Metal processing lubricating oil composition and process for producing the same

Disclosed are a metal processing lubricating oil composition and a process for producing the same. A metal processing lubricating oil composition according to this invention comprises mineral oil, synthetic oil or a mixture thereof, and phosphoric ester and orthophosphoric acid mixed and heated in the mineral oil, synthetic oil or mixture thereof. The lubricating oil composition gets rid of the tiresome pre-treatment associated with the conventional lubricating method, and exhibits a high seizure prevention performance in cold plastic working only by coating it on workpieces. The lubricating oil composition may further comprise metallic phosphate to suppress corrosivity against ferrous materials.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a high performance lubricating oil composition, 
which allows easy cold plastic working for metal materials only by coating 
and which is less corrosive to ferrous materials, and a process for 
producing the same. 
2. Discussion of the Related Art 
The following lubricating method has been widely used for cold plastic 
working for steel: This lubricating method forms zinc phosphate coating 
with zinc stearate and sodium stearate on workpieces. It has been widely 
employed because the film formed by this method offers good cold plastic 
working performance. When this method is applied to workpieces to be 
plastically cold-worked, it shows a good performance in suppressing the 
seizure between the workpieces and a die. This method is applicable to a 
case where a workpiece having a complicated shaped should be formed, and a 
case where a workpiece should be processed in severe cold plastic working 
conditions. 
Other than the above lubricating method, a method has been known in which a 
commercially available or a known lubricating oil is employed. The 
lubricating oil comprises a base oil mixed with a sulfur additive, a 
phosphorus additive or zinc dialkyldithiophosphate (hereinafter 
abbreviated to ZnDTP). This method does not require the film forming as 
required for the above lubricating method, in which zInce phosphate 
coating with zinc stearate and sodium stearate is formed on workpieces 
before cold plastic working. In this method, it is only necessary to apply 
the lubricating oil by spraying it to a workpiece before cold plastic 
working. Accordingly, this method has an advantage overcoming the 
following problems associated with the above lubricating method, in which 
a metal soap film is formed on workpieces before cold plastic working: A 
whole cold plastic working process cannot be automated, sludge and scale 
should be removed and dumped, and the waste of metallic soap solution 
should be properly treated. 
The lubricating method, in which a metal soap film is formed on a 
workpieces, requires that the above lubricant film is formed before cold 
plastic working. The above lubricant film forming process comprises the 
following steps requiring very tiresiome operations and done in the 
following order: pickling, washing with water, zinc phosphate coating, 
washing with water, neutralizing, metallic soap coating and drying. 
Consequently, the lubricant film process cannot be incorporated into a 
series of processing line ranging from a material cutting process to a 
cold plastic working process, and shold be left alone as a separate and 
independent process. Thus, the lubricant film forming process interrupts 
the operation between the material cutting process and the cold plastic 
working process in a cold plastic working line employing this lubricating 
method. As a result, such a cold plastic process automation cannot be 
realized, and this is a serious problem in satisfying the following 
requirement assigned to current manufacturing shops: providing required 
goods in required quantities at required times. Further, sludge and scale 
should be removed and dumped because they are produced in the phosphate 
coating process. Furthermore, the waste of metallic soap solution should 
be properly treated. Therefore, this lubricating method has drawbacks 
resulting in increased labor, costs and times. 
The other method, in which the lubricating oil comprising a base oil mixed 
with a sulfur additive, a phosphorus additive or ZnDTP is employed, has a 
poorer seizure prevention performance in cold plastic working than that of 
the lubricating method in which a metal soap film is formed on workpieces. 
Accordingly, this method has a critical drawback, i.e. it is only 
applicable to cold plastic working in milder conditions. Its poor seizure 
prevention performance results from the fact that the seizure prevention 
is done only by the lubricating oil film and the reaction film generated 
during cold plastic working. 
SUMMARY OF THE INVENTION 
It is therefore an object of this invention to provide a high performance 
lubricating oil composition whch gets rid of the tiresome pre-treatment 
only by coating it on a metal material surface before processing. 
It is another object of this invention to provide a high performance 
lubricating oil composition exhibiting a performance equivalent to or 
higher than that of the lubricating method, in which a metal soap film is 
formed on workpieces. 
A further object of this invention is to provide a high performance 
lubricating oil composition making cold plastic working for metal 
materials easier and being less corrosive to ferrous materials, and a 
process for producing the same. 
A lubricating oil composition of this invention comprises mineral oil, 
synthetic oil or a mixture thereof, and phosphoric ester by 0.1 weight % 
or more in phosphorus concentration and orthophosphoric acid by 0.1 weight 
% or more in phosphorus concentration. The composition is then heated at 
80.degree. C. or more to form associations of phosphoric ester and 
orthophosphoric acid. 
In addition to the above components, the lubricating oil composition of 
this invention may further comprise metallic phosphate by 0.01 weight % or 
more in phosphorus concentration. 
The mineral oil, synthetic oil or a mixture thereof is a base oil, i.e. a 
major component of lubricating oil composition of this invention. 
The phosphoric ester may be tributylphosphate, trioctylphosphate, 
trioleylphosphate, dibutylphosphate, dioctylphosphate, monobutylphosphate, 
monodecylphosphate, and a mixture of diester and monoester like octyl 
hydrogen phosphate, decyl hydrogen phosphate and oleyl hydrogen phosphate. 
The orthophosphoric acid may be a commercially available aqueous solution 
of orthophosphoric acid, and the water content may be at one's discretion. 
The metallic phosphate may be calcium phosphate, manganese phosphate, iron 
phosphate and zinc phosphate. 
The phosphoric ester may be mixed in the base oil by 0.1 weight % or more 
in phosphorus concentration, and the content may preferably be from 0.5 to 
5 weight % in phosphorus concentration. 
The orthophosphoric acid may be mixed in the base oil by 0.1 weight % or 
more in phosphorus concentration, and the content may preferably be from 
0.3 to 5 weight % in phosphorus concentration. 
The metallic phosphate may be mixed in the base oil by 0.01 weight % or 
more in phosphorus concentration, and the content may preferably be from 
0.01 to 0.5 weight % in phosphorus concentration. 
When the phosphoric ester and orthophosphoric acid contents are less than 
0.1 weight % in phosphorus concentration, the effect of their addition 
decreases. When the phosphoric ester and orthophosphoric acid contents are 
more than 5 weight % in phosphorus concentration, the performance of 
lubricating oil composition does not improve any further and their 
addition is not economical. 
When the metallic phosphate content is less than 0.01 weight %, the 
lubricating oil composition shows corrosion suppressing effect in a lesser 
degree. When the metallic phosphate content is more than 0.5 weight %, the 
cold plastic working performance of lubricating oil composition decreases 
to an unfavorable level. 
The lubricating oil composition, in which the phosphoric ester and 
orthophosphoric acid and/or metallic phosphate are mixed, may be heated at 
80.degree. C. or more, and the heating temperature may preferably fall in 
a range of 100.degree. tio 200.degree. C. Time required for the heat 
treatment depends on the heating temperature. Namely, when the heating 
temperature is higher, the heat treatment may take a shorter period of 
time, and when the heating temperature is lower, the heat treatment may 
take a longer period of time. However, it is preferable to heat the 
lubricating oil composition for at least 3 minutes, and more preferably 
for 15 minutes or more. When the heating temperature is less than 
80.degree. C. and the heating period is less than 3 minutes, the cold 
plastic working performance of lubricating oil composition improves less. 
On the other hand, when the heating temperature exceeds 200.degree. C., it 
is not economical because the mineral oil as the base oil degrades and the 
cold plastic working performance of lubricating oil composition does not 
improve any more. While heating the lubricating oil composition, it may be 
stirred with a stirrer, or it may be stood still. It is preferred to carry 
out the heating in an open system rather than a closed system. After the 
heating, the lubricating oil composition may be cooled to room temperature 
by any method. 
In case, metallic phosphate is further added to the above lubricating oil 
composition and undissolved metallic phosphate remains in the lubricating 
oil composition after heating, the undissolved metallic phosphate is 
removed by filtering. After the filtering, the lubricating oil composition 
may be cooled to room temperature by any method as mentioned above. 
The lubricating oil composition thus produced contains the associations of 
phosphoric ester and orthophosphoric acid. The concentration and degree of 
associations depend on the contents of phosphoric ester and 
orthophosphoric acid and the conditions of heating, i.e. heating 
temperature and heating time, and they can not be expressed explicitly. 
After the heating, however, it is preferable that a spectrum of .sup.1 
H--NMR analysis on the lubricating oil composition exhibits the following: 
decrease in height of peak resulting from the hydrogen atom of --OH group 
of free orthophosphoric acid and shift of the peak to lower magnetic 
field, and increase in height of peak resulting from the hydrogen atom of 
--OH group of phosphoric ester. Thus, qualitatively, it is preferred to 
verify that the association is occurred between the phosphoric ester and 
orthophosphoric acid by the heating, and quantitatively, it is preferred 
that the integrated value of peak resulting from the hydrogen atom of --OH 
group of orthophosphoric acid decreases by 90% or less after the heating. 
If necessary, the following may be added to the lubricating oil composition 
of this invention: a compatibility improving agent for improving 
solubility of the components, a dispersion agent for improving 
dispersibility of the components, an antioxidation agent for improving the 
thermal stability of lubricating oil composition, and a corrosion 
prevention agent for improving the anti-corrosion property of the 
lubricating oil composition. 
The orthophosphoric acid used in this invention is an aqueous solution. 
Consequently, obtained lubricating oil composition is a heterogeneous 
solution when the phosphoric ester and orthophosphoric acid are only added 
to the base oil. The phosphoric ester is dissolved mainly in the oil 
phase, and the orthophosphoric acid is dissolved mainly in the aqueous 
phase. Accordingly, the phosphoric ester and orthophosphoric acid interact 
less. 
But when the lubricating oil composition is heated, the water evaporates 
and the water content in the lubricating oil composition decreases. As a 
result, the phosphoric ester and orthophosphoric acid interact more and 
the association develops with the hydrogen bond formed between the 
phosphoric ester and orthophosphoric acid. The higher the heating 
temperature becomes and the larger the heating time becomes, the more the 
association develops between the phosphoric ester and orthophosphoric 
acid. The association develops until it reaches the saturation. 
Following structural formulas show the associations comprising one molecule 
of phosphoric esters and one molecule of orthophosphoric acid. The 
association in this invention basically results from the hydrogen bond 
between P--OH and O.dbd.P, i.e. [P--OH . . . O.dbd.P]. The manner of 
association is basically identical whether the phosphoric ester is 
monoester, diester or triester. The association may comprise not only the 
two molecules as illustrated below, but also a plurality of molecules 
successively bonded with the hydrogen bonds. 
##STR1## 
Spectra of .sup.1 H--NMR analysis on the lubricating oil compositions 
comprising orthophosphoric acid and oleyl hydrogen phosphate; a mixture of 
phosphoric monoester and phosphoric diester are illustrated in FIG. 5, and 
they will be described later in DETAILED DESCRIPTION OF THE PREFERRED 
EMBODIMENTS section. Here, it is enough to observe that the hydrogen bond 
is generated between --OH group and O.dbd.P group and the association is 
formed after the heating. Although only the following is observed to 
verify that the association develops between the phosphoric triester and 
orthophosphoric acid in the case where the lubricating oil composition 
contains phosphoric triester, it could be verified that the association 
develops even between the phosphoric triester and orthophosphoric acid 
from the results of anaylsis on the cases where the lubricating oil 
comprises phosphoric monoester or diester and from the fact that the 
hydrogen bond generated between --OH group and O.dbd.P group can result in 
forming the association. Namely, in case where the lubricating oil 
comprises phosphoric triester, the following is observed: no peak 
.circle.1 appears but only peak .circle.2 resulting from 
orthophosphoric acid appears in the spectrum like FIG. 5 because the 
phosphoric triester does not have --ON group in its molecule. Peak 
.circle.2 decreases the height and shifts to lower magnetic field, i.e. 
to the left, after heating. 
The association of phosphoric ester and orthophosphoric acid has much 
greater reactivity to steel than those of free phosphoric ester and 
orthophosphoric acid. Since the lubricating oil composition of this 
invention comprises the phosphoric ester and orthophosphoric acid mixed 
and heated in the base oil, a strong reaction film comprising iron 
phosphate is formed on the surfaces of steel material when the lubricating 
oil composition of this invention is coated on the surfaces of steel 
material and the steel material is processed. 
The metallic phosphate itself hardly dissolves in the base oil. If the 
metallic phosphate coexists with the phosphoric ester and orthophosphoric 
acid, it dissolves in the base oil by forming association or complex among 
the three. The metallic phosphate has low reactivity to metals. 
Accordingly, when the reaction time is short as in the forging, the 
metallic phosphate hardly reacts with the surfaces of metal materials and 
does not hinder the reaction between the surfaces of metal materials and 
phosphoric ester and orthophosphoric acid. On the other hand, when the 
lubricating oil composition contacts with the surfaces of metal materials 
in a longer period of time, the formation of stable reaction film on the 
surfaces of metal materials depends on components of lubricating oil 
composition and conditions of the surfaces of metal materials. When the 
lubricating oil composition contains the metallic phosphate, not only 
excessive reaction between the surfaces of metal materials and phosphoric 
ester and orthophosphoric acid can be prevented, but also coming-off and 
dissolving of the reaction film can be prevented. 
The reaction film obtained from the lubricating oil composition of this 
invention offers better lubrication in the cold plastic working than the 
conventional lubricating oil applied by coating and the lubricating oil 
composition obtained only by mixing the base oil with the phosphoric ester 
and orthophosphoric acid do. 
The lubricating oil composition of this invention has remarkably great 
reactivity to the surfaces of metal materials, and a reaction film having 
sufficient strength can be formed quickly and simultaneously with the cold 
plastic working only by coating it on the surfaces of metal materials. 
Further, when the metallic phosphate is added to the lubricating oil 
composition, excessive action of the lubricating oil composition to the 
surfaces of metal materials can be suppressed. Namely, when the 
lubricating oil composition of this invention contains the metallic 
phosphate, the lubricating oil composition can be made less corrosive to 
ferrous materials. 
The reaction film obtained from the lubricating oil composition of this 
invention is appropriate for preventing the seizure in the cold plastic 
working for metals. Accordingly, when products should be manufactured 
under sever cold working conditions to which the conventional lubricating 
oils have not been applicable, such products can be manufactured by cold 
plastic working by only applying the lubricating oil composition of this 
invention to them.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
First Preferred Embodiments 
Paraffinic mineral oil having a kinematic viscosity of 96 cSt. at 
40.degree. C., trioleylphosphate, dioctylphosphate and oleyl hydrogen 
phosphate as phosphoric ester, and orthophosphoric acid were employed to 
prepare 10 types of lubricating oil compositions listed in Table 1, i.e. 
Nos. 1 through 10. Quantities in parentheses in Table 1 are phosphorus 
concentrations expressed in weight %. The phosphoric esters and 
orthophosphoric acid were mixed in the paraffinic mineral oil to obtain 
the compositions having the phosphorus concentrations. Lubricating oil 
composition Nos. 1, 3 and 5 were heated at 150.degree. C. for 1 hour. 
Then, reaction films obtained from these lubricating oil compositions were 
evaluated on their cold plastic working performance by a ball inserting 
test. FIG. 1 illustrates the arrangement of a testing apparatus employed 
for the ball inserting test. The testing apparatus includes a die 4 made 
of high speed tool steel and having a through bore of 30 mm inside 
diameter, a cylindrical test piece 1 having 29.8 mm outside diameter and a 
center bore of various inside diameters and disposed in the through bore 
of die 4, a counter punch 5 disposed at the bottom end of the through bore 
of die 4, and a ball 2 having diameter larger than the inside diameter of 
the center bore of test piece 1 and disposed at the top end of the test 
piece 1. The ball 2 is pushed into in the center bore of test piece 1 by a 
250 ton knuckle joint press to evaluate seizure between the test piece 1 
and ball 2. 
For the test piece 1, two types of test pieces 1 as listed in Table 2 were 
prepared. They were made of low carbon steel, S10C as per Japanese 
Industrial Standards (hereinafter referred to as JIS), and had a center 
bore having inside diameter of 14.5 and 15.0 mm. The surfaces of test 
pieces 1 were coated with one of the lubricating oil compositions listed 
in Table 1. 
For the ball 2, three types of balls 2 were prepared. They were made of 
steel for bearing, SUJ2 as per JIS, and had diameter of 15.88, 16.67 and 
17.46 mm. The ball inserting test was performed after combining the 
diameter of ball 2 (db) and the inside diameter of center bore (di) of 
test piece 1 as listed in Table 2. 
The reduction in cross-section area (R) in the ball inserting tests were 4, 
6, 8, 10, 12 and 14%. Here, the surface area reduction rate (R) is 
calculated by the following equation: 
EQU R(%)={(db.sup.2 -di.sup.2)/(30.sup.2 -di.sup.2)}.times.100 
The greater surface area reduction rate means that the cold plastic working 
condition becomes severed and that the seizure is more likely to occur. 
The cold plastic working performance of lubricating oil compositions was 
evaluated by visually observing the inner surface of test piece 1 and by 
examining the maximum surface area reduction rate (Rmax) which allows the 
cold plastic working free from the seizure. The greater maximum surface 
area reduction rate (Rmax) means that the lubricating oil composition 
shows high performance in a cold plastic working. The testing was done at 
room temperature. 
TABLE 1 
______________________________________ 
Components Heating Condition 
(Phosphorus Concentration 
Temp. 
No. in Weight %) (.degree.C.) 
Time (h.) 
______________________________________ 
1 Trioleylphosphate (1.0) 150 1 
Orthophosphoric acid 
(0.54) 
2 Trioleylphosphate (1.0) * * 
Orthophosphoric acid 
(0.54) 
3 Dioctylphosphate (1.0) 150 1 
Orthophosphoric acid 
(0.54) 
4 Dioctylphosphate (1.0) * * 
Orthophosphoric acid 
(0.54) 
5 Oleyl hydrogen phosphate 
(1.0) 150 1 
Orthophosphoric acid 
(0.54) 
6 Oleyl hydrogen phosphate 
(1.0) * * 
Orthophosphoric acid 
(0.54) 
7 Trioleylphosphate (1.0) * * 
8 Dioctylphosphate (1.0) * * 
9 Oleyl hydrogen phosphate 
(1.0) * * 
10 Orthophosphoric acid 
(0.54) * * 
______________________________________ 
Lines marked with "*" mean that no heating was performed. 
TABLE 2 
______________________________________ 
di (mm) 
db (mm) R (%) di (mm) db (mm) 
R (%) 
______________________________________ 
15.88 4 15.88 6 
15.0 16.67 8 14.5 16.67 10 
17.46 12 17.46 14 
______________________________________ 
di: Inside Diameter of Center Bore of Test Piece 1 
db: Diameter of Ball 2 
R: Surface Area Reduction Rate; R (%) = {(db.sup.2 - di.sup.2)/(30.sup.2 
di.sup.2)} .times. 100 
FIG. 2 shows results of the ball inserting test. The results show that the 
lubricating oil compositions of this invention, i.e. Nos. 1, 3 and 5, in 
which the phosphoric ester and orthophosphoric acid were mixed and heated 
in the paraffinic mineral oil, exhibited greater maximum reduction in 
cross-sectional area than lubricating oil composition Nos. 2, 4, 6, 7, 8, 
9 and 10 do. Note that lubricating oil composition Nos. 2, 4 and 6 
includes both the phosphoric ester and orthophosphoric acid but no heating 
was performed and also note that lubricating oil composition Nos. 7, 8, 9 
annd 10 contain either the phosphoric ester or orthophosphoric acid and no 
heating was performed. Particularly, lubricating oil composition No. 1 
exhibited greater maximum surface area reduction than lubricating oil 
composition No. 2 does, lubricating oil composition No. 3 exhibited 
greater maximum surface area reduction than lubricating oil composition 
No. 4 does, and lubricating oil composition No. 5 exhibited greater 
maximum surface area reduction than lubricating oil composition No. 6 
does. It is thus apparent that the lubricating oil compositions of this 
invention had an improved cold plastic working performance. 
Second Preferred Embodiments 
Oleyl hydrogen phosphate as phosphoric ester and orthophosphoric acid were 
mixed in the same mineral oil employed by the first preferred embodiments, 
i.e. paraffinic mineral oil. oleyl hydrogen phosphate and orthophosphoric 
acid contents were respectively 1.0 and 0.54 weight % in phosphorus 
concentration. Lubricating oil composition No. 11 was heated at 60.degree. 
C. for 1 hour, lubricating oil composition No. 12 was heated at 80.degree. 
C. for 1 hour, and lubricating oil composition No. 13 was heated at 
120.degree. C. for 1 hour. Thus, three lubricating oil compositions were 
prepared. Two lubricating oil compositions prepared in the first preferred 
embodiments, i.e. Nos. 5 and 6, were evaluated together with the above 
three lubricating oil compositions of these second preferred embodiments. 
These five lubricating oil compositions are listed in Table 3 below. 
TABLE 3 
______________________________________ 
Components Heating Condition 
(Phosphorus Concentration 
Temp. 
No. in Weight %) (.degree.C.) 
Time (h.) 
______________________________________ 
6 Oleyl hydrogen phosphate 
(1.0) * * 
Orthophosphoric acid 
(0.54) 
11 Oleyl hydrogen phosphate 
(1.0) 60 1 
Orthophosphoric acid 
(0.54) 
12 Oleyl hydrogen phosphate 
(1.0) 80 1 
Orthophosphoric acid 
(0.54) 
13 Oleyl hydrogen phosphate 
(1.0) 120 1 
Orthophosphoric acid 
(0.54) 
5 Oleyl hydrogen phosphate 
(1.0) 150 1 
Orthophosphoric acid 
(0.54) 
______________________________________ 
Lines marked with "*" mean that no heating was performed. 
Seizure prevention performance in cold plastic working of the five 
lubricating oil compositions listed in Table 3 were evaluated by the same 
ball inserting test as described in First Preferred Embodiments section. 
In addition, a commercially available cold forging lubricating oil with 
sulfur additive (Comparative Example 1) and another commercially available 
cold forging lubricating oil with phosphorus additive (Comparative Example 
2) were also evaluated by the ball inserting test. Results of this 
evaluation are illustrated in FIG. 3. 
It is apparent from FIG. 3 that effects of heating are obvious in the 
lubricating oil compositions heated at 80.degree. C. or more, i.e., Nos. 
12, 13 and 5. Namely, lubricating oil composition Nos. 12, 13 and 5 
exhibited greater maximum surface area reduction rate (Rmax) than 
lubricating oil composition No. 6, which was not subjected to heating, 
did. Further, Rmax value increased as the temperature of heating 
increased. Accordingly, it is apparent that seizure prevention performance 
improved as the temperature of heating increased. Among the heated 
lubricating oil compositions, the lubricating oil compositions heated at 
120.degree. C. or more, i.e. Nos. 13 and 5, was particularly superior in 
seizure prevention performance to the commercially available forging 
lubricating oils, i.e. Comparative Examples 1 and 2. 
(Quantitative Analysis with X-ray Micro Analyzer) 
Then, a quantitative analysis with an X-ray micro analyzer (hereinafter 
referred to as EPMA) was done in order to examine how the reaction between 
the lubricating oil compositions and the test pieces 1 developed. First, 
the test pieces 1 were coated with lubricating oil composition Nos. 5, 6, 
9 and 10 of Table 1, and the ball inserting test was conducted at the 
surface area reduction rate of 4%. The quantitative analysis with the EPMA 
was then conducted to determine quantities of phosphorus and oxygen 
elements in the surfaces of test pieces 1 after the ball inserting test. 
Results of this quantitative analysis are shown in FIG. 4. 
FIG. 4 reveals that lubricating oil composition No. 5 of this invention 
formed the reaction film on the inner surface of test piece 1 in greater 
quantity than lubricating oil composition No. 6, which was not heated, 
did. It is believed that the reaction film is mainly composed of iron 
phosphate, and that the seizure prevention performance results from the 
high reactivity of heated lubricating oil composition to the surfaces of 
metal materials. 
(Spectrometric Analysis on Lubricating Oil Composition) 
Furthermore, four lubricating oil compositions, i.e. Nos. 6, 12, 13 and 5 
of Table 3, were analyzed by .sup.1 H-NMR, .sup.31 P-NMR and infrared 
spectroscopy, and the water content in the lubricating oil compositions 
were measured. Results of .sup.1 H-NMR analysis and the water content 
measurement are shown in FIG. 5, in which .sup.1 H-NMR spectra of the 
lubricating oil compositions are marked with their respective numbers, 
heating temperatures and water contents. However, in .sup.31 P-NMR and 
infrared spectroscopy analyses, no appreciable difference resulting from 
the heating was seen among lubricating oil compositions Nos. 6, 12, 13 and 
5. 
In FIG. 5, there appears peak .circle.1 clearly separated from peak 
.circle.2 in the spectrum of lubricating oil composition No. 6, which was 
not subjected to the heating. Peak .circle.1 results from the hydrogen 
of --OH group of oleyl hydrogen phosphate, and peak .circle.2 results 
from the hydrogen of --OH group of orthophosphoric acid. As the heating 
temperature increases and the water content decreases, peak .circle.2 
becomes shorter and approaches peak .circle.1 , and peak .circle.1 
becomes taller. Accordingly, the variation in the spectra of .sup.1 H-NMR 
according to the heating is believed to show that the following had 
happened: The associations were formed between oleyl hydrogen phosphate 
and orthophosphoric acid with the hydrogen bond, and the number of 
associations were increased as the heating temperature increased. 
Therefore, it is understood that the high reactivity of heated lubricating 
oil composition of this invention to the surfaces of metal materials 
resulted from the association between oleyl hydrogen phosphate and 
orthophosphoric acid, and that the action of association between oleyl 
hydrogen phosphate and orthophosphoric acid improved the seizure 
prevention performance in cold plastic working remarkably. 
Third Preferred Embodiments 
Paraffinic mineral oil having a kinematic vicosity of 96 cSt. at 40.degree. 
C., oleyl hydrogen phosphate as phosphoric ester, orthophosphoric acid, 
and calcium phosphate, manganese phosphate, iron phosphate and zinc 
phosphate as metallic phosphate were employed to prepare 8 types of 
lubricating oil compositions listed in Table 4, i.e. Nos. 14 through 21. 
The same ball inserting test, done in the first preferred embodiments, were 
conducted to evaluate the cold plastic working performance of reaction 
film obtained from lubricating oil compositions of these third preferred 
embodiments. 
TABLE 4 
______________________________________ 
Components Heating Condition 
(Phosphorus Concentration 
Temp. 
No. in Weight %) (.degree.C.) 
Time (h.) 
______________________________________ 
Oleyl hydrogen phosphate 
(1.0) 
14 Orthophosphoric acid 
(0.5) 80 3 
Calcium phosphate (0.02) 
Oleyl hydrogen phosphate 
(1.0) 
15 Orthophosphoric acid 
(0.5) 80 3 
Manganese phosphate 
(0.02) 
Oleyl hydrogen phosphate 
(1.0) 
16 Orthophosphoric acid 
(0.5) 80 3 
Iron phosphate (0.11) 
Oleyl hydrogen phosphate 
(1.0) 
17 Orthophosphoric acid 
(0.5) 110 3 
Zinc phosphate (0.13) 
18 Oleyl hydrogen phosphate 
(1.0) 
Orthophosphoric acid 
(0.5) 110 3 
19 Oleyl hydrogen phosphate 
(1.0) * * 
Orthophosphoric acid 
(0.5) 
20 Oleyl hydrogen phosphate 
(1.0) * * 
21 Orthophosphoric acid 
(0.5) * * 
______________________________________ 
Lines marked with "*" mean that no heating was performed. 
Results of the evaluation are summarized in Table 5. In Table 5, 
Comparative Example 3 was a commercially available cold forging 
lubricating oil with phosphorus additive. The results show that the 
lubricating oil compositions of this invention, i.e. Nos. 14, 15, 16, 17 
and 18, in which the phosphoric ester, orthophosphoric acid and/or 
metallic phosphate were mixed and heated in the paraffinic mineral oil, 
exhibited greater maximum reduction in cross-sectional area than 
lubricating oil composition Nos. 19, 20 and 21 did. Note that lubricating 
oil composition Nos. 19 includes both the phosphoric ester and 
orthophosphoric acid but no heating was performed and also note that 
lubricating oil composition Nos. 20 and 21 contain either the phosphoric 
ester or orthophosphoric acid and no heating was performed. Particularly, 
lubricating oil composition Nos. 14 through 18 exhibited greater maximum 
surface area reduction than lubricating oil composition No. 19 did, and 
lubricating oil composition No. 19 exhibited greater maximum surface area 
reduction rate than lubricating oil composition Nos. 20 and 21 did. It is 
thus apparent that the lubricating oil compositions of this invention had 
an improved seizure prevention performance in cold plastic working. 
Furthermore, the lubricating oil compositions of this invention had better 
seizure prevention performance in cold plastic working than Comparative 
Example 3, the commercially available cold forging lubricating oil with 
phosphorus additive. 
TABLE 5 
______________________________________ 
Lubricating Oil 
Rmax Value (%) Obtained by 
Composition No. 
Ball Inserting Test 
______________________________________ 
No. 14 12 
No. 15 12 
No. 16 12 
No. 17 12 
No. 18 12 
No. 19 8 
No. 20 4 
No. 21 4 
Comparative Example 3 
8 
______________________________________ 
Table 6 summarizes results of the quantitative analysis with the EPMA on 
elements in the surfaces of test pieces 1 after the ball inserting test. 
The elements to be detected were phosphorus, oxygen and zinc. 
TABLE 6 
______________________________________ 
Lubricating Oil 
X-ray Intensity Ratio of Elements (%) 
Composition No. 
Phosphorus Oxygen Zinc 
______________________________________ 
No. 17 0.61 5.99 0.04 
No. 18 0.63 6.22 0 
No. 19 0.18 1.71 0 
No. 20 0.01 0.10 0 
No. 21 0.04 0.10 0 
______________________________________ 
Table 6 tells us that lubricating oil compositions Nos. 17 and 18 exhibited 
greater X-ray intensity rates than lubricating oil composition No. 19 did. 
Therefore, it is understood from Table 6 that lubricating oil composition 
Nos. 17 and 18 subjected to the heating generated much reaction film on 
the surfaces of test pieces 1 than lubricating oil composition No. 19 
without being subjected to the heating did. The reaction film is believed 
to be mainly composed of iron phosphate. Thus, it is apparent that the 
high reactivity of heated lubricating oil compositions contributed to the 
high seizure prevention performance in cold plastic working. The high 
reactivity resulted from the association formed between phosphoric ester 
and orthophosphoric acid by heating. 
Further, in lubricating oil composition No. 17 with zinc phosphate added, a 
trace of zinc was detected as summarized in Table 6. Accordingly, zinc 
phosphate, i.e. the metallic phosphate, did not take part in the reaction 
with iron surfaces. Namely, the metallic phosphate does not react with the 
iron surfaces in the reaction like the cold plastic working done in a 
short period of time. As a result, the metallic phosphate does not hinder 
the iron phosphate forming reaction, which forms the reaction film 
effective to high seizure prevention performance in cold plastic working 
and which results from the action of phosphoric ester and orthophosphoric 
acid. 
(Static Corrosion Test) 
Corrosivity of lubricating oil compositions listed in Table 4 against 
ferrous materials was evaluated by a static corrosion test. 
The static corrosion test was done by measuring weight difference of a test 
piece made of SPCC steel (as per JIS) and by observing surface state of 
the test piece after immersing and leaving the test piece in the 
lubricating oil compositions for one week. The surface area ratio of test 
piece to the amount of lubricating oil compositions was 0.37 cm.sup.2 per 
1 gram of lubricating oil compositions. The temperatures of lubricating 
oil compositions and the test piece was kept constant by conducting the 
static corrosion test in a constant temperature bath. 
Table 7 summarizes results of the static corrosion test. In the static 
corrosion test of lubricating oil composition No. 18, in which only 
phosphoric ester and orthophosphoric acid were mixed and heated in the 
paraffinic mineral oil, and Comparative Example 3, i.e. a commercially 
available cold forging lubricating oil with phosphorus additive, the test 
pieces dissolved in the lubricating oil composition No. 18 and Comparative 
Example 3 due to the occurrence of heavy corrosion, and lost their weight. 
On the other hand, in the static corrosion test of the lubricating oil 
compositions Nos. 14, 15, 16 and 17, the test pieces did not lost their 
weight but they gained weight by the weight of reaction film formed on 
their surfaces resulting from the reaction of phosphoric ester and 
orthophosphoric acid. Especially, among them, lubricating oil composition 
No. 16 containing iron phosphate and lubricating oil composition No. 17 
containing zinc phosphate corroded the test pieces least, and the surfaces 
of test pieces immersed in these lubricating oil compositions were in 
gentle condition. Therefore, it is apparent that the corrosivity of 
lubricating oil compositions containing phosphoric ester and 
orthophosphoric acid against ferrous materials has been improved by 
further mixing the metallic phosphate. 
TABLE 7 
______________________________________ 
Test Piece Test Piece 
Rank of 
Lubricating 
Weight Difference 
Surface Improve- 
Oil (mg/cm.sup.2) Condition ment 
Composition No. 
[Note 1] [Note 2] [Note 3] 
______________________________________ 
No. 14 +2.23 X D 
No. 15 +0.74 X D 
No. 16 +0.33 O B 
No. 17 +0.35 O B 
No. 18 -0.89 X F 
Comparative 
-0.94 X F 
Example 3 
______________________________________ 
(Test Temperature: 60.degree. C.) 
Note 1: +: Weight Gained, -: Weight Decreased 
Note 2: O: Gently Affected, .DELTA.: Slighty Roughed, X: Heavily Roughed 
Note 3: A: No weight and surface condition differences B: Weight gained 
and gently affected surface C: Weight gained and slightly roughed surface 
D: Weight gained and heavily roughed surface E: Weight decreased and 
gently affected surface F: Weight decreased and heavily roughed surface 
Table 8 summarizes results of the quantitative analysis with the EPMA on 
elements in the surfaces of test pieces 1 after the static corrosion test. 
The elements to be detected were phosphorus, oxygen and zinc. 
TABLE 8 
______________________________________ 
Lubricating Oil 
X-ray Intensity Ratio of Elements (%) 
Composition No. 
Phosphorus Oxygen Zinc 
______________________________________ 
No. 17 2.43 21.5 1.32 
No. 18 3.70 27.4 0 
______________________________________ 
Table 8 tells us that zinc as well as phosphorus and oxygen were detected 
in the surfaces of test pieces immersed in lubricating oil composition No. 
17 containing zinc phosphate. On the contrary, no zinc was detected in the 
surfaces of test pieces immersed in lubrication oil composition No. 18 
free from the metallic phosphate. Therefore, the following is apparent: 
When the lubricating oil composition No. 17 and the test piece made of 
iron were in contact for a long time, zinc phosphate as the metallic 
phosphate took part in the reaction among phosphoric ester, 
orthophosphoric acid and the surfaces of test piece. Thus, the metallic 
phosphate helped to form the stable reaction film less likely to dissolve 
in the lubricating oil or less likely to come off, and suppressed the 
corrosion. 
Fourth Preferred Embodiments 
Phosphoric ester, orthophosphoric acid and metallic phosphate were mixed, 
heated and stirred in the same mineral oil employed by the third preferred 
embodiments, i.e. paraffinic mineral oil, to prepare five lubricating oil 
compositions listed in Table 9. Oleyl hydrogen phosphate and iron 
phosphate were employed respectively for the phosphoric ester and the 
metallic phosphate. The oleyl hydrogen phosphate and orthophosphoric acid 
contents were fixed for all of the five lubricating oil compositions, but 
the iron phosphate content was varied. 
TABLE 9 
______________________________________ 
Components Heating Condition 
(Phosphorus Concentration 
Temp. 
No. in Weight %) (.degree.C.) 
Time (h.) 
______________________________________ 
Oleyl hydrogen phosphate 
(1.0) 
22 Orthophosphoric acid 
(0.5) 80 3 
Iron phosphate (0.03) 
Oleyl hydrogen phosphate 
(1.0) 
23 Orthophosphoric acid 
(0.5) 80 3 
Iron phosphate (0.06) 
Oleyl hydrogen phosphate 
(1.0) 
24 Orthophosphoric acid 
(0.5) 80 3 
Iron phosphate (0.08) 
Oleyl hydrogen phosphate 
(1.0) 
16 Orthophosphoric acid 
(0.5) 80 3 
Iron phosphate (0.11) 
Oleyl hydrogen phosphate 
(1.0) 
25 Orthophosphoric acid 
(0.5) 80 3 
Iron phosphate (0.15) 
______________________________________ 
Seizure prevention performance of the five lubricating oil compositions 
listed in Table 9 were evaluated by the same ball inserting test as 
described in the first preferred embodiments. In addition, corrosivity of 
the lubricating oil compositions listed in Table 9 against ferrous 
materials was evaluated by the same static corrosion test described in the 
third preferred embodiments. Table 10 summarizes results of the ball 
inserting test, and Table 11 summarizes results of the static corrosion 
test. 
It is understood from Table 11 that mixing iron phosphate improved the 
corrosivity of lubricating oil compositions without decreasing the weight 
of test pieces. Namely, as in lubricating oil composition No. 22, the 
effect was obtained by mixing iron phosphate by an extremely small amount 
of 0.03 weight % in phosphorus concentration. Further, as the iron 
phosphate content increased, the test piece surface condition was found to 
be affected more gently and the corrosivity of lubricating oil 
compositions was also found to be suppressed. However, when the iron 
phosphate content is increased extremely, the seizure prevention 
performance in cold plastic working deteriorates. Namely, as in the case 
of lubricating oil composition No. 25 containing 0.15 weight % of iron 
phosphate in phosphorus concentration, lubricating oil composition No. 25 
exhibited lower Rmax value of 8% as shown in Table 10 and had deteriorated 
cold plastic working performance. Accordingly, it is necessary to 
determine the metallic phosphate content in accordance with circumstances 
to which the lubricating oil composition is coated, i.e. performance 
required for the lubricating oil composition, application for the 
lubricating oil composition and so on. 
TABLE 10 
______________________________________ 
Lubricating Oil 
Rmax Value (%) Obtained by 
Composition No. 
Ball Inserting Test 
______________________________________ 
No. 22 12 
No. 23 12 
No. 24 12 
No. 16 12 
No. 25 8 
______________________________________ 
TABLE 11 
______________________________________ 
Test Piece Test Piece 
Rank of 
Lubricating 
Weight Difference 
Surface Improve- 
Oil (mg/cm.sup.2) Condition ment 
Composition No. 
[Note 1] [Note 2] [Note 3] 
______________________________________ 
No. 22 +0.25 X D 
No. 23 +0.30 .DELTA. C 
No. 24 +0.49 .DELTA. C 
No. 16 +0.33 O B 
No. 25 +0.28 O B 
______________________________________ 
(Test Temperature: 25.degree. C.) 
Note 1: +: Weight Gained, -: Weight Decreased 
Note 2: O: Gently Affected, .DELTA.: Slighty Roughed, X: Heavily Roughed 
Note 3: A: No weight and surface condition differences B: Weight gained 
and gently affected surface C: Weight gained and slightly roughed surface 
D: Weight gained and heavily roughed surface E: Weight decreased and 
gently affected surface F: Weight decreased and heavily roughed surface