CA2122718C

CA2122718C - Homogeneous electro-viscous liquids

Info

Publication number: CA2122718C
Application number: CA002122718A
Authority: CA
Inventors: Dietrich Pirck; Hans-Dieter Grasshoff; Harald Kohnz
Original assignee: RWE Dea AG fuer Mineraloel und Chemie
Current assignee: Wintershall Dea International AG
Priority date: 1991-11-28
Filing date: 1992-11-30
Publication date: 2002-10-29
Anticipated expiration: 2012-11-30
Also published as: ATE150480T1; EP0624185A1; AU670404B2; CZ287038B6; EP0624185B1; KR100209184B1; JP3236296B2; BR9206842A; WO1993011209A1; CA2122718A1; AU2940892A; DE4139065A1; DE59208255D1; DE4294095D2; JPH07501357A; CZ130994A3; AU2838095A; RU2114904C1; AU658949B2

Abstract

Homogeneous electro-viscous fluids are provided which comprise aluminium soaps based on products obtained by reacting one or more polycarboxylic acid(s) or the anhydrides or semi-esters thereof with aluminium alcoholates. The aforersaid fluids manifest a high electro-rheological effect and are completely homogeneous.

Description

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) .~~

- 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 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 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.

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 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 21~2~18 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.

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

Claims

CLAIMS:

1. A homogeneous electro-viscous fluid comprising an aluminium soap produced by reacting at least one member selected from the group consisting of saturated and unsaturated monomeric, oligomeric and polymeric C3 to C32 polycarboxylic acids having one or more carboxylic group, the anhydrides and semi-esters thereof which alcohol component comprise straight and branched, monohydric and polyhydric C1 to C12 alcohols and oligomers thereof with one or more aluminium alcoholate(s), the alcohol component(s) thereof comprising one or more aliphatic straight or branched, mono- or polyhydric C1 to C18 alcohols.

2. The electro-viscous fluid of claim 1, wherein the polycarboxylic acid, anhydride or semi-ester has 3 to 18 carbon atoms.

3. The electro-viscous fluid of claim 1, wherein the polycarboxylic acid, anhydride or semi-ester has 12 to 18 carbon atoms.

4. The electro-viscous fluid of claim 1, wherein the at least one member of the group is an alkenyl succinic acid or semi-ester thereof having 5 to 18 carbon atoms.

5. The electro-viscous fluid of claim 1, wherein the at least one member of the group is an alkenyl succinic acid or semi-ester thereof having 12 to 18 carbon atoms.

6. The electro-viscous fluid according to any one of claims 1 to 5, wherein, in the reaction producing the aluminium soap, all or part of the valences of the aluminium have been reacted.

7. The electro-viscous fluid according to any one of claims 1 to 6, wherein the one or more polycarboxylic acid, anhydride, or semi-ester thereof comprises one or more free OH groups.

8. The electro-viscous fluid of claim 7, comprising the semi-ester which comprises one or more free OH groups.

9. The electro-viscous fluid according to any one of claims 1 to 8, wherein the alcohol component(s) of the semi-ester is (are) comprised of di- to tetrahydric alcohols with 1 to 6 carbon atoms, or an oligomer thereof.

10. The electro-viscous fluid according to any one of claims 1 to 8, wherein the alcohol component(s) of the semi-ester is (are) comprised of di- to tetrahydric alcohols with 2 to 5 carbon atoms, or an oligomer thereof.

11. The electro-viscous fluid according to any one of claims 1 to 10, which is comprised of (a) 2 to 50 wt.-% of the aluminium soap in homo-geneous solution with (b) 50 to 98 wt.-% of a hydraulic base fluid, each percentage based on the total weight of the composition.

12. The electro-viscous fluid according to claim 11, which additionally comprises:
(c) up to 10 wt.-% of soluble hydraulic oil additives known per se, based on the total weight of the composition.

13. The electro-viscous fluid according to any one of claims 1 to l0, which is comprised of:
(a) 5 to 40 wt.-% of the aluminium soap in homo-geneous solution with (b) 60 to 95 wt.-% of a hydraulic base fluid, each percentage based on the total weight of the composition.

14. The electro-viscous fluid according to claim 13, which additionally comprises:
(c) up to 5 wt.-% of soluble hydraulic oil additives known per se, based upon the total weight of the composition.

15. The electro-viscous fluid according to any one of the claims 1 to 10, which is comprised of:
(a) 10 to 35 wt.-% of the aluminium soap in homo-geneous solution with (b) 65 to 90 wt.-% of a hydraulic base fluid, each percentage based on the total weight of the composition.

16. The electro-viscous fluid according to claim 15, which additionally comprises:
(c) up to 2 wt.-% of soluble hydraulic oil additives known per se, based upon the total weight of the composition.