Note: Descriptions are shown in the official language in which they were submitted.
~L'3L;Z~L~L 6~ '
2 This invention relates to mineral oil compositions
3 which have significan~ly improved oxidation stability and com-
4 prise a paraffinic mineral oil basestock and a selected amount
of a branched, multiring cycloparaffin component. More par-
6 ticularly, the invention is directed to a mineral oil compo-
7 sition which has a major amount of a paraffinic base oil a~d
8 from about 0.1 to about 50 percent by weight of a cycloparaf-
3 fin component which is substantially made up of cycloparafins
having up to 7 rings and an average number of from about 3 to
11 about 8 alkyl branches per molecule.
12 One of the importan~ performance properties generally
13 deslred in mineral oils, particularly at high temperature and
14 specia}ty applications requiring long service life is oxida-
tion stability or the ability to resist oxidation. It is well
16 known that lubrlcating oils derived from paraffinic crudes
17 have better oxidation stabilLty than oils derived from naph-
18 thenic crudes. In many instances where a very high degree
19 of st bility is required in the lubricating oil, a significant
amount of process refining Ls needed to obtain a formulation
21 with satisfactvry properties~ OfteQtimes this is accompanied
22 by the addition of an oxidation inhibitor to ~he composition.
23 Indeed a large number of antioxidants have been employed in a
24 variety of lubricating oil compositions and prominent among
the general classes of such compounds are ~he sulfides, sul~-
26 oxides, phosphites, amines t phenols, selenides and zinc thio-
27 phosphates as disclosed in '~ubricant Additives" by C.V.
.. ~
1 Smalkeer et al, 1967, pO 7.
2 While the use of antioxidant additives does im~
3 prove the oxidation stability of the lubricating composi-
4 tion, they do not all act the ~ame in a given formulation or
under a variety of conditions. Consequently, besides the
6 added cost involv~d in using such additives, it is also nec-
7 essary to evaluate the overall efec~s each additiv~ has on
8 the sys~em before an appropriate one is selected.
9 Accordingly, it is deslred to develop a mineral oil
lubricating composition with improved 02idation stability
11 properties wit~out the need for antioxidant additives and
12 without the need for extensive process refining.
13 SUMMARY OF THE INVENTION
14 Now it has been discovered that a mineral oil h~-
ing particularly improved oxldation stabillty is provlded by
16 a composition comprising a major amount of a paraflnic min-
17 eral oil basestock and a sel cted amount of a branched multi~
18 ri~g cycloparaffin component.
The present invention relates to a mineral oil com~
21 position having impro~ed oxidation stability which is made up
22 of a major amount, i.e. about 5070 by weight or more~ of a
23 paraffinic mineral oil basestock and a selected amount of a
24 branched multiring cycloparaffin (often referred t~ as naph-
thene) component.
26 Th~ mineral oil basestoc~ material used in this
27 inven~ion and referred to as a paraffinic mineral oil base-
4~1
-- 3 -- .
1 stock is the refined or light ends dlstillate portion of a
2 parafinic crude oil from which the polar and aromatic por-
3 tions have been substantially removed. Thus, the paraffinic
4 mineral oll basestoc~ of this in~ention is comprised largely
S of parain hydrocarbons, eit~er straight or branched chain,
6 and cycloparaffins or naphthenes. While it is indicated that
7 the aromatic, as well as the polar) portions have been sub-
8 stantially removed from the refined basestock, use of the
9 term "paraffinic mineral oil basestoc~" throughout this appli-
cation is intended to include minor amounts of aromatic com-
11 pounds and other components which are difficult to separate
12 and may remain along with the paraffins and cycloparaffins.
13 The mineral oil basestock material may be obtained from crude -
14 oil using conventional reining techniques which include one
or mor2 steps such as distillation, extraetion, hydrofining
16 and dewaxing.
17 The cyclopara~fin component used in the compositian
18 of this invention will ~e pr~marily made up of branched multi-
l9 ring cycloparafins having up to 7 rings,:and an average num-
ber of from~about 3 to about 8 alkyl branches per molecule.
21 ~hile some monocyclic (or l-ring) paraffins will be included
22 in this component, the major portion of it, i.e. about 50% or
23 ~ore by weight, will be made up of multiring cyclaparaffins
24 having at least 2 rlngs, preferably 2 ~o 6, and more prefe.-
ably 2 to 4 rings. The amount of monocyclic paraffin in this
26 component will prefcrably be le~s than about 35 percent by
27 weight and more preferably less than about 10 percent by weight.
3L~L'~qL6:~
-- 4 --
The llusber of carbon~ found in the ring s~ructure (i. e.
2 not including the branch carbons~ will generally be 5 and
3 6 with possibly some 7 carbs:n ring s~ructures being present.
4 In other words, the cycloparaf~ins will be predominantly 5
5 aIld 6 membered rings. The number of carb~n ato~s in the
6 braslches will generally vary from ab~ut 1 to about 6, pre:f-
7 erably about 1 eo about 3, and more preferably abaut 3. As
8 indicated above, the number of alkyL branches on the multi-
9 ring cycloparaff~ns will vary froro an avera~P nt2mber o about
lû 3 to about 8 with at least about 4 being pre~erre~ and even
11 more preferable at least about 6 alkyl branches.
lZ l~ is to be no~ed that ~he hydrocar~on partions of
13 both the mineral oil basestoc~c and the cycloparafin compo-
14 ~e~ as de~ned abu~e will comprise a mixture of the differ~
15 ent hydrocarbons a~d the numbers generally re~erred to will
16 be ntlmber avera$es.
17 The amoun~ of cycloparaffin component ~sed in ~he
18 mineral oil of the inven~ion will vaxy rrom aboue O.L to
19 abvut 50 perc nt by ~eight ~ p ~ eferably from about 0.1 to '
about 5, and more prefexably from ab~ut 0.5 to about 1.5 per~
21 cent by weight based on the tota~ weight of the min ral oil
22 compo~ition.
23 The cyclopar~ffinic component may be obtained from
24 the saturaeed partion of refined crudP oil by known separation
2S techniques and one particularly useful method irlvolves thermal
26 dif~usion and silica gel chromaeography as further described
27 and exe~plified in an article entitled "Composition and
0 ~ 6.
1 Oxidation o~ Pe~roleu~ Fractions'7 by G.E. Cranton in
2 5~E~L.9~5~ 14 ~1916) pp 201-208.
: 3 O~her addi~ives conventiona:Lly used in oil compo-
4 sitions ~ this general type may also be lncluded in the
5 oil compcsitio~ of this invention. Generally~ such addi-
6 tives will be included wi~h the basestock ma~erial in maki~g
7 up the major amount of the oil composltion.
8 The mineral compos~tions of this in~ention have
significantly improved oxid~tion stability as illustrated
below~ Thls ver~ desirable proper~y o~ high oxida~ion resis-
11 tanco makes these mineral oil compositions particularly use~
12 ful ln applications requiring hlgh ~ervice life under hig~
13 te0perature and o~her eæ~reme conditionsO The mineral oils
14 of ehis in~ention are also useful in applications such ~s
transformer and elcctrical oilsO
The following example is set forth to illustrate
17 ~he inventio~ and should not be construed as a limi~ation
18 ~here~f.
19
A ~aturated light ends portion of a mineral oil
21 was obtained from crude oil by con~entional refining tech-
22 nl~ues and contained a significan~ amount of paraffinic hydro~
23 carbon material (44% by weight) and a lar~e amoun~ (54% by
24 weight) of monocyclic paraffins with a li~ited amount or 2-
ri~g cycloparaffins ~a~out 2% by weight) also presene. This
26 portion was used as the basestoc~ in the following described
27 mi~tures.
346
-- 6 --
A branched cycloparaffin component was ob~ained
? from the saturate por~ion of previously re~in~od mineral
3 crude by the ~hermal difuslon technique as described by
4 J. Denis and G~ Parc in ~ , 59 (1972) 75,
followed by liquid/solld chromatography through silica gel.
6 This component contained aSout 30 percent by weight of mono-
7 cyclic paraffins with the balance being multiring cycloparaf-
8 fins of 2 to 6 rings (31% of 2-ring) 23a/~ of 3-ring, 12% of
9 4-ring, 3% of 5-ring and 1% 6-ring cycloparaffins). The com-
ponent mixture had an average number of 6.7 al~yl branches
11 per molecule~
12 Taking various proportions of the cycloparaffin
13 component and mixing with the mineral oil basestock defined
14 above, a series of miner~l oil mixtures was prepared. Oxi-
dation stabllity of the different mixtures was measured by
16 isothermal differen~ial scanning calorimetry in atmospheric
17 oxygen. The appara~us used was a Par~in-Elmer differential
18 scanning calorimeter Model DSC l-B. Oxygen was 1ushed
19 throu~h che system at 30 ml/min with a sample size of 0.5mg~
The oxidation life as determined by this technique was the
21 time it took for the onset of degradation at 160~C and the
22 results are as follows:
a6:~L
Oxidation Li~e
2Wt.~10 of Cycloparaffin Minutes at 160C
3Compon nt in Basestoc~c
4 0 ~.5
1 14
6 50 : 10
7 g9 7.5
$ 10~ 7
9 E'rom the above results; it is quite apparent that
10 adding only a small amount of ~he branched, multiring cyclo~
11 paraffin component to the mineral oil basestock improved the
12 oxidation life of the oil by a surpr~ singly significant
13 amount making the combination particularly desirable for
14 applications requiring unusual o~idation stability.
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