High flow polypropylene composition for injection moulding applications

Patent metadata

Field	Value
Publication number	US-12404394-B2
Application number	US-202318847967-A
Country	US
Kind code	B2
Filing date	Mar 21, 2023
Priority date	Mar 23, 2022
Publication date	Sep 2, 2025
Grant date	Sep 2, 2025

Abstract

The present invention relates to polypropylene compositions having a meltflow rate MFR 2 of 75 to 250 g/10 min suitable especially for injection moulding applications comprising a heterophasic propylene copolymer and a particulate inorganic nucleating agent, a process for producing said polypropylene composition, an article comprising said polypropylene composition and the use of said polypropylene composition for injection molding of articles.

First claim

The invention claimed is:

1. A polypropylene composition comprising
(A) at least 95.0 wt % of a heterophasic propylene copolymer; and
(B) up to 1.5 wt % of a particulate inorganic nucleating agent,
wherein all percentages refer to a total composition, and wherein

the heterophasic propylene copolymer (A) comprises a matrix phase and an elastomeric phase dispersed therein and
the polypropylene composition has
a soluble fraction (SF) and a crystalline fraction (CF), determined according to CRYSTEX QC analysis;
a soluble fraction (SF) content determined according to CRYSTEX QC analysis in a range from 15.0 wt % to 30.0 wt %;
an ethylene content of the soluble fraction C2(SF), as determined by FT-IR spectroscopy calibrated by quantitative 13 C-NMR spectroscopy, in a range from 25.0 to 40.0 wt %;
an intrinsic viscosity of the soluble fraction iV(SF), as measured in decalin according to DIN ISO 1628/1 at 135° C., of 2.0 dl/g to 3.5 dl/g;
a ratio of ethylene contents of the soluble fraction and crystalline fraction (C2(SF)/C2(CF)) of 11.0 to 15.0; and
a melt flow rate MFR 2 (230° C., 2.16 kg, ISO 1133) of 75 to 250 g/10 min.

2. The polypropylene composition according to claim 1 , wherein the particulate inorganic nucleating agent (B) is talc.

3. The polypropylene composition according to claim 1 , wherein the particulate inorganic nucleating agent (B) has
a median particle size d 50 before compounding of 0.5 to 7.5 micrometers; and/or
a top-cut particle size d 95 before compounding of 2.0 to 20.0 micrometers.

4. The polypropylene composition according to claim 1 having
a crystalline fraction (CF) content determined according to CRYSTEX QC analysis in a range from 70.0 to 85.0 wt %; and/or
an ethylene content in the crystalline fraction C2(CF), as determined by FT-IR spectroscopy calibrated by quantitative 13 C-NMR spectroscopy, of 1.5 to 3.0 wt %; and/or
an intrinsic viscosity of the crystalline fraction iV(CF), as measured in decalin according to DIN ISO 1628/1 at 135° C. of 0.7 to 1.7 dl/g; and/or
a ratio of intrinsic viscosities of the soluble fraction and crystalline fraction (iV(SF)/iV(CF)) of 2.2 to 3.0; and/or
a total content of units derived from ethylene (C2), as determined by FT-IR spectroscopy calibrated by quantitative 13 C-NMR spectroscopy, of 5.5 to 12.5 wt %.

5. The polypropylene composition according to claim 1 having
a number average particle size of the particles of the elastomeric phase dispersed in the matrix phase of from 1150 to 1325 nm, determined as described in the experimental section; and/or
a melt temperature Tm of from 155 to 175° C., measured by differential scanning calorimetry (DSC) according to ISO 11357/part 3/method C2; and/or
a crystallization temperature Tc of from 120 to 140° C., measured by differential scanning calorimetry (DSC) according to ISO 11357/part 3/method C2; and/or
a heat deflection temperature HDT B of from 92 to 110° C., determined on injection molded test specimens of 80×10×4 mm 3 prepared according to ISO 1873-2.

6. The polypropylene composition according to claim 1 having
a tensile modulus of from 1250 MPa to 1600 MPa; and/or
a tensile elongation at break of from 4.0 to 25.0%,
all measured according to ISO 527-2 (cross head speed=1 mm/min; test speed 50 mm/min at 23° C.) using injection molded specimens 1B prepared as described in EN ISO 1873-2 (dog bone shape, 4 mm thickness).

7. The polypropylene composition according to claim 1 having
a Charpy Notched Impact Strength at 23° C. (CNIS at 23° C.) of from 2.5 to 6.4 kJ/m 2 ; and/or
a Charpy Notched Impact Strength at −20° C. (CNIS at −20° C.) of from 2.0 to 5.5 kJ/m 2 ,
all measured according to ISO 179-1 eA at +23° C. and at −20° C. on injection molded specimens of 80×10×4 mm 3 prepared according to EN ISO 1873-2.

8. The polypropylene composition according to claim 1 having
a puncture energy of from 4.5 to 20.0 J, when determined in the instrumented puncture test according to ISO 6603-2 at 23° C., and/or
puncture energy of from 3.5 to 15.0 J, when determined in the instrumented puncture test according to ISO 6603-2 at −20° C.

9. A process for preparing a polypropylene composition according to claim 1 comprising:
polymerizing the heterophasic propylene copolymer (A) in the presence of a Ziegler-Natta catalyst system in a multistage process comprising at least two polymerization reactors connected in series, and
blending the heterophasic propylene copolymer (A) with the particulate inorganic nucleating agent (B).

10. The process according to claim 9 comprising:
a) polymerizing propylene in the presence of the Ziegler-Natta catalyst system in a first polymerization reactor for producing a first propylene homopolymer fraction;
b) transferring a polymerization mixture comprising the Ziegler-Natta catalyst system and the first propylene homopolymer fraction from the first polymerization reactor to a second polymerization reactor;
c) polymerizing propylene in the presence of the Ziegler-Natta catalyst system in the second polymerization reactor for producing a second propylene homopolymer fraction;
d) transferring a polymerization mixture comprising the Ziegler-Natta catalyst system and the first and second propylene homopolymer fractions from the second polymerization reactor to a third polymerization reactor;
e) polymerizing propylene and ethylene in the presence of the Ziegler-Natta catalyst system in the third polymerization reactor for producing a first propylene-ethylene copolymer fraction;
f) transferring a polymerization mixture comprising the Ziegler-Natta catalyst system, the first and second propylene homopolymer fractions and the first propylene-ethylene copolymer fraction from the third polymerization reactor to a fourth polymerization reactor;
g) polymerizing propylene and ethylene in the presence of the Ziegler-Natta catalyst system in the fourth polymerization reactor for producing a second propylene-ethylene copolymer fraction;
h) withdrawing a polymerization mixture comprising the Ziegler-Natta catalyst system, the first and second propylene homopolymer fractions and the first and second propylene-ethylene copolymer fractions from the fourth polymerization reactor; and
i) obtaining the heterophasic propylene copolymer (A) comprising the first and second propylene homopolymer fractions and the first and second propylene-ethylene copolymer fractions.

11. The process according to claim 9 , wherein the Ziegler-Natta catalyst system is a solid Ziegler-Natta catalyst system, which comprises compounds of a transition metal of Group 4 to 6 of IUPAC, a Group 2 metal compound, and an internal donor.

12. The process according to claim 10 , wherein a combined first and second propylene homopolymer fractions obtained from the second polymerization reactor has a melt flow rate MFR 2 (230° C., 2.16 kg, ISO 1133) of 250 to 600 g/10 min.

13. An article comprising the polypropylene composition according to claim 1 .

14. The article according to claim 13 having
a coefficient of linear thermal expansion at a temperature range from +23 to +80° C. at a heating rate of 1° C./min in machine direction (CLTE 23-80° C., MD) of below 130 μm/m° C., and/or
a coefficient of linear thermal expansion at a temperature range from +23 to +80° C. at a heating rate of 1° C./min in transverse direction (CLTE 23-80° C., TD) of below 140 μm/m° C., and/or
a coefficient of linear thermal expansion at a temperature range from −30 to +80° C. at a heating rate of 1° C./min in machine direction (CLTE-30-80° C., MD) of below 115 μm/m° C., and/or
a coefficient of linear thermal expansion

Assignees

• Borealis Ag

Inventors

• Lummerstorfer Thomas
• Kniesel Claudia
• Mileva Daniela
• Horill Thomas
• Abbasi Mahdi
• Tranninger Cornelia Anita
• Gahleitner Markus
• Costa Francis Reny

Classifications

• 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

• C08L2314/02

  Ziegler natta catalyst · CPC title

• C08L2207/02

  Heterophasic composition · CPC title

• C08L2205/035

  containing four or more polymers in a blend · CPC title