Elastic substantially linear ethylene polymers

Abstract

Elastic ethylene polymers are disclosed which have processability similar to highly branched low density polyethylene (LDPE), but the strength and toughness of linear low density polyethylene (LLDPE). The polymers have processing indices (PI's) less than or equal to 70 percent of those of a comparative linear ethylene polymer and a critical shear rate at onset of surface melt fracture of at least 50 percent greater than the critical shear rate at the onset of surface melt fracture of a traditional linear ethylene polymer at about the same I 2 and M w /M n . The novel polymers can also have from about 0.01 to about 3 long chain branches/1000 total carbons and have higher low/zero shear viscosity and lower high shear viscosity than comparative linear ethylene polymers. The novel polymers can also be characterized as having a melt flow ratio, I 10 /I 2 ,≧5.63, a molecular weight distribution, M w /M n , defined by the equation: M w /M n ≦(I 10 /I 2 )−4.63, a critical shear stress at onset of gross melt fracture greater than about 4×10 6 dyne/cm 2 , and a single DSC melt peak between −30 C. and 150 C.

We claim:  
     
         1 . An ethylene polymer having: 
 a) a melt flow ratio, I 10 /I 2 ,≧5.63,    b) a molecular weight distribution, M w /M n , defined by the equation:     M   w   /M   n #( I   10   /I   2 )≦4.63,   and    c) a critical shear stress at onset of gross melt fracture greater than about 4×10 6  dyne/cm 2 , and    d) a single melting point as determined by differential scanning calorimetry between −30 C. and 150 C.    
     
     
         2 . An ethylene polymer having: 
 a) a melt flow ratio, I 10 /I 2 ,≧5.63,    b) a molecular weight distribution, M w /M n , defined by the equation:     M   w   /M   n #( I   10   /I   2 )≦4.63,   and    c) a critical shear rate at onset of surface melt fracture at least 50 percent greater than the critical shear rate at the onset of surface melt fracture of a linear ethylene polymer having an I 2 , M w /M n  and density within ten percent of the ethylene polymer, and    d) a single melting point as determined by differential scanning calorimetry between −30 C. and 150 C.    
     
     
         3 . An ethylene polymer having: 
 a) a melt flow ratio, I 10 /I 2 ,≧5.63,    b) a molecular weight distribution, M w /M n  of from about 1.5 to about 2.5, and    c) a single melting peak as determined by DSC between −30 C. and 150 C.    
     
     
         4 . An ethylene polymer having: 
 a) a melt flow ratio, I 10 /I 2 ,≧5.63,    b) a molecular weight distribution, M w /M n  of from about 1.5 to about 2.5,    c) a critical shear rate at onset of surface melt fracture of at least 50 percent greater than the critical shear rate at the onset of surface melt fracture of a linear ethylene polymer having an I 2 , M w /M n  and density within ten percent of the ethylene polymer, and    d) a single melting point as determined by differential scanning calorimetry between −30 C. and 150 C.    
     
     
         5 . An ethylene polymer having (i) a critical shear rate at onset of surface melt fracture of at least 50 percent greater than the critical shear rate at the onset of surface melt fracture of a linear ethylene polymer having an I 2 , M w /M n  and density within ten percent of the ethylene polymer, and (ii) a single melting point as determined by differential scanning calorimetry between −30 C. and 150 C.  
     
     
         6 . An ethylene polymer characterized in that the ethylene polymer is a substantially linear ethylene polymer having: 
 (a) from about 0.01 to about 3 long chain branches/1000 total carbons and    (b) a critical shear stress at onset of gross melt fracture of greater than about 4×10 6  dyne/cm 2 , and    (c) a single melting point as determined by differential scanning calorimetry between −30 C. and 150 C.    
     
     
         7 . An ethylene polymer characterized in that the ethylene polymer is a substantially linear ethylene polymer having: 
 (a) from about 0.01 to about 3 long chain branches/1000 total carbons,    (b) a critical shear rate at onset of surface melt fracture of at least 50 percent greater than the critical shear rate at the onset of surface melt fracture of a linear ethylene polymer having an I 2 , M w /M n  and density within ten percent of the ethylene polymer, and    (c) a single melting point as determined by differential scanning calorimetry between −30 C. and 150 C.    
     
     
         8 . An ethylene polymer characterized in that the ethylene polymer is a substantially linear ethylene polymer having: 
 (a) from about 0.01 t about 3 long chain branches/1000 total carbons,    (b) a melt flow ratio, I 10 /I 2 ,≧5.63, and    (c) a molecular weight distribution, M w /M n  from about 1.5 to about 2.5, and    d) a single melting point as determined by differential scanning calorimetry between −30 C. and 150 C.    
     
     
         9 . The ethylene polymer of any of claims  1 - 8 , wherein the ethylene polymer is: 
 (A) an ethylene homopolymer, or    (B) an interpolymer of ethylene with at least one C 4 -C 18  diolefin.    
     
     
         10 . The ethylene polymer of any of claims  1 - 8 , wherein the ethylene polymer is selected from the group consisting of: 
 (A) an ethylene homopolymer, or    (B) an interpolymer of ethylene with at least one C 3 -C 20  alpha-olefin.    
     
     
         11 . The ethylene polymer of any of claims  1 - 7  in which the M w /M n  is less than about 5.  
     
     
         12 . The ethylene polymer of any of claims  1 - 7  wherein the ethylene polymer has a M w /M n  less than about 3.5.  
     
     
         13 . The ethylene polymer of any of claims  1 - 7  in which the M w /M n  is between about 1.5 and about 2.5.  
     
     
         14 . The ethylene polymer of any of claims  1 - 7  wherein the ethylene polymer has a M w /M n  from about 1.7 to about 2.3.  
     
     
         15 . The ethylene polymer of any of claims  1 - 5  wherein the ethylene polymer is a substantially linear ethylene polymer having from about 0.01 to about 3 long chain branches/1000 total carbons.  
     
     
         16 . The ethylene polymer of any of claims  1 - 8  further characterized as containing less than about 20 ppm aluminum.  
     
     
         17 . The ethylene polymer of any of claims  1 - 8  further characterized as containing less than about 10 ppm aluminum.  
     
     
         18 . The ethylene polymer of any of claims  1 - 8  further characterized as containing less than about 5 ppm aluminum.  
     
     
         19 . A process of preparing a substantially linear ethylene polymer having a melt flow ratio, I 10 /I 2 ,≧5.63, a molecular weight distribution, M w /M n , defined by the equation: 
 M w /M n ≦(I 10 /I 2 )−4.63, and a single melting point as determined by differential scanning calorimetry between −30 C. and 150 C., said process characterized by continuously contacting ethylene alone or ethylene and one or more C 3 -C 20  alpha-olefins with a catalyst composition under polymerization conditions, wherein said catalyst composition is characterized as:  
                     
  wherein:  
 M w /M n  is a metal of group 3-10, or the Lanthanide series of the Periodic Table of the Elements;  
 Cp* is a cyclopentadienyl or substituted cyclopentadienyl group bound in an O 5  bonding mode to M;  
 Z is a moiety comprising boron, or a member of group 14 of the Periodic Table of the Elements, and optionally sulfur or oxygen, said moiety having up to 20 non-hydrogen atoms, and optionally Cp* and Z together form a fused ring system;  
 X independently each occurrence is an anionic ligand group or neutral Lewis base ligand group having up to 30 non-hydrogen atoms;  
 n is 0, 1, 2, 3, or 4 and is 2 less than the valence of M; and  
 Y is an anionic or nonanionic ligand group bonded to Z and M comprising nitrogen, phosphorus, oxygen or sulfur and having up to 20 non-hydrogen atoms, optionally Y and Z together form a fused ring system, and 
 (b) an activating cocatalyst.  
 
 
     
     
         20 . The process of  claim 14  wherein (a) corresponds to the formula:  
       
         
           
           
               
               
           
         
       
       wherein: 
 R′ each occurrence is independently selected from the group consisting of hydrogen, alkyl, aryl, silyl, germyl, cyano, halo and combinations thereof having up to 20 non-hydrogen atoms;  
 X each occurrence independently is selected from the group consisting of hydride, halo, alkyl, aryl, silyl, germyl, aryloxy, alkoxy, amide, siloxy, neutral Lewis base ligands and combinations thereof having up to 20 non-hydrogen atoms;  
 Y is —O—, —S—, —NR*—, —PR*—, or a neutral two electron donor ligand selected from the group consisting of OR*, SR*, NR* 2  or PR* 2 ;  
 M is a metal of group 3-10, or the Lanthanide series of the Periodic Table of the Elements; and  
 Z is SiR* 2 , CR* 2 , SiR* 2 SiR* 2 , CR* 2 CR* 2 , CR*═CR*, CR* 2 SiR* 2 , GeR* 2 , BR*, BR* 2 ; wherein  
 R* each occurrence is independently selected from the group consisting of hydrogen, alkyl, aryl, silyl, halogenated alkyl, halogenated aryl groups having up to 20 non-hydrogen atoms, and mixtures thereof, or two or more R* groups from Y, Z, or both Y and Z form a fused ring system; and n is 1 or 2.  
 
     
     
         21 . The process of  claim 14  wherein (a) is an amidosilane or amidoalkanediyl compound corresponding to the formula:  
       
         
           
           
               
               
           
         
       
       wherein: 
 M is titanium, zirconium or hafnium, bound in an eta 5  bonding mode to the cyclopentadienyl group;  
 R′ each occurrence is independently selected from the group consisting of hydrogen, silyl, alkyl, aryl and combinations thereof having up to 10 carbon or silicon atoms;  
 E is silicon or carbon;  
 X independently each occurrence is hydride, halo, alkyl, aryl, aryloxy or alkoxy of up to 10 carbons;  
 m is 1 or 2; and  
 n is 1 or 2.  
 
     
     
         22 . The process of any of the claims  19  in which component b) is an inert, noncoordinating boron cocatalyst.  
     
     
         23 . The process of any of the claims  19  in which the cocatalyst is tris(pentafluorophenyl)borane.  
     
     
         24 . The process of any of the claims  19  wherein the process is: 
 (A) a gas phase process, or  
 (B) a suspension process, or  
 (C) a solution process, or  
 (D) a slurry process.  
 
     
     
         25 . The solution process of  claim 24  wherein the polymerization conditions comprise a reaction temperature and ethylene concentration sufficient to form the substantially linear ethylene polymer.  
     
     
         26 . The process of  claim 25  wherein the polymerization conditions comprise a reaction temperature and ethylene concentration sufficient to form a substantially linear ethylene polymer having a I 10 /I 2  of at least about 8.  
     
     
         27 . The process of  claim 26  wherein the polymerization conditions comprise a reaction temperature and an ethylene concentration sufficient to form the substantially linear ethylene polymer, wherein the polymer has a I 10 /I 2  of at least about 9.  
     
     
         28 . The product obtainable by any of the processes of claims  19 .  
     
     
         29 . A composition comprising an ethylene polymer and at least one other natural or synthetic polymer, wherein the ethylene polymer is characterized as the ethylene polymer of any of claims  1 - 8 .  
     
     
         30 . A composition comprising an ethylene polymer and at least one other natural or synthetic polymer, wherein the ethylene polymer is characterized as: 
 (A) an ethylene/alph-olefin substantially linear ethylene polymer, or    (B) a substantially linear ethylene homopolymer.    
     
     
         31 . The composition of  claim 30  wherein the synthetic polymer is a conventional Ziegler polymerized ethylene/alpha-olefin polymer.  
     
     
         32 . A fabricated article comprising an ethylene polymer, characterized in that the ethylene polymer is the ethylene polymer of any of claims  1 - 8 .  
     
     
         33 . The fabricated article of  claim 32  wherein the article is: 
 (A) a film, or  
 (B) a fiber, or  
 (C) a sheet, or  
 (D) a woven fabric, or  
 (E) a nonwoven fabric, or  
 (F) a molded article, or  
 (G) a wire and cable coating.  
 
     
     
         34 . The fabricated article of  claim 33  wherein the film is a blown film.  
     
     
         35 . The blown film of  claim 33  wherein the ethylene polymer is an ethylene/alpha-olefin copolymer having a density from 0.90 g/cm 3  to 0.92 g/cm 3 .  
     
     
         36 . The blown film of  claim 35  wherein the ethylene/alpha-olefin copolymer has a molecular weight distribution, M w /M n , from about 1.5 to about 2.5.  
     
     
         37 . The blown film of  claim 36  wherein the film has a heat seal strength equal to or higher than a film made from a heterogeneous Ziegler polymerized polymer at the same heat seal temperature, wherein the melt index, molecular weight distribution and density of the substantially linear ethylene polymer and the heterogeneous Ziegler polymerized polymer are within ten percent of one another.  
     
     
         38 . The process of any of  claim 19 , wherein the polymerization temperature is from 20 C. to 250 C., wherein the ethylene concentration is from 6.7 to 12.5 percent by weight of the reactor contents, and wherein the concentration of the substantially linear ethylene polymer is less than 5 percent by weight of the reactor contents.  
     
     
         39 . The process of  claim 38  wherein the ethylene concentration is further characterized as not more than 8 percent of the reactor contents to form a substantially linear ethylene polymer having a I 10 /I 2  of at least about 8.  
     
     
         40 . The process of  claim 38  wherein the ethylene concentration is further characterized as not more than about 6 percent of the reactor contents to form a substantially linear ethylene polymer having a I 10 /I 2  of at least about 9.  
     
     
         41 . The product obtainable by any one of the processes of claims  19 .  
     
     
         42 . A composition comprising an ethylene polymer and at least one other natural or synthetic polymer, wherein the ethylene polymer is characterized as the substantially linear ethylene polymer of any of claims  19 .  
     
     
         43 . The composition of  claim 42  wherein the synthetic polymer is a conventional Ziegler polymerized ethylene/alpha-olefin polymer.  
     
     
         44 . A fabricated article comprising an ethylene polymer, characterized in that the ethylene polymer is the substantially linear ethylene polymer of any of claims  19 .  
     
     
         45 . The fabricated article of  claim 44  wherein the article is: 
 (A) a film, or  
 (B) a fiber, or  
 (C) a sheet, or  
 (D) a woven fabric, or  
 (E) a nonwoven fabric, or  
 (F) a molded article, or  
 (G) a wire and cable coating.  
 
     
     
         46 . The fabricated article of  claim 45  wherein the film is a blown film.  
     
     
         47 . The blown film of  claim 46  wherein the substantially linear ethylene polymer is an ethylene/alpha-olefin copolymer having a density from 0.9 g/cm 2  to 0.92 g/cm 3 .  
     
     
         48 . The blown film of  claim 47  wherein the ethylene/alpha-olefin copolymer has a molecular weight distribution, M w /M n , from about 1.5 to about 2.5.  
     
     
         49 . The blown film of  claim 48  wherein the film has a heat seal strength equal to or higher than a film made from a heterogeneous Ziegler polymerized polymer at the same heat seal temperature, wherein the melt index, polydispersity and density of the substantially linear ethylene polymer and the heterogeneous Ziegler polymerized polymer are within ten percent of one another.  
     
     
         50 . The substantially linear ethylene polymer of any of claims  19  wherein the substantially linear ethylene polymer is an ethylene homopolymer.  
     
     
         51 . The substantially linear ethylene polymer of any of claims  19  wherein the substantially linear ethylene polymer is an interpolymer of ethylene with at least one a C 3 -C 20  alpha-olefin.  
     
     
         52 . The substantially linear ethylene polymer of any of claims  19  wherein the substantially linear ethylene polymer is a copolymer of ethylene and a C 3 -C 20  alpha-olefin.  
     
     
         53 . The substantially linear ethylene polymer of any of claims  19  wherein the substantially linear ethylene polymer is further characterized as a copolymer of ethylene and 1-octene.  
     
     
         54 . The polymer of any one of claims  1 - 8  in which the density is at least about 0.87 g/cm 2 .  
     
     
         55 . The polymer of any one of claims  1 - 8  in which the density is at least about 0.90 g/cm 2 .  
     
     
         56 . The polymer of any one of claims  1 - 8  in which the density do not exceed about 0.94 g/cm 2 .  
     
     
         57 . The polymer of any one of claims  1 - 8  in which the density do not exceed about 0.92 g/cm 2 .  
     
     
         58 . The polymer of any one of claims  1 - 8  further characterized as having a melt tension of at least about 2 grams.  
     
     
         59 . The polymer of any one of claims  1 - 8  further characterized as having a processing index of less than about 15 kpoise.  
     
     
         60 . The polymer of any one of claims  1 - 8  in the form of a pellet.  
     
     
         61 . The polymer of any one of claims  1 - 8  further characterized as being pelletizable at ambient temperature.  
     
     
         62 . The polymer of any one of claims  1 - 8  further characterized as being pelletizable at cool water temperatures.  
     
     
         63 . The polymer of any one of claims  1 - 8  further characterized as comprising at least one antioxidant.  
     
     
         64 . The polymer of any one of claims  1 - 8  further characterized as comprising at least one phenolic antioxidant and at least one phosphite antioxidant.