Polyethylene composition having high swell ratio

Patent metadata

Field	Value
Publication number	US-9512308-B2
Application number	US-201615140022-A
Country	US
Kind code	B2
Filing date	Apr 27, 2016
Priority date	Oct 22, 2012
Publication date	Dec 6, 2016
Grant date	Dec 6, 2016

Abstract

The present disclosure relates to a polyethylene composition with improved swell ratio and mechanical properties, particularly suited for preparing blow-moulded articles, said composition having the following features:
1) a density from 0.952 to 0.960 g/cm 3 ; 2) an MIF/MIP ratio from 17 to 30; and 3) a Shear-Induced Crystallization Index SIC from 2.5 to 5.0.

First claim

What is claimed is:

1. A polyethylene composition comprising:
1) a density from 0.952 to 0.960 g/cm 3 as determined according to ISO 1183 at 23° C.;
2) a MIF/MIP ratio from 17 to 30, wherein MIF is the melt flow index at 190° C. with a load of 21.60 kg, and MIP is the melt flow index at 190° C. with a load of 5 kg, both determined according to ISO 1133; and
3) a SIC Index from 2.5 to 5.0;
wherein the SIC Index is the Shear-Induced Crystallization Index, determined according to the following relation:
SIC Index=(( t onset,SIC @1000× t onset,quiescent )/((HLMI)*100)

where t onset,SIC @1000 is measured in seconds and is the time required for crystallization onset under shear rate of 1000 s −1 , the t onset, quiescent is measured in seconds and is the crystallization onset time at temperature of 125° C. under no shear, determined in isothermal mode by differential scanning calorimetry; HLMI is the melt flow index determined at 190° C. with a load of 21.6 kg, according to ISO 1133.

2. The polyethylene composition of claim 1 , comprising one or more ethylene copolymers.

3. The polyethylene composition of claim 2 , containing 1% by weight or less of comonomer.

4. The polyethylene composition of claim 3 , wherein the comonomer or comonomers present in the ethylene copolymers are selected from olefins having formula CH 2 ═CHR wherein R is an alkyl radical, linear or branched, having from 1 to 10 carbon atoms.

5. The polyethylene composition of claim 1 , obtained by using a Ziegler-Natta polymerization catalyst.

6. The polyethylene composition of claim 1 , having at least one of the following additional features:
a Mw equal to or greater than 250000 g/mol;
a Long Chain Branching index equal to or greater than 0.70;
a MIP of 0.05-0.5 g/10 min.; and
a MIF of 1-15 g/10 min.

7. The polyethylene composition of claim 1 , comprising:
A) 40-60% by weight of an ethylene homopolymer or copolymer with density equal to or greater than 0.960 g/cm 3 and melt flow index MIE at 190° C. with a load of 2.16 kg, according to ISO 1133, of 2-30 g/10 min.; and
B) 40-60% by weight of an ethylene copolymer having a MIE value lower than the MIE value of A).

Assignees

• Basell Polyolefine Gmbh

Inventors

• Vittorias Iakovos
• Wiesecke Jens
• Marczinke Bernd Lothar
• Meier Gerhardus
• Schüller Ulf
• Dolle Volker
• Enderle Johannes-Friedrich
• Lilge Dieter
• Gall Barbara

Classifications

• C08L2205/025

  containing two or more polymers of the same hierarchy C08L, and differing only in parameters such as density, comonomer content, molecular weight, structure · CPC title

• C08L2314/02

  Ziegler natta catalyst · CPC title

• C08L23/0815 Primary

  with aliphatic 1-olefins containing one carbon-to-carbon double bond · CPC title

• C08F210/16

  Copolymers of ethene with alpha-alkenes, e.g. EP rubbers · CPC title

• C08J2423/08

  Copolymers of ethene (C08J2423/16 takes precedence) · CPC title