Ratios polypropylene copolymer compositions with improved impact strength for pipe applications

Abstract

FIELD: polypropylene compositions for use in pipes.SUBSTANCE: polypropylene composition for pipelines is proposed, containing a base resin (A) and a nucleating agent (B), where the base resin (A) consists of a bimodal propylene copolymer (PP) with at least one comonomer that is ethylene, where the bimodal propylene copolymer (PP) contains (PP1) a first propylene copolymer component and (PP2) a second propylene copolymer component, and where the first propylene copolymer component (PP1) differs from the second propylene copolymer component (PP2), and where the weight ratio of the first propylene copolymer component (PP1), including an optional prepolymer component, to the second propylene copolymer component (PP2) is from 30:70 to 70:30, and the nucleating agent (B) is a polymer of a vinyl compound in accordance with the following formula: CH2=CH-CHR1R2, where R1 and R2 are disclosed in the application materials, wherein the mass ratio of the content of the comonomer of the first component of the propylene copolymer (PP1) to the content of the comonomer of the second component of the propylene copolymer (PP2), which are expressed in % by mass, C2PP1 / C2PP2, is 0.36 to 0.54; a method for producing the proposed polypropylene composition, a pipeline containing the proposed polypropylene composition, and the use of the proposed composition for the production of pipelines.EFFECT: production of polypropylene composites for pipes with an improved balance of rigidity and impact strength without the addition of impact strength modifiers or without mixing with polyethylene.11 cl, 2 tbl, 2 ex

Description

[0001] The present invention relates to polypropylene compositions containing a nucleated propylene copolymer having an improved balance of properties with respect to mechanical properties, including stiffness and impact strength, which are particularly suitable for use in pipes. The invention also relates to corresponding methods for producing such polypropylene compositions, an article containing the polypropylene compositions, and the use of the polypropylene compositions for the production of an article.

[0002] Polypropylene materials are often used for various pipe and pipe fitting applications, such as transporting fluids such as water or natural gas, where the fluid is under pressure and / or heated. Specifically, polypropylene materials are used in plumbing and heating systems, such as domestic pipes and fittings for hot and cold water under pressure, underfloor and wall heating systems, and radiator connections.

[0003] Therefore, propylene random copolymers (PPRC) are particularly suitable for the application of hot water supply and industrial pressure pipes, since random copolymers have, among other things, good impact resistance, rigidity, creep resistance and slow cracking properties, as well as long-term pressure resistance.

[0004] In particular, polypropylene random copolymers in hot and cold water applications require a good balance of rigidity (resistance to static loads - hydrostatic pressure) and impact toughness (resistance to dynamic loads - impact action at low temperatures).

[0005] The expression "pressure pipe" used in the description refers to a pipe that is subject to excessive pressure when used, that is, the pressure inside the pipe is higher than the pressure outside the pipe.

[0006] It is well known that increasing one of the impact or stiffness properties leads to deterioration of the other.

[0007] However, for high-pressure pipes, a good balance between impact resistance and rigidity is necessary to ensure sufficient resistance to internal pressure. Furthermore, excellent processability of the random propylene copolymer material is required to facilitate pipe extrusion and injection molding of fittings. To increase the rigidity of the random propylene copolymer material to the required level, the amount of comonomers in the polymer can be reduced, which, however, negatively affects the material's impact strength. For example, random propylene polymer grades for hot and cold water applications often lack satisfactory impact resistance, especially at low temperatures.

[0008] Another widely used approach to improving impact performance while maintaining high rigidity is to produce block copolymers in which ethylene-rich rubber particles are dispersed in a homopolypropylene matrix. However, block copolymers are not preferred for use in pressure pipes because the rubber particles form weak domains with respect to internal pressure, resulting in insufficient pressure resistance of the pipes.

[0009] The balance of stiffness and impact toughness of bimodal PCB materials is significantly improved by a multimodal reactor design, where the comonomer-rich material produced in the second reactor improves the impact toughness of the material without significantly compromising the stiffness.

[0010] Alternatively, impact modifiers such as polyethylene (PE) or styrene-ethylene-butylene-styrene copolymer (SEBS) can be added to random propylene copolymers to improve impact properties. However, this also has a negative impact on stiffness and, consequently, pressure resistance. Furthermore, bimodal PPSS / PE blends with carefully selected concentrations have been shown to have a good balance of stiffness and impact strength at the expense of an additional mixing step and have material quality inconsistencies due to mixing unless the proper compounding method and steps are used.

[0011] Achieving a stiffness / (impact strength) balance that can meet and exceed the requirements of hot and cold water applications with a bimodal material without PE blend or impact modifier is a challenging task.

[0012] Accordingly, there is a need in the art for propylene copolymer materials having improved impact resistance properties without sacrificing rigidity.

[0013] Thus, the objective of the present invention is to produce a propylene copolymer suitable for pipe applications that exhibits a highly achievable balance between impact and stiffness properties, wherein this balance preferably contributes to pressure resistance. In particular, the objective is to produce polypropylene composites with an improved balance of stiffness and impact strength without the addition of impact modifiers or without blending with PE.

[0014] Accordingly, the present invention relates to a polypropylene composition comprising:

[0015] base resin (A) and nucleating agent (B),

[0016] wherein the base resin (A) consists of a bimodal copolymer of propylene (PP) with at least one comonomer which is ethylene,

[0017] wherein the bimodal propylene copolymer (PP) comprises, preferably consists of:

[0018] (PP1) first component of propylene copolymer and

[0019] (PP2) the second component of propylene copolymer, and

[0020] wherein the first component of the propylene copolymer (PP1) is different from the second component of the propylene copolymer (PP2), and

[0021] wherein the weight ratio of the first propylene copolymer component (PP1) including the optional prepolymer component to the second propylene copolymer component (PP2) is from 30:70 to 70:30, and

[0022] wherein the polypropylene composition has

[0023] (a) Melt flow index MFR2(2.16 kg, 230°C) 0.15 to 0.50 g / 10 min, determined according to ISO 1133 at 230°C and a load of 2.16 kg,

[0024] (b) a total comonomer content of from 3.5 to 5.0% by weight based on the total weight of the bimodal propylene copolymer (PP), determined as described below,

[0025] (c) a xylene cold solubles (XCS) content equal to or less than 8.2% by weight based on the total weight of the bimodal propylene copolymer (PP), determined according to ISO 16152, and

[0026] (d) Charpy notched impact strength at 23°C from 45.0 to 95.0 kJ / m 2 and a Charpy notched impact strength at 0°C of at least 6.0 kJ / m 2 , determined in accordance with ISO 179 / eA:2000 using injection moulded specimens with type 1A notches.

[0027] It has been unexpectedly found that the polypropylene composition according to the invention has an advantageous property ratio between stiffness and impact strength, which can be seen from the flexural modulus, the tensile modulus for stiffness and the Charpy notched impact strength at a low temperature of 0°C, as well as at room temperature. The balance between the flexural modulus, the tensile modulus and the Charpy notched impact strength ensures sufficient stiffness and good impact properties of the polypropylene composition according to the invention, and this balance preferably contributes to pressure resistance, as shown in the experimental section, which makes the composition highly suitable for use in pipes, more preferably for use in pressure pipes for supplying hot and cold water.

[0028] Furthermore, the present polypropylene composition preferably provides the resulting pipes with suitable pressure resistance, which is necessary for use in pressure pipes.

[0029] Preferably, the present polypropylene composition also has advantageous technological properties in terms of pipe extrusion capability, which can be seen from the rheological properties, in particular the eta value 300 .

[0030] The invention also relates to a method for producing a polypropylene composition according to any of the preceding claims, wherein a bimodal copolymer of propylene (PP) with at least one comonomer which is ethylene is polymerized in a multi-stage polymerization process in the presence of:

[0031] (I) a solid catalyst component containing a magnesium halide, a titanium halide and an internal electron donor; and

[0032] (II) a cocatalyst comprising an alkylaluminum and optionally an external electron donor, and

[0033] (III) an optional nucleating agent (B), preferably in the presence of a nucleating agent (B);

[0034] and this multi-stage method includes the steps:

[0035] (a) continuously polymerizing propylene together with a comonomer selected from alpha-olefins with 2 or 4-8 carbon atoms, preferably with ethylene, in a first polymerization stage by introducing streams of propylene, hydrogen and ethylene into the first polymerization stage at a temperature of from 60 to 80°C and a pressure of from 3000 to 6500 kPa to obtain a first component of a propylene copolymer, wherein said first component of a propylene copolymer (PP1) preferably has a melt flow index MFR2 of from 0.4 to 2.0 g / 10 min, (2.16 kg; 230°C; ISO 1133);

[0036] (b) removing from the first stage of polymerization a stream containing said first component of propylene copolymer (PP1) and moving said stream to the second stage of polymerization;

[0037] (c) polymerizing propylene together with a comonomer selected from alpha-olefins with 2 or 4-8 carbon atoms, preferably with ethylene, in said second polymerization stage by introducing streams of propylene, ethylene and optionally hydrogen into said second polymerization stage at a temperature of from 70 to 90°C and a pressure of from 1000 to 3000 kPa to obtain a bimodal propylene copolymer (PP) of said first propylene copolymer component (PP1) and second propylene copolymer component (PP2);

[0038] (d) continuously withdrawing a stream containing said bimodal propylene copolymer (PP) from the second polymerization stage and optionally mixing said bimodal propylene copolymer (PP) with additives; and

[0039] (e) extruding a mixture of said bimodal propylene copolymer into pellets that have a melt flow index MFR2(2.16 kg; 230°C; ISO 1133) of 0.15 to 0.5 g / 10 min,

[0040] and wherein the first propylene copolymer component (PP1) is different from the second propylene copolymer component (PP2), and preferably has a higher MFR than the second propylene copolymer component (PP2).

[0041] The invention also provides a polypropylene composition obtained by the said method.

[0042] The invention also relates to an article containing the polypropylene composition according to the invention.

[0043] The invention also relates to the use of the polypropylene composition according to the invention for the production of an article.

[0044] The invention is described in more detail below.

[0045] Definitions

[0046] The polypropylene composition according to the invention means a polymer obtained from at least 50 mol% of propylene monomer units and additional comonomer units.

[0047] Propylene copolymer means a polymer consisting of propylene monomer units and comonomer units in an amount of at least 0.1 mol%. In a random propylene copolymer, the comonomer units are randomly distributed in the polymer chain.

[0048] The term "different" means that a polymer component differs from another polymer component in at least one measurable property. Suitable properties for differentiating polymer components include weight-average molecular weight, melt flow index (MFR2), density, or comonomer content.

[0049] Basic Provisions

[0050] The polypropylene composition of the invention comprises a base resin (A) and a nucleating agent (B), wherein the base resin (A) consists of a bimodal propylene copolymer (PP) with at least one comonomer that is ethylene (also referred to herein as a propylene copolymer). Accordingly, the polypropylene composition of the invention is a bimodal polypropylene composition.

[0051] The term "base resin (A)" refers to the polymer component of the composition. Therefore, the propylene composition does not contain any polymer components other than the bimodal propylene copolymer (PP). In particular, the composition does not contain LLDPE or any other type of polyethylene.

[0052] A bimodal copolymer of propylene (PP) with at least one comonomer which is ethylene is a random copolymer of propylene.

[0053] A random propylene copolymer means a copolymer of propylene monomer units and comonomer units, in which the comonomer units are randomly distributed in the polymer chain. Thus, the random propylene copolymer includes a fraction that is insoluble in xylene - a xylene cold insoluble fraction (XCU), in an amount of at least 70% by weight, more preferably at least 80% by weight, even more preferably at least 85% by weight, and most preferably at least 91.8% by weight, based on the total amount of the random propylene copolymer.

[0054] Bimodal random propylene copolymer does not contain an elastomeric polymer phase dispersed therein.

[0055] As known to a person skilled in the art, a random copolymer differs from a heterophasic polypropylene, which is a propylene copolymer containing a propylene homo- or random copolymer matrix component (1) and an elastomeric copolymer component (2) of propylene with one or more copolymers of ethylene and a C4-C8 alpha-olefin, wherein the elastomeric (amorphous) copolymer component (2) is dispersed in said propylene homo- or random copolymer matrix polymer (1).

[0056] In addition, the bimodal propylene copolymer does not contain LLDPE, more preferably does not contain any polyethylene.

[0057] Typically, a propylene polymer containing at least two fractions (two components) of propylene polymer obtained under different polymerization conditions resulting in different (weight average) molecular weights and / or different comonomer contents in the fractions, preferably obtained by polymerization in several polymerization stages under different polymerization conditions, is called "multimodal". The prefix "multi" refers to the number of different polymer fractions that make up the propylene polymer. As an example of a multimodal polypropylene, a propylene polymer consisting of only two fractions is called "bimodal", while a propylene polymer consisting of only three fractions is called "trimodal".

[0058] The term "different" means that the propylene polymer fractions differ from each other in at least one property, preferably in weight average molecular weight or comonomer content, or both, more preferably in at least weight average molecular weight.

[0059] The shape of the molecular weight distribution curve, that is, the appearance of the graph of the mass fraction of the polymer as a function of its molecular weight, of such a multimodal propylene polymer is at least noticeably broadened compared to the curves of the individual fractions.

[0060] The propylene copolymer (PP) used in the invention is a bimodal random propylene copolymer comprising a first propylene copolymer component (PP1) and a second propylene copolymer component (PP2). Preferably, the bimodal random propylene copolymer (PP) consists of two propylene copolymer fractions (PP1) and (PP2).

[0061] The random copolymer of propylene (PP) used in the polypropylene composition of the invention contains at least one comonomer which is ethylene.

[0062] A random copolymer of propylene (PP) may contain only ethylene as a comonomer, but may also contain one or more other types of comonomers.

[0063] Such other comonomers of said propylene (PP) random copolymer may preferably be selected from C2- and C4-C6-alpha-olefins.

[0064] Preferably, the random copolymer of propylene (PP) contains only ethylene as a comonomer.

[0065] Both fractions (PP1) and (PP1) are fractions of a random propylene copolymer, and the first component of the propylene copolymer (PP1) is different from the second component of the propylene copolymer (PP2).

[0066] It is preferable that the bimodal random copolymer of propylene (PP), which is preferably a random copolymer of propylene with only one ethylene as a comonomer, contains, preferably consists of, at least a random copolymer of propylene having a low molecular weight (low molecular weight (LMW) fraction) and a random copolymer of propylene having a high molecular weight (high molecular weight (HMW) fraction). Thus, the LMW fraction has a lower weight average molecular weight than the HMW fraction.

[0067] It is well known that the melt flow index (MFR) of a polymer is an indicator of the weight-average molecular weight (Mw) of the polymer. The higher the MFR, the lower the Mw of the polymer, and, correspondingly, the lower the MFR, the higher the Mw of the polymer. Thus, the MFR of the low-molecular-weight fraction is higher than the MFR of the high-molecular-weight fraction.

[0068] Preferably, the first component of the propylene copolymer (PP1) has a higher MFR2 than the second component of the propylene copolymer (PP2). Thus, preferably, the first component of the propylene copolymer (PP1) is a low molecular weight (LMW) fraction, and the second component of the propylene copolymer (PP2) is a high molecular weight (HMW) fraction.

[0069] More preferably, the first component of the propylene copolymer (PP1) has a melt flow index MFR2 of 0.4 to 2.0 g / 10 min, more preferably of 0.5 to 1.5 g / 10 min, determined according to ISO 1133 at 230°C and a load of 2.16 kg.

[0070] The bimodal propylene copolymer (PP) has preferably a melt flow index MFR2 of 0.15 to 0.50 g / 10 min, more preferably of 0.20 to 0.40 g / 10 min, most preferably of 0.23 to 0.35 g / 10 min, determined according to ISO 1133 at 230°C and a load of 2.16 kg.

[0071] The MFR2 values ​​and hence the molecular weight of the first component propylene copolymer (PP1) and the second component propylene copolymer (PP2), as well as the bimodal random propylene copolymer (PP), can be adjusted by the amount of chain transfer agent and the amount of (PP1) and (PP2) in the final polymer, that is, by separation.

[0072] It is also preferable that the MFR2 of the first and second components of the propylene copolymer (PP1) and (PP2) and the MFR2 of the bimodal random propylene copolymer (PP) have a certain ratio. More preferably, the ratio of the MFR2 of the bimodal propylene copolymer (PP) to the MFR2 of the first component of the propylene copolymer (PP1), MFR 2(ПП) / MFR 2(ПП1) is from 0.20 to 0.50, more preferably from 0.22 to 0.48.

[0073] The first propylene copolymer component (PP1) and the second propylene copolymer component (PP2) are random propylene copolymers which may have substantially the same or different comonomer contents. Therefore, it is preferable that the comonomer content of the high-molecular fraction, that is, the second propylene copolymer component (PP2), is equal to or greater than, preferably greater than, the comonomer content of the low-molecular fraction, that is, the first propylene copolymer component (PP1). It is also preferable that the comonomer content of the obtained bimodal random propylene copolymer (PP) is higher than the comonomer content of the first component of the random propylene copolymer (PP1).

[0074] The comonomer content of the first component propylene copolymer (PP1) is preferably from 1.0 to 4.0 mass%, more preferably from 2.0 to 3.5 mass%, even more preferably from 2.3 to 3.1 mass%, most preferably from 2.4 to 3.0 mass%, based on the total mass of the first component propylene copolymer (PP1).

[0075] The comonomer content of the second component propylene copolymer (PP2) is preferably 4.5 to 9.0 mass%, more preferably 4.8 to 8.0 mass%, most preferably 5.0 to 7.0 mass%, based on the total mass of the second component propylene copolymer (PP2).

[0076] The comonomer content of the first component of the propylene copolymer (PP1) is preferably from 1.5 to 6.0 mol%, more preferably from 3.0 to 5.5 mol%, even more preferably from 3.5 to 5.0 mol%, most preferably from 3.5 to 4.5 mol%, based on the total content of monomer units in the first component of the propylene copolymer (PP1).

[0077] The comonomer content of the second component of the propylene copolymer (PP2) is preferably from 6.1 to 15.0 mol%, more preferably from 7.0 to 12.0 mol%, even more preferably from 7.5 to 10.5 mol%, most preferably from 7.8 to 10.0 mol%, based on the total content of monomer units in the second component of the propylene copolymer (PP2).

[0078] In a preferred embodiment, the first component of the propylene copolymer (PP1) has a lower molecular weight than the second component of the propylene copolymer (PP2), that is, the first component of the propylene copolymer (PP1) is a low molecular weight (LMW) fraction, and the second component of the propylene copolymer (PP2) is a high molecular weight (HMW) fraction, and the second component of the propylene copolymer (PP2) has a higher content of comonomer, preferably ethylene comonomer, than the first component of the propylene copolymer (PP1). In this preferred embodiment, the content of comonomer, preferably ethylene comonomer, in the first and second components of the propylene copolymer (PP1) and (PP2) is within the preferred ranges defined above, and preferably ethylene is the only comonomer used in both (PP1) and (PP2), that is, there is no additional comonomer.

[0079] The total comonomer content of the bimodal random propylene (PP) copolymer is from 3.5 to 5.0 mass%, preferably from 4.0 to 4.8 mass%, based on the total mass of the bimodal propylene (PP) copolymer.

[0080] The total comonomer content of the bimodal random propylene (PP) copolymer is preferably 4.0 to 9.5 mol%, more preferably 5.0 to 9.0 mol%, most preferably 5.5 to 8.0 mol%, based on the total molar content of the random propylene (PP) copolymer.

[0081] The comonomer content of the first component propylene copolymer (PP1) and the second component propylene copolymer (PP2), as well as the bimodal random propylene copolymer (PP), can be adjusted by the amount of comonomer in (PP1) and (PP2) and the amount of (PP1) and (PP2) in the final polymer, that is, by separation.

[0082] It is also preferable that the comonomer content of the first and second components of the propylene copolymer (PP1) and (PP2) and the total comonomer content of the bimodal random propylene copolymer (PP) have a certain relationship.

[0083] Preferably, the mass ratio of the comonomer content of the first component of the propylene copolymer (PP1) to the comonomer content of the bimodal propylene copolymer (PP), which are expressed in % by mass, C2 ПП1 / C2 ПП , is from 0.40 to 0.75, more preferably 0.50 to 0.70, most preferably 0.52 to 0.68.

[0084] Furthermore, the mass ratio of the comonomer content of the first component of the propylene copolymer (PP1) to the comonomer content of the second component of the propylene copolymer (PP2), C2 is preferable ПП1 / C2 ПП2 , is from 0.36 to 0.54, more preferably from 0.38 to 0.52, most preferably from 0.40 to 0.50.

[0085] According to a preferred embodiment of the invention, the ratio C2 ПП1 / C2 ПП is from 0.40 to 0.75, more preferably from 0.50 to 0.70, most preferably from 0.52 to 0.68, and the MFR ratio 2(ПП) / MFR 2(ПП1) ranges from 0.20 to 0.50, most preferably from 0.22 to 0.48.

[0086] The weight ratio of the first propylene copolymer component (PP1) including the optional prepolymer component to the second propylene copolymer component (PP2) is from 30:70 to 70:30. Preferably, the weight ratio of the first propylene copolymer component (PP1) including the optional prepolymer component to the second propylene copolymer component (PP2) is from 38:62 to 60:40, preferably from 40:60 to 50:50, most preferably from 42:58 to 46:54.

[0087] The first propylene copolymer component (PP1) is preferably present in the bimodal propylene copolymer in an amount of 30 to 70% by weight, more preferably in an amount of 38 to 60% by weight, more preferably in an amount of 40 to 50% by weight, and most preferably in an amount of 42 to 46% by weight, based on the total amount of the random propylene copolymer (PP) (100% by weight). The second propylene copolymer component (PP2) is preferably present in the random propylene copolymer in an amount of 70 to 30% by weight, more preferably in an amount of 62 to 40% by weight, more preferably in an amount of 60 to 50% by weight, and most preferably in an amount of 58 to 54% by weight, based on the total amount of the random propylene copolymer (PP) (100% by weight).

[0088] The bimodal random copolymer of propylene (PP) may additionally contain a prepolymer fraction. If a prepolymer fraction is present, said fraction is calculated relative to the amount (% by weight) of the low-molecular-weight fraction or the high-molecular-weight fraction, preferably relative to the amount of the low-molecular-weight fraction. The prepolymer fraction may be a propylene homopolymer or copolymer.

[0089] Bimodal random copolymer of propylene (PP) preferably has a density of 890 to 910 kg / m3 3 , preferably from 895 to 905 kg / m 3 .

[0090] It is particularly preferable that the polypropylene composition of the invention consists of a random copolymer of propylene (PP), a nucleating agent (B) and optional further additives as defined above or below.

[0091] Accordingly, the amount of the bimodal random copolymer of propylene (PP) is preferably from 90.0 to 99.75 mass%, more preferably from 95.0 to 99.75 mass%, and even more preferably from 96.5 to 99.75 mass%, based on the total mass of the polypropylene composition (100 mass%).

[0092] Nucleating agent here means a compound or composition that is added specifically to enhance the rate of crystallization in a solid polymer and results in an increased degree of crystallinity (and often a smaller crystal size) of the solid polymer.

[0093] The nucleating agent (B) used in the polypropylene composition of the invention is preferably a polymeric nucleating agent, preferably a polymer of a vinyl compound, more preferably a polymeric nucleating agent obtained by polymerizing vinylcycloalkane monomers or vinylalkane monomers.

[0094] The polymer nucleating agent is more preferably a polymerized vinyl compound according to the following formula:

[0095] CH2=CH-CHR 1 R 2 (BI),

[0096] where are the substituents R 1 and R 2 together form a 5- or 6-membered saturated, unsaturated or aromatic ring, optionally containing substituents, or independently represent an alkyl group containing from 1 to 4 carbon atoms, wherein when R 1 and R 2 form an aromatic ring, the hydrogen atom in the -CHR fragment 1 R 2 absent.

[0097] Even more preferably, the polymer nucleating agent is selected from vinyl cycloalkane polymer, preferably vinyl cyclohexane (VCH) polymer, vinyl cyclopentane polymer, 3-methyl-1-butene polymer, and vinyl-2-methylcyclohexane polymer. The most preferred nucleating agent is vinyl cyclohexane (VCH) polymer.

[0098] As mentioned above, in a preferred embodiment, the nucleating agent is a polymeric nucleating agent, more preferably a polymer of a vinyl compound of formula (BI) as defined above, even more preferably a vinylcyclohexane (VCH) polymer.

[0099] The amount of the nucleating agent is preferably not more than 10,000 ppm by mass (meaning parts per million based on the total mass of the polypropylene composition (100% by mass), also abbreviated as ppm), more preferably not more than 6,000 ppm, even more preferably not more than 5,000 ppm, based on the total mass of the bimodal random copolymer of propylene (PP) (100% by mass).

[0100] The amount of the nucleating agent is even more preferably not more than 500 ppm, preferably 0.025 to 200 ppm, more preferably 0.1 to 200 ppm, more preferably 0.3 to 200 ppm, most preferably 0.3 to 100 ppm, based on the total mass of the propylene (PP) random copolymer (100% by mass).

[0101] In a preferred embodiment, the nucleating agent is a polymeric nucleating agent, most preferably a polymer of a vinyl compound of the formula (BI) as described above, even more preferably a vinyl cyclohexane (VCH) polymer as defined above, and the amount of said nucleating agent (B) is not more than 200 ppm, more preferably is from 0.025 to 200 ppm, and more preferably is from 0.1 to 200 ppm, more preferably is from 0.3 to 200 ppm, most preferably is from 0.3 to 100 ppm, based on the total weight of the bimodal random copolymer of propylene (PP) (100% by weight).

[0102] The nucleating agent can be introduced into the propylene (PP) random copolymer, for example, during the polymerization process of the propylene (PP) random copolymer, or can be introduced into the propylene (PP) random copolymer by mechanically mixing with a nucleated polymer containing a polymer nucleating agent (the so-called masterbatch technology) or by mixing the propylene (PP) random copolymer with the nucleating agent itself.

[0103] Thus, a nucleating agent can be introduced into a random copolymer of propylene (PP) during the polymerization process of the random copolymer of propylene (PP). The nucleating agent is preferably introduced into the random copolymer of propylene (PP) by pre-polymerizing the above-mentioned vinyl compound of formula (BI) defined above, even more preferably vinyl cyclohexane (VCH), in the presence of the catalyst system described above, comprising a solid Ziegler-Natta catalyst component, a cocatalyst and an optional external donor, and the resulting reaction mixture of the polymer of the vinyl compound of formula (BI), as described above, even more preferably vinyl cyclohexane (VCH) polymer, and the catalyst system is then used to produce a bimodal random copolymer of propylene (PP).

[0104] A general method for preparing such a modified catalyst system is described, for example, in documents EP 1 028 984 or WO 00 / 6831.

[0105] In another embodiment, the polymeric nucleating agent is added using the so-called masterbatch technology, wherein an already nucleated polymer, preferably a propylene homopolymer containing a polymeric nucleating agent (masterbatch), is mixed with a random copolymer of propylene (PP). Such a masterbatch is preferably prepared by polymerizing propylene in a sequential polymerization process.

[0106] The polypropylene composition of the invention may further comprise additives. Typical additives include acid scavengers, antioxidants, colorants, light stabilizers, plasticizers, friction reducers, anti-scratch agents, dispersants, processing aids, lubricants, pigments, fillers, and the like. Each additive can be used, for example, in conventional amounts, and the total amount of additives present in the propylene composition is preferably as described below.

[0107] Such additives are commercially available and are described, for example, in the publication “Plastic Additives Handbook”, 6th ed., 2009, Hans Zweifel (pp. 1141-1190).

[0108] The total amount of the optional further additives is preferably between 0.0001 and 10% by mass, preferably between 0.0001 and 5.0% by mass, preferably between 0.0001 and 2.5% by mass, more preferably between 0.0001 and 1.5% by mass, even more preferably between 0.0001 and 1.0% by mass, based on the total weight of the polypropylene composition (100% by mass). In the case where the nucleating agent (B) and / or any optional additives are added to the optional masterbatch, the carrier material, such as the carrier polymer, the additives are calculated relative to the (total) amount of the additive(s) based on the total weight of the polypropylene composition (100% by mass).

[0109] The polypropylene composition of the invention has a melt flow index MFR2(2.16 kg, 230°C) of 0.15 to 0.5 g / 10 min, preferably 0.2 to 0.4 g / 10 min, more preferably 0.23 to 0.35 g / 10 min, determined according to ISO 1133 at 230°C and a load of 2.16 kg.

[0110] The polypropylene composition of the invention has a total comonomer content of 3.5 to 5.0% by weight, preferably 4.0 to 4.8% by weight, based on the total weight of the bimodal propylene copolymer (PP), determined as described above.

[0111] The polypropylene composition has a total comonomer content of preferably 4.0 to 9.5 mol%, more preferably 5.0 to 9.0 mol%, most preferably 5.5 to 8.0 mol%, based on the total molar content of the propylene random copolymer (PP).

[0112] Furthermore, the polypropylene composition of the invention has a xylene cold solubles (XCS) content equal to or lower than 8.2% by mass, preferably from 4.0 to 8.0% by mass, more preferably from 5.0 to 7.9% by mass, determined according to ISO 16152 at 25°C.

[0113] In addition, the polypropylene composition has a Charpy notched impact strength at 23°C of 45.0 to 95.0 kJ / m 2 , preferably from 50.0 to 90 kJ / m 2 , more preferably from 55 to 85 kJ / m 2 , determined in accordance with ISO 179 / 1eA:2000 using injection moulded specimens with type 1A notches.

[0114] In addition, the polypropylene composition has a Charpy notched impact strength at 0°C of at least 6.0 kJ / m 2 , preferably at least 6.5 kJ / m 2 and more preferably at least 7.0 kJ / m 2, determined according to ISO 179 / 1eA:2000 using injection-molded notched specimens of type 1A. The upper limit of the Charpy impact strength of a notched specimen at 0°C is typically no higher than 15 kJ / m 2 .

[0115] Also, the polypropylene composition preferably has a flexural modulus of 700 to 1400 MPa, more preferably 740 to 1200 MPa, and most preferably 780 to 1100 MPa, determined according to ISO 178 using injection molded specimens of dimensions 80×10×4.0 mm 3 (length × width × thickness).

[0116] Also, the polypropylene composition preferably has a tensile modulus of 700 to 1200 MPa, preferably 750 to 1100 MPa, more preferably 800 to 1000 MPa, determined according to ISO 527-2 using injection molded type 1A specimens.

[0117] In addition, the polypropylene composition preferably has a melting point T плfrom 135 to 155°C, preferably from 137 to 152°C, preferably from 140 to 150°C, determined according to ISO 11357-3.

[0118] Also, the polypropylene composition preferably has a crystallization temperature T кр not less than 100°C, preferably from 105 to 130°C, preferably from 107 to 127°C, preferably from 110 to 125°C, determined according to ISO 11357-3.

[0119] Furthermore, the polypropylene composition preferably has a complex viscosity at 300 rad / sec eta* of 400 to 1000 Pa⋅sec, more preferably 450 to 900 Pa⋅sec, most preferably 500 to 800 Pa⋅sec, determined according to ISO 6721-1 and 6721-10.

[0120] Furthermore, the polypropylene composition preferably has a weight average molecular weight Mw of 400 to 800 kg / mol, determined according to ISO 16014-1:2003 and ISO 16014-4:2003.

[0121] Furthermore, the polypropylene composition preferably has a number-average molecular weight Mn of 30 to 60 kg / mol, determined according to ISO 16014-1:2003 and ISO 16014-4:2003

[0122] Furthermore, the polypropylene composition preferably has a molecular weight distribution (MWD = Mw / Mn, where Mn represents the number average molecular weight and Mw represents the weight average molecular weight) of 10 to 20, more preferably 11 to 19, most preferably 12 to 18, when determined according to ISO 16014-1:2003 and ISO 16014-4:2003.

[0123] Method

[0124] The polypropylene composition of the invention is preferably produced in a continuous, multi-stage process in a conventional manner. It should be understood that once a favorable balance of properties has been found in the invention, resulting in a polypropylene composition, then, in the case of industrial-scale production, a skilled artisan can adjust the process parameters and controls to achieve these properties in the polypropylene composition. Preferably, the process comprises at least two polymerization stages.

[0125] Thus, the invention relates to a method for producing a polypropylene composition, wherein a bimodal random copolymer of propylene (PP), with at least one comonomer representing ethylene, is polymerized in a multi-stage polymerization process in the presence of:

[0126] (I) a solid catalyst component containing a magnesium halide, a titanium halide and an internal electron donor; and

[0127] (II) a cocatalyst comprising an alkylaluminum and optionally an external electron donor, and

[0128] (III) an optional nucleating agent (B), preferably in the presence of a nucleating agent (B);

[0129] wherein the multi-stage method includes the following stages:

[0130] (a) continuously polymerizing propylene together with a comonomer selected from alpha-olefins with 2 or 4-8 carbon atoms, preferably with ethylene, in a first polymerization stage by introducing streams of propylene, hydrogen and ethylene into the first polymerization stage at a temperature of from 60 to 80°C and a pressure of from 3000 to 6500 kPa to obtain a first component of a random propylene copolymer (PP1), wherein said first random propylene copolymer has a melt flow index MFR2 of from 0.4 to 2.0 g / 10 min (2.16 kg; 230°C; ISO 1133);

[0131] (b) removing from the first stage of polymerization a stream containing said first component of a random propylene copolymer (PP1) and moving said stream to the second stage of polymerization;

[0132] (c) polymerizing propylene together with a comonomer selected from alpha-olefins with 2 or 4-8 carbon atoms, preferably with ethylene, in said second polymerization stage by introducing streams of propylene, ethylene and optionally hydrogen into said second polymerization stage at a temperature of from 70 to 90°C and a pressure of from 1000 to 3000 kPa to obtain a bimodal random copolymer of propylene (PP) of said first component random copolymer of propylene (PP1) and a second component random copolymer of propylene (PP2);

[0133] (d) continuously withdrawing a stream containing said bimodal random copolymer of propylene (PP) from the second polymerization stage and optionally mixing said bimodal random copolymer of propylene with additives; and

[0134] (e) extruding a mixture of said bimodal random propylene copolymer into pellets that have a melt flow index MFR2(2.16 kg; 230°C; ISO 1133) of 0.15 to 0.5 g / 10 min,

[0135] and where the first component of the random propylene copolymer (PP1) is different from the second component of the random propylene copolymer (PP2), preferably the first component of the random propylene copolymer (PP1) has a higher MFR than the second component of the random propylene copolymer (PP2).

[0136] It is particularly preferable that the method of the present invention comprises the following process steps:

[0137] (aa) polymerizing a vinyl compound of formula (BI) defined above or below, preferably vinylcyclohexane (VCH), in the presence of a catalyst system containing a solid catalyst component (I), to obtain a modified catalyst system, which is a reaction mixture containing a solid catalyst component (I) and the obtained polymer, preferably a vinyl compound of formula (BI), and wherein the weight ratio (g) of the polymer of the vinyl compound of formula (BI) to the solid catalyst component (I) reaches up to 5 (5:1), preferably up to 3 (3:1), most preferably is from 0.5 (1:2) to 2 (2:1), and the obtained modified catalyst system is fed to the polymerization stage (a) of a multi-stage process for producing a bimodal propylene copolymer (PP).

[0138] The method of the invention is described in more detail below.

[0139] Thus, conventional polymerization technologies such as gas phase polymerization, solution polymerization, suspension polymerization, or bulk polymerization can be used.

[0140] In most cases, a combination of a slurry (or bulk) reactor and at least one gas-phase reactor is preferred for the polymerization of bimodal random copolymers of propylene (PP). It is also preferable for the reactors to be arranged in the following order: a slurry (or bulk) reactor, then one or more gas-phase reactors.

[0141] In the case of propylene polymerization in slurry reactors, the reaction temperature will generally be in the range of 60 to 110°C, for example, 60 to 85°C, the reaction pressure will be in the range of 5 to 80 bar, for example, 20 to 60 bar, and the residence time will generally be in the range of 0.1 to 5 hours, for example, 0.3 to 2 hours. A monomer is usually used as the reaction medium.

[0142] For gas-phase reactors, the reaction temperature used will typically be in the range of 60 to 115°C, for example, 70 to 110°C, the reaction pressure will typically be in the range of 10 to 25 bar, and the residence time will typically be in the range of 0.5 to 8 hours, for example, 0.5 to 4 hours. The gas used is typically the monomer, optionally in the form of a mixture with a non-reactive gas such as nitrogen or propane.

[0143] In addition to the actual polymerization stages and reactors, the method may include any additional polymerization stages, such as a prepolymerization stage, as well as any other post-reactor processing stages known in the art.

[0144] Preferably, the bimodal random copolymer of propylene (PP) is obtained in a sequential polymerization process comprising at least two polymerization zones operating under different conditions to produce the bimodal random copolymer of propylene (PP). The polymerization zones can be operated under suspension, solution or gas phase conditions or combinations thereof. Suitable processes are disclosed, among others, in documents WO-A-98 / 58975, WO-A-98 / 58976, EP-A-887380 and WO-A-98 / 58977.

[0145] In a preferred embodiment, the prepolymerization is carried out continuously as bulk suspension polymerization in liquid propylene, i.e., the liquid phase primarily comprises propylene with minor amounts of other reactants and optionally inert components dissolved therein. Preferably, the prepolymerization is carried out in a stirred-tank flow reactor or a loop reactor, preferably in a loop reactor.

[0146] The polymerization reaction is generally carried out at a temperature of 0 to 60°C, preferably 10 to 50°C, and more preferably 20 to 45°C.

[0147] The pressure in the polymerization 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, for example, from 30 to 70 bar.

[0148] The reaction conditions are well known in the art, as described, among others, in document GB 1580635.

[0149] Comonomers can also be fed into the prepolymerization step. Examples of suitable comonomers include ethylene or alpha-olefins having 4 to 8 carbon atoms. Particularly suitable comonomers include ethylene, 1-butene, 1-hexene, 1-octene, or mixtures thereof. Ethylene is particularly preferred as a comonomer.

[0150] In a preferred embodiment for the polymerization of the bimodal random copolymer of propylene (PP), the first component of the random copolymer of propylene (PP1) is preferably obtained in the first polymerization stage. Said first component of the random copolymer of propylene (PP1) most preferably reflects the low molecular weight (LMW) fraction of the bimodal random copolymer of propylene (PP), as defined above.

[0151] The first component of the random propylene copolymer (PP1) is obtained by introducing a polymerization catalyst, optionally through a prepolymerization step as described above, into the first polymerization step together with a first monomer mixture containing propylene and a comonomer selected from ethylene and alpha-olefins containing from 4 to 8 carbon atoms. The comonomer content is controlled to obtain the desired comonomer content in the first component of the random propylene copolymer. The comonomer content of said first component of the random propylene copolymer (PP1) preferably reflects the comonomer content of the low molecular weight (LMW) fraction of the bimodal random propylene copolymer (PP), as defined above.

[0152] The first component of the random propylene copolymer (PP1) obtained in the first polymerization step preferably has an MFR2 of 0.4 to 2.0 g / 10 min. More preferably, the MFR2 of the first component of the random propylene copolymer (PP1), preferably the low molecular weight (LMW) fraction of the bimodal random propylene copolymer (PP), is from 0.5 to 1.5 g / 10 min. It is preferable that the MFR2 of the first component of the random propylene copolymer (PP1) remains within these limits.

[0153] The polymerization in the first polymerization zone is preferably carried out in suspension in a loop reactor. For this reason, in the context of the present invention, the terms "first polymerization stage" and "loop reactor" can be used interchangeably. Then, the polymer particles formed during the polymerization, together with the catalyst fragmented and dispersed within the particles, are suspended in a liquid hydrocarbon. The suspension is stirred to ensure the transfer of reactants from the liquid to the particles. In loop reactors, the suspension is circulated at high speed through a closed pipe using a circulation pump. Circulation reactors are generally known in the art and examples are given, for example, in documents US-A-4582816, US-A-3405109, US-A-3324093, EP-A-479186 and US-A-5391654.

[0154] Slurry polymerization is preferably a so-called bulk polymerization. By "bulk polymerization" is meant a process wherein the polymerization is carried out in liquid monomer substantially in the absence of an inert diluent. However, as is known to those skilled in the art, the monomers used in industrial production are never pure, but always contain aliphatic hydrocarbons as impurities. For example, propylene monomer may contain up to 5% propane as an impurity. Since propylene is consumed in the reaction and also recycled from the reaction effluent back to the polymerization, inert components tend to accumulate, and therefore the reaction medium may contain up to 40% by weight of compounds other than the monomer. It should be understood, however, that such a polymerization process still corresponds to the meaning of "bulk polymerization" as defined above.

[0155] The temperature in suspension polymerization is generally from 50 to 110°C, preferably from 60 to 80°C, and more preferably from 65 to 75°C. The pressure is from 1 to 150 bar, preferably from 10 to 100 bar, and most preferably from 30 to 65 bar.

[0156] The slurry can be withdrawn from the reactor either continuously or intermittently. A preferred method of intermittent withdrawal is to use settling legs, where the solids concentration of the slurry is allowed to rise before the batch of concentrated slurry is withdrawn from the reactor. The use of settling legs is disclosed, among others, in documents US-A-3374211, US-A-3242150 and EP-A-1310295. Continuous withdrawal is disclosed, among others, in documents EP-A-891990, EP-A-1415999, EP-A-1591460 and EP-A-1860125. Continuous withdrawal can be combined with a suitable concentration method, as described in documents EP-A-1860125 and EP-A-1591460.

[0157] Other components are also added to the suspension polymerization stage, as is known in the art. Thus, hydrogen is used to regulate the polymer's molecular weight. Process additives, such as antistatic agents, can be added to the reactor to facilitate stable operation of the process.

[0158] Preferably, the ratio of comonomer to propylene in the first stage polymerization is from 0.2 to 20 mol / kmol, more preferably from 0.5 to 15 mol / kmol, even more preferably from 0.5 to 10 mol / kmol, and most preferably from 1 to 10 mol / kmol.

[0159] Preferably, the ratio of hydrogen to propylene in the first stage polymerization is from 0.1 to 5.0 mol / kmol, more preferably from 0.1 to 4.5 mol / kmol, even more preferably from 0.2 to 4.0 mol / kmol, and most preferably from 0.3 to 3.0 mol / kmol.

[0160] The slurry is preferably fed directly to the second polymerization stage, which is preferably a gas-phase polymerization stage, to produce the second random propylene copolymer. The term "directly" means that the slurry is introduced from the loop reactor into the gas-phase reactor without a flash step between the slurry and gas-phase polymerization stages to remove at least part of the reaction mixture from the polymer. Thus, substantially the entire slurry stream withdrawn from the first polymerization stage is fed directly to the second polymerization stage. This type of direct feeding is described in EP-A-887379, EP-A-887380, EP-A-887381 and EP-A-991684. Preferably, the entire slurry stream withdrawn from the loop reactor is fed to the gas-phase reactor without any intermediate step between them.However, it is within the scope of the present invention to collect small samples or stream samples from the polymer or from the liquid phase, or from both, for polymer and / or reaction mixture composition analysis. As is known to those skilled in the art, the volume of such stream samples is small compared to the total slurry stream withdrawn from the loop reactor and, as a rule, is much less than 1% by weight of the total stream, for example, it is at most 0.1% or 0.01% or even 0.001% by weight.

[0161] When the entire slurry stream from the first polymerization stage is introduced into the second polymerization stage, significant amounts of propylene, comonomer and hydrogen are introduced into the second polymerization stage along with the polymer.

[0162] As discussed above, a certain amount of propylene and comonomer are introduced into the second polymerization stage from the first polymerization stage. However, this is generally insufficient to maintain the desired propylene and comonomer concentrations in the second polymerization stage. Therefore, propylene and comonomer are usually additionally introduced into the second polymerization stage. They are introduced to maintain the desired propylene concentration and achieve the desired comonomer to propylene ratio in the fluidizing gas. Although the actual comonomer to monomer ratio required to achieve the desired comonomer content in the polymer depends on the catalyst used in the process, the composition of the fed monomer and comonomer is appropriately selected so that the comonomer to propylene ratio in the fluidizing gas is approximately 10 to 100 mol / kmol, preferably 15 to 70 mol / kmol.Such ratios have been found to give good results for some catalysts.

[0163] It is also often necessary to introduce additional hydrogen into the second polymerization stage to control the melt index of the copolymer mixture. The hydrogen supply is adjusted to maintain a constant hydrogen-to-propylene ratio in the fluidizing gas. The actual ratio depends on the catalyst. Good results are achieved by maintaining the ratio in the range of 0.1 to 3 mol / kmol, preferably 0.2 to 2.5 mol / kmol.

[0164] In a gas-phase fluidized bed reactor, olefins are polymerized in the presence of a polymerization catalyst in an upward-moving gas stream. The reactor typically has a fluidized bed containing growing polymer particles incorporating the active catalyst, with the bed having a base above a fluidization grid.

[0165] The polymer bed is fluidized using a fluidizing gas containing an olefin monomer, possible comonomers, possible chain regulators or chain transfer agents such as hydrogen, and a possible inert gas. The fluidizing gas is fed into an inlet chamber at the bottom of the reactor. To ensure uniform distribution of the gas flow over the cross-sectional area of ​​the inlet chamber, the inlet nozzle can be equipped with a flow separating element, as is known in the art, for example from documents US-A-4933149 and EP-A-684871. One or more of the aforementioned components can be continuously added to the fluidizing gas to compensate for losses due to, among other things, the reaction or product withdrawal.

[0166] From the inlet chamber, the gas stream passes upward through a fluidization grate into the fluidized bed. The purpose of the fluidization grate is to uniformly distribute the gas flow over the cross-sectional area of ​​the bed. Sometimes the fluidization grate can be arranged so as to entrain the gas stream along the walls of the reactor, as described in document WO-A-2005 / 087361. Other types of fluidization grates are disclosed, among others, in publications US-A-4578879, EP 600414 and EP-A-721798. A review is given in the publication: Geldart, Bayens "The Design of Distributors for Gas-fluidized Beds", Powder Technology, Vol. 42, 1985.

[0167] A fluidizing gas passes through a fluidized bed. The superficial velocity of the fluidizing gas must be higher than the minimum fluidization velocity of the particles in the bed, otherwise fluidization will not occur. Conversely, the gas velocity must be lower than the terminal velocity, otherwise the entire bed will be entrained in the fluidizing gas. The minimum fluidization velocity and terminal velocity can be calculated using generally accepted engineering practice when the particle characteristics are known. A review is provided, inter alia, in Geldart, "Gas Fluidization Technology," J. Wiley & Sons, 1986.

[0168] When a fluidizing gas comes into contact with a bed containing an active catalyst, chemically active components of the gas, such as monomers and chain transfer agents, react in the presence of the catalyst to form a polymer product. The gas is heated by the heat of reaction.

[0169] 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 heating of the bed due to the reaction. The gas can be cooled to a temperature at which a portion of it condenses. When liquid droplets enter the reaction zone, they evaporate. The heat of vaporization then contributes to the removal of the heat of reaction. This type of operation is called the condensing mode, and variations thereof are disclosed, among others, in publications WO-A-2007 / 025640, US-A-4543399, EP-A-699213 and WO-A-94 / 25495. Condensing agents can also be added to the recycle gas stream, as described in publication EP-A-696293. Condensing agents are non-polymerizable components such as n-pentane, isopentane, n-butane or isobutane, which are at least partially condensed in the cooler.

[0170] The gas is then compressed and recirculated into the reactor inlet chamber. Before entering the reactor, fresh reactants are added to the fluidizing gas stream to compensate for losses due to the reaction and product removal. It is common knowledge that the composition of the fluidizing gas must be analyzed and gas components added to maintain a constant composition. The actual composition is determined by the desired product properties and the catalyst used in the polymerization.

[0171] 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, among others, in document WO-A-00 / 29452. Intermittent withdrawal is disclosed, among others, in documents US-A-4621952, EP-A-188125, EP-A-250169, and EP-A-579426.

[0172] The upper section of a gas-phase reactor may include a so-called separation zone. In this zone, the reactor diameter is increased to reduce gas velocity and allow particles carried out of the bed by the fluidizing gas to settle back into the bed.

[0173] The bed level can be measured by various methods known in the art. For example, the pressure difference between the bottom of the reactor and a specific bed height can be recorded over the entire length of the reactor, and the bed level can be calculated based on the pressure difference values. Such a calculation yields a time-averaged level. Ultrasonic sensors or radioactivity sensors can also be used. These methods can obtain instantaneous levels, which, of course, can then be averaged over time to obtain a time-averaged bed level. In addition, an antistatic agent can be added to the gas-phase reactor if necessary. Suitable antistatic agents and methods for using them are described, among other things, in documents US-A-5026795, US-A-4803251, US-A-4532311, US-A-4855370 and EP-A-560035. They are typically polar compounds and include, among others, water, ketones, aldehydes and alcohols.

[0174] The reactor may also include a mechanical stirrer to further facilitate mixing within the fluidized bed. An example of a suitable stirrer design is provided in document EP-A-707513.

[0175] Generally, the fluidized bed polymerization reactor operates at a temperature in the range of 50 to 100°C, preferably 70 to 90°C. The pressure is 10 to 40 bar, preferably 10 to 30 bar.

[0176] In the second polymerization step, a copolymer mixture is preferably formed containing a first component of a random propylene copolymer (PP1) and a second copolymer component (PP2).

[0177] Said first component of the random propylene copolymer (PP1) preferably reflects the low molecular weight (LMW) fraction of the bimodal random propylene copolymer (PP) and said second component of the random propylene copolymer (PP2) preferably reflects the high molecular weight (HMW) fraction of the bimodal random propylene copolymer (PP), as defined above. Thus, the copolymer mixture containing the first component of the random propylene copolymer (PP1) and the second component of the random propylene copolymer (PP2) preferably means a mixture of the low molecular weight (LMW) fraction and the high molecular weight (HMW) fraction of the bimodal random propylene copolymer (PP), as described above. Thus, the amount of any fraction of the prepolymer preferably complements the amount of the low molecular weight fraction.

[0178] A copolymer mixture is obtained by introducing particles of the first component of a random propylene copolymer (PP1), containing an active catalyst dispersed therein, together with additional propylene and a comonomer, into a second polymerization stage. This results in the formation of a second copolymer component (PP2) on particles containing the first random propylene copolymer. The second polymerization stage is preferably carried out in a gas-phase fluidized bed reactor. For this reason, in the context of the present invention, the terms "second polymerization stage" and "gas-phase reactor" can be used interchangeably.

[0179] The comonomer is selected from ethylene and alpha-olefins containing from 4 to 8 carbon atoms. The comonomer used in the second polymerization stage may be the same or different from the comonomer used in the first polymerization stage, provided that ethylene is used as a comonomer in at least one polymerization stage. Preferably, the same comonomer is used in both the first and second polymerization stages. Ethylene is preferably used as a comonomer in both the first and second polymerization stages.

[0180] Also in the second polymerization stage, the comonomer content is controlled to achieve the desired comonomer content in the copolymer mixture. The resulting reaction mixture is a bimodal random copolymer of propylene (PP).

[0181] The comonomer content of the first component propylene copolymer (PP1) is preferably from 1.0 to 4.0 mass%, more preferably from 2.0 to 3.5 mass%, even more preferably from 2.3 to 3.1 mass%, most preferably from 2.4 to 3.0 mass%, based on the total mass of the first component propylene copolymer (PP1).

[0182] The comonomer content of the second component propylene copolymer (PP2) is preferably 4.5 to 9.0 mass%, more preferably 4.8 to 8.0 mass%, most preferably 5.0 to 7.0 mass%, based on the total mass of the second component propylene copolymer (PP2).

[0183] The comonomer content of the first component of the propylene copolymer (PP1) is preferably from 1.5 to 6.0 mol%, more preferably from 3.0 to 5.5 mol%, even more preferably from 3.5 to 5.0 mol%, most preferably from 3.5 to 4.5 mol%, based on the total content of monomer units in the first component of the propylene copolymer (PP1).

[0184] The comonomer content of the second component of the propylene copolymer (PP2) is preferably 6.1 to 15.0 mol%, more preferably 7.0 to 12.0 mol%, even more preferably 7.5 to 10.5 mol%, most preferably 7.8 to 10.0 mol%, based on the total content of monomer units in the second component of the propylene copolymer (PP2).

[0185] Preferably, the obtained bimodal random copolymer of propylene (PP) has a total comonomer content of from 3.5 to 5.0% by weight based on the total weight of the random copolymer of propylene (PP), and preferably as further defined above or in the claims.

[0186] Furthermore, it is preferable that the comonomer content of the obtained bimodal random copolymer of propylene (PP) is higher than the comonomer content of the first component of the random copolymer of propylene (PP1). Preferably, the ratio of the comonomer content of the first component of the random copolymer of propylene (PP1) to the comonomer content of the obtained bimodal random copolymer of propylene (PP) (both expressed in mass%) is C2 ПП1 / C2 ПП , is from 0.40 to 0.75, more preferably from 0.50 to 0.70, preferably from 0.52 to 0.68.

[0187] Furthermore, it is preferable that the comonomer content of the second component of the random propylene copolymer (PP2) is higher than the comonomer content of the first component of the random propylene copolymer (PP1). Preferably, the ratio of the comonomer content of the first component of the propylene copolymer (PP1) to the comonomer content of the second component of the propylene copolymer (PP2) (both expressed in mass %) is C2 ПП1 / C2 ПП2 , is from 0.36 to 0.54, more preferably from 0.38 to 0.52, most preferably from 0.40 to 0.50.

[0188] Preferably, the MFR2 of the obtained bimodal random copolymer of propylene (PP) is from 0.15 to 0.50 g / 10 min, more preferably from 0.20 to 0.40 g / 10 min, most preferably from 0.23 to 0.35 g / 10 min.

[0189] Furthermore, the MFR of the obtained bimodal random propylene copolymer (PP) is lower than the MFR of the first random propylene copolymer (PP1). Preferably, the ratio of MFR2 of the obtained bimodal random propylene copolymer (PP) to MFR2 of the first component random propylene copolymer (PP1), MFR 2(ПП) / MFR 2(ПП1) , is from 0.20 to 0.50, most preferably from 0.22 to 0.48.

[0190] According to a preferred embodiment of the invention, the ratio C2 ПП1 / C2 ППis from 0.40 to 0.75, more preferably from 0.50 to 0.70, most preferably from 0.52 to 0.68, and the MFR ratio 2(ПП) / MFR 2(ПП1) ranges from 0.20 to 0.50, most preferably from 0.22 to 0.48.

[0191] The obtained bimodal random propylene copolymer (PP) contains a first propylene copolymer component (PP1), including an optional prepolymer component, and a second propylene copolymer component (PP2) in a weight ratio of 30:70 to 70:30, and preferably as defined above or in the claims. The corresponding amounts and preferred amounts of (PP1) and (PP2) are defined above.

[0192] Regarding the catalyst, the bimodal random copolymer of propylene (PP) can be obtained by polymerization in the presence of any conventional complex catalyst system comprising a Ziegler-Natta catalyst, chromium, and a single-site catalyst (such as a metallocene catalyst), preferably in the presence of a Ziegler-Natta catalyst system. Such a Ziegler-Natta catalyst system typically comprises a solid catalyst component, preferably a solid transition metal component, and a cocatalyst, and optionally an external electron donor. The solid catalyst component most preferably comprises a magnesium halide, a titanium halide, and an internal electron donor. Such catalysts are well known in the art.

[0193] It is preferable that the nucleating agent (B) is introduced into the bimodal random copolymer of propylene (PP) during the polymerization process of the bimodal random copolymer of propylene (PP).

[0194] More preferably, a vinyl compound of formula (BI) as described above or below, preferably vinylcyclohexane (VCH), is polymerized in the presence of a catalyst system containing a solid catalyst component, preferably a solid Ziegler-Natta catalyst component, to obtain a modified catalyst system, which is a reaction mixture containing the solid catalyst component and the produced polymer of the vinyl compound of formula (BI). In the obtained modified catalyst system, the weight ratio (g) of the polymer of the vinyl compound of formula (BI) to the solid catalyst component preferably reaches 5 (5:1), preferably up to 3 (3:1), most preferably is from 0.5 (1:2) to 2 (2:1). The obtained modified catalyst system is then used to polymerize the bimodal random copolymer of propylene (PP) of the invention, as described above.

[0195] A general method for preparing a modified catalyst system according to the invention and a polypropylene nucleated with a vinyl compound (I) is disclosed, for example, in document EP 1028984.

[0196] As a solid Ziegler-Natta catalyst component used for modification, said catalyst component preferably contains a transition metal component, which is preferably a titanium halide and a magnesium halide. These compounds can be supported on a particulate carrier such as an inorganic oxide such as silica or alumina, or usually a magnesium halide, to form the above-mentioned solid carrier. Examples of such solid catalyst components are disclosed, among others, in documents WO 87 / 07620, WO 92 / 21705, WO 93 / 11165, WO 93 / 11166, WO 93 / 19100, WO 97 / 36939, WO 98 / 12234, WO 99 / 33842.

[0197] The solid components of the bimodal random copolymer propylene (PP) polymerization catalyst generally contain, in addition to the magnesium halide and the transition metal compound, an electron donor (internal electron donor).

[0198] Suitable electron donors include, among others, carboxylic acid esters, such as phthalates, citraconates, and succinates. Oxygen- or nitrogen-containing silicon compounds can also be used. Examples of suitable compounds are provided in documents WO 92 / 19659, WO 92 / 19653, WO 92 / 19658, US 4,347,160, US 4,382,019, US 4,435,550, US 4,465,782, US 4,473,660, US 4,530,912, and US 4,560,671.

[0199] Furthermore, said solid catalyst component is preferably used in combination with well-known external electron donors, including, but not limited to, ethers, ketones, amines, alcohols, phenols, phosphines and silanes, for example, organosilane compounds containing Si-OCOR, Si-OR or Si-NR2 bonds having a silicon atom as a central atom, and where R is alkyl, alkenyl, aryl, arylalkyl or cycloalkyl with 1-20 carbon atoms; and well-known cocatalysts, which preferably include an alkylaluminum compound, as known in the art, for the polymerization of a bimodal random copolymer of propylene (PP).

[0200] When the nucleating agent (B) is introduced into the polymerization process of the bimodal random copolymer of propylene (PP), the amount of the nucleating agent (B) present in the bimodal random copolymer of propylene (PP) is preferably not more than 500 ppm, more preferably is from 0.025 to 200 ppm, even more preferably is from 1 to 100 ppm, and most preferably is from 5 to 100 ppm, based on the bimodal random copolymer of propylene (PP) and the nucleating agent (B), preferably based on the total weight of the polypropylene composition (100% by weight).

[0201] The invention thus relates to a polypropylene composition obtainable by the method described above.

[0202] Extrusion

[0203] After the polymer has been removed from the last polymerization stage, it is preferably subjected to process steps to remove residual hydrocarbons from the polymer. Such methods are well known in the art and may include pressure reduction steps, purging steps, stripping steps, extraction steps, etc. Combinations of different steps are also possible. After removing the residual hydrocarbons, the second propylene copolymer composition is preferably mixed with additives, as is well known in the art. Such additives include antioxidants, process stabilizers, neutralizers, lubricants, nucleating agents, pigments, etc. The polymer particles are then extruded into pellets, as is well known in the art. Preferably, a co-rotating twin-screw extruder is used in the extrusion stage. Such extruders are manufactured, for example, by Coperion (Werner & Pfleiderer) and Japan Steel Works.

[0204] Invented article

[0205] Furthermore, the invention relates to an article containing the polypropylene composition of the invention described above.

[0206] Preferably, the article contains a polypropylene composition in an amount greater than 80% by weight, more preferably in an amount of at least 90% by weight, even more preferably at least 95% by weight, even more preferably 98% by weight, for example 99% by weight of the polypropylene composition. It is particularly preferred that the article consists of a polypropylene composition.

[0207] Preferably, said article is a molded article, preferably an article manufactured by injection molding (IM) or an article manufactured by blow molding, preferably an article manufactured by extrusion blow molding, more preferably an article manufactured by injection molding, preferably for use in pipelines, including pipe fittings, articles required for pipe connections such as couplings or pipes.

[0208] Such pipe fittings, necessary for pipe connections of a product or pipe, produced from the polypropylene composition of the invention, preferably have the advantageous properties as described above and shown below in the experimental section. Thus, the pipe of the invention is classified as a pressure pipe, more preferably as a pressure pipe for hot and cold water.

[0209] The pipe according to the invention may be:

[0210] - a monolayer pipe, in which the pipe layer comprises, preferably consists of, a multimodal polypropylene composition according to the invention, or

[0211] - a multilayer pipe in which at least one layer comprises, preferably consists of, a multimodal polypropylene composition according to the invention.

[0212] A preferred pipe according to the invention has at least one layer comprising, preferably consisting of, the multimodal polypropylene composition of the present invention. More preferably, the pipe is intended for pressure pipe applications, preferably a pipe for use in hot and cold water supply pressure pipes.

[0213] The pipe also preferably has a pressure resistance of at least 22 hours, more preferably 100 hours, most preferably at least 165 hours, determined according to ISO 1167-1:2006 at a hoop stress of 4.5 MPa and at 95°C. The upper limit is usually not more than 10,000 hours.

[0214] The pipe also preferably has a pressure resistance of at least 1 hour, more preferably at least 2 hours, most preferably at least 5 hours, determined according to ISO 1167-1:2006 at a hoop stress of 16 MPa and at 20°C. The upper limit is usually not more than 10,000 hours.

[0215] The fitting of the present invention is preferably comprised of the multimodal polypropylene composition of the invention.

[0216] The invention also relates to the use of the polypropylene composition of the present invention for the production of an article as defined above.

[0217] Production of pipe according to invention

[0218] Pipes can be produced from the bimodal polypropylene composition of the invention using methods known in the art. According to one preferred method, the polypropylene composition is extruded through a die with an annular nozzle to the desired internal diameter, after which the polypropylene composition is cooled.

[0219] Pipe extruders preferably operate at relatively low temperatures, and therefore excessive heat accumulation should be avoided. Preferred extruders have a high length-to-diameter ratio (L / D) of greater than 15, preferably at least 20, and in particular at least 25. Modern extruders typically have an L / D ratio of approximately 30 to 35.

[0220] The polymer melt is extruded through a die with an annular nozzle, which can be configured with either an end-feed or side-feed configuration. Side-feed annular nozzle dies are often mounted with their axis parallel to the extruder axis, requiring a right-angle rotation when connecting to the extruder. The advantage of side-feed dies is that the mandrel can be pulled through the die, allowing, for example, easy access for cooling water lines to the mandrel.

[0221] After the molten plastic exits the die, it is calibrated to the desired diameter. In one method, the extrudate is placed in a metal tube (calibration sleeve). Pressure is created inside the extrudate, forcing the plastic against the tube wall.

[0222] According to another method, the extrudate exiting the die is directed into a tube with a perforated section in the center. A slight vacuum is created through the perforation to hold the tube against the walls of the calibration chamber.

[0223] After calibration, the pipe is usually cooled in a water bath of about 5 meters or more in length.

[0224] Production of fittings according to the invention

[0225] The fittings of the invention can be manufactured from the bimodal polypropylene composition of the invention using methods and equipment known in the art. Thus, according to one preferred method, the polypropylene composition is molded, preferably by injection molding or blow molding, more preferably by injection molding, in a conventional manner using conventional molding equipment, into the shape of a pipe fitting.

[0226] Examples

[0227] 1. Methods of determination

[0228] a) Melt flow index

[0229] The melt flow index (MFR) is determined according to ISO 1133 and is expressed in g / 10 min. The MFR value is an indicator of the flowability and, therefore, the processability of the polymer. The higher the melt flow index, the lower the viscosity of the polymer. The MFR of polypropylene is measured at a temperature of 230°C and a load of 2.16 kg.

[0230] The melt index MFR2 is estimated here by following the below mixing rule (Equation 1):

[0231] ,

[0232] where w refers to the mass fraction of the component in the mixture, MI refers to the melt index MFR2, and the subscripts b, 1 and 2 refer to the mixture (PP), component 1 (PP1) and component 2 (PP2), respectively.

[0233] b) Density

[0234] The polymer density is measured according to ISO 1183-1:2004, Method A, on samples obtained by compression molding according to EN ISO 1872-2 or ISO 19069-2, and is indicated in kg / m3 3 .

[0235] c) Comonomer content

[0236] The comonomer content is determined by quantitative Fourier transform infrared spectroscopy (FTIR) after basic interpretation calibrated by quantitative spectroscopy 13 Nuclear magnetic resonance (NMR) is a well-known technique in the field. Thin films are pressed to a thickness of 100-500 µm, and spectra are recorded in transmission mode.

[0237] Specifically, the ethylene content of the polypropylene-ethylene copolymer was determined using the baseline-corrected peak area of ​​the quantitative bands detected at 720-722 and 730-733 cm -1 For example, the butene or hexene content of a polypropylene copolymer is determined using the baseline-corrected peak area of ​​the quantitative bands found at 1377-1379 cm -1 Quantitative results are obtained taking into account the film thickness.

[0238] In this case, it is assumed that the comonomer content follows the mixing rule (equation 2):

[0239] ,

[0240] where C denotes the monomer content in mass%, w denotes the mass fraction of the component in the mixture, and the subscripts b, 1 and 2 refer to the total mixture (TM), component 1 (TM1) and component 2 (TM2), respectively.

[0241] As is well known to one skilled in the art, the comonomer content by weight in a binary copolymer can be converted to the comonomer content in moles using the following equation:

[0242] ,

[0243] where c m means the molar fraction of comonomer units in the copolymer, c w means the mass fraction of comonomer units in the copolymer, MW c means the molecular weight of the comonomer (e.g. ethylene) and MW m means the molecular weight of the main monomer (i.e., propylene).

[0244] d) Cold xylene soluble substances

[0245] Xylene soluble substances (XCS, wt %) is determined at 25°C according to ISO 16152; first edition; 2005-07-01.

[0246] The xylene-soluble polymer content is considered to follow the mixing rule (Equation 4) in this case:

[0247] ,

[0248] where XS denotes the xylene-soluble polymer content in mass%, w denotes the mass fraction of the component in the mixture, and the subscripts b, 1 and 2 refer to the whole mixture (PP), component 1 (PP1) and component 2 (PP2), respectively.

[0249] e) Flexural modulus of elasticity

[0250] The flexural modulus is determined according to ISO 178. The test specimen has dimensions of 80×10×4.0 mm 3 (length x width x thickness), are produced by injection molding according to EN ISO 1873-2 or ISO 19069-2. The length of the gap between supports is 64 mm, the testing speed is 2 mm / min.

[0251] f) Tensile modulus of elasticity

[0252] The tensile modulus of elasticity is determined in accordance with ISO 527-2 using a Type 1A molded test specimen having a thickness of 4 mm at a speed of 1 mm / min and at 23°C, injection molding is carried out in accordance with ISO 1873-2:2007 or ISO 19069-2.

[0253] g) Charpy notched impact strength

[0254] The Charpy notched impact strength (NIS) is determined according to ISO 179 / eA:2000 on a Type 1A injection molded notched test specimen. The test temperature is 23±2°C for Charpy NIS at 23°C and 0±2°C for Charpy NIS at 0°C. Injection molding is carried out according to ISO 1873-2:2007 or ISO 19069-2, and the specimens are conditioned for 24 hours after injection molding.

[0255] h) Crystallization temperature, melting point

[0256] Crystallization temperature T кр and melting point T плThe crystallization temperature is measured according to ISO 11357-3:1999 using a Mettler TA820 differential scanning calorimeter (DSC) on 10±3 mg samples. The crystallization temperature is obtained by scanning with cooling at 10°C / min and heating between 30 and 225°C.

[0257] Crystallization temperatures are taken as exotherm maxima for the indicated peaks.

[0258] Melting points are taken as endotherm maxima.

[0259] i) Rheological properties

[0260] Determination of polymer melt properties by dynamic shear measurements complies with ISO 6721-1 and 6721-10. Measurements are performed on an Anton Paar MCR501 controlled-stress rotational rheometer equipped with a 25 mm diameter parallel plate geometry. Measurements are performed on pressed plates under a nitrogen atmosphere and with deformation set to a linear viscoelastic regime. Oscillatory shear tests are conducted at T = 200°C in the frequency range from 0.01 to 600 rad / sec and with a gap setting of 1.3 mm.

[0261] In a dynamic shear experiment, the probe is subjected to uniform deformation under a sinusoidally varying shear strain or shear stress (controlled strain and stress mode, respectively). In a controlled strain experiment, the probe is subjected to sinusoidal deformation, which can be expressed as follows:

[0262] … (1).

[0263] If the applied strain is within the linear viscoelastic regime, the resulting sinusoidal stress response can be given by:

[0264] … (2),

[0265] where

[0266] And represent the amplitudes of stress and strain, respectively,

[0267] means angular frequency,

[0268] means phase shift (loss angle between applied strain and stress response),

[0269] t means time.

[0270] The results of dynamic tests are typically expressed in terms of several different rheological functions, namely, the shear elastic modulus G', the shear loss modulus G', the complex shear elastic modulus G*, the complex shear viscosity ƞ*, the dynamic shear viscosity ƞ', the out-of-phase component of the complex shear viscosity ƞ” and the loss tangent, tan δ, which can be expressed as follows:

[0271] [Pa] … (3)

[0272] [Pa] … (4)

[0273] [Pa] … (5)

[0274] [Pa⋅sec] … (6)

[0275] [Pa⋅sec] … (7)

[0276] [Pa⋅sec] … (8)

[0277] The determination of the so-called shear viscosity thinning index (SHI), which correlates with MWD and depends on Mw, is performed as described in equation 9:

[0278] .

[0279] For example, SHI (0,1 / 100)is determined by the value of the complex viscosity in Pa⋅sec, determined for a G* value of 0.1 kPa, divided by the value of the complex viscosity in Pa⋅sec, determined for a G* value of 100 kPa.

[0280] The values ​​of elastic modulus (G'), loss modulus (G"), complex elastic modulus (G*) and complex viscosity (ƞ*) are obtained depending on the frequency (ω).

[0281] Thus, for example, ƞ*300 (eta*300) is used as an abbreviation for the complex viscosity at a frequency of 300 rad / sec, and ƞ*0.05 (eta*0.05) is used as an abbreviation for the complex viscosity at a frequency of 0.05 rad / sec.

[0282] These values ​​are determined using the single-point interpolation procedure defined by the Rheoplus software. In situations where the specified G* value is not achieved experimentally, the value is determined by extrapolation using the same procedure as before. In both cases (interpolation or extrapolation), the Rheoplus options "Interpolate y values ​​into x values ​​from parameter" and "Logarithmic interpolation type" are used.

[0283] Links:

[0284] [1] “Rheological characterization of polyethylene fractions”, Heino, E.L., Lehtinen, A., Tanner J., Seppälä, J., Neste Oy, Porvoo, Finland, Theor. Appl. Rheol., Proc. Int. Congr. Rheol, 11th (1992), 1, 360-362.

[0285] [2] “The influence of molecular structure on some rheological properties of polyethylene”, Heino, E.L., Borealis Polymers Oy, Porvoo, Finland, Annual Transactions of the Nordic Rheology Society, 1995.

[0286] [3] “Definition of terms relating to the non-ultimate mechanical properties of polymers”, Pure & Appl. Chem., Vol. 70, No. 3, pp. 701-754, 1998.

[0287] j) Molecular weight distribution MWD (Mw, Mn)

[0288] The weight average molecular weight Mw and molecular weight distribution (MWD=Mw / Mn, where Mn stands for the number average molecular weight and Mw stands for the weight average molecular weight) were measured according to the method based on ISO 16014-1:2003 and ISO 16014-4:2003. A Waters Alliance GPCV 2000 equipped with a refractive index detector and an online viscometer was used, with 3 TosoHaas TSK-gel (GMHXL-HT) columns, and with 1,2,4-trichlorobenzene (TCB stabilized with 200 mg / L 2,6-di-tert-butyl-4-methyl-phenol) as a solvent at 145°C, with a constant flow rate of 1 mL / min. For analysis, 216.5 µL of sample solution is injected. The column set is calibrated using a relative calibration using 19 polystyrene (PS) standards with a narrow MWD ranging from 0.5 to 11,500 kg / mol and a set of well-characterized polypropylene standards with a broad MWD.All samples were prepared by dissolving 5-10 mg of polymer in 10 ml (at 160°C) of stabilized TCB (same as the mobile phase) and incubating for 3 hours with continuous shaking before sampling into the GPC / SEC instrument.

[0289] In the case of PP, the constants are: K=19×10 -3 ml / g and a=0.725 for PP.

[0290] k) Hydrostatic Pressure Test (HPT)

[0291] Resistance to internal pressure is determined by pressure testing. Pressure tests on unnotched SDR 11 pipes measuring 32 x 3 mm and 450 mm in length are conducted in an aqueous environment, both internally and externally, in accordance with ISO 1167-1:2006. Type A end caps are used. The time to failure is determined in hours. A ring stress of 4.5 MPa at 95°C or a ring stress of 16 MPa at 20°C is used.

[0292] 2. Examples

[0293] a) Preparation of catalyst

[0294] First, 0.1 mol of MgCl2×3EtOH is suspended under inert conditions in 250 ml of decane in a reactor at atmospheric pressure. The solution is cooled to -15°C and 300 ml of cooled TiCl4 is added, while the temperature is maintained at the specified level. Then, the temperature of the suspension is slowly raised to 20°C. At this temperature, 0.02 mol of diethylhexyl phthalate (DOP) is added to the suspension. After the addition of the phthalate, the temperature is raised to 135°C over 90 minutes and the suspension is kept at rest for 60 minutes. Then another 300 ml of TiCl4 is added and the temperature is maintained at 135°C for 120 minutes. After this, the catalyst is filtered from the liquid and washed six times with 300 ml of heptane at 80°C. Then the solid catalyst component is filtered and dried. The catalyst and the concept for its preparation are described in general, for example, in patent publications EP 491566, EP 591224 and EP 586390.

[0295] b) Obtaining IE1 and IE2 examples and CE comparison example

[0296] To ​​prepare Examples IE1 and IE2, triethylaluminum (TEAL), dicyclopentyldimethoxysilane (DCPDMS) as a donor (Do), the catalyst obtained above, and vinylcyclohexane (VCH) are added to oil such as mineral oil such as Technol 68 (kinematic viscosity at 40°C 62-74 cSt) in such an amount that the Al / Ti ratio is 3-4 mol / mol, the Al / Do ratio is also 3-4 mol / mol, and the VCH / (solid catalyst) weight ratio is 1:1. The mixture is heated to 60-65°C and allowed to react until the content of unreacted vinylcyclohexane in the reaction mixture is less than 1000 ppm. The catalyst concentration in the final oil-catalyst slurry is 10-20% by weight.

[0297] To obtain comparative example CE, the preparation of the oil-catalyst slurry is carried out as described above for examples IE1 and IE2, except that vinylcyclohexane (VCH) is not added to the oil and the VCH polymerization step at 60-65°C is not carried out.

[0298] For polymerization of Examples IE1 and IE2 and Comparative Example CE, the catalyst is fed into the prepolymerization reactor along with propylene. Triethylaluminum is used as a cocatalyst and dicyclopentyldimethoxysilane as a donor. The polymerization and feeding conditions are listed in Table 1.

[0299] The slurry from the prepolymerization stage is fed directly to the circulation reactor. Propylene, hydrogen, and ethylene are also added to the circulation reactor. Polymerization and feeding conditions are listed in Table 1.

[0300] The slurry from the loop reactor is introduced into the gas-phase reactor via a direct feed line, meaning there is no rapid evaporation of monomer between the reactors. Propylene, ethylene, and hydrogen are fed to the gas-phase reactor. The polymerization and feed conditions are listed in Table 1.

[0301] The final content of poly-VCG in the obtained final polymers of Examples IE1 and IE2 is 200 ppm or less.

[0302] In Examples IE1 and IE2, as well as in Comparative Example CE, the low-molecular-weight fraction of the random propylene copolymer is polymerized in a loop reactor, while the high-molecular-weight fraction of the random propylene copolymer is polymerized in a subsequent gas-phase reactor in the presence of the low-molecular-weight fraction. The polymerization conditions for IE1 and IE2 and Comparative Example CE are presented in Table 1.

[0303] c) Compounding and extrusion of pipes

[0304] The polypropylene resins of the claimed examples IE1 and IE2 and the comparative example CE, leaving the gas-phase reactor (identified as reactor powder) are compounded together with conventional antioxidants and Ca-stearate (R-PP composition, the same amounts are used for examples IE1 and IE2, as well as in the comparative example CE) and granulated in a W&P ZSK 70 twin-screw extruder (Coperion) at a melting temperature of 250°C and an extruder capacity of 200 kg / hour.

[0305] The polymer granules of the claimed examples IE1 and IE2, as well as in the comparative example CE, are obtained for testing the test specimens listed below in Table 2, or extruded into pipes for testing the pressure resistance and processability of the compositions. The test pipe blank made of the polymers of the comparative example and the claimed examples is extruded using a Krauss Maffei pipe extruder. The extruder capacity is 50 to 60 kg / h, the melt pressure is 100 to 120 bar (g), and the melt temperature is 220 to 230°C. The test pipes have a diameter of 32.3 mm and a wall thickness of 3 mm. The shrinkage of the obtained test pipes is clearly less than 5%.

[0306] Table 1: Polymerization conditions of claimed examples IE1 and IE2 and comparative example CE

[0307] CE IE1 IE2 Prepolymerization Catalyst type As in IE1, 2 but without the modification of the pVCG PVCH modified catalyst PVCH modified catalyst Temperature °C 30 30 30 Pressure bar 54 54 54 Donor submission [g / t(C3)] 40 35 35 TEAL Submission [g / t(C3)] 150 150 150 Circulation reactor Temperature °C 70 70 70 Pressure bar 54 54 54 H2 / C3 supply mol / kmol 0,78 0,71 0,71 MFR2 g / 10 min 0,85 0,75 0,75 XCS % mass. 3,0 3,5 3,6 Content of C2 (C2PP1) % mass. 2,30 2,67 2,70 Bifurcation % mass. 45 44,2 43,6 Gas-phase reactor Temperature °C 75 75 75 Pressure bar.hut 22 22 22 H2 / C3 supply mol / kmol 2,0 1,8 1,8 C2 / C3 mol / kmol 32,0 36,4 36,6 Content of C2 in the HFR fraction, calculated* (C2PP2) % mass. 6,5 5,6 5,7 Final MFR2 g / 10 min 0,30 0,27 0,27 Final XCS % mass. 8,2 6,4 6,8 Final C2 content (C2PP) % mass. 4,6 4,3 4,4 Separation % mass. 55 55,8 56,4 R-PP composition MFR2 g / 10 min 0,30 0,27 0,27 C2 content (C2PP)** % mass. 4,6 4,4 4,4 XCS % mass. 8,2 6,5 6,8 C2PP1 / C2PP2*** 0,50 0,62 0,61 C2PP1 / C2PP2**** 0,35 0,48 0,47 MFR2(PP) / MFR2(PP1)) 0,35 0,36 0,36

[0308] C2 content refers to the content of ethylene comonomer; C3 refers to the feed of propylene monomer;

[0309] * Calculated for polymer polymerized in a gas-phase reactor (high molecular weight (HMW) fraction);

[0310] ** Measured for the final polypropylene composition after compounding step (a) as described above;

[0311] *** C2 content of the circulation reactor (PP1) in % by weight / final C2 content in the gas-phase reactor in % by weight (C2 ПП1 / C2 ПП );

[0312] **** C2 content of the circulation reactor (PP1) in wt.% / C2 content calculated in the gas phase reactor component (PP2) in wt.% (C2 ПП1 / C2 ПП2 )

[0313] Table 2: Properties of claimed examples IE1 and IE2 and comparative example CE

[0314] Unit of measurement CE IE1 IE2 MFR2 granules g / 10 min 0,30 0,27 0,27 Charpy, NIS, 23°C kJ / m2 38 75,2 78,0 Charpy, NIS, 0°C kJ / m2 6,9 8,9 9,1 Flexural modulus of elasticity MPa 889 895 951 Tensile modulus of elasticity MPa 851 940 910 Tkr C 104,7 114,5 115,1 Tpl C 141,4 143,4 144,0 Mw (g / mol) 656100 662000 678500 Mn (g / mol) 46800 45100 41550 Mw / Mn 14,0 14,8 16,3 ETA (300 rad / sec) Pa⋅sec 666 703 681 HPT (4.5 MPa, 95°C) hour 1036 2550 2615 HPT (16 MPa, 20°C) hour 13 25 16

[0315] From the results in Tables 1 and 2, it can be seen that the examples IE1 and IE2 according to the invention show an improved balance of properties in the values ​​of Charpy notched impact strength at room temperature (23°C) and low temperature (0°C), flexural modulus, tensile modulus, XCS, eta 300 Both claimed examples show improved Charpy impact strength at room temperature (23°C) and low temperature (0°C), while the flexural modulus and tensile modulus remain at least at a high level. Moreover, processability is comparable, as can be seen from the MFR2 and eta values. 300In addition, the pressure resistance in IE1 and IE2 examples is improved.

[0316] The invention is based on the unexpected discovery that such an advantageous balance between stiffness and impact resistance can be achieved, in particular, by carefully selecting the comonomer content in the LMW fraction (PP1) and the HMW fraction (PP2) and the molecular weight, as can be seen from the MFR2 values ​​of the propylene copolymer and the bimodal molecular weight distribution.

[0317] This is achieved by carefully selecting the comonomer content and molecular weight of the LMW fractions (PP1) and VM fractions (PP2) together, as can be seen from the MFR ratio 2 ПП / MFR 2 ПП1 , in a bimodal propylene copolymer and the ratio of C2 comonomers ПП1 / C2 ПП2 , as well as a slightly higher overall ratio of C2 comonomers ПП1 / C2 ППMoreover, by regulating the separations, the final comonomer content and MFR2 of the claimed example, even with a very similar molecular weight distribution, which can be seen from M w / M n, significantly improve the rigidity (flexural modulus) and achieve a better balance of rigidity and impact resistance, which can be seen in the better properties of HPT pipes, due to the use of the claimed examples.

Claims

1. A polypropylene composition for pipelines containing base resin (A) and nucleating agent (B), wherein the base resin (A) consists of a bimodal copolymer of propylene (PP) with at least one comonomer which is ethylene, where the bimodal propylene copolymer (PP) contains (PP1) the first component of the propylene copolymer (PP2) the second component of the propylene copolymer, and where the first component of the propylene copolymer (PP1) is different from the second component of the propylene copolymer (PP2), and where the weight ratio of the first component of the propylene copolymer (PP1), including the optional prepolymer component, to the second component of the propylene copolymer (PP2) is from 30:70 to 70:30, and where the polypropylene composition has (b) a total comonomer content of 3.5 to 5.0% by weight, based on the total weight of the bimodal propylene copolymer (PP), (c) a xylene cold solubles (XCS) content equal to or less than 8.2% by weight based on the total weight of the bimodal propylene copolymer (PP), determined according to ISO 16152, wherein the nucleating agent (B) is a polymer of a vinyl compound according to the following formula: CH2=CH-CHR 1 R 2 (BI), where R 1 and R 2 together form a 5- or 6-membered saturated, unsaturated or aromatic ring, optionally containing substituents, or independently represent an alkyl group containing from 1 to 4 carbon atoms, wherein in the case where R 1 and R 2 form an aromatic ring, the hydrogen atom in the fragment - CH 1 R2 2 is not present, and where is the mass ratio of the content of the comonomer of the first component of the propylene copolymer (PP1) to the content of the comonomer of the second component of the propylene copolymer (PP2), which are expressed in % by mass, C2 ПП1 / C2 ПП2 , ranges from 0.36 to 0.

54.

2. A polypropylene composition according to claim 1, in which the mass ratio of the content of the comonomer of the first component of the propylene copolymer (PP1) to the content of the comonomer of the bimodal propylene copolymer (PP), which are expressed in % by mass, C2 ПП1 / C2 ПП , ranges from 0.40 to 0.

75.

3. A polypropylene composition according to claim 1, in which the content of the comonomer of the second component of the propylene copolymer (PP2) is from 4.5 to 9.0% by weight, based on the total weight of the second component of the propylene copolymer (PP2).

4. The polypropylene composition according to claim 1, wherein the first component of the propylene copolymer (PP1) has a higher MFR2 than the second component of the propylene copolymer (PP2), preferably the first component of the propylene copolymer (PP1) has a melt flow index MFR2 from 0.4 to 2.0 g / 10 min, and / or wherein the bimodal propylene copolymer (PP) has a melt flow index MFR2 from 0.15 to 0.50 g / 10 min.

5. The polypropylene composition according to claim 1, in which the ratio of MFR2 of the bimodal propylene copolymer (PP) to the MFR2 of the first component propylene copolymer (PP1), MFR2 ПП / MFR2 ПП1 , ranges from 0.20 to 0.

50.

6. The polypropylene composition according to claim 1, wherein the weight ratio of the first component of the propylene copolymer (PP1), including the optional prepolymer component, to the second component of the propylene copolymer (PP2) is from 38:62 to 60:

40.

7. A polypropylene composition according to claim 1, wherein the bimodal propylene copolymer (PP) has a xylene soluble substances (XCS) content of 4.0 to 8.0% by weight, determined according to ISO 16152 at 25°C.

8. The polypropylene composition according to claim 1, wherein the bimodal propylene copolymer (PP) does not contain an elastomeric polymer phase dispersed therein, and / or the bimodal propylene copolymer does not contain LLDPE.

9. A method for producing a polypropylene composition according to any of the preceding claims, wherein a bimodal copolymer of propylene (PP) with at least one comonomer which is ethylene is polymerized in a multi-stage polymerization process in the presence of: (I) a solid catalyst component comprising a magnesium halide, a titanium halide and an internal electron donor; and (II) a cocatalyst comprising an alkylaluminium and optionally an external electron donor, and (III) nucleating agent (B); wherein the multi-stage method includes the following stages: (a) continuously polymerising propylene together with a comonomer selected from alpha-olefins with 2 or 4-8 carbon atoms, preferably with ethylene, in a first polymerisation stage by introducing streams of propylene, hydrogen and ethylene into the first polymerisation stage at a temperature of 60 to 80°C and a pressure of 3000 to 6500 kPa to obtain a first propylene copolymer component, said first propylene copolymer component (PP1) preferably having a melt flow index MFR2 of 0.4 to 2.0 g / 10 min, as determined according to ISO 1133 at 230°C and a load of 2.16 kg; (b) removing from the first stage of polymerization a stream containing said first component of propylene copolymer (PP1) and moving said stream to the second stage of polymerization; (c) polymerizing propylene together with a comonomer selected from alpha-olefins with 2 or 4-8 carbon atoms, preferably with ethylene, in said second polymerization stage by introducing streams of propylene, ethylene and optionally hydrogen into said second polymerization stage at a temperature of from 70 to 90°C and a pressure of from 1000 to 3000 kPa to obtain a bimodal propylene copolymer (PP) of said first propylene copolymer component (PP1) and a second propylene copolymer component (PP2); (d) continuously withdrawing a stream containing said bimodal propylene copolymer (PP) from the second polymerization stage and optionally mixing said bimodal propylene copolymer (PP) with additives; and (e) extruding a mixture of said bimodal copolymer into pellets that have a melt flow index MFR2, determined according to ISO 1133 at 230°C and a load of 2.16 kg, of from 0.15 to 0.5 g / 10 min, and wherein the first propylene copolymer component (PP1) is different from the second propylene copolymer component (PP2), and preferably has a higher MFR than the second propylene copolymer component (PP2), wherein The nucleating agent (B) is a polymer of a vinyl compound according to the following formula: CH2=CH-CHR 1 R 2 (BI), where R 1 and R 2 together form a 5- or 6-membered saturated, unsaturated or aromatic ring, optionally containing substituents, or independently represent an alkyl group containing from 1 to 4 carbon atoms, wherein in the case where R 1 and R 2 form an aromatic ring, the hydrogen atom in the -CHR fragment 1 R 2 is not present, and where is the mass ratio of the content of the comonomer of the first component of the propylene copolymer (PP1) to the content of the comonomer of the second component of the propylene copolymer (PP2), which are expressed in % by mass, C2 ПП1 / C2 ПП2 , ranges from 0.36 to 0.54, and wherein the nucleating agent is introduced into the random bimodal copolymer of propylene (PP) during one of: a process for polymerizing a vinyl compound of formula (BI) in the presence of a catalytic system comprising a solid catalyst component to produce a modified catalytic system which is a reaction mixture comprising a solid catalyst component and the resulting polymer of a vinyl compound of formula (BI); or mechanical mixing with the nucleating agent itself; or mechanical mixing with a nucleated polymer containing a nucleated agent.

10. A pipeline containing a polypropylene composition according to any one of paragraphs 1-8.

11. Use of a polypropylene composition according to any of paragraphs 1-8 for the production of pipelines.

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