U.S. patent application number 13/376700 was filed with the patent office on 2012-05-03 for lubricating oil composition.
Invention is credited to Mark D. Andrews, Benjamin R. Elvidge.
Application Number | 20120103299 13/376700 |
Document ID | / |
Family ID | 41259520 |
Filed Date | 2012-05-03 |
United States Patent
Application |
20120103299 |
Kind Code |
A1 |
Elvidge; Benjamin R. ; et
al. |
May 3, 2012 |
LUBRICATING OIL COMPOSITION
Abstract
A lubricating oil composition that is free of organic friction
modifiers, comprising (A) an oil of lubricating viscosity in a
major proportion; (B) as an additive component in a minor
proportion, a separately-prepared oil-soluble zinc salt of a
dithiophosphoric acid, the dithiophosphoric acid being the reaction
product of phosphorus pentasulphide with one or more alcohols, at
least 50 mole % of the alcohol(s) having formula ROH where R is
linear C18 to C26 saturated or double-bond unsaturated hydrocarbyl
group; and (C) as an additive component in a minor proportion, a
separately-prepared oil-soluble zinc salt of a dithiophosphoric
acid, the dithiophosphoric acid being the reaction product of a
phosphorus pentasulphide with one or more aliphatic alcohols
consisting of an alcohol or alcohols each having from three to
eight carbon atoms.
Inventors: |
Elvidge; Benjamin R.;
(Oxfordshire, GB) ; Andrews; Mark D.;
(Oxfordshire, GB) |
Family ID: |
41259520 |
Appl. No.: |
13/376700 |
Filed: |
June 9, 2010 |
PCT Filed: |
June 9, 2010 |
PCT NO: |
PCT/EP10/58085 |
371 Date: |
January 20, 2012 |
Current U.S.
Class: |
123/196R ;
508/370 |
Current CPC
Class: |
C10N 2030/06 20130101;
C10M 137/10 20130101; C10N 2070/02 20200501; C10N 2030/40 20200501;
C10N 2030/42 20200501; C10M 2223/045 20130101; C10N 2040/25
20130101; C10N 2030/70 20200501; C10N 2020/069 20200501; C10M
141/10 20130101; C10M 2223/045 20130101; C10N 2010/04 20130101;
C10M 2223/045 20130101; C10M 2223/045 20130101; C10M 2223/045
20130101; C10N 2010/04 20130101 |
Class at
Publication: |
123/196.R ;
508/370 |
International
Class: |
F01M 9/00 20060101
F01M009/00; C10M 137/10 20060101 C10M137/10 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 10, 2009 |
EP |
09162431.2 |
Claims
1. A lubricating oil composition that is free of organic friction
modifiers comprising, or made by admixing: (A) an oil of
lubricating viscosity in a major proportion; (B) as an additive
component in a minor proportion, a separately prepared oil-soluble
zinc salt of a dithiophosphoric acid, the dithiophosphoric acid
being the reaction product of phosphorus pentasulphide with one or
more alcohols, at least 50 mole % of the alcohol or alcohols having
the formula ROH where R is a linear C18 to C26 saturated or
double-bond unsaturated hydrocarbyl group; and (C) as an additive
component in a minor proportion, a separately-prepared oil-soluble
zinc salt of a dithiophosphoric acid, the dithiophosphoric acid
being the reaction product of phosphorus pentasulphide with one or
more aliphatic alcohols consisting of an alcohol or alcohols each
having from three to eight carbon atoms.
2. A composition as claimed in claim 1 wherein in (B) 70 to 100
mole % of the alcohol or alcohols have said formula ROH.
3. A composition as claimed in claim 1 or 2 wherein in (B) any
alcohol or alcohols, other than those of formula ROH, have the
formula R.sup.1OH where R.sup.1 has 3 to 12, such as 3 to 10, such
as 5 to 8, carbon atoms and is an alkyl or alkenyl, preferably
alkyl, group.
4. A composition as claimed in any of claims 1 to 3 wherein in (B)
R is a linear C18 to C22 saturated or unsaturated hydrocarbyl
group.
5. A composition as claimed in claim 4 where R is a linear C18
saturated or unsaturated hydrocarbyl group.
6. A composition as claimed in claim 5 where R is an oleyl
group.
7. A composition as claimed in any of claims 1 to 5 where, in (C),
the one or more aliphatic alcohols comprise one or more secondary
aliphatic alcohols such as greater than 60, such as greater than
70, such as greater than 80, such as greater than 90, such as 100,
mole %.
8. A composition as claimed in any of claims 1 to 7 where, in (C),
the one or more secondary aliphatic alcohols have 4 to 8 carbon
atoms.
9. A composition as claimed in any of claims 1 to 8 wherein other
additive components, different from (B) and from (C), are present
and are selected from one or more of ashless dispersants, metal
detergents, corrosion inhibitors, antioxidants, pour point
depressants, antiwear agents, friction modifiers, demulsifiers,
antifoam agents and viscosity modifiers.
10. A composition as claimed in any of claims 1 to 9 wherein (B)
and (C) together introduce 0.02 to 0.09, such as 0.02 to 0.09, such
as 0.02 to 0.08, such as 0.02 to 0.06, mass % of phosphorus,
expressed as phosphorus atoms, into the composition.
11. A method of improving the friction modification properties of a
lubricating oil composition, which method comprises incorporating
into the composition in a minor amount an additive component (B) as
defined in any of claims 1 to 6.
12. A method of lubricating surfaces of the combustion chamber of
an internal combustion chamber during its operation comprising: (i)
providing, in respective minor amounts, zinc salts (B) and (C) as
defined in any of claims 1 to 8 in a major amount of an oil of
lubricating viscosity to make a lubricating oil composition, to
improve the friction modification properties of the composition;
(ii) providing the lubricating oil composition in the combustion
chamber; (iii) providing a hydrocarbon fuel in the combustion
chamber; and (iv) combusting the fuel in the combustion chamber.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to automotive lubricating oil
compositions, more especially to automotive lubricating oil
compositions for use in piston engines, especially gasoline
(spark-ignited) and diesel (compression-ignited), crankcase
lubrication, such compositions being referred to as crankcase
lubricants. In particular, the present invention relates to use of
additives with friction modification properties in automotive
lubricating oil compositions.
BACKGROUND OF THE INVENTION
[0002] A crankcase lubricant is an oil used for general lubrication
in an internal combustion engine where an oil sump is situated
generally below the crankshaft of the engine and to which
circulated oil returns. It is well known to include additives in
crankcase lubricants for several purposes.
[0003] Friction modifiers, also referred to as friction-reducing
agents, may be boundary additives that operate by lowering friction
coefficient and hence improve fuel economy; the use of glycerol
monoesters as friction modifiers has been described in the art, for
example in U.S. Pat. No. 4,495,088; U.S. Pat. No. 4,683,069; EP-A-0
092 946; and WO-A-01/72933. Glycerol monoester friction modifiers
have been and are used commercially. Further, phosphorus in the
form of dihydrocarbyl dithiophosphate metal salts have been used as
extreme pressure, antiwear and antioxidant additives in lubricating
oil compositions for internal combustion engines. The metal may be
zinc, an alkali or alkaline earth metal, or aluminium, lead, tin,
molybdenum, manganese, nickel or copper. Of these, zinc salts of
dihydrocarbyl dithiophosphate (ZDDPs) are most commonly used.
[0004] Organic friction modifiers may have a limited treat rate in
lubricants because of their tendency to become incompatible with
metal detergent colloids, used in the lubricant, at higher treat
rates. U.S. Pat. No. 5,013,465 (465) discusses the problem of using
ZDDP's in combination with friction modifiers (column 1, lines
24-39). It proposes a solution, namely using a mixture of simple
C.sub.4-C.sub.10 alcohols and certain more polar substituted
alcohols, in appropriate proportions, to make friction-modified
ZDDP's with excellent handling properties. '465 states that,
usually, there is more of the simple alcohol than the polar
substituted alcohol, on a molar basis, to produce a mobile liquid
oil-soluble product (column 2, lines 57-59). EP-A-2 161 326
describes use of similar additives in combination with molybdenum
additives.
[0005] DE 941 218 C describes the zinc salt of the oleyl
alcohol/P.sub.2S.sub.5 reaction product, but nowhere describes or
suggests that it has lubricant friction modification
properties.
SUMMARY OF THE INVENTION
[0006] As noted above, '465's disclosure is limited in the amount
of friction modifying entity that can be incorporated into
ZDDP.
[0007] The present invention meets the above problem by
manufacturing ZDDP's from certain alcohols that have been found to
confer friction modification properties on a lubricant without the
need for substantial, separate additions of organic friction
modifiers. In contrast to '465's solution, the present invention
uses an alcohol that is less polar than the simple alcohol and in a
molar proportion greater than that of the simple alcohol. Thus, a
much higher proportion of friction modifier may be incorporated,
and the simple alcohol may not need to be used.
[0008] In accordance with a first aspect, the present invention
provides a lubricating oil composition that is free of organic
friction modifiers, comprising, or made by admixing: [0009] (A) an
oil of lubricating viscosity in a major proportion; [0010] (B) as
an additive component in a minor proportion, a separately prepared
oil-soluble zinc salt of a dithiophosphoric acid, the
dithiophosphoric acid being the reaction product of phosphorus
pentasulphide with one or more alcohols, at least 50 mole % of the
alcohol or alcohols having the formula ROH where R is a linear C18
to C26 saturated or double-bond unsaturated hydrocarbyl group; and
[0011] (C) as an additive component in a minor proportion, a
separately-prepared oil-soluble zinc salt of a dithiophosphoric
acid, the dithiophosphoric acid being the reaction product of
phosphorus pentasulphide with one or more aliphatic alcohols
consisting of an alcohol or alcohols each having from three to
eight carbon atoms.
[0012] According to a second aspect, the present invention provides
a method of improving the friction modification properties of a
lubricating oil composition, which method comprises incorporating
into the composition in a minor amount an additive component (B) as
defined in the first aspect of the invention.
[0013] According to a third aspect, the present invention provides
a method of lubricating surfaces of the combustion chamber of an
internal combustion chamber during its operation comprising: [0014]
(i) providing, in respective minor amounts, zinc salts (B) and (C)
as defined in the first aspect of the invention in a major amount
of an oil of lubricating viscosity to make a lubricating oil
composition, to improve the friction modification properties of the
composition; [0015] (ii) providing the lubricating oil composition
in the combustion chamber; [0016] (iii) providing a hydrocarbon
fuel in the combustion chamber; and [0017] (iv) combusting the fuel
in the combustion chamber.
[0018] In this specification, the following words and expressions,
if and when used, have the meanings ascribed below: [0019] "active
ingredients" or "(a.i.)" refers to additive material that is not
diluent or solvent; [0020] "comprising" or any cognate word
specifies the presence of stated features, steps, or integers or
components, but does not preclude the presence or addition of one
or more other features, steps, integers, components or groups
thereof. The expressions "consists of" or "consists essentially of"
or cognates may be embraced within "comprises" or cognates, wherein
"consists essentially of" permits inclusion of substances not
materially affecting the characteristics of the composition to
which it applies; [0021] "hydrocarbyl" means a chemical group of a
compound that contains only hydrogen and carbon atoms and that is
bonded to the remainder of the compound directly via a carbon atom.
[0022] "oil-soluble" or "oil-dispersible", or cognate terms, used
herein do not necessarily indicate that the compounds or additives
are soluble, dissolvable, miscible, or are capable of being
suspended in the oil in all proportions. These do mean, however,
that they are, for example, soluble or stably dispersible in oil to
an extent sufficient to exert their intended effect in the
environment in which the oil is employed. Moreover, the additional
incorporation of other additives may also permit incorporation of
higher levels of a particular additive, if desired; [0023] "major
amount" means in excess of 50 mass % of a composition; [0024]
"minor amount" means less than 50 mass % of a composition; [0025]
"TBN" means total base number as measured by ASTM D2896; [0026]
"phosphorus content" is measured by ASTM D5185; [0027] "sulfur
content" is measured by ASTM D2622; and [0028] "sulfated ash
content" is measured by ASTM D874.
[0029] Also, it will be understood that various components used,
essential as well as optimal and customary, may react under
conditions of formulation, storage or use and that the invention
also provides the product obtainable or obtained as a result of any
such reaction.
[0030] Further, it is understood that any upper and lower quantity,
range and ratio limits set forth herein may be independently
combined.
DETAILED DESCRIPTION OF THE INVENTION
[0031] The features of the invention relating, where appropriate,
to each and all aspects of the invention, will now be described in
more detail as follows:
[0032] Oil of Lubricating Viscosity (A)
[0033] The oil of lubricating viscosity (sometimes referred to as
"base stock" or "base oil") is the primary liquid constituent of a
lubricant, into which additives and possibly other oils are
blended, for example to produce a final lubricant (or lubricant
composition).
[0034] A base oil is useful for making concentrates as well as for
making lubricating oil compositions therefrom, and may be selected
from natural (vegetable, animal or mineral) and synthetic
lubricating oils and mixtures thereof. It may range in viscosity
from light distillate mineral oils to heavy lubricating oils such
as gas engine oil, mineral lubricating oil, motor vehicle oil and
heavy duty diesel oil. Generally the viscosity of the oil ranges
from 2 to 30, especially 5 to 20, mm.sup.2 s.sup.-1 at 100.degree.
C.
[0035] Natural oils include animal and vegetable oils (e.g. castor
and lard oil), liquid petroleum oils and hydrorefined,
solvent-treated mineral lubricating oils of the paraffinic,
naphthenic and mixed paraffinic-naphthenic types. Oils of
lubricating viscosity derived from coal or shale are also useful
base oils.
[0036] Synthetic lubricating oils include hydrocarbon oils such as
polymerized and interpolymerized olefins (e.g. polybutylenes,
polypropylenes, propylene-isobutylene copolymers, chlorinated
polybutylenes, poly(1-hexenes), poly(1-octenes), poly(1-decenes));
alkylbenzenes (e.g. dodecylbenzenes, tetradecylbenzenes,
dinonylbenzenes, di(2-ethylhexyl)benzenes); polyphenols (e.g.
biphenyls, terphenyls, alkylated polyphenols); and alkylated
diphenyl ethers and alkylated diphenyl sulfides and the
derivatives, analogues and homologues thereof.
[0037] Another suitable class of synthetic lubricating oils
comprises the esters of dicarboxylic acids (e.g. phthalic acid,
succinic acid, alkyl succinic acids and alkenyl succinic acids,
maleic acid, azelaic acid, suberic acid, sebacic acid, fumaric
acid, adipic acid, linoleic acid dimer, malonic acid, alkylmalonic
acids, alkenyl malonic acids) with a variety of alcohols (e.g.
butyl alcohol, hexyl alcohol, dodecyl alcohol, 2-ethylhexyl
alcohol, ethylene glycol, diethylene glycol monoether, propylene
glycol). Specific examples of these esters include dibutyl adipate,
di(2-ethylhexyl)sebacate, di-n-hexyl fumarate, dioctyl sebacate,
diisooctyl azelate, diisodecyl azelate, dioctyl phthalate, didecyl
phthalate, dieicosyl sebacate, the 2-ethylhexyl diester of linoleic
acid dimer, and the complex ester formed by reacting one mole of
sebacic acid with two moles of tetraethylene glycol and two moles
of 2-ethylhexanoic acid.
[0038] Esters useful as synthetic oils also include those made from
C.sub.5 to C.sub.12 monocarboxylic acids and polyols, and polyol
ethers such as neopentyl glycol, trimethylolpropane,
pentaerythritol, dipentaerythritol and tripentaerythritol.
[0039] Unrefined, refined and re-refined oils can be used in the
compositions of the present invention. Unrefined oils are those
obtained directly from a natural or synthetic source without
further purification treatment. For example, a shale oil obtained
directly from retorting operations, a petroleum oil obtained
directly from distillation or ester oil obtained directly from an
esterification process and used without further treatment would be
unrefined oil. Refined oils are similar to the unrefined oils
except they have been further treated in one or more purification
steps to improve one or more properties. Many such purification
techniques, such as distillation, solvent extraction, acid or base
extraction, filtration and percolation are known to those skilled
in the art. Re-refined oils are obtained by processes similar to
those used to obtain refined oils applied to refined oils which
have been already used in service. Such re-refined oils are also
known as reclaimed or reprocessed oils and often are additionally
processed by techniques for approval of spent additive and oil
breakdown products.
[0040] Other examples of base oil are gas-to-liquid ("GTL") base
oils, i.e. the base oil may be an oil derived from Fischer-Tropsch
synthesised hydrocarbons made from synthesis gas containing H.sub.2
and CO using a Fischer-Tropsch catalyst. These hydrocarbons
typically require further processing in order to be useful as a
base oil. For example, they may, by methods known in the art, be
hydroisomerized; hydrocracked and hydroisomerized; dewaxed; or
hydroisomerized and dewaxed.
[0041] Base oil may be categorised in Groups I to V according to
the API EOLCS 1509 definition.
[0042] When the oil of lubricating viscosity is used to make a
concentrate, it is present in a concentrate-forming amount (e.g.,
from 30 to 70, such as 40 to 60, mass %) to give a concentrate
containing for example 1 to 90, such as 10 to 80, preferably 20 to
80, more preferably 20 to 70, mass % active ingredient of an
additive or additives of the invention, optionally with one or more
co-additives. The oil of lubricating viscosity used in a
concentrate is a suitable oleaginous, typically hydrocarbon,
carrier fluid, e.g. mineral lubricating oil, or other suitable
solvent. Oils of lubricating viscosity such as described herein, as
well as aliphatic, naphthenic, and aromatic hydrocarbons, are
examples of suitable carrier fluids for concentrates.
[0043] Concentrates constitute a convenient means of handling
additives before their use, as well as facilitating solution or
dispersion of additives in lubricating oil compositions. When
preparing a lubricating oil composition that contains more than one
type of additive (sometime referred to as "additive components"),
each additive may be incorporated separately, each in the form of a
concentrate. In many instances, however, it is convenient to
provide a so-called additive "package" (also referred to as an
"adpack") comprising one or more additives, such as described
hereinafter, in a single concentrate.
[0044] The oil of lubricating viscosity may be provided in a major
amount, in combination with minor amounts of additive components,
(B) and (C) as defined herein and, if necessary, one or more
co-additives, such as described hereinafter, constituting a
lubricating oil composition. This preparation may be accomplished
by adding the additive directly to the oil or by adding it in the
form of a concentrate thereof to disperse or dissolve the additive.
Additives may be added to the oil by any method known to those
skilled in the art, either before, at the same time as, or after
addition of other additives.
[0045] Preferably, the oil of lubricating viscosity is present in
an amount of greater than 55 mass %, more preferably greater than
60 mass %, even more preferably greater than 65 mass %, based on
the total mass of the lubricating oil composition. Preferably, the
oil of lubricating viscosity is present in an amount of less than
98 mass %, more preferably less than 95 mass %, even more
preferably less than 90 mass %, based on the total mass of the
lubricating oil composition.
[0046] In the present invention, the oil of lubricating viscosity
may be provided in a major amount, in combination with respective
minor amounts of components (B) and (C) and, if necessary, one or
more co-additives, such as described hereinafter, constituting a
lubricating oil composition. This preparation may be accomplished
by adding the additive directly to the oil or by adding it in the
form of a concentrate thereof to disperse or dissolve the additive.
Additives may be added to the oil by any method known to those
skilled in the art, either before, at the same time as, or after
addition of other additives.
[0047] The terms "oil-soluble" or "oil-dispersible", or cognate
terms, used herein do not necessarily indicate that the compounds
or additives are soluble, dissolvable, miscible, or are capable of
being suspended in the oil in all proportions. These do mean,
however, that they are, for example, soluble or stably dispersible
in oil to an extent sufficient to exert their intended effect in
the environment in which the oil is employed. Moreover, the
additional incorporation of other additives may also permit
incorporation of higher levels of a particular additive, if
desired.
[0048] The lubricating oil compositions of the invention may be
used to lubricate mechanical engine components, particularly in
internal combustion engines, e.g. spark-ignited or
compression-ignited two- or four-stroke reciprocating engines, by
adding the composition thereto. Preferably, they are crankcase
lubricants.
[0049] The lubricating oil compositions of the invention comprise
defined components that may or may not remain the same chemically
before and after mixing with an oleaginous carrier. This invention
encompasses compositions which comprise the defined components
before mixing, or after mixing, or both before and after
mixing.
[0050] When concentrates are used to make the lubricating oil
compositions, they may for example be diluted with 3 to 100, e.g. 5
to 40, parts by mass of oil of lubricating viscosity per part by
mass of the concentrate.
[0051] The lubricating oil composition of the present invention may
contain low levels of phosphorus, namely not greater than 0.09 mass
%, preferably up to 0.08 mass %, more preferably up to 0.06 mass %
of phosphorus, expressed as atoms of phosphorus, based on the total
mass of the composition.
[0052] Typically, the lubricating oil composition may contain low
levels of sulfur. Preferably, the lubricating oil composition
contains up to 0.4, more preferably up to 0.3, most preferably up
to 0.2, mass % sulfur, expressed as atoms of sulfur, based on the
total mass of the composition.
[0053] Typically, the lubricating oil composition may contain low
levels of sulfated ash. Preferably, the lubricating oil composition
contains up to 1.0, preferably up to 0.8, mass % sulfated ash,
based on the total mass of the composition.
[0054] Suitably, the lubricating oil composition may have a total
base number (TBN) of between 4 to 15, preferably 5 to 11.
[0055] Additive Component (B)
[0056] In (B), R is, as stated, a linear C18 to C26 saturated or a
double-bond unsaturated hydrocarbyl group. Preferably, R is a C18
to C22, more preferably a C18 group.
[0057] A saturated hydrocarbyl group is an alkyl group. An
unsaturated hydrocarbyl group has one or more sources of
double-bond unsaturation; thus it may, for example, be an alkenyl
group or an alkadienyl group.
[0058] A stearyl group and an oleyl group, particularly oleyl, are
noteworthy examples of R.
[0059] (B) is obtainable by reacting a basic zinc compound with a
dithiophosphoric acid obtainable by reacting phosphorus
pentasulfide with one or more alcohols, at least 50 mole % of which
have the formula ROH. For example, from 60 to 100, such as 70 to
100, such as 75 to 100, such as 90 to 100, mole % of the alcohol or
alcohols may have the formula ROH. In particular, all of the
alcohol(s) may have the formula ROH.
[0060] R may be a mixture, i.e. derived from a mixture of alcohols
ROH as defined herein.
[0061] Any alcohol or alcohols, other than those of the formula
ROH, may have the formula R.sup.1OH where R.sup.1 is an alkyl or
alkenyl, preferably alkyl, group and has 3 to 12, such as 3 to 10,
such as 5 to 8, carbon atoms.
[0062] Thus, the additive component (B) is formed by reacting a
basic zinc compound with a dithiophosphoric acid obtainable by
reacting phosphorus pentasulfide with a mixture comprising 50 up to
100 mole % of the alcohol(s) of the formula ROH, and alcohol(s) of
the formula R.sup.1OH as the balance, if any.
[0063] The dithiophosphoric acid obtainable from ROH may have the
formula (RO).sub.2P(S)SH and the zinc salt obtainable therefrom may
have the formula [(RO).sub.2P(S)S].sub.2Zn.
[0064] Additive Component (C)
[0065] Additive component (C) is made exclusively from aliphatic
alcohol(s) having 3-8 carbon atoms and therefore contains
correspondingly small aliphatic groups. It is present to enhance
properties such as the anti-wear properties of the lubricating oil
composition. Examples of additive component (C) are known in the
art and are used commercially. The aliphatic, preferably alkyl,
groups may all be secondary or all primary or both secondary and
primary; they may, for example, contain 4 to 8 carbon atoms; they
may be the same or different.
[0066] Preferably, at least a proportion of the aliphatic groups
comprises secondary aliphatic groups. For example, greater than 60
mole %, preferably greater than 70 mole %, more preferably greater
than 80 mole %, even more preferably greater than 90 mole %, such
as all, of the aliphatic groups may be secondary aliphatic groups.
As examples, of secondary aliphatic groups there may be mentioned
sec-butyl and 4-methyl-2-pentyl. Any balance may be primary
aliphatic groups.
[0067] Suitably, the lubricating oil composition contains an amount
of additive components (B) and (C) that introduce 0.02 to 0.09 wt.
%, preferably 0.02 to 0.08 wt. %, more preferably 0.02 to 0.06 wt.
% of phosphorus into the composition.
[0068] Suitably, the additive components (B) and (C) are present in
an amount of 0.1 to 10 mass %, preferably 0.1 to 5 mass %, more
preferably 0.1 to 2 mass %, of the lubricating oil composition,
based on the total mass of the lubricating oil composition.
[0069] Suitably, (B) constitutes more than 50 mole % of the total
number of moles of (B) and (C), such as 70 to 95, for example 75 to
90, mole %.
[0070] In accordance with a preferred embodiment of the present
invention, the additive components (B) and (C) represent the sole
phosphorus-containing additive components in the lubricating oil
composition.
[0071] One or more of each of additive components (B) and (C) may
be present.
[0072] Organic friction modifiers are excluded. Examples of
excluded organic friction modifiers are glyceryl monoesters of
higher fatty acids, for example, glyceryl mono-oleate; esters of
long chain polycarboxylic acids with diols, for example, the butane
diol ester of a dimerized unsaturated fatty acid; oxazoline
compounds; and alkoxylated alkyl-substituted mono-amines, diamines
and alkyl ether amines, for example, ethoxylated tallow amine and
ethoxylated tallow ether amine.
[0073] Co-Additives
[0074] Co-additives, with representative effective amounts, that
may also be present, different from additive components (B) and
(C), are listed below. All the values listed are stated as mass
percent active ingredient.
TABLE-US-00001 Mass % Mass % Additive (Broad) (Preferred) Ashless
Dispersant 0.1-20 1-8 Metal Detergents 0.1-15 0.2-9 Friction
modifier 0-5 0-1.5 Corrosion Inhibitor 0-5 0-1.5 Metal
Dihydrocarbyl 0-10 0-4 Dithiophosphate Anti-Oxidants 0-5 0.01-3
Pour Point Depressant 0.01-5 0.01-1.5 Anti-Foaming Agent 0-5
0.001-0.15 Supplement Anti-Wear Agents 0-5 0-2 Viscosity Modifier
(1) 0-6 0.01-4 Mineral or Synthetic Base Oil Balance Balance (1)
Viscosity modifiers are used only in multi-graded oils.
[0075] The final lubricating oil composition, typically made by
blending the or each additive into the base oil, may contain from 5
to 25, preferably 5 to 18, typically 7 to 15, mass % of the
co-additives, the remainder being oil of lubricating viscosity.
[0076] The above mentioned co-additives are discussed in further
detail as follows; as is known in the art, some additives can
provide a multiplicity of effects, for example, a single additive
may act as a dispersant and as an oxidation inhibitor.
[0077] A dispersant is an additive whose primary function is to
hold solid and liquid contaminations in suspension, thereby
passivating them and reducing engine deposits at the same time as
reducing sludge depositions. For example, a dispersant maintains in
suspension oil-insoluble substances that result from oxidation
during use of the lubricant, thus preventing sludge flocculation
and precipitation or deposition on metal parts of the engine.
[0078] Dispersants are usually "ashless", as mentioned above, being
non-metallic organic materials that form substantially no ash on
combustion, in contrast to metal-containing, and hence ash-forming
materials. They comprise a long hydrocarbon chain with a polar
head, the polarity being derived from inclusion of e.g. an O, P, or
N atom. The hydrocarbon is an oleophilic group that confers
oil-solubility, having, for example 40 to 500 carbon atoms. Thus,
ashless dispersants may comprise an oil-soluble polymeric
backbone.
[0079] A preferred class of olefin polymers is constituted by
polybutenes, specifically polyisobutenes (PIB) or poly-n-butenes,
such as may be prepared by polymerization of a C.sub.4 refinery
stream.
[0080] Dispersants include, for example, derivatives of long chain
hydrocarbon-substituted carboxylic acids, examples being
derivatives of high molecular weight hydrocarbyl-substituted
succinic acid. A noteworthy group of dispersants is constituted by
hydrocarbon-substituted succinimides, made, for example, by
reacting the above acids (or derivatives) with a
nitrogen-containing compound, advantageously a polyalkylene
polyamine, such as a polyethylene polyamine. Particularly preferred
are the reaction products of polyalkylene polyamines with alkenyl
succinic anhydrides, such as described in U.S. Pat. No. 3,202,678;
U.S. Pat. No. 3,154,560; U.S. Pat. No. 3,172,892; U.S. Pat. No.
3,024,195; U.S. Pat. No. 3,024,237, U.S. Pat. No. 3,219,666; and
U.S. Pat. No. 3,216,936, that may be post-treated to improve their
properties, such as borated (as described in U.S. Pat. No.
3,087,936 and U.S. Pat. No. 3,254,025) fluorinated and oxylated.
For example, boration may be accomplished by treating an acyl
nitrogen-containing dispersant with a boron compound selected from
boron oxide, boron halides, boron acids and esters of boron
acids.
[0081] A detergent is an additive that reduces formation of piston
deposits, for example high-temperature varnish and lacquer
deposits, in engines; it normally has acid-neutralising properties
and is capable of keeping finely divided solids in suspension. Most
detergents are based on metal "soaps", that is metal salts of
acidic organic compounds.
[0082] Detergents generally comprise a polar head with a long
hydrophobic tail, the polar head comprising a metal salt of an
acidic organic compound. The salts may contain a substantially
stoichiometric amount of the metal when they are usually described
as normal or neutral salts and would typically have a total base
number or TBN (as may be measured by ASTM D2896) of from 0 to 80.
Large amounts of a metal base can be included by reaction of an
excess of a metal compound, such as an oxide or hydroxide, with an
acidic gas such as carbon dioxide. The resulting overbased
detergent comprises neutralised detergent as an outer layer of a
metal base (e.g. carbonate) micelle. Such overbased detergents may
have a TBN of 150 or greater, and typically of from 250 to 500 or
more.
[0083] Detergents that may be used include oil-soluble neutral and
overbased sulfonates, phenates, sulfurized phenates,
thiophosphonates, salicylates, and naphthenates and other
oil-soluble carboxylates of a metal, particularly the alkali or
alkaline earth metals, e.g. sodium, potassium, lithium, calcium and
magnesium. The most commonly-used metals are calcium and magnesium,
which may both be present in detergents used in a lubricant, and
mixtures of calcium and/or magnesium with sodium.
[0084] Particularly preferred metal detergents are neutral and
overbased alkali or alkaline earth metal salicylates having a TBN
of from 50 to 450, preferably a TBN of 50 to 250. Highly preferred
salicylate detergents include alkaline earth metal salicylates,
particularly magnesium and calcium, especially, calcium
salicylates. Preferably, the alkali or alkaline earth metal
salicylate detergent is the sole detergent in the lubricating oil
composition. Unexpectedly, it has been found that the use of a
salicylate detergent improves the phosphorus retention of a
lubricating oil composition containing a ZDDP additive,
particularly additive component (B) in the lubricating oil
composition of the present invention.
[0085] Metal-containing (or ash-generating) friction modifiers may
be included. Examples include oil-soluble organo-molybdenum
compounds. Such organo-molybdenum friction modifiers also provide
antioxidant and antiwear credits to a lubricating oil composition.
Suitable oil-soluble organo-molybdenum compounds have a
molybdenum-sulfur core. As examples there may be mentioned
dithiocarbamates, dithiophosphates, dithiophosphinates, xanthates,
thioxanthates, sulfides, and mixtures thereof. Particularly
preferred are molybdenum dithiocarbamates, dialkyldithiophosphates,
alkyl xanthates and alkylthioxanthates. The molybdenum compound is
dinuclear or trinuclear.
[0086] One class of preferred organo-molybdenum compounds useful in
all aspects of the present invention is tri-nuclear molybdenum
compounds of the formula Mo.sub.3S.sub.kL.sub.nQ.sub.z and mixtures
thereof wherein L are independently selected ligands having organo
groups with a sufficient number of carbon atoms to render the
compounds soluble or dispersible in the oil, n is from 1 to 4, k
varies from 4 through to 7, Q is selected from the group of neutral
electron donating compounds such as water, amines, alcohols,
phosphines, and ethers, and z ranges from 0 to 5 and includes
non-stoichiometric values. At least 21 total carbon atoms should be
present among all the ligands' organo groups, such as at least 25,
at least 30, or at least 35 carbon atoms.
[0087] The molybdenum compounds may be present in a lubricating oil
composition at a concentration in the range 0.1 to 2 mass %, or
providing at least 10 such as 50 to 2,000 ppm by mass of molybdenum
atoms.
[0088] Preferably, the molybdenum from the molybdenum compound is
present in an amount of from 10 to 1500, such as 20 to 1000, more
preferably 30 to 750, ppm based on the total weight of the
lubricating oil composition. For some applications, the molybdenum
is present in an amount of greater than 500 ppm.
[0089] Anti-oxidants are sometimes referred to as oxidation
inhibitors; they increase the resistance of the composition to
oxidation and may work by combining with and modifying peroxides to
render them harmless, by decomposing peroxides, or by rendering an
oxidation catalyst inert. Oxidative deterioration can be evidenced
by sludge in the lubricant, varnish-like deposits on the metal
surfaces, and by viscosity growth.
[0090] They may be classified as radical scavengers (e.g.
sterically hindered phenols, secondary aromatic amines, and
organo-copper salts); hydroperoxide decomposers (e.g., organosulfur
and organophosphorus additives); and multifunctionals (e.g. zinc
dihydrocarbyl dithiophosphates, which may also function as
anti-wear additives, and organo-molybdenum compounds, which may
also function as friction modifiers and anti-wear additives).
[0091] Examples of suitable antioxidants are selected from
copper-containing antioxidants, sulfur-containing antioxidants,
aromatic amine-containing antioxidants, hindered phenolic
antioxidants, dithiophosphates derivatives, metal thiocarbamates,
and molybdenum-containing compounds.
[0092] Dihydrocarbyl dithiophosphate metals salts other than (B)
and (C) may be used. They are frequently used as antiwear and
antioxidant agents. The metal may be an alkali or alkaline earth
metal, or aluminium, lead, tin, zinc molybdenum, manganese, nickel
or copper. Zinc salts are most commonly used in lubricating oil
such as in amounts of 0.1 to 10, preferably 0.2 to 2, mass %, based
upon the total mass of the lubricating oil compositions. They may
be prepared in accordance with known techniques by first forming a
dihydrocarbyl dithiophosphoric acid (DDPA), usually by reaction of
one or more alcohols or a phenol with P.sub.2S.sub.5, and then
neutralising the formed DDPA with a zinc compound. For example, a
dithiophosphoric acid may be made by reaction with mixtures of
primary and secondary alcohols. Alternatively, multiple
dithiophosphoric acids can be prepared where the hydrocarbyl groups
on one acid are entirely secondary in character and the hydrocarbyl
groups on the other acids are entirely primary in character. To
make the zinc salt, any basic or neutral zinc compound could be
used but the oxides, hydroxides and carbonates are most generally
employed. Commercial additives frequently contain an excess of zinc
due to use of an excess of the basic zinc compound in the
neutralisation reaction.
[0093] Anti-wear agents reduce friction and excessive wear and are
usually based on compounds containing sulfur or phosphorous or
both, for example that are capable of depositing polysulfide films
on the surfaces involved. Noteworthy are the dihydrocarbyl
dithiophosphates, such as the zinc dialkyl dithiophosphates
(ZDDP's) discussed herein.
[0094] Examples of ashless anti-wear agents include
1,2,3-triazoles, benzotriazoles, thiadiazoles, sulfurised fatty
acid esters, and dithiocarbamate derivatives.
[0095] Rust and corrosion inhibitors serve to protect surfaces
against rust and/or corrosion. As rust inhibitors there may be
mentioned non-ionic polyoxyalkylene polyols and esters thereof,
polyoxyalkylene phenols, and anionic alkyl sulfonic acids.
[0096] Pour point depressants, otherwise known as lube oil flow
improvers, lower the minimum temperature at which the oil will flow
or can be poured. Such additives are well known. Typical of these
additive are C.sub.8 to C.sub.18 dialkyl fumerate/vinyl acetate
copolymers and polyalkylmethacrylates.
[0097] Additives of the polysiloxane type, for example silicone oil
or polydimethyl siloxane, can provide foam control.
[0098] A small amount of a demulsifying component may be used. A
preferred demulsifying component is described in EP-A-330,522. It
is obtained by reacting an alkylene oxide with an adduct obtained
by reaction of a bis-epoxide with a polyhydric alcohol. The
demulsifier should be used at a level not exceeding 0.1 mass %
active ingredient. A treat rate of 0.001 to 0.05 mass % active
ingredient is convenient.
[0099] Viscosity modifiers (or viscosity index improvers) impart
high and low temperature operability to a lubricating oil.
Viscosity modifiers that also function as dispersants are also
known and may be prepared as described above for ashless
dispersants. In general, these dispersant viscosity modifiers are
functionalised polymers (e.g. interpolymers of ethylene-propylene
post grafted with an active monomer such as maleic anhydride) which
are then derivatised with, for example, an alcohol or amine.
[0100] The lubricant may be formulated with or without a
conventional viscosity modifier and with or without a dispersant
viscosity modifier. Suitable compounds for use as viscosity
modifiers are generally high molecular weight hydrocarbon polymers,
including polyesters. Oil-soluble viscosity modifying polymers
generally have weight average molecular weights of from 10,000 to
1,000,000, preferably 20,000 to 500,000, which may be determined by
gel permeation chromatography or by light scattering.
Examples
[0101] The invention will now be particularly described in the
following examples which are not intended to limit the scope of the
claims hereof.
[0102] The following ZDDP's were tested. All were oil-soluble zinc
salts of a dithiophosphoric acid, the salts being made
substantially as described in U.S. Pat. No. 5,013,465.
[0103] Z1: the acid was the reaction product of P.sub.2S.sub.5 with
oleyl alcohol (100 mole %).
[0104] Z2.dagger.: the acid was the reaction product of
P.sub.2S.sub.5 with sec-C.sub.6 alcohol (100 mole %).
[0105] Z3: the acid was the reaction product of P.sub.2S.sub.5 with
a mixture of sec-C.sub.6 alcohol (47 mole %) and oleyl alcohol (53
mole %).
[0106] Z4.dagger.: the acid was the reaction product of
P.sub.2S.sub.5 with a mixture of sec-C.sub.6 alcohol (89 mole %)
and oleyl alcohol (11 mole %).
[0107] Z5: the acid was the reaction product of P.sub.2S.sub.5 with
stearyl alcohol (100 mole %).
[0108] Z6: the acid was the reaction product of P.sub.2S.sub.5 with
a mixture of sec-C.sub.6 alcohol (47 mole %) and stearyl alcohol
(53 mole %).
[0109] Z7: the acid was the reaction product of P.sub.2S.sub.5 with
a mixture of 90 mole % sec-C4 alcohol and 10 mole % prim-C8
alcohol.
[0110] * the sec-C.sub.6 alcohol is 4-methylpentan-2-ol.
[0111] .dagger. indicates ZDDP's used in comparative examples.
[0112] All other ZDDP's were used in examples of the invention,
though Z7 is also used in a comparative example.
[0113] The preparation of Z1 is given below in detail as an
illustration of the preparative methods used.
[0114] DDPA Synthesis
[0115] A 1 litre baffled flange flask was charged with 310.45 g
(1.156 mol) of oleyl alcohol (ex Aldrich; MW=268.48). The flask was
fitted with a coiled water cooled condenser, mechanical stirrer
using glass rod with PTFE paddle, nitrogen inlet, glass pocket
containing oil for thermocouple and nitrogen outlet at top of
condenser. The outlet led to two traps containing sodium hydroxide
32 g (2.9 eq) dissolved in 1 litre of water (800 ml and 200 ml) and
one of potassium permanganate (13.6 g) dissolved in 150 ml of
water. The stirrer was set at 400 rpm and the nitrogen flow at
40-50 ml/min. The mixture was heated to 65.degree. C. over 20 mins
using a WEST controlled mantle. Approximately 61.56 g (0.2753 mol)
of phosphorus pentasulphide (ex Phosphorus Derivatives Inc) having
a phosphorus content of 27.70% (=MW of 223.61) was added to the
reactor by screwfeed over 40 mins allowing a mild exotherm to take
place with external heating after 35 mins. The actual amount
added=62.33-0.30 g (in screwfeed)=62.03 g. The mixture was then
heat-soaked at 85.degree. C. for 5 hrs 24 mins during which most of
the solid dissolved, and cooled with compressed air to 50.degree.
C. The weighed solution was finally filtered under vacuum through a
sintered glass funnel into a 1 litre three-necked round-bottomed
flask for subsequent nitrogen sparging. The solid remaining in the
pot was filtered, washing out with toluene to determine the
unreacted weight of P.sub.2S.sub.5. Solids adhering to parts of the
apparatus were washed with heptane, dried and weighed before and
after removal with a wipall. This operation determined the exact
weight of P.sub.2S.sub.5 consumed in the synthesis. P.sub.2S.sub.5
in pot=0.22 g, P.sub.2S.sub.5 in apparatus=0.08 g.
[0116] Extra wt in trap 1=9.56 g (Theo=9.41 g). No extra wt in trap
2.
[0117] Yield of DDPA=361.54 g-0.22 g=361.32 g (=99.6%) (Theo=362.77
g).
[0118] The Wt % of Phosphorus in the DDPA product was calculated
using the following formula;
Wt % of Phosphorus = Wt % of P 2 S 5 consumed .times. % of P in P 2
S 5 Wt of D D P A produced = 61.73 .times. 27.70 / 361.32 = 4.7324
% P ##EQU00001##
[0119] 355.95 g of product was isolated as a clear green
liquid.
[0120] ZDDP Synthesis
[0121] The DDPA in a 1 litre three-necked round-bottomed flask was
sparged with nitrogen at 300 ml min with magnetic stirring for 1
hour to remove any residual H.sub.2S. The outlet led to the same
trap system as that used in the DDPA preparation.
[0122] A 1 litre baffled flange flask was charged with 28.00 g
(0.34408 mol) of zinc oxide (ex GH Chemicals), 0.763 g (0.0034756
mol) of zinc acetate dihydrate (ex Aldrich) and 34.51 g of
SN150(FAW). The flask was fitted with a coiled water-cooled
condenser, mechanical stirrer using glass rod with PTFE paddle,
nitrogen inlet, glass pocket containing oil for thermocouple and
nitrogen outlet at top of condenser. The outlet led to the same
trap system as that used in the DDPA preparation. The stirrer was
set at 400 rpm and the nitrogen flow at 300 ml/min. 348 g of Prim
C18(oleyl) DDPA (E00007-010) was added to the slurry through a 500
ml pressure equalizing dropping funnel with no external heating.
One quarter of the charge was added over 18 mins causing a
temperature rise to 28.2.degree. C. A WEST controlled mantle was
then used to raise the temperature of the mixture to 85.degree. C.
over 20 mins maintaining the DDPA addition rate. The total addition
time was 73 mins. The mixture was heat-soaked for 73 mins at
85.degree. C. and the weighed product rotary evaporated in a 2
litre flask under vacuum at 85.degree. C. for 2 hrs.
[0123] Crude yield=407.96 g (=99.2%) prior to rotary evaporation.
(theo=411.27 g)
[0124] Wt loss after rotary evaporation=2.40 g (from 399.35 g of
product)
[0125] Estimated Wt loss from total product=1.43 g (theo for
water=6.26 g, for alcohol=14.24 g C18)
[0126] No increase in trap weights was observed for whole of
experimental procedure.
[0127] 2% by weight of celite 521 filter aid (7.96 g) was added to
the product and rotated on a rotary evaporator at 85.degree. C. for
a few minutes at atmospheric pressure. 10 g of celite 521 slurried
in 150 ml SN150(FAW) was then added to a filter press preheated to
80.degree. C. and filtered to provide a pad. The product was added
to this and filtered at 80 psi for 13 mins.
[0128] 365.75 g of clear pale yellow/green oil was obtained which
became slight hazy on cooling.
[0129] Each of the above ZDDP's was blended into a lubricating oil
composition at a treat rate to allow 0.077 wt % of phosphorus to be
delivered to the formulation. Apart from the identity of the ZDDP,
each composition was the same and comprised an adpack consisting of
detergents, antifoam, dispersants, antioxidant and diluent blended
with a viscosity modifier, pour point depressant, base stock and
the ZDDP. The formulations contained no organic friction
modifiers.
[0130] Testing and Results
[0131] First Set
[0132] A high frequency reciprocating rig was used to evaluate the
coefficient of friction of each of the above compositions.
Experimentation was carried out using a step ramp profile:
coefficient of friction was measured for 5 minutes at each
temperature as the temperature was increased from 40.degree. C. to
140.degree. C. at 20.degree. C. intervals. A 4 N load was applied
via a 400 g weight and the upper specimen reciprocated over a
distance of 1 mm at a frequency of 40 Hz.
[0133] Sample results are set out in the table below in which a
representative coefficient of friction value at each temperature is
given.
TABLE-US-00002 TABLE 1 Composition (identified 21 s; 571 s; 866 s;
1181 s; 1466 s; 1776 s; by ZDDP) 40.degree. C. 60.degree. C.
80.degree. C. 100.degree. C. 120.degree. C. 140.degree. C. Z1 0.130
0.136 0.132 0.124 0.106 0.096 Z2.dagger. 0.140 0.140 0.155 0.149
0.149 0.141 Z3 0.129 0.129 0.124 0.117 0.109 0.096 Z4.dagger. 0.142
0.137 0.145 0.148 0.143 0.146 Z5 0.115 0.113 0.111 0.111 0.107
0.112 Z6 0.116 0.119 0.125 0.125 0.119 0.107
[0134] It is seen that the ZDDP's of the invention generally gave
rise to better (i.e. smaller) coefficient of friction values than
the comparison ZDDP's.
[0135] Second Set
[0136] The same high frequency reciprocating rig was used to
evaluate the coefficient of friction of a second set of lubricating
oil compositions. Each such composition contained one or both of Z1
(oleyl alcohol) and Z7 (mainly secondary) together with components
known in the art. They did not contain organic friction modifiers.
The compositions were identical other than in respect of the
presence and amounts of Z1 and Z7.
[0137] Six Compositions were Tested:
TABLE-US-00003 mass % Z1: 1.883 1.600 1.412 0.941 0.471 -- mass %
Z7: -- 0.144 0.241 0.481 0.722 0.963
[0138] Sample results, being an average of two runs, are set out in
the table below in which a representative coefficient of friction
value at each temperature is given.
TABLE-US-00004 TABLE 2 Composition Z1/Z7 21 s; 571 s; 866 s; 1181
s; 1466 s; 1776 s; (mole %) 40.degree. C. 60.degree. C. 80.degree.
C. 100.degree. C. 120.degree. C. 140.degree. C. 100/0 0.131 0.132
0.122 0.114 0.105 0.094 .sup. 85/15 * 0.127 0.127 0.123 0.115 0.105
0.094 .sup. 75/25 * 0.127 0.129 0.123 0.115 0.106 0.095 50/50 0.128
0.124 0.128 0.136 0.136 0.136 25/75 0.115 0.130 0.143 0.144 0.149
0.150 0/100 0.111 0.136 0.146 0.154 0.157 0.157
[0139] Lower values in the table indicate superior performance and
most significance should be given to the values obtained at the
higher temperatures, i.e. 100.degree. C., 120.degree. C. and
140.degree. C., because they more closely represent working
temperatures, e.g. in the valve train. It is seen that all
Z1-containing compositions performed better than the composition
(0/100) that lacked Z1. This illustrates the friction modification
effect of Z1 in the absence of an organic friction modifier. The
asterisked compositions performed better than the compositions with
higher proportions of Z7 and the 50/50 combination gives an
improvement over the 25/75 and 0/100 combinations. The 100/0
composition performed well in the tests but the addition of Z7, as
is known in the art, would improve the anti-wear properties of the
formulation.
* * * * *