Electrorheological fluid containing carbonaceous particles

#1) Field of the Invention

#The present invention relates to a water-free, electrorheological fluid capable of controlling the viscosity by application of an electric field.

#2) Prior Art

#FIG. 1 is an electron microscope picture of carbonaceous particles having a shape anisotropy according to Example 4 of the present invention.

#FIG. 2 is an electron microscope picture of carbonaceous particles not spun into a fiber form according to comparative Example 3.

#Dispersible carbonaceous particles for use in the present invention include, for example, various carbonblacks; finely pulverized coals such as anthracite, bituminous coal, etc.; finely pulverized petroleum pitches obtained by heat treatment of petroleum heavy oils such as naphtha residue, asphalt, fluidized catalytic cracking residue oil, etc.; finely pulverized coal pitches obtained by heat treatment of coal heavy oils such as coal tar, etc.; finely pulverized carbides of paraffins, olefins, etc. having 15 to about 20 carbon atoms; finely pulverized carbides of low molecular weight aromatic compounds such as naphthalene, biphenyl, etc.; finely pulverized carbides of polymers obtained by carbonizing polymers such as polyethylene, polymethylacrylate, polyvinyl chloride, phenol resin, polyacrylonitrile, etc., and also include mesophase microspheres obtained by mesophase (liquid crystal) conversion of petroleum pitches, coal pitches, carbides of polyvinyl chloride, etc. or particles containing the mesophase microspheres. Mesophase microspheres can be isolated as insoluble in a solvent such as quinoline, etc. In the first aspect of the present invention, dispersible carbonaceous particles obtained from petroleum pitches or coal pitches can be preferably used.

#In the second aspect of the present invention, petroleum pitches, coal pitches, carbides of polyacrylonitrile, etc., which can be readily made into fibers, are preferable as carbonaceous particles, and particularly petroleum pitches and coal pitches are preferable.

#In the first aspect of the present invention, dispersible carbonaceous particles can be oxidized according to well known oxidation procedures. For example, the dispersible carbonaceous particles can be slowly oxidized with an oxidizing gas such as oxygen, ozone, air, nitrogen oxides, halogen, sulfur dioxide gas, etc. in a gas phase or in a liquid phase using a hydrocarbon solvent at a temperature of 20.degree. to 400.degree. C., preferably 20.degree. to 350.degree. C. usually for 0.1 minute to 5 hours. The oxidation-treated dispersible carbonaceous particles of the first aspect of the present invention has an oxygen concentration of 0.3% by weight or more, preferably 0.5 to 25% by weight, and an oxygen concentration on the particle surface being at least 1.3 times, preferably 1.5 to 80 times, that in the particle interior. Below 0.3% by weight, a high electrorheological effect is hard to obtain, whereas above 25% by weight the current is easy to pass, resulting in a risk of short circuit. When the oxygen concentration on the particle surface is less than 1.3 times that in the particle interior, a high electrorheological effect is hard to obtain, whereas when it exceeds 80 times a stable electrorheological effect is hard to obtain.