Ethylene polymer, preparation process thereof and molded articles of the same

Abstract

The present invention provides ethylene polymers capable of preparing various molded articles such as films, sheets or the like, and having excellent moldability, particularly excellent high-speed moldability. The ethylene polymers of the present invention have a density and molecular weight distribution in specific ranges. The first ethylene polymer is characterized by having (C) a ratio (MFR 10 /MFR 2 ) of a melt flow rate (MFR 10 ) at 190° C. under a load of 10 Kg to a melt flow rate (MFR 2 ) at 190° C. under a load of 2.16 Kg of from 16.2 to 50. The second ethylene polymer is characterized by having (C) a ratio (MFR 10 /MFR 2 ) from 12 to 50. The third ethylene polymer is characterized by having (D) a relation of ω2/ω1≧18 where ω1 and ω2 denote angular velocity (rad/sec) when complex elastic modulus G* (dyne/cm 2 ) at 200° C. is 5.0×10 5 dyne/cm 2 and 2.0×10 6 dyne/cm 2 , respectively, which are determined by measurement of the angular velocity dependence of the complex elastic modulus of the copolymer.

1 . An ethylene polymer having: 
 (A) a density of from 0.930 to 0.970 g/cm 3 , (B) a ratio (Mw/Mn) of a weight average molecular weight (Mw) to a number average molecular weight (Mn), as measured by GPC, of from 1.2 to 10, and    (C) a ratio (MFR 10 /MFR 2 ) of a melt flow rate (MFR 10 ) at 190° C. under a load of 10 Kg to a melt flow rate (MFR 2 ) at 190° C. under a load of 2.16 Kg of from 16.2 to 50.    
     
     
         2 . An ethylene polymer having: 
 (A) a density of 0.921 g/cm 3  or more but less than 0.930 g/cm 3 ,    (B) a ratio (Mw/Mn) of a weight average molecular weight (Mw) to a number average molecular weight (Mn), as measured by GPC, of from 1.2 to 4.0, and    (C) a ratio (MFR 10 /MFR 2 ) of a melt flow rate (MFR 10 ) at 190° C. under a load of 10 Kg to a melt flow rate (MFR 2 ) at 190° C. under a load of 2.16 Kg of from 12 to 50.    
     
     
         3 . An ethylene polymer having: 
 (A) a density of from 0.850 to 0.970 g/cm 3 ,    (B) a ratio (Mw/Mn) of a weight average molecular weight (Mw) to a number average molecular weight (Mn), as measured by GPC, of from 1.2 to 10, and    (D) a relation of ω2/ω1≧18 where ω1 and ω2 denote angular velocity (rad/sec) when complex elastic modulus G* (dyne/cm 2 ) at 200° C. is 5.0×10 5  dyne/cm 2  and 2.0×10 6  dyne/cm 2 , respectively, which are determined by measurement of the angular velocity dependence of the complex elastic modulus of the copolymer.    
     
     
         4 . A process for preparing an ethylene polymer, which process comprises preparing said ethylene polymer in the presence of an olefin polymerization catalyst comprising an organic hafnium compound having at least one substituted cyclopentadienyl group and an organic boron compound essentially, wherein the ethylene polymer has: 
 (A) a density of from 0.850 to 0.970 g/cm 3 ,    (B) a ratio (Mw/Mn) of a weight average molecular weight (Mw) to a number average molecular weight (Mn), as measured by GPC, of from 1.2 to 10, and    (C) a ratio (MFR 10 /MFR 2 ) of a melt flow rate (MFR 10 ) at 190° C. under a load of 10 Kg to a melt flow rate (MFR 2 ) at 190° C. under a load of 2.16 Kg of from 12 to 50.    
     
     
         5 . A process for preparing an ethylene polymer, which process comprises preparing said ethylene polymer in the presence of an olefin polymeirization catalyst comprising an organic hafnium compound having at least one substituted cyclopentadienyl group and an organic boron compound essentially, wherein the ethylene polymer has: 
 (A) a density of from 0.850 to 0.970 g/cm 3 ,    (B) a ratio (Mw/Mn) of a weight average molecular weight (Mw) to a number average molecular weight (Mn), as measured by GPC, of from 1.2 to 10, and    (D) a relation of ω2/ω1≧13 where ω1 and ω2 denote angular velocity (rad/sec) when complex elastic modulus G* (dyne/cm 2 ) at 200° C. is 5.0×10 5  dyne/cm 2  and 2.0×10 6  dyne/cm respectively, which are determined by measurement of the angular velocity dependence of the complex elastic modulus of the copolymer.    
     
     
         6 . A molded article selected from the group consisting of (a) injection molded articles, (b) hollow or extrusion molded articles, (c) rotational molded articles, (d) film or sheet molded articles and (e) extrusion coating molded articles, which article comprises, as an essential component, an ethylene polymer as claimed in any one of  claims 1  to  3  or an ethylene polymer prepared by a preparation process as claimed in  claim 4  or  5 .