Polyethylene of raised temperature resistance

1. A polyethylene composition comprising:

1) a density (ISO 1183, 23° C.) from 0.935-0.945 g/cm 3 ;

2) a melt flow index (MIF; ISO 113, 190° C., 21.60 kg) from 10-18 g/10 min;

3) a melt flow index (MIP; ISO 113, 190° C., 5 kg) from 1-2.5 g/10 min; and

4) a MIF/MIP ratio from 6-9;

5) an M w /M n ratio, where M w is the weight average molar mass and M n the numerical average molar mass, both measured by GPC (gel permeation chromatography) of 5 or more.

2. The polyethylene composition of claim 1 , prepared by using in polymerization a catalyst composition comprising at least two different single-site polymerization catalysts A) and B), of which A) is at least one metallocene polymerization catalyst and B) is at least one polymerization catalyst based on a non-metallocene transition metal complex.

3. The polyethylene composition of claim 1 , wherein the density of the polyethylene composition ranges from 0.936-0.943 g/cm 3 .

4. The polyethylene composition of claim 1 , wherein the melt flow index MIF at 190° C. with a load of 21.60 kg, determined according to ISO 113, ranges from 12-18 g/10 min.

5. The polyethylene composition of claim 1 , further comprising one or more of:

6) an intrinsic viscosity [η], determined according to ISO 1628-1 and ISO 1628-3 in decalin at 135° C. by capillary viscosity measurement, from 1.8-2.8 dl/g;

7) a substantially linear chain structure;

8) a content of vinyl groups, determined by means of infrared (IR) analysis in accordance with ASTM D 6248-98, of 0.3-0.7 vinyl groups/1000 carbon atoms; and

9) a content of vinyl groups in the polymer fraction having an intrinsic viscosity [η] of less than 0.5 dl/g and more than 0.3 vinyl groups/1000 carbon atoms.

6. The polyethylene composition of claim 5 , wherein the content of vinyl groups in the polymer fraction having an intrinsic viscosity [η] of less than 0.5 dl/g and from 0.4-0.9 vinyl groups/1000 carbon atoms.

7. The polyethylene composition of claim 5 , prepared by using in polymerization a catalyst composition comprising at least two different single-site polymerization catalysts A) and B), of which A) is at least one metallocene polymerization catalyst and B) is at least one polymerization catalyst based on a non-metallocene transition metal complex.

8. The polyethylene composition of claim 5 , wherein the M w /M n ratio ranges from 5-10.

9. The polyethylene composition of claim 8 , wherein the M w /M n ratio ranges from 5.5-8.

10. A pipe comprising the polyethylene composition of claim 1 .

11. The pipe of claim 10 , wherein the pipe is a hot water pipe or a floor heating pipe.

12. The pipe of claim 10 comprising two or more layers, wherein at least one layer comprises the polyethylene composition of claim 1 .

13. The pipe of claim 12 , wherein the pipe is a hot water pipe or a floor heating pipe.