Screw cap composition
View Patent ↗A screw cap is disclosed comprising a composition based on a multimodal ethylene polymer having a standard density (SD) greater than 950 kg/m 3 and a melt flow index MI 2 of less than 10 g/10 min, said multimodal ethylene polymer comprising from 35 to 65 wt %, based on the total weight of the multimodal ethylene polymer, of a fraction of ethylene polymer (A) having an SD(A) of more than 965 kg/m 3 and a melt flow index MI 2 (A) of at least 10 g/10 min, and from 65 to 35 wt % based on the total weight of the multimodal ethylene polymer, of a fraction of a copolymer (B) of ethylene and at least one alpha-olefin containing from 3 to 12 carbon atoms, and having a melt flow index MI 2 (B) of less than 10 g/10 min and a content of said alpha-olefin(s) of from 0.1 to 5 mol %. This composition is said to demonstrate an excellent balance between ESCR, injectability and impact resistance, together with excellent organoleptic properties.
1. A screw cap comprising a screw cap formed from a composition based on a multimodal ethylene polymer having a standard density (SD) greater than 950 kg/m 3 and a melt flow index MI 2 of from 0.8 to less than 2 g/10 min, wherein said multimodal ethylene polymer includes from 35 to 65 wt %, based on the total weight of the multimodal ethylene polymer, of a fraction of ethylene polymer (A) having an SD(A) of more than 965 kg/m 3 and a melt flow index MI 2 (A) from 80 to 200 g/10 min, and from 65 to 35 wt %, based on the total weight of the multimodal ethylene polymer, of a fraction of a copolymer (B) of ethylene and at least one alpha-olefin containing from 3 to 12 carbon atoms, and having a melt flow index MI 2 (B) of at least 0.03 g/10 min, but less than 10 g/10 min and a content of said at least one alpha-olefin of from 0.1 to 5 mol %.
2. The screw cap according to claim 1 , wherein the multimodal ethylene polymer has a melt flow index MI 2 of from 1.2 to less than 2 g/10 min.
3. The screw cap according to claim 1 , wherein the multimodal ethylene polymer has an SD of no more than 960 kg/m 3 .
4. The screw cap according to claim 2 , wherein the multimodal ethylene polymer has an SD of no more than 960 kg/m 3 .
5. The screw cap according to claim 3 , wherein the SD is 951-958 kg/m 3 .
6. The screw cap according to claim 4 , wherein the SD is 951-958 kg/m 3 .
7. The screw cap according to claim 1 , wherein MI 2 (B) is less than 0.8 g/10 min.
8. The screw cap according to claim 7 , wherein MI 2 (B) is less than 0.5 g/10 min.
9. Screw cap according to claim 1 , wherein SD (A) is at least 969 kg/m 3 .
10. The screw cap according to claim 1 , wherein said multimodal ethylene polymer includes from 45 to 55 wt % of ethylene polymer (A) and from 55 to 45% of copolymer (B).
11. Screw cap according to claim 1 , wherein copolymer (B) contains monomer units derived from ethylene and butene-1.
12. Screw cap according to claim 1 , wherein the multimodal ethylene polymer is obtained by polymerization in at least two reactors connected in series.
13. A screw cap comprising a screw cap formed from a composition based on a multimodal ethylene polymer having a standard density (SD) greater than 950 kg/m 3 , a melt flow index MI 2 of from 0.8 to less than 2 g/10 min, an ESCR(B) greater than 800 hours, a notched Charpy impact resistance greater than 7 kJ/m 2 , and an injectability greater than 2.8 s, wherein said multimodal ethylene polymer includes from 35 to 65 wt %, based on the total weight of the multimodal ethylene polymer, of a fraction of ethylene polymer (A) having an SD(A) of more than 965 kg/m 3 and a melt flow index MI 2 (A) of from 80 to 200 g/10 min, and from 65 to 35 wt %, based on the total weight of the multimodal ethylene polymer, of a fraction of a copolymer (B) of ethylene and at least one alpha-olefin containing from 3 to 12 carbon atoms, and having a melt flow index MI 2 (B) of at least 0.03 g/10 min, but less than 10 g/10 min and a content of said at least one alpha-olefin of from 0.1 to 5 mol %.