Technical Field
[0001] The present invention relates to a lubricating oil for two-cycle engines. More specifically,
it relates to a lubricating oil for two-cycle engines, by the use of which an engine
can remarkably reduce smoke, remarkably improve starting performance, be kept clean,
even at high or low temperature, enough to prevent its exhaust system from clogging
with carbon, and have an excellent anti-seizure performance.
Background Art
[0002] Due to its lubricating mechanism, a two-cycle engine releases unburnt lubricating
oil together with exhaust gas, which causes smoke.
[0003] From the viewpoint of environmental pollution, it has been desired to reduce smoke
as much as possible. In Japan, there has already been extensively marketed low-smoke
types of lubricating oil for two-cycle engines whose base oil contains polybutene
or polyisobutylene as a major component that generates smoke less than mineral oils.
[0004] However, since polybutene accelerates friction between a piston and a cylinder due
to its viscosity(stickiness), it inevitably reduces engine power more than mineral
oils. Furthermore, starting becomes hard or troublesome when such a type of oil is
applied in motors whose capacity is too small to start with a starter motor, or recoil
types of engine such as a lawn-mower engine started by winding and then pulling a
string around a crank pulley, a chain saw or a generator.
[0005] Polybutene has been considered to cause clogging with carbon in an exhaust system
less frequently than mineral oils. It, however, has been reported that polybutene
produces more emulsion sludge at low temperature than mineral oils when used in particular
two-cycle engines, for example, an engine of a motorcycle used for newspaper delivery
which is exposed to frequent repetition of start-and-stop. Clogging of an exhaust
system with carbon or emulsion causes deterioration of combustion performance of an
engine, which leads to reduction of engine power.
[0006] Therefore, it has been desired to develop a lubricating oil for two-cycle engines
which can maintain their cleanliness to minimize power reduction, deterioration of
starting performance and carbon clogging of their exhaust system.
[0007] As the result of extensive researches to develop a lubricating oil suitable for two-cycle
engines, the present inventors have found that a lubricating oil whose base oil is
a polyalkylene glycol derivative with a particular structure is much more preferable
with regard to engine power, starting performance and reduction of carbon clogging
of an exhaust system than commercially available, conventional lubricating oils.
Disclosure of the Invention
[0008] The present invention provides a lubricating oil for two-cycle engines which contains
a polyalkylene glycol derivative of formula (1)(hereinafter referred to as "component
A") as a base oil.

In this formula, R¹ and R² represent hydrogen atoms; alkyl groups having 1 to 22
carbon atoms; cycloalkyl or alkylcycloalkyl groups having 5 to 20 carbon atoms; or
aryl, alkylaryl or arylalkyl groups having 6 to 20 carbon atoms.
[0009] Specifically, R¹ and R² include hydrogen atoms; alkyl groups such as methyl, ethyl,
propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl,
tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl and eicosyl groups,
and isomeric forms thereof; alkenyl groups such as propenyl, isopropenyl, butenyl,
pentenyl, hexenyl, heptenyl, octenyl, nonenyl, decenyl, undecenyl, dodecenyl, tridecenyl,
tetradecenyl, pentadecenyl, hexadecenyl, heptadecenyl, octadecenyl, nonadecenyl and
eicosenyl groups, and isomeric forms thereof; cycloalkyl groups such as cyclopentyl,
cyclohexyl and cycloheptyl groups; alkylcycloalkyl groups such as methylcyclopentyl,
ethylcyclopentyl, propylcyclopentyl, butylcyclopentyl, dimethylcyclopentyl, ethylmethylcyclopentyl,
diethylcyclopentyl, dipropylcyclopentyl, dibutylcyclopentyl, methylcyclohexyl, ethylcyclohexyl,
propylcyclohexyl, butylcyclohexyl, dimethylcyclohexyl, ethylmethylcyclohexyl, diethylcyclohexyl,
dipropylcyclohexyl, dibutylcyclohexyl, methylcycloheptyl, ethylcycloheptyl, propylcycloheptyl,
butylcycloheptyl, dimethylcycloheptyl, ethylmethylcycloheptyl, diethylcycloheptyl,
dipropylcycloheptyl and dibutylcycloheptyl groups, and isomeric forms thereof; aryl
groups such as phenyl and naphthyl groups including all isomeric forms thereof; alkylaryl
groups such as tolyl, ethylphenyl, propylphenyl, butylphenyl, pentylphenyl, hexylphenyl,
heptylphenyl, octylphenyl, nonylphenyl, decylphenyl, undecylphenyl, dodecylphenyl,
xylyl, ethylmethylphenyl, diethylphenyl, dipropylphenyl, dibutylphenyl, methylnaphthyl,
ethylnaphthyl, propylnaphthyl, butylnaphtyl, dimethylnaphthyl, ethylmethylnaphthyl,
diethylnaphthyl, dipropylnaphthyl and dibutylnaphthyl groups, and isomeric forms thereof;
or arylalkyl groups such as benzyl, phenylethyl and phenylpropyl groups, and isomeric
forms thereof.
[0010] R¹ and R² in formula (1) are preferably hydrogen atoms, straight-chain or branched
alkyl group having 1 to 18 carbon atoms, phenyl groups, or alkylphenyl groups, whose
alkyl chains are straight or branched, having 7 to 18 carbon atmos. Specifically,
R¹ and R² are preferably hydrogen atoms; methyl, ethyl, propyl, butyl, pentyl, hexyl,
heptyl, octyl, decyl, dodecyl, tetradecyl, hexadecyl, octadecyl, phenyl, tolyl, ethylphenyl,
propylphenyl, butylphenyl, pentylphenyl, hexylphenyl, heptylphenyl, octylphenyl, nonylphenyl,
decylphenyl, dodecylphenyl or xylyl groups; or isomeric forms thereof.
[0011] Furthermore, in the light of cleanliness, R¹ in formula (1) is preferably a hydrogen
atom or a straight-chain or branched alkyl group having 1 to 4 carbon atoms (preferably
a straight-chain alkyl group), more preferably a hydrogen atom, methyl, ethyl or propyl
group or any one of their isomeric forms.
[0012] From the same viewpoint, R² in formula (1) is preferably a hydrocarbon group such
as a straight-chain or branched alkyl group having 1 to 4 carbon atoms (preferably
a straight-chain alkyl group), or an alkylphenyl group having 7 to 18 carbon atoms
which consists of a phenyl group substituted by a straight-chain or branched alkyl
group, among which methyl, ethyl, propyl, butyl, phenyl, tolyl, ethylphenyl, propylphenyl,
butylphenyl, pentylphenyl, hexylphenyl, heptylphenyl, octylphenyl, nonylphenyl, decylphenyl,
dodecylphenyl or xylyl group, or any one of isomeric forms thereof.
[0013] On the other hand, R³, R⁴, R⁵ and R⁶ in formula (1) represent hydrogen atoms, methyl
or ethyl groups, and the total number of carbons of R³, R⁴, R⁵ and R⁶ is 1 or 2.
[0014] Furthermore,
a in formula (1) is an integer of 1 to 200, preferably 2 to 100, more preferably 5
to 50.
Best Mode for Carrying out the Invention
[0015] As described above, polyoxyalkylene glycol derivatives which can be used in a lubricating
oil for two-cycle engines of the present invention have polyalkylene chains of formula
(5).

The structure of formula (5) is one of the followings.
1)a homopolymer structure which has a single constitutional unit selected from the
members of the group represented by formula (6);

2)a random copolymer or block copolymer structure which has at least two kinds of
constitutional unit selected from the members of the group represented by formula
(6), where a in formula (5) denotes the sum of polymerization degrees of the different oxyalkylene
groups;
3)combination of at least two polymer structures selected from those included in the
above 1) or 2), where a in formula (5) denotes the sum of polymerization degrees of the different oxyalkylene
groups.
[0016] From the practical viewpoint, viscosity of component A at 100°C, although there is
no restriction, is preferably 1 to 100 mm²/s, more preferably 5 to 50 mm²/s, but not
limited to them.
[0017] If necessary, the lubricating oils of the present invention, which contain component
A as a base oil, can contain at least one of mineral lubricating oils, synthetic lubricating
oils and/or mineral diluents as base oils, which are soluble in component A. In general,
the total amount of the base-oil ingredients other than component A is preferably
100 parts or less to 100 parts of component A by weight, more preferably 50 parts
or less as long as they do not deteriorate the characteristics of the lubricating
oils of the present invention, but not limited to them.
[0018] Although the lubricating oil of the present invention exclusively containing component
A can give an excellent performance, at least one of the nitrogen-containing compounds
of the following (a)-(d)(hereinafter referred to as "component B") can be added to
improve cleanliness of an engine.
(a)a nitrogen-containing compound of formula (2)[hereinafter referred to as "component
(a)"];

wherein R⁷ is an alkyl group having 1 to 22 carbon atoms, an alkenyl group having
3 to 22 carbon atoms, a cycloalkyl or alkylcycloalkyl group having 5 to 15 carbon
atoms, or an aryl, alkylaryl or arylalkyl group having 6 to 18 carbon atoms; R⁸ and
R⁹ are hydrogen atoms or alkyl groups having 2 to 6 carbon atoms, where the total
number of carbons of R⁸ and R ⁹ is 2 to 8; b is an integer of 1 to 8; and c is an integer of 5 to 40;
(b)a boronated compound (a)[hereinafter referred to as "compound (b)"];
(c)a nitrogen-containing compound of formula (3)(hereinafter referred to as "component
(c)];

wherein X is a hydrogen atom or an acyl group having 6 to 30 carbon atoms derived
from a fatty acid; Y is an acyl group having 6 to 30 carbon atoms derived from a fatty
acid; R¹⁰ is an alkylene group having 2 to 4 carbon atoms d is an integer of 0 to 11; e is an integer of 0 to 11;

; and one molecule contains at least one acyl group;
(d)a boronated compound (c)[hereinafter referred to as "component (d)"].
[0019] Component (a) is a nitrogen-containing compound represented by formula (2);

In formula (2), R⁷ is an alkyl group having 1 to 22 carbon atoms, an alkenyl group
having 3 to 22 carbon atoms, a cycloalkyl or alkylcycloalkyl group having 5 to 15
carbon atoms, or an aryl, alkylaryl or arylalkyl group having 6 to 18 carbon atoms.
Specifically, R⁷ is an alkyl group such as methyl, ethyl, propyl, butyl, pentyl, hexyl,
heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl,
heptadecyl, octadecyl, nonadecyl and eicosyl groups, and any one of isomeric forms
thereof; an alkenyl group such as propenyl, isopropenyl, butenyl, pentenyl, hexenyl,
heptenyl, octenyl, nonenyl, decenyl, undecenyl, dodecenyl, tridecenyl, tetradecenyl,
pentadecenyl, hexadecenyl, heptadecenyl, octadecenyl, nonadecenyl and eicosenyl groups,
and any one of isomeric forms thereof; a cycloalkyl group such as cyclopentyl, cyclohexyl
and cycloheptyl groups; an alkylcycloalkyl group such as methylcyclopentyl, ethylcyclopentyl,
propylcyclopentyl, butylcyclopentyl, dimethylcyclopentyl, ethylmethylcyclopentyl,
diethylcyclopentyl, dipropylcyclopentyl, dibutylcyclopentyl, methylcyclohexyl, ethylcyclohexyl,
propylcyclohexyl, butylcyclohexyl, dimethylcyclohexyl, ethylmethylcyclohexyl, diethylcyclohexyl,
dipropylcyclohexyl, dibutylcyclohexyl, methylcycloheptyl, ethylcycloheptyl, propylcycloheptyl,
butylcycloheptyl, dimethylcycloheptyl, ethylmethylcycloheptyl, diethylcycloheptyl,
dipropylcycloheptyl and dibutylcycloheptyl groups, and any one of isomeric forms thereof;
an aryl group such as phenyl and naphthyl groups including all isomeric forms thereof;
an alkylaryl group such as tolyl, ethylphenyl, propylphenyl, butylphenyl, pentylphenyl,
hexylphenyl, heptylphenyl, octylphenyl, nonylphenyl, decylphenyl, undecylphenyl, dodecylphenyl,
xylyl, ethylmethylphenyl, diethylphenyl, dipropylphenyl, dibutylphenyl, methylnaphthyl,
ethylnaphthyl, propylnaphthyl, butylnaphtyl, dimethylnaphthyl, ethylmethylnaphthyl,
diethylnaphthyl, dipropylnaphthyl and dibutylnaphthyl groups, and any one of isomeric
forms thereof; or an arylalkyl group such as benzyl, phenylethyl and phenylpropyl
groups, and any one of isomeric forms thereof.
[0020] R⁷ in formula (2) is preferably a straight-chain or branched alkyl group having 1
to 18 carbon atoms, phenyl, or an alkylphenyl group having 7 to 18 carbon atoms whose
alkyl chains are straight or branched. Specifically, R⁷ is methyl, ethyl, propyl,
butyl, pentyl, hexyl, heptyl, octyl, decyl, dodecyl, tetradecyl, hexadecyl, octadecyl,
phenyl, tolyl, ethylphenyl, propylphenyl, butylphenyl, pentylphenyl, hexylphenyl,
heptylphenyl, octylphenyl, nonylphenyl, decylphenyl, dodecylphenyl or xylyl group,
or any one of their isomeric forms.
[0021] R⁸ and R ⁹ in formula (2) include hydrogen atoms or alkyl groups having 2 to 6 carbon
atoms, and the total number of carbons of R⁸ and R⁹ is 2 to 8, preferably 2 to 6.
Specifically, R⁸ and R⁹ are ethyl, propyl, butyl, pentyl or hexyl group, or any one
of isomeric forms thereof, most preferably ethyl group.
[0022] In formula (2),
b is an integer of 1 to 8, preferably 1 to 6, and
c is an integer of 5 to 40, preferably 10 to 30.
[0023] Furthermore, component (b) mentioned above is a compound obtained through reaction
of component (a) with a boronating agent.
[0024] The above boronating agent can be any of boronating agents capable of reacting with
component (a) to form a nitrogen-containing boron compound, for example, an acid such
as orthoboric acid(H₃BO₃), metaboric acid(HBO₂), tetraboric acid(H₂B₄O₇) or boric
anhydride; an oxide of boron such as boron oxide(B₂O₃); a boron halide such as boron
fluoride, boron chloride and boron bromide; a borate such as ammonium borate, sodium
borate and potassium borate; or a lower alkyl ester of boric acid represented by formula
(7);

wherein R¹⁷ is an alkyl group having 1 to 6 carbon atoms,
g is an integer of 1 to 3
h is an integer of 0 to 2, and

.
[0025] The boronating agent is preferably mono-, di- or trimethyl borate; mono-, di- or
triethyl borate; mono-, di- or tripropyl borate; mono-, di- or tributyl borate; mono-,
di- or tripentyl borate; mono-, di- or trihexyl borate; or any one of mixtures thereof,
more preferably, an acid of boron, a lower alkyl ester of boric acid or any one of
mixtures thereof.
[0026] It is preferable to use the boronating agent in an adequate amount in the boronating
reaction to obtain a final boron compound containing boron in the range of 0.05-7.0
wt%, but not limited to it. The ratio of boron atoms of a boronating agent to nitrogen
atoms of a nitrogen-containing compound of formula (2) is preferably 0.05-10:1, more
preferably 0.1-2:1.
[0027] Boronation with a boronating agent is carried out by heating a nitrogen-containing
compound of formula (2) with the boronating agent. The boronation can be carried out
in the presence of water, alcohol and/or hydrocarbon, as convenient. In the reaction,
water or alcohol is a "reactive solvent" which reacts with the boronating agent to
form a reactive intermediate suitable for the boronation, resulting in an increase
of yield, while hydrocarbon is an "inert solvent" which can azeotropically remove
the water produced during the boronation.
[0028] Alcohols preferably used in the reaction include methanol, ethanol, propanol, isopropanol,
n-butanol, sec-butanol, pentanol(amyl or iso-amyl alcohol), hexanol, ethylene glycol,
propylene glycol, butylene glycol, pentylene glycol, hexylene glycol and so forth.
[0029] Hydrocarbons preferably used in the reaction include those whose boiling point is
60°C or above, for example, benzene, toluene, xylene, benzine, lygroin, mineral spirit,
cleaning solvent, petroleum naphtha, cyclohexane, hexane, mineral oil, and naphtha
fraction, kerosine fraction, gas oil fraction or lubricating oil fraction of mineral
oil.
[0030] In order to react a boronating agent with a nitrogen-containing compound represented
by formula (2), reaction temperature during the boronation reaction should be to some
extent higher than ambient temperature, preferably 50 to 250°C, more preferably 80
to 180°C, and a refluxing temperature of the solvent used is usually chosen. Since
a boronation reaction can be usually completed in a short period of time, the reaction
will be carried out for 0.5 to 8 hours, preferably 2 to 6 hours.
[0031] After completing the boronation, the reaction mixture is heated to distill off the
water produced during the reaction and any other solvents if used, and the water is
usually removed by a desiccant such as sodium sulfate and magnesium sulfate. Then,
the desired compound, component (b), can be obtained either 1)by diluting the reaction
mixture with organic solvent such as benzene, toluene, xylene, hexane, benzine, gasoline
for rubber or petroleum ether and removing the unreacted boronating agent by filtration
or solvent extraction, or 2)through purification process such as distillation under
a reduced pressure, as appropriate.
[0032] The ratio of the number of nitrogen atoms to the number of boron atoms in the nitrogen-containing
compound can be controlled by adjusting the ratio of the amount of a boronating agent
to a nitrogen-containing compound, and is preferably from 1:0.05 to 1:5, more preferably
from 1:0.1 to 1:2.
[0033] Component (c) is a nitrogen-containing compound represented by formula (3);

In formula (3), X is a hydrogen atom or an acyl group having 6 to 30, preferably
12 to 20 carbon atoms which is derived from a fatty acid; Y is an acyl group having
6 to 30, preferably 12 to 20 carbon atoms which is derived from a fatty acid; R¹⁰
is an alkylene group having 2 to 4, preferably 2 or 3 carbon atoms;
d is an integer of 0 to 11, preferably 3 to 11, more preferably 4 to 11;
e is an integer of 0 to 11;

; and one molecule contains at least one acyl group. The fatty acid from which X
or Y is derived can be a saturated or unsaturated fatty acid having 6 to 30 carbon
atoms, preferably a saturated fatty acid having 12 to 20 carbon atoms, for example,
a straight-chain or branched acid such as dodecanoic acid, tridecanoic acid ,tetradecanoic
acid, pentadecanoic acid, hexadecanoic acid, heptadecanoic acid, octadecanoic acid,
nonadecanoic acid, eicosanic acid, isododecanoic acid, isotridecanoic acid, isotetradecanoic
acid, isopentadecanoic acid, isohexadecanoic acid, isoheptadecanoic acid, isooctadecanoic
acid, isononadecanoic acid, isoeicosanic acid, or any one of mixtures thereof. The
alkylene group, R¹⁰, can be ethylene, propylene, trimethylene, tetramethylene, butylene,
isobutylene or methyltrimethylene group, preferably ethelene, propylene or trimethylene
group, most preferably ethylene group.
[0034] Component (c) is commercially available, or can be prepared by acylation of a polyalkylenepolyamine
whose preferable structure is represented by formula (8).
H₂N(-R¹⁰-NH)
i-H (8)
In formula (8), R¹⁰ represents the same as R¹⁰ in formula (3), and
i is an integer of 2 to 11, preferably 3 to 11, more preferably 4 to 11.
[0035] Examples of the above polyalkylenepolyamine include diethylenetriamine, triethylenetetramine,
tetraethylenepentamine, pentaethylenehexamine, hexaethyleneheptamine, heptaethyleneoctamine,
octaethylenenonamine, nonaethylenedecamine, decaethyleneundecamine, undecaethylenedodecamine,
dipropylenetriamine, tripropylenetetramine, tetrapropylenepentamine, pentapropylenehexamine,
hexapropyleneheptamine, heptapropyleneoctamine, octapropylenenonamine, nonapropylenedecamine,
decapropyleneundecamine, undecapropylenedodecamine, di(trimethylene)triamine, tri(trimethylene)tetramine,
penta(trimethylene)hexamine, hexa(trimethylene)heptamine, hepta(trimethylene)octamine,
octa(trimethylene)nonamine, nona(trimethylene)decamine, deca(trimethylene)undecamine
and undeca(trimethylene)dodecamine.
[0036] Examples of the above acylating agent include a fatty acid having 6 to 30, preferably
12 to 20 carbon atoms, and its derivative such as an acid halide and an acid anhydride.
[0037] An acylating agent for the above polyalkylenepolyamine is used preferably in the
amount of 0.1-1 moles per 1 mole of the polyalkylenepolyamine. The acylation can be
carried out under the conditions, e. g., reaction temperature, reaction time, catalyst
and solvent, analogous to those usually applied to an acylation reaction and which
are determined taking into consideration the types of the polyalkylenepolyamine and/or
the acylating agent used, as convenient.
[0038] Component (d) can be obtained by a reaction of component (c) with a boronating agent,
in which the boronating agent and the procedure of the boronation can be analogous
to those used in the preparation of component (b), except that the amount of the boronating
agent is from 0.05 to 5.0, preferably from 0.1 to 3.0 moles per 1 mol of component
(c). It is recommended that in the reaction system the ratio of boron atoms to nitrogen
atoms of compound (d) in number is 0.02-10, preferably 0.05-5.0, more preferably 0.1-2.
[0039] Component B is added to a lubricating oil for two-cycle engines comprising compound
A as a base oil either directly or in the form of dilution of kerosine, lubricating
oil or the like, to form a lubricating oil composition of the present invention, in
which the content of compound B is 0.5-30 wt%, preferably 1-20 wt%, more preferably
3-10 wt%. Cleanliness will not be improved very much if the content of component B
is below that range, while, if above, compound B does not improve cleanliness in proportion
to the amount used, resulting in decrease of an economical efficiency. Hence, neither
of these cases are preferable.
[0040] Although there is no limitation in a process of mixing component A and B to prepare
a lubricating oil composition for two-cycle engines of the present invention, it can
be usually obtained by stirring a mixture of these compounds at 20 to 80°C for 30
min to 3 hours.
[0041] The lubricating oil composition for two-cycle engines of the present invention, which
is excellent in cleanliness at low or high temperature, can be obtained by adding
at least one nitrogen-containing compound selected from component (c) and (d) preferably
to a polyalkylene glycol derivative as a base oil represented by formula (4);

wherein R¹¹ and R¹² represent hydrogen atoms, alkyl groups having 1 to 4 carbon atoms,
aryl, alkylaryl or arylalkyl groups having 6 to 20 carbon atoms, and R¹¹ and/or R¹²
are aryl, alkylaryl or arylalkyl groups having 6 to 20 carbon atoms; R¹³, R¹⁴, R¹⁵
and R¹⁶ are hydrogen atoms, methyl groups or ethyl groups, and the total number of
carbons of R¹³, R¹⁴, R¹⁵ and R¹⁶ is 1 or 2; and
f is an integer of 1 to 200.
[0042] In order to further improve the excellent characteristics of the lubricating oil
for two-cycle engines of the present invention, if necessary, known additives for
lubricating oil such as antioxidant, load-resistant additive, metallic cleaner, ash-free
dispersant, metal-inactivating agent, viscosity index improver, pour point depressant
and defoaming agent, can be added to the lubricating oil, either solely or in combination
of two or more thereof. It is important that these additives except deforming agent
can be homogenously dissolved in a base oil of the lubricating oil for two-cycle engines
of the present invention without turbidity or precipitation, and that, if added, they
should be deliberately chosen. It is preferable to control the total content of the
additives below or equal to 20 wt% to the total weight of the composition, but not
limited.
[0043] Two-cycle engines referred to in the present invention are engines having a mechanism
by which combustion is completed in one rotation of a crank-shaft. The two-cycle engines
can be used for various kinds of machine, for example, motorcycles, carts, snowmobiles,
outboard motors, motorboats, marine skis, generators, chain saws, lawn mowers, sprays,
pilotless light airplanes, fire pumps and so forth, without particular limitations.
[0044] The lubricating oil or oil composition for two-cycle engines of the present invention
can be used to lubricate two-cycle engines without particular limitations in its usage.
For example, the above-mentioned lubricating oil or oil composition( hereinafter referred
to as "the Oil") can be fed into an engine in 1) a "mixed-oil system" in which the
Oil and fuel are pre-mixed, placed in a fuel tank and vaporized to be fed into a crank
case used as a pilot pressure chamber, or 2) a "separate-oil system" in which fuel
and the Oil are placed in separate tanks and the Oil is fed into a crank case by an
oil pump. The Oil fed into a crank case in a manner described above lubricates bearing
portions and frictional portions of the engine. The bearing portions herein include
crank bearings, connecting rod small end bearings, connecting rod large end bearings
and a piston pin, and the frictional portions include a piston, a cylinder and a piston
ring.
Examples
[0045] Next, although the present invention will be more specifically described in reference
to examples and comparative examples, it is to be understood that the scope of the
present invention should not be limited to these examples at all.
[0046] In the following examples, derivatives A to I used as base oils belong to component
A, each of which is specifically shown in Table 1 by specifying R¹ to R⁶ and
a in formula (1).

In the following examples, nitrogen-containing compound A belongs to component
(a) and is represented by formula (9).

A boronated nitrogen-containing compound A in the following examples belongs to
component (b) and was prepared by the following boronation.
Boronation
[0047] In one-liter flask equipped with a condenser having a water trap, a nitrogen-blowing
tube, a thermometer and a stirrer were placed 600g of nitrogen-containing compound
A and 10.6g of orthoboric acid, and then were heated with stirring under nitrogen
stream. Reaction was carried out at 120°C for about 3 hours. When water was condensed
as much as 3 ml in the trap, the reaction mixture was transferred to a one-liter egg-plant
type flask and was distilled at 120°C under the pressure of 0.1 mmHg for 1 hour to
obtain a yellowish transparent viscous product of boronated nitrogen-containing compound
A, i.e., a boric-acid-modified compound). The result of its elemental analysis( nitrogen
1.6 wt%; boron 0.59 wt%) indicated that the product was the compound represented by
formula (10).

Nitrogen-containing compound B used in Example 1 is the compound represented by
formula (11), which was prepared by the following process.

Preparation Example
[0048] In a one liter round-bottom flask equipped with a stirrer, a reflux condenser, a
thermometer and a nitrogen-blowing tube were placed 0.1 mol(19g) of tetraethylenepentamine,
200 ml of 10% sodium hydroxide and 300 ml of benzene, and the flask was cooled on
an ice bath to 5°C or below. Next, 0.2 mol(60.5 g) of isooctadecanoyl chloride was
dropped over 1 hour, and then, the solution was stirred at 5°C or below for further
1 hour. The solution was heated to reflux at the boiling point of benzene for 1 hour,
and then allowed to cool. The contents in the reaction vessel were transferred into
a one liter separatory funnel, and the lower layer was removed. The upper benzene
layer was washed 5 times with 300ml of purified water. After drying over anhydrous
sodium sulfate, benzene was evaporated to obtain a light yellow transparent viscous
liquid. Yield was 68g. The result of elemental analysis of the product was carbon
75.2 wt%, hydrogen 13.1 wt% and nitrogen 9.2 wt%.
[0049] The boronated nitrogen-containing compound B used in the following examples is a
compound prepared by boronation of nitrogen-containing compound B according to the
process described below.
Boronation
[0050] Fifty grams of nitrogen-containing compound B prepared in the above preparation example
was placed in the same type of 500-ml reaction vessel as that used in the above preparation
example having a water trap between the flask and a reflux condenser, and 300 ml of
toluene and 0.14 mol(8.6g) of boric acid were then added. With stirring the solution
was heated to reflux at the boiling point of toluene. Heating was stopped when about
2 ml of water was condensed in the trap(after about 3 hours). After cooling, the solution
was dried over anhydrous sodium sulfate, and toluene was evaporated.
[0051] The reaction product was more viscous liquid than nitrogen-containing compound B
prepared in the above preparation example.
Examples 1 to 17 and Comparative Examples 1 to 4
[0052] In Examples 1 to 17, the components shown in Table 2(I)-(VI) were blended to prepare
lubricating oils for two-cycle engines of the present invention.
Performance Evaluation
[0053] Performance of the lubricating oils for two-cycle engines of the present invention
shown in Table 2(I)-(VI) were evaluated as described below, whose results are shown
in Table 2(I)-(VI).
[0054] For comparison, the same evaluation was carried out with mineral oil (Comparative
Example 1), polybutene(Comparative Example 2) and commercially available two-cycle
engine oils(Comparative Examples 3 and 4), whose results are shown in Table 2(VI).
(1)Smoke Test
[0055] Using a motorcycle equipped with a two-cycle engine(air-cooling type, 49 cc), concentration
of smoke exhausted from its muffler was visually evaluated. Specifically, evaluation
was performed under three kinds of driving condition(idling, rapid starting, steady-state
running at 40 km/hr), and smokes observed were rated into 6 grades of 0 to 5(0 = best).
(2) Starting Performance Test
High-Temperature Cleanliness Test Using a Motorcycle Engine
[0057] For the lubricating oils for two-cycle engines of Examples 1, 10, 11, 15 and 17 of
the present invention and the commercially available lubricating oils for two-cycle
engines of Comparative Examples 3 and 4, high-temperature cleanliness was tested using
a motorcycle engine.
[0058] An air-cooling type of two-cycle engine for motorcycles having a 123 cc displacement
single cylinder was driven for 5 hours under conditions of an engine rotational frequency
of 5000rpm, full load, a plug seat temperature of 200°C and a fuel:oil mixing ratio
of 40:1. Then, cleanliness of the engine was visually evaluated. The results are shown
in Table 3. Cleanliness was rated into 11 grades of 0 to 10(10 = best).

Low-temperature Cleanliness Test
[0059] For the lubricating oils for two-cycle engines of Exmaples 14, 15 and 17 of the present
invention and the commercially available lubricating oil for two-cycle engines of
Comparative Example 3, low-temperature cleanliness was tested using a motorcycle engine.
The test was conducted using a generator. The engine was discontinuously driven at
a plug seat temperature of about 130°C, and then cleanliness of the engine was visually
evaluated. The test conditions were determined to simulate running conditions with
an engine whose inner temperature does not rise very much, e. g., an engine of a motorcycle
for newspaper delivery which is exposed to frequent repetition of start-and-stop.
The results are shown in Table 4. Cleanliness was rated into 11 grades of 0 to 10(10
= best).

Evaluation of Clogging of an Exhaust System
[0060] To evaluate a degree of power reduction due to deposition of carbon and so on in
a muffler, clogging of an exhaust system was tested for the lubricating oils for two-cycle
engines of Examples 1, 14, 15 and 17 of the present invention, and the mineral oil-based
lubricating oil for two-cycle engines of Comparative Example 1 and the low-smoke type
of polybutene-based lubricating oil for two-cycle engines of Comparative Example 3,
in accordance with JASO M343-92 of Society of Automotive Engineers of Japan's Standards.
The test was conducted using a generator in compliance with the procedure described
in the JASO Standards. In this test was measured the time required to raise an inlet
negative pressure to 2 kPa under mode driving in which load condition, i. e., non-load
or 750 W load, was controlled through monitoring a temperature of exhaust gas. The
results are shown in Table 5, in which values are clogging indexes assuming that the
clogging index of the standard oil(JATRE-1) is 100, according to the evaluation method
prescribed in JASO M343-92, and the larger an index, the less likely clogging occurs.
JATRE-1 is used as a standard oil because its performance represents that of a low-smoke
type of lubricating oil for two-cycle engines. JASO M 345-93 prescribes that a low-smoke
type of lubricating oil should have an clogging index of 90 or above, using JATRE-1(=100)
as a standard.
Table 5
Evaluation of Clogging of an Exhaust System |
|
Ex. 1 |
Ex.14 |
Ex.15 |
Ex.17 |
Comp. Ex. 1 |
Comp. Ex. 3 |
Clogging Index of an Exhaust System (JATRE-1=100) |
300 |
300 |
320 |
317 |
54 |
90 |
[0061] The compositions of Examples 1 to 17 are the lubricating oils for two-cycle engines,
which contain polyalkylene glycol derivatives of the present invention as a base oil.
As is apparent from the results of the performance evaluation in Table 2, these lubricating
oils produce smoke remarkably less in comparison with a mineral oil(Comparative Example
1), and also less in comparison with polybutene(Comparative Example 2) or commercially
available low-smoke type of lubricating oils for two-cycle engines containing polybutene
as a component of a base oil(Comparative Examples 3 and 4).
[0062] On the other hand, the time required to start an engine is usually desired to be
less than or equal to that of a lubricating oil containing mineral oil(Comparative
Example 1). Any of the lubricating oils for two-cycle engines of Examples 1 to 17
of the present invention gave the time less than an oil containing mineral oil(Comparative
Example 1) or a commercially available lubricating oil(Comparative Example 3 or 4),
showing an excellent starting performance. In contrast to that, addition of polybutene
has caused deterioration of starting performance of an engine(Comparative Example
2) due to its high viscosity.
[0063] As is apparent from the results in Table 3, the lubricating oils for two-cycle engines
containing component B(Examples 10, 11, 15 and 17) have provided a high-temperature
cleanliness superior to the lubricating oil of Example 1, definitely showing effectiveness
of addition of component B.
[0064] Moreover, as is apparent from the results in Table 4, the lubricating oil for two-cycle
engines containing component (c) or (d)(Examples 15 or 17) has provided a low-temperature
cleanliness superior to the lubricating oil without component (c) or (d)(Example 14),
definitely showing effectiveness of addition of component (c) or (d).
[0065] In addition, as is apparent from the results in Table 5, the lubricating oils for
two-cycle engines of the present invention(Examples 1, 14, 15 and 17) have provided
the time taken to occur clogging of a muffler three or more times longer than a conventional
lubricating oil for two-cycle engines containing mineral oil (Comparative Example
1) or a conventional low-smoke type of lubricating oil for two-cycle engines(Comparative
Example 3).
Industrial Applicability
[0066] As described above, a lubricating oil for two-cycle engines of the present invention
can remarkably inhibit generation of smoke and remarkably improve engine characteristics
such as starting performance, cleanliness to prevent clogging with carbon of an exhaust
system, high- or low temperature cleanliness of an engine, and anti-seizure performance.
1. A lubricating oil for two-cycle engines which as a base oil comprises a polyoxyalkylene
glycol derivative represented by formula (1);

wherein R¹ and R² are hydrogen atoms, alkyl groups having 1 to 22 carbon atoms, alkenyl
groups having 3 to 22 carbon atoms, cycloalykyl groups or alkylcycloalkyl groups having
5 to 20 carbon atoms, or aryl, alkylaryl or arylalkyl groups having 6 to 20 carbon
atoms; R³, R⁴, R⁵ and R⁶ are hydrogen atoms, methyl groups or ethyl groups, and the
total number of carbons of R³, R⁴, R⁵ and R⁶ is 1 or 2; and
a is an integer of 1 to 200.
2. A lubricating oil composition for two-cycle engines which comprises
A) as a base oil a polyoxyalkylene glycol derivative represented by formula (1);

wherein R¹ and R² are hydrogen atoms, alkyl groups having 1 to 22 carbon atoms, alkenyl
groups having 3 to 22 carbon atoms, cycloalykyl groups or alkylcycloalkyl groups having
5 to 20 carbon atoms, or aryl, alkylaryl or arylalkyl groups having 6 to 20 carbon
atoms; R³, R⁴, R⁵ and R⁶ are hydrogen atoms, methyl groups or ethyl groups, and the
total number of carbons of R³, R⁴, R⁵ and R⁶ is 1 or 2; and a is an integer of 1 to 200; and
B) at least one nitrogen-containing compound selected from the following (a) to (d)
in the amount of 0.5 to 30 wt% to the total weight of the composition;
(a) a nitrogen-containing compound represented by formula (2);

wherein R⁷ is an alkyl group having 1 to 22 carbon atoms, an alkenyl group having
3 to 22 carbon atoms, a cycloalkyl or alkylcycloalkyl group having 5 to 15 carbon
atoms, or an aryl, alkylaryl or arylalkyl group having 6 to 18 carbon atoms; R⁸ and
R⁹ are hydrogen atoms or alkyl groups having 2 to 6 carbon atoms, and the total number
of carbon atoms of R⁸ and R⁹ is from 2 to 8; b is an integer of 1 to 8; and c is an integer of 5 to 40;
(b) a boronated nitrogen-containing compound (a);
(c) a nitrogen-containing compound represented by formula (3);

wherein X is a hydrogen atom or an acyl group having 6 to 30 carbon atoms derived
from a fatty acid;; Y is an acyl group having 6 to 30 carbon atoms derived from a
fatty acid; R¹⁰ is an alkylene group having 2 to 4 carbon atoms; d is an integer of 0 to 11; e is an integer of 0 to 11 and

; and one molecule has at least one acyl group;
(d) a boronated nitrogen-containing compound (c).
3. A lubricating oil composition for two-cycle engines which comprises
(A) as a base oil a polyalkylene glycol derivative represented by formula (4);

wherein R¹¹ and R¹² are hydrogen atoms, alkyl groups having 1 to 4 carbon atoms,
aryl, alkylaryl or arylalkyl groups having 6 to 20 carbon atoms, and at least one
of R¹¹ and R¹² is an aryl, alkylaryl or arylalkyl group having 6 to 20 carbon atoms;
R¹³, R¹⁴, R¹⁵ and R¹⁶ are hydrogen atoms, methyl groups or ethyl groups, and the total
number of carbon atoms of R¹³, R¹⁴, R¹⁵ and R¹⁶ is 1 or 2; and f is an integer of 1 to 200; and
(B) at least one nitrogen-containing compound selected from the following (c) and
(d), in the amount of 0.5 to 30 wt% to the total weight of the composition;
(c) a nitrogen-containing compound represented by formula (3);

wherein X is a hydrogen atom or an acyl group having 6 to 30 carbon atoms derived
from a fatty acid; Y is an acyl group having 6 to 30 carbon atoms derived from a fatty
acid; R¹⁰ is an alkylene group having 2 to 4 carbon atoms; d is an integer of 0 to 11; e is an integer of 0 to 11 and

; and one molecule has at least one acyl group;
(d) a boronated nitrogen-containing compound (c).
4. A process for lubrication of a two-cycle engine, wherein a lubricating oil for two-cycle
engines is fed into the two-cycle engine separately from fuel or mixed with fuel to
lubricate bearing portions and frictional portions of the said engine, wherein the
lubricating oil for two-cycle engines comprises a polyalkylene glycol derivative represented
by formula (1) as a base oil;

wherein R¹ and R² are hydrogen atoms, alkyl groups having 1 to 22 carbon atoms, alkenyl
groups having 3 to 22 carbon atoms, cycloalkyl groups or alkylcycloalkyl groups having
5 to 20 carbon atoms, or aryl, alkylaryl or arylalkyl groups having 6 to 20 carbon
atoms; R³, R⁴, R⁵ and R⁶ are hydrogen atoms, methyl groups or ethyl groups, and the
total number of carbons of R³, R⁴, R⁵ and R⁶ is 1 or 2; and
a is an integer of 1 to 200.
5. A process for lubrication of a two-cycle engine, wherein a lubricating oil composition
for two-cycle engines is fed into the two-cycle engine separately from fuel or mixed
with fuel to lubricate bearing portions and frictional portions of the said engine,
wherein the said lubricating oil composition for two-cycle engines comprises
(A) as a base oil a polyoxyalkylene glycol derivative represented by formula (1);

wherein R¹ and R² are hydrogen atoms, alkyl groups having 1 to 22 carbon atoms, alkenyl
groups having 3 to 22 carbon atoms, cycloalykyl groups or alkylcycloalkyl groups having
5 to 20 carbon atoms, or aryl, alkylaryl or arylalkyl groups having 6 to 20 carbon
atoms; R³, R⁴, R⁵ and R⁶ are hydrogen atoms, methyl groups or ethyl groups, and the
total number of carbons of R³, R⁴, R⁵ and R⁶ is 1 or 2; and a is an integer of 1 to 200;
and
(B) at least one nitrogen-containing compound selected from the following (a) to (d),
in the amount of 0.5 to 30 wt% to the total weight of the composition;
(a) a nitrogen-containing compound represented by formula (2);

wherein R⁷ is an alkyl group having 1 to 22 carbon atoms, an alkenyl group having
3 to 22 carbon atoms, a cycloalkyl or alkylcycloalkyl group having 5 to 15 carbon
atoms, or an aryl, alkylaryl or arylalkyl group having 6 to 18 carbon atoms; R⁸ and
R⁹ are hydrogen atoms or alkyl groups having 2 to 6 carbon atoms, and the total number
of carbon atoms of R⁸ and R⁹ is from 2 to 8; b is an integer of 1 to 8; and c is an integer of 5 to 40;
(b) a boronated nitrogen-containing compound (a);
(c) a nitrogen-containing compound represented by formula (3);

wherein X is a hydrogen atom or an acyl group having 6 to 30 carbon atoms derived
from a fatty acid; Y is an acyl group having 6 to 30 carbon atoms derived from a fatty
acid; R¹⁰ is an alkylene group having 2 to 4 carbon atoms; d is an integer of 0 to 11; e is an integer of 0 to 11 and

; and one molecule has at least one acyl group;
(d) a boronated nitrogen-containing compound (c).
6. A process for lubrication of a two-cycle engine, wherein a lubricating oil composition
for two-cycle engines is fed into the two-cycle engine separately from fuel or mixed
with fuel to lubricate bearing portions and frictional portions of the said engine,
wherein the said lubricating oil composition for two-cycle engines comprises
(A) as a base oil a polyalkylene glycol derivative represented by formula (4);

wherein R¹¹ and R¹² are hydrogen atoms, alkyl groups having 1 to 4 carbon atoms,
aryl, alkylaryl or arylalkyl groups having 6 to 20 carbon atoms, and at least one
of R¹¹ and R¹² is an aryl, alkylaryl or arylalkyl group having 6 to 20 carbon atoms;
R¹³, R¹⁴, R¹⁵ and R¹⁶ are hydrogen atoms, methyl groups or ethyl groups, and the total
number of carbon atoms of R¹³, R¹⁴, R¹⁵ and R¹⁶ is 1 or 2; and f is an integer of 1 to 200;
and
(B) at least one nitrogen-containing compound selected from the following (c) and
(d), in the amount of 0.5 to 30 wt% to the total weight of the composition:
(c) a nitrogen-containing compound represented by formula (3);

wherein X is a hydrogen atom or an acyl group having 6 to 30 carbon atoms derived
from a fatty acid; Y is an acyl group having 6 to 30 carbon atoms derived from a fatty
acid; R¹⁰ is an alkylene group having 2 to 4 carbon atoms; d is an integer of 0 to 11; e is an integer of 0 to 11 and

; and one molecule has at least one acyl group;
(d) a boronated nitrogen-containing compound (c).