HUILES HYDRAULIQUES BASSE TEMPERATURE ENTIEREMENT PARAFFINIQUES

ALL PARAFFINIC, LOW TEMPERATURE HYDRAULIC OILS

Abrégé français

L'invention concerne une huile hydraulique à indice de stabilité au cisaillement compris entre 0 et 20, module de perte inférieur à 7 % mesuré selon la norme ASTM D5621, et viscosité égale ou supérieure à celle d'une huile naphténique ayant une qualité de viscosité identique. L'huile hydraulique comprend, en poids, entre 5 % et 90 % d'une première huile paraffinique ayant un KV à 100 ·C de 2 à 6 cSt, puis entre 5 % et 90 % d'une seconde huile paraffinique ayant un KV à 100 ·C de 3 à 14 cSt et enfin entre 5 % et 10 % d'un agent d'amélioration d'indice de viscosité au polyméthacrylate.

Abrégé anglais

A paraffinic hydraulic oil having a shear stability index of from 0 to 20, a
shear loss of less than 7% as measured by ASTM D5621 and a Brookfield
viscosity the same or better than a naphthenic oil of the same viscosity grade
is provided. The hydraulic oil includes 5 wt% to 90 wt% of a first paraffinic
oil having a KV at 100~C of 2 to 6 cSt, 5 wt% to 90 wt% of a second paraffinic
oil having a KV at 100~C of 3 to 14 cSt and 5 wt% to 10 wt% of a
polymethacrylate viscosity index improver.

Revendications

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CLAIMS:
1. A hydraulic oil composition comprising:
(a) 5 wt% to 90 wt%, based on the composition, of a first
paraffinic oil having a viscosity at 100°C of between 2 to 6 cSt;
(b) 5 wt% to 90 wt%, based on the composition of a second
paraffinic oil having a viscosity at 100°C of between 3 to 15 cSt; and
(c) 5 wt% to 10 wt%, based on the composition, of a
polymethacrylate viscosity index improver having a shear stability index in
the
range of 0 to 20
wherein the composition has a shear loss of less than 7% after 40
minutes as measured by ASTM 5621 and wherein for any given viscosity grade
the composition has at least substantially the same or better Brookfield
viscosity
at 0°F and -20°F as a naphthenic oil containing hydraulic
composition of the
same viscosity grade.
2. An oil composition according to claim 1 wherein for each
viscosity grade listed below the composition has the properties listed:
<IMG>

-10-
3. The composition of claims 1 and 2 wherein the viscosity index
improver has an average molecular weight of from 10,000 to 1,000,000.
4. The composition of claim 3 including a minor amount of at least
one hydraulic oil additive.
5. The composition of claim 4 wherein the additive is at least one
of pour point depressant, antiwear additive, corrosion inhibitor, antioxidant
and
defoamant.
6. A hydraulic oil composition comprising:
(a) 5 wt% to 90 wt% of a first paraffinic oil having a viscosity of
2 to 6 cSt at 100°C and a VI of 85 to 95;
(b) 5 wt% to 90 wt% of a second paraffinic oil having a viscosity
of 3 to 15 cSt at 100°C and a VI of 90 to 95; and
(c) 5 wt% to 10 wt% of a polymethacrylate viscosity index
improver having a shear stability of 0 to 20;
wherein the wt% are based on the total weight of the composition;
wherein the composition has a shear loss of less than 7% after 40
minutes as measured by ASTM 5621; and
wherein for each viscosity grade listed below the composition has
the maximum pour point and Brookfield viscosities (BV) listed:
<IMG>

Description

CA 02517455 2005-08-29
WO 2004/087851 PCT/US2004/009893
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ALL PARAFFINIC. LOW TEMPERATURE HYDRAULIC OILS
Field of the Invention
[0001] The present invention relates to hydraulic oils. More particularly the
present invention relates to low temperature, multi grade, hydraulic oils.
B ack~round of the Invention
[0002] Hydraulic fluids are used in a wide variety of applications. For
example, hydraulic fluids are used in vehicle transmissions, differentials,
brakes
and the like and in non-vehicular equipment and machinery used for example in
injection molding and general manufacturing.
[000] Hydraulic fluids are commercially available in different viscosity
grades in order to meet equipment manufacture requirements. l~lany of these
standard hydraulic fluids have difficulty, however, in meeting all of the
viscometric properties required for the advanced designs of equipn~cnt now
being developed and put into use. For example, in order to formulate low
temperature, multi-grade hydraulic oils it has been necessary to use
naphthenic
base stocks or severely hydrotreated basestocks. Each of these approaches has
disadvantages.
[0004] One disadvantage in using naphthenic basestocks is cost. Naphthenic
basestocks are relatively more expensive than similar viscosity paraffinic
basestocks. Another disadvantage is availability. There are fewer producers of
naphthenic basestocks than paraffinic basestocks.
[0005] As with naphthenic basestocks, severely hydrotreated basestocks are
more expensive than similar viscosity paraffinic basestocks for substantially
the

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WO 2004/087851 PCT/US2004/009893
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same reasons. Basically fewer refineries produce severely hydrotreated
basestocks compared to paraffinic basestocks.
[0006] It would be desirable therefore to be able to have a low temperature,
multi-grade hydraulic oil that did not require the use of a naphthenic
basestock
or a severely hydrotreated basestock.
Summary of Invention
[0007] Broadly stated the present invention comprises a multi-grade
hydraulic oil comprising:
(a) 5 wt% to 90 wt% of a first paraffinic oil having a kinematic viscosity
at 100°C of between 2 to 6 cSt;
(b) 5 wt% to 90 wt% of a second paraffinic oil having a l~inematic
viscosity at 100°C of betv~een 3 to 14 cSt; and
(c) 5 wt% to 10 wt% of a polymethacrylate viscosity index improver
having a shear stability index in the range of 0 to 20, wherein the
composition
has a shear loss of less than 7% after 40 minutes as n~easure~ by ASTl~ D5621
and wherein for any given viscosity grade the composition has at least
substantially the same or better Brookfield viscosity at 0°F and -
20°F as a
naphthenic oil containing hydraulic fluid of the same viscosity grade.
Detailed I~escri~tion of the Invention
[0008] The composition of the present invention include two Group I
paraffinic oils. Group I paraffin oils typically have viscosity indicies in
the
range of about 80 to 120, contain < 90% saturates and > 0.03% sulfur.
[0009] The first Group I paraffinic oil of the present invention is one having
a
viscosity of 2 to 6 cSt at 100°C and a viscosity index (VI) of 85 to
95. Also, the

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WO 2004/087851 PCT/US2004/009893
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first Group I paraffinic oil will comprise from 5 wt% to 90 wt%, based on the
total weight of the composition.
[0010] The second Group I paraffinic oil is one having a viscosity of 3 to 15
cSt at 100°C and a VI of 90 to 95. The second Group I oil will be
present in the
composition in an amount in the range of 5 wt% to 90 wt% based on the total
weight of the composition.
[0011] The hydraulic oil also contains a poly methacrylate viscosity index
improver (VII) having a shear stability index in the range of 0 to 20, and
preferably 10 to 20. Typically suitable polymethacrylate VIPs will have
average
molecular weights in the range of about 10,000 to 1,000,000, and more
typically
between about 20,000 to about 500,000. The amount of this VII compo~mnt is
frorrz 5 wt% to 10 wt%, preferably from 6 wt% to 7.5 wt%~ based on the weight
of the composition.
[00~1~] The foregoing components must be carefully selected ~d their
relative amounts balanced to obtain compositions that will have a shear loss
of
less than 7% after 40 minutes for any given viscosity grade having at least
substantially the same low temperature properties as a naphthenic oil
containing
hydraulic fluid composition of the same viscosity grade. For hydraulic oils of
viscosity grades 15 to 150 the compositions preferably have the properties
shown in Table 1.

CA 02517455 2005-08-29
WO 2004/087851 PCT/US2004/009893
- 4 -
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WO 2004/087851 PCT/US2004/009893
-5-
[0013] In addition to the foregoing components the hydraulic oil composition
will typically include a minor amount of a conventional additive typically
used
in hydraulic oils such as pour point depressants, anti-oxidants, anti-foam
agents
and the like.
Examples
[0014] The invention will be illustrated by the following examples which
include preferred embodiments thereof. For the examples the following
components were used to prepare hydraulic fluids of the specified IS~
viscosity
grade:
I A Group I paraffinic oil having a viscosity of about 2.6 cSt at
100°C
andaVIof~S.
II A Group I paraffinic oil having a viscosity of about 4 cSt at
100°C
and a VI of 95.
III A Group I paraffinic oil having a viscosity of about 5.4 cSt at
100°C
and a VI of 9~.
IV A Group I paraffinic oil having a viscosity of about 7 and a VI of 95.
V A Group I paraffinic oil having a viscosity of about 14 cSt at
100°C
and a VI of 90.
VI A poly methacrylate VII having a shear stability index of about 14
and sold by RohMax under the trade name Viscoplex 8-219.
VII A commercial additive package containing a pour point depressant
and components such as an antiwear additive, corrosion inhibitor, antioxidant
and defoamant. These various components were used in the amounts shown in
Table 2 and the properties thereof are also given.

CA 02517455 2005-08-29
WO 2004/087851 PCT/US2004/009893
- 6 -
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CA 02517455 2005-08-29
WO 2004/087851 PCT/US2004/009893
_ '7 _
For comparative purposes three ISO 32 mufti-grade hydraulic oils were prepared
and their properties determined. The compositions and results are given in
Table
3 which also includes properties for a commercial, naphthenic containing,
hydraulic oil. As can be seen while Blend 1 had a shear loss less than 7% it
did
not have low temperature properties. Blend 2 failed on shear loss and pour
point
and blend 3 failed the Brookfield - 20°F viscosity and pour point.

CA 02517455 2005-08-29
WO 2004/087851 PCT/US2004/009893
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