Method for producing magnesium compound particle, method for controlling shape of olefin polymer particle, and olefin polymer particle

A method for controlling the shape of an olefin polymer particle, the method comprising:

• a contact step of bringing
• (A) a magnesium-containing compound solution comprising
• (A-1) a magnesium-containing compound and
• (A-2) a compound comprising an element selected from elements in Group 15 and Group 16 of the periodic table, and
• (B) an organometallic compound comprising a metal element (MB), excluding magnesium, selected from elements in Group 1, Group 2, and Group 13 of the periodic table into contact with each other in a temperature range of −20 to 10° C.;
• and
• a step of polymerizing an olefin in the presence of an olefin polymerization catalyst comprising a magnesium compound particle having an average particle size of 0.05 to 0.90 μm produced through the contact step and a transition metal compound component to produce an olefin polymer particle,
• the method comprising controlling a ratio ([Mg]/[MB]) of a molar content [Mg] of magnesium atoms to a molar content [MB] of atoms of the metal element (MB) in the magnesium compound particle within a range of 1.0 or more and 20 or less.

An olefin polymer particle having:

• an average particle size of 3 to 25 μm,
• an intrinsic viscosity [η] at 135° C. in decalin of 5 to 50 dl/g;
• and
• a pore volume in a pore size range of 0.1 to 1 μm, as determined with a mercury porosimeter, of 25 to 100 mm3/g.