Abstract: The present invention provides acicular fine particles made up of iron and carbon, and these acicular metal iron fine particles can be prepared by contacting acicular iron carbide fine particles with a reducing agent containing no carbon atom. Further, the present invention provides a magnetic coating composition and magnetic recording medium containing the above acicular metal iron fine particles.

Abstract: An acicular fine particulate material which is coated with a compound containing at least one element selected from among elements of Groups III and IV of the Periodic Table in Periods 5 and 6, the acicular fine particulate material being one of (i) an acicular fine particulate material containing iron carbide, (ii) an acicular fine particulate material containing iron carbide, metallic iron and carbon, and (iii) an acicular fine particulate metallic iron containing carbon, is prepared by a promoted reduction reaction while being effectively prevented from sintering and consequently affords magnetic recording media having a high recording density.

Abstract: The present invention provides an acicular fine particles obtained by reducing an iron carbide starting material and containing metal iron, iron carbide and free carbon, the acicular fine particles having a mean particle size (long axis) of 0.1 to 0.5 .mu.m and an average axial ratio of 3 to 15 and containing 15 to 80 wt. % of metal iron, 10 to 75 wt. % of iron carbide and 5 to 13 wt. % of free carbon, process thereof, magnetic coating composition and magnetic recording medium containing the same.

Abstract: The present invention provides acicular particles (A) containing an iron carbide, which have (a) a free carbon content of at most 20 wt. %, and (b) and Fe.sub.5 C.sub.2 ratio(x) of at least 70% and a coercive force of 3.times.+300 to 7.times.+270 Oe, the ratio(x) being expressed by ##EQU1## where S1 is the X-ray diffraction strength of Fe.sub.5 C.sub.2, and S2 is the X-ray diffraction strength of Fe.sub.3 O.sub.4.The invention further provides particles (B) containing nickel and an iron carbide.The invention further provides acicular particles containing an iron carbide which are obtained by heating an aqueous dispersion of ferric hydroxide in an alkaline system in the presence of a water-soluble compound capable of coordinating to iron to obtain acicular .alpha.-ferric oxide and contacting the product with a carbon-containing reducing-and-carburizing agent or with a mixture of the agent and a carbon-free reducing agent, with or without contacting the product with the carbon-free reducing agent.

Abstract: A magnetic coating composition comprising acicular particles containing iron carbide and a main magnetic material.

Abstract: The present invention provides a process for preparing a magnetic coating composition with use of magnetic particles containing carbon or magnetic particles consisting primarily of an iron carbide, the process being characterized in that the process includes the step of pre-kneading the magnetic particles with an organic solvent.

Abstract: The present invention provides a process for preparing iron carbide fine particles having an average particle size (long axis) of 0.1 to 2 .mu.m and an average axial ratio of 3 to 20, which comprises,(a) optionally contacting an iron compound selected from the group consisting of iron oxyhydroxide fine particles and iron oxide fine particles with a reducing agent which does not contain carbon atom, the iron compound being, prior to the above contact, coated with iron compound or iron compound and cobalt compound, and with aluminum compound or silicon compound, and(b) contacting the iron compound of the above (a) with a reducing-and-carburizing agent containing carbon atom or a mixture thereof with a reducing agent which does not contain carbon atom.

Abstract: Fine iron carbide particles consisting essentially of iron carbide, which are characterized in that, in the step of the variation of the weight under the condition of combustion, the increase of the weight in the equilibrium after arrival at the maximum weight is 22% or less, on the basis of the weight before combustion.

Abstract: Particles containing FeC are prepared by mixing (a) a boron compound or alkaline earth metal compound with (b) iron oxyhydroxide or iron oxide particles, or coating the former compound (a) to the latter particles (b), and then carburizing the mixture or coated particles with a carburizing agent.

Abstract: The present invention provides acicular particles (A) containing an iron carbide, which have (a) a free carbon content of at most 20 wt. %, and (b) an Fe.sub.5 C.sub.2 ratio(x) of at least 70% and a coercive force of 3x+300 to 7x+270 Oe, the ratio(x) being expressed by ##EQU1## wherein S1 is the X-ray diffraction strength of Fe.sub.5 C.sub.2, and S2 is the X-ray diffraction strength of Fe.sub.3 O.sub.4. The invention further provides particles (B) containing nickel and an iron carbide. The invention further provides acicular particles containing an iron carbide which are obtained by heating an aqueous dispersion of ferric hydroxide in an alkaline system in the presence of a water-soluble compound capable of coordinating to iron to obtain acicular .alpha.-ferric oxide and contacting the product with a carbon-containing reducing-and-carburizing agent or with a mixture of the agent and a carbon-free reducing agent, with or without contacting the product with the carbon-free reducing agent.

Abstract: A process for producing cobalt-modified iron oxide particles, which comprises the steps of:(1) adding to magnetic iron oxide particles(a) a cobalt compound,(b) an iron component which is either (b.sub.1) a ferric compound at an atomic ratio to the cobalt compound in the range of 0.68 to 2 or (b.sub.2) a combination of a ferrous compound and a ferric compound, and(c) an alkali at a concentration enough to cause the cobalt and iron to precipitate as hydroxides; and(2) heating the mixture at a temperature of at least 50.degree. C. and not higher than the reflux temperature thereof in a non-oxidizing atmosphere.

Abstract: A process of electrostatic printing which comprises the steps of forming a reverse image of a dielectric toner on an electroconductive support or a photoconductive support, fixing the reverse image to give an electrostatic printing master sheet, and conducting electrostatic printing in which electrification of the dielectric toner image on the master sheet, development with a toner, transfer of the resulting toner image to a material to be printed and fixing are repeatedly carried out to give numerous sheets of duplicates.

Abstract: A polymer containing perfluoroalkyl group in its side chain which is an addition reaction product of a polymer having the following general formula: ##STR1## wherein R is phenyl group or alkoxyl group having 1 to 12 carbon atoms, R.sup.1 is alkyl group having 1 to 12 carbon atoms, and n is an integer of 10 to 2,000, with an epoxy compound selected from the group consisting of ##STR2## wherein R.sub.f is perfluoroalkyl group having 3 to 20 carbon atoms and R.sup.2 is alkyl group having 1 to 12 carbon atoms, the addition reaction product containing 0.1 to 50% by mole of the group derived from the epoxy compound having the formulae (IIa) to (IIc) per 1 mole of the recurring unit of the polymer having the formula (I). The polymer is good in compatibility with film-forming resins and solvents and improves the leveling property of a coating composition when incorporated thereinto and the surface smoothness of the film obtained from the composition.