WO2020102970A1

WO2020102970A1 - Fiber-reinforced polypropylene composition with high oil resistance

Info

Publication number: WO2020102970A1
Application number: PCT/CN2018/116411
Authority: WO
Inventors: Rock ZHU; Wanfeng SUN; Ben Chen
Original assignee: Borouge Compounding Shanghai Co., Ltd.
Priority date: 2018-11-20
Filing date: 2018-11-20
Publication date: 2020-05-28
Also published as: CN112996851A; JP2022506145A; JP7252329B2; CN112996851B

Abstract

Disclosed a fiber-reinforced polypropylene composition (C) comprising a propylene polymer (PP) having a xylene soluble content XCS equal or below 5.0 wt. -%, fibers (F) and an adhesion promoter (AP). Further, provided an injection-molded article comprising said fiber-reinforced polypropylene composition (C).

Description

Fiber-reinforced polypropylene composition with high oil resistance

The present invention is directed to a fiber-reinforced polypropylene composition (C) comprising a propylene polymer (PP) having a xylene soluble content XCS equal or below 5.0 wt. -%, fibers (F) and an adhesion promoter (AP) . Further, the present invention is directed to an article comprising said fiber-reinforced polypropylene composition (C) .

The excellent mechanical performance of fiber-reinforced polypropylene compositions, especially the stiffness and strength, is highly appreciated in the automotive industry. In particular, increasing the fiber content leads to an increase of stiffness and strength.

A widely used approach to improve the impact behavior of such compositions is the application of heterophasic propylene copolymers as base resins. However, the oil resistance of fiber-reinforced compositions comprising a heterophasic system is often not satisfying due to the presence of the amorphous phase.

Accordingly, there is a need in the art for a fiber-reinforced polypropylene composition showing a good resistance to engine oil while the mechanical properties remain on a high level.

Therefore, it is an object of the present invention to provide a fiber-reinforced polypropylene composition featured by a good oil resistance as well as high stiffness and strength.

Accordingly, the present invention is directed to a Fiber-reinforced polypropylene composition (C) , comprising

i) a propylene polymer (PP) having a xylene soluble content XCS equal or below 5.0 wt. -%,

ii) fibers (F) , and

iii) an adhesion promoter (AP) ,

wherein the fiber-reinforced polypropylene composition fulfils in-equation (I)

wherein w (PP) is the weight fraction [in wt. -%] of the propylene polymer (PP) , based on the overall weight of the fiber-reinforced polypropylene composition (C) , and w (AP) is the weight fraction [in wt. -%] of the adhesion promoter (AP) , based on the overall weight of the fiber-reinforced polypropylene composition (C) .

According to one embodiment of the present invention, the propylene polymer (PP) is monophasic.

According to another embodiment of the present invention, the fiber-reinforced polypropylene composition (C) contains no propylene polymers having a xylene soluble content XCS above 5.0 wt. -%.

According to another embodiment of the present invention, the fiber-reinforced polypropylene composition (C) fulfils in-equation (II)

wherein w (F) is the weight fraction [in wt. -%] of the fibers (F) , based on the overall weight of the fiber-reinforced polypropylene composition (C) , and w (AP) is the weight fraction [in wt. -%] of the adhesion promoter (AP) , based on the overall weight of the fiber-reinforced polypropylene composition (C) .

According to a further embodiment of the present invention, the propylene polymer (PP) is at least bimodal.

It is especially preferred that the propylene polymer (PP) is a propylene homopolymer (H-PP) .

According to one embodiment of the present invention, the propylene polymer (PP) comprises

i) a first propylene polymer (PP1) having a melt flow rate MFR ₂ (230 ℃, 2.16 kg) determined according to ISO 1133 equal or below 20 g/10 min, and

ii) optionally a second propylene polymer (PP2) having a melt flow rate MFR ₂ (230 ℃, 2.16 kg) determined according to ISO 1133 above 20 g/10 min.

According to a further embodiment of the present invention, the fibers (F) are short fibers (SF) .

It is especially preferred that the fibers (F) are glass fibers (GF) , more preferably short glass fibers (SGF) .

Preferably, the short fibers (SF) , more preferably the short glass fibers (SGF) have

i) an average length of 1.0 to 10.0 mm, and/or

ii) an average diameter of 8 to 20 μm.

According to one embodiment of the present invention, the adhesion promoter (AP) is a polar modified polypropylene (PM-PP) being a propylene homo-or copolymer grafted with maleic anhydride having a melt flow rate MFR (190 ℃, 2.16 kg) determined according to ISO 1133 of at least 80.0 g/10 min.

According to another embodiment of the present invention, the fiber-reinforced polypropylene composition (C) comprises

i) 50.0 to 80.0 wt. -%of the propylene polymer (PP) having a xylene soluble content XCS equal or below 5.0 wt. -%,

ii) 15.0 to 40.0 wt. -%of the fibers (F) ,

iii) 3.0 to 10.0 wt. -%of the adhesion promoter (AP) , and

iv) optionally 0.1 to 4.0 wt. -%of additives (AD) ,

based on the overall weight of the fiber-reinforced polypropylene composition (C) .

The present invention is further directed to an article, comprising the fiber-reinforced polypropylene composition (C) described above.

Preferably, the article comprises at least 90 wt. -%of the fiber-reinforced polypropylene composition (C) .

According to one embodiment of the present invention, the article is an automotive article, preferably an automotive engine article.

It is especially preferred that the article is an air-intake manifold of engine.

In the following, the present invention is described in more detail.

The fiber-reinforced polypropylene composition (C)

As outlined above, the present invention is directed to a fiber-reinforced polypropylene composition (C) comprising a propylene polymer (PP) having a xylene soluble content XCS equal or below 5.0 wt. -%, fibers (F) and an adhesion promoter (AP) .

The fiber-reinforced polypropylene composition fulfils in-equation (I) , preferably in-equation (Ia) , more preferably in-equation (Ib)

Additionally or alternatively to the previous paragraph, it is preferred that the fiber-reinforced polypropylene composition (C) fulfils in-equation (II) , more preferably in-equation (IIa) , still more preferably in-equation (IIb)

Preferably, the fiber-reinforced polypropylene composition (C) comprises

i) 50.0 to 80.0 wt. -%, more preferably 53.0 to 75.0 wt. -%, still more preferably 55.0 to 70.0 wt. -%, like 56.0 to 61.0 wt. -%of the propylene polymer (PP) having a xylene soluble content XCS equal or below 5.0 wt. -%,

ii) 15.0 to 40.0 wt. -%, more preferably 20.0 to 38.0 wt. -%, still more preferably 25.0 to 36.0 wt. -%, like 30.0 to 35.0 wt. -%of the fibers (F) , and

iii) 3.0 to 10.0 wt. -%, more preferably 3.2 to 8.0 wt. -%, still more preferably 3.5 to 6.0 wt. -%, like 4.0 to 5.0 wt. -%of the adhesion promoter (AP) ,

Further, the fiber-reinforced polypropylene composition (C) may comprise additives (AD) .

Accordingly, the fiber-reinforced polypropylene composition (C) comprises

ii) 15.0 to 40.0 wt. -%, more preferably 20.0 to 38.0 wt. -%, still more preferably 25.0 to 36.0 wt. -%, like 30.0 to 35.0 wt. -%of the fibers (F) ,

iii) 3.0 to 10.0 wt. -%, more preferably 3.2 to 8.0 wt. -%, still more preferably 3.5 to 6.0 wt. -%, like 4.0 to 5.0 wt. -%of the adhesion promoter (AP) , and

iv) optionally 0.1 to 4.0 wt. -%, more preferably 1.0 to 3.0 wt. -%, still more preferably 1.5 to 2.8 wt. -%, like 2.0 to 2.6 wt. -%of additives (AD) ,

As outlined in more detail below, the propylene polymer (PP) having a xylene soluble content XCS equal or below 5.0 wt. -%can be bimodal or not. Accordingly, the propylene polymer (PP) preferably comprises a first propylene polymer (PP1) and optionally a second propylene polymer (PP2) having a higher melt flow rate MFR ₂ (230 ℃, 2.16 kg) determined according to ISO 1133 than the first propylene polymer (PP1) .

Accordingly, it is preferred that the fiber-reinforced polypropylene composition (C) comprises, more preferably consists of

i) 50.0 to 80.0 wt. -%, more preferably 51.0 to 70.0 wt. -%, still more preferably 53.0 to 65.0 wt. -%, like 55.0 to 60.0 wt. -%of the first propylene polymer (PP1) ,

ii) optionally 0.1 to 15.0 wt. -%, more preferably 1.0 to 10.0 wt. -%, still more preferably 1.5 to 5.0 wt. -%, like 2.0 to 4.0 wt. -%of the second propylene polymer (PP2) ,

iii) 15.0 to 40.0 wt. -%, more preferably 20.0 to 38.0 wt. -%, still more preferably 25.0 to 36.0 wt. -%, like 30.0 to 35.0 wt. -%of the fibers (F) ,

iv) 3.0 to 10.0 wt. -%, more preferably 3.2 to 8.0 wt. -%, still more preferably 3.5 to 6.0 wt. -%, like 4.0 to 5.0 wt. -%of the adhesion promoter (AP) , and

v) optionally 0.1 to 4.0 wt. -%, more preferably 1.0 to 3.0 wt. -%, still more preferably 1.5 to 2.8 wt. -%, like 2.0 to 2.6 wt. -%of additives (AD) ,

As indicated above, it is preferred that the fiber-reinforced polypropylene composition (C) does not contain any amorphous propylene polymers. In other words, it is preferred that the fiber-reinforced polypropylene composition (C) does not contain any propylene polymers having a xylene soluble content XCS equal or above 5.0 wt. -%, more preferably equal or above 3.0 wt. -%, still more preferably equal or above 2.3 wt. -%.

More preferably, the fiber-reinforced polypropylene composition (C) has a xylene soluble content XCS equal or below 5.0 wt. -%, more preferably equal or below 3.0 wt. -%, still more preferably equal or below 2.3 wt. -%.

Additionally, it is preferred that the fiber-reinforced polypropylene composition (C) has a melt flow rate MFR ₂ (230 ℃, 2.16 kg) determined according to ISO 1133 in the range of 0.1 to 15.0 g/10 min, more preferably in the range of 1.0 to 10.0 g/10 min, still more preferably in the range of 2.0 to 8.0 g/10 min, like in the range of 3.0 to 5.0 g/10 min.

Further, it is preferred that the fiber-reinforced polypropylene composition (C) is featured by excellent mechanical properties. Accordingly, it is preferred that the fiber-reinforced polypropylene composition (C) has a tensile modulus determined by ISO 527 of at least 3000 MPa, more preferably in the range of 4000 to 11000 MPa, still more preferably in the range of 6000 to 10000 MPa, like in the range of 7000 to 9000 MPa.

Additionally or alternatively to the previous paragraph, it is preferred that the fiber-reinforced polypropylene composition (C) has a flexural modulus determined by ISO 178 of at least 3000 MPa, more preferably in the range of 4000 to 11000 MPa, still more preferably in the range of 6000 to 10000 MPa, like in the range of 7000 to 9000 MPa.

Further, it is preferred that the fiber-reinforced polypropylene composition (C) has a tensile strength determined according to ISO 527 of at least 70 MPa, more preferably in the range of 75 to 150 MPa, still more preferably in the range of 90 to 140 MPa, like in the range of 100 to 130 MPa.

As outlined above, the fiber-reinforced polypropylene composition (C) is featured by a high engine oil resistance. Accordingly, it is preferred that the mechanical properties of the fiber-reinforced polypropylene composition (C) remains on a high level after exposure to oil.

In particular, it is preferred that the fiber-reinforced polypropylene composition (C) fulfils in-equation (III) ,

wherein TS _R250 is the tensile strength retention after dipping the fiber-reinforced polypropylene composition (C) in oil for 250 h, TS ₂₅₀ is the tensile strength [in MPa] after dipping the fiber-reinforced polypropylene composition (C) in oil for 250 h, and TS is the tensile strength [in MPa] before dipping the fiber-reinforced polypropylene composition (C) in oil.

Further, it is preferred that the fiber-reinforced polypropylene composition (C) fulfils in-equation (IV) ,

wherein TS _R500 is the tensile strength retention after dipping the fiber-reinforced polypropylene composition (C) in oil for 500 h, TS ₅₀₀ is the tensile strength [in MPa] after dipping the fiber-reinforced polypropylene composition (C) in oil for 500 h, and TS is the tensile strength [in MPa] before dipping the fiber-reinforced polypropylene composition (C) in oil.

Additionally or alternatively to the previous paragraphs, it is preferred that the fiber-reinforced polypropylene composition (C) fulfils in-equation (V) ,

wherein TS _R1000 is the tensile strength retention after dipping the fiber-reinforced polypropylene composition (C) in oil for 1000 h, TS ₁₀₀₀ is the tensile strength [in MPa] after dipping the fiber-reinforced polypropylene composition (C) in oil for 1000 h, and TS is the tensile strength [in MPa] before dipping the fiber-reinforced polypropylene composition (C) in oil.

Next to the tensile strength, the tensile modulus of the fiber-reinforced polypropylene composition (C) also remains on a high level after exposure to oil.

Accordingly, it is preferred that the fiber-reinforced polypropylene composition (C) fulfils in-equation (VI) ,

wherein TM _R250 is the tensile modulus retention after dipping the fiber-reinforced polypropylene composition (C) in oil for 250 h, TM ₂₅₀ is the tensile modulus [in MPa] after dipping the fiber-reinforced polypropylene composition (C) in oil for 250 h, and TM is the tensile modulus [in MPa] before dipping the fiber-reinforced polypropylene composition (C) in oil.

Further, it is preferred that the fiber-reinforced polypropylene composition (C) fulfils in-equation (VII) ,

wherein TM _R500 is the tensile modulus retention after dipping the fiber-reinforced polypropylene composition (C) in oil for 500 h, TM ₅₀₀ is the tensile modulus [in MPa] after dipping the fiber-reinforced polypropylene composition (C) in oil for 500 h, and TM is the tensile modulus [in MPa] before dipping the fiber-reinforced polypropylene composition (C) in oil.

Additionally or alternatively to the previous paragraphs, it is preferred that the fiber-reinforced polypropylene composition (C) fulfils in-equation (VIII) ,

wherein TM _R1000 is the tensile modulus retention after dipping the fiber-reinforced polypropylene composition (C) in oil for 1000 h, TM ₁₀₀₀ is the tensile modulus [in MPa] after dipping the fiber-reinforced polypropylene composition (C) in oil for 1000 h, and TM is the tensile modulus [in MPa] before dipping the fiber-reinforced polypropylene composition (C) in oil.

In the following, the propylene polymer (PP) , the fibers (F) and the adhesion promoter (AP) are described in more detail.

The propylene polymer (PP)

As outlined above, the fiber-reinforced polypropylene composition (C) comprises a propylene polymer (PP) .

The propylene polymer (PP) can be a propylene copolymer or a propylene homopolymer, the latter being preferred.

In case the propylene polymer (PP) is a propylene copolymer, the propylene polymer (PP) comprises monomers copolymerizable with propylene, for example comonomers such as ethylene and/or C ₄ to C ₈ α-olefins, in particular ethylene and/or C ₄ to C ₆ α-olefins, e.g. ethylene, 1-butene and/or 1-hexene. Preferably the propylene polymer (PP) 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 propylene polymer (PP) of this invention comprises -apart from propylene -units derivable from ethylene and/or 1-butene. In a preferred embodiment the propylene polymer (PP) comprises units derivable from ethylene and propylene only.

The comonomer content of the propylene polymer (PP) is in the range of 0.0 to 5.0 wt-%, yet more preferably in the range of 0.0 to 3.0 wt-%, still more preferably in the range of 0.0 to 1.0 wt-%.

According to the present invention the expression “propylene homopolymer” relates to a polypropylene that consists substantially, i.e. of at least 99.0 wt. -%, more preferably of at least 99.5 wt. -%, still more preferably of at least 99.8 wt. -%, like of at least 99.9 wt. -%, of propylene units. In another embodiment only propylene units are detectable, i.e. only propylene has been polymerized.

Preferably the propylene polymer (PP) , like the propylene homopolymer (H-PP) , is isotactic. Accordingly, it is preferred that the propylene polymer (PP) , like the propylene homopolymer (H-PP) , has a rather high pentad concentration (mmmm%) i.e. more than 94.1 %, more preferably more than 94.4 %, like more than 94.4 to 98.5 %, still more preferably at least 94.7 %, like in the range of 94.7 to 98.5 %.

It is preferred that the propylene polymer (PP) , like the propylene homopolymer (H-PP) , is featured by rather low cold xylene soluble (XCS) content, i.e. by a xylene cold soluble (XCS) below 3.1 wt. -%. Accordingly, the propylene polymer (PP) , like the propylene homopolymer (H-PP) , has preferably a xylene cold soluble content (XCS) in the range of 1.0 to 3.0 wt. -%, more preferably in the range of 1.5 to 2.8 wt. -%, still more preferably in the range of 2.0 to 2.6 wt. -%.

The amount of xylene cold solubles (XCS) additionally indicates that the propylene polymer (PP) , like the propylene homopolymer (H-PP) , is preferably free of any elastomeric polymer component, like an ethylene propylene rubber. In other words, the propylene polymer (PP) , like the propylene homopolymer (H-PP) , shall be not a heterophasic polypropylene, i.e. a system consisting of a polypropylene matrix in which an elastomeric phase is dispersed. Such systems are featured by a rather high xylene cold soluble content.

The amount of xylene cold solubles (XCS) additionally indicates that the propylene polymer (PP) , like the propylene homopolymer (H-PP) , preferably does not contain elastomeric (co) polymers forming inclusions as a second phase for improving mechanical properties. A polymer containing elastomeric (co) polymers as insertions of a second phase would by contrast be called heterophasic and is preferably not part of the present invention. The presence of second phases or the so called inclusions are for instance visible by high resolution microscopy, like electron microscopy or atomic force microscopy, or by dynamic mechanical thermal analysis (DMTA) . Specifically in DMTA the presence of a multiphase structure can be identified by the presence of at least two distinct glass transition temperatures.

Further, the propylene polymer (PP) , like the propylene homopolymer (H-PP) , is preferably a crystalline propylene homopolymer. The term “crystalline” indicates that the propylene polymer (PP) , like the propylene homopolymer (H-PP) , has a rather high melting temperature. Accordingly throughout the invention the propylene polymer (PP) , like the propylene homopolymer (H-PP) , is regarded as crystalline unless otherwise indicated. Therefore, the propylene polymer (PP) , like the propylene homopolymer (H-PP) , preferably has a melting temperature Tm measured by differential scanning calorimetry (DSC) of at least 160 ℃, more preferably at least 161 ℃, still more preferably at least 163 ℃, like in the range of 163 ℃ to 167 ℃.

Further it is preferred that the propylene polymer (PP) , like the propylene homopolymer (H-PP) , has a crystallization temperature Tc measured by differential scanning calorimetry (DSC) of equal or more than 108 ℃, more preferably in the range of 110 to 130 ℃, more preferably in the range of 120 to 130 ℃.

It is appreciated that the propylene polymer (PP) is featured by a rather low melt flow rate. Accordingly, it is preferred that the propylene polymer (PP) has a melt flow rate MFR ₂ (230 ℃, 2.16 kg) determined according to ISO 1133 below 50.0 g/10 min, more preferably in the range of 0.1 to 40.0 g/10 min, still more preferably in the range of 1.0 to 30.0 g/10 min, yet more preferably in the range of 3.0 to 20.0 g/10 min, still more preferably in the range of 5.0 to 15.0 g/10 min, like in the range of 6.0 to 10.0 g/10 min.

According to a preferred embodiment of the present invention, the propylene polymer (PP) is preferably bimodal.

Accordingly, it is preferred that the propylene polymer (PP) comprises at least two propylene polymers. It is especially preferred that the propylene polymer (PP) comprises two propylene polymers , i.e. a first propylene polymer (PP1) and a second propylene polymer (PP2) .

Preferably, the first propylene polymer (PP1) and the second propylene polymer (PP2) have different melt flow rates MFR ₂ (230 ℃, 2.16 kg) determined according to ISO 1133.

The first propylene polymer (PP1) and the second propylene polymer (PP2) can be propylene copolymers or propylene homopolymers, respectively.

In case the first propylene polymer (PP1) and/or the second propylene polymer (PP2) are propylene copolymers, said propylene polymers comprise monomers copolymerizable with propylene, for example comonomers such as ethylene and/or C ₄ to C ₈ α-olefins, in particular ethylene and/or C ₄ to C ₆ α-olefins, e.g. 1-butene and/or 1-hexene. Preferably the first propylene polymer (PP1) and/or the second propylene polymer (PP2) according to this invention comprise, especially consist of, monomers copolymerizable with propylene from the group consisting of ethylene, 1-butene and 1-hexene. More specifically the first propylene polymer (PP1) and/or the second propylene polymer (PP2) of this invention comprise -apart from propylene -units derivable from ethylene and/or 1-butene. In a preferred embodiment the propylene polymer (PP) comprises units derivable from ethylene and propylene only.

As outlined in more detail below, the first propylene polymer (PP1) may comprise a first propylene polymer fraction (PP1a) and a second propylene polymer fraction (PP1b) . Thus, in an embodiment wherein the propylene polymer (PP) comprises the first propylene polymer (PP1) only and the first propylene polymer (PP1) comprises the first propylene polymer fraction (PP1a) and the second propylene polymer fraction (PP1b) , the propylene polymer (PP) is also bimodal.

The comonomer contents of the first propylene polymer (PP1) and/or the second propylene polymer (PP2) are in the range of 0.0 to 5.0wt-%, yet more preferably in the range of 0.0 to 3.0wt%-%, still more preferably in the range of 0.0 to 1.0wt-%, respectively.

As outlined above, however, it is preferred that the propylene polymer (PP) is a propylene homopolymer (H-PP) . Thus, it is preferred that all propylene polymers of the propylene polymer (PP) , i.e. the first propylene polymer (PP1) and the second propylene polymer (PP2) are propylene homopolymers. Regarding the expression “propylene homopolymer” , reference is made to the definition provided above.

In the following, the first propylene polymer (PP1) and the second propylene polymer (PP2) are described in more detail.

The first propylene polymer (PP1)

The first propylene polymer (PP1) preferably has a low melt flow rate MFR ₂ (230 ℃, 2.16 kg) determined according to ISO 1133. Accordingly, it is preferred that the first propylene polymer (PP1) has a melt flow rate MFR ₂ (230 ℃, 2.16 kg) determined according to ISO 1133 below 50.0 g/10 min, more preferably in the range of 0.1 to 40.0 g/10 min, still more preferably in the range of 1.0 to 30.0 g/10 min, yet more preferably in the range of 3.0 to 20.0 g/10 min, still more preferably in the range of 5.0 to 15.0 g/10 min, like in the range of 6.0 to 10.0 g/10 min.

A further characteristic of the first propylene polymer (PP1) is the low amount of misinsertions of propylene within the polymer chain, which indicates that the first propylene polymer (PP1) is produced in the presence of a Ziegler-Natta catalyst, preferably in the presence of a Ziegler-Natta catalyst (ZN-C1) as defined in more detail below. Accordingly, the first propylene polymer (PP1) 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.

It is preferred that the first propylene polymer (PP1) is featured by rather low cold xylene soluble (XCS) content, i.e. by a xylene cold soluble (XCS) below 4.1 wt. -%Accordingly, the first propylene polymer (PP1) has preferably a xylene cold soluble content (XCS) in the range of 1.0 to 4.0 wt. -%, more preferably in the range of 1.0 to 2.0 wt. -%.

The amount of xylene cold solubles (XCS) additionally indicates that the first propylene polymer (PP1) is preferably free of any elastomeric polymer component, like an ethylene propylene rubber. In other words, the first propylene polymer (PP1) shall be not a heterophasic polypropylene, i.e. a system consisting of a polypropylene matrix in which an elastomeric phase is dispersed. Such systems are featured by a rather high xylene cold soluble content.

The amount of xylene cold solubles (XCS) additionally indicates that the first propylene polymer (PP1) preferably does not contain elastomeric (co) polymers forming inclusions as a second phase for improving mechanical properties. A polymer containing elastomeric (co) polymers as insertions of a second phase would by contrast be called heterophasic and is preferably not part of the present invention. The presence of second phases or the so called inclusions are for instance visible by high resolution microscopy, like electron microscopy or atomic force microscopy, or by dynamic mechanical thermal analysis (DMTA) . Specifically in DMTA the presence of a multiphase structure can be identified by the presence of at least two distinct glass transition temperatures.

Further, the first propylene polymer (PP1) is preferably a crystalline propylene homopolymer. The term “crystalline” indicates that the first propylene polymer (PP1) has a rather high melting temperature. Accordingly throughout the invention the first propylene polymer (PP1) is regarded as crystalline unless otherwise indicated. Therefore, the first propylene polymer (PP1) preferably has a melting temperature Tm measured by differential scanning calorimetry (DSC) of at least 158 ℃, more preferably at least 160 ℃, still more preferably at least 161 ℃, like in the range of 161 ℃ to 168 ℃.

Further it is preferred that the first propylene polymer (PP1) has a crystallization temperature Tc measured by differential scanning calorimetry (DSC) of equal or more than 110 ℃, more preferably in the range of 110 to 140 ℃, more preferably in the range of 120 to 130 ℃.

According to a preferred embodiment of the present invention, the first propylene polymer (PP1) is bimodal.

Accordingly, it is preferred that the first propylene polymer (PP1) comprises at least two propylene polymer fractions. It is especially preferred that the first propylene polymer (PP1) comprises two propylene polymer fractions, i.e. a first propylene polymer fraction (PP1a) and a second propylene polymer fraction (PP1b) .

Preferably, the first propylene polymer fraction (PP1a) and the second propylene polymer fraction (PP1b) have different melt flow rates MFR ₂ (230 ℃, 2.16 kg) determined according to ISO 1133 and/or different comonomer contents.

The first propylene polymer fraction (PP1a) and the second propylene polymer fraction (PP1b) can be propylene copolymers or propylene homopolymers, respectively.

In case the first propylene polymer fraction (PP1a) and/or the second propylene polymer fraction (PP1b) are propylene copolymers, said propylene polymers comprise monomers copolymerizable with propylene, for example comonomers such as ethylene and/or C ₄ to C ₈ α-olefins, in particular ethylene and/or C ₄ to C ₆ α-olefins, e.g. 1-butene and/or 1-hexene. Preferably the first propylene polymer fraction (PP1a) and/or the second propylene polymer fraction (PP1b) according to this invention comprise, especially consist of, monomers copolymerizable with propylene from the group consisting of ethylene, 1-butene and 1-hexene. More specifically the first propylene polymer fraction (PP1a) and/or the second propylene polymer fraction (PP1b) of this invention comprise -apart from propylene -units derivable from ethylene and/or 1-butene. In a preferred embodiment the first propylene polymer (PP1) comprises units derivable from ethylene and propylene only.

Preferably, the first propylene polymer (PP1) is nucleated, more preferably α-nucleated. Accordingly, it is preferred that the first propylene polymer (PP1) is prepared in the presence of a nucleating agent, preferably an α-nucleating agent.

In case the first propylene polymer (PP1) comprises an α-nucleating agent, it is preferred that it is free of β-nucleating agents. The α-nucleating agent is preferably selected from the group consisting of

(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 C ₁-C ₈-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-O- [ (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 aluminum-hydroxy-bis [2, 2'-methylene-bis (4, 6-di-t-butylphenyl) phosphate] , and

(iv) vinylcycloalkane polymer and vinylalkane polymer (as discussed in more detail below) , and

(v) mixtures thereof.

Such additives are generally commercially available and are described, for example, in "Plastic Additives Handbook", pages 871 to 873, 5th edition, 2001 of Hans Zweifel.

Preferably the first propylene polymer (PP1) contains up to 5.0 wt. -%of the α-nucleating agent. In a preferred embodiment, the propylene homopolymer contains not more than 500 ppm, more preferably of 0.025 to 200 ppm, more preferably of 0.1 to 200 ppm, still more preferably 0.3 to 200 ppm, most preferably 0.3 to 100 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 1, 2, 3, -trideoxy-4, 6: 5, 7-bis-O- [ (4-propylphenyl) methylene] -nonitol, sodium 2, 2'-methylenebis (4, 6, -di-tert-butylphenyl) phosphate, vinylcycloalkane polymer, vinylalkane polymer, and mixtures thereof.

Preferably, the first propylene polymer (PP1) is obtained by polymerizing propylene in the presence of a Ziegler-Natta catalyst as defined below. More preferably, the first propylene polymer (PP1) according to this invention is obtained by a process as defined in detail below by using the Ziegler-Natta catalyst.

The first propylene polymer (PP1) according to this invention is preferably produced in the presence of

(a) a Ziegler-Natta catalyst (ZN-C1) comprising compounds (TC) of a transition metal of Group 4 to 6 of IUPAC, a Group 2 metal compound (MC) and an internal donor (ID) ;

(b) optionally a co-catalyst (Co) , and

(c) optionally an external donor (ED) .

Preferably, the first propylene polymer (PP1) is produced in a polymerization process as further described below comprising at least one reactor, like two reactors (R1) and (R2) . Preferably, the first propylene polymer (PP1) is produced in one polymerization reactor (R1) .

The process for the preparation of the propylene homopolymer as well as the Ziegler-Natta catalyst are further described in detail below.

The polymerization reactor (R1) can be a gas phase reactor (GPR) or a slurry reactor (SR) . A gas phase reactor (GPR) according to this invention is preferably a fluidized bed reactor, a fast fluidized bed reactor or a settled bed reactor or any combination thereof.

Preferably, the polymerization reactor (R1) is a slurry reactor (SR) which 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 polymerization reactor (R2) and any subsequent reactor, if present, are preferably gas phase reactors (GPRs) . Such gas phase reactors (GPR) can be any mechanically mixed or fluid bed reactors. Preferably the gas phase reactors (GPRs) 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.

If any subsequent reactor is present, the propylene homopolymer of the first polymerization reactor (R1) , is preferably directly fed into the second polymerization reactor (R2) , i.e. into the (first) gas phase reactor (GPR1) , without a flash step between the stages. This kind of direct feed is described in EP 887379 A, EP 887380 A, EP 887381 A and EP 991684 A. By "direct feed" is meant a process wherein the content of the first polymerization reactor (R1) , i.e. of the loop reactor (LR) , is led directly to the next stage gas phase reactor.

Alternatively, the propylene homopolymer of the first polymerization reactor (R1) , more preferably polymer slurry of the loop reactor (LR) , may be also directed into a flash step or through a further concentration step before fed into the second polymerization reactor (R2) , i.e. into the gas phase reactor (GPR) . Accordingly, this "indirect feed" refers to a process wherein the content of the first polymerization reactor (R1) , of the loop reactor (LR) , i.e. the polymer slurry, is fed into the second polymerization reactor (R2) , into the (first) gas phase reactor (GPR1) , via a reaction medium separation unit and the reaction medium as a gas from the separation unit.

However, it is preferred that the propylene polymer (PP1) is prepared in one reactor, i.e. the polymerization reactor (R1) being a loop reactor (LR) .

If needed prior to the slurry reactor (SR) , i.e. the loop reactor (LR) , a pre-polymerization reactor is placed.

The Ziegler-Natta catalyst is fed into the polymerization reactor (R1) . If the process covers also a pre-polymerization step it is preferred that all of the Ziegler-Natta catalyst is fed in the pre-polymerization reactor. Subsequently the pre-polymerization product containing the Ziegler-Natta catalyst is transferred into the polymerization reactor (R1) .

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.

Especially good results are achieved in case the temperature in the reactors is carefully chosen.

Accordingly it is preferred that the operating temperature in the polymerization reactor (R1) is in the range of 62 to 90 ℃, more preferably in the range of 65 to 85 ℃, still more preferably in the range of 67 to 83 ℃.

Typically the pressure in the polymerization reactor (R1) , preferably in the loop reactor (LR) , is in the range from 20 to 80 bar, preferably 30 to 70 bar, like 35 to 65 bar.

Preferably hydrogen is added in each polymerization reactor in order to control the molecular weight, i.e. the melt flow rate MFR ₂.

Preferably the average residence time is rather long in the polymerization reactors (R1) . In general, the average residence time (τ) is defined as the ratio of the reaction volume (V _R) to the volumetric outflow rate from the reactor (Q _o) (i.e. V _R/Q _o) , i.e τ = V _R/Q _o [tau = V _R/Q _o] . In case of a loop reactor the reaction volume (V _R) equals to the reactor volume.

Accordingly the average residence time (τ) in the polymerization reactor (R1) is preferably at least 15 min, more preferably in the range of 15 to 90 min, still more preferably in the range of 20 to 80 min, like in the range of 24 to 60 min.

As mentioned above the preparation of the propylene homopolymer can comprise in addition to the (main) polymerization of the propylene homopolymer in the polymerization reactor (R1) prior thereto a pre-polymerization in a pre-polymerization reactor (PR) upstream to the polymerization reactor (R1) .

In the pre-polymerization reactor (PR) a polypropylene (Pre-PP) is produced. The pre-polymerization is conducted in the presence of the Ziegler-Natta catalyst. According to this embodiment the Ziegler-Natta catalyst, the co-catalyst (Co) , and the external donor (ED) are all introduced to the pre-polymerization step. However, this shall not exclude the option that at a later stage for instance further co-catalyst (Co) and/or external donor (ED) is added in the polymerization process, for instance in the first reactor (R1) . In one embodiment the Ziegler-Natta catalyst, the co-catalyst (Co) , and the external donor (ED) are only added in the pre-polymerization reactor (PR) , if a pre-polymerization is applied.

The pre-polymerization reaction is typically conducted at a temperature of 0 to 60 ℃, preferably from 15 to 50 ℃, and more preferably from 20 to 45 ℃.

The pressure in the pre-polymerization 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.

In a preferred embodiment, the pre-polymerization is conducted as bulk slurry polymerization in liquid propylene, i.e. the liquid phase mainly comprises propylene, with optionally inert components dissolved therein. Furthermore, according to the present invention, an ethylene feed is employed during pre-polymerization as mentioned above.

It is possible to add other components also to the pre-polymerization stage. Thus, hydrogen may be added into the pre-polymerization stage to control the molecular weight of the polypropylene (Pre-PP) 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 pre-polymerization conditions and reaction parameters is within the skill of the art.

Due to the above defined process conditions in the pre-polymerization, preferably a mixture (MI) of the Ziegler-Natta catalyst and the polypropylene (Pre-PP) produced in the pre-polymerization reactor (PR) is obtained. Preferably the Ziegler-Natta catalyst is (finely) dispersed in the polypropylene (Pre-PP) . In other words, the Ziegler-Natta catalyst particles introduced in the pre-polymerization reactor (PR) split into smaller fragments which are evenly distributed within the growing polypropylene (Pre-PP) . The sizes of the introduced Ziegler-Natta catalyst particles as well as of the obtained fragments are not of essential relevance for the instant invention and within the skilled knowledge.

As mentioned above, if a pre-polymerization is used, subsequent to said pre-polymerization, the mixture (MI) of the Ziegler-Natta catalyst and the polypropylene (Pre-PP) produced in the pre-polymerization reactor (PR) is transferred to the first reactor (R1) . Typically the total amount of the polypropylene (Pre-PP) in the final propylene polymer (PP1) is rather low and typically not more than 5.0 wt. -%, more preferably not more than 4.0 wt. -%, still more preferably in the range of 0.5 to 4.0 wt. -%, like in the range 1.0 of to 3.0 wt. -%.

In case that pre-polymerization is not used, propylene and the other ingredients such as the Ziegler-Natta catalyst are directly introduced into the first polymerization reactor (R1) .

Accordingly, the propylene homopolymer is preferably produced in a process comprising the following steps under the conditions set out above

(a) in the first polymerization reactor (R1) , i.e. in a loop reactor (LR) , propylene is polymerized obtaining the first propylene polymer (PP1) .

A pre-polymerization as described above can be accomplished prior to step (a) .

In the process described above a Ziegler-Natta catalyst (ZN-C1) for the preparation of the first propylene polymer (PP1) is applied. This Ziegler-Natta catalyst (ZN-C1) can be any stereospecific Ziegler-Natta catalyst (ZN-C1) for propylene polymerization, which preferably is capable of catalyzing the polymerization and copolymerization of propylene and optional comonomers at a pressure of 500 to 10000 kPa, in particular 2500 to 8000 kPa, and at a temperature of 40 to 110℃, in particular of 60 to 110℃.

Preferably, the Ziegler-Natta catalyst (ZN-C1) comprises a high-yield Ziegler-Natta type catalyst including an internal donor component, which can be used at high polymerization temperatures of 80℃ or more. Such high-yield Ziegler-Natta catalyst (ZN-C1) can comprise a succinate, a diether, a phthalate etc., or mixtures therefrom as internal donor (ID) and are for example commercially available from LyondellBasell under the Avant ZN trade name. Examples of the Avant ZN series are Avant ZN 126 and Avant ZN 168. Avant ZN 126 is a Ziegler-Natta catalyst with 3.5 wt%titanium and a diether compound as internal electron donor, which is commercially available from LyondellBasell. Avant ZN 168 is a Ziegler-Natta catalyst with 2.6 wt %titanium and a succinate compound as internal electron donor, which is commercially available from LyondellBaselll. A further example of the Avant ZN series is the catalyst ZN180M of LyondellBasell.

Additional suitable catalysts are described for example in WO 2012/007430, EP2610271, EP261027 and EP2610272.

The Ziegler-Natta catalyst (ZN-C1) is preferably used in association with an alkyl aluminum cocatalyst and optionally external donors.

As further component in the instant polymerization process an external donor (ED) is preferably present. Suitable external donors (ED) include certain silanes, ethers, esters, amines, ketones, heterocyclic compounds and blends of these. It is especially preferred to use a silane. It is most preferred to use silanes of the general formula

R ^a _pR ^b _qSi (OR ^c) _(4-p-q)

wherein R ^a, R ^b and R ^c denote a hydrocarbon radical, in particular an alkyl or cycloalkyl group,

and wherein p and q are numbers ranging from 0 to 3 with their sum p + q being equal to or less than 3. R ^a, R ^b and R ^c can be chosen independently from one another and can be the same or different. Specific examples of such silanes are (tert-butyl) ₂Si (OCH ₃) ₂,

(cyclohexyl) (methyl) Si (OCH ₃) ₂, (phenyl) ₂Si (OCH ₃) ₂ and (cyclopentyl) ₂Si (OCH ₃) ₂, or of general formula

Si (OCH ₂CH ₃) ₃ (NR ³R ⁴)

wherein R3 and R4 can be the same or different, and represent a hydrocarbon group having 1 to 12 carbon atoms.

R3 and R4 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 R3 and R4 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 ³ and R ⁴ are the same, yet more preferably both R ³ and R ⁴ are an ethyl group.

Especially preferred external donors (ED) are the dicyclopentyl dimethoxy silane donor (D donor) or the cyclohexylmethyl dimethoxy silane donor (C-Donor) .

In addition to the Ziegler-Natta catalyst (ZN-C1) and the optional external donor (ED) a cocatalyst can be used. The co-catalyst is preferably a compound of group 13 of the periodic table (IUPAC) , e.g. organo aluminum, such as an aluminum compound, like aluminum alkyl, aluminum halide or aluminum alkyl halide compound. Accordingly, in one specific embodiment the co-catalyst (Co) is a trialkylaluminum, like triethylaluminum (TEAL) , dialkyl aluminum chloride or alkyl aluminum dichloride or mixtures thereof. In one specific embodiment the co-catalyst (Co) is triethylaluminum (TEAL) .

Preferably the ratio between the co-catalyst (Co) and the external donor (ED) [Co/ED] and/or mthe ratio between the co-catalyst (Co) and the transition metal (TM) [Co/TM] should be carefully chosen.

Accordingly,

(a) the mol-ratio of co-catalyst (Co) to external donor (ED) [Co/ED] must be in the range of 5 to 45, preferably is in the range of 5 to 35, more preferably is in the range of 5 to 25;

and optionally

(b) the mol-ratio of co-catalyst (Co) to titanium compound (TC) [Co/TC] must be in the range of above 80 to 500, preferably is in the range of 90 to 350, still more preferably is in the range of 100 to 300.

In a further embodiment, the Ziegler-Natta catalyst (ZN-C1) can be modified by polymerizing 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:

CH ₂=CH-CHR ⁵R ⁶

wherein R ⁵ and R ⁶ 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 first propylene polymer (PP1) according to this invention. The polymerized vinyl compound can act as an α-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.

The second propylene polymer (PP2)

The second propylene polymer (PP2) preferably has a moderate melt flow rate. Accordingly, it is preferred that the melt flow rate MFR ₂ (230 ℃, 2.16 kg) determined according to ISO 1133 of the second propylene polymer (PP2) is in the range of 20.0 to 150.0 g/10 min, more preferably in the range of 30.0 to 120.0 g/10 min, still more preferably in the range of 40.0 to 90.0 g/10 min, like in the range of 50.0 to 65.0 g/10 min.

It is preferred that the second propylene polymer (PP2) is featured by rather low cold xylene soluble (XCS) content, i.e. by a xylene cold soluble (XCS) below 4.1 wt. -%Accordingly, the second propylene polymer (PP2) has preferably a xylene cold soluble content (XCS) in the range of 1.0 to 4.0 wt. -%, more preferably in the range of 1.0 to 3.0 wt. -%, still more preferably in the range of 1.5 to 2.5 wt. -%.

Thus, similar to the first propylene polymer (PP1) , it is preferred that the second propylene polymer (PP2) is free of any elastomeric component. In this regard, reference is made to the definitions provided above.

Further, the second propylene polymer (PP2) is preferably a crystalline propylene homopolymer. Regarding the term “crystalline” , reference is made to the definition provided above. Therefore, second propylene polymer (PP2) preferably has a melting temperature Tm measured by differential scanning calorimetry (DSC) of at least 145 ℃, more preferably at least 150 ℃, still more preferably at least 155 ℃, like in the range of 150 ℃ to 160 ℃.

Further it is preferred that the second propylene polymer (PP2) has a crystallization temperature Tc measured by differential scanning calorimetry (DSC) of equal or more than 108 ℃, more preferably in the range of 110 to 130 ℃, more preferably in the range of 115 to 125 ℃.

Preferably, the second propylene polymer (PP2) is obtained by polymerizing propylene in the presence of a Ziegler-Natta catalyst. More preferably, the second propylene polymer (PP2) according to this invention is obtained by a process using the Ziegler-Natta catalyst.

For the preparation of the second propylene polymer (PP2) , the polymerization process and Ziegler-Natta catalyst described above for the first propylene polymer (PP1) can be used. Therefore, reference is made to the process and Ziegler-Natta catalyst described above for the first propylene polymer (PP1) .

The fibers (F)

Essential components of the present fiber-reinforced polypropylene composition (C) are the fibers (F) .

Preferably, said fibers (F) are short fibers (SF) .

Preferably the short fibers (SF) are selected from the group consisting of glass fibers, metal fibers, mineral fibers, ceramic fibers, carbon fibers and graphite fibers. Glass fibers are especially preferred. Accordingly, it is preferred that the short fibers (SF) are short glass fibers (SGF) . In particular, the short glass fibers (SGF) are cut glass fibers, also known as short fibers or chopped strands.

The cut or short fibers (SF) , like the short glass fibers (SGF) used in the fiber-reinforced polypropylene composition (C) preferably have an average length in the range of from 1.0 to 10.0 mm, more preferably in the range of 2.0 to 8.0 mm, still more preferably in the range of 3.0 to 5.0 mm, like in the range of 3.0 to 4.5 mm.

The cut or short fibers (SF) , like the short glass fibers (SGF) used in the fiber-reinforced polypropylene composition (C) preferably have an average diameter of from 8 to 20 μm, more preferably from 9 to 16 μm, still more preferably 9 to 14 μm, like 9 to 13 μm.

Preferably, the short fibers (SF) , like the short glass fibers (SGF) have an aspect ratio of 125 to 650, preferably of 200 to 600, more preferably 300 to 600, still more preferably 400 to 550. The aspect ratio is the relation between average length and average diameter of the fibers.

The adhesion promoter (AP)

In accordance with the present invention, the fiber-reinforced polypropylene composition (C) further comprises an adhesion promoter (AP) . The adhesion promoter (AP) is specified as being a polar modified polypropylene (PM-PP) homo-or copolymer.

The polar modified polypropylene (PM-PP) homo-or copolymer comprises a low molecular weight compound having reactive polar groups. Modified polypropylene homopolymers and copolymers, like copolymers of propylene and ethylene or with other α-olefins, e.g. C ₄ to C ₁₀ α-olefins, are most preferred, as they are highly compatible with the propylene polymer (PP) of the inventive fiber-reinforced polypropylene composition (C) .

In terms of structure, the polar modified polypropylene (PM-PP) homo-or copolymer are preferably selected from graft homo-or copolymers.

In this context, preference is given to polar modified polypropylene (PM-PP) homo-or copolymers containing groups derived from polar compounds, in particular selected from the group consisting of acid anhydrides, carboxylic acids, carboxylic acid derivatives, primary and secondary amines, hydroxyl compounds, oxazoline and epoxides, and also ionic compounds.

Specific examples of said polar compounds are unsaturated cyclic anhydrides and their aliphatic diesters, and the diacid derivatives. In particular, one can use maleic anhydride and compounds selected from C ₁ to C ₁₀ linear and branched dialkyl maleates, C ₁ to C ₁₀ linear and branched dialkyl fumarates, itaconic anhydride, C ₁ to C ₁₀ linear and branched itaconic acid dialkyl esters, acrylic acid, maleic acid, fumaric acid, itaconic acid and mixtures thereof.

Particular preference is given to use a polypropylene homo-or copolymer grafted with maleic anhydride or acrylic acid as the polar modified polypropylene (PM-PP) homo-or copolymer, i.e. the adhesion promoter (AP) .

The modified polymer, i.e. the adhesion promoter, can commercially available or be produced in a simple manner by reactive extrusion of the polymer, for example with maleic anhydride or acrylic acid in the presence of free radical generators (like organic peroxides) , as disclosed for instance in US 4,506,056, US 4,753,997 or EP 1 805 238.

Preferred amounts of the polar modified polypropylene (PM-PP) homo-or copolymer, i.e. the adhesion promoter (AP) , in the present fiber-reinforced polypropylene composition (C) , are from 1 to 10 wt. -%. For example, in the range of 2.0 wt. -%to 8 wt. -%, preferable in the range of 3.0 wt. -%to 6 wt. -%, and most preferably in the range of 3.0 wt. -%to 6.0 wt. -%.

Preferred amounts of groups derived from polar compounds in the polar modified polypropylene (PM-PP) homo-or copolymer, i.e. the adhesion promoter (AP) , are from 0.5 to 10 wt. -%. For example, in the range of 0.5 wt. -%to 8 wt. -%, preferable in the range of 0.5 wt. -%to 6 wt. -%, more preferably in the range of 0.5 wt. -%to 4 wt. -%and most preferably in the range of 0.5 wt. -%to 3.5 wt. -%.

Preferred values of the melt flow rate MFR ₂ (190 ℃) for the polar modified polypropylene (PM-PP) homo-or copolymer, i.e. for the adhesion promoter (AP) , are from 30 to 200 g/10 min. It is particularly preferred that the polar modified polypropylene (PM-PP) homo-or copolymer has a melt flow rate MFR ₂ (190 ℃) of at least 80 g/10 min. In one preferred embodiment of the present invention, the adhesion promoter (AP) is a maleic anhydride modified polypropylene homo-or copolymer and/or an acrylic acid modified polypropylene homo-or copolymer. Preferably, the adhesion promoter (AP) is a maleic anhydride modified polypropylene homopolymer and/or an acrylic acid modified polypropylene homopolymer and preferably a maleic anhydride modified polypropylene homopolymer. For example, suitable polar modified polypropylene (PM-PP) homo-or copolymers include, for example, a polypropylene homopolymer grafted with maleic anhydride (PP-g-MAH) and a polypropylene homopolymer grafted with acrylic acid (PP-g-AA) .

The additives (AD)

In addition to the propylene polymer (PP) , the adhesion promoter (AP) and the fibers (F) , the fiber-reinforced polypropylene composition (C) of the invention may include additives (AD) . Typical additives are acid scavengers, antioxidants, colorants, light stabilisers, plasticizers, slip agents, anti-scratch agents, dispersing agents, processing aids, lubricants, pigments, and the like.

Such additives are commercially available and for example described in “Plastic Additives Handbook” , 6 ^th edition 2009 of Hans Zweifel (pages 1141 to 1190) .

Furthermore, the term “additives (AD) ” according to the present invention also includes carrier materials, in particular polymeric carrier materials.

The Polymeric Carrier Material

Preferably the fiber-reinforced polypropylene composition (C) of the invention does not comprise (a) further polymer (s) different to the propylene polymer (PP) and the adhesion promoter (AP) , in an amount exceeding 15 wt. -%, preferably in an amount exceeding 10 wt. -%, more preferably in an amount exceeding 5 wt. -%, based on the weight of the fiber reinforced-polypropylene composition (C) . Any polymer being a carrier material for additives (AD) is not calculated to the amount of polymeric compounds as indicated in the present invention, but to the amount of the respective additive.

The polymeric carrier material of the additives (AD) is a carrier polymer to ensure a uniform distribution in the fiber-reinforced polypropylene composition (C) of the invention. The polymeric carrier material is not limited to a particular polymer. The polymeric carrier material may be ethylene homopolymer, ethylene copolymer obtained from ethylene and α-olefin comonomer such as C ₃ to C ₈ α-olefin comonomer, propylene homopolymer and/or propylene copolymer obtained from propylene and α-olefin comonomer such as ethylene and/or C ₄ to C ₈ α-olefin comonomer, most preferably propylene homopolymer. It is preferred that the polymeric carrier material does not contain monomeric units derivable from styrene or derivatives thereof.

The article

The present invention also relates to an injection molded article, like an injection molded automotive article, comprising the fiber-reinforced polypropylene composition (C) as defined above. The present invention in particular relates to an injection molded article, like an injection molded automotive article, comprising at least 60 wt. -%, more preferably at least 80 wt. -%, still more preferably at least 90 wt. -%, like at least 95 wt. -%or at least 99 wt. -%, of the fiber reinforced polypropylene composition (C) as defined above. In an especially preferred embodiment the present invention relates to an injection molded article, like an injection molded automotive article, consisting of the fiber-reinforced polypropylene composition (C) as defined above.

It is especially preferred that said injection molded automotive article is an automotive engine article, like an air-intake manifold of the engine.

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

EXAMPLES

1. Measuring methods

MFR ₂ (230 ℃) is measured according to ISO 1133 (230 ℃, 2.16 kg load) .

The melt flow rate MFR ₂ (230 ℃) of the propylene polymer (PP) is calculated according to equation (IX)

log MFR (PP) =w (PP1) ·log MFR (PP1) + w (PP2) ·log MFR （PP2） (IX) ,

Wherein

w (PP1) is the weight fraction of the first propylene polymer (PP1)

w (PP2) is the weight fraction of the second propylene polymer (PP2)

MFR (PP1) is the melt flow rate MFR ₂ (230 ℃, 2.16 kg) in g/10 min of the first propylene polymer (PP1)

MFR (PP2) is the melt flow rate MFR ₂ (230 ℃, 2.16 kg) in g/10 min of the second propylene polymer (PP2) ,

MFR (PP) is the melt flow rate MFR ₂ (230 ℃, 2.16 kg) in g/10 min of the propylene polymer (PP)

The same applies to bimodal polymer PP1 and two fractions PP1a and PP1b of bimodal PP1.

Quantification of microstructure by NMR spectroscopy

Quantitative nuclear-magnetic resonance (NMR) spectroscopy was used to quantify the comonomer content and comonomer sequence distribution 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 (Singh, G., Kothari, A., Gupta, V., Polymer Testing 28 5 (2009) , 475) . 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 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 (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, 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 using proprietary computer programs. 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. Characteristic signals corresponding to the incorporation of ethylene were observed Cheng, H. N., Macromolecules 17 (1984) , 1950) .

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) , 1157; 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., Macromoleucles 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:

P ₁₂ = I _CH3 + P _12e

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

P _total = P ₁₂ + P _21e

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

[21e] mol%= 100 * (P _21e /P _total )

For copolymers characteristic signals corresponding to the incorporation of ethylene were observed (Cheng, H.N., Macromolecules 17 (1984) , 1950) .

With regio defects also observed (Resconi, L., Cavallo, L., Fait, A., Piemontesi, F., Chem. Rev. 2000, 100, 1253; Wang, W-J., Zhu, S., Macromolecules 33 (2000) , 1157; Cheng, H.N., Macromolecules 17 (1984) , 1950) correction for the influence of such defects on the comonomer content was required.

The comonomer fraction was quantified using the method of Wang et. al. (Wang, W-J., Zhu, S., Macromolecules 33 (2000) , 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.

For systems where only isolated ethylene in PPEPP sequences was observed the method of Wang et. al. was modified to reduce the influence of non-zero integrals of sites that are known to not be present. This approach reduced the overestimation of ethylene content for such systems and was achieved by reduction of the number of sites used to determine the absolute ethylene content to:

E = 0.5 (Sββ + Sβγ + Sβδ + 0.5 (Sαβ + Sαγ) )

Through the use of this set of sites the corresponding integral equation becomes:

E = 0.5 (I _H +I _G + 0.5 (I _C + I _D) )

using the same notation used in the article of Wang et. al. (Wang, W-J., Zhu, S.,

Macromolecules 33 (2000) , 1157) . Equations used for absolute propylene content were not modified.

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

E [mol%] = 100 *fE

The weight percent comonomer incorporation was calculated from the weight fraction:

E [wt%] = 100 * (fE *28.06) / ( (fE *28.06) + ( (1-fE) *42.08) )

The comonomer sequence distribution at the triad level was determined using the analysis method of Kakugo et al. (Kakugo, M., Naito, Y., Mizunuma, K., Miyatake, T.

Macromolecules 15 (1982) 1150) . This method was chosen for its robust nature and integration regions slightly adjusted to increase applicability to a wider range of comonomer contents.

DSC analysis, melting temperature (T _m) and heat of fusion (H _f) , crystallization temperature (T _c) and melt enthalpy (Hm) : measured with a TA Instrument Q200 differential scanning calorimetry (DSC) on 5 to 7 mg samples. DSC is run according to ISO 11357 /part 3 /method C2 in a heat /cool /heat cycle with a scan rate of 10 ℃/min in the temperature range of -30 to +225 ℃. The crystallization temperature (Tc) is determined from the cooling step, while melting temperature (T _m) and melting enthalpy (H _m) are determined from the second heating step. The crystallinity is calculated from the melting enthalpy by assuming an Hm-value of 209 J/g for a fully crystalline polypropylene (see Brandrup, J., Immergut, E. H., Eds. Polymer Handbook, 3rd ed. Wiley, New York, 1989; Chapter 3) .

The xylene solubles (XCS, wt. -%) : Content of xylene cold solubles (XCS) is determined at 25 ℃ according ISO 16152; first edition; 2005-07-01. The part which remains insoluble is the xylene cold insoluble (XCI) fraction.

Ash content is measured according to ISO 3451-1 (1997) standard.

Charpy notched and unnotched impact strength is determined according to ISO 179-1/1eA and ISO 179-1 /1eU at 23 ℃ by using injection moulded test specimens as described in ISO 19069-2 (80 x 10 x 4 mm) .

Tensile properties were determined on injection molded dogbone specimens prepared in accordance with ISO 527-1A (170 x 10 x 4 mm) . Tensile modulus was determined according to ISO 527-1A at 1 mm/min. and 23℃. To determine stress at yield and strain at yield, a speed of 50 mm/min. was used.

Oil resistance was determined by dipping tensile specimens as described above into engine oil “ow-20” available from Mobil Corp. at room temperature for 250 h, 500 h and 1000 h, respectively and then determining tensile strength (TS) and tensile modulus (TM) as described above. The retention rates were determined as follows:

Elongation at break is determined according to ISO 527/2/5A at 50 mm/min and 23℃ on 4 mm thick compression moulded samples prepared according to EN ISO 1873-2.

Flexural Modulus: The flexural modulus was 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.

Average fiber diameter is determined according to ISO 1888: 2006 (E) , Method B, microscope magnification of 1000.

2. Examples

The following inventive example IE was prepared by compounding on a co-rotating twin-screw extruder. In particular, the propylene polymer (PP) , i.e. the first propylene polymer (PP1) and optionally the second propylene polymer (PP2) were premixed with the additives (AD) and the adhesion promoter (AP) . The thus obtained base resin was fed into the main feeder of the extruder and the short fibers (SF) were added through a side feeder. The material was extruded at a temperature of 210 to 230 ℃. The composition and properties are summarized in Table 1.

Table 1: Composition and properties of the inventive and comparative examples

CE is a commercial fiber-reinforced propylene copolymer compounds comprising 53 wt. -%of a propylene homopolymer, 8.0 wt. -%of a propylene/ethylene copolymer rubber, 36 wt. -%of glass fibers and 1.5 wt. -%of an adhesion promoter being a polypropylene functionalized with maleic anhydride.

PP1 is a propylene homopolymer having a melt flow rate MFR ₂ (230 ℃, 2.16 kg) of 8.0 g/10 min and a xylene soluble content XCS of 1.0 wt. -%.

PP2 is a propylene homopolymer having a melt flow rate MFR ₂ (230 ℃) of 60 g/10 min and a xylene soluble content XCS of 2.0wt%wt. -%and comprises 0.8 wt-%of ethylene comonomer units.

SF is the commercial product 249A of Owens Corning (US) having a diameter of 10.0 μm and a strand length of 4.5 mm.

AP is the adhesion promoter SCONA TPPP 8112 GA by

BYK-Chemie GmbH (Germany) being a polypropylene functionalized with maleic anhydride having a maleic anhydride content of 1.4 wt. -%and a MFR (190 ℃) above 80 g/10 min.

AD is a composition comprising 24 parts by weight of a polymeric carrier material being a propylene homopolymer, 24 parts by weight of the antioxidant DSTDP of BASF, 8 parts by weight of the antioxidant Irgafos 168 of BASF, 16 parts by weight of the antioxidant Irganox 1010 of BASF, 8 parts by weight of the antioxidant Richnox XL-1 of Rich Yu Chemical Co. Ltd (Taiwan) , and 20 parts by weight of carbon black.

As can be gathered from Table 1, the retention of the tensile modulus and tensile strength of the inventive fiber-reinforced polypropylene composition is higher than the corresponding values of the comparative composition comprising a polypropylene compounds with rubber.

Claims

Fiber-reinforced polypropylene composition (C) , comprising

i) a propylene polymer (PP) having a xylene soluble content XCS equal or below 5.0 wt. -%,

ii) fibers (F) , and

iii) an adhesion promoter (AP) ,

wherein the fiber-reinforced polypropylene composition fulfils in-equation (I)

wherein w (PP) is the weight fraction [in wt. -%] of the propylene polymer (PP) , based on the overall weight of the fiber-reinforced polypropylene composition (C) , and w (AP) is the weight fraction [in wt. -%] of the adhesion promoter (AP) , based on the overall weight of the fiber-reinforced polypropylene composition (C) .
Fiber-reinforced polypropylene composition (C) according to claim 1, wherein the propylene polymer (PP) is monophasic.
Fiber-reinforced polypropylene composition (C) according to claim 1 or 2, containing no propylene polymers having a xylene soluble content XCS above 5.0 wt. -%.
Fiber-reinforced polypropylene composition (C) according to any one of the preceding claims, wherein the fiber-reinforced polypropylene composition (C) fulfils in-equation (II)

wherein w (F) is the weight fraction [in wt. -%] of the fibers (F) , based on the overall weight of the fiber-reinforced polypropylene composition (C) , and w (AP) is the weight fraction [in wt. -%] of the adhesion promoter (AP) , based on the overall weight of the fiber-reinforced polypropylene composition (C) .
Fiber-reinforced polypropylene composition (C) according to any one of the preceding claims, wherein the propylene polymer (PP) is bimodal.
Fiber-reinforced polypropylene composition (C) according to any one of the preceding claims, wherein the propylene polymer (PP) is a propylene homopolymer (H-PP) .
Fiber-reinforced polypropylene composition (C) according to any one of the preceding claims, wherein the propylene polymer (PP) comprises

i) a first propylene polymer (PP1) having a melt flow rate MFR ₂ (230 ℃, 2.16 kg) determined according to ISO 1133 equal or below 20 g/10 min, and

ii) a second propylene polymer (PP2) having a melt flow rate MFR ₂ (230 ℃, 2.16 kg) determined according to ISO 1133 above 20 g/10 min.
Fiber-reinforced polypropylene composition (C) according to any one of the preceding claims, wherein the fibers (F) are short fibers (SF) .
Fiber-reinforced polypropylene composition (C) according to any one of the preceding claims, wherein the fibers (F) are glass fibers (GF) , preferably short glass fibers (SGF) .
Fiber-reinforced polypropylene composition (C) according to claim 8 or 9, wherein the short fibers (SF) , preferably the short glass fibers (SGF) , have

i) an average length of 1.0 to 10.0 mm, and/or

ii) an average diameter of 8 to 20 μm.
Fiber-reinforced polypropylene composition (C) according to any one of the preceding claims, wherein the adhesion promoter (AP) is a polar modified polypropylene (PM-PP) being a propylene homo-or copolymer grafted with maleic anhydride having a melt flow rate MFR (190 ℃, 2.16 kg) determined according to ISO 1133 of at least 80.0 g/10 min.
Fiber-reinforced polypropylene composition (C) according to any one of the preceding claims, comprising

i) 50.0 to 80.0 wt. -%of the propylene polymer (PP) having a xylene soluble content XCS equal or below 5.0 wt. -%,

ii) 15.0 to 40.0 wt. -%of the fibers (F) ,

iii) 3.0 to 10.0 wt. -%of the adhesion promoter (AP) , and

iv) optionally 0.1 to 4.0 wt. -%of additives (AD) ,

based on the overall weight of the fiber-reinforced polypropylene composition (C) .
Article, comprising the fiber-reinforced polypropylene composition (C) according to any one of claims 1 to 12.
Article according to claim 13, comprising at least 90 wt. -%of the fiber-reinforced polypropylene composition (C) .
Article according to claim 13 or 14, wherein the article is an automotive article, preferably an automotive engine article.
Article according to any one of claims 13 to 15, wherein the article is an air-intake manifold of engine of automotive.