Classifications

• • 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
• • 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

Definitions

• the invention relates to a liquid composition which is characterized by a low tendency to sedimentation for particulate solids dispersed therein, and the use of such a composition as a magnetorheological liquid (MRF).
• MRF magnetorheological liquid
• Magnetorheological fluids are functional working media, the flow behavior of which can be changed over a wide range by applying a permanent or variable electromagnetic field.
• MRF products can be used in a variety of ways for both hydrodynamic, hydrostatic and lubrication tasks.
• Known application potentials lie in the areas of adaptive damping, coupling and programmable braking systems, but also for fixing wear protection agents and as a sealing medium for moving shafts.
• composition of known experimental magnetorheological liquids basically consists of a carrier liquid, ferromagnetic particles and optional additives to improve certain application properties of the respective products.
• additive components are required to minimize the tendency to sedimentation or centrifugal ejection of the specifically heavy magnetic particles.
• prior art for the selection of such additives can be found, for example, in the PCT application PCT / US
• liquids mentioned require very special additives that cannot be used universally, which inevitably leads to excessive costs and an unnecessary variety of types.
• the additive components used for the above-mentioned synthetic base liquids have an insufficient stabilization with regard to the sedimentation tendency of the particulate when used in hydrocarbon base liquids
• the object of the invention is to remedy the disadvantages resulting therefrom.
• the liquid composition according to the invention contains, as component A, a hydrocarbon as the base liquid, as component B one or more particulate solids, the mean diameter of the particles being less than 50 ⁇ m, and as
• Components D and E may optionally be included.
• Component D is a partially esterified polyol as a dispersant and component E is an acrylic ester and / or a methacrylic ester polymer as a viscosity index improver.
• the optional additional components D and E interact with the essential components A, B and C and allow the theological flow behavior to be set in a targeted manner, depending on the application, while maintaining or further improving the sedimentation stability.
• composition advantageously consists of:
• the components A to E add up to about 100 particularly advantageously (the preferred percentages by weight apply independently of one another).
• Component A is a hydrocarbon as the base liquid.
• a hydrocarbon compound is a compound which predominantly (> 90 atom%, better> 95 atom%) consists of carbon and hydrogen atoms.
• the base liquid / the base liquid mixture is preferably not easily evaporating and has a boiling point of greater than 100 ° C.
• Hydrogenated spindle oils hydrocarbon mixtures, e.g. commercial products Tanex DN7, DEA
• solvent refinates hydrocarbon mixtures, e.g.
• Hydraulic or transmission fluids of the ATF type have, for example, the following typical composition: approx. 85-92% by weight solvent raffinate, paraffin-based approx. 2 to 6% by weight Vl improver based on polymethacrylate with dispersant function approx. 4 to 8% by weight) of an additive package, of which, in addition to antioxidants, corrosion protection additives, wear protection additives, and friction improvers, represent approximately 0.5 to 3.5% by weight of dispersant additives which are similar in effect to the additional component D.
• Component B is one or more particulate solids, the mean diameter of the particles being less than 50 ⁇ m. In particular, about transition metals and / or transition metal compounds.
• transition metal compounds in the sense of the invention includes alloys which contain transition metals. Transition metals in the sense of the invention are
• transition metals / transition metal compounds in metallic or oxidic form.
• those transition metals and / or transition metal compounds which have magnetic properties are particularly preferred, and Fe, Co and / or Ni are mentioned in particular.
• the particulate solids preferably have an average diameter of 0.5 to 20 ⁇ m.
• Iron / iron oxide powders have proven to be preferred. These can e.g. have a silica coating. Carbonyl iron powders with a low carbon, nitrogen and / or oxygen content post-treated in particular have proven to be suitable.
• Carbonyl iron powders from BASF AG are e.g. the SQ series or CN series, Whiskers A 234 (Fe whiskers) or ferrite material from BASF AG or Kaschke KG, Göttingen (Sr, Mn and Mn / Zn ferrite).
• liquid compositions according to the invention are also excellently suspended in the liquid compositions according to the invention.
• Molybdenum disulfide or graphite may be mentioned here.
• Such liquid compositions are suitable as lubricants, inter alia in combination with the ferromagnetic particulate solids.
• the polyurea compounds according to the invention are commercially available, for example, as ingredients in the lubricant SRI / 2 from Chevron. This contains about 6 to 10% by weight ( ⁇ 8% by weight) of the polyurea component to be used according to the invention.
• the polyurea compound according to the invention is in particular a compound of the type
• X for each n is independently a divalent hydrocarbon radical having 1 to 26 carbon atoms, preferably having 2 to 18 carbon atoms in the case that X is aliphatic and having 6 to 13 carbon atoms in the case that X contains aromatic carbon atoms, and
• R ', R "independently of one another are hydrogen or a hydrocarbon radical having 1 to 30, preferably a hydrocarbon radical having 6 to 20, carbon atoms.
• hydrocarbon radical X or R 'or R' ' can be linear, branched or cyclic, as well as saturated, unsaturated or aromatic (including combinations), preferably linear and saturated and / or aromatic.
• saturated, unsaturated or aromatic including combinations
• Such polyurea compounds are described, for example, in US 3,242,210.
• a nonionic surfactant based on partially esterified polyols is used as component D. This should have an HLB value (hydrophilic-lipophilic balance) between 1 to 9, preferably 2 to 6. Such surfactants are available on the market and act as dispersants. Sorbitan oleates, for example, are preferred. The following are mentioned as examples of the additional component D (including proof of a possible commercial product):
• Component E consists of mineral oil-soluble polymers, which preferably have an N-dispersant function.
• Polymethacrylates which are particularly preferably provided with functional amino, amide or imide groups as the N-dispersant function are suitable, such as those e.g. are commercially available as so-called viscosity index improvers for use in hydraulic and internal combustion engine supplies.
• Polymer contents of ⁇ 3% by weight in the liquid compositions lead to the formation of bulges on rotating shafts in terms of flow behavior. For such applications, the liquid compositions should therefore be adjusted to over 3% by weight of component E.
• the polymethacrylates are mentioned as examples of the additional component E (including detection of a possible commercial product):
• Plexol ® 966 from Rohm and Haas
• additives of the composition according to the invention are commercially available, soluble P / S wear protection components (phosphorus and / or sulfur compounds such as phosphoric acid esters, thiophosphoric acid esters or sulfurized polyolefins) and / or additives such as molybdenum disulfide, graphite, antioxidants and / or corrosion inhibitors.
• the subject of this invention is therefore a basic additive system which can be used in a versatile and advantageous manner in a universal and flexible manner in connection with mineral base oils or mineral oil-miscible, synthetic hydrocarbon oils such as hydrocrackates and polyalfa olefins.
• the liquid composition preferably contains no water.
• the mineral base allows the technically very valuable use of conventionally proven lubricant additives, in particular for the optimal setting of the anti-wear properties and the corrosion protection behavior of the MRF. It is also possible to use commercial, already application-optimized lubricating oils / substances as the starting material for an additional one
• MRF components include selected greases, damping fluids or gear fluids.
• Measuring cylinder detected Measuring cylinder detected.
• the example blends of the second series of experiments (Tab. II) document the interrelationships of the thickening component according to the invention (Example 9) with optional surfactant and polymer additives.
• the carbonyl iron powder (CEP) content for these examples is 50% by weight.
• Example Table II The percentage of each additional component can be found in Example Table II.
• the remaining weight fraction again consists of the naphthenic mineral oil cut according to example series 1.
• the test for sedimentation stability is now extended to a period of 90 days.
• compositions with a higher proportion of carbonyl iron powder are also possible and advantageous (Example 22):
• the tabular information is supplemented by examples with complete flow curves (see Graph I).
• the surprisingly clear variability of the respective flow behavior through the additional components D and E can be demonstrated in the examples shown in graph I using the different flow curves (liquid composition with a constant 15% by weight SRI / 2).
• Graph II shows the flow behavior of the liquid composition according to Example 22 in the magnetic field - measured using a rotary viscometer.
• the magnetic field was generated by a coil with a core, which was integrated into a lower plate.
• the field strength actually generated was not measured, but only compared based on the voltage in volts applied to the coil.
• Non-ferromagnetic materials can also be permanently dispersed according to the invention.
• Liquid compositions with the following composition were examined (left). The sedimentation behavior remained stable over 42 days (measured at room temperature). The shear stress ( ⁇ in Pa) was determined at 40 ° C using the shear rate D (right):

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• 1996
  • 1996-12-27 DE DE19654461A patent/DE19654461A1/de not_active Ceased
• 1997
  • 1997-12-20 JP JP52953798A patent/JP4502151B2/ja not_active Expired - Lifetime
  • 1997-12-20 US US09/331,725 patent/US6245253B1/en not_active Expired - Fee Related
  • 1997-12-20 EP EP97953659A patent/EP0953034B1/de not_active Expired - Lifetime
  • 1997-12-20 WO PCT/DE1997/002992 patent/WO1998029521A1/de active IP Right Grant
  • 1997-12-20 DE DE59703627T patent/DE59703627D1/de not_active Expired - Lifetime

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