Polyolefins and methods to produce polyolefins having increased melt properties at low shear rates

Abstract

This invention relates to a method for increasing melt properties such as melt strength, melt viscosity, hot tack and processability of a polyolefin by combining a networking agent with a polyolefin preferably by combining substituted or unsubstituted sorbitol or isomers or derivatives thereof with a polyolefin.

I claim: 
     
       1. A method to increase low shear rate melt viscosity of a polyolefin having a molecular weight distribution of 3 or less, said method comprising blending said polyolefin with 0.005 weight percent to 1.0 weight percent of dibenzylidene sorbitol, based upon the weight of the polyolefin to form a blend, wherein the melt viscosity of the blend as compared to the polyolefin is increased by at least about 50 percent at deformation rates of 1 sec -1  or less and by 10 percent or less at deformation rates of greater than about 100 sec -1  or more. 
     
     
       2. The method of claim 1 wherein the polyolefin is a polymer of one or more C 2  to C 30  alpha-olefins. 
     
     
       3. The method of claim 2 wherein the polyolefin is a homopolymer or copolymer of ethylene. 
     
     
       4. The method of claim 2 wherein the polyolefin is a copolymer of ethylene and hexene. 
     
     
       5. The method of claim 3 wherein the dibenzylidene sorbitol is present at about 0.01 weight percent to about 0.8 weight percent based upon the weight of the polyolefin. 
     
     
       6. The method of claim 3 wherein the dibenzylidene sorbitol is present at about 0.2 weight percent to about 0.6 weight percent based upon the weight of the polyolefin. 
     
     
       7. The method of claim 3 wherein the polyolefin has a composition distribution breadth index of 50% or more. 
     
     
       8. The method of claim 2 wherein the polyolefin is a homopolymer or copolymer of propylene. 
     
     
       9. The method of claim 3 wherein the polyolefin has a composition distribution breadth index of 60% or more. 
     
     
       10. The method of claim 3 wherein the polyolefin has a composition distribution breadth index of 70% or more.