Screw cap composition

Abstract

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 - 15 . (canceled)  
     
     
         16 . Screw cap 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 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) of at least 10 g/10 min but less than 400 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 at least one alpha-olefin of from 0.1 to 5 mol %.  
     
     
         17 . Screw cap according to  claim 16 , wherein the multimodal ethylene polymer has a melt flow index MI 2  of 0.5 to 1.8 g/10 min.  
     
     
         18 . Screw cap according to  claim 16  or  17 , wherein the multimodal ethylene polymer has an SD of no more than 960 kg/m 3 .  
     
     
         19 . Screw cap according to  claim 16 , wherein MI 2 (B) is less than 0.8 g/10 min.  
     
     
         20 . Screw cap according to  claim 19 , wherein MI 2 (B) is less than 0.5 g/10 min.  
     
     
         21 . Screw cap according to  claim 16 , wherein MI 2 (A) is 80-200 g/10 min.  
     
     
         22 . Screw cap according to  claim 16 , wherein SD (A) is at least 969 kg/m 3 .  
     
     
         23 . Screw cap according to  claim 16 , wherein said multimodal ethylene polymer includes from 45 to 55 wt % of ethylene polymer (A) and from 45 to 55% of copolymer (B).  
     
     
         24 . Screw cap according to  claim 16 , wherein copolymer (B) contains monomer units derived from ethylene and butene-1.  
     
     
         25 . Screw cap according to  claim 16 , wherein the multimodal ethylene polymer is obtained by polymerization in at least two reactors connected in series.  
     
     
         26 . Screw cap comprising a composition based on a multimodal ethylene polymer and having an ESCR(B) greater than 800 hours, a notched Charpy impact resistance greater than 7kJ/m 2 , and an injectability greater than 2.8s, wherein the composition is 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 2 g/10 min, said multimodal ethylene polymer including 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 but less than 400 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 at least one alpha-olefin of from 0.1 to 5 mol %.  
     
     
         27 . Screw cap according to  claim 26 , wherein the composition has a standard density greater than 950 kg/m 3 .  
     
     
         28 . Screw cap according to  claim 26  or  27 , wherein the composition has a melt flow index MI 2  of less than 10 g/10 min.  
     
     
         29 . Screw cap according to  claim 18 , wherein the SD is 951-958 kg/m 3 .