EP0566931A1 - Suspensions magnétodilatantes - Google Patents

Suspensions magnétodilatantes Download PDF

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Publication number
EP0566931A1
EP0566931A1 EP93105739A EP93105739A EP0566931A1 EP 0566931 A1 EP0566931 A1 EP 0566931A1 EP 93105739 A EP93105739 A EP 93105739A EP 93105739 A EP93105739 A EP 93105739A EP 0566931 A1 EP0566931 A1 EP 0566931A1
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EP
European Patent Office
Prior art keywords
magnetodilatant
suspensions
magnetic particles
magnetic
suspension
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Application number
EP93105739A
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German (de)
English (en)
Inventor
Claudius Dr. Kormann
Ekkehard Dr. Schwab
Martin Dr. Laun
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BASF SE
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BASF SE
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Publication date
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Publication of EP0566931A1 publication Critical patent/EP0566931A1/fr
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
    • H01F1/44—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of magnetic liquids, e.g. ferrofluids
    • H01F1/447—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of magnetic liquids, e.g. ferrofluids characterised by magnetoviscosity, e.g. magnetorheological, magnetothixotropic, magnetodilatant liquids

Definitions

  • the invention relates to sedimentation-stable, magnetodilatant suspensions and their use.
  • Magnetorheological fluids and suspensions i.e. Liquids and suspensions, the viscosity of which can be adjusted by the action of an external magnetic field
  • these systems have a pseudoplastic, i.e. shear thinning or Newtonian flow behavior.
  • systems have been described that show the so-called dilated flow behavior. (E.J.W. Verwey et al., Rec. Trav. Chim. 57 (1939) 383 to 389).
  • a disadvantage of the known dilatant suspensions is that they are either not stable to sedimentation or that their viscosity cannot be influenced within wide limits by applying an external magnetic field.
  • sedimentation-stable dispersions consisting essentially of magnetic particles with a particle size of less than 1 ⁇ m of a dispersing substance and a solvent with a boiling point of at least 100 ° C., have a magnetorheological effect, measured in a magnetic field of 100 kA / m , show at least 500 Pa and show dilated flow behavior.
  • Suspensions in the sense of the invention are suspensions in which the quotient dln ⁇ / dln ⁇ exceeds the value of 0.3 without the action of an external magnetic field in at least a partial range of the shear rate interval from 0.1 to 100,000 s ⁇ 1, with ⁇ the shear viscosity and ⁇ mean the shear rate.
  • the suspensions according to the invention contain the magnetic particles with a volume fraction of at least 10, preferably at least 15% and up to 80% by volume, a range between 20 and 65% by volume being particularly advantageous.
  • the volume of the magnetic particles used is the total volume, which means that the layer of dispersing substance must also be added to the respective particle.
  • Suitable magnetic particles for the suspensions according to the invention with an average particle size of less than 1 ⁇ m, usually with a particle size of 10 to 100 nm, are preferably those with a high specific saturation magnetization.
  • Preferred classes of substances are superparamagnetic iron oxides such as Fe3O4, ⁇ -Fe2O3, Berthollide and in particular the cubic ferrites of the composition M v Mn w Zn x Fe y O z described in US Pat. No. 4,810,401.
  • the magnetodilatant suspensions contain magnetic particles which, in the sense of a core-shell arrangement, consist only partially of the magnetic substance.
  • the shell consists of magnetic material that has been struck on an inorganic or organic core.
  • Part of the Replace magnetic particles with an admixture of non-magnetic particles taking into account the intended volume filling level.
  • hard magnetic particles of this size can also be used.
  • Particularly suitable non-magnetic admixture pigments are those that can even be processed into dilatant suspensions, such as the latex particles described in DE-A 30 25 562. While the particle size of the magnetic particles is always less than 1 ⁇ m, the particle size of the non-magnetic pigment admixtures should be 2 nm to 200 ⁇ m.
  • These magnetic particles or mixtures containing these particles are coated with polyelectrolytes in the magnetodilatant suspensions according to the invention.
  • the polyelectrolytes not only effect a suitable steric stabilization but also an increase in the surface charge of the solid particles. What is important here is the pH, by which the rheological properties of the suspension are influenced.
  • the charge carrier concentration in the polyelectrolytes and the volume of the adsorbate layer can be adjusted in a suitable manner by varying the pH.
  • anionic polyelectrolytes it has been found to be expedient for the pH to be greater than their acid constant (pKa), while for cationic polyelectrolytes the pH is preferably less than the pKa.
  • the flow properties can be influenced favorably by adjusting the ionic strength.
  • a large number of polyelectrolytes with a molecular weight between 500 and 250,000 are suitable. These polymers preferably have 5 to 1000 charges in the molecular structure.
  • Polyelectrolytes from the group of polyacrylate acrylic acid / acrylamide copolymers, modified polyacrylates, phosphonomethylated polycarboxylates, polyvinylphosphonic acids, polyvinylphosphoric acids, polyamines, polyvinylamines, polysulfonic acids, polyphosphoric acids are particularly suitable.
  • a pH range between 2 and 12 has proven to be particularly advantageous for the polyacrylates.
  • other ligands which increase the surface charge can also be used.
  • the solvents contained in the magnetodilatant suspensions according to the invention can be polar or non-polar, water also being suitable.
  • Particularly suitable solvents are ethylene glycol, triethylene glycol, tetraethylene glycol and mixtures thereof.
  • the polarity can be varied either by choosing a different solvent or by mixing different solvents.
  • the viscosity of the solvent (mixture) at 25 ° C. is expediently in the range from 1 to 10,000 mPas, preferably from 1 to 1000 mPas. If magnetodilatant suspensions are produced in water, a certain surface charge of the magnetizable particles must be set by choosing the appropriate pH in the range from 2 to 12, preferably from 5 to 11.
  • magnetodilatant suspensions according to the invention remain flowable almost indefinitely because of the extremely low tendency to sedimentation. Their dilatant flow behavior and the possibility of reversibly influencing the viscosity by an external magnetic field are properties that make these suspensions useful for numerous applications.
  • These magnetodilatant suspensions are particularly suitable for the controllable damping of vibrations and movements within shorter time intervals, e.g. for shock absorbers, engine vibration dampers, and also couplings.
  • Magnetodilatant suspensions are also suitable for controlling forces and motion sequences in automotive auxiliary units such as air conditioning systems, alternators, power steering, motion or acceleration sensors, and small motor clutches. There are also possible uses for vibration damping in washing machines, centrifuges, sensitive electronic devices and for accelerating weighing processes.
  • the BET surface area measured in the following examples was measured in accordance with DIN 66 132 using a Ströhlein Areameter from Ströhlein, Düsseldorf, using the single point difference method according to Haul and Dümbgen.
  • the magnetic properties were determined in a vibration magnetometer in an external magnetic field of 400 kA / m.
  • the viscosity measurements and the determination of the magnetorheological effect were carried out with a Couette rheometer (CRM) with switchable magnetic field of 100 kA / m performed at room temperature.
  • CCM Couette rheometer
  • the test sample is located in the gap between a cylindrical, fixed iron stator 1 with the radius R 1 and a polyamide cup 2 rotating at the angular velocity ⁇ with the inner radius R 2.
  • the torque M acting on the stator is measured. If H is the height of the stator, the wall shear stress ⁇ on the stator follows in the field-free case The apparent wall shear rate ⁇ (neglected wall sliding) results in Due to the geometry of the pole pieces 3 and 3 ', only parts of the sample are within the two sectors with the angle ⁇ (in rad) in the magnetic field.
  • An aqueous suspension of soft magnetic MnZn ferrite pigments with a stoichiometry as described in Example 12 of US Pat. No. 4,810,401 was prepared.
  • Figure 2 shows the dependence of the viscosity ⁇ [Pas] of the suspension against the shear rate ⁇ [s ⁇ 1] without a magnetic field (a) and in the magnetic field (b) and the dependence of the magnetic rheological effect MR [Pa] also against the shear rate.
  • Example 2 60 g of freeze-dried latex particles used in Example 2 were mixed with 60 g of ethylene glycol, 12 g of soft magnetic ferrite according to Example 1 and 235 g of water on the Ultra-Turrax disperser for half an hour. A pH of 9 was set by adding 1.2 g of NaOH. The water was drawn off on a rotary evaporator and a flowable, non-sedimenting suspension was obtained, which was characterized as follows: minimum viscosity (at a shear rate of approx. 30 s ⁇ 1): 1.2 Pas, viscosity at 140 s ⁇ 1: 6 Pas, magnetorheological Effect (at 140 s ⁇ 1): 2000 Pa.
EP93105739A 1992-04-24 1993-04-07 Suspensions magnétodilatantes Withdrawn EP0566931A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE19924213513 DE4213513A1 (de) 1992-04-24 1992-04-24 Magnetodilatante Suspensionen
DE4213513 1992-04-24

Publications (1)

Publication Number Publication Date
EP0566931A1 true EP0566931A1 (fr) 1993-10-27

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EP93105739A Withdrawn EP0566931A1 (fr) 1992-04-24 1993-04-07 Suspensions magnétodilatantes

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EP (1) EP0566931A1 (fr)
JP (1) JPH0620822A (fr)
DE (1) DE4213513A1 (fr)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0579229A2 (fr) * 1992-07-16 1994-01-19 Nippon Oil Co., Ltd. Huile ayant des effets magnétiques et électrorheologues simultanément
EP0776813A1 (fr) * 1995-11-30 1997-06-04 Trw Inc. Direction comportant des embrayages à fluide magnétorhéologique
US5702630A (en) * 1992-07-16 1997-12-30 Nippon Oil Company, Ltd. Fluid having both magnetic and electrorheological characteristics
CN111584223A (zh) * 2020-04-02 2020-08-25 湖南纳金新材料技术有限公司 一种高电阻片状软磁粉体的制备方法

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7896019B2 (en) * 2005-11-12 2011-03-01 Massachusetts Institute For Technology Active controlled energy absorber using responsive fluids

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0421249A1 (fr) * 1989-10-05 1991-04-10 BASF Aktiengesellschaft Fluides magnétiques à haute viscosité
WO1991014260A1 (fr) * 1990-03-12 1991-09-19 Societe Anonyme Des Ciments Vicat Composition magnetique et ses applications
EP0534234A2 (fr) * 1991-09-25 1993-03-31 BASF Aktiengesellschaft Fluide magnétorheologique

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0421249A1 (fr) * 1989-10-05 1991-04-10 BASF Aktiengesellschaft Fluides magnétiques à haute viscosité
WO1991014260A1 (fr) * 1990-03-12 1991-09-19 Societe Anonyme Des Ciments Vicat Composition magnetique et ses applications
EP0534234A2 (fr) * 1991-09-25 1993-03-31 BASF Aktiengesellschaft Fluide magnétorheologique

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
ACTA PHYS.SLOVACA Bd. 39, Nr. 4, 1989, Seiten 264 - 266 P.KOPCANSKY ET AL *
IEEE TRANSACTIONS ON MAGNETICS. Bd. 23, Nr. 5, September 1987, NEW YORK US Seiten 3239 - 3241 T.AMARI ET AL 'Creep measurements on magnetic suspension' *

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0579229A2 (fr) * 1992-07-16 1994-01-19 Nippon Oil Co., Ltd. Huile ayant des effets magnétiques et électrorheologues simultanément
EP0579229A3 (fr) * 1992-07-16 1994-04-13 Nippon Oil Co Ltd
US5702630A (en) * 1992-07-16 1997-12-30 Nippon Oil Company, Ltd. Fluid having both magnetic and electrorheological characteristics
EP0776813A1 (fr) * 1995-11-30 1997-06-04 Trw Inc. Direction comportant des embrayages à fluide magnétorhéologique
US5732791A (en) * 1995-11-30 1998-03-31 Trw Inc. Steering apparatus
CN111584223A (zh) * 2020-04-02 2020-08-25 湖南纳金新材料技术有限公司 一种高电阻片状软磁粉体的制备方法

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Publication number Publication date
JPH0620822A (ja) 1994-01-28
DE4213513A1 (de) 1993-10-28

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