Technical Field
[0001] The present invention relates to additive compositions containing a metal salt of
a phosphorus-containing compound for lubricating oils.
Background Art
[0002] Metal salts of phosphorus-containing compounds such as dialkylthiophosphoric acid
esters, dialkylphosphoric acid esters or the like, which are solids or viscous liquids
at ambient temperatures have problems that they are poor in handleability during the
production and transportation thereof, cannot be dissolved in a base oil kept at ambient
temperature, or are poor in storage stability after being dissolved. A technology
has been, therefore, proposed wherein such metal salts are dissolved in an amine compound
or the like beforehand to be liquefied (see Patent Literature 1 below). However, since
addition of a metal salt of a phosphorus-containing compound having been dissolved
in such an amine compound to a lubricating oil would lead to adverse effects such
as causing rubber seals to swell, the use of the metal salt are restricted to a large
extent.
Citation List
Patent Literature
Summary of Intention
Technical Problem
[0004] The present invention provides an additive composition for a lubricating oil that
does not give adverse effects such as causing rubber seals to swell, is excellent
in storage stability and contains a metal salt of a dialkylthiophosphoric acid ester
or a dialkylphosphoric acid ester that and is solid or viscous liquid at ambient temperatures,
in a dissolved state and also a process for producing an additive composition for
a lubricating oil comprising dissolving the above-mentioned compound in a base oil
at a relatively low temperature of 60° or lower for a short period of time.
Solution to Problem
[0005] As the results of the extensive studies and research conducted by the inventors,
the present invention has been accomplished on the basis of the finding that the use
of a specific hydrocarbon solvent enables a metal salt of a phosphorus-containing
compound to dissolve at a high concentration and a relatively low temperature of 60°C
or lower and the dissolved metal salt is excellent in storage stability.
[0006] That is, the present invention relates to an additive composition for a lubricating
oil, comprising a metal salt of a phosphorus-containing compound represented by formula
(1) in an amount of 10 to 90 percent by mass on the basis of the composition, contained
in a hydrocarbon solvent selected from a mineral oil, a hydrocarbon synthetic oil
and a mixture thereof, the hydrocarbon solvent having a 100°C kinematic viscosity
of 0.5 to 4.5 mm
2/s, a %C
A of 3 or less, and a sulfur content of 0.05 percent by mass or less:

wherein X
1 and X
2 are each independently oxygen or sulfur, R
1, R
2, R
3, and R
4 are each independently a straight-chain alkyl group having 3 to 12 carbon atoms,
the average of the carbon number is 5 or greater, and M is a divalent metal atom.
[0007] The present invention also relates to a process for producing an additive composition
for a lubricating oil, comprising dissolving a metal salt of a phosphorus-containing
compound represented by formula (1) in an amount of 10 to 90 percent by mass on the
basis of the composition in a hydrocarbon solvent selected from a mineral oil, a hydrocarbon
synthetic oil and a mixture thereof, the hydrocarbon solvent having a 100°C kinematic
viscosity of 0.5 to 4.5 mm
2/s, a %C
A of 3 or less, and a sulfur content of 0.05 percent by mass or less:

wherein X
1 and X
2 are each independently oxygen or sulfur, R
1, R
2, R
3, and R
4 are each a straight-chain alkyl group having 3 to 12 carbon atoms, the average of
the carbon number is 5 or greater, and M is a divalent metal atom.
[0008] The present invention also relates to a lubricating oil composition comprising the
foregoing additive composition.
Advantageous Effects of Invention
[0009] The additive composition for a lubricating oil of the present invention can be produced
at a relative low temperature that is 60°C or lower for a short period of time, does
not have adverse effects such as causing rubber seals to swell, and is excellent in
storage stability.
Best Mode for Carrying out the Invention
[0010] The present invention will be described in more details below.
The hydrocarbon solvent used in the lubricating oil additive composition of the present
invention is a solvent selected from a mineral oil, a hydrocarbon synthetic oil, and
a mixture thereof, having a 100°C kinematic viscosity of 0.5 to 4.5 mm
2/s, a %C
A of 3 or less, and a sulfur content of 0.05 percent by mass or less.
[0011] Specific examples of the mineral base oil include those which can be produced by
subjecting a lubricating oil fraction produced by vacuum-distilling an atmospheric
distillation bottom oil resulting from atmospheric distillation of a crude oil, to
any one or more treatments selected from solvent deasphalting, solvent extraction,
hydrocracking, solvent dewaxing, and hydrorefining; wax-isomerized mineral oils; and
those produced by isomerizing GTL WAX (Gas to Liquid Wax) produced through Fischer-Tropsch
process.
[0012] Specific examples of the synthetic base oil include polybutenes and hydrogenated
compounds thereof; poly-α-olefins such as 1-octene oligomer and 1-decene oligomer,
and hydrogenated compounds thereof; aromatic synthetic oils such as alkylnaphthalenes
and alkylbenzenes; and mixtures of two or more of these oils.
[0013] The hydrocarbon solvent used in the present invention may be a mineral oil, a hydrocarbon
synthetic oil or any mixture of two more types selected from these oils. For example,
the solvent may be a mixture of more than one mineral oils, a mixture of more than
one hydrocarbon synthetic oils, or a mixture of one or more mineral oil and one or
more hydrocarbon synthetic oil.
[0014] The hydrocarbon solvent used in the present invention has a 100°C kinematic viscosity
of necessarily 0.5 to 4.5mm
2/s, preferably 1.0 to 4.3 mm
2/s, more preferably 1.5 to 4.2 mm
2/s, most preferably 2.0 to 4.1 mm
2/s. A hydrocarbon solvent having a 100°C kinematic viscosity of less than 0.5 mm
2/s is not preferable with the objective of evaporation loss. A hydrocarbon solvent
having a 100°C kinematic viscosity of greater than 4.5 mm
2/s is not also preferable because of its poor dissolubility of a metal salt of a phosphorus-containing
compound.
[0015] The hydrocarbon solvent used in the present invention has a %C
A of necessarily 3 or less, preferably 2.5 or less, more preferably 2.0 or less, more
preferably 1.5 or less. A hydrocarbon solvent having a %C
A of greater than 3 is not preferable because it tends to be reduced in dissolubility
of a metal salt of a phosphorus-containing compound. The hydrocarbon solvent may have
a %C
A of 0.
The %C
A used herein denote the percentages of the aromatic carbon number in the total carbon
number, determined by a method (n-d-M ring analysis) in accordance with ASTM D 3238-85.
[0016] The hydrocarbon solvent used in the present invention has a sulfur content of necessarily
0.05 percent by mass or less, preferably 0.04 percent by mass or less, more preferably
0.03 percent by mass or less, particularly preferably 0.02 percent by mass or less.
A hydrocarbon solvent having a sulfur content of more than 0.05 percent by mass is
not preferable because it tends to be reduced in dissolubility of a metal salt of
a phosphorus-containing compound.
[0017] Generally, the sulfur content of a hydrocarbon solvent varies on the sulfur content
of its raw material. For example, in the case of using a raw material containing substantially
no sulfur such as a synthetic wax produced through a Fischer-Tropsch reaction, a hydrocarbon
solvent containing substantially no sulfur can be produced. In the case of using a
raw material containing sulfur such as a slack wax produced through the refining process
of a hydrocarbon solvent or a micro wax produced through wax refining, the sulfur
content of the resulting hydrocarbon solvent is usually 0.01 percent by mass or more.
In the present invention, the sulfur content is necessarily 0.05 percent by mass or
less.
The sulfur content referred herein is measured in accordance with the method described
in JIS K2541-1996.
[0018] No particular restriction is imposed on the viscosity index of the hydrocarbon solvent
used in the present invention. However, the viscosity index is preferably 80 or greater,
100 or greater, most preferably 120 or greater such that excellent viscosity characteristics
can be obtained at from low temperatures to high temperatures. No particular restriction
is imposed on the upper limit of the viscosity index. Those with a viscosity index
of 135 to 180 such as normal paraffins, slack waxes, GTL waxes or isoparaffin mineral
oil produced by isomerizing them may be used. A hydrocarbon solvent with a viscosity
index of less than 80 would tend to be reduced in dissolubility of a metal salt of
a phosphorus-containing compound.
[0019] The additive composition for a lubricating oil of the present invention comprises
the above-described hydrocarbon solvent and one or more metal salt of a phosphorus-containing
compound represented by formula (1) below (hereinafter simply referred to as "a metal
salt of a phosphorus-containing compound) in an amount of 10 to 90 percent by mass
on the basis of the total mass of the composition.
[0020]

[0021] In formula (1) , X
1 and X
2 are each oxygen or sulfur. R
1, R
2, R
3 and R
4 are each independently a straight-chain alkyl group having 3 to 12, preferably 4
to 11, more preferably 4 to 10, most preferably 4 to 8 carbon atoms. An alkyl group
having fewer than 3 carbon atoms would cause the resulting metal salt to be poor in
dissolubility while an alkyl group having more than 12 carbon atoms would makes it
difficult to produce the metal salt. The average carbon number of R
1, R
2, R
3 and R
4 is necessarily 5 or greater. M is a divalent metal atom, specific examples of which
include zinc, copper, nickel, cobalt, calcium and magnesium. Preferred is zinc.
[0022] Examples of the straight-chain alkyl group includen-propyl, n-butyl, n-pentyl, n-hexyl,
n-heptyl, n-octyl, n-nonyl, n-decyl, n-undecyl, and n-dodecyl groups.
[0023] Specific examples of the phosphorus-containing compound include di-n-butylphosphate,
di-n-hexylphosphate, di-n-octylphosphate, di-n-decylphosphate, di-n-dodecylphosphate,
n-butyl-n-hexylphosphate, n-butyl-n-octylphosphate, di-n-butylthiophosphate, di-n-hexylthiophosphate,
di-n-octylthiophospahte, n-butyl-n-hexylthiophosphate, n-butyl-n-octylthiophosphate,
and mixtures thereof.
Specific examples of the compounds represented by formula (1) include metal salts,
such as zinc, copper, nickel, cobalt, calcium, and magnesium salts of the above-described
phosphorus-containing compounds.
[0024] The mix ratio of the metal salt of the phosphorus-containing compound to the hydrocarbon
solvent is from 10 to 90 percent by mass, preferably from 30 to 85 percent by mass,
more preferably from 35 to 80 percent by mass, most preferably from 40 to 75 percent
by mass on the basis of the total mass of the composition. When the mix ratio is less
than 10 percent by mass, the amount of the additive to be added during the process
of production of a lubricating oil would be increased, possibly causing an increase
in the evaporation loss of the lubricating oil. When the mix ratio is more than 90
percent by mass, the additive would separate from the lubricating oil during the storage
thereof.
[0025] The additive composition for a lubricating oil of the present invention has a 100°C
kinematic viscosity of preferably 0.5 to 4.5 mm
2/s, more preferably 1.0 to 4.3 mm
2/s, more preferably 1.5 to 4.2 mm
2/s.
[0026] The additive composition of the present invention can be easily produced by, for
example, adding a metal salt of a phosphorus-containing compound having been finely
crushed, to a hydrocarbon solvent heated to a temperature of 30 to 60 °C and stirring
the mixture at a revolution number of about 300 rpm or alternatively dissolving a
metal salt of a phosphorous-containing compound in an organic solvent such as hexane
and then mixing the metal salt with a hydrocarbon solvent, followed by removal of
the organic solvent.
[0027] The resulting additive composition for a lubricating oil of the present invention
is used as an additive for various lubricating oils.
Examples
[0028] The present invention will be described more specifically with reference to the following
Examples and Comparative Examples but not limited thereto.
[0029] [Examples 1 to 8, Comparative Examples 1 to 16]
The following metal salts of phosphorous-containing compounds were added to the following
hydrocarbon solvents to prepare additive compositions for lubricating oils (Examples
1 to 8, Comparative Examples 1 to16) having formulations set forth in Tables 1 and
2 below. The hydrocarbon solvents and metal salts of phosphorous-containing compounds
in the tables are as follows.
[0030] (1) Hydrocarbon solvents
Solvent 1: Paraffinic solvent refined mineral oil (100°C kinematic viscosity: 2.1
mm2/s, %CA: 5, sulfur content: 800 ppm by mass)
Solvent 2: Hydrogenated refined mineral oil (100°C kinematic viscosity: 2.7 mm2/s, %CA: 0, sulfur content: 0 ppm by mass)
Solvent 3: Poly-α-olefin (PAO) (100°C kinematic viscosity: 4.0 mm2/s, %CA: 0, sulfur content: 0 ppm by mass)
[0031] (2) Metal salts of phosphorus-containing compounds
Phosphorus compound A: zinc n-butyl-n-hexylphosphate (average carbon number: 5, phosphorus
content: 11.5 percent by mass, zinc content: 11.9 percent by mass)
Phosphorus compound B: zinc di-n-hexylphosphate (average carbon number: 6, phosphorus
content: 10.4 percent by mass, zinc content: 10.7 percent by mass)
Phosphorus compound C: zinc n-butyl-n-octylphosphate (average carbon number: 6, phosphorus
content: 10.4 percent by mass, zinc content: 10.7 percent by mass)
Phosphorus compound D: zinc n-butyl-n-octylthiophosphate (average carbon number: 6,
phosphorus content: 9.8 percent by mass, zinc content: 10.1 percent by mass, sulfur
content: 10.1 percent by mass)
Phosphorus compound E: zinc di-n-butylphosphate (average carbon number: 4, phosphorus
content: 12.8 percent by mass, zinc content: 13.1 percent by mass)
Phosphorus compound F: zinc di-n-butylthiophosphate (average carbon number: 4, phosphorus
content: 11.9 percent by mass, zinc content: 12.3 percent by mass, sulfur content:
12.3 percent by mass)
Phosphorus compound G: zinc n-butyl-n-hexylphosphate (average carbon number: 4.5,
phosphorus content: 12.2 percent by mass, zinc content: 12.6 percent by mass)
Phosphorus compound H: zinc di-2-ethylhexylphosphate (phosphorus content: 8.8 percent
by mass, zinc content: 9.1 percent by mass)
Phosphorus compound I: zinc di-2-ethylhexyldithiophosphate (phosphorus content: 8.4
percent by mass, zinc content: 8.7 percent by mass, sulfur content: 8.7 percent by
mass)
[0032] The additive compositions for a lubricating oil of Examples 1 to 8 and Comparative
Examples 1 50 16 were subjected to a storage test at normal temperature to observe
whether they were liquefied at a temperature of 60°C and whether insoluble precipitated
after 1 week, 2 weeks, 3 weeks and 4 weeks. The results are set forth in Tables 1
and 2. A stable additive composition for a lubricating oil cannot be produced in the
case of using solvent 1 not having the properties defined by the present invention
and phosphorus-containing compounds having a branched alkyl group.
[0033] [Table 1]
Test Oil No. |
|
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
9 |
10 |
11 |
12 |
|
|
Example 1 |
Example 2 |
Example 3 |
Example 4 |
Example 5 |
Example 6 |
Example 7 |
Example 8 |
Comparative Example 1 |
Comparative Example 2 |
Comparative Example 3 |
Comparative Example 4 |
Solvent I |
mass% |
- |
- |
- |
- |
- |
- |
- |
- |
balance |
balance |
balance |
balance |
Solvent 2 |
mass% |
balance |
- |
balance |
- |
balance |
- |
balance |
- |
- |
- |
- |
- |
Solvent 3 |
mass% |
- |
balance |
- |
balance |
- |
balance |
- |
balance |
- |
- |
- |
- |
Phosphorus Compound A |
mass% |
50 |
50 |
- |
- |
- |
- |
- |
- |
50 |
- |
- |
- |
Phosphorus Compound B |
mass% |
- |
- |
50 |
50 |
- |
- |
- |
- |
- |
50 |
- |
- |
Phosphorus Compound C |
mass% |
- |
- |
- |
- |
50 |
50 |
- |
- |
- |
- |
50 |
- |
Phosphorus Compound D |
mass% |
- |
- |
- |
- |
- |
- |
50 |
50 |
- |
- |
- |
50 |
Phosphorus Compound E |
mass% |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
Phosphorus Compound F |
mass% |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
Phosphorus Compound G |
mass% |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
Phosphorus Compound H |
mass% |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
Phosphorus Compound I |
mass% |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
Average Carbon Number of Phosphorus Compound |
|
5 |
5 |
6 |
6 |
6 |
6 |
6 |
6 |
5 |
6 |
6 |
6 |
Liquefaction at 60°C |
|
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Stability at room temperature (Insoluble) |
one week |
No |
No |
No |
No |
No |
No |
No |
No |
No |
No |
No |
No |
|
two weeks |
No |
No |
No |
No |
No |
No |
No |
No |
Yes |
No |
Yes |
Yes |
|
three weeks |
No |
No |
No |
No |
No |
No |
No |
No |
Yes |
Yes |
Yes |
Yes |
|
four weeks |
No |
No |
No |
No |
No |
No |
No |
No |
Yes |
Yes |
Yes |
Yes |
[Table 2]
Test Oil No. |
|
13 |
14 |
15 |
16 |
17 |
18 |
19 |
20 |
21 |
22 |
23 |
24 |
|
|
Comparative Example 5 |
Comparative Example6 |
Comparative Example 7 |
Comparative Example8 |
Comparative Example 9 |
Comparative Example 10 |
Comparative Example 11 |
Comparative Example 12 |
Comparative Example 13 |
Comparative Example 14 |
Comparative Example 15 |
Comparative Example 16 |
Solvent 1 |
mass% |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
balance |
balance |
Solvent 2 |
mass% |
balance |
- |
balance |
- |
balance |
- |
balance |
- |
balance |
- |
- |
- |
Solvent 3 |
mass% |
- |
balance |
- |
balance |
- |
balance |
- |
balance |
- |
balance |
- |
- |
Phosphorus Compound A |
mass% |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
Phosphorus Compound B |
mass% |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
Phosphorus Compound C |
mass% |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
Phosphorus Compound D |
mass% |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
Phosphorus Compound E |
mass% |
50 |
50 |
- |
- |
- |
- |
- |
- |
- |
- |
50 |
- |
Phosphorus Compound F |
mass% |
- |
- |
50 |
50 |
- |
- |
- |
- |
- |
- |
- |
- |
Phosphorus Compound G |
mass% |
- |
- |
- |
- |
50 |
50 |
- |
- |
- |
- |
- |
- |
Phosphorus Compound H |
mass% |
- |
- |
- |
- |
- |
- |
50 |
50 |
- |
- |
- |
50 |
Phosphorus Compound I |
mass% |
- |
- |
- |
- |
- |
- |
- |
- |
50 |
50 |
- |
- |
Average Carbon Number of Phosphorus Compound |
|
4 |
4 |
4 |
4 |
4.5 |
4.5 |
8 |
8 |
8 |
8 |
4 |
8 |
Liquefaction at 60°C |
|
Yes |
Yes |
No |
No |
Yes |
Yes |
No |
No |
No |
No |
Yes |
No |
Stability at room temperature (Insoluble) |
one week |
Yes |
Yes |
|
|
Yes |
Yes |
|
|
|
|
Yes |
No |
|
two weeks |
|
|
|
|
|
|
|
|
|
|
|
|
|
three weeks |
|
|
|
|
|
|
|
|
|
|
|
|
|
four weeks |
|
|
|
|
|
|
|
|
|
|
|
|
Industrial Applicability
[0034] The additive composition for a lubricating oil of the present invention is significantly
large in industrial value because it can be produced at a relatively low temperature,
which is 60°C or lower for a short period of time, does not have any adverse effect
such as causing rubber seals to swell, and is excellent in storage stability.