Impact strength polypropylene

Abstract

This invention relates to the use of a linear dialkyl peroxide having an hexyne or an hexene backbone, for producing a controlled rheology polypropylene heterophasic copolymer of melt index MI2 larger than 15 g/10 min, having simultaneously a very high impact resistance and a high flexural modulus.

1 - 18 . (canceled)  
     
     
         19 . A degraded polypropylene (co)polymer produced by degrading a precursor polypropylene copolymer with a linear dialkyl peroxide having a double or triple bond, said degraded polypropylene copolymer retaining an Izod notched impact strength larger than 20 kJ/m 2  for melt flow indices greater than 15 g/10 min. and for a degradation rate MI2 fluff /MI2 degraded  larger than 5.  
     
     
         20 . The degraded polypropylene (co)polymer of  claim 19  characterized by a degradation rate MI2 fluff /MI2 degraded  of at least 10.  
     
     
         21 . The degraded polypropylene (co)polymer of  claim 19  characterized by a degradation rate MI2 fluff /MI2 degraded  of at least 20.  
     
     
         22 . The degraded polypropylene (co)polymer of  claim 19  characterized by an Izod notched impact strength greater than 30 kJ/m 2  for melt flow indices greater than 15 g/10 min.  
     
     
         23 . The degraded polypropylene (co)polymer of  claim 19  characterized by an Izod notched impact strength greater than 40 kJ/m 2  for melt flow indices greater than 15 g/10 min.  
     
     
         24 . The degraded polypropylene (co)polymer of  claim 19  wherein said copolymer is a polypropylene heterophasic copolymer containing from 5-20 wt. % of ethylene.  
     
     
         25 . The degraded polypropylene (co)polymer of  claim 24  wherein said copolymer contains from 9 to 15 wt. % of ethylene.  
     
     
         26 . The degraded polypropylene (co)polymer of  claim 24  wherein said copolymer contains from 11 to 14 wt. % of ethylene.  
     
     
         27 . The degraded polypropylene (co)polymer of  claim 19  characterized by an impact strength when the melt flow index reaches a threshold value that increases with decreasing extrusion temperature.  
     
     
         28 . The degraded polypropylene (co)polymer of  claim 19  wherein the linear dialkyl peroxide has at least two peroxide groups and a hexene or hexyne backbone.  
     
     
         29 . The degraded polypropylene (co)polymer of  claim 28  wherein said linear dialkyl peroxide is characterized by the formula:  
       
         
           
           
               
               
           
         
       
       wherein: 
 each R is the same or different and is a hydrocarbon or a carboxy or a heteroatom, and each R′ or R″ is the same or different and is an alkyl group having one or more carbon atoms or an aryl group, provided that at least one R′ and at least one R″ is an alkyl group having one or more carbon atoms or the formula:  
                     
 wherein:  
 each R* is the same or different and is a hydrocarbon or a carboxy or a heteroatom, each R $ , R $$  or R** is the same or different and is an alkyl group having one or more carbon atoms or an aryl group provided that at least one R $  and at least one R $$  is an alkyl group having one or more carbon atoms.  
 
     
     
         30 . The degraded polypropylene (co)polymer of  claim 29  wherein the peroxide is a linear dialkyl peroxide containing at least two peroxide groups and where each of R′ and R″ or each of R**, R $  and R $$  is an alkyl group.  
     
     
         31 . The degraded polypropylene (co)polymer of  claim 30  wherein each of the substituents R′ and R″ or R**, R $  and R $$  is a methyl group and the linear dialkyl peroxide has a hexyne or a hexene backbone.  
     
     
         32 . The degraded polypropylene (co)polymer of  claim 28  wherein the linear dialkyl peroxide is 2,5-dimethyl-2,5-di(tert-butyl-peroxy)-hexyne(3).  
     
     
         33 . A process for producing a degraded polypropylene (co)polymer comprising: 
 a. providing a precursor polypropylene (co)polymer;    b. extruding said precursor polypropylene (co)polymer with a linear dialkyl peroxide having a double or triple bond in an extruder at a temperature sufficient to maintain said (co)polymer in a molten state and which does not exceed 200° C. to produce a degraded polypropylene (co)polymer having an Izod notched impact strength greater than 20 kJ/m 2  for melt flow indices greater than 15 g/10 min. and a degradation rate MI2 fluff /MI2 degraded  larger than 5; and    c. recovering said degraded polypropylene (co)polymer from said extruder.    
     
     
         34 . The process of  claim 33  wherein said extruder is operated at a temperature within the range of 160-200° C.  
     
     
         35 . The process of  claim 33  wherein said extrusion at a temperature within the range of 160-190° C.  
     
     
         36 . The process of  claim 33  wherein said polypropylene (co)polymer precursor incorporates at least one of an elastomeric modifier and a particulate filler selected from the group consisting of glass, talc, calcium carbonate, and a clay mineral.  
     
     
         37 . The process of  claim 36  wherein said (co)polymer is extruded with a filler selected from the group consisting of a glass, talc, calcium carbonate, and a clay mineral.  
     
     
         38 . The process of  claim 37  wherein the linear dialkyl peroxide has at least two peroxide groups and a hexene or hexyne backbone.  
     
     
         39 . The process of  claim 38  wherein the linear dialkyl peroxide is 2,5-dimethyl-2,5-di(tert-butyl-peroxy)-hexyne(3).