Process for producing heterophasic copolymers of propylene

Abstract

The present invention provides a process for producing a heterophasic copolymer composition. The polymerisation is conducted in the presence of an olefin polymerisation catalyst comprising a solid catalyst component further comprising titanium, magnesium, halogen and an internal donor, and a cocatalyst, the process comprising the steps of: (1) introducing streams of the solid catalyst component, the cocatalyst, propylene monomer and hydrogen into a first polymerisation reactor; (2) producing a first polymer of propylene in the first polymerisation reactor, the first polymer of propylene having a first melt flow rate MFR 2 of from 0.1 to 2.0 g/ 10 min; (3) withdrawing a stream comprising the first polymer of propylene from the first polymerisation reactor and passing it to a second polymerisation reactor; (4) introducing a stream of propylene monomer into the second polymerisation reactor; (5) producing a first polymer mixture comprising the first polymer of propylene and a second polymer of propylene in the second polymerisation reactor, the first polymer mixture having a second melt flow rate MFR 2 of from 0.05 to 1.0 g/ 10 min and which second melt flow rate is less than the first melt flow rate; (6) withdrawing a stream comprising the first polymer mixture from the second polymerisation reactor and passing it to a third polymerisation reactor; (7) introducing streams of propylene monomer and the co-monomer into the third polymerisation reactor; (8) producing the heterophasic copolymer composition comprising the first polymer mixture and a third copolymer

What is claimed: 
     
         1 . A heterophasic copolymer obtained by a process for producing a heterophasic copolymer comprising propylene monomer and a comonomer selected from ethylene, alpha-olefins having 4 to 10 carbon atoms and their mixtures, in the presence of an olefin polymerisation catalyst that comprises a solid catalyst component and a cocatalyst, wherein the solid catalyst component comprises titanium, magnesium, halogen and an internal donor, the process comprising the steps of:
 (1) introducing streams of the solid catalyst component, the cocatalyst, propylene monomer, hydrogen and optionally comonomer into a first polymerisation reactor;   (2) producing a first polymer of propylene in the first polymerisation reactor, the first polymer of propylene having a first melt flow rate MFR2 of from 0.1 to 4.0 g/10 min;   (3) withdrawing a stream comprising the first polymer of propylene from the first polymerisation reactor and passing it to a second polymerisation reactor;   (4) introducing streams of propylene monomer and optionally hydrogen and comonomer into the second polymerisation reactor;   (5) producing a first polymer mixture comprising the first polymer of propylene and a second polymer of propylene in the second polymerisation reactor, the first polymer mixture having a second melt flow rate MFR2 of from 0.05 to 2.0 g/10 min and which second melt flow rate is less than the first melt flow rate;   (6) withdrawing a stream comprising the first polymer mixture from the second polymerisation reactor and passing it to a third polymerisation reactor;   (7) introducing streams of propylene monomer and the comonomer into the third polymerisation reactor;   (8) producing the heterophasic copolymer comprising the first polymer mixture and a third copolymer of propylene in the third polymerisation reactor, the heterophasic copolymer having a third melt flow rate MFR2 of from 0.05 to 2.0 g/10 min, said heterophasic copolymer having a content of comonomer units of from 5 to 25% by mole;   wherein the amount of xylene soluble fraction in the heterophasic copolymer determined according to ISO 16152 is from 14 to 35% by weight and intrinsic viscosity measured from the amorphous polymer (AM) of the heterophasic copolymer is from 1.5 to 4.4 dl/g; and   (9) recovering the heterophasic copolymer from the third polymerisation reactor;
 wherein the internal donor is a compound having the structure according to formula (I): 
   
       
         
           
           
               
               
           
         
         
           and wherein R1 and R2 are the same or different being a linear or branched C1-C12-alkyl group and R is hydrogen or a linear, branched or cyclic C1 to C12-alkyl; and 
         
         the heterophasic copolymer comprising 
         (A) a first polymer of propylene, selected from homopolymers of propylene and random copolymers of propylene containing from 0.1 to 5% by mole of a comonomer selected from the group consisting of ethylene, alpha-olefins having from 4 to 10 carbon atoms, and mixtures thereof and having a melt flow rate MFR2 of from 0.1 to 4.0 g/10 min; 
         (B) a second polymer of propylene, selected from homopolymers of propylene and random copolymers of propylene containing from 0.1 to 5% by mole of a comonomer selected from the group consisting of ethylene, alpha-olefins having from 4 to 10 carbon atoms, and mixtures thereof and having a melt flow rate MFR2 of from 0.05 to 0.3 g/10 min and which is less than the MFR2 of the first polymer of propylene; 
         (C) a third polymer of propylene selected from random copolymers of propylene containing from 35 to 75% by mole of units of a comonomer selected from the group consisting of ethylene, alpha-olefins having from 4 to 10 carbon atoms and mixtures thereof; 
         and wherein the heterophasic copolymer contains from 1 to 30 ppm magnesium originating from the catalyst and no phthalic acid esters originating from the catalyst. 
       
     
     
         2 . The heterophasic copolymer according to  claim 1 , wherein the compound having the structure according to formula (I) is a bis(2-ethylhexyl)citraconate. 
     
     
         3 . The heterophasic copolymer according to  claim 1 , wherein the first polymer of propylene is a homopolymer of propylene. 
     
     
         4 . The heterophasic copolymer according to  claim 1 , wherein the second polymer of propylene is a homopolymer of propylene. 
     
     
         5 . The heterophasic copolymer according to  claim 1 , wherein the first polymer mixture comprises from 35 to 60% by weight of the first polymer of propylene and from 40 to 65% by weight of the second polymer of propylene. 
     
     
         6 . The heterophasic copolymer according to  claim 1 , wherein the heterophasic copolymer comprises from 65 to 86% by weight of the first polymer mixture and from 14 to 35% by weight of the third copolymer. 
     
     
         7 . The heterophasic copolymer according to  claim 6 , wherein the heterophasic copolymer comprises from 70 to 86% by weight of the first polymer mixture and from 14 to 30% by weight of the third copolymer. 
     
     
         8 . The heterophasic copolymer according to  claim 1 , wherein the first polymerisation reactor is a loop reactor. 
     
     
         9 . The heterophasic copolymer according to  claim 1 , wherein the second polymerisation reactor is a gas phase reactor. 
     
     
         10 . The heterophasic copolymer according to  claim 1 , wherein the third polymerisation reactor is a gas phase reactor. 
     
     
         11 . The heterophasic copolymer according to  claim 1  wherein the third polymer is a copolymer of propylene and ethylene. 
     
     
         12 . The heterophasic copolymer according to  claim 11 , wherein the molar ratio of ethylene to propylene in the third polymerisation reactor is from 200 to 700 mol/kmol. 
     
     
         13 . The heterophasic polymer according to  claim 1 , wherein the heterophasic copolymer contains from 2 to 20 ppm magnesium originating from the catalyst. 
     
     
         14 . A heterophasic copolymer of propylene obtained by a process for producing a heterophasic copolymer comprising propylene monomer and a comonomer selected from ethylene, alpha-olefins having 4 to 10 carbon atoms and their mixtures, in the presence of an olefin polymerisation catalyst that comprises a solid catalyst component and a cocatalyst, wherein the solid catalyst component comprises titanium, magnesium, halogen and an internal donor,
 the process comprising the steps of:   (1) introducing streams of the solid catalyst component, the cocatalyst, propylene monomer, hydrogen and optionally comonomer into a first polymerisation reactor;   (2) producing a first polymer of propylene in the first polymerisation reactor, the first polymer of propylene having a first melt flow rate MFR 2  of from 0.1 to 4.0 g/10 min;   (3) withdrawing a stream comprising the first polymer of propylene from the first polymerisation reactor and passing it to a second polymerisation reactor;   (4) introducing streams of propylene monomer and optionally hydrogen and comonomer into the second polymerisation reactor;   (5) producing a first polymer mixture comprising the first polymer of propylene and a second polymer of propylene in the second polymerisation reactor, the first polymer mixture having a second melt flow rate MFR2 of from 0.05 to 2.0 g/10 min and which second melt flow rate is less than the first melt flow rate;   (6) withdrawing a stream comprising the first polymer mixture from the second polymerisation reactor and passing it to a third polymerisation reactor;   (7) introducing streams of propylene monomer and the comonomer into the third polymerisation reactor;   (8) producing the heterophasic copolymer comprising the first polymer mixture and a third copolymer of propylene in the third polymerisation reactor;   wherein the amount of xylene soluble fraction in the heterophasic copolymer determined according to ISO 16152 is from 14 to 35% by weight and intrinsic viscosity measured from the amorphous polymer (AM) of the heterophasic copolymer is from 1.5 to 4.4 dl/g; and   (9) recovering the heterophasic copolymer from the third polymerisation reactor;
 wherein the internal donor is a compound having the structure according to formula (I): 
   
       
         
           
           
               
               
           
         
         
           and wherein R1 and R2 are the same or different being a linear or branched C1-C12-alkyl group and R is hydrogen or a linear, branched or cyclic C1 to C12-alkyl; 
         
         said heterophasic copolymer comprising from 5 to 25% by mole of units derived from the comonomer and from 75 to 95% by mole of propylene units and being further characterized by a melt index MFR 2  of from 0.05 to 2.0 g/10 min. 
       
     
     
         15 . A pipe made of heterophasic copolymer of propylene according to  claim 1 . 
     
     
         16 . A pipe made of heterophasic copolymer of propylene according to  claim 14 .