the alcohol varying from l0 to 18 and preferably from 13
to 16. More specifically, alcohols suitable for the purpose are
alcohols definable by the formula:
CHa-(CHz)~-CH-(CHz)n-CHs (I)
. (
CHa-0H
where m is a whole number and n is zero or a whole number, with
the condition that the total number of carbon atoms in the
molecule is between l0 and l8 and preferably between 13 and 16.

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Preferred mixtures are those in which the -CH2-OH
l group is
prevalently in position 2 of the chain.
Mixtures of alcohols (I) suitable for the purpose
include the
branched fraction of the oxo-alcohols obtained
by
W 5 hydroformylation, using carbon monoxide and hydrogen,
of linear or
essentially linear olefins with a statistical internal
or terminal
double bond, operating with cobalt or rhodium catalysts.
This
branched oxo-alcohol fraction can be separated
from the linear
fraction by fractional crystallization operating
in the presence
of a hydrocarbon or ether solvent, as described
for example in
U.S. patent 4,670,806. According to this patent,
a mixture of
linear and branched chain oxo-alcohols is dissolved
in a liquid
hydrocarbon solvent containing from 3 to 5 carbon
atoms in the
molecule, or in methyl tert-butyl ether. The solution
is cooled
to a temperature within the range of -20C to -52C
to cause
separation of a solid phase consisting of the linear
oxo-alcohols,
and a liquid phase consisting of a solution of
the branched oxo-
alcohols in the chosen solvent. The branched oxo-alcohols
can
generally be separated form this solution with
a purity of the
order of 95%, and be purified by further crystallization
to obtain
the mixture of alcohols (I) suitable for the purposes
of the
present invention, with a purity exceeding 98%
and preferably
exceeding 99%.
Such a mixture of alcohols (I) is then transesterified
with a
lower dialkyl carbonate to give component b) of
the composition of
the present invention. This reaction can be effected
by bringing
the reagents into contact in the presence of a
basic catalyst

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operating at high temperature and under reduced pressure, and
eliminating the lower aliphatic alcohol evolved as the reaction
by-product, as is well known in the art and described in the
examples given in European patent application publication No.
89,909. Preferred lower dialkyl carbonates are dimethyl carbonate
and diethyl carbonate. Active transesterification catalysts
useful for the purpose are sodium methylate and sodium ethylate.
On termination of the transesterification reaction the long-chain
dialkyl carbonate is recovered to constitute component b) of the
composition of the present invention, its characteristics falling
generally within the following value ranges (general and
preferred):
Average molecular weight: 340-560
(preferred 420-510)
Viscosity 100°C cSt (ASTM D455): 3-12
(preferred 4-B)
Viscosity -30°C cP (ASTM D2602): 800-5000
Viscosity index V.I. (ASTM D2270): 120-140
Pour point (°C) (ASTAi D9~): -60 to -30
Plash point COC (°C) (ASTM D92): 220-350
Noack volatility (%) (DIN 51581): 15-2
Copper corrosion (ASTM D130): la-lb
TAN (mg K0H/g) (ASTM D 974): 0.01-0.05
Such a dialkyl carbonate also has desirable characteristics in
relation to low temperature rheology values, oxidation stability,
elastomer compatibility, biodegradability and toxicity.
Component d) of the composition of the present invention consists

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of a parcel of additives usually used in lubricants and
specifically dispersants, antiwear and antirust additives, metal
passivators and copper deactiwators, detergent additives
(superbasic and neutral) and antioxidants. These additives are
usually chosen from the following classes of compounds:
alkyl/allcenyl succinimides, succinic esters; alkyl/aryl
dithiophosphates of ainc and olefins; ethoxylates, esters and
hemiesters of substituted succinic acids; unsaturated or carbonyl
compounds of chelating action; heterocyclic compounds; metal salts
(neutral and superbasic) of alkyl and aryl sulphonic acids,
salicylic acids, phenols and substituted phenols; sterically
hindered amines and phenols; sulphurated compounds.
Component e) of the composition of the present invention consists
of a collection of additives able to raise the viscosity index and
lower the pour point of the resultant lubricant composition.
These additives are usually chosen from the following classes of
compounds: olefinic copolymers, methacrylic copolymers,
olefinic/methacrylic copolymers. Said additives can also have
other properties such as antioxidant, dispersant and antiwear,
together with the basic properties of viscosity index and pour
point improvers.
Typical lubricant compositions suitable for four-stroke gasoline
and diesel engines contain the aforesaid components in the
following weight percentages:
Composition 1 2 3 4 5 6
a) BO 40 20 0 0 0

b) 10 20 30 40 42 44
c) 10 20 30 40 42 44
d) 10 10 10 10 8 6
e) 10 10 10 10 8 6
The long-chain dialkyl carbonate used as component
c) in the
lubricant compositions enables lubricant compositions
for
autotraction to be formulated possessing unexpectedly
good overall
rheological and engine performance characteristics.
In this
. respect, the particular dialkyl carbonate structure
enables a high
viscosity index, a low pour point and a low volatility
to be
- obtained simultaneously. In addition the high polarity
of the
carbonate group together with its structural characteristics
enables high engine performance to be obtained
together with a
reduction in the level of addition of component
d). In particular
' 15 the high polarity results in good dispersing action
towards engine
sludge (enabling dispersants to be reduced by about
30% in the
lubricant composition), the greasing of metal surfaces
subject to
wear (enabling antiwear additives to be reduced
by about 20% in
the lubricant composition), and an antirust and
eleetr ochemical
protection action on ferrous and non-ferrous metal
surfaces
(enabling antirust additives, metal passivators
and copper
deactivators to be reduced by about 30%). The high
thermal and
oxidative stability of component c) enables the
antioxidant
additives to be reduced by about 30% in the lubricant
composition,
and the absence of acid compounds deriving from
decompcasition
phenomena enables the superbasic detergent additives
to be reduced
by about 20%. Finally, component c) of the composition
is

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practically inert towards the elastomers usually present in the ,
lubrication circuit. As a result, lubricant compositions can be
formulated with a medium-high nitrogen content, avoiding the
addition of specific additives normally introduced to overcome the
elastomer compatibility tests scheduled in the most severe
specifications such as CCMC and VW specifications.
It should be noted that in the known art oxo-alcohols are
described as alcohols suitable for preparing long-chain dialkyl
carbonates for lubricant compositions, however without separation
of the linear fraction from the branched fraction. According to
the present invention the use of the mixture of alcohols (I) with
the aforesaid characteristics is critical in order to obtain the
required characteristics for the dialkyl carbonates and for the
lubricant compositions which incorporate them, as will be apparent
from the experimental examples which are given hereinafter to
better illustrate the present invention.
EXAMPLE 1
A mixture of oxo-alcohols of the following characteristics is
used:
- number of carbon atoms 13-1&
- average molecular weight 220
- linear fraction 40%
- branched fraction 60%
This oxo-alcohol mixture is the product of the hydroformylation of
substantially linear olefins with carbon monoxide and hydrogen in
the presence of a catalyst.
The mixture is subjected to fractional crystallization at low

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temperature in the presence of a hydrocarbon solvent as described
in U.S, patent 4,670,606, to separate a solid
linear alcohol
fraction from a liquid fraction containing 95%
by weight of
branched alcohols. This liquid fraction is purified
by a second
fractional crystallization similar to the first,
to separate a
liquid fraction with a branched alcohol content
exceeding 99% by
weight.
In this manner a mixture of alcohols of formula
(I) is obtained
having the following distribution:
- Cas alcohol content 6% by weight
- Ci4 alcohol content 48% by weight
- Cas alcohol content 42% by weight
- Cas alcohol content 4% by weight
EXAMPLE 2
The mixture of branched alcohols (I) obtained
in Example 1 is
transesterified with dimethyl carbonate operating
with sodium
ethylate as catalyst, as described in European
patent application
No. 89,709, to obtain a dialkyl carbonate (I)
with an average
molecular weight of 470 and having the following
characteristics:
Viscosity 100C cSt 4.16
Viscosity -30C cP 1600
Viscosity index V.I. 125
Pour point (C) -40
COC Flash point (C) 240
Noack volatility (%) 13
Copper corrosion la
TAN (mg KOH/g) 0.05

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EXAMPLE 3
For comparison purposes the linear and branched oxo-alcohol
mixture obtained in the hydroformylation reaction is
transesterified (without previous separation) with dimethyl
carbonate using sodium ethylate as catalyst in accordance with
Example 2, to obtain a dialkyl carbonate (II) with an average
molecular weight of 490, a viscosity index of 130, a pour point of
+12°C and a Noack volatility of 15%.
EXAMPLE 4
The lubricant composition (A) of the presewt invention and the
comparison lubricant composition (B) are prepared in accordance
with the following Table I.
TABLE I
Composition (A) (B)
____________________.._ _____ _,___
mineral base oil 43 43
synthetic base oil 10 10
dialkyl carbonate (I) 30 -_
dialkyl carbonate (II) _- 30
additives parcel 8 g
viscosity index and pour point
improvement additives 9 9
The compositions (A) and (B) are subjected to a series of
rheological and laboratory tests aimed at evaluating the extent to.
which they satisfy the requirements of the European Sequence
scheduled by constructors for CCMC oil classification and the
requirements of the American sequence scheduled by constructors

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for API oil classification. The results are given in the
following Table II.
TABLE II
Rheological and laboratory evaluation
Characteristics Comp. (A) Comp. (B) Limits*
viscosity at 100°C (cSt) 13.5 13.7 12.5-16.3
viscosity at -2S°C (cPs) 3450 >6000 3500 max
BPT (°C) -39 ~ --15 -30 max
stable pour point (°C) -42 -18 -35 max
HTS viscosity at 150°C
l0e sec- (ePs) 3.6 3.6 3.5 min
Noack volatility (%) 12 14 13 max
elastomer compatibility yes yes
foaming no no
* specification APIand CCMC limits for 5W/40 grading.
From the aforegoing data it can be seen that the lubricant
composition (A) in accordance with the present invention satisfies
all the requirements of the American API and European CCMC
Sequences. In contrast, the comparison lubricant composition (B)
does not satisfy the requirements of viscosity at -25°C, BPT,
stable pour point or Noack volatility. This behaviour is related
to the different physico-chemical characteristics of the dialkyl
carbonates (I) and (II) used in the compositions.
With regard to the engine tests scheduled by the same American API
and European CCMC sequences, both the lubricant compositions
satisfy all tests by a wide margin on the set limits. However

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only by using the dialkyl carbonates (I) of 'the present invention
are lubricant compositions obtained cahich have optimum performance
characteristics from both the engine and rheological aspects.

Representative Drawing