WO2020124475A1

WO2020124475A1 - Polypropylene composition for light weight external parts of automotives

Info

Publication number: WO2020124475A1
Application number: PCT/CN2018/122296
Authority: WO
Inventors: Rock ZHU; Henry ZHOU
Original assignee: Borouge Compounding Shanghai Co., Ltd.
Priority date: 2018-12-20
Filing date: 2018-12-20
Publication date: 2020-06-25
Also published as: CN113166486A; CN113166486B

Abstract

The present invention relates to a polypropylene composition comprising a polypropylene random copolymer, a fiber-reinforced composition comprising said polypropylene composition, a process for forming said fiber-reinforced composition, an automotive article formed from said fiber-reinforced composition and a use of said fiber-reinforced composition for the preparation of an automotive exterior article.

Description

Polypropylene composition for light weight external parts of automotives

Polypropylene is a material used in a wide variety of technical fields, wherein glass fiber reinforced polypropylenes have gained great commercial relevance. Amongst the glass fiber reinforced polypropylenes, long-fiber reinforced thermoplastics represent easily mouldable thermoplastics that have already been used for the production of a great diversity of automotive parts.

However, there is a continued demand in the industry for improved automobile parts having lower weight and reduced thickness without substantially compromising mechanical properties. It has been also found that weight reduction and further reduction of the thickness of articles by optimizing the direct long fiber thermoplastic moulding process is difficult to do.Therefore, alternative approaches to achieve such objectives are highly desired.

Accordingly, the object of the present invention is to provide a polypropylene composition that after fiber-reinforcement it can be used for the production of automotive parts with reduced weight and lower thickness and still has acceptable mechanical performance characteristics.

The finding of the present invention is that a polypropylene random copolymer can at least partially replace propylene homopolymers in compositions to be used for preparing automotive parts with good stiffness and excellent impact strength by direct long fiber thermoplastic moulding whereas the overall weight and thickness of such automotive parts can even be reduced.

Another finding of the present invention is that the partial replacement of propylene homopolymer by polypropylene random copolymer in the fiber reinforced compositions for preparing automotive articles facilitates the direct moulding pressure process to reduce thickness and weight of the articles due to lower crystal content and lower stiffness.

Therefore, the present invention is directed to a polypropylene composition (PP) comprising

(a) a polypropylene random copolymer (PP-RACO) comprising a comonomer selected from ethylene and/or C ₄ to C ₈ α-olefin,

(b) at least one propylene homopolymer (H-PP) , and

(c) an adhesion promoter (AP) being a polar modified polypropylene,

wherein

(i) the polypropylene composition (PP) has a melt flow rate MFR ₂ (230 ℃) measured according to ISO 1133 in the range of 30 to 200 g/10min, preferably in the range of 60 to 130 g/10min,

(ii) the polypropylene random copolymer (PP-RACO) has a melt flow rate MFR ₂ (230 ℃) measured according to ISO 1133 in the range of 20 to 180 g/10min, preferably in the range of 50 to 120 g/10min.

In a preferred embodiment of the polypropylene composition (PP) , the polypropylene random copolymer (PP-RACO) comprises 1.0 to 5.0 wt%of ethylene and/or C ₄ to C ₈ α-olefin.

In another preferred embodiment of the polypropylene composition (PP) , the polypropylene random copolymer (PP-RACO) has a xylene cold soluble content (XCS) measured according ISO 6427 (23 ℃) in the range of 2 to 20 wt. -%, preferably in the range of 3 to 10 wt. -%.

In another preferred embodiment of the polypropylene composition (PP) , the polypropylene random copolymer (PP-RACO) has a melting temperature in the range of 145 to 160℃, more preferably in the range of 148 to 158℃, as determined by differential scanning calorimetry (DSC) .

In another preferred embodiment of the polypropylene composition (PP) , the at least one propylene homopolymer (H-PP) has a melt flow rate MFR ₂ (230 ℃) measured according to ISO 1133 in the range of 5 to 220 g/10min, more preferably in the range of 40 to 150 g/10min.

In another preferred embodiment of the polypropylene composition (PP) , the at least one propylene homopolymer (H-PP) has tensile strength at yield of at least 30 MPa, more preferably of at least 35 MPa, as measured by ISO-527.

In another preferred embodiment of the polypropylene composition (PP) , the adhesion promoter (AP) comprises a maleic anhydride-grafted polypropylene.

In another preferred embodiment of the polypropylene composition (PP) , the polypropylene composition (PP) is monophasic.

In another preferred embodiment of the polypropylene composition (PP) , (a) the polypropylene random copolymer (PP-RACO) , (b) the at least one propylene homopolymer (H-PP) , and (c) the adhesion promoter (AP) being a polar modified polypropylene add up to at least 90 wt. -%, more preferably to at least 95 wt. -%, based on the total weight of the polypropylene composition (PP) .

In another preferred embodiment of the polypropylene composition (PP) , the polypropylene composition (PP) comprises:

(a) 60 to 85 wt. -%of the polypropylene random copolymer (PP-RACO) ,

(b) 13.5 to 35 wt. -%of at least one propylene homopolymer (H-PP) ,

(c) 1.3 to 5.0 wt. -%of a polar modified polypropylene as adhesion promoter (AP) , and

(d) 0.2 to 5.0 wt. -%of additives.

In another aspect, the present invention is directed to a fiber reinforced composition (FRC) comprising a polymer matrix and fibers (F) embedded in the polymer matrix, wherein

(a) the polymer matrix comprises the polypropylene composition (PP) mentioned above, and

(b) the fibers (F) are selected from the group consisting of glass fibers, metal fibers, mineral fibers, ceramic fibers, carbon fibers, polymeric fibers, graphite fibers, and mixtures thereof, and

(c) the polymer matrix is monophasic.

In a preferred embodiment of the fiber reinforced composition (FRC) , the fibers (F) are glass fibers.

In another preferred embodiment of the fiber reinforced composition (FRC) , the composition comprises

(a) 50 to 90 wt. -%of the polypropylene composition (PP) ,

(b) 10 to 50 wt. -%fibers (F) ,

based on the total weight of the fiber reinforced composition.

In another aspect, the present invention is directed to a direct process of long fiber reinforced thermoplastics for preparing exteriors of automotives by molding-pressure, comprising the steps of

(a) providing the polypropylene composition (PP) of the present invention,

(b) adding and mixing fibers (F) to said polypropylene composition (PP) , and

(c) extruding the mixture comprising said polypropylene (PP) and said fibers in an extruder to obtain a sheet of the fiber reinforced composition (FRC) , and

(d) molding the sheet in a molding-pressure machine to form an exterior.

In another aspect, the present invention is directed to an automotive article comprising the fiber reinforced composition (FRC) of the present invention.

In a preferred embodiment of the automotive article, the automotive article is a moulded article, or even more preferably a compression-moulded article.

In another preferred embodiment of the automotive article, the automotive article is selected from external automotive parts, preferably body shields, side trims, step assists, body panels, and spoilers, most preferably body shields.

In another aspect, the present invention is directed to a use of the fiber reinforced composition of the present invention comprising the polypropylene random copolymer (PP-RACO) of the present invention for the preparation of an automotive exterior article.

The present invention will now be described in more detail.

The desired mechanical properties of the fiber reinforced composite and any moulded article obtained from such fiber reinforced composition (FRC) are largely affected by the properties selected for the polypropylene composition (PP) comprising the polypropylene random copolymer (PP-RACO) , the at least one propylene homopolymer (H-PP) , and the adhesion promoter (AP) , which is predominantly added for improving the adhesion and insertion of the fibers.

The polypropylene composition (PP)

Since the polypropylene composition (PP) and the fiber reinforced composition (FRC) comprising the polypropylene composition (PP) are intended to be processed to moulded automotive articles, preferably by compression moulding, the polypropylene composition (PP) , as well as the fiber reinforced composition (FRC) needs to have a defined processability, i.e. a defined mouldability. Therefore, it is critical for the polypropylene composition (PP) , as well as for the fiber reinforced composition (FRC) , that these compositions have a defined melt flow rate.

Accordingly, the polypropylene composition (PP) has an MFR ₂ (230 ℃) of at least 30 g/10min. An upper limit may be given by 200 g/10 min. It is preferred that the polypropylene composition (PP) has a melt flow rate MFR ₂ (230 ℃) in the range of 45 to 150 g/10min, more preferably in the range of 60 to 130 g/10min, still more preferably in the range of 70 to 110 g/10min, and most preferably in the range of 80 to 100 g/10min.

Preferably, the polypropylene composition (PP) has tensile stress of at least 25 MPa, more preferably in the range of 27 to 35 MPa, or even more preferably in the range of 28 to 33 MPa, as measured by ISO 527.

Preferably, the polypropylene composition (PP) has flexural modulus of at least 950 MPa, more preferably in the range of 1000 to 1450 MPa, or even more preferably in the range of 1150 to 1300 MPa, as measured by ISO-178.

Preferably, the polypropylene composition (PP) is characterized by a Charpy notched impact strength at 23℃ in the range of 2.5 to 6.0 kJ/m ², more preferably 3.0 to 5.0 kJ/m ², and most preferably 3.2 to 4.0 kJ/m ², as determined according to ISO 179 1eA.

The polypropylene composition (PP) of the present invention comprises several essential components, including the polypropylene random copolymer (PP-RACO) , at least one propylene homopolymer (H-PP) and an adhesion promoter (AP) . Accordingly, the polypropylene composition (PP) comprises

(b) at least one propylene homopolymer (H-PP) , and

(c) an adhesion promoter (AP) being a polar modified polypropylene, wherein

(i) the polypropylene composition (PP) has a melt flow rate MFR ₂ (230 ℃) measured according to ISO 1133 in the range of 30 to 200 g/10min, preferably in the range of 60 to 130 g/10min, and

The polypropylene composition (PP) of the present invention can comprise further components, in addition to the essential components as defined above. However, it is preferred that (a) the polypropylene random copolymer (PP-RACO) , (b) the at least one propylene homopolymer (H-PP) , and (c) the adhesion promoter (AP) being a polar modified polypropylene add up to at least 90 wt. -%, more preferably to at least 95 wt. -%, based on the total weight of the polypropylene composition (PP) .

The polypropylene composition (PP) of the present invention has the following preferred quantitative composition of components:

One preferred composition of the polypropylene composition (PP) comprises:

(a) 60 to 85 wt. -%of the polypropylene random copolymer (PP-RACO) ,

(b) 13.5 to 35 wt. -%of at least one propylene homopolymer (H-PP) ,

(d) 0.2 to 5.0 wt. -%of additives.

Another preferred composition of the polypropylene composition (PP) consists of:

(a) 60 to 85 wt. -%of the polypropylene random copolymer (PP-RACO) ,

(b) 13.5 to 35 wt. -%of at least one propylene homopolymer (H-PP) ,

(d) 0.2 to 5.0 wt. -%of additives.

Another preferred composition of the polypropylene composition (PP) comprises:

(a) 60 to 85 wt. -%of the polypropylene random copolymer (PP-RACO) ,

(b) 13.5 to 35 wt. -%of at least one propylene homopolymer (H-PP) ,

(d) 0.1 to 1.5 wt. -%of antioxidants, and

(e) 0.1 to 1.0 wt. -%of a coloring agent.

(a) 60 to 85 wt. -%of the polypropylene random copolymer (PP-RACO) ,

(b) 13.5 to 35 wt. -%of at least one propylene homopolymer (H-PP) ,

(d) 0.1 to 1.5 wt. -%of antioxidants, and

(e) 0.1 to 1.0 wt. -%of a coloring agent.

Another preferred composition of the polypropylene composition (PP) comprises:

(a) 60 to 85 wt. -%of the polypropylene random copolymer (PP-RACO) ,

(b) 13.5 to 35 wt. -%of at least one propylene homopolymer (H-PP) ,

(d) 0.1 to 1.5 wt. -%of antioxidants, and

(e) 0.1 to 1.0 wt. -%of carbon black.

(a) 60 to 85 wt. -%of the polypropylene random copolymer (PP-RACO) ,

(b) 13.5 to 35 wt. -%of at least one propylene homopolymer (H-PP) ,

(d) 0.1 to 1.5 wt. -%of antioxidants, and

(e) 0.1 to 1.0 wt. -%of carbon black.

Preparing and further processing the polypropylene composition (PP) includes mixing the individual components of the instant polypropylene composition (PP) , for instance by use of a conventional compounding or blending apparatus, e.g. a Banbury mixer, a 2-roll rubber mill, Buss-co-kneader or a twin screw extruder. A typical extruding temperature is in the range of 160 to 210℃, or more preferably in the range of 180 to 200℃. The polymer material recovered from the extruder is usually in the form of pellets. These pellets are then preferably further processed to obtain the fiber reinforced composition (FRC) , and subsequently by compression molding to generate the automotive articles, i.e. the (exterior) automotive articles.

The polypropylene random copolymer (PP-RACO)

The main component of the polypropylene composition (PP) of the present invention is the polypropylene random copolymer (PP-RACO) .

The polypropylene random copolymer (PP-RACO) of the present invention has a melt flow rate MFR ₂ (230 ℃) measured according to ISO 1133 in the range of 20 to 180 g/10min, preferably in the range of 35 to 140 g/10min, more preferably in the range of 50 to 120 g/10min, and most preferably in the range of 60 to 90 g/10min.

In a preferred embodiment, the polypropylene random copolymer (PP-RACO) is monophasic. The term “monophasic” indicates that the polypropylene random copolymer (PP-RACO) forms one continuous phase but not more than one continuous phase.

As comonomer (s) , the polypropylene random copolymer (PP-RACO) comprises, preferably consists of, ethylene and/or at least one C ₄ to C ₈ α-olefin, preferably at least one α-olefin selected from the group consisting of ethylene, 1-butene, 1-pentene, 1-hexene and 1-octene, more preferably ethylene and/or 1-butene, yet most preferably ethylene.

It is preferred that the polypropylene random copolymer (PP-RACO) of the present invention comprises a content of less than 6 wt%of ethylene and/or C ₄ to C ₈ α-olefin. More preferably, the content of ethylene and/or C ₄ to C ₈ α-olefin is in the range of 1.0 to 5.0 wt%, or even more preferably in the range of 2.0 to 4.0 wt%, like especially in the range of 3.0 to 3.8 wt%.

It is further preferred that the polypropylene random copolymer (PP-RACO) has a xylene cold soluble content (XCS) measured according ISO 6427 (23 ℃) in the range of 2 to 20 wt.-%, preferably in the range of 3 to 10 wt. -%, more preferably in the range of 4 to 8 wt%, and most preferably in the range of 4.5 to 6.0 wt%.

It is also preferred that the polypropylene random copolymer (PP-RACO) has a melting temperature in the range of 145 to 160℃, more preferably in the range of 148 to 158℃, even more preferably in the range of 150 to 156℃, and most preferably in the range of 152 to 155℃, as determined by differential scanning calorimetry (DSC) .

It is also preferred that the polypropylene random copolymer (PP-RACO) has a crystallisation temperature in the range of 105 to 135℃, more preferably in the range of 115 to 140℃, even more preferably in the range of 120 to 135℃, and most preferably in the range of 123 to 130℃, as determined by differential scanning calorimetry (DSC) .

Preferably, the polypropylene random copolymer (PP-RACO) has tensile stress at yield of at least 25 MPa, more preferably in the range of 26 to 35 MPa, or even more preferably in the range of 27 to 30 MPa, as measured by ISO 527.

Preferably, the polypropylene random copolymer (PP-RACO) has flexural modulus of at least 850 MPa, more preferably in the range of 950 to 1500 MPa, or even more preferably in the range of 1050 to 1300 MPa, as measured by ISO 178.

Preferably, the polypropylene composition (PP) is characterized by a Charpy notched impact strength at 23℃ in the range of 2.5 to 6.0 kJ/m ², more preferably 3.5 to 5.0 kJ/m ², and most preferably 4.0 to 4.8 kJ/m ², as determined according to ISO 179 1eA.

The propylene homopolymer (H-PP)

As another essential component, the polypropylene composition (PP) comprises at least one propylene homopolymer (H-PP) . It is preferred that the at least one propylene homopolymer (H-PP) is only present in the polypropylene composition (PP) as one single propylene homopolymer (H-PP) . In contrast thereto, it is also possible that more than one propylene homopolymer (H-PP) is present in the polypropylene composition (PP) , like for instance a first propylene homopolymer (H-PP-1) in combination with a second propylene homopolymer (H-PP-2) , or even another third propylene homopolymer (H-PP-3) .

Most importantly, the at least one propylene homopolymer (H-PP) is included in the present invention to preserve sufficient stiffness of the polypropylene composition (PP) of the present invention as well as the moulded articles prepared therefrom. In addition, when mixing the at least one propylene homopolymer (H-PP) with the polypropylene random copolymer (PP-RACO) to obtain the polypropylene composition (PP) , the at least one propylene homopolymer (H-PP) is also used to adjust the processability of the polypropylene composition (PP) by adjusting the melt flow rate of the latter to allow proper mouldability.

It is preferred that the at least one propylene homopolymer (H-PP) has a melt flow rate MFR ₂ (230 ℃) measured according to ISO 1133 in the range of 5 to 220 g/10min, more preferably in the range of 40 to 150 g/10min, even more preferably in the range of 50 to 80 g/10min. If only one propylene homopolymer (H-PP) is included into the polypropylene composition (PP) of the present invention, the melt flow rate of said propylene homopolymer (H-PP) component must be as defined above.

However, if there is more than one propylene homopolymer (H-PP) in the polypropylene composition (PP) , i.e. if there is a blend of two, three or more than three propylene homopolymers (H-PP-1, H-PP-2, H-PP-3, etc. ) in the polypropylene composition (PP) of the present invention, the melt flow rate MFR ₂ (230 ℃) measured according to ISO 1133 of only one propylene homopolymer (H-PP-1) must be in the range of 5 to 220 g/10min, more preferably in the range of 40 to 150 g/10min, even more preferably in the range of 50 to 80 g/10min, while the melt flow rate MFR ₂ (230 ℃) measured according to ISO 1133 of the other propylene homopolymers (H-PP-2, H-PP-3, etc. ) present in the polypropylene composition (PP) of the present invention can be in a range different to the range as defined for the first propylene homopolymer (H-PP-1) .

For instance, if there is more than one propylene homopolymer (H-PP) in the polypropylene composition (PP) , any additional propylene homopolymer (H-PP-2, H-PP-3, etc) can have a melt flow rate MFR ₂ (230 ℃) measured according to ISO 1133 in the very high range of 1000 to 2000 g/10min, more preferably in the range of 1500 to 1900 g/10min, or even more preferably in the range of 1700 to 1850 g/10min. Such additional propylene homopolymer (H-PP-2, H-PP-3, etc. ) is ideal for adjusting the melt flow rate of the polypropylene composition (PP) to the upside based on the addition of only relatively limited amounts of additional component. One such preferred propylene homopolymer (H-PP-2) having exceptionally high melt flow rate is commercially available under the trademark Metocene MF650Y of LyondellBasell.

Preferably, the at least one propylene homopolymer (H-PP) has tensile strength at yield of at least 30 MPa, more preferably of at least 35 MPa, as measured by ISO 527. If more than one propylene homopolymer (H-PP) is present, only one propylene homopolymer (H-PP-1) needs to have tensile strength at yield of at least 30 MPa, more preferably of at least 35 MPa, as measured by ISO 527.

The at least one propylene homopolymer (H-PP) preferably has flexural modulus of at least 1500 MPa, more preferably in the range of 1600 to 2000 MPa, or even more preferably in the range of 1600 to 1750 MPa, as measured by ISO 178. If more than one propylene homopolymer (H-PP) is present, only one propylene homopolymer (H-PP-1) needs to have flexural modulus as defined above.

The at least one propylene homopolymer (H-PP) preferably has Charpy notched impact strength at 23℃ in the range of 1.5 to 5.0 kJ/m ², more preferably 2.0 to 4.0 kJ/m ², and most preferably 2.5 to 3.0 kJ/m ², as determined according to ISO 179 1eA . If more than one propylene homopolymer (H-PP) is present, only one propylene homopolymer (H-PP-1) needs to have Charpy notched impact strength at 23℃ as defined above.

The adhesion promoter (AP)

The polypropylene composition (PP) also comprises an adhesion promoter (AP) .

The adhesion promoter (AP) preferably comprises a modified (functionalized) polymer and optionally a low molecular weight compound having reactive polar groups. Modified α-olefin polymers, in particular propylene homopolymers and copolymers, like copolymers of ethylene and propylene with each other or with other α-olefins, are most preferred, as they are highly compatible with the polymers of the fiber reinforced composition. Modified polyethylene can be used as well.

In terms of structure, the modified polymers are preferably selected from graft or block copolymers.

In this context, preference is given to modified polymers containing groups deriving 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 the 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, maleic acid, fumaric acid, itaconic acid and mixtures thereof.

Particular preference is given to the use of a propylene polymer grafted with maleic anhydride as the modified polymer, i.e. as the adhesion promoter (AP) .

The modified polymer, i.e. the adhesion promoter (AP) , can be produced in a simple manner by reactive extrusion of the polymer, for example with maleic anhydride in the presence of free radical generators (like organic peroxides) , as disclosed for instance in EP 0 572 028.

Preferred amounts of groups deriving from polar compounds in the modified polymer, i.e. the adhesion promoter (AP) , are from 0.5 to 5.0 wt. -%, more preferably from 0.5 to 4.0 wt. -%, still more preferably from 0.5 to 3.0 wt. -%.

Preferred values of the melt flow rate MFR ₂ (230 ℃) for the modified polymer, i.e. for the adhesion promoter (AP) , are from 1.0 to 500 g/10 min., more preferably 10 to 200g/10min.

The additives

The instant composition may additionally contain typical other additives useful for instance in the automobile sector, like carbon black, other pigments, antioxidants, UV stabilizers, nucleating agents, antistatic agents and slip agents, in amounts usual in the art.

Preferred additives are antioxidants. Another important additive having high relevance for the polypropylene composition of the present invention, which is used for obtaining moulded automotive articles are coloring agents including pigments, especially carbon black.

Optionally, a masterbatch can also be included into the polypropylene composition (PP) of the present invention. The term masterbatch means polymer-bound additives, for instance color and additive concentrates physically or chemically bound onto or into polymers. It is appreciated that such masterbatches contain as less polymer as possible.

The preparation process for the polypropylene random copolymer (PP-RACO)

The polymerization system for the preparation of the polypropylene random copolymer (PP-RACO) can comprise one or more conventional stirred slurry reactors and/or one or more gas phase reactors. Preferably, the reactors used are selected from the group of loop and gas phase reactors and, in particular, the process employs at least one loop reactor. It is also possible to use several reactors of each type, e.g. one loop and two or three gas phase reactors, or two loops and one or two gas phase reactors, in series.

Preferably, the process comprises also a prepolymerization with the chosen catalyst system, as described in detail below, comprising the Ziegler-Natta procatalyst, the external donor and the 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 prepolymerisation reaction is typically conducted at a temperature of 0 to 50 ℃, preferably from 10 to 45 ℃, and more preferably from 15 to 40 ℃.

The pressure in the prepolymerisation 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 prepolymerisation 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 prepolymerisation stage and the remaining part into subsequent polymerisation stages. Also in such cases, it is necessary to introduce so much cocatalyst into the prepolymerisation stage that a sufficient polymerisation reaction is obtained therein.

It is possible to add other components also to the prepolymerisation stage. Thus, hydrogen may be added into the prepolymerisation 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.

A slurry reactor designates any reactor, such as a continuous or simple batch stirred tank reactor or loop reactor, operating in bulk or slurry and in which the polymer forms in particulate form. "Bulk" means a polymerization in reaction medium that comprises at least 60 wt. -%monomer. According to a preferred embodiment, the slurry reactor comprises a bulk loop reactor.

"Gas phase reactor" means any mechanically mixed or fluid bed reactor. Preferably, the gas phase reactor comprises a mechanically agitated fluid bed reactor with gas velocities of at least 0.2 m/sec.

A preferred multistage process is a slurry-gas phase process, such as developed by Borealis and known as the

technology. In this respect, reference is made to EP 0 887 379 A1, WO 92/12182, WO 2004/000899, WO 2004/111095, WO 99/24478, WO 99/24479 and WO 00/68315. They are incorporated herein by reference.

A further suitable slurry-gas phase process is the

process of Basell.

Preferably, the polypropylene random copolymer (PP-RACO) according to this invention is produced by using a special Ziegler-Natta procatalyst in combination with a special external donor, as described below in detail, preferably in the

or in the

-PP process.

One preferred multistage process may therefore comprise the steps of:

- producing a polypropylene random copolymer (PP-RACO) in the presence of the chosen catalyst system, as for instance described in detail below, comprising the special Ziegler-Natta procatalyst (i) , an external donor (iii) and the cocatalyst (ii) in a first slurry reactor and optionally in a second slurry reactor, both slurry reactors using the same polymerization conditions,

- optionally transferring the slurry reactor product into at least one first gas phase reactor, like one gas phase reactor or a first and a second gas phase reactor connected in series,

- recovering the polymer product for further processing.

With respect to the above-mentioned preferred slurry or slurry-gas phase process, the following general information can be provided with respect to the process conditions.

Temperature is preferably from 40 to 110 ℃, preferably between 50 and 100 ℃, in particular between 60 and 90 ℃, with a pressure in the range of from 20 to 80 bar, preferably 30 to 60 bar, with the option of adding hydrogen in order to control the molecular weight in a manner known per se.

The reaction product of the slurry polymerization, which preferably is carried out in a loop reactor, is optionally transferred to the subsequent gas phase reactor (s) , wherein the temperature preferably is within the range of from 50 to 130 ℃, more preferably 60 to 100 ℃, at a pressure in the range of from 5 to 50 bar, preferably 8 to 35 bar, again with the option of adding hydrogen in order to control the molecular weight in a manner known per se.

The average residence time can vary in the reactor zones identified above. In one embodiment, the average residence time in the slurry reactor, for example a loop reactor, is in the range of from 0.5 to 5 hours, for example 0.5 to 2 hours, while the average residence time in the gas phase reactor generally will be from 1 to 8 hours.

If desired, the polymerization may be effected in a known manner under supercritical conditions in the slurry, preferably loop reactor, and/or as a condensed mode in the gas phase reactor.

According to the invention, the polypropylene random copolymer (PP-RACO) is obtained by a 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 is prepared by

a) reacting a spray crystallized or emulsion solidified adduct of MgCl ₂ and a C ₁-C ₂ alcohol with TiCl ₄

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

wherein R ^1’and R ^2’are independently at least a C ₅ alkyl

under conditions where a transesterification between said C ₁ to C ₂ 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 TiCl ₄.

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 MgCl ₂ and a C ₁-C ₂ alcohol of the formula MgCl ₂*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 MgCl ₂*nROH, wherein R is methyl or ethyl, preferably ethyl and n is 1 to 6, is contacting with TiCl ₄ to form a titanized carrier, followed by the steps of

· adding to said titanized carrier

(i) a dialkylphthalate of formula (I) with R ^1’and R ^2’being independently at least a C ₅-alkyl, like at least a C ₈-alkyl,

or preferably

(ii) a dialkylphthalate of formula (I) with R ^1’and R ^2’being the same and being at least a C ₅-alkyl, like at least a C ₈-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 ℃, preferably between 100 to 150 ℃, more preferably between 130 to 150 ℃, 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 R ¹ and R ² 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 MgCl ₂*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 titanized 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 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 10 wt.-%.

More preferably the procatalyst used according to the 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.

In one preferred embodiment, the procatalyst is obtained by the emulsion technology developed by Borealis. Reference in this regard is made to WO 2009/040201. Thus, preferably the procatalyst is obtained by a process comprising the steps of:

a) preparing a solution of a complex of a Group 2 metal and an electron donor by reacting a compound of said metal with said electron donor or a precursor thereof in an organic liquid reaction medium;

b) adding said solution of said complex to at least one compound of a transition metal of any of groups 4 -6 to produce an emulsion the dispersed phase of which contains more than 50 mol%of the Group 2 metal in said complex;

c) agitating the emulsion, optionally in the presence of an emulsion stabilizer, in order to maintain the droplets of said dispersed phase within an average particle size range of suitably 5 to 200 μm, preferably 10 to 100 μm, even more preferably 20 to 50 μm;

d) solidifying said droplets of the dispersed phase; and

e) recovering the obtained solidified particles of the olefin polymerisation catalyst.

The Group 2 metal used in the preparation of the procatalyst according to the emulsion technology is preferably magnesium and the liquid organic medium for reacting the group 2 metal compound preferably comprises a C ₆-C ₁₀ aromatic hydrocarbon, preferably toluene. An electron donor compound to be reacted with the Group 2 metal compound preferably is a mono-or diester of an aromatic carboxylic acid or diacid, the latter being able to form a chelate-like structured complex. Said aromatic carboxylic acid ester or diester can be formed in situ by reaction of an aromatic carboxylic acid chloride or diacid dichloride with a C ₂-C ₁₆ alkanol and/or diol, and is preferably dioctyl phthalate or bis- (2-ethylhexyl) phthalate. The reaction for the preparation of the Group 2 metal complex is generally carried out at a temperature of 20 to 80 ℃, and in case that the Group 2 metal is magnesium, the preparation of the magnesium complex may advantageously be carried out at a temperature of 50 to 70 ℃. The compound of a group 4 -6 metal is preferably a compound of a Group 4 metal. The Group 4 metal is preferably titanium, and its compound to be reacted with the complex of a Group 2 metal is preferably a halide. In a still further embodiment of the invention, the compound of a group 4 -6 metal can also be selected from Group 5 and Group 6 metals, such as Cu, Fe, Co, Ni and/or Pd compounds. In a preferred embodiment of the production process of the catalyst a turbulence minimizing agent (TMA) is added to the reaction mixture before solidifying said particles of the dispersed phase, the TMA being inert and soluble in the reaction mixture under the reaction conditions. The turbulence minimizing agent (TMA) or mixtures thereof are preferably polymers having linear aliphatic carbon backbone chains, which might be branched with only short side chains in order to serve for uniform flow conditions when stirring. Said TMA is in particular preferably selected from α-olefin polymers having a high molecular weight Mw (as measured by gel permeation chromatography) of about 1 to 40 x 10 ⁶, or mixtures thereof. Especially preferred are polymers of α-olefin monomers with 6 to 20 carbon atoms, and more preferably polyoctene, polynonene, polydecene, polyundecene or polydodecene or mixtures thereof, having the molecular weight and general backbone structure as defined before, and most preferably TMA is polydecene. Usually, said turbulence minimizing agent can be added in any process step before particle formation starts, i.e. at the latest before solidification of the emulsion, and is added to the emulsion in an amount of 1 to 1000 ppm, preferably 5 to 100 ppm and more preferable 5 to 50 ppm, based on the total weight of the reaction mixture. A preferred embodiment of the present invention the procatalyst is obtained by: preparing a solution of a magnesium complex by reacting an alkoxy magnesium compound and an electron donor or precursor thereof in a C ₆-C ₁₀ aromatic liquid reaction medium comprising C ₆-C ₁₀ aromatic hydrocarbon or a mixture of C ₆-C ₁₀ aromatic hydrocarbon and C ₅-C ₉ aliphatic hydrocarbon; reacting said magnesium complex with a compound of at least one fourvalent group 4 metal at a temperature greater than 10 ℃ and less than 60 ℃, to produce an emulsion of a denser, TiCl ₄/toluene-insoluble, oil dispersed phase having group 4 metal/Mg mol ratio 0.1 to 10 in an oil disperse phase having group 4 metal/Mg mol ratio 10 to 100; maintaining the droplets of said dispersed phase within the size range 5 to 200 μm by agitation in the presence of an emulsion stabiliser while heating the emulsion to solidify said droplets and adding turbulence minimising agent into the reaction mixture before solidifying said droplets of the dispersed phase, said turbulence minimising agent being inert and soluble in the reaction mixture under the reaction conditions; and solidifying said particles of the dispersed phase by heating and recovering the obtained catalyst particles. The said disperse and dispersed phases are thus distinguishable from one another by the fact that the denser oil, if contacted with a solution of titanium tetrachloride in toluene, will not dissolve in it. A suitable TiCl ₄/toluene solution for establishing this criterion would be one having a TiCl ₄/toluene mol ratio of 0.1 to 0.3. The disperse and dispersed phase are also distinguishable by the fact that the great preponderance of the Mg provided (as complex) for the reaction with the Group 4 metal compound is present in the dispersed phase, as revealed by comparison of the respective Group 4 metal/Mg mol ratios. In effect, therefore, virtually the entirety of the reaction product of the Mg complex with the Group 4 metal, which is the precursor of the final catalyst, becomes the dispersed phase, and proceeds through the further processing steps to the final dry particulate form. The disperse phase, still containing a useful quantity of Group 4 metal, can be reprocessed for recovery of that metal. The production of a two-phase, rather than single-phase reaction product is encouraged by carrying out the Mg complex/Group 4 metal compound reaction at low temperature, specifically above 10 ℃ but below 60 ℃, preferably between 20 ℃ and 50 ℃. Since the two phases will naturally tend to separate into a lower, denser phase and supernatant lighter phase, it is necessary to maintain the reaction product as an emulsion by agitation, preferably in the presence of an emulsion stabiliser. The resulting particles from the dispersed phase of the emulsion are of a size, shape (spherical) and uniformity, which render the final catalyst extremely effective in olefin polymerisation. This morphology is preserved during the heating to solidify the particles, and of course throughout the final washing and drying steps. It is, by contrast, difficult to the point of impossibility to achieve such morphology through precipitation, because of the fundamental uncontrollability of nucleation and growth, and the large number of variables, which affect these events. The electron donor is preferably an aromatic carboxylic acid ester, particularly favoured esters being dioctyl phthalate and bis- (2-ethylhexyl) phthalate. The donor may conveniently be formed in situ by reaction of an aromatic carboxylic acid chloride precursor with a C ₂-C ₁₆ alkanol and/or diol. The liquid reaction medium preferably comprises toluene. Furthermore, emulsifying agents/emulsion stabilisers can be used additionally in a manner known in the art for facilitating the formation and/or stability of the emulsion. For the said purposes e.g. surfactants, e.g. a class based on acrylic or methacrylic polymers can be used. Preferably, said emulsion stabilizers are acrylic or methacrylic polymers, in particular those with medium sized ester side chains having more than 10, preferably more than 12 carbon atoms and preferably less than 30, and preferably 12 to 20 carbon atoms in the ester side chain. Particular preferred are unbranched C ₁₂-C ₂₀ acrylates such as poly (hexadecyl) -methacrylate and poly (octadecyl) -methacrylate. It has been found that the best results are obtained when the Group 4 metal/Mg mol ratio of the denser oil is 1 to 5, preferably 2 to 4, and that of the disperse phase oil is 55 to 65. Generally the ratio of the mol ratio Group 4 metal/Mg in the disperse phase oil to that in the denser oil is at least 10. Solidification of the dispersed phase droplets by heating is suitably carried out at a temperature of 70 -150 ℃, usually at 90 -110 ℃.

The finally obtained procatalyst is desirably in the form of particles having an average size range of 5 to 200 μm, preferably 10 to 100 μm, more preferably 20 to 50 μm. The reagents can be added to the aromatic reaction medium in any order. However, it is preferred that in a first step the alkoxy magnesium compound is reacted with a carboxylic acid halide precursor of the electron donor to form an intermediate; and in a second step the obtained product is further reacted with the Group 4 metal. The magnesium compound preferably contains from 1 to 20 carbon atoms per alkoxy group, and the carboxylic acid should contain at least 8 carbon atoms. Reaction of the magnesium compound, carboxylic acid halide and alcohol proceeds satisfactorily at temperatures in the range 20 to 80 ℃, preferably 50 to 70 ℃. The product of that reaction, the "Mg complex" , is reacted with the Group 4 metal compound at a lower temperature, to bring about the formation of a two-phase, oil-in-oil, product. The reaction medium used as solvent can be aromatic or a mixture of aromatic and aliphatic hydrocarbons, the latter one containing preferably 5 -9 carbon atoms, more preferably 5 -7 carbon atoms, or mixtures thereof. Preferably, the liquid reaction medium used as solvent in the reaction is aromatic and is more preferably selected from hydrocarbons such as substituted and unsubstituted benzenes, preferably from alkylated benzenes, even more preferably from toluene and the xylenes, and is most preferably toluene. The molar ratio of said aromatic medium to magnesium is preferably less than 10, for instance from 4 to 10, preferably from 5 to 9. The alkoxy magnesium compound group is preferably selected from the group consisting of magnesium dialkoxides, complexes of a magnesium dihalide and an alcohol, and complexes of a magnesium dihalide and a magnesium dialkoxide. It may be a reaction product of an alcohol and a magnesium compound selected from the group consisting of dialkyl magnesium, alkyl magnesium alkoxides, alkyl magnesium halides and magnesium dihalides.

It can further be selected from the group consisting of dialkyloxy magnesiums, diaryloxy magnesiums, alkyloxy magnesium halides, aryloxy magnesium halides, alkyl magnesium alkoxides, aryl magnesium alkoxides and alkyl magnesium aryloxides. The magnesium dialkoxide may be the reaction product of a magnesium dihalide such as magnesium dichloride or a dialkyl magnesium of the formula R'xR"yMg, wherein x + y = 2 and x and y are in the range of 0.3 -1.7 and each one of R'and R"is a similar or different C ₁-C ₂₀ alkyl, preferably a similar or different C ₄-C ₁₀ alkyl. Typical magnesium alkyls are ethylbutyl magnesium, dibutyl magnesium, dipropyl magnesium, propylbutyl magnesium, dipentyl magnesium, butylpentylmagnesium, butyloctyl magnesium and dioctyl magnesium. Preferably, R'is a butyl group and R"is an octyl group, i.e. the dialkyl magnesium compound is butyl octyl magnesium, most preferably the dialkyl magnesium compound is Mg[(Bu) _1.5 (Oct) _0.5] .

Dialkyl magnesium, alkyl magnesium alkoxide or magnesium dihalide can react with a polyhydric alcohol R (OH) _m, with m being in the range of 2-4, or a monohydric alcohol ROH or mixtures thereof. Typical C ₂ to C ₆ polyhydric alcohols may be straight-chain or branched and include ethylene glycol, propylene glycol, trimethylene glycol, 1, 2-butylene glycol, 1, 3-butylene glycol, 1, 4-butylene glycol, 2, 3-butylene glycol, 1, 5-pentanediol, 1, 6-hexanediol, 1, 8-octanediol, pinacol, diethylene glycol, triethylene glycol, and triols such as glycerol, methylol propane and pentareythritol. The aromatic reaction medium may also contain a monohydric alcohol, which may be straight or branched chain. Typical C ₁-C ₅ monohydric alcohols are methanol, ethanol, n-propanol, iso-propanol, n-butanol, iso-butanol, sec. butanol, tert. butanol, n-amyl alcohol, iso-amyl alcohol, sec. amyl alcohol, tert. amyl alcohol, diethyl carbinol, akt. amyl alcohol, sec. isoamyl alcohol, tert. butyl carbinol. Typical C ₆-C ₁₀ monohydric alcohols are hexanol, 2-ethyl-1-butanol, 4-methyl-2-pentanol, 1-heptanol, 2-heptanol, 4-heptanol, 2, 4-dimethyl-3-pentanol, 1-octanol, 2-octanol, 2-ethyl-1-hexanol, 1-nonanol, 5-nonanol, diisobutyl carbinol, 1-decanol and 2, 7-dimethyl-2-octanol. Typical >C ₁₀ monohydric alcohols are n-1-undecanol, n-1-dodecanol, n-1-tridecanol, n-1-tetradecanol, n-1-pentadecanol, 1-hexadecanol, n-1-heptadecanol and n-1-octadecanol. The monohydric alcohols may be unsaturated, as long as they do not act as catalyst poisons. Preferable monohydric alcohols are those of formula ROH in which R is a C ₂-C ₁₆ alkyl group, most preferably a C ₄-C ₁₂ alkyl group, particularly 2-ethyl-1-hexanol or 1-octanol.

Preferably, essentially all of the aromatic carboxylic acid ester is a reaction product of a carboxylic acid halide, preferably a dicarboxylic acid dihalide, more preferably an unsaturated, dicarboxylic acid dihalide, most preferably phthalic acid dichloride, with the monohydric alcohol.

The compound of a fourvalent Group 4 metal containing a halogen is preferably a titanium tetrahalide. Equivalent to titanium tetrahalide is the combination of an alkoxy titanium halide and a halogenation agent, which are able to form a titanium tetrahalide in situ. The most preferred halide is the chloride.

As is known, the addition of at least one halogenated hydrocarbon during the procatalyst preparation process can lead to further improved catalytic activity. Reactive halogenated hydrocarbons preferably have the formula R'"X'" _n wherein R'"is a C ₁-C ₂₀ hydrocarbyl group, particularly a C ₁-C ₁₀ aliphatic hydrocarbyl group, X'"is a halogen, preferably chlorine, and n is an integer from 1 to 4.

Such chlorinated hydrocarbons include monochloromethane, dichloromethane, trichloromethane (chloroform) , tetrachloromethane, monochloroethane, (1, 1) -dichloroethane, (1, 2) -dichloroethane, (1, 1, 1) -trichloroethane, (1, 1, 2) -trichloroethane, (1, 1, 1, 2) -tetrachloroethane, (1, 1, 2, 2) -tetrachloroethane, pentachloroethane, hexachloroethane, 1-chloropropane, 2-chloropropane, (1, 2) -dichloropropane, (1, 3) -dichloropropane, (1 2, 3) trichloropropane, 1-chlorobutane, 2-chlorobutane, isobutyl chloride, tert. butyl chloride, (1, 4) -dichlorobutane, 1-chloropentane and (1, 5) -dichloropentane. The chlorinated hydrocarbons may also be unsaturated, provided that the unsaturation does not act as catalyst poison in the final catalyst.

In the above formula, R'"is preferably a C ₁-C ₁₀ alkyl group, X'"is preferably chlorine and n is preferably 1 or 2. Preferred compounds include butyl chloride (BuCl) , dichloroalkanes such as (1, 4) -dichlorobutane, and tertiary butyl chloride.

The catalyst preparation as described herein can be carried out batchwise, semi-continuously or continuously. In such a semi-continuous or continuous process, the solution of the complex of the group 2 metal and said electron donor, which is prepared by reacting the compound of said metal with said electron donor in an organic liquid reaction medium, is mixed with at least one compound of a transition metal, which might be solved in the same or different organic liquid reaction medium. The so obtained solution is then agitated, possibly in the presence of an emulsion stabiliser, and then the agitated emulsion is fed into a temperature gradient reactor, in which the emulsion is subjected to a temperature gradient, thus leading to solidifying the droplets of a dispersed phase of the emulsion. The TMA is preferably contained in the solution of the complex or added to the solution before feeding the agitated solution to the temperature gradient reactor.

When feeding said agitated emulsion to the temperature gradient reactor, an inert solvent, in which the droplets are not soluble, can additionally be fed into that gradient reactor in order to improve the droplet formation and thus leading to a uniform grain size of the particles of the catalyst, which are formed in the temperature gradient reactor when passing through said line. Such additional solvent might be the same as the organic liquid reaction medium, which is used for preparing the solution of the complex of the group 2 metal as explained above in more detail.

The solidified particles of the catalyst can subsequently be recovered by an in-stream filtering unit and are preferably subjected to washing in order to remove unreacted starting components.

The recovered particulate product is washed at least once, preferably at least twice, most preferably at least three times with a hydrocarbon, which preferably is selected from aromatic and aliphatic hydrocarbons, preferably with toluene, particularly with hot (e.g. 90 ℃) toluene, which may include a small amount, preferably about 0.01 -10 vol%of TiCl ₄ or an alkyl aluminium chloride, such as diethyl aluminium chloride (DEAC) , in it. A further washing step is advantageously performed with heptane, most preferably with hot (e.g. 90 ℃) heptane, and a still further washing step with pentane. A washing step typically includes several substeps. A favoured washing sequence is, for example, one washing step with toluene at 90 ℃, two washing steps with heptane at 90 ℃ and one or two washing steps with pentane at room temperature.

Finally, the washed catalyst is dried, e.g. by evaporation or flushing with nitrogen.

The catalyst system, which is used according to the present invention, also comprises a cocatalyst, preferably an aluminium alkyl compound, as defined in detail below. In case the procatalyst is produced by emulsion technology the cocatalyst is added, in pure form or in the form of a solution, from shortly before the beginning of the emulsion formation until adding it to the washing liquid, e.g. toluene, in such an amount that the final Al content of the particles is from 0.05 to 1 wt%, preferably 0.1 to 0.8 wt%and most preferably 0.2 to 0.7 wt%by weight of the final catalyst particles. The most preferred Al content may vary depending upon the type of the Al compound and on the adding step. For example, in some cases the most preferred amount may be 0.1 to 0.4 wt%.

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, an external donor and a cocatalyst, which vinyl compound has the formula:

CH ₂=CH-CHR ³R ⁴

wherein R ³ and R ⁴ 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 polypropylene random copolymer (PP-RACO) 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.

As mentioned above, for the production of the polypropylene random copolymer (PP-RACO) according to the 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 (III)

Si (OCH ₃) ₂R ₂ ⁵ (III)

wherein R ⁵ 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 R ⁵ is selected from the group consisting of iso-propyl, iso-butyl, iso-pentyl, tert. -butyl, tert. -amyl, neopentyl, cyclopentyl, cyclohexyl, methylcyclopentyl and cycloheptyl.

More specific examples of the hydrocarbyloxy silane compounds which are useful as external electron donors in the invention are diphenyldimethoxy silane, dicyclopentyldimethoxy silane (D-Donor) , dicyclopentyldiethoxy silane, cyclopentylmethyldimethoxy silane, cyclopentylmethyldiethoxy silane, dicyclohexyldimethoxy silane, dicyclohexyldiethoxy silane, cyclohexylmethyldimethoxy silane (C-Donor) , cyclohexylmethyldiethoxy silane, methylphenyldimethoxy silane, diphenyldiethoxy silane, cyclopentyltrimethoxy silane, phenyltrimethoxy silane, cyclopentyltriethoxy silane, phenyltriethoxy silane. Most preferably, the organo silane compounds are diethylamino-triethoxy-silane (U-Donor) , cyclohexylmethyl dimethoxy silane (C-Donor) , or dicyclopentyl dimethoxy silane (D-Donor) , the latter especially preferred.

The additives as stated above are added afterwards to the polypropylene random copolymer (PP-RACO) , which is collected from the final reactor of the polymer production process. Preferably, these additives are mixed into the polypropylene random copolymer (PP-RACO) or during the extrusion process in a one-step compounding process. Alternatively, a master batch may be formulated, wherein the polypropylene random copolymer (PP-RACO) is first mixed with only some of the additives.

The properties of the polypropylene random copolymer comprising ethylene and/or C ₄ to C ₈ α-olefin (PP-RACO) , produced with the above-outlined process may be adjusted and controlled with the process conditions as known to the skilled person, for example by one or more of the following process parameters: temperature, hydrogen feed, comonomer feed, propylene feed, catalyst, type and amount of external donor, split between two or more components of a multimodal polymer.

For mixing the individual components of the instant fiber reinforced composition, 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. Preferably, mixing is accomplished in a co-rotating twin screw extruder. The polymer materials recovered from the extruder are usually in the form of pellets. These pellets are then preferably further processed, e.g. by compression molding to generate articles and products of the inventive fiber reinforced composition.

The fiber-reinforced composition (FRC)

One essential component of the fiber reinforced polypropylene composition (FRC) is the polypropylene composition (PP) . The polypropylene composition (PP) is part of the polymer matrix of the fiber reinforced composition (FRP) , in which the fibers (F) are embedded as reinforcing structure.

Preferably, the polypropylene composition (PP) and the fibers (F) add up to at least 90 wt. %, more preferably at least 95 wt. %, based on the total weight of the fiber reinforced composition (FRC) . In the most preferred embodiment, the polymer matrix of the fiber reinforced polypropylene composition (FRP) consists of the polypropylene composition (PP) and the fibers (F) . In other words, in this most preferred embodiment, the fiber reinforced composition (FRP) is formed by only two components: the first component is the polypropylene composition (PP) forming a polymer matrix of the fiber reinforced composition (FRP) and the second component are the fibers (F) , which are embedded into said polymer matrix.

It is also preferred that the polymer matrix of the fiber reinforced composition (FRP) comprising the polypropylene composition (PP) is monophasic. In other words, the polypropylene composition (PP) being part of or completely forming the matrix of the fiber reinforced composition (FRP) does not contain more than one phase. In other words, the polypropylene composition (PP) is neither a heterophasic propylene copolymer nor does contain a heterophasic propylene copolymer, nor does it contain additional elastomer phases aiming to alter the mechanical properties in some way.

The content of the polypropylene composition (PP) in the fiber reinforced composition (FRP) is preferably in the range from 50 to 90 wt. %, more preferably in the range from 60 to 88 wt. -%, even more preferably in the range of 70 to 86 wt. -%, and most preferably in the range of 75 to 84 wt. -%, based on the total weight of the fiber reinforced composition (FRC) .

The content of the fibers (F) in the fiber reinforced composition (FRC) is preferably in the range from 10 to 50 wt. %, more preferably in the range from 12 to 40 wt. -%, even more preferably in the range of 14 to 30 wt. -%, and most preferably in the range of 16 to 25 wt. -%, based on the total weight of the fiber reinforced composition (FRC) .

In one embodiment, the fibers (F) are dispersed individually within the polymer matrix of the fiber reinforced composition (FRP) .

The fiber reinforced composition (FRC) is prepared by a process comprising the steps of (a) providing the polypropylene composition (PP) , (b) adding and mixing fibers (F) to said polypropylene composition (PP) , and (c) extruding the mixture comprising said polypropylene (PP) and said fibers in an extruder to obtain the fiber reinforced composition (FRC) in the form of sheets or pellets, preferably sheets.

In another embodiment, an exterior article of automotive, preferably body shields, can be prepared by a direct long fiber thermoplastic molding process (D-LFT) , which allows a direct compression molding step following a step of extruding sheets of the fiber reinforced composition (FRC) by use of an extruder.

The fibers (F)

Another essential component of the fiber reinforced polypropylene composition (FRC) are fibers embedded in the polymer matrix comprising the polypropylene composition (PP) .

Preferably, the fibers (F) are selected from the group consisting of glass fibers, metal fibers, mineral fibers, ceramic fibers, carbon fibers, polymer fibers, graphite fibers and mixtures thereof. Glass fibers are preferred. In particular, the fibers (F) are obtained from glass rovings. This means that in a preferred embodiment, the preferred fibers are glass fibers. It is especially preferred that the fibers (F) are long fibers (LF) , i.e. long fibers, which are glass fibers. The length of long fibers are not limited. After fed into the extruder, long fibers become short fibers by the screw of the extruder.

The fibers (F) used in the fiber reinforced composition (FRC) preferably have an average diameter of at least 10 μm, more preferably from 12 to 25 μm, more preferably from 14 to 20 μm.

The content of the fibers (F) in the fiber reinforced composition (FRC) is preferably in the range from 10 to 50 wt. %, more preferably in the range from 12 to 40 wt. -%, even more preferably in the range of 14 to 30 wt. -%, and most preferably in the range of 16 to 25 wt. -%, based on the total weight of the fiber reinforced composition (FRC) . Accordingly, the content of the polypropylene composition (PP) in the fiber reinforced composition (FRP) is preferably in the range from 50 to 90 wt. %, more preferably in the range from 60 to 88 wt. -%, even more preferably in the range of 70 to 86 wt. -%, and most preferably in the range of 75 to 84 wt. -%, based on the total weight of the fiber reinforced composition (FRC) .

The automotive article

The present invention also relates to automotive articles comprising the fiber-reinforced composition as defined above. The automotive articles preferably are moulded articles.

As used herein the term "moulded article" is intended to encompass articles that are produced by any conventional moulding technique, including stretch moulding, compression moulding, or roto-moulding. However, it is especially preferred that the moulded article is obtained by compression moulding, i.e. the moulded automotive article is a compression moulded article.

The moulded article can be an exterior or interior automotive article. Preferred embodiments include moulded articles like door modules, seat structures, tail gates, arm rests, roof structures, chassis beams, pedals, side trims, step assists, body panels, spoilers, dashboards, and interior trims.

Especially preferred moulded automotive articles are exterior automotive articles. The term "exterior" indicates that the article is not part of the car interior but part of the car's exterior. Preferred exterior automotive articles are selected from external automotive parts like body shields, side trims, step assists, body panels, and spoilers. One especially preferred exterior automotive article are body shields.

Preferably, the automotive article, i.e. the exterior automotive article, comprises equal or more than 80 wt. -%, more preferably equal or more than 90 wt. -%, yet more preferably equal or more than 95 wt. -%, still more preferably equal or more than 99 wt. -%, still yet more preferably consists, of the fiber reinforced composition (FRC) .

In another aspect, the present invention is directed to the use of said fiber reinforced composition (FRC) as already defined above comprising said polypropylene random copolymer (PP-RACO) as already defined above for the preparation of an automotive exterior article.

This use of the present invention is special in view of the prior art because this use, which is effectively a partial replacement of a propylene homopolymer (H-PP) by a polypropylene random copolymer (PP-RACO) , allows preparing a weight-reduced automotive exterior article in a direct long fiber-reinforced thermoplastics process relative to the same automotive exterior article, in which the propylene homopolymer (H-PP) has not been at least partially replaced by a polypropylene random copolymer (PP-RACO) . This is especially important considering that the inventors could further demonstrate that such partial replacement of a propylene homopolymer (H-PP) by the polypropylene random copolymer (PP-RACO) in an automotive exterior article can be achieved while the mechanical properties like stiffness and toughness are not overly altered by such at least partial replacement.

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

EXAMPLES

1. Definitions/Measuring Methods

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

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

Melting temperature Tm and crystallization temperature Tc is measured according to ISO 11357-3

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

Quantification of comonomer content by FTIR spectroscopy

The comonomer content is determined by quantitative Fourier transform infrared spectroscopy (FTIR) after basic assignment calibrated via quantitative ¹³C nuclear magnetic resonance (NMR) spectroscopy in a manner well known in the art. Thin films are pressed to a thickness of between 100-500 μm and spectra recorded in transmission mode.

Specifically, the ethylene content of a polypropylene-co-ethylene copolymer is determined using the baseline corrected peak area of the quantitative bands found at 720-722 and 730-733 cm ^-1. Quantitative results are obtained based upon reference to the film thickness.

Tensile Modulus; Tensile strength; Elongation at break; Yield Stress are measured according to ISO 527-2 (cross head speed = 50 mm/min; 23 ℃) using injection molded specimens as described in EN ISO 1873-2 (dog bone shape, 4 mm thickness) .

Charpy impact test: The Charpy (notched) impact strength (Charpy NIS /IS) is measured according to ISO 179 2C at 23 ℃ and -25℃, using injection molded bar test specimens of 80x10x4 mm3 prepared in accordance with ISO 294-1: 1996.

Flexural strength; Flexural molulus are measured according to ISO 178.

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

Average fiber diameter:

Determined according to ISO 1888: 2006 (E) , Method B, microscope magnification of 1000.

2. Examples

The propylene compositions of following Inventive Examples IE1 and IE2 and Comparative example CE1 were prepared based on the recipes as indicated in Table 1 by compounding on a co-rotating twin-screw extruder using a temperature range between 180 and 200℃.

Table 1: Polypropylene Composition (PP) of inventive Examples and comparative Example used for compounding with fibers:

Ingredient	Unit	IE1	IE2	CE1
PP-RACO	wt%	70	70
H-PP-1	wt%	21.3	25.3	91.5
H-PP-2	wt%	4
AP	w-%	2.5	2.5	2.5
PP-H, GD, 225	wt%	1	1	2.2
Irganox 1076	wt%	0.4	0.4
dstdp	wt%			1.3
Irgafos 168	wt%	0.2	0.2	0.75
Irganox 1010	wt%	0.4	0.4	0.75
Black CMB	wt%	0.2	0.2	1

PP-RACO is a polypropylene random copolymer obtained in a sequential polymerization process as described below having final MFR ₂ (230℃, 2,16 kg) of 70 g/10 min (ISO1133) , an ethylene content in the range of 3.6 wt%and XCS in the range of 5.0 wt%;

The catalyst used for the preparation of PP-RACO is a self-supported Ziegler-Natta catalyst described in WO 2004/029112; as co-catalyst triethyl-aluminium (TEAL) and as donor dicyclo pentyl dimethoxy silane was used;

H-PP-1 is a commercial propylene homopolymer of Borouge with an MFR ₂ of 60 g/10 min (ISO1033) , flexural modulus of 1750 MPa (5 mm/min; ISO 178) , and charpy notched impact strength (23℃; ISO 179/1eA) of 2.5 kJ;

H-PP-2 is the commercial propylene homopolymer “Metocene MF650Y” of Lyondell Basell having an MFR ₂ (230℃, 2, 16 kg) of 1800 g/10 min (ISO1133-1) and a density of 0.90 g/cm ³ (ASTM D792) ;

AP is the commercial maleic anhydride functionalized polypropylene “TPPP8112” of Exxon Mobil with MFR ₂ of > 80 g/10min and an MAH content of 1.4 mol. -%;

PP-H, GD 225 Propylene homopolymer carrier in powder form having melting temperature of 160℃;

Irganox 1076 Octadecyl-3- (3, 5-di-tert. butyl-4-hydroxyphenyl) propionate (CAS-no. 2082-79-3) of BASF SE having melting temperature of 50℃;

dstdp Di-stearyl-thio-di-propionate of BASF SE (CAS-no. 211-750-5) having melting temperature of 64℃

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

Irganox 1010 Irganox 1010 of BASF SE;

Black CMB is the commercial carbon black masterbatch “CMB 520 black 7 -PE 30” of QolorTech bv, Netherlands, consisting of 30 wt. -%Pigment Black 7, 40 wt. -%CaCO ₃, and 30 wt. -%LDPE

Table 2: Preparation of polypropylene random copolymer (PP-RACO) by sequential polymerization:

Loop
Property	Unit
T	[℃]	70
p	[bar]	55
t _RES	[h]	0.8
MFR	g/10min	70
XCS	wt%	4.0
C ₂	wt%	1.6
Gas phase
T	[℃]	80
p	[bar]	21
t _RES	[h]	1.7
MFR	g/10min	70
XCS	wt%	5.0
C ₂	wt%	3.6
Split Loop/GPR	[%]	45/55

C ₂ is ethylene content;

T is the temperature within the reactor;

p is the pressure within the reactor;

t _RES is the average residence time in the reactor;

Table 3: Additivation of polypropylene random copolymer PP-RACO:

Additives	wt%
PP-RACO	97.54
Irganox 1010	0.05
Irgafos 168	0.05
Ca stearate	0.05
DMDBS	0.17
GMS95	0.14
HC205TF	2.0

DMDBS 1, 3 : 2, 4 bis (3, 4-dimethylbenzylidene) sorbitol (CAS-no. 135861-56-2) , commercially available as Millad 3988 of Milliken;

GMS95 95 wt%glyceryl monostearate;

HC205TF low melt flow rate propylene homopolymer having melt flow rate (230℃, 2.16 kg) of 4 g/10min (ISO 1183) and a density of 905 kg/m ³ (ISO 1183) as commercially available from Borealis AG;

Table 4: Compounding Process of Polypropylene Composition (PP) of Inventive Examples in Extruder

	IE1	IE2
Temperature /℃
Zone 1 (feeding zone)	100	100
Zone 2	180	180
Zone 3	190	190
Zone 4	200	200
Zone 5	200	200
Zone 6	200	200
Zone 7	200	200
Zone 8	200	200
Zone 9	200	200
Zone 10	200	200
Zone 11	195	195
Die	205	205

Troughput /kg/h	50	50
Screw speed /rpm	280	280
Torque /%	50	50
Vacuum /MPa	0.06	0.06

Compounding process of comparative example CE1 is similar to inventive Examples.

Based on the above recipe, compositions IE1, IE2 and CE1 are prepared and properties of the compositions are tested and listed as follows in Table 5.

Table 5: Properties of inventive and comparative test samples

As an exterior automotive part, a body shield was formed by a direct long fiber-reinforced thermoplastics process, i.e. mixing the polypropylene compositions of IE1, IE2 and CE1 and 20 wt%glass fiber, then extruding into a sheet by a twin-screw extruder, and directly compression moulding the sheet in a compression moulding machine. The mechanical properties of the resulting body shield were characterized and tested as indicated below.

Table 6: Properties of body shields of inventive and comparative test samples

The above tests illustrate that the polypropylene composition (PP) of the present invention, which is largely based on the polypropylene random copolymer (PP-RACO) can be used to prepare a body shield with reducd weight and thickness by a direct long fiber reinforced thermoplastics process, relative to previous materials that were based on propylene homopolymers. In addition, flowability could also be increased as indicated by increased melt flow rate, while the balance of mechanical properties could essentially be preserved.

Claims

Polypropylene composition (PP) comprising

(a) a polypropylene random copolymer (PP-RACO) comprising a comonomer selected from ethylene and/or C ₄ to C ₈ α-olefin,

(b) at least one propylene homopolymer (H-PP) , and

(c) an adhesion promoter (AP) being a polar modified polypropylene,

wherein

(i) the polypropylene composition (PP) has a melt flow rate MFR ₂ (230 ℃) measured according to ISO 1133 in the range of 30 to 200 g/10min, preferably in the range of 60 to 130 g/10min,

(ii) the polypropylene random copolymer (PP-RACO) has a melt flow rate MFR ₂ (230 ℃) measured according to ISO 1133 in the range of 20 to 180 g/10min, preferably in the range of 50 to 120 g/10min.
Polypropylene composition (PP) according to claim 1, wherein the polypropylene random copolymer (PP-RACO) comprises 1.0 to 5.0 wt%of ethylene and/or C ₄ to C ₈ α-olefin.
Polypropylene composition (PP) according to claim 1 or 2, wherein the polypropylene random copolymer (PP-RACO) has a xylene cold soluble content (XCS) measured according ISO 6427 (23 ℃) in the range of 2 to 20 wt.-%, preferably in the range of 3 to 10 wt.-%.
Polypropylene composition (PP) according to any one of the preceding claims 1 to 3, wherein the polypropylene random copolymer (PP-RACO) has a melting temperature in the range of 145 to 160℃, more preferably in the range of 148 to 158℃, as determined by differential scanning calorimetry (DSC) .
Polypropylene composition (PP) according to any one of the preceding claims 1 to 4, wherein the at least one propylene homopolymer (H-PP) has a melt flow rate MFR ₂ (230 ℃) measured according to ISO 1133 in the range of 5 to 220 g/10min, more preferably in the range of 40 to 150 g/10min.
Polypropylene composition (PP) according to any one of the preceding claims 1 to 5, wherein the at least one propylene homopolymer (H-PP) has tensile strength at yield of at least 30 MPa, more preferably of at least 35 MPa, as measured by ISO-527.
Polypropylene composition (PP) according to any one of the preceding claims 1 to 6, wherein the adhesion promoter (AP) comprises a maleic anhydride-grafted polypropylene.
Polypropylene composition (PP) according to any one of the preceding claims 1 to 7, wherein the polypropylene composition (PP) is monophasic.
Polypropylene composition (PP) according to any one of the preceding claims 1 to 8, wherein (a) the polypropylene random copolymer (PP-RACO) , (b) the at least one propylene homopolymer (H-PP) , and (c) the adhesion promoter (AP) being a polar modified polypropylene add up to at least 90 wt.-%, more preferably to at least 95 wt.-%, based on the total weight of the polypropylene composition (PP) .
Polypropylene composition (PP) according to any one of the preceding claims 1 to 9, wherein the polypropylene composition comprises:

(a) 60 to 85 wt.-%of the polypropylene random copolymer (PP-RACO) ,

(b) 13.5 to 35 wt.-%of at least one propylene homopolymer (H-PP) ,

(c) 1.3 to 5.0 wt.-%of a polar modified polypropylene as adhesion promoter (AP) , and

(d) 0.2 to 5.0 wt.-%of additives.
Fiber reinforced composition (FRC) comprising a polymer matrix and fibers (F) embedded in the polymer matrix, wherein

(a) the polymer matrix comprises the polypropylene composition (PP) according to any one of the preceding claims 1 to 10, and

(b) the fibers (F) are selected from the group consisting of glass fibers, metal fibers, mineral fibers, ceramic fibers, carbon fibers, polymeric fibers, graphite fibers, and mixtures thereof, and

(c) the polymer matrix is monophasic.
Fiber reinforced composition (FRC) according to claim 11, wherein the fibers (F) are glass fibers.
Fiber reinforced composition (FRC) according to claim 11 or 12, wherein the composition comprises

(a) 50 to 90 wt.-%of the polypropylene composition (PP) ,

(b) 10 to 50 wt.-%fibers (F) ,

based on the total weight of the fiber reinforced composition.
Direct process of long fiber reinforced thermoplastics for preparing exteriors of automotives by molding-pressure, comprising the steps of

(a) providing the polypropylene composition (PP) according to any one of the preceding claims 1 to 10,

(b) adding and mixing fibers (F) to said polypropylene composition (PP) , and

(c) extruding the mixture comprising said polypropylene (PP) and said fibers in an extruder to obtain a sheet of the fiber reinforced composition (FRC) , and

(d) molding the sheet in a molding-pressure machine to form an exterior
Automotive article comprising the fiber reinforced composition (FRC) according to any one of the preceding claims 11 to 13.
Automotive article according to claim 15, wherein the automotive article is a moulded article, preferably a compression moulded article.
Automotive article according to claim 15 or 16, wherein the automotive article is selected from external automotive parts, preferably body shields, side trims, step assists, body panels, and spoilers, most preferably body shields.
Use of a fiber reinforced composition as defined in claims 11 to 13 comprising the polypropylene random copolymer (PP-RACO) as defined in claims 1 to 10 for the preparation of an automotive exterior article.