Propylene butene copolymer
The invention provides a multimodal propylene butene random copolymer having a melt flow rate (MFR2) of 1.0 to 20.0 g/10 min and a butene content of 1.5 to 8.0 wt %, wherein said copolymer is prepared using a single site catalyst and wherein said copolymer comprises (i) 30 to 70 wt % of a propylene butene copolymer (A) having an MFR2 of 0.5 to 20.0 g/10 min and a butene content of 0.5 to 10.0 wt %; and (ii) 70 to 30 wt % of a propylene butene copolymer (B) having an MFR2 of 0.5 to 20.0 g/10 min and a butene content of 1.0 to 8.0 wt %; wherein copolymers (A) and (B) are different.
1. A multimodal propylene butene random copolymer having a melt flow rate (MFR 2 ) of 1.0 to 20.0 g/10 min when determined under 2.16 kg load at 230° C. and a butene content of 1.5 to 8.0 wt %, wherein said copolymer is prepared using a single site catalyst and wherein said copolymer comprises:
(i) 30 to 70 wt % of a propylene butene copolymer (A) having an MFR 2 of 0.5 to 20.0 g/10 min when determined under 2.16 kg load at 230° C. and a butene content of 0.5 to 10.0 wt %; and
(ii) 70 to 30 wt % of a propylene butene copolymer (B) having an MFR 2 of 0.5 to 20.0 g/10 min when determined under 2.16 kg load at 230° C. and a butene content of 1.0 to 8.0 wt %;
wherein copolymers (A) and (B) are different and wherein said multimodal copolymer is substantially free of ethylene.
2. The multimodal propylene butene random copolymer as claimed in claim 1 , wherein said single site catalyst is a metallocene catalyst.
3. The multimodal propylene butene random copolymer as claimed in claim 1 , wherein the butene content of said multimodal copolymer is in the range 3.0 to 5.0 wt %.
4. The multimodal propylene butene random copolymer as claimed claim 1 , wherein a xylene soluble fraction is less than 6.0 wt % when determined at 25° C.
5. The multimodal propylene butene random copolymer as claimed in claim 1 , wherein said multimodal copolymer has a flexural modulus of at least 850 MPa.
6. The multimodal propylene butene random copolymer as claimed in claim 1 , wherein said multimodal copolymer has a molecular weight distribution (Mw/Mn) of less than 4.5.
7. The multimodal propylene butene random copolymer as claimed in claim 1 , wherein the MFR 2 of said multimodal copolymer is in the range 4.0 to 10.0 g/10 min.
8. The multimodal propylene butene random copolymer as claimed in claim 1 , wherein the comonomer content of copolymer (B) is less than the comonomer content of copolymer (A).
9. A process for the preparation of the multimodal propylene butene random copolymer as defined in claim 1 , said process comprising:
(i) polymerising propylene and butene in a first polymerisation stage in the presence of a single site catalyst to prepare a first propylene butene copolymer having a MFR 2 from 0.5 to 20.0 g/10 min when determined under 2.16 kg load at 230° C. and a butene content of 0.5 to 10.0 wt %;
(ii) polymerising propylene and butene in a second polymerisation stage in the presence of said catalyst and said first propylene butene copolymer to prepare said multimodal propylene butene copolymer.
10. The process as claimed in claim 9 , wherein the first polymerisation stage is carried out in a loop reactor and the second polymerisation stage is carried out in a gas phase reactor.
11. An article comprising the multimodal propylene butene copolymer as defined in claim 1 .
12. The article as claimed in claim 11 , wherein said article is a film.
13. The article of claim 12 , wherein the film is a monolayer film.