Note: Descriptions are shown in the official language in which they were submitted.
Nomogtneous Electro-Viscous Fluids
This invention relates to homogeneous electro-viscous fluids {EVF).
Electro-viscous fluids are known for some time in the form of
finely divided hydrophilic solids dispersed in hydrophobic fluids.
The special features of such fluids are that their flow character-
istics and, thus, their viscosities can be changed within a large
ifl range by subjection to an electrical field, thereby providing a
great variety of applications. Electro-viscous fluids are partic-
ularly intended for use in the field of industrial and vehicle
hydraulics, e.g. for machine and engine bearings or dampers, for
positioning work-pieces, for levelling out, cushioning and damping
is vehicles, for hydrodynamic power transmission and automatic
clutches.
The composition of known electro-viscous fluids for said applica-
tions may be rather different. Usually, electro-viscous fluids
zo comprise three components: a dispersed phase containing silicates,
zeolites, titanates, semiconductors, polysaccharides or organic
polymers; an electrical, non-conducting hydrophobic fluid as liquid
phase; a dispersant. In DE 35 3fi 934 A1 electro-viscous fluids have
been described the dispersed phase of which comprises aluminium
z5 silicates having a water content of from 1 to 25 wt.-% and an A1/Si
atomic ratio on its surface of between 0.15 and 0.80.
However, since aTl heretofore known electro-viscous fluids are
dispersions they have the disadvantage of requiring a considerable
3o amount of additional dispersive components to reduce the material-
related tendency to sedimentation. Therefore, for use in modern
hydraulic aggregates most of the known products have proved to he
unsatisfactory, especially when used over long periods. In partic-
ular, conventional dispersions manifest techno-hydraulic disadvan-
~s tapes some of which are listed in the following:
- tendency to very high abrasion
- evaporation of water of crystallisation
- nonfilterability {no separation of foreign matter)
.~~
-2-
- presence of components which are criticdl under toxicological
and safety aspects
s - incompatibilities with elastomeric sealants.
Furthermore, it is known that a great number of high-polar fluids,
too, change their flow characteristics in a high-voltage field. But
since these effects are only weak, no technical use can be made of
io them.
Therefore, it is the object of this invention to provide homoge-
neous electro-viscous fluids which comply with the technical re-
quirements made on a modern industrial hydraulic fluid and which do
r5 not have the foregoing disadvantages, but rather manifest a high
electro-viscous effect.
According to the present invention, the problem is solved by pro
viding electro-viscous fluids comprising aluminium soaps prepared
2o by reacting
one or more saturated and/or unsaturated monomeric, oligomeric
and/or polymeric polycarboxylic acid{s} having one or more carboxyl
group{s) and 3 to 32, preferably 3 to 18, particularly 12 to 18
carbon atoms,
2s the anhydrides and/or semi-esters thereof the alcohol components)
of which is {are) straight or branched monohydric or polyhydric
alcohois with 1 to 12, preferably 1 to 6, particularly 2 to 5
carbon atoms, and/or the oligomers thereof,
with one or more aluminium alcoholate(s}, the alcohol components)
so of which is {are) one or more aliphatic, straight or branched,
monohydric or polyhydric alcohol(s) with 1 to 18, preferably 2 to
8, particularly 2 to 5 carbon atoms.
It was surprisingly found that by doping with aluminium a great
3s electro-Theological effect is attained. The resultant products are
completely homogeneous.
The aluminium soaps used according to this invention are the prod-
ucts obtained by the reaction of polycarboxylic acids, anhydrides
~'~~27~8
-3-
or semi-esters with aluminium alcoholates, all or part of the
valences of the aluminium having been converted. Preferably, those
s aluminium soaps are used which have been obtained by reacting
polycarboxylic acids, the anhydrides and, particularly, the semi-
esters thereof which comprise one or more free OH group{s) with
aluminium alcoholates. In particular, the aluminium soaps are
produced by reacting one or more alkenyl succinic acids) and/or
lo the semi-esters thereof with 5 to 18 carbon atoms, preferably 12 to
18 carbon atoms.
It is preferred that the electro-viscous fluids according to the
invention comprise the following components:
is component (a): 2 to 50 wt.-%, preferably 5 to ~0 wt.-%,
particularly 10 to 35 wt.-% of the aforesaid
aluminium soap, in homogeneous solution with
component (b): 50 to 98 Nt.-%, preferably 60 to 95 wt.-%,
particularly 65 to 90 wt.-% of a Conventional
Zo hydraulic base fluid, and additionally
component {c): 0 to 10 wt.-%, preferably 0 to 5 wt.-%,
particularly 0.1 to 2 wt.-% of soluble
hydraulic additives known as such,
each referring to the total composition.
Component (a) consists of oligomeric complex aluminium soaps based
on reaction adducts of polycarboxylic acids or olefin carboxylic
acids, the anhydrides, semi-esters or oligomers thereof with alu-
minium alcohoiates. Saponification takes place, wholly or in part,
3o for example by controlled partial hydrolysis yielding hydroxyl soap
Structures.
By olefin carboxylic acids are meant carboxylic acids obtained by
reaction of unsaturated carboxylic acids with each other or with
Olefins. The oligomers thereof used are compounds consisting of 2
to 10, preferably 2 to 6 units.
The alcohol components of the aluminium alcoholates used are lower
straight and branched alcohols, particularly such with 1 to 6
2~p2~~~8
-4-
carbon atoms. The alcohols are set free during reaction and are
eliminated. If the reaction is performed with anhydrides, straight-
s chain or branched alcohols with up to 18 carbon atoms can be used
as the alcohol component. Since these alcohols add to the molecule,
most of them remain in the reaction product.
As alcohol components of the polycarboxylic acid semi-esters
io straight-chain or branched monohydric or polyhydric alcohols are
used. It is advantageous that the carbon number be determined by
the base fluid in order to ensure that the corresponding reaction
products are soluble.
is Examples of component (a) are partial ester/aluminium alcoholate
adducts based on alkenyl succinic anhydrides, particularly n-
hexenyl-succinic anhydrides, diisobutenyl-succinic anhydrides,
tetrapropenyl-succinic anhydrides, dodecenyl-succinic anhydrides
and polyisobutenyl-succinic anhydrides.
2o Also suitable are e.g. olefin addition products of itaconic,
citraconic and mesaconic acid.
Furthermore, copolymerisates of unsaturated carboxylic acids, e.g.
of malefic, fumaric, acrylic or methacrylic acid are appropriate.
2s Carboxyl group-carrying polyesters based on saturated or aromatic
dicarboxylic acids, such as adipinic acid or phthalic acid, are
also suitable.
Suitable aluminium alcohoiates are e.g. aluminium triisopropoxides,
3o aluminium-tri-sec-butoxides or complex mixed alcohols and partial
chelates, such as DOROX D 15, DOROX D 300, and DOROX 0 310 (com-
mercial products of CONDEA Chemie GmbH, Hamburg).
Preferably, those aluminium alcoholates are used all the aluminium
as bonds of which carry alcoholate groups. Also suitable are aluminium
alcoholates one or two aluminium bonds of which carry hydroxyl
groups.
X1227 18
r~
Component (b), the hydraulic base fluid, is a
basically non-conducting fluid capable of homogeneously
dissolving carboxylic' acid aluminum salts, or the reaction
product of the aluminum compr_~und with the carboxylic acid
compound, to be used as the hydraulir_ base fluid component.
Component (b) comprises hydraulic° media, such as conventional
mineral oil selective raffinates, h ydrocracking products,
hydrogeroates, poly-aapha-olef ins or synthet is esters . "Base
fluid" is meant to irmaicate t: hat component (b) is the main
part: or ingredient tc> whir_h others components are added.
The viscos:Lt:ies of the aforesaid fluids are
selected in dependen<~e on the intended use of the end
produr_t .
Examples of component (b) are:
Spindle oil raffinate 6/20 of DEA, Hamburg
Kinematic viscosity (40°C:) : 4.2 mm2/s
Density (15°C): 840 kg/m3
Solvent raffinate SN 45 of DEA, Hamburg
Kinematic 'viscosity (40°(:): 6.5 mm2/s
Density (lSt~C) : 842 kg/m3
Hydrocracking product UHVI-light of DEA, Hamburg
Kinematic viscosity (40oC): 30.4 mm2/s
Density ( l5c~C) : 854 kg/m3
Hitec 162, PAO of Ethyl, St. Louis
Kinemati<: viscosity (40°C) : 5.0 mm2/s
Density ( 1 5C~C ) : 800 kg/m3
Priolube 3958 of Unichema, Gouda
70830-38
2122? 18
5a
Kinematic viscosity (40°C): 10.5 mm2/s
Density (15°C): 921 kg/m3
Component (c) comprises customary hydraulic
additives for optimizing the hydraulic product character-
istics, such as wear resistance, resistance to ageing,
friction characteristics, resistance to foaming, corrosion
resistance and low-temperature characteristics.
Examples of component (c) are:
Addition RC 3212 of Rhein-Chemie, Manneheim
2-Ethylhexyl-Zn-dithiophosphate
. 1
70830-38
21~2~18
-6-
Irganox L 107 of Ciba-Geigy, Basel
2,6-di-tert-butylphenol
s
Viscoplex 1-300 of RShm, Darmstadt
Polymethacrylate, 70 % solution in neutral raffinate
In a preferred embodiment of the process for producing electro-
io viscous fluids the dilute olefin carboxylic acid semi-ester is
placed into the vessel and blended with the aluminium carrier com-
ponent in the absence of moisture. After the chemical reaction is
complete, a sufficient amount of component (b) is added to adjust
the viscosity to the rated value, and component (c) is added as
is required.
In a voltage field of from about 500 Y/mm field strength, the
fluids thus prepared show a significant increase in viscosity as
the field strength increases. Optimum response is reached between
zo 3 and 8 kV/mm field strength, the aluminium content being prefer-
ably 0.1 to 0.5 %. The initial viscosity of the electro-viscous
fluids may be in the range of from I5 to 6,000 mPa~s at 40 'C.
zs Embodiments of the Iwention
In the embodiments described in the following, Example I is based
on an olefin carboxylic acid not reacted with aluminium alcoholate.
The acid proved to be ineffective.
Example 2 is based on a reaction with Li-aicoholate. The electro-
rheological effect of the product is extremely weak and only de-
tectable in a static test.
3s Examples 3 to 5 describe reaction products of the invention. The
corresponding eiectro-rheological measurement results are shown in
Figures 1 to 5.
2~2~718
Exa~ple 1 (Comparison)
s 100 grams of an alkenyl succinic acid semi-ester having the
following characteristics
Density (i5 'C) 985 kg/m3
Kinematic viscosity (40 'C) 1,750 mm2/s
- Viscosity (100 'C) 31 mm2/s
Io Flash point P.M. 175 'C
Mineral oil content 37 wt.-
Acid number 144 mg KOH/g
Hydroxyl number 43 mg KOH/g
were diluted with 100 g of a naphthenic
mineral oil
cut.
I5
Added to this mixture were:
0.1 % of a commercially available dernulsifier and
0.1 % of a commercially available defoamer.
2o The final mixture had a
viscosity of 39 mm2/s at 40 'C and an
acid number of 72 mg KOH/g.
When testing the aforesaid mixture in a high-voltage rotary
z5 rheometer, no increase in yield stress was detectable up to a field
strength of 8 KV/mm at a shear rate of D = 1/I00.
~~ple 2 (Comparison)
100 grams of the final mixture as described in Comparison Example 1
were blended with a dispersion of 1 gram of lithium-sec-butylate in
5 ml of light oil by intensively stirring over a period of 30
minutes in the absence of moisture. The temperature was slowly
3s increased to 80 'C over a period of 60 minutes where it was main-
tained for 90 minutes.
After cooling, the reaction product was diluted with 100 ml of
petroleum ether and washed four times with 60 ml of H20.
~ ~. ~~'"~~~
_8_
After filtration and vaporisation of the petroleum ether, 73 grams
of a product having a
s viscosity of I60 mm2/s at 20 "C and a
lithium content of O.I1
were obtained.
When testing the aforesaid mixture in a high-voltage rotary rheo-
lo meter, no increase in ,yield stress was detectable up to a field
strength of 8 KV/mn at a shear rate of D = 1/100.
E~ (according to this invention)
The procedure was the same as described in Example 2, the differ-
ence being that the reaction was performed with a solution of
2.5 grams of aluminium-sec-butylate in 10 ml of light oil"
zo The end product had a
viscosity of 330 mm2/s at 40 'C and do
aluminium content of 0.24 %.
The product showed a pronounced electro-viscous effect, as illus-
2s traced by the results in Figures 1 and 2.
Example 4 (according to this invention)
3o The procedure was the same as described in Example 2, the differ
ence being that the reaction was performed with a solution of
1.7 grams of aluminium-sec-butylate in 8 ml of light oil.
The end product had a
3s viscosity of 826 n~n2/s at 40 'C and an
aluminium content of 0.17 %.
The product showed a pronounced electro-viscous effect, as illus-
trated by the results in Figure 3.
~1~~'~ ~~
_g_
~'~mnle 5 (according to this invention)
s The procedure was the same as described in Example 2, the differ
ence being that the reaction was performed with a solution of
1.2 grams of aluminium-sec-butylate in 5 ml of light oil.
The end product had a
viscosity of 800 rr~2/s at 20 'C and an
aluminium content of 0.14 %.
The product showed a pronounced electro-viscous effect, as illus-
trated by the results in Figures 4 and 5.
is
