EP0483774B1 - Fluide électrovisqueux - Google Patents

Fluide électrovisqueux Download PDF

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Publication number
EP0483774B1
EP0483774B1 EP19910118452 EP91118452A EP0483774B1 EP 0483774 B1 EP0483774 B1 EP 0483774B1 EP 19910118452 EP19910118452 EP 19910118452 EP 91118452 A EP91118452 A EP 91118452A EP 0483774 B1 EP0483774 B1 EP 0483774B1
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EP
European Patent Office
Prior art keywords
wet
fluid
electroviscous
method silica
silica
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.)
Expired - Lifetime
Application number
EP19910118452
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German (de)
English (en)
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EP0483774A1 (fr
Inventor
Takashi Nakamura
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
DuPont Toray Specialty Materials KK
Original Assignee
Dow Corning Toray Silicone Co Ltd
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Publication of EP0483774A1 publication Critical patent/EP0483774A1/fr
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Classifications

    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
    • C10M171/00—Lubricating compositions characterised by purely physical criteria, e.g. containing as base-material, thickener or additive, ingredients which are characterised exclusively by their numerically specified physical properties, i.e. containing ingredients which are physically well-defined but for which the chemical nature is either unspecified or only very vaguely indicated
    • C10M171/001—Electrorheological fluids; smart fluids

Definitions

  • the present invention relates to an electroviscous fluid which is a fluid whose viscosity can be changed by the impression or application of an external voltage.
  • silica is easily obtained on an industrial basis and is highly amenable to improvement and manipulation, it has been considered potentially useful for certain sectors of application, for example, machinery which would be used in the vicinity of room temperature and which would undergo little abrading motion.
  • Silica-based electroviscous fluids are disclosed in United States Patent Number 3,047,507 and in Japanese Patent Application Laid Open [Kokai or Unexamined] Number 61-44998 [44,998/86], but in each case these exhibit an impractically weak Winslow effect.
  • Japanese Patent Application Laid Open Number 01-284595 discloses an electroviscous fluid in the form of a dispersion in an electrically insulating fluid of wet-method silica whose surface adsorbed water has been replaced by polyvalent alcohol. Based on the formation of an electrical double layer by the polyvalent alcohol, this electroviscous fluid exhibits an electroviscous behavior more or less equal to that of the dispersion of the unmodified silica, but also retains its characteristics at higher temperatures (90°C). However, even in this case, the intensity of the Winslow effect is still merely more or less equal to that of the prior wet-method silica-based systems. Moreover, because the dielectric constant of the polyvalent alcohol declines with increasing temperature, the Winslow effect still declines at higher temperatures.
  • electro-rheological fluids which comprise an electrically insulating liquid as dispersion medium and a porous solid particulate material as dispersed phase.
  • the dispersed phase is, for example, a silica gel.
  • the electro-rheological fluid of EP-A 0 342 041 is treated with a polyhydric alcohol together with water or in the absence of water in such a way that the polyhydric alcohol forms a film and is stably adsorbed on the solid particles.
  • the properties of this electro-rheological fluid are not satisfying.
  • the present invention introduces a silica dispersion- type electroviscous fluid which develops a Winslow effect sufficient to satisfy industrial applications.
  • the present inventor carried out extensive investigations with a view to solving the aforementioned problems, and discovered as a result that the aforementioned problems are substantially reduced by the use as the disperse phase of silica prepared by replacing the water adsorbed on the surface of wet-method silica with a particular type of compound.
  • the present invention was developed based on this discovery.
  • the object of the present invention is the introduction of an electroviscous fluid which develops an excellent Winslow effect.
  • the object of the present invention is also to utilize a dispersion of 0.1 to 50 weight percent silica particles which comprise wet-method silica particles whose surface adsorbed water has been replaced by an organic compound which contains within its molecule at least one nitrile group, hydroxyl group, or acid group, and wherein the wet-method silica particles have an average particle diameter of 10 to 500 micrometers and have a pH that does not exceed 6.5,in an electrically insulating fluid.
  • a further object of the present invention is to provide an electroviscous fluid which provides a substantial increase in yield value at low voltages and excellent shear stability.
  • the present invention relates to an electroviscous fluid comprising a dispersion of silica particles in an electrically insulating fluid, the improvement comprising using 0.1 to 50 weight% wet-method silica particles whose surface adsorbed water has been replaced by an organic compound having in its molecule at least one nitrile group, wherein the wet-method silica particles have an average particle size of 10 to 500 micrometers and a pH of not greater than 6.5.
  • the pH (hydrogen ion concentration) of the wet-method silica particles are preferably measured in a 4 weight percent aqueous suspension, however the method of testing the particles for pH is not critical to the present invention.
  • wet-method silica particles employed by the present invention are prepared by the production of silica by the addition of acid under wet conditions to water glass starting material.
  • These wet-method silica particles are an ideal disperse phase for electroviscous fluids because their surfaces possess a layer of adsorbed water, which is ideal for the development of the Winslow effect, and because they have optimal particle sizes.
  • Their average particle size should fall within the range of 10 to 500 micrometers and preferably falls within the range of 50 to 200 micrometers. When the particle size is less than 10 micrometers, the particles exhibit a large orientability, but the interparticle forces are small and a satisfactory viscosity will not be achieved.
  • the orientability is diminished and the thickening effect is reduced.
  • the particle size itself begins to pose significant problems.
  • the particle shape should be as close to truly spherical as possible.
  • the effective interparticle contact area declines and the cohesive forces are then weak.
  • the narrower With regard to the particle size distribution, the narrower the better.
  • the particle orientability becomes increasingly uniform as the particle size distribution becomes narrower, which provides for a more efficient viscosity rise.
  • Various methods can be devised for the production of silica particles which have a narrow particle size distribution and are as close to spherical as possible, but such particles are obtained mainly by devising a suitable drying process. For example, spray drying methods are ideal.
  • the quantity of ion in the silica is also a crucial factor in determining the targeted Winslow effect. While not limiting the present invention to any particular theory, it is believed that the principal ion present in the silica is the sodium ion, and this is mainly the excess from the sodium ion used in order to neutralize the solid acid present as an impurity in the water glass starting material. Accordingly, the fluidity of the silica is governed by the magnitude of this quantity of sodium ion. According to experiments by the inventor, the presence of free ion in the silica brings about a retardation in particle orientation.
  • the fluidity index according to the present invention is defined as follows: the pH of a 4 wt% aqueous suspension of said silica must not exceed 6.5 and more preferably does not exceed 5.5. A useful Winslow effect does not appear at values in excess of 6.5. In order to obtain wet-method silica which has such a fluidity, the excess sodium ion must be removed to the maximum possible extent, or, alternatively, a pure water glass which contains only traces of solid acid must be employed as the starting material.
  • wet-method silica employed by the present invention may be selected from among commercial wet-method silicas, for example, Nipsil A Q-S from Nippon Silica Kogyo Kabushiki Kaisha and its equivalents.
  • the water adsorbed on the surface of this wet-method silica is then replaced by an organic compound which contains a nitrile group,
  • the surface of wet-method silica is normally covered with a layer of adsorbed water. While the particular weight proportion for this adsorbed water in the total silica weight will vary with the particular type of wet-method silica, in general it will fall within the range of 5% to 10%. Since this layer of adsorbed water is merely hydrogen bonded to a layer of structural water which resides immediately inward, it can be almost completely eliminated by heating to around 100°C. However, as discussed above, this adsorbed water layer plays a significant role in the development of the Winslow effect.
  • this adsorbed water layer on the surface of wet-method silica is replaced with an organic compound which contains a nitrile group
  • the nitrile group-containing organic compound as specified herein is exemplified by aliphatic nitriles such as acetonitrile, propionitrile, n-capronitrile, succinonitrile, etc., and by aromatic nitriles such as benzonitrile, alpha-tolunitrile, and so forth. All of these are suitable and no particular restrictions apply to these compounds.
  • the wet-method silica particles are placed under a nitrogen current at 150°C in order to remove the surface adsorbed water.
  • the substituting compound is then added in a quantity corresponding to the weight loss due to the desorbed water with mixing to physical homogeneity in, for example, a mixer.
  • the surface of the wet-method silica particles will be covered by a layer of the substituting compound. Due to the high dielectric constant of same, a Winslow effect can be developed which is at least equivalent to that for the adsorbed water.
  • the electroviscous fluid according to the present invention comprises the dispersion of wet-method silica particles as specified hereinbefore in an electrically insulating fluid.
  • the electrically insulating fluid itself is not particularly restricted as long as it is a liquid at room temperature and is electrically insulating.
  • Such electrically insulating fluids are exemplified by mineral oils, dibutyl sebacate, chlorinated paraffins, fluorine oils, and silicone oils. Among the preceding, silicone oils are preferred for their strong electrical insulation, low temperature-dependent viscosity variation, and so forth.
  • silicone oils are exemplified by the fluid diorganopolysiloxanes with the following chemical structure: wherein R in the preceding formula comprises monovalent hydrocarbon groups as exemplified by alkyl groups such as methyl, ethyl, and propyl, and aryl groups such as phenyl and naphthyl. It is preferred within the present invention that methyl comprise at least 30% of the groups R. Moreover, while the degree of polymerization n is not particularly specified, it preferably does not exceed 1,000 in order to achieve a practical viscosity range. Values not exceeding 100 are even more preferred. Silicone oils with this structure are available in the form of a large number of commercial products, for example, SH200 from Toray Dow Corning Silicone Company, Limited.
  • fluoroalkyl-containing diorganopolysiloxanes are particularly preferred because they enhance the Winslow effect and inhibit the particle sedimentation caused by specific gravity differences.
  • R is defined as above
  • R2 is a fluoroalkyl group having 10 or fewer carbons
  • m and p are integers with values not exceeding 1,000.
  • the structure of the aforementioned C ⁇ 10 fluoroalkyl group is not particularly specified, but the 3,3,3- trifluoropropyl group is preferred from the standpoint of ease of synthesis.
  • each molecule In order to obtain a substantial enhancement of the Winslow effect, it will be preferable for each molecule to contain at least 30 mole% fluoroalkyl group.
  • the degree of polymerization m is again not particularly specified, it preferably does not exceed 1,000 in order to achieve a practical viscosity range. Values not exceeding 100 are even more preferred.
  • the mechanism by which the fluoroalkyl group enhances the Winslow effect is not clear.
  • fluoroalkyl-containing diorganopolysiloxanes are commercially available, for example, as FS1265 from Toray Dow Corning Silicone Company, Limited.
  • the electroviscous fluid according to the present invention comprises the dispersion of wet-method silica particles as described hereinbefore in an electrically insulating fluid as described hereinbefore.
  • the quantity dispersed should fall within the range of 0.1 to 50 wt% and preferably is in the range of 10 to 40 wt%. A satisfactory thickening effect is not obtained at less than 0.1 wt%. At values exceeding 50 wt%, the viscosity of the system is so substantially increased as to be impractical.
  • the electroviscous fluid according to the present invention as described above is useful as the working oil or functional oil in particular types of machinery, for example, machinery which will be employed in the vicinity of room temperature and where there will be little abrading motion.
  • the electroviscous behavior was measured as follows.
  • the resulting cylindrical cell was set up vertically, and the cup was linearly accelerated from a shear rate (D) of zero to 330 s ⁇ 1 over 40 seconds.
  • D shear rate
  • S shear stress
  • the D-versus-S curve was drawn on an X-Y recorder.
  • the rotor was electrically grounded and D-versus-S curves were also recorded while applying a direct-current voltage to the cup.
  • the intersection of the extrapolation of the linear segment with the S-axis was designated as the yield value at the particular field strength.
  • the thermal and shear stress stability and the sedimentability of the wet-method silica particles were also examined.
  • the electroviscosity test was also set up in such a manner that the cell temperature could be varied.
  • Electroviscous fluid in the form of the suspension prepared in Example 1 was heated for 1 week at 90°C in an open system under air, then removed and cooled. After this heat treatment, the electroviscous behavior of the resulting suspension was measured, and these results are reported in Table 1.
  • Example 1 An electroviscous fluid in the form of a suspension was prepared as in Example 1, but in this case using 1,2- propanediol in place of the acetonitrile used in Example 1. The electroviscous behavior of this fluid was measured as in Example 1, and these results are reported in Table 1 below.
  • Example 1 An electroviscous fluid in the form of a suspension was prepared as in Example 1, but in this case using acetic acid in place of the acetonitrile used in Example 1. The electroviscous behavior of this fluid was measured as in Example 1, and these results are reported in Table 1 below.
  • the electroviscous behavior of this suspension was measured at a cell temperature of 25°C, and these results are reported in Table 1 below.
  • Example 1 An electroviscous fluid in the form of a suspension was prepared as in Example 1, but in this case using the wet- method silica prior to its acetonitrile treatment in place of the acetonitrile-treated wet-method silica employed in Example 1.
  • the electroviscous behavior of this fluid was measured as in Example 1, and these measurement results are reported in Table 1 below.
  • Electroviscous fluid as prepared in Comparison Example 1 was heated for 1 week at 90°C in an open system under air, then removed and cooled.
  • the electroviscous behavior of the electroviscous fluid obtained from this heat treatment was measured at a cell temperature of 25°C, and these results are reported in Table I.
  • the electroviscous behavior of this fluid was measured as in Example 1, and these measurement results are reported in Table 1 below.
  • the electroviscous behavior of this fluid was measured as in Example 1, and these measurement results are reported in Table 1 below.
  • Table I EXAMPLE THERMAL TREATMENT YIELD VALUE SHEAR STRESS STABILITY PARTICLE SEDIMENTABILITY 1 KV/mm 2KV/mm EX. 1 (i) none 240 490 high medium EX. 2 (i) none 205 460 high medium EX.
  • the electroviscous fluid according to the present invention comprises a dispersion of 0.1 to 50 weight percent wet-method silica particles whose surface adsorbed water has been replaced by a particular type of organic compound in an electrically insulating fluid, this electroviscous fluid is characterized by a substantial increase in yield value at low voltages and an excellent shear stability.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Organic Chemistry (AREA)
  • Lubricants (AREA)
  • Tires In General (AREA)
  • Detergent Compositions (AREA)

Claims (1)

  1. Dans un fluide électro-visqueux comprenant une dispersion de particules de silice dans un fluide électriquement isolant, le perfectionnement consistant à utiliser de 0,1 à 50 % en poids de particules de silice produites par voie humide dont l'eau adsorbée en surface a été remplacée par un composé organique ayant dans sa molécule au moins un groupe nitrile, dans lequel les particules de silice produites par voie humide ont une taille de particules moyenne de 10 à 500 »m et dans lequel une suspension aqueuse à 4 % en poids a un pH non supérieur à 6,5.
EP19910118452 1990-10-29 1991-10-29 Fluide électrovisqueux Expired - Lifetime EP0483774B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP291010/90 1990-10-29
JP29101090A JPH04164996A (ja) 1990-10-29 1990-10-29 電気粘性液体

Publications (2)

Publication Number Publication Date
EP0483774A1 EP0483774A1 (fr) 1992-05-06
EP0483774B1 true EP0483774B1 (fr) 1995-02-15

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EP19910118452 Expired - Lifetime EP0483774B1 (fr) 1990-10-29 1991-10-29 Fluide électrovisqueux

Country Status (4)

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EP (1) EP0483774B1 (fr)
JP (1) JPH04164996A (fr)
CA (1) CA2054433A1 (fr)
DE (1) DE69107406T2 (fr)

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1994005749A1 (fr) * 1992-09-09 1994-03-17 Lord Corporation Materiaux electrorheologiques a resistance elevee et faible conductivite
WO1995004121A1 (fr) * 1993-07-29 1995-02-09 Lord Corporation Matieres electrorheologiques a haute resistance et faible conductivite
US5925288A (en) * 1994-01-31 1999-07-20 Tonen Corporation Electrorheological fluid containing silica particles esterified by an alcohol-modified silicone oil
DE10115302A1 (de) 2001-03-28 2002-10-02 Matthias Hahn Verfahren zum Entfernen eines Ölteppichs oder dergleichen von einer Wasseroberfläche und Vorrichtung dazu
FI122069B (fi) * 2006-05-24 2011-08-15 Kemira Oyj Menetelmä happosilikaattiliuoksen valmistamiseksi
JP5233343B2 (ja) * 2008-03-18 2013-07-10 凸版印刷株式会社 防眩性積層体の製造方法

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR1488158A (fr) * 1965-08-02 1967-07-07 Textron Electronics Compositions électrovisqueuses perfectionnées
GB2210893A (en) * 1987-10-12 1989-06-21 American Cyanamid Co Electrorheological fluids
DE68908469T2 (de) * 1988-05-12 1993-12-09 Toa Nenryo Kogyo Kk Elektrorheologische Flüssigkeiten.
JPH02164438A (ja) * 1988-12-17 1990-06-25 Bridgestone Corp 電気粘性液体

Also Published As

Publication number Publication date
DE69107406D1 (de) 1995-03-23
DE69107406T2 (de) 1995-07-20
JPH04164996A (ja) 1992-06-10
CA2054433A1 (fr) 1992-04-30
EP0483774A1 (fr) 1992-05-06

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