Propylene-ethylene random copolymer with improved irradiation resistance
The present invention deals with a new unimodal propylene-ethylene random copolymer providing improved resistance against gamma irradiation as well as compositions comprising the new unimodal propylene-ethylene random copolymer and final articles made therefrom.
1. A unimodal polypropylene random copolymer of propylene and 2.0-4.5 wt.-% of ethylene as comonomer characterised by a comonomer distribution (CD) determined via a-TREF of at most 16.0[−] and being polymerized in the presence of a Ziegler-Natta catalyst, wherein the unimodal polypropylene random copolymer has a Melt Flow Rate determined according to ISO1133 at 230° C. and 2.16 kg (MFR230/2.16) of 10.0 to 25.0 g/10 min.
2. The unimodal polypropylene random copolymer according to claim 1 further characterised by a randomness (Koenig B) of at least 0.8 [−].
3. The unimodal polypropylene random copolymer according to claim 1 , having a Melt Flow Rate determined according to ISO1133 at 230° C. and 2.16 kg (MFR230/2.16) of 15.0 to 22.0 g/10 min.
4. The unimodal polypropylene random copolymer according to claim 1 , being free of phthalic acid esters as well as their respective decomposition products.
5. The unimodal polypropylene random copolymer according to claim 1 being polymerized in the presence of a Ziegler-Natta catalyst, wherein the Ziegler Natta catalyst comprises
a) at least one compound of a transition metal of Group 4 to 6 of IUPAC,
b) a Group 2 metal compound,
c) an internal donor, wherein said internal donor is a non-phthalic compound,
d) optionally a co-catalyst, and
e) optionally an external donor.
6. The unimodal polypropylene random copolymer according to claim 5 , wherein the internal donor is selected from (di)esters of non-phthalic carboxylic (di)acids, 1,3-diethers, derivatives and mixtures thereof.
7. A moulded article comprising the unimodal propylene-ethylene random copolymer according to claim 1 .
8. The moulded article according to claim 7 wherein the moulded article is a medical, pharmaceutical or diagnostic article.
9. A method comprising sterilizing the moulded article according to claim 8 via gamma-irradiation.
10. A polypropylene random copolymer composition comprising a unimodal polypropylene random copolymer of propylene and 2.0-4.5 wt.-% of ethylene as comonomer, wherein the unimodal polypropylene random copolymer comprised by said polypropylene random copolymer composition is characterised by a comonomer distribution (CD) determined via a-TREF of at most 16.0 [−] and has a Melt Flow Rate determined according to ISO1133 at 230° C. and 2.16 kg (MFR230/2.16) of 10.0 to 25.0 g/10 min.
11. The polypropylene random copolymer composition according to claim 10 , wherein the unimodal polypropylene random copolymer comprised by said polypropylene random copolymer composition is characterised by a randomness (Koenig B) of at least 0.8 [−].
12. The polypropylene random copolymer composition according to claim 10 , characterised by a retained notched Impact Strength rNIS after irradiation with 50 kGy (rNIS(50; days)) according the formula
rNIS
(
50
;
days
)
[
%
]
=
γ
NIS
(
50
;
days
)
*
100
NIS
(
0
;
days
)
of at least 85.0%, wherein “days” is heat exposure at 80° C. for at least 60 days.
13. The polypropylene random copolymer composition according to claim 10 , comprising at least 50 wt.-% of the unimodal polypropylene random copolymer.
14. The polypropylene random copolymer composition according to claim 10 , wherein the polypropylene random copolymer composition has a Melt Flow Rate determined according to ISO1133 at 230° C. and 2.16 kg (MFR230/2.16) of 15.0-22.0 g/10 min.
15. The polypropylene random copolymer composition according to claim 12 , wherein “days” is heat exposure at 80° C. for at least 90 days.
16. A moulded article comprising the polypropylene random copolymer composition according to claim 10 .
17. The moulded article according to claim 16 , wherein the moulded article is medical, pharmaceutical or diagnostic article.
18. A method comprising sterilizing the moulded article according to claim 17 via gamma-irradiation.