Note: Descriptions are shown in the official language in which they were submitted.
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WATER BASED FUNCTIONAL FLUIDS
The present invention relates to the use of water
based functional fluids which can be used for example as
hydraulic fluids, lubricants, drilling or cutting fluids.
Functional fluids based upon mixtures of water and
polyether glycols are well known and are used in a wide variety
of applications eg as cutting fluids, hydraulic fluids and the
like.
Typical formulations of water-based hydraulic fluids
(known as HF-C fluids) comprise approximately 15-30% of a high-
viscosity polyether glycol, and 35-45% water, with the balance
(up to 50%) being simples glycol and small amounts of additives
known to the skilled man. Typically these hydraulic fluids
have a viscosity of 32-6.8 cSt at 40°C.
There is a growing trend however to reduce the
polyether glycol content. of such functional fluids. For
example it would ultimately be desirable to reduce the
polyether glycol content. of hydraulic fluids to 10% or possibly
even less. There is also a trend to produce what can be
described as High Water Based Fluids (HWBFs), containing
typically 50-98 percent water, by additionally removing some or
all of the glycol.
A problem arises when attempts are made to reduce the
polyether glycol content of hydraulic fluids in that the
viscosity of the hydraulic fluid is reduced. This arises
because standard polyether glycol fluids do not possess
sufficient thickening power. Simply increasing the viscosity
of the polymer does not achieve the required effect, because
the increase in solution viscosity becomes marginal, and the
polymer becomes unstable under conditions of high shear.
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It has previously been proposed for example in US 4
767 555 and US 4 288 639 to achieve the required viscosity of
such hydraulic fluids by incorporation of small amounts of
materials which (a) are water compatible and (b) increase the
viscosity of the hydraulic fluids by intermolecular association
in solution. Such materials are known as associative
thickeners.
The hydraulic fluids previously described as high-
water-based fluids (HWBb's), usually incorporating either no
simple glycol, or only a;mall amounts as antifreeze, have a
number of disadvantages when compared to HFC water glycol
fluids, viz
i) Although the HWBFs normally exhibit 'permanent shear
stability', that is the viscosity of the fluid remains stable
over a long period of operation, they none-the-less exhibit
temporary loss of viscosity in high shear zones, as evidenced
by loss of flow rate and pump efficiency in hydraulic systems,
in other words they lack: 'temporary shear stability'.
ii) Under such conditions of temporary viscosity loss,
hydrodynamic lubricity of the fluid also suffers. Lubrication
is maintained only by additives which provide boundary
lubrication (EP additives). Despite such additives being
highly developed, these conditions can result in enhanced wear.
Additionally the best of these additives in many instances are
toxic, hydrolytically unstable and environmentally undesirable.
iii) The viscosity index: of such fluids is often poor which can
give problems with pump start-up.
iv) HWBFs are sensitive: to water loss, which has a dramatic
and undesirable effect an fluid viscosity.
US 3 538 033 discloses a family of polyether
derivatives of diepoxides which can be used as thickeners in
textile printing emulsions, cosmetic emulsions, aqueous pigment
suspensions and the like:.
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The problem to be solved is therefore to produce
functional fluids, suitable for the applications described
above, which have
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good permanent and temporary shear stability, contain low
concentrations of the associative thickener, have good
resistance to water loss in terms of viscosity change, have
good apparent viscosity indices, and which maintain
hydrodynamic lubrication under high shear conditions.
According to the present invention there is provided a
functional fluid composition for use as a hydraulic fluid,
lubricant, a cutting fluid or a drilling fluid which
comprises:
(a) from 20 to 98% by weight water,
(b) a finite amount of up to 80% by weight of a glycol and
(c) from 0.5 to 25% by weight of a thickening agent prepared
by (a) relatively reacting one mole of a monofunctional,
active-hydrogen-containing compound having at least 10
carbon atoms with between 20 and 400 moles of one or more
alkylene oxides and (b) thereafter reacting the product
of step (a) with a diepoxide in an amount such that the
molar ratio of diepoxide to hydroxyl groups in the
product of step (a) is between 0.2:1 and 5:1.
The present invention solves the problem defined above by
employing a thickening agent of the type defined in US 3538033
in the applications described above, together with the
formulation technology which is detailed below.
Considering the water component of the composition first,
it is preferred that this comprises between 36 and 95% of the
functional fluid most preferably between 45 and 80%.
As regards the glycol, this can be in principle any
glycol which is miscible with water and includes monoethylene
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glycol and monopropylene glycol and low molecular weight
oligomers thereof (ie having up to 6 ethylene and/or propylene
glycol units). Preferably the glycol is selected from
monoethylene glycol, diethylene glycol and triethylene glycol.
It is preferred that the glycol comprises between 20 and 60%
of the functional fluid.
The first stage of preparing the thickening agent
involves reacting the monofunctional active-hydrogen-
containing compound with one or more alkylene oxides. By the
term 'active-hydrogen-containing compound' is meant one which
contains hydrogen measurable by the Zerewitinoff* active
hydrogen test. Such compounds include alcohols, phenols,
thiols, fatty acids and amines. The preferred compounds are
C16 to C20 monohydric alcohol or thiols, C16 to C20 alkyl
phenols and C16 to C20 aliphatic amines.
The active hydrogen containing compound is alkoxylated
with one or more alkylene oxides using either a base or a
Lewis acid as a catalyst. Typically the alkylene oxide is one
or more of ethylene oxide, propylene oxide or the isomers of
butylene oxide. Suitably between 20 and 400 moles of the
alkylene oxide are added to the active hydrogen containing
compound of which 20 to 100 mole % (most preferably 65 to 85
mole ~) is ethylene oxide and 0 to 80% (most preferably 15 to
35%) is propylene and/or butylene oxide.
In the second stage of manufacture the product of the
first stage is reacted with a diepoxide. The diepoxide can in
* Trade-mark
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principle be any organic compound having two epoxide
groupings. Suitable diepoxides are those having between 4 and
30 carbon atoms and include vinylcyclohexene diepoxide,
bisphenol A/epichlorohydrin condensate and the like. It is
5 preferred to use the diepoxide in amounts such that the molar
ratio of diepoxide to hydroxyl groups (in the product of stage
1) is in the range 0.2 to 1 to 5 to 1. The second stage of
the process can also be catalysed by either a base or a Lewis
acid.
It is preferred that the thickening agent comprises
between 2 and 10% by weight of the functional fluid
composition. It is also preferred that the thickener itself
should have a neat viscosity in excess of 4000 cSt at 40°C.
Concerning the antiwear components, these are typically
metal or amine salts of organo sulphur, phosphorus or boron
derivatives, or carboxylic acids. Typically these include
salts of C1 to C22 carboxylic acids, aliphatic or aromatic;
sulphur acids such as aromatic sulphonic acids, phosphorus
acids, for example acid phosphate esters and analogous sulphur
compounds, eg thiophosphoric and dithiophosphoric acid. Many
further antiwear agents are suitable, and known to the skilled
man.
Inhibitors for corrosion of metals can be organic or
inorganic, for example metal nitrites, hydroxyamines,
neutralised fatty acid carboxylates, phosphates, sarcosines
and succinimides etc. Most useful are amines such as
alkano~amines, e.g. ethanolamine, diethanolamine and
triethanolamine. Non-ferrous metal inhibitors include for
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example aromatic triazoles.
It is preferred to include in the formulation 0.5 to 15%
of a surfactant as a co-thickening agent, which may be non-
ionic, cationic, anionic or amphoteric. Examples of suitable
surfactants include linear alcohol alkoxylates, nonylphenol
ethoxylates, fatty acid soaps, amine oxides etc. Most
preferred are linear secondary alcohol alkoxylates, e.g. those
commercially available from BP Chemicals under the registered
trade-mark Softanol*. The surfactants behave synergistically
with the associative thickener, such that a given viscosity
can be achieved with a lower total thickener content of the
blend compared to use of the associative thickener alone.
In addition to the above the functional fluid composition
may also contain optional components such as extreme pressure
additives, antifoams, antimicrobials and the like which are
well known to the skilled man. It is also possible to add
further known thickening agents and co-thickening agents if
desired.
The functional fluid compositions of the present
invention may be prepared by mixing the four main components
and any additional materials which are required in a vessel of
suitable size.
In the preferred embodiments of the invention, that is
those formulations containing 20 or more percent of glycol, it
has been found that temporary shear stability is conferred to
the fluids. This enhances the capability of the fluids to
* Trade-mark
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provide hydrodynamic lubrication under high shearing
conditions. The presence of the 20 or more percent glycol,
and of the surfactant co-thickener also improves the apparent
viscosity index of the fluids when compared against fluids
containing no glycol or surfactant.
In those embodiments of the invention containing less
than 20 percent glycol, the problem of temporary shear is also
addressed, by use of associative thickeners of the present
invention with high inherent polymer viscosity (e. g. greater
than 20,000 cSt at 40°C). In high shear environments,
thickening achieved by association is lost when the fluids
shear temporarily. However, the viscosity of the fluid is
maintained at an intermediate level by the normal thickening
of a high viscosity polymer, typically to a level of 10-20 cSt
at 50°C. This limits the loss of pump efficiency, and ensures
that hydrodynamic lubricity is retained. This approach also
enhances the characteristics of the fluid concerning viscosity
change on water loss and viscosity index.
The functional fluid compositions of the present
invention are particularly useful as hydraulic fluids in
piston, gear or vane hydraulic pumps, motors and general
hydraulic systems, e.g. hydraulic rams, robots and the like.
The invention is now illustrated by the following
examples:
Example 1
A commercial sample of oleyl/cetyl alcohol (85/15) was
catalysed with potassium hydroxide (0.3% by weight on the
target alkoxylate), dried, and reacted with a 70/30
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(weight/weight) mixture of ethylene oxide and propylene oxide
at 115-125°C to produce an alkoxylate having an experimentally
determined molecular weight of 6000 (by hydroxyl
determination).
500 grams of the above un-neutralised alkoxylate was
reacted at 130°C with 15.9 grams bisphenol A/epichlorohydrin
condensate (Epikote* 828 - ex Shell) for three hours. The
residual catalyst was removed by treatment with magnesium
silicate to leave an associative thickener with a neat
viscosity of 5000 cSt at 40°C. A 10% aqueous solution
viscosity was determined as 193 cSt at 40°C.
Example 2
500 grams of the above-mentioned un-neutralised
alkoxylate from example 1 was reacted at 130°C with 31.8 grams
of bisphenol A/epichlorohydrin condensate for 3 hours, the
catalyst was removed with magnesium silicate treatment, to
leave an associative thickener with a neat viscosity of
17,300 cSt at 40°C. A 10% aqueous solution viscosity was
determined as 2100 cSt at 40°C.
Example 3
A commercial sample of oleyl/cetyl alcohol (85/15) was
reacted in the manner described in example 1 with an 80/20
mixture of ethylene oxide and propylene oxide to produce an
alkoxylate having a molecular weight of 6000.
* Trade-mark
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9
300 grams of the above-mentioned un-neutralised
polyalkylene glycol was reacted with 14.0 grams of
vinylcyclohexene diepoxide for three hours at 140-150°C. The
resulting associative thickener had a neat viscosity of
4,900 cSt at 40°C and a 10% aqueous solution viscosity of
1427 cSt at 40°C.
Example 4
A commercial sample of oleyl/cetyl alcohol (85/15) was
reacted in the manner described in example 1 with an 75/25
mixture of ethylene oxide and propylene oxide to produce an
intermediate having a molecular weight of 2950, then with
further ethylene oxide to produce an alkoxylate having a
molecular weight of 3100.
2000 grams of the above-mentioned un-neutralised
polyalkylene glycol was reacted with 175 grams of
vinylcyclohexene diepoxide at 140-150°C for 6 hours to yield
an associative thickener with a 10% aqueous solution viscosity
of 1742 cSt.
Examples 5 - 8
Dodecan-1-ol, Tetradecan-1-ol, Hexadecan-1-of and
Octadecan-1-of were reacted under base catalysis with 80/20
blends of ethylene oxide/propylene oxide to produce
alkoxylates having molecular weights of 6000. 200 grams of
each alkoxylate was reacted with 9.4 grams of vinylcyclohexane
diepoxide in the manner described for example 3 to yield four
associative thickeners. The products were used to provide a
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comparison of solution viscosity versus hydrophobe chain
length.
EXAMPLE Comparison 5 6 7 8
PRODUCT Breox 75W18000# C-12 C-14 C-16 C-18
5 Viscosity, neat,
cSt at 40°C 18,000 22,400 10,400 27,400 21,400
Viscosity, 10%
cSt at 40°C 5 117 461 4,680 34,000
# Trade-Mark. Standard polyglycol thickener.
10 Example 9
The thickener (8%) from example 1 was formulated into a
hydraulic fluid at 46 cSt at 40°C containing water (36%),
diethylene glycol (50%), a fatty acid and morpholine. This
was subjected to a four ball test (IP239) at 40 kg for 1h, and
gave a wear scar of 0.56mm, a result similar to that of a
similarly formulated hydraulic fluid using 15% of a
conventional polyglycol thickener.
The same thickener at a level of 7% in a high water based
fluid of 46 cSt at 40°C was subjected to 50 passes in a Kurt
Orban* shear stability tester (IP294) and suffered no
permanent loss of solution viscosity.
Example 10
The thickener from example 4 was formulated at a level of
* Trade-mark
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10a
8% into a hydraulic fluid containing 30% diethylene glycol and
58% water, the balance being an antiwear and anticorrosion
package. The said hydraulic fluid was circulated over 24
hours in a 7 kW Vickers* PFB-5 axial piston pump at 50°C and
170 bar. The flow rate, which can be directly related to the
fluid viscosity, was monitored to indicate viscosity in the
high shear regions of the pump. The said hydraulic fluid was
compared to a similar hydraulic fluid containing only 10%
diethylene glycol and 80% water, and with a further hydraulic
fluid, based on a commercially available, low-viscosity,
associative thickener, a fatty alcohol ethoxylate capped with
an olefin epoxide, and containing no diethylene glycol.
Absolute Apparent % Retained Pump Flow
Viscosity Viscosity Viscosity 1/m
cP at in Shear Under High
47C Zone cP Shear
Example 10 38 31 81% 14.6
10% DEG Fluid 27 12 44% 14.11
Fluid from
commercial 21 3.4 16% 12.46
low viscosity
Associative
Thickener
* Trade-mark
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lOb
Example 11
The thickener from example 1 (6.2%) and a 5 mole
ethoxylate of a linear secondary C-12/14 alcohol (1.55%)
(Softanol* 50 - ex BP Chemicals) were blended with diethylene
glycol (40%) and water (50%), the balance consisting of
functional antiwear, anticorrosion and antifoam agents (2.25%)
to give a hydraulic fluid of 45.5 cSt at 40°C. The following
data were determined.
Four ball wear scar, mm (lh, 40kg, IP239): 0.61
Shear Stability (IP294), % viscosity change: -7
Example 12
The associative thickener from example 3 (3.6%) and a 5-
mole ethoxylate of a linear secondary C-12/14 alcohol (0.9%)
were blended with diethylene glycol (20%) and water (73.4%),
the balance being additives (2%), to give a hydraulic fluid of
49.3 cSt at 40°C. The following data were determined.
Four ball wear scar, mm (lh, 40kg, IP239): 0.62
Shear Stability (IP294), % viscosity change: +5
Example 13
The associative thickener from example 3 (5.4%) and a 12
mole ethoxylate of a linear secondary C-12/14 alcohol (3.6%)
(Softanol* 120 - ex BP Chemicals) were blended with diethylene
glycol (39%) and water (50%), the balance consisting of
antiwear, anticorrosion, and antifoam additives (2%), to give
* Trade-mark
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lOC
a hydraulic fluid of 46.8 cSt at 40°C. The following data
were determined.
Four ball wear scar, mm (lh, 40kg, IP239): 0.61
Shear Stability (IP294), % viscosity change: +2.9
Example 14
The thickener from example 2 (5.0%) and a 12 mole
ethoxylate of a linear, secondary, C12/14 alcohol (1.25%) were
blended with diethylene glycol (20%) and water (70%), the
balance consisting of antiwear, anticorrosion and antifoam
agents (3.75%) to give a hydraulic fluid of 46.1 cSt at 40°C.
The following data were determined.
Four ball wear scar, mm (lh, 40kg, IP239): 0.68
Example 15
To demonstrate the effect of diethylene glycol on
apparent viscosity index two ISO* 68 fluids were prepared from
the thickener from example 3. Fluid 1 containing 6.0 percent
of thickener, 30 percent of diethylene glycol and 64 percent
of water. Fluid 2 containing 5.0 percent thickener and 95
percent water. The combined effect of the presence of
diethylene glycol and the slightly increased thickener
requirement in fluid 1 results in a significantly lower
viscosity fluid at 20°C than that observed for fluid 2,
demonstrating that the apparent viscosity index of fluid 1 is
higher than that of fluid 2.
* Trade-mark
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lOd
Visc. @ 40°C, cSt Visc. @ 20°C, cSt
Fluid 1 72.5 585
Fluid 2 71.5 985
Examp 1 a 16
To demonstrate the effect of co-thickeners on apparent
viscosity index, two fluids of 550 cSt at 40°C were prepared
as follows: Fluid 1 contained 6.0 percent of thickener from
example 2, 4.0 percent of a 12 mole ethoxylate of a C-12/14
linear secondary alcohol, 10 percent diethylene glycol and 80
percent water. Fluid 2 contained 10.0 percent thickener from
example 2, 10 percent diethylene glycol and 80 percent water.
The presence of surfactant in fluid 1 and reduced thickener
requirement results in a significantly lower viscosity fluid
at 20°C than observed for fluid 2, demonstrating that the
apparent viscosity index of fluid 1 is higher than that for
fluid 2.
Visc. @ 40°C, cSt Visc. @ 20°C, cSt
Fluid 1. 550 4000
Fluid 2 550 5000
