Patent ID: 7601423

Claim:
Ethylene-based polymer microparticles obtained by a process comprising polymerizing ethylene alone or ethylene with at least one monomer selected from linear or branched α-olefins having 3 to 6 carbon atoms, cycloolefins, polar group-containing olefins, dienes, trienes, and aromatic vinyl compounds, in the presence of a polymerization catalyst component comprising a solid catalyst component, wherein the solid catalyst component comprises a transition metal compound or a liquid titanium compound, which compound being supported on non-agglomerated spherical magnesium-containing microparticles, wherein the non-agglomerated spherical magnesium-containing microparticles contain a magnesium atom, an aluminum atom, and an alkoxy group having 1 to 20 carbon atoms, wherein the non-agglomerated spherical magnesium-containing microparticles are insoluble in hydrocarbon solvents, wherein the non-agglomerated spherical magnesium-containing microparticles have a median diameter (d 50 ) measured by laser diffraction scattering of 0.1 μm≦d 50 ≦5 μm, and a variation coefficient of particle diameter (Cv) or 20% or less, and wherein the ethylene-based polymer microparticles have properties (A) to (E) below simultaneously: (A) the intrinsic viscosity [η] measured in decalin at 135° C. is in the range of 0.1 to 50 dl/g, (B) at least 95 wt % or more of particles pass through a mesh screen having an opening of 37 μm, (C) the median diameter (d 50 ) measured by laser diffraction scattering is 3 μm≦d 50 ≦25 μm, (D) the circularity coefficient is 0.85 or more, and (E) the variation coefficient of particle diameter (Cv) is 20% or less.