Polyethylene composition for drip irrigation pipes or tapes

1. Pellets comprising a polyethylene composition, the polyethylene composition comprising:

a) at least 60.0 wt. % of a multimodal ethylene polymer (a), based on the total weight (100.0 wt. %) of the polyethylene composition, and

b) from 0.5 to 13.0 wt. % of carbon black product (b), based on the total weight (100.0 wt. %) of the polyethylene composition,

wherein the polyethylene composition has

i) a MFR 2 (ISO 1133, 2.16 kg load) of 0.2 to 0.3 g/10 min, and

ii) a density measured according to ASTM D792 of at least 959 kg/m 3 .

2. The pellets according to claim 1 , wherein the multimodal ethylene polymer (a) has:

a) a density measured according to ASTM D792 in the range from 950 to 965 kg/m 3 , and/or

b) a MFR 2 (ISO 1133, 2.16 kg load) of 0.2 to 0.3 g/10 min, and/or

c) a MFR 5 (ISO 1133, 5 kg load) of 0.5 to 1.5 g/10 min, and/or

d) a MFR 21 (ISO 1133, 21.6 kg load) of 20 to 35 g/10 min, and/or

e) a FRR 21/2 (ISO 1133, 21.6 kg load/2.16 kg load) of 90 to 130 g/10 min.

3. The pellets according to claim 1 , wherein the carbon black product (b) is carbon black as such or a carbon black masterbatch comprising carbon black and carrier polymer(s).

4. The pellets according to claim 1 , wherein the carbon black product (b) is carbon black as such (neat) and present in the polyethylene composition in an amount from 0.5 to 10.0 wt. %, based on the total weight (100.0 wt.-%) of the polyethylene composition, or the carbon black product (b) is a carbon black masterbatch and present in the polyethylene composition in an amount from 0.5 to 10.0 wt., based on the total weight (100.0 wt.-%) of the polyethylene composition.

5. The pellets according to claim 1 , wherein the polyethylene composition has:

a) a MFR 5 (ISO 1133, 5 kg load) of 0.5 to 1.5 g/10 min, and/or

b) a MFR 21 (ISO 1133, 21.6 kg load) of 20 to 35 g/10 min, and/or

c) a FRR 21/2 (ISO 1133, 21.6 kg load/2.16 kg load) of 100 to 140 g/10 min.

6. The pellets according to claim 1 , wherein the polyethylene composition has:

a) an eta (0.05 rad/s) of at least 51 000 Pas, and/or

b) a SHI 2.7/210 of 30 to 50, and/or

c) a die swell (190° C., 2.16 kg load) of at least 1.25.

7. The pellets according to any one of claims 1 to 6 , wherein the polyethylene composition has:

a) a stress at yield measured according to ISO 527-2 of at least 28 MPa, and/or

b) a stress at break measured according to ISO 527-2 of at least 28 MPa, and/or

c) a strain at break measured according to ISO 527-2 of at least 800%.

8. A pipe or pipe system comprising the pellets according to claim 1 .

9. The pipe or pipe system according to claim 8 , wherein the pipe or pipe system is a drip irrigation pipe or drip irrigation pipe system.

10. The pipe or pipe system according to claim 8 , wherein the pipe or pipe system has a wall thickness of less than 0.4 mm.

11. The pipe or pipe system according to claim 8 , wherein the pipe or pipe system has a wall thickness of less than 0.2 mm and a burst pressure of more than 0.26 MPa.

12. A process for the preparation of a pipe or pipe system comprising the steps of:

a) providing pellets according to claim 1 ,

b) extruding the pellets of step a), whereby a temperature profile of up to 270° C. is maintained over the length of the extruder, such as to obtain a pipe or pipe system,

c) introducing perforations for irrigation into the pipe or pipe system obtained in step b).

13. The process according to claim 12 , wherein the line speed is in the range from 190 to 280 m/min.

14. The process according to claim 12 , wherein the pellets of step a) are prepared by compounding the multimodal ethylene polymer (a) and the carbon black product (b) at a temperature profile of up to 270° C.

15. The process according to claim 14 , wherein the multimodal ethylene polymer (a) is prepared by

i) polymerizing ethylene such as to form a LMW component (A), and

ii) polymerizing ethylene and optionally at least one C3-20 alpha olefin comonomer in the presence of component (A) obtained in step i) such as to form a HMW component (B), and

iii) compounding the product obtained in step ii) to yield pellets.