Propylene copolymer composition with improved long-term mechanical properties

Patent metadata

Field	Value
Publication number	US-2018037716-A1
Application number	US-201615552191-A
Country	US
Kind code	A1
Filing date	Feb 23, 2016
Priority date	Feb 25, 2015
Publication date	Feb 8, 2018
Grant date	—

Abstract

Propylene-ethylene random copolymers with improved long-term mechanical properties, especially improved impact strength retention, their manufacture as well as their use, e.g. for the production of moulded articles, particularly injection moulded articles, such as thin-walled plastic containers for packaging.

First claim

1 : Propylene-ethylene random copolymers having:
(i) a melt flow rate MFR 2 (according to ISO 1133, 230° C., 2.16 kg) in the range of 50 to 120 g/10 min, (ii) a total ethylene comonomer content of 3.0 to 9.0 mol % (iii) a content of the orthorhombic gamma-crystal phase 100·Kγ of less than 45% as determined by wide-angle X-ray diffraction (WAXS) on a 60×60×2 mm 3 injection moulded test specimens as described in the experimental part, and comprising: 0.0001 to 1.0 wt %, based on the total weight of the propylene-ethylene random copolymer, of a polymeric α-nucleating agent (pNA).

2 : The propylene-ethylene random copolymers according to claim 1 , comprising two propylene copolymer fractions:
a) a first propylene copolymer fraction (PP-COPO-1) having an ethylene comonomer content of at most 3.5 mol %, and b) a second propylene copolymer fraction (PP-COPO-2),
said first propylene copolymer fraction (PP-COPO-1) having a higher MFR 2 and/or a lower ethylene comonomer content than said second propylene copolymer fraction (PP-COPO-2).

3 : Propylene-ethylene copolymers according to claim 2 , wherein the first propylene copolymer fraction (PP-COPO-1) has an ethylene comonomer content of at least 1.0 mol % and at most 3.5 mol % and the second propylene copolymer fraction (PP-COPO-2) has an ethylene comonomer content in the range of 2.0 mol % to at most 11.0 mol %, whereby the first propylene copolymer fraction (PP-COPO-1) has an ethylene comonomer content below that of the second propylene copolymer fraction (PP-COPO-2).

4 : Propylene-ethylene copolymers according to claim 2 , wherein the first propylene copolymer fraction (PP-COPO-1) has a melt flow rate MFR 2 (230° C.) in the range of 50.0 to 150 g/10 min and the second propylene copolymer fraction (PP-COPO-2) has a melt flow rate MFR 2 (230° C.) in the range of 40.0 to 120 g/10 min, whereby the MFR 2 of the second propylene copolymer fraction (PP-COPO-2) is lower than the MFR 2 of the first propylene copolymer fraction (PP-COPO-1).

5 : Propylene-ethylene copolymers according to claim 2 , wherein the second propylene copolymer fraction (PP-COPO-2) has an ethylene comonomer content which is higher than the ethylene comonomer content of the first propylene copolymer fraction (PP-COPO-1) and has an MFR 2 which is lower than the MFR 2 of the first propylene copolymer fraction (PP-COPO-1).

6 : Propylene-ethylene copolymers according to claim 1 , wherein the polymeric α-nucleating agent is a polymerized vinyl compound of formula (I):

wherein R 1 and R 2 together form a 5 or 6 membered saturated or unsaturated or aromatic ring or they stand independently for a lower alkyl comprising 1 to 4 carbon atoms.

7 : Propylene-ethylene copolymers according to claim 6 , whereby the polymerized vinyl compound is selected from the group consisting of vinyl cycloalkanes.

8 : Propylene-ethylene copolymers according to claim 1 , wherein the propylene-ethylene copolymers have been polymerized in the presence of:
a) a Ziegler-Natta catalyst (ZN-C) comprising compounds (TC) of a transition metal of Group 4 to 6 of IUPAC, a Group 2 metal compound (MC) and an internal donor (ID), wherein said internal donor (ID) is a non-phthalic compound; b) optionally a co-catalyst (Co), and c) optionally an external donor (ED).

9 : Propylene-ethylene copolymers according to claim 7 , wherein:
a) the internal donor (ID) is selected from optionally substituted malonates, maleates, succinates, glutarates, cyclohexene-1,2-dicarboxylates, benzoates and derivatives and/or mixtures thereof; and b) the molar-ratio of co-catalyst (Co) to external donor (ED) [Co/ED] is 5 to 45.

10 : Propylene-ethylene copolymers according to claim 1 , wherein the propylene-ethylene copolymers are produced in a sequential polymerization process, comprising a prepolymerization reactor (PPR) and at least one reactor (R1) or at least two reactors (R1) and (R2), whereby in the prepolymerization reactor a vinyl compound is first polymerized with a catalyst system, comprising a Ziegler-Natta catalyst component, a cocatalyst and optional external donor, the reaction mixture of the polymer of the vinyl compound and the catalyst system is then introduced in a first polymerization reactor (R1), whereby in the first reactor (R1) a first propylene copolymer fraction (PP-COPO-1) is produced and subsequently transferred into the second reactor (R2), in the second reactor (R2) a second propylene copolymer fraction (PP-COPO-2) is produced in the presence of the first propylene copolymer fraction (PP-COPO-1).

11 . (canceled)

12 : Moulded articles, comprising a propylene-ethylene copolymer according to claim 1 .

13 : Thin wall packaging made by injection moulding, comprising a propylene-ethylene copolymer according to claim 1 .

14 : Moulded articles according to claim 12 , having:
a tensile modulus (measured according to ISO 527) measured after 96 hours of storage at +23±1° C. and 50% relative humidity (standard conditions) of at least 1050 MPa and tensile modulus (measured according to ISO 527) measured after 1440 hours of storage under standard conditions of at least 1100 MPa and
simultaneously by a puncture energy (measured according to ISO 6603-2; 60×60×2 mm 3 specimens) measured after 96 hours of storage under standard conditions of at least 23 J, and measured after 1440 hours of storage under standard conditions of at least 19 J.

Assignees

• Borealis Ag

Inventors

• Braun Juliane
• Boragno Luca
• Wang Jingbo
• Leskinen Pauli
• Lilja Johanna
• Gahleitner Markus

Classifications

• C08F2/001

  Multistage polymerisation processes characterised by a change in reactor conditions without deactivating the intermediate polymer (C08F295/00, C08F297/00 take precedence) · CPC title

• B29C45/0001

  characterised by the choice of material · CPC title

• C08K5/0083 Primary

  Nucleating agents promoting the crystallisation of the polymer matrix · CPC title

• C08F210/06

  Propene · CPC title

• C08L23/16

  Ethylene-propylene or ethylene-propylene-diene copolymers · CPC title