Moulded article with improved stress whitening

Patent metadata

Field	Value
Publication number	US-9296844-B2
Application number	US-201314400626-A
Country	US
Kind code	B2
Filing date	May 8, 2013
Priority date	May 18, 2012
Publication date	Mar 29, 2016
Grant date	Mar 29, 2016

Abstract

The present invention relates to a molded article comprising a polypropylene composition, wherein the polypropylene composition comprises comonomer units derived from ethylene in an amount of from 0.5 wt % to 35 wt %, and from at least one C 5-12 alpha-olefin in an amount of from 1.0 mol % to 3.0 mol %, wherein the polypropylene composition has an amount of xylene solubles XS of from 20 wt % to 39 wt %, and the xylene solubles have an amount of ethylene-derived comonomer units of from 4.0 wt % to 70 wt %.

First claim

What is claimed is:

1. A moulded article comprising a polypropylene composition, wherein the polypropylene composition comprises comonomer units derived from ethylene in an amount of from 0.5 wt % to 35 wt %, and from at least one C 5-12 alpha-olefin in an amount of from 1.0 mol % to 3.0 mol %, wherein the polypropylene composition has an amount of xylene solubles XS of from 20 wt % to 39 wt %, and the xylene solubles have an amount of ethylene-derived comonomer units of from 4.0 wt % to 70 wt %, and the article has a tensile modulus of less than 700 MPa.

2. The moulded article according to claim 1 , wherein the at least one C 5-12 alpha-olefin is selected from 1-hexene, 1-octene, or any mixture thereof.

3. The moulded article according to claim 1 , wherein the following relation is satisfied:
[ C 2( XS )× XS/ 100]/ C 2(total)≧0.9

wherein
C2(XS) is the amount in wt % of the ethylene-derived comonomer units in the xylene solubles,
XS is the amount in wt % of xylene solubles of the polypropylene composition,
C2(total) is the amount in wt % of the ethylene-derived comonomer units in the polypropylene composition.

4. The moulded article according to claim 1 , wherein the xylene solubles of the polymer composition contain an amount of comonomer units which are derived from the at least one C 5-12 alpha-olefin of from 0.01 mol % to 2.0 mol %.

5. The moulded article according to claim 1 , wherein the total amount of comonomer units in the polypropylene composition is from 1.7 mol % to 33 mol %.

6. The moulded article according to claim 1 , wherein the polypropylene composition is a blend comprising the following propylene polymer fractions P1, P2 and P3:
(P1) a propylene homopolymer or a propylene copolymer comprising comonomer units derived from at least one C 5-12 alpha-olefin in an amount of less than 1.0 mol %,
(P2) a propylene copolymer comprising comonomer units derived from at least one C 5-12 alpha-olefin in an amount of from 2.0 mol % to 7.0 mol %, and
(P3) a propylene copolymer comprising ethylene-derived comonomer units in an amount of from 4.0 wt % to 70 wt %.

7. The moulded article according to claim 1 , wherein the moulded article is an injection moulded article.

8. The moulded article according to claim 1 , having a stress whitening intensity of less than 3.0, wherein the stress whitening is determined utilizing a tensile test carried out at 23° C. and at a test speed of 5 mm/min with an injection moulded modified F3/4 specimen according to DIN 53455/1981 where the width of the specimen is reduced in the middle with two round edgewise notches from 10 to 8 mm, and where the clamped length is 110 mm and the measured length is 50 mm, and wherein the whitening of the sample is then determined with an optical sensor in the narrowed part of the specimen where from the resulting force and light intensity versus elongation the stress whitening intensity is determined.

9. The moulded article according to claim 1 , wherein the xylene solubles of the polymer composition contain an amount of comonomer units which are derived from the at least one C 5-12 alpha-olefin of from 0.05 mol % to 1.0 mol %.

10. The moulded article according to claim 1 , wherein the total amount of comonomer units derived from ethylene and at least one C 5-12 alpha-olefin in the polypropylene composition is from 1.7 mol % to 33 mol %.

11. The moulded article according to claim 1 , wherein the polypropylene composition is a reactor blend comprising the following propylene polymer fractions P1, P2 and P3:
(P1) a propylene homopolymer or a propylene copolymer comprising comonomer units derived from at least one C 5-12 alpha-olefin in an amount of less than 1.0 mol %,
(P2) a propylene copolymer comprising comonomer units derived from at least one C 5-12 alpha-olefin in an amount of from 2.0 mol % to 7.0 mol %, and
(P3) a propylene copolymer comprising ethylene-derived comonomer units in an amount of from 4.0 wt % to 70 wt %.

Assignees

• Borealis Ag

Inventors

• Reichelt Kristin

Classifications

• C08L23/10 Primary

  Homopolymers or copolymers of propene · CPC title

• C08L23/14

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

• C08F210/16

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

• C08L23/16

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

• C08L2205/02

  containing two or more polymers of the same C08L -group · CPC title