Polyethylene blend component and blends containing the same

1. A polymer blend comprising:

(a) 5 to 60 wt. % of a low-density polyethylene, having:

a melt MFR 2 of 2.5 to 10.0 g/10 min index;

a density of 910 to 935 kg/m 3 , and

a dynamic viscosity η 0.05 at a shear rate of 0.05 rad/s and a dynamic viscosity η 300 at a shear rate of 300 rad/s which satisfy the following relationship:

η 300 ≦108 Pa*s+0.0253*η 0.05

 and

(b) 40 to 95 wt % of a multimodal linear low density polyethylene prepared in the presence of a transition metal catalyst and which comprises:

30 to 70 wt %, based on the total multimodal linear low density ethylene polymer, of a low molecular weight component having a density of from 930 to 950 kg/m 3 , and

70 to 30 wt %, multimodal linear low density ethylene polymer, of a high molecular weight component having a density of from 880 to 915 kg/m 3 .

2. A polymer blend comprising:

(a) 5 to 60 wt. % of a low-density polyethylene, having:

a melt index MFR 2 of 2.5 to 10.0 g/10 min,

a density of 910 to 935 kg/M 3 , and

a phase shift δ 0.5 at a frequency of 0.5 rad/s and a, phase shift δ 300 at a frequency of 300 rad/s, which satisfy the following relationship:

tan δ 300 ≧0.45+0.164*tan δ 0 . . . 5

 and

(b) 40 to 95 wt % of a multimodal linear low density polyethylene prepared in the presence of a transition metal catalyst and which comprises:

30 to 70 wt %, based on the total multimodal linear low density ethylene polymer, of a low molecular weight component having a density of from 930 to 950 kg/m 3 , and

70 to 30 wt %, multimodal linear low density ethylene polymer, of a high molecular weight component having a density of from 880 to 915 kg/m 3 .

3. The polymer blend of claim 1 , wherein the low-density polyethylene, simultaneously satisfies the following relationships:

η 300 ≦108 Pa*s 0.0253*η 0.05 , and

tan δ 300 ≧0.45+0.164*tan δ 0 . . . 5 .

4. The polymer blend according to claim 1 , wherein the low-density polyethylene has a melt index MFR 2 is within the range of 2.5 to 6.5 g/10 min.

5. The polymer blend according to claim 1 , wherein the low-density polyethylene has a dynamic viscosity η 0.05 at a shear rate of 0.05 rad/s is within the range of 1000 to 10000 Pa*s.

6. The polymer blend according to claim 1 , wherein the low-density polyethylene has a tan δ 0.5 at a frequency of 0.5 rad/s within the range of 1.5 to 3.0.

7. The polymer blend according to claim 1 , wherein the low-density polyethylene has a tan δ 300 at a frequency of 300 rad/s within the range of 0.8 to 1.0.

8. The polymer blend according to claim 1 , wherein the low-density polyethylene has a shear thinning index SHI 1/100 of 20 to 60.

9. The polymer blend according to claim 1 , wherein the low-density polyethylene has a number average molecular weight M n of 8000 to 30000 g/mol.

10. The polymer blend according to claim 1 , wherein the low-density polyethylene has a weight average molecular weight M n of 400000 to 600000 g/mol.

11. The polymer blend according to claim 1 , wherein the low-density polyethylene has a z-average molecular weight M z of 2000000 to 4000000 g/mol.

12. The polymer blend according to claim 1 , wherein the low-density polyethylene has a molecular weight distribution M w /M n of 20 to 50.

13. The polymer blend according to claim 1 , wherein the low-density polyethylene has a storage modulus G′(5 kPa), measured at a loss modulus G″ of 5 kPa, within the range of 3000 to 3600 Pa.

14. The polymer blend according to claim 1 , wherein the multimodal linear low density polyethylene has a melt index MFR 2 of from 3 to 40 g/10 min.

15. The polymer blend according to claim 1 , wherein the multimodal linear low density polyethylene has a density from 900 to 935 kg/m 3 .

16. The polymer blend according to claim 1 , wherein the multimodal linear low density polyethylene has been produced by polymerising ethylene and at least one alpha-olefin comonomer having from 4 to 10 carbon atoms in the presence of a single site polymerisation catalyst.

17. The polymer blend according to claim 1 , wherein the blend has a value of the dynamic viscosities η 300 and η 0.5 meeting the following condition: η 300 ≦0.233·n 0.5 +50.

18. The polymer blend according to claim 1 , wherein the blend has a value of tan δ 0.5 of about 10 or less.

19. The polymer blend according to claim 1 , wherein the blend has a value of tan δ 300 of about 2.0 or less.

20. The polymer blend according to claim 1 , wherein the blend has a density within the range from 900 kg/m 3 to 965 kg/m 3 .

21. The polymer blend according to claim 1 , wherein the density, ρ, and the inciting temperature, T m , of the blend satisfy the following relationship:

T m ≧1.6·ρ−1360.

22. A polymer blend, comprising:

5 to 60 wt % of a low-densitypolyethylene, having:

a melt MFR 2 of 2.5 to 10.0 g/10 min index;

a density of 910 to 935 kg/m 3 , and

a dynamic viscosity η 0.0 at a shear rate of 0.05 rad/s and a dynamic viscosity η 300 at a shear rate of 300 rad/s which satisfy the following relationship:

η 300 ≦108 Pa*s+0.0253*η 0.05 , and

40 to 95 wt % of the multimodal linear low density polyethylene comprising:

a) a low molecular weight fraction having a lower molecular weight and a lower amount of alpha-olefin comonomers than the multimodal linear low density polyethylene, and

b) a high molecular weight fraction having a higher molecular weight and a higher amount of alpha-olefin comonomers than the multimodal linear low density polyethylene,

wherein the multimodal linear low density ethylene polymer has been produced by polymerising ethylene and at least one alpha-olefin comonomer in the presence of a single site polymerisation catalyst; and

wherein the blend has a density within the range from 900 kg/m 3 to 965 kg/m 3 , an MFR 2 of from 2 to 50 g/10 min, and a value of the dynamic viscosities η 300 and η 0.5 meeting the following condition: η 300 ≦0.233·η 0.5 +50.

23. A process for the preparation of the polymer blend according to claim 1 , wherein the low-density polyethylene is polymerized in a high pressure process and blended with the multimodal linear low density polyethylene.

24. The process according to claim 23 , wherein the polymerization reactor comprises at least two reaction zones and one or more initiators are separately fed to at least two of these reaction zones.

25. The process according to claim 24 , wherein 50 to 80 wt % of the initiator(s) are fed into a first reaction zone and 50 to 20 wt % of the initiator(s) are fed into a second reaction zone which is located downstream from the first reaction zone.

26. The process according to claim 24 , wherein the one or more initiators are selected from peroxides.

27. Extrusion coating comprising the polymer blend according to claim 1 .