Enhanced ESCR bimodal rotomolding resin

Patent metadata

Field	Value
Publication number	US-9540505-B2
Application number	US-201514856622-A
Country	US
Kind code	B2
Filing date	Sep 17, 2015
Priority date	Nov 18, 2013
Publication date	Jan 10, 2017
Grant date	Jan 10, 2017

Abstract

The present disclosure provides a resin suitable for use in rotational molding having an environmental stress crack resistance of greater than 1000 hours. The resin has a density from 0.937 to 0.942 g/cm 3 , a melt index I 2 determined according to ASTM D 1238 (2.16 kg/190° C.—I 2 ) from 4.0 to 7.0 g/10 min, an I 21 determined according to ASTM D 1238 (21.6 kg/190° C.—I 21 ) from 160 to 200 g/10 min, an I 21 /I 2 from 30 to 40 and a terminal vinyl unsaturation greater than 0.06, per 1000 carbon atoms; and a primary structure parameter (PSP2) of from 4 to 7, and an overall Mw/Mn from 2.7 to 3.5 comprising from 2 to 5 weight % of one or more C 4-8 alpha olefin comonomers.

First claim

What is claimed is:

1. A bimodal polyethylene composition having a density from 0.935 to 0.942 g/cm 3 , a melt index I 2 determined according to ASTM D 1238 (2.16 kg 190° C.—I 2 ) from 4.0 to 7.0 g/10 min, and I 21 determined according to ASTM D 1238 (21.6 kg 190 C—I 21 ) from 150 to 210 g/10 min, an I 21 /I 2 from 28 to 40, a bent strip ESCR as determined by ASTM D 1693 in 100% octoxynol −9 for conditions A and B of greater than 1000 hours, a terminal vinyl unsaturation from 0.07 to 0.14 per 1000 carbon atoms, a number average molecular weight (Mn) from 11,000 to 35,000 as determined by GPC, a weight average molecular weight (Mw) from 55,000 to 82,000 as determined by GPC, a Z average molecular weight (Mz) from 140,000 to 2000,000 as determined by GPC, an overall Mw/Mn from 2.8 to 4.0, an index of Mz/Mw from 2 to 2.9 (paragraph 60) comprising from 0.1 to 8 weight % of one or more C 4-8 alpha olefin comonomers as determined by FTIR which when de-convoluted into two components consists of:
(i) from 20 to 45 weight % of a first component consisting of from 1 to 25 wt. % of one or more C 4-8 alpha olefin comonomers and the balance ethylene, said component having a density as determined according to ASTM D 792 from 0.920 to 0.930 g/cm 3 ; a weight average molecular weight (Mw) from 100,000 to 180,000 g/mol, a polydispersity between 2 and 3, and a degree of short chain branching from 3 to 13 per 1000 carbon atoms as determined by GPC-FTIR; and
(ii) from 80 to 55 weight % of a second component comprising one or more of C 4-8 alpha olefin comonomers and the balance ethylene said component having a density as determined according to ASTM D 792 from 0.945 to 0.955 g/cm 3 , a weight average molecular weight (Mw) from 15,000 to 70,000, a polydispersity of less than 3, and a degree of short chain branching less than 5 per 1000 carbon atoms as determined by GPC FTIR wherein in the difference in densities between components (i) and (ii) is less than 0.030 g/cm 3 .

2. The bimodal polyethylene composition according to claim 1 , having a primary structure parameter (PSP2) from 4 to 7.

3. The bimodal polyethylene composition according to claim 2 , wherein component (i) is present in an amount from 20 to 35 weight %.

4. The bimodal polyethylene composition according to claim 3 , wherein component (i) has a weight average molecular weight (Mw) from 120,000 to 150,000 g/mol.

5. The bimodal polyethylene composition according to claim 4 , wherein component (ii) is present in an amount from 80 to 65 weight %.

6. The bimodal polyethylene composition according to claim 5 , wherein component (ii) has a weight average molecular weight (Mw) from 20,000 to 50,000 and a polydispersity of less than 3.

7. The bimodal polyethylene composition according to claim 6 , wherein the difference in densities between components (i) and (ii) is less than 0.027 g/cc.

Assignees

• Nova Chemicals International Sa

Inventors

• Bellehumeur Celine
• Hoidas Mark

Classifications

• C08F2/44

  Polymerisation in the presence of compounding ingredients, e.g. plasticisers, dyestuffs, fillers · CPC title

• B29C41/04

  Rotational or centrifugal casting, i.e. coating the inside of a mould by rotating the mould · CPC title

• C08L23/08 Primary

  Copolymers of ethene (C08L23/16 takes precedence) · CPC title

• C08F10/02

  Ethene · CPC title

• B29C41/003

  characterised by the choice of material · CPC title