Process for preparation of olefin polymers

A preparation method of olefin polymer from olefin monomer using a catalyst composition comprising a transition metal compound and one or more of cocatalyst compounds represented by the following Formulae 6 and 7, wherein the preparation method comprises a step of introducing a scavenger to a reactor in the amount of 0.443 to 3.103 times the total content of water, expressed as a molar ratio, and the scavenger comprises a compound represented by Formula 1:

• D(R)3 Formula 1
• wherein, R's are the same as or different from each other, and are each independently halogen;
• a hydrocarbon having 1 to 20 carbon atoms;
• or a hydrocarbon having 1 to 20 carbon atoms which is substituted by halogen;
• and D is aluminum;
• D(R8)3 Formula 6
• wherein, R8's are the same as or different from each other, and are each independently a halogen;
• a hydrocarbon having 1 to 20 carbon atoms;
• or a hydrocarbon having 1 to 20 carbon atoms which is substituted with halogen;
• D is boron;
• [L-H]+[BA4]− or [L]+[BA4]− Formula 7
• wherein, L is a neutral Lewis base;
• [L-H]+ is a cationic conjugate acid of Lewis base L;
• H is a hydrogen atom;
• and A's are the same as or different from each other, and are each independently an aryl radical having 6 to 20 carbon atoms, or an alkyl radical having 1 to 20 carbon atoms, at which at least one hydrogen atom is substituted with halogen, an alkoxy, phenoxy or hydrocarbon, having 1 to 20 carbon atoms;
• wherein the olefin polymer is produced by a continuous solution polymerization process, a solvent is used in the continuous solution polymerization process, the scavenger is mixed with the solvent, and then the mixture of the scavenger and the solvent is injected to the reactor separately from the catalyst composition comprising the transition metal compound;
• and
• based on the scavenger to water molar ratio, the olefin conversion rate is 89.65 wt % to 93.14 wt %.