WO2015089688A1

WO2015089688A1 - Polypropylene composition with low coefficient of linear thermal expansion and high dimension stability

Info

Publication number: WO2015089688A1
Application number: PCT/CN2013/001605
Authority: WO
Inventors: Weili QIANG; Jianglei ZHU; Jiandong ZHANG; Shih Ping CHEN
Original assignee: Borouge Compounding Shanghai Co., Ltd.
Priority date: 2013-12-20
Filing date: 2013-12-20
Publication date: 2015-06-25
Also published as: CN105829437B; CN105829437A

Abstract

The present invention relates to a polypropylene composition comprising heterophasic propylene copolymer, propylene homopolymer, elastomeric ethylene copolymer and inorganic filler, and having dimensional stability and balanced mechanical properties.

Description

Polypropylene composition with low coefficient of linear thermal expansion and

dimension stability

The present invention is directed to a polyolefin composition having low coefficient of linear thermal expansion (CLTE) and high dimension stability.

Polypropylene is the material of choice in many applications as it can be tailored to specific purposes needed. In particular, heterophasic polypropylenes are widely used in the automobile industry as they provide a combination of good stiffness and reasonable impact strength behavior. Heterophasic polypropylenes contain a polypropylene matrix in which an amorphous phase is dispersed. The amorphous phase typically contains a propylene copolymer rubber, like an ethylene propylene rubber or an ethylene propylene diene monomer polymer. Further the heterophasic polypropylene contains a crystalline polyethylene to some extent. In the automobile industry such heterophasic polypropylene grades contain an amount of up to about 30 wt.-% propylene copolymer rubber, which normally is produced directly in one or two gas phase reactors or added externally to the matrix via a compounding step.

In the field of automotives, particularly of automotive exterior applications, the thermal expansion of a polymer is of great importance. The coefficient of linear thermal expansion (CLTE) determines the minimum gap width between two parts. Most of the time, the parts are made from different materials. To avoid big gaps and high stresses in the parts, the coefficient of linear thermal expansion (CLTE) of a material should be as low as possible. On the other hand the mechanical properties, like impact and stiffness, should not be negatively affected when reducing shrinkage of the material.

Thus the object of the present invention is to provide a polyolefin composition of low coefficient of linear thermal expansion (CLTE) without compromising the general mechanical properties, particularly impact strength and stiffness of said composition.

Accordingly, there is the objective of developing polypropylene compositions which have low coefficient of linear thermal expansion and high dimensional stability together with balanced mechanical properties like impact strength and stiffness. The foregoing and other objectives are solved by the subject-matter of the present invention.

The specific finding of the present invention is to provide a polypropylene composition (PP) comprising,

(a) a heterophasic propylene copolymer (HECO) having a melt flow rate MFR₂ (230 °C, 2, 16 kg) measured according to ISO 1 133 in the range of from 16 to 100 g/lOmin, like in the range of 16.0 to 80.0 g/lOmin,

(b) a propylene homopolymer (homo-PP) having a melt flow rate MFR₂ (230°C, 2, 16 kg) measured according to ISO 1 133 in the range of from 40 to 70 g/l Omin. like in the range of from 40.0 to 65.0 g/10 min,

(c) an elastomeric ethylene copolymer (EEC) having a melt flow rate MFR₂ (190°C, 2, 16 kg) measured according to ISO 1 133 in the range of from 0.2 to 20.0 g/l Omin, and

(d) an inorganic filler (F).

In a preferred embodiment of the present invention, the heterophasic propylene copolymer (HECO) has

(i) a xylene cold soluble (XCS) fraction measured according to ISO 16152 (25 °C) in the range of from 13.0 to 25.0 wt.-%, like in the range from 15.0 to 20.0 wt.-%, based on the total weight of the heterophasic propylene copolymer (HECO), and/or

(ii) a comonomer content, preferably an ethylene content, of equal or below 15 wt.-%, like of equal or below 12.0 wt.-%, based on the total weight of the heterophasic propylene copolymer (HECO).

In another preferred embodiment of the present invention, the xylene cold soluble (XCS) fraction of the heterophasic propylene copolymer (HECO) has

(i) an intrinsic viscosity (IV) in the range of 2.0 to 3.5 dl/g, like in the range of 2.0 to 3.0 dl/g, and/or

(ii) a comonomer content, preferably an ethylene content, in the range of 25.0 to 45.0 wt- %, like in the range of 30.0 to 45.0 wt.-%.

In another preferred embodiment of the present invention, the polypropylene composition (PP) comprises (a) 35.0 to 49.0 wt.-%, preferably 40.0 to 49.0 wt.-%, of the heterophasic propylene copolymer (HECO), and/or

(b) 5.0 to 15.0 wt.-%, preferably 5.0 to 13.0 wt-%, of the propylene homopolymer

(homo-PP), and/or

(c) 5.0 to 14.0 wt.-%, preferably 5.0 to 12.0 wt.-%, of the elastomeric ethylene copolymer (EEC), and/or

(d) 21.0 to 35.0 wt.-%, preferably 25.0 to 35.0 wt.-%, of the inorganic filler (F), based on the total weight of the composition. In a further embodiment the heterophasic propylene copolymer (HECO) preferably comprises a polypropylene homopolymer (PP-1) as matrix and an elastomeric propylene copolymer (E-l) being dispersed in said matrix.

In another preferred embodiment of the present invention, the propylene homopolymer (homo-PP) has a flexural modulus measured according to ISO 178 of at least 1 ,550 MPa, preferably of at least 1 ,650 MPa.

In another preferred embodiment of the present invention, the weight ratio of the heterophasic propylene copolymer (FIECO) to the inorganic filler (F) [EIECO / F] is from 1.0 to 2.3, preferably 1.1 to 2.0, more preferably from 1.2 to 1.7.

In another preferred embodiment of the present invention, the weight ratio of propylene homopolymer (homo-PP) to the inorganic filler (F) [homo-PP F] is from 0.14 to 0.72, preferably from 0.14 to 0.52, more preperably from 0.14 to 0.34.

In another preferred embodiment of the present invention, the elastomeric ethylene copolymer (EEC) has a density in the range of from 850 to 900 kg/m³.

In another preferred embodiment of the present invention, the polypropylene composition (PP) has flexural modulus according to ISO 178 of at least 2,500 MPa, preferably at least 2,800 MPa. In a preferred embodiment of the present invention, the polypropylene composition (PP) has

(a) a notched izod strength measured according to ISO 180 / 1 A at 23 °C of at least 10 kJ/m², more preferably at least 14 kJ/m²,

(b) a flexural modulus measured according to ISO 178 of at least 2,500 MPa, more

preferably of at least 2800 MPa, and

(c) a coefficient of linear thermal expansion (CLTE) measured according to ASTM E 831 in flow direction of equal to or below 4.8K^"1, more preferably not higher than 4.7K^"'.

Another preferred embodiment of the present invention is directed to an article comprising the polypropylene composition (PP) according to the present invention. Preferably the article is a molded article, like an injection molded article, more preferably the article is selected from the group consisting of household articles, medical articles, automotive articles, and/or articles of pipes and toys. Another preferred embodiment of the present invention is directed to the use of the polypropylene composition (PP) according to the present invention for the production of household articles, medical articles, automotive articles, and/or articles of pipes and toys.

Another preferred embodiment of the present invention is directed to the use of a polypropylene composition (PP) for the preparation of an article, wherein the preparation includes a molding technique, preferably injection molding.

It has been surprisingly found out that the polypropylene composition (PP) according to the present invention exhibits good dimension stability and modulus while retaining balanced stiffness and impact strength.

In the following, the invention and all of its components are described in more detail.

When in the following reference is made to preferred embodiments or technical details of the inventive polypropylene composition (PP), it is to be understood that these preferred embodiments or technical details also refer to the inventive article comprising the polypropylene composition (PP). As already mentioned above, the polypropylene composition (PP) according to the present invention comprises a heterophasic propylene copolymer (HECO) as an essential component.

The expression "heterophasic" indicates that an elastomeric propylene copolymer (E-l) is (finely) dispersed in a polypropylene homopolymer matrix (PP-1). In other words, the elastomeric propylene copolymer (E-l ) forms inclusions in the matrix. Thus, the matrix contains (finely) dispersed inclusions being not part of the matrix and said inclusions contain the elastomeric propylene copolymer (E-l). The term "inclusion" according to this invention shall preferably indicate that the matrix and the inclusion form different phases within the heterophasic propylene copolymer, said inclusions are for instance visible by high resolution microscopy, like electron microscopy or scanning force microscopy.

The final composition is probably of a complex structure. For example, the polypropylene homopolymer matrix (PP- 1 ) of the heterophasic propylene copolymer (HECO) together with the propylene homopolymer (homo-PP) may form a continuous phase being the matrix of the composition wherein the elastomeric copolymers and optional additives form together or individually inclusions dispersed therein.

The heterophasic propylene copolymer (HECO)

The heterophasic propylene copolymer (HECO) is preferably a heterophasic system in which the polypropylene homopolymer (PP-1) as defined herein constitutes the matrix in which an elastomeric propylene copolymer (E-l ) is dispersed. The heterophasic propylene copolymer (HECO) is present in the polypropylene composition according to the present invention in an amount of at least 30.0 wt.-% based on the total weight of the polypropylene composition (PP). Preferred are amounts in the range of from 30.0 to 49.0 wt.-%, more preferred amounts are in the range of from 35.0 to 49.0 wt.-%, still more preferred are amounts in the range of from 40.0 to 49.0 wt.-%, yet more preferred amounts are in the range of from 45.0 to 49.0 wt.-%. Accordingly, the heterophasic propylene copolymer (HECO) being part of the polypropylene composition (PP) comprises apart from propylene also comonomers. Preferably, the heterophasic propylene copolymer (HECO) being part of the polypropylene composition (PP) comprises apart from propylene ethylene and/or C₄ to C_l2 a-olefins. Accordingly, the term heterophasic propylene copolymer (HECO) according to this invention is understood as a polypropylene comprising, preferably consisting of, units derivable from

(a) propylene

and

(b) ethylene and/or C₄ to Q₂ a-olefins.

Thus, the heterophasic propylene copolymer (HECO) according to this invention, i.e. the heterophasic propylene copolymer (HECO) being part of the polypropylene composition (PP), comprises monomers copolymerizable with propylene, for example comonomers such as ethylene and/or C₄ to C_n a-olefins, in particular ethylene and/or C₄ to Cs a-olefins, e.g. ethylene, 1-butene and/or 1 -hexene. Preferably, the heterophasic propylene copolymer (HECO) according to this invention comprises, especially consists of, monomers

copolymerizable with propylene from the group consisting of ethylene, 1 -butene and 1 - hexene. More specifically, the heterophasic propylene copolymer (HECO) of this invention comprises - apart from propylene - units derivable from ethylene and/or 1 -butene. In a preferred embodiment, the heterophasic propylene copolymer (HECO) according to this invention comprises units derivable from propylene and ethylene only. Still more preferably only the elastomeric propylene copolymer (E- 1 ) contains ethylene comonomers.

It is thus appreciated that the elastomeric propylene copolymer (E-1 ) dispersed in the polypropylene homopolymer (PP- 1 ) comprises propylene monomer units and comonomer units selected from ethylene and/or C₄ to C^ a-olefin. For example, the elastomeric propylene copolymer (E- 1 ) dispersed in the polypropylene homopolymer matrix (PP- 1 ) comprises only propylene monomer units and ethylene comonomer units. Accordingly, the elastomeric propylene copolymer (E- 1 ) is preferably an ethylene propylene rubber (EPR), whereas the matrix in which the elastomeric propylene copolymer (E- 1 ) is dispersed is a polypropylene homopolymer (PP- 1 ). It is appreciated that the heterophasic propylene copolymer (HECO) being part of the polypropylene composition (PP) preferably has a comonomer content, preferably an ethylene content, of < 15.0 wt.-%, more preferably < 12.0 wt.-%, still more preferably from 3.0 to equal or below 12.0 wt.-%, yet more preferably from 5.0 to 10.0 wt.-%, based on the total weight of the heterophasic propylene copolymer (HECO).

The xylene cold soluble (XCS) fraction (23 °C) of the heterophasic propylene copolymer (HECO) being part of the polypropylene composition (PP) is preferably of from 13.0 to 25.0 wt.-%, more preferably from 14.0 to 22.0 wt.-%, still more preferably from 15.0 to 20.0 wt- %, based on the total weight of the heterophasic propylene copolymer (HECO).

Additionally or alternatively, the heterophasic propylene copolymer (HECO) being part of the polypropylene composition (PP) has a melt flow rate MFR₂ (230 °C, 2.16 kg) of from 16.0 to 100.0 g/10 min, more preferably from 16.0 to 80.0 g/10 min, still more preferably from 16.0 to 70.0 g/10 min, yet more preferably from 18.0 to 70.0 g/10 min. For example, the heterophasic propylene copolymer (HECO) being part of the polypropylene composition (PP) has a melt flow rate MFR₂ (230 °C, 2.16 kg) of from 18.0 to 40.0 g/10 min. The polypropylene homopolymer (PP- ) being part of the heterophasic propylene copolymer (HECO) is a propylene homopolymer.

The expression propylene homopolymer used in the instant invention relates to a polypropylene that consists substantially, i.e. of more than 99.7 wt.-%, still more preferably of at least 99.8 wt.-%, of propylene units. In a preferred embodiment only propylene units in the propylene homopolymer are detectable.

Furthermore, it is appreciated that the xylene cold soluble (XCS) fraction of the

polypropylene homopolymer (PP-1 ) being part of the heterophasic propylene copolymer (HECO) is rather low. Accordingly, the xylene cold soluble (XCS) fraction of the polypropylene homopolymer (PP-1) (25 °C) is preferably of from 0.6 to 3.0 wt.-%, more preferably from 0.8 to 3.0 wt.-% and most preferably from 0.8 to 2.5 wt.-%, based on the total weight of the polypropylene homopolymer (PP-1) of the heterophasic propylene copolymer (HECO). For example, the xylene cold soluble (XCS) fraction of the

polypropylene homopolymer (PP-1) (25 °C) is from 0.8 to 2.0 wt.-%, based on the total weight of the polypropylene homopolymer (PP-1) of the heterophasic propylene copolymer (HECO).

Additionally or alternatively, the polypropylene homopolymer (PP-1) being part of the heterophasic propylene copolymer (HECO) has a rather high melt flow rate. Accordingly, it is preferred that the polypropylene homopolymer (PP-1) has a melt flow rate MFR₂ (230 °C, 2.16 kg) of from 30.0 to 250.0 g/10 min, preferably from 33.0 to 170.0 g/l Omin, more preferably from 35.0 to 100.0 g/10 min, even more preferably from 38.0 to 80.0 g/10 min and most preferably from 38.0 to 60.0 g/10 min.

A further essential component of the heterophasic propylene copolymer (HECO) being part of the polypropylene composition (PP) is the elastomeric propylene copolymer (E-1) dispersed in the polypropylene homopolymer (PP-1 ).

Concerning the comonomers used in the elastomeric propylene copolymer (E-1) it is referred to the information provided for the heterophasic propylene copolymer (HECO). Accordingly, the elastomeric propylene copolymer (E-1) comprises monomers copolymerizable with propylene, for example comonomers such as ethylene and/or C₄ to Q₂ a-olefins, in particular ethylene and/or C₄ to C₈ a-olefins, e.g. 1 -butene and/or 1-hexene. Preferably, the elastomeric propylene copolymer (E-1 ) comprises, especially consists of, monomers copolymerizable with propylene from the group consisting of ethylene, 1 -butene and 1 -hexene. More specifically, the elastomeric propylene copolymer (E-1 ) comprises - apart from propylene - units derivable from ethylene and/or 1 -butene. Thus, in an especially preferred embodiment the elastomeric propylene copolymer (E-1 ) comprises units derivable from propylene and ethylene only. It is thus appreciated that the elastomeric propylene copolymer (E-1) dispersed in the polypropylene homopolymer (PP-1 ) comprises propylene monomer units and comonomer units selected from ethylene and/or C₄ to C₁₂ a-olefin. For example, the elastomeric propylene copolymer (E-1) dispersed in the polypropylene homopolymer (PP-1 ) comprises propylene monomer units and ethylene comonomer units.

Since almost all amount of the elastomeric propylene copolymer (E-1) is soluble in cold xylene, the comonomer content of the elastomeric propylene copolymer (E-1) equates with the comonomer content of the xylene cold soluble (XCS) fraction.

Accordingly the comonomer content, preferably the ethylene content, of the elastomeric propylene copolymer (E-1 ), i.e. of the xylene cold soluble (XCS) fraction, is comparatively not low. Accordingly, in one embodiment the comonomer content, more preferably ethylene content, of the elastomeric propylene copolymer (E-1 ), i.e. of the xylene cold soluble (XCS) fraction of the heterophasic propylene copolymer (HECO), is preferably from 25.0 to 45.0 wt.-%, more preferably from 28.0 to 42.0 wt.-%, still more preferably from 30.0 to 40.0 wt- %.

According to one embodiment of the present invention, the intrinsic viscosity (IV) of the xylene cold soluble (XCS) fraction of the heterophasic propylene copolymer (HECO) is preferably from 2.0 to 3.5 dl/g, more preferably from 2.0 to 3.0 dl/g, still more preferably from 2.2 to 2.8 dl/g.

As will be explained below, the heterophasic propylene copolymer (HECO) as well its individual components (matrix and elastomeric copolymer) can be produced by blending different polymer types, i.e. of different molecular weight and/or comonomer content.

However it is preferred that the heterophasic propylene copolymer (HECO) as well its individual components (matrix and elastomeric copolymer) are produced in a sequential step process, using reactors in serial configuration and operating at different reaction conditions. As a consequence, each fraction prepared in a specific reactor will have its own molecular weight distribution and/or comonomer content distribution. The heterophasic propylene copolymer (HECO) according to the present invention is preferably produced in a sequential polymerization process, i.e. in a multistage process, known in the art, wherein the polypropylene (PP-1 ) is produced at least in one slurry reactor, preferably in a slurry reactor and optionally in a subsequent gas phase reactor, and subsequently the elastomeric propylene copolymer (E-l) is produced at least in one, or two, gas phase reactor(s).

Accordingly it is preferred that the heterophasic propylene copolymer (HECO) is produced in a sequential polymerization process comprising the steps of

(a) polymerizing propylene and optionally at least one ethylene and/or C₄ to Q₂ -olefin in a first reactor (Rl) obtaining the first polypropylene fraction of the polypropylene (PP-1), preferably said first polypropylene fraction is a first propylene homopolymer,

(b) transferring the first polypropylene fraction into a second reactor (R2),

(c) polymerizing in the second reactor (R2) and in the presence of said first

polypropylene fraction propylene and optionally at least one ethylene and/or C to Co a-olefin obtaining thereby the second polypropylene fraction, preferably said second polypropylene fraction is a second propylene homopolymer, said first polypropylene fraction and said second polypropylene fraction form the

polypropylene (PP-1), like the propylene homopolymer (PP-1 ), i.e. the matrix of the heterophasic propylene copolymer (HECO),

(d) transferring the polypropylene (PP-1) of step (c) into a third reactor (R3),

(e) polymerizing in the third reactor (R3) and in the presence of the polypropylene (PP-1 ) obtained in step (c) propylene and at least one of ethylene and/or C₄ to Cn a-olefin obtaining thereby a first elastomeric propylene copolymer fraction, the first elastomeric propylene copolymer fraction is dispersed in the polypropylene (PP- 1),

(f) transferring the polypropylene (PP-1) in which the first elastomeric propylene

copolymer fraction is dispersed into a fourth reactor (R4), and

(g) polymerizing in the fourth reactor (R4) and in the presence of the mixture obtained in step (e) propylene and at least one of ethylene and/or C₄ to C_u a-olefin obtaining thereby the second elastomeric propylene copolymer fraction,

the polypropylene (PP-1), the first elastomeric propylene copolymer fraction, and the second elastomeric propylene copolymer fraction form the heterophasic propylene copolymer (HECO). Alternatively the elastomeric propylene copolymer (E- 1 ) can be also produced in one gas phase reactor, i.e. the fourth reactor (R4) is optional.

Of course, in the first reactor (Rl) the second polypropylene fraction can be produced and in the second reactor (R2) the first polypropylene fraction can be obtained. The same holds true for the elastomeric propylene copolymer phase. Accordingly in the third reactor (R3) the second elastomeric propylene copolymer fraction can be produced whereas in the fourth reactor (R4) the first elastomeric propylene copolymer fraction is made. Preferably between the second reactor (R2) and the third reactor (R3) and optionally between the third reactor (R3) and fourth reactor (R4) the monomers are flashed out.

The term "sequential polymerization process" indicates that the heterophasic propylene copolymer (HECO) is produced in at least two, like three or four reactors connected in series. Accordingly the present process comprises at least a first reactor (Rl ) and a second reactor (R2), more preferably a first reactor (Rl ), a second reactor (R2), a third reactor (R3) and a fourth reactor (R4), and more preferably a first reactor (Rl), a second reactor (R2), and a third reactor (R3). The term "polymerization reactor" shall indicate that the main

polymerization takes place. Thus in case the process consists of four or three 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.

The first reactor (Rl) 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 (Rl) is a slurry reactor (SR), like a 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 three, preferably three polymerization reactors, namely a slurry reactor (SR), like a loop reactor (LR), a first gas phase reactor (GPR-1), and a second gas phase reactor (GPR-2) 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 BORSTAR® technology) described e.g. in patent literature, such as in EP 0 887 379, WO 92/12182, WO 2004/000899, WO 2004/11 1095, WO 99/24478, WO 99/24479 or in WO 00/68315.

A further suitable slurry-gas phase process is the Spheripol process of Basell.

Preferably, in the instant process for producing the heterophasic propylene copolymer (HECO) as defined above the conditions for the first reactor (Rl), i.e. the slurry reactor (SR), like a loop reactor (LR), of step (a) may be as follows:

the temperature is within the range of 50 °C to 1 10 °C, preferably between 60 °C and 100 °C, more preferably between 68 and 95 °C,

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 (a) is transferred to the second reactor (R2), i.e. gas phase reactor (GPR-1), i.e. to step (c), whereby the conditions in step (c) are preferably as follows:

the temperature is within the range of 50 °C to 130 °C, preferably between 60 °C and 100 °C, the pressure is within the range of 5 bar to 50 bar, preferably between 15 bar to 35 bar,

hydrogen can be added for controlling the molar mass in a manner known per se. The condition in the third reactor (R3) and the fourth reactor (R4), preferably in the second gas phase reactor (GPR-2) and third gas phase reactor (GPR-3), is similar to the second reactor (R2).

The residence time can vary in the three reactor zones.

In one embodiment of the process for producing the polypropylene the residence time in bulk reactor, e.g. loop is in the range 0.1 to 2.5 hours, e.g. 0.15 to 1.5 hours and the residence time in gas phase reactor will generally be 0.2 to 6.0 hours, like 0.5 to 4.0 hours. If desired, the polymerization may be effected in a known manner under supercritical conditions in the first reactor (Rl), i.e. in the slurry reactor (SR), like in the loop reactor (LR), and/or as a condensed mode in the gas phase reactors (GPR).

Preferably the process comprises also a prepolymerization with the catalyst system, as described in detail below, comprising a Ziegler-Natta procatalyst, an external donor and optionally a cocatalyst.

In a preferred embodiment, the prepolymerization is conducted as bulk slurry polymerization in liquid propylene, i.e. the liquid phase mainly comprises propylene, with minor amount of other reactants and optionally inert components dissolved therein.

The prepolymerization reaction is typically conducted at a temperature of 10 to 60 °C, preferably frorrl 15 to 50 °C, and more preferably from 20 to 45 °C. The pressure in the prepolymerization reactor is not critical but must be sufficiently high to maintain the reaction mixture in liquid phase. Thus, the pressure may be from 20 to 100 bar, for example 30 to 70 bar. The catalyst components are preferably all introduced to the prepolymerization step.

However, where the solid catalyst component (i) and the cocatalyst (ii) can be fed separately it is possible that only a part of the cocatalyst is introduced into the prepolymerization stage and the remaining part into subsequent polymerization stages. Also in such cases it is necessary to introduce so much cocatalyst into the prepolymerization stage that a sufficient polymerization reaction is obtained therein.

It is possible to add other components also to the prepolymerization stage. Thus, hydrogen may be added into the prepolymerization stage to control the molecular weight of the prepolymer as is known in the art. Further, antistatic additive may be used to prevent the particles from adhering to each other or to the walls of the reactor.

The precise control of the prepolymerization conditions and reaction parameters is within the skill of the art.

According to the present invention the heterophasic propylene copolymer (HECO) is obtained by a multistage polymerization process, as described above, in the presence of a catalyst system comprising as component (i) a Ziegler-Natta procatalyst which contains a trans-esterification product of a lower alcohol and a phthalic ester.

The procatalyst used according to the invention for preparing the heterophasic propylene copolymer (HECO) is prepared by

a) reacting a spray crystallized or emulsion solidified adduct of MgCl₂ and a C_rC₂ alcohol with TiCl₄

b) reacting the product of stage a) with a dialkylphthalate of formula (I)

wherein R¹ and R² are independently at least a C₅ alkyl under conditions where a transesterification between said Q to C2 alcohol and said dialkylphthalate of formula (I) takes place to form the internal donor

c) washing the product of stage b) or

d) optionally reacting the product of step c) with additional TiCl₄

The procatalyst is produced as defined for example in the patent applications WO 87/07620, WO 92/19653, WO 92/19658 and EP 0 491 566. The content of these documents is herein included by reference. First an adduct of MgCl₂ and a C C alcohol of the formula MgCl₂*nROH, wherein R is methyl or ethyl and n is 1 to 6, is formed. Ethanol is preferably used as alcohol.

The adduct, which is first melted and then spray crystallized or emulsion solidified, is used as catalyst carrier.

In the next step the spray crystallized or emulsion solidified adduct of the formula

MgCl₂*nROH, wherein R is methyl or ethyl, preferably ethyl and n is 1 to 6, is contacting with TiCl₄ to form a titanized carrier, followed by the steps of

• adding to said titanised carrier

(i) a dialkylphthalate of formula (I) with R¹ and R² being independently at least a C₅-alkyl, like at least a C₈-alkyl,

or preferably

(ii) a dialkylphthalate of formula (I) with R¹ and R² being the same and being at least a C₅-alkyl, like at least a Cg-alkyl,

or more preferably

(iii) a dialkylphthalate of formula (I) selected from the group consisting of propylhexylphthalate (PrHP), dioctylphthalate (DOP), di-iso- decylphthalate (DIDP), and ditridecylphthalate (DTDP), yet more preferably the dialkylphthalate of formula (I) is a dioctylphthalate (DOP), like di-iso-octylphthalate or diethylhexylphthalate, in particular diethylhexylphthalate,

to form a first product, • subjecting said first product to suitable transesterification conditions, i.e. to a temperature above 100 °C, preferably between 100 to 150 °C, more preferably between 130 to 150 °C, such that said methanol or ethanol is transesterified with said ester groups of said dialkylphthalate of formula (I) to form preferably at least 80 mol-%, more preferably 90 mol-%, most preferably 95 mol.-%, of a dialkylphthalate of formula (II)

with R¹ and R² being methyl or ethyl, preferably ethyl,

the dialkylphthalat of formula (II) being the internal donor and

· recovering said transesterification product as the procatalyst composition

(component (i)).

The adduct of the formula MgCl₂*nROH, wherein R is methyl or ethyl and n is 1 to 6, is in a preferred embodiment melted and then the melt is preferably injected by a gas into a cooled solvent or a cooled gas, whereby the adduct is crystallized into a morphologically advantageous form, as for example described in WO 87/07620.

This crystallized adduct is preferably used as the catalyst carrier and reacted to the procatalyst useful in the present invention as described in WO 92/19658 and WO 92/19653.

As the catalyst residue is removed by extracting, an adduct of the titanised carrier and the internal donor is obtained, in which the group deriving from the ester alcohol has changed.

In case sufficient titanium remains on the carrier, it will act as an active element of the procatalyst.

Otherwise the titanization is repeated after the above treatment in order to ensure a sufficient titanium concentration and thus activity. Preferably the procatalyst used according to the present invention contains 2.5 wt.-% of titanium at the most, preferably 2.2% wt.-% at the most and more preferably 2.0 wt.-% at the most. Its donor content is preferably between 4 to 12 wt.-% and more preferably between 6 and l0 wt.-%.

More preferably the procatalyst used according to the present invention has been produced by using ethanol as the alcohol and dioctylphthalate (DOP) as dialkylphthalate of formula (I), yielding diethyl phthalate (DEP) as the internal donor compound.

Still more preferably the catalyst used according to the present invention is the catalyst as described in the example section; especially with the use of dioctylphthalate as

dialkylphthalate of formula (I). For the production of the heterophasic propylene copolymer (HECO) according to the present invention the catalyst system used preferably comprises in addition to the special Ziegler-Natta procatalyst an organometallic cocatalyst as component (ii).

Accordingly it is preferred to select the cocatalyst from the group consisting of

trialkylaluminium, like triethylaluminium (TEA), dialkyl aluminium chloride and alkyl aluminium sesquichloride.

Component (iii) of the catalysts system used is an external donor represented by formula (Ilia) or (Illb). Formula (Ilia) is defined by

Si(OCH₃)₂R₂ ⁵ (IHa)

wherein R³ represents a branched-alkyl group having 3 to 12 carbon atoms, preferably a branched-alkyl group having 3 to 6 carbon atoms, or a cyclo-alkyl having 4 to 12 carbon atoms, preferably a cyclo-alkyl having 5 to 8 carbon atoms. It is in particular preferred that R⁵ is selected from the group consisting of iso-propyl, iso- butyl, iso-pentyl, tert.-butyl, tert.-amyl, neopentyl, cyclopentyl, cyclohexyl,

methylcyclopentyl and cycloheptyl. Formula (Illb) is defined by

Si(OCH₂CH₃)₃( R^xR^y) (Illb)

wherein R^x and R^y can be the same or different a represent a hydrocarbon group having 1 to 12 carbon atoms.

R^x and R^y are independently selected from the group consisting of linear aliphatic hydrocarbon group having 1 to 12 carbon atoms, branched aliphatic hydrocarbon group having 1 to 12 carbon atoms and cyclic aliphatic hydrocarbon group having 1 to 12 carbon atoms. It is in particular preferred that R^x and R^y are independently selected from the group consisting of methyl, ethyl, n-propyl, n-butyl, octyl, decanyl, iso-propyl, iso-butyl, iso-pentyl, tert.-butyl, tert.-amyl, neopentyl, cyclopentyl, cyclohexyl, methylcyclopentyl and

cycloheptyl. More preferably both R^x and R^y are the same, yet more preferably both R^x and R^y are an ethyl group.

More preferably the external donor is of formula (Ilia), like dicyclopentyl dimethoxy silane [Si(OCH₃)₂(cyclo-pentyl)₂] or diisopropyl dimethoxy silane [Si(OCH₃)2(CH(CH₃)₂)₂].

Most preferably the external donor of formula (Illb) is diethylaminotriethoxysilane.

In a further embodiment, the Ziegler-Natta procatalyst can be modified by polymerising a vinyl compound in the presence of the catalyst system, comprising the special Ziegler-Natta procatalyst (component (i)), an external donor (component (iii) and optionally a cocatalyst (component (iii)), which vinyl compound has the formula:

CH₂=CH-CHR³R⁴ wherein R³ and R⁴ together form a 5- or 6-membered saturated, unsaturated or aromatic ring or independently represent an alkyl group comprising 1 to 4 carbon atoms, and the modified catalyst is used for the preparation of the heterophasic propylene copolymer (HECO) according to the present invention. The polymerized vinyl compound can act as an a- nucleating agent.

Concerning the modification of catalyst reference is made to the international applications WO 99/24478, WO 99/24479 and particularly WO 00/68315, incorporated herein by reference with respect to the reaction conditions concerning the modification of the catalyst as well as with respect to the polymerization reaction.

Accordingly it is appreciated that the heterophasic propylene copolymer (HECO) is a- nucleated. In case the a-nucleation is not effected by a vinylcycloalkane polymer or a vinylalkane polymer as indicated above, the following a-nucleating agents may be present

(i) salts of monocarboxylic acids and polycarboxylic acids, e.g. sodium benzoate or aluminum tert-butylbenzoate, and

(ii) dibenzylidenesorbitol (e.g. 1 ,3 : 2,4 dibenzylidenesorbitol) and Ci-C₈-alkyl- substituted dibenzylidenesorbitol derivatives, such as methyldibenzylidenesorbitol, ethyldibenzylidenesorbitol or dimethyldibenzylidenesorbitol (e.g. 1,3 : 2,4 di(methylbenzylidene) sorbitol), or substituted nonitol-derivatives, such as 1 ,2,3,- trideoxy-4,6:5,7-bis-0-[(4-propylphenyl)methylene]-nonitol, and

(iii) salts of diesters of phosphoric acid, e.g. sodium 2,2'-methylenebis (4, 6,-di-tert- butylphenyl) phosphate or aluminium-hydroxy-bis[2,2'-methylene-bis(4,6-di-t- butylphenyl)phosphate], and

(iv) mixtures thereof.

In one preferred embodiment the heterophasic propylene copolymer (HECO) is the only heterophasic polymer which is used in the propylene composition (PP). That is that the propylene composition (PP) especially does not contain a further heterophasic propylene copolymer which comprises a polypropylene acting as a matrix and an elastomeric propylene copolymer being dispersed in said matrix.

Propylene homopolymer (homo-PP) Another essential component of the polypropylene composition (PP) according to the present invention is a propylene homopolymer (homo-PP).

The propylene homopolymer (homo-PP) is added to the polypropylene composition (PP) according to the present invention to improve the stiffness.

It is appreciated that the polypropylene composition (PP) comprises the propylene homopolymer (homo-PP) in an amount of from 5.0 to 15.0 wt.-%, preferably of from 5.0 to 13.0 wt.-%, and even more preferably of from 5.0 to 10.0 wt.-% based on the total weight of the polypropylene composition (PP).

It comes apparent from the wording that the propylene homopolymer (homo-PP) is not a heterophasic polymer, i.e. a system comprising a crystalline matrix phase in which an elastomeric phase is dispersed. Accordingly, it is preferred that the propylene homopolymer (homo-PP) is monophasic, i.e. in DMTA no multiphase structure can be identified as there exists just one glass transition temperature.

Further, the propylene homopolymer (homo-PP) preferably has a melting temperature of more than 155°C, i.e. of more than 155 to 169 °C, more preferably of at least 158°C, i.e. in the range of from 158 to 168 °C, still more preferably in the range of from 162 to 168°C.

Preferably, a further characteristic of the propylene homopolymer (homo-PP) is the low amount of misinsertions of propylene within the polymer chain, which indicates that the propylene homopolymer (homo-PP) is produced in the presence of a Ziegler-Natta catalyst. Accordingly the propylene homopolymer (homo-PP) is preferably featured by low amount of 2, 1 erythro regio-defects, i.e. of equal or below 0.4 mol.-%, more preferably of equal or below than 0.2 mol.-%, like of not more than 0.1 mol. -%, determined by ¹³C-NMR spectroscopy. In an especially preferred embodiment no 2, 1 erythro regio-defects are detectable.

The propylene homopolymer (homo-PP) preferably has a melt flow rate MFR₂ (230°C) measured according to ISO 1 133 in the range of from 40.0 to 70.0 g/lOmin, preferably in the range of from 40.0 to 65.0 g/10 min, preferably in the range of from 40.0 to 60.0 g/lOmin, like in the range of from 45.0 to 55.0 g/lOmin.

The propylene homopolymer (homo-PP) can be chemically identical to the matrix (M) of the heterophasic propylene copolymer (HECO) which is described in more detail above. In another preferred embodiment, the propylene homopolymer (homo-PP) is chemical different, preferably different in the melt flow rate, to the matrix, i.e. to the propylene homopolymer (PP-1), of the heterophasic propylene copolymer (HECO). In one preferred embodiment, the propylene homopolymer (homo-PP) has a melt flow rate MFR₂ (230°C) which is higher, preferably at least 5 g/l Omin higher, more preferably at least 8 g/lOmin higher, even more preferably 5 to 50 g lOmin higher, yet more preferably 8 to 20 g/l Omin higher, than the matrix, i.e. the propylene homopolymer (PP-1), of the heterophasic propylene copolymer (HECO).

Preferably, the propylene homopolymer (homo-PP) has a flexural modulus measured according to ISO ISO 178 of at least 1 ,600 MPa, more preferably of at least 1,650 MPa, and even more preferably of at least 1 ,800 MPa, like in the range of from 1,650 to 2,200 MPa. The propylene homopolymer (homo-PP) is known in the art and is preferably made with a Ziegler-Natta catalyst.

Elastomeric ethylene copolymer (EEC) As another essential component, the instant polypropylene composition (PP) comprises an elastomeric ethylene copolymer (EEC).

The elastomeric ethylene copolymer is added to the polypropylene composition (PP) according to the present invention for good dimension stability and good impact properties. According to the present invention the elastomeric ethylene copolymer (EEC) has a melt flow rate MFR₂ (190°C) in the range of from 0.2 to 20 g/lOmin, preferably in the range of from 0.5 to 15.0 g/lOmin, and even more preferably in the range of from 0.5 to 7.0 g/lOmin. Preferably, the elastomeric ethylene copolymer (EEC) has a density in the range of from 820 to 940 kg/m³, preferably in the range of from 830 to 920 kg/m³ and even more preferably in the range of from 850 to 900 kg/m³.

The elastomeric ethylene copolymer (EEC) is an ethylene homopolymer or an ethylene copolymer, while the latter ethylene copolymer is preferred.

Preferably the elastomeric ethylene copolymer (EEC) differs from the elastomeric propylene copolymer (E-l) in comonomer type and/or ethylene content. Accordingly it is preferred that the ethylene content in the elastomeric ethylene copolymer (EEC) is higher than in the elastomeric propylene copolymer (E-l ).

Accordingly it is preferred that the elastomeric ethylene copolymer (EEC) comprises at least 55 wt.-% units derivable from ethylene, more preferably at least 60 wt.-% of units derived from ethylene. Accordingly, the content of ethylene units in the elastomeric ethylene copolymer (EEC) is in the range of 50.0 to 80.0 wt.-%, preferably in the range of from 55.0 to 80.0 wt.-%.

The comonomers present in the elastomeric ethylene copolymer (EEC) are C₄ to C₂o - olefins, like 1-butene, 1 -hexene and 1 -octene, the latter especially preferred. Accordingly in one specific embodiment the elastomeric ethylene copolymer (EEC) is an ethylene- 1 -octene polymer with the amounts given in this paragraph.

One important aspect of the present invention is that the amount of elastomeric ethylene copolymer (EEC) in the polypropylene composition (PP) is rather low. Accordingly, it is preferred that the elastomeric ethylene copolymer is present in the polypropylene composition (PP) according to the present invention in an amount of between 5.0 and 14.0 wt.-%, preferably in an amount between 5.0 and 12.0 wt.-%, and even more preferably in an amount between 5.0 and 10.0 wt.-% based on the total weight of the polypropylene composition (PP).

The elastomeric ethylene copolymer (EEC) is known in the art and belongs in a preferred embodiment to the Exact and Engage series, respectively.

As mentioned above, the elastomeric ethylene copolymer (EEC) preferably is also dispersed in the matrix, i.e. in the polypropylene (PP) of the heterophasic propylene copolymer (HECO), by compounding, and thus forming the overall polyolefin composition.

Inorganic filler (F)

As another essential component, the polypropylene composition (PP) according to the present invention comprises inorganic filler (F).

The inorganic filler is added to the polypropylene composition according to the present invention for a good modulus.

The inorganic filler (F) is present in the polypropylene composition (PP) in amounts of up to 40 wt.-%. It is preferred that the amount of inorganic filler (F) is in the range of from 21.0 to 38.0 wt.-%, more preferably in the range of from 21.0 to 35.0 wt.-%, and even more preferably in the range of from 25.0 to 35.0 wt.-%, even more preferably in the range of from 30.0 to 35.0 wt.%, based on the total weight of the polypropylene composition (PP). Preferably the inorganic filler (F) is mica, wollastonite, kaolinite, smectite, calcium carbonate, montmorillonite, talc, phyllosilicate or a mixture thereof. The most preferred inorganic filler (F) is talc.

The inorganic filler (F) preferably has a median particle size d₅o calculated from the particle size distribution in mass percent and measured by laser diffraction in the range of 0.2 to

20.0 μιη, more preferably in the range of 0.3 to 15.0 μπι, still more preferably in the range of 0.4 to 10.0 μ^ηι. The most preferred median particle size d₅₀ is in the range of 0.45 to 5.0 μπι, including the most appropriate median particle size d₅₀ in the range of from 0.45 to 1.2 μπι.

Additionally or alternatively, the inorganic filler (F) has a specific surface area BET in the range from 1.0 to 50.0 m²/g, more preferably in the range from 5.0 to 40.0 m²/g, still more preferably in the range from 10.0 to 30.0 m²/g and even more preferably in the range of 10.0 to 20.0 m²/g.

It is preferred that the inorganic filler (F) is present in a specific weight ratio relative to the heterophasic propylene copolymer (FTECO) in the polypropylene composition (PP).

For example, the weight ratio of the heterophasic propylene copolymer (FTECO to the inorganic filler (F) [HECO / F] is from 0.9 to 2.5, preferably 1.0 to 2.3. More preferably, the weight ratio of the heterophasic propylene copolymer (HECO) to the inorganic filler (F) [HECO / F] is from 1.1 to 2.0, and even more preferably from 1.2 to 1.7.

Additionally or alternatively, the weight ratio of propylene homopolymer (homo-PP) to the inorganic filler (F) [homo-PP/F] is from 0.08 to 1.0. Preferably, the weight ratio of polypropylene homopolymer (homo-PP) to the inorganic filler (F) [homo-PP/F] is from 0.14 to 0.72, and more preferably from 0.14 to 0.52, and more preferably from 0.14 to 0.33.

It is appreciated that the polypropylene composition (PP) according to the present invention may further (optionally) comprise at least one typical additive selected from the group consisting of acid scavengers, antioxidants, colorants, pigments, light stabilizers, UV- stabilizers, slip agents, anti-scratch agents, dispersing agents, carriers and colorants.

Preferably the amount of these additives (excluding the inorganic filler (F) and alpha- nucleating agents) shall not exceed 10.0 wt.-%, preferably not more than 7.0 wt.-%, even more preferably not more than 5.0 wt.-%, and most preferably not more than 4.0 wt.-% based on the total weight of the polypropylene composition (PP), within the instant polypropylene composition (PP). The polypropylene composition (PP) according to the present invention contains preferably an a-nucleating agent. Even more preferred the present invention is free of β-nucleating agents. According to the present invention the nucleating agent is understood as a nucleating agent different to the inorganic filler (F). Accordingly, the nucleating agent is preferably selected from the group consisting of

(ii) dibenzylidenesorbitol (e.g. 1,3 : 2,4 dibenzylidenesorbitol) and C_rC₈-alkyl- substituted dibenzylidenesorbitol derivatives, such as methyldibenzylidenesorbitol, ethyldibenzylidenesorbitol or dimethyldibenzylidenesorbitol (e.g. 1 ,3 : 2,4 di(methylbenzylidene) sorbitol), or substituted nonitol-derivatives, such as 1 ,2,3,- trideoxy-4,6:5,7-bis-0-[(4-propylphenyl)methylene]-nonitol, and

(iv) vinylcycloalkane polymer and vinylalkane polymer (as discussed above), and

(v) mixtures thereof.

Such additives are generally commercially available and are described, for example, in "Plastic Additives Handbook", 5th edition, 2001 of Hans Zweifel.

Most preferably the a-nucleating agent is part of the heterophasic propylene copolymer (HECO) thus of the polypropylene composition (PP). Accordingly the α-nucleating agent content of the heterophasic propylene copolymer (HECO) and thus of the polypropylene composition (PP) is preferably up to 5.0 wt.-%. In a preferred embodiment, the heterophasic propylene copolymer (HECO) and thus the polypropylene composition (PP) contain(s) not more than 3,000 ppm, more preferably of 1 to 2,000 ppm of a α-nucleating agent, in particular selected from the group consisting of dibenzylidenesorbitol (e.g. 1,3 : 2,4 dibenzylidene sorbitol), dibenzylidenesorbitol derivative, preferably

dimethyldibenzylidenesorbitol (e.g. 1 ,3 : 2,4 di(methylbenzylidene) sorbitol), or substituted nonitol-derivatives, such as l,2,3,-trideoxy-4,6:5,7-bis-0-[(4-propylphenyl)methylene]- nonitol, vinylcycloalkane polymer, vinylalkane polymer, and mixtures thereof. In a preferred embodiment the heterophasic propylene copolymer (HECO) and thus the polypropylene composition (PP) contains a vinylcycloalkane, like vinylcyclohexane (VCH), polymer and/or vinylalkane polymer, as the a-nucleating agent. Preferably in this embodiment, the heterophasic propylene copolymer (HECO) contains a vinylcycloalkane, like vinylcyclohexane (VCH), polymer and/or vinylalkane polymer, preferably

vinylcyclohexane (VCH). Preferably the vinylcycloalkane is vinylcyclohexane (VCH) polymer which is optionally introduced into the heterophasic propylene copolymer (HECO) and thus into the polypropylene composition (PP) by the BNT technology. More preferably in this preferred embodiment, the amount of vinylcycloalkane, like vinylcyclohexane (VCH), polymer and/or vinylalkane polymer, more preferably of vinylcyclohexane (VCH) polymer, in the heterophasic propylene copolymer (HECO) is not more than 500 ppm, more preferably of 0.5 to 200 ppm, most preferably 1 to 100 ppm,. Accordingly it is thus preferred that the polypropylene composition (PP) contains not more than 500 ppm, more preferably of 0.1 to 200 ppm, most preferably 0.2 to 100 ppm, of vinylcyclohexane (VCH) polymer.

With regard to the BNT-technology reference is made to the international applications WO 99/24478, WO 99/24479 and particularly WO 00/68315. According to this technology a catalyst system, preferably a Ziegler-Natta procatalyst, can be modified by polymerising a vinyl compound in the presence of the catalyst sy stem, comprising in particular the special Ziegler-Natta procatalyst, an external donor and a cocatalyst, which vinyl compound has the formula:

CH₂=CH-CHR³R⁴

wherein R³ and R⁴ together form a 5- or 6-membered saturated, unsaturated or aromatic ring or independently represent an alkyl group comprising 1 to 4 carbon atoms, and the modified catalyst is used for the preparation of the heterophasic polypropylene according to this invention, i.e. of the heterophasic propylene copolymer (HECO). The polymerized vinyl compound acts as an a-nucleating agent. The weight ratio of vinyl compound to solid catalyst component in the modification step of the catalyst is preferably of up to 5 (5: 1 ), preferably up to 3 (3 : 1) most preferably from 0.5 ( 1 :2) to 2 (2: 1 ). The most preferred vinyl compound is vinylcyclohexane (VCH). The polypropylene composition (PP) according to the present invention is preferably featured by a specific melt flow rate. Accordingly in a preferred embodiment the polypropylene composition (PP) according to this invention has a melt flow rate MFR₂ (230 °C, 2.16 kg) measured according to ISO 1 133 in the range of from 8.0 to 25.0 g/lOmin, more preferably in the range of 12.0 to 20.0 g/lOmin, like in the range of 13.0 to 18.0 g/lOmin.

The polypropylene composition (PP) according to the present invention due to the unique combination of its individual components has balanced mechanical properties while the dimension stability is also high as it is indicated by the low coefficient of linear thermal expansion.

For instance, the polypropylene composition (PP) according to the present invention has impact strength defined by notched izod strength according to industrial standard ISO 180 of at least 10 KJ/m², preferably at least 14 KJ/m², and/or flexural modulus measured according to ISO 178 of at least 2,500 MPa, preferably of at least 2,800 MPa.

Alternatively or additionally, the polypropylene composition (PP) according to the present invention has high dimension stability as defined by the coefficient of linear thermal expansion (CLTE) measured according to ASTM E 831 in flow direction which is equal to or below 4.8K^"1, more preferably not higher than 4.7 K^"1, and a linear thermal expansion (CLTE) measured according to ASTM E 83 1 in cross flow direction which is equal to or below 6.5 K^"1, more preferably not higher than 6.1 K \ Accordingly, the polypropylene composition (PP) according to the present invention has in particular

(a) a notched izod strength measured according to ISO 180 / 1A at 23 °C of at least 10 kJ/m², more preferably at least 14 kJ/m²,

(b) a flexural modulus measured according to ISO 178 of at least 2,500 MPa, more preferably of at least 2,800 MPa, and a coefficient of linear thermal expansion (CLTE) measured according to ASTM E 831 in flow direction of equal to or below 4.8 K^"1, more preferably not higher than 4.7K-¹. According to another aspect of the present invention, the polypropylene composition (PP) is prepared by blending the heterophasic propylene copolymer (HECO) with the propylene homopolymer (homo-PP), the elastomeric ethylene copolymer (EEC), the inorganic filler (F),optionally including further additives in an extruder, and extruding the obtained blend of the heterophasic propylene copolymer (HECO), the homo-polymeric polypropylene (homo- PP), elastomeric ethylene copolymer (EEC), the inorganic filler (F), and optionally further additives in the extruder. The term "blending" refers according to the present invention to the action of providing a blend out of at least two different, pre-existing materials, i.e. the heterophasic propylene copolymer (FIECO), the propylene homopolymer (homo-PP), elastomeric ethylene copolymer (EEC), the inorganic filler (F), and further optional additives.

For blending the individual components of the instant composition, i.e. the heterophasic propylene copolymer (HECO), with the propylene homopolymer (homo-PP), elastomeric ethylene copolymer (EEC), the inorganic filler (F), and further additives, a conventional compounding or blending apparatus, e.g. a Banbury mixer, a 2-roll rubber mill, Buss-co- kneader or a twin screw extruder may be used. The polymer materials recovered from the extruder are usually in the form of pellets. These pellets are then preferably further processed, e.g. by injection moulding to generate articles and products of the inventive composition.

The polypropylene composition (PP) of the present invention is preferably used for the production of articles in the field of household appliances, medical appliances, automotive articles, particularly moulded automotive articles or automotive injection moulded articles, and/or articles of pipes and toys. Even more preferred is the use for the production of car exteriors, like side trims, body panels, door panels, spoilers, fender liner, tailgates, and the like.

For example, the article, especially the article as defined in the previous paragarph or in the following paragraphs, comprises the polypropylene composition (PP) in an amount of at least 60.0 wt.-%, more preferably at least 80.0 wt.-% and most preferably at least 95.0 wt.-%, based on the total weight of the article. In one embodiment the article does not comprise further polymers to those defined in the present invention, i.e. the heterophasic propylene copolymer (HECO), the propylene homopolymer (homo-PP) and the elastomeric ethylene copolymer (EEC).

In one specific embodiment of the present invention, the article consists of the instant polypropylene composition (PP). It is preferred that the article is a moulded article, preferably an injection moulded article. Preferred examples of such injection moulded articles are large parts for applications in the automotive or household industry. For example, the present invention is directed to automotive articles, especially to car interiors and exteriors, like body panels, spoilers, fender liner, tailgates and/or door panels.

Accordingly the present invention is especially directed to automotive articles, especially to car interiors and exteriors, like body panels, spoilers, fender liner, tailgates, door panels and the like, in particular body panel and/or door panels, comprising at least 60.0 wt.-%, more preferably at least 80.0 wt.-%, yet more preferably at least 95.0 wt.-%, like consisting, of the instant polypropylene composition (PP).

The use of the polypropylene composition (PP) according to the present invention particularly refers to the preparation of the article by molding techniques, preferably injection molding. The present invention is in particular directed to the use of the polypropylene composition (PP) to the preparation of the article selected from the group consisting of household appliances, medical appliances, automotive articles, particularly moulded automotive articles or automotive injection moulded articles, and/or articles of pipes and toys. Even more preferred is the use for the production of car exteriors, like side trims, body panels, door panels, spoilers, fender liner, tailgates, and the like

The present invention will now be described in further detail by the examples provided below. 30

E X A M P L E S

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.

Quantification of microstructure by NMR spectroscopy

Quantitative nuclear-magnetic resonance (NMR) spectroscopy is used to quantify the isotacticity and regio-regularity of the polypropylene homopolymers.

Quantitative ¹ C {¾ 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 Ή and ¹³C respectively. All spectra were recorded using a ¹³C optimised 10 mm extended temperature probehead at 125°C using nitrogen gas for all pneumatics.

For polypropylene homopolymers approximately 200 mg of material was dissolved in 1,2- tetrachloroethane-A (TCE-i¾- To ensure a homogenous solution, after initial sample preparation in a heat block, the NMR tube was further heated in a rotatary 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 needed for tacticity distribution quantification (Busico, V., Cipullo, R., Prog. Polym. Sci. 26 (2001 ) 443; Busico, V.; Cipullo, R., Monaco, G., Vacatello, M., Segre, A.L., Macromolecules 30 (1997) 6251). Standard single-pulse excitation was employed utilising the NOE and bi-level WALTZ16 decoupling scheme (Zhou, Z.,

Kuemmerle, R., Qiu, X., Redwine, D., Cong, R., Taha, A., Baugh, D. Winniford, B., J. Mag. Reson. 187 (2007) 225; Busico, V., Carbonniere, P., Cipullo, R., Pellecchia, R., Severn, J., Talarico, G., Macromol. Rapid Commun. 2007, 28, 1 1289). A total of 8192 (8k) transients were acquired per spectra.

Quantitative ¹³C{'H} NMR spectra were processed, integrated and relevant quantitative properties determined from the integrals using proprietary computer programs.

For polypropylene homopolymers all chemical shifts are internally referenced to the methyl isotactic pentad (mmmm) at 21.85 ppm.

Characteristic signals corresponding to regio defects (Resconi, L., Cavallo, L., Fait, A., Piemontesi, F., Chem. Rev. 2000, 100, 1253;; Wang, W-J., Zhu, S., Macromolecules 33 (2000), 1 157; Cheng, H. N., Macromolecules 17 (1984), 1950) or comonomer were observed. The tacticity distribution was quantified through integration of the methyl region between 23.6-19.7 ppm correcting for any sites not related to the stereo sequences of interest (Busico, V., Cipullo, R., Prog. Polym. Sci. 26 (2001) 443; Busico, V., Cipullo, R., Monaco, G., Vacatello, M, Segre, A.L., Macromolecules 30 (1997) 6251).

Specifically the influence of regio-defects and comonomer on the quantification of the tacticity distribution was corrected for by subtraction of representative regio-defect and comonomer integrals from the specific integral regions of the stereo sequences.

The isotacticity was determined at the pentad level and reported as the percentage of isotactic pentad (mmmm) sequences with respect to all pentad sequences:

[mmmm] % = 100 * (mmmm / sum of all pentads)

The presence of 2, 1 erythro regio-defects was indicated by the presence of the two methyl sites at 17.7 and 17.2 ppm and confirmed by other characteristic sites. Characteristic signals corresponding to other types of regio-defects were not observed (Resconi, L., Cavallo, L., Fait, A., Piemontesi, F., Chem. Rev. 2000, 100, 1253).

The amount of 2, 1 erythro regio-defects was quantified using the average integral of the two characteristic methyl sites at 17.7 and 17.2 ppm:

P_21e = (I_e6 + I_e8) / 2

The amount of 1 ,2 primary inserted propene was quantified based on the methyl region with correction undertaken for sites included in this region not related to primary insertion and for primary insertion sites excluded from this region:

The total amount of propene was quantified as the sum of primary inserted propene and all other present regio-defects:

Ptotal ⁼ P l 2 + P21e

The mole percent of 2, 1- erythro regio-defects was quantified with respect to all propene:

[21e] mol.-% = 100 * (P.i_e / P_to_tai)

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 1 157, through integration of multiple signals across the whole spectral region in the ¹³C{'H} 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.

Melting temperature (T_m): measured with a TA Instrument Q2000 differential scanning calorimetry (DSC) on 5 to 7 mg samples. DSC is run according to ISO 1 1357 / part 3 /method C2 in a heat / cool / heat cycle with a scan rate of 10 °C/min in the temperature range of -30 to +225°C. Melting temperature is determined from the second heating step. Density is measured according to ISO 1 183-1 - method A (2004). Sample preparation is done by compression moulding in accordance with ISO 1872-2:2007.

MFR₂ (230°C) is measured according to ISO 1 133 (230°C, 2.16 kg load).

MFR₂ (190°C) is measured according to ISO 1 133 ( 190°C, 2.16 kg load).

The xylene cold solubles (XCS, wt.-%): Content of xylene cold solubles (XCS) is determined at 25 °C according to ISO 16152; first edition; 2005-07-01

Intrinsic viscosity is measured according to DIN ISO 1628/1, October 1999 (in Decalin at 135 °C).

Flexural Modulus and flexural strength were determined in 3-point-bending according to ISO 178 on injection molded specimens of 80 x 10 x 4 mm prepared in accordance with ISO 294-1 : 1996.

Izod notched impact strength is determined according to ISO 180 / 1A at 23 °C by using injection moulded test specimens as described in EN ISO 1873-2 (80 x 10 x 4 mm)

Median particle size d₅₀ (Laser diffraction) is calculated from the particle size distribution [mass percent] as determined by laser diffraction (Mastersizer) according to ISO 13320-1. Specific surface area is determined as the BET surface according to DIN 66131/2.

Coefficient of linear thermal expansion: The coefficient of linear thermal expansion (CLTE) was determined in accordance with ASTM E 83 1.

The test is conducted on a TMA (Thermal Mechanical Analysis) equipment, commercially available from Perkin Elmer Inc, MA, USA, with the model of " Pyrus Diamond TMA STD " , S N - 10100575000008. In the test, temperature range for test is from -30 °C to 80 °C, and temperature increases at a rate of 5 °C/min.

2. Examples

The present invention is illustrated by the following examples.

Heterophasic propylene copolymer (HECO) used for the inventive examples was prepared with one slurry loop reactor and two gas phase reactors by the known Borstar^® technology, as disclosed in EP 0 887 379 Al.

The catalyst used in the polymerization process of the HECO has been produced as follows: First, 0.1 mol of MgC^ x 3 EtOH was suspended under inert conditions in 250 ml of decane in a reactor at atmospheric pressure. The solution was cooled to the temperature of -15°C and 300 ml of cold TiCl₄ was added while maintaining the temperature at said level. Then, the temperature of the slurry was increased slowly to 20 °C. At this temperature, 0.02 mol of dioctylphthalate (DOP) was added to the slurry. After the addition of the phthalate, the temperature was raised to 135 °C during 90 minutes and the slurry was allowed to stand for 60 minutes. Then, another 300 ml of TiCl₄ was added and the temperature was kept at 135 °C for 120 minutes. After this, the catalyst was filtered from the liquid and washed six times with 300 ml heptane at 80 °C. Then, the solid catalyst component was filtered and dried. Catalyst and its preparation concept is described e.g. in patent publications EP491566, EP591224 or EP586390. The catalyst was prepolymerized with vinyl cyclohexane in an amount to achieve a concentration of 200 ppm poly(vinyl cyclohexane) (PVCH) in the final polymer (see EP 1 183307 Al). As co-catalyst triethyl-aluminium (TEAL) and as donor dicyclo pentyl dimethoxy silane (D-donor) were used. The aluminium to donor ratio is indicated in Table 1.

Table 1: Preparation and Properties of HECO

Compounding compositions of IE1 to IE4 were prepared as follows:

IE1 to IE4 based on the recipe as summarized in Table 2 are prepared by using a Coperion STS-35 twin-screw extruder (available from Coperion Corporation, Nanjing, China) with a diameter of 35 mm. The twin-screw extruder runs at an average screw speed of 550 rpm with a temperature profile of zones 1 -1 1 from 170°C to 220 °C. It has a L/D of 44. The temperature of each zone, throughput and the screw speed of the extruder for preparing the compositions of inventive examples are listed in Table 3.

The temperature of each zone, throughput and screw speed of the extruder are initiative parameters, and are set on control panel of the extruder. Melt temperature (temperature of the melt in the die) and torque of the extruder are passive parameters shown on control panel of the extruder. A vacuum bump is located in zone 9 and generates a vacuum of -0.03 MPa inside the extruder.

Table 2: Recipe for compositions of IE 1 to ΓΕ4

*) rest to 100 wt.-% were PP powder additive (1.9 wt.-% HC001A-B 1 for IE 1-2 and 4, but 0.9 wt.-% HC001A-B1 for IE3), antioxidants (0.1 wt.-% of Irganox 1076 and 0.1 wt.-% of Irgafos 168), light stabilizer UV absorber (0.2 wt.-% UV-3808PP5), calcium stearate (0.2 wt.-%) and carbon black master batch (0.5 wt.-%).

"Homo-PPl" is the commercial propylene homopolymer HJ325MO of Borealis AG having a

MFR₂ of 50 g/lOmin (230°C/2.16 kg) and a tensile modulus of 1 ,650 MPa.

"Homo-PP2" is the commercial propylene homopolymer HJ31 1MO of Borealis AG having a

MFR₂ of 60 g/lOmin (230°C/2.16 kg) and a flexural modulus of 1,650 MPa.

"EEC" is the commercial ethylene/octylene copolymer Engage 8100 of Dow Elastomers having MFR₂ of 1.0 g/lOmin ( 190°C/2.16 kg) and a density of 0.870 g/cm³.

"Inorganic filler" is the commercial Jetfine® 3CA talc-based mineral filler of Imerys having d₅₀ of 0.8 μπι, and a BET of 14.5m²/g.

"HC001A-B 1" is commercially available from Borealis AG, Vienna, Austria.

"Irganox 1076" and "Irgafos 168" are commercially available from Ciba Inc., China.

"UV-3808PP5" is commercially available from Cytec Chemical, USA. Table 3: Extruder conditions of the compounding compositions of LEI to IE4

Results

The mechanical properties of inventive compounding compositions of lEs 1-4 are shown below in Table 4 and compared with the mechanical properties of prior commercial polymer material "EF 209AEC-9502" (CEl)of Borouge Pte Ltd., China.

Table 4: Properties

Conclusions

The compounding compositions of EEs 1-4 show an improvement in dimension stability and modulus, and meanwhile retain a balanced stiffness and impact, as compared with CE 1. The compounding compositions of IEs 1 -4 are especially suitable for preparing door panel or body panel of automotive.

Claims

C L A I M S

Polypropylene composition (PP) comprising,

(a) a heterophasic propylene copolymer (HECO) having a melt flow rate MFR₂

(230 °C, 2,16 kg) measured according to ISO 1 133 in the range of from 16.0 to 100.0 g/lOmin,

(b) a propylene homopolymer (homo-PP) having a melt flow rate MFR₂ (230°C, 2,16 kg) measured according to ISO 1 133 of from 40.0 to 70.0 g/10 min,

(c) an elastomeric ethylene copolymer (EEC) having a melt flow rate MFR₂ ( 190°C, 2, 16 kg) measured according to ISO 1 133 in the range of from 0.2 to 20.0 g/lOmin, and

(d) an inorganic filler (F).

Polypropylene composition (PP) according to claim 1 having a melt flow rate MFR₂ (230 °C, 2, 16 kg) measured according to ISO 1 133 in the range of from 8.0 to 25.0 g/l Omin.

Polypropylene composition (PP) according to claim 1 or 2, wherein the heterophasic propylene copolymer (HECO) has

(a) a xylene cold soluble (XCS) fraction measured according to ISO 16152 (25 °C) of from 13.0 to 25.0 wt-%, based on the total weight of the heterophasic propylene copolymer (HECO), and/or

(b) a comonomer content, preferably an ethylene content, of equal or below 15.0 wt.-%, based on the total weight of the heterophasic propylene copolymer (HECO).

Polypropylene composition (PP) according to any one of the preceding claims, wherein the xylene cold soluble (XCS) fraction of the heterophasic propylene copolymer (HECO) has

(a) an intrinsic viscosity (IV) of from 2.0 to 3.5 dl/g, and/or

(b) a comonomer content, preferably ethylene content, of 25.0 to 45.0 wt.-%.

5. Polypropylene composition (PP) according to any one of the preceding claims, wherein the polypropylene composition (PP) comprises,

(a) 35.0 to 49.0 wt%, preferably 40.0 to 49.0 wt.-% of the heterophasic propylene copolymer (HECO),

(b) 5.0 to 15.0 wt%, preferably 5.0 to 13.0 wt.-%, of the propylene homopolymer

(homo-PP),

(c) 5.0 to 14.0 wt.-%, preferably 5.0 to 12.0 wt.-%, of the elastomeric ethylene

copolymer (EEC), and

(d) 21.0 to 35.0 wt.-%, preferably 25.0 to 35.0 wt.-%, of the inorganic filler (F), based on the total weight of the composition.

6. Polypropylene composition (PP) according to any one of the preceding claims, wherein the heterophasic propylene copolymer (HECO) comprises a polypropylene, like a propylene homopolymer (PP-1), being the matrix in which an elastomeric propylene copolymer (E-l) is dispersed.

7. Polypropylene composition (PP) according to any one of the preceding claims, wherein the propylene homopolymer (homo-PP) has a flexural modulus measured according to ISO 178 of at least 1 ,550 MPa.

8. Polypropylene composition (PP) according to any one of the preceding claims, wherein the weight ratio of the heterophasic propylene copolymer (HECO) to the inorganic filler (F) [HECO / F] is from 0.9 to 2.5. 9. Polypropylene composition (PP) according to any one of the preceding claims, wherein the weight ratio of propylene homopolymer (homo-PP) to the inorganic filler (F)

[homo-PP/F] is from 0.14 to 0.72.

10. Polypropylene composition (PP) according to any one of the preceding claims, wherein the elastomeric ethylene copolymer (EEC) has a density in the range of from 850 to 900 kg/m³.

1 1. Polypropylene composition (PP) according to any one of the preceding claims having a flexural modulus according to ISO 178 of at least 2,500 MPa.

12. Polypropylene composition (PP) according to any one of the preceding claims having coefficient of linear thermal expansion measured according to ASTME E 831 in flow direction of equal to or below 4.8 K^"1.

13. Article comprising a polypropylene composition (PP) according to any one of the preceding claims.

14. Article according to claim 13, wherein the article is selected from the group consisting of household articles, medical articles, automotive articles, pipes and toys.

15. Use of the polypropylene composition (PP) according to any one of the preceding claims 1 to 12 for the production of articles, like articles selected from the group consisting of household articles, medical articles, automotive articles, pipes and toys.