Polymer composition suitable for gamma-ray sterilization
The present invention is directed to a polymer composition (C) comprising a first propylene homopolymer (H-PP), at least one hydrocarbon oil, at least one nucleating agent and at least one antioxidant, a moulded article formed from said polymer composition, a process for gamma-ray sterilization of said moulded article and uses of hydrocarbon oil in said polymer composition for improving resistance to gamma-ray radiation and reducing discoloration after gamma-ray sterilization in said polymer composition.
1. A polymer composition (C), comprising, based on the total weight of the polymer composition (C):
(a) 91.0 to 98.0 wt.-% of a propylene homopolymer (H-PP),
(b) 1.98 to 8.98 wt.-% of at least one hydrocarbon oil (WO),
(c) 0.01 to 0.7 wt.-% of at least one nucleating agent (NA), and
(d) 0.01 to 2.0 wt.-% of at least one antioxidant (AO);
wherein the sum of components (a), (b), (c) and (d) adds up to at least 95 wt.-% of the total weight of the polymer composition (C) and the propylene homopolymer (H-PP) is an isotactic propylene homopolymer defined by
(i) a melt flow rate MFR2 determined according to IS01133 at 230 ° C. and 2.16 kg in the range from 4.0 to 22.0 g/10 min;
(ii) a melting temperature in the range of 145 to 162° C. as determined by differential scanning calorimetry (DSC); and
(iii) a content of 2,1 erythro regio-defects in the range from 0.1 to 1.3 mol % as determined by 13C-NMR spectroscopy.
2. The polymer composition (C) according to claim 1 , having a melt flow rate MFR2 determined according to IS01133 at 230° C. and 2.16 kg in the range from 5.0 to 25.0 g/10 min.
3. The polymer composition (C) according to claim 1 , wherein the propylene homopolymer (H-PP) has a polydispersity (Mw/Mn) in the range from 2.0 to 4.5 as determined by GPC according to ISO 16014.
4. The polymer composition (C) according to claim 1 , wherein the propylene homopolymer (H-PP) is prepared in the presence of a metallocene catalyst.
5. The polymer composition (C) according to claim 1 , wherein the propylene homopolymer (H-PP) is characterized by a high isotacticity, defined as pentad regularity <mmmm> of more than 96.0 mol % as determined by 13C-NMR spectroscopy.
6. A moulded article comprising at least 90 wt. % of the polymer composition (C) as defined in claim 1 , based on the total weight of the moulded article.
7. The moulded article according to claim 6 being a medical, pharmaceutical or diagnostic article.
8. The moulded article according to claim 6 , which has been gamma-ray sterilized at a dose of at least 15 kGy.
9. The moulded article according to claim 6 , having an overall migration in the polymer composition (C) as determined according to EN ISO 1186-14:2002 on injection moulded plaques, 60×60×1 mm 3 of less than 60.0 mg/dm 2 .
10. The moulded article according to claim 6 , having a discoloration of the polymer composition (C) after gamma-ray sterilization at 50 kGy and 60 days of aging as defined by yellowness index of not higher than 23 as determined on injection moulded plaques 60×60×1 mm 3 according to standard method ASTM E313.
11. The moulded article according to claim 6 , having a Charpy notched impact strength in the range of 2.5 to 15.0 kJ/m 2 , as determined according to ISO 179 1 eA, and a retention of said impact strength after gamma-ray sterilization at 50kGy and 60 days of aging of more than 75%.
12. A process for gamma-ray sterilization of articles comprising the steps of:
providing the moulded article as defined by claim 6 , and
subjecting said moulded article to gamma-ray sterilization.
13. The process according to claim 12 , wherein the gamma-ray sterilization is carried out at a dose in the range of 15 to 150 kGy.