Maleated polypropylenes and processes for the preparation thereof

Abstract

Disclosed are methods for advantageously producing maleated polypropylenes having a relatively high percentage of bound maleic anhydride, based on the total amount of maleic anhydride moieties present in the grafting reaction product, and the maleated polypropylenes produced therefrom. The methods produce maleated polypropylenes wherein at least about 60% of the maleic anhydride moieties in the grafting reaction product are bound to the polypropylene.

1 . A maleic anhydride grafting process comprising: 
 providing a molten polyolefin wax having a backbone of polypropylene or derived from polypropylene, wherein said polyolefin wax has an average molecular weight (Mw) of no greater than about 50,000;    adding maleic anhydride to said molten polyolefin wax to form a melt reaction mixture; and    maintaining said reaction mixture at a temperature greater than the peak melt point of the polyolefin wax and less than about 200° C. until at least about 60% of said maleic anhydride, based upon the total amount of maleic anhydride in the grafting reaction product, is bound to the polymer backbone.    
   
   
       2 . The maleic anhydride grafting process according to  claim 1  wherein said polyolefin wax has a molecular weight (Mw) of no greater than about 25,000.  
   
   
       3 . The maleic anhydride grafting process according to  claim 1  wherein said polyolefin wax has a molecular weight (Mw) of about 10,000 to about 20,000.  
   
   
       4 . The maleic anhydride grafting process according to  claim 1  further comprising adding a catalyst to said molten polyolefin wax.  
   
   
       5 . The maleic anhydride grafting process according to  claim 4  wherein said catalyst is selected from the group consisting of dialkyl peroxides, butyl peroxides, tertiary butyl hydroperoxide, cumene hydroperoxide, p-menthane peroxide, and p-menthane hydroperoxide.  
   
   
       6 . The maleic anhydride grafting process according to  claim 5  wherein said catalyst is added to said wax concurrently with said addition of said maleic anhydride.  
   
   
       7 . The maleic anhydride grafting process according to  claim 6  wherein said catalyst is added at a rate of about 0.01 to about 3 weight percent per hour based upon the weight of the melt reaction mixture.  
   
   
       8 . The maleic anhydride grafting process according to  claim 1  wherein said polyolefin wax is a crystallizable poly-alpha-olefin.  
   
   
       9 . The maleic anhydride grafting process according to  claim 8  wherein said crystallizable poly-alpha-olefin is selected from homopolymers and copolymers of ethylene, propylene, 1-butene, 4-methyl-1-pentene, 3-methyl-1-butene, 4,4-dimethyl-1-pentene, 3-methyl-1-pentene, 4-methyl-1-hexene, 5-ethyl-1-hexene, 6-methyl-1-heptene, 1-hexene, 1-heptene, 1-octene, 1-nonene, and 1-decene.  
   
   
       10 . The maleic anhydride grafting process according to  claim 1  wherein said polyolefin wax is selected from polypropylene and copolymers of propylene and ethylene wherein said ethylene has a concentration by weight of less than about 10%.  
   
   
       11 . The maleic anhydride grafting process according to  claim 1  wherein said polyolefin wax has a peak melt point of about 100° C. to about 150° C.  
   
   
       12 . The maleic anhydride grafting process according to  claim 1  wherein said polyolefin wax has a viscosity of no greater than about 2,500 cps at 190° C.  
   
   
       13 . The maleic anhydride grafting process according to  claim 1  wherein said reaction mixture is maintained at a temperature of about 180° C. to about 190° C. until at least about 60% of said maleic anhydride, based upon the total amount of maleic anhydride in the grafting reaction product, is bound to the polymer backbone.  
   
   
       14 . The maleic anhydride grafting process according to  claim 1  wherein said maleic anhydride is added to said molten polyolefin wax at a rate sufficient to maintain the concentration of unreacted maleic anhydride in the melt reaction mixture less than about 2.5 weight percent based upon the weight of the reaction mixture during at least 50% of the grafting process  
   
   
       15 . The maleic anhydride grafting process according to  claim 1  wherein said polyolefin wax and said maleic anhydride are combined in a weight ratio of from about 5:1 to about 40:1, respectively.  
   
   
       16 . The maleic anhydride grafting process according to  claim 1  wherein said process is a batch process and said maleic anhydride is added at a rate of less than 0.045 pounds per pound of polyolefin wax per hour.  
   
   
       17 . A maleated polypropylene reaction product prepared by: 
 providing a molten polyolefin wax having a backbone of polypropylene or derived from polypropylene, wherein said polyolefin wax has an average molecular weight (Mw) of no greater than about 50,000;    adding maleic anhydride to said molten polyolefin wax to form a melt reaction mixture; and    maintaining said reaction mixture at a temperature greater than the peak melt point of the polyolefin wax and less than about 200° C. until at least about 60% of said maleic anhydride, based upon the total amount of maleic anhydride in the grafting reaction product, is bound to the polymer backbone.    
   
   
       18 . The maleated polypropylene reaction product of  claim 17  wherein said polyolefin wax has a molecular weight (Mw) of no greater than about 25,000.  
   
   
       19 . The maleated polypropylene reaction product of  claim 18  wherein said polyolefin wax has a molecular weight (Mw) of about 10,000 to about 20,000.  
   
   
       20 . The maleated polypropylene reaction product of  claim 17  wherein said reaction mixture is maintained at a temperature of about 180° C. to about 190° C. until at least about 60% of said maleic anhydride, based upon the total amount of maleic anhydride in the grafting reaction product, is bound to the polymer backbone.