RU2843268C9 - Pipe containing polypropylene composition - Google Patents

Abstract

FIELD: chemistry; performing operations.

SUBSTANCE: present invention relates to a pipe containing a polypropylene composition, wherein the polypropylene composition contains: (A) 70 to 95 wt.%, based on the total weight of the polypropylene composition, of a propylene copolymer with comonomer links obtained from 1-butene or 1-hexene, having total comonomer content of 0.5-5.0 wt.%; melt flow index MFI₂ from 0.10 to 2.0 g/10 min, determined according to ISO 1133 at load of 2.16 kg and temperature of 230 °C, and the ratio of the weight average molecular weight to the number average molecular weight Mw/Mn is from 2.5 to 6.0, determined by gel-penetrating chromatography (GPC) according to ISO 16014-4:2003 and ASTM D 6474-99, and (B) from 5 to 30 wt.%, based on the total weight of the polypropylene composition, of an ethylene copolymer with comonomer links obtained from 1-butene and/or 1-hexene, having total comonomer content of 1.0-25.0 wt.%; density from 910.0 to 940.0 kg/m³, determined according to ISO 1183, and melt flow index MFI₂ from 0.05 to 3.0 g/10 min, determined according to ISO 1133 at load of 2.16 kg and temperature of 190 °C; wherein the polypropylene composition has a melt flow index MFI₂ from 0.1 to 1.0 g/10 min, determined according to ISO 1133 at load of 2.16 kg and temperature of 230 °C. Described is a method of making said pipe, involving the following steps: a) polymerising propylene and 1-butene or 1-hexene in a multistep process in the presence of a single-centre catalyst system to obtain propylene copolymer (A) with comonomer units derived from 1-butene or 1-hexene; b) mixing propylene copolymer (A) with ethylene copolymer (B) with comonomer units derived from 1-butene and/or 1-hexene to produce a polypropylene composition, and c) forming a pipe from the polypropylene composition. Also described is use of said polypropylene composition to make a pipe.

EFFECT: disclosed is pipe containing a polypropylene composition.

15 cl, 3 dwg, 2 tbl, 1 ex

Description

The present invention relates to a pipe containing a polypropylene composition which includes a propylene copolymer with comonomer units obtained from 1-butene or 1-hexene and an ethylene copolymer with comonomer units obtained from 1-butene and/or 1-hexene, a method for producing said pipe and the use of said polypropylene composition for producing a pipe.

State of the art

Polypropylene materials are often used for various piping applications, such as transporting liquids under pressure and/or heat. Specifically, polypropylene materials are used in plumbing and heating systems, such as pressure pipes and fittings for hot and cold water, underfloor and wall heating systems, and radiator connections.

In this regard, propylene copolymers are particularly suitable for hot water pressure pipes and industrial pipes, since propylene copolymers are characterized by good impact properties, rigidity, creep resistance, slow cracking properties and long-term pressure resistance.

It is common knowledge that increasing impact properties negatively impacts stiffness, and vice versa. However, high-pressure pipes require a good balance between impact properties and stiffness to ensure adequate resistance to internal pressure. Furthermore, excellent processability of the propylene copolymer material is essential to facilitate pipe extrusion and injection molding of fittings. To increase the stiffness of the propylene copolymer material to the required level, the amount of comonomer in the polymer can be reduced, which, however, negatively impacts the material's strength. Particularly, propylene copolymer grades for hot and cold water applications often lack satisfactory impact resistance, especially at low temperatures.

EP 3567061 A1 describes a polypropylene composition containing a random copolymer of propylene and 1-hexene, produced in the presence of a single-site catalyst, suitable for use in pressure pipes. These pipes exhibit a good balance of properties in terms of rigidity and pressure resistance, but have relatively low impact strength.

Accordingly, there is a need in the art for propylene copolymer materials that exhibit improved impact properties without sacrificing rigidity and pressure resistance.

The present invention is based on the discovery that excellent pipe properties can be achieved using a polypropylene composition comprising a propylene copolymer with comonomer units derived from 1-butene or 1-hexene, which is polymerized in the presence of a single-center catalyst system, and an ethylene copolymer with comonomer units derived from 1-butene and/or 1-hexene.

The essence of the invention

The present invention relates to a pipe comprising a polypropylene composition, wherein the polypropylene composition comprises

(A) from 70 to 95 wt. %, based on the total weight of the polypropylene composition, of a copolymer of propylene with comonomer units derived from 1-butene or 1-hexene, having

- total comonomer content from 0.5 to 5.0 mass %;

- melt flow index MFI ₂ from 0.10 to 2.0 g/10 min, determined according to ISO 1133 under a load of 2.16 kg and a temperature of 230°C, and

- the ratio of the average molecular weight to the average number molecular weight Mw/Mn from 2.5 to 6.0, determined by gel permeation chromatography (GPC) in accordance with ISO 16014-4:2003 and ASTM D 6474-99, and

(B) from 5 to 30 wt. %, based on the total weight of the polypropylene composition, of a copolymer of ethylene with comonomer units obtained from 1-butene and/or 1-hexene, having

- total comonomer content from 1.0 to 25.0 mass %;

- density from 910.0 to 940.0 kg/ ^m3 , determined according to ISO 1183, and

- melt flow index MFI ₂ from 0.05 to 3.0 g/10 min, determined according to ISO 1133 at a load of 2.16 kg and a temperature of 190°C;

wherein the polypropylene composition has a melt flow rate index MFI ₂ from 0.1 to 1.0 g/10 min, determined according to ISO 1133 under a load of 2.16 kg and a temperature of 230°C.

Furthermore, the present invention relates to a method for producing a pipe as described above or below, comprising the steps of:

a) polymerization of propylene and 1-butene or 1-hexene in a multi-stage process in the presence of a single-site catalytic system to produce a copolymer (A) of propylene with comonomer units derived from 1-butene or 1-hexene;

b) mixing the propylene copolymer (A) with the ethylene copolymer (B) with comonomer units obtained from 1-butene and/or 1-hexene to obtain a polypropylene composition, and

c) forming a pipe from a polypropylene composition.

Furthermore, the present invention relates to the use of a polypropylene composition having a melt flow index MFI ₂ of 0.1 to 1.0 g/10 min, determined in accordance with ISO 1133 under a load of 2.16 kg and a temperature of 230°C, and comprising

(A) from 70 to 95 wt. %, based on the total weight of the polypropylene composition, of a copolymer of propylene with comonomer units derived from 1-butene or 1-hexene, having

- total comonomer content from 0.5 to 5.0 mass %;

- melt flow index MFI ₂ from 0.10 to 2.0 g/10 min, determined according to ISO 1133 under a load of 2.16 kg and a temperature of 230°C, and

- the ratio of the average molecular weight to the average number molecular weight Mw/Mn from 2.5 to 6.0, determined by gel permeation chromatography (GPC) in accordance with ISO 16014-4:2003 and ASTM D 6474-99, and

(B) from 5 to 30 wt. %, based on the total weight of the polypropylene composition, of a copolymer of ethylene with comonomer units obtained from 1-butene and/or 1-hexene, having

- total comonomer content from 1.0 to 25.0 mass %;

- density from 910.0 to 940.0 kg/ ^m3 , determined according to ISO 1183, and

- melt flow index MFI ₂ from 0.05 to 3.0 g/10 min, determined according to ISO 1133 at a load of 2.16 kg and a temperature of 190°C,

to obtain a pipe.

The addition of ethylene copolymer (B), described above or below, in amounts of 5 to 30% by weight to the polypropylene composite unexpectedly increases the impact properties of the resulting pipes, as demonstrated by the Charpy notched impact strength test and the pipe impact strength test, without degrading the compressive strength in the compressive strength test. Stiffness remains acceptable, as evidenced by a slightly lower, but acceptable, flexural modulus.

Definitions

The random propylene copolymer is a copolymer of propylene monomer units and comonomer units, in this case, 1-butene or 1-hexene comonomer units, wherein the comonomer units are distributed randomly along the polypropylene chain. The random propylene copolymer thus comprises a fraction that is insoluble in xylene, the cold xylene insoluble (CXI) fraction, in an amount of at least 90 wt. %, more preferably at least 95 wt. %, even more preferably at least 96 wt. %, based on the total amount of the random propylene copolymer. Accordingly, the random propylene copolymer does not contain an elastomeric polymer phase dispersed therein.

Propylene homopolymer is a polymer essentially composed of propylene monomer units. Due to impurities, particularly during industrial polymerization processes, propylene homopolymer may contain up to 0.1 mol% comonomer units, preferably up to 0.05 mol% comonomer units, and most preferably up to 0.01 mol% comonomer units.

"Ethylene homopolymer" means a polymer consisting essentially of ethylene monomer units. Due to the requirements of large-scale polymerization, it is possible that the ethylene homopolymer includes a minor amount of comonomer units, which typically constitute less than 0.1 mol%, preferably less than 0.05 mol%, and most preferably less than 0.01 mol% of the ethylene homopolymer.

A polymer is called an "ethylene copolymer" if it is derived from ethylene monomer units and at least one alpha-olefin comonomer. The alpha-olefin comonomer is selected from 1-butene and/or 1-hexene. A polymer with ethylene monomer units and comonomer units derived from 1-butene and 1-hexene is called an "ethylene terpolymer."

Ethylene polymers are typically classified by their density, such as low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), medium-density polyethylene (MDPE), and high-density polyethylene (HDPE). In the literature, catalyzed polyethylenes with densities between 910 and 945 kg/ ^m3 are typically classified as linear low-density polyethylene (LLDPE) or medium-density polyethylene (MDPE).

A polymer containing more than one fraction differing from one another in at least one property, such as average molecular weight or comonomer content, is called "multimodal." If a multimodal polymer comprises two distinct fractions, it is called "bimodal," and if it comprises three distinct fractions, it is called "trimodal." The shape of the molecular weight distribution curve, i.e., the appearance of the plot of the polymer mass fraction versus its molecular weight, of such a multimodal polymer has two or more maxima depending on the modality or is at least noticeably broadened compared to the curves of the individual fractions.

Unlike the “multimodal” polymer, the unimodal polymer exhibits only one maximum on the graph of the dependence of the mass fraction of the polymer on its molecular weight and a uniform distribution of comonomers.

Further quantities are given in % by weight (wt.%) unless otherwise stated.

Detailed description of the invention

In a first aspect, the present invention relates to a pipe comprising a polypropylene composition, wherein the polypropylene composition comprises

(A) from 70 to 95 wt. %, based on the total weight of the polypropylene composition, of a copolymer of propylene with comonomer units derived from 1-butene or 1-hexene, having

- total comonomer content from 0.5 to 5.0 mass %;

- melt flow index MFI ₂ from 0.10 to 2.0 g/10 min, determined according to ISO 1133 under a load of 2.16 kg and a temperature of 230°C, and

- the ratio of the average molecular weight to the average number of other molecular weights Mw/Mn from 2.5 to 6.0, determined by gel permeation chromatography (GPC) in accordance with ISO 16014-4:2003 and ASTM D 6474-99, and

(B) from 5 to 30 wt. %, based on the total weight of the polypropylene composition, of a copolymer of ethylene with comonomer units obtained from 1-butene and/or 1-hexene, having

- total comonomer content from 1.0 to 25.0 mass %;

- density from 910.0 to 940.0 kg/ ^m3 , determined according to ISO 1183, and

- melt flow index MFI ₂ from 0.05 to 3.0 g/10 min, determined according to ISO 1133 at a load of 2.16 kg and a temperature of 190°C;

wherein the polypropylene composition has a melt flow rate index MFI ₂ from 0.1 to 1.0 g/10 min, determined according to ISO 1133 under a load of 2.16 kg and a temperature of 230°C.

The pipe exhibits an improved balance of properties in terms of stiffness, impact properties and pressure resistance.

Preferably, the pipe has a pressure test stability of at least 5000 hours, more preferably at least 5750 hours, determined in accordance with ISO 1167-1 and -2, at a temperature of 95°C and a hoop stress of 4.6 MPa.

The upper limit is usually no more than 15,000 hours, preferably no more than 12,500 hours.

Furthermore, the pipe preferably has a pressure test stability of at least 5 hours, more preferably at least 10 hours, determined in accordance with ISO 1167-1 and -2, at a temperature of 20°C and a hoop stress of 16 MPa.

In addition, the pipe preferably does not show failure when tested for impact strength at 0°C in accordance with ISO 9854-2.

The pipe is therefore classified as a pressure pipe, preferably a pressure pipe for hot and cold water.

The pipe comprises a polypropylene composition preferably in an amount of 90 to 100% by weight, more preferably 95 to 100% by weight, based on the total weight of the pipe. In a preferred embodiment, the pipe consists of a polypropylene composition.

The polypropylene composition contains a propylene copolymer (A) and an ethylene copolymer (B).

The polypropylene composition may further comprise additional polymer components that differ from the propylene copolymer (A) and the ethylene copolymer (B). The amount of said additional polymer components is typically from 0 to 10 wt.%, preferably from 0 to 5 wt.%.

Preferably, the propylene copolymer (A) and the ethylene copolymer (B) are the only polymer components of the polypropylene composition.

The polypropylene composition may additionally contain non-polymer components, such as additives. Examples of such additives include, but are not limited to, antioxidants, process stabilizers, UV stabilizers, pigments, fillers, antistatic additives, anti-adhesives, nucleating agents, and acid scavengers.

Suitable antioxidants and stabilizers are, for example, 2,6-di-tert-butyl-p-cresol, tetrakis-[methylene-3-(3',5-di-tert-butyl-4'-hydroxyphenyl)propionate]methane, octadecyl-3-3(3'5'-di-tert-butyl-4'-hydroxyphenyl)propionate, dilauryl thiodipropionate, distearyl thiodipropionate, tris-(nonylphenyl)phosphate, distearyl pentaerythritol diphosphite and tetrakis(2,4-di-tert-butylphenyl)-4,4'-biphenylene diphosphonite.

Some hindered phenols are sold under the trade names Irganox 1076 and Irganox 1010. Commercially available mixtures of antioxidants and process stabilizers are also available, such as Irganox B225, sold by Ciba-Geigy.

Suitable acid scavengers include, for example, metal stearates, such as calcium stearate and zinc stearate. They are used in amounts generally known in the art, typically from 500 to 10,000 ppm, and preferably from 500 to 5,000 ppm.

The polypropylene composition preferably has a polymer fraction eluting at a temperature of from 31 to 80°C, excluding the purge fraction, and a logM of from 4.5 to 6.0, in an amount of from 4 to 25 wt.%, more preferably in an amount of from 6 to 20 wt.%, even more preferably in an amount of from 8 to 15 wt.%, determined by cross-fraction chromatography (CFC).

Furthermore, the polypropylene composition preferably has a profile comprising two peaks in a temperature rising elution fractionation (TREF) elugram obtained by cross-fractionation chromatography (CFC) analysis, wherein the first peak Tp(1) preferably elutes at a temperature of 45 to 90°C, more preferably at 50 to 80°C, even more preferably at 55 to 70°C, and the second peak Tp(2) preferably elutes at a temperature of 85 to 100°C, more preferably at 87 to 99°C, even more preferably at 90 to 98°C.

The polypropylene composition preferably has a cold xylene solubles (CXS) content of 1.0 to 3.5 wt.%, more preferably 1.2 to 3.2 wt.%, even more preferably 1.5 to 3.0 wt.%, determined in accordance with ISO 16152.

Furthermore, the polypropylene composition preferably has a first melting temperature Tm1 from 135 to 145°C, more preferably from 137°C to 142°C, determined according to ISO 11357/part 3.

In addition, the polypropylene composition preferably has a second melting temperature Tm2 from 115 to 130°C, more preferably from 117°C to 125°C, determined according to ISO 11357/part 3.

Tpl1 is usually higher than Tpl2.

In addition, the polypropylene composition preferably has a crystallization temperature Tcr from 100 to 110°C, more preferably from 102 to 107°C, determined in accordance with ISO 11357/part 3.

Furthermore, the polypropylene composition preferably has a first melting enthalpy Hpl of 30 to 45 J/g, more preferably 32 to 42 J/g, determined in accordance with ISO 11357/part 3.

In addition, the polypropylene composition preferably has a second melting enthalpy Hpl2 of 35 to 50 J/g, more preferably 37 to 47 J/g, determined according to ISO 11357/part 3.

Npl1 is usually lower than Npl2.

The polypropylene composition exhibits high impact strength with acceptable rigidity.

Preferably, the polypropylene composition has a flexural modulus of 700 to 1000 MPa, more preferably 800 to 950 MPa, even more preferably 850 to 925 MPa, determined in accordance with ISO 178 on injection moulded test specimens manufactured in accordance with EN ISO 1872-2.

In addition, the polypropylene composition preferably has a Charpy notched impact strength at 23°C of 7.5 to 15.0 kJ/ ^m2 , more preferably of 8.5 to 14.0 kJ/ ^m2 , even more preferably of 9.5 to 13.0 kJ/ ^m2 .

In addition, the polypropylene composition preferably has a Charpy notched impact strength at 0°C of 2.5 to 5.0 kJ/ ^m2 , more preferably of 3.0 to 4.5 kJ/ ^m2 , even more preferably of 3.0 to 4.0 kJ/ ^m2 .

In addition, the polypropylene composition preferably has a Charpy notched impact strength at -20°C of 1.5 to 4.0 kJ/ ^m2 , more preferably of 1.7 to 3.5 kJ/ ^m2 , even more preferably of 1.8 to 3.0 kJ/ ^m2 .

The Charpy notched impact strength at 23°C, 0°C and -20°C is determined in accordance with ISO 179 1eA on injection moulded test specimens prepared in accordance with EN ISO 1872-2.

The polypropylene composition contains a propylene copolymer (A) in an amount of 70 to 95 wt.%, preferably 75 to 93 wt.%, more preferably 80 to 90 wt.%, based on the total weight of the polypropylene composition.

The propylene copolymer (A) is a copolymer of propylene with comonomer units derived from 1-butene or 1-hexene. Preferably, the propylene copolymer (A) is a copolymer of propylene with comonomer units derived from 1-hexene.

The term "propylene copolymer with comonomer units derived from 1-butene" means that the propylene copolymer (A) contains only units derived from propylene and 1-butene.

The term "propylene copolymer with comonomer units derived from 1-hexene" means that the propylene copolymer (A) contains only units derived from propylene and 1-hexene.

The propylene copolymer (A) has a total comonomer content, i.e. a content of comonomer units derived from 1-butene or 1-hexene, of from 0.5 to 5.0 wt.%, more preferably from 1.0 to 4.0 wt.%, even more preferably from 2.0 to 3.0 wt.%, based on the total weight of the propylene copolymer (A).

Preferably, the comonomer units are distributed randomly in the polymer chains of the propylene copolymer (A). Thus, the propylene copolymer (A) is preferably a random propylene copolymer.

The propylene copolymer (A) additionally has a melt flow rate index MFR ₂ of 0.10 to 2.0 g/10 min, preferably of 0.15 to 1.5 g/10 min, more preferably of 0.20 to 1.0 g/10 min, determined in accordance with ISO 1133 at a load of 2.16 kg and a temperature of 230°C.

Furthermore, the propylene copolymer (A) has a ratio of the weight-average molecular weight to the number-average molecular weight Mw/Mn from 2.5 to 6.0, preferably from 3.0 to 5.5, even more preferably from 3.5 to 5.0, determined by gel permeation chromatography (GPC) according to ISO 16014-4:2003 and ASTM D 6474-99.

Preferably, the propylene copolymer (A) has a cold xylene solubles (CSSC) content of 0.2 to 2.5 wt.%, more preferably 0.5 to 2.3 wt.%, determined in accordance with ISO 16152.

The propylene copolymer (A) preferably has a melting point Tm of 135 to 145°C, determined according to ISO 11357/part 3.

In addition, the propylene copolymer (A) preferably has a crystallization temperature Tcr from 100 to 105°C, determined according to ISO 11357/part 3.

Furthermore, the propylene copolymer (A) preferably has a melting enthalpy Hm of 70 to 80 J/g, determined according to ISO 11357/part 3.

Propylene copolymer (A) can be obtained by polymerization in the presence of a single-center catalyst system.

The catalytic system preferably comprises

(i) a catalyst having the following structure

Where

M represents zirconium or hafnium;

each X independently represents a sigma-donor ligand;

L represents a bridge of the formula -(ER ¹⁰ ₂ ) _y- ;

y represents 1 or 2;

E represents C or Si;

each R ¹⁰ independently represents a C ₁ -C ₂₀ hydrocarbyl group, a tri(C ₁ -C ₂₀ alkyl)silyl group, a C ₆ -C ₂₀ aryl group, a C ₇ -C ₂₀ arylalkyl group or a C ₇ -C ₂₀ alkylaryl group, or L represents an alkylene group such as methylene or ethylene;

each R ¹ , independently the same or different from each other, represents a CH ₂ -R ¹¹ group, where R ¹¹ represents H or a linear or branched C ₁ -C ₆ alkyl group, C ₃ -C ₈ cycloalkyl group, C ₆ -C ₁₀ aryl group;

each ^R3 , ^R4 and ^R5 , independently the same or different from one another, is H or a linear or branched _C1 - _C6 alkyl group, a _C7 - _C20 arylalkyl group, a _C7 - _C20 alkylaryl group or a _C6 - _C20 aryl group, with the proviso that if a total of four or more ^R3 , ^R4 and ^R5 groups other than H are present, one or more of ^R3 , ^R4 and ^R5 are other than a tert-butyl group;

each R ⁷ and R ⁸ , independently the same or different from each other, represents H, a CH ₂ -R ¹² group, where R ¹² represents H or a linear or branched C ₁ -C ₆ alkyl group, SiR ¹³ ₃ , GeR ¹³ ₃ , OR ¹³ , SR ¹³ , NR ¹³ ₂ ,

where R ¹³ represents a linear or branched C ₁ -C ₆ alkyl group, a C ₇ -C ₂₀ alkylaryl group and a C ₇ -C ₂₀ arylalkyl group or a C ₆ -C ₂₀ aryl group,

each R ⁹ , independently identical or different, represents H or a linear or branched C ₁ -C ₆ alkyl group, and

all R ² and R ⁶ are H, and

(ii) a cocatalyst system comprising an aluminoxane cocatalyst.

It should be emphasized that in some cases the use of such a cocatalyst system may not be required.

The catalyst system can be used in unsupported or solid form. The catalyst system according to the invention can be used as a homogeneous catalyst system or a heterogeneous catalyst system.

The catalyst system in solid form, preferably in the form of solid particles, can either be supported on an external support material such as silica or alumina, or, in a particularly preferred embodiment, not contain an external support but still be in solid form. For example, the solid catalyst system can be prepared by a method in which

(a) forming a liquid/liquid emulsion system, wherein said liquid/liquid emulsion system comprises a solution of the catalyst components (i) and (ii) dispersed in a solvent to form dispersed droplets, and

(b) form solid particles by solidifying said dispersed droplets.

Specific complexes of the invention include:

Rac-anti-dimethylsilandiyl[2-methyl-4-(4-tert-butylphenyl)-5,6,7-trihydro-s-indacen-1-yl][2-methyl-4-(4-tert-butylphenyl)-5-methoxy-6-tert-butylindenyl zirconium dichloride or dimethyl,

Rac-anti-dimethylsilandiyl[2-isobutyl-4-(4-tert-butylphenyl)-5,6,7-trihydro-s-indacen-1-yl][2-methyl-4-(4-tert-butylphenyl)-5-methoxy-6-tert-butylindenyl zirconium dichloride or dimethyl,

Rac-anti-dimethylsilandiyl[2-neopentyl-4-(4-tert-butylphenyl)-5,6,7-trihydro-s-indacen-1-yl][2-methyl-4-(4-tert-butylphenyl)-5-methoxy-6-tert-butylindenyl zirconium dichloride or dimethyl,

Rac-anti-dimethylsilandiyl[2-benzyl-4-(4-tert-butylphenyl)-5,6,7-trihydro-s-indacen-1-yl][2-methyl-4-(4-tert-butylphenyl)-5-methoxy-6-tert-butylindenyl zirconium dichloride or dimethyl,

Rac-anti-dimethylsilandiyl[2-cyclohexylmethyl-4-(4-tert-butylphenyl)-5,6,7-trihydro-s-indacen-1-yl][2-methyl-4-(4-tert-butylphenyl)-5-methoxy-6-tert-butylindenyl zirconium dichloride or dimethyl,

Rac-anti-dimethylsilandiyl[2-methyl-4-(3,5-dimethylphenyl)-5,6,7-trihydro-s-indacen-1-yl][2-methyl-4-(3,5-dimethylphenyl)-5-methoxy-6-tert-butylindenyl zirconium dichloride or dimethyl,

Rac-anti-dimethylsilandiyl[2-isobutyl-4-(3,5-dimethylphenyl)-5,6,7-trihydro-s-indacen-1-yl][2-methyl-4-(3,5-dimethylphenyl)-5-methoxy-6-tert-butylindenyl zirconium dichloride or dimethyl,

Rac-anti-dimethylsilandiyl[2-neopentyl-4-(3,5-dimethylphenyl)-5,6,7-trihydro-s-indacen-1-yl][2-methyl-4-(3,5-dimethylphenyl)-5-methoxy-6-tert-butylindenyl zirconium dichloride or dimethyl,

Rac-anti-dimethylsilandiyl[2-benzyl-4-(3,5-dimethylphenyl)-5,6,7-trihydro-s-indacen-1-yl][2-methyl-4-(3,5-dimethylphenyl)-5-methoxy-6-tert-butylindenyl zirconium dichloride or dimethyl, and

Rac-anti-dimethylsilandiyl[2-cyclohexylmethyl-4-(3,5-dimethylphenyl)-5,6,7-trihydro-s-indacen-1-yl][2-methyl-4-(3,5-dimethylphenyl)-5-methoxy-6-tert-butylindenyl zirconium dichloride or dimethyl.

Catalysts have been described, inter alia, in document WO 2015/011135, which is incorporated herein by reference. A particularly preferred catalyst is catalyst number 3 of WO 2015/011135. The preparation of metallocenes is described in document WO 2013/007650, which is incorporated herein by reference. The complex preparation of a particularly preferred catalyst is described as E2 in WO 2013/007650.

For the avoidance of doubt, any narrower definition of a substituent proposed above may be combined with any other broad or narrower definition of any other substituent.

In the above description, where a narrower definition of a substituent is provided, that narrower definition is considered to be disclosed together with all broader and narrower definitions of other substituents in the application.

The ligands required for complex formation and, consequently, the catalyst/catalytic system, can be synthesized by any method, and an experienced organic chemist will be able to develop various synthetic protocols for producing the required ligand materials. For example, WO 2007/116034 discloses the required chemical composition. Synthetic protocols can also generally be found in WO 2002/02576, WO 2011/135004, WO 2012/084961, WO 2012/001052, WO 2011/076780, and WO 2015/158790. The examples section also provides sufficient guidance to the skilled chemist.

As noted above, a cocatalyst system is not always required. However, when used, the cocatalyst system includes an aluminoxane cocatalyst.

The alumoxane cocatalyst may be a single compound of formula (X):

where n is typically between 6 and 20 and R has the meaning given below.

Aluminoxanes are formed by partial hydrolysis of organoaluminum compounds, for example compounds of the formula AlR ₃ , AlR ₂ Y and Al ₂ R ₃ Y ₃ , where R can be, for example, C ₁ -C ₁₀ alkyl, preferably C ₁ -C ₅ alkyl, or C ₃ -C ₁₀ cycloalkyl, C ₇ -C ₁₂ arylalkyl or alkylaryl and/or phenyl or naphthyl, and where Y can be hydrogen, halogen, preferably chlorine or bromine, or C ₁ -C ₁₀ alkoxyl, preferably methoxyl or ethoxyl. The resulting oxygen-containing aluminoxanes are usually not pure compounds, but mixtures of oligomers of formula (X).

The preferred aluminoxane is methylaluminoxane (MAO). Since the aluminoxanes used as cocatalysts in this invention are not pure compounds due to their production process, the molarity of aluminoxane solutions is based on their aluminum content.

The molar ratio of Al in the aluminoxane to the metal ion of the metallocene may be from 1:1 to 2000:1 mol/mol, preferably from 10:1 to 1000:1, and more preferably from 50:1 to 500:1 mol/mol.

The cocatalyst system may further include a boron-containing cocatalyst.

Interesting boron-based cocatalysts include those of formula (Z)

BY ₃ (Z),

where Y is independently the same or may be different and represents a hydrogen atom, an alkyl group containing from 1 to about 20 carbon atoms, an aryl group containing from 6 to about 15 carbon atoms, alkylaryl, arylalkyl, haloalkyl or haloaryl, each of which has from 1 to 10 carbon atoms in the alkyl radical and from 6 to 20 carbon atoms in the aryl radical or contains fluorine, chlorine, bromine or iodine. Preferred examples of Y are methyl, propyl, isopropyl, isobutyl or trifluoromethyl, unsaturated groups such as aryl or haloaryl, such as phenyl, tolyl, benzyl groups, p-fluorophenyl, 3,5-difluorophenyl, pentachlorophenyl, pentafluorophenyl, 3,4,5-trifluorophenyl and 3,5-di(trifluoromethyl)phenyl. Preferred embodiments are trifluoroborane, triphenylborane, tris(4-fluorophenyl)borane, tris(3,5-difluorophenyl)borane, tris(4-fluoromethylphenyl)borane, tris(2,4,6-trifluorophenyl)borane, tris(pentafluorophenyl)borane, tris(tolyl)borane, tris(3,5-dimethylphenyl)borane, tris(3,5-difluorophenyl)borane and/or tris(3,4,5-trifluorophenyl)borane.

Particular preference is given to tris(pentafluorophenyl)borane.

Borates, i.e., compounds containing the borate ion 3+, can be used. Such ionic cocatalysts preferably contain a non-coordinating anion, such as tetrakis(pentafluorophenyl)borate and tetraphenylborate. Suitable counterions are protonated amines or aniline derivatives, such as methylammonium, anilinium, dimethylammonium, diethylammonium, N-methylanilinium, diphenylammonium, N,N-dimethylanilinium, trimethylammonium, triethylammonium, tri-n-butylammonium, methyldiphenylammonium, pyridinium, p-bromo-N,N-dimethylanilinium, or p-nitro-N,N-dimethylanilinium.

Preferred ionic compounds that can be used according to the present invention include:

triethylammonium tetra(phenyl)borate,

tributylammonium tetra(phenyl)borate,

trimethylammonium tetra(tolyl)borate,

tributylammonium tetra(tolyl)borate,

tributylammonium tetra(pentafluorophenyl)borate,

tripropylammonium tetra(dimethylphenyl)borate,

tributylammonium tetra(trifluoromethylphenyl)borate,

tributylammonium tetra(4-fluorophenyl)borate,

N,N-dimethylcyclohexylammonium tetrakis(pentafluorophenyl) borate,

N,N-dimethylbenzylammonium tetrakis(pentafluorophenyl)borate,

N,N-dimethylaniline tetra(phenyl)borate,

N,N-diethylanilinium tetra(phenyl)borate,

N,N-dimethylanilinium tetrakis(pentafluorophenyl) borate,

N,N-di(propyl)ammonium tetrakis(pentafluorophenyl)borate,

di(cyclohexyl)ammonium tetrakis(pentafluorophenyl)borate,

triphenylphosphonium tetrakis(phenyl)borate,

triethylphosphonium tetrakis(phenyl)borate,

diphenylphosphonium tetrakis(phenyl)borate,

tri(methylphenyl)phosphonium tetrakis(phenyl)borate,

tri(dimethylphenyl)phosphonium tetrakis(phenyl)borate,

triphenylcarbenium tetrakis(pentafluorophenyl)borate,

or ferrocentetrakis(pentafluorophenyl)borate.

Preference is given to triphenylcarbenium tetrakis(pentafluorophenyl)borate,

N,N-dimethylcyclohexylammonium tetrakis(pentafluorophenyl)borate or

N,N-dimethylbenzylammonium tetrakis(pentafluorophenyl)borate.

Suitable amounts of cocatalyst are well known to those skilled in the art.

The molar ratio of boron to the metal ion of the metallocene may be from 0.5:1 to 10:1 mol/mol, preferably from 1:1 to 10:1, especially from 1:1 to 5:1 mol/mol.

The catalyst can be supported or unsupported. The particulate support material used is preferably an organic or inorganic material, such as silica, alumina, or zirconia, or a mixed oxide, such as an aluminosilicate, particularly silica, alumina, or aluminosilicate. A silica support is preferably used. Those skilled in the art are familiar with the procedures required for supporting the metallocene catalyst on the support.

The carrier is particularly preferably a porous material so that the complex can be loaded into the pores of the carrier, for example using a method similar to that described in WO 94/14856 (Mobil), WO 95/12622 (Borealis) and WO 2006/097497. The particle size is not critical, but is preferably in the range of 5 to 200 μm, more preferably 20 to 80 μm. The use of these carriers is common in the art.

In an alternative embodiment, no support is used at all. Such a catalyst system can be prepared in solution, for example, in an aromatic solvent such as toluene, by contacting the metallocene (as a solid or solution) with a cocatalyst, for example, methylaluminoxane, previously dissolved in the aromatic solvent, or can be prepared by sequentially adding dissolved catalyst components to the polymerization medium.

In one particularly preferred embodiment, an external support is not used, but the catalyst is still present in solid particulate form. Thus, no external support, such as an inert organic or inorganic support such as silicon dioxide, as described above, is used.

To obtain the catalyst of the invention in solid form but without the use of an external carrier, it is preferable to use a liquid/liquid emulsion system. The method involves forming a dispersion of catalyst components (i) and (ii) in a solvent and solidifying said dispersed droplets to form solid particles.

In particular, the method includes preparing a solution of one or more catalyst components; dispersing said solution in a solvent to form an emulsion in which said one or more catalyst components are present in droplets of the dispersed phase; immobilizing the catalyst components in the dispersed droplets in the absence of an external porous carrier in the form of particles to form solid particles containing said catalyst, and possibly extracting said particles.

This method enables the production of active catalyst particles with improved morphology, such as a desired spherical shape, surface properties, and particle size, without the use of any additional external porous support material, such as an inorganic oxide such as silica. The term "preparing a solution of one or more catalyst components" means that the catalyst-forming compounds can be combined into a single solution that is dispersed in an immiscible solvent, or, alternatively, at least two separate catalyst solutions can be prepared for each portion of the catalyst-forming compounds, which are then sequentially dispersed in the solvent.

In a preferred method for preparing the catalyst, at least two separate solutions may be prepared for each or a portion of said catalyst, which are then sequentially dispersed in an immiscible solvent.

More preferably, a solution of a complex comprising a transition metal compound and a cocatalyst is combined with a solvent to form an emulsion, wherein the inert solvent forms a continuous liquid phase, and the solution containing the catalyst components forms a dispersed phase (discrete phase) in the form of dispersed droplets. The droplets then solidify to form solid catalyst particles, and the solid particles are separated from the liquid and optionally washed and/or dried. The solvent forming the continuous phase can be immiscible with the catalyst solution, at least under the conditions (e.g., temperatures) used in the dispersion step.

The term “immiscible with the catalyst solution” means that the solvent (continuous phase) is completely or partially immiscible, i.e., not completely miscible with the solution of the dispersed phase.

Preferably, said solvent is inert with respect to the compounds of the resulting catalytic system. A full description of the required method can be found in WO 03/051934. The inert solvent must be chemically inert, at least under the conditions (e.g., temperature) used in the dispersion step. Preferably, the solvent of said continuous phase does not contain any significant amount of catalyst-forming compounds dissolved therein. Thus, solid catalyst particles are formed in droplets from compounds originating from the dispersed phase (i.e., they enter the emulsion in a solution dispersed in the continuous phase).

The terms "immobilization" and "solidification" are used interchangeably in this document for the same purpose, i.e., to form free-flowing solid catalyst particles in the absence of an external porous particulate support such as silica. Solidification thus occurs within the droplets. This step can be accomplished in various ways, as described in WO 03/051934. Preferably, solidification is induced by an external stimulus to the emulsion system, such as a solidifying temperature change. Thus, during this step, the catalyst component(s) remain "fixed" within the formed solid particles. It is also possible that one or more catalyst components may participate in the solidification/immobilization reaction.

Accordingly, solid particles of uniform composition having a predetermined range of particle sizes can be obtained.

In addition, the particle size of the catalyst according to the invention can be controlled by the size of the droplets in the solution, and spherical particles with a uniform particle size distribution can be obtained.

The method also offers industrial advantages, as it allows for the production of solid particles in a single reactor. Continuous or semi-continuous processes are also possible for catalyst production.

The polypropylene composition contains ethylene copolymer (B) in an amount of 5 to 30 mass %, preferably 7 to 25 mass %, more preferably 10 to 20 mass %, based on the total weight of the polypropylene composition.

The ethylene copolymer (B) is a copolymer of ethylene with comonomer units derived from 1-butene and/or 1-hexene. Preferably, the ethylene copolymer (B) is a terpolymer of ethylene with comonomer units derived from 1-butene and 1-hexene.

The term "ethylene copolymer with comonomer units derived from 1-butene" means that the ethylene copolymer (B) contains only units derived from ethylene and 1-butene.

The term "ethylene copolymer with comonomer units derived from 1-hexene" means that the ethylene copolymer (B) contains only units derived from ethylene and 1-hexene.

The term "terpolymer of ethylene with comonomer units derived from 1-butene and 1-hexene" means that the ethylene copolymer (B) contains only units derived from ethylene, 1-butene and 1-hexene.

The ethylene copolymer (B) has a total comonomer content, i.e. a content of comonomer units derived from 1-butene and/or 1-hexene, of from 1.0 to 25.0 wt.%, preferably from 1.5 to 22.5 wt.%, even more preferably from 2.0 to 20.0 wt.%.

The ethylene copolymer (B) preferably has a 1-butene content of 0.1 to 5.0 mass %, more preferably 0.2 to 3.5 mass %, even more preferably 0.3 to 2.0 mass %, based on the total weight of the ethylene copolymer (B).

The ethylene copolymer (B) preferably has a 1-hexene content of 5.0 to 25.0 mass %, more preferably of 6.0 to 22.5 mass %, even more preferably of 7.5 to 20.0 mass %, based on the total weight of the ethylene copolymer (B).

Ethylene copolymer (B) can be unimodal with respect to comonomer distribution. This means that comonomer units derived from 1-butene and/or 1-hexene are uniformly distributed throughout the ethylene copolymer (B).

The ethylene copolymer (B) may be multimodal with respect to comonomer distribution.

This means that the ethylene copolymer (B) contains components with different.

In the case of a copolymer of ethylene and comonomer units derived from 1-butene or 1-hexene, the ethylene copolymer (B) in one embodiment may comprise an ethylene homopolymer component and a copolymer component of ethylene and 1-butene or 1-hexene.

In the case of a copolymer of ethylene and comonomer units obtained from 1-butene or 1-hexene, the ethylene copolymer (B) in another embodiment may contain two components - copolymers of ethylene and 1-butene or 1-hexene with different comonomer contents.

In the case of a terpolymer of ethylene and comonomer units derived from 1-butene and 1-hexene, the ethylene copolymer (B) in one embodiment may comprise an ethylene homopolymer component, an ethylene-1-butene copolymer component, and an ethylene-1-hexene copolymer component.

In the case of a terpolymer of ethylene and comonomer units obtained from 1-butene and 1-hexene, the ethylene copolymer (B) in another embodiment may comprise a component - an ethylene homopolymer and a component - a terpolymer of ethylene, 1-butene and 1-hexene.

In the case of a terpolymer of ethylene and comonomer units derived from 1-butene and 1-hexene, the ethylene copolymer (B) in another embodiment may comprise a component - a copolymer of ethylene and 1-butene and a component - a copolymer of ethylene and 1-hexene.

In a preferred embodiment, the ethylene copolymer (B) is a terpolymer of ethylene with comonomer units selected from 1-butene and 1-hexene, with a 1-butene content of 0.1 to 5.0 wt.%, preferably 0.2 to 3.5 wt.%, even more preferably 0.3 to 2.0 wt.% and a 1-hexene content of 5.0 to 24.9 wt.%, more preferably 6.0 to 22.3 wt.%, even more preferably 7.5 to 19.7 wt.%, based on the total weight of the ethylene copolymer (B).

The ethylene copolymer (B) has a density of 910.0 to 940.0 kg/ ^m3 , preferably 912.0 to 938.0 kg/ ^m3 , even more preferably 915.0 to 935 kg/ ^m3 , determined according to ISO 1183.

The ethylene copolymer (B) is preferably a linear low density polyethylene (LLDPE).

The ethylene copolymer (B) has a melt flow rate MFR ₂ of 0.05 to 3.0 g/10 min, preferably 0.10 to 2.5 g/10 min, more preferably 0.50 to 2.0 g/10 min, determined according to ISO 1133 at a load of 2.16 kg and a temperature of 190°C.

The ethylene copolymer (B) preferably has an intrinsic viscosity iV of 1.5 to 2.5 dl/g, more preferably of 1.7 to 2.2 dl/g, determined according to DIN ISO 1628/1, October 1999 (in decalin at 135°C).

Furthermore, the ethylene copolymer (B) preferably has a ratio of the weight-average molecular weight to the number-average molecular weight Mw/Mn from 2.0 to 5.0, preferably from 2.5 to 4.5, more preferably from 3.0 to 4.0, determined by gel permeation chromatography (GPC) according to ISO 16014-4:2003 and ASTM D 6474-99.

The ethylene copolymer (B) can preferably be obtained by polymerization in the presence of a single-site catalyst system. The single-site catalyst system preferably comprises a catalytically active metallocene compound or complex in combination with a cocatalyst. The metallocene compound or complex is also referred to in this document as the organometallic compound (C).

An organometallic compound (C) contains a transition metal (M) of groups 3 to 10 of the Periodic Table (IUPAC 2007) or an actinide or lanthanide.

The term "organometallic compound (C)" according to the present invention includes any metallocene compound of a transition metal that carries at least one organic (coordination) ligand and exhibits catalytic activity alone or together with a cocatalyst. Compounds of transition metals are well known in the art and preferably encompass compounds of metals from groups 3 to 10, for example, groups 3 to 7 or 3 to 6, such as groups 4 to 6 of the Periodic Table (IUPAC 2007), as well as lanthanides or actinides.

In one embodiment, the organometallic compound (C) has the following formula (1):

Where

"M" represents a transition metal (M) from groups 3-10 of the Periodic Table (IUPAC 2007),

each "X" independently represents a monoanionic ligand, such as an o-ligand,

each "L" independently represents an organic ligand that coordinates to a transition metal "M",

"R" represents a bridging group linking the indicated organic ligands (L),

"m" represents 1, 2 or 3, preferably 2,

"n" represents 0, 1 or 2, preferably 1,

"q" represents 1, 2 or 3, preferably 2 and

m+q is equal to the valence of the transition metal (M).

“M” is preferably selected from the group consisting of zirconium (Zr), hafnium (Hf) or titanium (Ti), more preferably selected from the group consisting of zirconium (Zr) and hafnium (Hf).

"X" is preferably halogen, most preferably Cl.

Most preferably, the organometallic compound (C) is a metallocene complex that contains a transition metal compound as defined above that contains a cyclopentadienyl, indenyl or fluorenyl ligand as a substituent "L". Furthermore, the ligands "L" may have substituents such as alkyl groups, aryl groups, arylalkyl groups, alkylaryl groups, silyl groups, siloxy groups, alkoxy groups or other heteroatom groups and the like. Suitable metallocene catalysts are known in the art and are disclosed, inter alia, in WO-A-95/12622, WO-A-96/32423, WO-A-97/28170, WO-A-98/32776, WO-A-99/61489, WO-A-03/010208, WO-A-03/051934, WO-A-03/051514, WO-A-2004/085499, EP-A-1752462 and EP-A-1739103.

Most preferably, the metallocene catalyst, i.e., the catalytically active metallocene complex defined above, is used together with a cocatalyst, also known as an activator. Suitable activators are metal alkyl compounds, especially alkylaluminum compounds, known in the art. Particularly suitable activators for use with metallocene catalysts are alkylaluminum oxycompounds such as methylaluminoxane (MAO), tetraisobutylaluminoxane (TIBAO), or hexaisobutylaluminoxane (HIBAO).

Way

In another aspect, the present invention relates to a method for producing a pipe as described above or below, comprising the steps of:

a) polymerization of propylene and 1-butene or 1-hexene in a multi-stage process in the presence of a single-site catalytic system to produce a copolymer (A) of propylene with comonomer units derived from 1-butene or 1-hexene;

b) mixing the propylene copolymer (A) with the ethylene copolymer (B) with comonomer units obtained from 1-butene and/or 1-hexene to obtain a polypropylene composition and

c) forming a pipe from a polypropylene composition.

The propylene copolymer (A) is preferably polymerized in the presence of a single site catalyst system as described above.

The propylene copolymer (A) is preferably polymerized in a multi-stage process, which is a sequential polymerization process with at least two polymerization reactors connected in series.

The multi-step process preferably includes the following steps:

(i) introducing a stream of propylene and 1-butene or 1-hexene, preferably 1-hexene, into the first reactor such that the ratio of the feed amount of 1-butene or 1-hexene, preferably 1-hexene, to the feed amount of propylene is from 2.0 to 4.0 mol/kmol, further introducing a stream of the catalyst system into the first reactor,

(ii) withdrawing a product stream containing the first intermediate compound (IP1) from the first reactor,

(iii) transferring the first intermediate compound (PP1) to a second reactor and further polymerizing in the second reactor the first intermediate compound by feeding an additional amount of propylene, 1-butene or 1-hexene, preferably 1-hexene, additionally in the presence of hydrogen, so that

the ratio of hydrogen concentration to propylene concentration is in the range of 0.1-0.8 mol/kmol, and additionally

the concentration of 1-butene or 1-hexene, preferably 1-hexene, relative to the concentration of propylene is in the range from 3.0 to 6.0 mol/kmol.

(iv) obtaining a powder of propylene copolymer (A) at the outlet.

Regarding the method as a whole, the propylene composition is obtained in a sequential polymerization process comprising at least two polymerization zones operating under different conditions to produce the propylene composition. The polymerization zones may operate under slurry, solution, or gas phase conditions, or a combination thereof. Suitable processes are disclosed, inter alia, in WO-A-98/58976, EP-A-887380, and WO-A-98/58977.

The catalyst can be transferred to the polymerization zone by any means known in the art. Thus, the catalyst can be suspended in a diluent and maintained in the form of a homogeneous suspension. It is particularly preferred to use an oil having a viscosity of 20 to 1500 mPa⋅s as the diluent, as described in WO-A-2006/063771. It is also possible to mix the catalyst with a viscous mixture of lubricant and oil and feed the resulting paste into the polymerization zone. Furthermore, it is possible to allow the catalyst to settle and introduce portions of the resulting catalytic slurry into the polymerization zone in a manner disclosed, for example, in EP-A-428054.

Gas-phase polymerization can be carried out in a fluidized bed reactor, a fast fluidized bed reactor, a packed bed reactor, or any combination thereof. When using a combination of reactors, the polymer is transferred from one polymerization reactor to another. Furthermore, some or all of the polymer from the polymerization stage can be recycled to the previous polymerization stage.

In a preferred embodiment, the prepolymerization is carried out continuously as a slurry polymerization in liquid propylene, i.e., the liquid phase primarily contains propylene with a small amount of other reactants and, possibly, inert components dissolved therein. Preferably, the prepolymerization is carried out in a continuous reactor with mechanical stirring or in a loop reactor.

The prepolymerization reaction is usually carried out at a temperature of from 0 to 40°C, preferably from 10 to 30°C, and more preferably from 15 to 25°C.

The pressure in the prepolymerization reactor is not critical, but it must be high enough to maintain the reaction mixture in the liquid phase. Therefore, the pressure can range from 20 to 100 bar (2 to 10 MPa), for example, from 30 to 70 bar (3 to 7 MPa).

The reaction conditions are well known in the art and are disclosed, inter alia, in GB 1580635.

At the pre-polymerization stage, comonomers can also be fed to the pre-polymerization stage.

On average, the amount of prepolymer on the catalyst is preferably from 10 to 1000 g per g of solid catalyst component, more preferably from 50 to 500 g per g of solid catalyst component.

As is known to those skilled in the art, not all catalyst particles removed from a continuous mechanically stirred prepolymerization reactor contain the same amount of prepolymer. Instead, each particle has its own characteristic amount, which depends on the residence time of that particle in the prepolymerization reactor. Since some particles remain in the reactor for a relatively long time, and some for a relatively short time, the amount of prepolymer on different particles also varies, and some individual particles may contain an amount of prepolymer that exceeds the above limits. However, the average amount of prepolymer on the catalyst is preferably within the limits specified above. The amount of prepolymer is known in the art, inter alia, from GB 1 580 635.

Other components can also be added during the prepolymerization stage. Thus, hydrogen can be added during the prepolymerization stage to control the molecular weight of the prepolymer, as is known in the art. Furthermore, an antistatic additive can be used to prevent particles from sticking to each other or to the reactor walls, as described in WO-A-00/66640.

Polymerization in the first polymerization zone can be carried out in suspension. The polymer particles formed during polymerization, along with the fragmented and dispersed catalyst within the particles, are then suspended in a liquid hydrocarbon. The suspension is agitated to ensure the transfer of reactants from the fluid to the particles.

Slurry polymerization is preferably so-called bulk polymerization. "Bulk polymerization" refers to a process in which polymerization is carried out in liquid monomer, essentially in the absence of an inert diluent. However, as is known to those skilled in the art, monomers used in industrial production are never pure, but always contain aliphatic hydrocarbons as impurities. For example, propylene monomer can contain up to 5% propane as an impurity. Since propylene is consumed in the reaction and also recycled from the reaction stream back into the polymerization, inert components tend to accumulate, and thus the reaction medium can contain up to 40% by weight of compounds other than the monomer. However, it should be understood that such a polymerization process still falls within the scope of the term "bulk polymerization" defined above.

The temperature of the suspension polymerization is typically from 50 to 110°C, preferably from 60 to 100°C, and in particular from 65 to 95°C. The pressure is from 1 to 150 bar (0.1 to 15 MPa), preferably from 10 to 100 bar (1 to 10 MPa). In some cases, it may be preferable to carry out the polymerization at a temperature that is above the critical temperature of the mixture of fluids constituting the reaction phase and at a pressure that is above the critical pressure of said mixture of fluids. Such reaction conditions are often referred to as "supercritical conditions." The phrase "supercritical fluid" is used to designate a fluid or mixture of fluids at a temperature and pressure that exceeds the critical temperature and pressure of said fluid or mixture of fluids.

Slurry polymerization can be carried out in any known reactor used for slurry polymerization. Such reactors include continuous stirred tank reactors and loop reactors. It is particularly preferred to carry out the polymerization in a loop reactor. In such reactors, the slurry is circulated at high velocity through a closed tube using a circulation pump. Loop reactors are generally known in the art, and examples are given, for example, in US-A-4,582,816, US-A-3,405,109, US-A-3,324,093, EP-A-479,186, and US-A-5,391,654.

The slurry can be withdrawn from the reactor either continuously or intermittently. A preferred method for intermittent withdrawal is the use of sedimentation columns, which allow the solids concentration of the slurry to increase before the concentrated slurry batch is withdrawn from the reactor. The use of sedimentation columns is disclosed, inter alia, in US-A-3,374,211, US-A-3,242,150 and EP-A-1,310,295. Continuous withdrawal is disclosed, inter alia, in EP-A-891,990, EP-A-1,415,999, EP-A-1,591,460 and EP-A-1,860,125. Continuous withdrawal can be combined with a suitable concentration method, as described in EP-A-1,860,125 and EP-A-1,591,460. Other components can also be introduced into the slurry polymerization stage, as is known in the art.

Technological additives can also be introduced into the reactor to facilitate stable operation of the method.

When a slurry polymerization stage is followed by a gas-phase polymerization stage, it is preferable to feed the slurry directly into the gas-phase polymerization zone without a flash stage between stages. This type of direct feed is described in EP-A-887379, EP-A-887380, EP-A-887381, and EP-A-991684.

The propylene copolymer (A) obtained by the multi-stage process can be extruded and pelletized, and then mixed with the ethylene copolymer (B) in pellet form. The propylene copolymer (A) obtained by the multi-stage process can also be mixed with the ethylene copolymer (B) in powder form.

The ethylene copolymer (B) is preferably polymerized in the presence of a single site catalyst system as described above.

The ethylene copolymer (B) can be obtained in any suitable polymerization process known in the art that includes at least one polymerization stage, where the polymerization is typically carried out in solution, suspension, bulk, or gas phase. Preferably, the ethylene copolymer (B) is obtained in a multi-stage polymerization process that includes at least two polymerization zones.

The first ethylene polymer component is preferably produced in the first polymerization zone, and the second ethylene polymer component is preferably produced in the second polymerization zone. The first polymerization zone and the second polymerization zone may be connected in any order, i.e., the first polymerization zone may precede the second polymerization zone, or the second polymerization zone may precede the first polymerization zone, or, alternatively, the polymerization zones may be connected in parallel. However, it is preferable to operate the polymerization zones in a cascade mode. The polymerization zones may operate under slurry, solution, or gas phase conditions, or combinations thereof.

Suitable processes comprising cascaded slurry and gas phase polymerisation steps are disclosed in, inter alia, WO-A-92/12182 and WO-A-96/18662.

It is often preferable to remove reactants from the previous polymerization stage from the polymer before introducing it into the subsequent polymerization stage. This is preferably done when transferring the polymer from one polymerization stage to another.

The catalyst can be transferred to the polymerization zone by any means known in the art. For example, the catalyst can be suspended in a diluent and maintained as a homogeneous slurry, mixed with a viscous mixture of lubricant and oil and fed into the polymerization zone, or the catalyst can be allowed to settle and the resulting catalyst slurry can be added to the polymerization zone in portions. Polymerization in the first polymerization zone is preferably carried out in suspension. The polymer particles formed during polymerization, along with the catalyst fragmented and dispersed within the particles, are then suspended in a liquid hydrocarbon. The suspension is agitated to ensure the transfer of reactants from the fluid to the particles.

Polymerization typically occurs in an inert diluent, typically a hydrocarbon diluent such as methane, ethane, propane, n-butane, isobutane, pentanes, hexanes, heptanes, octanes, etc., or mixtures thereof. Preferably, the diluent is a low-boiling hydrocarbon having from 1 to 4 carbon atoms, or a mixture of such hydrocarbons, and propane is the preferred diluent.

The ethylene content in the fluid phase of the suspension may be from 2 to about 50 mol.%, preferably from about 2 to about 20 mol.% and, in particular, from about 3 to about 12 mol.%.

The suspension polymerization temperature is typically from 50 to 115°C, preferably from 60 to 110°C and in particular from 70 to 100°C. The pressure is from 1 to 150 bar (0.1 to 15 MPa), preferably from 10 to 100 bar (1 to 10 MPa).

Suspension polymerization can be carried out in any known reactor used for suspension polymerization.

Such reactors include continuous stirred tank reactors and loop reactors. It is particularly preferred to conduct polymerization in a loop reactor. In such reactors, the slurry is circulated at high velocity through a closed tube using a circulation pump. Loop reactors are generally known in the art, and examples are given, for example, in US-A-4,582,816, US-A-3,405,109, US-A-3,324,093, EP-A-479,186, and US-A-5,391,654.

It is sometimes advantageous to carry out suspension polymerization at a temperature and pressure of the fluid mixture above the critical temperature and pressure. Such an operation is described in US-A-5,391,654. In such an operation, the temperature is typically from 85 to 110°C, preferably from 90 to 105°C, and the pressure is from 30 to 150 bar (3 to 15 MPa), preferably from 50 to 100 bar (5 to 10 MPa).

The suspension can be withdrawn from the reactor either continuously or intermittently. The preferred method for intermittent withdrawal is the use of sedimentation columns, which allow the suspension to be concentrated before the batch of concentrated suspension is withdrawn from the reactor. Continuous withdrawal is advantageously combined with a suitable concentration method, such as that disclosed in EP-A-1310295 and EP-A-1591460.

Hydrogen can be fed into the reactor to control the polymer molecular weight, as is known in the art. Additionally, 1-butene and/or 1-hexene, for example, can be added to the reactor to control the density of the polymer product. The actual amount of hydrogen and 1-butene and/or 1-hexene fed depends on the catalyst used and the desired melt flow rate (or molecular weight) and density (or comonomer content) of the resulting polymer.

The polymerization in the second polymerization zone is preferably carried out in the gas phase, preferably in a fluidized bed reactor, a fast fluidized bed reactor, or a packed bed reactor, or any combination thereof. The polymerization in the second polymerization zone is more preferably carried out in a gas-phase fluidized bed reactor, in which ethylene is polymerized together with 1-butene and/or 1-hexene in the presence of a polymerization catalyst and, preferably, in the presence of the reaction mixture from the first polymerization zone in an ascending gas flow. The reactor typically comprises a fluidized bed comprising growing polymer particles containing an active catalyst located above a fluidization grid. The polymer bed is fluidized using a fluidizing gas containing an olefin monomer, possible comonomer(s), possible chain growth regulators or chain transfer agents such as hydrogen, and a possible inert gas. A fluidizing gas is introduced into the inlet chamber at the bottom of the reactor. One or more of the above components can be continuously added to the fluidizing gas to compensate for losses caused by, among other things, the reaction or product rejection. The fluidizing gas passes through the fluidized bed. The superficial velocity of the fluidizing gas must be higher than the minimum fluidization velocity of the particles contained in the bed, otherwise fluidization will not occur. Conversely, the gas velocity must be lower than the initial pneumatic transport velocity, otherwise the entire bed will be entrained in the fluidizing gas. When the fluidizing gas contacts the bed containing the active catalyst, reactive components of the gas, such as monomers and chain transfer agents, react in the presence of the catalyst to form the polymer product. At the same time, the gas is heated by the heat of reaction.

Unreacted fluidizing gas is removed from the top of the reactor and cooled in a heat exchanger to remove the heat of reaction. The gas is cooled to a temperature below the bed temperature to prevent the bed from heating up due to the reaction. The gas can also be cooled to a temperature at which some of it condenses. When liquid droplets enter the reaction zone, they evaporate. The heat of evaporation then contributes to the removal of the heat of reaction. This type of operation is called the condensed mode, and variations of it are disclosed, among other things, in WO-A-2007/025640, USA-4543399, EP-A-699213, and WO-A-94/25495. It is also possible to add condensing agents to the recycle gas stream, as described in EP-A-696293. Condensing agents are non-polymerizing components such as n-pentane, isopentane, n-butane or isobutane that are at least partially condensed in the refrigerator.

The gas is then compressed and returned to the reactor inlet chamber. Before entering the reactor, fresh reactants are added to the fluidizing gas stream to compensate for losses caused by the reaction and product removal. As is common knowledge, the composition of the fluidizing gas is analyzed, and gas components are added to maintain a constant composition. The actual composition is determined by the desired properties of the product and the catalyst used in the polymerization.

The catalyst can be introduced into the reactor in various ways, either continuously or intermittently. If the gas-phase reactor is part of a reactor cascade, the catalyst is typically dispersed within the polymer particles from the preceding polymerization stage. The polymer particles can be introduced into the gas-phase reactor as described in EP-A-1415999 and WO-A-00/26258. In particular, if the preceding reactor is a slurry reactor, feeding the slurry directly into the fluidized bed of the gas-phase reactor, as described in EP-A-887379, EP-A-887380, EP-A-887381 and EP-A-991684, is advantageous.

The polymer product can be withdrawn from the gas-phase reactor either continuously or intermittently. A combination of these methods can also be used. Continuous withdrawal is disclosed, inter alia, in WO-A-00/29452. Intermittent withdrawal is disclosed, inter alia, in US-A-4621952, EP-A-188125, EP-A-250169, and EP-A-579426.

If necessary, antistatic agents such as water, ketones, aldehydes, and alcohols can also be added to the gas-phase reactor. The reactor can also include a mechanical stirrer to further facilitate mixing in the fluidized bed. Typically, the fluidized bed polymerization reactor operates at a temperature in the range of 50 to 100°C, preferably 65 to 90°C. Suitable pressures range from 10 to 40 bar (1 to 4 MPa), preferably 15 to 30 bar (1.5 to 3 MPa).

The polymerization of the first ethylene polymer component and the second ethylene polymer component in the first and second polymerization zones may be preceded by a prepolymerization step. The purpose of prepolymerization is to polymerize a small amount of polymer on the catalyst at low temperatures and/or low monomer concentrations. Prepolymerization can improve the performance of the catalyst in suspension and/or alter the properties of the final polymer.

The prepolymerization step can be carried out in suspension or in the gas phase. Preferably, the prepolymerization is carried out in suspension, preferably in a loop reactor. In this case, the prepolymerization is preferably carried out in an inert diluent, preferably a low-boiling hydrocarbon having from 1 to 4 carbon atoms, or a mixture of such hydrocarbons.

The temperature in the pre-polymerization step is usually from 0 to 90°C, preferably from 20 to 80°C, and more preferably from 25 to 70°C.

The pressure is not critical and is usually between 1 and 150 bar (0.1 and 15 MPa), preferably between 10 and 100 bar (1 and 10 MPa).

All catalyst components are preferably introduced at the pre-polymerization stage.

Preferably, the reaction product of the pre-polymerization stage is then introduced into the first polymerization zone.

Ethylene copolymer (B) obtained by a multi-stage process can be extruded and pelletized, and then mixed with propylene copolymer (A) in pellet form. Ethylene copolymer (B) obtained by a multi-stage process can also be mixed with propylene copolymer (A) in powder form.

Extrusion can be carried out using methods well known in the art, preferably in a twin-screw extruder. One example of a suitable twin-screw extruder is a co-rotating twin-screw extruder. These are manufactured by, among others, Coperion and Japan Steel Works. Another example is a counter-rotating twin-screw extruder. Such extruders are manufactured by, among others, Kobe Steel and Japan Steel Works. Extruders typically include a melting section, in which the polymer is melted, and a mixing section, in which the polymer melt is homogenized. Melting and homogenization are achieved by supplying energy to the polymer. The more energy supplied to the polymer, the better the homogenization effect. However, supplying too much energy leads to polymer degradation and deterioration of mechanical properties. A suitable specific energy input (SEI) level is from about 200 to about 450 kWh/t polymer, preferably from 240 to 350 kWh/t.

The typical average residence time of a polymer in an extruder ranges from approximately 30 seconds to approximately 10 minutes. This value varies somewhat depending on the extruder type. However, for most extruder types, values between 1 minute and 5 minutes provide a good balance of polymer homogeneity and mechanical properties.

Suitable extrusion methods are described, inter alia, in EP-A-1 600 276 and WO-A-98/15591.

Before extrusion, desired additives are mixed with the polymers.

Application

In another aspect, the present invention relates to the use of a polypropylene composition having a melt flow index MFI ₂ of 0.1 to 1.0 g/10 min, determined according to ISO 1133 under a load of 2.16 kg and a temperature of 230°C, and comprising

(A) from 70 to 95 wt. %, based on the total weight of the polypropylene composition, of a copolymer of propylene with comonomer units derived from 1-butene or 1-hexene, having

- total comonomer content from 0.5 to 5.0 mass %;

- melt flow index MFI ₂ from 0.10 to 2.0 g/10 min, determined according to ISO 1133 under a load of 2.16 kg and a temperature of 230°C, and

- the ratio of the average molecular weight to the average number molecular weight Mw/Mn from 2.5 to 6.0, determined by gel permeation chromatography (GPC) in accordance with ISO 16014-4:2003 and ASTM D 6474-99, and

(B) from 5 to 30 wt. %, based on the total weight of the polypropylene composition, of a copolymer of ethylene with comonomer units obtained from 1-butene and/or 1-hexene, having

- total comonomer content from 1.0 to 25.0 mass %;

- density from 910.0 to 940.0 kg/ ^m3 , determined according to ISO 1183, and

- melt flow index MFI ₂ from 0.05 to 3.0 g/10 min, determined according to ISO 1133 at a load of 2.16 kg and a temperature of 190°C,

to obtain a pipe.

All aspects of the polypropylene composition and pipe described above or below are also relevant in the case of application according to the invention.

The present composition is further illustrated by means of examples.

Examples

1. Methods of determination

The following definitions of terms and definition methods apply to the above general description of the invention, as well as to the examples given below, unless otherwise indicated.

Quantitative determination of the microstructure of copolymers by NMR spectroscopy

Determination of comonomer

Content of 1-hexene in copolymers of propylene and 1-hexene

Quantitative ^13C { ^1H } NMR spectra were recorded in the molten state using a Bruker Avance III 500 NMR spectrometer operating at 500.13 and 125.76 MHz for ^1H and ^13C , respectively. All spectra were recorded using a ^13C -optimized 7 mm magic angle spinning (MAS) probe at 180°C using nitrogen gas for all pneumatic systems. Approximately 200 mg of material was placed in a 7 mm OD zirconia MAS rotor and spun at 4 kHz. This setup was chosen primarily due to the high sensitivity required for rapid identification and accurate quantification. (Klimke, K., Parkinson, M., Piel, S., Kaminsky, W., Spiess, HW, Wilhelm, M., Macromol. Chem. Phys. 2006;207:382., Parkinson, M., Klimke, K., Spiess, HW, Wilhelm, M., Macromol. Chem. Phys. 2007;208:2128., Castignolles, P., Graf, R., Parkinson, M., Wilhelm, M., Gaborieau, M., Polymer 50 (2009) 2373). Standard single-pulse excitation was used using the nuclear Overhauser effect (NOE) with short recirculation delays of 3 s (Klimke, K., Parkinson, M., Piel, C, Kaminsky, W., Spiess, HW, Wilhelm, M., Macromol. Chem. Phys. 2006;207:382, Pollard, M., Klimke, K., Graf, R., Spiess, HW, Wilhelm, M., Sperber, O., Piel, C, Kaminsky, W., Macromolecules 2004;37:813) and the RS-HEPT decoupling scheme (Filip, X., Tripon, C, Filip, C, J. Mag. Resn. 2005, 176, 239, Griffin, J.M., Tripon, C, Samoson, A., Filip, C, and Brown, SP, Mag. Res. in Chem. 2007 45, S1, S198). A total of 16384 (16k) transitions were recorded in each spectrum.

Quantitative ^13C { ^1H } NMR spectra were processed, integrated, and the corresponding quantitative properties were determined from the integrals. All chemical shifts were internally referenced to the methyl isotactic pentad (mmmm) at 21.85 ppm.

The characteristic signals corresponding to the incorporation of 1-hexene were observed and the comonomer content was quantified as follows.

The amount of 1-hexene incorporated into isolated RNR sequences was quantified using the αB4 site integral at 44.2 ppm, taking into account the number of informative sites per comonomer:

H=I _αB4 /2

The amount of 1-hexene incorporated twice in a row in the PHHP sequence was quantified using the integral of the ααB4 site at 41.7 ppm, taking into account the number of informative sites per comonomer:

НН=2 * I _ααB4

When double sequential incorporation was observed, the amount of 1-hexene incorporated into isolated RNR sequences had to be compensated for due to the overlap of the αB4 and αB4B4 signals at 44.4 ppm:

H=(I _αВ4 -2*I _ααВ4 )/2

The total content of 1-hexene was calculated from the sum of isolated and sequentially introduced 1-hexene:

H _total = H + HH

When no areas indicating sequential incorporation were observed, the total 1-hexene comonomer content was calculated solely based on this amount:

H _total = H

Characteristic signals indicative of 2,1-erythro regiodefects were observed (Resconi, L., Cavallo, L., Fait, A., Piemontesi, F., Chem. Rev. 2000, 100, 1253).

The presence of 2,1-erythro regiodefects was indicated by the presence of methyl sites Pαβ (21e8) and Pαγ (21e6) at 17.7 and 17.2 parts per million, which was confirmed by other characteristic signals.

The total amount of secondary (2,1-erythro)propene insertion was quantified based on the methylene site of αα21e9 at 42.4 ppm:

P21=I _αα21e9

The total amount of primary (1,2) incorporated propene was quantified based on the Sαα major methylene sites at 46.7 ppm and compensation for the relative amount of 2,1-erythro, αB4, and ααB4B4 methylene propene units that were not accounted for (note: the number of H and HH hexene monomers is counted per sequence, not the number of sequences):

P12=I _sαα +2*P21+Н+НН/2

The total amount of propene was quantified as the sum of primary (1,2) and secondary (2,1-erythro) incorporated propene:

P _total =P ₁₂ +P ₂₁ =I _Sαα +3*I _αα21e9 +(I _αB4 -2*I _ααB4 )/2+I _ααB4

This expression simplifies to:

P _total =I _Sαα +3*I _αα21e9 +0.5*I _αB4

The total mole fraction of 1-hexene in the polymer was then calculated as:

f _H = H _total / (H _total + P _total )

The complete integral equation for the mole fraction of 1-hexene in the polymer:

f _Н =(((I _αB4 -2*I _ααB4 )/2)+(2*I _ααB4 ))/((I _Sαα +3*I _αα21e9 +0.5*I _αB4 )+((I _αB4 -2*I _ααB4 )/2)+(2*I _ααB4 ))

This expression simplifies to:

f _Н =(I _αB4 /2+I _ααB4 )/(I _Sαα +3*I _αα21e9 +I _αВ4 +I _ααВ4 )

The total amount of incorporated 1-hexene comonomer in mole percent was calculated from the mole fraction in the usual way:

H [mol.%]=100*f _H

The total amount of incorporated 1-hexene comonomer in mass percent was calculated from the mole fraction in the standard manner:

N [mass. %]=100*(f _N * 84.16)/((f _N *84.16)+((1-f _N )*42.08))

Content of comonomers 1-butene and 1-hexene in linear low density polyethylene (LLDPE)

Quantitative ^13C { ^1H } NMR spectra were recorded in the molten state using a Bruker Avance III 500 NMR spectrometer operating at 500.13 and 125.76 MHz for ^1H and ^13C , respectively. All spectra were recorded using a 7 mm magic angle spinning (MAS) probe optimized for ^13C at 150°C using nitrogen gas for all pneumatic systems.

Approximately 200 mg of material was placed in a 7 mm OD zirconia MAS rotor and spun at 4 kHz. This setup was chosen primarily because of the high sensitivity required for rapid identification and accurate quantification. (Klimke, K., Parkinson, M., Piel, C., Kaminsky, W., Spiess, H.W., Wilhelm, M., Macromol. Chem. Phys. 2006;207:382., Parkinson, M., Klimke, K., Spiess, H.W., Wilhelm, M., Macromol. Chem. Phys. 2007;208:2128., Castignolles, P., Graf, R., Parkinson, M., Wilhelm, M., Gaborieau, M., Polymer 50 (2009) 2373). Standard single-pulse excitation was used using a NEO with short recirculation delays of 3 s (Pollard, M., Klimke, K., Graf, R., Spiess, H.W., Wilhelm, M., Sperber, O., Piel, C, Kaminsky, W., Macromolecules 2004;37:813., Klimke, K., Parkinson, M., Piel, C, Kaminsky, W., Spiess, H.W., Wilhelm, M., Macromol. Chem. Phys. 2006;207:382.) and an RS-HEPT decoupling scheme (Filip, X., Tripon, C, Filip, C, J. Mag. Resn. 2005, 176, 239, Griffin, J.M., Tripon, C, Samoson, A., Filip, C, and Brown, S.P., Mag. Res. in Chem. 2007 45, S1, S198). A total of 1024 (1k) transitions were recorded in each spectrum. This setup was chosen because of its high sensitivity to low comonomer content.

Quantitative ^13C { ^1H } NMR spectra were processed, integrated, and the corresponding quantitative properties were determined using specialized spectral analysis automation programs. All chemical shifts were internally referenced to the bulk methylene signal (δ+) at 30.00 ppm (J. Randall, Macromol. Sci., Rev. Macromol. Chem. Phys. 1989, C29, 201). The amount of ethylene was determined using the integral of the methylene (δ+) sites at 30.00 ppm, taking into account the number of informative sites per monomer:

E=I _δ+ /2

the presence of isolated comonomer units was corrected based on the number of isolated comonomer units present:

E _total =E+(3*B+2*H)/2,

where B and H were determined for their respective comonomers. Correction for sequential and non-sequential comonomer incorporation, if present, was performed in a similar manner.

Characteristic signals corresponding to the incorporation of 1-butene (J. Randall, Macromol. Sci., Rev. Macromol. Chem. Phys. 1989, C29, 201) were observed and quantified relative to all other monomers present in the polymer.

The amount of isolated 1-butene incorporated into the EEBEE sequences was quantified using the *B2 site integral at 38.3 ppm, taking into account the number of informative sites per comonomer:

B=I _*B2

The amount of 1-butene incorporated sequentially in the EEBBEE sequence was quantified using the ααB2 B2 site integral at 39.4 ppm, taking into account the number of informative sites per comonomer:

ВВ=2*I _ααВ2В2

The amount of 1-butene non-sequentially incorporated into the EEBEE sequences was quantified using the ββB2B2 site integral at 24.7 ppm, taking into account the number of informative sites per comonomer:

BEV=2*I _ββB2B2

Due to the overlap of the *B2 and *βB2B2 regions of isolated (EEBEE) and non-sequentially introduced (EEBEE) 1-butene, respectively, the total amount of isolated introduction of 1-butene is adjusted based on the amount of non-sequentially introduced 1-butene present:

B=I _*B2 -2*I _ββB2B2

The total content of 1-butene was calculated based on the sum of isolated, sequentially and non-sequentially introduced 1-butene:

In _total = B+BB+VEV

The total mole fraction of 1-butene in the polymer was then calculated as follows:

f _B =(V _total )/(E _total +V _total +N _total )

Characteristic signals corresponding to the incorporation of 1-hexene were observed (J. Randall, Macromol. Sci., Rev. Macromol. Chem. Phys. 1989, C29, 201), and all contents were calculated relative to all other monomers present in the polymer.

The amount of isolated 1-hexene incorporated into isolated EEE sequences was quantified using the *B4 site integral at 39.9 ppm, taking into account the number of informative sites per comonomer:

H=I _*B4

The amount of 1-hexene incorporated sequentially in the EENHEE sequence was quantified using the ααB4B4 site integral at 40.5 ppm, taking into account the number of informative sites per comonomer:

НН=2*I _ααВ4В4

The amount of non-sequentially incorporated 1-hexene in the EENENEE sequence was quantified using the ββB4B4 site integral at 24.7 ppm, taking into account the number of informative sites per comonomer:

HEN=2*I _ββB4B4

Due to the overlap of the ββB2B2 sections of non-sequentially introduced (EEBEEEE) 1-butene and the ββB4B4 sections of non-sequentially introduced (EENEEE) 1-hexene, the total amount of non-sequentially introduced (EEBEEEE) 1-butene was assumed to be proportional to the amount of isolated inclusion of 1-butene (B) and the total amount of non-sequentially introduced (EENEEE) 1-hexene was assumed to be proportional to the amount of isolated 1-hexene (H).

The total mole fraction of 1-hexene in the polymer was then calculated as:

f _N =(N _total )/(E _total +B _total +N _total )

The molar percentage of incorporated comonomers was calculated based on the molar fractions:

B [mol.%]=100*f _B

H [mol.%]=100*f _H

The mass percentage of incorporated comonomers was calculated based on mole fractions:

B [mass %] = 100*(f _B * 56.11)/((f _B * 56.11)+(f _H *84.16)+((1-(f _B +f _H ))*28.05))

H [wt. %]=100*(f _H *84.16)/((f _B *56.11)+(f _H *84.16)+((1-(f _B +f _H ))*28.05))

Melt flow index (MFI)

The melt flow rate (MFR) or melt index (MI) is measured according to ISO 1133. If different loads can be used, the load is usually indicated as a subscript, for example, MFR ₂ , which indicates a load of 2.16 kg. The temperature is selected according to ISO 1133 for a specific polymer, for example, 230°C for polypropylene and 190°C for polyethylene. Thus, for polypropylene, MFR ₂ is measured at a temperature of 230°C and a load of 2.16 kg, and for polyethylene, MFR ₂ is measured at a temperature of 190°C and a load of 2.16 kg.

Density

Density is measured according to ISO 1183-187. Samples are prepared by pressing in accordance with ISO 1872-2:2007.

Analytical Temperature Elevated Elution Fractionation (TREF) obtained by Cross-Fraction Chromatography (CFC) The chemical composition distribution as well as the determination of the molecular weight distribution and the corresponding average molecular weights (Mn, Mw and Mv) at a specific elution temperature (polymer crystallinity in solution) were determined by fully automated Cross-Fraction Chromatography (CFC) as described in Ortin A., Monrabal B., Sancho-Tello J., Macromol. Symp., 2007, 257, 13-28.

A CFC instrument (PolymerChar, Valencia, Spain) was used to perform cross-fraction chromatography (TREFxSEC). A four-band infrared detector IR5 (PolymerChar, Valencia, Spain) was used to monitor the concentration. Approximately 40 mg of the polymer sample was dissolved in 25 mL of trichlorobenzene (TCB) in a stainless steel vessel for 150 minutes at 150°C. After complete sample dissolution, a 0.5 mL aliquot was loaded onto the TREF column and stabilized for some time at 110°C. The polymer crystallized at 30°C and precipitated using a constant cooling rate of 0.1°C/min. The batch elution method is carried out using the following temperature stages: (30, 40, 50, 60, 70, 75, 80, 84, 88, 92, 95, 98, 100, 102, 104, 106, 108, 110, 115, 120, 130 and 140).

In the second dimension, GPC/SEC analysis, three PL Olexis columns and one Olexis Guard column from Agilent (Church Stretton, UK) were used as the stationary phase. The eluent was 1,2,4-trichlorobenzene (TCB, stabilized with 250 mg/L 2,6-di-tert-butyl-4-methylphenol) at 150°C and a constant flow rate of 1 mL/min. The column set was calibrated using a universal calibration (according to ISO 16014-2:2003) with at least 15 narrow molecular weight distribution (MWD) polystyrene (PS) standards ranging from 0.5 kg/mol to 11,500 kg/mol. The following Mark Houwink constants were used to convert PS molecular weights to PP molecular weight equivalents.

K _PS =19×10 ^-3 ml/g, α _PS =0.655

K _PP =19×10 ^-3 ml/g, α _PP =0.725

A third-order polynomial fit was used to approximate the calibration data. Data processing was performed using PolymerChar software with a CFC instrument.

Determination of the polymer fraction eluted at temperatures from 31 to 80°C and logM from 4.5 to 6.0

The polymer fraction eluted at a temperature of 31 to 80°C and a molecular weight logM of 4.5 to 6 is calculated as follows, based on the CFC data:

The polymer fraction eluted at 30°C in the batch elution method (see above) is considered as a purge fraction and is not included in the above calculation, which starts at 31°C.

GPC: Average molecular weights, molecular weight distribution and polydispersity index (Mn, Mw, Mw/Mn)

Average molecular weights (Mw, Mn), molecular weight distribution (MWD) and its width described by the polydispersity index, PDI=Mw/Mn (where Mn is the number average molecular weight and Mw is the weight average molecular weight), were determined by gel permeation chromatography (GPC) according to ISO 16014-4:2003 and ASTM D 6474-99.

A PolymerChar GPC instrument equipped with an infrared (IR) detector, three Olexis columns and one Olexis Guard column from Polymer Laboratories, and 1,2,4-trichlorobenzene (TCB, stabilized with 250 mg/L 2,6-di-tert-butyl-4-methylphenol) as a solvent were used at 160°C and a constant flow rate of 1 mL/min. For each analysis, 200 μL of sample solution were injected. The column set was calibrated using a universal calibration (according to ISO 16014-2:2003) with at least 15 polystyrene (PS) standards with a narrow MWD ranging from 0.5 kg/mol to 11,500 kg/mol. The Mark Houwink constants for the PS, PE, and PP used correspond to those described in ASTM D 6474-99. All samples were prepared by dissolving 5.0–9.0 mg of polymer in 8 ml (at 160°C) of stabilized TCB (the same as the mobile phase) for 2.5 hours for PP or 3 hours for PE at a maximum temperature of 160°C with continuous gentle shaking in the automatic sampler of the GPC/SEC instrument.

DSC analysis, melting point (Tm) and crystallization temperature (Tcr): were measured using a TA Instrument Q2000 differential scanning calorimetry (DSC) instrument on samples weighing from 5 to 7 mg. DSC was carried out in accordance with ISO 11357/part 3/method C2 using a heating/cooling/heating cycle at a scanning rate of 10°C/min over a temperature range of -30 to +225°C.

The crystallization temperature (Tcr) and the heat of crystallization (Hcr) are determined at the cooling stage, while the melting temperature (Tm) and the heat of melting (Hm) are determined at the second heating stage.

Xylene Soluble Substances (XSS) The xylene soluble substances (XSS) fraction, as defined and described in the present invention, is determined according to ISO 16152 as follows: 2.0 g of polymer was dissolved in 250 ml of p-xylene at 135°C with stirring. After 30 minutes, the solution was allowed to cool for 15 minutes at ambient temperature and then allowed to settle for 30 minutes at 25±0.5°C. The solution was filtered through filter paper into two 100 ml flasks. The solution from the first 100 ml vessel was evaporated under a stream of nitrogen and the residue was dried in a vacuum at 90°C until constant weight was achieved. The xylene soluble substances fraction (as a percentage) can then be determined as follows:

RQV [%]=(100⋅m⋅V ₀ )/(m ₀ ⋅V); m0 = initial amount of polymer [g]; m = mass of residue [g]; V ₀ = initial volume [ml]; V = volume of analyzed sample [ml].

Determination of Al and Zr (ICP method)

Elemental analysis of the catalyst was performed by collecting a solid sample of mass M and cooling it with dry ice. The samples were diluted to a known volume V by dissolving in nitric acid ( _HNO3 , 65%, 5% of V) and freshly prepared deionized (DI) water (5% of V). The solution was then added to hydrofluoric acid (HF, 40%, 3% of V), diluted with DI water to a final volume V, and left to stabilize for two hours.

The analysis was carried out at room temperature using a Thermo Elemental iCAP 6300 inductively coupled plasma-optical emission spectrometer (ICP-OES), which was calibrated using a blank (5% _HNO3 , 3% HF in DI water) and 6 standards of 0.5 ppm, 1 ppm, 10 ppm, 50 ppm, 100 ppm, and 300 ppm Al with 0.5 ppm, 1 ppm, 5 ppm, 20 ppm, 50 ppm, and 100 ppm Hf and Zr in ₅ % HNO3, 3% HF in DI water.

Immediately prior to analysis, recalibration is performed using a blank sample and a standard of 100 ppm Al, 50 ppm Hf, and Zr. A control sample (20 ppm Al, 5 ppm Hf, and Zr in a solution of 5% HNO3 and ₃ % HF in deionized water) is run to confirm recalibration. A QC sample (control sample) is also run after every fifth sample and at the end of the planned set of analyses.

Hafnium content was monitored at 282.022 nm and 339.980 nm, while zirconium content was monitored at 339.198 nm. Aluminum content was monitored at 167.079 nm when the Al concentration in the ICP sample was between 0 and 10 ppm (calibrated only to 100 ppm), and at 396.152 nm when the Al concentration was above 10 ppm.

The values obtained are the average of three consecutive aliquots taken from the same sample and are related to the original catalyst by entering the original sample mass and dilution volume into the software.

When analyzing the elemental composition of prepolymerized catalysts, the polymer portion is cleaved by ashing so that the elements can be freely dissolved by acids. The total content is calculated as the corresponding mass % of the prepolymerized catalyst.

Catalyst activity

The catalyst activity was calculated based on the following formula:

Performance

The overall performance was calculated as follows:

For both catalytic activity and productivity, catalyst loading represents either grams of catalyst after prepolymerization or grams of metallocene present in that amount of catalyst after prepolymerization.

Degree of prepolymerization (DP): weight of polymer/weight of solid catalyst before the prepolymerization step. The catalyst composition (before the offline prepolymerization step) was determined by ICP as described above. The metallocene content of the catalysts after prepolymerization was calculated from the ICP data as follows:

Equation 1

Equation 2

Equation 3

Equation 4

Particle size

Particle size distribution was measured according to ISO 13320-1 using a Coulter LS 200 particle size analyzer. This instrument measures particle size distributions in the range of 0.4–2000 µm. The method utilizes laser diffraction, in which a laser beam is directed at a sample moving in a flow cell. N-heptane was used as the sample fluid.

The polymer sample was first pre-treated by screening out particles larger than 2 mm. The screened sample was mixed with isopropanol and placed in an ultrasonic device to separate the particles. The pre-treated sample was then placed in a sample block and analyzed. The results were calculated using the software included with the device.

The SPAN (also called SPAN) was determined using the following equation (3):

where d ₅₀ (D _v50 ) is the median volume diameter of the particles, d ₉₀ (D _v90 ) is the smallest particle diameter at which 90% of the particles have a diameter smaller than d ₉₀ ; d ₁₀ (D _v10 ) is the smallest particle diameter at which 10% of the particles have a diameter smaller than d ₁₀ .

The following particle size and particle size distribution parameters were used in the experiments:

D _v90 = volumetric amount of particle diameter at 90% of the cumulative size,

D _v10 = volumetric amount of particle diameter at 10% cumulative size,

D _v50 = volumetric amount of particle diameter at 50% cumulative size (median volumetric particle size),

SPAN=(D _v90 -D _v10 )/D _v50 .

Flexural modulus of elasticity

The flexural modulus is determined according to ISO 178. The test specimens have dimensions of 80×10×4.0 ^mm3 (length × width × thickness) and are manufactured by injection moulding according to EN ISO 1873-2. The span between supports is 64 mm, the testing speed is 2 mm/min.

Notched Impact Strength (NIS)

The Charpy notched impact strength (NIS) was measured according to ISO 179 1eA at +23°C using injection moulded test specimens of 80×10×4 ^mm3 dimensions prepared in accordance with EN ISO 1873-2.

Pressure testing of pipes The pressure test performance of pipes made from the inventive composition and the comparative composition was tested in accordance with ISO 1167-1 and -2.

Pipes with a diameter of 32 mm and a wall thickness of 3 mm were produced in accordance with ISO 1167-2 on a conventional pipe extrusion line and then subjected to hoop stresses of 4.6 MPa and 4.9 MPa at a temperature of 95°C in a water-in-water test facility in accordance with ISO 1167-1. The time to failure was recorded in hours, with time values appended with "still working" indicating that the failure time had not yet occurred at the time of filing this patent application.

Impact strength testing of pipes

The Charpy impact strength of the pipe was determined according to ISO 9854-2. Specimens were cut from the pipe (manufacturing details are given below) with dimensions of 50 x 6 x 3 ^mm³ . Testing was conducted at 0°C, with 10 specimens tested each time. The failure mode (failure/no failure) and the number of specimens with each failure mode were recorded.

2. Polymers used in examples

a) Propylene copolymer

Polymerization of propylene copolymer was carried out on a pilot scale using a loop reactor-gas-phase reactor setup.

The polymerization catalyst used for the polymerization of the propylene copolymer was prepared as described in detail in WO 2015/011135 A1 (metallocene complex MC1 with methylaluminoxane (MAO) and borate, to obtain catalyst 3 described in WO 2015/011135 A1), with the proviso that the surfactant is 2,3,3,3-tetrafluoro-2-(1,1,2,2,3,3,3-heptafluoropropoxy)-1-propanol. The metallocene complex (MC1 in WO 2015/011135 A1) was prepared as described in WO 2013/007650 A1 (metallocene E2 in WO 2013/007650 A1).

In all cases, hexene was used as a comonomer, and hexene was fed to both the loop reactor and the gas phase reactor to control the required hexene content in the final product.

The polymerization conditions are shown in Table 1.

b) Ethylene copolymer

The ethylene copolymer used in example IE1 according to the invention is the linear low density polyethylene example IE1 from EP 3 257 895 A1, having a 1-butene content of 0.3 mol% (0.6 wt%), a 1-hexene content of 2.6 mol% (8.1 wt%), a density of 918 kg/ ^m3 and a melt flow index MFI ₂ (190°C, 2.16 kg) of 1.5 g/10 min.

3. Polypropylene composites and pipes

To obtain the polypropylene composition of Comparative Example CE, the propylene copolymer as described above was mixed together with additives (1000 ppm Irganox B215 from BASF, which is a 1:2 mixture of pentaerythrityl tetrakis(3-(3',5'-di-tert-butyl-4-hydroxyphenyl)propionate, CAS No. 6683-19-8, and tris(2,4-di-tert-butylphenyl)phosphite, CAS No. 31570-04-4) and 500 ppm calcium stearate from Baerlocher) in a co-rotating twin screw extruder at 220°C.

To obtain a polypropylene composition according to Example IE of the invention, a propylene copolymer and 15 wt. % of an ethylene copolymer as indicated above are mixed together with additives (1000 ppm of Irganox B215 supplied by BASF, which is a 1:2 mixture of pentaerythrityl tetrakis(3-(3',5'-di-tert-butyl-4-hydroxyphenyl)propionate, CAS No. 6683-19-8, and tris(2,4-di-tert-butylphenyl)phosphite, CAS No. 31570-04-4) and 500 ppm of calcium stearate from Baerlocher) in a co-rotating twin screw extruder at 220°C.

Pipes with a diameter of 32 mm and a wall thickness of 3 mm were produced on a Battenfeld Pro pipe extrusion line. Typical conditions are as follows:

Melting point: 224°C

Productivity: 30 kg/h

Auger rotation speed: 38 rpm.

Cooling water temperature: 20°C

Vacuum spray tank: 0.23 bar (0.023 MPa)

Water flow rate at the calibrator inlet: 4 l/h.

The properties of polypropylene composites and pipes of CE and IE examples are given in Table 2.

Fig. 1 shows the TREF fractogram and the corresponding viscosity-average molecular weight of IE1 and CE1 obtained from CFC analysis.

Fig. 2 shows the CFC contour plot for IE1. The claimed polymer fraction with an elution temperature from 31 to 80°C and a logM from 4.5 to 6 is highlighted by a square.

Fig. 3 shows the CFC contour plot for CE1. The claimed polymer fraction with an elution temperature from 31 to 80°C and a logM from 4.5 to 6 is highlighted by a square.

The pipe according to the invention in Example IE demonstrates a good balance of properties in terms of good surface quality, acceptable pressure resistance, and improved impact toughness. In contrast, the pipe from Comparative Example CE exhibits failure in an impact test at 0°C.

Claims (75)

1. A pipe containing a polypropylene composition, wherein the polypropylene composition contains (A) from 70 to 95 wt. %, based on the total weight of the polypropylene composition, of a copolymer of propylene with comonomer units derived from 1-butene or 1-hexene, having - total comonomer content from 0.5 to 5.0 mass %; - melt flow index MFI ₂ from 0.10 to 2.0 g/10 min, determined according to ISO 1133 under a load of 2.16 kg and a temperature of 230°C, and - the ratio of the average molecular weight to the average number molecular weight Mw/Mn from 2.5 to 6.0, determined by gel permeation chromatography (GPC) according to ISO 16014-4:2003 and ASTM D 6474-99, and (B) from 5 to 30 wt. %, based on the total weight of the polypropylene composition, of a copolymer of ethylene with comonomer units obtained from 1-butene and/or 1-hexene, having - total comonomer content from 1.0 to 25.0 mass %; - density from 910.0 to 940.0 kg/ ^m3 , determined according to ISO 1183, and - melt flow index MFI ₂ from 0.05 to 3.0 g/10 min, determined according to ISO 1133 under a load of 2.16 kg and a temperature of 190°C; wherein the polypropylene composition has a melt flow rate index MFI ₂ from 0.1 to 1.0 g/10 min, determined according to ISO 1133 under a load of 2.16 kg and a temperature of 230°C. 2. A pipe according to claim 1, wherein the polypropylene composition has a polymer fraction eluting at a temperature of 31 to 80°C, excluding the purge fraction, and a logM of 4.5 to 6.0, in an amount of 4 to 25 mass %, determined using cross-fractional chromatography (CFC), and/or a profile containing two peaks on the analytical temperature increasing elution fractionation (TREF) elugram obtained as a result of cross-fractional chromatography (CFC) analysis, where the first peak Tp(1) eluted at a temperature of 45 to 90°C, and the second peak Tp(2) eluted at a temperature of 85 to 100°C. 3. A pipe according to claim 1 or 2, wherein the polypropylene composition has a flexural modulus of 700 to 1000 MPa, determined according to ISO 178 on injection moulded test specimens prepared according to EN ISO 1872-2. 4. A pipe according to any one of claims 1 to 3, wherein the polypropylene composition has a Charpy notched impact strength at 23°C of 7.5 to 15.0 kJ/ ^m2 and/or a Charpy notched impact strength at 0°C of 2.5 to 5.0 kJ/ ^m2 and/or a Charpy notched impact strength at -20°C of 1.5 to 4.0 kJ/ ^m2 , determined according to ISO 179 1eA on test specimens obtained by injection molding and prepared according to EN ISO 1872-2. 5. A pipe according to any one of claims 1 to 4, wherein the polypropylene composition has one or more, preferably all, of the following properties: - content of cold xylene soluble substances (CXS) from 1.0 to 3.5 wt.%, determined according to ISO 16152; - melting point Tm from 135 to 145°C, determined according to ISO 11357/part 3; - crystallization temperature Tcr from 100 to 110°C, determined according to ISO 11357/part 3, and/or - enthalpy of melting Hpl from 30 to 45 J/g, determined according to ISO 11357/part 3. 6. A pipe according to any one of paragraphs 1-5, wherein the propylene copolymer (A) has one or more, preferably all, of the following properties: - content of cold xylene soluble substances (CXS) from 0.2 to 2.5 mass %, determined according to ISO 16152; - melting point Tm from 135 to 145°C, determined according to ISO 11357/part 3; - crystallization temperature Tcr from 100 to 105°C, determined according to ISO 11357/part 3, and/or - enthalpy of melting Hpl from 70 to 80 J/g, determined according to ISO 11357/part 3. 7. A pipe according to any one of paragraphs 1-6, in which the propylene copolymer (A) can be obtained by polymerization in the presence of a single-center catalytic system, wherein the catalytic system comprises: (i) a catalyst having the following structure Where M represents zirconium or hafnium; each X independently represents a sigma-donor ligand; L represents a bridge of the formula -(ER ¹⁰ ₂ ) _y- ; y represents 1 or 2; E represents C or Si; each R ¹⁰ independently represents a C ₁ -C ₂₀ hydrocarbyl group, a tri(C ₁ -C ₂₀ alkyl)silyl group, a C ₆ -C ₂₀ aryl group, a C ₇ -C ₂₀ arylalkyl group or a C ₇ -C ₂₀ alkylaryl group, or L represents an alkylene group such as methylene or ethylene; each R ¹ , independently the same or different from each other, represents a CH ₂ -R ¹¹ group, where R ¹¹ represents H or a linear or branched C ₁ -C ₆ alkyl group, C ₃ -C ₈ cycloalkyl group, C ₆ -C ₁₀ aryl group; each ^R3 , ^R4 and ^R5 , independently the same or different from one another, is H or a linear or branched _C1 - _C6 alkyl group, a _C7 - _C20 arylalkyl group, a _C7 - _C20 alkylaryl group or a _C6 - _C20 aryl group, with the proviso that if in total four or more ^R3 , ^R4 and ^R5 groups other than H are present, one or more of ^R3 , ^R4 and ^R5 are other than a tert-butyl group; each R ⁷ and R ⁸ , independently the same or different from each other, represents H, a CH ₂ -R ¹² group, where R ¹² represents H or a linear or branched C ₁ -C ₆ alkyl group, SiR ¹³ ₃ , GeR ¹³ ₃ , OR ¹³ , SR ¹³ , NR ¹³ ₂ , where R ¹³ represents a linear or branched C ₁ -C ₆ alkyl group, a C ₇ -C ₂₀ alkylaryl group and a C ₇ -C ₂₀ arylalkyl group or a C ₆ -C ₂₀ aryl group, each R ⁹ , independently identical or different, represents H or a linear or branched C ₁ -C ₆ alkyl group, and all R ² and R ⁶ are H, and (ii) a cocatalyst system comprising an aluminoxane cocatalyst. 8. A pipe according to any one of claims 1 to 7, wherein the ethylene copolymer (B) is a terpolymer of ethylene with comonomer units selected from 1-butene and 1-hexene, having a 1-butene content of 0.1 to 5.0 wt.% and a 1-hexene content of 5.0 to 24.9 wt.%. 9. A pipe according to any one of claims 1 to 8, wherein the ethylene copolymer (B) has an intrinsic viscosity iV of 1.5 to 2.5 dl/g, determined according to DIN ISO 1628/1, October 1999 (in decalin at 135°C). 10. A pipe according to any one of claims 1 to 9, wherein the ethylene copolymer (B) can be obtained by polymerization in the presence of a single-site catalyst system. 11. A pipe according to any one of paragraphs 1-10, which is a pressure pipe, preferably a pressure pipe for hot or cold water. 12. A method for producing a pipe according to any of paragraphs 1-11, comprising the steps of: a) polymerization of propylene and 1-butene or 1-hexene in a multi-stage process in the presence of a single-site catalytic system to produce a copolymer (A) of propylene with comonomer units derived from 1-butene or 1-hexene; b) mixing the propylene copolymer (A) with the ethylene copolymer (B) with comonomer units obtained from 1-butene and/or 1-hexene to obtain a polypropylene composition, and c) forming a pipe from a polypropylene composition. 13. The method of claim 12, wherein the multi-stage process is a sequential polymerization process with at least two polymerization reactors connected in series. 14. The method according to claim 12 or 13, wherein the catalytic system comprises: (i) a catalyst having the following structure Where M represents zirconium or hafnium; each X independently represents a sigma-donor ligand; L represents a bridge of the formula -(ER ¹⁰ ₂ ) _y- ; y represents 1 or 2; E represents C or Si; each R ¹⁰ independently represents a C ₁ -C ₂₀ hydrocarbyl group, a tri(C ₁ -C ₂₀ alkyl)silyl group, a C ₆ -C ₂₀ aryl group, a C ₇ -C ₂₀ arylalkyl group or a C ₇ -C ₂₀ alkylaryl group, or L represents an alkylene group such as methylene or ethylene; each R ¹ , independently the same or different from each other, represents a CH ₂ -R ¹¹ group, where R ¹¹ represents H or a linear or branched C ₁ -C ₆ alkyl group, C ₃ -C ₈ cycloalkyl group, C ₆ -C ₁₀ aryl group; each ^R3 , ^R4 and ^R5 , independently the same or different from one another, is H or a linear or branched _C1 - _C6 alkyl group, a _C7 - _C20 arylalkyl group, a _C7 - _C20 alkylaryl group or a _C6 - _C20 aryl group, with the proviso that if in total four or more ^R3 , ^R4 and ^R5 groups other than H are present, one or more of ^R3 , ^R4 and ^R5 are other than a tert-butyl group; each R ⁷ and R ⁸ , independently the same or different from each other, represents H, a CH ₂ -R ¹² group, where R ¹² represents H or a linear or branched C ₁ -C ₆ alkyl group, SiR ¹³ ₃ , GeR ¹³ ₃ , OR ¹³ , SR ¹³ , NR ¹³ ₂ , where R ¹³ represents a linear or branched C ₁ -C ₆ alkyl group, a C ₇ -C ₂₀ alkylaryl group and a C ₇ -C ₂₀ arylalkyl group or a C ₆ -C ₂₀ aryl group, each R ⁹ , independently identical or different, represents H or a linear or branched C ₁ -C ₆ alkyl group, and all R ² and R ⁶ are H, and (ii) a cocatalyst system comprising an aluminoxane cocatalyst. 15. The use of a polypropylene composition having a melt flow index MFI ₂ from 0.1 to 1.0 g/10 min, determined according to ISO 1133 under a load of 2.16 kg and a temperature of 230°C, and including (A) from 70 to 95 wt. %, based on the total weight of the polypropylene composition, of a copolymer of propylene with comonomer units derived from 1-butene or 1-hexene, having - total comonomer content from 0.5 to 5.0 mass %; - melt flow index MFI ₂ from 0.10 to 2.0 g/10 min, determined according to ISO 1133 under a load of 2.16 kg and a temperature of 230°C, and - the ratio of the average molecular weight to the average number molecular weight Mw/Mn from 2.5 to 6.0, determined by gel permeation chromatography (GPC) according to ISO 16014-4:2003 and ASTM D 6474-99, and (B) from 5 to 30 wt. %, based on the total weight of the polypropylene composition, of a copolymer of ethylene with comonomer units obtained from 1-butene and/or 1-hexene, having - total comonomer content from 1.0 to 25.0 mass %; - density from 910.0 to 940.0 kg/ ^m3 , determined according to ISO 1183, and - melt flow index MFI ₂ from 0.05 to 3.0 g/10 min, determined according to ISO 1133 at a load of 2.16 kg and a temperature of 190°C, to obtain a pipe.