Advanced transition metal catalytic systems in terms of comonomer incorporations and methods for preparing ethylene homopolymers or copolymers of ethylene and a-olefins using the same

Abstract

Provided is a homogeneous catalytic system for use in preparing an ethylene homopolymer or a copolymer of ethylene and α-olefin, and more particularly a Group 4 transition metal compound in which a cyclopentadienyl derivative 3,4-positions of which are substituted with alkyls and an electron-donating substituent are crosslinked around a Group 4 transition metal. Also provided is a method of preparing an ethylene homopolymer or a copolymer of ethylene and α-olefin, having high molecular weight, under high-temperature solution polymerization conditions using the catalytic system including such a transition metal compound and a co-catalyst composed of an aluminum compound, a boron compound or a mixture thereof. The catalyst according to present invention has high thermal stability and enables the incorporation of α-olefin, and is thus effective in preparing an ethylene homopolymer or a copolymer of ethylene and α-olefin, having various properties, in industrial polymerization processes.

1 . A transition metal compound represented by Chemical Formula 1 below: 
       
         
           
           
               
               
           
         
         [wherein, M is a Group 4 transition metal of the periodic table; 
         R 1  and R 2  are a (C1-C7) alkyl group; 
         D is —O—, —S—, —N(R 5 )— or —P(R 6 )—, in which R 5  and R 6  are independently a hydrogen atom, a (C1-C20) alkyl group, a (C3-C20) cycloalkyl group, a (C6-C30) aryl group, a (C6-C30) aryl(C1-C20) alkyl group, a (C1-C20) alkylcarbonyl group, or a (C3-C20) cycloalkylcarbonyl group; 
         R 3  and R 4  are independently a hydrogen atom, a (C1-C20) alkyl group, a (C6-C30) aryl group, a (C6-C30) aryl(C1-C20) alkyl group, a (C1-C20) alkoxy group, or a (C1-C20) alkyl or (C3-C20) cycloalkyl substituted siloxy group; 
         X is independently a halogen atom, a (C1-C20) alkyl group, a (C6-C30) aryl group, a (C6-C30) aryl(C1-C20) alkyl group, a (C1-C20) alkoxy group, a (C1-C20) alkyl or (C3-C20) cycloalkyl substituted siloxy group, a (C1-C20) alkyl, (C6-C30) aryl, (C6-C30) aryl(C1-C20) alkyl or tri(C1-C20) alkylsilyl substituted amino group, a (C1-C20) alkyl, (C6-C30) aryl, (C6-C30) aryl(C1-C20) alkyl or tri(C1-C20) alkylsilyl substituted amide group, a (C1-C20) alkyl, (C6-C30) aryl, (C6-C30) aryl(C1-C20) alkyl or tri(C1-C20) alkylsilyl substituted phosphine group, or a (C1-C20) alkyl, (C6-C30) aryl, (C6-C30) aryl(C1-C20) alkyl or tri(C1-C20) alkylsilyl substituted phosphido group, in which the case where X is a cyclopentadienyl derivative is excluded; 
         the alkyl group of R 1  and R 2 , the alkyl group, aryl group, arylalkyl group and alkoxy group of R 3  and R 4 , the alkyl group, cycloalkyl group, aryl group, arylalkyl group, alkylcarbonyl group and cycloalkylcarbonyl group of R 5  and R 6 , the alkyl group, aryl group, arylalkyl group and alkoxy group of X may be further substituted with one or more selected from among a (C1-C20) alkyl group, a (C3-C20) cycloalkyl group, a (C6-C30) aryl group, and a (C6-C30) aryl(C1-C20) alkyl group; and 
         n is an integer of 1˜4]. 
       
     
     
         2 . The transition metal compound of  claim 1 , wherein the M is titanium, zirconium, or hafnium. 
     
     
         3 . The transition metal compound of  claim 1 , wherein the R 1  and R 2  are independently selected from among a methyl group, an ethyl group, a n-propyl group, an isopropyl group, a n-butyl group, a sec-butyl group, a tert-butyl group, and a n-pentyl group. 
     
     
         4 . The transition metal compound of  claim 1 , wherein the R 5  and R 6  are independently selected from among a methyl group, an ethyl group, a n-propyl group, an isopropyl group, a sec-butyl group, a tert-butyl group, a cyclohexyl group, a dicyclohexylmethyl group, an adamantyl group, a phenyl group, a phenylmethyl group, a methylcarbonyl group, an ethylcarbonyl group, a n-propylcarbonyl group, an isopropylcarbonyl group, a tert-butylcarbonyl group, and an adamantylcarbonyl group. 
     
     
         5 . A transition metal catalyst composition for preparing an ethylene homopolymer or a copolymer of ethylene and α-olefin, comprising the transition metal compound of  claim 1 ; and a co-catalyst selected from among an aluminum compound, a boron compound, and mixtures thereof. 
     
     
         6 . The transition metal catalyst composition of  claim 5 , wherein the aluminum compound is a co-catalyst comprising one or more selected from aluminoxane and organic aluminum, and is selected from among methylaluminoxane, modified methylaluminoxane, tetraisobutylaluminoxane, trialkylaluminum, dialkylaluminum chloride, alkylaluminium dichloride, dialkylaluminum hydride and mixtures thereof; and the boron compound is selected from among N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate, triphenylmethyl tetrakis(pentafluorophenyl)borate, and mixtures thereof. 
     
     
         7 . The transition metal catalyst composition of  claim 5 , wherein as a ratio of transition metal compound to co-catalyst, a molar ratio of transition metal (M) to aluminum atom (Al) is 1:50˜5,000. 
     
     
         8 . The transition metal catalyst composition of  claim 5 , wherein as a ratio of transition metal compound to co-catalyst, a molar ratio of transition metal (M) to boron atom (B) to aluminum atom (Al) is 1:0.5˜5:25˜500. 
     
     
         9 . A method of preparing an ethylene homopolymer or a copolymer of ethylene and α-olefin using the transition metal catalyst composition of  claim 5 , wherein a comonomer which is polymerized with ethylene is one or more selected from among propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene, 1-undecene, 1-dodecene, 1-tetradecene, 1-hexadecene, and 1-itocene, and the copolymer of ethylene and α-olefin has an ethylene content of 50 wt % or more. 
     
     
         10 . The method of  claim 9 , wherein a pressure of the ethylene in a reactor is 6˜150 atom, and a polymerization temperature is 60˜250° C. 
     
     
         11 . The method of  claim 9 , wherein the copolymer has a weight average molecular weight of 80,000˜500,000 and a molecular weight distribution (Mw/Mn) of 1.5˜4.1. 
     
     
         12 . An ethylene homopolymer or a copolymer of ethylene and α-olefin, prepared using the transition metal compound of  claim 1  as a catalyst. 
     
     
         13 . An ethylene homopolymer or a copolymer of ethylene and α-olefin, prepared using the transition metal catalyst composition of  claim 5 .