WO2021109071A1

WO2021109071A1 - Polyolefin compositions with electromagnetic interference shielding properties

Info

Publication number: WO2021109071A1
Application number: PCT/CN2019/123289
Authority: WO
Inventors: Henry ZHOU; Alfred GAO
Original assignee: Borouge Compounding Shanghai Co., Ltd.
Priority date: 2019-12-05
Filing date: 2019-12-05
Publication date: 2021-06-10
Also published as: CN114729168A

Abstract

A polyolefin composition (C) comprising: a) from 55.0 to 90.0 wt. -% of a polypropylene (PP) having a melt flow rate (MFR 2) in the range from 2.0 to 120.0 g/10 min; b) from 2.0 to 10.0 wt. -% of carbon nanotubes (CNT); c) from 5.0 to 40.0 wt. -% of an inorganic filler (F); d) from 0.3 to 1.0 wt. -% of dispersant (D); e) from 0.1 to 5.0 wt. -% of at least one additive (A) other than the inorganic filler (F) and the dispersant (D).

Description

POLYOLEFIN COMPOSITIONS WITH ELECTROMAGNETIC INTERFERENCE SHIELDING PROPERTIES

The present invention relates to a polyolefin composition comprising a polypropylene, carbon nanotubes, and inorganic filler, a dispersant and additives, articles comprising said composition.

As is well known in the field of polypropylene compositions, carbon nanotubes have long been used in processes such as extrusion and thermo-compression to prepare articles with electromagnetic interference (EMI) shielding properties. That said, it is difficult to prepare such articles via injection molding processes, since the carbon nanotubes are known to congregate towards the centre of the mold, resulting in a poor dispersion of the carbon nanotubes through the article. It is thought that this problem affects carbon nanotubes in particular due to their nanoscale dimensions. This low dispersion directly affects the surface resistivity properties of the article, resulting in articles with considerably worse EMI shielding properties. Other fillers, such as carbon black, may be used in the preparation of automotive articles with desirable EMI shielding properties. The required content of these fillers is quite high, however, which often results in a degradation of the mechanical properties (stiffness, as given by flexural modulus, and impact strength) . In the automotive industry, these mechanical properties are central to the function of the automotive articles.

As such, the development of compositions that combine favourable EMI shielding properties (i.e. low surface resistivity) with a high balance of stiffness (flexural modulus) and impact strength is required by the automotive industry. Articles comprising said composition would be excellent candidates for, in particular, automotive articles that house electrical equipment, such as an instrument panel carrier.

The finding of the present invention is that the addition of an inorganic filler, such as talc, to carbon nanotube-containing polypropylene compositions, improves not just the balance of mechanical properties, but also the dispersion of carbon nanotubes within the polymer composition, resulting in a reduced surface resistivity. The presence of carbon nanotubes in said compositions is beneficial for not only the electromagnetic interference shielding properties but also both the flexural modulus and the impact strength.

Therefore, the present invention is directed to a polyolefin composition (C) comprising

a) from 55.0 to 90.0 wt. -%, based on the total weight of the composition, of a polypropylene (PP) , preferably a copolymer, having a melt flow rate (MFR ₂) measured according to ISO 1133 at 230℃and 2.16 kg in the range from 2.0 to 120.0 g/10 min, preferably in the range from 2.0 to 60.0 g/10 min;

b) from 2.0 to 10.0 wt. -%, based on the total weight of the composition, of carbon nanotubes (CNT) ;

c) from 5.0 to 40.0 wt. -%, based on the total weight of the composition, of an inorganic filler (F) ;

d) from 0.3 to 1.0 wt. -%, based on the total weight of the composition, of dispersant (D) ;

e) from 0.1 to 5.0 wt. -%, based on the total weight of the composition, of at least one additive (A) other than the inorganic filler (F) and the dispersant (D) .

In a preferred embodiment, the polypropylene (PP) is a heterophasic propylene copolymer.

In another preferred embodiment, the polypropylene (PP) has one or more, preferably all, of the following properties:

i) an ethylene (C2) content in the range from 6.0 to 18.0 wt. -%, preferably in the range from 7.0 to 15.0 wt. -%, most preferably in the range from 8.0 to 12.0 wt. -%;

ii) a xylene cold solubles (XCS) content in the range from 20.0 to 32.0 wt. -%, preferably in the range from 22.0 to 29.0 wt. -%, most preferably in the range from 23.0 to 26.0 wt. -%;

iii) an ethylene content of the xylene cold soluble fraction (C2 (XCS) ) in the range from 30.0 to 45.0 wt. -%, preferably in the range from 33.0 to 42.0 wt. -%, most preferably in the range from 36.0 to 40.0 wt. -%;

iv) an intrinsic viscosity of the xylene cold soluble fraction (IV (XCS) ) in the range from 2.0 to 4.0 dl/g, preferably in the range from 2.5 to 3.7 dl/g, most preferably in the range from 3.0 to 3.4 dl/g.

In another preferred embodiment, the carbon nanotubes have a density in the range from 1.8 to 2.1 g/cm ³, and/or a diameter in the range from 2.0 to 25.0 nm, and/or a length in the range from 0.1 to 10.0 μm.

In another preferred embodiment, the inorganic filler (F) has an average particle size (d50) in the range from 0.8 to 40 μm, preferably selected from the group containing talc, calcium carbonate, barium sulfate, mica, and mixtures thereof, most preferably the inorganic filler (F) is talc.

In another preferred embodiment, the dispersant (D) is selected from the group containing calcium stearate, polyethylene wax, oleamide, erucamide, and mixtures thereof, preferably the dispersant (D) is an oleamide.

In another preferred embodiment, the polymer composition (C) further comprises

f) from 0.1 to 3.0 wt. -%, based on the total weight of the composition, of a polar-modified polypropylene (PMP) , preferably a maleic anhydride-modified polypropylene.

In a further preferred embodiment, the polar modified polypropylene (PMP) has a polar group loading in the range from 0.5 to 3.0 wt. -%.

In another preferred embodiment, the polyolefin composition (C) has a flexural modulus of at least 1800 MPa, and/or a Charpy notched impact strength of at least 8.0 kJ/m ².

In another preferred embodiment, the polyolefin composition (C) has a surface resistivity of at most 1,000,000 Ohm/m ².

In another aspect, the present invention is directed to a process for the preparation of said polyolefin composition, comprising the steps of:

a) providing a mixture of additives (A) and dispersant (D) and optionally a polar-modified polypropylene (PMP) , preferably in the form of a master batch;

b) providing a polypropylene (PP) ;

c) blending the carbon nanotubes (CNT) and the inorganic filler (F) to obtain a mixed blend of carbon nanotubes (CNT) and inorganic filler (F) ;

d) blending and extruding the polypropylene (PP) with the mixture of additives (A) and dispersant (D) and the blend of carbon nanotubes (CNT) and inorganic filler (F) at a temperature in the range from 180℃ to 250℃ in an extruder, preferably a twin-screw extruder.

In a further aspect, the present invention is directed to an article comprising more than 75 wt. -%of the polyolefin composition (C) , preferably a molded article, most preferably an injection molded article or a foam injection molded article.

In a preferred embodiment, the article is a part of automotive articles, especially of car interiors and exteriors, like instrumental carriers, shrouds, structural carriers, bumpers, side trims, step assists, body panels, spoilers, dashboards, interior trims and the like.

In another aspect, the present invention is directed to a use of the polyolefin composition (C) for the preparation of automotive articles with improved electro-magnetic interference shielding properties.

The present invention will now be described in more detail.

The polypropylene (PP)

The main component of the polyolefin composition is the polypropylene (PP) .

The polypropylene (PP) of the present invention has a melt flow rate (MFR ₂) measured according to ISO 1133 at 230℃ and 2.16 kg in the range from 2.0 to 120.0 g/10 min, preferably in the range from 2.0 to 60.0 g/10 min, more preferably in the range from 3.0 to 40.0 g/10 min, yet more preferably in the range from 4.0 to 20.0 g/10 min, most preferably in the range from 5.0 to 10.0 g/10 min.

The polypropylene (PP) of the present invention is preferably a copolymer of propylene, more preferably a copolymer of propylene and ethylene and/or an alpha-olefin having 4 to 12 carbon atoms, most preferably the polypropylene (PP) of the present invention is a copolymer of propylene and ethylene.

It is particularly preferred that the polypropylene (PP) of the present invention is a heterophasic propylene copolymer (HECO) .

A heterophasic propylene copolymer (HECO) comprises at least two distinct phases, namely a polypropylene homopolymer crystalline matrix phase (M) and an elastomeric ethylene-propylene copolymer (EC) . The combination of these two very different phases creates a composition with a beneficial balance of mechanical properties, as given by the stiffness and impact strength.

In such cases, it is especially preferred that both the crystalline matrix (M) and elastomeric ethylene-propylene copolymer (EC) of the heterophasic propylene copolymer (HECO) of the present invention are bimodal.

It is preferred that the polypropylene (PP) of the present invention has an comonomer content in the range from 6.0 to 18.0 wt. -%, preferably in the range from 7.0 to 15.0 wt. -%, most preferably in the range from 8.0 to 12.0 wt. -%, as determined by quantitative ¹³C-NMR spectroscopy.

It is preferred that the polypropylene (PP) of the present invention has an ethylene (C2) content in the range from 6.0 to 18.0 wt. -%, preferably in the range from 7.0 to 15.0 wt. -%, most preferably in the range from 8.0 to 12.0 wt. -%, as determined by quantitative ¹³C-NMR spectroscopy.

It is preferred that the polypropylene (PP) of the present invention has a xylene cold solubles (XCS) content in the range from 20.0 to 32.0 wt. -%, preferably in the range from 22.0 to 29.0 wt. -%, most preferably in the range from 23.0 to 26.0 wt. -%.

It is preferred that the polypropylene (PP) of the present invention has an ethylene content of the xylene cold soluble fraction (C2 (XCS) ) in the range from 30.0 to 45.0 wt. -%, preferably in the range from 33.0 to 42.0 wt. -%, most preferably in the range from 36.0 to 40.0 wt. -%.

It is preferred that the polypropylene (PP) of the present invention has an intrinsic viscosity of the xylene cold soluble fraction (IV (XCS) ) in the range from 2.0 to 4.0 dl/g, preferably in the range from 2.5 to 3.7 dl/g, most preferably in the range from 3.0 to 3.4 dl/g.

It is preferred that the polypropylene (PP) of the present invention has a flexural modulus measured according to ISO 178 in the range from 800 to 1500 MPa, more preferably from 900 to 1400 MPa, yet more preferably from 1000 to 1300 MPa, most preferably from 1050 to 1200 MPa.

It is preferred that the polypropylene (PP) of the present invention has a Charpy Notched Impact Strength measured according to ISO 179/1eA at +23 ℃ in the range from 20.0 to 100.0 kJ/m ², more preferably in the range from 30.0 to 90.0 kJ/m ², yet more preferably from 40.0 to 85.0 kJ/m ², most preferably from 50.0 to 80.0 kJ/m ²

It is preferred that the polypropylene (PP) of the present invention has a Charpy Notched Impact Strength measured according to ISO 179/1eA at -20 ℃ in the range from 3.0 to 30.0 kJ/m ², more preferably in the range from 4.5 to 25.0 kJ/m ², yet more preferably from 6.0 to 20.0 kJ/m ², most preferably from 7.5 to 15.0 kJ/m ²

The polypropylene (PP) of the present invention may either be synthesized or selected from commercially available polypropylenes.

The carbon nanotubes (CNT)

As another essential component, the polyolefin composition (C) comprises carbon nanotubes (CNT) .

It is preferred that the carbon nanotubes (CNT) have a density in the range from 1.8 to 2.1 g/cm ³

It is further preferred that the carbon nanotubes (CNT) have a diameter in the range from 2.0 to 25.0 nm, more preferably in the range from 3.0 to 15.0 nm, most preferably in the range from 3.0 to 8.0 nm.

It is further preferred that the carbon nanotubes (CNT) have a length in the range from 0.1 to 10.0 μm, more preferably in the range from 1.0 to 8.0 μm, most preferably in the range from 2.0 μm to 6.0 μm.

Suitable carbon nanotubes include multi-wall carbon nanotubes from CNT Solution Co., Ltd, Korea.

The inorganic filler (F)

Another essential component of the polyolefin composition (C) is the inorganic filler (F) .

It is preferred that the inorganic filler is selected from the group containing talc, calcium carbonate, barium sulfate, mica, and mixtures thereof.

Most preferably, the inorganic filler (F) is talc.

It is preferred that the inorganic filler (F) has an average particle size (d50) in the range from 0.8 to 40.0 μm, more preferably d50 in the range from 0.8 to 20.0 μm, especially more preferably d50 in the range from 1.0 to 10.0 μm.

It is preferred that the inorganic filler (F) has an average particle size (d95) in the range from 1.0 to 45.0 μm, more preferably d95 in the range from 2.0 to 20.0 μm, especially more preferably d95 in the range from 3.0 to 10.0 μm.

It is preferred that the inorganic filler (F) has a specific surface area B. E. T in the range from 1.0 to 30.0 m ²/g, more preferably B. E. T in the range from 5.0 to 20.0 m ²/g, especially more preferably B. E. T in the range from 8.0 to 15.0 m ²/g.

The dispersant (D)

As a further essential component, the polyolefin composition comprises a dispersant (D) .

A dispersant is an polyolefin additive that helps to disperse the inorganic filler and carbon nanotubes in the polyolefin composition (C) .

It is preferred that the dispersant (D) is selected from the group containing calcium stearate, polyethylene wax, oleamide, erucamide, and mixtures thereof.

Most preferably the dispersant (D) is an oleamide.

The additives (A)

The polyolefin composition (C) of the present invention may contain additives (A) in an amount of from 0.1 to 5.0 wt. -%. The skilled practitioner would be able to select suitable additives that are well known in the art.

The additives (A) are preferably selected from antioxidants, UV-stabilisers, anti-scratch agents, mould release agents, acid scavengers, lubricants, anti-static agents, and mixtures thereof.

It is understood that the content of additives (A) , given with respect to the total weight of the polyolefin composition (C) , includes any carrier polymers used to introduce the additives to said polyolefin composition (C) , i.e. masterbatch carrier polymers. An example of such a carrier polymer would be a polypropylene homopolymer in the form of powder.

The polar modified polypropylene (PMP)

In certain preferred embodiments, the polyolefin composition (C) of the invention may further comprise a polar-modified polypropylene (PMP) .

Whilst not wishing to be bound by any theory, it is believed that the polar-modified polypropylene (PMP) is used as a compatibilizer in the composition, which further helps to disperse the inorganic filler and carbon nanotubes within the polyolefin composition (C) .

It is preferred that the polar-modified polypropyplene (PMP) has a content of polar groups content in the range from 0.5 to 3.0 wt. -%, more preferably in the range from 0.8 to 2.0 wt. -%, most preferably in the range from 1.0 to 1.5 wt. -%.

It is also preferred that the polar-modified polypropylene (PMP) has a melt flow rate (MFR ₂) measured according to ISO 1133 at 230℃ and 2.16 kg of at least 30.0 g/10 min, more preferably of at least 50.0 g/10 min, yet more preferably of at least 70 g/10 min, most preferably of at least 80 g/10 min.

It is especially preferred that the polar-modified polypropylene (PMP) is a maleic anhydride-modified polypropylene.

Suitable commercially available polar-modified polypropylenes include SCONA TPPP 8112 GA, avaialable from Byk-Cera (Germany) .

The polyolefin composition

The polyolefin composition of the present invention comprises several essential components, including the polypropylene (PP) , the carbon nanotubes (CNT) , the inorganic filler (F) , the dispersant (D) and at least one additive (A) other than the inorganic filler (F) and the dispersant (D) . Accordingly the polyolefin composition (C) comprises:

a) from 55.0 to 90.0 wt. -%, based on the total weight of the composition, of a polypropylene (PP) having a melt flow rate (MFR ₂) measured according to ISO 1133 at 230℃ and 2.16 kg in the range from 2.0 to 120.0 g/10 min;

The polyolefin composition (C) may further comprise:

f) from 0.1 to 3.0 wt. -%, based on the total weight of the composition, of a polar-modified polypropylene (PMP) .

The polypropylene composition (PC) of the present invention can comprise further components, in addition to the essential components as defined above. However, it is preferred that the individual contents of the polypropylene (PP) , the carbon nanotubes (CNT) , the inorganic filler (F) , the dispersant (D) , the additives (A) and the optional polar-modified polypropylene (PMP) add up to at least 90 wt. -%, more preferably to at least 95 wt. -%, based on the total weight of the polypropylene composition (PC) . Most preferably the polypropylene composition (PC) consists of only the polypropylene (PP) , the carbon nanotubes (CNT) , the inorganic filler (F) , the dispersant (D) , the additives (A) and the optional polar-modified polypropylene (PMP) .

The polypropylene (PP) is present in the polyolefin composition in an amount of from 55.0 to 90.0 wt. -%, based on the total weight of the composition, more preferably in an amount of from 65.0 to 80.0 wt. -%, most preferably in an amount from 68.0 to 75.0 wt. -%, based on the total weight of the composition.

The carbon nanotubes (CNT) are present in the polyolefin composition in an amount of from 2.0 to 10.0 wt. -%, based on the total weight of the composition, more preferably in an amount of from 2.5 to 9.0 wt. -%, most preferably in an amount of from 3.0 to 8.0 wt. -%based on the total weight of the composition.

The inorganic filler (F) is present in the polyolefin composition in an amount of from 5.0 to 40.0 wt. -%, based on the total weight of the composition, more preferably in an amount of from 10.0 to 30.0 wt. -%, most preferably in an amount of from 15.0 to 25.0 wt. -%based on the total weight of the composition.

The dispersant (D) is present in the polyolefin composition in an amount of from 0.3 to 1.0 wt. -%, based on the total weight of the composition, more preferably in an amount of from 0.4 to 0.9 wt. -%, most preferably in an amount of from 0.5 to 0.8 wt. -%based on the total weight of the composition.

It is preferred that the polar-modified polypropylene (PMP) is present in the polyolefin composition in an amount of from 0.1 to 3.0 wt. -%, based on the total weight of the composition, more preferably in an amount of from 0.3 to 2.0 wt. -%, most preferably in an amount of from 0.5 to 1.5 wt. -%based on the total weight of the composition.

Accordingly, in one preferred embodiment, the polyolefin composition comprises, preferably consists of:

e) from 0.1 to 5.0 wt. -%, based on the total weight of the composition, of at least one additive (A) other than the inorganic filler (F) and the dispersant (D) ;

f) optionally from 0.1 to 3.0 wt. -%, based on the total weight of the composition, of a polar-modified polypropylene (PMP) .

Accordingly, in a further preferred embodiment, the polyolefin composition comprises, preferably consists of:

a) from 65.0 to 80.0 wt. -%, based on the total weight of the composition, of a polypropylene (PP) having a melt flow rate (MFR ₂) measured according to ISO 1133 at 230℃ and 2.16 kg in the range from 2.0 to 120.0 g/10 min;

b) from 2.5 to 9.0 wt. -%, based on the total weight of the composition, of carbon nanotubes (CNT) ;

c) from 10.0 to 30.0 wt. -%, based on the total weight of the composition, of an inorganic filler (F) ;

d) from 0.4 to 0.9 wt. -%, based on the total weight of the composition, of dispersant (D) ;

f) optionally from 0.3 to 2.0 wt. -%, based on the total weight of the composition, of a polar-modified polypropylene (PMP) .

Accordingly, in yet another preferred embodiment, the polyolefin composition comprises, preferably consists of:

a) from 68.0 to 75.0 wt. -%, based on the total weight of the composition, of a polypropylene (PP) having a melt flow rate (MFR ₂) measured according to ISO 1133 at 230℃ and 2.16 kg in the range from 2.0 to 120.0 g/10 min;

b) from 3.0 to 8.0 wt. -%, based on the total weight of the composition, of carbon nanotubes (CNT) ;

c) from 15.0 to 25.0 wt. -%, based on the total weight of the composition, of an inorganic filler (F) ;

d) from 0.5 to 0.8 wt. -%, based on the total weight of the composition, of dispersant (D) ;

f) optionally from 0.5 to 1.5 wt. -%, based on the total weight of the composition, of a polar-modified polypropylene (PMP) .

In order to be suitable for use in automotive articles with electromagnetic interference shielding properties, the polyolefin composition (C) according to the present invention requires beneficial mechanical properties, such as stiffness and impact strength, in addition to good electromagnetic shielding properties.

Accordingly, it is preferred that the polyolefin composition (C) has a flexural modulus measured according to ISO 178 of at least 1800 MPa, more preferably of at least 1900 MPa, most preferably of at least 2000 MPa.

The flexural modulus will not typically exceed 2500 MPa

It is also preferred that the polyolefin composition (C) has a Charpy notched impact strength measured according to ISO 179/1eA at +23℃ of at least 8.0 kJ/m ², more preferably of at least 8.5 kJ/m ², most preferably of at least 9.0 kJ/m ².

The flexural modulus will not typically exceed 20.0 kJ/m ²

Furthermore, it is preferred that the polyolefin composition (C) has a surface resistivity of at most 1,000,000 Ohm/m ², more preferably at most 500,000 Ohm/m ², most preferably at most 200,000 Ohm/m ².

Preparation process for the polypropylene (PP)

The polypropylene (PP) comprised in the composition according to this invention is preferably produced in a sequential polymerization process in the presence of a Ziegler-Natta catalyst, more preferably in the presence of a catalyst (system) as defined below.

Preferably, the process for the preparation of the polypropylene is a process for the production of a heterophasic propylene copolymer (HECO) , comprising a polypropylene homopolymer crystalline matrix (M) and an elastomeric ethylene-propylene copolymer (EC) .

Preferably the heterophasic propylene copolymer (HECO) is reactor made, preferably has been produced in a sequential polymerization process, wherein the crystalline matrix (M) has been produced in at least one reactor, preferably in two reactors, and subsequently the elastomeric ethylene-propylene copolymer (EC) has been produced in at least two further reactors, preferably in two further reactors, wherein a first elastomeric ethylene-propylene copolymer fraction (EC1) has been produced in one of the two further reactors and the second elastomeric ethylene-propylene copolymer fraction (EC2) has been produced in the other one of the two further reactors. It is especially preferred that first the first elastomeric ethylene-propylene copolymer fraction (EC1) is produced and subsequently the second elastomeric ethylene-propylene copolymer fraction (EC2) .

The term “polymerization reactor” shall indicate that the main polymerization takes place. Thus in case the process consists of four polymerization reactors, this definition does not exclude the option that the overall process comprises for instance a pre-polymerization step in a pre-polymerization reactor. The term “consist of”is only a closing formulation in view of the main polymerization reactors, i.e. does not exclude prepolymerisation reactors.

Preferably, said process comprises the steps of

(a1) polymerizing propylene and optionally ethylene and/or at least one C ₄ to C ₁₂ alpha-olefin in a first reactor (R1) obtaining the first polypropylene fraction (PP1) , preferably said first polypropylene fraction (PP1) is a first propylene homopolymer fraction (H-PP1) ,

(b1) transferring the first polypropylene fraction (PP1) in a second reactor (R2) ,

(c1) polymerizing in the second reactor (R2) and in the presence of said first polypropylene fraction (PP1) propylene and optionally ethylene and/or a C4 to C ₁₂ alpha-olefin obtaining thereby the second polypropylene fraction (PP2) , preferably said second polypropylene fraction (PP2) is a second propylene homopolymer fraction (H-PP2) , the first polypropylene fraction (PP1) together with the second polypropylene fraction (PP2) forms the crystalline matrix (M) ,

(d1) transferring the crystalline matrix (M) of step (c1) in a third reactor (R3) ,

(e1) polymerizing in the third reactor (R3) and in the presence of the polypropylene (PP) obtained in step (c1) propylene and ethylene and, optionally, a C ₄ to C ₁₂ alpha-olefin obtaining thereby the first elastomeric ethylene-propylene copolymer fraction (EC1) , said crystalline matrix (M) and said first elastomeric ethylene-propylene copolymer fraction (EC1) form a mixture (M1) ,

(f1) transferring said mixture (M1) in a fourth reactor (R4) , and

(g1) polymerizing in the fourth reactor (R4) and in the presence of the mixture (M1) propylene and ethylene and, optionally, a C ₄ to C ₁₂ alpha-olefin obtaining thereby the second elastomeric ethylene-propylene copolymer fraction (EC2) , the mixture (M1) and the second elastomeric ethylene-propylene copolymer fraction (EC2) form the heterophasic propylene copolymer (HECO) .

Per definition the xylene cold soluble (XCS) of said mixture (M1) is regarded as the first elastomeric ethylene-propylene copolymer fraction (EC1) .

Preferably, in step (e1) and (g1) only propylene and ethylene are polymerized. Thus a C ₄ to C ₁₂ alpha-olefin is preferably not present in steps (e1) and (g1) .

For preferred embodiments of the heterophasic propylene copolymer (HECO) , the crystalline matrix (M) , the first polypropylene (PP1) , the second polypropylene (PP2) , first elastomeric ethylene-propylene copolymer fraction (EC1) , as well as for the second elastomeric ethylene-propylene copolymer fraction (EC2) reference is made to the definitions given above.

The first reactor (R1) is preferably a slurry reactor (SR) and can be any continuous or simple stirred batch tank reactor or loop reactor operating in bulk or slurry. Bulk means a polymerization in a reaction medium that comprises of at least 60 % (w/w) monomer. According to the present invention the slurry reactor (SR) is preferably a (bulk) loop reactor (LR) .

The second reactor (R2) , the third reactor (R3) and the fourth reactor (R4) are preferably gas phase reactors (GPR) . Such gas phase reactors (GPR) can be any mechanically mixed or fluid bed reactors. Preferably the gas phase reactors (GPR) comprise a mechanically agitated fluid bed reactor with gas velocities of at least 0.2 m/sec. Thus it is appreciated that the gas phase reactor is a fluidized bed type reactor preferably with a mechanical stirrer.

Thus in a preferred embodiment the first reactor (R1) is a slurry reactor (SR) , like loop reactor (LR) , whereas the second reactor (R2) , the third reactor (R3) and the fourth reactor (R4) are gas phase reactors (GPR) . Accordingly for the instant process at least four, preferably four polymerization reactors, namely a slurry reactor (SR) , like loop reactor (LR) , a first gas phase reactor (GPR-1) , a second gas phase reactor (GPR-2) and a third gas phase reactor (GPR-3) connected in series are used. If needed prior to the slurry reactor (SR) a pre-polymerization reactor is placed.

A preferred multistage process is a “loop-gas phase” -process, such as developed by Borealis A/S, Denmark (known as

technology) described e.g. in patent literature, such as in EP 0 887 379, WO 92/12182 WO 2004/000899, WO 2004/111095, WO 99/24478, WO 99/24479 or in WO 00/68315.

A further suitable slurry-gas phase process is the

process of Basell described e.g. in figure 20 of the paper by Galli and Vecello, Prog. Polym. Sci. 26 (2001) 1287-1336.

Preferably, in the instant process for producing the crystalline matrix (M) as defined above the conditions for the first reactor (R1) , i.e. the slurry reactor (SR) , like a loop reactor (LR) , of step (a1) may be as follows:

- the temperature is within the range of 40 ℃ to 110 ℃, preferably between 60 ℃ and 100 ℃, like 68 to 95 ℃,

- the pressure is within the range of 20 bar to 80 bar, preferably between 40 bar to 70 bar,

- hydrogen can be added for controlling the molar mass in a manner known per se.

Subsequently, the reaction mixture from step (a1) containing preferably the first propylene copolymer fraction (PP1) is transferred to the second reactor (R2) , i.e. the first gas phase reactor (GPR-1) , whereby the conditions are preferably as follows:

- the temperature is within the range of 50 ℃ to 130 ℃, preferably between 60 ℃ and 100 ℃,

- the pressure is within the range of 5 bar to 50 bar, preferably between 15 bar to 35 bar,

If desired, the polymerization may be effected in a known manner under supercritical conditions in the first reactor (R1) , i.e. in the slurry reactor (SR) , like in the loop reactor (LR) , and/or as a condensed mode in the gas phase reactor (GPR-1) .

The gas phase reactors (GPR-2) and (GPR-3) of steps (e1) and (g1) are preferably also operated within the above conditions, preferably with the exception that in gas phase reactors (GPR-2) and (GPR-3) -the pressure is within the range of 5 bar to 50 bar, preferably between 10 bar to 30 bar.

The residence time can vary in the above different reactors.

In one embodiment of the process for producing the propylene copolymer the residence time the first reactor (R1) , i.e. the slurry reactor (SR) , like a loop reactor (LR) , is in the range 0.2 to 4 hours, e.g. 0.3 to 1.5 hours and the residence time in the gas phase reactors (GPR1 to GPR3) will generally be 0.2 to 6.0 hours, like 0.5 to 4.0 hours.

In the process of the invention a well-known prepolymerization step may precede before the actual polymerization in the reactors (R1) to (R4) . The prepolymerisation step is typically conducted at a temperature of 0 to 50 ℃, preferably from 10 to 45 ℃, and more preferably from 15 to 40 ℃.

More preferably the heterophasic propylene copolymer (HECO) is obtained in the presence of

(I) a solid catalyst component comprising a magnesium halide, a titanium halide and an internal electron donor; and

(II) a cocatalyst comprising an aluminium alkyl and optionally an external electron donor, and

(III) an optional nucleating agent, preferably in the presence of a nucleating agent as defined above or below;

and in a sequential polymerization process as defined in the present invention.

It is especially preferred that the process according to the present invention includes the following process steps:

polymerizing a vinyl compound as defined above, preferably vinyl cyclohexane (VCH) , in the presence of a catalyst system comprising the solid catalyst component to obtain a modified catalyst system which is the reaction mixture comprising the solid catalyst system and the produced polymer of the vinyl compound, preferably, and wherein, the weight ratio (g) of the polymer of the vinyl compound to the solid catalyst system is up to 5 (5: 1) , preferably up to 3 (3: 1) most preferably is from 0.5 (1: 2) to 2 (2: 1) , and the obtained modified catalyst system is fed to polymerization step (a1) of the process for producing the heterophasic propylene copolymer (HECO) .

The used catalyst is preferably a Ziegler-Natta catalyst system and even more preferred a modified Ziegler Natta catalyst system as defined in more detail below.

Such a Ziegler-Natta catalyst system typically comprises a solid catalyst component, preferably a solid transition metal component, and a cocatalyst, and optionally an external donor. The solid catalyst component comprises most preferably a magnesium halide, a titanium halide and an internal electron donor. Such catalysts are well known in the art. Examples of such solid catalyst components are disclosed, among others, in WO 87/07620, WO 92/21705, WO 93/11165, WO 93/11166, WO 93/19100, WO 97/36939, WO 98/12234, WO 99/33842.

Suitable electron donors are, among others, esters of carboxylic acids, like phthalates, citraconates, and succinates. Also oxygen-or nitrogen-containing silicon compounds may be used. Examples of suitable compounds are shown in WO 92/19659, WO 92/19653, WO 92/19658, US 4,347,160, US 4,382,019, US 4,435,550, US 4,465,782, US 4,473,660, US 4,530,912 and US 4,560,671.

Moreover, said solid catalyst components are preferably used in combination with well known external electron donors, including without limiting to, ethers, ketones, amines, alcohols, phenols, phosphines and silanes, for example organosilane compounds containing Si-OCOR, Si-OR, or Si-NR ₂ bonds, having silicon as the central atom, and R is an alkyl, alkenyl, aryl, arylalkyl or cycloalkyl with 1-20 carbon atoms; and well known cocatalysts, which preferably comprise an aluminium alkyl compound as known in the art, to polymerise the propylene copolymer.

When a nucleating agent is introduced to the heterophasic propylene copolymer (HECO) during the polymerisation process of the propylene copolymer, the amount of nucleating agent present in the heterophasic propylene copolymer (HECO) is preferably not more than 500 ppm, more preferably is 0.025 to 200 ppm, still more preferably is 1 to 100 ppm, and most preferably is 5 to 100 ppm, based on the heterophasic propylene copolymer (HECO) and the nucleating agent, preferably based on the total weight of the heterophasic propylene copolymer (HECO) including all additives.

The process for preparing the polyolefin composition (C)

The present invention is additionally directed to a process for the preparation of the polyolefin composition (C) of the present invention, comprising the steps of:

b) providing a polypropylene (PP) ;

In particular, it is preferred to use a conventional compounding or blending apparatus, e.g. a Banbury mixer, a 2-roll rubber mill, Buss-co-kneader or a twin-screw extruder. More preferably, mixing is accomplished in a co-rotating twin-screw extruder. The polymer materials recovered from the extruder are usually in the form of pellets. These pellets are then preferably further processed, e.g. by compression molding to generate articles and products of the inventive polyolefin composition (C) .

The article and uses

The present invention also relates to articles comprising the polyolefin composition (C) of the invention.

Preferably the article of the invention comprises more than 75 wt. -%of the polyolefin composition (C) , more preferably more than 85 wt. -%, yet more preferably more than 90 wt. -%, most preferably more than 95 wt. -%of the of the polyolefin composition (C) .

The article is preferably a molded article, most preferably an injection molded article or a foam injection molded article.

Preferably the article is a part of automotive articles, especially of car interiors, like instrumental carriers, dashboards, interior trims and the like.

The present invention is directed to the use of the polyolefin composition (C) for the preparation of automotive articles with improved electro-magnetic interference shielding properties.

EXAMPLES

1. Definitions/Measuring Methods

The following definitions of terms and determination methods apply for the above general description of the invention as well as to the below examples unless otherwise defined.

Density is measured according to ISO 1183-187. Sample preparation is done by compression molding in accordance with ISO 1872-2: 2007

Melting temperature Tm is measured according to ISO 11357-3

MFR ₂: The melt flow rate (MFR) is determined according to ISO 1133 and is indicated in g/10 min. The MFR is an indication of the flowability, and hence the processability, of the polymer. The higher the melt flow rate, the lower the viscosity of the polymer. The MFR ₂ of polypropylene is determined at a temperature of 230 ℃ and a load of 2.16 kg.

Quantification of copolymer microstructure by NMR spectroscopy

Quantitative nuclear-magnetic resonance (NMR) spectroscopy was used to quantify the comonomer content of the polymers.

Quantitative ¹³C { ¹H} NMR spectra were recorded in the solution-state using a Bruker Advance III 400 NMR spectrometer operating at 400.15 and 100.62 MHz for ¹H and ¹³C respectively. All spectra were recorded using a ¹³C optimised 10 mm extended temperature probehead at 125 ℃ using nitrogen gas for all pneumatics. Approximately 200 mg of material was dissolved in 3 ml of 1, 2-tetrachloroethane-d ₂ (TCE-d ₂) along with chromium- (III) -acetylacetonate (Cr (acac) ₃) resulting in a 65 mM solution of relaxation agent in solvent as described in G. Singh, A. Kothari, V. Gupta, Polymer Testing 2009, 28 (5) , 475.

To ensure a homogenous solution, after initial sample preparation in a heat block, the NMR tube was further heated in a rotatory oven for at least 1 hour. Upon insertion into the magnet the tube was spun at 10 Hz. This setup was chosen primarily for the high resolution and quantitatively needed for accurate ethylene content quantification. Standard single-pulse excitation was employed without NOE, using an optimised tip angle, 1 s recycle delay and a bi-level WALTZ16 decoupling scheme as described in Z. Zhou, R. Kuemmerle, X. Qiu, D. Redwine, R. Cong, A. Taha, D. Baugh, B. Winniford, J. Mag. Reson. 187 (2007) 225 and V. Busico, P. Carbonniere, R. Cipullo, C. Pellecchia, J. Severn, G. Talarico, Macromol. Rapid Commun. 2007, 28, 1128. A total of 6144 (6k) transients were acquired per spectra. Quantitative ¹³C { ¹H} NMR spectra were processed, integrated and relevant quantitative properties determined from the integrals. All chemical shifts were indirectly referenced to the central methylene group of the ethylene block (EEE) at 30.00 ppm using the chemical shift of the solvent. This approach allowed comparable referencing even when this structural unit was not present.

With characteristic signals corresponding to 2, 1 erythro regio-defects observed (as described in L. Resconi, L. Cavallo, A. Fait, F. Piemontesi, Chem. Rev. 2000, 100 (4) , 1253, in Cheng, H. N., Macromolecules 1984, 17, 1950, and in W-J. Wang and S. Zhu, Macromolecules 2000, 33 1157) the correction for the influence of the regio-defects on determined properties was required. Characteristic signals corresponding to other types of regio-defects were not observed.

Characteristic signals corresponding to the incorporation of ethylene were observed (as described in Cheng, H.N., Macromolecules 1984, 17, 1950) and the comonomer fraction calculated as the fraction of ethylene in the polymer with respect to all monomer in the polymer.

The comonomer fraction was quantified using the method of W-J. Wang and S. Zhu, Macromolecules 2000, 33 1157, through integration of multiple signals across the whole spectral region in the ¹³C { ¹H} spectra. This method was chosen for its robust nature and ability to account for the presence of regio-defects when needed. Integral regions were slightly adjusted to increase applicability across the whole range of encountered comonomer contents.

The mole percent comonomer incorporation was calculated from the mole fraction.

The weight percent comonomer incorporation was calculated from the mole fraction.

Calculation of comonomer content of the second elastomeric ethylene-propylene copolymer fraction (EC2) (herein calculated for the second elastomeric ethylene-propylene copolymer fraction (EC2) , but the formula can be applied for the other fractions as well) :

wherein

w (PP1) is the weight fraction [in wt. -%] of the first elastomeric ethylene-propylene copolymer fraction (EC1) , e.g. the xylene cold soluble (XCS) fraction after the third reactor (e.g. comprising the matrix (M) and the first elastomeric fraction) ;

w (PP2) is the weight fraction [in wt. -%] of the second elastomeric ethylene-propylene copolymer fraction (EC2) , e.g. of the amount of xylene cold soluble fraction (XCS) produced in the fourth reactor (e.g. the second elastomeric fraction produced in the fourth reactor) ;

C (PP1) is the comonomer content [in mol-%] of the first elastomeric ethylene-propylene copolymer fraction (EC1) , e.g. of the xylene cold soluble (XCS) fraction after the third reactor (e.g. comprising the matrix (M) and the first elastomeric fraction) ;

C (PP) is the comonomer content [in mol-%] of the xylene soluble fraction of the final heterophasic propylene copolymer (HECO) ,

C (PP2) is the calculated comonomer content [in mol-%] of the second elastomeric ethylene-propylene copolymer fraction (EC2) .

Maleic anhydride content: FT-IR standards are prepared by blending a PP homopolymer with different amounts of MAH to create a calibration curve (absorption/thickness in cm versus MAH content in weight %) . The MAH content is determined in the solid-state by IR spectroscopy using a Bruker Vertex 70 FTIR spectrometer on 25x25 mm square films of 100 μm thickness (with an accuracy of ± 1 μm) prepared by compression moulding at 190 ℃ with 4 -6 mPa clamping force. Standard transmission FTIR spectroscopy is employed using a spectral range of 4000-400 cm ^-1, an aperture of 6 mm, a spectral resolution of 2 cm ^-1, 16 background scans, 16 spectrum scans, an interferogram zero filling factor of 32 and Norton Beer strong apodisation.

At the adsorption band peak of 1787 cm ^-1 MAH is measured. For the calculation of the MAH content the range between 1830-1727 cm ^-1 is evaluated (after a base line correction) following the calibration standard curve.

The xylene soluble fraction (XCS) at room temperature (XCS, wt. -%) : The amount of the polymer soluble in xylene is determined at 25 ℃ according to ISO 16152; first edition; 2005-07-01. The remaining part is the xylene cold insoluble (XCU) fraction.

The intrinsic viscosity (IV) is measured according to ISO 1628-1 (at 135 ℃ in decalin) .

Charpy impact test: The Charpy notched impact strength (NIS) was measured according to ISO 179-1 eA at +23 ℃ and -20 ℃, using injection-molded bar test specimens of 80x10x4 mm ³ prepared in accordance with ISO 1873-2: 2007.

Flexural Modulus: The flexural modulus was determined in 3-point-bending at 23℃ according to ISO 178 on 80x10x4 mm ³ test bars injection moulded in line with EN ISO 1873-2.

Tensile Strength: measured according to ISO527 on 170x10x4 mm ³ test bars injection moulded in line with EN ISO 1873-2.

Particle size d ₅₀ and top cut d ₉₅ were calculated from the particle size distribution [mass percent] as determined by gravitational liquid sedimentation according to ISO 13317-3 (Sedigraph) .

Surface Resistivity: measured by using a test equipment “HS-699” commercially available from Shenzhen Hoslen Electronic Co., Ltd, Guangdong, China, on a test sample, i.e. a plate with a size of 150mm (length) *90mm (width) *3mm (height) , injection moulded in line with EN ISO 1873-2, under test conditions of temperature 23℃ and relative humidity 50%.

2. Examples

2.1. Synthesis of polypropylene (PP1)

The catalyst used in the polymerizations was a Ziegler-Natta catalyst from Borealis having Ti-content of 1.9 wt-% (as described in EP 591 224) . Before the polymerization, the catalyst was prepolymerized with vinyl-cyclohexane (VCH) as described in EP 1 028 984 and EP 1 183 307. The ratio of VCH to catalyst of 1: 1 was used in the preparation, thus the final Poly-VCH content was less than 100 ppm. In the first stage the catalyst described above was fed into prepolymerization reactor together with propylene and small amount of hydrogen (2.5 g/h) and ethylene (330 g/h) . Triethylaluminium as a cocatalyst and dicyclopentyldimethoxysilane as a donor was used. The aluminium to donor ratio was 7.5 mol/mol and aluminium to titanium ratio was 300 mol/mol. Reactor was operated at a temperature of 30 ℃and a pressure of 55 barg.

The subsequent polymerization has been effected under the following conditions.

Table 1: Polymerization conditions for PP1

2.2. Compounding of examples

The propylene compositions of Inventive examples IE1 to IE3 and comparative examples CE1 and CE2 were prepared based on the recipes indicated in Table 2 by compounding in a co-rotating twin-screw extruder under the conditions described in Table 3. The extruder has 11 heating zones.

Table 2: Recipes for Comparative and Inventive examples

PP2 propylene homopolymer with a trade name of HD915CF, commercially available from Borouge Sales & Marketing (Shanghai) . Co. Ltd., Shanghai, China, having a MFR ₂ of 8 g/10min.

PP3 propylene homopolymer with a trade name of HJ311AI, commercially available from Borouge Sales & Marketing (Shanghai) . Co. Ltd., Shanghai, China, having a MFR ₂ of 62 g/10min

CNT Multi-wall carbon nanotubes commercially available from CNT Solution (Korea) , diameter 5 nm, length 4 μm, density 1.9 g/cm ³;

F Talc with a trade name of Jetfine T1CA commercially available from Imerys (France) , with median diameter d50 of 1.3 μm, diameter d95 of 4.2 μm and specific surface area BET of 12.6 m ²/g;

D oleamide dispersant with a trade name of Crodamide VRX commercially available from Croda Chemicals Europe Ltd (UK) , CAS-no. 301-02-0, having a melting point of 75 ℃;

PMP maleic anhydride-grafted polypropylene with a trade name of SCONA TPPP 8112 GA, commercially available from BYK-Cera (Germany) , having a maleic anhydride content of 1.4 wt. -%.

Irgafos 168 Antioxidant tris (2, 4-di-t-butylphenyl) phosphite (CAS-no. 31570-04-4) , of BASF SE having melting temperature of 182 ℃;

Irganox 1010 Antioxidant pentaerythritol tetrakis (3- (3, 5-di-t-butyl-4-hydroxyphenyl) propionate (CAS-no. 6683-19-8) , of BASF SE having melting temperature of 115 ℃;

h-PP Propylene homopolymer carrier of additives, in powder form and having melting temperature of 160 ℃;

CB Carbon black

Yuch black-1906 Yuch black-1906 pigment, commercially available from Cabot Corporation (USA)

Table 3: Compounding conditions for Comparative and Inventive examples

Table 4: Properties of comparative and inventive examples

As can be seen from the examples in Table 4, the compositions comprising both carbon nanotubes and filler (i.e. IE1 to IE3) have a much lower surface resistivity than the example without the talc (CE2) , as well as much lower surface resistivity than a typical carbon black-based composition (CE1) that would often be used in similar applications.

Additionally, the inventive examples clearly show a markedly improved balance of mechanical properties (flexural modulus and Charpy NIS) compared to the comparative examples. The presence of carbon nanotubes in the composition appears to improve both the flexural modulus and the Charpy NIS (compare IE1, IE2 and IE3) , which is a difficult effect to achieve in polypropylene compositions.

The combination of a desirable balance of mechanical properties with improved electromagnetic interference shielding properties (i.e. low surface resistivity) makes the inventive compositions ideal candidates for the manufacture of automotive articles involved in housing electrical equipment (e.g. the instrument carrier panel) .

Claims

A polyolefin composition (C) comprising

a) from 55.0 to 90.0 wt. -%, based on the total weight of the composition, of a polypropylene (PP) , preferably a copolymer, having a melt flow rate (MFR2) measured according to ISO 1133 at 230℃ and 2.16 kg in the range from 2.0 to 120.0 g/10 min, preferably in the range from 2.0 to 60.0 g/10 min;

b) from 2.0 to 10.0 wt. -%, based on the total weight of the composition, of carbon nanotubes (CNT) ;

c) from 5.0 to 40.0 wt. -%, based on the total weight of the composition, of an inorganic filler (F) ;

d) from 0.3 to 1.0 wt. -%, based on the total weight of the composition, of dispersant (D) ;

e) from 0.1 to 5.0 wt. -%, based on the total weight of the composition, of at least one additive (A) other than the inorganic filler (F) and the dispersant (D) .
The polyolefin composition (C) according to any one of the preceding claims, wherein the polypropylene (PP) is a heterophasic propylene copolymer.
The polyolefin composition (C) according to any one of the preceding claims, wherein the polypropylene (PP) has one or more, preferably all, of the following properties

i) an ethylene (C2) content in the range from 6.0 to 18.0 wt. -%, preferably in the range from 7.0 to 15.0 wt. -%, most preferably in the range from 8.0 to 12.0 wt. -%;

ii) a xylene cold solubles (XCS) content in the range from 20.0 to 32.0 wt. -%, preferably in the range from 22.0 to 29.0 wt. -%, most preferably in the range from 23.0 to 26.0 wt. -%;

iii) an ethylene content of the xylene cold soluble fraction (C2 (XCS) ) in the range from 30.0 to 45.0 wt. -%, preferably in the range from 33.0 to 42.0 wt. -%, most preferably in the range from 36.0 to 40.0 wt. -%;

iv) an intrinsic viscosity of the xylene cold soluble fraction (IV (XCS) ) in the range from 2.0 to 4.0 dl/g, preferably in the range from 2.5 to 3.7 dl/g, most preferably in the range from 3.0 to 3.4 dl/g.
The polyolefin composition (C) according to any one of the preceding claims, wherein the carbon nanotubes have a density in the range from 1.8 to 2.1 g/cm ³, and/or a diameter in the range from 2.0 to 25.0 nm, and/or a length in the range from 0.1 to 10.0 μm.
The polyolefin composition (C) according to any one of the preceding claims, wherein the inorganic filler (F) has an average particle size (d50) in the range from 0.8 to 40 μm, preferably selected from the group containing talc, calcium carbonate, barium sulfate, mica, and mixtures thereof, most preferably the inorganic filler (F) is talc.
The polyolefin composition (C) according to any one of the preceding claims, wherein the dispersant (D) is selected from the group containing calcium stearate, polyethylene wax, oleamide, erucamide, and mixtures thereof, preferably the dispersant (D) is an oleamide.
The polyolefin composition (C) according to any one of the preceding claims, further comprising f) from 0.1 to 3.0 wt. -%, based on the total weight of the composition, of a polar-modified polypropylene (PMP) , preferably a maleic anhydride-modified polypropylene.
The polyolefin composition (C) according to claim 7, wherein the polar-modified polypropylene (PMP) has a content of polar groups in the range from 0.5 to 3.0 wt. -%.
The polyolefin composition (C) according to any one of the preceding claims, wherein the polyolefin composition (C) has a flexural modulus of at least 1800 MPa, and/or a Charpy notched impact strength of at least 8.0 kJ/m ².
The polyolefin composition (C) according to any one of the preceding claims, wherein the polyolefin composition (C) has a surface resistivity of at most 1,000,000 Ohm/m ².
A process for the preparation of a polyolefin composition according to any one of the preceding claims, comprising the steps of:

a) providing a mixture of additives (A) and dispersant (D) and optionally a polar-modified polypropylene (PMP) , preferably in the form of a master batch;

b) providing a polypropylene (PP) ;

c) blending the carbon nanotubes (CNT) and the inorganic filler (F) to obtain a mixed blend of carbon nanotubes (CNT) and inorganic filler (F) ;

d) blending and extruding the polypropylene (PP) with the mixture of additives (A) and dispersant (D) and the blend of carbon nanotubes (CNT) and inorganic filler (F) at a temperature in the range from 180℃ to 250℃ in an extruder, preferably a twin-screw extruder.
An article comprising more than 75 wt. -%of the polyolefin composition (C) according to any one of claims 1 to 10, preferably a molded article, most preferably an injection molded article or a foam injection molded article.
The article according to claim 12, wherein the article is a part of automotive articles, especially of car interiors, like instrumental carriers, dashboards, interior trims and the like.
A use of the polyolefin composition (C) according to any one of claims 1 to 10 for the preparation of automotive articles with improved electromagnetic interference shielding properties.