BACKGROUND OF THE INVENTION
1. Field of the Invention:
[0001] This invention relates to gear and transmission lubricant compositions, having improved
sludge-dispersibility, particularly, those useful for automotive gear and transmission
fluids.
2. Description of the Prior Art:
[0002] Heretofore, in order to improve anti-wear or lubricating qualities and sludge-dispersibility,
required for automotive gear and transmission fluids, there have been known those
containing added thereto anti-wear or lubricating agents comprising phosphorus-containing
organic compound, such as phosphate or phosphite esters or amine salts thereof, together
with lower molecular weight dispersants, such as succinimides and benzyl amine. For
example, US Patent 4,800,029 discloses an aotomatic transmission fluid (ATF) comprising
a solvent-purified 150 neutral oil, containing added thereto an oleamide phosphate
as anti-wear agent and polybutenyl succinimide as dispersant.
[0003] These fluids containing added thereto phosphorus-containing organic compounds together
with lower molecular weight dispersants, however, have drawbacks, such that dispersabilities
become insufficient under severe service conditions likely to form larger sludge,
encounterd with friction or wear, accompanied with recent tendency of miniturization
and output power up of automobiles; and it is desired to improve the dispersibility.
SUMMARY OF THE INVENTION
[0004] It is an object of the present invention to provide a gear or transmission lubricant
composition having improved sludge-dispersibility.
[0005] It is another object of this invention to provide a gear or transmission lubricant
composition capable of providing reduced sludge formation.
[0006] It is still another object of the invention to provide a gear or transmission lubricant
composition capable of maintaining good sludge-dispersibility even at severe service
conditions.
[0007] It is yet another object of the invention to provide a gear oil or a transmission
fluid, particularly ATF, having improved sludge-dispersibility.
[0008] Briefly, these and other objects of the present In vention as hereinafter will become
more readily apparent have been attained broadly by a gear or transmission lubricant
composition, which comprises a major portion of mineral base oil, containing added
thereto a minor proportion of (A) at least one phosphorus-containing metal-free organic
compound and (B) at least one oil-soluble copolymer containing 92∼99 % by weight of
monomer unis of (a) alkyl (meth)acrylate and 1∼8 % by weight of monomer unis of (b)
N,N-dialkylaminoalkyl (meth)acrylate.
[0009] [In the above and hereinafter, (meth)acrylate represents acrylate and/or methacrylate;
and similar expressions are used hereinafter].
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Base Oil
[0010] Suitable base oils used in the present invention include mineral oils, having a viscosity
of usually 1∼50 cSt (centistokes), preferably 2∼30 cSt at 100°C. Base oils having
a viscosity higher than 50 cSt give rise to energy loss because of too high viscosity
resistance. Oils of less than 1 cSt are liable to result in evaporation during use
at elevated temperature and to cause seizing on account of shortage of oil film exposed
to extreme pressure at lubricationg parts. Viscosity index (hereinafter referred to
as VI) of base oils is generally at least 60, preferably at least 70. Oils of VI less
than 60 do not provide satisfactory viscosity-temperature properties. Illustrative
of suitable base oils are 100 neutral oil, 150 neutral oil, 300 neutral oil, 500 neutral
oil, 150 bright stoch and the like.
(A) Phosphorus-containing Organic Compound
[0011] Suitable phosphorus-containing metal-free organic compound (A) include phosphate
esters, phosphite esters, phosphonate esters, and amine salts of these esters; as
well as mixtures of two or more of these compounds.
[0012] Examples of these compounds include ones represented by any of the following formulae
(1), (2), (3) and (4).
O=P(OR)
p(OH)
3-p (1)
O=P(OR)
q(OH)
3-q · NH
rR'
3-r (2)
P(OR)
p(OH)
3-p (3)
P(OR)
q(OH)
3-q · NH
rR'
3-r (4)
In the formulae (1), (2), (3) and (4), p is an integer of 1, 2 or 3; q and r are
independently integers of 1 or 2.
[0013] R and R' are independently selected from the group consisting of saturated or unsaturated
alkyl groups containing at least 4 carbon atoms, aryl groups and alkyl-subsituted
aryl groups. Examples of R and R' include straight-chain or branched, saturated or
unsaturated alkyl groups (aliphatic hydrocarbyl groups) containing 4∼30 or more, preferably
4∼20 carbon atoms, such as n-, iso-, sec- and t-butyl, hexyl, octyl, 2-ethylhexyl,
decyl, dodecyl, tridecyl, tetradecyl, hexadecyl, octadecyl, eicocyl, and oleyl groups;
aryl groups, such as phenyl and naphthyl groups; and aryl groups subsituted substituted
with one or more alkyl groups containing 1∼20, preferably 1∼10 carbon atoms in the
alkyl group, such as tolyl group. These alkyl, aryl and alkyl-subsituted aryl groups
may be ether group-containing ones, such as lauroxyethyl, lauroxypropyl, oleoxyethyl
groups.
[0014] Illustrative examples of these compounds of the following formulae (1), (2), (3)
and (4) are as follows:
(1) mono-, di- and tri-alkyl and/or aryl phospates, such as mono-oleyl phosphate,
tricrezyl phosphate, and dibutyl lauroxypropyl phosphate;
(2) salts of mono- or di-alkyl and/or aryl phospates as above, with mono- or di-alkyl
amine, such as di-2-ethylhexyl amine;
(3) mono-, di- and tri-alkyl and/or aryl phospites, such as di-n-butyl phospite, tributyl
phospite,
(4) salts of mono- or di-alkyl and/or aryl phospites as above, with mono- or di-alkyl
amine, such as di-2-ethylhexyl amine.
[0015] Phosphorus-containing compounds, as written in C.J.Boner "Gear and Transmission Lubricants"
(1964 Reinhold Publishing Corp.), page 94, Table 3.8, may also be used.
[0016] Among these phosphorus-containing metal-free organic compound (A), preferred are
those of the formula (1), particularly alkyl phosphate containing 4∼18 carbon atoms
in the alkyl group. The most preferred is mono-oleyl phosphate.
[0017] The amount of the phosphorus-containing metal-free organic compound (A), usually
0.01∼5 %, preferably 0.1∼3 %, based on the weight of the lubricant composition.
(B) Oil-soluble Copolymer
[0018] Suitable alkyl (meth)acrylates (a), constituting said oil-soluble copolymer (B),
are ones contains 1∼24 carbon atoms in the alkyl group; and include, for example:
(a₁) C8∼20 alkyl (meth)acrylates, such as octyl, decyl, dodecyl, tridecyl, tetradecyl,
hexadecyl, octadecyl and eicocyl (meth)acrylates; (a₂) C1∼4 alkyl (meth)acrylates,
such as methyl, ethyl, propyl and butyl (meth)acrylates; (a₃) C5∼7 alkyl (meth)acrylates,
such as pentyl, hexyl and heptyl (meth)acrylates; (a₄) C21∼24 alkyl (meth)acrylates,
such as Nafol 20+ and Nafol 22+ (produced by Kondea-Chemie; and combinations of two
or more of them.
[0019] Among these, preferred are (a₁) (particularly decyl methacrylate and dodecyl methacrylate),
and combinations thereof with (a₂) (particularly methyl methacrylate).
[0020] Suitable N,N-dialkylaminoalkyl (meth)acrylate (b), constituting said oil-soluble
copolymer (B), include one by the following formula (5):

wherein R₁ and R₂ are the same or different alkyl groups containing not more than
10 carbon atoms, R₃ is an alkylene group containing 2∼10 carbon atoms, and R₄ is hydrogen
atom or methyl group.
[0021] Illustrative of (b) are N,N-dimethylaminoethyl (meth)acrylates, N,N-diethylaminoethyl
(meth)acrylates, N,N-diethylaminohexyl (meth)acrylates, N,N-dimethylaminopropyl (meth)acrylates,
N,N-dibutylaminooctyl (meth)acrylates, and mixtures of two or more of them. Among
these, preferred are N,N-dimethylaminoethyl methacrylate and N,N-diethylaminoethyl
methacrylate.
[0022] Said oil-soluble copolymer (B) may contain monomer unis of (c) one or more of N-vinyl-pyrrolidone
and morpholinoalkyl (meth)acrylates, to improve sludge dispersibility. Suitable morpholinoalkyl
(meth)acrylates include ones containing 2∼4 or more carbon atoms in the alkylene,
such as morpholinoethyl and morpholinopropyl (meth)acrylates. Among these, preferred
is N-vinylpyrrolidone.
[0023] Said copolymer (B) may further contain monomer unis of (d) one or more additional
monomers. Exemplery of additional monomers (d) are aromatic vinyl compounds, such
as styrene and vinyltoluene; esters (such as alkyl esters containing not more than
20 carbon atoms in the alkyl group) of unsaturated dicarboxylic acid (such as maleic,
fumaric and itaconic acids), for example, dibutyl, dioctyl and dilauryl maleates,
and dihexyl, dihexadecyl and dioctadecyl fumarates; and vinyl esters (ones containing
not more than 5 carbon atoms in the alkyl group), such as vinyl acetate and vinyl
propionate; and so on. Among these, preferred is styrene, in view of VI and bodying
effects.
[0024] The contents of these monomers unis of (a), (b), (c) and (d) in said oil-solubult
copolymer (B) are as follows:
|
Usually |
preferably |
(a) |
92∼99 % |
94∼98 % |
(a₁) |
52∼99 % |
64∼93 % |
(a₂) |
0∼40 % |
5∼30 % |
(b) |
1∼8 % |
2∼6 % |
(c) |
0∼10 % |
∼ % |
(d) |
0∼30 % |
0∼20 % |
[0025] In the above and hereinafter, % represents % by weight.
[0026] Copolymer (B) can be produced by usual polymerization thechniques, for instance,
by radical polymerization of (a) and (b) with or without (c) and/or (d), within a
solvent, such as mineral oil. There may be used any polymerization catalysts, for
example, azo compounds, such as azobis-isobutyrenitrile (hereinafter referred to as
AIBN) and azobisvaleronitrile, and peroxides, such as benzoyl peroxide, cumyl peroxide
and lauryl peroxide, with or without chain transfer agents, such as mercaptans (lauryl
mercaptan and the like).
[0027] Said copolymer (B) is oil-soluble and is effective as a VI improver in addition to
dispersant. To attain these effects, (B) has a weight-average molecular weight (hereinafter
referred to as

), as measured by GPC (gel permeation chromatography) using calibration curve of polystyrene,
of generally 20,000∼200,000, preferably 30,000∼150,000. Polymer of too high molecualr
weight causes degradation to form shorter chain polymer when subjected to shearing
and cannot maintain necessary viscosity and VI for a long period of time. Polymer
of too low molecular weight is to be used in a larger amount in order to attain sufficient
viscosity.
[0028] The gear or transmission lubricant composition of the present invention, usually
contains, as a practical use level of the lubricant, 0.01∼5 %, preferably 0.05∼3 %,
more preferably 0.1∼2 % of said phosphorus-containing organic compound (A) and 1∼30
%, preferably 2∼25 %, more preferably 3∼20 % of said oil-soluble copolymer (B).
[0029] Concentrate containing (A) and/or (B) in higher concentration than the above range
may be prepared, and this is diluted to lebel of practical use.
[0030] The composition of this invention may further contains one or more additives, usually
used in gear and transmission lubricants. Such additives include, for example, detergents,
such as sulfonates, salicylates, phenates and naphthenates; dispersants, such as alkenylsuccinimides
and Mannich condensates; anti-oxidants, such as thiophosphates, amines and hindered
phenols; oiliness additives, such as fatty acids and esters thereof; antiwear agent,
other than (A), such as molybdenum dithiophosphate and molybdenum carbamate; and extreme
pressure agents, such as sulfur-containing compounds, phosphorus-containing compounds
and chlorine-containing compounds. These additives can be used in such amounts : 0∼10
% of the detergent, 0∼10 % of the dispersant, 0∼5 % of the anti-oxidant, 0∼3 % of
the oiliness additive, 0∼10 % of the antiwear agent, and 0∼10 % of the extreme pressure
agent.
[0031] Compositions of the invention, containing said phosphorus-containing organic compound
(A) and said oil-soluble copolymer (B), are useful as gear and transmission lubricants,
particularly automotive gear lubricants. Excellent effects can be attained especially
when used as automatic transmission fluid for torque converters.
[0032] Having generally described the invention, a more complete understanding can be obtained
by reference to certain specific examples, which are included for purposes of illustration
only and are not intended to be limiting unless otherwise specified.
[0033] In the following examples, parts represents parts by weight.
Preparation of Copolymers
[0034] Into a reaction vessel equipped with a stirrer, a thermometer and a condensor, 150
parts of a mineral oil (100 neutral oil) were charged and heated to 70°C under an
atmosphere of nitrogen. Then, thereto were added dropwise the monomers (parts) written
in Table 1 together with 1.7 parts of AIBN and 2.0 parts of lauryl mercaptan over
2 hours at the temperature, followed by heating to 100°C for 3 hours to complete the
polymerization to obtain a solution of copolymer having

as written in Table 1.

Examples 1 to 10, and Comparative Examples 1 to 6
[0035] According to the following Formulation I or II (%), mineral oil compositions were
prepared.
Formulation |
I |
II |
Each copolymer solution |
10 |
18 |
Oleyl amine salt of dilauryl phosphate |
1 |
- |
Octyl amine salt of dioleyl phosphate |
- |
1 |
Polybutenylsuccinimide (Hitec E638*) |
3 |
- |
Polyolefin sulfide (TLA369, produced by Texaco) |
- |
5 |
Perbasic calcium sulfonate (Hitec E611*) |
1 |
1 |
Dialkylzinc dithiophosphate (Amoco 194) |
0.3 |
- |
Dialkylzinc dithiophosphate (Amoco 198) |
- |
0.5 |
2,6-di-tert-butyl-p-crezole (Lubrizol 817) |
0.2 |
- |
A mineral oil (100 neutral) |
84.5 |
74.5 |
(Notes) *:produced by Ethyl Cooper. |
[0036] Resistance to oxidation of each composition was evaluated in accordance with JIS
K2514, measuring the amounts of sludge (pentane-insuluble matter, %) of Methods A
and B. Method A represents the amount of sludge obtained by centrifuging the oil after
the test, and Method B represents the amount of sludge obtained by centrifuging the
oil to which a flocculant was added after the test. The amounts of Methds A and B
show resistance to oxidation, and the difference between the amounts of Methds A and
B means sludge dispersability.
[0037] The results were as shown in Table 2.

[0038] As apparent from Tables 1 and 2, compositions of the present invention provided extremely
small amount of sludge and showed excellent sludge dispersibility and resistance to
oxidation.
[0039] Compositions of this invention, when used as gear and transmission lubricants, particularly
automatic transmission fluid for torque converters, can attain excellent sludge dispersibility
with remarkably reducing sludge formation.
1. A gear or transmission lubricant composition, which comprises
a major portion of mineral base oil, having a viscosity of 1∼50 cSt. at 100°C and
having a viscosity index of at least 60; containing, based on the weight of the composition,
0.01∼5 % of (A) at least one phosphorus-containing metal-free organic compound, selected
from the group consisting of phosphate esters, phosphite esters, phosphonate esters,
and amine salts of these esters;
and 1∼30 % of (B) at least one oil-soluble copolymer containing 92∼99 %, preferably
94∼98 % by weight of monomer unis of (a) alkyl acrylate or methacrylate preferavly
containing 1∼24 carbon atoms in the alkyl group, and 1∼8 %, preferably 2∼6 % by weight
of monomer unis of (b) N,N-dlalkylaminoalkyl acrylate or methacrylate.
2. A composition according to Claim 1, wherein (A) is selected from the group consisting
of compounds represented by any of the following formulae (1), (2), (3) and (4):
O=P(OR)p(OH)3-p (1)
O=P(OR)q(OH)3-q · NHrR' 3-r (2)
P(OR)p(OH)3-p (3)
P(OR)q(OH)3-q · NHrR' 3-r (4)
wherein p is an integer of 1∼3; q and r are independently integers of 1 or 2; R and
R' are independently selected from the group consisting of saturated or unsaturated
alkyl groups containing at least 4 carbon atoms, aryl groups and alkyl-subsituted
aryl groups.
3. A composition according to Claim 1 or 2, wherein the monomer (a) comprises (a₁) alkyl
acrylate or methacrylate containing 8∼20 carbon atoms in the alkyl group, and optionally
(a₂) alkyl acrylate or methacrylate containing 1∼4 carbon atoms in the alkyl group.
4. A composition according to Claim 3, wherein said copolymer contains 52∼99 %, preferably
64∼93 % by weight of monomer unis of (a₁), and 0∼40 %, preferably 5∼30 % by weight
of mononer unis of (a₂).
5. A composition according to any one of Claims 1 to 4, wherein said copolymer further
contains upto 10 % by weight of monomer unis of (c) at least one monomer selected
from the group consisting of N-vinyl-pyrrolidone, morpholinoalkyl acrylate and morpholinoalkyl
methacrylate; and/or upto 30 % by weight of monomer unis of (d) at least one monomer
selected from the group consisting of aromatic vinyl compound, alkyl esters of unsaturated
dicarboxylic acid containing not more than 20 carbon atoms in the alkyl group, and
vinyl esters.
6. A composition according to any one of Claims 1 to 5, wherein said copolymer has a
weight-average molecular weight of 20,000∼200,000.
7. A composition according to any one of Claims 1 to 6, which further contains one or
more additives as follows:
1) detergent preferably selected from sulfonates, salicylates, phenates and naphthenates;
2) dispersant preferably selected from alkenylsuccinimides and Mannich condensates;
3) anti-oxidant preferably selected from thiophosphates, amines and hindered phenols;
4) oiliness additive preferably selected from fatty acids and esters thereof;
5) antiwear agent preferably selected from molybdenum dithiophosphate and molybdenum
carbamate; and
6) extreme pressure agent preferably selected from sulfur-containing compounds, phosphorus-containing
compounds and chlorine-containing compounds.
8. A composition according to Claim 7, which contains said additive in such amounts as
follows:
1) 0∼10 % by weight of said detergent,
2) 0∼10 % by weight of said dispersant,
3) 0∼5 % by weight of said anti-oxidant,
4) 0∼3 % by weight of said oiliness additive,
5) 0∼10 % by weight of said antiwear agent, and
6) 0∼10 % by weight of said extreme pressure agent.
9. A gear oil, particularly an automatic transmission fluid, comprising the composition
according to any one of Claims 1 to 8.
10. A torque converter, contained therein the automatic transmission fluid according to
Claim 9.