Electrorheological compositions

Abstract

An electrorheological composition has corrosion-inhibiting properties and contains at least one organic ionic compound as an electrolyte. Also disclosed are methods for the production thereof and the use thereof.

Claims

1. An electrorheological composition, comprising: a polymer or polymer mixture; at least one electrolyte dissolved or dispersed in the polymer or polymer mixture; at least one dispersing agent; and at least one non-aqueous dispersion medium; wherein the at least one electrolyte is at least one organic ionic compound selected from a group consisting of lithium acetate, lithium stearate, lithium benzoate, lithium trifluoromethane sulfonate, lithium oxalate, magnesium citrate, silver citrate, zinc gluconate and sodium lauryl sulfate, and wherein the composition contains from 110.sup.6 to 510.sup.3 weight percent of inorganic anions.

2. The electrorheological composition according to claim 1, wherein the polymer or polymer mixture consists of linear or branched polyethers or oligomonomers thereof, or a reaction or conversion product of said polyethers or said oligomonomers thereof with mono- or oligo-functional compounds.

3. The electrorheological composition according to claim 1, wherein the polymer or polymer mixture consists of linear or branched, functionalized polyethers or oligomonomers thereof, or a reaction or conversion product of said polyethers or said oligomonomers thereof with mono- or oligo-functional compounds.

4. The electrorheological composition according to claim 1, wherein the polymer or polymer mixture, or mono- and/or oligo-meric initial substances thereof, are present in a liquid form during a dispersing process for producing the composition.

5. The electrorheological composition according to claim 1, wherein the polymer or polymer mixture, or mono- and/or oligo-meric initial substances thereof, are present in a liquid form during a dispersing process for producing the composition, and are converted into a higher viscosity or solid form through an addition of reactive additives before, during or after the dispersing process.

6. The electrorheological composition according to claim 1, wherein the at least one non-aqueous dispersion medium is at least one compound selected from a group consisting of silicone oils, fluorine-containing siloxanes and hydrocarbons.

7. The electrorheological composition according to claim 1, wherein the at least one dispersing agent is at least one compound selected from a group consisting of polysiloxane-polyether-copolymerisates, amino group-containing alkoxypolysiloxanes and amino group-containing acetoxypolysiloxanes.

8. The electrorheological composition according to claim 1, having a corrosion-inhibiting property.

9. The electrorheological composition according to claim 1, further comprising at least one additive that is miscible with a solution of the at least one electrolyte dissolved in the polymer or polymer mixture.

10. The electrorheological composition according to claim 1, further comprising at least one viscosity-increasing additive that reacts with the polymer or polymer mixture.

11. The electrorheological composition according to claim 10, containing from 110.sup.6 to 110.sup.3 weight percent of the inorganic anions.

12. The electrorheological composition according to claim 1, containing from 110.sup.6 to 110.sup.3 weight percent of the inorganic anions.

13. The electrorheological composition according to claim 1, consisting essentially of the polymer or polymer mixture, the at least one electrolyte, the at least one dispersing agent, the at least one non-aqueous dispersion medium, and containing from 110.sup.6 to 510.sup.3 weight percent of the inorganic anions.

14. The electrorheological composition according to claim 1, consisting essentially of the polymer or polymer mixture, the at least one electrolyte, the at least one dispersing agent, the at least one non-aqueous dispersion medium, optionally at least one additive that is miscible with a solution of the at least one electrolyte dissolved in the polymer or polymer mixture, optionally at least one viscosity-increasing additive that reacts with the polymer or polymer mixture, and containing from 110.sup.6 to 510.sup.3 weight percent of the inorganic anions.

15. A combination comprising the electrorheological composition according to claim 1 incorporated in a component selected from a group consisting of adaptive shock, vibration and/or impact dampers, electrically controllable clutches and/or brakes, sport and/or medical exercise devices, haptic and/or tactile systems, operating elements, mechanical fixing devices, hydraulic valves, devices for simulation of viscous, elastic and/or visco-elastic properties, devices for simulation of a consistency distribution of an object, devices for training and/or development purposes, protective clothing, and medical devices.

16. A method of producing the electrorheological composition according to claim 1, comprising preparing and dispersing the polymer or polymer mixture, the at least one electrolyte, the at least one dispersing agent, and the at least one non-aqueous dispersion medium, and removing therefrom excessive inorganic anions to result in a content of the inorganic anions therein from 110.sup.6 to 510.sup.3 weight percent.

17. The electrorheological composition according to claim 1, containing more than 25 weight percent and up to 40 weight percent of the at least one electrolyte with respect to a total weight of particles contained in the electrorheological composition.

18. The electrorheological composition according to claim 17, wherein the total weight of the particles amounts to at least 63 weight percent and up to 70 weight percent of the electrorheological composition.

19. The electrorheological composition according to claim 18, containing more than 25 weight percent of the at least one electrolyte with respect to a total weight of the electrorheological composition.

Description

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS OF THE INVENTION

(1) The following examples serve to explain the invention. The invention is, however, not limited to these examples.

(2) The chemicals used for the syntheses, to the extent not otherwise mentioned, were obtained from Momentive Performance Materials Inc., Kurt Obermeier GmbH & Co. KG, Sigma Aldrich, Alfa Aesar, Merck KGaA, VWR and Carl Roth, and used directly or pre-treated with Molsieb (3 ) as well as ion exchangers (e.g. DOWEX* G-26 (H) or DOWEX MAC-3).

(3) The utilized glass and metal apparatuses were dried in a drying cabinet at 120 C. To exclude water, the reactions were provided with a drying tube (drying agent CaCl.sub.2) or covered with argon or nitrogen as a protective gas.

(4) The ERF that were produced as described in the following were examined and their properties were determined according to DIN 51480-1 in a modified rotational viscometer as has already been described by W. M. Winslow in J. Appl. Phys. 20 (1949), pages 1137-1140.

(5) The measurement geometry is constructed as follows: cylinder diameter (of the rotating cylinder) 16.66 mm, gap width between the electrodes 0.7055 mm and length of the measuring gap 254.88 mm (standard according to ISO 3219). In dynamic measurements, the shear loading can be adjusted to a maximum of 1000 s.sup.1. The measuring range of the viscometer (Anton Paar, MCR 300 rheometer, Ostfildern, Germany) amounts to a maximum of 50 N. Both static as well as dynamic measurements are possible with this apparatus. The energization or excitation of the ERF can take place both with direct DC voltage as well as with alternating AC voltage.

(6) Furthermore, the ERF properties were examined and measured in a test stand for determining hydraulic properties in the flowing mode. In that regard, an ER valve with an annular gap construction was utilized.

(7) By producing a constant volume flow q and specifying various different voltage values (modulatable high voltage amplifier 0 to 6 kV; 130 W; rise time 0.5 to 5 kV at 1 nF max. 0.57 ms; decay time 5 to 0.5 kV at 1 nF 0.175 ms; model: RheCon, company Fludicon GmbH, D-64293 Darmstadt), therewith the ER properties could be determined from the measured static pressure differences at the ER valve (pressure and temperature sensors at the inlet and outlet). The mathematical approximation used in that regard is based on the equivalent flat gap. The length L corresponds to the length of the electrode surface. For that purpose, the inlet and outlet of the annular gap were ignored or omitted as negligible. For calculating the width W, the average annular gap diameter d.sub.m=(d.sub.1+d.sub.2)/2 was utilized. Then the gap width W is given by W=d.sub.m. The gap height H corresponds to the spacing distance of the electrode to the outer pipe and is calculated according to: H=(d.sub.2d.sub.1)/2 (dimensions: length L=100 mm; inner electrode diameter d.sub.1=39.5 mm; outer electrode diameter d.sub.2=40.5 mm; thereby there arises a gap height H=0.5 mm; and an average annular gap diameter d.sub.m=40 mm).

(8) Using a Bingham-type material law, from the measured pressure differences, the field-strength-dependent yield point or liquid flow limit .sub.0(E) was determined.
.sub.12=.sub.0(E)sin({dot over ()})+{dot over ()} for {dot over ()}0

(9) Therein, .sub.12 represents the shear stress (or thrust stress), E represents the electric field strength, represents the dynamic base viscosity, and {dot over ()} represents the shear rate (10000 s.sup.1). With the explained parameters, then the dynamic base viscosity can be calculated according to the following equation.

(10) $=\frac{{\mathrm{WH}}^3}{12L}\frac{p_1}{q}$

(11) For the determination of the yield point, the corresponding field strength is calculated from the prescribed voltage values U.sub.i according to:

(12) $E_i=\frac{U_i}{H}$

(13) The measured pressure differences p.sub.i are converted by calculation into a pressure gradient

(14) $P_i=\frac{p_i}{L}$

(15) Furthermore, the abovementioned system parameters are calculated into an intermediate value (geometry factor)

(16) ${}_i=\arccos \left(\frac{12q}{{\mathrm{WP}}_i{H}^3}-1\right)$
from which the values of the field-strength-dependent yield point can be calculated by

(17) ${}_{0,i}=P_{i}H\cos \left(\frac{{}_i}{3}+\frac{4}{3}\right)$

(18) The ER properties can be judged or evaluated via a graphical plot or a tabular representation of the measured and calculated parameters.

(19) A simple static test was called upon for the evaluation of the corrosion-inhibiting properties. Two electrode plates (electrode surface area 2500 mm.sup.2, material: structural steel S235JR+AR; spacing distance 0.5 mm) arranged parallel to one another had 6 kV (modulatable high voltage amplifier 0 to 6 kV; 130 W; rise time 0.5 to 5 kV at 1 nF max. 0.57 ms; decay time 5 to 0.5 kV at 1 nF 0.175 ms; model: RheCon, company Fludicon GmbH, Darmstadt) applied to them over 24 h (80 C.) in a tempered solution of the respective ER fluid. Thereafter, the surface corrosion was optically or visually compared and divided into three categories (+ no corrosion visible; slight changes of the surface; strong corrosion of the surface (rust formation)).

Comparative Example 1

(20) 1902 g of trifunctional polyethylene glycol were heated to 60 C., then 6.6 g of lithium chloride and 16.7 g of diazocyclo[2.2.2]octane were added and stirred for 2 h. After cooling to RT, 2300 g of silicone oil (polymethylsiloxane: viscosity mm.sup.2/s; density 0.9 g/cm.sup.3 at 25 C.) and 43.5 g of emulsifier OF 7745 (Momentive Performance Materials Holding GmbH, Leverkusen) were added and homogenized with a jet disperser (1 h, 6 bar). The resulting emulsion was then mixed with 536 g of toluoldiisocyanate. The dispersion was cured overnight at 30 to 60 C.

Example 1

(21) 1900 g of trifunctional polyethylene glycol were heated to 60 C., then 1.7 g of lithium acetate and 5.5 g of diazocyclo[2.2.2]octane were added and stirred for 2 h. After cooling to RT, 2300 g of silicone oil (polymethylsiloxane: viscosity 5 mm.sup.2/s; density 0.9 g/cm.sup.3 (at 25 C.)) and 43.5 g of emulsifier OF 7745 (Momentive Performance Materials Holding GmbH, Leverkusen) were added and homogenized with a jet disperser (1 h, 9 bar). The resulting emulsion was then mixed with 524 g of toluoldiisocyanate. The dispersion was cured overnight at 30 to 60 C.

Example 2

(22) Production according to the Example 1, except the polyethylene glycol was doped with 7.5 g of lithium stearate. For that, a precursor solution of 300 g of polyethylene glycol was stirred overnight at 60 C. and then homogenized at RT with the Ultra-Turrax (IKA-Werke GmbH, Staufen, Germany) and provided to the synthesis.

Example 3

(23) Production according to Comparative Example 1, except the polyethylene glycol was doped with 3.3 g of lithium benzoate.

Example 4

(24) Production according to Comparative Example 1, except the polyethylene glycol was doped with 4.0 g of lithium trifluoromethane sulfonate.

Example 5

(25) Production according to Comparative Example 1, except the polyethylene glycol was doped with 2.7 g of lithium oxalate.

Example 6

(26) Production according to Comparative Example 1, except the polyethylene glycol was doped with 5.5 g of magnesium citrate.

Example 7

(27) Production according to Comparative Example 1, except the polyethylene glycol was doped with 1.1 g of silver citrate.

Example 8

(28) Production according to Comparative Example 1, except the polyethylene glycol was doped with 11.8 g of zinc gluconate.

Example 9

(29) Production according to Comparative Example 1, except the polyethylene glycol was doped with 7.4 g of sodium lauryl sulfate. For that, a precursor solution of 300 g of polyethylene glycol was stirred overnight at 60 C., homogenized with the Ultra-Turrax (IKA-Werke GmbH, Staufen, Germany), and provided to the synthesis.

Example 10

(30) 39 g of trifunctional polyethylene glycol are heated to 60 C., then 0.04 g of lithium acetate and 0.1 g of diazacyclo[2.2.2]octane are added and stirred for 2 h. After cooling to RT, 50 g of silicone oil (polymethylsiloxane: viscosity 5 mm.sup.2/s; density 0.9 g/cm.sup.3 (at 25 C.)) and 1 g of emulsifier OF 7745 (Momentive Performance Materials Holding GmbH, Leverkusen) are added and homogenized with the Ultra-Turrax (IKA-Werke GmbH, Staufen, Germany). The resulting emulsion is thereafter slowly mixed with 11 g of toluoldiisocyanate. The dispersion is cured overnight at 30 to 60 C.

Example 11

(31) Production according to Example 10, however alternatively 0.04 g of lithium benzoate and 0.03 g of zinc acetate are used.

Example 12

(32) Production according to Example 11, except alternatively 0.07 g of lithium stearate are used.

(33) TABLE-US-00001 TABLE 1 Property Overview of ER Compositions Dyn. Base Yield Current Example Viscosity Point Density Corrosion No.: [mPa * s] [Pa] mA/cm.sup.2 Behavior* comparative 40 5500 40 example 1 30 5000 4 + 2 35 4500 2 + 3 22 2000 4 + 4 30 2000 28 5 28 2000 3 + 6 28 3500 5 + 7 35 4200 5 + 8 22 3000 4 + 9 22 2000 18 + *+ no corrosion visible; slight changes of the surface; strong corrosion of the surface; measurement in the annular gap: at 40 C.; shear rate 10000 s.sup.1; yield point at 2.5 kV applied voltage.

(34) The ERF produced according to the Examples 1 to 9 comprised excellent corrosion-inhibiting properties.