Heterophasic polypropylene with improved stiffness/impact balance

Patent metadata

Field	Value
Publication number	US-10308795-B2
Application number	US-201515521179-A
Country	US
Kind code	B2
Filing date	Oct 16, 2015
Priority date	Oct 27, 2014
Publication date	Jun 4, 2019
Grant date	Jun 4, 2019

Abstract

Heterophasic polypropylene composition with an advantageous, respectively stiffness/impact balance and its use.

First claim

The invention claimed is:

1. A heterophasic polypropylene composition comprising:
(A) 70 to 90 wt % of a crystalline isotactic propylene homopolymer matrix having a pentad concentration as determined by 13 C-NMR spectroscopy of more than 96 mol % and a matrix melt flow rate (MFR M ) as determined at 230° C. and 2.16 kg load according ISO 1133 in the range of 0.5 to 50 g/10 min,
(B) 10 to 30 wt % of a predominantly amorphous propylene copolymer with 32 to 50 wt % of ethylene and/or an α-olefin with 4-10 carbon atoms, being present in the composition as dispersed particles, and
(C) 0 to 5.0 wt % of a crystalline ethylene copolymer with an α-olefin with 3-10 carbon atoms being present in the composition as inclusions of the dispersed particles of (B),
(D) 0 to 1.0 wt % of an alpha nucleating agent for the α- and/or γ-phase of isotactic polypropylene,
said composition being further characterized by a total melt flow rate (MFR T ) as determined at 230° C. and 2.16 kg load according ISO 1133 in the range of 0.5 to 45 g/10 min, a fraction soluble in xylene (XCS) determined at 25° C. according ISO 16152 in the range of 11 to 27 wt %, and ratio of MFR T /MFR M of ≥1.0, and
wherein said composition has a crystalline polypropylene content with a melting point (T m1 ) from DSC analysis according ISO 11357 in the range of 160 to 170° C. whereby the associated melting enthalpy (H m1 ) is in the range of 70 to 100 J/g and optionally a crystalline polyethylene content with a melting point (T m2 ) from DSC analysis according ISO 11357 in the range of 105 to 130° C. whereby the associated melting enthalpyl (H m2 ) is less than 7.0 J/g.

2. A heterophasic polypropylene composition according to claim 1 , wherein the intrinsic viscosity of the XCS fraction as measured according to DIN ISO 1628/1 in decalin at 135° C. is in the range of 1.2 to 4.5 dl/g and wherein the comonomer content, of the XCS fraction is in the range of 35.0 to 52.0 wt %.

3. A heterophasic polypropylene composition according to claim 1 , wherein a flexural modulus determined according to ISO 178 (FM) on an injection moulded specimen of 80×10×4 mm 3 is in the range of 800 to 1700 MPa and furthermore fulfilling the inequation:
FM[MPa]>1660−33.4*XCS[wt %]

wherein XCS is the total fraction soluble in xylene (XCS) determined at 25° C. according ISO 16152 of the heterophasic polypropylene composition.

4. A heterophasic polypropylene composition according to claim 1 , having a Charpy notched impact strength at +23° C. as measured according to ISO 179-1eA in the range of 4.0 to 80.0 kJ/m 2 and a Charpy notched impact strength at −20° C. as measured according to ISO 179-1eA in the range of 3.0 to 10.0 kJ/m 2 .

5. A heterophasic polypropylene composition according to claim 1 , having a total comonomer content defined as the sum of contents of ethylene and α-olefins with 4-10 carbon atoms in the range of 3.5 to 17.0 wt %.

6. A heterophasic polypropylene composition according to claim 1 , wherein at least two glass transition points (T g ) as determined by dynamic mechanical thermal analysis according ISO 6721-7, with one T g (T g (1)) associated to the crystalline isotactic propylene homopolymer matrix being in the range of −4 to 4° C. and another T g (T g (2)) associated to the predominantly amorphous propylene copolymer being in the range of −65 to −50° C.

7. A heterophasic polypropylene composition according to claim 1 , further comprising 0.0001 to 1.0 wt % of a nucleating agent for the α- and/or γ-phase of isotactic polypropylene and having a crystallization temperature from DSC analysis according ISO 11357 of more than 120° C.

8. A heterophasic polypropylene composition according to claim 1 , comprising a content of volatiles (VOC) as determined according to VDA 278:2002 of less than 250 ppm and furthermore fulfilling the inequation:
VOC[ppm]<110+7.0*MFR T [g/10min]
wherein MFR T is the total melt flow rate in g/10 min of said composition as determined at 230° C. and 2.16 kg load according ISO 1133.

9. A heterophasic polypropylene composition according to claim 1 , wherein the composition has been polymerized in the presence of:
a) a Ziegler-Natta catalyst comprising compounds (TC) of a transition metal of Group 4 to 6 of IUPAC, a Group 2 metal compound and an internal donor, wherein said internal donor is a non-phthalic compound;
b) a co-catalyst (Co), and
c) optionally an external donor (ED).

10. A propylene polymer composition according to claim 9 , wherein said internal donor is selected from the group comprising malonates, maleates, succinates, citraconates, glutarates, cyclohexene-1,2-dicarboxylates and benzoates, and any derivatives and/or mixtures thereof.

11. A heterophasic polypropylene composition according to claim 9 , wherein compounds (TC) of a transition metal of Group 4 to 6 is a titanium compound and wherein the molar ratio of co-catalyst (Co) to external donor (ED) [Co/ED] is in the range of 5 to 45, and the molar ratio of co-catalyst (Co) to titanium compound (TC) [Co/TC] is in the range of above 80 to 500.

Assignees

• Borealis Ag

Inventors

• Wang Jingbo
• Leskinen Pauli
• Lilja Johanna
• Gahleitner Markus

Classifications

• C08L2308/00

  Chemical blending or stepwise polymerisation process with the same catalyst · CPC title

• C08J2323/12

  Polypropene · CPC title

• C08L2314/02

  Ziegler natta catalyst · CPC title

• C08L2205/02

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

• C08L2205/03

  containing three or more polymers in a blend · CPC title